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Sample records for intensity-modulated radiotherapy-based stereotactic

  1. Phase I dose-escalation study of helical intensity-modulated radiotherapy-based stereotactic body radiotherapy for hepatocellular carcinoma

    PubMed Central

    Kim, Jun Won; Seong, Jinsil; Lee, Ik Jae; Woo, Joong Yeol; Han, Kwang-Hyub

    2016-01-01

    Background Phase I trial was conducted to determine feasibility and toxicity of helical intensity-modulated radiotherapy (IMRT)-based stereotactic body radiotherapy (SBRT) for hepatocellular carcinoma (HCC). Results Eighteen patients (22 lesions) were enrolled. With no DLT at 52 Gy (13 Gy/fraction), protocol was amended for further escalation to 60 Gy (15 Gy/fraction). Radiologic complete response rate was 88.9%. Two outfield intrahepatic, 2 distant, 4 concurrent local and outfield, and 1 concurrent local, outfield and distant failures (no local failure at dose levels 3–4) occurred. The worst toxicity was grade 3 hematologic in five patients, with no gastrointestinal toxicity > grade 1. At median follow-up of 28 months for living patients, 2-year local control, progression-free (PFS), and overall survival rates were 71.3%, 49.4% and 69.3%, respectively. Multi-segmental recurrences prior to SBRT was independent prognostic factor for PFS (p = 0.033). Materials and Methods Eligible patients had Child-Pugh's class A or B, unresectable HCC, ≤ 3 lesions, and cumulative tumor diameter ≤ 6 cm. Starting at 36 Gy in four fractions, dose was escalated with 2 Gy/fraction per dose-level. CTCAE v 3.0 ≥ grade 3 gastrointestinal toxicity and radiation induced liver disease defined dose-limiting toxicity (DLT). Conclusions Helical IMRT-based SBRT was tolerable and showed encouraging results. Confirmatory phase II trial is underway. PMID:27213593

  2. Intensity-Modulated Radiotherapy-Based Stereotactic Body Radiotherapy for Medically Inoperable Early-Stage Lung Cancer: Excellent Local Control

    SciTech Connect

    Videtic, Gregory M.M.; Stephans, Kevin; Reddy, Chandana; Gajdos, Stephen; Kolar, Matthew; Clouser, Edward; Djemil, Toufik

    2010-06-01

    Purpose: To validate the use of stereotactic body radiotherapy (SBRT) using intensity-modulated radiotherapy (IMRT) beams for medically inoperable Stage I lung cancer. Methods and Materials: From February 2004 to November 2006, a total of 26 patients with 28 lesions received SBRT using a Novalis/BrainLAB system. Immobilization involved a Bodyfix vacuum cushion. A weighted abdominal belt limited respiratory excursion. Computed tomographic simulation images were acquired at rest, full inhalation, and full exhalation and were merged to generate an internal gross tumor volume (ITV). Dose was prescribed to cover the planning target volume (PTV), defined as PTV = ITV + 3-5 mm set-up margin. Heterogeneity corrections were used. Delivery of 50 Gy in five sequential fractions typically used seven nonopposing, noncoplanar beams. Image-guided target verification was provided by BrainLAB-ExacTrac. Results: Among the 26 patients, the mean age was 74 years (range, 49-88 years). Of the patients, 50% were male and 50% female. The median Karnofsky performance status was 70 (range, 40-100). The median follow-up was 30.9 months (range, 10.4-51.4 months). Tissue diagnosis was contraindicated in seven patients (26.9%). There were 22 T1 (78.6%) and six T2 (21.4%) tumors. The median conformality index was 1.38 (range, 1.12-1.8). The median heterogeneity index was 1.08 (range, 1.04-1.2). One patient (3.6%) developed acute Grade 3 dyspnea and one patient developed late Grade 2 chest wall pain. Actuarial local control and overall survival at 3 years were 94.4% and 52%, respectively. Conclusions: Use of IMRT-based delivery of SBRT using restriction of tumor motion in medically inoperable lung cancer demonstrates excellent local control and favorable survival.

  3. Stereotactic Image-Guided Intensity Modulated Radiotherapy Using the HI-ART II Helical Tomotherapy System

    SciTech Connect

    Holmes, Timothy W. Hudes, Richard; Dziuba, Sylwester; Kazi, Abdul; Hall, Mark; Dawson, Dana

    2008-07-01

    The highly integrated adaptive radiation therapy (HI-ART II) helical tomotherapy unit is a new radiotherapy machine designed to achieve highly precise and accurate treatments at all body sites. The precision and accuracy of the HI-ART II is similar to that provided by stereotactic radiosurgery systems, hence the historical distinction between external beam radiotherapy and stereotactic procedures based on differing precision requirements is removed for this device. The objectives of this work are: (1) to describe stereotactic helical tomotherapy processes (SRS, SBRT); (2) to show that the precision and accuracy of the HI-ART meet the requirements defined for SRS and SBRT; and (3) to describe the clinical implementation of a stereotactic image-guided intensity modulated radiation therapy (IG-IMRT) system that incorporates optical motion management.

  4. Optimization of Isocenter Location for Intensity Modulated Stereotactic Treatment of Small Intracranial Targets

    SciTech Connect

    Salter, Bill J. Fuss, Martin; Sarkar, Vikren; Wang, Brian; Rassiah-Szegedi, Prema; Papanikolaou, Niko; Hollingshaus, Scott; Shrieve, Dennis C.

    2009-02-01

    Purpose: To quantify the impact of isocenter location on treatment plan quality for intensity-modulated stereotactic treatment of small intracranial lesions. Methods and Materials: For 18 patients previously treated by stereotactic-intensity modulated radiosurgery (IMRS) or intensity-modulated radiation therapy (IMRT), a retrospective virtual planning study was conducted wherein the impact of isocenter location on plan quality was measured. Treatment indications studied included six arteriovenous malformations, six acoustic neuromas, and six intracranial metastases, ranging in volume from 0.71 to 3.21 cm{sup 3} (mean = 2.26 cm{sup 3}), 1.08 to 2.84 cm{sup 3} (mean = 1.73 cm{sup 3}), and 0.19 to 2.30 cm{sup 3} (mean = 0.79 cm{sup 3}), respectively. Variation of isocenter location causes the geometric grid of pencil beams into which the target is segmented for intensity-modulated treatment to be altered. The impact of this pencil-beam-grid redefinition on achievable conformity index was quantified for three collimators (Varian Millennium 120; BrainLab MM3; Nomos binary Mimic) and three treatment planning systems (TPS; Varian Eclipse v6.5; BrainLab BrainScan v5.31; Best-Nomos Corvus v6.2), resulting in the evaluation of 3,446 treatment plans. Results: For all patients, collimator, and TPS combinations studied, a significant variation in plan quality was observed as a function of isocenter and pencil-beam-grid relocation. Optimization of isocenter location resulted in treatment plan conformity variations as large as 109% (min = 15%, mean = 51%, max = 109%). Conclusion: Optimization of isocenter location for IMRT/IMRS treatment of small intracranial lesions in which pencil-beam dimensions are comparable to target dimensions, can result in significant improvements in treatment plan quality.

  5. Intensity-modulated stereotactic radiotherapy (IMSRT) for skull-base meningiomas

    SciTech Connect

    Yenice, Kamil M. . E-mail: kyenice@radonc.uchicago.edu; Narayana, Ashwatha; Chang, Jenghwa; Gutin, Philip H.; Amols, Howard I.

    2006-11-15

    Purpose: To investigate the potential benefits of a micromultileaf collimator ({mu}MLC) -based intensity-modulated stereotactic radiotherapy (IMSRT) in skull-base meningiomas. Methods and Materials: Seven patients with inoperable or recurrent small-volume (1.7-15.5 cc) skull-base meningiomas were treated with IMSRT to 54 Gy in 30 fractions using a {mu}MLC in the dynamic mode. IMSRT plan quality was evaluated in comparison with the conformal stereotactic radiotherapy technique, using the same beam arrangement and static delivery with the {mu}MLC. Plans were compared using multiple dose distributions and dose-volume histograms for the planning target volume and organs at risk. The conformity and uniformity metrics, as well as normal-tissue complication probabilities, were calculated for the two techniques. Follow-up with MRI and clinical examination was performed at regular intervals. Results: With a mean follow-up of 17 months, local control has been achieved in all cases, and no treatment-related toxicities have been noted. For cavernous sinus tumors overlapping with optic apparatus, IMSRT has improved the dose uniformity within the target on average by 8%, which resulted in a reduction of the estimated chiasm normal-tissue complication probability by up to 65%. Conclusions: Intensity-modulated stereotactic radiotherapy can be safely delivered to improve the dose distributions in select skull-base meningiomas with an appreciable concomitant dose reduction to involved critical structures. Longer follow-up with a larger patient group is necessary to demonstrate sustained tumor control and low morbidity with IMSRT for small inoperable, recurrent, or subtotally resected meningiomas.

  6. Dose to the intracranial arteries in stereotactic and intensity-modulated radiotherapy for skull base tumors

    SciTech Connect

    Nieder, Carsten . E-mail: cnied@hotmail.com; Grosu, Anca L.; Stark, Sybille; Wiedenmann, Nicole; Busch, Raymonde; Kneschaurek, Peter; Molls, Michael

    2006-03-15

    Purpose: To examine retrospectively the maximum dose to the large skull base/intracranial arteries in fractionated stereotactic radiotherapy (FSRT) and intensity-modulated radiotherapy (IMRT), because of the potential risk of perfusion disturbances. Methods and Materials: Overall, 56 patients with tumors adjacent to at least one major artery were analyzed. Our strategy was to perform FSRT with these criteria: 1.8 Gy per fraction, planning target volume (PTV) enclosed by the 95% isodose, maximum dose 107%. Dose limits were applied to established organs at risk, but not the vessels. If FSRT planning failed to meet any of these criteria, IMRT was planned with the same objectives. Results: In 31 patients (median PTV, 23 cm{sup 3}), the FSRT plan fulfilled all criteria. No artery received a dose {>=}105%. Twenty-five patients (median PTV, 39 cm{sup 3}) needed IMRT planning. In 11 of 25 patients (median PTV, 85 cm{sup 3}), no plan satisfying all our criteria could be calculated. Only in this group, moderately increased maximum vessel doses were observed (106-110%, n = 7, median PTV, 121 cm{sup 3}). The median PTV dose gradient was 29% (significantly different from the 14 patients with satisfactory IMRT plans). Three of the four patients in this group had paranasal sinus tumors. Conclusion: The doses to the major arteries should be calculated in IMRT planning for critical tumor locations if a dose gradient >13% within the PTV can not be avoided because the PTV is large or includes air cavities.

  7. Salvage image-guided intensity modulated or stereotactic body reirradiation of local recurrence of prostate cancer

    PubMed Central

    Jereczek-Fossa, B A; Fodor, C; Bazzani, F; Maucieri, A; Ronchi, S; Ferrario, S; Colangione, S P; Gerardi, M A; Caputo, M; Cecconi, A; Gherardi, F; Vavassori, A; Comi, S; Cambria, R; Garibaldi, C; Cattani, F; De Cobelli, O; Orecchia, R

    2015-01-01

    Objective: To retrospectively evaluate external beam reirradiation (re-EBRT) delivered to the prostate/prostatic bed for local recurrence, after radical or adjuvant/salvage radiotherapy (RT). Methods: 32 patients received re-EBRT between February 2008 and October 2013. All patients had clinical/radiological local relapse in the prostate or prostatic bed and no distant metastasis. re-EBRT was delivered with selective RT technologies [stereotactic RT including CyberKnifeTM (Accuray, Sunnyvale, CA); image-guidance and intensity-modulated RT etc.]. Toxicity was evaluated using the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer criteria. Biochemical control was assessed according to the Phoenix definition (NADIR + 2 ng ml−1). Results: Acute urinary toxicity: G0, 24 patients; G1, 6 patients; G2, 2 patients. Acute rectal toxicity: G0, 28 patients; G1, 2 patients; and G2, 1 patient. Late urinary toxicity (evaluated in 30 cases): G0, 23 patients; G1, 6 patients; G2, 1 patient. Late renal toxicity: G0, 25 patients; G1, 5 patients. A mean follow-up of 21.3 months after re-EBRT showed that 13 patients were free of cancer, 3 were alive with biochemical relapse and 12 patients were alive with clinically evident disease. Four patients had died: two of disease progression and two of other causes. Conclusion: re-EBRT using modern technology is a feasible approach for local prostate cancer recurrence offering 2-year tumour control in about half of the patients. Toxicity of re-EBRT is low. Future studies are needed to identify the patients who would benefit most from this treatment. Advances in knowledge: Our series, based on experience in one hospital alone, shows that re-EBRT for local relapse of prostate cancer is feasible and offers a 2-year cure in about half of the patients. PMID:26055506

  8. [Intensity-modulated radiation therapy and stereotactic body radiation therapy for head and neck tumors: evidence-based medicine].

    PubMed

    Lapierre, A; Martin, F; Lapeyre, M

    2014-10-01

    Over the last decade, there have been many technical advances in radiation therapy, such as the spread of intensity-modulated conformal radiotherapy, and the rise of stereotactic body radiation therapy. By allowing better dose-to-target conformation and thus better organs at risk-sparing, these techniques seem very promising, particularly in the field of head and neck tumors. The present work aims at analyzing the level of evidence and recommendation supporting the use of high-technology radiotherapy in head and neck neoplasms, by reviewing the available literature.

  9. Integral test phantom for dosimetric quality assurance of image guided and intensity modulated stereotactic radiotherapy

    SciTech Connect

    Letourneau, Daniel; Keller, Harald; Sharpe, Michael B.; Jaffray, David A.

    2007-05-15

    The objective of this work is to develop a dosimetric phantom quality assurance (QA) of linear accelerators capable of cone-beam CT (CBCT) image guided and intensity-modulated radiotherapy (IG-IMRT). This phantom is to be used in an integral test to quantify in real-time both the performance of the image guidance and the dose delivery systems in terms of dose localization. The prototype IG-IMRT QA phantom consisted of a cylindrical imaging phantom (CatPhan) combined with an array of 11 radiation diodes mounted on a 10 cm diameter disk, oriented perpendicular to the phantom axis. Basic diode response characterization was performed for 6 and 18 MV photons. The diode response was compared to planning system calculations in the open and penumbrae regions of simple and complex beam arrangements. The clinical use of the QA phantom was illustrated in an integral test of an IG-IMRT treatment designed for a clinical spinal radiosurgery case. The sensitivity of the phantom to multileaf collimator (MLC) calibration and setup errors in the clinical setting was assessed by introducing errors in the IMRT plan or by displacing the phantom. The diodes offered good response linearity and long-term reproducibility for both 6 and 18 MV. Axial dosimetry of coplanar beams (in a plane containing the beam axes) was made possible with the nearly isoplanatic response of the diodes over 360 deg. of gantry (usually within {+-}1%). For single beam geometry, errors in phantom placement as small as 0.5 mm could be accurately detected (in gradient {>=}1%/mm). In clinical setting, MLC systematic errors of 1 mm on a single MLC bank introduced in the IMRT plan were easily detectable with the QA phantom. The QA phantom demonstrated also sufficient sensitivity for the detection of setup errors as small as 1 mm for the IMRT delivery. These results demonstrated that the prototype can accurately and efficiently verify the entire IG-IMRT process. This tool, in conjunction with image guidance capabilities

  10. Volumetric-Modulated Arc Therapy for Stereotactic Body Radiotherapy of Lung Tumors: A Comparison With Intensity-Modulated Radiotherapy Techniques

    SciTech Connect

    Holt, Andrea; Vliet-Vroegindeweij, Corine van; Mans, Anton; Belderbos, Jose S.; Damen, Eugene M.F.

    2011-12-01

    Purpose: To demonstrate the potential of volumetric-modulated arc therapy (VMAT) compared with intensity-modulated radiotherapy (IMRT) techniques with a limited number of segments for stereotactic body radiotherapy (SBRT) for early-stage lung cancer. Methods and Materials: For a random selection of 27 patients eligible for SBRT, coplanar and noncoplanar IMRT and coplanar VMAT (using SmartArc) treatment plans were generated in Pinnacle{sup 3} and compared. In addition, film measurements were performed using an anthropomorphic phantom to evaluate the skin dose for the different treatment techniques. Results: Using VMAT, the delivery times could be reduced to an average of 6.6 min compared with 23.7 min with noncoplanar IMRT. The mean dose to the healthy lung was 4.1 Gy for VMAT and noncoplanar IMRT and 4.2 Gy for coplanar IMRT. The volume of healthy lung receiving >5 Gy and >20 Gy was 18.0% and 5.4% for VMAT, 18.5% and 5.0% for noncoplanar IMRT, and 19.4% and 5.7% for coplanar IMRT, respectively. The dose conformity at 100% and 50% of the prescribed dose of 54 Gy was 1.13 and 5.17 for VMAT, 1.11 and 4.80 for noncoplanar IMRT and 1.12 and 5.31 for coplanar IMRT, respectively. The measured skin doses were comparable for VMAT and noncoplanar IMRT and slightly greater for coplanar IMRT. Conclusions: Coplanar VMAT for SBRT for early-stage lung cancer achieved plan quality and skin dose levels comparable to those using noncoplanar IMRT and slightly better than those with coplanar IMRT. In addition, the delivery time could be reduced by {<=}70% with VMAT.

  11. Stereotactic Radiotherapy of Central Nervous System and Head and Neck Lesions, Using a Conformal Intensity-Modulated Radiotherapy System (Peacock™ System)

    PubMed Central

    Ammirati, Mario; Bernardo, Antonio; Ramsinghani, Nilam; Yakoob, Richard; Al-Ghazi, Matthew; Kuo, Jeffrey; Ammirati, Giuseppe

    2001-01-01

    The objective of this article is to evaluate single-fraction or fractionated stereotactic radiotherapy of central nervous system (CNS) and head and neck lesions using intensity-modulated radiotherapy (IMRT) with a commercially available system (Peacock™, Nomos Corporation, Sewickley, PA). This system allows tomotherapeutic delivery of intensity-modulated radiation, that is, the slice-by-slice treatment of the volume of interest with an intensity-modulated beam, making the delivery of highly conformal radiation to the target possible in both single or multiple fractions mode. During an 18-month period, 43 (21 males and 22 females) patients were treated, using a removable cranial screw-fixation device. Ages ranged from 10 to 77 years (mean, 52.2; median, 53.5). Intra- and extra-axial lesions, including head and neck malignancies and spine metastases, were treated. Clinical target volume ranged from 0.77 to 195 cm3 (mean, 47.8; median, 29.90). The dose distribution was normalized to the maximum and was prescribed, in most cases, at the 80% or 90% isodose line (range, 65 to 96%; median, 85%; mean, 83.4%) and ranged from 14 to 80 Gy (mean, 48; median, 50). The number of fractions ranged from 1 to 40 (mean, 23; median, 25). In all but one patient, 90% of the prescription isodose line covered 100% of the clinical target volume. The heterogeneity index (the ratio between the maximum radiation dose and the prescribed dose) ranged between 1.0 and 1.50, whereas the conformity index (the ratio between the volume encompassed by the prescription isodose line and the clinical target volume) ranged between 1.0 and 4.5. There were no complications related to the radiation treatment. With a median follow-up of 6 months, more than 70% of our patients showed decreased lesion size. Stereotactic IMRT of CNS and head and neck lesions can be delivered safely and accurately. The Peacock system delivers stereotactic radiation in single or multiple fractions and has no volume limitations

  12. Hypofractionated Boost to the Dominant Tumor Region With Intensity Modulated Stereotactic Radiotherapy for Prostate Cancer: A Sequential Dose Escalation Pilot Study

    SciTech Connect

    Miralbell, Raymond; Molla, Meritxell; Rouzaud, Michel; Hidalgo, Alberto; Toscas, Jose Ignacio; Lozano, Joan; Sanz, Sergi B.Sc.; Ares, Carmen; Jorcano, Sandra; Linero, Dolors; Escude, Lluis

    2010-09-01

    Purpose: To evaluate the feasibility, tolerability, and preliminary outcomes in patients with prostate cancer treated according to a hypofractionated dose escalation protocol to boost the dominant tumor-bearing region of the prostate. Methods and Materials: After conventional fractionated external radiotherapy to 64 to 64.4Gy, 50 patients with nonmetastatic prostate cancer were treated with an intensity-modulated radiotherapy hypofractionated boost under stereotactic conditions to a reduced prostate volume to the dominant tumor region. A rectal balloon inflated with 60cc of air was used for internal organ immobilization. Five, 8, and 8 patients were sequentially treated with two fractions of 5, 6, or 7Gy, respectively (normalized total dose in 2Gy/fraction [NTD{sub 2Gy}] < 100Gy, low-dose group), whereas 29 patients received two fractions of 8Gy each (NTD{sub 2Gy} > 100Gy, high-dose group). Androgen deprivation was given to 33 patients. Acute and late toxicities were assessed according to the Radiation Therapy Oncology Group/European Organisation for Research and Treatment of Cancer (RTOG/EORTC) scoring system. Results: Two patients presented with Grade 3 acute urinary toxicity. The 5-year probabilities of {>=}Grade 2 late urinary and late low gastrointestinal (GI) toxicity-free survival were 82.2% {+-} 7.4% and 72.2% {+-} 7.6%, respectively. The incidence and severity of acute or late toxicities were not correlated with low- vs. high-dose groups, pelvic irradiation, age, or treatment with or without androgen deprivation. The 5-year biochemical disease-free survival (b-DFS) and disease-specific survival were 98% {+-} 1.9% and 100%, respectively. Conclusion: Intensity-modulated radiotherapy hypofractionated boost dose escalation under stereotactic conditions was feasible, and showed excellent outcomes with acceptable long-term toxicity. This approach may well be considered an alternative to high-dose-rate brachytherapy.

  13. Dosimetric comparisons of helical tomotherapy treatment plans and step-and-shoot intensity-modulated radiosurgery treatment plans in intracranial stereotactic radiosurgery

    SciTech Connect

    Han Chunhui . E-mail: chan@coh.org; Liu An; Schultheiss, Timothy E.; Pezner, Richard D.; Chen Yijen; Wong, Jeffrey Y.C.

    2006-06-01

    Purpose: To evaluate dose conformity, dose homogeneity, and dose gradient in helical tomotherapy treatment plans for stereotactic radiosurgery, and compare results with step-and-shoot intensity-modulated radiosurgery (IMRS) treatment plans. Methods and Materials: Sixteen patients were selected with a mean tumor size of 14.65 {+-} 11.2 cm{sup 3}. Original step-and-shoot IMRS treatment plans used coplanar fields because of the constraint of the beam stopper. Retrospective step-and-shoot IMRS plans were generated using noncoplanar fields. Helical tomotherapy treatment plans were generated using the tomotherapy planning station. Dose conformity index, dose gradient score index, and homogeneity index were used in plan intercomparisons. Results: Noncoplanar IMRS plans increased dose conformity and dose gradient, but not dose homogeneity, compared with coplanar IMRS plans. Tomotherapy plans increased dose conformity and dose gradient, yet increased dose heterogeneity compared with noncoplanar IMRS plans. The average dose conformity index values were 1.53 {+-} 0.38, 1.35 {+-} 0.15, and 1.26 {+-} 0.10 in coplanar IMRS, noncoplanar IMRS, and tomotherapy plans, respectively. The average dose homogeneity index values were 1.15 {+-} 0.05, 1.13 {+-} 0.04, and 1.18 {+-} 0.09 in coplanar IMRS, noncoplanar IMRS, and tomotherapy plans, respectively. The mean dose gradient score index values were 1.37 {+-} 19.08, 22.32 {+-} 19.20, and 43.28 {+-} 13.78 in coplanar IMRS, noncoplanar IMRS, and tomotherapy plans, respectively. The mean treatment time in tomotherapy was 42 {+-} 16 min. Conclusions: We were able to achieve better dose conformity and dose gradient in tomotherapy plans compared with step-and-shoot IMRS plans for intracranial stereotactic radiosurgery. However, tomotherapy treatment time was significantly larger than that in step-and-shoot IMRS.

  14. Predictors of Local Control After Single-Dose Stereotactic Image-Guided Intensity-Modulated Radiotherapy for Extracranial Metastases

    SciTech Connect

    Greco, Carlo; Zelefsky, Michael J.; Lovelock, Michael; Fuks, Zvi; Hunt, Margie; Rosenzweig, Kenneth; Zatcky, Joan; Kim, Balem; Yamada, Yoshiya

    2011-03-15

    Purpose: To report tumor local control after treatment with single-dose image-guided intensity-modulated radiotherapy (SD-IGRT) to extracranial metastatic sites. Methods and Materials: A total of 126 metastases in 103 patients were treated with SD-IGRT to prescription doses of 18-24 Gy (median, 24 Gy) between 2004 and 2007. Results: The overall actuarial local relapse-free survival (LRFS) rate was 64% at a median follow-up of 18 months (range, 2-45 months). The median time to failure was 9.6 months (range, 1-23 months). On univariate analysis, LRFS was significantly correlated with prescription dose (p = 0.029). Stratification by dose into high (23 to 24 Gy), intermediate (21 to 22 Gy), and low (18 to 20 Gy) dose levels revealed highly significant differences in LRFS between high (82%) and low doses (25%) (p < 0.0001). Overall, histology had no significant effect on LRFS (p = 0.16). Renal cell histology displayed a profound dose-response effect, with 80% LRFS at the high dose level (23 to 24 Gy) vs. 37% with low doses ({<=}22 Gy) (p = 0.04). However, for patients who received the high dose level, histology was not a statistically significant predictor of LRFS (p = 0.90). Target organ (bone vs. lymph node vs. soft tissues) (p = 0.5) and planning target volume size (p = 0.55) were not found to be associated with long-term LRFS probability. Multivariate Cox regression analysis confirmed prescription dose to be a significant predictor of LRFS (p = 0.003). Conclusion: High-dose SD-IGRT is a noninvasive procedure resulting in high probability of local tumor control. Single-dose IGRT may be effectively used to locally control metastatic deposits regardless of histology and target organ, provided sufficiently high doses (> 22 Gy) of radiation are delivered.

  15. Clinical Value of [{sup 11}C]Methionine PET for Stereotactic Radiation Therapy With Intensity Modulated Radiation Therapy to Metastatic Brain Tumors

    SciTech Connect

    Miwa, Kazuhiro; Matsuo, Masayuki; Shinoda, Jun; Aki, Tatsuki; Yonezawa, Shingo; Ito, Takeshi; Asano, Yoshitaka; Yamada, Mikito; Yokoyama, Kazutoshi; Yamada, Jitsuhiro; Yano, Hirohito; Iwama, Toru

    2012-12-01

    Purpose: This study investigated the clinical impact of {sup 11}C-labeled methionine-positron emission tomography (MET-PET) for stereotactic radiation therapy with intensity modulated radiation therapy (SRT-IMRT) in metastatic brain tumors. Methods and Materials: Forty-two metastatic brain tumors were examined. All tumors were treated with SRT-IMRT using a helical tomotherapy system. Gross tumor volume (GTV) was defined and drawn on the stereotactic magnetic resonance (MR) image, taking into account the respective contributions of MR imaging and MET-PET. Planning target volume (PTV) encompassed the GTV-PET plus a 2-mm margin. SRT-IMRT was performed, keeping the dose for PTV at 25-35 Gy in 5 fractions. The ratio of the mean value of MET uptake to the contralateral normal brain (L/N ratio) was plotted for the PTV prior to SRT-IMRT, at 3 months following SRT-IMRT, and at 6 months following SRT-IMRT. Tumor characteristic changes of MET uptake before and after SRT-IMRT were evaluated quantitatively, comparing them with MRI examination. Results: Mean {+-} SD L/N ratios were 1.95 {+-} 0.83, 1.18 {+-} 0.21, and 1.12 {+-} 0.25 in the pre-SRT-IMRT group, in the 3 months post-SRT-IMRT group, and in the 6 months post-SRT-IMRT group, respectively. Differences in the mean L/N ratio between the pre-SRT-IMRT group and the 3-month post-SRT-IMRT group and between the pre-SRT-IMRT group and the 6 month post-SRT-IMRT group were statistically significant, irrespective of MRI examination. Conclusions: We showed examples of metastatic lesions demonstrating significant decreases in MET uptake following SRT-IMRT. MET-PET seems to have a potential role in providing additional information, although MRI remains the gold standard for diagnosis and follow-up after SRT-IMRT. The present study is a preliminary approach, but to more clearly define the impact of PET-based radiosurgical assessment, further experimental and clinical analyses are required.

  16. A pilot study of intensity modulated radiation therapy with hypofractionated stereotactic body radiation therapy (SBRT) boost in the treatment of intermediate- to high-risk prostate cancer.

    PubMed

    Oermann, Eric K; Slack, Rebecca S; Hanscom, Heather N; Lei, Sue; Suy, Simeng; Park, Hyeon U; Kim, Joy S; Sherer, Benjamin A; Collins, Brian T; Satinsky, Andrew N; Harter, K William; Batipps, Gerald P; Constantinople, Nicholas L; Dejter, Stephen W; Maxted, William C; Regan, James B; Pahira, John J; McGeagh, Kevin G; Jha, Reena C; Dawson, Nancy A; Dritschilo, Anatoly; Lynch, John H; Collins, Sean P

    2010-10-01

    Clinical data suggest that large radiation fractions are biologically superior to smaller fraction sizes in prostate cancer radiotherapy. The CyberKnife is an appealing delivery system for hypofractionated radiosurgery due to its ability to deliver highly conformal radiation and to track and adjust for prostate motion in real-time. We report our early experience using the CyberKnife to deliver a hypofractionated stereotactic body radiation therapy (SBRT) boost to patients with intermediate- to high-risk prostate cancer. Twenty-four patients were treated with hypofractionated SBRT and supplemental external radiation therapy plus or minus androgen deprivation therapy (ADT). Patients were treated with SBRT to a dose of 19.5 Gy in 3 fractions followed by intensity modulated radiation therapy (IMRT) to a dose of 50.4 Gy in 28 fractions. Quality of life data were collected with American Urological Association (AUA) symptom score and Expanded Prostate Cancer Index Composite (EPIC) questionnaires before and after treatment. PSA responses were monitored; acute urinary and rectal toxicities were assessed using Common Toxicity Criteria (CTC) v3. All 24 patients completed the planned treatment with an average follow-up of 9.3 months. For patients who did not receive ADT, the median pre-treatment PSA was 10.6 ng/ml and decreased in all patients to a median of 1.5 ng/ml by 6 months post-treatment. Acute effects associated with treatment included Grade 2 urinary and gastrointestinal toxicity but no patient experienced acute Grade 3 or greater toxicity. AUA and EPIC scores returned to baseline by six months post-treatment. Hypofractionated SBRT combined with IMRT offers radiobiological benefits of a large fraction boost for dose escalation and is a well tolerated treatment option for men with intermediate- to high-risk prostate cancer. Early results are encouraging with biochemical response and acceptable toxicity. These data provide a basis for the design of a phase II clinical

  17. Three-dimensional conformal versus intensity-modulated radiotherapy dose planning in stereotactic radiotherapy: Application of standard quality parameters for plan evaluation

    SciTech Connect

    Grzadziel, Aleksandra; Grosu, Anca-Ligia . E-mail: anca-ligia.grosu@lrz.tum.de; Kneschaurek, Peter

    2006-11-15

    Purpose: The implementation of intensity-modulated radiotherapy (IMRT) technique into clinical practice is becoming routine, but still lacks a generally accepted method for plan evaluation. We present a comparison of the dose distribution of conformal three-dimensional radiotherapy plans with IMRT plans for cranial lesions in stereotactic radiotherapy. The primary aim of this study was to judge the quality of the treatment plans. The next purpose was to assess the usefulness of several quality factors for plan evaluation. Methods and Materials: Five patients, who were treated in our department, were analyzed. Four had meningioma and one had pituitary adenoma. For each case, 10 different plans were created and analyzed: 2 conventional conformal three-dimensional plans and 8 IMRT plans, using the 'step and shoot' delivery method. The first conventional plan was an individually designed beam arrangement and was used for patient treatment. The second plan was a standard plan with the same beam arrangement for all patients. Beam arrangements from the conformal plans were the base for the inversely planned IMRT. To evaluate the plans, the following factors were investigated: minimal and maximal dose to the planning target volume, homogeneity index, coverage index, conformity index, and tumor control probabilities and normal tissue complication probabilities. These quantities were incorporated into scoring factors and assigned to each plan. Results: The greatest homogeneity was reached in the conformal plans and IMRT plans with high planning target volume priority in the optimization process. This consequently led to a better probability of tumor control. Better protection of organs at risk and thereby lower normal tissue complication probabilities were achieved in the IMRT plans with increased weighting of the organs at risk. Conclusion: These results show the efficiency, as well as some limitations, of the IMRT techniques. The use of different quality factors allowed us

  18. Stereotactic body radiation therapy planning with duodenal sparing using volumetric-modulated arc therapy vs intensity-modulated radiation therapy in locally advanced pancreatic cancer: A dosimetric analysis

    SciTech Connect

    Kumar, Rachit; Wild, Aaron T.; Ziegler, Mark A.; Hooker, Ted K.; Dah, Samson D.; Tran, Phuoc T.; Kang, Jun; Smith, Koren; Zeng, Jing; Pawlik, Timothy M.; Tryggestad, Erik; Ford, Eric; Herman, Joseph M.

    2013-10-01

    Stereotactic body radiation therapy (SBRT) achieves excellent local control for locally advanced pancreatic cancer (LAPC), but may increase late duodenal toxicity. Volumetric-modulated arc therapy (VMAT) delivers intensity-modulated radiation therapy (IMRT) with a rotating gantry rather than multiple fixed beams. This study dosimetrically evaluates the feasibility of implementing duodenal constraints for SBRT using VMAT vs IMRT. Non–duodenal sparing (NS) and duodenal-sparing (DS) VMAT and IMRT plans delivering 25 Gy in 1 fraction were generated for 15 patients with LAPC. DS plans were constrained to duodenal D{sub max} of<30 Gy at any point. VMAT used 1 360° coplanar arc with 4° spacing between control points, whereas IMRT used 9 coplanar beams with fixed gantry positions at 40° angles. Dosimetric parameters for target volumes and organs at risk were compared for DS planning vs NS planning and VMAT vs IMRT using paired-sample Wilcoxon signed rank tests. Both DS VMAT and DS IMRT achieved significantly reduced duodenal D{sub mean}, D{sub max}, D{sub 1cc}, D{sub 4%}, and V{sub 20} {sub Gy} compared with NS plans (all p≤0.002). DS constraints compromised target coverage for IMRT as demonstrated by reduced V{sub 95%} (p = 0.01) and D{sub mean} (p = 0.02), but not for VMAT. DS constraints resulted in increased dose to right kidney, spinal cord, stomach, and liver for VMAT. Direct comparison of DS VMAT and DS IMRT revealed that VMAT was superior in sparing the left kidney (p<0.001) and the spinal cord (p<0.001), whereas IMRT was superior in sparing the stomach (p = 0.05) and the liver (p = 0.003). DS VMAT required 21% fewer monitor units (p<0.001) and delivered treatment 2.4 minutes faster (p<0.001) than DS IMRT. Implementing DS constraints during SBRT planning for LAPC can significantly reduce duodenal point or volumetric dose parameters for both VMAT and IMRT. The primary consequence of implementing DS constraints for VMAT is increased dose to other organs at

  19. Treatment Plan Technique and Quality for Single-Isocenter Stereotactic Ablative Radiotherapy of Multiple Lung Lesions with Volumetric-Modulated Arc Therapy or Intensity-Modulated Radiosurgery.

    PubMed

    Quan, Kimmen; Xu, Karen M; Lalonde, Ron; Horne, Zachary D; Bernard, Mark E; McCoy, Chuck; Clump, David A; Burton, Steven A; Heron, Dwight E

    2015-01-01

    The aim of this study is to provide a practical approach to the planning technique and evaluation of plan quality for the multi-lesion, single-isocenter stereotactic ablative radiotherapy (SABR) of the lung. Eleven patients with two or more lung lesions underwent single-isocenter volumetric-modulated arc therapy (VMAT) radiosurgery or IMRS. All plans were normalized to the target maximum dose. For each plan, all targets were treated to the same dose. Plan conformity and dose gradient were maximized with dose-control tuning structures surrounding targets. For comparison, multi-isocenter plans were retrospectively created for four patients. Conformity index (CI), homogeneity index (HI), gradient index (GI), and gradient distance (GD) were calculated for each plan. V5, V10, and V20 of the lung and organs at risk (OARs) were collected. Treatment time and total monitor units (MUs) were also recorded. One patient had four lesions and the remainder had two lesions. Six patients received VMAT and five patients received intensity-modulated radiosurgery (IMRS). For those treated with VMAT, two patients received 3-arc VMAT and four received 2-arc VMAT. For those treated with IMRS, two patients were treated with 10 and 11 beams, respectively, and the rest received 12 beams. Prescription doses ranged from 30 to 54 Gy in three to five fractions. The median prescribed isodose line was 84% (range: 80-86%). The median maximum dose was 57.1 Gy (range: 35.7-65.1 Gy). The mean combined PTV was 49.57 cm(3) (range: 14.90-87.38 cm(3)). For single-isocenter plans, the median CI was 1.15 (range: 0.97-1.53). The median HI was 1.19 (range: 1.16-1.28). The median GI was 4.60 (range: 4.16-7.37). The median maximum radiation dose (Dmax) to total lung was 55.6 Gy (range: 35.7-62.0 Gy). The median mean radiation dose to the lung (Dmean) was 4.2 Gy (range: 1.1-9.3 Gy). The median lung V5 was 18.7% (range: 3.8-41.3%). There was no significant difference in CI, HI, GI, GD, V5, V10

  20. Intensity-modulated radiation therapy.

    PubMed

    Goffman, Thomas E; Glatstein, Eli

    2002-07-01

    Intensity-modulated radiation therapy (IMRT) is an increasingly popular technical means of tightly focusing the radiation dose around a cancer. As with stereotactic radiotherapy, IMRT uses multiple fields and angles to converge on the target. The potential for total dose escalation and for escalation of daily fraction size to the gross cancer is exciting. The excitement, however, has greatly overshadowed a range of radiobiological and clinical concerns.

  1. Tumor Control Outcomes After Hypofractionated and Single-Dose Stereotactic Image-Guided Intensity-Modulated Radiotherapy for Extracranial Metastases From Renal Cell Carcinoma

    SciTech Connect

    Zelefsky, Michael J.; Greco, Carlo; Motzer, Robert; Magsanoc, Juan Martin; Pei Xin; Lovelock, Michael; Mechalakos, Jim; Zatcky, Joan; Fuks, Zvi; Yamada, Yoshiya

    2012-04-01

    Purpose: To report tumor local progression-free outcomes after treatment with single-dose, image-guided, intensity-modulated radiotherapy and hypofractionated regimens for extracranial metastases from renal cell primary tumors. Patients and Methods: Between 2004 and 2010, 105 lesions from renal cell carcinoma were treated with either single-dose, image-guided, intensity-modulated radiotherapy to a prescription dose of 18-24 Gy (median, 24) or hypofractionation (three or five fractions) with a prescription dose of 20-30 Gy. The median follow-up was 12 months (range, 1-48). Results: The overall 3-year actuarial local progression-free survival for all lesions was 44%. The 3-year local progression-free survival for those who received a high single-dose (24 Gy; n = 45), a low single-dose (<24 Gy; n = 14), or hypofractionation regimens (n = 46) was 88%, 21%, and 17%, respectively (high single dose vs. low single dose, p = .001; high single dose vs. hypofractionation, p < .001). Multivariate analysis revealed the following variables were significant predictors of improved local progression-free survival: 24 Gy dose compared with a lower dose (p = .009) and a single dose vs. hypofractionation (p = .008). Conclusion: High single-dose, image-guided, intensity-modulated radiotherapy is a noninvasive procedure resulting in high probability of local tumor control for metastatic renal cell cancer generally considered radioresistant according to the classic radiobiologic ranking.

  2. Tumor Control Outcomes Following Hypofractionated and Single-Dose Stereotactic Image-Guided Intensity-Modulated Radiotherapy for Extracranial Metastases from Renal Cell Carcinoma

    PubMed Central

    Zelefsky, Michael J; Greco, Carlo; Motzer, Robert; Magsanoc, Juan Martin; Pei, Xin; Lovelock, Michael; Mechalakos, Jim; Zatcky, Joan; Fuks, Zvi; Yamada, Yoshiya

    2014-01-01

    Purpose To report tumor local progression-free outcomes following treatment with single-dose image-guided intensity-modulated radiotherapy (SD-IGRT) and hypofractionated regimens for extracranial metastases from renal cell primary tumors. Methods and Materials Between 2004 and 2010, a total of 105 lesions from renal cell carcinomas were treated with either SD-IGRT to prescription doses of 18–24 Gy (median, 24 Gy) or hypofractionation (3 or 5 fractions) with prescription doses ranging between 20 and 30 Gy. The median follow-up was 12 months (range, 1–48 months). Results The overall 3-year actuarial local progression-free survival (LPFS) for all lesions was 44%. The 3-year LPFS for those who received high single-dose (24 Gy; n = 45), low single-dose (< 24 Gy; n = 14), and hypofractionation regimens (n = 46) were 88%, 21%, and 17%, respectively (high single dose versus low single dose, p = 0.001; high single dose versus hypofractionation, p < 0.001). Multivariate analysis revealed the following variables as significant predictors of improved LPFS: dose of 24 Gy compared with lower dose (p = 0.009), and single dose versus hypofractionation (p = 0.008). Conclusion High-dose SD-IGRT is a non-invasive procedure resulting in high probability of local tumor control for metastatic renal cell cancers, generally considered radioresistant according to classical radiobiological ranking. PMID:21596489

  3. SU-E-T-394: The Use of Jaw Tracking in Intensity Modulated and Volumetric Modulated Arc Radiotherapy for Spine Stereotactic Radiosurgery

    SciTech Connect

    Chin, K; Wen, N; Huang, Y; Kim, J; Zhao, B; Siddiqui, S; Chetty, I; Ryu, S

    2014-06-01

    Purpose: To evaluate the potential advantages of jaw tracking for intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in spine radiosurgery. Methods: VMAT and IMRT plans were retrospectively generated for ten patients. Six plans for each patient were created in the Eclipse treatment planning system for a Varian Truebeam equipped with a Millennium 120 MLC. Plans were created to study IMRT and VMAT plans with and without jaw tracking, as well as IMRT plans of different flattening filter free (FFF) energies. Plans were prescribed to the 90% isodose line to 16 or 18 Gy in one fraction to cover 95% of the target. Planning target volume (PTV) coverage, conformity index (CI), dose to spinal cord, distance to fall off from the 90% to 50% isodose line (DTF), as well as delivery time were evaluated. Ion chamber and film measurements were performed to verify calculated and measured dose distributions. Results: Jaw tracking decreased the spinal cord dose for both IMRT and VMAT plans, but a larger decrease was seen with the IMRT plans (p=0.004 vs p=0.04). The average D10% for the spinal cord was least for the 6MV FFF IMRT plan with jaw tracking and was greatest for the 10MV FFF plan without jaw tracking. Treatment times between IMRT and VMAT plans with or without jaw tracking were not significantly different. Measured plans showed greater than 98.5% agreement for planar dose gamma analysis (3%/2 mm) and less than 2.5% for point dose analysis compared to calculated plans. Conclusion: Jaw tracking can be used to help decrease spinal cord dose without any change in treatment delivery or calculation accuracy. Lower dose to the spinal cord was achieved using 6 MV beams compared to 10 MV beams, though 10 MV may be justified in some cases to decrease skin dose.

  4. SU-E-T-338: Dosimetric Study of Volumetric Modulated Arc Therapy (VMAT) and Intensity Modulated Radiation Therapy (IMRT) for Stereotactic Body Radiation Therapy (SBRT) in Early Stage Lung Cancer

    SciTech Connect

    Ahmad, I; Quinn, K; Seebach, A; Wang, H; Yah, R

    2015-06-15

    Purpose: This study evaluates the dosimetric differences using volumetric modulated arc therapy (VMAT) in patients previously treated with intensity modulated radiation therapy IMRT for stereotactic body radiotherapy (SBRT) in early stage lung cancer. Methods: We evaluated 9 consecutive medically inoperable lung cancer patients at the start of the SBRT program who were treated with IMRT from November 2010 to October 2011. These patients were treated using 6 MV energy. The 9 cases were then re-planned with VMAT performed with arc therapy using 6 MV flattening filter free (FFF) energy with the same organs at risk (OARS) constraints. Data collected for the treatment plans included target coverage, beam on time, dose to OARS and gamma pass rate. Results: Five patients were T1N0 and four patients were T2N0 with all tumors less than 5 cm. The average GTV was 13.02 cm3 (0.83–40.87) and average PTV was 44.65 cm3 (14.06–118.08). The IMRT plans had a mean of 7.2 angles (6–9) and 5.4 minutes (3.6–11.1) per plan. The VMAT plans had a mean of 2.8 arcs (2–3) and 4.0 minutes (2.2–6.0) per plan. VMAT had slightly more target coverage than IMRT with average increase in D95 of 2.68% (1.24–5.73) and D99 of 3.65% (0.88–8.77). VMAT produced lower doses to all OARs. The largest reductions were in maximum doses to the spinal cord with an average reduction of 24.1%, esophagus with an average reduction of 22.1%, and lung with an average reduction in the V20 of 16.3% The mean gamma pass rate was 99.8% (99.2–100) at 3 mm and 3% for VMAT with comparable values for IMRT. Conclusion: These findings suggest that using VMAT for SBRT in early stage lung cancer is superior to IMRT in terms of dose coverage, OAR dose and a lower treatment delivery time with a similar gamma pass rate.

  5. Intensity modulated proton therapy

    PubMed Central

    Grassberger, C

    2015-01-01

    Intensity modulated proton therapy (IMPT) implies the electromagnetic spatial control of well-circumscribed “pencil beams” of protons of variable energy and intensity. Proton pencil beams take advantage of the charged-particle Bragg peak—the characteristic peak of dose at the end of range—combined with the modulation of pencil beam variables to create target-local modulations in dose that achieves the dose objectives. IMPT improves on X-ray intensity modulated beams (intensity modulated radiotherapy or volumetric modulated arc therapy) with dose modulation along the beam axis as well as lateral, in-field, dose modulation. The clinical practice of IMPT further improves the healthy tissue vs target dose differential in comparison with X-rays and thus allows increased target dose with dose reduction elsewhere. In addition, heavy-charged-particle beams allow for the modulation of biological effects, which is of active interest in combination with dose “painting” within a target. The clinical utilization of IMPT is actively pursued but technical, physical and clinical questions remain. Technical questions pertain to control processes for manipulating pencil beams from the creation of the proton beam to delivery within the patient within the accuracy requirement. Physical questions pertain to the interplay between the proton penetration and variations between planned and actual patient anatomical representation and the intrinsic uncertainty in tissue stopping powers (the measure of energy loss per unit distance). Clinical questions remain concerning the impact and management of the technical and physical questions within the context of the daily treatment delivery, the clinical benefit of IMPT and the biological response differential compared with X-rays against which clinical benefit will be judged. It is expected that IMPT will replace other modes of proton field delivery. Proton radiotherapy, since its first practice 50 years ago, always required the

  6. Intensity-Modulated Radiation Therapy (IMRT)

    MedlinePlus

    ... Resources Professions Site Index A-Z Intensity-Modulated Radiation Therapy (IMRT) Intensity-modulated radiotherapy (IMRT) uses linear ... and after this procedure? What is Intensity-Modulated Radiation Therapy and how is it used? Intensity-modulated ...

  7. Dose as a Function of Lung Volume and Planned Treatment Volume in Helical Tomotherapy Intensity-Modulated Radiation Therapy-Based Stereotactic Body Radiation Therapy for Small Lung Tumors

    SciTech Connect

    Baisden, Joseph M.; Romney, Davis A.; Reish, Andrew G.; Cai Jing; Sheng Ke; Jones, David R.; Benedict, Stanley H.; Read, Paul W.; Larner, James M. . E-mail: JML2P@virginia.edu

    2007-07-15

    Purpose: To evaluate the limitations of Hi-Art Helical Tomotherapy (Middleton, WI) stereotactic body radiotherapy (SBRT) for lung lesions, and to provide an initial report on patients treated with this method. Stereotactic body radiotherapy was shown to be an effective, well-tolerated treatment for early-stage, non-small-cell lung carcinoma (NSCLC). The Radiation Therapy Oncology Group (RTOG) 0236 protocol is currently evaluating three-dimensional conformal SBRT that delivers 60 Gy in three fractions. Methods and Materials: Inverse treatment planning for hypothetical lung gross tumor volumes (GTV) and planned treatment volume (PTV) expansions were performed. We tested the hypothesis that the maximum acceptable dose (MAD) to be delivered to the lesion by SBRT could be predicted by PTV and lung volume. Dose constraints on normal tissue were as designated by the RTOG protocol. Inverse planning was performed to find the maximum tolerated SBRT dose up to 60 Gy. Results: Regression analysis of the data obtained indicated a linear relationship between MAD, PTV, and lung volume. This generated two equations which may be useful predictive tools. Seven patients with Stage I and II NSCLC treated at University of Virginia with this method tolerated the treatment extremely well, and suffered no greater than grade I toxicity, with no evidence of disease recurrence in follow-up from 2-20 months. Conclusions: Helical tomotherapy SBRT for lung lesions is well-tolerated. In addition, the likely MAD for patients considered for this type of treatment can be predicted by PTV and lung volume.

  8. Light intensity modulation in phototherapy

    NASA Astrophysics Data System (ADS)

    Lukyanovich, P. A.; Zon, B. A.; Kunin, A. A.; Pankova, S. N.

    2015-04-01

    A hypothesis that blocking ATP synthesis is one of the main causes of the stimulating effect is considered based on analysis of the primary photostimulation mechanisms. The light radiation intensity modulation is substantiated and the estimates of such modulation parameters are made. An explanation is offered to the stimulation efficiency decrease phenomenon at the increase of the radiation dose during the therapy. The results of clinical research of the medical treatment in preventive dentistry are presented depending on the spectrum and parameters of the light flux modulation.

  9. Lossless intensity modulation in integrated photonics.

    PubMed

    Sandhu, Sunil; Fan, Shanhui

    2012-02-13

    We present a dynamical analysis of lossless intensity modulation in two different ring resonator geometries. In both geometries, we demonstrate modulation schemes that result in a symmetrical output with an infinite on/off ratio. The systems behave as lossless intensity modulators where the time-averaged output optical power is equal to the time-averaged input optical power.

  10. Fan-beam intensity modulated proton therapy

    PubMed Central

    Hill, Patrick; Westerly, David; Mackie, Thomas

    2013-01-01

    Purpose: This paper presents a concept for a proton therapy system capable of delivering intensity modulated proton therapy using a fan beam of protons. This system would allow present and future gantry-based facilities to deliver state-of-the-art proton therapy with the greater normal tissue sparing made possible by intensity modulation techniques. Methods: A method for producing a divergent fan beam of protons using a pair of electromagnetic quadrupoles is described and particle transport through the quadrupole doublet is simulated using a commercially available software package. To manipulate the fan beam of protons, a modulation device is developed. This modulator inserts or retracts acrylic leaves of varying thickness from subsections of the fan beam. Each subsection, or beam channel, creates what effectively becomes a beam spot within the fan area. Each channel is able to provide 0–255 mm of range shift for its associated beam spot, or stop the beam and act as an intensity modulator. Results of particle transport simulations through the quadrupole system are incorporated into the MCNPX Monte Carlo transport code along with a model of the range and intensity modulation device. Several design parameters were investigated and optimized, culminating in the ability to create topotherapy treatment plans using distal-edge tracking on both phantom and patient datasets. Results: Beam transport calculations show that a pair of electromagnetic quadrupoles can be used to create a divergent fan beam of 200 MeV protons over a distance of 2.1 m. The quadrupole lengths were 30 and 48 cm, respectively, with transverse field gradients less than 20 T/m, which is within the range of water-cooled magnets for the quadrupole radii used. MCNPX simulations of topotherapy treatment plans suggest that, when using the distal edge tracking delivery method, many delivery angles are more important than insisting on narrow beam channel widths in order to obtain conformal target coverage

  11. Fan-beam intensity modulated proton therapy

    SciTech Connect

    Hill, Patrick; Westerly, David; Mackie, Thomas

    2013-11-15

    Purpose: This paper presents a concept for a proton therapy system capable of delivering intensity modulated proton therapy using a fan beam of protons. This system would allow present and future gantry-based facilities to deliver state-of-the-art proton therapy with the greater normal tissue sparing made possible by intensity modulation techniques.Methods: A method for producing a divergent fan beam of protons using a pair of electromagnetic quadrupoles is described and particle transport through the quadrupole doublet is simulated using a commercially available software package. To manipulate the fan beam of protons, a modulation device is developed. This modulator inserts or retracts acrylic leaves of varying thickness from subsections of the fan beam. Each subsection, or beam channel, creates what effectively becomes a beam spot within the fan area. Each channel is able to provide 0–255 mm of range shift for its associated beam spot, or stop the beam and act as an intensity modulator. Results of particle transport simulations through the quadrupole system are incorporated into the MCNPX Monte Carlo transport code along with a model of the range and intensity modulation device. Several design parameters were investigated and optimized, culminating in the ability to create topotherapy treatment plans using distal-edge tracking on both phantom and patient datasets.Results: Beam transport calculations show that a pair of electromagnetic quadrupoles can be used to create a divergent fan beam of 200 MeV protons over a distance of 2.1 m. The quadrupole lengths were 30 and 48 cm, respectively, with transverse field gradients less than 20 T/m, which is within the range of water-cooled magnets for the quadrupole radii used. MCNPX simulations of topotherapy treatment plans suggest that, when using the distal edge tracking delivery method, many delivery angles are more important than insisting on narrow beam channel widths in order to obtain conformal target coverage

  12. Virtual micro-intensity modulated radiation therapy.

    PubMed

    Siochi, R A

    2000-11-01

    Virtual micro-intensity modulated radiation therapy (VMIMRT) combines a 10 x 5 mm2 intensity map with a 5 x 10 mm2 intensity map, delivered at orthogonal collimator settings. The superposition of these component maps (CM) yields a 5 x 5 mm2 virtual micro-intensity map (VMIM) that can be delivered with a 1 cm leaf width MLC. A pair of CMs with optimal delivery efficiency and quality must be chosen, since a given VMIM can be delivered using several different pairs. This is possible since, for each group of four VMIM cells that can be covered by an MLC leaf in either collimator orientation, the minimum intensity can be delivered from either collimator setting. By varying the proportions of the minimum values that go into each CM, one can simultaneously minimize the number of potential junction effects and the number of segments required to deliver the VMIM. The minimization is achieved by reducing high leaf direction gradients in the CMs. Several pseudoclinical and random VMIMs were studied to determine the applicability of this new technique. A nine level boost map was also studied to investigate dosimetric and spatial resolution issues. Finally, clinical issues for this technique are discussed.

  13. Film Dosimetry for Intensity Modulated Radiation Therapy

    NASA Astrophysics Data System (ADS)

    Benites-Rengifo, J.; Martínez-Dávalos, A.; Celis, M.; Lárraga, J.

    2004-09-01

    Intensity Modulated Radiation Therapy (IMRT) is an oncology treatment technique that employs non-uniform beam intensities to deliver highly conformal radiation to the targets while minimizing doses to normal tissues and critical organs. A key element for a successful clinical implementation of IMRT is establishing a dosimetric verification process that can ensure that delivered doses are consistent with calculated ones for each patient. To this end we are developing a fast quality control procedure, based on film dosimetry techniques, to be applied to the 6 MV Novalis linear accelerator for IMRT of the Instituto Nacional de Neurología y Neurocirugía (INNN) in Mexico City. The procedure includes measurements of individual fluence maps for a limited number of fields and dose distributions in 3D using extended dose-range radiographic film. However, the film response to radiation might depend on depth, energy and field size, and therefore compromise the accuracy of measurements. In this work we present a study of the dependence of Kodak EDR2 film's response on the depth, field size and energy, compared with those of Kodak XV2 film. The first aim is to devise a fast and accurate method to determine the calibration curve of film (optical density vs. doses) commonly called a sensitometric curve. This was accomplished by using three types of irradiation techniques: Step-and-shoot, dynamic and static fields.

  14. Tomotherapy and stereotactic radiosurgery

    NASA Astrophysics Data System (ADS)

    Soisson, Emilie T.

    Currently, at the University of Wisconsin-Madison, a linear accelerator equipped with circular collimators and a floor stand is used for stereotactic radiosurgery (SRS) delivery. In the interest of providing a more efficient delivery option for patients with multiple brain metastases, a Tomotherapy-based radiosurgery program was developed to serve as an intensity modulated compliment to our existing delivery method. The unique advantage of Tomotherapy over other radiotherapy delivery units is the on board megavoltage CT that can be used for both stereotactic localization and treatment planning. As such, a workflow was designed in which the planning image is acquired on the treatment unit itself and, instead using a patient-frame based coordinate system for stereotactic localization, volumetric imaging is used to precisely locate the target at the time of treatment. Localization and delivery accuracy was found to be comparable to conventional approaches and well within stated tolerances. A Tomotherapy-specific treatment planning technique was also developed using the Tomotherapy treatment planning system that reliably produces plans that achieve both conformal target coverage and sufficiently steep dose falloff into surrounding normal brain. Tomotherapy plans have been compared to conventional circular collimator based plans for both the treatment of brain metastases and arteriovenous malformations in terms of both target conformity and dose to normal brain. To determine the effect of plan differences on patient outcome, clinical data was used to predict the resulting risk of treatment induced symptomatic brain necrosis for both conventional and Tomotherapy based plans. Overall, it was determined that plans generated using the described planning technique are acceptable for radiosurgery. In addition, delivery time for complex cases is comparable to or improved over conventional isocentric approaches. Finally, this work explores the impact of future product

  15. Intensity-Modulated Radiotherapy for Pancreatic Adenocarcinoma

    SciTech Connect

    Abelson, Jonathan A.; Murphy, James D.; Minn, Ann Yuriko; Chung, Melody; Fisher, George A.; Ford, James M.; Kunz, Pamela; Norton, Jeffrey A.; Visser, Brendan C.; Poultsides, George A.; Koong, Albert C.; Chang, Daniel T.

    2012-03-15

    Purpose: To report the outcomes and toxicities in patients treated with intensity-modulated radiotherapy (IMRT) for pancreatic adenocarcinoma. Methods and Materials: Forty-seven patients with pancreatic adenocarcinoma were treated with IMRT between 2003 and 2008. Of these 47 patients, 29 were treated adjuvantly and 18 definitively. All received concurrent 5-fluorouracil chemotherapy. The treatment plans were optimized such that 95% of the planning target volume received the prescription dose. The median delivered dose for the adjuvant and definitive patients was 50.4 and 54.0 Gy, respectively. Results: The median age at diagnosis was 63.9 years. For adjuvant patients, the 1- and 2-year overall survival rate was 79% and 40%, respectively. The 1- and 2-year recurrence-free survival rate was 58% and 17%, respectively. The local-regional control rate at 1 and 2 years was 92% and 80%, respectively. For definitive patients, the 1-year overall survival, recurrence-free survival, and local-regional control rate was 24%, 16%, and 64%, respectively. Four patients developed Grade 3 or greater acute toxicity (9%) and four developed Grade 3 late toxicity (9%). Conclusions: Survival for patients with pancreatic cancer remains poor. A small percentage of adjuvant patients have durable disease control, and with improved therapies, this proportion will increase. Systemic therapy offers the greatest opportunity. The present results have demonstrated that IMRT is well tolerated. Compared with those who received three-dimensional conformal radiotherapy in previously reported prospective clinical trials, patients with pancreatic adenocarcinoma treated with IMRT in our series had improved acute toxicity.

  16. Robust optimization of intensity modulated proton therapy

    SciTech Connect

    Liu Wei; Zhang Xiaodong; Li Yupeng; Mohan, Radhe

    2012-02-15

    Purpose: Intensity modulated proton therapy (IMPT) is highly sensitive to range uncertainties and uncertainties caused by setup variation. The conventional inverse treatment planning of IMPT optimized based on the planning target volume (PTV) is not often sufficient to ensure robustness of treatment plans. In this paper, a method that takes the uncertainties into account during plan optimization is used to mitigate the influence of uncertainties in IMPT. Methods: The authors use the so-called ''worst-case robust optimization'' to render IMPT plans robust in the face of uncertainties. For each iteration, nine different dose distributions are computed--one each for {+-} setup uncertainties along anteroposterior (A-P), lateral (R-L) and superior-inferior (S-I) directions, for {+-} range uncertainty, and the nominal dose distribution. The worst-case dose distribution is obtained by assigning the lowest dose among the nine doses to each voxel in the clinical target volume (CTV) and the highest dose to each voxel outside the CTV. Conceptually, the use of worst-case dose distribution is similar to the dose distribution achieved based on the use of PTV in traditional planning. The objective function value for a given iteration is computed using this worst-case dose distribution. The objective function used has been extended to further constrain the target dose inhomogeneity. Results: The worst-case robust optimization method is applied to a lung case, a skull base case, and a prostate case. Compared with IMPT plans optimized using conventional methods based on the PTV, our method yields plans that are considerably less sensitive to range and setup uncertainties. An interesting finding of the work presented here is that, in addition to reducing sensitivity to uncertainties, robust optimization also leads to improved optimality of treatment plans compared to the PTV-based optimization. This is reflected in reduction in plan scores and in the lower normal tissue doses for the

  17. Feasibility of an online adaptive replanning method for cranial frameless intensity-modulated radiosurgery

    SciTech Connect

    Calvo, Juan Francisco; San José, Sol; Garrido, LLuís; Puertas, Enrique; Moragues, Sandra; Pozo, Miquel; Casals, Joan

    2013-10-01

    To introduce an approach for online adaptive replanning (i.e., dose-guided radiosurgery) in frameless stereotactic radiosurgery, when a 6-dimensional (6D) robotic couch is not available in the linear accelerator (linac). Cranial radiosurgical treatments are planned in our department using intensity-modulated technique. Patients are immobilized using thermoplastic mask. A cone-beam computed tomography (CBCT) scan is acquired after the initial laser-based patient setup (CBCT{sub setup}). The online adaptive replanning procedure we propose consists of a 6D registration-based mapping of the reference plan onto actual CBCT{sub setup}, followed by a reoptimization of the beam fluences (“6D plan”) to achieve similar dosage as originally was intended, while the patient is lying in the linac couch and the original beam arrangement is kept. The goodness of the online adaptive method proposed was retrospectively analyzed for 16 patients with 35 targets treated with CBCT-based frameless intensity modulated technique. Simulation of reference plan onto actual CBCT{sub setup}, according to the 4 degrees of freedom, supported by linac couch was also generated for each case (4D plan). Target coverage (D99%) and conformity index values of 6D and 4D plans were compared with the corresponding values of the reference plans. Although the 4D-based approach does not always assure the target coverage (D99% between 72% and 103%), the proposed online adaptive method gave a perfect coverage in all cases analyzed as well as a similar conformity index value as was planned. Dose-guided radiosurgery approach is effective to assure the dose coverage and conformity of an intracranial target volume, avoiding resetting the patient inside the mask in a “trial and error” way so as to remove the pitch and roll errors when a robotic table is not available.

  18. Leaf sequencing and dosimetric verification in intensity-modulated radiotherapy

    NASA Astrophysics Data System (ADS)

    Agazaryan, Nzhde

    Although sophisticated means to calculate and deliver intensity modulated radiotherapy (IMRT) have been developed by many groups, methods to verify the delivery, as well as definitions of acceptability of a treatment in terms of these measurements are the most problematic at this stage of advancement of IMRT. Present intensity modulated radiotherapy systems fail to account for many dosimetric characteristics of the delivery system. In this dissertation, a dosimetrically based leaf sequencing algorithm is developed and implemented for multileaf collimated intensity modulated radiotherapy. The dosimetric considerations are investigated and are shown to significantly improve the outcome in terms of an agreement between desired and delivered radiation dose distributions. Subsequently, a system for determining the desirability of a produced intensity modulated radiotherapy plan in terms of deliverability of calculated profiles with the use of a multileaf collimator is developed. Three deliverability scoring indices are defined to evaluate the deliverability of the profiles. Gradient Index (GI) is a measure of the complexity of the profile in terms of gradients. Baseline Index (BI) is the fraction of the profile that is planned to get lower than the minimum level of transmission radiation. Cumulative Monitor Unit Index (CMUI) is the ratio of the cumulative monitor units (CMU) required for obtaining the desired profile to an average dose level in the profile. The dosimetric investigations of the deliverability scoring indices are presented, showing a clear correlation between scoring indices and dosimetric accuracy. Finally, materials and methods are developed for verification of intensity modulated radiotherapy. Dosimetric verification starts from investigations of the developed leaf sequencing algorithm, then extends to dosimetric verification in terms of deliverability, and lastly, dosimetric verification of complete clinical IMRT plans is performed.

  19. Performance analysis of the ultra-linear optical intensity modulator

    NASA Astrophysics Data System (ADS)

    Madamopoulos, Nicholas; Dingel, Benjamin

    2006-10-01

    The linear optical intensity modulator is a key component in any broadband optical access-based analog fiber-optic link systems such as sub-carrier multiplexing (SCM) systems, ultra-dense CATV, Radio-over-Fiber (RoF) communications, and other platform access systems. Previously, we have proposed a super-linear optical modulator, having SFDR = 130 -140 dB-Hz 2/3, based on a unique combination of phase-modulator (PM) and a weak ring resonator (RR) modulator within a Mach-Zehnder interferometer (MZI). We presented some of its unique features. In this paper, we characterize further this ultra-linear optical intensity modulator, analyze its RF performance and provide method for parameter optimization. Other excellent features of this modulator design such as high manufacturing tolerance, effect of link insertion loss, adaptive characteristic and device simplicity are also discussed.

  20. Clinical implementation of intensity-modulated arc therapy.

    PubMed

    Shepard, David M; Cao, Daliang

    2011-01-01

    Intensity-modulated arc therapy (IMAT) is a rotational approach to radiation therapy delivered on a conventional linear accelerator using a conventional multileaf collimator. There are 2 key advantages of IMAT. First, the rotational nature of the delivery provides great flexibility in shaping each dose distribution. As a result, IMAT can provide dosimetric advantages relative to fixed-field intensity-modulated radiation therapy (IMRT). The second advantage is the highly efficient nature of the delivery. For centers with an active IMRT program, the clinical implementation of IMAT should be relatively straightforward. For clinical implementation of IMAT, it is important to fully characterize the accuracy of the dose model used, and the performance of the quality assurance equipment.

  1. New techniques in hadrontherapy: intensity modulated proton beams.

    PubMed

    Cella, L; Lomax, A; Miralbell, R

    2001-01-01

    Inverse planning and intensity modulated (IM) X-ray beam treatment techniques can achieve significant improvements in dose distributions comparable to those obtained with forward planned proton beams. However, intensity modulation can also be applied to proton beams and further optimization in dose distribution can reasonably be expected. A comparative planning exercise between IM X-rays and IM proton beams was carried out on two different tumor cases: a pediatric rhabdomyosarcoma and a prostate cancer. Both IM X-rays and IM protons achieved equally homogenous coverage of the target volume in the two tumor sites. Predicted NTCPs were equally low for both treatment techniques. Nevertheless, a reduced low-to-medium dose to the organs at risk and a lesser integral non-target mean dose for IM protons in the two cases favored the use of IM proton beams.

  2. Arc binary intensity modulated radiation therapy (AB IMRT)

    NASA Astrophysics Data System (ADS)

    Yang, Jun

    The state of the art Intensity Modulate Radiation Therapy (IMRT) has been one of the most significant breakthroughs in the cancer treatment in the past 30 years. There are two types of IMRT systems. The first system is the binary-based tomotherapy, represented by the Peacock (Nomos Corp) and Tomo unit (TomoTherapy Inc.), adopting specific binary collimator leafs to deliver intensity modulated radiation fields in a serial or helical fashion. The other uses the conventional dynamic multileaf collimator (MLC) to deliver intensity modulated fields through a number of gantry positions. The proposed Arc Binary IMRT attempts to deliver Tomo-like IMRT with conventional dynamic MLC and combines the advantages of the two types of IMRT techniques: (1) maximizing the number of pencil beams for better dose optimization, (2) enabling conventional linear accelerator with dynamic MLC to deliver Tomo-like IMRT. In order to deliver IMRT with conventional dynamic MLC in a binary fashion, the slice-by-slice treatment with limited slice thickness has been proposed in the thesis to accommodate the limited MLC traveling speed. Instead of moving the patient to subsequent treatment slices, the proposed method offsets MLC to carry out the whole treatment, slice by slice sequentially, thus avoid patient position error. By denoting one arc pencil beam set as a gene, genetic algorithm (GA) is used as the searching engine for the dose optimization process. The selection of GA parameters is a crucial step and has been studied in depth so that the optimization process will converge with reasonable speed. Several hypothetical and clinical cases have been tested with the proposed IMRT method. The comparison of the dose distribution with other commercially available IMRT systems demonstrates the clear advantage of the new method. The proposed Arc Binary Intensity Modulated Radiation Therapy is not only theoretically sound but practically feasible. The implementation of this method would expand the

  3. Intensity Modulated Radiotherapy with High Energy Photon and Hadron Beams

    NASA Astrophysics Data System (ADS)

    Oelfke, U.

    2004-07-01

    This short contribution will briefly describe the basic concepts of intensity modulated radiation therapy with high energy photons (IMRT) and charged particle beams (IMPT). Dose delivery and optimization strategies like the `Inverse Planning' approach will be explained for both radiation modalities and their potential advantages are demonstrated for characteristic clinical examples. Finally, future development like image guided radiotherapy (IGRT) and adaptive radiation therapy, based on functional imaging methods, will be introduced.

  4. Time domain referencing in intensity modulation fiber optic sensing systems

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory

    1986-01-01

    Intensity modulation sensors are classified by the way in which the reference and signal channels are separated: in space, wavelength, or time domains. To implement the time-domain referencing, different types of fiber-optic loops have been used. A pulse of short duration sent into the loop results in a series of pulses of different amplitudes. The information about the measured parameter is retrieved from the relative amplitudes of pulses in the same train.

  5. Time domain referencing in intensity modulation fiber optic sensing systems

    NASA Technical Reports Server (NTRS)

    Adamovsky, G.

    1986-01-01

    Intensity modulation sensors are classified depending on the way in which the reference and signal channels are separated: in space, wavelength (frequency), or time domains. To implement the time domain referencing different types of fiber optic (FO) loops have been used. A pulse of short duration sent into the loop results in a series of pulses of different amplitudes. The information about the measured parameter is retrieved from the relative amplitudes of pulses in the same train.

  6. Intensity modulation with electrons: calculations, measurements and clinical applications.

    PubMed

    Karlsson, M G; Karlsson, M; Zackrisson, B

    1998-05-01

    Intensity modulation of electron beams is one step towards truly conformal therapy. This can be realized with the MM50 racetrack microtron that utilizes a scanning beam technique. By adjusting the scan pattern it is possible to obtain arbitrary fluence distributions. Since the monitor chambers in the treatment head are segmented in both x- and y-directions it is possible to verify the fluence distribution to the patient at any time during the treatment. Intensity modulated electron beams have been measured with film and a plane parallel chamber and compared with calculations. The calculations were based on a pencil beam method. An intensity distribution at the multileaf collimator (MLC) level was calculated by superposition of measured pencil beams over scan patterns. By convolving this distribution with a Gaussian pencil beam, which has propagated from the MLC to the isocentre, a fluence distribution at isocentre level was obtained. The agreement between calculations and measurements was within 2% in dose or 1 mm in distance in the penumbra zones. A standard set of intensity modulated electron beams has been developed. These beams have been implemented in a treatment planning system and are used for manual optimization. A clinical example (prostate) of such an application is presented and compared with a standard irradiation technique.

  7. Spine radiosurgery for the local treatment of spine metastases: Intensity-modulated radiotherapy, image guidance, clinical aspects and future directions

    PubMed Central

    de Moraes, Fabio Ynoe; Taunk, Neil Kanth; Laufer, Ilya; Neves-Junior, Wellington Furtado Pimenta; Hanna, Samir Abdallah; de Andrade Carvalho, Heloisa; Yamada, Yoshiya

    2016-01-01

    Many cancer patients will develop spinal metastases. Local control is important for preventing neurologic compromise and to relieve pain. Stereotactic body radiotherapy or spinal radiosurgery is a new radiation therapy technique for spinal metastasis that can deliver a high dose of radiation to a tumor while minimizing the radiation delivered to healthy, neighboring tissues. This treatment is based on intensity-modulated radiotherapy, image guidance and rigid immobilization. Spinal radiosurgery is an increasingly utilized treatment method that improves local control and pain relief after delivering ablative doses of radiation. Here, we present a review highlighting the use of spinal radiosurgery for the treatment of metastatic tumors of the spine. The data used in the review were collected from both published studies and ongoing trials. We found that spinal radiosurgery is safe and provides excellent tumor control (up to 94% local control) and pain relief (up to 96%), independent of histology. Extensive data regarding clinical outcomes are available; however, this information has primarily been generated from retrospective and nonrandomized prospective series. Currently, two randomized trials are enrolling patients to study clinical applications of fractionation schedules spinal Radiosurgery. Additionally, a phase I clinical trial is being conducted to assess the safety of concurrent stereotactic body radiotherapy and ipilimumab for spinal metastases. Clinical trials to refine clinical indications and dose fractionation are ongoing. The concomitant use of targeted agents may produce better outcomes in the future. PMID:26934240

  8. Metadevice for intensity modulation with sub-wavelength spatial resolution

    PubMed Central

    Cencillo-Abad, Pablo; Zheludev, Nikolay I.; Plum, Eric

    2016-01-01

    Effectively continuous control over propagation of a beam of light requires light modulation with pixelation that is smaller than the optical wavelength. Here we propose a spatial intensity modulator with sub-wavelength resolution in one dimension. The metadevice combines recent advances in reconfigurable nanomembrane metamaterials and coherent all-optical control of metasurfaces. It uses nanomechanical actuation of metasurface absorber strips placed near a mirror in order to control their interaction with light from perfect absorption to negligible loss, promising a path towards dynamic diffraction and focusing of light as well as holography without unwanted diffraction artefacts. PMID:27857221

  9. Linear algebraic methods applied to intensity modulated radiation therapy.

    PubMed

    Crooks, S M; Xing, L

    2001-10-01

    Methods of linear algebra are applied to the choice of beam weights for intensity modulated radiation therapy (IMRT). It is shown that the physical interpretation of the beam weights, target homogeneity and ratios of deposited energy can be given in terms of matrix equations and quadratic forms. The methodology of fitting using linear algebra as applied to IMRT is examined. Results are compared with IMRT plans that had been prepared using a commercially available IMRT treatment planning system and previously delivered to cancer patients.

  10. Smartphone-based portable intensity modulated force sensor

    NASA Astrophysics Data System (ADS)

    Negri, Lucas H.; Schiefer, Elberth M.; Paterno, Aleksander S.; Muller, Marcia; Fabris, José L.

    2015-09-01

    This work proposes a low-cost force sensor, based on intensity modulation in an optical fibre. The transducer element is composed of a knot in a single mode fibre embedded to a silicone adhesive cuboid, and can be easily fabricated. A simple sensing scheme is devised by using a visible light source and a CCD camera of a smartphone, allowing implementation costs to be reduced. Experimental results have shown that the sensor presents a linear response and a standard uncertainty of 1:07N within the dynamical range from 0 to 30 N.

  11. Intensity-modulated arc therapy: principles, technologies and clinical implementation

    NASA Astrophysics Data System (ADS)

    Yu, Cedric X.; Tang, Grace

    2011-03-01

    Intensity-modulated arc therapy (IMAT) was proposed by Yu (1995 Phys. Med. Biol. 40 1435-49) as an alternative to tomotherapy. Over more than a decade, much progress has been made. The advantages and limitations of the IMAT technique have also been better understood. In recent years, single-arc forms of IMAT have emerged and become commercially adopted. The leading example is the volumetric-modulated arc therapy (VMAT), a single-arc form of IMAT that delivers apertures of varying weights with a single-arc rotation that uses dose-rate variation of the treatment machine. With commercial implementation of VMAT, wide clinical adoption has quickly taken root. However, there remains a lack of general understanding for the planning of such arc treatments, as well as what delivery limitations and compromises are made. Commercial promotion and competition add further confusion for the end users. It is therefore necessary to provide a summary of this technology and some guidelines on its clinical implementation. The purpose of this review is to provide a summary of the works from the radiotherapy community that led to wide clinical adoption, and point out the issues that still remain, providing some perspective on its further developments. Because there has been vast experience in IMRT using multiple intensity-modulated fields, comparisons between IMAT and IMRT are also made in the review within the areas of planning, delivery and quality assurance.

  12. Treatment planning, optimization, and beam delivery technqiues for intensity modulated proton therapy

    NASA Astrophysics Data System (ADS)

    Sengbusch, Evan R.

    , beamlet weight, the number of delivered beamlets, and the number of delivery angles. These methods are evaluated via treatment planning studies including left-sided whole breast irradiation, lung stereotactic body radiotherapy, nasopharyngeal carcinoma, and whole brain radiotherapy with hippocampal avoidance. Improvements in efficiency and efficacy relative to traditional proton therapy and intensity modulated photon radiation therapy are discussed.

  13. Clinical Realization of Sector Beam Intensity Modulation for Gamma Knife Radiosurgery: A Pilot Treatment Planning Study

    SciTech Connect

    Ma, Lijun; Mason, Erica; Sneed, Penny K.; McDermott, Michael; Polishchuk, Alexei; Larson, David A.; Sahgal, Arjun

    2015-03-01

    Purpose: To demonstrate the clinical feasibility and potential benefits of sector beam intensity modulation (SBIM) specific to Gamma Knife stereotactic radiosurgery (GKSRS). Methods and Materials: SBIM is based on modulating the confocal beam intensities from individual sectors surrounding an isocenter in a nearly 2π geometry. This is in contrast to conventional GKSRS delivery, in which the beam intensities from each sector are restricted to be either 0% or 100% and must be identical for any given isocenter. We developed a SBIM solution based on available clinical planning tools, and we tested it on a cohort of 12 clinical cases as a proof of concept study. The SBIM treatment plans were compared with the original clinically delivered treatment plans to determine dosimetric differences. The goal was to investigate whether SBIM would improve the dose conformity for these treatment plans without prohibitively lengthening the treatment time. Results: A SBIM technique was developed. On average, SBIM improved the Paddick conformity index (PCI) versus the clinically delivered plans (clinical plan PCI = 0.68 ± 0.11 vs SBIM plan PCI = 0.74 ± 0.10, P=.002; 2-tailed paired t test). The SBIM plans also resulted in nearly identical target volume coverage (mean, 97 ± 2%), total beam-on times (clinical plan 58.4 ± 38.9 minutes vs SBIM 63.5 ± 44.7 minutes, P=.057), and gradient indices (clinical plan 3.03 ± 0.27 vs SBIM 3.06 ± 0.29, P=.44) versus the original clinical plans. Conclusion: The SBIM method is clinically feasible with potential dosimetric gains when compared with conventional GKSRS.

  14. Effects of intensity-modulated radiotherapy on human oral microflora.

    PubMed

    Shao, Zi-Yang; Tang, Zi-Sheng; Yan, Chao; Jiang, Yun-Tao; Ma, Rui; Liu, Zheng; Huang, Zheng-Wei

    2011-01-01

    This study aimed to evaluate changes in the biodiversity of the oral microflora of patients with head and neck cancer treated with postoperative intensity-modulated radiotherapy (IMRT) or conventional radiotherapy (CRT). Pooled dental plaque samples were collected during the radiation treatment from patients receiving IMRT (n = 13) and CRT (n = 12). Denaturing gradient gel electrophoresis (DGGE) was used to analyze the temporal variation of these plaque samples. The stimulated and unstimulated salivary flow rates were also compared between IMRT and CRT patients. Reductions in the severity of hyposalivation were observed in IMRT patients compared with CRT patients. We also observed that the temporal stability of the oral ecosystem was significantly higher in the IMRT group (69.96 ± 7.82%) than in the CRT group (51.98 ± 10.45%) (P < 0.05). The findings of the present study suggest that IMRT is more conducive to maintaining the relative stability of the oral ecosystem than CRT.

  15. Palliative intensity modulated radiation therapy for symptomatic adrenal metastasis.

    PubMed

    Mod, H; Patel, V

    2013-05-01

    Metastasis to the adrenal glands is quite common; especially from melanomas, breast, lung, renal and gastro-intestinal tumours. The most common tumour found in the adrenals in post mortem series is a metastatic tumour; incidence ranging from 13 to 27%. The diagnosis of adrenal metastasis is now more common and easier due to staging and subsequent follow up with Computed tomography /Magnetic resonance imaging and or positron emission tomography-computed tomography imaging studies. Most of the times these metastatic lesions are clinically occult and those that do have clinical symptoms complain of pain, nausea, vomiting and early satiety. We irradiated a patient of non small cell lung cancer with adrenal metastasis with palliative Intensity Modulated Radiation Therapy and achieved a good response in terms of pain relief, stable disease and no side effects of the treatment.

  16. Vertical-cavity saturable-absorber intensity modulator

    NASA Astrophysics Data System (ADS)

    Guina, M.; Vainionpää, A.; Harkonen, A.; Orsila, L.; Lyytikäinen, J.; Okhotnikov, O. G.

    2003-01-01

    We propose and demonstrate a reflection-type optical modulator, with surface-normal architecture, that exploits the optical saturation of absorption in semiconductor quantum wells. The modulation section of the modulator, which is composed of quantum wells placed within a Fabry-Perot cavity, is optically controlled by an intensity-modulated beam generated by an in-plane laser integrated monolithically on the same wafer and grown in a single epitaxial step. The modulation section and the in-plane laser share the same medium; therefore, efficient coupling between the control beam and the signal beam is achieved. The device was successfully used for active mode locking of an erbium-doped fiber laser.

  17. Commissioning of Peacock System for intensity-modulated radiation therapy.

    PubMed

    Saw, C B; Ayyangar, K M; Thompson, R B; Zhen, W; Enke, C A

    2001-01-01

    The Peacock System was introduced to perform tomographic intensity-modulated radiation therapy (IMRT). Commissioning of the Peacock System included the alignment of the multileaf intensity-modulating collimator (MIMiC) to the beam axis, the alignment of the RTA device for immobilization, and checking the integrity of the CRANE for indexing the treatment couch. In addition, the secondary jaw settings, couch step size, and transmission through the leaves were determined. The dosimetric data required for the CORVUS planning system were divided into linear accelerator-specific and MIMiC-specific. The linear accelerator-specific dosimetric data were relative output in air, relative output in phantom, percent depth dose for a range of field sizes, and diagonal dose profiles for a large field size. The MIMiC-specific dosimetric data were the in-plane and cross-plane dose profiles of a small and a large field size to derive the penumbra fit. For each treatment unit, the Beam Utility software requires the data be entered into the CORVUS planning system in modular forms. These modules were treatment unit information, angle definition, configuration, gantry and couch angles range, dosimetry, results, and verification plans. After the appropriate machine data were entered, CORVUS created a dose model. The dose model was used to create known simple dose distribution for evaluation using the verification tools of the CORVUS. The planned doses for phantoms were confirmed using an ion chamber for point dose measurement and film for relative dose measurement. The planning system calibration factor was initially set at 1.0 and will be changed after data on clinical cases are acquired. The treatment unit was released for clinical use after the approval icon was checked in the verification plans module.

  18. Prone Breast Intensity Modulated Radiation Therapy: 5-Year Results

    SciTech Connect

    Osa, Etin-Osa O.; DeWyngaert, Keith; Roses, Daniel; Speyer, James; Guth, Amber; Axelrod, Deborah; Fenton Kerimian, Maria; Goldberg, Judith D.; Formenti, Silvia C.

    2014-07-15

    Purpose: To report the 5-year results of a technique of prone breast radiation therapy delivered by a regimen of accelerated intensity modulated radiation therapy with a concurrent boost to the tumor bed. Methods and Materials: Between 2003 and 2006, 404 patients with stage I-II breast cancer were prospectively enrolled into 2 consecutive protocols, institutional trials 03-30 and 05-181, that used the same regimen of 40.5 Gy/15 fractions delivered to the index breast over 3 weeks, with a concomitant daily boost to the tumor bed of 0.5 Gy (total dose 48 Gy). All patients were treated after segmental mastectomy and had negative margins and nodal assessment. Patients were set up prone: only if lung or heart volumes were in the field was a supine setup attempted and chosen if found to better spare these organs. Results: Ninety-two percent of patients were treated prone, 8% supine. Seventy-two percent had stage I, 28% stage II invasive breast cancer. In-field lung volume ranged from 0 to 228.27 cm{sup 3}, mean 19.65 cm{sup 3}. In-field heart volume for left breast cancer patients ranged from 0 to 21.24 cm{sup 3}, mean 1.59 cm{sup 3}. There was no heart in the field for right breast cancer patients. At a median follow-up of 5 years, the 5-year cumulative incidence of isolated ipsilateral breast tumor recurrence was 0.82% (95% confidence interval [CI] 0.65%-1.04%). The 5-year cumulative incidence of regional recurrence was 0.53% (95% CI 0.41%-0.69%), and the 5-year overall cumulative death rate was 1.28% (95% CI 0.48%-3.38%). Eighty-two percent (95% CI 77%-85%) of patients judged their final cosmetic result as excellent/good. Conclusions: Prone accelerated intensity modulated radiation therapy with a concomitant boost results in excellent local control and optimal sparing of heart and lung, with good cosmesis. Radiation Therapy Oncology Group protocol 1005, a phase 3, multi-institutional, randomized trial is ongoing and is evaluating the equivalence of a similar dose and

  19. Segmentation and leaf sequencing for intensity modulated arc therapy

    SciTech Connect

    Gladwish, Adam; Oliver, Mike; Craig, Jeff; Chen, Jeff; Bauman, Glenn; Fisher, Barbara; Wong, Eugene

    2007-05-15

    A common method in generating intensity modulated radiation therapy (IMRT) plans consists of a three step process: an optimized fluence intensity map (IM) for each beam is generated via inverse planning, this IM is then segmented into discrete levels, and finally, the segmented map is translated into a set of MLC apertures via a leaf sequencing algorithm. To date, limited work has been done on this approach as it pertains to intensity modulated arc therapy (IMAT), specifically in regards to the latter two steps. There are two determining factors that separate IMAT segmentation and leaf sequencing from their IMRT equivalents: (1) the intrinsic 3D nature of the intensity maps (standard 2D maps plus the angular component), and (2) that the dynamic multileaf collimator (MLC) constraints be met using a minimum number of arcs. In this work, we illustrate a technique to create an IMAT plan that replicates Tomotherapy deliveries by applying IMAT specific segmentation and leaf-sequencing algorithms to Tomotherapy output sinograms. We propose and compare two alternative segmentation techniques, a clustering method, and a bottom-up segmentation method (BUS). We also introduce a novel IMAT leaf-sequencing algorithm that explicitly takes leaf movement constraints into consideration. These algorithms were tested with 51 angular projections of the output leaf-open sinograms generated on the Hi-ART II treatment planning system (Tomotherapy Inc.). We present two geometric phantoms and 2 clinical scenarios as sample test cases. In each case 12 IMAT plans were created, ranging from 2 to 7 intensity levels. Half were generated using the BUS segmentation and half with the clustering method. We report on the number of arcs produced as well as differences between Tomotherapy output sinograms and segmented IMAT intensity maps. For each case one plan for each segmentation method is chosen for full Monte Carlo dose calculation (NumeriX LLC) and dose volume histograms (DVH) are calculated

  20. Benchmarking Dosimetric Quality Assessment of Prostate Intensity-Modulated Radiotherapy

    SciTech Connect

    Senthi, Sashendra; Gill, Suki S.; Haworth, Annette; Kron, Tomas; Cramb, Jim; Rolfo, Aldo; Thomas, Jessica; Duchesne, Gillian M.; Hamilton, Christopher H.; Joon, Daryl Lim; Bowden, Patrick; Foroudi, Farshad

    2012-02-01

    Purpose: To benchmark the dosimetric quality assessment of prostate intensity-modulated radiotherapy and determine whether the quality is influenced by disease or treatment factors. Patients and Methods: We retrospectively analyzed the data from 155 consecutive men treated radically for prostate cancer using intensity-modulated radiotherapy to 78 Gy between January 2007 and March 2009 across six radiotherapy treatment centers. The plan quality was determined by the measures of coverage, homogeneity, and conformity. Tumor coverage was measured using the planning target volume (PTV) receiving 95% and 100% of the prescribed dose (V{sub 95%} and V{sub 100%}, respectively) and the clinical target volume (CTV) receiving 95% and 100% of the prescribed dose. Homogeneity was measured using the sigma index of the PTV and CTV. Conformity was measured using the lesion coverage factor, healthy tissue conformity index, and the conformity number. Multivariate regression models were created to determine the relationship between these and T stage, risk status, androgen deprivation therapy use, treatment center, planning system, and treatment date. Results: The largest discriminatory measurements of coverage, homogeneity, and conformity were the PTV V{sub 95%}, PTV sigma index, and conformity number. The mean PTV V{sub 95%} was 92.5% (95% confidence interval, 91.3-93.7%). The mean PTV sigma index was 2.10 Gy (95% confidence interval, 1.90-2.20). The mean conformity number was 0.78 (95% confidence interval, 0.76-0.79). The treatment center independently influenced the coverage, homogeneity, and conformity (all p < .0001). The planning system independently influenced homogeneity (p = .038) and conformity (p = .021). The treatment date independently influenced the PTV V{sub 95%} only, with it being better at the start (p = .013). Risk status, T stage, and the use of androgen deprivation therapy did not influence any aspect of plan quality. Conclusion: Our study has benchmarked measures

  1. Planning and delivery of intensity-modulated radiation therapy.

    PubMed

    Yu, Cedric X; Amies, Christopher J; Svatos, Michelle

    2008-12-01

    Intensity modulated radiation therapy (IMRT) is an advanced form of external beam radiation therapy. IMRT offers an additional dimension of freedom as compared with field shaping in three-dimensional conformal radiation therapy because the radiation intensities within a radiation field can be varied according to the preferences of locations within a given beam direction from which the radiation is directed to the tumor. This added freedom allows the treatment planning system to better shape the radiation doses to conform to the target volume while sparing surrounding normal structures. The resulting dosimetric advantage has shown to translate into clinical advantages of improving local and regional tumor control. It also offers a valuable mechanism for dose escalation to tumors while simultaneously reducing radiation toxicities to the surrounding normal tissue and sensitive structures. In less than a decade, IMRT has become common practice in radiation oncology. Looking forward, the authors wonder if IMRT has matured to such a point that the room for further improvement has diminished and so it is pertinent to ask what the future will hold for IMRT. This article attempts to look from the perspective of the current state of the technology to predict the immediate trends and the future directions. This article will (1) review the clinical experience of IMRT; (2) review what we learned in IMRT planning; (3) review different treatment delivery techniques; and finally, (4) predict the areas of advancements in the years to come.

  2. Regularization of inverse planning for intensity-modulated radiotherapy.

    PubMed

    Chvetsov, Alexei V; Calvetti, Daniela; Sohn, Jason W; Kinsella, Timothy J

    2005-02-01

    The performance of a variational regularization technique to improve robustness of inverse treatment planning for intensity modulated radiotherapy is analyzed and tested. Inverse treatment planning is based on the numerical solutions to the Fredholm integral equation of the first kind which is ill-posed. Therefore, a fundamental problem with inverse treatment planning is that it may exhibit instabilities manifested in nonphysical oscillations in the beam intensity functions. To control the instabilities, we consider a variational regularization technique which can be applied for the methods which minimize a quadratic objective function. In this technique, the quadratic objective function is modified by adding of a stabilizing functional that allows for arbitrary order regularization. An optimal form of stabilizing functional is selected which allows for both regularization and good approximation of beam intensity functions. The regularized optimization algorithm is shown, by comparison for a typical case of a head-and-neck cancer treatment, to be significantly more accurate and robust than the standard approach, particularly for the smaller beamlet sizes.

  3. Intensity modulated radiation therapy for breast cancer: current perspectives

    PubMed Central

    Buwenge, Milly; Cammelli, Silvia; Ammendolia, Ilario; Tolento, Giorgio; Zamagni, Alice; Arcelli, Alessandra; Macchia, Gabriella; Deodato, Francesco; Cilla, Savino; Morganti, Alessio G

    2017-01-01

    Background Owing to highly conformed dose distribution, intensity modulated radiation therapy (IMRT) has the potential to improve treatment results of radiotherapy (RT). Postoperative RT is a standard adjuvant treatment in conservative treatment of breast cancer (BC). The aim of this review is to analyze available evidence from randomized controlled trials (RCTs) on IMRT in BC, particularly in terms of reduction of side effects. Methods A literature search of the bibliographic database PubMed, from January 1990 through November 2016, was performed. Only RCTs published in English were included. Results Ten articles reporting data from 5 RCTs fulfilled the selection criteria and were included in our review. Three out of 5 studies enrolled only selected patients in terms of increased risk of toxicity. Three studies compared IMRT with standard tangential RT. One study compared the results of IMRT in the supine versus the prone position, and one study compared standard treatment with accelerated partial breast IMRT. Three studies reported reduced acute and/or late toxicity using IMRT compared with standard RT. No study reported improved quality of life. Conclusion IMRT seems able to reduce toxicity in selected patients treated with postoperative RT for BC. Further analyses are needed to better define patients who are candidates for this treatment modality. PMID:28293119

  4. Signal restoration in intensity-modulated optical OFDM access systems.

    PubMed

    Vanin, Evgeny

    2011-11-15

    It is well known that deliberate signal clipping in an intensity-modulated (IM) laser transmitter helps to overcome the optical orthogonal frequency division multiplexing (OFDM) system performance limitation that is related to the signal high peak-to-average power ratio. The amplitude of a clipped OFDM signal has to be optimized in order to minimize the optical power that is required to achieve a specified system performance. However, the signal clipping introduces nonlinear distortion (so-called clipping noise) and leads to a system performance penalty. In this Letter, the performance of the IM optical OFDM system with digital baseband clipping distortion in the transmitter and clipping noise compensation by means of signal restoration in the digital signal processing unit of the system receiver is analytically evaluated. It is demonstrated that the system bit-error ratio can be reduced by more than an order of magnitude, from 10(-3) to 3.5×10(-5), by applying only the first iteration of the signal restoration algorithm proposed in this Letter. The results of the analytical analysis are verified with brute-force numerical simulations based on direct error counting.

  5. Intensity-Modulated Radiation Therapy in Childhood Ependymoma

    SciTech Connect

    Schroeder, Thomas M.; Chintagumpala, Murali; Okcu, M. Fatih; Chiu, J. Kam; Teh, Bin S.; Woo, Shiao Y.; Paulino, Arnold C.

    2008-07-15

    Purpose: To determine the patterns of failure after intensity-modulated radiation therapy (IMRT) for localized intracranial ependymoma. Methods and Materials: From 1994 to 2005, 22 children with pathologically proven, localized, intracranial ependymoma were treated with adjuvant IMRT. Of the patients, 12 (55%) had an infratentorial tumor and 14 (64%) had anaplastic histology. Five patients had a subtotal resection (STR), as evidenced by postoperative magnetic resonance imaging. The clinical target volume encompassed the tumor bed and any residual disease plus margin (median dose 54 Gy). Median follow-up for surviving patients was 39.8 months. Results: The 3-year overall survival rate was 87% {+-} 9%. The 3-year local control rate was 68% {+-} 12%. There were six local recurrences, all in the high-dose region of the treatment field. Median time to recurrence was 21.7 months. Of the 5 STR patients, 4 experienced recurrence and 3 died. Patients with a gross total resection had significantly better local control (p = 0.024) and overall survival (p = 0.008) than those with an STR. At last follow-up, no patient had developed visual loss, brain necrosis, myelitis, or a second malignancy. Conclusions: Treatment with IMRT provides local control and survival rates comparable with those in historic publications using larger treatment volumes. All failures were within the high-dose region, suggesting that IMRT does not diminish local control. The degree of surgical resection was shown to be significant for local control and survival.

  6. Monte Carlo dose verification for intensity-modulated arc therapy

    NASA Astrophysics Data System (ADS)

    Li, X. Allen; Ma, Lijun; Naqvi, Shahid; Shih, Rompin; Yu, Cedric

    2001-09-01

    Intensity-modulated arc therapy (IMAT), a technique which combines beam rotation and dynamic multileaf collimation, has been implemented in our clinic. Dosimetric errors can be created by the inability of the planning system to accurately account for the effects of tissue inhomogeneities and physical characteristics of the multileaf collimator (MLC). The objective of this study is to explore the use of Monte Carlo (MC) simulation for IMAT dose verification. The BEAM/DOSXYZ Monte Carlo system was implemented to perform dose verification for the IMAT treatment. The implementation includes the simulation of the linac head/MLC (Elekta SL20), the conversion of patient CT images and beam arrangement for 3D dose calculation, the calculation of gantry rotation and leaf motion by a series of static beams and the development of software to automate the entire MC process. The MC calculations were verified by measurements for conventional beam settings. The agreement was within 2%. The IMAT dose distributions generated by a commercial forward planning system (RenderPlan, Elekta) were compared with those calculated by the MC package. For the cases studied, discrepancies of over 10% were found between the MC and the RenderPlan dose calculations. These discrepancies were due in part to the inaccurate dose calculation of the RenderPlan system. The computation time for the IMAT MC calculation was in the range of 20-80 min on 15 Pentium-III computers. The MC method was also useful in verifying the beam apertures used in the IMAT treatments.

  7. Pitfalls in normalization for intensity-modulated radiation therapy planning

    SciTech Connect

    Williams, Greg . E-mail: greg.williams@hci.utah.edu; Tobler, Matt; Leavitt, Dennis

    2005-01-01

    Three-dimensional (3D) treatment planning often involves complex combinations of beam energies, treatment fields, and beam modifying devices. Even when a plan is devised that meets many treatment-planning objectives, limitations in the planner's ability to further adjust beam characteristics may require the radiation dose prescription to be normalized to an isodose level that best covers the target volume. While these normalizations help meet the volume coverage goals, they also result in adjustment of the dose delivered to the normal tissues and must be carefully evaluated. Intensity-modulated radiation therapy (IMRT) treatment planning allows combinations of complex dose patterns, in order to achieve the desired treatment planning goals. These dose patterns are created by defining a set of treatment planning objectives and then allowing the treatment planning computer to create intensity patterns, through the use of moving multileaf collimation that will meet the requested goals. Often, when an IMRT treatment plan is created that meets many of the treatment planning goals but falls short of volume coverage requirements, the planner is tempted to apply normalization principles similar to those utilized with 3D treatment planning. Again, these normalizations help meet the volume coverage goals, but unlike 3D planning situations, may result in avoidable delivery of additional doses to the normal tissues. The focus of this study is to evaluate the effect of application of normalization for IMRT planning using multiple patient situations. Recommendations would favor re-optimization over normalization in most planning situations.

  8. Quantitative shadowgraphy and proton radiography for large intensity modulations

    NASA Astrophysics Data System (ADS)

    Kasim, Muhammad Firmansyah; Ceurvorst, Luke; Ratan, Naren; Sadler, James; Chen, Nicholas; Sävert, Alexander; Trines, Raoul; Bingham, Robert; Burrows, Philip N.; Kaluza, Malte C.; Norreys, Peter

    2017-02-01

    Shadowgraphy is a technique widely used to diagnose objects or systems in various fields in physics and engineering. In shadowgraphy, an optical beam is deflected by the object and then the intensity modulation is captured on a screen placed some distance away. However, retrieving quantitative information from the shadowgrams themselves is a challenging task because of the nonlinear nature of the process. Here, we present a method to retrieve quantitative information from shadowgrams, based on computational geometry. This process can also be applied to proton radiography for electric and magnetic field diagnosis in high-energy-density plasmas and has been benchmarked using a toroidal magnetic field as the object, among others. It is shown that the method can accurately retrieve quantitative parameters with error bars less than 10%, even when caustics are present. The method is also shown to be robust enough to process real experimental results with simple pre- and postprocessing techniques. This adds a powerful tool for research in various fields in engineering and physics for both techniques.

  9. Multibeam tomotherapy: A new treatment unit devised for multileaf collimation, intensity-modulated radiation therapy

    SciTech Connect

    Achterberg, Nils; Mueller, Reinhold G.

    2007-10-15

    A fully integrated system for treatment planning, application, and verification for automated multileaf collimator (MLC) based, intensity-modulated, image-guided, and adaptive radiation therapy (IMRT, IGRT and ART, respectively) is proposed. Patient comfort, which was the major development goal, will be achieved through a new unit design and short treatment times. Our device for photon beam therapy will consist of a new dual energy linac with five fixed treatment heads positioned evenly along one plane but one electron beam generator only. A minimum of moving parts increases technical reliability and reduces motion times to a minimum. Motion is allowed solely for the MLCs, the robotic patient table, and the small angle gantry rotation of {+-}36 deg. . Besides sophisticated electron beam guidance, this compact setup can be built using existing modules. The flattening-filter-free treatment heads are characterized by reduced beam-on time and contain apertures restricted in one dimension to the area of maximum primary fluence output. In the case of longer targets, this leads to a topographic intensity modulation, thanks to the combination of 'step and shoot' MLC delivery and discrete patient couch motion. Owing to the limited number of beam directions, this multislice cone beam serial tomotherapy is referred to as 'multibeam tomotherapy.' Every patient slice is irradiated by one treatment head at any given moment but for one subfield only. The electron beam is then guided to the next head ready for delivery, while the other heads are preparing their leaves for the next segment. The 'Multifocal MLC-positioning' algorithm was programmed to enable treatment planning and optimize treatment time. We developed an overlap strategy for the longitudinally adjacent fields of every beam direction, in doing so minimizing the field match problem and the effects of possible table step errors. Clinical case studies show for the same or better planning target volume coverage, better

  10. Multibeam tomotherapy: a new treatment unit devised for multileaf collimation, intensity-modulated radiation therapy.

    PubMed

    Achterberg, Nils; Müller, Reinhold G

    2007-10-01

    A fully integrated system for treatment planning, application, and verification for automated multileaf collimator (MLC) based, intensity-modulated, image-guided, and adaptive radiation therapy (IMRT, IGRT and ART, respectively) is proposed. Patient comfort, which was the major development goal, will be achieved through a new unit design and short treatment times. Our device for photon beam therapy will consist of a new dual energy linac with five fixed treatment heads positioned evenly along one plane but one electron beam generator only. A minimum of moving parts increases technical reliability and reduces motion times to a minimum. Motion is allowed solely for the MLCs, the robotic patient table, and the small angle gantry rotation of +/- 36 degrees. Besides sophisticated electron beam guidance, this compact setup can be built using existing modules. The flattening-filter-free treatment heads are characterized by reduced beam-on time and contain apertures restricted in one dimension to the area of maximum primary fluence output. In the case of longer targets, this leads to a topographic intensity modulation, thanks to the combination of "step and shoot" MLC delivery and discrete patient couch motion. Owing to the limited number of beam directions, this multislice cone beam serial tomotherapy is referred to as "multibeam tomotherapy." Every patient slice is irradiated by one treatment head at any given moment but for one subfield only. The electron beam is then guided to the next head ready for delivery, while the other heads are preparing their leaves for the next segment. The "Multifocal MLC-positioning" algorithm was programmed to enable treatment planning and optimize treatment time. We developed an overlap strategy for the longitudinally adjacent fields of every beam direction, in doing so minimizing the field match problem and the effects of possible table step errors. Clinical case studies show for the same or better planning target volume coverage, better

  11. 3D treatment planning and intensity-modulated radiation therapy.

    PubMed

    Purdy, J A

    1999-10-01

    Three-dimensional (3D) image-based treatment planning and new delivery technologies have spurred the implementation of external beam radiation therapy techniques, in which the high-dose region is conformed much more closely to the target volume than previously possible, thus reducing the volume of normal tissues receiving a high dose. This form of external beam irradiation is referred to as 3D conformal radiation therapy (3DCRT). 3DCRT is not just an add-on to the current radiation oncology process; it represents a radical change in practice, particularly for the radiation oncologist. Defining target volumes and organs at risk in 3D by drawing contours on CT images on a slice-by-slice basis, as opposed to drawing beam portals on a simulator radiograph, can be challenging, because radiation oncologists are generally not well trained in cross-sectional imaging. Currently, the 3DCRT approach will increase the time and effort required by physicians inexperienced with 3D treatment planning. Intensity-modulated radiation therapy (IMRT) is a more advanced form of 3DCRT, but there is considerable developmental work remaining. The instrumentation and methods used for IMRT quality assurance procedures and testing are not well established. Computer optimization cost functions are too simplistic, and thus time-consuming. Subjective plan evaluation by the radiation oncologist is still the norm. In addition, many fundamental questions regarding IMRT remain unanswered. For example, the radiobiophysical consequences of altered time-dose-fraction are unknown. Also, the fact that there is much greater dose heterogeneity for both the target and normal critical structures with IMRT compared to traditional irradiation techniques challenges current radiation oncology planning principles. However, this new process of planning and treatment delivery shows significant potential for improving the therapeutic ratio. In addition, while inefficient today, these systems, when fully developed

  12. Dosimetrically Triggered Adaptive Intensity Modulated Radiation Therapy for Cervical Cancer

    SciTech Connect

    Lim, Karen; Stewart, James; Kelly, Valerie; Xie, Jason; Brock, Kristy K.; Moseley, Joanne; Cho, Young-Bin; Fyles, Anthony; Lundin, Anna; Rehbinder, Henrik; Löf, Johan; Jaffray, David A.; Milosevic, Michael

    2014-09-01

    Purpose: The widespread use of intensity modulated radiation therapy (IMRT) for cervical cancer has been limited by internal target and normal tissue motion. Such motion increases the risk of underdosing the target, especially as planning margins are reduced in an effort to reduce toxicity. This study explored 2 adaptive strategies to mitigate this risk and proposes a new, automated method that minimizes replanning workload. Methods and Materials: Thirty patients with cervical cancer participated in a prospective clinical study and underwent pretreatment and weekly magnetic resonance (MR) scans over a 5-week course of daily external beam radiation therapy. Target volumes and organs at risk (OARs) were contoured on each of the scans. Deformable image registration was used to model the accumulated dose (the real dose delivered to the target and OARs) for 2 adaptive replanning scenarios that assumed a very small PTV margin of only 3 mm to account for setup and internal interfractional motion: (1) a preprogrammed, anatomy-driven midtreatment replan (A-IMRT); and (2) a dosimetry-triggered replan driven by target dose accumulation over time (D-IMRT). Results: Across all 30 patients, clinically relevant target dose thresholds failed for 8 patients (27%) if 3-mm margins were used without replanning. A-IMRT failed in only 3 patients and also yielded an additional small reduction in OAR doses at the cost of 30 replans. D-IMRT assured adequate target coverage in all patients, with only 23 replans in 16 patients. Conclusions: A novel, dosimetry-triggered adaptive IMRT strategy for patients with cervical cancer can minimize the risk of target underdosing in the setting of very small margins and substantial interfractional motion while minimizing programmatic workload and cost.

  13. Uncertainty Estimation in Intensity-Modulated Radiotherapy Absolute Dosimetry Verification

    SciTech Connect

    Sanchez-Doblado, Francisco . E-mail: paco@us.es; Hartmann, Guenther H.; Pena, Javier; Capote, Roberto; Paiusco, Marta; Rhein, Bernhard; Leal, Antonio; Lagares, Juan Ignacio

    2007-05-01

    Purpose: Intensity-modulated radiotherapy (IMRT) represents an important method for improving RT. The IMRT relative dosimetry checks are well established; however, open questions remain in reference dosimetry with ionization chambers (ICs). The main problem is the departure of the measurement conditions from the reference ones; thus, additional uncertainty is introduced into the dose determination. The goal of this study was to assess this effect systematically. Methods and Materials: Monte Carlo calculations and dosimetric measurements with five different detectors were performed for a number of representative IMRT cases, covering both step-and-shoot and dynamic delivery. Results: Using ICs with volumes of about 0.125 cm{sup 3} or less, good agreement was observed among the detectors in most of the situations studied. These results also agreed well with the Monte Carlo-calculated nonreference correction factors (c factors). Additionally, we found a general correlation between the IC position relative to a segment and the derived correction factor c, which can be used to estimate the expected overall uncertainty of the treatment. Conclusion: The increase of the reference dose relative standard uncertainty measured with ICs introduced by nonreference conditions when verifying an entire IMRT plan is about 1-1.5%, provided that appropriate small-volume chambers are used. The overall standard uncertainty of the measured IMRT dose amounts to about 2.3%, including the 0.5% of reproducibility and 1.5% of uncertainty associated with the beam calibration factor. Solid state detectors and large-volume chambers are not well suited to IMRT verification dosimetry because of the greater uncertainties. An action level of 5% is appropriate for IMRT verification. Greater discrepancies should lead to a review of the dosimetric procedure, including visual inspection of treatment segments and energy fluence.

  14. SU-E-T-409: Intensity Modulated Robotic Radiotherapy

    SciTech Connect

    Wang, B; Jin, L; Li, J; Chen, L; Ma, C; Fan, J; Zhang, C

    2014-06-01

    Purpose: As compared with the IRIS-based models, the MLC-based CyberKnife system allows more efficient treatment delivery due to its improved coverage of large lesions and intensity modulation. The treatment delivery efficiency is mainly determined by the number of selected nodes. This study aimed to demonstrate that relatively small sets of optimally selected nodes could produce high-quality plans. Methods: The full body path of the CyberKnife system consists of 110 nodes, from which we selected various sets for 4 prostate cancer cases using our in-house beamselection software. With the selected nodes we generated IMRT plans using our in-house beamlet-based inverse-planning optimization program. We also produced IMRT plans using the MultiPlan treatment planning system (version 5.0) for the same cases. Furthermore, the nodes selected by MultiPlan were used to produce plans with our own optimization software so that we could compare the quality of the selected sets of nodes. Results: Our beam-selection program selected one node-set for each case, with the number of nodes ranging from 23 to 34. The IMRT plans based on the selected nodes and our in-house optimization program showed adequate target coverage, with favorable critical structure sparing for the cases investigated. Compared with the plans using the nodes selected by MultiPlan, the plans generated with our selected beams provided superior rectum/bladder sparing for 75% of the cases. The plans produced by MultiPlan with various numbers of nodes also suggested that the plan quality was not compromised significantly when the number of nodes was reduced. Conclusion: Our preliminary results showed that with beamletbased planning optimization, one could produce high-quality plans with an optimal set of nodes for MLC-based robotic radiotherapy. Furthermore, our beam-selection strategy could help further improve critical structure sparing.

  15. Prostate Bed Motion During Intensity-Modulated Radiotherapy Treatment

    SciTech Connect

    Klayton, Tracy; Price, Robert; Buyyounouski, Mark K.; Sobczak, Mark; Greenberg, Richard; Li, Jinsheng; Keller, Lanea; Sopka, Dennis; Kutikov, Alexander; Horwitz, Eric M.

    2012-09-01

    Purpose: Conformal radiation therapy in the postprostatectomy setting requires accurate setup and localization of the prostatic fossa. In this series, we report prostate bed localization and motion characteristics, using data collected from implanted radiofrequency transponders. Methods and Materials: The Calypso four-dimensional localization system uses three implanted radiofrequency transponders for daily target localization and real-time tracking throughout a course of radiation therapy. We reviewed the localization and tracking reports for 20 patients who received ultrasonography-guided placement of Calypso transponders within the prostate bed prior to a course of intensity-modulated radiation therapy at Fox Chase Cancer Center. Results: At localization, prostate bed displacement relative to bony anatomy exceeded 5 mm in 9% of fractions in the anterior-posterior (A-P) direction and 21% of fractions in the superior-inferior (S-I) direction. The three-dimensional vector length from skin marks to Calypso alignment exceeded 1 cm in 24% of all 652 fractions with available setup data. During treatment, the target exceeded the 5-mm tracking limit for at least 30 sec in 11% of all fractions, generally in the A-P or S-I direction. In the A-P direction, target motion was twice as likely to move posteriorly, toward the rectum, than anteriorly. Fifteen percent of all treatments were interrupted for repositioning, and 70% of patients were repositioned at least once during their treatment course. Conclusion: Set-up errors and motion of the prostatic fossa during radiotherapy are nontrivial, leading to potential undertreatment of target and excess normal tissue toxicity if not taken into account during treatment planning. Localization and real-time tracking of the prostate bed via implanted Calypso transponders can be used to improve the accuracy of plan delivery.

  16. Prospective Trial of Accelerated Partial Breast Intensity-Modulated Radiotherapy

    SciTech Connect

    Leonard, Charles . E-mail: charles.leonard@usoncology.com; Carter, Dennis; Kercher, Jane; Howell, Kathryn; Henkenberns, Phyllis; Tallhamer, Michael; Cornish, Patricia C.; Hunter, Kari C.; Kondrat, Janis

    2007-04-01

    Purpose: To examine the feasibility and acute toxicities of an accelerated, partial breast, intensity-modulated radiotherapy (IMRT) protocol. Methods and Materials: Between February 2004 and August 2005, 55 patients with Stage I breast cancer and initial follow-up were enrolled at four facilities on a HealthONE and Western institutional review board-approved accelerated partial breast IMRT protocol. All patients were treated in 10 equal fractions delivered twice daily within 5 consecutive days. The first 7 patients were treated to 34 Gy, and the remaining 48 patients were treated to 38.5 Gy. Results: The median follow-up after IMRT was 10 months (range, <1-19) and after diagnosis was 11.5 months (range, 2-21). No local or distant recurrences developed. The T stage distribution was as follows: T1a in 11 patients, T1b in 24, and T1c in 20. The median tumor size was 9 mm (range, 1-20 mm). Breast cosmesis was judged by the patient as poor by 2, good by 12, and excellent by 40 (1 patient was legally blind) and by the physician as poor for 1, good for 10, and excellent for 44 patients. Breast pain, as judged by patient, was none in 34, mild in 19, moderate in 2, and severe in 0 patients. There was a single report of telangiectasia but no incidents of significant edema. Compared with historic controls for whom three-dimensional treatment planning techniques were used, IMRT provided similar dose delivery to the target while reducing the volume of normal breast included in the 100%, 75%, and 50% isodose lines. Conclusion: This initial report prospectively explored the feasibility of accelerated partial breast IMRT. After short-term follow-up, the dose delivery and clinical outcomes were very acceptable. We believe this regimen deserves additional investigation under institutional review board guidance.

  17. Intensity Modulated Radiation Therapy With Dose Painting to Treat Rhabdomyosarcoma

    SciTech Connect

    Yang, Joanna C.; Dharmarajan, Kavita V.; Wexler, Leonard H.; La Quaglia, Michael P.; Happersett, Laura; Wolden, Suzanne L.

    2012-11-01

    Purpose: To examine local control and patterns of failure in rhabdomyosarcoma patients treated with intensity modulated radiation therapy (RT) with dose painting (DP-IMRT). Patients and Methods: A total of 41 patients underwent DP-IMRT with chemotherapy for definitive treatment. Nineteen also underwent surgery with or without intraoperative RT. Fifty-six percent had alveolar histologic features. The median interval from beginning chemotherapy to RT was 17 weeks (range, 4-25). Very young children who underwent second-look procedures with or without intraoperative RT received reduced doses of 24-36 Gy in 1.4-1.8-Gy fractions. Young adults received 50.4 Gy to the primary tumor and lower doses of 36 Gy in 1.8-Gy fractions to at-risk lymph node chains. Results: With 22 months of median follow-up, the actuarial local control rate was 90%. Patients aged {<=}7 years who received reduced overall and fractional doses had 100% local control, and young adults had 79% (P=.07) local control. Three local failures were identified in young adults whose primary target volumes had received 50.4 Gy in 1.8-Gy fractions. Conclusions: DP-IMRT with lower fractional and cumulative doses is feasible for very young children after second-look procedures with or without intraoperative RT. DP-IMRT is also feasible in adolescents and young adults with aggressive disease who would benefit from prophylactic RT to high-risk lymph node chains, although dose escalation might be warranted for improved local control. With limited follow-up, it appears that DP-IMRT produces local control rates comparable to those of sequential IMRT in patients with rhabdomyosarcoma.

  18. Intensity-modulated radiotherapy for lymphoma involving the mediastinum

    SciTech Connect

    Goodman, Karyn A.; Toner, Sean; Hunt, Margie; Wu, Elisa J.; Yahalom, Joachim . E-mail: yahalomj@mskcc.org

    2005-05-01

    Purpose: To determine the feasibility, potential advantage, and indications for intensity-modulated radiotherapy (IMRT) in the treatment of Hodgkin's lymphoma or non-Hodgkin's lymphoma involving excessively large mediastinal disease volumes or requiring repeat RT. Methods and materials: Sixteen patients with Hodgkin's lymphoma (n = 11) or non-Hodgkin's lymphoma (n = 5) undergoing primary radiotherapy or repeat RT delivered via an IMRT plan were studied. The indications for using an IMRT plan were previous mediastinal RT (n = 5) or extremely large mediastinal treatment volumes (n 11). For each patient, IMRT, conventional parallel-opposed (AP-PA), and three-dimensional conformal (3D-CRT) plans were designed using 6-MV X-rays to deliver doses ranging from 18 to 45 Gy (median, 36 Gy). The plans were compared with regard to dose-volume parameters. The IMRT/AP-PA and IMRT/3D-CRT ratios were calculated for each parameter. Results: For all patients, the mean lung dose was reduced using IMRT, on average, by 12% compared with AP-PA and 14% compared with 3D-CRT. The planning target volume coverage was also improved using IMRT compared with AP-PA but was not different from the planning target volume coverage obtained with 3D-CRT. Conclusion: In selected patients with Hodgkin's lymphoma and non-Hodgkin's lymphoma involving the mediastinum, IMRT provides improved planning target volume coverage and reduces pulmonary toxicity parameters. It is feasible for RT of large treatment volumes and allows repeat RT of relapsed disease without exceeding cord tolerance. Additional follow-up is necessary to determine whether improvements in dose delivery affect long-term morbidity and disease control.

  19. Quantification of beam complexity in intensity-modulated radiation therapy treatment plans

    SciTech Connect

    Du, Weiliang Cho, Sang Hyun; Zhang, Xiaodong; Kudchadker, Rajat J.; Hoffman, Karen E.

    2014-02-15

    Purpose: Excessive complexity in intensity-modulated radiation therapy (IMRT) plans increases the dose uncertainty, prolongs the treatment time, and increases the susceptibility to changes in patient or target geometry. To date, the tools for quantitative assessment of IMRT beam complexity are still lacking. In this study, The authors have sought to develop metrics to characterize different aspects of beam complexity and investigate the beam complexity for IMRT plans of different disease sites. Methods: The authors evaluated the beam complexity scores for 65 step-and-shoot IMRT plans from three sites (prostate, head and neck, and spine) and 26 volumetric-modulated arc therapy (VMAT) plans for the prostate. On the basis of the beam apertures and monitor unit weights of all segments, the authors calculated the mean aperture area, extent of aperture shape irregularity, and degree of beam modulation for each beam. Then the beam complexity values were averaged to obtain the complexity metrics of the IMRT plans. The authors studied the correlation between the beam complexity metrics and the quality assurance (QA) results. Finally, the effects of treatment planning parameters on beam complexity were studied. Results: The beam complexity scores were not uniform among the prostate IMRT beams from different gantry angles. The lateral beams had larger monitor units and smaller shape irregularity, while the anterior-posterior beams had larger modulation values. On average, the prostate IMRT plans had the smallest aperture irregularity, beam modulation, and normalized monitor units; the head and neck IMRT plans had large beam irregularity and beam modulation; and the spine stereotactic radiation therapy plans often had small beam apertures, which may have been associated with the relatively large discrepancies between planned and QA measured doses. There were weak correlations between the beam complexity scores and the measured dose errors. The prostate VMAT beams showed

  20. Optimization and quality assurance of an image-guided radiation therapy system for intensity-modulated radiation therapy radiotherapy.

    PubMed

    Tsai, Jen-San; Micaily, Bizhan; Miyamoto, Curtis

    2012-01-01

    To develop a quality assurance (QA) of XVI cone beam system (XVIcbs) for its optimal imaging-guided radiotherapy (IGRT) implementation, and to construe prostate tumor margin required for intensity-modulated radiation therapy (IMRT) if IGRT is unavailable. XVIcbs spatial accuracy was explored with a humanoid phantom; isodose conformity to lesion target with a rice phantom housing a soap as target; image resolution with a diagnostic phantom; and exposure validation with a Radcal ion chamber. To optimize XVIcbs, rotation flexmap on coincidency between gantry rotational axis and that of XVI cone beam scan was investigated. Theoretic correlation to image quality of XVIcbs rotational axis stability was elaborately studied. Comprehensive QA of IGRT using XVIcbs has initially been explored and then implemented on our general IMRT treatments, and on special IMRT radiotherapies such as head and neck (H and N), stereotactic radiation therapy (SRT), stereotactic radiosurgery (SRS), and stereotactic body radiotherapy (SBRT). Fifteen examples of prostate setup accounted for 350 IGRT cone beam system were analyzed. IGRT accuracy results were in agreement ± 1 mm. Flexmap 0.25 mm met the manufacturer's specification. Films confirmed isodose coincidence with target (soap) via XVIcbs, otherwise not. Superficial doses were measured from 7.2-2.5 cGy for anatomic diameters 15-33 cm, respectively. Image quality was susceptible to rotational stability or patient movement. IGRT using XVIcbs on general IMRT treatments such as prostate, SRT, SRS, and SBRT for setup accuracy were verified; and subsequently coordinate shifts corrections were recorded. The 350 prostate IGRT coordinate shifts modeled to Gaussian distributions show central peaks deviated off the isocenter by 0.6 ± 3.0 mm, 0.5 ± 4.5 mm in the X(RL)- and Z(SI)-coordinates, respectively; and 2.0 ± 3.0 mm in the Y(AP)-coordinate as a result of belly and bladder capacity variations. Sixty-eight percent of confidence was within

  1. Optimization and quality assurance of an image-guided radiation therapy system for intensity-modulated radiation therapy radiotherapy

    SciTech Connect

    Tsai, Jen-San; Micaily, Bizhan; Miyamoto, Curtis

    2012-10-01

    To develop a quality assurance (QA) of XVI cone beam system (XVIcbs) for its optimal imaging-guided radiotherapy (IGRT) implementation, and to construe prostate tumor margin required for intensity-modulated radiation therapy (IMRT) if IGRT is unavailable. XVIcbs spatial accuracy was explored with a humanoid phantom; isodose conformity to lesion target with a rice phantom housing a soap as target; image resolution with a diagnostic phantom; and exposure validation with a Radcal ion chamber. To optimize XVIcbs, rotation flexmap on coincidency between gantry rotational axis and that of XVI cone beam scan was investigated. Theoretic correlation to image quality of XVIcbs rotational axis stability was elaborately studied. Comprehensive QA of IGRT using XVIcbs has initially been explored and then implemented on our general IMRT treatments, and on special IMRT radiotherapies such as head and neck (H and N), stereotactic radiation therapy (SRT), stereotactic radiosurgery (SRS), and stereotactic body radiotherapy (SBRT). Fifteen examples of prostate setup accounted for 350 IGRT cone beam system were analyzed. IGRT accuracy results were in agreement {+-} 1 mm. Flexmap 0.25 mm met the manufacturer's specification. Films confirmed isodose coincidence with target (soap) via XVIcbs, otherwise not. Superficial doses were measured from 7.2-2.5 cGy for anatomic diameters 15-33 cm, respectively. Image quality was susceptible to rotational stability or patient movement. IGRT using XVIcbs on general IMRT treatments such as prostate, SRT, SRS, and SBRT for setup accuracy were verified; and subsequently coordinate shifts corrections were recorded. The 350 prostate IGRT coordinate shifts modeled to Gaussian distributions show central peaks deviated off the isocenter by 0.6 {+-} 3.0 mm, 0.5 {+-} 4.5 mm in the X(RL)- and Z(SI)-coordinates, respectively; and 2.0 {+-} 3.0 mm in the Y(AP)-coordinate as a result of belly and bladder capacity variations. Sixty-eight percent of confidence was

  2. [Modalities of breast cancer irradiation in 2016: Aims and indications of intensity modulated radiation therapy].

    PubMed

    Bourgier, C; Fenoglietto, P; Lemanski, C; Ducteil, A; Charissoux, M; Draghici, R; Azria, D

    2016-10-01

    Irradiation techniques for breast cancer (arctherapy, tomotherapy) are evolving and intensity-modulated radiation therapy is being increasingly considered for the management of these tumours. Here, we propose a review of intensity-modulated radiation therapy planning issues, clinical toxicities and indications for breast cancer.

  3. Intensity-modulated radiotherapy for neoadjuvant treatment of gastric cancer

    SciTech Connect

    Knab, Brian; Rash, Carla; Farrey, Karl; Jani, Ashesh B. . E-mail: jani@rover.uchicago.edu

    2006-01-01

    Radiation therapy plays an integral role in the treatment of gastric cancer in the postsurgery setting, the inoperable/palliative setting, and, as in the case of the current report, in the setting of neoadjuvant therapy prior to surgery. Typically, anterior-posterior/posterior-anterior (AP/PA) or 3-field techniques are used. In this report, we explore the use of intensity-modulated radiotherapy (IMRT) treatment in a patient whose care was transferred to our institution after 3-field radiotherapy (RT) was given to a dose of 30 Gy at an outside institution. If the 3-field plan were continued to 50 Gy, the volume of irradiated liver receiving greater than 30 Gy would have been unacceptably high. To deliver the final 20 Gy, an opposed parallel AP/PA plan and an IMRT plan were compared to the initial 3-field technique for coverage of the target volume as well as dose to the kidneys, liver, small bowel, and spinal cord. Comparison of the 3 treatment techniques to deliver the final 20 Gy revealed reduced median and maximum dose to the whole kidney with the IMRT plan. For this 20-Gy boost, the volume of irradiated liver was lower for both the IMRT plan and the AP/PA plan vs. the 3-field plan. Comparing the IMRT boost plan to the AP/PA boost-dose range (<10 Gy) in comparison to the AP/PA plan; however, the IMRT plan irradiated a smaller liver volume within the higher dose region (>10 Gy) in comparison to the AP/PA plan. The IMRT boost plan also irradiated a smaller volume of the small bowel compared to both the 3-field plan and the AP/PA plan, and also delivered lower dose to the spinal cord in comparison to the AP/PA plan. Comparison of the composite plans revealed reduced dose to the whole kidney using IMRT. The V20 for the whole kidney volume for the composite IMRT plan was 30% compared to approximately 60% for the composite AP/PA plan. Overall, the dose to the liver receiving greater than 30 Gy was lower for the composite IMRT plan and was well below acceptable limits

  4. Prioritized efficiency optimization for intensity modulated proton therapy.

    PubMed

    Müller, Birgit S; Wilkens, Jan J

    2016-12-07

    A high dosimetric quality and short treatment time are major goals in radiotherapy planning. Intensity modulated proton therapy (IMPT) plans obtain dose distributions of great conformity but often result in long delivery times which are typically not incorporated into the optimization process. We present an algorithm to optimize delivery efficiency of IMPT plans while maintaining plan quality, and study the potential trade-offs of these interdependent objectives. The algorithm is based on prioritized optimization, a stepwise approach to implemented objectives. First the quality of the plan is optimized. The second step of the prioritized efficiency optimization (PrEfOpt) routine offers four alternatives for reducing delivery time: minimization of the total spot weight sum (A), maximization of the lowest spot intensity of each energy layer (B), elimination of low-weighted spots (C) or energy layers (D). The trade-off between dosimetric quality (step I) and treatment time (step II) is controlled during the optimization by option-dependent parameters. PrEfOpt was applied to a clinical patient case, and plans for different trade-offs were calculated. Delivery times were simulated for two virtual facilities with constant and variable proton current, i.e. independent and dependent on the optimized spot weight distributions. Delivery times decreased without major degradation of plan quality; absolute time reductions varied with the applied method and facility type. Minimizing the total spot weight sum (A) reduced times by 28% for a similar plan quality at a constant current (changes of minimum dose in the target  <1%). For a variable proton current, eliminating low-weighted spots (C) led to remarkably faster delivery (16%). The implementation of an efficiency-optimization step into the optimization process can yield reduced delivery times with similar plan qualities. A potential clinical application of PrEfOpt is the generation of multiple plans with different trade

  5. Prioritized efficiency optimization for intensity modulated proton therapy

    NASA Astrophysics Data System (ADS)

    Müller, Birgit S.; Wilkens, Jan J.

    2016-12-01

    A high dosimetric quality and short treatment time are major goals in radiotherapy planning. Intensity modulated proton therapy (IMPT) plans obtain dose distributions of great conformity but often result in long delivery times which are typically not incorporated into the optimization process. We present an algorithm to optimize delivery efficiency of IMPT plans while maintaining plan quality, and study the potential trade-offs of these interdependent objectives. The algorithm is based on prioritized optimization, a stepwise approach to implemented objectives. First the quality of the plan is optimized. The second step of the prioritized efficiency optimization (PrEfOpt) routine offers four alternatives for reducing delivery time: minimization of the total spot weight sum (A), maximization of the lowest spot intensity of each energy layer (B), elimination of low-weighted spots (C) or energy layers (D). The trade-off between dosimetric quality (step I) and treatment time (step II) is controlled during the optimization by option-dependent parameters. PrEfOpt was applied to a clinical patient case, and plans for different trade-offs were calculated. Delivery times were simulated for two virtual facilities with constant and variable proton current, i.e. independent and dependent on the optimized spot weight distributions. Delivery times decreased without major degradation of plan quality; absolute time reductions varied with the applied method and facility type. Minimizing the total spot weight sum (A) reduced times by 28% for a similar plan quality at a constant current (changes of minimum dose in the target  <1%). For a variable proton current, eliminating low-weighted spots (C) led to remarkably faster delivery (16%). The implementation of an efficiency-optimization step into the optimization process can yield reduced delivery times with similar plan qualities. A potential clinical application of PrEfOpt is the generation of multiple plans with different trade

  6. Stereotactic radiosurgery - discharge

    MedlinePlus

    ... pg=stereotactic . Accessed July 22, 2016. Read More Acoustic neuroma Brain tumor - primary - adults Cerebral arteriovenous malformation ... A.M. Editorial team. Related MedlinePlus Health Topics Acoustic Neuroma Arteriovenous Malformations Brain Tumors Childhood Brain Tumors ...

  7. Assessment of Planning Target Volume Margins for Intensity-Modulated Radiotherapy of the Prostate Gland: Role of Daily Inter- and Intrafraction Motion

    SciTech Connect

    Tanyi, James A.; He, Tongming; Summers, Paige A.; Mburu, Ruth G.; Kato, Catherine M.; Rhodes, Stephen M.; Hung, Arthur Y.; Fuss, Martin

    2010-12-01

    Purpose: To determine planning target volume margins for prostate intensity-modulated radiotherapy based on inter- and intrafraction motion using four daily localization techniques: three-point skin mark alignment, volumetric imaging with bony landmark registration, volumetric imaging with implanted fiducial marker registration, and implanted electromagnetic transponders (beacons) detection. Methods and Materials: Fourteen patients who underwent definitive intensity-modulated radiotherapy for prostate cancer formed the basis of this study. Each patient was implanted with three electromagnetic transponders and underwent a course of 39 treatment fractions. Daily localization was based on three-point skin mark alignment followed by transponder detection and patient repositioning. Transponder positioning was verified by volumetric imaging with cone-beam computed tomography of the pelvis. Relative motion between the prostate gland and bony anatomy was quantified by offline analyses of daily cone-beam computed tomography. Intratreatment organ motion was monitored continuously by the Calypso (registered) System for quantification of intrafraction setup error. Results: As expected, setup error (that is, inter- plus intrafraction motion, unless otherwise stated) was largest with skin mark alignment, requiring margins of 7.5 mm, 11.4 mm, and 16.3 mm, in the lateral (LR), longitudinal (SI), and vertical (AP) directions, respectively. Margin requirements accounting for intrafraction motion were smallest for transponder detection localization techniques, requiring margins of 1.4 mm (LR), 2.6 mm (SI), and 2.3 mm (AP). Bony anatomy alignment required 2.1 mm (LR), 9.4 mm (SI), and 10.5 mm (AP), whereas image-guided marker alignment required 2.8 mm (LR), 3.7 mm (SI), and 3.2 mm (AP). No marker migration was observed in the cohort. Conclusion: Clinically feasible, rapid, and reliable tools such as the electromagnetic transponder detection system for pretreatment target localization

  8. [Intensity-modulated radiotherapy in head and neck cancer: ethics and methodology].

    PubMed

    Lapeyre, M; Biau, J; Miroir, J; Servagi-Vernat, S; Giraud, P

    2014-10-01

    Numerous studies have shown that intensity-modulated radiation therapy is the standard technique for the radiation treatment of head and neck cancers. Intensity-modulated radiation therapy reduces side effects (xerostomia, dysphagia, fibrosis, etc.) and improves the results for cancer localizations with highly complex shapes such as the cavum or nasal cavity. Intensity-modulated radiation therapy is also a costly technique that necessitates a numerous staff, highly trained, with regular practice. If this technique cannot be available (understaffing, overwork, etc.) the choice between entrusting the patient to a colleague and treating the patient with a less sophisticated technique such as 3-dimensional conformal radiation therapy depends on different objective and ethical criteria.

  9. Optical Tracking Technology in Stereotactic Radiation Therapy

    SciTech Connect

    Wagner, Thomas H. . E-mail: thomas.wagner@orhs.org; Meeks, Sanford L.; Bova, Frank J.; Friedman, William A.; Willoughby, Twyla R.; Kupelian, Patrick A.; Tome, Wolfgang

    2007-07-01

    The last decade has seen the introduction of advanced technologies that have enabled much more precise application of therapeutic radiation. These relatively new technologies include multileaf collimators, 3-dimensional conformal radiotherapy planning, and intensity modulated radiotherapy in radiotherapy. Therapeutic dose distributions have become more conformal to volumes of disease, sometimes utilizing sharp dose gradients to deliver high doses to target volumes while sparing nearby radiosensitive structures. Thus, accurate patient positioning has become even more important, so that the treatment delivered to the patient matches the virtual treatment plan in the computer treatment planning system. Optical and image-guided radiation therapy systems offer the potential to improve the precision of patient treatment by providing a more robust fiducial system than is typically used in conventional radiotherapy. The ability to accurately position internal targets relative to the linac isocenter and to provide real-time patient tracking theoretically enables significant reductions in the amount of normal tissue irradiated. This report reviews the concepts, technology, and clinical applications of optical tracking systems currently in use for stereotactic radiation therapy. Applications of radiotherapy optical tracking technology to respiratory gating and the monitoring of implanted fiducial markers are also discussed.

  10. Optimization of Breast Cancer Treatment by Dynamic Intensity Modulated Electron Radiotherapy

    DTIC Science & Technology

    2006-04-01

    AD_________________ Award Number: DAMD17-01-1-0435 TITLE: Optimization of Breast Cancer Treatment by...Optimization of Breast Cancer Treatment by Dynamic Intensity Modulated Electron Radiotherapy 5b. GRANT NUMBER DAMD17-01-1-0435 5c. PROGRAM ELEMENT

  11. Image-Guided Stereotactic Spine Radiosurgery on a Conventional Linear Accelerator

    SciTech Connect

    Wang Jiazhu Rice, Roger; Mundt, Arno; Sandhu, Ajay; Murphy, Kevin

    2010-04-01

    Stereotactic radiosurgery for spinal metastasis consists of a high radiation dose delivered to the tumor in 1 to 5 fractions. Due to the high radiation dose in a single or fewer treatments, the precision of tumor localization and dose delivery is of great concern. Many groups have published their experiences of spinal radiosurgery with the use of CyberKnife System (Accuray Inc.). In this study, we report in detail our approach to stereotactic spine radiosurgery (SSRS) using a conventional linear accelerator (Varian Trilogy), utilizing the features of kilovolt on-board imaging (kV-OBI) and cone beam computed tomography (CBCT) for image guidance. We present our experience in various aspects of the SSRS procedure, including patient simulation and immobilization, intensity-modulated radiation treatment (IMRT) planning and beam selection, portal dosimetry for patient planning quality assurance (QA), and the use of image guidance in tumor localization prior to and during treatment delivery.

  12. Image-guided stereotactic spine radiosurgery on a conventional linear accelerator.

    PubMed

    Wang, Jia-Zhu; Rice, Roger; Mundt, Arno; Sandhu, Ajay; Murphy, Kevin

    2010-01-01

    Stereotactic radiosurgery for spinal metastasis consists of a high radiation dose delivered to the tumor in 1 to 5 fractions. Due to the high radiation dose in a single or fewer treatments, the precision of tumor localization and dose delivery is of great concern. Many groups have published their experiences of spinal radiosurgery with the use of CyberKnife System (Accuray Inc.). In this study, we report in detail our approach to stereotactic spine radiosurgery (SSRS) using a conventional linear accelerator (Varian Trilogy), utilizing the features of kilovolt on-board imaging (kV-OBI) and cone beam computed tomography (CBCT) for image guidance. We present our experience in various aspects of the SSRS procedure, including patient simulation and immobilization, intensity-modulated radiation treatment (IMRT) planning and beam selection, portal dosimetry for patient planning quality assurance (QA), and the use of image guidance in tumor localization prior to and during treatment delivery.

  13. Stereotactic surgery for eating disorders

    PubMed Central

    Sun, Bomin; Liu, Wei

    2013-01-01

    Eating disorders (EDs) are a group of severely impaired eating behaviors, which include three subgroups: anorexia nervosa (AN), bulimia nervosa (BN), and ED not otherwise specified (EDNOS). The precise mechanism of EDs is still unclear and the disorders cause remarkable agony for the patients and their families. Although there are many available treatment methods for EDs today, such as family therapy, cognitive behavioral therapy, medication, psychotherapy, and so on, almost half of the patients are refractory to all current medical treatment and never fully recover. For treatment-refractory EDs, stereotactic surgery may be an alternative therapy. This review discusses the history of stereotactic surgery, the modern procedures, and the mostly used targets of stereotactic surgery in EDs. In spite of the limited application of stereotactic surgery in ED nowadays, stereotactic lesion and deep brain stimulation (DBS) are promising treatments with the development of modern functional imaging techniques and the increasing understanding of its mechanism in the future. PMID:23682343

  14. Stereotactic surgery for eating disorders.

    PubMed

    Sun, Bomin; Liu, Wei

    2013-01-01

    EATING DISORDERS (EDS) ARE A GROUP OF SEVERELY IMPAIRED EATING BEHAVIORS, WHICH INCLUDE THREE SUBGROUPS: anorexia nervosa (AN), bulimia nervosa (BN), and ED not otherwise specified (EDNOS). The precise mechanism of EDs is still unclear and the disorders cause remarkable agony for the patients and their families. Although there are many available treatment methods for EDs today, such as family therapy, cognitive behavioral therapy, medication, psychotherapy, and so on, almost half of the patients are refractory to all current medical treatment and never fully recover. For treatment-refractory EDs, stereotactic surgery may be an alternative therapy. This review discusses the history of stereotactic surgery, the modern procedures, and the mostly used targets of stereotactic surgery in EDs. In spite of the limited application of stereotactic surgery in ED nowadays, stereotactic lesion and deep brain stimulation (DBS) are promising treatments with the development of modern functional imaging techniques and the increasing understanding of its mechanism in the future.

  15. MO-F-CAMPUS-T-02: Optimizing Orientations of Hundreds of Intensity-Modulated Beams to Treat Multiple Brain Targets

    SciTech Connect

    Ma, L; Dong, P; Larson, D; Keeling, V; Hossain, S; Ahmad, S; Sahgal, A

    2015-06-15

    Purpose: To investigate a new modulated beam orientation optimization (MBOO) approach maximizing treatment planning quality for the state-of-the-art flattening filter free (FFF) beam that has enabled rapid treatments of multiple brain targets. Methods: MBOO selects and optimizes a large number of intensity-modulated beams (400 or more) from all accessible beam angles surrounding a patient’s skull. The optimization algorithm was implemented on a standalone system that interfaced with the 3D Dicom images and structure sets. A standard published data set that consisted of 1 to 12 metastatic brain tumor combinations was selected for MBOO planning. The planning results from various coplanar and non-coplanar configurations via MBOO were then compared with the results obtained from a clinical volume modulated arc therapy (VMAT) delivery system (Truebeam RapidArc, Varian Oncology). Results: When planning a few number of targets (n<4), MBOO produced results equivalent to non-coplanar multi-arc VMAT planning in terms of target volume coverage and normal tissue sparing. For example, the 12-Gy and 4-Gy normal brain volumes for the 3-target plans differed by less than 1 mL ( 3.0 mLvs 3.8 mL; and 35.2 mL vs 36.3 mL, respectively) for MBOO versus VMAT. However, when planning a larger number of targets (n≥4), MBOO significantly reduced the dose to the normal brain as compared to VMAT, though the target volume coverage was equivalent. For example, the 12-Gy and 4-Gy normal brain volumes for the 12-target plans were 10.8 mL vs. 18.0 mL and 217.9 mL vs. 390.0 mL, respectively for the non-coplanar MBOO versus the non-coplanar VMAT treatment plans, yielding a reduction in volume of more than 60% for the case. Conclusion: MBOO is a unique approach for maximizing normal tissue sparing when treating a large number (n≥4) of brain tumors with FFF linear accelerators. Dr Ma and Dr Sahgal are currently on the board of international society of stereotactic radiosurgery. Dr Sahgal has

  16. A comparison of intensity modulated x-ray therapy to intensity modulated proton therapy for the delivery of non-uniform dose distributions

    NASA Astrophysics Data System (ADS)

    Flynn, Ryan

    2007-12-01

    The distribution of biological characteristics such as clonogen density, proliferation, and hypoxia throughout tumors is generally non-uniform, therefore it follows that the optimal dose prescriptions should also be non-uniform and tumor-specific. Advances in intensity modulated x-ray therapy (IMXT) technology have made the delivery of custom-made non-uniform dose distributions possible in practice. Intensity modulated proton therapy (IMPT) has the potential to deliver non-uniform dose distributions as well, while significantly reducing normal tissue and organ at risk dose relative to IMXT. In this work, a specialized treatment planning system was developed for the purpose of optimizing and comparing biologically based IMXT and IMPT plans. The IMXT systems of step-and-shoot (IMXT-SAS) and helical tomotherapy (IMXT-HT) and the IMPT systems of intensity modulated spot scanning (IMPT-SS) and distal gradient tracking (IMPT-DGT), were simulated. A thorough phantom study was conducted in which several subvolumes, which were contained within a base tumor region, were boosted or avoided with IMXT and IMPT. Different boosting situations were simulated by varying the size, proximity, and the doses prescribed to the subvolumes, and the size of the phantom. IMXT and IMPT were also compared for a whole brain radiation therapy (WBRT) case, in which a brain metastasis was simultaneously boosted and the hippocampus was avoided. Finally, IMXT and IMPT dose distributions were compared for the case of non-uniform dose prescription in a head and neck cancer patient that was based on PET imaging with the Cu(II)-diacetyl-bis(N4-methylthiosemicarbazone (Cu-ATSM) hypoxia marker. The non-uniform dose distributions within the tumor region were comparable for IMXT and IMPT. IMPT, however, was capable of delivering the same non-uniform dose distributions within a tumor using a 180° arc as for a full 360° rotation, which resulted in the reduction of normal tissue integral dose by a factor of

  17. Filter Bank Multicarrier (FBMC) for long-reach intensity modulated optical access networks

    NASA Astrophysics Data System (ADS)

    Saljoghei, Arsalan; Gutiérrez, Fernando A.; Perry, Philip; Barry, Liam P.

    2017-04-01

    Filter Bank Multi Carrier (FBMC) is a modulation scheme which has recently attracted significant interest in both wireless and optical communications. The interest in optical communications arises due to FBMC's capability to operate without a Cyclic Prefix (CP) and its high resilience to synchronisation errors. However, the operation of FBMC in optical access networks has not been extensively studied either in downstream or upstream. In this work we use experimental work to investigate the operation of FBMC in intensity modulated Passive Optical Networks (PONs) employing direct detection in conjunction with both direct and external modulation schemes. The data rates and propagation lengths employed here vary from 8.4 to 14.8 Gb/s and 0-75 km. The results suggest that by using FBMC it is possible to accomplish CP-Less transmission up to 75 km of SSMF in passive links using cost effective intensity modulation and detection schemes.

  18. Scintillation effect on intensity modulated laser communication systems—a laboratory demonstration

    NASA Astrophysics Data System (ADS)

    Popoola, W. O.; Ghassemlooy, Z.; Lee, C. G.; Boucouvalas, A. C.

    2010-06-01

    This paper shows the impact of atmospheric turbulence-induced fading on the symbol decision position in the on-off keying (OOK) and the binary phase shift keying (BPSK) subcarrier intensity modulated (SIM) laser communication link. Weak turbulence is simulated in the laboratory using a chamber equipped with heating elements and fans. We have shown that in atmospheric turbulence, it is advantageous to employ modulation schemes such as pulse time and subcarrier intensity modulations that do not directly impress data on the optical irradiance as is the case with the OOK. For the OOK-modulated laser communication system, atmospheric turbulence imposes complexity on the symbol decision subsystem and by extension places a limit on the achievable bit error rate (BER) performance.

  19. Stereotactic radiotherapy for malignancies involving the trigeminal and facial nerves.

    PubMed

    Cuneo, K C; Zagar, T M; Brizel, D M; Yoo, D S; Hoang, J K; Chang, Z; Wang, Z; Yin, F F; Das, S K; Green, S; Ready, N; Bhatti, M T; Kaylie, D M; Becker, A; Sampson, J H; Kirkpatrick, J P

    2012-06-01

    Involvement of a cranial nerve caries a poor prognosis for many malignancies. Recurrent or residual disease in the trigeminal or facial nerve after primary therapy poses a challenge due to the location of the nerve in the skull base, the proximity to the brain, brainstem, cavernous sinus, and optic apparatus and the resulting complex geometry. Surgical resection caries a high risk of morbidity and is often not an option for these patients. Stereotactic radiosurgery and radiotherapy are potential treatment options for patients with cancer involving the trigeminal or facial nerve. These techniques can deliver high doses of radiation to complex volumes while sparing adjacent critical structures. In the current study, seven cases of cancer involving the trigeminal or facial nerve are presented. These patients had unresectable recurrent or residual disease after definitive local therapy. Each patient was treated with stereotactic radiation therapy using a linear accelerator based system. A multidisciplinary approach including neuroradiology and surgical oncology was used to delineate target volumes. Treatment was well tolerated with no acute grade 3 or higher toxicity. One patient who was reirradiated experienced cerebral radionecrosis with mild symptoms. Four of the seven patients treated had no evidence of disease after a median follow up of 12 months (range 2-24 months). A dosimetric analysis was performed to compare intensity modulated fractionated stereotactic radiation therapy (IM-FSRT) to a 3D conformal technique. The dose to 90% (D90) of the brainstem was lower with the IM-FSRT plan by a mean of 13.5 Gy. The D95 to the ipsilateral optic nerve was also reduced with IM-FSRT by 12.2 Gy and the D95 for the optic chiasm was lower with FSRT by 16.3 Gy. Treatment of malignancies involving a cranial nerve requires a multidisciplinary approach. Use of an IM-FSRT technique with a micro-multileaf collimator resulted in a lower dose to the brainstem, optic nerves and chiasm

  20. Simplified polarization demultiplexing based on Stokes vector analysis for intensity-modulation direct-detection systems

    NASA Astrophysics Data System (ADS)

    Zhou, Xinyu; Yan, Lianshan; Chen, Zhiyu; Yi, Anlin; Pan, Yan; Jiang, Lin; Pan, Wei; Luo, Bin

    2016-10-01

    A simple and effective polarization demultiplexing method is proposed based on the improved Stokes vector analysis and digital signal processor algorithm for the intensity-modulation direct-detection optical communication systems. Such a scheme could significantly simplify optical receivers with low system cost. The experimental results demonstrate the feasibility of our proposed method and show that only 1- and 1.7-dB power penalties are measured for 10- and 25-km transmissions compared to back-to-back case.

  1. Coherent BOTDA sensor with intensity modulated local light and IQ demodulation.

    PubMed

    Li, Zonglei; Yan, Lianshan; Shao, Liyang; Pan, Wei; Luo, Bin

    2015-06-15

    Coherent Brillouin optical time domain analysis (BOTDA) sensing system with intensity modulated local (IML) light and fast IQ demodulation is proposed and demonstrated. IML light instead of phase modulated local (PML) light is utilized to reduce the coherent and multiple sidebands induced noises. A spatial resolution of 3-m and ± 1.8°C temperature accuracy at the far end of the fiber are obtained over 40-km sensing distance.

  2. Hybrid intensity-modulation-to-phase-remodulation optical wavelength reuse transport system

    NASA Astrophysics Data System (ADS)

    Chang, Ching-Hung; Tseng, Meng-Chun; Tseng, Cheng-Han

    2015-12-01

    A hybrid intensity-modulation (IM)-to-phase-remodulation optical wavelength reuse transport system is proposed and demonstrated experimentally. Based on the transport system, an optical carrier can be intensity-modulated with an orthogonal frequency-division multiplexing (OFDM) signal and then phase-remodulated with a radio frequency (RF) signal prior to communicating its destination through a span of single mode fiber. The OFDM signal at the receiver end can be directly detected using a photodetector (PD), and the phase-modulated RF signal can be detected by another PD after being converted back to intensity-modulation format by a semiconductor laser. In this study, the working window of the semiconductor laser-composed phase-modulation-format-to-IM-format converter is not fixed. The converter can be flexibly adjusted to align with the wavelength of the employed optical carrier. Experimental results prove that both OFDM and RF signals can be clearly detected with an error-free transmission. Evident interference is not found between both signals at the receiver end.

  3. Possibilities for intensity-modulated brachytherapy: technical limitations on the use of non-isotropic sources

    NASA Astrophysics Data System (ADS)

    Ebert, M. A.

    2002-07-01

    An investigation was undertaken into possible dose conformity advantages and technical limitations of utilizing radially asymmetric internally applied radiation sources for intensity-modulated brachytherapy (IMBT). A feasible form of a source for IMBT would be a linear source with a high-intensity angular region, with some fractional transmission through the remainder of the source, which inhibits the resolution achievable in intensity modulation. Indexed rotation of the source about its axis would provide radial intensity modulation, which could compensate for variations in the spatial relationship between the source position and location of the target edge. Two treatment situations were simulated - one two-dimensional and one three-dimensional - both utilizing a single source (single catheter). The optimal intensity distribution of the source was determined by simulated annealing optimization using a conformality-based objective. The parameters in the optimization included the angular size of the source high-intensity region, and the fractional transmission through the low-intensity part of the source. Results indicate that limitations in source design suggest an optimal high-intensity resolution of approximately π/4 to π/8. The advantages of IMBT are rapidly reduced when fractional transmission through the low-intensity side of the source is increased.

  4. Value of Intensity-Modulated Radiotherapy in Stage IV Head-and-Neck Squamous Cell Carcinoma

    SciTech Connect

    Dirix, Piet; Nuyts, Sandra

    2010-12-01

    Purpose: To review outcome and toxicity of Stage IVa and IVb head-and-neck squamous cell carcinoma patients treated with concomitant chemotherapy and intensity-modulated radiotherapy (IMRT) according to a hybrid fractionation schedule. Methods and Materials: Between 2006 and 2008, 42 patients with Stage IV head-and-neck squamous cell carcinoma were irradiated according to a hybrid fractionation schedule consisting of 20 fractions of 2 Gy (once daily), followed by 20 fractions of 1.6 Gy (twice daily), to a total dose of 72 Gy. Chemotherapy (cisplatinum, 100mg/m{sup 2}) was administered at the start of Weeks 1 and 4. Treatment outcome and toxicity were retrospectively compared with a previous patient group (n = 55), treated according to the same schedule, but without intensity modulation. Results: Locoregional control (LRC) and overall survival were 81% and 56% after 2 years, respectively. In comparison with the previous cohort, no significant differences were observed regarding either LRC (66%, p = 0.38) or overall survival (73%, p = 0.29). No Grade 4 or 5 toxicity was reported in the IMRT group, either acute or chronic. The use of IMRT significantly reduced the incidence of late Grade 2 or 3 xerostomia (52.9% vs. 90.2%, p < 0.001). No difference was observed regarding late Grade 2 or 3 dysphagia (p = 0.66). Conclusions: Intensity-modulated chemoradiotherapy does not compromise LRC and significantly reduces late toxicity, especially regarding xerostomia.

  5. Stereotactic Body Radiation Therapy in Spinal Metastases

    SciTech Connect

    Ahmed, Kamran A.; Stauder, Michael C.; Miller, Robert C.; Bauer, Heather J.; Rose, Peter S.; Olivier, Kenneth R.; Brown, Paul D.; Brinkmann, Debra H.; Laack, Nadia N.

    2012-04-01

    Purpose: Based on reports of safety and efficacy, stereotactic body radiotherapy (SBRT) for treatment of malignant spinal tumors was initiated at our institution. We report prospective results of this population at Mayo Clinic. Materials and Methods: Between April 2008 and December 2010, 85 lesions in 66 patients were treated with SBRT for spinal metastases. Twenty-two lesions (25.8%) were treated for recurrence after prior radiotherapy (RT). The mean age of patients was 56.8 {+-} 13.4 years. Patients were treated to a median dose of 24 Gy (range, 10-40 Gy) in a median of three fractions (range, 1-5). Radiation was delivered with intensity-modulated radiotherapy (IMRT) and prescribed to cover 80% of the planning target volume (PTV) with organs at risk such as the spinal cord taking priority over PTV coverage. Results: Tumor sites included 48, 22, 12, and 3 in the thoracic, lumbar, cervical, and sacral spine, respectively. The mean actuarial survival at 12 months was 52.2%. A total of 7 patients had both local and marginal failure, 1 patient experienced marginal but not local failure, and 1 patient had local failure only. Actuarial local control at 1 year was 83.3% and 91.2% in patients with and without prior RT. The median dose delivered to patients who experienced local/marginal failure was 24 Gy (range, 18-30 Gy) in a median of three fractions (range, 1-5). No cases of Grade 4 toxicity were reported. In 1 of 2 patients experiencing Grade 3 toxicity, SBRT was given after previous radiation. Conclusion: The results indicate SBRT to be an effective measure to achieve local control in spinal metastases. Toxicity of treatment was rare, including those previously irradiated. Our results appear comparable to previous reports analyzing spine SBRT. Further research is needed to determine optimum dose and fractionation to further improve local control and prevent toxicity.

  6. [Stereotactic radiotherapy for pelvic tumors].

    PubMed

    Mazeron, R; Fumagalli, I

    2014-01-01

    Extracranial stereotactic radiotherapy is booming. The development and spread of dedicated accelerators coupled with efficient methods of repositioning can now allow treatments of mobile lesions with moderate size, with high doses per fraction. Intuitively, except for the prostate, pelvic tumours, often requiring irradiation of regional lymph node drainage, lend little to this type of treatment. However, in some difficult circumstances, such as boost or re-radiation, stereotactic irradiation condition is promising and clinical experiences have already been reported.

  7. Dosimetric Comparison of Three-Dimensional Conformal Proton Radiotherapy, Intensity-Modulated Proton Therapy, and Intensity-Modulated Radiotherapy for Treatment of Pediatric Craniopharyngiomas

    SciTech Connect

    Boehling, Nicholas S.; Grosshans, David R.; Bluett, Jaques B.; Palmer, Matthew T.; Song, Xiaofei; Amos, Richard A.; Sahoo, Narayan; Meyer, Jeffrey J.; Mahajan, Anita; Woo, Shiao Y.

    2012-02-01

    Purpose: Cranial irradiation in pediatric patients is associated with serious long-term adverse effects. We sought to determine whether both three-dimensional conformal proton radiotherapy (3D-PRT) and intensity-modulated proton therapy (IMPT) compared with intensity-modulated radiotherapy (IMRT) decrease integral dose to brain areas known to harbor neuronal stem cells, major blood vessels, and other normal brain structures for pediatric patients with craniopharyngiomas. Methods and Materials: IMRT, forward planned, passive scattering proton, and IMPT plans were generated and optimized for 10 pediatric patients. The dose was 50.4 Gy (or cobalt Gy equivalent) delivered in 28 fractions with the requirement for planning target volume (PTV) coverage of 95% or better. Integral dose data were calculated from differential dose-volume histograms. Results: The PTV target coverage was adequate for all modalities. IMRT and IMPT yielded the most conformal plans in comparison to 3D-PRT. Compared with IMRT, 3D-PRT and IMPT plans had a relative reduction of integral dose to the hippocampus (3D-PRT, 20.4; IMPT, 51.3%{sup Asterisk-Operator }), dentate gyrus (27.3, 75.0%{sup Asterisk-Operator }), and subventricular zone (4.5, 57.8%{sup Asterisk-Operator }). Vascular organs at risk also had reduced integral dose with the use of proton therapy (anterior cerebral arteries, 33.3{sup Asterisk-Operator }, 100.0%{sup Asterisk-Operator }; middle cerebral arteries, 25.9%{sup Asterisk-Operator }, 100%{sup Asterisk-Operator }; anterior communicating arteries, 30.8{sup Asterisk-Operator }, 41.7%{sup Asterisk-Operator }; and carotid arteries, 51.5{sup Asterisk-Operator }, 77.6{sup Asterisk-Operator }). Relative reduction of integral dose to the infratentorial brain (190.7{sup Asterisk-Operator }, 109.7%{sup Asterisk-Operator }), supratentorial brain without PTV (9.6, 26.8%{sup Asterisk-Operator }), brainstem (45.6, 22.4%{sup Asterisk-Operator }), and whole brain without PTV (19.4{sup Asterisk

  8. SU-E-T-503: Intensity Modulated Proton Therapy (IMPT) Versus Intensity Modulated X-Ray Therapy (IMRT) for Patient with Hepatocellular Carcinoma: A Dosimetric Comparison

    SciTech Connect

    Singh, H; Zhao, L; Prabhu, K; Rana, S; Zheng, Y

    2015-06-15

    Purpose This study compares the dosimetric parameters in treatment of unresectable hepatocellular carcinoma between intensity modulated proton therapy (IMPT) and intensity modulated x-ray radiation therapy (IMRT). Methods and Materials: We studied four patients treated at our institution. All patients were simulated supine with 4D-CT using a GE light speed simulator with a maximum slice thickness of 3mm. The average CT and an internal target volume to account for respiration motion were used for planning. Both IMRT and IMPT plans were created using Elekta’s CMSXiO treatment planning system (TPS). The prescription dose was 58.05 CGE in 15 fractions. The IMRT plans had five beams with combination of co-planar and non-co-planar. The IMPT plans had 2 to 3 beams. Dose comparison was performed based on the averaged results of the four patients. Results The mean dose and V95% to PTV were 58.24CGE, 98.57% for IMPT, versus 57.34CGE and 96.68% for IMRT, respectively. The V10, V20, V30 and mean dose of the normal liver for IMPT were 23.10%, 18.61%, 13.75% and 9.78 CGE; and 47.19%, 37.55%, 22.73% and 17.12CGE for IMRT. The spinal cord didn’t receive any dose in IMPT technique, but received a maximum of 18.77CGE for IMRT. The IMPT gave lower maximum dose to the stomach as compared to IMRT (19.26 vs 26.35CGE). V14 for left and right kidney was 0% and 2.32% for IMPT and 3.89% and 29.54% for IMRT. The mean dose, V35, V40 and V45 for small bowl were similar in both techniques, 0.74CGE, 6.27cc, 4.85cc and 3.53 cc for IMPT, 3.47CGE, 9.73cc, 7.61cc 5.35cc for IMRT. Conclusion Based on this study, IMPT plans gave less dose to the critical structures such as normal liver, kidney, stomach and spinal cord as compared to IMRT plans, potentially leading to less toxicity and providing better quality of life for patients.

  9. Bridging the gap between IMRT and VMAT: Dense angularly sampled and sparse intensity modulated radiation therapy

    SciTech Connect

    Li, Ruijiang; Xing, Lei

    2011-09-15

    Purpose: To propose an alternative radiation therapy (RT) planning and delivery scheme with optimal angular beam sampling and intrabeam modulation for improved dose distribution while maintaining high delivery efficiency. Methods: In the proposed approach, coined as dense angularly sampled and sparse intensity modulated RT (DASSIM-RT), a large number of beam angles are used to increase the angular sampling, leading to potentially more conformal dose distributions as compared to conventional IMRT. At the same time, intensity modulation of the incident beams is simplified to eliminate the dispensable segments, compensating the increase in delivery time caused by the increased number of beams and facilitating the plan delivery. In a sense, the proposed approach shifts and transforms, in an optimal fashion, some of the beam segments in conventional IMRT to the added beams. For newly available digital accelerators, the DASSIM-RT delivery can be made very efficient by concatenating the beams so that they can be delivered sequentially without operator's intervention. Different from VMAT, the level of intensity modulation in DASSIS-RT is field specific and optimized to meet the need of each beam direction. Three clinical cases (a head and neck (HN) case, a pancreas case, and a lung case) are used to evaluate the proposed RT scheme. DASSIM-RT, VMAT, and conventional IMRT plans are compared quantitatively in terms of the conformality index (CI) and delivery efficiency. Results: Plan quality improves generally with the number and intensity modulation of the incident beams. For a fixed number of beams or fixed level of intensity modulation, the improvement saturates after the intensity modulation or number of beams reaches to a certain level. An interplay between the two variables is observed and the saturation point depends on the values of both variables. For all the cases studied here, the CI of DASSIM-RT with 15 beams and 5 intensity levels (0.90, 0.79, and 0.84 for the HN

  10. Optimization of intensity-modulated very high energy (50-250 MeV) electron therapy

    NASA Astrophysics Data System (ADS)

    Yeboah, C.; Sandison, G. A.; Moskvin, V.

    2002-04-01

    This work evaluates the potential of very high energy (50-250 MeV) electron beams for dose conformation and identifies those variables that influence optimized dose distributions for this modality. Intensity-modulated plans for a prostate cancer model were optimized as a function of the importance factors, beam energy and number of energy bins, number of beams, and the beam orientations. A trial-and-error-derived constellation of importance factors for target and sensitive structures to achieve good conformal dose distributions was 500, 50, 10 and 1 for the target, rectum, bladder and normal tissues respectively. Electron energies greater than 100 MeV were found to be desirable for intensity-modulated very high energy electron therapy (VHEET) of prostate cancer. Plans generated for lower energy beams had relatively poor conformal dose distributions about the target region and delivered high doses to sensitive structures. Fixed angle beam treatments utilizing a large number of fields in the range 9-21 provided acceptable plans. Using more than 21 beams at fixed gantry angles had an insignificant effect on target coverage, but resulted in an increased dose to sensitive structures and an increased normal tissue integral dose. Minor improvements in VHEET plans utilizing a `small' number (=<9) of beams may be achieved if, in addition to intensity modulation, energy modulation is implemented using a small number (=<3) of beam energies separated by 50 to 100 MeV. Rotation therapy provided better target dose homogeneity but unfortunately resulted in increased rectal dose, bladder dose and normal tissue integral dose relative to the 21-field fixed angle treatment plan. Modulation of the beam energy for rotation therapy had no beneficial consequences on the optimized dose distributions. Lastly, selection of beam orientations influenced the optimized treatment plan even when a large number of beams (approximately 15) were employed.

  11. Clinical Outcomes of Intensity-Modulated Pelvic Radiation Therapy for Carcinoma of the Cervix

    SciTech Connect

    Hasselle, Michael D.; Rose, Brent S.; Kochanski, Joel D.; Nath, Sameer K.; Bafana, Rounak; Yashar, Catheryn M.; Hasan, Yasmin; Roeske, John C.; Mundt, Arno J.; Mell, Loren K.

    2011-08-01

    Purpose: To evaluate disease outcomes and toxicity in cervical cancer patients treated with pelvic intensity-modulated radiation therapy (IMRT). Methods and Materials: We included all patients with Stage I-IVA cervical carcinoma treated with IMRT at three different institutions from 2000-2007. Patients treated with extended field or conventional techniques were excluded. Intensity-modulated radiation therapy plans were designed to deliver 45 Gy in 1.8-Gy daily fractions to the planning target volume while minimizing dose to the bowel, bladder, and rectum. Toxicity was graded according to the Radiation Therapy Oncology Group system. Overall survival and disease-free survival were estimated by use of the Kaplan-Meier method. Pelvic failure, distant failure, and late toxicity were estimated by use of cumulative incidence functions. Results: The study included 111 patients. Of these, 22 were treated with postoperative IMRT, 8 with IMRT followed by intracavitary brachytherapy and adjuvant hysterectomy, and 81 with IMRT followed by planned intracavitary brachytherapy. Of the patients, 63 had Stage I-IIA disease and 48 had Stage IIB-IVA disease. The median follow-up time was 27 months. The 3-year overall survival rate and the disease-free survival rate were 78% (95% confidence interval [CI], 68-88%) and 69% (95% CI, 59-81%), respectively. The 3-year pelvic failure rate and the distant failure rate were 14% (95% CI, 6-22%) and 17% (95% CI, 8-25%), respectively. Estimates of acute and late Grade 3 toxicity or higher were 2% (95% CI, 0-7%) and 7% (95% CI, 2-13%), respectively. Conclusions: Intensity-modulated radiation therapy is associated with low toxicity and favorable outcomes, supporting its safety and efficacy for cervical cancer. Prospective clinical trials are needed to evaluate the comparative efficacy of IMRT vs. conventional techniques.

  12. Direct experimental observation of periodic intensity modulation along a straight hollow-core optical waveguide

    SciTech Connect

    Pfeifer, T.; Downer, M. C.

    2007-05-15

    We report the direct observation of periodic intensity modulation of a laser pulse propagating in a hollow-core waveguide. A series of equally spaced plasma sparks along the gas-filled capillary is produced. This effect can be explained by the beating of different fiber modes, which are excited by controlling the size of the focal spot at the capillary entrance. As compared with an artificial modulated waveguide structure, our presented approach represents an easier and more flexible quasi-phase-matching scheme for nonlinear-optical frequency conversion.

  13. A Comparison of Helical Intensity-Modulated Radiotherapy, Intensity-Modulated Radiotherapy, and 3D-Conformal Radiation Therapy for Pancreatic Cancer

    SciTech Connect

    Poppe, Matthew M.; Narra, Venkat; Yue, Ning J.; Zhou Jinghao; Nelson, Carl; Jabbour, Salma K.

    2011-01-01

    We assessed dosimetric differences in pancreatic cancer radiotherapy via helical intensity-modulated radiotherapy (HIMRT), linac-based IMRT, and 3D-conformal radiation therapy (3D-CRT) with regard to successful plan acceptance and dose to critical organs. Dosimetric analysis was performed in 16 pancreatic cases that were planned to 54 Gy; both post-pancreaticoduodenectomy (n = 8) and unresected (n = 8) cases were compared. Without volume modification, plans met constraints 75% of the time with HIMRT and IMRT and 13% with 3D-CRT. There was no statistically significantly improvement with HIMRT over conventional IMRT in reducing liver V35, stomach V45, or bowel V45. HIMRT offers improved planning target volume (PTV) dose homogeneity compared with IMRT, averaging a lower maximum dose and higher volume receiving the prescription dose (D100). HIMRT showed an increased mean dose over IMRT to bowel and liver. Both HIMRT and IMRT offer a statistically significant improvement over 3D-CRT in lowering dose to liver, stomach, and bowel. The results were similar for both unresected and resected patients. In pancreatic cancer, HIMRT offers improved dose homogeneity over conventional IMRT and several significant benefits to 3D-CRT. Factors to consider before incorporating IMRT into pancreatic cancer therapy are respiratory motion, dose inhomogeneity, and mean dose.

  14. Comparison of intensity modulated radiotherapy (IMRT) with intensity modulated particle therapy (IMPT) using fixed beams or an ion gantry for the treatment of patients with skull base meningiomas

    PubMed Central

    2012-01-01

    Background To examine the potential improvement in treatment planning for patients with skull base meningioma using IMRT compared to carbon ion or proton beams with and without a gantry. Methods Five patients originally treated with photon IMRT were selected for the study. Ion beams were chosen using a horizontal beam or an ion gantry. Intensity controlled raster scanning and the intensity modulated particle therapy mode were used for plan optimization. The evaluation included analysis of dose-volume histograms of the target volumes and organs at risk. Results In comparison with carbon and proton beams only with horizontal beams, carbon ion treatment plans could spare the OARs more and concentrated on the target volumes more than proton and photon IMRT treatment plans. Using only a horizontal fixed beam, satisfactory plans could be achieved for skull base tumors. Conclusion The results of the case studies showed that using IMPT has the potential to overcome the lack of a gantry for skull base tumors. Carbon ion plans offered slightly better dose distributions than proton plans, but the differences were not clinically significant with established dose prescription concepts. PMID:22439607

  15. [Stereotactic radiosurgery and radiotherapy for brain metastases].

    PubMed

    Tanguy, Ronan; Métellus, Philippe; Mornex, Françoise; Mazeron, Jean-Jacques

    2013-01-01

    Brain metastases management is still controversial even though many trials are trying to define the respective roles of neurosurgery, whole-brain radiotherapy, single-dose stereotactic radiotherapy and fractionated stereotactic radiotherapy. In this article, we review data from trials that examine the role of radiosurgery and fractionated stereotactic radiotherapy in the management of brain metastases.

  16. Intensity-modulated radiotherapy for pituitary adenomas: The preliminary report of Cleveland Clinic experience

    SciTech Connect

    Mackley, Heath B. . E-mail: hmackley@alumni.upenn.edu; Reddy, Chandana A. M.S.; Lee, S.-Y.; Harnisch, Gayle A.; Mayberg, Marc R.; Hamrahian, Amir H.; Suh, John H.

    2007-01-01

    Purpose: Intensity-modulated radiotherapy (IMRT) is being increasingly used for the treatment of pituitary adenomas. However, there have been few published data on the short- and long-term outcomes of this treatment. This is the initial report of Cleveland Clinic's experience. Methods and Materials: Between February 1998 and December 2003, 34 patients with pituitary adenomas were treated with IMRT. A retrospective chart review was conducted for data analysis. Results: With a median follow-up of 42.5 months, the treatment has proven to be well tolerated, with performance status remaining stable in 90% of patients. Radiographic local control was 89%, and among patients with secretory tumors, 100% had a biochemical response. Only 1 patient required salvage surgery for progressive disease, giving a clinical progression free survival of 97%. The only patient who received more than 46 Gy experienced optic neuropathy 8 months after radiation. Smaller tumor volume significantly correlated with subjective improvements in nonvisual neurologic complaints (p = 0.03), and larger tumor volume significantly correlated with subjective worsening of visual symptoms (p = 0.05). New hormonal supplementation was required for 40% of patients. Younger patients were significantly more likely to require hormonal supplementation (p 0.03). Conclusions: Intensity-modulated radiation therapy is a safe and effective treatment for pituitary adenomas over the short term. Longer follow-up is necessary to determine if IMRT confers any advantage with respect to either tumor control or toxicity over conventional radiation modalities.

  17. Intensity-Modulated Radiotherapy for Sinonasal Cancer: Improved Outcome Compared to Conventional Radiotherapy

    SciTech Connect

    Dirix, Piet; Vanstraelen, Bianca; Jorissen, Mark; Vander Poorten, Vincent; Nuyts, Sandra

    2010-11-15

    Purpose: To evaluate clinical outcome and toxicity of postoperative intensity-modulated radiotherapy (IMRT) for malignancies of the nasal cavity and paranasal sinuses. Methods and Materials: Between 2003 and 2008, 40 patients with cancer of the paranasal sinuses (n = 34) or nasal cavity (n = 6) received postoperative IMRT to a dose of 60 Gy (n = 21) or 66 Gy (n = 19). Treatment outcome and toxicity were retrospectively compared with that of a previous patient group (n = 41) who were also postoperatively treated to the same doses but with three-dimensional conformal radiotherapy without intensity modulation, from 1992 to 2002. Results: Median follow-up was 30 months (range, 4-74 months). Two-year local control, overall survival, and disease-free survival were 76%, 89%, and 72%, respectively. Compared to the three-dimensional conformal radiotherapy treatment, IMRT resulted in significantly improved disease-free survival (60% vs. 72%; p = 0.02). No grade 3 or 4 toxicity was reported in the IMRT group, either acute or chronic. The use of IMRT significantly reduced the incidence of acute as well as late side effects, especially regarding skin toxicity, mucositis, xerostomia, and dry-eye syndrome. Conclusions: Postoperative IMRT for sinonasal cancer significantly improves disease-free survival and reduces acute as well as late toxicity. Consequently, IMRT should be considered the standard treatment modality for malignancies of the nasal cavity and paranasal sinuses.

  18. Evaluation of Dose Distribution in Intensity Modulated Radiosurgery for Lung Cancer under Condition of Respiratory Motion

    PubMed Central

    Yoon, Mee Sun; Jeong, Jae-Uk; Nam, Taek-Keun; Ahn, Sung-Ja; Chung, Woong-Ki; Song, Ju-Young

    2016-01-01

    The dose of a real tumor target volume and surrounding organs at risk (OARs) under the effect of respiratory motion was calculated for a lung tumor plan, based on the target volume covering the whole tumor motion range for intensity modulated radiosurgery (IMRS). Two types of IMRS plans based on simulated respiratory motion were designed using humanoid and dynamic phantoms. Delivery quality assurance (DQA) was performed using ArcCHECK and MapCHECK2 for several moving conditions of the tumor and the real dose inside the humanoid phantom was evaluated using the 3DVH program. This evaluated dose in the tumor target and OAR using the 3DVH program was higher than the calculated dose in the plan, and a greater difference was seen for the RapidArc treatment than for the standard intensity modulated radiation therapy (IMRT) with fixed gantry angle beams. The results of this study show that for IMRS plans based on target volume, including the whole tumor motion range, tighter constraints of the OAR should be considered in the optimization process. The method devised in this study can be applied effectively to analyze the dose distribution in the real volume of tumor target and OARs in IMRT plans targeting the whole tumor motion range. PMID:27648949

  19. NOTE: Verification of intensity modulated profiles using a pixel segmented liquid-filled linear array

    NASA Astrophysics Data System (ADS)

    Pardo, J.; Roselló, J. V.; Sánchez-Doblado, F.; Gómez, F.

    2006-06-01

    A liquid isooctane (C8H18) filled ionization chamber linear array developed for radiotherapy quality assurance, consisting of 128 pixels (each of them with a 1.7 mm pitch), has been used to acquire profiles of several intensity modulated fields. The results were compared with film measurements using the γ test. The comparisons show a very good matching, even in high gradient dose regions. The volume-averaging effect of the pixels is negligible and the spatial resolution is enough to verify these regions. However, some mismatches between the detectors have been found in regions where low-energy scattered photons significantly contribute to the total dose. These differences are not very important (in fact, the measurements of both detectors are in agreement using the γ test with tolerances of 3% and 3 mm in most of those regions), and may be associated with the film energy dependence. In addition, the linear array repeatability (0.27% one standard deviation) is much better than the film one (~3%). The good repeatability, small pixel size and high spatial resolution make the detector ideal for the real time profile verification of high gradient beam profiles like those present in intensity modulated radiation therapy and radiosurgery.

  20. A compact linac for intensity modulated proton therapy based on a dielectric wall accelerator.

    PubMed

    Caporaso, G J; Mackie, T R; Sampayan, S; Chen, Y-J; Blackfield, D; Harris, J; Hawkins, S; Holmes, C; Nelson, S; Paul, A; Poole, B; Rhodes, M; Sanders, D; Sullivan, J; Wang, L; Watson, J; Reckwerdt, P J; Schmidt, R; Pearson, D; Flynn, R W; Matthews, D; Purdy, J

    2008-06-01

    A novel compact CT-guided intensity modulated proton radiotherapy (IMPT) system is described. The system is being designed to deliver fast IMPT so that larger target volumes and motion management can be accomplished. The system will be ideal for large and complex target volumes in young patients. The basis of the design is the dielectric wall accelerator (DWA) system being developed at the Lawrence Livermore National Laboratory (LLNL). The DWA uses fast switched high voltage transmission lines to generate pulsed electric fields on the inside of a high gradient insulating (HGI) acceleration tube. High electric field gradients are achieved by the use of alternating insulators and conductors and short pulse times. The system will produce individual pulses that can be varied in intensity, energy and spot width. The IMPT planning system will optimize delivery characteristics. The system will be capable of being sited in a conventional linac vault and provide intensity modulated rotational therapy. Feasibility tests of an optimization system for selecting the position, energy, intensity and spot size for a collection of spots comprising the treatment are underway. A prototype is being designed and concept designs of the envelope and environmental needs of the unit are beginning. The status of the developmental new technologies that make the compact system possible will be reviewed. These include, high gradient vacuum insulators, solid dielectric materials, SiC photoconductive switches and compact proton sources.

  1. PDM-16QAM vector signal generation and detection based on intensity modulation and direct detection

    NASA Astrophysics Data System (ADS)

    Chen, Long; Yu, Jianjun; Li, Xinying

    2016-07-01

    We experimentally demonstrate a novel and simple method to generate and detect high speed polarization-division-multiplexing 16-ary quadrature-amplitude-modulation (PDM-16QAM) vector signal enabled by Mach-Zehnder modulator-based (MZM-based) optical-carrier-suppression (OCS) intensity modulation and direct detection. Due to the adoption of OCS intensity modulation, carrier beating can be avoided at the receiver, and thus polarization de-multiplexing can be implemented by digital-signal-processing-based (DSP-based) cascaded multi-modulus algorithm (CMMA) equalization instead of a polarization tracking system. The change of both amplitude and phase information due to the adoption of OCS modulation can be equalized by DSP-based amplitude and phase precoding at the transmitter. Up to 64-Gb/s PDM-16QAM vector signal is generated and detected after 2-km single-mode fiber-28 (SMF-28) or 20-km large-effective-area fiber (LEAF) transmission with a bit-error-ratio (BER) less than the hard-decision forward-error-correction (HD-FEC) threshold of 3.8×10-3.

  2. Apparatus-dependent dosimetric differences in spine stereotactic body radiotherapy.

    PubMed

    Ma, Lijun; Sahgal, Arjun; Cozzi, Luca; Chang, Eric; Shiu, Almon; Letourneau, Daniel; Yin, Fang-Fang; Fogliata, Antonella; Kaissl, Wolfgang; Hyde, Derek; Laperriere, Normand J; Shrieve, Dennis C; Larson, David A

    2010-12-01

    The purpose of this investigation was to study apparatus-dependent dose distribution differences specific to spine stereotactic body radiotherapy (SBRT) treatment planning. This multi-institutional study was performed evaluating an image-guided robotic radiosurgery system (CK), intensity modulated protons (IMP), multileaf collimator (MLC) fixed-field IMRT with 5 mm (11 field), 4 mm (9 field), and 2.5 mm (8- and 9-field) leaf widths and intensity modulated volumetric arc therapy (IMVAT) with a 2.5 mm MLC. Treatment plans were systematically developed for targets consisting of one, two and three consecutive thoracic vertebral bodies (VBs) with the esophagus and spinal cord contoured as the organs at risk. It was found that all modalities achieved acceptable treatment planning constraints. However, following normalization fixed field IMRT with a 2.5 mm MLC, IMVAT and IMP systems yielded the smallest ratio of maximum dose divided by the prescription dose (MD/PD) for one-, two- and three-VB PTVs (ranging from 1.1-1.16). The 2.5 mm MLC 9-field IMRT, IMVAT and CK plans resulted in the least dose to 0.1 cc volumes of spinal cord and esophagus. CK plans had the greatest degree of target dose inhomogeneity. As the level of complexity increased with an increasing number of vertebral bodies, distinct apparatus features such as the use of a high number of beams and a finer leaf size MLC were favored. Our study quantified apparatus-dependent dose-distribution differences specific to spine SBRT given strict, but realistic, constraints and highlights the need to benchmark physical dose distributions for multi-institutional clinical trials.

  3. Simulational study of a dosimetric comparison between a Gamma Knife treatment plan and an intensity-modulated radiotherapy plan for skull base tumors.

    PubMed

    Nakazawa, Hisato; Mori, Yoshimasa; Komori, Masataka; Tsugawa, Takahiko; Shibamoto, Yuta; Kobayashi, Tatsuya; Hashizume, Chisa; Uchiyama, Yukio; Hagiwara, Masahiro

    2014-05-01

    Fractionated stereotactic radiotherapy (SRT) is performed with a linear accelerator-based system such as Novalis. Recently, Gamma Knife Perfexion (PFX) featured the Extend system with relocatable fixation devices available for SRT. In this study, the dosimetric results of these two modalities were compared from the viewpoint of conformity, heterogeneity and gradient in target covering. A total of 14 patients with skull base tumors were treated with Novalis intensity-modulated (IM)-SRT. Treatment was planned on an iPlan workstation. Five- to seven-beam IM-SRT was performed in 14-18 fractions with a fraction dose of 2.5 or 3 Gy. With these patients' data, additional treatment planning was simulated using a GammaPlan workstation for PFX-SRT. Reference CT images with planning structure contour sets on iPlan, including the planning target volume (PTV, 1.1-102.2 ml) and organs at risk, were exported to GammaPlan in DICOM-RT format. Dosimetric results for Novalis IM-SRT and PFX-SRT were evaluated in the same prescription doses. The isocenter number of PFX was between 12 and 50 at the isodose contour of 50-60%. The PTV coverage was 95-99% for Novalis and 94-98% for PFX. The conformity index (CI) was 1.11-1.61 and 1.04-1.15, the homogeneity index (HI) was 1.1-3.62 and 2.3-3.25, and the gradient index (GI) was 3.72-7.97 and 2.54-3.39 for Novalis and PFX, respectively. PTV coverage by Novalis and PFX was almost equivalent. PFX was superior in CI and GI, and Novalis was better in HI. Better conformality would be achieved by PFX, when the homogeneity inside tumors is less important.

  4. Simulational study of a dosimetric comparison between a Gamma Knife treatment plan and an intensity-modulated radiotherapy plan for skull base tumors

    PubMed Central

    Nakazawa, Hisato; Mori, Yoshimasa; Komori, Masataka; Tsugawa, Takahiko; Shibamoto, Yuta; Kobayashi, Tatsuya; Hashizume, Chisa; Uchiyama, Yukio; Hagiwara, Masahiro

    2014-01-01

    Fractionated stereotactic radiotherapy (SRT) is performed with a linear accelerator-based system such as Novalis. Recently, Gamma Knife Perfexion (PFX) featured the Extend system with relocatable fixation devices available for SRT. In this study, the dosimetric results of these two modalities were compared from the viewpoint of conformity, heterogeneity and gradient in target covering. A total of 14 patients with skull base tumors were treated with Novalis intensity-modulated (IM)-SRT. Treatment was planned on an iPlan workstation. Five- to seven-beam IM-SRT was performed in 14–18 fractions with a fraction dose of 2.5 or 3 Gy. With these patients' data, additional treatment planning was simulated using a GammaPlan workstation for PFX-SRT. Reference CT images with planning structure contour sets on iPlan, including the planning target volume (PTV, 1.1–102.2 ml) and organs at risk, were exported to GammaPlan in DICOM-RT format. Dosimetric results for Novalis IM-SRT and PFX-SRT were evaluated in the same prescription doses. The isocenter number of PFX was between 12 and 50 at the isodose contour of 50–60%. The PTV coverage was 95–99% for Novalis and 94–98% for PFX. The conformity index (CI) was 1.11–1.61 and 1.04–1.15, the homogeneity index (HI) was 1.1–3.62 and 2.3–3.25, and the gradient index (GI) was 3.72–7.97 and 2.54–3.39 for Novalis and PFX, respectively. PTV coverage by Novalis and PFX was almost equivalent. PFX was superior in CI and GI, and Novalis was better in HI. Better conformality would be achieved by PFX, when the homogeneity inside tumors is less important. PMID:24351459

  5. Dose to Larynx Predicts for Swallowing Complications After Intensity-Modulated Radiotherapy

    SciTech Connect

    Caglar, Hale B.; Tishler, Roy B.; Burke, Elaine; Li Yi; Goguen, Laura; Norris, Carl M.; Allen, Aaron M.

    2008-11-15

    Purpose: To evaluate early swallowing after intensity-modulated radiotherapy for head and neck squamous cell carcinoma and determine factors correlating with aspiration and/or stricture. Methods and Materials: Consecutive patients treated with intensity-modulated radiotherapy with or without chemotherapy between September 2004 and August 2006 at the Dana Farber Cancer Institute/Brigham and Women's Hospital were evaluated with institutional review board approval. Patients underwent swallowing evaluation after completion of therapy; including video swallow studies. The clinical- and treatment-related variables were examined for correlation with aspiration or strictures, as well as doses to the larynx, pharyngeal constrictor muscles, and cervical esophagus. The correlation was assessed with logistic regression analysis. Results: A total of 96 patients were evaluated. Their median age was 55 years, and 79 (82%) were men. The primary site of cancer was the oropharynx in 43, hypopharynx/larynx in 17, oral cavity in 13, nasopharynx in 11, maxillary sinus in 2, and unknown primary in 10. Of the 96 patients, 85% underwent definitive RT and 15% postoperative RT. Also, 28 patients underwent induction chemotherapy followed by concurrent chemotherapy, 59 received concurrent chemotherapy, and 9 patients underwent RT alone. The median follow-up was 10 months. Of the 96 patients, 31 (32%) had clinically significant aspiration and 36 (37%) developed a stricture. The radiation dose-volume metrics, including the volume of the larynx receiving {>=}50 Gy (p = 0.04 and p = 0.03, respectively) and volume of the inferior constrictor receiving {>=}50 Gy (p = 0.05 and p = 0.02, respectively) were significantly associated with both aspiration and stricture. The mean larynx dose correlated with aspiration (p = 0.003). Smoking history was the only clinical factor to correlate with stricture (p = 0.05) but not aspiration. Conclusion: Aspiration and stricture are common side effects after

  6. Hypofractionated Concomitant Intensity-Modulated Radiotherapy Boost for High-Risk Prostate Cancer: Late Toxicity

    SciTech Connect

    Quon, Harvey; Cheung, Patrick C.F.; Loblaw, D. Andrew; Morton, Gerard; Pang, Geordi; Szumacher, Ewa; Danjoux, Cyril; Choo, Richard; Thomas, Gillian; Kiss, Alex; Mamedov, Alexandre; Deabreu, Andrea

    2012-02-01

    Purpose: To report the acute and late toxicities of patients with high-risk localized prostate cancer treated using a concomitant hypofractionated, intensity-modulated radiotherapy boost combined with long-term androgen deprivation therapy. Methods and Materials: A prospective Phase I-II study of patients with any of the following: clinical Stage T3 disease, prostate-specific antigen level {>=}20 ng/mL, or Gleason score 8-10. A dose of 45 Gy (1.8 Gy/fraction) was delivered to the pelvic lymph nodes with a concomitant 22.5 Gy prostate intensity-modulated radiotherapy boost, to a total of 67.5 Gy (2.7 Gy/fraction) in 25 fractions within 5 weeks. Image guidance was performed using three gold seed fiducials. The National Cancer Institute Common Terminology Criteria for Adverse Events, version 3.0, and Radiation Therapy Oncology Group late morbidity scores were used to assess the acute and late toxicities, respectively. Biochemical failure was determined using the Phoenix definition. Results: A total of 97 patients were treated and followed up for a median of 39 months, with 88% having a minimum of 24 months of follow-up. The maximal toxicity scores were recorded. The grade of acute gastrointestinal toxicity was Grade 0 in 4%, 1 in 59%, and 2 in 37%. The grade of acute urinary toxicity was Grade 0 in 8%, 1 in 50%, 2 in 39%, and 3 in 4%. The grade of late gastrointestinal toxicity was Grade 0 in 54%, 1 in 40%, and 2 in 7%. No Grade 3 or greater late gastrointestinal toxicities developed. The grade of late urinary toxicity was Grade 0 in 82%, 1 in 9%, 2 in 5%, 3 in 3%, and 4 in 1% (1 patient). All severe toxicities (Grade 3 or greater) had resolved at the last follow-up visit. The 4-year biochemical disease-free survival rate was 90.5%. Conclusions: A hypofractionated intensity-modulated radiotherapy boost delivering 67.5 Gy in 25 fractions within 5 weeks combined with pelvic nodal radiotherapy and long-term androgen deprivation therapy was well tolerated, with low rates

  7. Interfractional Dose Variations in Intensity-Modulated Radiotherapy With Breath-Hold for Pancreatic Cancer

    SciTech Connect

    Nakamura, Mitsuhiro; Shibuya, Keiko; Nakamura, Akira; Shiinoki, Takehiro; Matsuo, Yukinori; Nakata, Manabu; Sawada, Akira; Mizowaki, Takashi; Hiraoka, Masahiro

    2012-04-01

    Purpose: To investigate the interfractional dose variations for intensity-modulated radiotherapy (RT) combined with breath-hold (BH) at end-exhalation (EE) for pancreatic cancer. Methods and Materials: A total of 10 consecutive patients with pancreatic cancer were enrolled. Each patient was fixed in the supine position on an individualized vacuum pillow with both arms raised. Computed tomography (CT) scans were performed before RT, and three additional scans were performed during the course of chemoradiotherapy using a conventional RT technique. The CT data were acquired under EE-BH conditions (BH-CT) using a visual feedback technique. The intensity-modulated RT plan, which used five 15-MV coplanar ports, was designed on the initial BH-CT set with a prescription dose of 39 Gy at 2.6 Gy/fraction. After rigid image registration between the initial and subsequent BH-CT scans, the dose distributions were recalculated on the subsequent BH-CT images under the same conditions as in planning. Changes in the dose-volume metrics of the gross tumor volume (GTV), clinical target volume (CTV = GTV + 5 mm), stomach, and duodenum were evaluated. Results: For the GTV and clinical target volume (CTV), the 95th percentile of the interfractional variations in the maximal dose, mean dose, dose covering 95% volume of the region of structure, and percentage of the volume covered by the 90% isodose line were within {+-}3%. Although the volume covered by the 39 Gy isodose line for the stomach and duodenum did not exceed 0.1 mL at planning, the volume covered by the 39 Gy isodose line for these structures was up to 11.4 cm{sup 3} and 1.8 cm{sup 3}, respectively. Conclusions: Despite variations in the gastrointestinal state and abdominal wall position at EE, the GTV and CTV were mostly ensured at the planned dose, with the exception of 1 patient. Compared with the duodenum, large variations in the stomach volume receiving high-dose radiation were observed, which might be beyond the

  8. Hypofractionated Intensity-Modulated Arc Therapy for Lymph Node Metastasized Prostate Cancer

    SciTech Connect

    Fonteyne, Valerie; De Gersem, Werner; De Neve, Wilfried; Jacobs, Filip; Lumen, Nicolaas; Vandecasteele, Katrien; Villeirs, Geert; De Meerleer, Gert

    2009-11-15

    Purpose: To determine the planning results and acute toxicity after hypofractionated intensity-modulated arc radiotherapy and androgen deprivation for lymph node metastasized (Stage N1) prostate cancer. Methods and Materials: A total of 31 patients with Stage T1-T4N1M0 prostate cancer were treated with intensity-modulated arc radiotherapy and 3 years of androgen deprivation as primary treatment. The clinical target volume (CTV{sub p}) was the prostate and seminal vesicles. Elective lymph node areas ({sub e}) were delineated and expanded by 2 mm to create the CTV{sub e}. The planning target volumes (PTV{sub p} and PTV{sub e}) were created using a three-dimensional expansion of the CTV{sub p} and CTV{sub e}, respectively, of 7 mm. A median dose of 69.3 Gy and 50 Gy was prescribed to the PTV{sub p} and PTV{sub e} respectively, to be delivered in 25 fractions. Upper and lower gastrointestinal toxicity was scored using the Radiation Therapy Oncology Group toxicity and radiotherapy-induced lower intestinal toxicity scoring system. Genitourinary toxicity was scored using a combined Radiation Therapy Oncology Group, LENT-SOMA (late effects normal tissue-subjective, objective, management, analytic), and Common Toxicity Criteria toxicity scoring system. Results: The median follow-up time was 3 months. The mean prescription dose to the CTV{sub p} and PTV{sub p} was 70.4 Gy and 68.6 Gy, respectively. The minimal dose to the CTV{sub e} and PTV{sub e} was 49.0 Gy and 47.0 Gy, respectively. No acute Grade 2 or greater gastrointestinal toxicity occurred. Fourteen patients developed acute Grade 2 lower gastrointestinal toxicity. Acute Grade 3 and 2 genitourinary toxicity developed in 2 and 14 patients, respectively. Conclusion: The results of our study have shown that hypofractionated intensity-modulated arc radiotherapy as primary therapy for N1 prostate cancer is feasible with low toxicity.

  9. Balancing control and simplicity: A variable aggregation method in intensity modulated radiation therapy planning*

    PubMed Central

    Süss, Philipp; Küfer, Karl-Heinz

    2008-01-01

    It is commonly believed that not all degrees of freedom are needed to produce good solutions for the treatment planning problem in intensity modulated radiation therapy (IMRT). However, typical methods to exploit this fact either increase the complexity of the optimization problem or are heuristic in nature. In this work we introduce a technique based on adaptively refining variable clusters to successively attain better treatment plans. The approach creates approximate solutions based on smaller models that may come arbitrarily close to the optimal solution. Although the method is illustrated using a specific treatment planning model, the components constituting the variable clustering and the adaptive refinement are independent of the particular optimization problem. PMID:19255600

  10. Matching Intensity-Modulated Radiation Therapy to an Anterior Low Neck Field

    SciTech Connect

    Amdur, Robert J. Liu, Chihray; Li, Jonathan; Mendenhall, William; Hinerman, Russell

    2007-10-01

    When using intensity-modulated radiation therapy (IMRT) to treat head and neck cancer with the primary site above the level of the larynx, there are two basic options for the low neck lymphatics: to treat the entire neck with IMRT, or to match the IMRT plan to a conventional anterior 'low neck' field. In view of the potential advantages of using a conventional low neck field, it is important to look for ways to minimize or manage the problems of matching IMRT to a conventional radiotherapy field. Treating the low neck with a single anterior field and the standard larynx block decreases the dose to the larynx and often results in a superior IMRT plan at the primary site. The purpose of this article is to review the most applicable studies and to discuss our experience with implementing a technique that involves moving the position of the superior border of the low neck field several times during a single treatment fraction.

  11. Modern head and neck brachytherapy: from radium towards intensity modulated interventional brachytherapy

    PubMed Central

    2014-01-01

    Intensity modulated brachytherapy (IMBT) is a modern development of classical interventional radiation therapy (brachytherapy), which allows the application of a high radiation dose sparing severe adverse events, thereby further improving the treatment outcome. Classical indications in head and neck (H&N) cancers are the face, the oral cavity, the naso- and oropharynx, the paranasal sinuses including base of skull, incomplete resections on important structures, and palliation. The application type can be curative, adjuvant or perioperative, as a boost to external beam radiation as well as without external beam radiation and with palliative intention. Due to the frequently used perioperative application method (intraoperative implantation of inactive applicators and postoperative performance of radiation), close interdisciplinary cooperation between surgical specialists (ENT-, dento-maxillary-facial-, neuro- and orbital surgeons), as well interventional radiotherapy (brachytherapy) experts are obligatory. Published results encourage the integration of IMBT into H&N therapy, thereby improving the prognosis and quality of life of patients. PMID:25834586

  12. Simple tool for prediction of parotid gland sparing in intensity-modulated radiation therapy

    SciTech Connect

    Gensheimer, Michael F.; Hummel-Kramer, Sharon M.; Cain, David; Quang, Tony S.

    2015-10-01

    Sparing one or both parotid glands is a key goal when planning head and neck cancer radiation treatment. If the planning target volume (PTV) overlaps one or both parotid glands substantially, it may not be possible to achieve adequate gland sparing. This finding results in physicians revising their PTV contours after an intensity-modulated radiation therapy (IMRT) plan has been run and reduces workflow efficiency. We devised a simple formula for predicting mean parotid gland dose from the overlap of the parotid gland and isotropically expanded PTV contours. We tested the tool using 44 patients from 2 institutions and found agreement between predicted and actual parotid gland doses (mean absolute error = 5.3 Gy). This simple method could increase treatment planning efficiency by improving the chance that the first plan presented to the physician will have optimal parotid gland sparing.

  13. Whole Pelvic Intensity-modulated Radiotherapy for Gynecological Malignancies: A Review of the Literature

    PubMed Central

    Hymel, Rockne; Jones, Guy C.; Simone, Charles B.

    2015-01-01

    Radiation therapy has long played a major role in the treatment of gynecological malignancies. There is increasing interest in the utility of intensity-modulated radiotherapy (IMRT) and its application to treat gynecological malignancies. Herein, we review the state-of-the-art use of IMRT for gynecological malignancies and report how it is being used alone as well as in combination with chemotherapy in both the adjuvant and definitive settings. Based on dosimetric and clinical evidence, IMRT can reduce gastrointestinal, genitourinary, and hematological toxicities compared with 3D conformal radiotherapy for gynecologic malignancies. We discuss how these attributes of IMRT may lead to improvements in disease outcomes by allowing for dose escalation of radiation therapy, intensification of chemotherapy, and limiting toxicity-related treatment breaks. Currently accruing trials investigating pelvic IMRT for cervical and endometrial cancers are discussed. PMID:25600840

  14. Experimental demonstration of light sensor-based visible light communications using time shift light intensity modulation

    NASA Astrophysics Data System (ADS)

    Kim, Yong-hyeon; Chung, Yeon-ho

    2016-09-01

    An experimental light sensor-based indoor visible light communication (VLC) is presented. Light-emitting diodes (LEDs) primarily used for illumination are employed to transmit wireless optical data over a short distance, while a smartphone's light sensor is used to receive the data. The light sensor in a smartphone is originally installed to function as a power saving method by adjusting the brightness of the smartphone screen. We propose an efficient and easy-to-use short range VLC based on this light sensor. To compensate for the inherent low sampling rate of the light sensor and also to avoid LED (transmitter) flickering, we propose time shift light intensity modulation. To verify the proposed light sensor VLC, experiments were conducted. The results demonstrate that the data can reliably be transmitted over the VLC link between the LEDs and the smartphone light sensor.

  15. MIMO Free-Space Optical Communication Employing Subcarrier Intensity Modulation in Atmospheric Turbulence Channels

    NASA Astrophysics Data System (ADS)

    Ghassemlooy, Zabih; Popoola, Wasiu O.; Ahmadi, Vahid; Leitgeb, Erich

    In this paper, we analyse the error performance of transmitter/receiver array free-space optical (FSO) communication system employing binary phase shift keying (BPSK) subcarrier intensity modulation (SIM) in clear but turbulent atmospheric channel. Subcarrier modulation is employed to eliminate the need for adaptive threshold detector. Direct detection is employed at the receiver and each subcarrier is subsequently demodulated coherently. The effect of irradiance fading is mitigated with an array of lasers and photodetectors. The received signals are linearly combined using the optimal maximum ratio combining (MRC), the equal gain combining (EGC) and the selection combining (SelC). The bit error rate (BER) equations are derived considering additive white Gaussian noise and log normal intensity fluctuations. This work is part of the EU COST actions and EU projects.

  16. [Intensity-modulated radiotherapy for head and neck cancer. Dose constraint for salivary gland and mandible].

    PubMed

    Pointreau, Y; Lizée, T; Bensadoun, R-J; Boisselier, P; Racadot, S; Thariat, J; Graff, P

    2016-10-01

    Intensity-modulated radiation therapy (IMRT) is the gold standard for head and neck irradiation. It allows better protection to the organs at risk such as salivary glands and mandible, and can reduce the frequency of xerostomia, trismus and osteoradionecrosis. At the time of treatment planning, the mean dose to a single parotid gland should be kept below 26Gy, the mean dose to a single submandibular gland below 39Gy, the mean dose to the mandible below 60 to 65Gy and the D2% to a single temporomandibular joint below 65Gy. These dose constraints could be further improved with data extracted from cohorts of patients receiving IMRT exclusively. The dose administered to the target volumes should not be lessened to spare the salivary glands or mandible.

  17. Intensity-modulated arc therapy to improve radiation dose delivery in the treatment of abdominal neuroblastoma.

    PubMed

    Gains, Jennifer E; Stacey, Christopher; Rosenberg, Ivan; Mandeville, Henry C; Chang, Yen-Ch'ing; D'Souza, Derek; Moroz, Veronica; Wheatley, Keith; Gaze, Mark N

    2013-03-01

    The standard European radiotherapy technique for children with neuroblastoma is a conventional parallel opposed pair. This frequently results in compromise on planning target volume coverage to stay within normal tissue tolerances. This study investigates the use of an intensity-modulated arc therapy (IMAT) technique to improve dose distribution and allow better protocol compliance. Among 20 previously treated patients, ten had received the full prescribed dose with conventional planning (protocol compliant) and ten had a compromise on planning target volume coverage (protocol noncompliant). All patients were replanned with IMAT. Dosimetric parameters of the conventional radiotherapy and IMAT were compared. The dose received by 98% of the planning target volume, homogeneity and conformity indices were all improved with IMAT (p < 0.001). IMAT would have enabled delivery of the full protocol dose in eight out of ten protocol-noncompliant patients. IMAT may improve outcomes through improved protocol compliance and better dose distributions.

  18. Tunable nonuniform sampling method for fast calculation and intensity modulation in 3D dynamic holographic display.

    PubMed

    Zhang, Zhao; Liu, Juan; Jia, Jia; Li, Xin; Han, Jian; Hu, Bin; Wang, Yongtian

    2013-08-01

    Heavy computational load of computer-generated hologram (CGH) and imprecise intensity modulation of 3D images are crucial problems in dynamic holographic display. The nonuniform sampling method is proposed to speed up CGH generation and precisely modulate the reconstructed intensities of phase-only CGH. The proposed method can eliminate the redundant information properly, where 70% reduction in the storage amount can be reached when it is combined with the novel lookup table method. Multigrayscale modulation of reconstructed 3D images can be achieved successfully. Numerical simulations and optical experiments are performed, and both are in good agreement. It is believed that the proposed method can be used in 3D dynamic holographic display.

  19. Implementation of intensity modulated radiotherapy for prostate cancer in a private radiotherapy service in Mexico

    PubMed Central

    Poitevin-Chacón, María Adela; Reséndiz González, Gabriel; Alvarado Zermeño, Adriana; Flores Castro, Jesús Manuel; Flores Balcázar, Christian Haydée; Rosales Pérez, Samuel; Pérez Pastenes, Miguel Angel; Rodríguez Laguna, Alejandro; Vázquez Fernández, Patricio; Calvo Fernández, Alejandro; Bastida Ventura, Jorge

    2014-01-01

    Intensity modulated radiation therapy (IMRT) allows physicians to deliver higher conformal doses to the tumour, while avoiding adjacent structures. As a result the probability of tumour control is higher and toxicity may be reduced. However, implementation of IMRT is highly complex and requires a rigorous quality assurance (QA) program both before and during treatment. The present article describes the process of implementing IMRT for localized prostate cancer in a radiation therapy department. In our experience, IMRT implementation requires careful planning due to the need to simultaneously implement specialized software, multifaceted QA programs, and training of the multidisciplinary team. Establishing standardized protocols and ensuring close collaboration between a multidisciplinary team is challenging but essential. PMID:25535587

  20. A comparison of three optimization algorithms for intensity modulated radiation therapy.

    PubMed

    Pflugfelder, Daniel; Wilkens, Jan J; Nill, Simeon; Oelfke, Uwe

    2008-01-01

    In intensity modulated treatment techniques, the modulation of each treatment field is obtained using an optimization algorithm. Multiple optimization algorithms have been proposed in the literature, e.g. steepest descent, conjugate gradient, quasi-Newton methods to name a few. The standard optimization algorithm in our in-house inverse planning tool KonRad is a quasi-Newton algorithm. Although this algorithm yields good results, it also has some drawbacks. Thus we implemented an improved optimization algorithm based on the limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) routine. In this paper the improved optimization algorithm is described. To compare the two algorithms, several treatment plans are optimized using both algorithms. This included photon (IMRT) as well as proton (IMPT) intensity modulated therapy treatment plans. To present the results in a larger context the widely used conjugate gradient algorithm was also included into this comparison. On average, the improved optimization algorithm was six times faster to reach the same objective function value. However, it resulted not only in an acceleration of the optimization. Due to the faster convergence, the improved optimization algorithm usually terminates the optimization process at a lower objective function value. The average of the observed improvement in the objective function value was 37%. This improvement is clearly visible in the corresponding dose-volume-histograms. The benefit of the improved optimization algorithm is particularly pronounced in proton therapy plans. The conjugate gradient algorithm ranked in between the other two algorithms with an average speedup factor of two and an average improvement of the objective function value of 30%.

  1. Genetic algorithm based deliverable segments optimization for static intensity-modulated radiotherapy.

    PubMed

    Li, Yongjie; Yao, Jonathan; Yao, Dezhong

    2003-10-21

    The static delivery technique (also called step-and-shoot technique) has been widely used in intensity-modulated radiotherapy (IMRT) because of the simple delivery and easy quality assurance. Conventional static IMRT consists of two steps: first to calculate the intensity-modulated beam profiles using an inverse planning algorithm, and then to translate these profiles into a series of uniform segments using a leaf-sequencing tool. In order to simplify the procedure and shorten the treatment time of the static mode, an efficient technique, called genetic algorithm based deliverable segments optimization (GADSO), is developed in our work, which combines these two steps into one. Taking the pre-defined beams and the total number of segments per treatment as input, the number of segments for each beam, the segment shapes and weights are determined automatically. A group of interim modulated beam profiles quickly calculated using a conjugate gradient (CG) method are used to determine the segment number for each beam and to initialize segment shapes. A modified genetic algorithm based on a two-dimensional binary coding scheme is used to optimize the segment shapes, and a CG method is used to optimize the segment weights. The physical characters of a multileaf collimator, such as the leaves interdigitation limitation and leaves maximum over-travel distance, are incorporated into the optimization. The algorithm is applied to some examples and the results demonstrate that GADSO is able to produce highly conformal dose distributions using 20-30 deliverable segments per treatment within a clinically acceptable computation time.

  2. Patterns of Failure and Toxicity after Intensity-Modulated Radiotherapy for Head and Neck Cancer

    SciTech Connect

    Schoenfeld, Gordon O.; Amdur, Robert J.; Morris, Christopher G.; Li, Jonathan G.; Hinerman, Russell W.; Mendenhall, William M.

    2008-06-01

    Purpose: To determine the outcome of patients treated with intensity-modulated radiotherapy (IMRT) for head and neck cancer. Methods and Materials: We reviewed the charts of 100 consecutive patients treated with IMRT for squamous cell carcinoma of the oropharynx (64%), nasopharynx (16%), hypopharynx (14%), and larynx (6%). Most patients were treated with a concomitant boost schedule to 72 Gy. Of the 100 patients, 54 (54%) received adjuvant chemotherapy, mostly concurrent cisplatin. The dosimetry plans for patients with either locoregional failure or Grade 4-5 complications were reviewed and fused over the computed tomography images corresponding with the location of the event. Marginal failures were defined as those that occurred at a region of high-dose falloff, where conventional fields would have provided better coverage. Results: The median follow-up of living patients was 3.1 years (range, 1-5.2 years). The 3-year rate of local control, locoregional control, freedom from relapse, cause-specific survival, and overall survival for all patients was 89%, 87%, 72%, 78%, and 71%, respectively. The 3-year rate of freedom from relapse, cause-specific survival, and overall survival for the 64 oropharynx patients was 86%, 92%, and 84%, respectively. Of the 10 local failures, 2 occurred at the margin of the high-dose planning target volume. Both regional failures occurred within the planning target volume. No locoregional failures occurred outside the planning target volume. Of the 100 patients, 8 and 5 had Grade 4 and 5 complications from treatment, respectively. All patients with Grade 5 complications had received adjuvant chemotherapy. No attempt was made to discriminate between the complications from IMRT and other aspects of the patients' treatment. Conclusion: Intensity-modulated radiotherapy did not compromise the outcome compared with what we have achieved with conventional techniques. The 2 cases of recurrence in the high-dose gradient region highlight the

  3. Fast intensity-modulated arc therapy based on 2-step beam segmentation

    SciTech Connect

    Bratengeier, Klaus; Gainey, Mark; Sauer, Otto A.; Richter, Anne; Flentje, Michael

    2011-01-15

    Purpose: Single or few arc intensity-modulated arc therapy (IMAT) is intended to be a time saving irradiation method, potentially replacing classical intensity-modulated radiotherapy (IMRT). The aim of this work was to evaluate the quality of different IMAT methods with the potential of fast delivery, which also has the possibility of adapting to the daily shape of the target volume. Methods: A planning study was performed. Novel double and triple IMAT techniques based on the geometrical analysis of the target organ at risk geometry (2-step IMAT) were evaluated. They were compared to step and shoot IMRT reference plans generated using direct machine parameter optimization (DMPO). Volumetric arc (VMAT) plans from commercial preclinical software (SMARTARC) were used as an additional benchmark to classify the quality of the novel techniques. Four cases with concave planning target volumes (PTV) with one dominating organ at risk (OAR), viz., the PTV/OAR combination of the ESTRO Quasimodo phantom, breast/lung, spine metastasis/spinal cord, and prostate/rectum, were used for the study. The composite objective value (COV) and other parameters representing the plan quality were studied. Results: The novel 2-step IMAT techniques with geometry based segment definition were as good as or better than DMPO and were superior to the SMARTARC VMAT techniques. For the spine metastasis, the quality measured by the COV differed only by 3%, whereas the COV of the 2-step IMAT for the other three cases decreased by a factor of 1.4-2.4 with respect to the reference plans. Conclusions: Rotational techniques based on geometrical analysis of the optimization problem (2-step IMAT) provide similar or better plan quality than DMPO or the research version of SMARTARC VMAT variants. The results justify pursuing the goal of fast IMAT adaptation based on 2-step IMAT techniques.

  4. Intensity Modulated Radiation Therapy for Primary Soft Tissue Sarcoma of the Extremity: Preliminary Results

    SciTech Connect

    Alektiar, Kaled M. . E-mail: alektiak@mskcc.org; Hong, Linda; Brennan, Murray F.; Della-Biancia, Cesar; Singer, Samuel

    2007-06-01

    Purpose: To report preliminary results on using intensity modulated radiation therapy (IMRT) as an adjuvant treatment in primary soft tissue sarcoma (STS) of the extremity. Methods and Materials: Between February 2002 and March 2005, 31 adult patients with primary STS of the extremity were treated with surgery and adjuvant IMRT. Tumor size was >10 cm in 74% of patients and grade was high in 77%. Preoperative IMRT was given to 7 patients (50 Gy) and postoperative IMRT (median dose, 63 Gy) was given to 24 patients. Complete gross resection including periosteal stripping or bone resection was required in 10, and neurolysis or nerve resection in 20. The margins were positive or within 1 mm in 17. Complications from surgery and radiation therapy (RT) were assessed using the Common Terminology Criteria for Adverse Events grading system. Results: Median follow-up time was 23 months. Grade 1 RT dermatitis developed in 71% of patients, Grade 2 in 16%, and Grade 3 in 10%. Infectious wound complications developed in 13% and noninfectious complications in 10%. Two patients (6.4%) developed fractures. Grade 1 neuropathy developed in 28% of patients and Grade 2 in 5%. The rates of Grade 1 and 2 joint stiffness were each 19%. Grade 1 edema was observed in 19% of patients and Grade 2 in 13%. The 2-year local control, distant control, and overall survival were 95%, 65%, and 81%, respectively. Conclusion: Intensity modulated RT appears to provide excellent local control in a difficult group of high-risk patients. The morbidity profile is also favorable, but longer follow-up is needed to confirm the results from this study.

  5. Radiation-Induced Cancers From Modern Radiotherapy Techniques: Intensity-Modulated Radiotherapy Versus Proton Therapy

    SciTech Connect

    Yoon, Myonggeun; Ahn, Sung Hwan; Kim, Jinsung; Shin, Dong Ho; Park, Sung Yong; Lee, Se Byeong; Shin, Kyung Hwan; Cho, Kwan Ho

    2010-08-01

    Purpose: To assess and compare secondary cancer risk resulting from intensity-modulated radiotherapy (IMRT) and proton therapy in patients with prostate and head-and-neck cancer. Methods and Materials: Intensity-modulated radiotherapy and proton therapy in the scattering mode were planned for 5 prostate caner patients and 5 head-and-neck cancer patients. The secondary doses during irradiation were measured using ion chamber and CR-39 detectors for IMRT and proton therapy, respectively. Organ-specific radiation-induced cancer risk was estimated by applying organ equivalent dose to dose distributions. Results: The average secondary doses of proton therapy for prostate cancer patients, measured 20-60cm from the isocenter, ranged from 0.4 mSv/Gy to 0.1 mSv/Gy. The average secondary doses of IMRT for prostate patients, however, ranged between 3 mSv/Gy and 1 mSv/Gy, approximately one order of magnitude higher than for proton therapy. Although the average secondary doses of IMRT were higher than those of proton therapy for head-and-neck cancers, these differences were not significant. Organ equivalent dose calculations showed that, for prostate cancer patients, the risk of secondary cancers in out-of-field organs, such as the stomach, lungs, and thyroid, was at least 5 times higher for IMRT than for proton therapy, whereas the difference was lower for head-and-neck cancer patients. Conclusions: Comparisons of organ-specific organ equivalent dose showed that the estimated secondary cancer risk using scattering mode in proton therapy is either significantly lower than the cases in IMRT treatment or, at least, does not exceed the risk induced by conventional IMRT treatment.

  6. Intensity-modulated radiation therapy, protons, and the risk of second cancers

    SciTech Connect

    Hall, Eric J. . E-mail: ejh1@columbia.edu

    2006-05-01

    Intensity-modulated radiation therapy (IMRT) allows dose to be concentrated in the tumor volume while sparing normal tissues. However, the downside to IMRT is the potential to increase the number of radiation-induced second cancers. The reasons for this potential are more monitor units and, therefore, a larger total-body dose because of leakage radiation and, because IMRT involves more fields, a bigger volume of normal tissue is exposed to lower radiation doses. Intensity-modulated radiation therapy may double the incidence of solid cancers in long-term survivors. This outcome may be acceptable in older patients if balanced by an improvement in local tumor control and reduced acute toxicity. On the other hand, the incidence of second cancers is much higher in children, so that doubling it may not be acceptable. IMRT represents a special case for children for three reasons. First, children are more sensitive to radiation-induced cancer than are adults. Second, radiation scattered from the treatment volume is more important in the small body of the child. Third, the question of genetic susceptibility arises because many childhood cancers involve a germline mutation. The levels of leakage radiation in current Linacs are not inevitable. Leakage can be reduced but at substantial cost. An alternative strategy is to replace X-rays with protons. However, this change is only an advantage if the proton machine employs a pencil scanning beam. Many proton facilities use passive modulation to produce a field of sufficient size, but the use of a scattering foil produces neutrons, which results in an effective dose to the patient higher than that characteristic of IMRT. The benefit of protons is only achieved if a scanning beam is used in which the doses are 10 times lower than with IMRT.

  7. Predictors for Clinical Outcomes After Accelerated Partial Breast Intensity-Modulated Radiotherapy

    SciTech Connect

    Reeder, Reed; Carter, Dennis L. Howell, Kathryn; Henkenberns, Phyllis; Tallhamer, Michael; Johnson, Tim; Kercher, Jane; Widner, Jodi; Kaske, Terese; Paul, Devchand; Sedlacek, Scot; Leonard, Charles E.

    2009-05-01

    Purpose: To correlate the treatment planning parameters with the clinical outcomes in patients treated with accelerated partial breast intensity-modulated radiotherapy. Methods and Materials: A total of 105 patients with Stage I breast cancer were treated between February 2004 and March 2007 in a Phase II prospective trial and had detailed information available on the planning target volume (PTV), ipsilateral breast volume (IBV), PTV/IBV ratio, lung volume, chest wall volume, surgery to radiotherapy interval, follow-up interval, breast pain, and cosmesis. The first 7 of these patients were treated to 34 Gy, and the remaining 98 were treated to 38.5 Gy. All patients were treated twice daily for 5 consecutive days. Univariate and multivariate analyses were performed. Results: The median follow-up was 13 months. No recurrences or deaths were observed. Of the 105 patients, 30 reported mild or moderate breast pain in their most recently recorded follow-up visit. The irradiated lung volume (p < 0.05) and chest wall volume receiving >35 Gy (p < 0.01) were associated with pain. The PTV, but not the PTV/IBV ratio, also correlated with pain (p < 0.01 and p = 0.42, respectively). A total of 72 patients reported excellent, 32 reported good, and 1 reported poor cosmesis. Physician-rated cosmesis reported 90 excellent and 15 good. None of the tested variables correlated with the cosmetic outcomes. Conclusion: Radiotherapy to the chest wall (chest wall volume receiving >35 Gy) and to lung correlated with reports of mild pain after accelerated partial breast intensity-modulated radiotherapy. Also, the PTV, but not the PTV/IBV ratio, was predictive of post-treatment reports of pain.

  8. Intensity-Modulated Radiotherapy for Head-and-Neck Cancer in the Community Setting

    SciTech Connect

    Seung, Steven Bae, Joseph; Solhjem, Matthew; Bader, Stephen; Gannett, David; Hansen, Eric K.; Louie, Jeannie; Underhill, Kelly Cha Christine

    2008-11-15

    Purpose: To review outcomes with intensity-modulated radiation therapy (IMRT) in the community setting for the treatment of nasopharyngeal and oropharyngeal cancer. Methods and Materials: Between April 2003 and April 2007, 69 patients with histologically confirmed cancer of the nasopharynx and oropharynx underwent IMRT in our practice. The primary sites included nasopharynx (11), base of tongue (18), and tonsil (40). The disease stage distribution was as follows: 2 Stage I, 11 Stage II, 16 Stage III, and 40 Stage IV. All were treated with a simultaneous integrated boost IMRT technique. The median prescribed doses were 70 Gy to the planning target volume, 59.4 Gy to the high-risk subclinical volume, and 54 Gy to the low-risk subclinical volume. Forty-five patients (65%) received concurrent chemotherapy. Toxicity was graded according to the Radiation Therapy Oncology Group toxicity criteria. Progression-free and overall survival rates were estimated with the Kaplan-Meier product-limit method. Results: Median duration of follow-up was 18 months. The estimated 2-year local control, regional control, distant control, and overall survival rates were 98%, 100%, 98%, and 90%, respectively. The most common acute toxicities were dermatitis (32 Grade 1, 32 Grade 2, 5 Grade 3), mucositis (8 Grade 1, 33 Grade 2, 28 Grade 3), and xerostomia (0 Grade 1, 29 Grade 2, 40 Grade 3). Conclusions: Intensity-modulated radiotherapy in the community setting can be accomplished safely and effectively. Systematic internal review systems are recommended for quality control until sufficient experience develops.

  9. Testbed measurements of subcarrier OQPSK versus digital OOK laser intensity modulation at 266 to 1244 Mbps

    NASA Astrophysics Data System (ADS)

    Carlson, Robert T.

    1995-04-01

    We report here on measurements made on a lasercom crosslink hardware testbed built on internal MITRE funds. Laser diodes rated at 150 mwatts were characterized to be flat to 100 MHz, rolling off 5 dB at 500 MHz. A microstrip laser driver with equalizer was implemented to provide flat, highly linear frequency response for analog modulation out to 550 MHz. Microstrip and hybrid versions of APD receivers were also fabricated with flat, linear response to 700 MHz (typically -3 dB at 850 - 1000 MHz), suitable for datarates up to 1.25 Gbps. The optical crosslink testbed with equalized driver, laser, and APD receiver exhibits +/- 0.25 dB flatness, +/- 2.5 degrees phase linearity deviation, and +/- 0.25 (eta) sec group delay variation over the full bandwidth for 650 Mbps. This testbed was evaluated with two modulation approaches: analog laser intensity modulation using an OQPSK subcarrier scheme, and baseband digital NRZ OOK laser intensity modulation, at datarates from 266 to 1244 Mbps. The QPSK subcarrier hardware characterization includes the high speed modem/demodulator and a pair of frequency converters. The digital NRZ hardware characterization includes the clock recovery and amplitude/timing decision circuit. Both the subcarrier QPSK and the digital OOK tests used the same laser and equalized laser driver, the same modulated laser power with 95% intensity modulatino depth, and the same APD receiver for these tests. As such, the comparison between these modulation schemes is an even-handed comparison of the end-to-end performance. Results and conclusions are presented.

  10. Robust Intensity Modulated Proton Therapy (IMPT) Increases Estimated Clinical Benefit in Head and Neck Cancer Patients

    PubMed Central

    van Dijk, Lisanne V.; Steenbakkers, Roel J. H. M.; ten Haken, Bennie; van der Laan, Hans Paul; van ‘t Veld, Aart A.; Langendijk, Johannes A.; Korevaar, Erik W.

    2016-01-01

    Purpose To compare the clinical benefit of robust optimized Intensity Modulated Proton Therapy (minimax IMPT) with current photon Intensity Modulated Radiation Therapy (IMRT) and PTV-based IMPT for head and neck cancer (HNC) patients. The clinical benefit is quantified in terms of both Normal Tissue Complication Probability (NTCP) and target coverage in the case of setup and range errors. Methods and Materials For 10 HNC patients, PTV-based IMRT (7 fields), minimax and PTV-based IMPT (2, 3, 4, 5 and 7 fields) plans were tested on robustness. Robust optimized plans differed from PTV-based plans in that they target the CTV and penalize possible error scenarios, instead of using the static isotropic CTV-PTV margin. Perturbed dose distributions of all plans were acquired by simulating in total 8060 setup (±3.5 mm) and range error (±3%) combinations. NTCP models for xerostomia and dysphagia were used to predict the clinical benefit of IMPT versus IMRT. Results The robustness criterion was met in the IMRT and minimax IMPT plans in all error scenarios, but this was only the case in 1 of 40 PTV-based IMPT plans. Seven (out of 10) patients had relatively large NTCP reductions in minimax IMPT plans compared to IMRT. For these patients, xerostomia and dysphagia NTCP values were reduced by 17.0% (95% CI; 13.0–21.1) and 8.1% (95% CI; 4.9–11.2) on average with minimax IMPT. Increasing the number of fields did not contribute to plan robustness, but improved organ sparing. Conclusions The estimated clinical benefit in terms of NTCP of robust optimized (minimax) IMPT is greater than that of IMRT and PTV-based IMPT in HNC patients. Furthermore, the target coverage of minimax IMPT plans in the presence of errors was comparable to IMRT plans. PMID:27030987

  11. Leaf position error during conformal dynamic arc and intensity modulated arc treatments.

    PubMed

    Ramsey, C R; Spencer, K M; Alhakeem, R; Oliver, A L

    2001-01-01

    Conformal dynamic arc (CD-ARC) and intensity modulated arc treatments (IMAT) are both treatment modalities where the multileaf collimator (MLC) can change leaf position dynamically during gantry rotation. These treatment techniques can be used to generate complex isodose distributions, similar to those used in fix-gantry intensity modulation. However, a beam-hold delay cannot be used during CD-ARC or IMAT treatments to reduce spatial error. Consequently, a certain amount of leaf position error will have to be accepted in order to make the treatment deliverable. Measurements of leaf position accuracy were taken with leaf velocities ranging from 0.3 to 3.0 cm/s. The average and maximum leaf position errors were measured, and a least-squares linear regression analysis was performed on the measured data to determine the MLC velocity error coefficient. The average position errors range from 0.03 to 0.21 cm, with the largest deviations occurring at the maximum achievable leaf velocity (3.0 cm/s). The measured MLC velocity error coefficient was 0.0674 s for a collimator rotation of 0 degrees and 0.0681 s for a collimator rotation of 90 degrees. The distribution in leaf position error between the 0 degrees and 90 degrees collimator rotations was within statistical uncertainty. A simple formula was developed based on these results for estimating the velocity-dependent dosimetric error. Using this technique, a dosimetric error index for plan evaluation can be calculated from the treatment time and the dynamic MLC leaf controller file.

  12. MAGIC-type polymer gel for three-dimensional dosimetry: intensity-modulated radiation therapy verification.

    PubMed

    Gustavsson, Helen; Karlsson, Anna; Bäck, Sven A J; Olsson, Lars E; Haraldsson, Pia; Engström, Per; Nyström, Håkan

    2003-06-01

    A new type of polymer gel dosimeter, which responds well to absorbed dose even when manufactured in the presence of normal levels of oxygen, was recently described by Fong et al. [Phys. Med. Biol. 46, 3105-3113 (2001)] and referred to by the acronym MAGIC. The aim of this study was to investigate the feasibility of using this new type of gel for intensity-modulated radiation therapy (IMRT) verification. Gel manufacturing was carried out in room atmosphere under normal levels of oxygen. IMRT inverse treatment planning was performed using the Helios software. The gel was irradiated using a linear accelerator equipped with a dynamic multileaf collimator, and intensity modulation was achieved using sliding window technique. The response to absorbed dose was evaluated using magnetic resonance imaging. Measured and calculated dose distributions were compared with regard to in-plane isodoses and dose volume histograms. In addition, the spatial and dosimetric accuracy was evaluated using the gamma formalism. Good agreement between calculated and measured data was obtained. In the isocenter plane, the 70% and 90% isodoses acquired using the different methods are mostly within 2 mm, with up to 3 mm disagreement at isolated points. For the planning target volume (PTV), the calculated mean relative dose was 96.8 +/- 2.5% (1 SD) and the measured relative mean dose was 98.6 +/- 2.2%. Corresponding data for an organ at risk was 34.4 +/- 0.9% and 32.7 +/- 0.7%, respectively. The gamma criterion (3 mm spatial/3% dose deviation) was fulfilled for 94% of the pixels in the target region. Discrepancies were found in hot spots the upper and lower parts of the PTV, where the measured dose was up to 11% higher than calculated. This was attributed to sub optimal scatter kernels used in the treatment planning system dose calculations. Our results indicate great potential for IMRT verification using MAGIC-type polymer gel.

  13. MIMO FSO communication using subcarrier intensity modulation over double generalized gamma fading

    NASA Astrophysics Data System (ADS)

    Yi, Xiang; Yao, Mingwu; Wang, Xiaoyang

    2017-01-01

    Atmospheric turbulence-induced fading is known to have a serious detrimental effect on the performance of free-space optical (FSO) communication. The involvement of multiple lasers and photodetectors in FSO systems offers an effective way to overcome fading. Very recently, a new generic fading model, called double-generalized gamma (double GG), is developed for accurately describing irradiance fading over a wide range of turbulence conditions. Therefore, for a general and exact study of the multiple-input multiple-output (MIMO) FSO system, the double GG fading model is adopted in this paper. We investigate the MIMO FSO systems using subcarrier intensity modulation. Two typical transmit diversity schemes, repetition code (RC) and orthogonal space-time block code (OSTBC), are considered. We first propose a new power series expression for the probability density function of the double GG fading. Then we derive the average error rate expressions for both schemes in terms of double power series. The truncated forms of the derived power series enable the rapid and accurate numerical computation of the error rates. Furthermore, we present the asymptotic error rate analyses at high electrical signal-to-noise ratio (SNR) for both schemes. Closed-form diversity order and coding gain for both schemes are also obtained. Our numerical results, verified by simulation, confirm that RC outperforms OSTBC for MIMO FSO systems with subcarrier intensity modulation in double GG fading. The asymptotic coding gain of the RC scheme over the OSTBC scheme is analytically quantified for varying degrees of the fading strength.

  14. Accelerated Partial Breast Irradiation with Intensity-Modulated Radiotherapy Is Feasible for Chinese Breast Cancer Patients

    PubMed Central

    He, Zhenyu; Wu, Sangang; Zhou, Juan; Sun, Jiayan; Lin, Qin; Lin, Huanxin; Guan, Xunxing

    2014-01-01

    Purpose Several accelerated partial breast irradiation (APBI) techniques are being investigated in patients with early-stage breast cancer. The present study evaluated the feasibility, early toxicity, initial efficacy, and cosmetic outcomes of accelerated partial breast intensity-modulated radiotherapy (IMRT) for Chinese female patients with early-stage breast cancer after breast-conserving surgery. Methods A total of 38 patients met the inclusion criteria and an accelerated partial breast intensity-modulated radiotherapy (APBI-IMRT) plan was designed for each patient. The prescription dose was 34 Gy in 10 fractions, 3.4 Gy per fraction, twice a day, in intervals of more than 6 hours. Results Of the 38 patients, six patients did not meet the planning criteria. The remaining 32 patients received APBI-IMRT with a mean target volume conformity index of 0.67 and a dose homogeneity index of 1.06. The median follow-up time was 53 months and no local recurrence or distant metastasis was detected. The most common acute toxicities observed within 3 months after radiotherapy were erythema, breast edema, pigmentation, and pain in the irradiated location, among which 43.8%, 12.5%, 31.3%, and 28.1% were grade 1 toxicities, respectively. The most common late toxicities occurring after 3 months until the end of the follow-up period were breast edema, pigmentation, pain in the irradiated location, and subcutaneous fibrosis, among which 6.2%, 28.1%, 21.9%, and 37.5% were grade 1 toxicities, respectively. Thirty-one patients (96.8%) had fine or excellent cosmetic outcomes, and only one patient had a poor cosmetic outcome. Conclusion It is feasible for Chinese females to receive APBI-IMRT after breast conserving surgery. The radiotherapeutic toxicity is acceptable, and both the initial efficacy and cosmetic outcomes are good. PMID:25320624

  15. Intensity-modulated radiotherapy in high-grade gliomas: Clinical and dosimetric results

    SciTech Connect

    Narayana, Ashwatha . E-mail: narayana@mskcc.org; Yamada, Josh; Berry, Sean; Shah, Priti B.S.; Hunt, Margie; Gutin, Philip H.; Leibel, Steven A.

    2006-03-01

    Purpose: To report preliminary clinical and dosimetric data from intensity-modulated radiotherapy (IMRT) for malignant gliomas. Methods and Materials: Fifty-eight consecutive high-grade gliomas were treated between January 2001 and December 2003 with dynamic multileaf collimator IMRT, planned with the inverse approach. A dose of 59.4-60 Gy at 1.8-2.0 Gy per fraction was delivered. A total of three to five noncoplanar beams were used to cover at least 95% of the target volume with the prescription isodose line. Glioblastoma accounted for 70% of the cases, and anaplastic oligodendroglioma histology (pure or mixed) was seen in 15% of the cases. Surgery consisted of biopsy only in 26% of the patients, and 80% received adjuvant chemotherapy. Results: With a median follow-up of 24 months, 85% of the patients have relapsed. The median progression-free survival time for anaplastic astrocytoma and glioblastoma histology was 5.6 and 2.5 months, respectively. The overall survival time for anaplastic glioma and glioblastoma was 36 and 9 months, respectively. Ninety-six percent of the recurrences were local. No Grade IV/V late neurologic toxicities were noted. A comparative dosimetric analysis revealed that regardless of tumor location, IMRT did not significantly improve target coverage compared with three-dimensional planning. However, IMRT resulted in a decreased maximum dose to the spinal cord, optic nerves, and eye by 16%, 7%, and 15%, respectively, owing to its improved dose conformality. The mean brainstem dose also decreased by 7%. Intensity-modulated radiotherapy delivered with a limited number of beams did not result in an increased dose to the normal brain. Conclusions: It is unlikely that IMRT will improve local control in high-grade gliomas without further dose escalation compared with conventional radiotherapy. However, it might result in decreased late toxicities associated with radiotherapy.

  16. Characteristics and performance of an intensity-modulated optically pumped magnetometer in comparison to the classical M(x) magnetometer.

    PubMed

    Schultze, Volkmar; Ijsselsteijn, Rob; Scholtes, Theo; Woetzel, Stefan; Meyer, Hans-Georg

    2012-06-18

    We compare the performance of two methods for the synchronization of the atomic spins in optically pumped magnetometers: intensity modulation of the pump light and the classical M(x) method using B(1) field modulation. Both techniques use the same set-up and measure the resulting features of the light after passing a micro-fabricated Cs cell. The intensity-modulated pumping shows several advantages: better noise-limited magnetic field sensitivity, misalignment between pumping and spin synchronization is excluded, and magnetometer arrays without any cross-talk can be easily set up.

  17. Stereotactic radiotherapy using Novalis for craniopharyngioma adjacent to optic pathways.

    PubMed

    Hashizume, Chisa; Mori, Yoshimasa; Kobayashi, Tatsuya; Shibamoto, Yuta; Nagai, Aiko; Hayashi, Naoki

    2010-06-01

    Craniopharyngioma has benign histological character. However, because of proximity to optic pathways, pituitary gland, and hypothalamus, it may cause severe and permanent damage to such critical structures and can even be life threatening. Total surgical resection is often difficult. This study aims to evaluate treatment results of Novalis stereotactic radiotherapy (SRT) for craniopharyngioma adjacent to optic pathways. Ten patients (six men, four women) with craniopharyngioma and median age of 56.5 years (range 10-74 years) were treated by SRT using Novalis from July 2006 through March 2009. Median volume of tumor was 7.9 ml (range 1.1-21 ml). Three-dimensional noncoplanar five- or seven-beam SRT or coplanar five-beam SRT with intensity modulation was performed. Total dose of 30-39 Gy in 10-15 fractions (median 33 Gy) was delivered to the target. Ten patients were followed up for 9-36 months (median 25.5 months). Response rate was 80% (8/10), and control rate was 100%. Improvement of neurological symptoms was observed in five patients. No serious complications due to SRT were found. SRT for craniopharyngioma may be a safe and effective treatment. Longer follow-up is necessary to determine long-term tumor control or late complications.

  18. Effect of spine hardware on small spinal stereotactic radiosurgery dosimetry

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Yang, James N.; Li, Xiaoqiang; Tailor, Ramesh; Vassilliev, Oleg; Brown, Paul; Rhines, Laurence; Chang, Eric

    2013-10-01

    Monte Carlo (MC) modeling of a 6 MV photon beam was used to study the dose perturbation from a titanium rod 5 mm in diameter in various small fields range from 2 × 2 to 5 × 5 cm2. The results showed that the rod increased the dose to water by ˜6% at the water-rod interface because of electron backscattering and decreased the dose by ˜7% in the shadow of the rod because of photon attenuation. The Pinnacle3 treatment planning system calculations matched the MC results at the depths more than 1 cm past the rod when the correct titanium density of 4.5 g cm-3 was used, but significantly underestimated the backscattering dose at the water-rod interface. A CT-density table with a top density of 1.82 g cm-3 (cortical bone) is a practical way to reduce the dosimetric error from the artifacts by preventing high density assignment to them, but can underestimates the attenuation by the titanium rod by 6%. However, when multi-beam with intensity modulation is used in actual patient spinal stereotactic radiosurgery treatment, the dosimetric effect of assigning 4.5 instead of 1.82 g cm-3 to titanium implants is complicated. It ranged from minimal effect to 2% dose difference affecting 15% target volume in the study. When hardware is in the beam path, density override to the titanium hardware is recommended.

  19. Fatal pneumonitis associated with intensity-modulated radiation therapy for mesothelioma

    SciTech Connect

    Allen, Aaron M. . E-mail: aallen@lroc.harvard.edu; Czerminska, Maria; Jaenne, Pasi A.; Sugarbaker, David J.; Bueno, Raphael; Harris, Jay R.; Court, Laurence; Baldini, Elizabeth H.

    2006-07-01

    Purpose: To describe the initial experience at Dana-Farber Cancer Institute/Brigham and Women's Hospital with intensity-modulated radiation therapy (IMRT) as adjuvant therapy after extrapleural pneumonectomy (EPP) and adjuvant chemotherapy. Methods and Materials: The medical records of patients treated with IMRT after EPP and adjuvant chemotherapy were retrospectively reviewed. IMRT was given to a dose of 54 Gy to the clinical target volume in 1.8 Gy daily fractions. Treatment was delivered with a dynamic multileaf collimator using a sliding window technique. Eleven of 13 patients received heated intraoperative cisplatin chemotherapy (225 mg/m{sup 2}). Two patients received neoadjuvant intravenous cisplatin/pemetrexed, and 10 patients received adjuvant cisplatin/pemetrexed chemotherapy after EPP but before radiation therapy. All patients received at least 2 cycles of intravenous chemotherapy. The contralateral lung was limited to a V20 (volume of lung receiving 20 Gy or more) of 20% and a mean lung dose (MLD) of 15 Gy. All patients underwent fluorodeoxyglucose positron emission tomography (FDG-PET) for staging, and any FDG-avid areas in the hemithorax were given a simultaneous boost of radiotherapy to 60 Gy. Statistical comparisons were done using two-sided t test. Results: Thirteen patients were treated with IMRT from December 2004 to September 2005. Six patients developed fatal pneumonitis after treatment. The median time from completion of IMRT to the onset of radiation pneumonitis was 30 days (range 5-57 days). Thirty percent of patients (4 of 13) developed acute Grade 3 nausea and vomiting. One patient developed acute Grade 3 thrombocytopenia. The median V20, MLD, and V5 (volume of lung receiving 5 Gy or more) for the patients who developed pneumonitis was 17.6% (range, 15.3-22.3%), 15.2 Gy (range, 13.3-17 Gy), and 98.6% (range, 81-100%), respectively, as compared with 10.9% (range, 5.5-24.7%) (p = 0.08), 12.9 Gy (range, 8.7-16.9 Gy) (p = 0.07), and 90% (range

  20. Computer-assisted selection of coplanar beam orientations in intensity-modulated radiation therapy*

    NASA Astrophysics Data System (ADS)

    Pugachev, A.; Xing, L.

    2001-09-01

    In intensity-modulated radiation therapy (IMRT), the incident beam orientations are often determined by a trial and error search. The conventional beam's-eye view (BEV) tool becomes less helpful in IMRT because it is frequently required that beams go through organs at risk (OARs) in order to achieve a compromise between the dosimetric objectives of the planning target volume (PTV) and the OARs. In this paper, we report a beam's-eye view dosimetrics (BEVD) technique to assist in the selection of beam orientations in IMRT. In our method, each beam portal is divided into a grid of beamlets. A score function is introduced to measure the `goodness' of each beamlet at a given gantry angle. The score is determined by the maximum PTV dose deliverable by the beamlet without exceeding the tolerance doses of the OARs and normal tissue located in the path of the beamlet. The overall score of the gantry angle is given by a sum of the scores of all beamlets. For a given patient, the score function is evaluated for each possible beam orientation. The directions with the highest scores are then selected as the candidates for beam placement. This procedure is similar to the BEV approach used in conventional radiation therapy, except that the evaluation by a human is replaced by a score function to take into account the intensity modulation. This technique allows one to select beam orientations without the excessive computing overhead of computer optimization of beam orientation. It also provides useful insight into the problem of selection of beam orientation and is especially valuable for complicated cases where the PTV is surrounded by several sensitive structures and where it is difficult to select a set of `good' beam orientations. Several two-dimensional (2D) model cases were used to test the proposed technique. The plans obtained using the BEVD-selected beam orientations were compared with the plans obtained using equiangular spaced beams. For all the model cases investigated

  1. Whole-Field Simultaneous Integrated-Boost Intensity-Modulated Radiotherapy for Patients With Nasopharyngeal Carcinoma

    SciTech Connect

    Wong, Frank C.S.; Ng, Alice W.Y.; Lee, Victor H.F.; Lui, Collin M.M.; Yuen, K.-K.; Sze, W.-K.; Leung, T.-W.; Tung, Stewart Y.

    2010-01-15

    Purpose: To retrospectively review the outcomes of our patients with newly diagnosed nondisseminated nasopharyngeal carcinoma treated with intensity-modulated radiotherapy using a whole-field simultaneous integrated-boost technique. Methods and Materials: A total of 175 patients treated with WF-SIB between mid-2004 and 2005 were eligible for study inclusion. The distribution of disease by stage was Stage IA in 10.9%, Stage IIA in 2.3%, Stage IIB in 21.7%, Stage III in 41.1%, Stage IVA in 14.9%, and Stage IVB in 9.1%. Of the 175 patients, 2 (1.2%), 10 (5.7%), and 163 (93.1%) had World Health Organization type I, II, and III histologic features, respectively. We prescribed 70 Gy, 60 Gy, and 54 Gy delivered in 33 fractions within 6.5 weeks at the periphery of three planning target volumes (PTV; PTV70, PTV60, and PTV54, respectively). Of the 175 patients, 46 with early T-stage disease received a brachytherapy boost, and 127 with advanced local or regional disease received chemotherapy. Results: The median follow-up period was 34 months. The overall 3-year local failure-free survival, regional failure-free survival, distant failure-free survival, and overall survival rate was 93.6%, 93.3%, 86.6%, and 87.2%, respectively. Cox regression analysis showed Stage N2-N3 disease (p = .029) and PTV (p = .024) to be independent factors predicting a greater risk of distant failure and poor overall survival, respectively. Grade 3 acute mucositis/pharyngitis occurred in 23.4% of patients, and Stage T4 disease was the only significant predictor of mucositis/pharyngitis (p = .021). Conclusion: Whole-field simultaneous integrated-boost intensity-modulated radiotherapy with a dose >70 Gy achieved excellent locoregional control, without an excess incidence of severe, acute mucositis/pharyngitis, in the present study. Strategies for using such highly conformal treatment for patients with a large tumor and late N-stage disease are potential areas of investigation for future studies.

  2. Treatment of extensive scalp lesions with segmental intensity-modulated photon therapy

    SciTech Connect

    Bedford, James L. . E-mail: James.Bedford@icr.ac.uk; Childs, Peter J.; Hansen, Vibeke Nordmark; Warrington, Alan P.; Mendes, Ruheena L.; Glees, John P.

    2005-08-01

    Purpose: To compare static electron therapy, electron arc therapy, and photon intensity-modulated radiation therapy (IMRT) for treatment of extensive scalp lesions and to examine the dosimetric accuracy of the techniques. Methods and Materials: A retrospective treatment-planning study was performed to evaluate the relative merits of static electron fields, arcing electron fields, and five-field photon IMRT. Thermoluminescent dosimeters (TLD) were used to verify the accuracy of the techniques. The required thickness of bolus was investigated, and an anthropomorphic phantom was also used to examine the effects of air gaps between the wax bolus used for the IMRT technique and the patient's scalp. Results: Neither static nor arcing electron techniques were able to provide a reliable coverage of the planning target volume (PTV), owing to obliquity of the fields in relation to the scalp. The IMRT technique considerably improved PTV dose uniformity, though it irradiated a larger volume of brain. Either 0.5 cm or 1.0 cm of wax bolus was found to be suitable. Air gaps of up to 1 cm between the bolus and the patient's scalp were correctly handled by the treatment-planning system and had negligible influence on the dose to the scalp. Conclusions: Photon IMRT provides a feasible alternative to electron techniques for treatment of large scalp lesions, resulting in improved homogeneity of dose to the PTV but with a moderate increase in dose to the brain.

  3. Effect of respiratory motion on the delivery of breast radiotherapy using SMLC intensity modulation

    SciTech Connect

    Liu, Qiang; McDermott, Patrick; Burmeister, Jay

    2007-01-15

    This study evaluates the effects of respiratory motion on breast radiotherapy delivered using segmented multileaf collimator (SMLC) intensity modulation. An anthropomorphic breast phantom was constructed of polystyrene plates between which radiographic films were inserted. The phantom was mounted on a moving platform to simulate one-dimensional sinusoidal oscillation with variable amplitude and frequency. The motion effect on two breast IMRT techniques, a beamlet-based plan created using the Corvus treatment planning system and an aperture-based plan, was evaluated via film comparison. Motion-induced differences in the treatment region are generally within {+-}5%, with the exception of the posterior field edge and the apex of the breast in the Corvus IMRT plan. Considering the experimental uncertainty arising from the setup and film dosimetry, this result indicates that respiratory motion-induced dose variations are generally relatively insignificant. It appears that the anterior hot spots observed in the Corvus IMRT plan result from the high intensity fluence delivered to the ''virtual bolus'' area which must be created during the planning process in order to provide ''flash'' for the respiratory motion. The potential magnitude of such effects resulting from the interplay between fluence modulation and patient motion are unique to the individual planning system and planning technique, as well as the delivery equipment and technique. Such effects should be carefully investigated prior to the implementation of IMRT for breast radiotherapy.

  4. Intelligence-guided beam angle optimization in treatment planning of intensity-modulated radiation therapy.

    PubMed

    Yan, Hui; Dai, Jian-Rong

    2016-10-01

    An intelligence guided approach based on fuzzy inference system (FIS) was proposed to automate beam angle optimization in treatment planning of intensity-modulated radiation therapy (IMRT). The model of FIS is built on inference rules in describing the relationship between dose quality of IMRT plan and irradiated region of anatomical structure. Dose quality of IMRT plan is quantified by the difference between calculated and constraint doses of the anatomical structures in an IMRT plan. Irradiated region of anatomical structure is characterized by the metric, covered region of interest, which is the region of an anatomical structure under radiation field while beam's eye-view is conform to target volume. Initially, an IMRT plan is created with a single beam. The dose difference is calculated for the input of FIS and the output of FIS is obtained with processing of fuzzy inference. Later, a set of candidate beams is generated for replacing the current beam. This process continues until no candidate beams is found. Then the next beam is added to the IMRT plan and optimized in the same way as the previous beam. The new beam keeps adding to the IMRT plan until the allowed beam number is reached. Two spinal cases were investigated in this study. The preliminary results show that dose quality of IMRT plans achieved by this approach is better than those achieved by the default approach with equally spaced beam setting. It is effective to find the optimal beam combination of IMRT plan with the intelligence-guided approach.

  5. Marginal Misses After Postoperative Intensity-Modulated Radiotherapy for Head and Neck Cancer

    SciTech Connect

    Chen, Allen M.; Farwell, D. Gregory; Luu, Quang; Chen, Leon M.; Vijayakumar, Srinivasan; Purdy, James A.

    2011-08-01

    Purpose: To describe the spatial distribution of local-regional recurrence (LRR) among patients treated postoperatively with intensity-modulated radiotherapy (IMRT) for head and neck cancer. Methods and Materials: The medical records of 90 consecutive patients treated by gross total resection and postoperative IMRT for squamous cell carcinoma of the head and neck from January 2003 to July 2009 were reviewed. Sites of disease were the oral cavity (43 patients), oropharynx (20 patients), larynx (15 patients), and hypopharynx (12 patients). Fifty patients (56%) received concurrent chemotherapy. Results: Seventeen of 90 patients treated with postoperative IMRT experienced LRR, yielding a 2-year estimate of local regional control of 80%. Among the LRR patients, 11 patients were classified as in-field recurrences, occurring within the physician-designated clinical target volume, and 6 patients were categorized as marginal recurrences. There were no out-of-field geographical misses. Sites of marginal LRRs included the contralateral neck adjacent to the spared parotid gland (3 patients), the dermal/subcutaneous surface (2 patients), and the retropharyngeal/retrostyloid lymph node region (1 patient). Conclusions: Although the incidence of geographical misses was relatively low, the possibility of this phenomenon should be considered in the design of target volumes among patients treated by postoperative IMRT for head and neck cancer.

  6. Clinical and dosimetric implications of intensity-modulated radiotherapy for early-stage glottic carcinoma

    SciTech Connect

    Ward, Matthew Christopher Pham, Yvonne D.; Kotecha, Rupesh; Zakem, Sara J.; Murray, Eric; Greskovich, John F.

    2016-04-01

    Conventional parallel-opposed radiotherapy (PORT) is the established standard technique for early-stage glottic carcinoma. However, case reports have reported the utility of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) with or without image guidance (image-guided radiotherapy, IGRT) in select patients. The proposed advantages of IMRT/VMAT include sparing of the carotid artery, thyroid gland, and the remaining functional larynx, although these benefits remain unclear. The following case study presents a patient with multiple vascular comorbidities treated with VMAT for early-stage glottic carcinoma. A detailed explanation of the corresponding treatment details, dose-volume histogram (DVH) analysis, and a review of the relevant literature are provided. Conventional PORT remains the standard of care for early-stage glottic carcinoma. IMRT or VMAT may be beneficial for select patients, although great care is necessary to avoid a geographical miss. Clinical data supporting the benefit of CRT are lacking. Therefore, these techniques should be used with caution and only in selected patients.

  7. Intensity modulated radiation therapy with field rotation--a time-varying fractionation study.

    PubMed

    Dink, Delal; Langer, Mark P; Rardin, Ronald L; Pekny, Joseph F; Reklaitis, Gintaras V; Saka, Behlul

    2012-06-01

    This paper proposes a novel mathematical approach to the beam selection problem in intensity modulated radiation therapy (IMRT) planning. The approach allows more beams to be used over the course of therapy while limiting the number of beams required in any one session. In the proposed field rotation method, several sets of beams are interchanged throughout the treatment to allow a wider selection of beam angles than would be possible with fixed beam orientations. The choice of beamlet intensities and the number of identical fractions for each set are determined by a mixed integer linear program that controls jointly for the distribution per fraction and the cumulative dose distribution delivered to targets and critical structures. Trials showed the method allowed substantial increases in the dose objective and/or sparing of normal tissues while maintaining cumulative and fraction size limits. Trials for a head and neck site showed gains of 25%-35% in the objective (average tumor dose) and for a thoracic site gains were 7%-13%, depending on how strict the fraction size limits were set. The objective did not rise for a prostate site significantly, but the tolerance limits on normal tissues could be strengthened with the use of multiple beam sets.

  8. Intensity-modulated radiation therapy for malignancies of the nasal cavity and paranasal sinuses

    SciTech Connect

    Daly, Megan E.; Chen, Allen M. . E-mail: allenmchen@yahoo.com; Bucci, M. Kara; El-Sayed, Ivan; Xia Ping; Kaplan, Michael J.; Eisele, David W.

    2007-01-01

    Purpose: To report the clinical outcome of patients treated with intensity-modulated radiation therapy (IMRT) for malignancies of the nasal cavity and paranasal sinuses. Methods and Materials: Between 1998 and 2004, 36 patients with malignancies of the sinonasal region were treated with IMRT. Thirty-two patients (89%) were treated in the postoperative setting after gross total resection. Treatment plans were designed to provide a dose of 70 Gy to 95% or more of the gross tumor volume (GTV) and 60 Gy to 95% or more of the clinical tumor volume (CTV) while sparing neighboring critical structures including the optic chiasm, optic nerves, eyes, and brainstem. The primary sites were: 13 ethmoid sinus, 10 maxillary sinus, 7 nasal cavity, and 6 other. Histology was: 12 squamous cell, 7 esthesioneuroblastoma, 5 adenoid cystic, 5 undifferentiated, 5 adenocarcinoma, and 2 other. Median follow-up was 51 months among surviving patients (range, 9-82 months). Results: The 2-year and 5-year estimates of local control were 62% and 58%, respectively. One patient developed isolated distant metastasis, and none developed isolated regional failure. The 5-year rates of disease-free and overall survival were 55% and 45%, respectively. The incidence of ocular toxicity was minimal with no patients reporting decreased vision. Late complications included xerophthalmia (1 patient), lacrimal stenosis (1 patient), and cataract (1 patient). Conclusion: Although IMRT for malignancies of the sinonasal region does not appear to lead to significant improvements in disease control, the low incidence of complications is encouraging.

  9. Dosimetric comparison of tools for intensity modulated radiation therapy with gamma analysis: a phantom study

    NASA Astrophysics Data System (ADS)

    Akbas, Ugur; Okutan, Murat; Demir, Bayram; Koksal, Canan

    2015-07-01

    Dosimetry of the Intensity Modulated Radiation Therapy (IMRT) is very important because of the complex dose distributions. Diode arrays are the most common and practical measurement tools for clinical usage for IMRT. Phantom selection is critical for QA process. IMRT treatment plans are recalculated for the phantom irradiation in QA. Phantoms are made in different geometrical shapes to measure the doses of different types of irradiation techniques. Comparison of measured and calculated dose distributions for IMRT can be made by using gamma analysis. In this study, 10 head-and-neck IMRT QA plans were created with Varian Eclipse 8.9 treatment planning system. Water equivalent RW3-slab phantoms, Octavius-2 phantom and PTW Seven29 2D-array were used for QA measurements. Gantry, collimator and couch positions set to 00 and QA plans were delivered to RW3 and Octavius phantoms. Then the positions set to original angles and QA plans irradiated again. Measured and calculated fluence maps were evaluated with gamma analysis for different DD and DTA criteria. The effect of different set-up conditions for RW3 and Octavius phantoms in QA plan delivery evaluated by gamma analysis. Results of gamma analysis show that using RW3-slab phantoms with setting parameters to 00 is more appropriate for IMRT QA.

  10. Risk of secondary cancers from scattered radiation during intensity-modulated radiotherapies for hepatocellular carcinoma

    PubMed Central

    2014-01-01

    Purpose To evaluate and compare the risks of secondary cancers from therapeutic doses received by patients with hepatocellular carcinoma (HCC) during intensity-modulated radiotherapy (IMRT), volumetric arc therapy (VMAT), and tomotherapy (TOMO). Methods Treatments for five patients with hepatocellular carcinoma (HCC) were planned using IMRT, VMAT, and TOMO. Based on the Biological Effects of Ionizing Radiation VII method, the excess relative risk (ERR), excess absolute risk (EAR), and lifetime attributable risk (LAR) were evaluated from therapeutic doses, which were measured using radiophotoluminescence glass dosimeters (RPLGDs) for each organ inside a humanoid phantom. Results The average organ equivalent doses (OEDs) of 5 patients were measured as 0.23, 1.18, 0.91, 0.95, 0.97, 0.24, and 0.20 Gy for the thyroid, lung, stomach, liver, small intestine, prostate (or ovary), and rectum, respectively. From the OED measurements, LAR incidence were calculated as 83, 46, 22, 30, 2 and 6 per 104 person for the lung, stomach, normal liver, small intestine, prostate (or ovary), and rectum. Conclusions We estimated the secondary cancer risks at various organs for patients with HCC who received different treatment modalities. We found that HCC treatment is associated with a high secondary cancer risk in the lung and stomach. PMID:24886163

  11. Intensity modulated radiotherapy induces pro-inflammatory and pro-survival responses in prostate cancer patients

    PubMed Central

    EL-SAGHIRE, HOUSSEIN; VANDEVOORDE, CHARLOT; OST, PIET; MONSIEURS, PIETER; MICHAUX, ARLETTE; DE MEERLEER, GERT; BAATOUT, SARAH; THIERENS, HUBERT

    2014-01-01

    Intensity modulated radiotherapy (IMRT) is one of the modern conformal radiotherapies that is widely used within the context of cancer patient treatment. It uses multiple radiation beams targeted to the tumor, however, large volumes of the body receive low doses of irradiation. Using γ-H2AX and global genome expression analysis, we studied the biological responses induced by low doses of ionizing radiation in prostate cancer patients following IMRT. By means of different bioinformatics analyses, we report that IMRT induced an inflammatory response via the induction of viral, adaptive, and innate immune signaling. In response to growth factors and immune-stimulatory signaling, positive regulation in the progression of cell cycle and DNA replication were induced. This denotes pro-inflammatory and pro-survival responses. Furthermore, double strand DNA breaks were induced in every patient 30 min after the treatment and remaining DNA repair and damage signaling continued after 18–24 h. Nine genes belonging to inflammatory responses (TLR3, SH2D1A and IL18), cell cycle progression (ORC4, SMC2 and CCDC99) and DNA damage and repair (RAD17, SMC6 and MRE11A) were confirmed by quantitative RT-PCR. This study emphasizes that the risk assessment of health effects from the out-of-field low doses during IMRT should be of concern, as these may increase the risk of secondary cancers and/or systemic inflammation. PMID:24435511

  12. Performance Characteristics Of An Intensity Modulated Advanced X-Ray Source (IMAXS) For Homeland Security Applications

    SciTech Connect

    Langeveld, Willem G. J.; Brown, Craig; Condron, Cathie; Ingle, Mike; Christensen, Phil A.; Johnson, William A.; Owen, Roger D.; Ross, Randy

    2011-06-01

    X-ray cargo inspection systems for the detection and verification of threats and contraband must address stringent, competitive performance requirements. High x-ray intensity is needed to penetrate dense cargo, while low intensity is desirable to minimize the radiation footprint, i.e. the size of the controlled area, required shielding and the dose to personnel. In a collaborative effort between HESCO/PTSE Inc., XScell Corp., Stangenes Industries, Inc. and Rapiscan Laboratories, Inc., an Intensity Modulated Advanced X-ray Source (IMAXS) was designed and produced. Cargo inspection systems utilizing such a source have been projected to achieve up to 2 inches steel-equivalent greater penetration capability, while on average producing the same or smaller radiation footprint as present fixed-intensity sources. Alternatively, the design can be used to obtain the same penetration capability as with conventional sources, but reducing the radiation footprint by about a factor of three. The key idea is to anticipate the needed intensity for each x-ray pulse by evaluating signal strength in the cargo inspection system detector array for the previous pulse. The IMAXS is therefore capable of changing intensity from one pulse to the next by an electronic signal provided by electronics inside the cargo inspection system detector array, which determine the required source intensity for the next pulse. We report on the completion of a 9 MV S-band (2998 MHz) IMAXS source and comment on its performance.

  13. A fast optimization algorithm for multicriteria intensity modulated proton therapy planning

    SciTech Connect

    Chen Wei; Craft, David; Madden, Thomas M.; Zhang, Kewu; Kooy, Hanne M.; Herman, Gabor T.

    2010-09-15

    Purpose: To describe a fast projection algorithm for optimizing intensity modulated proton therapy (IMPT) plans and to describe and demonstrate the use of this algorithm in multicriteria IMPT planning. Methods: The authors develop a projection-based solver for a class of convex optimization problems and apply it to IMPT treatment planning. The speed of the solver permits its use in multicriteria optimization, where several optimizations are performed which span the space of possible treatment plans. The authors describe a plan database generation procedure which is customized to the requirements of the solver. The optimality precision of the solver can be specified by the user. Results: The authors apply the algorithm to three clinical cases: A pancreas case, an esophagus case, and a tumor along the rib cage case. Detailed analysis of the pancreas case shows that the algorithm is orders of magnitude faster than industry-standard general purpose algorithms (MOSEK's interior point optimizer, primal simplex optimizer, and dual simplex optimizer). Additionally, the projection solver has almost no memory overhead. Conclusions: The speed and guaranteed accuracy of the algorithm make it suitable for use in multicriteria treatment planning, which requires the computation of several diverse treatment plans. Additionally, given the low memory overhead of the algorithm, the method can be extended to include multiple geometric instances and proton range possibilities, for robust optimization.

  14. Radiochromic film based transit dosimetry for verification of dose delivery with intensity modulated radiotherapy

    SciTech Connect

    Chung, Kwangzoo; Lee, Kiho; Shin, Dongho; Kyung Lim, Young; Byeong Lee, Se; Yoon, Myonggeun; Son, Jaeman; Yong Park, Sung

    2013-02-15

    Purpose: To evaluate the transit dose based patient specific quality assurance (QA) of intensity modulated radiation therapy (IMRT) for verification of the accuracy of dose delivered to the patient. Methods: Five IMRT plans were selected and utilized to irradiate a homogeneous plastic water phantom and an inhomogeneous anthropomorphic phantom. The transit dose distribution was measured with radiochromic film and was compared with the computed dose map on the same plane using a gamma index with a 3% dose and a 3 mm distance-to-dose agreement tolerance limit. Results: While the average gamma index for comparisons of dose distributions was less than one for 98.9% of all pixels from the transit dose with the homogeneous phantom, the passing rate was reduced to 95.0% for the transit dose with the inhomogeneous phantom. Transit doses due to a 5 mm setup error may cause up to a 50% failure rate of the gamma index. Conclusions: Transit dose based IMRT QA may be superior to the traditional QA method since the former can show whether the inhomogeneity correction algorithm from TPS is accurate. In addition, transit dose based IMRT QA can be used to verify the accuracy of the dose delivered to the patient during treatment by revealing significant increases in the failure rate of the gamma index resulting from errors in patient positioning during treatment.

  15. Meningioma Causing Visual Impairment: Outcomes and Toxicity After Intensity Modulated Radiation Therapy

    SciTech Connect

    Maclean, Jillian; Fersht, Naomi; Bremner, Fion; Stacey, Chris; Sivabalasingham, Suganya; Short, Susan

    2013-03-15

    Purpose: To evaluate ophthalmologic outcomes and toxicity of intensity modulated radiation therapy (IMRT) in patients with meningiomas causing visual deficits. Methods and Materials: A prospective observational study with formal ophthalmologic and clinical assessment of 30 consecutive cases of meningioma affecting vision treated with IMRT from 2007 to 2011. Prescriptions were 50.4 Gy to mean target dose in 28 daily fractions. The median follow-up time was 28 months. Twenty-six meningiomas affected the anterior visual pathway (including 3 optic nerve sheath meningiomas); 4 were posterior to the chiasm. Results: Vision improved objectively in 12 patients (40%). Improvements were in visual field (5/16 patients), color vision (4/9 patients), acuity (1/15 patients), extraocular movements (3/11 patients), ptosis (1/5 patients), and proptosis (2/6 patients). No predictors of clinical response were found. Two patients had minor reductions in tumor dimensions on magnetic resonance imaging, 1 patient had radiological progression, and the other patients were stable. One patient experienced grade 2 keratitis, 1 patient had a minor visual field loss, and 5 patients had grade 1 dry eye. Conclusion: IMRT is an effective method for treating meningiomas causing ophthalmologic deficits, and toxicity is minimal. Thorough ophthalmologic assessment is important because clinical responses often occur in the absence of radiological change.

  16. On Linear Infeasibility Arising in Intensity-Modulated Radiation Therapy Inverse Planning.

    PubMed

    Censor, Yair; Ben-Israel, Adi; Xiao, Ying; Galvin, James M

    2008-03-01

    Intensity-modulated radiation therapy (IMRT) gives rise to systems of linear inequalities, representing the effects of radiation on the irradiated body. These systems are often infeasible, in which case one settles for an approximate solution, such as an {α, β}-relaxation, meaning that no more than α percent of the inequalities are violated by no more than β percent. For real-world IMRT problems, there is a feasible {α, β}-relaxation for sufficiently large α, β > 0, however large values of these parameters may be unacceptable medically.The {α, β}-relaxation problem is combinatorial, and for given values of the parameters can be solved exactly by Mixed Integer Programming (MIP), but this may be impractical because of problem size, and the need for repeated solutions as the treatment progresses.As a practical alternative to the MIP approach we present a heuristic non-combinatorial method for finding an approximate relaxation. The method solves a Linear Program (LP) for each pair of values of the parameters {α, β} and progresses through successively increasing values until an acceptable solution is found, or is determined non-existent. The method is fast and reliable, since it consists of solving a sequence of LP's.

  17. Improved outcomes with intensity modulated radiation therapy combined with temozolomide for newly diagnosed glioblastoma multiforme.

    PubMed

    Aherne, Noel J; Benjamin, Linus C; Horsley, Patrick J; Silva, Thomaz; Wilcox, Shea; Amalaseelan, Julan; Dwyer, Patrick; Tahir, Abdul M R; Hill, Jacques; Last, Andrew; Hansen, Carmen; McLachlan, Craig S; Lee, Yvonne L; McKay, Michael J; Shakespeare, Thomas P

    2014-01-01

    Purpose. Glioblastoma multiforme (GBM) is optimally treated by maximal debulking followed by combined chemoradiation. Intensity modulated radiation therapy (IMRT) is gaining widespread acceptance in other tumour sites, although evidence to support its use over three-dimensional conformal radiation therapy (3DCRT) in the treatment of gliomas is currently lacking. We examined the survival outcomes for patients with GBM treated with IMRT and Temozolomide. Methods and Materials. In all, 31 patients with GBM were treated with IMRT and 23 of these received chemoradiation with Temozolomide. We correlated survival outcomes with patient functional status, extent of surgery, radiation dose, and use of chemotherapy. Results. Median survival for all patients was 11.3 months, with a median survival of 7.2 months for patients receiving 40.05 Gray (Gy) and a median survival of 17.4 months for patients receiving 60 Gy. Conclusions. We report one of the few series of IMRT in patients with GBM. In our group, median survival for those receiving 60 Gy with Temozolomide compared favourably to the combined therapy arm of the largest randomised trial of chemoradiation versus radiation to date (17.4 months versus 14.6 months). We propose that IMRT should be considered as an alternative to 3DCRT for patients with GBM.

  18. An intensity modulation and coherent balanced detection intersatellite microwave photonic link using polarization direction control

    NASA Astrophysics Data System (ADS)

    Li, Xuan; Zhu, Zihang; Zhao, Shanghong; Li, Yongjun; Han, Lei; Zhao, Jing

    2014-03-01

    A simple approach for high loss intersatellite microwave photonic link with intensity modulation and coherent balanced detection is proposed. In the transmitter, the double sideband-suppressed carrier (DSB-SC) modulated optical signal and optical carrier (OC) are combined by employing a polarization combiner to chose and control the signals polarization directions, while in the receiver, they are selected respectively by using a polarization splitter for they have orthogonal polarization directions. The separated DSB-SC signal and OC put into balanced detectors and the coherent detection is realized without a local oscillator (LO). At the output, the fundamental signal is augmented and the third-order distortion is suppressed for the DSB-SC modulation, the second-order distortion is removed for the balanced detection and the noise is reduced for the polarization direction control. The signal to noise and distortion ratio (SNDR) can be optimized by adjusting the power of OC and modulation index. The simulation results show that, a SNDR higher than 30 dB can be obtained for the proposed method, which is in agreement with the theoretical analysis.

  19. A novel linear programming approach to fluence map optimization for intensity modulated radiation therapy treatment planning.

    PubMed

    Romeijn, H Edwin; Ahuja, Ravindra K; Dempsey, James F; Kumar, Arvind; Li, Jonathan G

    2003-11-07

    We present a novel linear programming (LP) based approach for efficiently solving the intensity modulated radiation therapy (IMRT) fluence-map optimization (FMO) problem to global optimality. Our model overcomes the apparent limitations of a linear-programming approach by approximating any convex objective function by a piecewise linear convex function. This approach allows us to retain the flexibility offered by general convex objective functions, while allowing us to formulate the FMO problem as a LP problem. In addition, a novel type of partial-volume constraint that bounds the tail averages of the differential dose-volume histograms of structures is imposed while retaining linearity as an alternative approach to improve dose homogeneity in the target volumes, and to attempt to spare as many critical structures as possible. The goal of this work is to develop a very rapid global optimization approach that finds high quality dose distributions. Implementation of this model has demonstrated excellent results. We found globally optimal solutions for eight 7-beam head-and-neck cases in less than 3 min of computational time on a single processor personal computer without the use of partial-volume constraints. Adding such constraints increased the running times by a factor of 2-3, but improved the sparing of critical structures. All cases demonstrated excellent target coverage (> 95%), target homogeneity (< 10% overdosing and < 7% underdosing) and organ sparing using at least one of the two models.

  20. Intensity-modulated radiosurgery with rapidarc for multiple brain metastases and comparison with static approach

    SciTech Connect

    Wang Jiazhu; Pawlicki, Todd; Rice, Roger; Mundt, Arno J.; Sandhu, Ajay; Lawson, Joshua; Murphy, Kevin T.

    2012-04-01

    Rotational RapidArc (RA) and static intensity-modulated radiosurgery (IMRS) have been used for brain radiosurgery. This study compares the 2 techniques from beam delivery parameters and dosimetry aspects for multiple brain metastases. Twelve patients with 2-12 brain lesions treated with IMRS were replanned using RA. For each patient, an optimal 2-arc RA plan from several trials was chosen for comparison with IMRS. Homogeneity, conformity, and gradient indexes have been calculated. The mean dose to normal brain and maximal dose to other critical organs were evaluated. It was found that monitor unit (MU) reduction by RA is more pronounced for cases with larger number of brain lesions. The MU-ratio of RA and IMRS is reduced from 104% to 39% when lesions increase from 2 to 12. The dose homogeneities are comparable in both techniques and the conformity and gradient indexes and critical organ doses are higher in RA. Treatment time is greatly reduced by RA in intracranial radiosurgery, because RA uses fewer MUs, fewer beams, and fewer couch angles.

  1. Combining segment generation with direct step-and-shoot optimization in intensity-modulated radiation therapy

    SciTech Connect

    Carlsson, Fredrik

    2008-09-15

    A method for generating a sequence of intensity-modulated radiation therapy step-and-shoot plans with increasing number of segments is presented. The objectives are to generate high-quality plans with few, large and regular segments, and to make the planning process more intuitive. The proposed method combines segment generation with direct step-and-shoot optimization, where leaf positions and segment weights are optimized simultaneously. The segment generation is based on a column generation approach. The method is evaluated on a test suite consisting of five head-and-neck cases and five prostate cases, planned for delivery with an Elekta SLi accelerator. The adjustment of segment shapes by direct step-and-shoot optimization improves the plan quality compared to using fixed segment shapes. The improvement in plan quality when adding segments is larger for plans with few segments. Eventually, adding more segments contributes very little to the plan quality, but increases the plan complexity. Thus, the method provides a tool for controlling the number of segments and, indirectly, the delivery time. This can support the planner in finding a sound trade-off between plan quality and treatment complexity.

  2. A Dosimetric Comparison of Proton and Intensity-Modulated Photon Radiotherapy for Pediatric Parameningeal Rhabdomyosarcomas

    SciTech Connect

    Kozak, Kevin R.; Adams, Judith; Krejcarek, Stephanie J.; Tarbell, Nancy J.; Yock, Torunn I.

    2009-05-01

    Purpose: We compared tumor and normal tissue dosimetry of proton radiation therapy with intensity-modulated radiation therapy (IMRT) for pediatric parameningeal rhabdomyosarcomas (PRMS). Methods and Materials: To quantify dosimetric differences between contemporary proton and photon treatment for pediatric PRMS, proton beam plans were compared with IMRT plans. Ten patients treated with proton radiation therapy at Massachusetts General Hospital had IMRT plans generated. To facilitate dosimetric comparisons, clinical target volumes and normal tissue volumes were held constant. Plans were optimized for target volume coverage and normal tissue sparing. Results: Proton and IMRT plans provided acceptable and comparable target volume coverage, with at least 99% of the CTV receiving 95% of the prescribed dose in all cases. Improved dose conformality provided by proton therapy resulted in significant sparing of all examined normal tissues except for ipsilateral cochlea and mastoid; ipsilateral parotid gland sparing was of borderline statistical significance (p = 0.05). More profound sparing of contralateral structures by protons resulted in greater dose asymmetry between ipsilateral and contralateral retina, optic nerves, cochlea, and mastoids; dose asymmetry between ipsilateral and contralateral parotids was of borderline statistical significance (p = 0.05). Conclusions: For pediatric PRMS, superior normal tissue sparing is achieved with proton radiation therapy compared with IMRT. Because of enhanced conformality, proton plans also demonstrate greater normal tissue dose distribution asymmetry. Longitudinal studies assessing the impact of proton radiotherapy and IMRT on normal tissue function and growth symmetry are necessary to define the clinical consequences of these differences.

  3. Escalated median dose for pituitary macroadenomas using intensity-modulated radiation therapy

    SciTech Connect

    Robinson, D.; Murray, B.; Underwood, L.; Halls, S.; Roa, W

    2004-03-31

    Three-dimensional conformal radiotherapy (3D CRT) has become an established treatment for pituitary macroadenomas. This study is an investigation into the possible dosimetric advantages of intensity-modulated radiotherapy for such critically located tumors. Three consecutive patients with pituitary macroadenoma previously treated with 3D CRT were replanned with inverse-planned IMRT using Helax-TMS (V.6.0, Helax AB, Uppsala, Sweden. Fusion of computed tomography (CT) with postoperative magnetic resonance imaging (MRI) was performed within the planning system to define the gross tumor volume (GTV), planning target volume (PTV), and normal structures including the optic chiasm. Dose-volume histograms (DVHs) for the 3D CRT plans were then compared with those of the corresponding prospective IMRT plans. Both techniques maintained critical structure doses below tolerance levels while maintaining a minimum dose of 45 Gy to 100% of the PTV. While IMRT plans deliver consistently more heterogeneous dose distributions to the PTV, the median PTV dose is elevated in the IMRT plans compared with the 3D CRT plans. For critically located tumors like these pituitary macroadenomas, IMRT allows escalation of the median dose to the tumor without an accompanying loss in critical structure sparing or creating unacceptable cold spots within the PTV.

  4. The Accuracy of Inhomogeneity Corrections in Intensity Modulated Radiation Therapy Planning in Philips Pinnacle System

    SciTech Connect

    Alaei, Parham; Higgins, Patrick D.

    2011-10-01

    The degree of accuracy of inhomogeneity corrections in a treatment planning system is dependent on the algorithm used by the system. The choice of field size, however, could have an effect on the calculation accuracy as well. There have been several evaluation studies on the accuracy of inhomogeneity corrections used by different algorithms. Most of these studies, however, focus on evaluating the dose in phantom using simplified geometry and open/static fields. This work focuses on evaluating the degree of dose accuracy in calculations involving intensity-modulated radiation therapy (IMRT) fields incident on a phantom containing both lung- and bone-equivalent heterogeneities using 6 and 10 MV beams. IMRT treatment plans were generated using the Philips Pinnacle treatment planning system and delivered to a phantom containing 55 thermoluminescent dosimeter (TLD) locations within the lung and bone and near the lung and bone interfaces with solid water. The TLD readings were compared with the dose predicted by the planning system. We find satisfactory agreement between planned and delivered doses, with an overall absolute average difference between measurement and calculation of 1.2% for the 6 MV and 3.1% for the 10 MV beam with larger variations observed near the interfaces and in areas of high-dose gradient. The results presented here demonstrate that the convolution algorithm used in the Pinnacle treatment planning system produces accurate results in IMRT plans calculated and delivered to inhomogeneous media, even in regions that potentially lack electronic equilibrium.

  5. Effect of intensity-modulated radiotherapy versus two-dimensional conventional radiotherapy alone in nasopharyngeal carcinoma

    PubMed Central

    OuYang, Pu-Yun; Shi, Dingbo; Sun, Rui; Zhu, Yu-Jia; Xiao, Yao; Zhang, Lu-Ning; Zhang, Xu-Hui; Chen, Ze-Ying; Lan, Xiao-Wen; Tang, Jie; Gao, Yuan-Hong; Ma, Jun; Deng, Wuguo; Xie, Fang-Yun

    2016-01-01

    Background Albeit intensity-modulated radiotherapy (IMRT) is currently the recommended radiation technique in treating nasopharyngeal carcinoma, the effect of IMRT versus two-dimensional conventional radiotherapy (2DCRT) alone is still contradictory. Results In the original unmatched cohort of 1198 patients, IMRT obtained comparable 5-year overall survival (OS) (91.3% vs 87.1%, P = 0.120), locoregional relapse-free survival (LRFS) (92.3% vs 90.4%, P = 0.221) and distant metastasis-free survival (DMFS) (92.9% vs 92.1%, P = 0.901) to 2DCRT. In the propensity-matched cohort of 604 patients, no significant survival differences were observed between the two arms (5-year OS 90.9% vs 90.5%, P = 0.655; LRFS 92.5% vs 92.4%, P = 0.866; DMFS 92.5% vs 92.9%, P = 0.384). In multivariate analysis, IMRT did not significantly lower the risk of death, locoregional relapse or distant metastasis, irrespective of tumor stage. Methods Overall, 1198 patients who underwent IMRT (316 patients) or 2DCRT (882 patients) without any chemotherapy was retrospectively analyzed. Patients in both arms were matched at equal ratio using propensity-score matching method. OS, LRFS and DMFS were assessed with Kaplan-Meier method, log-rank test and Cox regression. Conclusions In this propensity-matched study, IMRT showed no survival advantage over 2DCRT alone in nasopharyngeal carcinoma. PMID:27058901

  6. Layered ACO-OFDM for intensity-modulated direct-detection optical wireless transmission.

    PubMed

    Wang, Qi; Qian, Chen; Guo, Xuhan; Wang, Zhaocheng; Cunningham, David G; White, Ian H

    2015-05-04

    Layered asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) with high spectral efficiency is proposed in this paper for optical wireless transmission employing intensity modulation with direct detection. In contrast to the conventional ACO-OFDM, which only utilizes odd subcarriers for modulation, leading to an obvious spectral efficiency loss, in layered ACO-OFDM, the subcarriers are divided into different layers and modulated by different kinds of ACO-OFDM, which are combined for simultaneous transmission. In this way, more subcarriers are used for data transmission and the spectral efficiency is improved. An iterative receiver is also proposed for layered ACO-OFDM, where the negative clipping distortion of each layer is subtracted once it is detected so that the signals from different layers can be recovered. Theoretical analysis shows that the proposed scheme can improve the spectral efficiency by up to 2 times compared with conventional ACO-OFDM approaches with the same modulation order. Meanwhile, simulation results confirm a considerable signal-to-noise ratio gain over ACO-OFDM at the same spectral efficiency.

  7. Rational use of intensity-modulated radiation therapy: the importance of clinical outcome.

    PubMed

    De Neve, Wilfried; De Gersem, Werner; Madani, Indira

    2012-01-01

    During the last 2 decades, intensity-modulated radiation therapy (IMRT) became a standard technique despite its drawbacks of volume delineation, planning, robustness of delivery, challenging quality assurance, and cost as compared with non-IMRT. The theoretic advantages of IMRT dose distributions are generally accepted, but the clinical advantages remain debatable because of the lack of clinical assessment of the effort that is required to overshadow the disadvantages. Rational IMRT use requires a positive advantage/drawback balance. Only 5 randomized clinical trials (RCTs), 3 in the breast and 2 in the head and neck, which compare IMRT with non-IMRT (2-dimensional technique in four fifths of the trials), have been published (as of March 2011), and all had toxicity as the primary endpoint. More than 50 clinical trials compared results of IMRT-treated patients with a non-IMRT group, mostly historical controls. RCTs systematically showed a lower toxicity in IMRT-treated patients, and the non-RCTs confirmed these findings. Toxicity reduction, counterbalancing the drawbacks of IMRT, was convincing for breast and head and neck IMRT. For other tumor sites, the arguments favoring IMRT are weaker because of the inability to control bias outside the randomized setting. For anticancer efficacy endpoints, like survival, disease-specific survival, or locoregional control, the balance between advantages and drawbacks is fraught with uncertainties because of the absence of robust clinical data.

  8. Extrapleural pneumonectomy, photodynamic therapy and intensity modulated radiation therapy for the treatment of malignant pleural mesothelioma.

    PubMed

    Du, Kevin L; Both, Stefan; Friedberg, Joseph S; Rengan, Ramesh; Hahn, Stephen M; Cengel, Keith A

    2010-09-01

    Intensity modulated radiation therapy (IMRT) has recently been proposed for the treatment of malignant pleural mesothelioma (MPM). Here, we describe our experience with a multimodality approach for the treatment of mesothelioma, incorporating extrapleural pneumonectomy, intraoperative photodynamic therapy and postoperative hemithoracic IMRT. From 2004-2007, we treated 11 MPM patients with hemithoracic IMRT, 7 of whom had undergone porfimer sodium-mediated PDT as an intraoperative adjuvant to surgical debulking. The median radiation dose to the planning treatment volume (PTV) ranged from 45.4-54.5 Gy. For the contralateral lung, V20 ranged from 1.4-28.5%, V5 from 42-100% and MLD from 6.8-16.5 Gy. In our series, 1 patient experienced respiratory failure secondary to radiation pneumonitis that did not require mechanical ventilation. Multimodality therapy combining surgery with increased doses of radiation using IMRT, and newer treatment modalities such as PDT , appears safe. Future prospective analysis will be needed to demonstrate efficacy of this approach in the treatment of malignant mesothelioma. Efforts to reduce lung toxicity and improve dose delivery are needed and provide the promise of improved local control and quality of life in a carefully chosen multidisciplinary approach.

  9. An open-loop RFOG based on harmonic division technique to suppress LD's intensity modulation noise

    NASA Astrophysics Data System (ADS)

    Ying, Diqing; Wang, Zeyu; Mao, Jianmin; Jin, Zhonghe

    2016-11-01

    A harmonic division technique is proposed for an open-loop resonator fiber optic gyro (RFOG) to suppress semiconductor laser diode's (LD's) intensity modulation noise. The theoretical study indicates the RFOG with this technique is immune to the intensity noise. The simulation and experimental results show this technique would lead to a diminished linear region, which still could be acceptable for an RFOG applied to low rotation rate detection. The tests for the gyro output signal are carried out with/without noise suppressing methods, including the harmonic division technique and previously proposed signal compensation technique. With the harmonic division technique at the rotation rate of 10 deg/s, the stability of gyro output signal is improved from 1.07 deg/s to 0.0361 deg/s, whose noise suppressing ratio is more than 3 times as that of the signal compensation technique. And especially, a 3.12 deg/s signal jump is significantly removed with the harmonic division technique; in contrast, a residual 0.36 deg/s signal jump still exists with the signal compensation technique. It is concluded the harmonic division technique does work in intensity noise suppressing under dynamic condition, and it is superior to the signal compensation technique.

  10. Intensity-Modulated Radiotherapy in Postoperative Treatment of Oral Cavity Cancers

    SciTech Connect

    Gomez, Daniel R. Zhung, Joanne E.; Gomez, Jennifer; Chan, Kelvin; Wu, Abraham J.; Wolden, Suzanne L.; Pfister, David G.; Shaha, Ashok; Shah, Jatin P.; Kraus, Dennis H.; Wong, Richard J.; Lee, Nancy Y.

    2009-03-15

    Purpose: To present our single-institution experience of intensity-modulated radiotherapy (IMRT) for oral cavity cancer. Methods and Materials: Between September 2000 and December 2006, 35 patients with histologically confirmed squamous cell carcinoma of the oral cavity underwent surgery followed by postoperative IMRT. The sites included were buccal mucosa in 8, oral tongue in 11, floor of the mouth in 9, gingiva in 4, hard palate in 2, and retromolar trigone in 1. Most patients had Stage III-IV disease (80%). Ten patients (29%) also received concurrent postoperative chemotherapy with IMRT. The median prescribed radiation dose was 60 Gy. Results: The median follow-up for surviving patients was 28.1 months (range, 11.9-85.1). Treatment failure occurred in 11 cases as follows: local in 4, regional in 2, and distant metastases in 5. Of the 5 patients with distant metastases, 2 presented with dermal metastases. The 2- and 3-year estimates of locoregional progression-free survival, distant metastasis-free survival, disease-free survival, and overall survival were 84% and 77%, 85% and 85%, 70% and 64%, and 74% and 74%, respectively. Acute Grade 2 or greater dermatitis, mucositis, and esophageal reactions were experienced by 54%, 66%, and 40% of the patients, respectively. Documented late complications included trismus (17%) and osteoradionecrosis (5%). Conclusion: IMRT as an adjuvant treatment after surgical resection for oral cavity tumors is feasible and effective, with promising results and acceptable toxicity.

  11. Validation of a track repeating algorithm for intensity modulated proton therapy: clinical cases study

    NASA Astrophysics Data System (ADS)

    Yepes, Pablo P.; Eley, John G.; Liu, Amy; Mirkovic, Dragan; Randeniya, Sharmalee; Titt, Uwe; Mohan, Radhe

    2016-04-01

    Monte Carlo (MC) methods are acknowledged as the most accurate technique to calculate dose distributions. However, due its lengthy calculation times, they are difficult to utilize in the clinic or for large retrospective studies. Track-repeating algorithms, based on MC-generated particle track data in water, accelerate dose calculations substantially, while essentially preserving the accuracy of MC. In this study, we present the validation of an efficient dose calculation algorithm for intensity modulated proton therapy, the fast dose calculator (FDC), based on a track-repeating technique. We validated the FDC algorithm for 23 patients, which included 7 brain, 6 head-and-neck, 5 lung, 1 spine, 1 pelvis and 3 prostate cases. For validation, we compared FDC-generated dose distributions with those from a full-fledged Monte Carlo based on GEANT4 (G4). We compared dose-volume-histograms, 3D-gamma-indices and analyzed a series of dosimetric indices. More than 99% of the voxels in the voxelized phantoms describing the patients have a gamma-index smaller than unity for the 2%/2 mm criteria. In addition the difference relative to the prescribed dose between the dosimetric indices calculated with FDC and G4 is less than 1%. FDC reduces the calculation times from 5 ms per proton to around 5 μs.

  12. SU-E-P-18: Intensity-Modulated Radiation Therapy for Cervical Esophageal Squamous Cell Carcinoma

    SciTech Connect

    Bai, W; Qiao, X; Zhou, Z; Song, Y; Zhang, R; Zhen, C

    2015-06-15

    Purpose: To retrospectively analyze the outcomes and prognostic factors of cervical esophageal squamous cell carcinoma (SCC) treated with intensity modulated radiation therapy (IMRT). Methods: Thirty-seven patients with cervical esophageal SCC treated with IMRT were analyzed retrospectively. They received 54–66 Gy in 27–32 fractions. Nineteen patients received concurrent (n=12) or sequential (n=7) platinum-based two drugs chemoradiotherapy. Overall survival (OS), local control rates (LCR) and prognostic factors were evaluated. Acute toxicities and patterns of first failures were observed. Results: The median follow-up was 46 months for alive patients. The l-, 3-, 4- and 5-year OS of the all patients were 83.8%, 59.1%, 47.5% and 32.6% respectively. The median survival time was 46 months. The l-, 3-,4- and 5-year LCR were 82.9%, 63.0%, 54.5% and 54.5%, respectively. Univariate and Multivariate analysis all showed that size of GTV was an independent prognostic factor (p=0.033, p=0.039). There were no patients with Grade 3 acute radiation esophagitis and Grade 2–4 acute pneumonitis. The local failure accounted for 70.0% of all treatment-related failures. Conclusion: IMRT is safe and effective in the treatment of cervical esophageal squamous cell carcinoma. Size of GTV is an independent prognostic factor. Local failure still remains the main reason of treatment failures. The authors declare no conflicts of interest in preparing this article.

  13. Validation of a track repeating algorithm for intensity modulated proton therapy: clinical cases study.

    PubMed

    Yepes, Pablo P; Eley, John G; Liu, Amy; Mirkovic, Dragan; Randeniya, Sharmalee; Titt, Uwe; Mohan, Radhe

    2016-04-07

    Monte Carlo (MC) methods are acknowledged as the most accurate technique to calculate dose distributions. However, due its lengthy calculation times, they are difficult to utilize in the clinic or for large retrospective studies. Track-repeating algorithms, based on MC-generated particle track data in water, accelerate dose calculations substantially, while essentially preserving the accuracy of MC. In this study, we present the validation of an efficient dose calculation algorithm for intensity modulated proton therapy, the fast dose calculator (FDC), based on a track-repeating technique. We validated the FDC algorithm for 23 patients, which included 7 brain, 6 head-and-neck, 5 lung, 1 spine, 1 pelvis and 3 prostate cases. For validation, we compared FDC-generated dose distributions with those from a full-fledged Monte Carlo based on GEANT4 (G4). We compared dose-volume-histograms, 3D-gamma-indices and analyzed a series of dosimetric indices. More than 99% of the voxels in the voxelized phantoms describing the patients have a gamma-index smaller than unity for the 2%/2 mm criteria. In addition the difference relative to the prescribed dose between the dosimetric indices calculated with FDC and G4 is less than 1%. FDC reduces the calculation times from 5 ms per proton to around 5 μs.

  14. Optimization of collimator parameters to reduce rectal dose in intensity-modulated prostate treatment planning

    SciTech Connect

    Chapek, Julie . E-mail: Julie.chapek@hci.utah.edu; Tobler, Matt; Toy, Beau J.; Lee, Christopher M.; Leavitt, Dennis D.

    2005-01-01

    The inability to avoid rectal wall irradiation has been a limiting factor in prostate cancer treatment planning. Treatment planners must not only consider the maximum dose that the rectum receives throughout a course of treatment, but also the dose that any volume of the rectum receives. As treatment planning techniques have evolved and prescription doses have escalated, limitations of rectal dose have remained an area of focus. External pelvic immobilization devices have been incorporated to aid in daily reproducibility and lessen concern for daily patient motion. Internal immobilization devices (such as the intrarectal balloon) and visualization techniques (including daily ultrasound or placement of fiducial markers) have been utilized to reduce the uncertainty of intrafractional prostate positional variation, thus allowing for minimization of treatment volumes. Despite these efforts, prostate volumes continue to abut portions of the rectum, and the necessary volume expansions continue to include portions of the anterior rectal wall within high-dose regions. The addition of collimator parameter optimization (both collimator angle and primary jaw settings) to intensity-modulated radiotherapy (IMRT) allows greater rectal sparing compared to the use of IMRT alone. We use multiple patient examples to illustrate the positive effects seen when utilizing collimator parameter optimization in conjunction with IMRT to further reduce rectal doses.

  15. Micro-optoelectromechanical systems accelerometer based on intensity modulation using a one-dimensional photonic crystal.

    PubMed

    Sheikhaleh, Arash; Abedi, Kambiz; Jafari, Kian; Gholamzadeh, Reza

    2016-11-10

    In this paper, we propose what we believe is a novel sensitive micro-optoelectromechanical systems (MOEMS) accelerometer based on intensity modulation by using a one-dimensional photonic crystal. The optical sensing system of the proposed structure includes an air-dielectric multilayer photonic bandgap material, a laser diode (LD) light source, a typical photodiode (1550 nm) and a set of integrated optical waveguides. The proposed sensor provides several advantages, such as a relatively wide measurement range, good linearity in the whole measurement range, integration capability, negligible cross-axis sensitivity, high reliability, and low air-damping coefficient, which results in a wider frequency bandwidth for a fixed resonance frequency. Simulation results show that the functional characteristics of the sensor are as follows: a mechanical sensitivity of 119.21 nm/g, a linear measurement range of ±38g and a resonance frequency of 1444 Hz. Thanks to the above-mentioned characteristics, the proposed MOEMS accelerometer is suitable for a wide spectrum of applications, ranging from consumer electronics to aerospace and inertial navigation.

  16. Compact multileaf collimator for conformal and intensity modulated fast neutron therapy: Electromechanical design and validation

    SciTech Connect

    Farr, J. B.; Maughan, R. L.; Yudelev, M.; Blosser, E.; Brandon, J.; Horste, T.; Forman, J. D.

    2006-09-15

    The electromechanical properties of a 120-leaf, high-resolution, computer-controlled, fast neutron multileaf collimator (MLC) are presented. The MLC replaces an aging, manually operated multirod collimator. The MLC leaves project 5 mm in the isocentric plane perpendicular to the beam axis. A taper is included on the leaves matching beam divergence along one axis. The 5-mm leaf projection width is chosen to give high-resolution conformality across the entire field. The maximum field size provided is 30x30 cm{sup 2}. To reduce the interleaf transmission a 0.254-mm blocking step is included. End-leaf steps totaling 0.762 mm are also provided allowing opposing leaves to close off within the primary radiation beam. The neutron MLC also includes individual 45 deg. and 60 deg. automated universal tungsten wedges. The automated high-resolution neutron collimation provides an increase in patient throughput capacity, enables a new modality, intensity modulated neutron therapy, and limits occupational radiation exposure by providing remote operation from a shielded console area.

  17. Accuracy of inhomogeneity correction algorithm in intensity-modulated radiotherapy of head-and-neck tumors

    SciTech Connect

    Yoon, Myonggeun; Lee, Doo-Hyun; Shin, Dongho; Lee, Se Byeong; Park, Sung Yong . E-mail: cool_park@ncc.re.kr; Cho, Kwan Ho

    2007-04-01

    We examined the degree of calculated-to-measured dose difference for nasopharyngeal target volume in intensity-modulated radiotherapy (IMRT) based on the observed/expected ratio using patient anatomy with humanoid head-and-neck phantom. The plans were designed with a clinical treatment planning system that uses a measurement-based pencil beam dose-calculation algorithm. Two kinds of IMRT plans, which give a direct indication of the error introduced in routine treatment planning, were categorized and evaluated. The experimental results show that when the beams pass through the oral cavity in anthropomorphic head-and-neck phantom, the average dose difference becomes significant, revealing about 10% dose difference to prescribed dose at isocenter. To investigate both the physical reasons of the dose discrepancy and the inhomogeneity effect, we performed the 10 cases of IMRT quality assurance (QA) with plastic and humanoid phantoms. Our result suggests that the transient electronic disequilibrium with the increased lateral electron range may cause the inaccuracy of dose calculation algorithm, and the effectiveness of the inhomogeneity corrections used in IMRT plans should be evaluated to ensure meaningful quality assurance and delivery.

  18. Intensity-modulated radiation therapy to bilateral lower limb extremities concurrently: a planning case study

    SciTech Connect

    Fitzgerald, Emma Miles, Wesley; Fenton, Paul; Frantzis, Jim

    2014-09-15

    Non-melanomatous skin cancers represent 80% of all newly diagnosed cancers in Australia with basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) being the most common. A previously healthy 71-year-old woman presented with widespread and tender superficial skin cancers on the lower bilateral limbs. External beam radiation therapy through the use of intensity-modulated radiation therapy (IMRT) was employed as the treatment modality of choice as this technique provides conformal dose distribution to a three-dimensional treatment volume while reducing toxicity to surrounding tissues. The patient was prescribed a dose of 60 Gy to the planning target volume (PTV) with 1.0 cm bolus over the ventral surface of each limb. The beam arrangement consisted of six treatment fields that avoided entry and exit through the contralateral limb. The treatment plans met the International Commission on Radiation Units and Measurements (ICRU) guidelines and produced highly conformal dosimetric results. Skin toxicity was measured against the National Cancer Institute: Common Terminology Criteria for Adverse Events (NCI: CTCAE) version 3. A well-tolerated treatment was delivered with excellent results given the initial extent of the disease. This case study has demonstrated the feasibility and effectiveness of IMRT for skin cancers as an alternative to surgery and traditional superficial radiation therapy, utilising a complex PTV of the extremities for patients with similar presentations.

  19. Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for Column CO2 Measurements

    NASA Astrophysics Data System (ADS)

    Campbell, J. F.; Lin, B.; Nehrir, A. R.; Harrison, F. W.; Obland, M. D.; Ismail, S.; Meadows, B.; Browell, E. V.

    2014-12-01

    Global atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity-Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud contamination. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby eliminating the need to correct for sidelobe bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper.

  20. Compact Dielectric Wall Accelerator Development For Intensity Modulated Proton Therapy And Homeland Security Applications

    SciTech Connect

    Chen, Y -; Caporaso, G J; Guethlein, G; Sampayan, S; Akana, G; Anaya, R; Blackfield, D; Cook, E; Falabella, S; Gower, E; Harris, J; Hawkins, S; Hickman, B; Holmes, C; Horner, A; Nelson, S; Paul, A; Pearson, D; Poole, B; Richardson, R; Sanders, D; Stanley, J; Sullivan, J; Wang, L; Watson, J; Weir, J

    2009-06-17

    Compact dielectric wall (DWA) accelerator technology is being developed at the Lawrence Livermore National Laboratory. The DWA accelerator uses fast switched high voltage transmission lines to generate pulsed electric fields on the inside of a high gradient insulating (HGI) acceleration tube. Its high electric field gradients are achieved by the use of alternating insulators and conductors and short pulse times. The DWA concept can be applied to accelerate charge particle beams with any charge to mass ratio and energy. Based on the DWA system, a novel compact proton therapy accelerator is being developed. This proton therapy system will produce individual pulses that can be varied in intensity, energy and spot width. The system will be capable of being sited in a conventional linac vault and provide intensity modulated rotational therapy. The status of the developmental new technologies that make the compact system possible will be reviewed. These include, high gradient vacuum insulators, solid dielectric materials, SiC photoconductive switches and compact proton sources. Applications of the DWA accelerator to problems in homeland security will also be discussed.

  1. Frequency domain approach for time-resolved pump-probe microscopy using intensity modulated laser diodes

    NASA Astrophysics Data System (ADS)

    Miyazaki, J.; Kawasumi, K.; Kobayashi, T.

    2014-09-01

    We present a scheme for time-resolved pump-probe microscopy using intensity modulated laser diodes. The modulation frequencies of the pump and probe beams are varied up to 500 MHz with fixed frequency detuning typically set at 15 kHz. The frequency response of the pump-probe signal is detected using a lock-in amplifier referenced at the beat frequency. This frequency domain method is capable of characterizing the nanosecond to picosecond relaxation dynamics of sample species without the use of a high speed detector or a high frequency lock-in amplifier. Furthermore, as the pump-probe signal is based on the nonlinear interaction between the two laser beams and the sample, our scheme provides better spatial resolution than the conventional diffraction-limited optical microscopes. Time-resolved pump-probe imaging of fluorescence beads and aggregates of quantum dots demonstrates that this method is useful for the microscopic analysis of optoelectronic devices. The system is implemented using compact and low-cost laser diodes, and thus has a broad range of applications in the fields of photochemistry, optical physics, and biological imaging.

  2. Improved Planning Time and Plan Quality Through Multicriteria Optimization for Intensity-Modulated Radiotherapy

    SciTech Connect

    Craft, David L.; Hong, Theodore S.; Shih, Helen A.; Bortfeld, Thomas R.

    2012-01-01

    Purpose: To test whether multicriteria optimization (MCO) can reduce treatment planning time and improve plan quality in intensity-modulated radiotherapy (IMRT). Methods and Materials: Ten IMRT patients (5 with glioblastoma and 5 with locally advanced pancreatic cancers) were logged during the standard treatment planning procedure currently in use at Massachusetts General Hospital (MGH). Planning durations and other relevant planning information were recorded. In parallel, the patients were planned using an MCO planning system, and similar planning time data were collected. The patients were treated with the standard plan, but each MCO plan was also approved by the physicians. Plans were then blindly reviewed 3 weeks after planning by the treating physician. Results: In all cases, the treatment planning time was vastly shorter for the MCO planning (average MCO treatment planning time was 12 min; average standard planning time was 135 min). The physician involvement time in the planning process increased from an average of 4.8 min for the standard process to 8.6 min for the MCO process. In all cases, the MCO plan was blindly identified as the superior plan. Conclusions: This provides the first concrete evidence that MCO-based planning is superior in terms of both planning efficiency and dose distribution quality compared with the current trial and error-based IMRT planning approach.

  3. Accounting for range uncertainties in the optimization of intensity modulated proton therapy.

    PubMed

    Unkelbach, Jan; Chan, Timothy C Y; Bortfeld, Thomas

    2007-05-21

    Treatment plans optimized for intensity modulated proton therapy (IMPT) may be sensitive to range variations. The dose distribution may deteriorate substantially when the actual range of a pencil beam does not match the assumed range. We present two treatment planning concepts for IMPT which incorporate range uncertainties into the optimization. The first method is a probabilistic approach. The range of a pencil beam is assumed to be a random variable, which makes the delivered dose and the value of the objective function a random variable too. We then propose to optimize the expectation value of the objective function. The second approach is a robust formulation that applies methods developed in the field of robust linear programming. This approach optimizes the worst case dose distribution that may occur, assuming that the ranges of the pencil beams may vary within some interval. Both methods yield treatment plans that are considerably less sensitive to range variations compared to conventional treatment plans optimized without accounting for range uncertainties. In addition, both approaches--although conceptually different--yield very similar results on a qualitative level.

  4. Risk of second malignant neoplasm following proton versus intensity-modulated photon radiotherapies for hepatocellular carcinoma

    NASA Astrophysics Data System (ADS)

    Taddei, Phillip J.; Howell, Rebecca M.; Krishnan, Sunil; Scarboro, Sarah B.; Mirkovic, Dragan; Newhauser, Wayne D.

    2010-12-01

    Hepatocellular carcinoma (HCC), the sixth most common cancer in the world, is a global health concern. Radiotherapy for HCC is uncommon, largely because of the likelihood of radiation-induced liver disease, an acute side effect that is often fatal. Proton beam therapy (PBT) and intensity-modulated radiation therapy (IMRT) may offer HCC patients a better option for treating the diseased liver tissue while largely sparing the surrounding tissues, especially the non-tumor liver. However, even advanced radiotherapies carry a risk of late effects, including second malignant neoplasms (SMNs). It is unclear whether PBT or IMRT confers less risk of an SMN than the other. The purpose of this study was to compare the predicted risk of developing an SMN for a patient with HCC between PBT and IMRT. For both treatments, radiation doses in organs and tissues from primary radiation were determined using a treatment planning system; doses in organs and tissues from stray radiation from PBT were determined using Monte Carlo simulations and from IMRT using thermo-luminescent dosimeter measurements. Risk models of SMN incidence were taken from the literature. The predicted absolute lifetime attributable risks of SMN incidence were 11.4% after PBT and 19.2% after IMRT. The results of this study suggest that using proton beams instead of photon beams for radiotherapy may reduce the risk of SMN incidence for some HCC patients.

  5. Modeling and Validation of Performance Limitations for the Optimal Design of Interferometric and Intensity-Modulated Fiber Optic Displacement Sensors

    SciTech Connect

    Moro, Erik A.

    2012-06-07

    Optical fiber sensors offer advantages over traditional electromechanical sensors, making them particularly well-suited for certain measurement applications. Generally speaking, optical fiber sensors respond to a desired measurand through modulation of an optical signal's intensity, phase, or wavelength. Practically, non-contacting fiber optic displacement sensors are limited to intensity-modulated and interferometric (or phase-modulated) methodologies. Intensity-modulated fiber optic displacement sensors relate target displacement to a power measurement. The simplest intensity-modulated sensor architectures are not robust to environmental and hardware fluctuations, since such variability may cause changes in the measured power level that falsely indicate target displacement. Differential intensity-modulated sensors have been implemented, offering robustness to such intensity fluctuations, and the speed of these sensors is limited only by the combined speed of the photodetection hardware and the data acquisition system (kHz-MHz). The primary disadvantages of intensity-modulated sensing are the relatively low accuracy (?m-mm for low-power sensors) and the lack of robustness, which consequently must be designed, often with great difficulty, into the sensor's architecture. White light interferometric displacement sensors, on the other hand, offer increased accuracy and robustness. Unlike their monochromatic-interferometer counterparts, white light interferometric sensors offer absolute, unambiguous displacement measurements over large displacement ranges (cm for low-power, 5 mW, sources), necessitating no initial calibration, and requiring no environmental or feedback control. The primary disadvantage of white light interferometric displacement sensors is that their utility in dynamic testing scenarios is limited, both by hardware bandwidth and by their inherent high-sensitivity to Doppler-effects. The decision of whether to use either an intensity-modulated

  6. [Extracranial stereotactic radiotherapy for early-stage non-small cell lung cancer and oligometastases].

    PubMed

    Riesterer, Oliver

    2013-10-16

    Stereotactic body radiotherapy (SBRT) is a new radiation technique that combines improvements in radiotherapy planning, intensity modulation and image guidance. The use of SBRT enables radiotherapy to be delivered instead of in six weeks in only a few days and with ablative total dose. Prospective phase II studies in patients with inoperable early stage non-small cell lung cancer demonstrate that the use of SBRT results in local control rates of 85-95% with acceptable toxicity. SBRT is also increasingly used for treatment of metastases in the lung, liver, retroperitoneum and in bones. Because SBRT enables a locally curative dose to be delivered in a time efficient manner this technique also opens up new perspectives for the treatment of patients with oligometastases.

  7. Intensity-Modulated Whole Abdominal Radiotherapy After Surgery and Carboplatin/Taxane Chemotherapy for Advanced Ovarian Cancer: Phase I Study

    SciTech Connect

    Rochet, Nathalie; Sterzing, Florian; Jensen, Alexandra D.; Dinkel, Julien; Herfarth, Klaus K.; Schubert, Kai; Eichbaum, Michael H.; Schneeweiss, Andreas; Sohn, Christof; Debus, Juergen; Harms, Wolfgang

    2010-04-15

    Purpose: To assess the feasibility and toxicity of consolidative intensity-modulated whole abdominal radiotherapy (WAR) after surgery and chemotherapy in high-risk patients with advanced ovarian cancer. Methods and Materials: Ten patients with optimally debulked ovarian cancer International Federation of Gynecology and Obstetrics Stage IIIc were treated in a Phase I study with intensity-modulated WAR up to a total dose of 30 Gy in 1.5-Gy fractions as consolidation therapy after adjuvant carboplatin/taxane chemotherapy. Treatment was delivered using intensity-modulated radiotherapy in a step-and-shoot technique (n = 3) or a helical tomotherapy technique (n = 7). The planning target volume included the entire peritoneal cavity and the pelvic and para-aortal node regions. Organs at risk were kidneys, liver, heart, vertebral bodies, and pelvic bones. Results: Intensity-modulated WAR resulted in an excellent coverage of the planning target volume and an effective sparing of the organs at risk. The treatment was well tolerated, and no severe Grade 4 acute side effects occurred. Common Toxicity Criteria Grade III toxicities were as follows: diarrhea (n = 1), thrombocytopenia (n = 1), and leukopenia (n = 3). Radiotherapy could be completed by all the patients without any toxicity-related interruption. Median follow-up was 23 months, and 4 patients had tumor recurrence (intraperitoneal progression, n = 3; hepatic metastasis, n = 1). Small bowel obstruction caused by adhesions occurred in 3 patients. Conclusions: The results of this Phase I study showed for the first time, to our knowledge, the clinical feasibility of intensity-modulated whole abdominal radiotherapy, which could offer a new therapeutic option for consolidation treatment of advanced ovarian carcinoma after adjuvant chemotherapy in selected subgroups of patients. We initiated a Phase II study to further evaluate the toxicity of this intensive multimodal treatment.

  8. Algorithm development for intensity modulated continuous wave laser absorption spectrometry in atmospheric CO2 measurements

    NASA Astrophysics Data System (ADS)

    Lin, B.; Harrison, F. W.; Browell, E. V.; Dobler, J. T.; Bryant, R. B.

    2011-12-01

    Currently, NASA Langley Research Center (LaRC) and ITT are jointly developing algorithms for demonstration of range discrimination using ITT's laser absorption spectrometer (LAS), which is being evaluated for the future NASA Active Sensing of CO2 Emissions during Nights, Days, and Seasons (ASCENDS) mission. The objective of this Decadal Survey mission is to measure atmospheric column CO2 mixing ratios (XCO2) for improved determination of atmospheric carbon sources and sinks. Intensity Modulated Continuous Wave (IM-CW) techniques are used in this LAS approach. The LAS is designed to simultaneously measure CO2 and O2 columns, and these measurements are used to determine the required XCO2 column. The LAS measurements are enabled by the multi-channel operation of the instrument at 1.57 and 1.26-um for CO2 and O2, respectively. The algorithm development for the IM-CW techniques of the multi-channel LAS is focused on addressing key retrieval issues such as surface signal detection, thin cloud and/or aerosol layer rejection, vertical atmospheric range resolution, and optimizing the size of the measurement footprint. With these considerations, the modulation algorithm needs to maintain high enough signal-to-noise ratio (SNR) so that the mission scientific goals can be reached. A basic selection of the modulation algorithms that make XCO2 measurement and thin cloud rejection possible is the stepped frequency modulation scheme and a similar scheme of swept sine modulation. The differences between these two schemes for thin cloud rejection are small, assuming the proper selection of parameters is made. The stepped frequency approach is only a quantified version of swept sine method for the frequencies used. Swept sine scheme is a very common modulation technique for range discrimination, while the consideration of the stepped frequency scheme is based on the history of the rolling-tone modulation used in the instrument in previous successful column CO2 measurements. The

  9. A particle swarm optimization algorithm for beam angle selection in intensity-modulated radiotherapy planning.

    PubMed

    Li, Yongjie; Yao, Dezhong; Yao, Jonathan; Chen, Wufan

    2005-08-07

    Automatic beam angle selection is an important but challenging problem for intensity-modulated radiation therapy (IMRT) planning. Though many efforts have been made, it is still not very satisfactory in clinical IMRT practice because of overextensive computation of the inverse problem. In this paper, a new technique named BASPSO (Beam Angle Selection with a Particle Swarm Optimization algorithm) is presented to improve the efficiency of the beam angle optimization problem. Originally developed as a tool for simulating social behaviour, the particle swarm optimization (PSO) algorithm is a relatively new population-based evolutionary optimization technique first introduced by Kennedy and Eberhart in 1995. In the proposed BASPSO, the beam angles are optimized using PSO by treating each beam configuration as a particle (individual), and the beam intensity maps for each beam configuration are optimized using the conjugate gradient (CG) algorithm. These two optimization processes are implemented iteratively. The performance of each individual is evaluated by a fitness value calculated with a physical objective function. A population of these individuals is evolved by cooperation and competition among the individuals themselves through generations. The optimization results of a simulated case with known optimal beam angles and two clinical cases (a prostate case and a head-and-neck case) show that PSO is valid and efficient and can speed up the beam angle optimization process. Furthermore, the performance comparisons based on the preliminary results indicate that, as a whole, the PSO-based algorithm seems to outperform, or at least compete with, the GA-based algorithm in computation time and robustness. In conclusion, the reported work suggested that the introduced PSO algorithm could act as a new promising solution to the beam angle optimization problem and potentially other optimization problems in IMRT, though further studies need to be investigated.

  10. Expert Consensus Contouring Guidelines for Intensity Modulated Radiation Therapy in Esophageal and Gastroesophageal Junction Cancer

    SciTech Connect

    Wu, Abraham J.; Bosch, Walter R.; Chang, Daniel T.; Hong, Theodore S.; Jabbour, Salma K.; Kleinberg, Lawrence R.; Mamon, Harvey J.; Thomas, Charles R.; Goodman, Karyn A.

    2015-07-15

    Purpose/Objective(s): Current guidelines for esophageal cancer contouring are derived from traditional 2-dimensional fields based on bony landmarks, and they do not provide sufficient anatomic detail to ensure consistent contouring for more conformal radiation therapy techniques such as intensity modulated radiation therapy (IMRT). Therefore, we convened an expert panel with the specific aim to derive contouring guidelines and generate an atlas for the clinical target volume (CTV) in esophageal or gastroesophageal junction (GEJ) cancer. Methods and Materials: Eight expert academically based gastrointestinal radiation oncologists participated. Three sample cases were chosen: a GEJ cancer, a distal esophageal cancer, and a mid-upper esophageal cancer. Uniform computed tomographic (CT) simulation datasets and accompanying diagnostic positron emission tomographic/CT images were distributed to each expert, and the expert was instructed to generate gross tumor volume (GTV) and CTV contours for each case. All contours were aggregated and subjected to quantitative analysis to assess the degree of concordance between experts and to generate draft consensus contours. The panel then refined these contours to generate the contouring atlas. Results: The κ statistics indicated substantial agreement between panelists for each of the 3 test cases. A consensus CTV atlas was generated for the 3 test cases, each representing common anatomic presentations of esophageal cancer. The panel agreed on guidelines and principles to facilitate the generalizability of the atlas to individual cases. Conclusions: This expert panel successfully reached agreement on contouring guidelines for esophageal and GEJ IMRT and generated a reference CTV atlas. This atlas will serve as a reference for IMRT contours for clinical practice and prospective trial design. Subsequent patterns of failure analyses of clinical datasets using these guidelines may require modification in the future.

  11. Automated Planning of Tangential Breast Intensity-Modulated Radiotherapy Using Heuristic Optimization

    SciTech Connect

    Purdie, Thomas G.; Dinniwell, Robert E.; Letourneau, Daniel; Hill, Christine; Sharpe, Michael B.

    2011-10-01

    Purpose: To present an automated technique for two-field tangential breast intensity-modulated radiotherapy (IMRT) treatment planning. Method and Materials: A total of 158 planned patients with Stage 0, I, and II breast cancer treated using whole-breast IMRT were retrospectively replanned using automated treatment planning tools. The tools developed are integrated into the existing clinical treatment planning system (Pinnacle{sup 3}) and are designed to perform the manual volume delineation, beam placement, and IMRT treatment planning steps carried out by the treatment planning radiation therapist. The automated algorithm, using only the radio-opaque markers placed at CT simulation as inputs, optimizes the tangential beam parameters to geometrically minimize the amount of lung and heart treated while covering the whole-breast volume. The IMRT parameters are optimized according to the automatically delineated whole-breast volume. Results: The mean time to generate a complete treatment plan was 6 min, 50 s {+-} 1 min 12 s. For the automated plans, 157 of 158 plans (99%) were deemed clinically acceptable, and 138 of 158 plans (87%) were deemed clinically improved or equal to the corresponding clinical plan when reviewed in a randomized, double-blinded study by one experienced breast radiation oncologist. In addition, overall the automated plans were dosimetrically equivalent to the clinical plans when scored for target coverage and lung and heart doses. Conclusion: We have developed robust and efficient automated tools for fully inversed planned tangential breast IMRT planning that can be readily integrated into clinical practice. The tools produce clinically acceptable plans using only the common anatomic landmarks from the CT simulation process as an input. We anticipate the tools will improve patient access to high-quality IMRT treatment by simplifying the planning process and will reduce the effort and cost of incorporating more advanced planning into clinical

  12. Concurrent Chemotherapy and Intensity-Modulated Radiotherapy for Locoregionally Advanced Laryngeal and Hypopharyngeal Cancers

    SciTech Connect

    Lee, Nancy Y. O'Meara, William; Chan, Kelvin; Della-Bianca, Cesar; Mechalakos, James G.; Zhung, Joanne; Wolden, Suzanne L.; Narayana, Ashwatha; Kraus, Dennis; Shah, Jatin P.; Pfister, David G.

    2007-10-01

    Purpose: To perform a retrospective review of laryngeal/hypopharyngeal carcinomas treated with concurrent chemotherapy and intensity-modulated radiotherapy (IMRT). Methods and Materials: Between January 2002 and June 2005, 20 laryngeal and 11 hypopharyngeal carcinoma patients underwent IMRT with concurrent platinum-based chemotherapy; most patients had Stage IV disease. The prescription of the planning target volume for gross, high-risk, and low-risk subclinical disease was 70, 59.4, and 54 Gy, respectively. Acute/late toxicities were retrospectively scored using the Common Toxicity Criteria scale. The 2-year local progression-free, regional progression-free, laryngectomy-free, distant metastasis-free, and overall survival rates were calculated using the Kaplan-Meier method. Results: The median follow-up of the living patients was 26 months (range, 17-58 months). The 2-year local progression-free, regional progression-free, laryngectomy-free, distant metastasis-free, and overall survival rate was 86%, 94%, 89%, 92%, and 63%, respectively. Grade 2 mucositis or higher occurred in 48% of patients, and all experienced Grade 2 or higher pharyngitis during treatment. Xerostomia continued to decrease over time from the end of RT, with none complaining of Grade 2 toxicity at this analysis. The 2-year post-treatment percutaneous endoscopic gastrostomy-dependency rate for those with hypopharyngeal and laryngeal tumors was 31% and 15%, respectively. The most severe late complications were laryngeal necrosis, necrotizing fascitis, and a carotid rupture resulting in death 3 weeks after salvage laryngectomy. Conclusion: These preliminary results have shown that IMRT achieved encouraging locoregional control of locoregionally advanced laryngeal and hypopharyngeal carcinomas. Xerostomia improved over time. Pharyngoesophageal stricture with percutaneous endoscopic gastrostomy dependency remains a problem, particularly for patients with hypopharyngeal carcinoma and, to a lesser

  13. Candidate Dosimetric Predictors of Long-Term Swallowing Dysfunction After Oropharyngeal Intensity-Modulated Radiotherapy

    SciTech Connect

    Schwartz, David L.; Hutcheson, Katherine; Barringer, Denise; Tucker, Susan L.; Kies, Merrill; Ang, K. Kian; Morrison, William H.; Rosenthal, David I.; Garden, Adam S.; Dong Lei; Lewin, Jan S.

    2010-12-01

    Purpose: To investigate long-term swallowing function in oropharyngeal cancer patients treated with intensity-modulated radiotherapy (IMRT), and to identify novel dose-limiting criteria predictive for dysphagia. Methods and Materials: Thirty-one patients with Stage IV oropharyngeal squamous carcinoma enrolled on a Phase II trial were prospectively evaluated by modified barium swallow studies at baseline, and 6, 12, and 24 months post-IMRT treatment. Candidate dysphagia-associated organs at risk were retrospectively contoured into original treatment plans. Twenty-one (68%) cases were base of tongue and 10 (32%) were tonsil. Stage distribution was T1 (12 patients), T2 (10), T3 (4), T4 (2), and TX (3), and N2 (24), N3 (5), and NX (2). Median age was 52.8 years (range, 42-78 years). Thirteen patients (42%) received concurrent chemotherapy during IMRT. Thirteen (42%) were former smokers. Mean dose to glottic larynx for the cohort was limited to 18 Gy (range, 6-39 Gy) by matching IMRT to conventional low-neck fields. Results: Dose-volume constraints (V30 < 65% and V35 < 35% for anterior oral cavity and V55 < 80% and V65 < 30% for high superior pharyngeal constrictors) predictive for objective swallowing dysfunction were identified by univariate and multivariate analyses. Aspiration and feeding tube dependence were observed in only 1 patient at 24 months. Conclusions: In the context of glottic laryngeal shielding, we describe candidate oral cavity and superior pharyngeal constrictor organs at risk and dose-volume constraints associated with preserved long-term swallowing function; these constraints are currently undergoing prospective validation. Strict protection of the glottic larynx via beam-split IMRT techniques promises to make chronic aspiration an uncommon outcome.

  14. Intensity-Modulated Proton Therapy Versus Helical Tomotherapy in Nasopharynx Cancer: Planning Comparison and NTCP Evaluation

    SciTech Connect

    Widesott, Lamberto Pierelli, Alessio; Fiorino, Claudio; Dell'Oca, Italo; Broggi, Sara; Cattaneo, Giovanni Mauro; Di Muzio, Nadia; Fazio, Ferruccio; Calandrino, Riccardo; Schwarz, Marco

    2008-10-01

    Purpose: To compare intensity-modulated proton therapy (IMPT) and helical tomotherapy (HT) treatment plans for nasopharynx cancer using a simultaneous integrated boost approach. Methods and Materials: The data from 6 patients who had previously been treated with HT were used. A three-beam IMPT technique was optimized in the Hyperion treatment planning system, simulating a 'beam scanning' technique. HT was planned using the tomotherapy treatment planning system. Both techniques were optimized to simultaneously deliver 66 Gy in 30 fractions to planning target volume (PTV1; GTV and enlarged nodes) and 54 Gy to PTV2 subclinical, electively treated nodes. Normal tissue complication probability calculation was performed for the parotids and larynx. Results: Very similar PTVs coverage and homogeneity of the target dose distribution for IMPT and HT were found. The conformity index was significantly lower for protons than for photons (1.19 vs. 1.42, respectively). The mean dose to the ipsilateral and contralateral parotid glands decreased by 6.4 Gy and 5.6 Gy, respectively, with IMPT. The volume of mucosa and esophagus receiving {>=}20 Gy and {>=}30 Gy with IMPT was significantly lower than with HT. The average volume of larynx receiving {>=}50 Gy was significantly lower with HT, while for thyroid, it was comparable. The volume receiving {>=}30, {>=}20, and {>=}10 Gy in total body volume decreased with IMPT by 14.5%, 19.4%, and 23.1%, respectively. The normal tissue complication probability for the parotid glands was significantly lower with IMPT for all sets of parameters; however, we also estimated an almost full recovery of the contralateral parotid with HT. The normal tissue complication probability for the larynx was not significantly different between the two irradiation techniques. Conclusion: Excellent target coverage, homogeneity within the PTVs, and sparing of the organs at risk were reached with both modalities. IMPT allows for better sparing of most organs at

  15. Intensity-Modulated Radiation Therapy for Anal Malignancies: A Preliminary Toxicity and Disease Outcomes Analysis

    SciTech Connect

    Pepek, Joseph M.; Willett, Christopher G.; Wu, Q. Jackie; Yoo, Sua; Clough, Robert W.; Czito, Brian G.

    2010-12-01

    Purpose: Intensity-modulated radiation therapy (IMRT) has the potential to reduce toxicities associated with chemoradiotherapy in the treatment of anal cancer. This study reports the results of using IMRT in the treatment of anal cancer. Methods and Materials: Records of patients with anal malignancies treated with IMRT at Duke University were reviewed. Acute toxicity was graded using the NCI CTCAEv3.0 scale. Overall survival (OS), metastasis-free survival (MFS), local-regional control (LRC) and colostomy-free survival (CFS) were calculated using the Kaplan-Meier method. Results: Forty-seven patients with anal malignancy (89% canal, 11% perianal skin) were treated with IMRT between August 2006 and September 2008. Median follow-up was 14 months (19 months for SCC patients). Median radiation dose was 54 Gy. Eight patients (18%) required treatment breaks lasting a median of 5 days (range, 2-7 days). Toxicity rates were as follows: Grade 4: leukopenia (7%), thrombocytopenia (2%); Grade 3: leukopenia (18%), diarrhea (9%), and anemia (4%); Grade 2: skin (93%), diarrhea (24%), and leukopenia (24%). The 2-year actuarial overall OS, MFS, LRC, and CFS rates were 85%, 78%, 90% and 82%, respectively. For SCC patients, the 2-year OS, MFS, LRC, and CFS rates were 100%, 100%, 95%, and 91%, respectively. Conclusions: IMRT-based chemoradiotherapy for anal cancer results in significant reductions in normal tissue dose and acute toxicities versus historic controls treated without IMRT, leading to reduced rates of toxicity-related treatment interruption. Early disease-related outcomes seem encouraging. IMRT is emerging as a standard therapy for anal cancer.

  16. Fast voxel and polygon ray-tracing algorithms in intensity modulated radiation therapy treatment planning.

    PubMed

    Fox, Christopher; Romeijn, H Edwin; Dempsey, James F

    2006-05-01

    We present work on combining three algorithms to improve ray-tracing efficiency in radiation therapy dose computation. The three algorithms include: An improved point-in-polygon algorithm, incremental voxel ray tracing algorithm, and stereographic projection of beamlets for voxel truncation. The point-in-polygon and incremental voxel ray-tracing algorithms have been used in computer graphics and nuclear medicine applications while the stereographic projection algorithm was developed by our group. These algorithms demonstrate significant improvements over the current standard algorithms in peer reviewed literature, i.e., the polygon and voxel ray-tracing algorithms of Siddon for voxel classification (point-in-polygon testing) and dose computation, respectively, and radius testing for voxel truncation. The presented polygon ray-tracing technique was tested on 10 intensity modulated radiation therapy (IMRT) treatment planning cases that required the classification of between 0.58 and 2.0 million voxels on a 2.5 mm isotropic dose grid into 1-4 targets and 5-14 structures represented as extruded polygons (a.k.a. Siddon prisms). Incremental voxel ray tracing and voxel truncation employing virtual stereographic projection was tested on the same IMRT treatment planning cases where voxel dose was required for 230-2400 beamlets using a finite-size pencil-beam algorithm. Between a 100 and 360 fold cpu time improvement over Siddon's method was observed for the polygon ray-tracing algorithm to perform classification of voxels for target and structure membership. Between a 2.6 and 3.1 fold reduction in cpu time over current algorithms was found for the implementation of incremental ray tracing. Additionally, voxel truncation via stereographic projection was observed to be 11-25 times faster than the radial-testing beamlet extent approach and was further improved 1.7-2.0 fold through point-classification using the method of translation over the cross product technique.

  17. A critical evaluation of worst case optimization methods for robust intensity-modulated proton therapy planning

    SciTech Connect

    Fredriksson, Albin Bokrantz, Rasmus

    2014-08-15

    Purpose: To critically evaluate and compare three worst case optimization methods that have been previously employed to generate intensity-modulated proton therapy treatment plans that are robust against systematic errors. The goal of the evaluation is to identify circumstances when the methods behave differently and to describe the mechanism behind the differences when they occur. Methods: The worst case methods optimize plans to perform as well as possible under the worst case scenario that can physically occur (composite worst case), the combination of the worst case scenarios for each objective constituent considered independently (objectivewise worst case), and the combination of the worst case scenarios for each voxel considered independently (voxelwise worst case). These three methods were assessed with respect to treatment planning for prostate under systematic setup uncertainty. An equivalence with probabilistic optimization was used to identify the scenarios that determine the outcome of the optimization. Results: If the conflict between target coverage and normal tissue sparing is small and no dose-volume histogram (DVH) constraints are present, then all three methods yield robust plans. Otherwise, they all have their shortcomings: Composite worst case led to unnecessarily low plan quality in boundary scenarios that were less difficult than the worst case ones. Objectivewise worst case generally led to nonrobust plans. Voxelwise worst case led to overly conservative plans with respect to DVH constraints, which resulted in excessive dose to normal tissue, and less sharp dose fall-off than the other two methods. Conclusions: The three worst case methods have clearly different behaviors. These behaviors can be understood from which scenarios that are active in the optimization. No particular method is superior to the others under all circumstances: composite worst case is suitable if the conflicts are not very severe or there are DVH constraints whereas

  18. Intensity-Modulated Radiation Therapy With Concurrent Chemotherapy as Preoperative Treatment for Localized Gastric Adenocarcinoma

    SciTech Connect

    Chakravarty, Twisha; Crane, Christopher H.; Ajani, Jaffer A.; Mansfield, Paul F.; Briere, Tina M.; Beddar, A. Sam; Mok, Henry; Reed, Valerie K.; Krishnan, Sunil; Delclos, Marc E.; Das, Prajnan

    2012-06-01

    Purpose: The goal of this study was to evaluate dosimetric parameters, acute toxicity, pathologic response, and local control in patients treated with preoperative intensity-modulated radiation therapy (IMRT) and concurrent chemotherapy for localized gastric adenocarcinoma. Methods: Between November 2007 and April 2010, 25 patients with localized gastric adenocarcinoma were treated with induction chemotherapy, followed by preoperative IMRT and concurrent chemotherapy and, finally, surgical resection. The median radiation therapy dose was 45 Gy. Concurrent chemotherapy was 5-fluorouracil and oxaliplatin in 18 patients, capecitabine in 3, and other regimens in 4. Subsequently, resection was performed with total gastrectomy in 13 patients, subtotal gastrectomy in 7, and other surgeries in 5. Results: Target coverage, expressed as the ratio of the minimum dose received by 99% of the planning target volume to the prescribed dose, was a median of 0.97 (range, 0.92-1.01). The median V{sub 30} (percentage of volume receiving at least 30 Gy) for the liver was 26%; the median V{sub 20} (percentage of volume receiving at least 20 Gy) for the right and left kidneys was 14% and 24%, respectively; and the median V{sub 40} (percentage of volume receiving at least 40 Gy) for the heart was 18%. Grade 3 acute toxicity developed in 14 patients (56%), including dehydration in 10, nausea in 8, and anorexia in 5. Grade 4 acute toxicity did not develop in any patient. There were no significant differences in the rates of acute toxicity, hospitalization, or feeding tube use in comparison to those in a group of 50 patients treated with preoperative three-dimensional conformal radiation therapy with concurrent chemotherapy. R0 resection was obtained in 20 patients (80%), and pathologic complete response occurred in 5 (20%). Conclusions: Preoperative IMRT for gastric adenocarcinoma was well tolerated, accomplished excellent target coverage and normal structure sparing, and led to appropriate

  19. Reduced Acute Bowel Toxicity in Patients Treated With Intensity-Modulated Radiotherapy for Rectal Cancer

    SciTech Connect

    Samuelian, Jason M.; Callister, Matthew D.; Ashman, Jonathan B.; Young-Fadok, Tonia M.; Borad, Mitesh J.; Gunderson, Leonard L.

    2012-04-01

    Purpose: We have previously shown that intensity-modulated radiotherapy (IMRT) can reduce dose to small bowel, bladder, and bone marrow compared with three-field conventional radiotherapy (CRT) technique in the treatment of rectal cancer. The purpose of this study was to review our experience using IMRT to treat rectal cancer and report patient clinical outcomes. Methods and Materials: A retrospective review was conducted of patients with rectal cancer who were treated at Mayo Clinic Arizona with pelvic radiotherapy (RT). Data regarding patient and tumor characteristics, treatment, acute toxicity according to the Common Terminology Criteria for Adverse Events v 3.0, tumor response, and perioperative morbidity were collected. Results: From 2004 to August 2009, 92 consecutive patients were treated. Sixty-one (66%) patients were treated with CRT, and 31 (34%) patients were treated with IMRT. All but 2 patients received concurrent chemotherapy. There was no significant difference in median dose (50.4 Gy, CRT; 50 Gy, IMRT), preoperative vs. postoperative treatment, type of concurrent chemotherapy, or history of previous pelvic RT between the CRT and IMRT patient groups. Patients who received IMRT had significantly less gastrointestinal (GI) toxicity. Sixty-two percent of patients undergoing CRT experienced {>=}Grade 2 acute GI side effects, compared with 32% among IMRT patients (p = 0.006). The reduction in overall GI toxicity was attributable to fewer symptoms from the lower GI tract. Among CRT patients, {>=}Grade 2 diarrhea and enteritis was experienced among 48% and 30% of patients, respectively, compared with 23% (p = 0.02) and 10% (p = 0.015) among IMRT patients. There was no significant difference in hematologic or genitourinary acute toxicity between groups. In addition, pathologic complete response rates and postoperative morbidity between treatment groups did not differ significantly. Conclusions: In the management of rectal cancer, IMRT is associated with a

  20. Intensity modulated radiation-therapy for preoperative posterior abdominal wall irradiation of retroperitoneal liposarcomas

    SciTech Connect

    Bossi, Alberto . E-mail: alberto.bossi@uz.kuleuven.ac.be; De Wever, Ivo; Van Limbergen, Erik; Vanstraelen, Bianca

    2007-01-01

    Purpose: Preoperative external-beam radiation therapy (preop RT) in the management of Retroperitoneal Liposarcomas (RPLS) typically involves the delivery of radiation to the entire tumor mass: yet this may not be necessary. The purpose of this study is to evaluate a new strategy of preop RT for RPLS in which the target volume is limited to the contact area between the tumoral mass and the posterior abdominal wall. Methods and Materials: Between June 2000 and Jan 2005, 18 patients with the diagnosis of RPLS have been treated following a pilot protocol of pre-op RT, 50 Gy in 25 fractions of 2 Gy/day. The Clinical Target Volume (CTV) has been limited to the posterior abdominal wall, region at higher risk for local relapse. A Three-Dimensional conformal (3D-CRT) and an Intensity Modulated (IMRT) plan were generated and compared; toxicity was reported following the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events v3.0. Results: All patients completed the planned treatment and the acute toxicity was tolerable: 2 patients experienced Grade 3 and 1 Grade 2 anorexia while 2 patients developed Grade 2 nausea. IMRT allows a better sparing of the ipsilateral and the contralateral kidney. All tumors were successfully resected without major complications. At a median follow-up of 27 months 2 patients developed a local relapse and 1 lung metastasis. Conclusions: Our strategy of preop RT is feasible and well tolerated: the rate of resectability is not compromised by limiting the preop CTV to the posterior abdominal wall and a better critical-structures sparing is obtained with IMRT.

  1. Lymphatic atlas-based target volume definition for intensity-modulated radiation therapy planning

    NASA Astrophysics Data System (ADS)

    Qatarneh, S. M.; Kiricuta, I. C.; Brahme, A.; Noz, M. E.; Ferreira, B.; Kim, W. C.; Lind, B. K.

    2007-10-01

    Despite the improvements in current imaging modalities such as CT and MRI, the detection of normal or malignant lymph nodes remains a challenge due to the large variability in lymph node characteristics and the variation in imaging quality and the limited imaging resolution. A computerized lymph node atlas could be the ideal tool for target volume definition based on the distribution of normal lymph nodes surrounding the verified malignant nodes to improve the accuracy of intensity-modulated radiation therapy planning. The standard lymph node topography in the newly constructed 3D lymph node atlas offers a detailed topographical distribution of discrete nodal locations in relation to surrounding organs at risk. In the present paper, the recently developed lymph node atlas is used for selection and delineation of target volumes in the head and neck, thorax and pelvic region. Image registration techniques were implemented to integrate the topography of the lymph node atlas into the patient's data set. By combining the knowledge-based lymph node distribution with the patient's data set, more detailed definitions of the target volumes were obtained to facilitate biologically based treatment plan optimization. The response values of the biologically optimized treatment plans were used to derive the probability of tumor control and the probability of complications in organs at risk. The treatment outcome of the lung reference plan showed a lower probability of recurrence in comparison to planning without the lymph node atlas. The lymph node atlas can improve and standardize the target volume definition by including more accurate anatomical knowledge for target volume definition and biologically optimized radiation therapy planning.

  2. SU-E-T-124: Dosimetric Comparison of HDR Brachytherapy and Intensity Modulated Proton Therapy

    SciTech Connect

    Wu, J; Wu, H; Das, I

    2014-06-01

    Purpose: Brachytherapy is known to be able to deliver more radiation dose to tumor while minimizing radiation dose to surrounding normal tissues. Proton therapy also provides superior dose distribution due to Bragg peak. Since both HDR and Intensity Modulated Proton Therapy (IMPT) are beneficial for their quick dose drop off, our goal in this study is to compare the pace of dose gradient drop-off between HDR and IMPT plans based on the same CT image data-set. In addition, normal tissues sparing were also compared among HDR, IMPT and SBRT. Methods: Five cervical cancer cases treated with EBRT + HDR boost combination with Tandem and Ovoid applicator were used for comparison purpose. Original HDR plans with prescribed dose of 5.5 Gy x 5 fractions were generated and optimized. The 100% isodose line of HDR plans was converted to a dose volume, and treated as CTV for IMPT and SBRT planning. The same HDR CT scans were also used for IMPT plan and SBRT plan for direct comparison. The philosophy of the IMPT and SBRT planning was to create the same CTV coverage as HDR plans. All three modalities treatment plans were compared to each other with a set of predetermined criteria. Results: With similar target volume coverage in cervix cancer boost treatment, HDR provides a slightly sharper dose drop-off from 100% to 50% isodose line, averagely in all directions compared to IMPT. However, IMPT demonstrated more dose gradient drop-off at the junction of the target and normal tissues by providing more normal tissue sparing and superior capability to reduce integral dose. Conclusion: IMPT is capable of providing comparable dose drop-off as HDR. IMPT can be explored as replacement for HDR brachytherapy in various applications.

  3. Phase II Trial of Hypofractionated Image-Guided Intensity-Modulated Radiotherapy for Localized Prostate Adenocarcinoma

    SciTech Connect

    Martin, Jarad M.; Rosewall, Tara; Bayley, Andrew; Bristow, Robert; Chung, Peter; Crook, Juanita; Gospodarowicz, Mary; McLean, Michael; Menard, Cynthia; Milosevic, Michael; Warde, Padraig; Catton, Charles

    2007-11-15

    Purpose: To assess in a prospective trial the feasibility and late toxicity of hypofractionated radiotherapy (RT) for prostate cancer. Methods and Materials: Eligible patients had clinical stage T1c-2cNXM0 disease. They received 60 Gy in 20 fractions over 4 weeks with intensity-modulated radiotherapy including daily on-line image guidance with intraprostatic fiducial markers. Results: Between June 2001 and March 2004, 92 patients were treated with hypofractionated RT. The cohort had a median prostate-specific antigen value of 7.06 ng/mL. The majority had Gleason grade 5-6 (38%) or 7 (59%) disease, and 82 patients had T1c-T2a clinical staging. Overall, 29 patients had low-risk, 56 intermediate-risk, and 7 high-risk disease. Severe acute toxicity (Grade 3-4) was rare, occurring in only 1 patient. Median follow-up was 38 months. According to the Phoenix definition for biochemical failure, the rate of biochemical control at 14 months was 97%. According to the previous American Society for Therapeutic Radiology and Oncology definition, biochemical control at 3 years was 76%. The incidence of late toxicity was low, with no severe (Grade {>=}3) toxicity at the most recent assessment. Conclusions: Hypofractionated RT using 60 Gy in 20 fractions over 4 weeks with image guidance is feasible and is associated with low rates of late bladder and rectal toxicity. At early follow-up, biochemical outcome is comparable to that reported for conventionally fractionated controls. The findings are being tested in an ongoing, multicenter, Phase III trial.

  4. Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for ASCENDS O2 Column Measurements

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.; Harrison, F. Wallace; Obland, Michael D.; Meadows, Byron

    2015-01-01

    Global atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity- Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud contamination. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby eliminating the need to correct for sidelobe bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These results are extended to include Richardson-Lucy deconvolution techniques to extend the resolution of the lidar beyond that implied by limit of the bandwidth of the modulation, where it is shown useful for making tree canopy measurements.

  5. A 2-D diode array and analysis software for verification of intensity modulated radiation therapy delivery.

    PubMed

    Jursinic, Paul A; Nelms, Ben E

    2003-05-01

    An analysis is made of a two-dimensional array of diodes that can be used for measuring dose generated in a plane by a radiation beam. This measuring device is the MapCHECK Model 1175 (Sun Nuclear, Melbourne, FL). This device has 445 N-type diodes in a 22 x 22 cm2 2-D array with variable spacing. The entire array of diodes is easily calibrated to allow for measurements in absolute dose. For IMRT quality assurance, each beam is measured individually with the beam central axis oriented perpendicular to the plane of diodes. Software is available to do the analytical comparison of measurements versus dose distributions calculated by a treatment planning system. Comparison criteria of percent difference and distance-to-agreement are defined by the operator. Data are presented that show the diode array has linear response when beam fluence changes by over 300-fold, which is typical of the level of modulation in intensity modulated radiation therapy, IMRT, beams. A linear dependence is also shown for a 100-fold change in monitors units delivered. Methods for how this device can be used in the clinic for quality assurance of IMRT fields are described. Measurements of typical IMRT beams that are modulated by compensators and MLCs are presented with comparisons to treatment planning system dose calculations. A time analysis is done for typical IMRT quality assurance measurements. The setup, calibration, and analysis time for the 2-D diode array are on the order of 20 min, depending on numbers of fields. This is significantly less time than required to do similar analysis with radiographic film. The 2-D diode array is ideal for per-plan quality assurance after an IMRT system is fully commissioned.

  6. Intensity-Modulated Radiotherapy for Sinonasal Tumors: Ghent University Hospital Update

    SciTech Connect

    Madani, Indira Bonte, Katrien; Vakaet, Luc; Boterberg, Tom; Neve, Wilfried de

    2009-02-01

    Purpose: To report the long-term outcome of intensity-modulated radiotherapy (IMRT) for sinonasal tumors. Methods and Materials: Between July 1998 and November 2006, 84 patients with sinonasal tumors were treated with IMRT to a median dose of 70 Gy in 35 fractions. Of the 84 patients, 73 had a primary tumor and 11 had local recurrence. The tumor histologic type was adenocarcinoma in 54, squamous cell carcinoma in 17, esthesioneuroblastoma in 9, and adenoid cystic carcinoma in 4. The tumors were located in the ethmoid sinus in 47, maxillary sinus in 19, nasal cavity in 16, and multiple sites in 2. Postoperative IMRT was performed in 75 patients and 9 patients received primary IMRT. Results: The median follow-up of living patients was 40 months (range, 8-106). The 5-year local control, overall survival, disease-specific survival, disease-free survival, and freedom from distant metastasis rate was 70.7%, 58.5%, 67%, 59.3%, and 82.2%, respectively. No difference was found in local control and survival between patients with primary or recurrent tumors. On multivariate analysis, invasion of the cribriform plate was significantly associated with lower local control (p = 0.0001) and overall survival (p = 0.0001). Local and distant recurrence was detected in 19 and 10 patients, respectively. Radiation-induced blindness was not observed. One patient developed Grade 3 radiation-induced retinopathy and neovascular glaucoma. Nonocular late radiation-induced toxicity comprised complete lacrimal duct stenosis in 1 patient and brain necrosis in 3 patients. Osteoradionecrosis of the maxilla and brain necrosis were detected in 1 of the 5 reirradiated patients. Conclusion: IMRT for sinonasal tumors provides low rates of radiation-induced toxicity without blindness with high local control and survival. IMRT could be considered as the treatment of choi0008.

  7. Kilovoltage Intrafraction Monitoring for Prostate Intensity Modulated Arc Therapy: First Clinical Results

    SciTech Connect

    Ng, Jin Aun; Booth, Jeremy T.; Poulsen, Per R.; Fledelius, Walther; Worm, Esben Schjodt; Eade, Thomas; Hegi, Fiona; Kneebone, Andrew; Kuncic, Zdenka; Keall, Paul J.

    2012-12-01

    Purpose: Most linear accelerators purchased today are equipped with a gantry-mounted kilovoltage X-ray imager which is typically used for patient imaging prior to therapy. A novel application of the X-ray system is kilovoltage intrafraction monitoring (KIM), in which the 3-dimensional (3D) tumor position is determined during treatment. In this paper, we report on the first use of KIM in a prospective clinical study of prostate cancer patients undergoing intensity modulated arc therapy (IMAT). Methods and Materials: Ten prostate cancer patients with implanted fiducial markers undergoing conventionally fractionated IMAT (RapidArc) were enrolled in an ethics-approved study of KIM. KIM involves acquiring kV images as the gantry rotates around the patient during treatment. Post-treatment, markers in these images were segmented to obtain 2D positions. From the 2D positions, a maximum likelihood estimation of a probability density function was used to obtain 3D prostate trajectories. The trajectories were analyzed to determine the motion type and the percentage of time the prostate was displaced {>=}3, 5, 7, and 10 mm. Independent verification of KIM positional accuracy was performed using kV/MV triangulation. Results: KIM was performed for 268 fractions. Various prostate trajectories were observed (ie, continuous target drift, transient excursion, stable target position, persistent excursion, high-frequency excursions, and erratic behavior). For all patients, 3D displacements of {>=}3, 5, 7, and 10 mm were observed 5.6%, 2.2%, 0.7% and 0.4% of the time, respectively. The average systematic accuracy of KIM was measured at 0.46 mm. Conclusions: KIM for prostate IMAT was successfully implemented clinically for the first time. Key advantages of this method are (1) submillimeter accuracy, (2) widespread applicability, and (3) a low barrier to clinical implementation. A disadvantage is that KIM delivers additional imaging dose to the patient.

  8. Proton energy optimization and reduction for intensity-modulated proton therapy.

    PubMed

    Cao, Wenhua; Lim, Gino; Liao, Li; Li, Yupeng; Jiang, Shengpeng; Li, Xiaoqiang; Li, Heng; Suzuki, Kazumichi; Zhu, X Ronald; Gomez, Daniel; Zhang, Xiaodong

    2014-11-07

    Intensity-modulated proton therapy (IMPT) is commonly delivered via the spot-scanning technique. To 'scan' the target volume, the proton beam is controlled by varying its energy to penetrate the patient's body at different depths. Although scanning the proton beamlets or spots with the same energy can be as fast as 10-20 m s(-1), changing from one proton energy to another requires approximately two additional seconds. The total IMPT delivery time thus depends mainly on the number of proton energies used in a treatment. Current treatment planning systems typically use all proton energies that are required for the proton beam to penetrate in a range from the distal edge to the proximal edge of the target. The optimal selection of proton energies has not been well studied. In this study, we sought to determine the feasibility of optimizing and reducing the number of proton energies in IMPT planning. We proposed an iterative mixed-integer programming optimization method to select a subset of all available proton energies while satisfying dosimetric criteria. We applied our proposed method to six patient datasets: four cases of prostate cancer, one case of lung cancer, and one case of mesothelioma. The numbers of energies were reduced by 14.3%-18.9% for the prostate cancer cases, 11.0% for the lung cancer cases and 26.5% for the mesothelioma case. The results indicate that the number of proton energies used in conventionally designed IMPT plans can be reduced without degrading dosimetric performance. The IMPT delivery efficiency could be improved by energy layer optimization leading to increased throughput for a busy proton center in which a delivery system with slow energy switch is employed.

  9. Proton energy optimization and reduction for intensity-modulated proton therapy

    NASA Astrophysics Data System (ADS)

    Cao, Wenhua; Lim, Gino; Liao, Li; Li, Yupeng; Jiang, Shengpeng; Li, Xiaoqiang; Li, Heng; Suzuki, Kazumichi; Zhu, X. Ronald; Gomez, Daniel; Zhang, Xiaodong

    2014-10-01

    Intensity-modulated proton therapy (IMPT) is commonly delivered via the spot-scanning technique. To ‘scan’ the target volume, the proton beam is controlled by varying its energy to penetrate the patient’s body at different depths. Although scanning the proton beamlets or spots with the same energy can be as fast as 10-20 m s-1, changing from one proton energy to another requires approximately two additional seconds. The total IMPT delivery time thus depends mainly on the number of proton energies used in a treatment. Current treatment planning systems typically use all proton energies that are required for the proton beam to penetrate in a range from the distal edge to the proximal edge of the target. The optimal selection of proton energies has not been well studied. In this study, we sought to determine the feasibility of optimizing and reducing the number of proton energies in IMPT planning. We proposed an iterative mixed-integer programming optimization method to select a subset of all available proton energies while satisfying dosimetric criteria. We applied our proposed method to six patient datasets: four cases of prostate cancer, one case of lung cancer, and one case of mesothelioma. The numbers of energies were reduced by 14.3%-18.9% for the prostate cancer cases, 11.0% for the lung cancer cases and 26.5% for the mesothelioma case. The results indicate that the number of proton energies used in conventionally designed IMPT plans can be reduced without degrading dosimetric performance. The IMPT delivery efficiency could be improved by energy layer optimization leading to increased throughput for a busy proton center in which a delivery system with slow energy switch is employed.

  10. Proton Versus Intensity-Modulated Radiotherapy for Prostate Cancer: Patterns of Care and Early Toxicity

    PubMed Central

    2013-01-01

    Background Proton radiotherapy (PRT) is an emerging treatment for prostate cancer despite limited knowledge of clinical benefit or potential harms compared with other types of radiotherapy. We therefore compared patterns of PRT use, cost, and early toxicity among Medicare beneficiaries with prostate cancer with those of intensity-modulated radiotherapy (IMRT). Methods We performed a retrospective study of all Medicare beneficiaries aged greater than or equal to 66 years who received PRT or IMRT for prostate cancer during 2008 and/or 2009. We used multivariable logistic regression to identify factors associated with receipt of PRT. To assess toxicity, each PRT patient was matched with two IMRT patients with similar clinical and sociodemographic characteristics. The main outcome measures were receipt of PRT or IMRT, Medicare reimbursement for each treatment, and early genitourinary, gastrointestinal, and other toxicity. All statistical tests were two-sided. Results We identified 27,647 men; 553 (2%) received PRT and 27,094 (98%) received IMRT. Patients receiving PRT were younger, healthier, and from more affluent areas than patients receiving IMRT. Median Medicare reimbursement was $32,428 for PRT and $18,575 for IMRT. Although PRT was associated with a statistically significant reduction in genitourinary toxicity at 6 months compared with IMRT (5.9% vs 9.5%; odds ratio [OR] = 0.60, 95% confidence interval [CI] = 0.38 to 0.96, P = .03), at 12 months post-treatment there was no difference in genitourinary toxicity (18.8% vs 17.5%; OR = 1.08, 95% CI = 0.76 to 1.54, P = .66). There was no statistically significant difference in gastrointestinal or other toxicity at 6 months or 12 months post-treatment. Conclusions Although PRT is substantially more costly than IMRT, there was no difference in toxicity in a comprehensive cohort of Medicare beneficiaries with prostate cancer at 12 months post-treatment. PMID:23243199

  11. Acute toxicity of hypofractionated intensity-modulated radiotherapy for prostate cancer

    PubMed Central

    Drodge, C.S.; Boychak, O.; Patel, S.; Usmani, N.; Amanie, J.; Parliament, M.B.; Murtha, A.; Field, C.; Ghosh, S.; Pervez, N.

    2015-01-01

    Background Dose-escalated hypofractionated radiotherapy (hfrt) using intensity-modulated radiotherapy (imrt), with inclusion of the pelvic lymph nodes (plns), plus androgen suppression therapy (ast) in high-risk prostate cancer patients should improve patient outcomes, but acute toxicity could limit its feasibility. Methods Our single-centre phase ii prospective study enrolled 40 high-risk prostate cancer patients. All patients received hfrt using imrt with daily mega-voltage computed tomography imaging guidance, with 95% of planning target volumes (ptv68 and ptv50) receiving 68 Gy and 50 Gy (respectively) in 25 daily fractions. The boost volume was targeted to the involved plns and the prostate (minus the urethra plus 3 mm and minus 3 mm from adjacent rectal wall) and totalled up to 75 Gy in 25 fractions. Acute toxicity scores were recorded weekly during and 3 months after radiotherapy (rt) administration. Results For the 37 patients who completed rt and the 3-month follow-up, median age was 65.5 years (range: 50–76 years). Disease was organ-confined (T1c–T2c) in 23 patients (62.1%), and node-positive in 5 patients (13.5%). All patients received long-term ast. Maximum acute genitourinary (gu) and gastrointestinal (gi) toxicity peaked at grade 2 in 6 of 36 evaluated patients (16.6%) and in 4 of 31 evaluated patients (12.9%) respectively. Diarrhea and urinary frequency were the chief complaints. Dose–volume parameters demonstrated no correlation with toxicity. The ptv treatment objectives were met in 36 of the 37 patients. Conclusions This hfrt dose-escalation trial in high-risk prostate cancer has demonstrated the feasibility of administering 75 Gy in 25 fractions with minimal acute gi and gu toxicities. Further follow-up will report late toxicities and outcomes. PMID:25908924

  12. Whole pelvic intensity-modulated radiotherapy for high-risk prostate cancer: a preliminary report

    PubMed Central

    Joo, Ji Hyeon; Kim, Yeon Joo; Choi, Eun Kyung; Kim, Jong Hoon; Lee, Sang-wook; Song, Si Yeol; Yoon, Sang Min; Kim, Su Ssan; Park, Jin-hong; Jeong, Yuri; Ahn, Hanjong; Kim, Choung-Soo; Lee, Jae-Lyun; Ahn, Seung Do

    2013-01-01

    Purpose To assess the clinical efficacy and toxicity of whole pelvic intensity-modulated radiotherapy (WP-IMRT) for high-risk prostate cancer. Materials and Methods Patients with high-risk prostate cancer treated between 2008 and 2013 were reviewed. The study included patients who had undergone WP-IMRT with image guidance using electronic portal imaging devices and/or cone-beam computed tomography. The endorectal balloon was used in 93% of patients. Patients received either 46 Gy to the whole pelvis plus a boost of up to 76 Gy to the prostate in 2 Gy daily fractions, or 44 Gy to the whole pelvis plus a boost of up to 72.6 Gy to the prostate in 2.2 Gy fractions. Results The study cohort included 70 patients, of whom 55 (78%) had a Gleason score of 8 to 10 and 50 (71%) had a prostate-specific antigen level > 20 ng/mL. The androgen deprivation therapy was combined in 62 patients. The biochemical failure-free survival rate was 86.7% at 2 years. Acute any grade gastrointestinal (GI) and genitourinary (GU) toxicity rates were 47% and 73%, respectively. The actuarial rate of late grade 2 or worse toxicity at 2 years was 12.9% for GI, and 5.7% for GU with no late grade 4 toxicity. Conclusion WP-IMRT was well tolerated with no severe acute or late toxicities, resulting in at least similar biochemical control to that of the historic control group with a small field. The long-term efficacy and toxicity will be assessed in the future, and a prospective randomized trial is needed to verify these findings. PMID:24501707

  13. Using individual patient anatomy to predict protocol compliance for prostate intensity-modulated radiotherapy

    SciTech Connect

    Caine, Hannah; Whalley, Deborah; Kneebone, Andrew; McCloud, Philip; Eade, Thomas

    2016-04-01

    If a prostate intensity-modulated radiation therapy (IMRT) or volumetric-modulated arc therapy (VMAT) plan has protocol violations, it is often a challenge knowing whether this is due to unfavorable anatomy or suboptimal planning. This study aimed to create a model to predict protocol violations based on patient anatomical variables and their potential relationship to target and organ at risk (OAR) end points in the setting of definitive, dose-escalated IMRT/VMAT prostate planning. Radiotherapy plans from 200 consecutive patients treated with definitive radiation for prostate cancer using IMRT or VMAT were analyzed. The first 100 patient plans (hypothesis-generating cohort) were examined to identify anatomical variables that predict for dosimetric outcome, in particular OAR end points. Variables that scored significance were further assessed for their ability to predict protocol violations using a Classification and Regression Tree (CART) analysis. These results were then validated in a second group of 100 patients (validation cohort). In the initial analysis of the hypothesis-generating cohort, percentage of rectum overlap in the planning target volume (PTV) (%OR) and percentage of bladder overlap in the PTV (%OB) were highlighted as significant predictors of rectal and bladder dosimetry. Lymph node treatment was also significant for bladder outcomes. For the validation cohort, CART analysis showed that %OR of < 6%, 6% to 9% and > 9% predicted a 13%, 63%, and 100% rate of rectal protocol violations respectively. For the bladder, %OB of < 9% vs > 9% is associated with 13% vs 88% rate of bladder constraint violations when lymph nodes were not treated. If nodal irradiation was delivered, plans with a %OB of < 9% had a 59% risk of violations. Percentage of rectum and bladder within the PTV can be used to identify individual plan potential to achieve dose-volume histogram (DVH) constraints. A model based on these factors could be used to reduce planning time, improve

  14. Role of Intensity-Modulated Radiotherapy in Reducing Toxicity in Dose Escalation for Localized Prostate Cancer

    SciTech Connect

    Al-Mamgani, Abrahim Heemsbergen, Wilma D.; Peeters, Stephanie T.H.; Lebesque, Joos V.

    2009-03-01

    Purpose: To compare the acute and late gastrointestinal (GI) and genitourinary (GU) toxicity in prostate cancer patients treated to a total dose of 78 Gy with either a three-conformal radiotherapy technique with a sequential boost (SEQ) or a simultaneous integrated boost using intensity-modulated radiotherapy (SIB-IMRT). Patients and Methods: A total of 78 prostate cancer patients participating in the randomized Dutch trial comparing 68 Gy and 78 Gy were the subject of this analysis. They were all treated at the same institution to a total dose of 78 Gy. The median follow-up was 76 and 56 months for the SEQ and SIB-IMRT groups, respectively. The primary endpoints were acute and late GI and GU toxicity. Results: A significantly lower incidence of acute Grade 2 or greater GI toxicity occurred in patients treated with SIB-IMRT compared with SEQ (20% vs. 61%, p = 0.001). For acute GU toxicity and late GI and GU toxicity, the incidence was lower after SIB-IMRT, but these differences were not statistically significant. No statistically significant difference were found in the 5-year freedom from biochemical failure rate (Phoenix definition) between the two groups (70% for the SIB-IMRT group vs. 61% for the SEQ group, p = 0.3). The same was true for the 5-year freedom from clinical failure rate (90% vs. 72%, p = 0.07). Conclusion: The results of our study have shown that SIB-IMRT reduced the toxicity without compromising the outcome in patients with localized prostate cancer treated to 78 Gy radiation.

  15. Postoperative Irradiation of Gynecologic Malignancies: Improving Treatment Delivery Using Aperture-Based Intensity-Modulated Radiotherapy

    SciTech Connect

    Nadeau, Sylvain . E-mail: sylvainn@rrsb.nb.ca; Bouchard, Myriam; Germain, Isabelle; Raymond, Paul-Emile; Beaulieu, Frederic; Beaulieu, Luc; Roy, Rene; Gingras, Luc

    2007-06-01

    Purpose: To evaluate dosimetric and treatment delivery advantages of aperture-based intensity-modulated radiotherapy (AB-IMRT) for the treatment of patients receiving whole pelvic radiotherapy for gynecologic malignancies. Methods and Materials: Nineteen patients undergoing pelvic radiotherapy after resection of endometrial cancers were selected. A 45-Gy dose was prescribed to the target volume delineated on a planning CT scan. An in-house inverse planning system, Ballista, was used to develop a treatment plan using aperture-based multileaf collimator segments. This approach was compared with conventional four-field, enlarged four-field, and static beamlet-based IMRT (BB-IMRT) techniques in terms of target coverage, dose-volume histogram statistics for surrounding normal tissues, and numbers of segments and monitor units (MU). Results: Three quarters (76.4%) of the planning target volume received the prescription dose with conventional four-field plans. With adequate target coverage, the Ballista plans significantly reduced the volume of bowel and bladder irradiated at the prescribed dose (p < 0.001), whereas the two approaches provided equivalent results for the rectum (p 0.5). On the other hand, AB-IMRT and BB-IMRT plans showed only small differences in dose-volume histogram statistics of unknown clinical impact, whereas Ballista plan delivery required on average 73% and 59% fewer segments and MU, respectively. Conclusion: With respect to conventional techniques, AB-IMRT for the treatment of gynecologic malignancies provides dosimetric advantages similar to those with BB-IMRT but with clear treatment delivery improvements.

  16. An Anatomically Validated Brachial Plexus Contouring Method for Intensity Modulated Radiation Therapy Planning

    SciTech Connect

    Van de Velde, Joris; Audenaert, Emmanuel; Speleers, Bruno; Vercauteren, Tom; Mulliez, Thomas; Vandemaele, Pieter; Achten, Eric; Kerckaert, Ingrid; D'Herde, Katharina; De Neve, Wilfried; Van Hoof, Tom

    2013-11-15

    Purpose: To develop contouring guidelines for the brachial plexus (BP) using anatomically validated cadaver datasets. Magnetic resonance imaging (MRI) and computed tomography (CT) were used to obtain detailed visualizations of the BP region, with the goal of achieving maximal inclusion of the actual BP in a small contoured volume while also accommodating for anatomic variations. Methods and Materials: CT and MRI were obtained for 8 cadavers positioned for intensity modulated radiation therapy. 3-dimensional reconstructions of soft tissue (from MRI) and bone (from CT) were combined to create 8 separate enhanced CT project files. Dissection of the corresponding cadavers anatomically validated the reconstructions created. Seven enhanced CT project files were then automatically fitted, separately in different regions, to obtain a single dataset of superimposed BP regions that incorporated anatomic variations. From this dataset, improved BP contouring guidelines were developed. These guidelines were then applied to the 7 original CT project files and also to 1 additional file, left out from the superimposing procedure. The percentage of BP inclusion was compared with the published guidelines. Results: The anatomic validation procedure showed a high level of conformity for the BP regions examined between the 3-dimensional reconstructions generated and the dissected counterparts. Accurate and detailed BP contouring guidelines were developed, which provided corresponding guidance for each level in a clinical dataset. An average margin of 4.7 mm around the anatomically validated BP contour is sufficient to accommodate for anatomic variations. Using the new guidelines, 100% inclusion of the BP was achieved, compared with a mean inclusion of 37.75% when published guidelines were applied. Conclusion: Improved guidelines for BP delineation were developed using combined MRI and CT imaging with validation by anatomic dissection.

  17. Disease-control rates following intensity-modulated radiation therapy for small primary oropharyngeal carcinoma

    SciTech Connect

    Garden, Adam S. . E-mail: agarden@mdanderson.org; Morrison, William H.; Wong, P.-F.; Tung, Sam S.; Rosenthal, David I.; Dong Lei; Mason, Brian M.S.; Perkins, George H.; Ang, K. Kian

    2007-02-01

    Background: The purpose of this study was to assess the ability of intensity-modulated radiation therapy (IMRT) to achieve favorable disease-control rates while minimizing parotid gland doses in patients treated for small primary tumors of the oropharynx. Methods and Materials: We retrospectively identified all patients who received IMRT as treatment for a small (<4 cm) primary tumor of the oropharynx between October 2000 and June 2002. Tumor characteristics, IMRT parameters, and patient outcomes were assessed. Results: Fifty-one patients met the criteria for our study. All patients had treatment to gross disease with margin (CTV1), and all but 1 had treatment to the bilateral necks. The most common treatment schedule (39 patients) was a once-daily fractionation of prescribed doses of 63-66 Gy to the CTV1 and 54 Gy to subclinical sites, delivered in 30 fractions. Twenty-one patients (40%) had gastrostomy tubes placed during therapy; in 4 patients, the tube remained in place for more than 6 months after completion of IMRT. The median follow-up was 45 months. The 2-year actuarial locoregional control, recurrence-free, and overall survival rates were 94%, 88%, and 94%, respectively. Conclusions: These preliminary data suggest that treatment with IMRT results in favorable locoregional control of small primary oropharynx tumors. IMRT did not appear to have a more favorable acute toxicity profile in this group with respect to the use of a feeding tube; however, the mean dose of radiation delivered to the parotid gland by IMRT was decreased, because 95% of patients had a mean dose of <30 Gy to at least one gland.

  18. Intensity-Modulated Radiotherapy for Head and Neck Cancer of Unknown Primary: Toxicity and Preliminary Efficacy

    SciTech Connect

    Klem, Michelle L. Mechalakos, James G.; Wolden, Suzanne L.; Zelefsky, Michael J.; Singh, Bhuvanesh; Kraus, Dennis; Shaha, Ashok; Shah, Jatin; Pfister, David G.; Lee, Nancy Y.

    2008-03-15

    Purpose: Unknown primary head and neck cancers often require comprehensive mucosal and bilateral neck irradiation. With conventional techniques, significant toxicity can develop. Intensity-modulated radiotherapy (IMRT) has the potential to minimize the toxicity. Methods and Materials: Between 2000 and 2005, 21 patients underwent IMRT for unknown primary head and neck cancer at our center. Of the 21 patients, 5 received IMRT with definitive intent and 16 as postoperative therapy; 14 received concurrent chemotherapy and 7 IMRT alone. The target volumes included the bilateral neck and mucosal surface. The median dose was 66 Gy. Acute and chronic toxicities, esophageal strictures, and percutaneous endoscopic gastrostomy tube dependence were evaluated. Progression-free survival, regional progression-free survival, distant metastasis-free survival, and overall survival were estimated with Kaplan-Meier curves. Results: With a median follow-up of 24 months, the 2-year regional progression-free survival, distant metastasis-free survival, and overall survival rate was 90%, 90%, and 85%, respectively. Acute grade 1 and 2 xerostomia was seen in 57% and 43% of patients, respectively. Salivary function improved with time. Percutaneous endoscopic gastrostomy tube placement was required in 72% with combined modality treatment and 43% with IMRT alone. Only 1 patient required percutaneous endoscopic gastrostomy support at the last follow-up visit. Two patients treated with combined modality and one treated with IMRT alone developed esophageal strictures, but all had improvement or resolution with dilation. Conclusion: The preliminary analysis of IMRT for unknown primary head and neck cancer has shown acceptable toxicity and encouraging efficacy. The analysis of the dosimetric variables showed excellent tumor coverage and acceptable doses to critical normal structures. Esophageal strictures developed but were effectively treated with dilation. Techniques to limit the esophageal dose

  19. Electromagnetic-Guided Dynamic Multileaf Collimator Tracking Enables Motion Management for Intensity-Modulated Arc Therapy

    SciTech Connect

    Keall, Paul J.; Sawant, Amit; Cho, Byungchul; Ruan, Dan; Wu Junqing; Poulsen, Per; Petersen, Jay; Newell, Laurence J.; Cattell, Herbert; Korreman, Stine

    2011-01-01

    Purpose: Intensity-modulated arc therapy (IMAT) is attractive because of high-dose conformality and efficient delivery. However, managing intrafraction motion is challenging for IMAT. The purpose of this research was to develop and investigate electromagnetically guided dynamic multileaf collimator (DMLC) tracking as an enabling technology to treat moving targets during IMAT. Methods and Materials: A real-time three-dimensional DMLC-based target tracking system was developed and integrated with a linear accelerator. The DMLC tracking software inputs a real-time electromagnetically measured target position and the IMAT plan, and dynamically creates new leaf positions directed at the moving target. Low- and high-modulation IMAT plans were created for lung and prostate cancer cases. The IMAT plans were delivered to a three-axis motion platform programmed with measured patient motion. Dosimetric measurements were acquired by placing an ion chamber array on the moving platform. Measurements were acquired with tracking, without tracking (current clinical practice), and with the phantom in a static position (reference). Analysis of dose distribution differences from the static reference used a {gamma}-test. Results: On average, 1.6% of dose points for the lung plans and 1.2% of points for the prostate plans failed the 3-mm/3% {gamma}-test with tracking; without tracking, 34% and 14% (respectively) of points failed the {gamma}-test. The delivery time was the same with and without tracking. Conclusions: Electromagnetic-guided DMLC target tracking with IMAT has been investigated for the first time. Dose distributions to moving targets with DMLC tracking were significantly superior to those without tracking. There was no loss of treatment efficiency with DMLC tracking.

  20. Performance evaluation of intensity modulated optical OFDM system with digital baseband distortion.

    PubMed

    Vanin, Evgeny

    2011-02-28

    Bit-Error-Ratio (BER) of intensity modulated optical orthogonal frequency division multiplexing (OFDM) system is analytically evaluated accounting for nonlinear digital baseband distortion in the transmitter and additive noise in the photo receiver. The nonlinear distortion that is caused by signal clipping and quantization is taken into consideration. The signal clipping helps to overcome the system performance limitation related to high peak-to-average power ratio (PAPR) of the OFDM signal and to minimize the value of optical power that is required for achieving specified BER. The signal quantization due to a limited bit resolution of the digital to analog converter (DAC) causes an optical power penalty in the case when the bit resolution is too low. By introducing an effective signal to noise ratio (SNR) the optimum signal clipping ratio, system BER and required optical power at the input to the receiver is evaluated for the OFDM system with multi-level quadrature amplitude modulation (QAM) applied to the optical signal subcarriers. Minimum required DAC bit resolution versus the size of QAM constellation is identified. It is demonstrated that the bit resolution of 7 and higher causes negligibly small optical power penalty at the system BER=10⁻³ when 256-QAM and a constellation of lower size is applied. The performance of the optical OFDM system is compared to the performance of the multi-level amplitude-shift keying (M-ASK) system for the same number of information bits transmitted per signal sample. It is demonstrated that in the case of the matched receiver the M-ASK system outperforms OFDM and requires 3-3.5 dB less of optical power at BER=10⁻³ when 1-4 data bits are transmitted per signal sample.

  1. Intensity-Modulated Radiation Therapy Significantly Improves Acute Gastrointestinal Toxicity in Pancreatic and Ampullary Cancers

    SciTech Connect

    Yovino, Susannah; Poppe, Matthew; Jabbour, Salma; David, Vera; Garofalo, Michael; Pandya, Naimesh; Alexander, Richard; Hanna, Nader; Regine, William F.

    2011-01-01

    Purpose: Among patients with upper abdominal malignancies, intensity-modulated radiation therapy (IMRT) can improve dose distributions to critical dose-limiting structures near the target. Whether these improved dose distributions are associated with decreased toxicity when compared with conventional three-dimensional treatment remains a subject of investigation. Methods and Materials: 46 patients with pancreatic/ampullary cancer were treated with concurrent chemoradiation (CRT) using inverse-planned IMRT. All patients received CRT based on 5-fluorouracil in a schema similar to Radiation Therapy Oncology Group (RTOG) 97-04. Rates of acute gastrointestinal (GI) toxicity for this series of IMRT-treated patients were compared with those from RTOG 97-04, where all patients were treated with three-dimensional conformal techniques. Chi-square analysis was used to determine if there was a statistically different incidence in acute GI toxicity between these two groups of patients. Results: The overall incidence of Grade 3-4 acute GI toxicity was low in patients receiving IMRT-based CRT. When compared with patients who had three-dimensional treatment planning (RTOG 97-04), IMRT significantly reduced the incidence of Grade 3-4 nausea and vomiting (0% vs. 11%, p = 0.024) and diarrhea (3% vs. 18%, p = 0.017). There was no significant difference in the incidence of Grade 3-4 weight loss between the two groups of patients. Conclusions: IMRT is associated with a statistically significant decrease in acute upper and lower GI toxicity among patients treated with CRT for pancreatic/ampullary cancers. Future clinical trials plan to incorporate the use of IMRT, given that it remains a subject of active investigation.

  2. Outcomes After Intensity-Modulated Versus Conformal Radiotherapy in Older Men With Nonmetastatic Prostate Cancer

    SciTech Connect

    Bekelman, Justin E.; Mitra, Nandita; Efstathiou, Jason; Liao Kaijun; Sunderland, Robert; Yeboa, Deborah N.; Armstrong, Katrina

    2011-11-15

    Purpose: There is little evidence comparing complications after intensity-modulated (IMRT) vs. three-dimensional conformal radiotherapy (CRT) for prostate cancer. The study objective was to test the hypothesis that IMRT, compared with CRT, is associated with a reduction in bowel, urinary, and erectile complications in elderly men with nonmetastatic prostate cancer. Methods and Materials: We undertook an observational cohort study using registry and administrative claims data from the SEER-Medicare database. We identified men aged 65 years or older diagnosed with nonmetastatic prostate cancer in the United States between 2002 and 2004 who received IMRT (n = 5,845) or CRT (n = 6,753). The primary outcome was a composite measure of bowel complications. Secondary outcomes were composite measures of urinary and erectile complications. We also examined specific subsets of bowel (proctitis/hemorrhage) and urinary (cystitis/hematuria) events within the composite complication measures. Results: IMRT was associated with reductions in composite bowel complications (24-month cumulative incidence 18.8% vs. 22.5%; hazard ratio [HR] 0.86; 95% confidence interval [CI], 0.79-0.93) and proctitis/hemorrhage (HR 0.78; 95% CI, 0.64-0.95). IMRT was not associated with rates of composite urinary complications (HR 0.93; 95% CI, 0.83-1.04) or cystitis/hematuria (HR 0.94; 95% CI, 0.83-1.07). The incidence of erectile complications involving invasive procedures was low and did not differ significantly between groups, although IMRT was associated with an increase in new diagnoses of impotence (HR 1.27, 95% CI, 1.14-1.42). Conclusion: IMRT is associated with a small reduction in composite bowel complications and proctitis/hemorrhage compared with CRT in elderly men with nonmetastatic prostate cancer.

  3. Patterns of Disease Recurrence Following Treatment of Oropharyngeal Cancer With Intensity Modulated Radiation Therapy

    SciTech Connect

    Garden, Adam S.; Dong, Lei; Morrison, William H.; Stugis, Erich M.; Glisson, Bonnie S.; Schwartz, David L.; Kies, Merill S.; Ang, K. Kian; Rosenthal, David I.

    2013-03-15

    Purpose: To report mature results of a large cohort of patients diagnosed with squamous cell carcinoma of the oropharynx who were treated with intensity modulated radiation therapy (IMRT). Methods and Materials: The database of patients irradiated at The University of Texas, M.D. Anderson Cancer Center was searched for patients diagnosed with oropharyngeal cancer and treated with IMRT between 2000 and 2007. A retrospective review of outcome data was performed. Results: The cohort consisted of 776 patients. One hundred fifty-nine patients (21%) were current smokers, 279 (36%) former smokers, and 337 (43%) never smokers. T and N categories and American Joint Committee on Cancer group stages were distributed as follows: T1/x, 288 (37%); T2, 288 (37%); T3, 113 (15%); T4, 87 (11%); N0, 88(12%); N1/x, 140 (18%); N2a, 101 (13%); N2b, 269 (35%); N2c, 122 (16%); and N3, 56 (7%); stage I, 18(2%); stage II, 40(5%); stage III, 150(19%); and stage IV, 568(74%). Seventy-one patients (10%) presented with nodes in level IV. Median follow-up was 54 months. The 5-year overall survival, locoregional control, and overall recurrence-free survival rates were 84%, 90%, and 82%, respectively. Primary site recurrence developed in 7% of patients, and neck recurrence with primary site control in 3%. We could only identify 12 patients (2%) who had locoregional recurrence outside the high-dose target volumes. Poorer survival rates were observed in current smokers, patients with larger primary (T) tumors and lower neck disease. Conclusions: Patients with oropharyngeal cancer treated with IMRT have excellent disease control. Locoregional recurrence was uncommon, and most often occurred in the high dose volumes. Parotid sparing was accomplished in nearly all patients without compromising tumor coverage.

  4. Disease Control and Ototoxicity Using Intensity-Modulated Radiation Therapy Tumor-Bed Boost for Medulloblastoma

    SciTech Connect

    Polkinghorn, William R.; Dunkel, Ira J.; Souweidane, Mark M.; Khakoo, Yasmin; Lyden, David C.; Gilheeney, Stephen W.; Becher, Oren J.; Budnick, Amy S.; Wolden, Suzanne L.

    2011-11-01

    Purpose: We previously reported excellent local control for treating medulloblastoma with a limited boost to the tumor bed. In order to decrease ototoxicity, we subsequently implemented a tumor-bed boost using intensity-modulated radiation therapy (IMRT), the clinical results of which we report here. Patients and Methods: A total of 33 patients with newly diagnosed medulloblastoma, 25 with standard risk, and 8 with high risk, were treated on an IMRT tumor-bed boost following craniospinal irradiation (CSI). Six standard-risk patients were treated with an institutional protocol with 18 Gy CSI in conjunction with intrathecal iodine-131-labeled monoclonal antibody. The majority of patients received concurrent vincristine and standard adjuvant chemotherapy. Pure-tone audiograms were graded according to National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0. Results: Median age was 9 years old (range, 4-46 years old). Median follow-up was 63 months. Kaplan-Meier estimates of progression-free survival (PFS) and overall survival (OS) rates for standard-risk patients who received 23.4 or 36 Gy CSI (not including those who received 18 Gy CSI with radioimmunotherapy) were 81.4% and 88.4%, respectively, at 5 years; 5-year PFS and OS rates for high-risk patients were both 87.5%. There were no isolated posterior fossa failures outside of the boost volume. Posttreatment audiograms were available for 31 patients, of whom 6%, at a median follow-up of 19 months, had developed Grade 3 hearing loss. Conclusion: An IMRT tumor-bed boost results in excellent local control while delivering a low mean dose to the cochlea, resulting in a low rate of ototoxicity.

  5. Hypofractionated Dose-Painting Intensity Modulated Radiation Therapy With Chemotherapy for Nasopharyngeal Carcinoma: A Prospective Trial

    SciTech Connect

    Bakst, Richard L.; Lee, Nancy; Pfister, David G.; Zelefsky, Michael J.; Hunt, Margie A.; Kraus, Dennis H.; Wolden, Suzanne L.

    2011-05-01

    Purpose: To evaluate the feasibility of dose-painting intensity-modulated radiation therapy (DP-IMRT) with a hypofractionated regimen to treat nasopharyngeal carcinoma (NPC) with concomitant toxicity reduction. Methods and Materials: From October 2002 through April 2007, 25 newly diagnosed NPC patients were enrolled in a prospective trial. DP-IMRT was prescribed to deliver 70.2 Gy using 2.34-Gy fractions to the gross tumor volume for the primary and nodal sites while simultaneously delivering 54 Gy in 1.8-Gy fractions to regions at risk of microscopic disease. Patients received concurrent and adjuvant platin-based chemotherapy similar to the Intergroup 0099 trial. Results: Patient and disease characteristics are as follows: median age, 46; 44% Asian; 68% male; 76% World Health Organization III; 20% T1, 52% T2, 16% T3, 12% T4; 20% N0, 36% N1, 36% N2, 8% N3. With median follow-up of 33 months, 3-year local control was 91%, regional control was 91%, freedom from distant metastases was 91%, and overall survival was 89%. The average mean dose to each cochlea was 43 Gy. With median audiogram follow-up of 14 months, only one patient had clinically significant (Grade 3) hearing loss. Twelve percent of patients developed temporal lobe necrosis; one patient required surgical resection. Conclusions: Preliminary findings using a hypofractionated DP-IMRT regimen demonstrated that local control, freedom from distant metastases, and overall survival compared favorably with other series of IMRT and chemotherapy. The highly conformal boost to the tumor bed resulted low rates of severe ototoxicity (Grade 3-4). However, the incidence of in-field brain radiation necrosis indicates that 2.34 Gy per fraction is not safe in this setting.

  6. Intensity-Modulated Radiotherapy for Cervical Lymph Node Metastases From Unknown Primary Cancer

    SciTech Connect

    Madani, Indira Vakaet, Luc; Bonte, Katrien; Boterberg, Tom; Neve, Wilfried de

    2008-07-15

    Purpose: To compare the effectiveness of intensity-modulated radiotherapy (IMRT) and conventional (two-dimensional) radiotherapy in the treatment of cervical lymph node metastases from unknown primary cancer (UPC). Methods and Materials: Between February 2003 and September 2006, 23 patients with UPC of squamous cell carcinoma were treated with IMRT. Extended putative mucosal and bilateral nodal sites were irradiated to a median dose of 66 Gy. In 19 patients, IMRT was performed after lymph node dissection, and in 4 patients primary radiotherapy was given. The conventional radiotherapy group (historical control group) comprised 18 patients treated to a median dose of 66 Gy between August 1994 and October 2003. Results: Twenty patients completed treatment. As compared with conventional radiotherapy, the incidence of Grade 3 acute dysphagia was significantly lower in the IMRT group (4.5% vs. 50%, p = 0.003). By 6 months, Grade 3 xerostomia was detected in 11.8% patients in the IMRT group vs. 53.4% in the historical control group (p = 0.03). No Grade 3 dysphagia or skin fibrosis was observed after IMRT but these were noted after conventional radiotherapy (26.7%, p = 0.01) and 26.7%, p = 0.03) respectively). With median follow-up of living patients of 17 months, there was no emergence of primary cancer. One patient had persistent nodal disease and another had nodal relapse at 5 months. Distant metastases were detected in 4 patients. The 2-year overall survival and distant disease-free probability after IMRT did not differ significantly from those for conventional radiotherapy (74.8% vs. 61.1% and 76.3% vs. 68.4%, respectively). Conclusions: Use of IMRT for UPC resulted in lower toxicity than conventional radiotherapy, and was similar in efficacy.

  7. Multivariate analysis of factors predicting prostate dose in intensity-modulated radiotherapy

    SciTech Connect

    Tomita, Tsuneyuki; Nakamura, Mitsuhiro; Hirose, Yoshinori; Kitsuda, Kenji; Notogawa, Takuya; Miki, Katsuhito; Nakamura, Kiyonao; Ishigaki, Takashi

    2014-01-01

    We conducted a multivariate analysis to determine relationships between prostate radiation dose and the state of surrounding organs, including organ volumes and the internal angle of the levator ani muscle (LAM), based on cone-beam computed tomography (CBCT) images after bone matching. We analyzed 270 CBCT data sets from 30 consecutive patients receiving intensity-modulated radiation therapy for prostate cancer. With patients in the supine position on a couch with the HipFix system, data for center of mass (COM) displacement of the prostate and the state of individual organs were acquired and compared between planning CT and CBCT scans. Dose distributions were then recalculated based on CBCT images. The relative effects of factors on the variance in COM, dose covering 95% of the prostate volume (D{sub 95%}), and percentage of prostate volume covered by the 100% isodose line (V{sub 100%}) were evaluated by a backward stepwise multiple regression analysis. COM displacement in the anterior-posterior direction (COM{sub AP}) correlated significantly with the rectum volume (δVr) and the internal LAM angle (δθ; R = 0.63). Weak correlations were seen for COM in the left-right (R = 0.18) and superior-inferior directions (R = 0.31). Strong correlations between COM{sub AP} and prostate D{sub 95%} and V{sub 100%} were observed (R ≥ 0.69). Additionally, the change ratios in δVr and δθ remained as predictors of prostate D{sub 95%} and V{sub 100%}. This study shows statistically that maintaining the same rectum volume and LAM state for both the planning CT simulation and treatment is important to ensure the correct prostate dose in the supine position with bone matching.

  8. Replanning During Intensity Modulated Radiation Therapy Improved Quality of Life in Patients With Nasopharyngeal Carcinoma

    SciTech Connect

    Yang Haihua; Hu Wei; Wang Wei; Chen Peifang; Ding Weijun; Luo Wei

    2013-01-01

    Purpose: Anatomic and dosimetric changes have been reported during intensity modulated radiation therapy (IMRT) in patients with nasopharyngeal carcinoma (NPC). The purpose of this study was to evaluate the effects of replanning on quality of life (QoL) and clinical outcomes during the course of IMRT for NPC patients. Methods and Materials: Between June 2007 and August 2011, 129 patients with NPC were enrolled. Forty-three patients received IMRT without replanning, while 86 patients received IMRT replanning after computed tomography (CT) images were retaken part way through therapy. Chinese versions of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire C30 and Head and Neck Quality of Life Questionnaire 35 were completed before treatment began and at the end of treatment and at 1, 3, 6, and 12 months after the completion of treatment. Overall survival (OS) data were compared using the Kaplan-Meier method. Results: IMRT replanning had a profound impact on the QoL of NPC patients, as determined by statistically significant changes in global QoL and other QoL scales. Additionally, the clinical outcome comparison indicates that replanning during IMRT for NPC significantly improved 2-year local regional control (97.2% vs 92.4%, respectively, P=.040) but did not improve 2-year OS (89.8% vs 82.2%, respectively, P=.475). Conclusions: IMRT replanning improves QoL as well as local regional control in patients with NPC. Future research is needed to determine the criteria for replanning for NPC patients undergoing IMRT.

  9. Incorporation of gantry angle correction for 3D dose prediction in intensity-modulated radiation therapy

    PubMed Central

    Sumida, Iori; Yamaguchi, Hajime; Kizaki, Hisao; Aboshi, Keiko; Tsujii, Mari; Yamada, Yuji; Yagi, Masashi; Ogawa, Kazuhiko

    2015-01-01

    Pretreatment dose verification with beam-by-beam analysis for intensity-modulated radiation therapy (IMRT) is commonly performed with a gantry angle of 0° using a 2D diode detector array. Any changes in multileaf collimator (MLC) position between the actual treatment gantry angle and 0° may result in deviations from the planned dose. We evaluated the effects of MLC positioning errors between the actual treatment gantry angles and nominal gantry angles. A gantry angle correction (GAC) factor was generated by performing a non-gap test at various gantry angles using an electronic portal imaging device (EPID). To convert pixel intensity to dose at the MLC abutment positions, a non-gap test was performed using an EPID and a film at 0° gantry angle. We then assessed the correlations between pixel intensities and doses. Beam-by-beam analyses for 15 prostate IMRT cases as patient-specific quality assurance were performed with a 2D diode detector array at 0° gantry angle to determine the relative dose error for each beam. The resulting relative dose error with or without GAC was added back to the original dose grid for each beam. We compared the predicted dose distributions with or without GAC for film measurements to validate GAC effects. A gamma pass rate with a tolerance of 2%/2 mm was used to evaluate these dose distributions. The gamma pass rate with GAC was higher than that without GAC (P = 0.01). The predicted dose distribution improved with GAC, although the dosimetric effect to a patient was minimal. PMID:25742866

  10. Clinical Outcome of Adjuvant Treatment of Endometrial Cancer Using Aperture-Based Intensity-Modulated Radiotherapy

    SciTech Connect

    Bouchard, Myriam; Nadeau, Sylvain M.Sc.; Gingras, Luc; Raymond, Paul-Emile; Beaulieu, Frederic; Beaulieu, Luc; Fortin, Andre; Germain, Isabelle

    2008-08-01

    Purpose: To assess disease control and acute and chronic toxicity with aperture-based intensity-modulated radiotherapy (AB-IMRT) for postoperative pelvic irradiation of endometrial cancer. Methods and Materials: Between January and July 2005, after hysterectomy for endometrial cancer, 15 patients received 45 Gy to the pelvis using AB-IMRT. The AB-IMRT plans were generated by an in-house treatment planning system (Ballista). The AB-IMRT plans were used for treatment and were dosimetrically compared with three other approaches: conventional four-field, enlarged four-field, and beamlet-based IMRT (BB-IMRT). Disease control and toxicity were prospectively recorded and compared with retrospective data from 30 patients treated with a conventional four-field technique. Results: At a median follow-up of 27 months (range, 23-30), no relapse was noted among the AB-IMRT group compared with five relapses in the control group (p = 0.1). The characteristics of each group were similar, except for the mean body mass index, timing of brachytherapy, and applicator type used. Patients treated with AB-IMRT experienced more frequent Grade 2 or greater gastrointestinal acute toxicity (87% vs. 53%, p 0.02). No statistically significant difference was noted between the two groups regarding the incidence or severity of chronic toxicities. AB-IMRT plans significantly improved target coverage (93% vs. 76% of planning target volume receiving 45 Gy for AB-IMRT vs. conventional four-field technique, respectively). The sparing of organs at risk was similar to that of BB-IMRT. Conclusion: The results of our study have shown that AB-IMRT provides excellent disease control with equivalent late toxicity compared with the conventional four-field technique. AB-IMRT provided treatment delivery and quality assurance advantages compared with BB-IMRT and could reduce the risk of second malignancy compared with BB-IMRT.

  11. Changes Mimicking New Leptomeningeal Disease After Intensity-Modulated Radiotherapy for Medulloblastoma

    SciTech Connect

    Muscal, Jodi A.; Jones, Jeremy Y.; Paulino, Arnold C.; Bertuch, Alison A.; Su, Jack; Woo, Shiao Y.; Mahoney, Donald H.; Chintagumpala, Murali

    2009-01-01

    Purpose: Acute and late changes in magnetic resonance imaging of the pediatric brain have been described after radiotherapy (RT). We report the post-RT neuroimaging changes in the posterior fossa after intensity-modulated RT (IMRT) in children with medulloblastoma and contrast them with those of leptomeningeal disease. Methods and Materials: We performed a retrospective review of 53 consecutive children with medulloblastoma who were treated with craniospinal RT followed by IMRT to the posterior fossa and chemotherapy between 1997 and 2006. Results: After IMRT to the posterior fossa, 8 (15%) of 53 patients developed increased fluid-attenuated inversion-recovery signal changes in the brainstem or cerebellum and patchy, multifocal, nodular contrast enhancement at a median of 6 months. The enhancement superficially resembled leptomeningeal disease. However, the enhancement resolved without intervention at a median of 6 months later. The accompanying fluid-attenuated inversion-recovery signal changes occasionally preceded the enhancement, were often parenchymal in location, and resolved or persisted to a lesser degree. All 8 patients with transient magnetic resonance imaging changes in the posterior fossa were alive at last follow-up. In contrast, leptomeningeal disease occurred in 8 (15%) of our 53 patients at a median of 19.5 months after IMRT completion. Of these 8 patients, 7 demonstrated initial nodular enhancement outside the conformal field, and 7 patients died. Conclusion: Magnetic resonance imaging changes can occur in the posterior fossa of children treated with IMRT for medulloblastoma. In our experience, these transient changes occur at a characteristic time and location after RT, allowing them to be distinguished from leptomeningeal disease.

  12. Local Control After Intensity-Modulated Radiotherapy for Head-and-Neck Rhabdomyosarcoma

    SciTech Connect

    Curtis, Amarinthia E.; Okcu, M. Fatih; Chintagumpala, Murali; Paulino, Arnold C.

    2009-01-01

    Purpose: To examine the patterns of failure in patients treated with intensity-modulated radiotherapy (IMRT) for head-and-neck rhabdomyosarcoma (RMS). Methods and Materials: Between 1998 and 2005, 19 patients with a diagnosis of head-and-neck RMS received IMRT at The Methodist Hospital. There were 11 male and 8 female patients, with a median age of 6 years at time of irradiation. Tumor location was parameningeal in 7, orbital in 6, and other head-and-neck RMS in 6. Chemotherapy was given to all patients, with vincristine, actinomycin D, and cyclophosphamide being the most common regimen (n = 18). The median prescribed dose was 5040 cGy. The clinical target volume included the gross tumor volume with a 1.5-cm margin. The median duration of follow-up for surviving patients was 56 months. Results: The 4-year overall survival and local control rates were 76% and 92.9%, respectively. One patient developed a local failure in the high-dose region of the radiation field; there were no marginal failures. Distant metastasis was seen in 4 patients. Overall survival was 42.9% for parameningeal sites and 100% for other sites (p < 0.01). Late toxicities were seen in 7 patients. Two secondary malignancies occurred in 1 child with embryonal RMS of the face and a p53 mutation. Conclusions: Local control was excellent in patients receiving IMRT for head-and-neck RMS. Patterns of local failure reveal no marginal failures in this group of patients.

  13. Intensity-modulated radiotherapy reduces gastrointestinal toxicity in locally advanced pancreas cancer

    PubMed Central

    Prasad, Shreya; Cambridge, Lajhem; Huguet, Florence; Chou, Joanne F.; Zhang, Zhigang; Wu, Abraham J.; O'Reilly, Eileen M.; Allen, Peter; Goodman, Karyn A.

    2016-01-01

    Purpose We compared gastrointestinal (GI) and hematologic toxicity in patients with locally advanced pancreas cancer (LAPC) undergoing definitive chemoradiation using intensity modulated radiotherapy (IMRT) or 3D conformal radiotherapy (3D-CRT) planning. Methods and Materials We retrospectively studied 205 patients with LAPC undergoing IMRT (n=134) and 3D-CRT (n=71) between 05/03 and 03/12. Patient, tumor, and treatment characteristics and acute GI/hematology toxicity according to Common Terminology Criteria for Adverse Events v3.0 were recorded. Multivariable logistic regression models were used to test association between acute grade 2+ GI and hematologic toxicity outcomes and predictors. Propensity score analysis for grade 2+ GI toxicity was performed to reduce bias for confounding variables: age, gender, radiation dose, field size, and chemotherapy type. Results Median follow-up time for survivors was 22 months, similar between groups. Median RT dose was significantly higher for IMRT vs. 3D-CRT (5600 cGy vs 5040 cGy, P<.001); concurrent chemotherapy was mainly gemcitabine (56%) or 5-fluorouracil (5-FU, 38%). Grade 2+ GI toxicity occurred in 34% (n=24) of 3D-CRT compared with 16% (n=21) of IMRT patients. Using propensity-score analysis, 3D-CRT had significantly higher grade 2+ GI toxicity (odds ratio, 1.26 [95%CI, 1.08-1.45], P=.001). Grade 2+ hematologic toxicity was similar between IMRT and 3D-CRT groups but was significantly greater in recipients of concurrent gemcitabine over 5-FU (62% vs 29%, P<.0001). Conclusions IMRT is associated with significant lower grade 2+ GI toxicity versus 3D-CRT for patients undergoing definitive chemoradiotherapy for LAPC. Since IMRT is better tolerated at higher doses and may allow further dose escalation, potentially improving local control for this aggressive disease. Further prospective studies of dose-escalated chemoradiation using IMRT are warranted. PMID:26577010

  14. Intensity-modulated radiotherapy for previously irradiated, recurrent head-and-neck cancer.

    PubMed

    Chen, Yi-Jen; Kuo, Jeffrey V; Ramsinghani, Nilam S; Al-Ghazi, Muthana S A L

    2002-01-01

    The purpose of this work is to evaluate our initial experience in treating previously irradiated, recurrent head-and-neck cancers using intensity-modulated radiotherapy (IMRT). Between July 1997 and September 1999, 12 patients with previously irradiated, locally recurrent head-and-neck cancers were treated with IMRT. These included cancers of the nasopharynx, oropharynx, hypopharynx, larynx, paranasal sinus, skin of the head-and-neck region, and malignant melanoma. Five of these 12 patients had received radiation as the primary treatment, with doses ranging from 66.0 to 126.0 Gy, and the remaining 7 patients had undergone definitive surgeries followed by an adjuvant course of radiation treatment, with doses ranging between 36.0 and 64.8 Gy. Recurrence after the initial course of radiation occurred in periods ranging from 4 to 35 months, with 11 of 12 cases recurring fully in the fields of previous irradiation. Recurrent tumors were treated with IMRT to total doses between 30 to 70 Gy (> 50 Gy in 10 cases) prescribed at the 75% to 92% isodose lines with daily fractions of 1.8 to 2 Gy. The results revealed that acute toxicities were acceptable except in 1 patient who died of aspiration pneumonia during the course of retreatment. There were 4 complete responders, 2 partial responders, and 2 patients with stable disease in the IMRT-treated volumes. Three patients received IMRT as adjuvant treatment following salvage surgery. At 4 to 16 months of follow-up, 7 patients were still alive, with 5 revealing no evidence of disease. In conclusion, this pilot study demonstrates that IMRT offers a viable mode of re-irradiation for recurrent head-and-neck cancers in previously irradiated sites. Longer follow-up time and a larger number of patients are needed to better define the therapeutic advantage of IMRT in recurrent, previously irradiated head-and-neck cancers.

  15. SU-E-T-814: Whole Breast Irradiation with Two Different Intensity Modulation Radiotherapy Techniques

    SciTech Connect

    Sun, T; Yin, Y; Lin, X; Zhang, G

    2015-06-15

    Purpose: Breast cancer now mainly received forward intensity modulation radiotherapy (f-IMRT) and inverse IMRT (i-IMRT). The purpose of this study was to observe the differences of two treatment methods. Methods: 10 patients after left breast-conserving surgery were selected to receive radiotherapy. For each patient, two treatment plans (f-IMRT and i-IMRT) were designed. For f-IMRT plans, two tangent beams were designed to the target, and in each tangent orientation two or three segment beams were designed to reduced high dose region in the target and the dose of lung received. For i-IMRT plans, two tangent beams were designed to the target and the treatment planning system optimize the dose according to the optimization parameters. For each plan 50Gy was prescribed. Results: In f-IMRT and i-IMRT plans, the average target conformal index (CI) were (0.67±0.06) and (0.66±0.06), (P>0.05); average homogeneity index (HI) were (28.2±6.0)% and (26.1±6.8)%, (P>0.05); volume of left lung received 20Gy (V20) were (18.7±3.3)% and (17.0±2.8)%, (P<0.05), V30 were (15.5±3.0)% and (14.0±2.6)%, (P<0.05); V30 of heart were (4.1±3.1)% and (3.5±2.5)%, (P>0.05); Monitor Unit (MU) were (262±5)MU and (308±14)MU. Conclusion: Compared with i-IMRT plan, for breast cancer, the differences of CI and HI were not significant. Because of fewer MU, f-IMRT plan could reduce the machine abrasion and treatment time, but dose of normal tissue received were higher significantly than i-IMRT plan.

  16. Adoption of Intensity Modulated Radiation Therapy For Early-Stage Breast Cancer From 2004 Through 2011

    SciTech Connect

    Wang, Elyn H.; Mougalian, Sarah S.; Soulos, Pamela R.; Smith, Benjamin D.; Haffty, Bruce G.; Gross, Cary P.; Yu, James B.

    2015-02-01

    Purpose: Intensity modulated radiation therapy (IMRT) is a newer method of radiation therapy (RT) that has been increasingly adopted as an adjuvant treatment after breast-conserving surgery (BCS). IMRT may result in improved cosmesis compared to standard RT, although at greater expense. To investigate the adoption of IMRT, we examined trends and factors associated with IMRT in women under the age of 65 with early stage breast cancer. Methods and Materials: We performed a retrospective study of early stage breast cancer patients treated with BCS followed by whole-breast irradiation (WBI) who were ≤65 years old in the National Cancer Data Base from 2004 to 2011. We used logistic regression to identify factors associated with receipt of IMRT (vs standard RT). Results: We identified 11,089 women with early breast cancer (9.6%) who were treated with IMRT and 104,448 (90.4%) who were treated with standard RT, after BCS. The proportion of WBI patients receiving IMRT increased yearly from 2004 to 2009, with 5.3% of WBI patients receiving IMRT in 2004 and 11.6% receiving IMRT in 2009. Further use of IMRT declined afterward, with the proportion remaining steady at 11.0% and 10.7% in 2010 and 2011, respectively. Patients treated in nonacademic community centers were more likely to receive IMRT (odds ratio [OR], 1.36; 95% confidence interval [CI], 1.30-1.43 for nonacademic vs academic center). Compared to privately insured patients, the uninsured patients (OR, 0.81; 95% CI, 0.70-0.95) and those with Medicaid insurance (OR, 0.87; 95% CI, 0.79-0.95) were less likely to receive IMRT. Conclusions: The use of IMRT rose from 2004 to 2009 and then stabilized. Important nonclinical factors associated with IMRT use included facility type and insurance status.

  17. Automation and Intensity Modulated Radiation Therapy for Individualized High-Quality Tangent Breast Treatment Plans

    SciTech Connect

    Purdie, Thomas G.; Dinniwell, Robert E.; Fyles, Anthony; Sharpe, Michael B.

    2014-11-01

    Purpose: To demonstrate the large-scale clinical implementation and performance of an automated treatment planning methodology for tangential breast intensity modulated radiation therapy (IMRT). Methods and Materials: Automated planning was used to prospectively plan tangential breast IMRT treatment for 1661 patients between June 2009 and November 2012. The automated planning method emulates the manual steps performed by the user during treatment planning, including anatomical segmentation, beam placement, optimization, dose calculation, and plan documentation. The user specifies clinical requirements of the plan to be generated through a user interface embedded in the planning system. The automated method uses heuristic algorithms to define and simplify the technical aspects of the treatment planning process. Results: Automated planning was used in 1661 of 1708 patients receiving tangential breast IMRT during the time interval studied. Therefore, automated planning was applicable in greater than 97% of cases. The time for treatment planning using the automated process is routinely 5 to 6 minutes on standard commercially available planning hardware. We have shown a consistent reduction in plan rejections from plan reviews through the standard quality control process or weekly quality review multidisciplinary breast rounds as we have automated the planning process for tangential breast IMRT. Clinical plan acceptance increased from 97.3% using our previous semiautomated inverse method to 98.9% using the fully automated method. Conclusions: Automation has become the routine standard method for treatment planning of tangential breast IMRT at our institution and is clinically feasible on a large scale. The method has wide clinical applicability and can add tremendous efficiency, standardization, and quality to the current treatment planning process. The use of automated methods can allow centers to more rapidly adopt IMRT and enhance access to the documented

  18. Acute Esophagus Toxicity in Lung Cancer Patients After Intensity Modulated Radiation Therapy and Concurrent Chemotherapy

    SciTech Connect

    Kwint, Margriet; Uyterlinde, Wilma; Nijkamp, Jasper; Chen, Chun; Bois, Josien de; Sonke, Jan-Jakob; Heuvel, Michel van den; Knegjens, Joost; Herk, Marcel van; Belderbos, Jose

    2012-10-01

    Purpose: The purpose of this study was to investigate the dose-effect relation between acute esophageal toxicity (AET) and the dose-volume parameters of the esophagus after intensity modulated radiation therapy (IMRT) and concurrent chemotherapy for patients with non-small cell lung cancer (NSCLC). Patients and Methods: One hundred thirty-nine patients with inoperable NSCLC treated with IMRT and concurrent chemotherapy were prospectively analyzed. The fractionation scheme was 66 Gy in 24 fractions. All patients received concurrently a daily dose of cisplatin (6 mg/m Superscript-Two ). Maximum AET was scored according to Common Toxicity Criteria 3.0. Dose-volume parameters V5 to V70, D{sub mean} and D{sub max} of the esophagus were calculated. A logistic regression analysis was performed to analyze the dose-effect relation between these parameters and grade {>=}2 and grade {>=}3 AET. The outcome was compared with the clinically used esophagus V35 prediction model for grade {>=}2 after radical 3-dimensional conformal radiation therapy (3DCRT) treatment. Results: In our patient group, 9% did not experience AET, and 31% experienced grade 1 AET, 38% grade 2 AET, and 22% grade 3 AET. The incidence of grade 2 and grade 3 AET was not different from that in patients treated with CCRT using 3DCRT. The V50 turned out to be the most significant dosimetric predictor for grade {>=}3 AET (P=.012). The derived V50 model was shown to predict grade {>=}2 AET significantly better than the clinical V35 model (P<.001). Conclusions: For NSCLC patients treated with IMRT and concurrent chemotherapy, the V50 was identified as most accurate predictor of grade {>=}3 AET. There was no difference in the incidence of grade {>=}2 AET between 3DCRT and IMRT in patients treated with concurrent chemoradiation therapy.

  19. Ototoxicity After Intensity-Modulated Radiation Therapy and Cisplatin-Based Chemotherapy in Children With Medulloblastoma

    SciTech Connect

    Paulino, Arnold C.; Lobo, Mark; Teh, Bin S.; Okcu, M. Fatih; South, Michael; Butler, E. Brian; Su, Jack; Chintagumpala, Murali

    2010-12-01

    Purpose: To report the incidence of Pediatric Oncology Group (POG) Grade 3 or 4 ototoxicity in a cohort of patients treated with craniospinal irradiation (CSI) followed by posterior fossa (PF) and/or tumor bed (TB) boost using intensity-modulated radiation therapy (IMRT). Methods and Materials: From 1998 to 2006, 44 patients with medulloblastoma were treated with CSI followed by IMRT to the PF and/or TB and cisplatin-based chemotherapy. Patients with standard-risk disease were treated with 18 to 23.4 Gy CSI followed by either a (1) PF boost to 36 Gy and TB boost to 54 to 55.8 Gy or (2) TB boost to 55.8 Gy. Patients with high-risk disease received 36 to 39.6 Gy CSI followed by a (1) PF boost to 54 to 55.8 Gy, (2) PF boost to 45 Gy and TB boost to 55.8 Gy, or (3) TB boost to 55.8 Gy. Median audiogram follow-up was 41 months (range, 11-92.4 months). Results: POG Grade Ototoxicity 0, 1, 2, 3. and 4 was found in 29, 32, 11, 13. and 3 ears. respectively, with POG Grade 3 or 4 accounting for 18.2% of cases. There was a statistically significant difference in mean radiation dose (D{sub mean}) cochlea according to degree of ototoxicity, with D{sub mean} cochlea increasing with severity of hearing loss (p = 0.027). Conclusions: Severe ototoxicity was seen in 18.2% of ears in children treated with IMRT boost and cisplatin-based chemotherapy. Increasing dose to the cochlea was associated with increasing severity of hearing loss.

  20. Prognostic Value of Prevertebral Space Involvement in Nasopharyngeal Carcinoma Based on Intensity-Modulated Radiotherapy

    SciTech Connect

    Zhou Guanqun; Mao YanPing; Chen Lei; Li Wenfei; Liu Lizhi; Sun Ying; Chen Yong; Tian Li; Lin Aihua; Li Li; and others

    2012-03-01

    Purpose: To investigate the prognostic significance of prevertebral space involvement (PSI) in patients with nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiotherapy (IMRT). Methods and Materials: A retrospective review of data from 506 biopsy-proven, nonmetastatic NPCs was performed. Patients underwent magnetic resonance imaging examinations and received IMRT as their primary treatment. Results: In this series, 161 NPC patients (31.8%) had PSI. Parapharyngeal space (p < 0.001), skull base (p < 0.001), and paranasal sinuses (p = 0.009) were associated with PSI after multivariate analysis. The 4-year overall survival (OS), local relapse-free survival (LRFS), distant metastasis-free survival (DMFS) for NPC patients with and without PSI was 69.1% and 89.2% (p < 0.0001), 83.9% and 96.4% (p < 0.0001), and 71.6% and 89.6% (p < 0.0001), respectively. Multivariate analysis identified PSI as an independent negative prognostic factor for both OS (HR = 1.478-4.380; p = 0.001) and DMFS (HR = 1.389-4.174; p = 0.002). Patients with PSI had similar survival rates in OS and DMFS (p = 0.241 and p = 0.493, respectively) to that of T4 disease, while the differences between PSI and T3 disease in both OS and DMFS were distinctly significant (p = 0.029 and p = 0.029, respectively). Conclusions: For NPC patients treated with IMRT, PSI was found to be an independent prognostic factor for both OS and DMFS. It seems reasonable that PSI should be classified as a T4 disease on the basis of the current American Joint Committee on Cancer staging classification criteria.

  1. The Effect of Intensity-Modulated Radiotherapy on Radiation-Induced Second Malignancies

    SciTech Connect

    Ruben, Jeremy D. Davis, Sidney; Evans, Cherie; Jones, Phillip; Gagliardi, Frank; Haynes, Matthew; Hunter, Alistair

    2008-04-01

    Purpose: To compare intensity-modulated radiotherapy (IMRT) with three-dimensional conformal radiotherapy (3D-CRT) in terms of carcinogenic risk for actual clinical scenarios. Method and Materials: Clinically equivalent IMRT plans were generated for prostate, breast, and head-and-neck cases treated with 3D-CRT. Two possible dose-response models for radiocarcinogenesis were generated based on A-bomb survivor data corrected for fractionation. Dose-volume histogram analysis was used to determine dose and its distribution to nontargeted tissues within the planning CT scan volume and thermoluminescent dosimetry for the rest of the body. Carcinogenic estimates were calculated with and without a correction factor accounting for cancer patients' advanced age and reduced longevity. Results: For the model assuming a plateau in risk above 2-Gy single-fraction-equivalent (SFE), IMRT and 3D-CRT produced risks of 1.7% and 2.1%, respectively, for prostate; 1.9% and 1.8%, respectively, for nasopharynx; 1% each for tonsil; and 1.4-2.2% and 1.5-1.6%, respectively, depending on technique, for breast. Assuming a reduction in risk above 2-Gy SFE, risks for IMRT and 3D-CRT were 1.1% and 1.5%, respectively, for prostate; 1.4% and 1.2%, respectively, for nasopharynx; 1% each for tonsil; and 1.3-1.8% vs. 1.3-1.6%, respectively, for breast. Applying a correction factor of 0.5 for cancer patients halved these risks and their relative differences. Conclusions: Carcinogenic risks were comparable in absolute terms between modalities. Risks are dependant on technique used. Risks with IMRT are influenced by monitor unit demand and are therefore software/hardware dependant. The dose-response model accounting for cell killing at higher doses fitted best with actual observed risks.

  2. Regional Relapse After Intensity-Modulated Radiotherapy for Head-and-Neck Cancer

    SciTech Connect

    Duprez, Frederic; Bonte, Katrien; De Neve, Wilfried; Boterberg, Tom; De Gersem, Werner; Madani, Indira

    2011-02-01

    Purpose: To evaluate the regional relapse rate in the elective neck using intensity-modulated radiotherapy (IMRT) for head-and-neck cancer. Methods and Materials: We retrospectively analyzed the data from 285 patients treated with IMRT between 2000 and 2008. The median dose prescription to the primary tumor and involved lymph nodes was 69 Gy in 32 fractions. The elective neck was treated simultaneously according to Protocol 1 (multiple dose prescription levels of 56-69 Gy; 2-Gy normalized isoeffective dose, 51-70 Gy; 222 patients) or Protocol 2 (one dose prescription level of 56 Gy; 2-Gy normalized isoeffective dose, 51 Gy; 63 patients). Primary surgery or lymph node dissection was performed before IMRT in 72 (25%) and 157 (55%) patients, respectively. Also, 92 patients (32%) received concomitant chemotherapy. The median follow-up of living patients was 27.4 months (range, 0.3-99). Results: Regional, local, and distant relapse were observed in 16 (5.6%), 35 (12.3%), and 47 (16.5%) patients, respectively. The 2- and 5-year rate of regional relapse was 7% and 10%, respectively, with a trend favoring Protocol 2 (p = 0.06). Seven isolated regional relapses were detected at a median follow-up of 7.3 months in patients treated with Protocol 1 and none in those treated with Protocol 2. Percutaneous gastrostomy was required more frequently in patients who received Protocol 1 (p = 0.079). Conclusion: Isolated regional relapse is rare after IMRT for head-and-neck cancer. Elective neck node doses >51 Gy for a 2-Gy normalized isoeffective dose do not seem to improve regional control.

  3. Radiation efficacy and biological risk from whole-breast irradiation via intensity modulated radiation therapy (IMRT)

    NASA Astrophysics Data System (ADS)

    Desantis, David M.

    Radiotherapy is an established modality for women with breast cancer. During the delivery of external beam radiation to the breast, leakage, scattered x-rays from the patient and the linear accelerator also expose healthy tissues and organs outside of the breast, thereby increasing the patient's whole-body dose, which then increases the chance of developing a secondary, radiation-induced cancer. Generally, there are three IntensityModulated Radiotherapy (IMRT) delivery techniques from a conventional linear accelerator; forward planned (FMLC), inverse planned 'sliding window' (DMLC), and inverse planned 'step-and-shoot' (SMLC). The goal of this study was to determine which of these three techniques delivers an optimal dose to the breast with the least chance of causing a fatal, secondary, radiation-induced cancer. A conventional, non-IMRT, 'Wedge' plan also was compared. Computerized Tomography (CT) data sets for both a large and small sized patient were used in this study. With Varian's Eclipse AAA algorithm, the organ doses specified in the revised ICRP 60 publication were used to calculate the whole-body dose. Also, an anthropomorphic phantom was irradiated with thermoluminescent dosimeters (TLD) at each organ site for measured doses. The risk coefficient from the Biological Effects of Ionizing Radiation (BEIR) VII report of 4.69 x 10-2 deaths per Gy was used to convert whole-body dose to risk of a fatal, secondary, radiation-induced cancer. The FMLC IMRT delivered superior tumor coverage over the 3D conventional plan and the inverse DMLC or SMLC treatment plans delivered clinically equivalent tumor coverage. However, the FMLC plan had the least likelihood of inadvertently causing a fatal, secondary, radiation-induced cancer compared to the inverse DMLC, SMLC, and Wedge plans.

  4. Gamma evaluation combined with isocenter optimal matching in intensity modulated radiation therapy quality assurance

    NASA Astrophysics Data System (ADS)

    Bak, Jino; Choi, Jin Hwa; Park, Suk Won; Park, Kwangwoo; Park, Sungho

    2015-12-01

    Two-dimensional (2D) dose comparisons are widely performed by using a gamma evaluation with patient-specific intensity modulated radiation therapy quality assurance (IMRT QA) or dose delivery quality assurance (DQA). In this way, a pass/fail determination is made for a particular treatment plan. When gamma evaluation results are close to the failure criterion, the pass/fail decision may change applying a small shift to the center of the 2D dose distribution. In this study, we quantitatively evaluated the meaning of such a small relative shift in a 2D dose distribution comparison. In addition, we propose the use of a small shift for a pass/fail criterion in gamma analysis, where the concept of isocenter optimal matching (IOM) is applied to IMRT QA of 20 patients. Gamma evaluations were performed to compare two dose distributions, one with and the other without IOM. In-house software was developed in C++ in order to find IOM values including both translational and rotational shifts. Upon gamma evaluation failure, further investigation was initiated using IOM. In this way, three groups were categorized: group 1 for `pass' on gamma evaluation, group 21 for `fail' on the gamma evaluation and `pass' on the gamma the evaluation with IOM, and group 22 for `fail' on the both gamma evaluations and the IOM calculation. IOM results revealed that some failures could be considered as a `pass'. In group 21, 88.98% (fail) of the averaged gamma pass rate changed to 90.45% (pass) when IOM was applied. On average, a ratio of γ ≥ 1 was reduced by 11.06% in 20 patients. We propose that gamma evaluations that do not pass with a rate of 85% to 90% may be augmented with IOM to reveal a potential pass result.

  5. The clinical implementation of respiratory-gated intensity-modulated radiotherapy

    SciTech Connect

    Keall, Paul . E-mail: pjkeall@vcu.edu; Vedam, Sastry; George, Rohini; Bartee, Chris; Siebers, Jeffrey; Lerma, Fritz; Weiss, Elisabeth; Chung, Theodore

    2006-07-01

    The clinical use of respiratory-gated radiotherapy and the application of intensity-modulated radiotherapy (IMRT) are 2 relatively new innovations to the treatment of lung cancer. Respiratory gating can reduce the deleterious effects of intrafraction motion, and IMRT can concurrently increase tumor dose homogeneity and reduce dose to critical structures including the lungs, spinal cord, esophagus, and heart. The aim of this work is to describe the clinical implementation of respiratory-gated IMRT for the treatment of non-small cell lung cancer. Documented clinical procedures were developed to include a tumor motion study, gated CT imaging, IMRT treatment planning, and gated IMRT delivery. Treatment planning procedures for respiratory-gated IMRT including beam arrangements and dose-volume constraints were developed. Quality assurance procedures were designed to quantify both the dosimetric and positional accuracy of respiratory-gated IMRT, including film dosimetry dose measurements and Monte Carlo dose calculations for verification and validation of individual patient treatments. Respiratory-gated IMRT is accepted by both treatment staff and patients. The dosimetric and positional quality assurance test results indicate that respiratory-gated IMRT can be delivered accurately. If carefully implemented, respiratory-gated IMRT is a practical alternative to conventional thoracic radiotherapy. For mobile tumors, respiratory-gated radiotherapy is used as the standard of care at our institution. Due to the increased workload, the choice of IMRT is taken on a case-by-case basis, with approximately half of the non-small cell lung cancer patients receiving respiratory-gated IMRT. We are currently evaluating whether superior tumor coverage and limited normal tissue dosing will lead to improvements in local control and survival in non-small cell lung cancer.

  6. Incorporation of gantry angle correction for 3D dose prediction in intensity-modulated radiation therapy.

    PubMed

    Sumida, Iori; Yamaguchi, Hajime; Kizaki, Hisao; Aboshi, Keiko; Tsujii, Mari; Yamada, Yuji; Yagi, Masashi; Ogawa, Kazuhiko

    2015-05-01

    Pretreatment dose verification with beam-by-beam analysis for intensity-modulated radiation therapy (IMRT) is commonly performed with a gantry angle of 0° using a 2D diode detector array. Any changes in multileaf collimator (MLC) position between the actual treatment gantry angle and 0° may result in deviations from the planned dose. We evaluated the effects of MLC positioning errors between the actual treatment gantry angles and nominal gantry angles. A gantry angle correction (GAC) factor was generated by performing a non-gap test at various gantry angles using an electronic portal imaging device (EPID). To convert pixel intensity to dose at the MLC abutment positions, a non-gap test was performed using an EPID and a film at 0° gantry angle. We then assessed the correlations between pixel intensities and doses. Beam-by-beam analyses for 15 prostate IMRT cases as patient-specific quality assurance were performed with a 2D diode detector array at 0° gantry angle to determine the relative dose error for each beam. The resulting relative dose error with or without GAC was added back to the original dose grid for each beam. We compared the predicted dose distributions with or without GAC for film measurements to validate GAC effects. A gamma pass rate with a tolerance of 2%/2 mm was used to evaluate these dose distributions. The gamma pass rate with GAC was higher than that without GAC (P = 0.01). The predicted dose distribution improved with GAC, although the dosimetric effect to a patient was minimal.

  7. Accelerated Whole Breast Irradiation With Intensity-Modulated Radiotherapy to the Prone Breast

    SciTech Connect

    Croog, Victoria J.; Wu, Abraham J.; McCormick, Beryl; Beal, Kathryn P.

    2009-01-01

    Purpose: Whole breast irradiation (WBI) is the standard of care for patients with early-stage breast cancer who opt for breast conservation. After a randomized trial demonstrated equivalent cosmesis and disease control with accelerated WBI (AWBI), our institution began to offer AWBI to appropriate patients. The aim of this study was to examine our unique experience with AWBI using prone positioning and simplified intensity-modulated radiotherapy (IMRT) planning with a sequential boost to the tumor bed. Methods and Materials: We identified 356 patients who had been treated with prone WBI using IMRT in our department between January 2004 and December 2006. Of these, 128 (36%) patients had received AWBI (representing 131 treated breasts), consisting of 16 daily fractions of 265 cGy to a total dose of 4,240 cGy followed by a conventionally fractionated boost. Results: Patients who opted for AWBI were similar demographically to the patients undergoing conventional WBI. In the AWBI cohort, 83% of the patients had Stage T1 disease and 22% had nodal involvement (N1). The tumors were estrogen receptor-positive, progesterone receptor-positive and Her-2/Neu-amplified in 82%, 69%, and 11%, respectively. The median duration of AWBI plus a boost was 29 days, and no patient required a toxicity-related treatment break. No Grade 3 or greater acute toxicity developed. At a median follow-up of 18 months, one ipsilateral breast recurrence developed that was salvaged with mastectomy and immediate reconstruction. Conclusion: AWBI to the prone breast using simplified IMRT with a sequential boost offers women requiring breast-only adjuvant radiotherapy an abbreviated treatment with early tumor control and cosmesis comparable to that with standard fractionation.

  8. Planning Hybrid Intensity Modulated Radiation Therapy for Whole-breast Irradiation

    SciTech Connect

    Farace, Paolo; Zucca, Sergio; Solla, Ignazio; Fadda, Giuseppina; Durzu, Silvia; Porru, Sergio; Meleddu, Gianfranco; Deidda, Maria Assunta; Possanzini, Marco; Orru, Sivia; Lay, Giancarlo

    2012-09-01

    Purpose: To test tangential and not-tangential hybrid intensity modulated radiation therapy (IMRT) for whole-breast irradiation. Methods and Materials: Seventy-eight (36 right-, 42 left-) breast patients were randomly selected. Hybrid IMRT was performed by direct aperture optimization. A semiautomated method for planning hybrid IMRT was implemented using Pinnacle scripts. A plan optimization volume (POV), defined as the portion of the planning target volume covered by the open beams, was used as the target objective during inverse planning. Treatment goals were to prescribe a minimum dose of 47.5 Gy to greater than 90% of the POV and to minimize the POV and/or normal tissue receiving a dose greater than 107%. When treatment goals were not achieved by using a 4-field technique (2 conventional open plus 2 IMRT tangents), a 6-field technique was applied, adding 2 non tangential (anterior-oblique) IMRT beams. Results: Using scripts, manual procedures were minimized (choice of optimal beam angle, setting monitor units for open tangentials, and POV definition). Treatment goals were achieved by using the 4-field technique in 61 of 78 (78%) patients. The 6-field technique was applied in the remaining 17 of 78 (22%) patients, allowing for significantly better achievement of goals, at the expense of an increase of low-dose ({approx}5 Gy) distribution in the contralateral tissue, heart, and lungs but with no significant increase of higher doses ({approx}20 Gy) in heart and lungs. The mean monitor unit contribution to IMRT beams was significantly greater (18.7% vs 9.9%) in the group of patients who required 6-field procedure. Conclusions: Because hybrid IMRT can be performed semiautomatically, it can be planned for a large number of patients with little impact on human or departmental resources, promoting it as the standard practice for whole-breast irradiation.

  9. Automated Weekly Replanning for Intensity-Modulated Radiotherapy of Cervix Cancer

    SciTech Connect

    Stewart, James

    2010-10-01

    Purpose: The adoption of intensity-modulated radiotherapy (IMRT) to treat cervical malignancies has been limited in part by complex organ and tumor motion during treatment. This study explores the limits of a highly adaptive, small-margin treatment scenario to accommodate this motion. In addition, the dosimetric consequences of organ and tumor motion are modeled using a combination of deformable registration and fractional dose accumulation techniques. Methods and Materials: Thirty-three cervix cancer patients had target volumes and organs-at-risk contoured on fused, pretreatment magnetic resonance-computed tomography images and weekly magnetic resonance scans taken during treatment. The dosimetric impact of interfraction organ and target motion was compared for two hypothetical treatment scenarios: a 3-mm margin plan with no replanning, and a 3-mm margin plan with an automated replan performed on the updated weekly patient geometry. Results: Of the 33 patients, 24 (73%) met clinically acceptable target coverage (98% of the clinical target volume receiving at least 95% of the prescription dose) using the 3-mm margin plan without replanning. The range in dose to 98% of the clinical target volume across all patients was 7.9% of the prescription dose if no replanning was performed. After weekly replanning, this range was tightened to 2.6% of the prescription dose and all patients met clinically acceptable target coverage while maintaining organ-at-risk dose sparing. Conclusions: The dosimetric impact of anatomical motion underscores the challenges of applying IMRT to treat cervix cancer. An appropriate adaptive strategy can ensure target coverage for small-margin IMRT treatments and maintain favorable organ-at-risk dose sparing.

  10. Feasibility Study of Intensity-Modulated Radiotherapy (IMRT) Treatment Planning Using Brain Functional MRI

    SciTech Connect

    Chang Jenghwa Kowalski, Alex; Hou, Bob; Narayana, Ashwatha

    2008-04-01

    The purpose of this work was to study the feasibility of incorporating functional magnetic resonance imaging (fMRI) information for intensity modulated radiotherapy (IMRT) treatment planning of brain tumors. Three glioma patients were retrospectively replanned for radiotherapy (RT) with additional fMRI information. The fMRI of each patient was acquired using a bilateral finger-tapping paradigm with a gradient echo EPI (Echo Planer Imaging) sequence. The fMRI data were processed using the Analysis of Functional Neuroimaging (AFNI) software package for determining activation volumes, and the volumes were fused with the simulation computed tomography (CT) scan. The actived pixels in left and right primary motor cortexes (PMCs) were contoured as critical structures for IMRT planning. The goal of replanning was to minimize the RT dose to the activation volumes in the PMC regions, while maintaining a similar coverage to the planning target volume (PTV) and keeping critical structures within accepted dose tolerance. Dose-volume histograms of the treatment plans with and without considering the fMRI information were compared. Beam angles adjustment or additional beams were needed for 2 cases to meet the planning criteria. Mean dose to the contralateral and ipsilateral PMC was significantly reduced by 66% and 55%, respectively, for 1 patient. For the other 2 patients, mean dose to contralateral PMC region was lowered by 73% and 69%. In general, IMRT optimization can reduce the RT dose to the PMC regions without compromising the PTV coverage or sparing of other critical organs. In conclusion, it is feasible to incorporate the fMRI information into the RT treatment planning. IMRT planning allows a significant reduction in RT dose to the PMC regions, especially if the region does not lie within the PTV.

  11. Intensity-modulated radiation therapy (IMRT) in the treatment of anal cancer: Toxicity and clinical outcome

    SciTech Connect

    Milano, Michael T.; Jani, Ashesh B.; Farrey, Karl J.; Rash, Carla C.; Heimann, Ruth; Chmura, Steven J. . E-mail: schmura@radonc.uchicago.edu

    2005-10-01

    Purpose: To assess survival, local control, and toxicity of intensity modulated radiation therapy (IMRT) in squamous cell carcinoma of the anal canal. Methods and Materials: Seventeen patients were treated with nine-field IMRT plans. Thirteen received concurrent 5-fluorouracil and mitomycin C, whereas 1 patient received 5-fluorouracil alone. Seven patients were planned with three-dimensional anteroposterior/posterior-anterior (AP/PA) fields for dosimetric comparison to IMRT. Results: Compared with AP/PA, IMRT reduced the mean and threshold doses to small bowel, bladder, and genitalia. Treatment was well tolerated, with no Grade {>=}3 acute nonhematologic toxicity. There were no treatment breaks attributable to gastrointestinal or skin toxicity. Of patients who received mitomycin C, 38% experienced Grade 4 hematologic toxicity. IMRT did not afford bone marrow sparing, possibly resulting from the clinical decision to prescribe 45 Gy to the whole pelvis in most patients, vs. the Radiation Therapy Oncology Group-recommended 30.6 Gy whole pelvic dose. Three of 17 patients, who did not achieve a complete response, proceeded to an abdominoperineal resection and colostomy. At a median follow-up of 20.3 months, there were no other local failures. Two-year overall survival, disease-free survival, and colostomy-free survival are: 91%, 65%, and 82% respectively. Conclusions: In this hypothesis-generating analysis, the acute toxicity and clinical outcome with IMRT in the treatment of anal cancer is encouraging. Compared with historical controls, local control is not compromised despite efforts to increase conformality and reduce normal structure dose.

  12. Linear Energy Transfer-Guided Optimization in Intensity Modulated Proton Therapy: Feasibility Study and Clinical Potential

    SciTech Connect

    Giantsoudi, Drosoula; Grassberger, Clemens; Craft, David; Niemierko, Andrzej; Trofimov, Alexei; Paganetti, Harald

    2013-09-01

    Purpose: To investigate the feasibility and potential clinical benefit of linear energy transfer (LET) guided plan optimization in intensity modulated proton therapy (IMPT). Methods and Materials: A multicriteria optimization (MCO) module was used to generate a series of Pareto-optimal IMPT base plans (BPs), corresponding to defined objectives, for 5 patients with head-and-neck cancer and 2 with pancreatic cancer. A Monte Carlo platform was used to calculate dose and LET distributions for each BP. A custom-designed MCO navigation module allowed the user to interpolate between BPs to produce deliverable Pareto-optimal solutions. Differences among the BPs were evaluated for each patient, based on dose–volume and LET–volume histograms and 3-dimensional distributions. An LET-based relative biological effectiveness (RBE) model was used to evaluate the potential clinical benefit when navigating the space of Pareto-optimal BPs. Results: The mean LET values for the target varied up to 30% among the BPs for the head-and-neck patients and up to 14% for the pancreatic cancer patients. Variations were more prominent in organs at risk (OARs), where mean LET values differed by a factor of up to 2 among the BPs for the same patient. An inverse relation between dose and LET distributions for the OARs was typically observed. Accounting for LET-dependent variable RBE values, a potential improvement on RBE-weighted dose of up to 40%, averaged over several structures under study, was noticed during MCO navigation. Conclusions: We present a novel strategy for optimizing proton therapy to maximize dose-averaged LET in tumor targets while simultaneously minimizing dose-averaged LET in normal tissue structures. MCO BPs show substantial LET variations, leading to potentially significant differences in RBE-weighted doses. Pareto-surface navigation, using both dose and LET distributions for guidance, provides the means for evaluating a large variety of deliverable plans and aids in

  13. Clinical response of advanced cancer patients to cellular immunotherapy and intensity-modulated radiation therapy

    PubMed Central

    Hasumi, Kenichiro; Aoki, Yukimasa; Wantanabe, Ryuko; Mann, Dean L

    2013-01-01

    Patients afflicted with advanced cancers were treated with the intratumoral injection of autologous immature dendritic cells (iDCs) followed by activated T-cell infusion and intensity-modulated radiation therapy (IMRT). A second round of iDCs and activated T cells was then administered to patients after the last radiation cycle. This complete regimen was repeated for new and recurring lesions after 6 weeks of follow-up. One year post therapy, outcome analyses were performed to evaluate treatment efficacy. Patients were grouped according to both the number and size of tumors and clinical parameters at treatment initiation, including recurrent disease after standard cancer therapy, Stage IV disease, and no prior therapy. Irrespective of prior treatment status, 23/37 patients with ≤ 5 neoplastic lesions that were ≤ 3 cm in diameter achieved complete responses (CRs), and 5/37 exhibited partial responses (PRs). Among 130 individuals harboring larger and more numerous lesions, CRs were observed in 7/74 patients that had received prior SCT and in 2/56 previously untreated patients. Some patients manifested immune responses including an increase in CD8+CD56+ lymphocytes among circulating mononuclear cells in the course of treatment. To prospectively explore the therapeutic use of these cells, CD8+ cells were isolated from patients that had been treated with cellular immunotherapy and IMRT, expanded in vitro, and injected into recurrent metastatic sites in 13 individuals who underwent the same immunoradiotherapeutic regimens but failed to respond. CRs were achieved in 34 of 58 of such recurrent lesions while PRs in 17 of 58. These data support the expanded use of immunoradiotherapy in advanced cancer patients exhibiting progressive disease. PMID:24349874

  14. Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for Column CO2 Measurements

    NASA Astrophysics Data System (ADS)

    Campbell, J. F.; Lin, B.; Nehrir, A. R.; Obland, M. D.; Liu, Z.; Browell, E. V.; Chen, S.; Kooi, S. A.; Fan, T. F.

    2015-12-01

    Global and regional atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission and Atmospheric Carbon and Transport (ACT) - America airborne investigation are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity-Modulated Continuous-Wave (IM-CW) lidar techniques are being investigated as a means of facilitating CO2 measurements from space and airborne platforms to meet the mission science measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud returns. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of intervening optically thin clouds, thereby minimizing bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the Earth's surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques and provides very high (at sub-meter level) range resolution. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These techniques are used in a new data processing architecture to support the ASCENDS CarbonHawk Experiment Simulator (ACES) and ACT-America programs.

  15. Beam angle optimization for intensity-modulated radiation therapy using a guided pattern search method

    NASA Astrophysics Data System (ADS)

    Rocha, Humberto; Dias, Joana M.; Ferreira, Brígida C.; Lopes, Maria C.

    2013-05-01

    Generally, the inverse planning of radiation therapy consists mainly of the fluence optimization. The beam angle optimization (BAO) in intensity-modulated radiation therapy (IMRT) consists of selecting appropriate radiation incidence directions and may influence the quality of the IMRT plans, both to enhance better organ sparing and to improve tumor coverage. However, in clinical practice, most of the time, beam directions continue to be manually selected by the treatment planner without objective and rigorous criteria. The goal of this paper is to introduce a novel approach that uses beam’s-eye-view dose ray tracing metrics within a pattern search method framework in the optimization of the highly non-convex BAO problem. Pattern search methods are derivative-free optimization methods that require a few function evaluations to progress and converge and have the ability to better avoid local entrapment. The pattern search method framework is composed of a search step and a poll step at each iteration. The poll step performs a local search in a mesh neighborhood and ensures the convergence to a local minimizer or stationary point. The search step provides the flexibility for a global search since it allows searches away from the neighborhood of the current iterate. Beam’s-eye-view dose metrics assign a score to each radiation beam direction and can be used within the pattern search framework furnishing a priori knowledge of the problem so that directions with larger dosimetric scores are tested first. A set of clinical cases of head-and-neck tumors treated at the Portuguese Institute of Oncology of Coimbra is used to discuss the potential of this approach in the optimization of the BAO problem.

  16. Retrospective estimate of the quality of intensity-modulated radiotherapy plans for lung cancer

    NASA Astrophysics Data System (ADS)

    Koo, Jihye; Yoon, Myonggeun; Chung, Weon Kuu; Kim, Dong Wook

    2015-07-01

    This study estimated the planning quality of intensity-modulated radiotherapy in 42 lung cancer cases to provide preliminary data for the development of a planning quality assurance algorithm. Organs in or near the thoracic cavity (ipsilateral lung, contralateral lung, heart, liver, esophagus, spinal cord, and bronchus) were selected as organs at risk (OARs). Radiotherapy plans were compared by using the conformity index (CI), coverage index (CVI), and homogeneity index (HI) of the planning target volume (PTV), the OAR-PTV distance and the OAR-PTV overlap volume, and the V10 Gy , V20 Gy , and equivalent uniform dose (EUD) of the OARs. The CI, CVI, and HI of the PTV were 0.54-0.89 (0.77 ± 0.08), 0.90-1.00 (0.98 ± 0.02), and 0.11-0.41, (0.15 ± 0.05), respectively. The mean EUDs (V10 Gy , V20 Gy ) of the ipsilateral lung, contralateral lung, esophagus, cord, liver, heart, and bronchus were 8.07 Gy (28.06, 13.17), 2.59 Gy (6.53, 1.18), 7.02 Gy (26.17, 12.32), 3.56 Gy (13.56, 4.48), 0.72 Gy (2.15, 0.91), 5.14 Gy (19.68, 8.62), and 10.56 Gy (36.08, 19.79), respectively. EUDs tended to decrease as the OAR-PTV distance increased and the OAR-PTV overlap volume decreased. Because the plans in this study were from a single department, relatively few people were involved in treatment planning. Differences in treatment results for a given patient would be much more pronounced if many departments were involved.

  17. A modular approach to intensity-modulated arc therapy optimization with noncoplanar trajectories

    NASA Astrophysics Data System (ADS)

    Papp, Dávid; Bortfeld, Thomas; Unkelbach, Jan

    2015-07-01

    Utilizing noncoplanar beam angles in volumetric modulated arc therapy (VMAT) has the potential to combine the benefits of arc therapy, such as short treatment times, with the benefits of noncoplanar intensity modulated radiotherapy (IMRT) plans, such as improved organ sparing. Recently, vendors introduced treatment machines that allow for simultaneous couch and gantry motion during beam delivery to make noncoplanar VMAT treatments possible. Our aim is to provide a reliable optimization method for noncoplanar isocentric arc therapy plan optimization. The proposed solution is modular in the sense that it can incorporate different existing beam angle selection and coplanar arc therapy optimization methods. Treatment planning is performed in three steps. First, a number of promising noncoplanar beam directions are selected using an iterative beam selection heuristic; these beams serve as anchor points of the arc therapy trajectory. In the second step, continuous gantry/couch angle trajectories are optimized using a simple combinatorial optimization model to define a beam trajectory that efficiently visits each of the anchor points. Treatment time is controlled by limiting the time the beam needs to trace the prescribed trajectory. In the third and final step, an optimal arc therapy plan is found along the prescribed beam trajectory. In principle any existing arc therapy optimization method could be incorporated into this step; for this work we use a sliding window VMAT algorithm. The approach is demonstrated using two particularly challenging cases. The first one is a lung SBRT patient whose planning goals could not be satisfied with fewer than nine noncoplanar IMRT fields when the patient was treated in the clinic. The second one is a brain tumor patient, where the target volume overlaps with the optic nerves and the chiasm and it is directly adjacent to the brainstem. Both cases illustrate that the large number of angles utilized by isocentric noncoplanar VMAT plans

  18. Dose-Dependent Pulmonary Toxicity After Postoperative Intensity-Modulated Radiotherapy for Malignant Pleural Mesothelioma

    SciTech Connect

    Rice, David C. Smythe, W. Roy; Liao Zhongxing; Guerrero, Thomas; Chang, Joe Y.; McAleer, Mary F.; Jeter, Melenda D.; Correa, Arlene Ph.D.; Vaporciyan, Ara A.; Liu, H. Helen; Komaki, Ritsuko; Forster, Kenneth M.; Stevens, Craig W.

    2007-10-01

    Purpose: To determine the incidence of fatal pulmonary events after extrapleural pneumonectomy and hemithoracic intensity-modulated radiotherapy (IMRT) for malignant pleural mesothelioma. Methods and Materials: We retrospectively reviewed the records of 63 consecutive patients with malignant pleural mesothelioma who underwent extrapleural pneumonectomy and IMRT at University of Texas M. D. Anderson Cancer Center. The endpoints studied were pulmonary-related death (PRD) and non-cancer-related death within 6 months of IMRT. Results: Of the 63 patients, 23 (37%) had died within 6 months of IMRT (10 of recurrent cancer, 6 of pulmonary causes [pneumonia in 4 and pneumonitis in 2], and 7 of other noncancer causes [pulmonary embolus in 2, sepsis after bronchopleural fistula in 1, and cause unknown but without pulmonary symptoms or recurrent disease in 4]). On univariate analysis, the factors that predicted for PRD were a lower preoperative ejection fraction (p = 0.021), absolute volume of lung spared at 10 Gy (p = 0.025), percentage of lung volume receiving {>=}20 Gy (V{sub 20}; p 0.002), and mean lung dose (p = 0.013). On multivariate analysis, only V{sub 20} was predictive of PRD (p = 0.017; odds ratio, 1.50; 95% confidence interval, 1.08-2.08) or non-cancer-related death (p = 0.033; odds ratio, 1.21; 95% confidence interval, 1.02-1.45). Conclusion: The results of our study have shown that fatal pulmonary toxicities were associated with radiation to the contralateral lung. V{sub 20} was the only independent determinant for risk of PRD or non-cancer-related death. The mean V{sub 20} of the non-PRD patients was considerably lower than that accepted during standard thoracic radiotherapy, implying that the V{sub 20} should be kept as low as possible after extrapleural pneumonectomy.

  19. Dosimetric comparison of intensity-modulated solutions for intact prostate cancer

    SciTech Connect

    Neill, Cory J.

    2014-01-01

    The purpose of this study is intended to investigate the implementation of a modified class solution for intact prostate intensity-modulated radiation therapy (IMRT). The class solution uses 2 additional optimization structures intended to increase target conformity and decrease unnecessary dose to healthy tissue. A total of 10 randomly selected intact prostate IMRT patients were chosen for this retrospective study. Each of the original IMRT plans was compared with a modified class solution. The class solution implemented 2 additional optimization structures. The 95{sub O}PT was intended to increase target conformity, and the Avoidance{sub 3}780 was intended to reduce normal tissue. Each plan was evaluated for minimum, maximum, and mean doses to the target. Additionally, mean normal tissue dose, total monitor units (MUs), and segments were investigated. Conformity index and normal healthy index were also compared. All comparisons were evaluated using a paired t-test using GraphPad software. Evaluations of MUs; segments; minimum, maximum, mean target doses; mean normal tissue dose; and conformity index did not demonstrate a significant difference between the modified class solution and the original plans. However, evaluation of healthy tissue conformity index indicated a significant difference. Overall, 70% of the original plans failed to demonstrate a satisfactory score (< 0.6) of properly sparing normal healthy tissue, whereas 70% of the modified plans exhibited a satisfactory score (> 0.6). Most (90%) of the modified plans demonstrated a greater number of segments than the compared original plan. A modified class solution provides a good starting point for planning intact prostate cancer. The addition of the Avoidance{sub 3}780 structure increases the healthy tissue conformity index score.

  20. Intensity-Modulated Radiation Therapy in the Salvage of Locally Recurrent Nasopharyngeal Carcinoma

    SciTech Connect

    Qiu Sufang; Lin Shaojun; Tham, Ivan W.K.; Pan Jianji; Lu Jun; Lu, Jiade J.

    2012-06-01

    Purpose: Local recurrences of nasopharyngeal carcinoma (NPC) may be salvaged by reirradiation with conventional techniques, but with significant morbidity. Intensity-modulated radiation therapy (IMRT) may improve the therapeutic ratio by reducing doses to normal tissue. The aim of this study was to address the efficacy and toxicity profile of IMRT for a cohort of patients with locally recurrent NPC. Methods and Materials: Between August 2003 and June 2009, 70 patients with radiologic or pathologically proven locally recurrent NPC were treated with IMRT. The median time to recurrence was 30 months after the completion of conventional radiation to definitive dose. Fifty-seven percent of the tumors were classified asrT3-4. The minimum planned doses were 59.4 to 60 Gy in 1.8- to 2-Gy fractions per day to the gross disease with margins, with or without chemotherapy. Results: The median dose to the recurrent tumor was 70 Gy (range, 50-77.4 Gy). Sixty-five patients received the planned radiation therapy; 5 patients received between 50 and 60 Gy because of acute side effects. With a median follow-up time of 25 months, the rates of 2-year locoregional recurrence-free survival, disease-free survival, and overall survival were 65.8%, 65.8%, and 67.4%, respectively. Moderate to severe late toxicities were noted in 25 patients (35.7%). Eleven patients (15.7%) had posterior nasal space ulceration, 17 (24.3%) experienced cranial nerve palsies, 12 (17.1%) had trismus, and 12 (17.1%) experienced deafness. Extended disease-free interval (relative risk 2.049) and advanced T classification (relative risk 3.895) at presentation were adverse prognostic factors. Conclusion: Reirradiation with IMRT provides reasonable long-term control in patients with locally recurrent NPC.

  1. TH-A-BRE-01: The Status of Intensity Modulated Proton and Ion Therapy

    SciTech Connect

    Dong, L; Zhu, X; Unkelbach, J; Schulte, R

    2014-06-15

    IMRT with photons has become a radiation therapy standard of care for many cancer treatment sites. The situation is quite different with intensity modulated particle (protons and ion) radiation therapy (IMPT). With the rapid development of beam scanning techniques and many of the newer proton facilities exclusively offering active beam scanning as their radiation delivery technique, it is timely to give an update on the status and challenges of IMPT. The leading principle in IMPT is to aim at the target from several, not necessarily coplanar, directions with multiple pencil beams that are modulated in their intensity and adjusted in their energy such that a desired dose distribution or, more generally, a desired bio-effective dose distribution is achieved. Different from low-LET photons, the varying relative biological effectiveness (RBE) along the beam path adds an additional dimension to the treatment planning process and will require biophysical modeling at least for carbon ion therapy. IMPT involves computationally challenging tasks, yet it needs to be very fast in order to be clinically relevant. To make IMPT computationally tractable, robust and efficient optimization methods are required. Lastly, IMPT planning is very sensitive to accurate knowledge of relative stopping and scattering powers of the intervening tissues as well as intra- and inter-fraction motion. Robust planning methods are being developed in order to obtain IMPT plans that are less sensitive against such uncertainties. This therapy symposium will present an update on the current status and emerging developments of IMPT from the medical physics perspective. Learning Objectives: Become familiar with current delivery techniques for IMPT and their limitations. Understand the basics of dose calculational algorithms and commissioning of IMPT. Learn how to assess the accuracy of planning and delivery of IMPT treatments. Get an overview of currently used and emerging optimization techniques. Learn

  2. Dosimetric effects of endorectal balloons on intensity-modulated radiation therapy plans for prostate cancer

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Sung; Chung, Jin-Beom; Kim, In-Ah; Eom, Keun-Yong

    2013-10-01

    We used an endorectal balloon (ERB) for prostate immobilization during intensity-modulated radiotherapy (IMRT) for prostate cancer treatment. To investigate the dosimetric effects of ERB-filling materials, we changed the ERB Hounsfield unit (HU) from 0 to 1000 HU in 200-HU intervals to simulate the various ERB fillings; 0 HU simulated a water-filled ERB, and 1000 HU simulated the densest material-filled ERB. Dosimetric data (coverage, homogeneity, conformity, maximal dose, and typical volume dose) for the tumor and the organs at risk (OARs) were evaluated in prostate IMRT treatment plans with 6-MV and 15-MV beams. The tumor coverage appeared to differ by approximately 1%, except for the clinical target volume (CTV) V100% and the planning target volume (PTV) V100%. The largest difference for the various ERB fillings was observed in the PTV V100%. In spite of increasing HU, the prostate IMRT plans at both energies had relatively low dosimetric effects on the PTV and the CTV. However, the maximal and the typical volume doses (D25%, D30%, and D50%) to the rectal wall and the bladder increased with increasing HU. For an air-filled ERB, the maximal doses to the rectal wall and the monitor units were lower than the corresponding values for the water-filled and the densest material-filled ERBs. An air-filled ERB spared the rectal wall because of its dosimetric effect. Thus, we conclude that the use of an air-filled ERB provides a dosimetric benefit to the rectal wall without a loss of target coverage and is an effective option for prostate IMRT treatment.

  3. Advanced intensity-modulation continuous-wave lidar techniques for ASCENDS CO2 column measurements

    NASA Astrophysics Data System (ADS)

    Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.; Harrison, F. W.; Obland, Michael D.; Meadows, Byron

    2015-10-01

    Global atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity- Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud contamination. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby eliminating the need to correct for sidelobe bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These results are extended to include Richardson-Lucy deconvolution techniques to extend the resolution of the lidar beyond that implied by limit of the bandwidth of the modulation, where it is shown useful for making tree canopy measurements.

  4. Prognostic Nomogram for Patients with Nasopharyngeal Carcinoma after Intensity-Modulated Radiotherapy

    PubMed Central

    Wu, Shixiu; Xia, Bing; Han, Fei; Xie, Ruifei; Song, Tao; Lu, Lixia; Yu, Wei; Deng, Xiaowu; He, Qiancheng; Zhao, Cong; Xie, Conghua

    2015-01-01

    This study was aimed to define possible predictors of overall survival in nasopharyngeal carcinoma (NPC). Patients were treated with intensity-modulated radiation therapy (IMRT), to establish an effective prognostic nomogram that could provide individualized predictions of treatment outcome in this setting. We reviewed the records of 533 patients with non-metastatic NPC who underwent IMRT with or without concurrent chemotherapy at the Department of Radiation Oncology of Sun Yat-Sen University from 2002 to 2009; none of these patients received induction or adjuvant chemotherapy. These data sets were used to construct a nomogram based on Cox regression. Nomogram performance was determined via a concordance index (C-index) and a calibration curve which was compared with the TNM staging system for NPC. The results were validated in an external cohort of 442 patients from the Department of Radiation Oncology of Wenzhou Medical College who were treated during the same period. Results showed that the greatest influence on survival were primary gross tumor volume, age, tumor stage and nodal stage (2002 Union for International Cancer Control [UICC] staging system), which were selected into the nomogram. The C-index of the nomogram for predicting survival was 0.748 (95%CI, 0.704–0.785), which was statistically higher than that of TNM staging system (0.684, P<0.001). The calibration curve exhibited agreement between nomogram-predicted and the actual observed probabilities for overall survival. In the validation cohort, the nomogram discrimination was superior to the TNM staging system (C-index: 0.768 vs 0.721; P = 0.026). In conclusion, the nomogram proposed in this study resulted in more-accurate prognostic prediction for patients with NPC after IMRT and compared favorably to the TNM staging system; this individualized information will aid in patient counseling and may be used for de-escalation trials in the future. PMID:26248338

  5. SU-E-T-353: Decoding the Beam Complexity in Intensity-Modulated Radiation Therapy Plans

    SciTech Connect

    Du, W; Cho, S; Zhang, X; Hoffman, K; Kudchadker, R

    2014-06-01

    Purpose: Modern IMRT relies on computers to generate treatment plans of varied complexity. A highly complex treatment plan may use a large number of small and irregular beam apertures in order to achieve high dose conformity. However, excessive beam complexity can increase dosimetric uncertainty, prolong treatment time, and increase susceptibility to target or organ motion. In this study we sought to develop metrics to assess the complexity of IMRT beams and plans. Methods: Based the information of leaf positions and MU for each beam segment, we calculated the following beam complexity metrics: aperture area, shape irregularity, and beam modulation. Then these beam complexity metrics were averaged to obtain the corresponding plan complexity metrics, using the beam MUs as weighting factors. We evaluated and compared the beam and plan complexity scores for 65 IMRT plans from 3 sites (prostate, head and neck, and spine). We also studied how the plan complexity scores were affected by adjusting inverse planning parameters. Results: For prostate IMRT, the lateral beams had large MUs and smaller shape irregularity, while the anterior or posterior beams had larger modulation values. On average, the prostate IMRT plans had the smallest shape irregularity and beam modulation; the HN IMRT plans had the largest aperture area, shape irregularity, and beam modulation; and the spine stereotactic IMRT plans often had small aperture area, which may be associated with relatively large discrepancies between calculated and measures doses. The plan complexity increased as the number of optimization iterations and the number of beam segments increased and as the minimum segment area decreased. Conclusion: Complexity of IMRT beams and plans were quantified in terms of aperture area, shape irregularity and beam modulation. The complexity metrics varied among IMRT plans for different disease sites and were affected when the planning parameters were adjusted.

  6. Patient specific quality control for Stereotactic Ablative Body Radiotherapy (SABR): it takes more than one phantom

    NASA Astrophysics Data System (ADS)

    Kron, T.; Ungureanu, E.; Antony, R.; Hardcastle, N.; Clements, N.; Ukath, J.; Fox, C.; Lonski, P.; Wanigaratne, D.; Haworth, A.

    2017-01-01

    Stereotactic Ablative Body Radiotherapy (SABR) is an extension of the concepts of Stereotactic Radiosurgery from intracranial procedures to extracranial targets. This brings with it new technological challenges for set-up of a SABR program and continuing quality assurance. Compared with intracranial procedures SABR requires consideration of motion and inhomogeneities and has to deal with a much larger variety of targets ranging from lung to liver, kidney and bone. To meet many of the challenges virtually all advances in modern radiotherapy, such as Intensity Modulated and Image Guided Radiation Therapy (IMRT and IGRT) are used. Considering the few fractions and high doses per fraction delivered to complex targets it is not surprising that patient specific quality control is considered essential for safe delivery. Given the variety of targets and clinical scenarios we employ different strategies for different patients to ensure that the most important aspects of the treatment are appropriately tested, be it steep dose gradients, inhomogeneities or the delivery of dose in the presence of motion. The current paper reviews the different approaches and phantoms utilised at Peter MacCallum Cancer Centre for SABR QA.

  7. Continuous-time method and its discretization to inverse problem of intensity-modulated radiation therapy treatment planning

    NASA Astrophysics Data System (ADS)

    Fujimoto, Ken'ichi; Tanaka, Yoshihiro; Abou Al-Ola, Omar M.; Yoshinaga, Tetsuya

    2014-06-01

    We propose a novel approach for solving box-constrained inverse problems in intensity-modulated radiation therapy (IMRT) treatment planning based on the idea of continuous dynamical methods and split-feasibility algorithms. Our method can compute a feasible solution without the second derivative of an objective function, which is required for gradient-based optimization algorithms. We prove theoretically that a double Kullback-Leibler divergence can be used as the Lyapunov function for the IMRT planning system.

  8. Electronic polarization-division demultiplexing based on digital signal processing in intensity-modulation direct-detection optical communication systems.

    PubMed

    Kikuchi, Kazuro

    2014-01-27

    We propose a novel configuration of optical receivers for intensity-modulation direct-detection (IM · DD) systems, which can cope with dual-polarization (DP) optical signals electrically. Using a Stokes analyzer and a newly-developed digital signal-processing (DSP) algorithm, we can achieve polarization tracking and demultiplexing in the digital domain after direct detection. Simulation results show that the power penalty stemming from digital polarization manipulations is negligibly small.

  9. A Dosimetric Evaluation of Conventional Helmet Field Irradiation Versus Two-Field Intensity-Modulated Radiotherapy Technique

    SciTech Connect

    Yu, James B.; Shiao, Stephen L.; Knisely, Jonathan . E-mail: jonathan.knisely@yale.edu

    2007-06-01

    Purpose: To compare dosimetric differences between conventional two-beam helmet field irradiation (external beam radiotherapy, EBRT) of the brain and a two-field intensity-modulated radiotherapy (IMRT) technique. Methods and Materials: Ten patients who received helmet field irradiation at our institution were selected for study. External beam radiotherapy portals were planned per usual practice. Intensity-modulated radiotherapy fields were created using the identical field angles as the EBRT portals. Each brain was fully contoured along with the spinal cord to the bottom of the C2 vertebral body. This volume was then expanded symmetrically by 0.5 cm to construct the planning target volume. An IMRT plan was constructed using uniform optimization constraints. For both techniques, the nominal prescribed dose was 3,000 cGy in 10 fractions of 300 cGy using 6-MV photons. Comparative dose-volume histograms were generated for each patient and analyzed. Results: Intensity-modulated radiotherapy improved dose uniformity over EBRT for whole brain radiotherapy. The mean percentage of brain receiving >105% of dose was reduced from 29.3% with EBRT to 0.03% with IMRT. The mean maximum dose was reduced from 3,378 cGy (113%) for EBRT to 3,162 cGy (105%) with IMRT. The mean percent volume receiving at least 98% of the prescribed dose was 99.5% for the conventional technique and 100% for IMRT. Conclusions: Intensity-modulated radiotherapy reduces dose inhomogeneity, particularly for the midline frontal lobe structures where hot spots occur with conventional two-field EBRT. More study needs to be done addressing the clinical implications of optimizing dose uniformity and its effect on long-term cognitive function in selected long-lived patients.

  10. Dosimetric comparison of volumetric modulated arc therapy and intensity-modulated radiation therapy for pancreatic malignancies

    SciTech Connect

    Ali, Arif N.; Dhabaan, Anees H.; Jarrio, Christie S.; Siddiqi, Arsalan K.; Landry, Jerome C.

    2012-10-01

    Volumetric-modulated arc therapy (VMAT) has been previously evaluated for several tumor sites and has been shown to provide significant dosimetric and delivery benefits when compared with intensity-modulated radiation therapy (IMRT). To date, there have been no published full reports on the benefits of VMAT use in pancreatic patients compared with IMRT. Ten patients with pancreatic malignancies treated with either IMRT or VMAT were retrospectively identified. Both a double-arc VMAT and a 7-field IMRT plan were generated for each of the 10 patients using the same defined tumor volumes, organs at risk (OAR) volumes, dose, fractionation, and optimization constraints. The planning tumor volume (PTV) maximum dose (55.8 Gy vs. 54.4 Gy), PTV mean dose (53.9 Gy vs. 52.1 Gy), and conformality index (1.11 vs. 0.99) were statistically similar between the IMRT and VMAT plans, respectively. The VMAT plans had a statistically significant reduction in monitor units compared with the IMRT plans (1109 vs. 498, p < 0.001). In addition, the doses to the liver, small bowel, and spinal cord were comparable between the IMRT and VMAT plans. However, the VMAT plans demonstrated a statistically significant reduction in the mean left kidney V{sub 25} (9.4 Gy vs. 2.3 Gy, p = 0.018), mean right kidney V{sub 15} (53.4 Gy vs. 45.9 Gy, p = 0.035), V{sub 20} (32.2 Gy vs. 25.5 Gy, p = 0.016), and V{sub 25} (21.7 Gy vs. 14.9 Gy, p = 0.001). VMAT was investigated in patients with pancreatic malignancies and compared with the current standard of IMRT. VMAT was found to have similar or improved dosimetric parameters for all endpoints considered. Specifically, VMAT provided reduced monitor units and improved bilateral kidney normal tissue dose. The clinical relevance of these benefits in the context of pancreatic cancer patients, however, is currently unclear and requires further investigation.

  11. Postoperative Intensity-Modulated Arc Therapy for Cervical and Endometrial Cancer: A Prospective Report on Toxicity

    SciTech Connect

    Vandecasteele, Katrien; Tummers, Philippe; Makar, Amin; Eijkeren, Marc van; Delrue, Louke; Denys, Hannelore; Lambert, Bieke; Beerens, Anne-Sophie; Van den Broecke, Rudy; Lambein, Kathleen; Fonteyne, Valerie; De Meerleer, Gert

    2012-10-01

    Purpose: To report on toxicity after postoperative intensity-modulated arc therapy (IMAT) for cervical (CC) and endometrial cancer (EC). Methods and Materials: Twenty-four CC and 41 EC patients were treated with postoperative IMAT. If indicated, para-aortic lymph node irradiation (preventive or when affected, PALN) and/or concomitant cisplatin (40 mg/m Superscript-Two , weekly) was administered. The prescribed dose for IMAT was 45 Gy (CC, 25 fractions) and 46 Gy (EC, 23 fractions), followed by a brachytherapeutic boost if possible. Radiation-related toxicity was assessed prospectively. The effect of concomitant cisplatin and PALN irradiation was evaluated. Results: Regarding acute toxicity (n = 65), Grade 3 and 2 acute gastrointestinal toxicity was observed in zero and 63% of patients (79% CC, 54% EC), respectively. Grade 3 and 2 acute genitourinary toxicity was observed in 1% and 18% of patients, respectively. Grade 2 (21%) and 3 (12%) hematologic toxicity (n = 41) occurred only in CC patients. Seventeen percent of CC patients and 2% of EC patients experienced Grade 2 fatigue and skin toxicity, respectively. Adding cisplatin led to an increase in Grade >2 nausea (57% vs. 9%; p = 0.01), Grade 2 nocturia (24% vs. 4%; p = 0.03), Grade {>=}2 hematologic toxicity (38% vs. nil, p = 0.003), Grade {>=}2 leukopenia (33% vs. nil, p = 0.009), and a strong trend toward more fatigue (14% vs. 2%; p = 0.05). Para-aortic lymph node irradiation led to an increase of Grade 2 nocturia (31% vs. 4%, p = 0.008) and a strong trend toward more Grade >2 nausea (44% vs. 18%; p = 0.052). Regarding late toxicity (n = 45), no Grade 3 or 4 late toxicity occurred. Grade 2 gastrointestinal toxicity, genitourinary toxicity, and fatigue occurred in 4%, 9%, and 1% of patients. Neither concomitant cisplatin nor PALN irradiation increased late toxicity rates. Conclusions: Postoperative IMAT for EC or CC is associated with low acute and late toxicity. Concomitant chemotherapy and PALN irradiation

  12. Elective Lymph Node Irradiation With Intensity-Modulated Radiotherapy: Is Conventional Dose Fractionation Necessary?

    SciTech Connect

    Bedi, Meena; Firat, Selim; Semenenko, Vladimir A.; Schultz, Christopher; Tripp, Patrick; Byhardt, Roger; Wang, Dian

    2012-05-01

    Purpose: Intensity-modulated radiation therapy (IMRT) is the standard of care for head-and-neck cancer (HNC). We treated patients with HNC by delivering either a moderate hypofractionation (MHF) schedule (66 Gy at 2.2 Gy per fraction to the gross tumor [primary and nodal]) with standard dose fractionation (54-60 Gy at 1.8-2.0 Gy per fraction) to the elective neck lymphatics or a conventional dose and fractionation (CDF) schedule (70 Gy at 2.0 Gy per fraction) to the gross tumor (primary and nodal) with reduced dose to the elective neck lymphatics. We analyzed these two cohorts for treatment outcomes. Methods and Materials: Between November 2001 and February 2009, 89 patients with primary carcinomas of the oral cavity, larynx, oropharynx, hypopharynx, and nasopharynx received definitive IMRT with or without concurrent chemotherapy. Twenty patients were treated using the MHF schedule, while 69 patients were treated with the CDF schedule. Patient characteristics and dosimetry plans were reviewed. Patterns of failure including local recurrence (LR), regional recurrence (RR), distant metastasis (DM), disease-free survival (DFS), overall survival (OS), and toxicities, including rate of feeding tube placement and percentage of weight loss, were reviewed and analyzed. Results: Median follow-up was 31.2 months. Thirty-five percent of patients in the MHF cohort and 77% of patients in the CDF cohort received chemotherapy. No RR was observed in either cohort. OS, DFS, LR, and DM rates for the entire group at 2 years were 89.3%, 81.4%, 7.1%, and 9.4%, respectively. Subgroup analysis showed no significant differences in OS (p = 0.595), DFS (p = 0.863), LR (p = 0.833), or DM (p = 0.917) between these two cohorts. Similarly, no significant differences were observed in rates of feeding tube placement and percentages of weight loss. Conclusions: Similar treatment outcomes were observed for MHF and CDF cohorts. A dose of 50 Gy at 1.43 Gy per fraction may be sufficient to electively

  13. Nasopharyngeal Carcinoma in Children: Comparison of Conventional and Intensity-Modulated Radiotherapy

    SciTech Connect

    Laskar, Siddhartha Bahl, Gaurav; Muckaden, MaryAnn; Pai, Suresh K.; Gupta, Tejpal; Banavali, Shripad; Arora, Brijesh; Sharma, Dayanand; Kurkure, Purna A.; Ramadwar, Mukta; Viswanathan, Seethalaxhmi; Rangarajan, Venkatesh; Qureshi, Sajid; Deshpande, Deepak D.; Shrivastava, Shyam K.; Dinshaw, Ketayun A.

    2008-11-01

    Purpose: To evaluate the efficacy of intensity-modulated radiotherapy (IMRT) in reducing the acute toxicities associated with conventional RT (CRT) in children with nasopharyngeal carcinoma. Patients and Methods: A total of 36 children with nonmetastatic nasopharyngeal carcinoma, treated at the Tata Memorial Hospital between June 2003 and December 2006, were included in this study. Of the 36 patients, 28 were boys and 8 were girls, with a median age of 14 years; 4 (11%) had Stage II and 10 (28%) Stage III disease at presentation. All patients had undifferentiated carcinoma and were treated with a combination of chemotherapy and RT. Of the 36 patients, 19 underwent IMRT and 17 underwent CRT. Results: After a median follow-up of 27 months, the 2-year locoregional control, disease-free, and overall survival rate was 76.5%, 60.6%, and 71.3%, respectively. A significant reduction in acute Grade 3 toxicities of the skin (p = 0.006), mucous membrane (p = 0.033), and pharynx (p = 0.035) was noted with the use of IMRT. The median time to the development of Grade 2 toxicity was delayed with IMRT (skin, 35 vs. 25 days, p = 0.016; mucous-membrane, 39 vs. 27 days, p = 0.002; and larynx, 50 vs. 28 days, p = 0.009). The duration of RT significantly influenced disease-free survival on multivariate analysis (RT duration >52 days, hazard ratio = 5.49, 95% confidence interval, 1.14-26.45, p = 0.034). The average mean dose to the first and second planning target volume was 71.8 Gy and 62.5 Gy with IMRT compared with 66.3 Gy (p = 0.001) and 64.4 Gy (p = 0.046) with CRT, respectively. Conclusion: The results of our study have shown that IMRT significantly reduces and delays the onset of acute toxicity, resulting in improved tolerance and treatment compliance for children with nasopharyngeal carcinoma. Also, IMRT provided superior target coverage and normal tissue sparing compared with CRT.

  14. Distant Metastases in Head-and-Neck Squamous Cell Carcinoma Treated With Intensity-Modulated Radiotherapy

    SciTech Connect

    Yao Min; Lu Minggen; Savvides, Panayiotis S.; Rezaee, Rod; Zender, Chad A.; Lavertu, Pierre; Buatti, John M.; Machtay, Mitchell

    2012-06-01

    Purpose: To determine the pattern and risk factors for distant metastases in head-and-neck squamous cell carcinoma (HNSCC) after curative treatment with intensity-modulated radiotherapy (IMRT). Methods and Materials: This was a retrospective study of 284 HNSCC patients treated in a single institution with IMRT. Sites included were oropharynx (125), oral cavity (70), larynx (55), hypopharynx (17), and unknown primary (17). American Joint Committee on Cancer stage distribution includes I (3), II (19), III (42), and IV (203). There were 224 males and 60 females with a median age of 57. One hundred eighty-six patients were treated with definitive IMRT and 98 postoperative IMRT. One hundred forty-nine patients also received concurrent cisplatin-based chemotherapy. Results: The median follow-up for all patients was 22.8 months (range, 0.07-77.3 months) and 29.5 months (4.23-77.3 months) for living patients. The 3-year local recurrence-free survival, regional recurrence-free survival, locoregional recurrence-free survival, distant metastasis-free survival, and overall survival were 94.6%, 96.4%, 92.5%, 84.1%, and 68.95%, respectively. There were 45 patients with distant metastasis. In multivariate analysis, distant metastasis was strongly associated with N stage (p = 0.046), T stage (p < 0.0001), and pretreatment maximum standardized uptake value of the lymph node (p = 0.006), but not associated with age, gender, disease sites, pretreatment standardized uptake value of the primary tumor, or locoregional control. The freedom from distant metastasis at 3 years was 98.1% for no factors, 88.6% for one factor, 68.3% for two factors, and 41.7% for three factors (p < 0.0001 by log-rank test). Conclusion: With advanced radiation techniques and concurrent chemotherapy, the failure pattern has changed with more patients failing distantly. The majority of patients with distant metastases had no local or regional failures, indicating that these patients might have microscopic distant

  15. Larynx-sparing techniques using intensity-modulated radiation therapy for oropharyngeal cancer

    SciTech Connect

    Bar Ad, Voichita; Lin, Haibo; Hwang, Wei-Ting; Deville, Curtiland; Dutta, Pinaki R.; Tochner, Zelig; Both, Stefan

    2012-01-01

    The purpose of the current study was to explore whether the laryngeal dose can be reduced by using 2 intensity-modulated radiation therapy (IMRT) techniques: whole-neck field IMRT technique (WF-IMRT) vs. junctioned IMRT (J-IMRT). The effect on planning target volumes (PTVs) coverage and laryngeal sparing was evaluated. WF-IMRT technique consisted of a single IMRT plan, including the primary tumor and the superior and inferior neck to the level of the clavicular heads. The larynx was defined as an organ at risk extending superiorly to cover the arytenoid cartilages and inferiorly to include the cricoid cartilage. The J-IMRT technique consisted of an IMRT plan for the primary tumor and the superior neck, matched to conventional antero-posterior opposing lower neck fields at the level of the thyroid notch. A central block was used for the anterior lower neck field at the level of the larynx to restrict the dose to the larynx. Ten oropharyngeal cancer cases were analyzed. Both the primary site and bilateral regional lymphatics were included in the radiotherapy targets. The averaged V95 for the PTV57.6 was 99.2% for the WF-IMRT technique compared with 97.4% (p = 0.02) for J-IMRT. The averaged V95 for the PTV64 was 99.9% for the WF-IMRT technique compared with 98.9% (p = 0.02) for J-IMRT and the averaged V95 for the PT70 was 100.0% for WF-IMRT technique compared with 99.5% (p = 0.04) for J-IMRT. The averaged mean laryngeal dose was 18 Gy with both techniques. The averaged mean doses within the matchline volumes were 69.3 Gy for WF-MRT and 66.2 Gy for J-IMRT (p = 0.03). The WF-IMRT technique appears to offer an optimal coverage of the target volumes and a mean dose to the larynx similar with J-IMRT and should be further evaluated in clinical trials.

  16. Larynx-sparing techniques using intensity-modulated radiation therapy for oropharyngeal cancer.

    PubMed

    Bar Ad, Voichita; Lin, Haibo; Hwang, Wei-Ting; Deville, Curtiland; Dutta, Pinaki R; Tochner, Zelig; Both, Stefan

    2012-01-01

    The purpose of the current study was to explore whether the laryngeal dose can be reduced by using 2 intensity-modulated radiation therapy (IMRT) techniques: whole-neck field IMRT technique (WF-IMRT) vs. junctioned IMRT (J-IMRT). The effect on planning target volumes (PTVs) coverage and laryngeal sparing was evaluated. WF-IMRT technique consisted of a single IMRT plan, including the primary tumor and the superior and inferior neck to the level of the clavicular heads. The larynx was defined as an organ at risk extending superiorly to cover the arytenoid cartilages and inferiorly to include the cricoid cartilage. The J-IMRT technique consisted of an IMRT plan for the primary tumor and the superior neck, matched to conventional antero-posterior opposing lower neck fields at the level of the thyroid notch. A central block was used for the anterior lower neck field at the level of the larynx to restrict the dose to the larynx. Ten oropharyngeal cancer cases were analyzed. Both the primary site and bilateral regional lymphatics were included in the radiotherapy targets. The averaged V95 for the PTV57.6 was 99.2% for the WF-IMRT technique compared with 97.4% (p = 0.02) for J-IMRT. The averaged V95 for the PTV64 was 99.9% for the WF-IMRT technique compared with 98.9% (p = 0.02) for J-IMRT and the averaged V95 for the PT70 was 100.0% for WF-IMRT technique compared with 99.5% (p = 0.04) for J-IMRT. The averaged mean laryngeal dose was 18 Gy with both techniques. The averaged mean doses within the matchline volumes were 69.3 Gy for WF-MRT and 66.2 Gy for J-IMRT (p = 0.03). The WF-IMRT technique appears to offer an optimal coverage of the target volumes and a mean dose to the larynx similar with J-IMRT and should be further evaluated in clinical trials.

  17. Experience-Based Quality Control of Clinical Intensity-Modulated Radiotherapy Planning

    SciTech Connect

    Moore, Kevin L.; Brame, R. Scott; Low, Daniel A.; Mutic, Sasa

    2011-10-01

    Purpose: To incorporate a quality control tool, according to previous planning experience and patient-specific anatomic information, into the intensity-modulated radiotherapy (IMRT) plan generation process and to determine whether the tool improved treatment plan quality. Methods and Materials: A retrospective study of 42 IMRT plans demonstrated a correlation between the fraction of organs at risk (OARs) overlapping the planning target volume and the mean dose. This yielded a model, predicted dose = prescription dose (0.2 + 0.8 [1 - exp(-3 overlapping planning target volume/volume of OAR)]), that predicted the achievable mean doses according to the planning target volume overlap/volume of OAR and the prescription dose. The model was incorporated into the planning process by way of a user-executable script that reported the predicted dose for any OAR. The script was introduced to clinicians engaged in IMRT planning and deployed thereafter. The script's effect was evaluated by tracking {delta} = (mean dose-predicted dose)/predicted dose, the fraction by which the mean dose exceeded the model. Results: All OARs under investigation (rectum and bladder in prostate cancer; parotid glands, esophagus, and larynx in head-and-neck cancer) exhibited both smaller {delta} and reduced variability after script implementation. These effects were substantial for the parotid glands, for which the previous {delta} = 0.28 {+-} 0.24 was reduced to {delta} = 0.13 {+-} 0.10. The clinical relevance was most evident in the subset of cases in which the parotid glands were potentially salvageable (predicted dose <30 Gy). Before script implementation, an average of 30.1 Gy was delivered to the salvageable cases, with an average predicted dose of 20.3 Gy. After implementation, an average of 18.7 Gy was delivered to salvageable cases, with an average predicted dose of 17.2 Gy. In the prostate cases, the rectum model excess was reduced from {delta} = 0.28 {+-} 0.20 to {delta} = 0.07 {+-} 0

  18. Effectiveness of robust optimization in intensity-modulated proton therapy planning for head and neck cancers

    SciTech Connect

    Liu Wei; Li Xiaoqiang; Park, Peter C.; Ronald Zhu, X.; Mohan, Radhe; Frank, Steven J.; Li Yupeng; Dong Lei

    2013-05-15

    Purpose: Intensity-modulated proton therapy (IMPT) is highly sensitive to uncertainties in beam range and patient setup. Conventionally, these uncertainties are dealt using geometrically expanded planning target volume (PTV). In this paper, the authors evaluated a robust optimization method that deals with the uncertainties directly during the spot weight optimization to ensure clinical target volume (CTV) coverage without using PTV. The authors compared the two methods for a population of head and neck (H and N) cancer patients. Methods: Two sets of IMPT plans were generated for 14 H and N cases, one being PTV-based conventionally optimized and the other CTV-based robustly optimized. For the PTV-based conventionally optimized plans, the uncertainties are accounted for by expanding CTV to PTV via margins and delivering the prescribed dose to PTV. For the CTV-based robustly optimized plans, spot weight optimization was guided to reduce the discrepancy in doses under extreme setup and range uncertainties directly, while delivering the prescribed dose to CTV rather than PTV. For each of these plans, the authors calculated dose distributions under various uncertainty settings. The root-mean-square dose (RMSD) for each voxel was computed and the area under the RMSD-volume histogram curves (AUC) was used to relatively compare plan robustness. Data derived from the dose volume histogram in the worst-case and nominal doses were used to evaluate the plan optimality. Then the plan evaluation metrics were averaged over the 14 cases and were compared with two-sided paired t tests. Results: CTV-based robust optimization led to more robust (i.e., smaller AUCs) plans for both targets and organs. Under the worst-case scenario and the nominal scenario, CTV-based robustly optimized plans showed better target coverage (i.e., greater D{sub 95%}), improved dose homogeneity (i.e., smaller D{sub 5%}- D{sub 95%}), and lower or equivalent dose to organs at risk. Conclusions: CTV

  19. Dosimetric investigation of breath-hold intensity-modulated radiotherapy for pancreatic cancer

    SciTech Connect

    Nakamura, Mitsuhiro; Kishimoto, Shun; Iwamura, Kohei; Shiinoki, Takehiro; Nakamura, Akira; Matsuo, Yukinori; Shibuya, Keiko; Hiraoka, Masahiro

    2012-01-15

    Purpose: To experimentally investigate the effects of variations in respiratory motion during breath-holding (BH) at end-exhalation (EE) on intensity-modulated radiotherapy (BH-IMRT) dose distribution using a motor-driven base, films, and an ionization chamber. Methods: Measurements were performed on a linear accelerator, which has a 120-leaf independently moving multileaf collimator with 5-mm leaf width at the isocenter for the 20-cm central field. Polystyrene phantoms with dimensions of 40 x 40 x 10 cm were set on a motor-driven base. All gantry angles of seven IMRT plans (a total of 35 fields) were changed to zero, and doses were then delivered to a film placed at a depth of 4 cm and an ionization chamber at a depth of 5 cm in the phantom with a dose rate of 600 MU/min under the following conditions: pulsation from the abdominal aorta and baseline drift with speeds of 0.2 mm/s (BD{sub 0.2mm/s}) and 0.4 mm/s (BD{sub 0.4mm/s}). As a reference for comparison, doses were also delivered to the chamber and film under stationary conditions. Results: In chamber measurements, means {+-} standard deviations of the dose deviations between stationary and moving conditions were -0.52% {+-} 1.03% (range: -3.41-1.05%), -0.07% {+-} 1.21% (range: -1.88-4.31%), and 0.03% {+-} 1.70% (range: -2.70-6.41%) for pulsation, BD{sub 0.2mm/s}, and BD{sub 0.4mm/s}, respectively. The {gamma} passing rate ranged from 99.5% to 100.0%, even with the criterion of 2%/1 mm for pulsation pattern. In the case of BD{sub 0.4mm/s}, the {gamma} passing rate for four of 35 fields (11.4%) did not reach 90% with a criterion of 3%/3 mm. The differences in {gamma} passing rate between BD{sub 0.2mm/s} and BD{sub 0.4mm/s} were statistically significant for each criterion. Taking {gamma} passing rates of > 90% as acceptable with a criterion of 3%/3 mm, large differences were observed in the {gamma} passing rate between the baseline drift of {<=}5 mm and that of >5 mm (minimum {gamma} passing rate: 92.0% vs 82

  20. EBT GAFCHROMIC{sup TM} film dosimetry in compensator-based intensity modulated radiation therapy

    SciTech Connect

    Vaezzadeh, Seyedali; Allahverdi, Mahmoud; Nedaie, Hasan A.; Ay, Mohammadreza; Shirazi, Alireza; Yarahmadi, Mehran

    2013-07-01

    The electron benefit transfer (EBT) GAFCHROMIC films possess a number of features making them appropriate for high-quality dosimetry in intensity-modulated radiation therapy (IMRT). Compensators to deliver IMRT are known to change the beam-energy spectrum as well as to produce scattered photons and to contaminate electrons; therefore, the accuracy and validity of EBT-film dosimetry in compensator-based IMRT should be investigated. Percentage-depth doses and lateral-beam profiles were measured using EBT films in perpendicular orientation with respect to 6 and 18 MV photon beam energies for: (1) different thicknesses of cerrobend slab (open, 1.0, 2.0, 4.0, and 6.0 cm), field sizes (5×5, 10×10, and 20×20 cm{sup 2}), and measurement depths (D{sub max}, 5.0 and 10.0 cm); and (2) step-wedged compensator in a solid phantom. To verify results, same measurements were implemented using a 0.125 cm{sup 3} ionization chamber in a water phantom and also in Monte Carlo simulations using the Monte Carlo N-particle radiation transport computer code. The mean energy of photons was increased due to beam hardening in comparison with open fields at both 6 and 18 MV energies. For a 20×20 cm{sup 2} field size of a 6 MV photon beam and a 6.0 cm thick block, the surface dose decreased by about 12% and percentage-depth doses increased up to 3% at 30.0 cm depth, due to the beam-hardening effect induced by the block. In contrast, at 18 MV, the surface dose increased by about 8% and depth dose reduced by 3% at 30.0 cm depth. The penumbral widths (80% to 20%) increase with block thickness, field size, and beam energy. The EBT film results were in good agreement with the ionization chamber dose profiles and Monte Carlo N-particle radiation transport computer code simulation behind the step-wedged compensator. Also, there was a good agreement between the EBT-film and the treatment-planning results on the anthropomorphic phantom. The EBT films can be accurately used as a 2D dosimeter for dose

  1. Salivary Gland Tumors Treated With Adjuvant Intensity-Modulated Radiotherapy With or Without Concurrent Chemotherapy

    SciTech Connect

    Schoenfeld, Jonathan D.; Sher, David J.; Norris, Charles M.; Haddad, Robert I.; Posner, Marshall R.; Balboni, Tracy A.; Tishler, Roy B.

    2012-01-01

    Purpose: To analyze the recent single-institution experience of patients with salivary gland tumors who had undergone adjuvant intensity-modulated radiotherapy (IMRT), with or without concurrent chemotherapy. Patients and Methods: We performed a retrospective analysis of 35 salivary gland carcinoma patients treated primarily at the Dana-Farber Cancer Institute between 2005 and 2010 with surgery and adjuvant IMRT. The primary endpoints were local control, progression-free survival, and overall survival. The secondary endpoints were acute and chronic toxicity. The median follow-up was 2.3 years (interquartile range, 1.2-2.8) among the surviving patients. Results: The histologic types included adenoid cystic carcinoma in 15 (43%), mucoepidermoid carcinoma in 6 (17%), adenocarcinoma in 3 (9%), acinic cell carcinoma in 3 (9%), and other in 8 (23%). The primary sites were the parotid gland in 17 (49%), submandibular glands in 6 (17%), tongue in 4 (11%), palate in 4 (11%), and other in 4 (11%). The median radiation dose was 66 Gy, and 22 patients (63%) received CRT. The most common chemotherapy regimen was carboplatin and paclitaxel (n = 14, 64%). A trend was seen for patients undergoing CRT to have more adverse prognostic factors, including Stage T3-T4 disease (CRT, n = 12, 55% vs. n = 4, 31%, p = .29), nodal positivity (CRT, n = 8, 36% vs. n = 1, 8%, p = .10), and positive margins (n = 13, 59% vs. n = 5, 38%, p = .30). One patient who had undergone CRT developed an in-field recurrence, resulting in an overall actuarial 3-year local control rate of 92%. Five patients (14%) developed distant metastases (1 who had undergone IMRT only and 4 who had undergone CRT). Acute Grade 3 mucositis, esophagitis, and dermatitis occurred in 8%, 8%, and 8% (1 each) of IMRT patients and in 18%, 5%, and 14% (4, 1, and 3 patients) of the CRT group, respectively. No acute Grade 4 toxicity occurred. The most common late toxicity was Grade 1 xerostomia (n = 8, 23%). Conclusions: Treatment of

  2. Origin of Tumor Recurrence After Intensity Modulated Radiation Therapy for Oropharyngeal Squamous Cell Carcinoma

    SciTech Connect

    Raktoe, Sawan A.S.; Dehnad, Homan; Raaijmakers, Cornelis P.J.; Braunius, Weibel; Terhaard, Chris H.J.

    2013-01-01

    Purpose: To model locoregional recurrences of oropharyngeal squamous cell carcinomas (OSCC) treated with primary intensity modulated radiation therapy (IMRT) in order to find the origins from which recurrences grow and relate their location to original target volume borders. Methods and Materials: This was a retrospective analysis of OSCC treated with primary IMRT between January 2002 and December 2009. Locoregional recurrence volumes were delineated on diagnostic scans and coregistered rigidly with treatment planning computed tomography scans. Each recurrence was analyzed with two methods. First, overlapping volumes of a recurrence and original target were measured ('volumetric approach') and assessed as 'in-field', 'marginal', or 'out-field'. Then, the center of mass (COM) of a recurrence volume was assumed as the origin from where a recurrence expanded, the COM location was compared with original target volume borders and assessed as 'in-field', 'marginal', or 'out-field'. Results: One hundred thirty-one OSCC were assessed. For all patients alive at the end of follow-up, the mean follow-up time was 40 months (range, 12-83 months); 2 patients were lost to follow-up. The locoregional recurrence rate was 27%. Of all recurrences, 51% were local, 23% were regional, and 26% had both local and regional recurrences. Of all recurrences, 74% had imaging available for assessment. Regarding volumetric analysis of local recurrences, 15% were in-field gross tumor volume (GTV), and 65% were in-field clinical tumor volume (CTV). Using the COM approach, we found that 70% of local recurrences were in-field GTV and 90% were in-field CTV. Of the regional recurrences, 25% were volumetrically in-field GTV, and using the COM approach, we found 54% were in-field GTV. The COM of local out-field CTV recurrences were maximally 16 mm outside CTV borders, whereas for regional recurrences, this was 17 mm. Conclusions: The COM model is practical and specific for recurrence assessment. Most

  3. Inverse planning for functional image-guided intensity-modulated radiation therapy

    NASA Astrophysics Data System (ADS)

    Xing, Lei; Cotrutz, Cristian; Hunjan, Sandeep; Boyer, Arthur L.; Adalsteinsson, Elfar; Spielman, Daniel

    2002-10-01

    Radiation therapy is an image-guided process whose success critically depends on the imaging modality used for treatment planning and the level of integration of the available imaging information. In this work, we establish a dose optimization framework for incorporating metabolic information from functional imaging modalities into the intensity-modulated radiation therapy (IMRT) inverse planning process and to demonstrate the technical feasibility of planning deliberately non-uniform dose distributions in accordance with functional imaging data. For this purpose, a metabolic map from functional images is discretized into a number of abnormality levels (ALs) and then fused with CT images. To escalate dose to the metabolically abnormal regions, we assume, for a given spatial point, a linear relation between the AL and the prescribed dose. But the formalism developed here is independent of the assumption and any other relation between AL and prescription is applicable. For a given AL and prescription relation, it is only necessary to prescribe the dose to the lowest AL in the target and the desired doses to other regions with higher AL values are scaled accordingly. To accomplish differential sparing of a sensitive structure when its functional importance (FI) distribution is known, we individualize the tolerance doses of the voxels within the structure according to their FI levels. An iterative inverse planning algorithm in voxel domain is used to optimize the system with inhomogeneous dose prescription. To model intra-structural trade-off, a mechanism is introduced through the use of voxel-dependent weighting factors, in addition to the conventional structure specific weighting factors which model the inter-structural trade-off. The system is used to plan a phantom case with a few hypothetical functional distributions and a brain tumour treatment with incorporation of magnetic resonance spectroscopic imaging data. The results indicated that it is technically

  4. Investigation of geometric uncertainty introduced dosimetric variation in intensity modulated proton therapy (IMPT) and its intervention

    NASA Astrophysics Data System (ADS)

    Zhang, Miao

    The intensity modulated proton therapy (IMPT) can generate plans with reduced normal tissue toxicity and increased target dose conformity. However, geometric uncertainty associated with the treatment process could introduce large dose variations between the delivered dose distribution and the planned. There are three common types of geometric uncertainty: setup uncertainty, inter-, and intra-fractional organ motion. This thesis work will investigate setup uncertainty and inter-fractional organ motion introduced dose variation and find solutions to minimize such variations. A proton treatment planning system was developed by using Geant4 Monte Carlo toolbox as the dose calculation engine. The setup uncertainty was studied on the head and neck cancer site. Plan delivery simulation shown large dose variation occurred even with small amount of setup uncertainty. Two intervention strategies were investigated: (i) different proton pencil beam sizes, and (ii) the energy margin. By varying proton pencil beam size, we found the larger the beam size the less the dose variation, nevertheless the higher normal tissue dose. The energy margin is a planning strategy incorporating the possible motion effect into the planning stage by assigning proton pencil beams an energy value large enough to guarantee protons will travel to where they are planned. The energy margin solution was tested to be effective to minimize the dose variation in the distal edge tracking (DET) based IMPT. The inter-fractional motion was studied by looking at the daily prostate shift in the prostate cancer treatment. Delivery simulation for prostate cancer IMPT shown large dose variation would result even if the image guidance (IG) technique was used to realign the prostate back to its original location on the planning CT. A novel on-line adaptive image guided IMPT (A-IG-IMPT) technique was proposed to minimize the dose variation. By updating the energy value for individual proton pencil beam from the on

  5. Introducing an on-line adaptive procedure for prostate image guided intensity modulate proton therapy.

    PubMed

    Zhang, M; Westerly, D C; Mackie, T R

    2011-08-07

    With on-line image guidance (IG), prostate shifts relative to the bony anatomy can be corrected by realigning the patient with respect to the treatment fields. In image guided intensity modulated proton therapy (IG-IMPT), because the proton range is more sensitive to the material it travels through, the realignment may introduce large dose variations. This effect is studied in this work and an on-line adaptive procedure is proposed to restore the planned dose to the target. A 2D anthropomorphic phantom was constructed from a real prostate patient's CT image. Two-field laterally opposing spot 3D-modulation and 24-field full arc distal edge tracking (DET) plans were generated with a prescription of 70 Gy to the planning target volume. For the simulated delivery, we considered two types of procedures: the non-adaptive procedure and the on-line adaptive procedure. In the non-adaptive procedure, only patient realignment to match the prostate location in the planning CT was performed. In the on-line adaptive procedure, on top of the patient realignment, the kinetic energy for each individual proton pencil beam was re-determined from the on-line CT image acquired after the realignment and subsequently used for delivery. Dose distributions were re-calculated for individual fractions for different plans and different delivery procedures. The results show, without adaptive, that both the 3D-modulation and the DET plans experienced delivered dose degradation by having large cold or hot spots in the prostate. The DET plan had worse dose degradation than the 3D-modulation plan. The adaptive procedure effectively restored the planned dose distribution in the DET plan, with delivered prostate D(98%), D(50%) and D(2%) values less than 1% from the prescription. In the 3D-modulation plan, in certain cases the adaptive procedure was not effective to reduce the delivered dose degradation and yield similar results as the non-adaptive procedure. In conclusion, based on this 2D phantom

  6. Dose-Volume Comparison of Proton Therapy and Intensity-Modulated Radiotherapy for Prostate Cancer

    SciTech Connect

    Vargas, Carlos Fryer, Amber; Mahajan, Chaitali; Indelicato, Daniel; Horne, David C.; Chellini, Angela; McKenzie, Craig C.; Lawlor, Paula C.; Henderson, Randal; Li Zuofeng; Lin Liyong; Olivier, Kenneth; Keole, Sameer

    2008-03-01

    Purpose: The contrast in dose distribution between proton radiotherapy (RT) and intensity-modulated RT (IMRT) is unclear, particularly in regard to critical structures such as the rectum and bladder. Methods and Materials: Between August and November 2006, the first 10 consecutive patients treated in our Phase II low-risk prostate proton protocol (University of Florida Proton Therapy Institute protocol 0001) were reviewed. The double-scatter proton beam plans used in treatment were analyzed for various dosimetric endpoints. For all plans, each beam dose distribution, angle, smearing, and aperture margin were optimized. IMRT plans were created for all patients and simultaneously analyzed. The IMRT plans were optimized through multiple volume objectives, beam weighting, and individual leaf movement. The patients were treated to 78 Gray-equivalents (GE) in 2-GE fractions with a biologically equivalent dose of 1.1. Results: All rectal and rectal wall volumes treated to 10-80 GE (percentage of volume receiving 10-80 GE [V{sub 10}-V{sub 80}]) were significantly lower with proton therapy (p < 0.05). The rectal V{sub 50} was reduced from 31.3% {+-} 4.1% with IMRT to 14.6% {+-} 3.0% with proton therapy for a relative improvement of 53.4% and an absolute benefit of 16.7% (p < 0.001). The mean rectal dose decreased 59% with proton therapy (p < 0.001). For the bladder and bladder wall, proton therapy produced significantly smaller volumes treated to doses of 10-35 GE (p < 0.05) with a nonsignificant advantage demonstrated for the volume receiving {<=}60 GE. The bladder V{sub 30} was reduced with proton therapy for a relative improvement of 35.3% and an absolute benefit of 15.1% (p = 0.02). The mean bladder dose decreased 35% with proton therapy (p = 0.002). Conclusion: Compared with IMRT, proton therapy reduced the dose to the dose-limiting normal structures while maintaining excellent planning target volume coverage.

  7. The importance of prostate bed tilt during postprostatectomy intensity-modulated radiotherapy

    SciTech Connect

    Bell, Linda J.; Cox, Jennifer; Eade, Thomas; Rinks, Marianne; Kneebone, Andrew

    2014-10-01

    Variations in rectal and bladder filling can create a tilt of the prostate bed, which generates the potential for a geographic miss during postprostatectomy radiotherapy. The aim of this study is to assess the effect that bladder and rectum filling has on planning target volume angle, to determine a method to assess prostate bed tilt leading to potential geographic miss, and to discuss possible implementation issues. The cone-beam computed tomography images (n = 377) of 40 patients who received postprostatectomy radiotherapy with intensity-modulated radiotherapy were reviewed. The amount of tilt in the prostate bed was defined as the angle change between 2 surgical clips, one in the upper prostate bed and another in the lower. A potential geographic miss was defined as movement of any clip of more than 1 cm in any direction or 0.5 cm posteriorly when aligned to bone anatomy. Variations in bladder and rectum size were correlated with the degree of prostate bed tilt, and the rate of potential geographic miss was determined. A possible clinical use of prostate bed tilt was then assessed for different imaging techniques. A tilt of more than 10° was seen in 20.2% of images, which resulted in a 57.9% geographic miss rate of the superior clip. When tilt remained within 10°, there was only a 9% rate of geographic miss. Potential geographic miss of the inferior surgical clip was rare, occurring in only 1.9% of all images reviewed. The most common occurrence when the prostate bed tilt increased by more than 10° was a smaller bladder and larger rectum (6.4% of all images). The most common occurrence when the prostate bed tilt decreased by more than 10° was a larger bladder and smaller rectum (1.3% of all images). Significant prostate bed tilt (>± 10°) occurred in more than 20% of images, creating a 58% rate of geographic miss. Greatest prostate bed tilt occurred when the bladder size increased or reduced by more than 2 cm or the superior rectum size increased by more

  8. Improving intensity-modulated radiation therapy using the anatomic beam orientation optimization algorithm

    SciTech Connect

    Potrebko, Peter S.; McCurdy, Boyd M. C.; Butler, James B.; El-Gubtan, Adel S.

    2008-05-15

    A novel, anatomic beam orientation optimization (A-BOO) algorithm is proposed to significantly improve conventional intensity-modulated radiation therapy (IMRT). The A-BOO algorithm vectorially analyses polygonal surface mesh data of contoured patient anatomy. Five optimal (5-opt) deliverable beam orientations are selected based on (1) tangential orientation bisecting the target and adjacent organ's-at-risk (OARs) to produce precipitous dose gradients between them and (2) parallel incidence with polygon features of the target volume to facilitate conformal coverage. The 5-opt plans were compared to standard five, seven, and nine equiangular-spaced beam plans (5-equi, 7-equi, 9-equi) for: (1) gastric, (2) Radiation Therapy Oncology Group (RTOG) P-0126 prostate, and (3) RTOG H-0022 oropharyngeal (stage-III, IV) cancer patients. In the gastric case, the noncoplanar 5-opt plan reduced the right kidney V 20 Gy by 32.2%, 23.2%, and 20.6% compared to plans with five, seven, and nine equiangular-spaced beams. In the prostate case, the coplanar 5-opt plan produced similar rectal sparing as the 7-equi and 9-equi plans with a reduction of the V 75, V 70, V 65, and V 60 Gy of 2.4%, 5.3%, 7.0%, and 9.5% compared to the 5-equi plan. In the stage-III and IV oropharyngeal cases, the noncoplanar 5-opt plan substantially reduced the V 30 Gy and mean dose to the contralateral parotid compared to plans with five, seven, and nine equiangular-spaced beams: (stage-III) 7.1%, 5.2%, 6.8%, and 5.1, 3.5, 3.7 Gy and (stage-IV) 10.2%, 10.2%, 9.8% and 7.0, 7.1, 7.2 Gy. The geometry-based A-BOO algorithm has been demonstrated to be robust for application to a variety of IMRT treatment sites. Beam orientations producing significant improvements in OAR sparing over conventional IMRT can be automatically produced in minutes compared to hours with existing dose-based beam orientation optimization methods.

  9. Intensity-Modulated vs. Conformal Radiotherapy of Parotid Gland Tumors: Potential Impact on Hearing Loss

    SciTech Connect

    Lamers-Kuijper, E. Schwarz, M.; Rasch, C.; Mijnheer, B.

    2007-01-01

    In 3-dimensional (3D) conformal radiotherapy of parotid gland tumors, little effort is made to avoid the auditory system or the oral cavity. Damage may occur when the ear is located inside the treatment field. The purpose of this study was to design and evaluate an intensity-modulation radiotherapy (IMRT) class solution, and to compare this technique to a 3D conformal approach with respect to hearing loss. Twenty patients with parotid gland cancer were retrospectively planned with 2 different techniques using the original planning target volume (PTV). First, a conventional technique using a wedged beam pair was applied, yielding a dose distribution conformal to the shape of the PTV. Next, an IMRT technique using a fluence map optimization with predefined constraints was designed. A dose of 66 Gy in the PTV was given at the International Commission on Radiation Units and Measures (ICRU) dose prescription point. Dose-volume histograms of the PTV and organs at risk (OARs), such as auditory system, oral cavity, and spinal cord, were compared. The dose in the OARs was lower in the IMRT plans. The mean volume of the middle ear receiving a dose higher than 50 Gy decreased from 66.5% to 33.4%. The mean dose in the oral cavity decreased from 19.4 Gy to 16.6 Gy. The auditory system can be spared if the distance between the inner ear and the PTV is 0.6 cm or larger, and if the overlap between the middle ear and the PTV is smaller than 10%. The maximum dose in the spinal cord was below 40 Gy in all treatment plans. The mean volume of the PTV receiving less than 95% of the prescribed dose increased in the IMRT plan slightly from 3.3% to 4.3 % (p = 0.01). The mean volume receiving more than 107% increased from 0.9% to 2.5% (p = 0.02). It can be concluded that the auditory system, as well as the oral cavity, can be spared with IMRT, but at the cost of a slightly larger dose inhomogeneity in the PTV. The IMRT technique can therefore, in most cases, be recommended as the treatment

  10. Verification of intensity modulated radiation therapy beams using a tissue equivalent plastic scintillator dosimetry system

    NASA Astrophysics Data System (ADS)

    Petric, Martin Peter

    This thesis describes the development and implementation of a novel method for the dosimetric verification of intensity modulated radiation therapy (IMRT) fields with several advantages over current techniques. Through the use of a tissue equivalent plastic scintillator sheet viewed by a charge-coupled device (CCD) camera, this method provides a truly tissue equivalent dosimetry system capable of efficiently and accurately performing field-by-field verification of IMRT plans. This work was motivated by an initial study comparing two IMRT treatment planning systems. The clinical functionality of BrainLAB's BrainSCAN and Varian's Helios IMRT treatment planning systems were compared in terms of implementation and commissioning, dose optimization, and plan assessment. Implementation and commissioning revealed differences in the beam data required to characterize the beam prior to use with the BrainSCAN system requiring higher resolution data compared to Helios. This difference was found to impact on the ability of the systems to accurately calculate dose for highly modulated fields, with BrainSCAN being more successful than Helios. The dose optimization and plan assessment comparisons revealed that while both systems use considerably different optimization algorithms and user-control interfaces, they are both capable of producing substantially equivalent dose plans. The extensive use of dosimetric verification techniques in the IMRT treatment planning comparison study motivated the development and implementation of a novel IMRT dosimetric verification system. The system consists of a water-filled phantom with a tissue equivalent plastic scintillator sheet built into the top surface. Scintillation light is reflected by a plastic mirror within the phantom towards a viewing window where it is captured using a CCD camera. Optical photon spread is removed using a micro-louvre optical collimator and by deconvolving a glare kernel from the raw images. Characterization of this

  11. Intensity Modulated Proton Beam Radiation for Brachytherapy in Patients With Cervical Carcinoma

    SciTech Connect

    Clivio, Alessandro; Kluge, Anne; Cozzi, Luca; Köhler, Christhardt; Neumann, Oliver; Vanetti, Eugenio; Wlodarczyk, Waldemar; Marnitz, Simone

    2013-12-01

    Purpose: To evaluate intensity modulated proton therapy (IMPT) in patients with cervical cancer in terms of coverage, conformity, and dose–volume histogram (DVH) parameters correlated with recommendations from magnetic resonance imaging (MRI)-guided brachytherapy. Methods and Materials: Eleven patients with histologically proven cervical cancer underwent primary chemoradiation for the pelvic lymph nodes, the uterus, the cervix, and the parametric region, with a symmetric margin of 1 cm. The prescription was for 50.4 Gy, with 1.8 Gy per fraction. The prescribed dose to the parametria was 2.12 Gy up to 59.36 Gy in 28 fractions as a simultaneous boost. For several reasons, the patients were unable to undergo brachytherapy. As an alternative, IMPT was planned with 5 fractions of 6 Gy to the cervix, including the macroscopic tumor with an MRI-guided target definition, with an isotropic margin of 5 mm for planning target volume (PTV) definition. Groupe-Europeen de Curietherapie and European society for Radiotherapy and Oncology (GEC-ESTRO) criteria were used for DVH evaluation. Reference comparison plans were optimized for volumetric modulated rapid arc (VMAT) therapy with the RapidArc (RA). Results: The dose to the high-risk volume was calculated with α/β = 10 with 89.6 Gy. For IMPT, the clinical target volume showed a mean dose of 38.2 ± 5.0 Gy (35.0 ±1.8 Gy for RA). The D{sub 98%} was 31.9 ± 2.6 Gy (RA: 30.8 ± 1.0 Gy). With regard to the organs at risk, the 2Gy Equivalent Dose (EQD2) (α/β = 3) to 2 cm{sup 3} of the rectal wall, sigmoid wall, and bladder wall was 62.2 ± 6.4 Gy, 57.8 ± 6.1 Gy, and 80.6 ± 8.7 Gy (for RA: 75.3 ± 6.1 Gy, 66.9 ± 6.9 Gy, and 89.0 ± 7.2 Gy, respectively). For the IMPT boost plans in combination with external beam radiation therapy, all DVH parameters correlated with <5% risk for grades 2 to 4 late gastrointestinal and genitourinary toxicity. Conclusion: In patients who are not eligible for brachytherapy, IMPT as a boost

  12. Disease Control After Reduced Volume Conformal and Intensity Modulated Radiation Therapy for Childhood Craniopharyngioma

    SciTech Connect

    Merchant, Thomas E.; Kun, Larry E.; Hua, Chia-Ho; Wu, Shengjie; Xiong, Xiaoping; Sanford, Robert A.; Boop, Frederick A.

    2013-03-15

    Purpose: To estimate the rate of disease control after conformal radiation therapy using reduced clinical target volume (CTV) margins and to determine factors that predict for tumor progression. Methods and Materials: Eighty-eight children (median age, 8.5 years; range, 3.2-17.6 years) received conformal or intensity modulated radiation therapy between 1998 and 2009. The study group included those prospectively treated from 1998 to 2003, using a 10-mm CTV, defined as the margin surrounding the solid and cystic tumor targeted to receive the prescription dose of 54 Gy. The CTV margin was subsequently reduced after 2003, yielding 2 groups of patients: those treated with a CTV margin greater than 5 mm (n=26) and those treated with a CTV margin less than or equal to 5 mm (n=62). Disease progression was estimated on the basis of additional variables including sex, race, extent of resection, tumor interventions, target volume margins, and frequency of weekly surveillance magnetic resonance (MR) imaging during radiation therapy. Median follow-up was 5 years. Results: There was no difference between progression-free survival rates based on CTV margins (>5 mm vs ≤5 mm) at 5 years (88.1% ± 6.3% vs 96.2% ± 4.4% [P=.6386]). There were no differences based on planning target volume (PTV) margins (or combined CTV plus PTV margins). The PTV was systematically reduced from 5 to 3 mm during the time period of the study. Factors predictive of superior progression-free survival included Caucasian race (P=.0175), no requirement for cerebrospinal fluid shunting (P=.0066), and number of surveillance imaging studies during treatment (P=.0216). Patients whose treatment protocol included a higher number of weekly surveillance MR imaging evaluations had a lower rate of tumor progression. Conclusions: These results suggest that targeted volume reductions for radiation therapy using smaller margins are feasible and safe but require careful monitoring. We are currently investigating

  13. Intrafractional 3D localization using kilovoltage digital tomosynthesis for sliding-window intensity modulated radiation therapy

    PubMed Central

    Zhang, Pengpeng; Hunt, Margie; Pham, Hai; Tang, Grace; Mageras, Gig

    2016-01-01

    Purpose To implement novel imaging sequences integrated into intensity modulated radiation therapy (IMRT) and determine 3D positions for intrafractional patient motion monitoring and management. Method In one method, we converted a static gantry IMRT beam into a series of arcs in which dose index and multileaf collimator positions for all control points were unchanged, but gantry angles were modified to oscillate ±3° around the original angle. Kilovoltage (kV) projections were acquired continuously throughout delivery and reconstructed to provide a series of 6° arc digital tomosynthesis (DTS) images which served to evaluate the in-plane positions of embedded-fiducials/vertebral-body. To obtain out-of-plane positions via triangulation, a 20° gantry rotation with beam hold-off was inserted during delivery to produce a pair of 6° DTS images separated by 14°. In a second method, the gantry remained stationary, but both kV source and detector moved over a 15° longitudinal arc using pitch and translational adjustment of the robotic arms. Evaluation of localization accuracy in an anthropomorphic Rando phantom during simulated intrafractional motion used programmed couch translations from customized scripts. Purpose-built software was used to reconstruct DTS images, register them to reference template images and calculate 3D fiducial positions. Result No significant dose difference (<0.5%) was found between the original and converted IMRT beams. For a typical hypofractionated spine treatment, 200 single DTS (6° arc) and 10 paired DTS (20° arc) images were acquired for each IMRT beam, providing in-plane and out-of-plane monitoring every 1.6 and 34.5 seconds, respectively. Mean ± standard deviation error in predicted position was −0.3±0.2 mm, −0.1±0.1 mm in-plane, and 0.2±0.4 mm out-of-plane with rotational gantry, 0.8±0.1 mm, −0.7±0.3 mm in-plane and 1.1±0.1 mm out-of-plane with translational source/detector. Conclusion Acquiring 3D fiducial positions

  14. Postoperative Intensity Modulated Radiation Therapy in High Risk Prostate Cancer: A Dosimetric Comparison

    SciTech Connect

    Digesu, Cinzia; Cilla, Savino; De Gaetano, Andrea; Massaccesi, Mariangela; Macchia, Gabriella; Ippolito, Edy; Deodato, Francesco; Panunzi, Simona; Iapalucci, Chiara; Mattiucci, Gian Carlo; D'Angelo, Elisa; Padula, Gilbert D.A.; Valentini, Vincenzo; Cellini, Numa

    2011-10-01

    The aim of this study was to compare intensity-modulated radiation therapy (IMRT) with 3D conformal technique (3D-CRT), with respect to target coverage and irradiation of organs at risk for high dose postoperative radiotherapy (PORT) of the prostate fossa. 3D-CRT and IMRT treatment plans were compared with respect to dose to the rectum and bladder. The dosimetric comparison was carried out in 15 patients considering 2 different scenarios: (1) exclusive prostate fossa irradiation, and (2) pelvic node irradiation followed by a boost on the prostate fossa. In scenario (1), a 3D-CRT plan (box technique) and an IMRT plan were calculated and compared for each patient. In scenario (2), 3 treatment plans were calculated and compared for each patient: (a) 3D-CRT box technique for both pelvic (prophylactic nodal irradiation) and prostate fossa irradiation (3D-CRT only); (b) 3D-CRT box technique for pelvic irradiation followed by an IMRT boost to the prostatic fossa (hybrid 3D-CRT and IMRT); and (c) IMRT for both pelvic and prostate fossa irradiation (IMRT only). For exclusive prostate fossa irradiation, IMRT significantly reduced the dose to the rectum (lower Dmean, V50%, V75%, V90%, V100%, EUD, and NTCP) and the bladder (lower Dmean, V50%, V90%, EUD and NTCP). When prophylactic irradiation of the pelvis was also considered, plan C (IMRT only) performed better than plan B (hybrid 3D-CRT and IMRT) as respect to both rectum and bladder irradiation (reduction of Dmean, V50%, V75%, V90%, equivalent uniform dose [EUD], and normal tissue complication probability [NTCP]). Plan (b) (hybrid 3D-CRT and IMRT) performed better than plan (a) (3D-CRT only) with respect to dose to the rectum (lower Dmean, V75%, V90%, V100%, EUD, and NTCP) and the bladder (Dmean, EUD, and NTCP). Postoperative IMRT in prostate cancer significantly reduces rectum and bladder irradiation compared with 3D-CRT.

  15. Factors influencing the incidence of sinusitis in nasopharyngeal carcinoma patients after intensity-modulated radiation therapy.

    PubMed

    Su, Yan-xia; Liu, Lan-ping; Li, Lei; Li, Xu; Cao, Xiu-juan; Dong, Wei; Yang, Xin-hua; Xu, Jin; Yu, Shui; Hao, Jun-fang

    2014-12-01

    The aim of the study was to investigate the incidence of sinusitis in nasopharyngeal carcinoma (NPC) patients before and after intensity-modulated radiation therapy (IMRT) and to analyze factors associated with the incidence of sinusitis following IMRT. We retrospectively analyzed 283 NPC patients who received IMRT in our hospital from March 2009 to May 2011. The diagnostic criteria for sinusitis are based on computed tomography (CT) or magnetic resonance imaging (MRI) findings. CT or MRI scans were performed before and after IMRT to evaluate the incidence of sinusitis. Factors influencing the incidence of sinusitis were analyzed by log-rank univariate and logistic multivariate analyses. Among the 283 NPC patients, 128 (45.2 %) suffered from sinusitis before radiotherapy. The incidence rates of sinusitis in patients with T1, T2, T3, and T4 NPC before radiotherapy were 22.6, 37.5, 46.8, and 61.3 %, respectively (χ 2 = 14.548, p = 0.002). Among the 155 NPC patients without sinusitis before radiotherapy, the incidence rates of sinusitis at the end of radiotherapy and at 1, 3, 6, 9, 12, and 18 months after radiotherapy were 32.9, 43.2, 61.3, 68.4, 73.5, 69.7, and 61.3 %, respectively (χ 2 = 86.461, p < 0.001). Univariate analysis showed that T stage, invasion of the nasal cavity, nasal irrigation, and radiation dose to the nasopharynx were associated with the incidence of sinusitis in NPC patients after IMRT (p = 0.003, 0.006, 0.002, and 0.020). Multivariate analysis showed that T stage, invasion of the nasal cavity, and nasal irrigation were influential factors for the incidence of sinusitis in NPC patients after IMRT (p = 0.002, 0.002, and 0.000). There was a higher incidence of sinusitis with higher T stage among NPC patients before radiotherapy, and the incidence of sinusitis in NPC patients after IMRT was high (45.2 %). The incidence of sinusitis increased rapidly within the first 3 months after IMRT, and the number of sinusitis cases peaked at 6-9 months after

  16. Treatment of Oral Cavity Squamous Cell Carcinoma With Adjuvant or Definitive Intensity-Modulated Radiation Therapy

    SciTech Connect

    Sher, David J.; Thotakura, Vijaya; Balboni, Tracy A.; Norris, Charles M.; Haddad, Robert I.; Posner, Marshall R.; Lorch, Jochen; Goguen, Laura A.; Annino, Donald J.; Tishler, Roy B.

    2011-11-15

    Purpose: The optimal management of oral cavity squamous cell carcinoma (OCSCC) typically involves surgical resection followed by adjuvant radiotherapy or chemoradiotherapy (CRT) in the setting of adverse pathologic features. Intensity-modulated radiation therapy (IMRT) is frequently used to treat oral cavity cancers, but published IMRT outcomes specific to this disease site are sparse. We report the Dana-Farber Cancer Institute experience with IMRT-based treatment for OCSCC. Methods and Materials: Retrospective study of all patients treated at Dana-Farber Cancer Institute for OCSCC with adjuvant or definitive IMRT between August 2004 and December 2009. The American Joint Committee on Cancer disease stage criteria distribution of this cohort included 5 patients (12%) with stage I; 10 patients (24%) with stage II (n = 10, 24%),; 14 patients (33%) with stage III (n = 14, 33%),; and 13 patients (31%) with stage IV. The primary endpoint was overall survival (OS); secondary endpoints were locoregional control (LRC) and acute and chronic toxicity. Results: Forty-two patients with OCSCC were included, 30 of whom were initially treated with surgical resection. Twenty-three (77%) of 30 surgical patients treated with adjuvant IMRT also received concurrent chemotherapy, and 9 of 12 (75%) patients treated definitively without surgery were treated with CRT or induction chemotherapy and CRT. With a median follow-up of 2.1 years (interquartile range, 1.1-3.1 years) for all patients, the 2-year actuarial rates of OS and LRC following adjuvant IMRT were 85% and 91%, respectively, and the comparable results for definitive IMRT were 63% and 64% for OS and LRC, respectively. Only 1 patient developed symptomatic osteoradionecrosis, and among patients without evidence of disease, 35% experienced grade 2 to 3 late dysphagia, with only 1 patient who was continuously gastrostomy-dependent. Conclusions: In this single-institution series, postoperative IMRT was associated with promising LRC

  17. Leaf-sequencing for intensity-modulated arc therapy using graph algorithms

    SciTech Connect

    Luan Shuang; Wang Chao; Cao Daliang; Chen, Danny Z.; Shepard, David M.; Yu, Cedric X.

    2008-01-15

    Intensity-modulated arc therapy (IMAT) is a rotational IMRT technique. It uses a set of overlapping or nonoverlapping arcs to create a prescribed dose distribution. Despite its numerous advantages, IMAT has not gained widespread clinical applications. This is mainly due to the lack of an effective IMAT leaf-sequencing algorithm that can convert the optimized intensity patterns for all beam directions into IMAT treatment arcs. To address this problem, we have developed an IMAT leaf-sequencing algorithm and software using graph algorithms in computer science. The input to our leaf-sequencing software includes (1) a set of (continuous) intensity patterns optimized by a treatment planning system at a sequence of equally spaced beam angles (typically 10 deg. apart), (2) a maximum leaf motion constraint, and (3) the number of desired arcs, k. The output is a set of treatment arcs that best approximates the set of optimized intensity patterns at all beam angles with guaranteed smooth delivery without violating the maximum leaf motion constraint. The new algorithm consists of the following key steps. First, the optimized intensity patterns are segmented into intensity profiles that are aligned with individual MLC leaf pairs. Then each intensity profile is segmented into k MLC leaf openings using a k-link shortest path algorithm. The leaf openings for all beam angles are subsequently connected together to form 1D IMAT arcs under the maximum leaf motion constraint using a shortest path algorithm. Finally, the 1D IMAT arcs are combined to form IMAT treatment arcs of MLC apertures. The performance of the implemented leaf-sequencing software has been tested for four treatment sites (prostate, breast, head and neck, and lung). In all cases, our leaf-sequencing algorithm produces efficient and highly conformal IMAT plans that rival their counterpart, the tomotherapy plans, and significantly improve the IMRT plans. Algorithm execution times ranging from a few seconds to 2 min are

  18. Influence of robust optimization in intensity-modulated proton therapy with different dose delivery techniques

    SciTech Connect

    Liu Wei; Li Yupeng; Li Xiaoqiang; Cao Wenhua; Zhang Xiaodong

    2012-06-15

    Purpose: The distal edge tracking (DET) technique in intensity-modulated proton therapy (IMPT) allows for high energy efficiency, fast and simple delivery, and simple inverse treatment planning; however, it is highly sensitive to uncertainties. In this study, the authors explored the application of DET in IMPT (IMPT-DET) and conducted robust optimization of IMPT-DET to see if the planning technique's sensitivity to uncertainties was reduced. They also compared conventional and robust optimization of IMPT-DET with three-dimensional IMPT (IMPT-3D) to gain understanding about how plan robustness is achieved. Methods: They compared the robustness of IMPT-DET and IMPT-3D plans to uncertainties by analyzing plans created for a typical prostate cancer case and a base of skull (BOS) cancer case (using data for patients who had undergone proton therapy at our institution). Spots with the highest and second highest energy layers were chosen so that the Bragg peak would be at the distal edge of the targets in IMPT-DET using 36 equally spaced angle beams; in IMPT-3D, 3 beams with angles chosen by a beam angle optimization algorithm were planned. Dose contributions for a number of range and setup uncertainties were calculated, and a worst-case robust optimization was performed. A robust quantification technique was used to evaluate the plans' sensitivity to uncertainties. Results: With no uncertainties considered, the DET is less robust to uncertainties than is the 3D method but offers better normal tissue protection. With robust optimization to account for range and setup uncertainties, robust optimization can improve the robustness of IMPT plans to uncertainties; however, our findings show the extent of improvement varies. Conclusions: IMPT's sensitivity to uncertainties can be improved by using robust optimization. They found two possible mechanisms that made improvements possible: (1) a localized single-field uniform dose distribution (LSFUD) mechanism, in which the

  19. Multifield Optimization Intensity Modulated Proton Therapy for Head and Neck Tumors: A Translation to Practice

    SciTech Connect

    Frank, Steven J.; Cox, James D.; Gillin, Michael; Mohan, Radhe; Garden, Adam S.; Rosenthal, David I.; Gunn, G. Brandon; Weber, Randal S.; Kies, Merrill S.; Lewin, Jan S.; Munsell, Mark F.; Palmer, Matthew B.; Sahoo, Narayan; Zhang, Xiaodong; Liu, Wei; Zhu, X. Ronald

    2014-07-15

    Background: We report the first clinical experience and toxicity of multifield optimization (MFO) intensity modulated proton therapy (IMPT) for patients with head and neck tumors. Methods and Materials: Fifteen consecutive patients with head and neck cancer underwent MFO-IMPT with active scanning beam proton therapy. Patients with squamous cell carcinoma (SCC) had comprehensive treatment extending from the base of the skull to the clavicle. The doses for chemoradiation therapy and radiation therapy alone were 70 Gy and 66 Gy, respectively. The robustness of each treatment plan was also analyzed to evaluate sensitivity to uncertainties associated with variations in patient setup and the effect of uncertainties with proton beam range in patients. Proton beam energies during treatment ranged from 72.5 to 221.8 MeV. Spot sizes varied depending on the beam energy and depth of the target, and the scanning nozzle delivered the spot scanning treatment “spot by spot” and “layer by layer.” Results: Ten patients presented with SCC and 5 with adenoid cystic carcinoma. All 15 patients were able to complete treatment with MFO-IMPT, with no need for treatment breaks and no hospitalizations. There were no treatment-related deaths, and with a median follow-up time of 28 months (range, 20-35 months), the overall clinical complete response rate was 93.3% (95% confidence interval, 68.1%-99.8%). Xerostomia occurred in all 15 patients as follows: grade 1 in 10 patients, grade 2 in 4 patients, and grade 3 in 1 patient. Mucositis within the planning target volumes was seen during the treatment of all patients: grade 1 in 1 patient, grade 2 in 8 patients, and grade 3 in 6 patients. No patient experienced grade 2 or higher anterior oral mucositis. Conclusions: To our knowledge, this is the first clinical report of MFO-IMPT for head and neck tumors. Early clinical outcomes are encouraging and warrant further investigation of proton therapy in prospective clinical trials.

  20. Hypofractionated intensity modulated radiotherapy with temozolomide in newly diagnosed glioblastoma multiforme.

    PubMed

    Ammirati, Mario; Chotai, Silky; Newton, Herbert; Lamki, Tariq; Wei, Lai; Grecula, John

    2014-04-01

    We conducted a phase I study to determine (a) the maximum tolerated dose of peri-radiation therapy temozolomide (TMZ) and (b) the safety of a selected hypofractionated intensity modulated radiation therapy (HIMRT) regimen in glioblastoma multiforme (GBM) patients. Patients with histological diagnosis of GBM, Karnofsky performance status (KPS)≥ 60 and adequate bone marrow function were eligible for the study. All patients received peri-radiation TMZ; 1 week before the beginning of radiation therapy (RT), 1 week after RT and for 3 weeks during RT. Standard 75 mg/m(2)/day dose was administered to all patients 1 week post-RT. Dose escalation was commenced at level I: 50mg/m(2)/day, level II: 65 mg/m(2)/day and level III: 75 mg/m(2)/day for 4 weeks. HIMRT was delivered at 52.5 Gy in 15 fractions to the contrast enhancing lesion (or surgical cavity) plus the surrounding edema plus a 2 cm margin. Six men and three women with a median age of 67 years (range, 44-81) and a median KPS of 80 (range, 80-90) were enrolled. Three patients were accrued at each TMZ dose level. Median follow-up was 10 months (range, 1-15). Median progression free survival was 3.9 months (95% confidence interval [CI]: 0.9-7.4; range, 0.9-9.9 months) and the overall survival 12.7 months (95% CI: 2.5-17.6; range, 2.5-20.7 months). Time spent in a KPS ≥ 70 was 8.1 months (95% CI: 2.4-15.6; range, 2.4-16 months). No instance of irreversible grade 3 or higher acute toxicity was noted. HIMRT at 52.5 Gy in 15 fractions with peri-RT TMZ at a maximum tolerated dose of 75 mg/m(2)/day for 5 weeks is well tolerated and is able to abate treatment time for these patients.

  1. A GPU-accelerated and Monte Carlo-based intensity modulated proton therapy optimization system

    SciTech Connect

    Ma, Jiasen Beltran, Chris; Seum Wan Chan Tseung, Hok; Herman, Michael G.

    2014-12-15

    Purpose: Conventional spot scanning intensity modulated proton therapy (IMPT) treatment planning systems (TPSs) optimize proton spot weights based on analytical dose calculations. These analytical dose calculations have been shown to have severe limitations in heterogeneous materials. Monte Carlo (MC) methods do not have these limitations; however, MC-based systems have been of limited clinical use due to the large number of beam spots in IMPT and the extremely long calculation time of traditional MC techniques. In this work, the authors present a clinically applicable IMPT TPS that utilizes a very fast MC calculation. Methods: An in-house graphics processing unit (GPU)-based MC dose calculation engine was employed to generate the dose influence map for each proton spot. With the MC generated influence map, a modified least-squares optimization method was used to achieve the desired dose volume histograms (DVHs). The intrinsic CT image resolution was adopted for voxelization in simulation and optimization to preserve spatial resolution. The optimizations were computed on a multi-GPU framework to mitigate the memory limitation issues for the large dose influence maps that resulted from maintaining the intrinsic CT resolution. The effects of tail cutoff and starting condition were studied and minimized in this work. Results: For relatively large and complex three-field head and neck cases, i.e., >100 000 spots with a target volume of ∼1000 cm{sup 3} and multiple surrounding critical structures, the optimization together with the initial MC dose influence map calculation was done in a clinically viable time frame (less than 30 min) on a GPU cluster consisting of 24 Nvidia GeForce GTX Titan cards. The in-house MC TPS plans were comparable to a commercial TPS plans based on DVH comparisons. Conclusions: A MC-based treatment planning system was developed. The treatment planning can be performed in a clinically viable time frame on a hardware system costing around 45

  2. Whole Abdominopelvic Intensity-Modulated Radiation Therapy for Desmoplastic Small Round Cell Tumor After Surgery

    SciTech Connect

    Pinnix, Chelsea C.; Fontanilla, Hiral P.; Hayes-Jordan, Andrea; Subbiah, Vivek; Bilton, Stephen D.; Chang, Eric L.; Grosshans, David R.; McAleer, Mary F.; Sulman, Eric P.; Woo, Shiao Y.; Anderson, Peter; Green, Holly L.; Mahajan, Anita

    2012-05-01

    Purpose: Desmoplastic small round cell tumor (DSCRT) is an uncommon pediatric tumor with a poor prognosis. Aggressive multimodality therapy is the current treatment approach; however. treatment toxicity is of concern. We report our results with whole abdominopelvic intensity-modulated radiation therapy (WAP-IMRT) as a component of multimodality therapy for DSCRT at a single institution. Materials/Methods: Medical records of all patients with DSCRT who received WAP-IMRT as part of definitive treatment at MD Anderson (2006-2010) were identified and reviewed. Results: Eight patients with DSRCT received WAP-IMRT with a median follow-up of 15.2 months. All patients received multiple courses of chemotherapy followed by surgical debulking of intra-abdominal disease; seven also had intraoperative hyperthermic cisplatin. WAP-IMRT was delivered to a total dose of 30 Gy postoperatively; four patients received a simultaneous boost (6-10 Gy) to sites of gross residual disease. Seven patients received concurrent chemotherapy during WAP-IMRT. No Radiation Therapy Oncology Group Grade 4 nausea, vomiting, or diarrhea occurred during RT. Red-cell transfusions were given to two patients to maintain hemoglobin levels >10 g/dL. Grade 4 cytopenia requiring growth factor support occurred in only one patient; no other significant cytopenias were noted. WAP-IMRT resulted in 25% lower radiation doses to the lumbosacral vertebral bodies and pelvic bones than conventional RT plans. The median time to local or distant failure after WAP-IMRT was 8.73 months in seven patients. One patient who had completed RT 20 months before the last follow-up remains alive without evidence of disease. Five patients (63%) experienced treatment failure in the abdomen. Distant failure occurred in three patients (37.5%). Conclusions: WAP-IMRT with concurrent radiosensitizing chemotherapy was well tolerated after aggressive surgery for DSCRT. Enhanced bone sparing with IMRT probably accounts for the low hematologic

  3. Temporary organ displacement coupled with image-guided, intensity-modulated radiotherapy for paraspinal tumors

    PubMed Central

    2013-01-01

    Background To investigate the feasibility and dosimetric improvements of a novel technique to temporarily displace critical structures in the pelvis and abdomen from tumor during high-dose radiotherapy. Methods Between 2010 and 2012, 11 patients received high-dose image-guided intensity-modulated radiotherapy with temporary organ displacement (TOD) at our institution. In all cases, imaging revealed tumor abutting critical structures. An all-purpose drainage catheter was introduced between the gross tumor volume (GTV) and critical organs at risk (OAR) and infused with normal saline (NS) containing 5-10% iohexol. Radiation planning was performed with the displaced OARs and positional reproducibility was confirmed with cone-beam CT (CBCT). Patients were treated within 36 hours of catheter placement. Radiation plans were re-optimized using pre-TOD OARs to the same prescription and dosimetrically compared with post-TOD plans. A two-tailed permutation test was performed on each dosimetric measure. Results The bowel/rectum was displaced in six patients and kidney in four patients. One patient was excluded due to poor visualization of the OAR; thus 10 patients were analyzed. A mean of 229 ml (range, 80–1000) of NS 5-10% iohexol infusion resulted in OAR mean displacement of 17.5 mm (range, 7–32). The median dose prescribed was 2400 cGy in one fraction (range, 2100–3000 in 3 fractions). The mean GTV Dmin and PTV Dmin pre- and post-bowel TOD IG-IMRT dosimetry significantly increased from 1473 cGy to 2086 cGy (p=0.015) and 714 cGy to 1214 cGy (p=0.021), respectively. TOD increased mean PTV D95 by 27.14% of prescription (p=0.014) while the PTV D05 decreased by 9.2% (p=0.011). TOD of the bowel resulted in a 39% decrease in mean bowel Dmax (p=0.008) confirmed by CBCT. TOD of the kidney significantly decreased mean kidney dose and Dmax by 25% (0.022). Conclusions TOD was well tolerated, reproducible, and facilitated dose escalation to previously radioresistant tumors

  4. Intrafractional 3D localization using kilovoltage digital tomosynthesis for sliding-window intensity modulated radiation therapy.

    PubMed

    Zhang, Pengpeng; Hunt, Margie; Pham, Hai; Tang, Grace; Mageras, Gig

    2015-09-07

    To implement novel imaging sequences integrated into intensity modulated radiation therapy (IMRT) and determine 3D positions for intrafractional patient motion monitoring and management.In one method, we converted a static gantry IMRT beam into a series of arcs in which dose index and multileaf collimator positions for all control points were unchanged, but gantry angles were modified to oscillate ± 3° around the original angle. Kilovoltage (kV) projections were acquired continuously throughout delivery and reconstructed to provide a series of 6° arc digital tomosynthesis (DTS) images which served to evaluate the in-plane positions of embedded-fiducials/vertebral-body. To obtain out-of-plane positions via triangulation, a 20° gantry rotation with beam hold-off was inserted during delivery to produce a pair of 6° DTS images separated by 14°. In a second method, the gantry remained stationary, but both kV source and detector moved over a 15° longitudinal arc using pitch and translational adjustment of the robotic arms. Evaluation of localization accuracy in an anthropomorphic Rando phantom during simulated intrafractional motion used programmed couch translations from customized scripts. Purpose-built software was used to reconstruct DTS images, register them to reference template images and calculate 3D fiducial positions.No significant dose difference (<0.5%) was found between the original and converted IMRT beams. For a typical hypofractionated spine treatment, 200 single DTS (6° arc) and 10 paired DTS (20° arc) images were acquired for each IMRT beam, providing in-plane and out-of-plane monitoring every 1.6 and 34.5 s, respectively. Mean ± standard deviation error in predicted position was -0.3 ± 0.2 mm, -0.1 ± 0.1 mm in-plane, and 0.2 ± 0.4 mm out-of-plane with rotational gantry, 0.8 ± 0.1 mm, -0.7 ± 0.3 mm in-plane and 1.1 ± 0.1 mm out-of-plane with translational source/detector.Acquiring 3D fiducial positions from kV-DTS during fixed gantry

  5. Bile Acid Malabsorption After Pelvic and Prostate Intensity Modulated Radiation Therapy: An Uncommon but Treatable Condition

    SciTech Connect

    Harris, Victoria; Benton, Barbara; Sohaib, Aslam; Dearnaley, David; Andreyev, H. Jervoise N.

    2012-12-01

    Purpose: Intensity modulated radiation therapy (IMRT) is a significant therapeutic advance in prostate cancer, allowing increased tumor dose delivery and increased sparing of normal tissues. IMRT planning uses strict dose constraints to nearby organs to limit toxicity. Bile acid malabsorption (BAM) is a treatable disorder of the terminal ileum (TI) that presents with symptoms similar to radiation therapy toxicity. It has not been described in patients receiving RT for prostate cancer in the contemporary era. We describe new-onset BAM in men after IMRT for prostate cancer. Methods and Materials: Diagnosis of new-onset BAM was established after typical symptoms developed, selenium-75 homocholic acid taurine (SeHCAT) scanning showed 7-day retention of <15%, and patients' symptoms unequivocally responded to a bile acid sequestrant. The TI was identified on the original radiation therapy plan, and the radiation dose delivered was calculated and compared with accepted dose-volume constraints. Results: Five of 423 men treated in a prospective series of high-dose prostate and pelvic IMRT were identified with new onset BAM (median age, 65 years old). All reported having normal bowel habits before RT. The volume of TI ranged from 26-141 cc. The radiation dose received by the TI varied between 11.4 Gy and 62.1 Gy (uncorrected). Three of 5 patients had TI treated in excess of 45 Gy (equivalent dose calculated in 2-Gy fractions, using an {alpha}/{beta} ratio of 3) with volumes ranging from 1.6 cc-49.0 cc. One patient had mild BAM (SeHCAT retention, 10%-15%), 2 had moderate BAM (SeHCAT retention, 5%-10%), and 2 had severe BAM (SeHCAT retention, <5%). The 3 patients whose TI received {>=}45 Gy developed moderate to severe BAM, whereas those whose TI received <45 Gy had only mild to moderate BAM. Conclusions: Radiation delivered to the TI during IMRT may cause BAM. Identification of the TI from unenhanced RT planning computed tomography scans is difficult and may impede accurate

  6. A new Monte Carlo-based treatment plan optimization approach for intensity modulated radiation therapy.

    PubMed

    Li, Yongbao; Tian, Zhen; Shi, Feng; Song, Ting; Wu, Zhaoxia; Liu, Yaqiang; Jiang, Steve; Jia, Xun

    2015-04-07

    Intensity-modulated radiation treatment (IMRT) plan optimization needs beamlet dose distributions. Pencil-beam or superposition/convolution type algorithms are typically used because of their high computational speed. However, inaccurate beamlet dose distributions may mislead the optimization process and hinder the resulting plan quality. To solve this problem, the Monte Carlo (MC) simulation method has been used to compute all beamlet doses prior to the optimization step. The conventional approach samples the same number of particles from each beamlet. Yet this is not the optimal use of MC in this problem. In fact, there are beamlets that have very small intensities after solving the plan optimization problem. For those beamlets, it may be possible to use fewer particles in dose calculations to increase efficiency. Based on this idea, we have developed a new MC-based IMRT plan optimization framework that iteratively performs MC dose calculation and plan optimization. At each dose calculation step, the particle numbers for beamlets were adjusted based on the beamlet intensities obtained through solving the plan optimization problem in the last iteration step. We modified a GPU-based MC dose engine to allow simultaneous computations of a large number of beamlet doses. To test the accuracy of our modified dose engine, we compared the dose from a broad beam and the summed beamlet doses in this beam in an inhomogeneous phantom. Agreement within 1% for the maximum difference and 0.55% for the average difference was observed. We then validated the proposed MC-based optimization schemes in one lung IMRT case. It was found that the conventional scheme required 10(6) particles from each beamlet to achieve an optimization result that was 3% difference in fluence map and 1% difference in dose from the ground truth. In contrast, the proposed scheme achieved the same level of accuracy with on average 1.2 × 10(5) particles per beamlet. Correspondingly, the computation

  7. Evaluation of a fast method of EPID-based dosimetry for intensity modulated radiation therapy

    PubMed Central

    Nelms, Benjamin E.; Rasmussen, Karl H.; Tomé, Wolfgang A.

    2010-01-01

    Electronic portal imaging devices (EPIDs) could potentially be useful for Intensity Modulated Radiation Therapy (IMRT) QA. The data density, high resolution, large active area, and efficiency of the MV EPID make it an attractive option. However, EPIDs were designed to be effective imaging devices, but not dosimeters, and as a result they do not measure dose in tissue-equivalent materials. EPIDose (Sun Nuclear, Melbourne, FL) is a tool designed for the use of EPIDs in IMRT QA that uses raw MV EPID images (no additional build-up and independent of gantry angle, but with dark and flood field corrections applied) to estimate absolute dose planes normal to the beam axis in a homogeneous media, i.e. similar to conventional IMRT QA methods. However, because of the inherent challenges of the EPID-based dosimetry, validating and commissioning such a system must be done very carefully, exploring the range of use cases and using well-proven “standards” for comparison. In this work, a multi-institutional study was performed to verify accurate EPID image to dose plane conversion over a variety of conditions. Converted EPID images were compared to 2D diode array absolute dose measurements for one hundred and eighty eight (188) fields from twenty eight (28) clinical IMRT treatment plans generated using a number of commercially available treatment planning systems (TPS) covering various treatment sites including prostate, head and neck, brain, and lung. The data included three beam energies (6, 10, and 15 MV) and both step-and-shoot and dynamic MLC fields. Out of 26,207 points of comparison over 188 fields analyzed the average overall field pass rate was 99.7% when 3mm/3% DTA criteria were used (range 94.0-100 per field). The pass rates for more stringent criteria were 97.8% for 2mm/2% DTA (range 82.0-100 per field), and 84.6% for 1mm/1% DTA (range 54.7-100 per field). Individual patient specific sites as well as different beam energies followed similar trends to the overall

  8. Including robustness in multi-criteria optimization for intensity-modulated proton therapy

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Unkelbach, Jan; Trofimov, Alexei; Madden, Thomas; Kooy, Hanne; Bortfeld, Thomas; Craft, David

    2012-02-01

    We present a method to include robustness in a multi-criteria optimization (MCO) framework for intensity-modulated proton therapy (IMPT). The approach allows one to simultaneously explore the trade-off between different objectives as well as the trade-off between robustness and nominal plan quality. In MCO, a database of plans each emphasizing different treatment planning objectives, is pre-computed to approximate the Pareto surface. An IMPT treatment plan that strikes the best balance between the different objectives can be selected by navigating on the Pareto surface. In our approach, robustness is integrated into MCO by adding robustified objectives and constraints to the MCO problem. Uncertainties (or errors) of the robust problem are modeled by pre-calculated dose-influence matrices for a nominal scenario and a number of pre-defined error scenarios (shifted patient positions, proton beam undershoot and overshoot). Objectives and constraints can be defined for the nominal scenario, thus characterizing nominal plan quality. A robustified objective represents the worst objective function value that can be realized for any of the error scenarios and thus provides a measure of plan robustness. The optimization method is based on a linear projection solver and is capable of handling large problem sizes resulting from a fine dose grid resolution, many scenarios, and a large number of proton pencil beams. A base-of-skull case is used to demonstrate the robust optimization method. It is demonstrated that the robust optimization method reduces the sensitivity of the treatment plan to setup and range errors to a degree that is not achieved by a safety margin approach. A chordoma case is analyzed in more detail to demonstrate the involved trade-offs between target underdose and brainstem sparing as well as robustness and nominal plan quality. The latter illustrates the advantage of MCO in the context of robust planning. For all cases examined, the robust optimization for

  9. In vivo verification of superficial dose for head and neck treatments using intensity-modulated techniques

    SciTech Connect

    Qi Zhenyu; Deng Xiaowu; Huang Shaomin; Zhang Li; He Zhichun; Allen Li, X.; Kwan, Ian; Lerch, Michael; Cutajar, Dean; Metcalfe, Peter; Rosenfeld, Anatoly

    2009-01-15

    Skin dose is one of the key issues for clinical dosimetry in radiation therapy. Currently planning computer systems are unable to accurately predict dose in the buildup region, leaving ambiguity as to the dose levels actually received by the patient's skin during radiotherapy. This is one of the prime reasons why in vivo measurements are necessary to estimate the dose in the buildup region. A newly developed metal-oxide-semiconductor-field-effect-transistor (MOSFET) detector designed specifically for dose measurements in rapidly changing dose gradients was introduced for accurate in vivo skin dosimetry. The feasibility of this detector for skin dose measurements was verified in comparison with plane parallel ionization chamber and radiochromic films. The accuracy of a commercial treatment planning system (TPS) in skin dose calculations for intensity-modulated radiation therapy treatment of nasopharyngeal carcinoma was evaluated using MOSFET detectors in an anthropomorphic phantom as well as on the patients. Results show that this newly developed MOSFET detector can provide a minimal but highly reproducible intrinsic buildup of 7 mg cm{sup -2} corresponding to the requirements of personal surface dose equivalent Hp (0.07). The reproducibility of the MOSFET response, in high sensitivity mode, is found to be better than 2% at the phantom surface for the doses normally delivered to the patients. The MOSFET detector agrees well with the Attix chamber and the EBT Gafchromic registered film in terms of surface and buildup region dose measurements, even for oblique incident beams. While the dose difference between MOSFET measurements and TPS calculations is within measurement uncertainty for the depths equal to or greater than 0.5 cm, an overestimation of up to 8.5% was found for the surface dose calculations in the anthropomorphic phantom study. In vivo skin dose measurements reveal that the dose difference between the MOSFET results and the TPS calculations was on

  10. Particle swarm optimizer for weighting factor selection in intensity-modulated radiation therapy optimization algorithms.

    PubMed

    Yang, Jie; Zhang, Pengcheng; Zhang, Liyuan; Shu, Huazhong; Li, Baosheng; Gui, Zhiguo

    2017-01-01

    In inverse treatment planning of intensity-modulated radiation therapy (IMRT), the objective function is typically the sum of the weighted sub-scores, where the weights indicate the importance of the sub-scores. To obtain a high-quality treatment plan, the planner manually adjusts the objective weights using a trial-and-error procedure until an acceptable plan is reached. In this work, a new particle swarm optimization (PSO) method which can adjust the weighting factors automatically was investigated to overcome the requirement of manual adjustment, thereby reducing the workload of the human planner and contributing to the development of a fully automated planning process. The proposed optimization method consists of three steps. (i) First, a swarm of weighting factors (i.e., particles) is initialized randomly in the search space, where each particle corresponds to a global objective function. (ii) Then, a plan optimization solver is employed to obtain the optimal solution for each particle, and the values of the evaluation functions used to determine the particle's location and the population global location for the PSO are calculated based on these results. (iii) Next, the weighting factors are updated based on the particle's location and the population global location. Step (ii) is performed alternately with step (iii) until the termination condition is reached. In this method, the evaluation function is a combination of several key points on the dose volume histograms. Furthermore, a perturbation strategy - the crossover and mutation operator hybrid approach - is employed to enhance the population diversity, and two arguments are applied to the evaluation function to improve the flexibility of the algorithm. In this study, the proposed method was used to develop IMRT treatment plans involving five unequally spaced 6MV photon beams for 10 prostate cancer cases. The proposed optimization algorithm yielded high-quality plans for all of the cases, without human

  11. Optimal beam design on intensity-modulated radiation therapy with simultaneous integrated boost in nasopharyngeal cancer

    SciTech Connect

    Cheng, Mei-Chun; Hu, Yu-Wen; Liu, Ching-Sheng; Lee, Jeun-Shenn; Huang, Pin-I; Yen, Sang-Hue; Lee, Yuh-Lin; Hsieh, Chun-Mei; Shiau, Cheng-Ying

    2014-10-01

    This study aims to determine the optimal beam design among various combinations of field numbers and beam trajectories for intensity-modulated radiation therapy (IMRT) with simultaneous integrated boost (SIB) technique for the treatment of nasopharyngeal cancer (NPC). We used 10 fields with gantry angles of 155°, 130°, 75°, 25°, 0° L, 0° R, 335°, 285°, 230°, and 205° denoted as F10. To decrease doses in the spinal cord, the F10 technique was designed by featuring 2 pairs of split-opposed beam fields at 155° to 335° and 205° to 25°, as well as one pair of manually split beam fields at 0°. The F10 technique was compared with 4 other common field arrangements: F7E, 7 fields with 50° equally spaced gantry angles; F7, the basis of F10 with 155°, 130°, 75°, 0°, 285°, 230°, and 205°; F9E, 9 fields with 40° equally spaced gantry angles; and FP, 7 posterior fields with 180°, 150°, 120°, 90°, 270°, 240°, and 210°. For each individual case of 10 patients, the customized constraints derived after optimization with the standard F10 technique were applied to 4 other field arrangements. The 4 new optimized plans of each individual case were normalized to achieve the same coverage of planning target volume (PTV){sub 63} {sub Gy} as that of the standard F10 technique. The F10 field arrangement exhibited the best coverage in PTV{sub 70} {sub Gy} and the least mean dose in the trachea-esophagus region. Furthermore, the F10 field arrangement demonstrated the highest level of conformity in the low-dose region and the least monitor unit. The F10 field arrangement performed more outstandingly than the other field arrangements in PTV{sub 70} {sub Gy} coverage and spared the central organ. This arrangement also exhibited the highest conformity and delivery efficiency. The F10 technique is recommended as the standard beam geometry for the SIB-IMRT of NPC.

  12. A feedback constraint optimization method for intensity-modulated radiation therapy of nasopharyngeal carcinoma

    PubMed Central

    LI, YONGWU; SUN, XIAONAN; WANG, QI; ZHOU, QINXUAN; GU, BENXING; SHI, GUOZHI; JIANG, DONGLIANG

    2015-01-01

    Intensity-modulated radiation therapy (IMRT) is able to achieve good target conformance with a limited dose to organs at risk (OARs); however, IMRT increases the irradiation volume and monitor units (MUs) required. The present study aimed to evaluate the use of an IMRT plan with fewer segments and MUs, while maintaining quality in the treatment of nasopharyngeal carcinoma. In the present study, two types of IMRT plan were therefore compared: The direct machine parameter optimization (DMPO)-RT method and the feedback constraint DMPO-RT (fc_DMPO-RT) method, which utilizes compensative feedback constraint in DMPO-RT and maintains optimization. Plans for 23 patients were developed with identical dose prescriptions. Each plan involved synchronous delivery to various targets, with identical OAR constraints, by means of 7 coplanar fields. The average dose, maximum dose, dose-volume histograms of targets and the OAR, MUs of the plan, the number of segments, delivery time and accuracy were subsequently compared. The fc_DMPO-RT exhibited superior dose distribution in terms of the average, maximum and minimum doses to the gross tumor volume compared with that of DMPO-RT (t=62.7, 20.5 and 22.0, respectively; P<0.05). The fc_DMPO-RT also resulted in a smaller maximum dose to the spinal cord (t=7.3; P<0.05), as well as fewer MUs, fewer segments and decreased treatment times than that of the DMPO-RT (t=6.2, 393.4 and 244.3, respectively; P<0.05). The fc_DMPO-RT maintained plan quality with fewer segments and MUs, and the treatment time was significantly reduced, thereby resulting in reduced radiation leakage and an enhanced curative effect. Therefore, introducing feedback constraint into DMPO may result in improved IMRT planning. In nasopharyngeal carcinoma specifically, feedback constraint resulted in the improved protection of OARs in proximity of targets (such as the brainstem and parotid) due to sharp dose distribution and reduced MUs. PMID:26622793

  13. SU-F-BRD-06: Robust Dose Calculation in Intensity Modulated Proton Therapy

    SciTech Connect

    Brosch, R; Liu, W

    2015-06-15

    Purpose: Commissioning data for intensity modulated proton therapy (IMPT) must be post-processed by fits to ad-hoc functions to derive the dose calculation kernel parameters in a treatment planning system (TPS). Whether from experimental measurement or Monte Carlo simulation, the limited and noisy nature of such data makes this task very challenging. We present a method to improve the modeling of the lateral dose distribution of clinical energy proton beams in water to commission an in-house IMPT dose calculation engine. Methods: A linear sum of three Gaussian distribution functions was fitted to the lateral dose data in logarithmic scale. Starting values of fitting solutions were determined from the Generalized Highland Approximation. We exhaustively optimized the combinations of data weights with upper bounds of the fitting solutions to minimize confidence intervals of the fitting solutions while maintaining the coefficient of determination (R{sup 2}). Results: Across all energies, average confidence bounds improved 72.88% [Max: 88.28%, Min: 55.05%] for small angle coulomb scattering, 114.25% [409.13%, 66.72%,] for nuclear scattering, and 68.66% [141.09%, 33.27%] for large angle coulomb scattering, while the coefficients of determination of the fits (R{sup 2}) remained comparable. On average R {sup 2} only changed 0.18% and were very close to 1 (approx. 0.999). Wilcoxon signed rank tests comparing unweighted/unbounded fits with weighted/bounded fits averaged 0.0146 (Max: 0.177, Min: 7.05×10−{sup 7}) for small angle Coulomb, 0.0903 (0.945, 7.05×10−{sup 7}) for nuclear, and 0.254 (0.871, 1.86×10−{sup 6}) for large angle Coulomb scattering. This allows rejection of the null hypothesis for small angle Coulomb scattering at the 0.015 level and nuclear interaction at the 0.1 level. Conclusion: Optimal weights assigned to IMPT lateral dose data minimized fitting to stochastic noise in the tail region. Optimizing the upper bounds of fitting parameters improved

  14. The importance of prostate bed tilt during postprostatectomy intensity-modulated radiotherapy.

    PubMed

    Bell, Linda J; Cox, Jennifer; Eade, Thomas; Rinks, Marianne; Kneebone, Andrew

    2014-01-01

    Variations in rectal and bladder filling can create a tilt of the prostate bed, which generates the potential for a geographic miss during postprostatectomy radiotherapy. The aim of this study is to assess the effect that bladder and rectum filling has on planning target volume angle, to determine a method to assess prostate bed tilt leading to potential geographic miss, and to discuss possible implementation issues. The cone-beam computed tomography images (n = 377) of 40 patients who received postprostatectomy radiotherapy with intensity-modulated radiotherapy were reviewed. The amount of tilt in the prostate bed was defined as the angle change between 2 surgical clips, one in the upper prostate bed and another in the lower. A potential geographic miss was defined as movement of any clip of more than 1cm in any direction or 0.5 cm posteriorly when aligned to bone anatomy. Variations in bladder and rectum size were correlated with the degree of prostate bed tilt, and the rate of potential geographic miss was determined. A possible clinical use of prostate bed tilt was then assessed for different imaging techniques. A tilt of more than 10° was seen in 20.2% of images, which resulted in a 57.9% geographic miss rate of the superior clip. When tilt remained within 10°, there was only a 9% rate of geographic miss. Potential geographic miss of the inferior surgical clip was rare, occurring in only 1.9% of all images reviewed. The most common occurrence when the prostate bed tilt increased by more than 10° was a smaller bladder and larger rectum (6.4% of all images). The most common occurrence when the prostate bed tilt decreased by more than 10° was a larger bladder and smaller rectum (1.3% of all images). Significant prostate bed tilt (>± 10°) occurred in more than 20% of images, creating a 58% rate of geographic miss. Greatest prostate bed tilt occurred when the bladder size increased or reduced by more than 2 cm or the superior rectum size increased by more

  15. Stereotactic hypothalamotomy for behaviour disorders

    PubMed Central

    Schvarcz, J. R.; Driollet, R.; Rios, E.; Betti, O.

    1972-01-01

    Posterior hypothalamotomy is a relatively simple stereotactic procedure. The radiological determination of the target and its physiological corroboration by electrical stimulation are accurate. The lesions have always been made in the site of maximum sympathetic response. In this respect, the cardiovascular changes (hypertension and tachycardia), which are always elicited from a more restricted area, are of particular importance. Depth recordings, however, have been less useful. Undesirable side-effects, if present, were mild and transitory. There was no postoperative intelligence deficit, at least with the standard tests. Images PMID:5035309

  16. Simple Carotid-Sparing Intensity-Modulated Radiotherapy Technique and Preliminary Experience for T1-2 Glottic Cancer

    SciTech Connect

    Rosenthal, David I.; Fuller, Clifton D.; Barker, Jerry L.; Mason, Bryan M.S.; Garcia, John A. C.; Lewin, Jan S.; Holsinger, F. Christopher; Stasney, C. Richard; Frank, Steven J.; Schwartz, David L.; Morrison, William H.; Garden, Adam S.; Ang, K. Kian

    2010-06-01

    Purpose: To investigate the dosimetry and feasibility of carotid-sparing intensity-modulated radiotherapy (IMRT) for early glottic cancer and to report preliminary clinical experience. Methods and Materials: Digital Imaging and Communications in Medicine radiotherapy (DICOM-RT) datasets from 6 T1-2 conventionally treated glottic cancer patients were used to create both conventional IMRT plans. We developed a simplified IMRT planning algorithm with three fields and limited segments. Conventional and IMRT plans were compared using generalized equivalent uniform dose and dose-volume parameters for in-field carotid arteries, target volumes, and organs at risk. We have treated 11 patients with this simplified IMRT technique. Results: Intensity-modulated radiotherapy consistently reduced radiation dose to the carotid arteries (p < 0.05) while maintaining the clinical target volume coverage. With conventional planning, median carotid V35, V50, and V63 were 100%, 100%, and 69.0%, respectively. With IMRT planning these decreased to 2%, 0%, and 0%, respectively (p < 0.01). Radiation planning and treatment times were similar for conventional radiotherapy and IMRT. Treatment results have been excellent thus far. Conclusions: Intensity-modulated radiotherapy significantly reduced unnecessary radiation dose to the carotid arteries compared with conventional lateral fields while maintaining clinical target volume coverage. Further experience and longer follow-up will be required to demonstrate outcomes for cancer control and carotid artery effects.

  17. Wavelength reused bidirectional transmission of adaptively modulated optical OFDM signals in WDM-PONs incorporating SOA and RSOA intensity modulators.

    PubMed

    Wei, J L; Hugues-Salas, E; Giddings, R P; Jin, X Q; Zheng, X; Mansoor, S; Tang, J M

    2010-05-10

    Detailed numerical investigations are undertaken of wavelength reused bidirectional transmission of adaptively modulated optical OFDM (AMOOFDM) signals over a single SMF in a colorless WDM-PON incorporating a semiconductor optical amplifier (SOA) intensity modulator and a reflective SOA (RSOA) intensity modulator in the optical line termination and optical network unit, respectively. A comprehensive theoretical model describing the performance of such network scenarios is, for the first time, developed, taking into account dynamic optical characteristics of SOA and RSOA intensity modulators as well as the effects of Rayleigh backscattering (RB) and residual downstream signal-induced crosstalk. The developed model is rigorously verified experimentally in RSOA-based real-time end-to-end OOFDM systems at 7.5 Gb/s. It is shown that the RB noise and crosstalk effects are dominant factors limiting the maximum achievable downstream and upstream transmission performance. Under optimum SOA and RSOA operating conditions as well as practical downstream and upstream optical launch powers, 10 Gb/s downstream and 6 Gb/s upstream over 40 km SMF transmissions of conventional double sideband AMOOFDM signals are feasible without utilizing in-line optical amplification and chromatic dispersion compensation. In particular, the aforementioned transmission performance can be improved to 23 Gb/s downstream and 8 Gb/s upstream over 40 km SMFs when single sideband subcarrier modulation is adopted in the downstream systems.

  18. Optimization of Stereotactic Radiotherapy Treatment Delivery Technique for Base-Of-Skull Meningiomas

    SciTech Connect

    Clark, Brenda G. Candish, Charles; Vollans, Emily; Gete, Ermias; Lee, Richard; Martin, Monty; Ma, Roy; McKenzie, Michael

    2008-10-01

    This study compares static conformal field (CF), intensity modulated radiotherapy (IMRT), and dynamic arcs (DA) for the stereotactic radiotherapy of base-of-skull meningiomas. Twenty-one cases of base-of-skull meningioma (median planning target volume [PTV] = 21.3 cm{sup 3}) previously treated with stereotactic radiotherapy were replanned with each technique. The plans were compared for Radiation Therapy Oncology Group conformity index (CI) and homogeneity index (HI), and doses to normal structures at 6 dose values from 50.4 Gy to 5.6 Gy. The mean CI was 1.75 (CF), 1.75 (DA), and 1.66 (IMRT) (p < 0.05 when comparing IMRT to either CF or DA plans). The CI (IMRT) was inversely proportional to the size of the PTV (Spearman's rho = -0.53, p = 0.01) and at PTV sizes above 25 cm{sup 3}, the CI (IMRT) was always superior to CI (DA) and CI (CF). At PTV sizes below 25 cm{sup 3}, there was no significant difference in CI between each technique. There was no significant difference in HI between plans. The total volume of normal tissue receiving 50.4, 44.8, and 5.6 Gy was significantly lower when comparing IMRT to CF and DA plans (p < 0.05). There was significantly improved dose sparing for the brain stem and ipsilateral temporal lobe with IMRT but no significant difference for the optic chiasm or pituitary gland. These results demonstrate that stereotactic IMRT should be considered to treat base-of-skull meningiomas with a PTV larger than 25 cm{sup 3}, due to improved conformity and normal tissue sparing, in particular for the brain stem and ipsilateral temporal lobe.

  19. An integral quality monitoring system for real-time verification of intensity modulated radiation therapy

    SciTech Connect

    Islam, Mohammad K.; Norrlinger, Bernhard D.; Smale, Jason R.; Heaton, Robert K.; Galbraith, Duncan; Fan, Cary; Jaffray, David A.

    2009-12-15

    Purpose: To develop an independent and on-line beam monitoring system, which can validate the accuracy of segment-by-segment energy fluence delivery for each treatment field. The system is also intended to be utilized for pretreatment dosimetric quality assurance of intensity modulated radiation therapy (IMRT), on-line image-guided adaptive radiation therapy, and volumetric modulated arc therapy. Methods: The system, referred to as the integral quality monitor (IQM), utilizes an area integrating energy fluence monitoring sensor (AIMS) positioned between the final beam shaping device [i.e., multileaf collimator (MLC)] and the patient. The prototype AIMS consists of a novel spatially sensitive large area ionization chamber with a gradient along the direction of the MLC motion. The signal from the AIMS provides a simple output for each beam segment, which is compared in real time to the expected value. The prototype ionization chamber, with a physical area of 22x22 cm{sup 2}, has been constructed out of aluminum with the electrode separations varying linearly from 2 to 20 mm. A calculation method has been developed to predict AIMS signals based on an elementwise integration technique, which takes into account various predetermined factors, including the spatial response function of the chamber, MLC characteristics, beam transmission through the secondary jaws, and field size factors. The influence of the ionization chamber on the beam has been evaluated in terms of transmission, surface dose, beam profiles, and depth dose. The sensitivity of the system was tested by introducing small deviations in leaf positions. A small set of IMRT fields for prostate and head and neck plans was used to evaluate the system. The ionization chamber and the data acquisition software systems were interfaced to two different types of linear accelerators: Elekta Synergy and Varian iX. Results: For a 10x10 cm{sup 2} field, the chamber attenuates the beam intensity by 7% and 5% for 6 and 18

  20. A novel software and conceptual design of the hardware platform for intensity modulated radiation therapy

    SciTech Connect

    Nguyen, Dan; Ruan, Dan; O’Connor, Daniel; Woods, Kaley; Low, Daniel A.; Sheng, Ke; Boucher, Salime

    2016-02-15

    Purpose: To deliver high quality intensity modulated radiotherapy (IMRT) using a novel generalized sparse orthogonal collimators (SOCs), the authors introduce a novel direct aperture optimization (DAO) approach based on discrete rectangular representation. Methods: A total of seven patients—two glioblastoma multiforme, three head & neck (including one with three prescription doses), and two lung—were included. 20 noncoplanar beams were selected using a column generation and pricing optimization method. The SOC is a generalized conventional orthogonal collimators with N leaves in each collimator bank, where N = 1, 2, or 4. SOC degenerates to conventional jaws when N = 1. For SOC-based IMRT, rectangular aperture optimization (RAO) was performed to optimize the fluence maps using rectangular representation, producing fluence maps that can be directly converted into a set of deliverable rectangular apertures. In order to optimize the dose distribution and minimize the number of apertures used, the overall objective was formulated to incorporate an L2 penalty reflecting the difference between the prescription and the projected doses, and an L1 sparsity regularization term to encourage a low number of nonzero rectangular basis coefficients. The optimization problem was solved using the Chambolle–Pock algorithm, a first-order primal–dual algorithm. Performance of RAO was compared to conventional two-step IMRT optimization including fluence map optimization and direct stratification for multileaf collimator (MLC) segmentation (DMS) using the same number of segments. For the RAO plans, segment travel time for SOC delivery was evaluated for the N = 1, N = 2, and N = 4 SOC designs to characterize the improvement in delivery efficiency as a function of N. Results: Comparable PTV dose homogeneity and coverage were observed between the RAO and the DMS plans. The RAO plans were slightly superior to the DMS plans in sparing critical structures. On average, the maximum and

  1. A novel conformity index for intensity modulated radiation therapy plan evaluation

    SciTech Connect

    Cheung, Fion W. K.; Law, Maria Y. Y.

    2012-09-15

    Purpose: Intensity modulated radiation therapy (IMRT) has gained popularity in the treatment of cancers. Manual evaluation of IMRT plans for head-and-neck cancers has been especially challenging necessitating efficient and objective assessment tools. In this work, the authors address this issue by developing a personalized conformity index (CI) for comparison of IMRT plans for head-and-neck cancers and evaluating its plan quality discerning power in comparison with other widely used CIs. Methods: A two-dimensional CI with dose and distance incorporated (CI{sub DD}) was developed using the MATLAB program language, to quantify the planning target volume (PTV) coverage. Valuable information contained in the digital imaging and communication in medicine (DICOM) RT objects were harvested for computation of each of the CI{sub DD} components. Apart from the dose penalty factor, a distance-based exponential function was employed by varying the penalty weight associated with the location of cold spots within the PTV. With the goal of deriving a customized penalty factor, the distances between individual pixel and its nearest PTV boundary was found. Using the exponential function, the impact of distance penalty was substantially larger for cold spots closer to the PTV centroid but petered out quickly wherever they were situated in the vicinity of PTV border. In order to evaluate the CI{sub DD} scoring system, three CT image data sets of nasopharyngeal carcinoma (NPC) patients were collected. Ten IMRT plans with degrading qualities were generated from each dataset and were ranked based on CI{sub DD} and other existing indices. The coefficient of variance was calculated for each dataset to compare the degree of variation. Results: The CI{sub DD} scoring system that considered spatial importance of each voxel within the PTV was successfully developed. The results demonstrated that the CI{sub DD} including four discrete factors could provide accurate rankings of plan quality by

  2. The impact of daily setup variations on head-and-neck intensity-modulated radiation therapy

    SciTech Connect

    Hong, Theodore S.; Tome, Wolfgang A.; Chappell, Richard J.; Chinnaiyan, Prakash; Mehta, Minesh P.; Harari, Paul M. . E-mail: harari@humonc.wisc.edu

    2005-03-01

    Purpose: Intensity-modulated radiation therapy (IMRT) in the treatment of head-and-neck (H and N) cancer provides the opportunity to diminish normal tissue toxicity profiles and thereby enhance patient quality of life. However, highly conformal treatment techniques commonly establish steep dose gradients between tumor and avoidance structures. Daily setup variations can therefore significantly compromise the ultimate precision of idealized H and N IMRT delivery. This study provides a detailed analysis regarding the potential impact of daily setup variations on the overall integrity of H and N IMRT. Methods and materials: A series of 10 patients with advanced H and N cancer were prospectively enrolled in a clinical trial to examine daily H and N radiation setup accuracy. These patients were treated with conventional shrinking field design using three-dimensional treatment planning techniques (not IMRT). Immobilization and alignment were performed using modern H and N practice techniques including conventional thermoplastic masking, baseplate fixation to the treatment couch, three-point laser alignment, and weekly portal film evaluation. After traditional laser alignment, setup accuracy was assessed daily for each patient by measuring 3 Cartesian and 3 angular deviations from the specified isocenter using a high-precision, optically guided patient localization system, which affords submillimeter setup accuracy. These positional errors were then applied to a distinct series of 10 H and N IMRT plans for detailed analysis regarding the impact of daily setup variation (without optical guidance) on the ultimate integrity of IMRT plans over a 30-day treatment course. Dose-volume histogram (DVH), equivalent uniform dose (EUD), mean total dose (mTd), and maximal total dose (MTD) for normal structures were analyzed for IMRT plans with and without incorporation of daily setup variation. Results: Using conventional H and N masking and laser alignment for daily positioning, the

  3. A novel software and conceptual design of the hardware platform for intensity modulated radiation therapy

    PubMed Central

    Nguyen, Dan; Ruan, Dan; O’Connor, Daniel; Woods, Kaley; Low, Daniel A.; Boucher, Salime; Sheng, Ke

    2016-01-01

    Purpose: To deliver high quality intensity modulated radiotherapy (IMRT) using a novel generalized sparse orthogonal collimators (SOCs), the authors introduce a novel direct aperture optimization (DAO) approach based on discrete rectangular representation. Methods: A total of seven patients—two glioblastoma multiforme, three head & neck (including one with three prescription doses), and two lung—were included. 20 noncoplanar beams were selected using a column generation and pricing optimization method. The SOC is a generalized conventional orthogonal collimators with N leaves in each collimator bank, where N = 1, 2, or 4. SOC degenerates to conventional jaws when N = 1. For SOC-based IMRT, rectangular aperture optimization (RAO) was performed to optimize the fluence maps using rectangular representation, producing fluence maps that can be directly converted into a set of deliverable rectangular apertures. In order to optimize the dose distribution and minimize the number of apertures used, the overall objective was formulated to incorporate an L2 penalty reflecting the difference between the prescription and the projected doses, and an L1 sparsity regularization term to encourage a low number of nonzero rectangular basis coefficients. The optimization problem was solved using the Chambolle–Pock algorithm, a first-order primal–dual algorithm. Performance of RAO was compared to conventional two-step IMRT optimization including fluence map optimization and direct stratification for multileaf collimator (MLC) segmentation (DMS) using the same number of segments. For the RAO plans, segment travel time for SOC delivery was evaluated for the N = 1, N = 2, and N = 4 SOC designs to characterize the improvement in delivery efficiency as a function of N. Results: Comparable PTV dose homogeneity and coverage were observed between the RAO and the DMS plans. The RAO plans were slightly superior to the DMS plans in sparing critical structures. On average, the maximum and

  4. In vitro study of cell survival following dynamic MLC intensity-modulated radiation therapy dose delivery

    SciTech Connect

    Moiseenko, Vitali; Duzenli, Cheryl; Durand, Ralph E.

    2007-04-15

    The possibility of reduced cell kill following intensity-modulated radiation therapy (IMRT) compared to conventional radiation therapy has been debated in the literature. This potential reduction in cell kill relates to prolonged treatment times typical of IMRT dose delivery and consequently increased repair of sublethal lesions. While there is some theoretical support to this reduction in cell kill published in the literature, direct experimental evidence specific to IMRT dose delivery patterns is lacking. In this study we present cell survival data for three cell lines: Chinese hamster V79 fibroblasts, human cervical carcinoma, SiHa and colon adenocarcinoma, WiDr. Cell survival was obtained for 2.1 Gy delivered as acute dose with parallel-opposed pair (POP), irradiation time 75 s, which served as a reference; regular seven-field IMRT, irradiation time 5 min; and IMRT with a break for multiple leaf collimator (MLC) re-initialization after three fields were delivered, irradiation time 10 min. An actual seven-field dynamic MLC IMRT plan for a head and neck patient was used. The IMRT plan was generated for a Varian EX or iX linear accelerator with 120 leaf Millenium MLC. Survival data were also collected for doses 1x, 2x, 3x, 4x, and 5x 2.1 Gy to establish parameters of the linear-quadratic equation describing survival following acute dose delivery. Cells were irradiated inside an acrylic cylindrical phantom specifically designed for this study. Doses from both IMRT and POP were validated using ion chamber measurements. A reproducible increase in cell survival was observed following IMRT dose delivery. This increase varied from small for V79, with a surviving fraction of 0.8326 following POP vs 0.8420 following uninterrupted IMRT, to very pronounced for SiHa, with a surviving fraction of 0.3903 following POP vs 0.5330 for uninterrupted IMRT. When compared to IMRT or IMRT with a break for MLC initialization, cell survival following acute dose delivery was

  5. A fixed-jaw method to protect critical organs during intensity-modulated radiotherapy

    SciTech Connect

    Chen, Jiayun; Chen, Xinyuan; Huang, Manni; Dai, Jianrong

    2014-01-01

    Intensity-modulated radiotherapy (IMRT) plays an important role in cancer radiotherapy. For some patients being treated with IMRT, the extremely low tolerances of critical organs (such as lens, ovaries, and testicles) cannot be met during treatment planning. The aim of this article is to introduce a new planning method to overcome that problem. In current planning practice, jaw positions are automatically set to cover all target volumes by the planning system (e.g., Pinnacle{sup 3} system). Because of such settings, critical organs may be fully blocked by the multileaf collimator (MLC), but they still sit in the field that is shaped by collimator jaws. These critical organs receive doses from the transmission and leakage of MLC leaves. We manually fixed jaw positions to block them to further reduce such doses. This method has been used for different treatment sites in our clinic, and it was thoroughly evaluated in patients with radical hysterectomy plus ovarian transposition after surgery. For each patient, 2 treatment plans were designed with the same optimization parameters: the original plan with automatically chosen jaw positions (called O-plan) and the plan with fixed-jaw positions (named F-plan). In the F-plan, the jaws were manually fixed to block the ovaries. For target coverage, the mean conformity index (CI) of the F-plan (1.28 ± 0.02) was remarkably lower than that of the O-plan (1.53 ± 0.09) (p < 0.05). The F-plan and the O-plan performed similarly in target dose homogeneity. Meanwhile, for the critical organ sparing, the mean dose of both ovaries were much lower in the F-plan than that in the O-plan (p < 0.05). The V{sub 20}, V{sub 30}, and V{sub 40} of bladder were also lower in the F-plan (93.57 ± 1.98, 73.99 ± 5.76, and 42.33 ± 3.7, respectively) than those in the O-plan (97.98 ± 1.11, 85.07 ± 4.04, and 49.71 ± 3.63, respectively) (p < 0.05). The maximum dose to the spinal cord planning organ at risk (OAR) volume (PRV) in the O-plan (3940

  6. Delivery confirmation of bolus electron conformal therapy combined with intensity modulated x-ray therapy

    SciTech Connect

    Kavanaugh, James A.; Hogstrom, Kenneth R.; Fontenot, Jonas P.; Henkelmann, Gregory; Chu, Connel; Carver, Robert A.

    2013-02-15

    Purpose: The purpose of this study was to demonstrate that a bolus electron conformal therapy (ECT) dose plan and a mixed beam plan, composed of an intensity modulated x-ray therapy (IMXT) dose plan optimized on top of the bolus ECT plan, can be accurately delivered. Methods: Calculated dose distributions were compared with measured dose distributions for parotid and chest wall (CW) bolus ECT and mixed beam plans, each simulated in a cylindrical polystyrene phantom that allowed film dose measurements. Bolus ECT plans were created for both parotid and CW PTVs (planning target volumes) using 20 and 16 MeV beams, respectively, whose 90% dose surface conformed to the PTV. Mixed beam plans consisted of an IMXT dose plan optimized on top of the bolus ECT dose plan. The bolus ECT, IMXT, and mixed beam dose distributions were measured using radiographic films in five transverse and one sagittal planes for a total of 36 measurement conditions. Corrections for film dose response, effects of edge-on photon irradiation, and effects of irregular phantom optical properties on the Cerenkov component of the film signal resulted in high precision measurements. Data set consistency was verified by agreement of depth dose at the intersections of the sagittal plane with the five measured transverse planes. For these same depth doses, results for the mixed beam plan agreed with the sum of the individual depth doses for the bolus ECT and IMXT plans. The six mean measured planar dose distributions were compared with those calculated by the treatment planning system for all modalities. Dose agreement was assessed using the 4% dose difference and 0.2 cm distance to agreement. Results: For the combined high-dose region and low-dose region, pass rates for the parotid and CW plans were 98.7% and 96.2%, respectively, for the bolus ECT plans and 97.9% and 97.4%, respectively, for the mixed beam plans. For the high-dose gradient region, pass rates for the parotid and CW plans were 93.1% and 94

  7. RT-01FRACTIONATED STEREOTACTIC RADIOTHERAPY FOR PITUITARY ADENOMA WITH NOVALIS

    PubMed Central

    Arakawa, Yoshiki; Mizowaki, Takashi; Ogura, Kengo; Sakanaka, Katsuyuki; Hojo, Masato; Hiraoka, Masahiro; Miyamoto, Susumu; Murata, Daiki

    2014-01-01

    BACKGROUND: Radiation therapy is an available treatment modality for pituitary adenoma. In particular, it is effective for the case unable to be removed with surgery or repeating recurrence. However, hypopituitarism and optic nerve injury associated with radiation therapy become a problem. Novalis® (Brain Lab) is an equipment of radiation to establish the detailed irradiation area, fractionated stereotactic radiotherapy (fSRT) and intensity-modulated radiation therapy (IMRT). Retrospectively, we review local control and morbidity following fSRT with Novalis in pituitary adenoma. PATIENTS AND METHODS: Between 2007 and 2012, 29 patients with pituitary adenoma (9 functioning, 20 non-functioning) received fSRT with Novalis in our institute. Total radiation dose was 50.4-54Gy (1.8 Gy per fraction) and prescribed to the gross target volume + 2 mm. The effectiveness of fSRT was evaluated by tumor volume and clinical symptoms on pre- fSRT, and every 1-year. RESULTS: The median follow-up time was 59.1 months (20 to 83 months). Tumor regrowth was observed in 2 cases. Progression free survival rate was 93%. New visual field deficit was observed in 1 case, and new pituitary dysfunction were not observed in all patients. CONCLUSION: fSRT with Novalis is safe and effective in the treatment for pituitary adenoma. Although follow-up time is short, any problematic complications were not observed. In the future, fSRT is expected to make for safe and effective treatment in pituitary adenoma impossible to cure surgically.

  8. Effect of spine hardware on small spinal stereotactic radiosurgery dosimetry.

    PubMed

    Wang, Xin; Yang, James N; Li, Xiaoqiang; Tailor, Ramesh; Vassilliev, Oleg; Brown, Paul; Rhines, Laurence; Chang, Eric

    2013-10-07

    Monte Carlo (MC) modeling of a 6 MV photon beam was used to study the dose perturbation from a titanium rod 5 mm in diameter in various small fields range from 2 × 2 to 5 × 5 cm(2). The results showed that the rod increased the dose to water by ∼6% at the water-rod interface because of electron backscattering and decreased the dose by ∼7% in the shadow of the rod because of photon attenuation. The Pinnacle(3) treatment planning system calculations matched the MC results at the depths more than 1 cm past the rod when the correct titanium density of 4.5 g cm(-3) was used, but significantly underestimated the backscattering dose at the water-rod interface. A CT-density table with a top density of 1.82 g cm(-3) (cortical bone) is a practical way to reduce the dosimetric error from the artifacts by preventing high density assignment to them, but can underestimates the attenuation by the titanium rod by 6%. However, when multi-beam with intensity modulation is used in actual patient spinal stereotactic radiosurgery treatment, the dosimetric effect of assigning 4.5 instead of 1.82 g cm(-3) to titanium implants is complicated. It ranged from minimal effect to 2% dose difference affecting 15% target volume in the study. When hardware is in the beam path, density override to the titanium hardware is recommended.

  9. Principles of Stereotactic Electroencephalography in Epilepsy Surgery.

    PubMed

    Lhatoo, Samden; Lacuey, Nuria; Ryvlin, Philippe

    2016-12-01

    Stereotactic electroencephalography is a method for the invasive study for the human epileptic brain as a prelude to epilepsy surgery. The discipline of stereotactic electroencephalography is underpinned by an anatomo-electro-clinical analysis of epileptic seizures of focal origin and goes beyond simple stereotactic placement of depth electrodes. Stringent analysis of semiological and electrophysiological features is coupled with an understanding of this information in 3D anatomical space. Stereotactic electroencephalography offers significant advantages over subdural grid implantations, allowing pinpoint accuracy access to sulcal areas and deep brain structures, such as the insula, cingulate, basal and mesial brain regions, while associated with lower complication rates. Recent times have seen an exponential growth in stereotactic electroencephalography interest, driven in part by increasing complexity of typical epilepsy surgery patients in epilepsy surgery centers. Such patients are much more likely to be magnetic resonance imaging negative, or reoperations, or to have multifocal or widespread areas of cortical abnormalities. Herein, we discuss the advantages of stereotactic electroencephalography, principles of patient selection, implantation, and interpretation.

  10. Image-Guided Intensity-Modulated Photon Radiotherapy Using Multifractionated Regimen to Paraspinal Chordomas and Rare Sarcomas

    SciTech Connect

    Terezakis, Stephanie A. Lovelock, D. Michael; Bilsky, Mark H.; Hunt, Margaret A.; Zatcky, Joan N.P.; Yamada, Yoshiya

    2007-12-01

    Purpose: Image-guided intensity-modulated radiotherapy enables delivery of high-dose radiation to tumors close to the spinal cord. We report our experience with multifractionated regimens using image-guided intensity-modulated radiotherapy to treat gross paraspinal disease to doses beyond cord tolerance. Methods and Materials: We performed a retrospective review of 27 consecutive patients with partially resected or unresectable paraspinal tumors irradiated to >5,300 cGy in standard fractionation. Results: The median follow-up was 17.4 months (range, 2.1-47.3). Eighteen sarcomas, seven chordomas, and two ependymomas were treated. The median dose to the planning target volume was 6,600 cGy (range, 5,396-7,080) in 180- or 200-cGy fractions. The median planning target volume was 164 cm{sup 3} (range, 29-1,116). Seven patients developed recurrence at the treatment site (26%), and 6 of these patients had high-grade tumors. Three patients with recurrence had metastatic disease at the time of radiotherapy. The 2-year local control rate was 65%, and the 2-year overall survival rate was 79%. Of the 5 patients who died, 4 had metastatic disease at death. Twenty-three patients (84%) reported either no pain or improved pain at the last follow-up visit. Sixteen patients discontinued narcotic use after treatment (62.5%). Twenty-three patients (89%) had a stable or improved American Spine Injury Association score at the last follow-up visit. No patient experienced radiation-induced myelopathy. Conclusions: The dose to paraspinal tumors has traditionally been limited to respect cord tolerance. With image-guided intensity-modulated radiotherapy, greater doses of radiation delivered in multiple fractions can be prescribed with excellent target coverage, effective palliation, and acceptable toxicity and local control.

  11. High-Dose, Single-Fraction Image-Guided Intensity-Modulated Radiotherapy for Metastatic Spinal Lesions

    SciTech Connect

    Yamada, Yoshiya Bilsky, Mark H.; Lovelock, D. Michael; Venkatraman, Ennapadam S.; Toner, Sean; Johnson, Jared; Zatcky, Joan N.P.; Zelefsky, Michael J.; Fuks, Zvi

    2008-06-01

    Purpose: To report tumor control and toxicity for patients treated with image-guided intensity-modulated radiotherapy (RT) for spinal metastases with high-dose single-fraction RT. Methods and Materials: A total of 103 consecutive spinal metastases in 93 patients without high-grade epidural spinal cord compression were treated with image-guided intensity-modulated RT to doses of 18-24 Gy (median, 24 Gy) in a single fraction between 2003 and 2006. The spinal cord dose was limited to a 14-Gy maximal dose. The patients were prospectively examined every 3-4 months with clinical assessment and cross-sectional imaging. Results: The overall actuarial local control rate was 90% (local failure developed in 7 patients) at a median follow-up of 15 months (range, 2-45 months). The median time to local failure was 9 months (range, 2-15 months) from the time of treatment. Of the 93 patients, 37 died. The median overall survival was 15 months. In all cases, death was from progression of systemic disease and not local failure. The histologic type was not a statistically significant predictor of survival or local control. The radiation dose was a significant predictor of local control (p = 0.03). All patients without local failure also reported durable symptom palliation. Acute toxicity was mild (Grade 1-2). No case of radiculopathy or myelopathy has developed. Conclusion: High-dose, single-fraction image-guided intensity-modulated RT is a noninvasive intervention that appears to be safe and very effective palliation for patients with spinal metastases, with minimal negative effects on quality of life and a high probability of tumor control.

  12. Progress in Y-00 physical cipher for Giga bit/sec optical data communications (intensity modulation method)

    NASA Astrophysics Data System (ADS)

    Hirota, Osamu; Futami, Fumio

    2014-10-01

    To guarantee a security of Cloud Computing System is urgent problem. Although there are several threats in a security problem, the most serious problem is cyber attack against an optical fiber transmission among data centers. In such a network, an encryption scheme on Layer 1(physical layer) with an ultimately strong security, a small delay, and a very high speed should be employed, because a basic optical link is operated at 10 Gbit/sec/wavelength. We have developed a quantum noise randomied stream cipher so called Yuen- 2000 encryption scheme (Y-00) during a decade. This type of cipher is a completely new type random cipher in which ciphertext for a legitimate receiver and eavesdropper are different. This is a condition to break the Shannon limit in theory of cryptography. In addition, this scheme has a good balance on a security, a speed and a cost performance. To realize such an encryption, several modulation methods are candidates such as phase-modulation, intensity-modulation, quadrature amplitude modulation, and so on. Northwestern university group demonstrated a phase modulation system (α=η) in 2003. In 2005, we reported a demonstration of 1 Gbit/sec system based on intensity modulation scheme(ISK-Y00), and gave a design method for quadratic amplitude modulation (QAM-Y00) in 2005 and 2010. An intensity modulation scheme promises a real application to a secure fiber communication of current data centers. This paper presents a progress in quantum noise randomized stream cipher based on ISK-Y00, integrating our theoretical and experimental achievements in the past and recent 100 Gbit/sec(10Gbit/sec × 10 wavelengths) experiment.

  13. Characterization and compensation of the residual chirp in a Mach-Zehnder-type electro-optical intensity modulator.

    PubMed

    Rogers, C E; Carini, J L; Pechkis, J A; Gould, P L

    2010-01-18

    We utilize various techniques to characterize the residual phase modulation of a waveguide-based Mach-Zehnder electro-optical intensity modulator. A heterodyne technique is used to directly measure the phase change due to a given change in intensity, thereby determining the chirp parameter of the device. This chirp parameter is also measured by examining the ratio of sidebands for sinusoidal amplitude modulation. Finally, the frequency chirp caused by an intensity pulse on the nanosecond time scale is measured via the heterodyne signal. We show that this chirp can be largely compensated with a separate phase modulator. The various measurements of the chirp parameter are in reasonable agreement.

  14. [Intensity-modulated radiotherapy of head and neck cancers. Dose constraint for spinal cord and brachial plexus].

    PubMed

    Boisselier, P; Racadot, S; Thariat, J; Graff, P; Pointreau, Y

    2016-10-01

    Given the ballistic opportunities it offers, intensity-modulated radiotherapy has emerged as the gold standard treatment for head and neck cancers. Protection of organs at risk is one of the objectives of optimization during the planning process. The compliance of dose constraints to the nervous system must be prioritized over all others. To avoid complications, it is recommended to respect a maximum dose of 50Gy to the spinal cord, and 60Gy to the brachial plexus using conventional fractionation of 2Gy per fraction. These constraints can be adapted depending on the clinical situation; they will probably be refocused by the follow-up of the IMRT studies.

  15. First Experiences in Intensity Modulated Radiation Surgery at the National Institute of Neurology and Neurosurgery: A Dosimetric Point of View

    NASA Astrophysics Data System (ADS)

    Lárraga-Gutiérrez, José M.; Celis-López, Miguel A.

    2003-09-01

    The National Institute of Neurology and Neurosurgery in Mexico City has acquired a Novalis® shaped beam radiosurgery unit. The institute is pioneer in the use of new technologies for neuroscience. The Novalis® unit allows the use of conformal beam radiosurgery/therapy and the more advanced modality of conformal therapy: Intensity Modulated Radiation Therapy (IMRT). In the present work we present the first cases of treatments that use the IMRT technique and show its ability to protect organs at risk, such as brainstem and optical vias.

  16. Phase-noise characteristics of a 25-GHz-spaced optical frequency comb based on a phase- and intensity-modulated laser.

    PubMed

    Ishizawa, Atsushi; Nishikawa, Tadashi; Mizutori, Akira; Takara, Hidehiko; Takada, Atsushi; Sogawa, Tetsuomi; Koga, Masafumi

    2013-12-02

    We investigated phase-noise characteristics of both a phase/intensity-modulated laser with 25-GHz mode spacing and a mode-locked fiber laser with carrier-envelope-offset (CEO) locking. As the separation from the frequency of the continuous wave (CW) laser diode (LD) for a seed light source increases, the integrated phase noise of each comb mode of both the phase/intensity-modulated laser and supercontinuum light originating from it increases with the same slope as a function of mode number. The dependence of the integrated phase noise on mode number with the phase/intensity-modulated laser is much larger than with the mode-locked fiber laser of the CEO locking. However, the phase noise of the phase/intensity-modulated laser is extremely lower than that of the mode-locked fiber laser with CEO locking in the frequency region around the CW LD. The phase noise of the phase/intensity-modulated laser with 25-GHz mode spacing and that of the mode-locked fiber laser with the CEO locking could be estimated and were found to be almost the same at the wavelengths required in an f-to-2f self-referencing interferometer. Our experimental results indicate the possibility of achieving an offset-frequency-locked frequency comb with the phase/intensity-modulated laser.

  17. Recommendations for Updating T and N Staging Systems for Nasopharyngeal Carcinoma in the Era of Intensity-Modulated Radiotherapy

    PubMed Central

    Liang, Zhong-Guo; Chen, Xiao-Qian; Niu, Zhi-Jie; Chen, Kai-Hua; Li, Ling; Qu, Song; Su, Fang; Zhao, Wei; Li, Ye; Pan, Xin-Bin; Zhu, Xiao-Dong

    2016-01-01

    Objective The aim of this study was to compare the 2008 Chinese and the 7th edition of the American Joint Committee on Cancer (AJCC) staging systems for nasopharyngeal carcinoma and to provide proposals for updating T and N staging systems of the present staging system. Methods Between January 2007 and December 2012, a cohort of 752 patients with biopsy-proven, newly diagnosed, non-metastatic nasopharyngeal carcinoma who were treated with intensity-modulated radiotherapy were retrospectively analysed. Prognoses were compared by T stage, N stage, and clinical stage according to the two staging systems for overall survival (OS), local relapse-free survival (LRFS), and distant metastasis-free survival (DMFS). Results In terms of both the T and N staging systems, the two current staging systems were comparable in predicting OS. The T classification of the 2008 Chinese staging system was better in predicting LRFS, while the N classification of the 7th edition AJCC staging system was superior in predicting DMFS. In the modern era of intensity-modulated radiotherapy, the staging system should be updated by down-staging the current stage T2 to T1, and it might be rational to merge subcategories N1 and N2. Conclusions The two current staging systems each had advantages in predicting prognosis. It seems reasonable to downstage T2 to T1 and to merge N1 and N2. PMID:27973544

  18. Three-dimensional conformal intensity-modulated radiation therapy of left femur foci does not damage the sciatic nerve

    PubMed Central

    Xu, Wanlong; Zhao, Xibin; Wang, Qing; Sun, Jungang; Xu, Jiangbo; Zhou, Wenzheng; Wang, Hao; Yan, Shigui; Yuan, Hong

    2014-01-01

    During radiotherapy to kill femoral hydatid tapeworms, the sciatic nerve surrounding the focus can be easily damaged by the treatment. Thus, it is very important to evaluate the effects of radiotherapy on the surrounding nervous tissue. In the present study, we used three-dimensional, conformal, intensity-modulated radiation therapy to treat bilateral femoral hydatid disease in Meriones meridiani. The focus of the hydatid disease on the left femur was subjected to radiotherapy (40 Gy) for 14 days, and the right femur received sham irradiation. Hematoxylin-eosin staining, electron microscopy, and terminal deoxynucleotidyl transferase-dUTP nick end labeling assays on the left femurs showed that the left sciatic nerve cell structure was normal, with no obvious apoptosis after radiation. Trypan blue staining demonstrated that the overall protoscolex structure in bone parasitized with Echinococcus granulosus disappeared in the left femur of the animals after treatment. The mortality of the protoscolex was higher in the left side than in the right side. The succinate dehydrogenase activity in the protoscolex in bone parasitized with Echinococcus granulosus was lower in the left femur than in the right femur. These results suggest that three-dimensional conformal intensity-modulated radiation therapy achieves good therapeutic effects on the secondary bone in hydatid disease in Meriones meridiani without damaging the morphology or function of the sciatic nerve. PMID:25422645

  19. Bone Marrow Sparing in Intensity Modulated Proton Therapy for Cervical Cancer: Efficacy and Robustness under Range and Setup Uncertainties

    PubMed Central

    Dinges, Eric; Felderman, Nicole; McGuire, Sarah; Gross, Brandie; Bhatia, Sudershan; Mott, Sarah; Buatti, John; Wang, Dongxu

    2015-01-01

    Background and Purpose This study evaluates the potential efficacy and robustness of functional bone marrow sparing (BMS) using intensity-modulated proton therapy (IMPT) for cervical cancer, with the goal of reducing hematologic toxicity. Material and Methods IMPT plans with prescription dose of 45 Gy were generated for ten patients who have received BMS intensity-modulated x-ray therapy (IMRT). Functional bone marrow was identified by 18F-flourothymidine positron emission tomography. IMPT plans were designed to minimize the volume of functional bone marrow receiving 5–40 Gy while maintaining similar target coverage and healthy organ sparing as IMRT. IMPT robustness was analyzed with ±3% range uncertainty errors and/or ±3mm translational setup errors in all three principal dimensions. Results In the static scenario, the median dose volume reductions for functional bone marrow by IMPT were: 32% for V5GY, 47% for V10Gy, 54% for V20Gy, and 57% for V40Gy, all with p<0.01 compared to IMRT. With assumed errors, even the worst-case reductions by IMPT were: 23% for V5Gy, 37% for V10Gy, 41% for V20Gy, and 39% for V40Gy, all with p<0.01. Conclusions The potential sparing of functional bone marrow by IMPT for cervical cancer is significant and robust under realistic systematic range uncertainties and clinically relevant setup errors. PMID:25981130

  20. Long-Term Outcome After Static Intensity-Modulated Total Body Radiotherapy Using Compensators Stratified by Pediatric and Adult Cohorts

    SciTech Connect

    Schneider, Ralf A. Schultze, Juergen; Jensen, J. Martin; Hebbinghaus, Dieter; Galalae, Razvan M.

    2008-01-01

    Purpose: To report the long-term outcome after total body irradiation with intensity-modulating compensators and allogeneic/autologous transplantation, especially in terms of therapy-related toxicity in pediatric and adult cohorts. Methods and Materials: A total of 257 consecutive patients (40 children and 217 adults) have been treated since 1983 with TBI using static intensity-modulated radiotherapy for hematologic malignancies. The total dose of 12 Gy was applied in six fractions within 3 days before allogeneic (n = 174) or autologous (n = 83) transplantation. The median follow-up was 9.2 years. Results: The 5-year overall survival rate was 47.9% (49.8% for the adults and 37.5% for the children, p = 0.171). The 5-year tumor-related mortality rate was 23%, and the 5-year treatment-related mortality rate 29.2% (29.5% in the adults and 27.5% in the pediatric patients). Interstitial pneumonitis developed in 28 (10.9%) of 257 patients and in 12.5% of the pediatric cohort. The interstitial pneumonitis rate was 25% in pediatric patients treated with a 12-Gy lung dose compared with 4.2% for those treated to an 11-Gy lung dose. The overall survival rate stratified by lung dose was 26.7% for 12 Gy and 52.4% for 11 Gy (p = 0.001). The incidence of veno-occlusive disease and cataract was 5.8% and 6.6% in all patients and 12.5% and 15% in the pediatric patients, respectively (p < 0.05). Secondary malignancies were found in 4.3% of all patients, all in the adult cohort at transplantation. Conclusion: Static intensity-modulated total body irradiation with a total dose of 12 Gy before allogeneic/autologous transplantation is a successful treatment with good long-term outcome and acceptable therapy-related toxicities. Constraining the lung dose to 11 Gy substantially lowered the actuarial treatment-related mortality. This effect was especially striking in the pediatric patients.

  1. Testing of the stability of intensity modulated beams generated with dynamic multileaf collimation, applied to the MM50 racetrack microtron.

    PubMed

    Dirkx, M L; Heijmen, B J

    2000-12-01

    Recently, we have published a method for the calculation of required leaf trajectories to generate optimized intensity modulated x-ray beams by means of dynamic multileaf collimation [Phys. Med. Biol. 43, 1171-1184 (1998)]. For the MM50 Racetrack Microtron it has been demonstrated that the dosimetric accuracy of this method, in combination with the dose calculation algorithm of the Cadplan 3D treatment planning system, is adequate for a clinical application (within 2% or 0.2 cm). Prior to initiating patient treatment with dynamic multileaf collimation (DMLC), tests have been performed to investigate the stability of DMLC fields generated at the MM50, (i) in time, (ii) subject to gantry rotation and (iii) in case of treatment interrupts, e.g., caused by an error detected by the treatment machine. The stability of relative dose profiles, normalized to a reference point in a relatively flat part of the modulated beam profile, was assessed from measurements with an electronic portal imaging device (EPID), with a linear diode array attached to the collimator and with film. The dose in the reference point was monitored using an ionization chamber. Tests were performed for several intensity modulated fields using 10 and 25 MV photon beams. Based on film measurements for sweeping 0.1 cm leaf gaps it was concluded that in an 80 days period the variation in leaf positioning was within 0.05 cm, without requiring any recalibration. For a uniform 10x10 cm2 field, realized dynamically by a scanning 0.4x10 cm2 slit beam, a maximum variation in slit width of 0.01 cm was derived from ionization chamber measurements, both in time and for gantry rotation. For a clinical example, the dose in the reference point reproduced within 0.2% (1 SD) over a period of 100 days. Apart from regions with very large dose gradients, variations in the relative beam profiles measured with the EPID were generally less than 1% (1 SD). For different gantry angles the dose profiles also reproduced within 1

  2. Stereotactic radiosurgery: comparing different technologies

    PubMed Central

    Schwartz, M

    1998-01-01

    Radiosurgery can be defined as 3-dimensional stereotactic irradiation of small intracranial targets by various radiation techniques. The goal is to deliver, with great accuracy, a large, single fraction dose to a small intracranial target, while minimizing the absorbed dose in the surrounding tissue. This article describes certain technical aspects of radiosurgery and compares the different methods of performing such treatment. The 2 most frequently used types of devices for radiosurgery are units with multiple cobalt sources (e.g., the Gamma Knife) and those based on a linear accelerator. In the former, highly collimated beams of radiation from the cobalt sources intersect at the target. In the latter, the source of a highly collimated beam of high-energy photons directed at the target turns through an arc or set of arcs. The accuracy of target localization, the steepness of fall-off of the radiation dose outside the target and the ability to irradiate an irregularly shaped target are all comparable for these 2 types of devices, despite claims to the contrary. PMID:9526480

  3. 4π Noncoplanar Stereotactic Body Radiation Therapy for Centrally Located or Larger Lung Tumors

    SciTech Connect

    Dong, Peng; Lee, Percy; Ruan, Dan; Long, Troy; Romeijn, Edwin; Low, Daniel A.; Kupelian, Patrick; Abraham, John; Yang, Yingli; Sheng, Ke

    2013-07-01

    Purpose: To investigate the dosimetric improvements in stereotactic body radiation therapy for patients with larger or central lung tumors using a highly noncoplanar 4π planning system. Methods and Materials: This study involved 12 patients with centrally located or larger lung tumors previously treated with 7- to 9-field static beam intensity modulated radiation therapy to 50 Gy. They were replanned using volumetric modulated arc therapy and 4π plans, in which a column generation method was used to optimize the beam orientation and the fluence map. Maximum doses to the heart, esophagus, trachea/bronchus, and spinal cord, as well as the 50% isodose volume, the lung volumes receiving 20, 10, and 5 Gy were minimized and compared against the clinical plans. A dose escalation study was performed to determine whether a higher prescription dose to the tumor would be achievable using 4π without violating dose limits set by the clinical plans. The deliverability of 4π plans was preliminarily tested. Results: Using 4π plans, the maximum heart, esophagus, trachea, bronchus and spinal cord doses were reduced by 32%, 72%, 37%, 44%, and 53% (P≤.001), respectively, and R{sub 50} was reduced by more than 50%. Lung V{sub 20}, V{sub 10}, and V{sub 5} were reduced by 64%, 53%, and 32% (P≤.001), respectively. The improved sparing of organs at risk was achieved while also improving planning target volume (PTV) coverage. The minimal PTV doses were increased by the 4π plans by 12% (P=.002). Consequently, escalated PTV doses of 68 to 70 Gy were achieved in all patients. Conclusions: We have shown that there is a large potential for plan quality improvement and dose escalation for patients with larger or centrally located lung tumors using noncoplanar beams with sufficient quality and quantity. Compared against the clinical volumetric modulated arc therapy and static intensity modulated radiation therapy plans, the 4π plans yielded significantly and consistently improved tumor

  4. A fast algorithm for solving a linear feasibility problem with application to Intensity-Modulated Radiation Therapy.

    PubMed

    Herman, Gabor T; Chen, Wei

    2008-03-01

    The goal of Intensity-Modulated Radiation Therapy (IMRT) is to deliver sufficient doses to tumors to kill them, but without causing irreparable damage to critical organs. This requirement can be formulated as a linear feasibility problem. The sequential (i.e., iteratively treating the constraints one after another in a cyclic fashion) algorithm ART3 is known to find a solution to such problems in a finite number of steps, provided that the feasible region is full dimensional. We present a faster algorithm called ART3+. The idea of ART3+ is to avoid unnecessary checks on constraints that are likely to be satisfied. The superior performance of the new algorithm is demonstrated by mathematical experiments inspired by the IMRT application.

  5. A model-aided segmentation in urethra identification based on an atlas human autopsy image for intensity modulated radiation therapy.

    PubMed

    Song, Yan; Muller, Boris; Burman, Chandra; Mychalczak, Borys; Song, Yulin

    2007-01-01

    In order to protect urethra in radiation therapy of prostate cancer, the urethra must be identified and localized as an organ at risk (OAR) for the inverse treatment planning in intensity modulated radiation therapy (IMRT). Because the prostatic urethra and its surrounding prostate tissue have similar physical characteristics, such as linear attenuation coefficient and density, it is difficult to distinct the OAR from the target in CT images. To localize the urethra without using contrast agent or additional imaging modalities other than planning CT images, a different approach was developed using a standard atlas of human anatomy image. This paper reports an investigation, in which an adult urethra was modeled based on a human anatomic image. An elastic model was build to account for a uniform tissue deformation of the prostate. This model was then applied to patients to localize their urethras and preliminary results are presented.

  6. First dose-map measured with a polycrystalline diamond 2D dosimeter under an intensity modulated radiotherapy beam

    NASA Astrophysics Data System (ADS)

    Scaringella, M.; Zani, M.; Baldi, A.; Bucciolini, M.; Pace, E.; de Sio, A.; Talamonti, C.; Bruzzi, M.

    2015-10-01

    A prototype of bidimensional dosimeter made on a 2.5×2.5 cm2 active area polycrystalline Chemical Vapour Deposited (pCVD) diamond film, equipped with a matrix of 12×12 contacts connected to the read-out electronics, has been used to evaluate a map of dose under Intensity Modulated Radiation Therapy (IMRT) fields for a possible application in pre-treatment verifications of cancer treatments. Tests have been performed under a 6-10 MVRX beams with IMRT fields for prostate and breast cancer. Measurements have been taken by measuring the 144 pixels in different positions, obtained by shifting the device along the x/y axes to span a total map of 14.4×10 cm2. Results show that absorbed doses measured by our pCVD diamond device are consistent with those calculated by the Treatment Planning System (TPS).

  7. [Intensity-modulated radiotherapy of head and neck cancers: Dose effects on the ocular, orbital and eyelid structures].

    PubMed

    Thariat, J; Racadot, S; Pointreau, Y; Boisselier, P; Grange, J-D; Graff, P; Weber, D C

    2016-10-01

    Radiation-induced damage of ocular, orbital and eyelid structures are mainly reported for the optic nerve, retina, lens and lacrimal gland. Dose-volume relationships are, however, inaccurate due to the small volume of most of the organs at risk involved and limited ability of irradiation techniques to spare these structures in the pre-IMRT (intensity-modulated radiation therapy) era. The ability of newest radiation techniques including IMRT and proton therapy to generate steep dose gradients may yield more accurate models in the future. Some toxicities are severe and irreversible, leading to vision loss, as in the case of radiation-induced optic neuropathy for which curative treatments are suboptimal. Other toxicities can lead to reversible vision loss but can be surgically corrected, as is the case for radiation-induced cataract. In this paper, we will review the dose effects for the ocular; orbital and eyelid structures.

  8. Optical coherence photoacoustic microscopy (OC-PAM) with an intensity-modulated continuous-wave broadband light source

    NASA Astrophysics Data System (ADS)

    Liu, Xiaojing; Wen, Rong; Li, Yiwen; Jiao, Shuliang

    2016-06-01

    We developed an optical coherence photoacoustic microscopy system using an intensity-modulated continuous-wave superluminescent diode with a center wavelength of 840 nm. The system can accomplish optical coherence tomography (OCT) and photoacoustic microscopy (PAM) simultaneously. Compared to the system with a pulsed light source, this system is able to achieve OCT imaging with quality as high as conventional spectral-domain OCT. Since both of the OCT and PAM images are generated from the same group of photons, they are intrinsically registered in the lateral directions. The system was tested for multimodal imaging the vasculature of mouse ear in vivo by using gold nanorods as contrast agent for PAM, as well as excised porcine eyes ex vivo. The OCT and PAM images showed complimentary information of the sample.

  9. Imaging of Radiation Dose for Stereotactic Radiosurgery

    SciTech Connect

    Guan, Timothy Y.; Almond, Peter R.; Park, Hwan C.; Lindberg, Robert D.; Shields, Christopher B.

    2015-01-15

    The distributions of radiation dose for stereotactic radiosurgery, using a modified linear accelerator (Philips SL-25 and SRS-200), have been studied by using three different dosimeters: (1) ferrous-agarose-xylenol orange (FAX) gels, (2) TLD, and (3) thick-emulsion GafChromic dye film. These dosimeters were loaded into a small volume of defect in a phantom head. A regular linac stereotactic radiosurgery treatment was then given to the phantom head for each type of dosimeter. The measured radiation dose and its distributions were found to be in good agreement with those calculated by the treatment planning computer.

  10. A Phase II Trial of Arc-Based Hypofractionated Intensity-Modulated Radiotherapy in Localized Prostate Cancer

    SciTech Connect

    Lock, Michael; Best, Lara; Wong, Eugene; Bauman, Glenn; D'Souza, David; Venkatesan, Varagur; Sexton, Tracy; Ahmad, Belal; Izawa, Jonathan; Rodrigues, George

    2011-08-01

    Purpose: To evaluate acute and late genitourinary (GU) and gastrointestinal (GI) toxicity and biochemical control of hypofractionated, image-guided (fiducial markers or ultrasound guidance), simplified intensity-modulated arc therapy for localized prostate cancer. Methods and Materials: This Phase II prospective clinical trial for T1a-2cNXM0 prostate cancer enrolled 66 patients who received 63.2 Gy in 20 fractions over 4 weeks. Fiducial markers were used for image guidance in 30 patients and daily ultrasound for the remainder. Toxicity was scored according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0. Results: Median follow-up was 36 months. Acute Phase Grade 2 and 3 toxicity was 34% and 9% for GU vs. 25% and 10% for GI symptoms. One Grade 4 acute GI toxicity occurred in a patient with unrecognized Crohn's disease. Late Grade 2 and 3 toxicity for GU was 14% and 5%, and GI toxicity was 25% and 3%. One late GI Grade 4 toxicity was observed in a patient with significant comorbidities (anticoagulation, vascular disease). Acute GI toxicity {>=}Grade 2 was shown to be a predictor for late toxicity Grade {>=}2 (p < 0.001). The biochemical disease-free survival at 3 years was 95%. Conclusions: Hypofractionated simplified intensity-modulated arc therapy radiotherapy given as 63.2 Gy in 20 fractions demonstrated promising biochemical control rates; however, higher rates of acute Grade 3 GU and GI toxicity and higher late Grade 2 GU and GI toxicity were noted. Ongoing randomized controlled trials should ultimately clarify issues regarding patient selection and the true rate of severe toxicity that can be directly attributed to hypofractionated radiotherapy.

  11. Intensity-Modulated Radiation Therapy for the Treatment of Squamous Cell Anal Cancer With Para-aortic Nodal Involvement

    SciTech Connect

    Hodges, Joseph C.; Das, Prajnan; Eng, Cathy; Reish, Andrew G.; Beddar, A. Sam; Delclos, Marc E.; Krishnan, Sunil; Crane, Christopher H.

    2009-11-01

    Purpose: To determine the rates of toxicity, locoregional control, distant control, and survival in anal cancer patients with para-aortic nodal involvement, treated with intensity-modulated radiotherapy (IMRT) and concurrent chemotherapy at a single institution. Methods and Materials: Between 2001 and 2007, 6 patients with squamous cell anal cancer and para-aortic nodal involvement were treated with IMRT and concurrent infusional 5-fluorouracil and cisplatin. The primary tumor was treated with a median dose of 57.5 Gy (range, 54-60 Gy), involved para-aortic, pelvic, and inguinal lymph nodes were treated with a median dose of 55 Gy (range, 50.5-55 Gy), and noninvolved nodal regions were treated with a median dose of 45 Gy (range, 43.5-45 Gy). Results: After a median follow-up of 25 months, none of the patients had a recurrence at the primary tumor, pelvic/inguinal nodes, or para-aortic nodes, whereas 2 patients developed distant metastases to the liver. Four of the 6 patients are alive. The 3-year actuarial locoregional control, distant control, and overall survival rates were 100%, 56%, and 63%, respectively. Four of the 6 patients developed Grade 3 acute gastrointestinal toxicity during chemoradiation. Conclusions: Intensity-modulated radiotherapy and concurrent chemotherapy could potentially serve as definitive therapy in anal cancer patients with para-aortic nodal involvement. Adjuvant chemotherapy may be indicated in these patients, as demonstrated by the distant failure rates. These patients need to be followed carefully because of the potential for treatment-related toxicities.

  12. SU-E-J-274: Responses of Medulloblastoma Cells to Radiation Dosimetric Parameters in Intensity-Modulated Radiation Therapy

    SciTech Connect

    Park, J; Park, J; Rogalla, S; Contag, C; Woo, D; Lee, D; Park, H; Suh, T

    2015-06-15

    Purpose: To evaluate radiation responses of the medulloblastoma cell line Daoy in intensity-modulated radiation therapy (IMRT), quantitative variations to variable radiation dosimetic parameters were tracked by bioluminescent images (BLIs). Methods: The luciferase and green fluorescent protein positive Daoy cells were cultured on dishes. The medulloblastoma cells irradiated to different dose rate, interval of fractionated doses, field margin and misalignment, and dose uniformity in IMRT were monitored using bioluminescent images. The cultured cells were placed into a dedicated acrylic phantom to deliver intensity-modulated fluences and calculate accurate predicted dose distribution. The radiation with dose rate from 0.5 Gy/min to 15 Gy/min was irradiated by adjusting monitor unit per minute and source-to-surface distances. The intervals of fractionated dose delivery were changed considering the repair time of double strand breaks (DSB) revealed by straining of gamma-H2AX.The effect of non-uniform doses on the cells were visualized by registering dose distributions and BLIs. The viability according to dosimetric parameters was correlated with bioluminescent intensities for cross-check of radiation responses. Results: The DSB and cell responses due to the first fractionated dose delivery significantly affected final tumor control rather than other parameters. The missing tumor volumes due to the smaller field margin than the tumor periphery or field misalignment caused relapse of cell responses on BLIs. The dose rate and gradient had effect on initial responses but could not bring out the distinguishable killing effect on cancer cells. Conclusion: Visualized and quantified bioluminescent images were useful to correlate the dose distributions with spatial radiation effects on cells. This would derive the effective combination of dose delivery parameters and fractionation. Radiation responses in particular IMRT configuration could be reflected to image based-dose re-optimization.

  13. Preliminary outcome and toxicity report of extended-field, intensity-modulated radiation therapy for gynecologic malignancies

    SciTech Connect

    Salama, Joseph K. . E-mail: jsalama@radonc.uchicago.edu; Mundt, Arno J.; Roeske, John; Mehta, Neil

    2006-07-15

    Purpose: The aim of this article is to report a preliminary analysis of our initial clinical experience with extended-field intensity-modulated radiotherapy for gynecologic malignancies. Methods and Materials: Between November 2002 and May 2005, 13 women with gynecologic malignancies were treated with extended-field radiation therapy. Of the women, 7 had endometrial cancer, 4 cervical cancer, 1 recurrent endometrial cancer, and 1 suspected cervical cancer. All women underwent computed tomography planning, with the upper vagina, parametria, and uterus (if present) contoured within the CTV. In addition, the clinical target volume contained the pelvic and presacral lymph nodes as well as the para-aortic lymph nodes. All acute toxicity was scored according to the Common Terminology Criteria for Adverse Events (CTCAE v 3.0). All late toxicity was scored using the Radiation Therapy Oncology Group late toxicity score. Results: The median follow-up was 11 months. Extended-field intensity-modulated radiation therapy (IMRT) for gynecologic malignancies was well tolerated. Two patients experienced Grade 3 or higher toxicity. Both patients were treated with concurrent cisplatin based chemotherapy. Neither patient was planned with bone marrow sparing. Eleven patients had no evidence of late toxicity. One patient with multiple previous surgeries experienced a bowel obstruction. One patient with bilateral grossly involved and unresectable common iliac nodes experienced bilateral lymphedema. Extended-field-IMRT achieved good local control with only 1 patient, who was metastatic at presentation, and 1 patient not able to complete treatment, experiencing in-field failure. Conclusions: Extended-field IMRT is safe and effective with a low incidence of acute toxicity. Longer follow-up is needed to assess chronic toxicity, although early results are promising.

  14. Risk Factors for Hearing Loss in Patients Treated With Intensity-Modulated Radiotherapy for Head-and-Neck Tumors

    SciTech Connect

    Zuur, Charlotte L.; Dreschler, Wouter A.; Balm, Alfons J.; Rasch, Coen R.

    2009-06-01

    Purpose: Radiotherapy (RT) is a common treatment of head-and-neck carcinoma. The objective of this study was to perform a prospective multivariate assessment of the dose-effect relationship between intensity-modulated RT and hearing loss. Methods and Materials: Pure tone audiometry at 0.250-16 kHz was obtained before and after treatment in 101 patients (202 ears). All patients received full-course intensity-modulated RT (range, 56-70 Gy), with a median cochlear dose of 11.4 Gy (range, 0.2-69.7). Results: Audiometry was performed 1 week before and a median of 9 weeks (range, 1-112) after treatment. The mean hearing deterioration at pure tone average air-conduction 1-2-4 kHz was small (from 28.6 dB HL to 30.1 dB HL). However, individual patients showed clinically significant hearing loss, with 10-dB threshold shift incidences of 13% and 18% at pure tone averages air-conduction 1-2-4 kHz and 8-10-12.5 kHz, respectively. Post-treatment hearing capability was unfavorable in the case of greater inner ear radiation doses (p <0.0001), unfavorable baseline hearing capability (p <0.0001), green-eyed patients (p <0.0001), and older age (p <0.0001). Using multivariate analysis, a prediction of individual hearing capabiltity after treatment was made. Conclusion: RT-induced hearing loss in the mean population is modest. However, clinically significant hearing loss was observed in older patients with green eyes and unfavorable pretreatment hearing. In these patients, the intended radiation dose may be adjusted according to the proposed predictive model, aiming to decrease the risk of ototoxicity.

  15. Recovery of acetylene absorption line profile basing on tunable diode laser spectroscopy with intensity modulation and photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Li; Thursby, Graham; Stewart, George; Arsad, Norhana; Uttamchandani, Deepak; Culshaw, Brian; Wang, Yiding

    2010-04-01

    A novel and direct absorption line recovery technique based on tunable diode laser spectroscopy with intensity modulation is presented. Photoacoustic spectroscopy is applied for high sensitivity, zero background and efficient acoustic enhancement at a low modulation frequency. A micro-electromechanical systems (MEMS) mirror driven by an electrothermal actuator is used for generating laser intensity modulation (without wavelength modulation) through the external reflection. The MEMS mirror with 10μm thick structure material layer and 100nm thick gold coating is formed as a circular mirror of 2mm diameter attached to an electrothermal actuator and is fabricated on a chip that is wire-bonded and placed on a PCB holder. Low modulation frequency is adopted (since the resonant frequencies of the photoacoustic gas cell and the electrothermal actuator are different) and intrinsic high signal amplitude characteristics in low frequency region achieved from measured frequency responses for the MEMS mirror and the gas cell. Based on the property of photoacoustic spectroscopy and Beer's law that detectable sensitivity is a function of input laser intensity in the case of constant gas concentration and laser path length, a Keopsys erbium doped fibre amplifier (EDFA) with opto-communication C band and high output power up to 1W is chosen to increase the laser power. High modulation depth is achieved through adjusting the MEMS mirror's reflection position and driving voltage. In order to scan through the target gas absorption line, the temperature swept method is adopted for the tunable distributed feed-back (DFB) diode laser working at 1535nm that accesses the near-infrared vibration-rotation spectrum of acetylene. The profile of acetylene P17 absorption line at 1535.39nm is recovered ideally for ~100 parts-per-million (ppm) acetylene balanced by nitrogen. The experimental signal to noise ratio (SNR) of absorption line recovery for 500mW laser power was ~80 and hence the

  16. The Failure Patterns of Oral Cavity Squamous Cell Carcinoma After Intensity-Modulated Radiotherapy-University of Iowa Experience

    SciTech Connect

    Yao Min . E-mail: min-yao@uiowa.edu; Chang, Kristi; Funk, Gerry F.; Lu Heming; Tan Huaming; Wacha, Judith C; Dornfeld, Kenneth J.; Buatti, John M.

    2007-04-01

    Purpose: Determine the failure patterns of oral cavity squamous cell carcinoma (SCC) treated with intensity-modulated radiotherapy (IMRT). Methods and Materials: Between May 2001 and July 2005, 55 patients with oral cavity SCC were treated with IMRT for curative intent. Forty-nine received postoperative IMRT, 5 definitive IMRT, and 1 neoadjuvant. Three target volumes were defined (clinical target CTV1, CTV2, and CTV3). The failure patterns were determined by coregistration or comparison of the treatment planning computed tomography to the images obtained at the time of recurrence. Results: The median follow-up for all patients was 17.1 months (range, 0.27-59.3 months). The median follow-up for living patients was 23.9 months (range, 9.3-59.3 months). Nine patients had locoregional failures: 4 local failures only, 2 regional failures only, and 3 had both local and regional failures. Five patients failed distantly; of these, 3 also had locoregional failures. The 2-year overall survival, disease-specific survival, local recurrence-free survival, locoregional recurrence-free survival, and distant disease-free survival was 68%, 74%, 85%, 82%, and 89%, respectively. The median time from treatment completion to locoregional recurrence was 4.1 months (range, 3.0-12.1 months). Except for 1 patient who failed in contralateral lower neck outside the radiation field, all failed in areas that had received a high dose of radiation. The locoregional control is strongly correlated with extracapsular extension. Conclusions: Intensity-modulated RT is effective for oral cavity SCC. Most failures are in-field failures. Further clinical studies are necessary to improve the outcomes of patients with high-risk features, particularly for those with extracapsular extension.

  17. Postoperative Intensity-Modulated Radiotherapy in Low-Risk Endometrial Cancers: Final Results of a Phase I Study

    SciTech Connect

    Macchia, Gabriella; Cilla, Savino M.P.; Ferrandina, Gabriella; Padula, Gilbert D.A.; Deodato, Francesco; Digesu, Cinzia; Caravatta, Luciana; Picardi, Vincenzo; Corrado, Giacomo; Piermattei, Angelo; Valentini, Vincenzo; Cellini, Numa; Scambia, Giovanni; Morganti, Alessio Giuseppe

    2010-04-15

    Purpose: To determine the maximum tolerated dose of short-course radiotherapy (intensity-modulated radiotherapy technique) to the upper two thirds of the vagina in endometrial cancers with low risk of local recurrence. Patients and Methods: A Phase I clinical trial was performed. Eligible patients had low-risk resected primary endometrial adenocarcinomas. Radiotherapy was delivered in 5 fractions over 1 week. The planning target volume was the clinical target volume plus 5 mm. The clinical target volume was defined as the upper two thirds of the vagina as evidenced at CT simulation by a vaginal radio-opaque device. The planning target volume was irradiated by a seven-field intensity-modulated radiotherapy technique, planned by the Plato Sunrise inverse planning system. A first cohort of 6 patients received 25 Gy (5-Gy fractions), and a subsequent cohort received 30 Gy (6-Gy fractions). The Common Toxicity Criteria scale, version 3.0, was used to score toxicity. Results: Twelve patients with endometrial cancer were enrolled. Median age was 58 years (range, 49-74 years). Pathologic stage was IB (83.3%) and IC (16.7%). Median tumor size was 30 mm (range, 15-50 mm). All patients completed the prescribed radiotherapy. No patient experienced a dose-limiting toxicity at the first level, and the radiotherapy dose was escalated from 25 to 30 Gy. No patients at the second dose level experienced dose-limiting toxicity. The most common Grade 2 toxicity was gastrointestinal, which was tolerable and manageable. Conclusions: The maximum tolerated dose of short-course radiotherapy was 30 Gy at 6 Gy per fraction. On the basis of this result, we are conducting a Phase II study with radiotherapy delivered at 30 Gy.

  18. Positron Emission Tomography-Guided, Focal-Dose Escalation Using Intensity-Modulated Radiotherapy for Head and Neck Cancer

    SciTech Connect

    Madani, Indira . E-mail: indira@krtkg1.ugent.be; Duthoy, Wim; Derie, Cristina R.N.; De Gersem, Werner Ir.; Boterberg, Tom; Saerens, Micky; Jacobs, Filip Ir.; Gregoire, Vincent; Lonneux, Max; Vakaet, Luc; Vanderstraeten, Barbara; Bauters, Wouter; Bonte, Katrien; Thierens, Hubert; Neve, Wilfried de

    2007-05-01

    Purpose: To assess the feasibility of intensity-modulated radiotherapy (IMRT) using positron emission tomography (PET)-guided dose escalation, and to determine the maximum tolerated dose in head and neck cancer. Methods and Materials: A Phase I clinical trial was designed to escalate the dose limited to the [{sup 18}-F]fluoro-2-deoxy-D-glucose positron emission tomography ({sup 18}F-FDG-PET)-delineated subvolume within the gross tumor volume. Positron emission tomography scanning was performed in the treatment position. Intensity-modulated radiotherapy with an upfront simultaneously integrated boost was employed. Two dose levels were planned: 25 Gy (level I) and 30 Gy (level II), delivered in 10 fractions. Standard IMRT was applied for the remaining 22 fractions of 2.16 Gy. Results: Between 2003 and 2005, 41 patients were enrolled, with 23 at dose level I, and 18 at dose level II; 39 patients completed the planned therapy. The median follow-up for surviving patients was 14 months. Two cases of dose-limiting toxicity occurred at dose level I (Grade 4 dermitis and Grade 4 dysphagia). One treatment-related death at dose level II halted the study. Complete response was observed in 18 of 21 (86%) and 13 of 16 (81%) evaluated patients at dose levels I and II (p < 0.7), respectively, with actuarial 1-year local control at 85% and 87% (p n.s.), and 1-year overall survival at 82% and 54% (p = 0.06), at dose levels I and II, respectively. In 4 of 9 patients, the site of relapse was in the boosted {sup 18}F-FDG-PET-delineated region. Conclusions: For head and neck cancer, PET-guided dose escalation appears to be well-tolerated. The maximum tolerated dose was not reached at the investigated dose levels.

  19. A Phase 1 Study of Everolimus + Weekly Cisplatin + Intensity Modulated Radiation Therapy in Head-and-Neck Cancer

    SciTech Connect

    Fury, Matthew G.; Lee, Nancy Y.; Sherman, Eric; Ho, Alan L.; Rao, Shyam; Heguy, Adriana; Shen, Ronglai; Korte, Susan; Lisa, Donna; Ganly, Ian; Patel, Snehal; Wong, Richard J.; Shaha, Ashok; Shah, Jatin; Haque, Sofia; Katabi, Nora; Pfister, David G.

    2013-11-01

    Purpose: Elevated expression of eukaryotic protein synthesis initiation factor 4E (eIF4E) in histologically cancer-free margins of resected head and neck squamous cell carcinomas (HNSCCs) is mediated by mammalian target of rapamycin complex 1 (mTORC1) and has been associated with increased risk of disease recurrence. Preclinically, inhibition of mTORC1 with everolimus sensitizes cancer cells to cisplatin and radiation. Methods and Materials: This was single-institution phase 1 study to establish the maximum tolerated dose of daily everolimus given with fixed dose cisplatin (30 mg/m{sup 2} weekly × 6) and concurrent intensity modulated radiation therapy for patients with locally and/or regionally advanced head-and-neck cancer. The study had a standard 3 + 3 dose-escalation design. Results: Tumor primary sites were oral cavity (4), salivary gland (4), oropharynx (2), nasopharynx (1), scalp (1), and neck node with occult primary (1). In 4 of 4 cases in which resected HNSCC surgical pathology specimens were available for immunohistochemistry, elevated expression of eIF4E was observed in the cancer-free margins. The most common grade ≥3 treatment-related adverse event was lymphopenia (92%), and dose-limiting toxicities (DLTs) were mucositis (n=2) and failure to thrive (n=1). With a median follow up of 19.4 months, 2 patients have experienced recurrent disease. The maximum tolerated dose was everolimus 5 mg/day. Conclusions: Head-and-neck cancer patients tolerated everolimus at therapeutic doses (5 mg/day) given with weekly cisplatin and intensity modulated radiation therapy. The regimen merits further evaluation, especially among patients who are status post resection of HNSCCs that harbor mTORC1-mediated activation of eIF4E in histologically negative surgical margins.

  20. Stereotactic Radiotherapy for Unilateral Orbital Lymphoma and Orbital Pseudo-Tumors: A Planning Study

    SciTech Connect

    Chino, Kazumi Tanyi, James A.; Stea, Baldassarre

    2009-04-01

    Orbital lymphoma and Grave's ophthalmopathy (GO) are successfully treated with radiation therapy. The lenses are blocked to prevent cataract formation. However, blocking of the lens by traditional methods can be difficult for tumors located anteriorly and extending into the retrobulbar space. We present a series of 3 patients with orbital lymphoma and 1 with GO treated with stereotactic intensity modulated radiation therapy (IMRT) to spare normal structures, including the lens. Three patients with orbital lymphomas and 1 with unilateral GO were treated with IMRT using a linac with stereotactic capabilities. Avoidance structures included the ipsilateral lens and globe, the contralateral lens and globe, the chiasm, and the brainstem. Two patients with orbital lymphoma were treated with 24 Gy in 12 fractions, and 1 patient was treated with 30.6 Gy in 17 fractions. The patient with GO was treated with 20 Gy in 10 fractions. The dosimetry was analyzed to determine the dose to normal tissues. Patient follow-up varies between 8 and 24 months. The mean minimal dose to the ipsilateral lens was 13.6% of the total dose, the mean maximal dose was 33.5%, and the mean median dose was 19.3%. The mean median dose to the contralateral eye was 1.1% of the total dose. The mean median dose to the chiasm was 14.9% of the total dose. The mean median dose to the brainstem was 1.9% of the total dose. No cataracts or other complications were noted in the 4 patients treated with this technique so far. IMRT gives a more conformal treatment to the orbital contents while sparing normal tissues such as the ipsilateral lens and adjacent critical structures. This should result in fewer complications such as cataracts.

  1. Clinical Outcome of Hypofractionated Stereotactic Radiotherapy for Abdominal Lymph Node Metastases

    SciTech Connect

    Bignardi, Mario; Navarria, Piera; Mancosu, Pietro; Cozzi, Luca; Fogliata, Antonella; Tozzi, Angelo; Castiglioni, Simona; Carnaghi, Carlo; Tronconi, Maria Chiara; Santoro, Armando; Scorsetti, Marta

    2011-11-01

    Purpose: We report the medium-term clinical outcome of hypofractionated stereotactic body radiotherapy (SBRT) in a series of patients with either a solitary metastasis or oligometastases from different tumors to abdominal lymph nodes. Methods and Materials: Between January 2006 and June 2009, 19 patients with unresectable nodal metastases in the abdominal retroperitoneal region were treated with SBRT. Of the patients, 11 had a solitary nodal metastasis and 8 had a dominant nodal lesion as part of oligometastatic disease, defined as up to five metastases. The dose prescription was 45 Gy to the clinical target volume in six fractions. The prescription had to be downscaled by 10% to 20% in 6 of 19 cases to keep within dose/volume constraints. The first 11 patients were treated with three-dimensional conformal techniques and the last 8 by volumetric intensity-modulated arc therapy. Median follow-up was 1 year. Results: Of 19 patients, 2 had a local progression at the site of SBRT; both also showed concomitant tumor growth at distant sites. The actuarial rate of freedom from local progression was 77.8% {+-} 13.9% at both 12 and 24 months. Eleven patients showed progressive local and/or distant disease at follow-up. The 12- and 24-month progression-free survival rates were 29.5% {+-} 13.4% and 19.7% {+-} 12.0%, respectively. The number of metastases (solitary vs. nonsolitary oligometastases) emerged as the only significant variable affecting progression-free survival (p < 0.0004). Both acute and chronic toxicities were minimal. Conclusions: Stereotactic body radiotherapy for metastases to abdominal lymph nodes was shown to be feasible with good clinical results in terms of medium-term local control and toxicity rates. Even if most patients eventually show progressive disease at other sites, local control achieved by SBRT may be potentially significant for preserving quality of life and delaying further chemotherapy.

  2. Implementation of a volumetric modulated arc therapy treatment planning solution for kidney and adrenal stereotactic body radiation therapy.

    PubMed

    Sonier, Marcus; Chu, William; Lalani, Nafisha; Erler, Darby; Cheung, Patrick; Korol, Renee

    2016-01-01

    To develop a volumetric modulated arc therapy (VMAT) treatment planning solution in the treatment of primary renal cell carcinoma and oligometastatic adrenal lesions with stereotactic body radiation therapy. Single-arc VMAT plans (n = 5) were compared with clinically delivered step-and-shoot intensity-modulated radiotherapy (IMRT) with planning target volume coverage normalized between techniques. Target volume conformity, organ-at-risk (OAR) dose, treatment time, and monitor units were compared. A VMAT planning solution, created from a combination of arc settings and optimization constraints, auto-generated treatment plans in a single optimization. The treatment planning solution was evaluated on 15 consecutive patients receiving kidney and adrenal stereotactic body radiation therapy. Treatment time was reduced from 13.0 ± 2.6 to 4.0 ± 0.9 minutes for IMRT and VMAT, respectively. The VMAT planning solution generated treatment plans with increased target homogeneity, improved 95% conformity index, and a reduced maximum point dose to nearby OARs but with increased intermediate dose to distant OARs. The conformity of the 95% isodose improved from 1.32 ± 0.39 to 1.12 ± 0.05 for IMRT and VMAT treatment plans, respectively. Evaluation of the planning solution showed clinically acceptable dose distributions for 13 of 15 cases with tight conformity of the prescription isodose to the planning target volume of 1.07 ± 0.04, delivering minimal dose to OARs. The introduction of a stereotactic body radiation therapy VMAT treatment planning solution improves the efficiency of planning and delivery time, producing treatment plans of comparable or superior quality to IMRT in the case of primary renal cell carcinoma and oligometastatic adrenal lesions.

  3. [Stereotactic ablative irradiation for lung cancer].

    PubMed

    Antoni, D; Srour, I; Noël, G; Mornex, F

    2014-01-01

    Stereotactic radiotherapy for lung cancer is a technique that is now well established in the therapeutic arsenal. Protocols are effective, with very high local control rate and an acceptable rate of survival if one takes into account the patient's age and comorbidities. Complications are rare. This review of the literature analyses the whole process of the therapeutic indications and future prospects.

  4. Imaging for Stereotactic Spine Radiotherapy: Clinical Considerations

    SciTech Connect

    Dahele, Max; Zindler, Jaap D.; Sanchez, Esther; Verbakel, Wilko F.; Kuijer, Joost P.A.; Slotman, Ben J.; Senan, Suresh

    2011-10-01

    There is growing interest in the use of stereotactic body radiation therapy (SBRT) for spinal metastases. With the need for accurate target definition and conformal avoidance of critical normal structures, high-quality multimodal imaging has emerged as a key component at each stage of the treatment process. Multidisciplinary collaboration is necessary to optimize imaging protocols and implement imaging advances into routine patient care.

  5. Lowering Whole-Body Radiation Doses in Pediatric Intensity-Modulated Radiotherapy Through the Use of Unflattened Photon Beams;Flattening filter; Pediatric; Intensity-modulated radiotherapy; Second cancers; Radiation-induced malignancies

    SciTech Connect

    Cashmore, Jason; Ramtohul, Mark; Ford, Dan

    2011-07-15

    Purpose: Intensity modulated radiotherapy (IMRT) has been linked with an increased risk of secondary cancer induction due to the extra leakage radiation associated with delivery of these techniques. Removal of the flattening filter offers a simple way of reducing head leakage, and it may be possible to generate equivalent IMRT plans and to deliver these on a standard linear accelerator operating in unflattened mode. Methods and Materials: An Elekta Precise linear accelerator has been commissioned to operate in both conventional and unflattened modes (energy matched at 6 MV) and a direct comparison made between the treatment planning and delivery of pediatric intracranial treatments using both approaches. These plans have been evaluated and delivered to an anthropomorphic phantom. Results: Plans generated in unflattened mode are clinically identical to those for conventional IMRT but can be delivered with greatly reduced leakage radiation. Measurements in an anthropomorphic phantom at clinically relevant positions including the thyroid, lung, ovaries, and testes show an average reduction in peripheral doses of 23.7%, 29.9%, 64.9%, and 70.0%, respectively, for identical plan delivery compared to conventional IMRT. Conclusions: IMRT delivery in unflattened mode removes an unwanted and unnecessary source of scatter from the treatment head and lowers leakage doses by up to 70%, thereby reducing the risk of radiation-induced second cancers. Removal of the flattening filter is recommended for IMRT treatments.

  6. Practical patterns for stereotactic body radiotherapy to hepatocellular carcinoma in Korea: a survey of the Korean Stereotactic Radiosurgery Group

    PubMed Central

    Bae, Sun Hyun; Kim, Mi-Sook; Jang, Won Il; Kay, Chul-Seung; Kim, Woochul; Kim, Eun Seog; Kim, Jin Ho; Kim, Jin Hee; Yang, Kwang Mo; Lee, Kyu Chan; Chang, A Ram; Jo, Sunmi

    2016-01-01

    Objective To investigate practical patterns for stereotactic body radiotherapy to hepatocellular carcinoma in Korea. Methods In June 2013, the Korean Stereotactic Radiosurgery Group of the Korean Society for Radiation Oncology conducted a national patterns-of-care survey about stereotactic body radiotherapy to the liver lesion in hepatocellular carcinoma, consisting of 19 questions and 2 clinical scenarios. Results All 208 radiation oncologists (100%), who are regular members of Korean Society for Radiation Oncology, responded to this survey. Among these, 95 radiation oncologists were specialists for hepatology; 64 physicians did not use stereotactic body radiotherapy for hepatocellular carcinoma, and 31 physicians used stereotactic body radiotherapy. Most physicians (52%) performed stereotactic body radiotherapy to hepatocellular carcinoma in ≤5 cases per year. Physicians applied stereotactic body radiotherapy according to tumour size and baseline Child–Pugh class. All physicians agreed the use of stereotactic body radiotherapy to 2.8-cm hepatocellular carcinoma with Child–Pugh class of A, while 23 physicians (74%) selected stereotactic body radiotherapy for Child–Pugh class of B. Nineteen physicians (61%) selected stereotactic body radiotherapy to 5-cm hepatocellular carcinoma with Child–Pugh class of A, and only 14 physicians (45%) selected stereotactic body radiotherapy for Child–Pugh class of B. On the other hand, the preferred dose scheme was same as 60 Gy in three fractions. Conclusions Among radiation oncologists in Korea, there was diversity in the practice for stereotactic body radiotherapy to the liver lesion in hepatocellular carcinoma. Additional prospective studies are necessary to standardize the practice and establish Korea-specific practice guidelines for hepatocellular carcinoma stereotactic body radiotherapy. PMID:26826720

  7. SU-E-T-489: Plan Comparisons of Re-Irradiation Treatment of Three Intensity Modulated Techniques

    SciTech Connect

    Lian, J; Tang, X; Liu, R

    2014-06-01

    Purpose: There have been controversial reports on the comparison of dosimetric quality of TomoTherapy (Tomo), VMAT and IMRT. One of the main reasons is the sampled cases are often not dosimetrically challenging enough to test the limit of optimization/delivery modalities. We chose difficult re-irradiation cases when certain organ at risk (OAR) requires extremely low dose to examine the ability of OAR sparing of three main intensity modulated techniques. Methods: Three previous treated patients with disease site on head and neck (HN), brain and lung are planned for reirradiation treatment. The Tomo planning used jaw 2.5cm and pitch 0.3. VMAT and IMRT were planned on Pinnacle for a Varian 21iX Linac with MLC leaf width 5mm. VMAT plan used 2 Arcs and IMRT plan had beams 11–13. The dosimetric endpoints and treatment time were compared for each technique of each patient. Results: Plans of three techniques cover PTV similarly. The HN case requires PTV dose 60Gy but to limit dose of cord which is 8mm away <12Gy. The cord dose of Tomo, VMAT and IMRT plan is 11.6Gy, 11.3Gy and 11.0Gy, respectively. The brain case has PTV prescription 50.4 Gy while requiring the dose of brainstem < 28Gy. Tomo, VMAT and IMRT plan generate brainstem dose 27.6Gy, 27.6Gy and 27.1Gy respectively. For the lung case, PTV was prescribed 42.5Gy but cord dose constraint was 22.5Gy. The cord dose is optimized to 22.3Gy, 20.8Gy and 21.4Gy by Tomo, VMAT and IMRT, respectively. The delivery time if normalized to Tomo is 47.0%/145.6% (VMAT/IMRT), 33.3%/106.3% and 74.1%/245.4% for HN, brain and lung case, respectively. Conclusion: Difficult re-irradiation cases were used to test the limit of three intensity modulated techniques. Tomo, VMAT and IMRT show similar dosimetry while VMAT is the most efficient one and IMRT is the least.

  8. Dosimetric research on intensity-modulated arc radiotherapy planning for left breast cancer after breast-preservation surgery

    SciTech Connect

    Yin Yong; Chen Jinhu; Sun Tao; Ma Changsheng; Lu Jie; Liu Tonghai; Wang Ruozheng

    2012-10-01

    Intensity-modulated radiotherapy (IMRT) has played an important role in breast cancer radiotherapy after breast-preservation surgery. Our aim was to study the dosimetric and implementation features/feasibility between IMRT and intensity-modulated arc radiotherapy (Varian RapidArc, Varian, Palo Alto, CA). The forward IMRT plan (f-IMRT), the inverse IMRT, and the RapidArc plan (RA) were generated for 10 patients. Afterward, we compared the target dose distribution of the 3 plans, radiation dose on organs at risk, monitor units, and treatment time. All 3 plans met clinical requirements, with RA performing best in target conformity. In target homogeneity, there was no statistical significance between RA and IMRT, but both of homogeneity were less than f-IMRT's. With regard to the V{sub 5} and V{sub 10} of the left lung, those in RA were higher than in f-IMRT but were lower than in IMRT; for V{sub 20} and V{sub 30}, the lowest was observed in RA; and in the V{sub 5} and V{sub 10} of the right lung, as well as the mean dose in normal-side breast and right lung, there was no statistically significance difference between RA and IMRT, and the lowest value was observed in f-IMRT. As for the maximum dose in the normal-side breast, the lowest value was observed in RA. Regarding monitor units (MUs), those in RA were higher than in f-IMRT but were lower than in IMRT. Treatment time of RA was 84.6% and 88.23% shorter than f-IMRT and IMRT, respectively, on average. Compared with f-IMRT and IMRT, RA performed better in target conformity and can reduce high-dose volume in the heart and left lung-which are related to complications-significantly shortening treatment time as well. Compared with IMRT, RA can also significantly reduce low-dose volume and MUs of the afflicted lung.

  9. Shortening Delivery Times of Intensity Modulated Proton Therapy by Reducing Proton Energy Layers During Treatment Plan Optimization

    SciTech Connect

    Water, Steven van de; Kooy, Hanne M.; Heijmen, Ben J.M.; Hoogeman, Mischa S.

    2015-06-01

    Purpose: To shorten delivery times of intensity modulated proton therapy by reducing the number of energy layers in the treatment plan. Methods and Materials: We have developed an energy layer reduction method, which was implemented into our in-house-developed multicriteria treatment planning system “Erasmus-iCycle.” The method consisted of 2 components: (1) minimizing the logarithm of the total spot weight per energy layer; and (2) iteratively excluding low-weighted energy layers. The method was benchmarked by comparing a robust “time-efficient plan” (with energy layer reduction) with a robust “standard clinical plan” (without energy layer reduction) for 5 oropharyngeal cases and 5 prostate cases. Both plans of each patient had equal robust plan quality, because the worst-case dose parameters of the standard clinical plan were used as dose constraints for the time-efficient plan. Worst-case robust optimization was performed, accounting for setup errors of 3 mm and range errors of 3% + 1 mm. We evaluated the number of energy layers and the expected delivery time per fraction, assuming 30 seconds per beam direction, 10 ms per spot, and 400 Giga-protons per minute. The energy switching time was varied from 0.1 to 5 seconds. Results: The number of energy layers was on average reduced by 45% (range, 30%-56%) for the oropharyngeal cases and by 28% (range, 25%-32%) for the prostate cases. When assuming 1, 2, or 5 seconds energy switching time, the average delivery time was shortened from 3.9 to 3.0 minutes (25%), 6.0 to 4.2 minutes (32%), or 12.3 to 7.7 minutes (38%) for the oropharyngeal cases, and from 3.4 to 2.9 minutes (16%), 5.2 to 4.2 minutes (20%), or 10.6 to 8.0 minutes (24%) for the prostate cases. Conclusions: Delivery times of intensity modulated proton therapy can be reduced substantially without compromising robust plan quality. Shorter delivery times are likely to reduce treatment uncertainties and costs.

  10. Four-Week Course of Radiation for Breast Cancer Using Hypofractionated Intensity Modulated Radiation Therapy With an Incorporated Boost

    SciTech Connect

    Freedman, Gary M. . E-mail: Gary.Freedman@FCCC.edu; Anderson, Penny R.; Goldstein, Lori J.; Ma Changming; Li Jinsheng; Swaby, Ramona F.; Litwin, Samuel; Watkins-Bruner, Deborah; Sigurdson, Elin R.; Morrow, Monica

    2007-06-01

    Purpose: Standard radiation for early breast cancer requires daily treatment for 6 to 7 weeks. This is an inconvenience to many women, and for some a barrier for breast conservation. We present the acute toxicity of a 4-week course of hypofractionated radiation. Methods and Materials: A total of 75 patients completed radiation on a Phase II trial approved by the hospital institutional review board. Eligibility criteria were broad to include any patient normally eligible for standard radiation: age {>=}18 years, invasive or in situ cancer, American Joint Committee on Cancer Stage 0 to II, breast-conserving surgery, and any systemic therapy not given concurrently. The median age was 52 years (range, 31-81 years). Of the patients, 15% had ductal carcinoma in situ, 67% T1, and 19% T2; 71% were N0, 17% N1, and 12% NX. Chemotherapy was given before radiation in 44%. Using photon intensity-modulated radiation therapy and incorporated electron beam boost, the whole breast received 45 Gy and the lumpectomy bed 56 Gy in 20 treatments over 4 weeks. Results: The maximum acute skin toxicity by the end of treatment was Grade 0 in 9 patients (12%), Grade 1 in 49 (65%) and Grade 2 in 17 (23%). There was no Grade 3 or higher skin toxicity. After radiation, all Grade 2 toxicity had resolved by 6 weeks. Hematologic toxicity was Grade 0 in most patients except for Grade 1 neutropenia in 2 patients, and Grade 1 anemia in 11 patients. There were no significant differences in baseline vs. 6-week posttreatment patient-reported or physician-reported cosmetic scores. Conclusions: This 4-week course of postoperative radiation using intensity-modulated radiation therapy is feasible and is associated with acceptable acute skin toxicity and quality of life. Long-term follow-up data are needed. This radiation schedule may represent an alternative both to longer 6-week to 7-week standard whole-breast radiation and more radically shortened 1-week, partial-breast treatment schedules.

  11. Initial Experience With Volumetric IMRT (RapidArc) for Intracranial Stereotactic Radiosurgery

    SciTech Connect

    Mayo, Charles S.; Ding, Linda; Addesa, Anthony; Kadish, Sidney; Fitzgerald, T.J.; Moser, Richard

    2010-12-01

    Purpose: Initial experience with delivering frameless stereotactic radiotherapy (SRT) using volumetric intensity-modulated radiation therapy (IMRT) delivered with RapidArc is presented. Methods and Materials: Treatment details for 12 patients (14 targets) with a mean clinical target volume (CTV) of 12.8 {+-} 4.0 cm{sup 3} were examined. Dosimetric indices for conformality, homogeneity, and dose gradient were calculated and compared with published results for other frameless, intracranial SRT techniques, including CyberKnife, TomoTherapy, and static-beam IMRT. Statistics on setup and treatment times and per patient dose validations were examined. Results: Dose indices compared favorably with other techniques. Mean conformality, gradient, and homogeneity index values were 1.10 {+-} 0.11, 64.9 {+-} 14.1, 1.083 {+-} 0.026, respectively. Median treatment times were 4.8 {+-} 1.7 min. Conclusion: SRT using volumetric IMRT is a viable alternative to other techniques and enables short treatment times. This is anticipated to have a positive impact on radiobiological effect and for facilitating wider use of SRT.

  12. Reconfigurable intensity modulation and direct detection optical transceivers for variable-rate wavelength-division-multiplexing passive optical networks utilizing digital signal processing-based symbol mapper

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiguo; Zhang, Bingbing; Chen, Yanxu; Chen, Xue

    2017-01-01

    Variable-rate intensity modulation and direct detection-based optical transceivers with software-controllable reconfigurability and transmission performance adaptability are experimentally demonstrated, utilizing M-QAM symbol mapping implemented in MATLAB® programs. A frequency division multiplexing-based symbol demapping and wavelength management method is proposed for the symbol demapper and tunable laser management used in colorless optical network unit.

  13. Assessment of the acceptability of the Elekta multileaf collimator (MLC) within the Corvus planning system for static and dynamic delivery of intensity modulated beams (IMBs).

    PubMed

    Linthout, Nadine; Verellen, Dirk; Van Acker, Swana; Van de Vondel, Iwein; Coppens, Luc; Storme, Guy

    2002-04-01

    The sliding window technique used for static and dynamic segmentation of intensity modulated beams is evaluated. Dynamic delivery is preferred since the resulting distributions correspond better with the calculated distributions, the treatment beam is used more efficiently and the delivery is less sensitive to small variations in the accuracy of the multileaf collimator (MLC).

  14. Mixing intensity modulated electron and photon beams: combining a steep dose fall-off at depth with sharp and depth-independent penumbras and flat beam profiles.

    PubMed

    Korevaar, E W; Heijmen, B J; Woudstra, E; Huizenga, H; Brahme, A

    1999-09-01

    For application in radiotherapy, intensity modulated high-energy electron and photon beams were mixed to create dose distributions that feature: (a) a steep dose fall-off at larger depths, similar to pure electron beams, (b) flat beam profiles and sharp and depth-independent beam penumbras, as in photon beams, and (c) a selectable skin dose that is lower than for pure electron beams. To determine the required electron and photon beam fluence profiles, an inverse treatment planning algorithm was used. Mixed beams were realized at a MM50 racetrack microtron (Scanditronix Medical AB, Sweden), and evaluated by the dose distributions measured in a water phantom. The multileaf collimator of the MM50 was used in a static mode to shape overlapping electron beam segments, and the dynamic multileaf collimation mode was used to realize the intensity modulated photon beam profiles. Examples of mixed beams were generated at electron energies of up to 40 MeV. The intensity modulated electron beam component consists of two overlapping concentric fields with optimized field sizes, yielding broad, fairly depth-independent overall beam penumbras. The matched intensity modulated photon beam component has high fluence peaks at the field edges to sharpen this penumbra. The combination of the electron and the photon beams yields dose distributions with the characteristics (a)-(c) mentioned above.

  15. A case study of radiotherapy planning for Intensity Modulation Radiation Therapy for the whole scalp with matching electron treatment

    SciTech Connect

    Sponseller, Patricia; Paravathaneni, Upendra

    2013-07-01

    The purpose of this report is to communicate a technique to match an electron field to the dose distribution of an Intensity-Modulated Radiation Therapy (IMRT) plan. A patient with multiple areas of squamous cell carcinoma over the scalp was treated using 60 Gy in 2.0-Gy fractions to the entire scalp and first echelon nodes with multiple 6-MV photon fields. To deliver an adequate dose to the scalp, a custom 1.0-cm bolus helmet was fashioned using a solid piece of aquaplast. Along with the IMRT scalp treatment, a left zygoma area was treated with electrons matching the anterior border of the IMRT dose distribution. The border was matched by creating a left lateral field with the multileaf collimator shaped to the IMRT dose distribution. The result indicated an adequate dose to the skin match between the IMRT plan and the electron field. Results were confirmed using optically stimulated luminescence placed at the skin match area, so that the dose matched the prescription within 10%.

  16. SU-E-T-07: 4DCT Robust Optimization for Esophageal Cancer Using Intensity Modulated Proton Therapy

    SciTech Connect

    Liao, L; Yu, J; Zhu, X; Li, H; Zhang, X; Li, Y; Lim, G

    2015-06-15

    Purpose: To develop a 4DCT robust optimization method to reduce the dosimetric impact from respiratory motion in intensity modulated proton therapy (IMPT) for esophageal cancer. Methods: Four esophageal cancer patients were selected for this study. The different phases of CT from a set of 4DCT were incorporated into the worst-case dose distribution robust optimization algorithm. 4DCT robust treatment plans were designed and compared with the conventional non-robust plans. Result doses were calculated on the average and maximum inhale/exhale phases of 4DCT. Dose volume histogram (DVH) band graphic and ΔD95%, ΔD98%, ΔD5%, ΔD2% of CTV between different phases were used to evaluate the robustness of the plans. Results: Compare to the IMPT plans optimized using conventional methods, the 4DCT robust IMPT plans can achieve the same quality in nominal cases, while yield a better robustness to breathing motion. The mean ΔD95%, ΔD98%, ΔD5% and ΔD2% of CTV are 6%, 3.2%, 0.9% and 1% for the robustly optimized plans vs. 16.2%, 11.8%, 1.6% and 3.3% from the conventional non-robust plans. Conclusion: A 4DCT robust optimization method was proposed for esophageal cancer using IMPT. We demonstrate that the 4DCT robust optimization can mitigate the dose deviation caused by the diaphragm motion.

  17. Obtaining Normal Tissue Constraints Using Intensity Modulated Radiotherapy (IMRT) in Patients with Oral Cavity, Oropharnygeal, and Laryngeal Carcinoma

    SciTech Connect

    Skinner, William K.J.

    2009-01-01

    The purpose of this study was to evaluate normal tissue dose constraints while maintaining planning target volume (PTV) prescription without reducing PTV margins. Sixteen patients with oral cavity carcinoma (group I), 27 patients with oropharyngeal carcinoma (group II), and 28 patients with laryngeal carcinoma (group III) were reviewed. Parotid constraints were a mean dose to either parotid < 26 Gy (PP1), 50% of either parotid < 30 Gy (PP2), or 20 cc of total parotid < 20 Gy (PP3). Treatment was intensity modulated radiation therapy (IMRT) with simultaneous integrated boost (SIB). All patients met constraints for cord and brain stem. The mandibular constraints were met in 66%, 29%, and 57% of patients with oral, oropharyngeal, and laryngeal cancers, respectively. Mean dose of 26 Gy (PP1) was achieved in 44%, 41%, and 38% of oral, oropharyngeal, and laryngeal patients. PP2 (parotid constraint of 30 Gy to less than 50% of one parotid) was the easiest to achieve (group I, II, and III: 82%, 76%, and 78%, respectively). PP3 (20 cc of total parotid < 20 Gy) was difficult, and was achieved in 25%, 17%, and 35% of oral, oropharyngeal, and laryngeal patients, respectively. Mean parotid dose of 26 Gy was met 40% of the time. However, a combination of constraints allowed for sparing of the parotid based on different criteria and was met in high numbers. This was accomplished without reducing PTV-parotid overlap. What dose constraint best correlates with subjective and objective functional outcomes remains a focus for future study.

  18. Vicious circle of acute radiation toxicities and weight loss predicts poor prognosis for nasopharyngeal carcinoma patients receiving intensity modulated radiotherapy

    PubMed Central

    Li, Guo; Jiang, Xiong-ying; Qiu, Bo; Shen, Lu-Jun; Chen, Chen; Xia, Yun-Fei

    2017-01-01

    Background: Weight loss during radiotherapy has been known as a negative prognostic factor for nasopharyngeal carcinoma (NPC) patients, but the factors related to weight loss during radiotherapy were not fully understood. Methods: A total of 322 newly diagnosed NPC patients receiving intensity modulated radiotherapy (IMRT) in Sun Yat-sen University Cancer Center between June 2002 and August 2006 were enrolled. Kaplan-Meier methods and log-rank test were applied for survival analysis; a multiple regression was used to identify the factors related to weight loss during radiotherapy. Results: The mean and median values of weight loss (%) during radiotherapy were 6.85% and 6.70%. NPC patients with critical weight loss (> 5.4%) have poorer overall survival (OS) and distant metastasis-free survival (DMFS) than the patients without critical weight loss (p = 0.002 and 0.021, respectively). Pre-radiotherapy weight, acute mucosal toxicity, acute pharynx and esophagus toxicity, and acute upper gastrointestinal toxicity were related to the weight loss during radiotherapy independently (p = 0.01, p < 0.001, p < 0.001, and p = 0.009, respectively). Conclusions: Acute radiation toxicities had significant and independent impact on weight loss during radiotherapy. The vicious circle of acute radiation toxicities and weight loss had bad effect on prognosis of NPC patients. PMID:28382146

  19. Stimulus intensity affects early sensory processing: sound intensity modulates auditory evoked gamma-band activity in human EEG.

    PubMed

    Schadow, Jeanette; Lenz, Daniel; Thaerig, Stefanie; Busch, Niko A; Fründ, Ingo; Herrmann, Christoph S

    2007-08-01

    We studied the effect of different sound intensities on the auditory evoked gamma-band response (GBR). Previous studies observed oscillatory gamma activity in the auditory cortex of animals and humans. For the visual modality, it has been demonstrated that the GBR can be modulated by top-down (attention, memory) as well as bottom-up factors (stimulus properties). Therefore, we expected to find a sound intensity modulation for the auditory GBR. 21 healthy participants without hearing deficits were investigated in a forced-choice discrimination task. Sinusoidal tones were presented at three systematically varied sound intensities (30, 45, 60 dB hearing level). The results of the auditory evoked potentials were predominantly consistent with previous studies. Furthermore, we observed an augmentation of the evoked GBR with increasing sound intensity. The analysis indicated that this intensity difference in the GBR amplitude most likely arises from increased phase-locking. The results demonstrate a distinct dependency between sound intensity and gamma-band oscillations. Future experiments that investigate the relationship between auditory evoked GBRs and higher cognitive processes should therefore select stimuli with an adequate sound intensity and control this variable to avoid confounding effects. In addition, it seems that gamma-band activity is more sensitive to exogenous stimulus parameters than evoked potentials.

  20. [Intensity modulated radiotherapy for head and neck cancer, dose constraint for normal tissue: Cochlea vestibular apparatus and brainstem].

    PubMed

    Guimas, V; Thariat, J; Graff-Cailleau, P; Boisselier, P; Pointreau, Y; Pommier, P; Montbarbon, X; Laude, C; Racadot, S

    2016-10-01

    Modern techniques such as intensity modulated radiation therapy (IMRT) have been proven to significantly decrease the dose delivered to the cochleovestibular apparatus, limiting consecutive toxicity especially for sensorineural hearing loss. However, recent data still report a 42% rate of radio-induced hypoacusia underscoring the need to protect the cochleovestibular apparatus. Due to the small size of the cochlea, a precise dose-volume analysis could not be performed, and recommendations only refer to the mean dose. Confusing factors such as age, concomitant chemotherapy, primary site and tumor stage should be taken into account at the time of treatment planning. (Non-coplanar) VMAT and tomotherapy have been proven better at sparing the cochlea in comparison with 3D CRT. Brainstem radio-induced injuries were poorly studied because of their infrequency and the difficulty of distinguishing between necrosis and tumor progression in the case of a primary tumor located at the base of skull. The following toxicities have been described: brainstem focal radionecrosis, cognitive disorders without dementia, cranial nerve injuries and sensori motor disability. Maximal dose to the brainstem should be kept to < 54Gy for conventional fractionation. This dose could be exceeded (no more than 10mL should receive more than 59Gy), provided this hot spot is located in the peripheral area of the organ.

  1. Carcinoma of the anal canal: Intensity modulated radiation therapy (IMRT) versus three-dimensional conformal radiation therapy (3DCRT)

    SciTech Connect

    Sale, Charlotte; Moloney, Phillip; Mathlum, Maitham

    2013-12-15

    Patients with anal canal carcinoma treated with standard conformal radiotherapy frequently experience severe acute and late toxicity reactions to the treatment area. Roohipour et al. (Dis Colon Rectum 2008; 51: 147–53) stated a patient's tolerance of chemoradiation to be an important prediction of treatment success. A new intensity modulated radiation therapy (IMRT) technique for anal carcinoma cases has been developed at the Andrew Love Cancer Centre aimed at reducing radiation to surrounding healthy tissue. A same-subject repeated measures design was used for this study, where five anal carcinoma cases at the Andrew Love Cancer Centre were selected. Conformal and IMRT plans were generated and dosimetric evaluations were performed. Each plan was prescribed a total of 54 Gray (Gy) over a course of 30 fractions to the primary site. The IMRT plans resulted in improved dosimetry to the planning target volume (PTV) and reduction in radiation to the critical structures (bladder, external genitalia and femoral heads). Statistically there was no difference between the IMRT and conformal plans in the dose to the small and large bowel; however, the bowel IMRT dose–volume histogram (DVH) doses were consistently lower. The IMRT plans were superior to the conformal plans with improved dose conformity and reduced radiation to the surrounding healthy tissue. Anecdotally it was found that patients tolerated the IMRT treatment better than the three-dimensional (3D) conformal radiation therapy. This study describes and compares the planning techniques.

  2. Can Intensity-Modulated Radiotherapy Preserve Oral Health-Related Quality of Life of Nasopharyngeal Carcinoma Patients?

    SciTech Connect

    Pow, Edmond H.N.; Kwong, Dora L.W.; Sham, Jonathan S.T.; Lee, Victor H.F.; Ng, Sherry C.Y.

    2012-06-01

    Purpose: To investigate the changes in salivary function and oral health-related quality of life for patients with nasopharyngeal carcinoma treated by intensity-modulated radiotherapy (IMRT). Methods and Materials: A total of 57 patients with early-stage nasopharyngeal carcinoma received IMRT. The parotid and whole saliva flow was measured, and the Medical Outcomes Study 36-item short form, European Organization for Research and Treatment of Cancer Quality of Life questionnaire-C30, European Organization for Research and Treatment of Cancer Quality of Life questionnaire 35-item head-and-neck module, and Oral Health Impact Profile questionnaires were completed at baseline and 2, 6, 12, 18, and 24 months after IMRT. Results: Parotid saliva flow recovered fully after 1 year and maintained. Whole saliva flow recovered partially to 40% of baseline. A general trend of deterioration in most quality of life scales was observed after IMRT, followed by gradual recovery. Persistent oral-related symptoms were found 2 years after treatment. Conclusion: IMRT for early-stage nasopharyngeal carcinoma could only partially preserve the whole salivary function and oral health-related quality of life.

  3. Efficacy of Concurrent Chemotherapy for Intermediate Risk NPC in the Intensity-Modulated Radiotherapy Era: a Propensity-Matched Analysis

    PubMed Central

    Zhang, Fan; Zhang, Yuan; Li, Wen-Fei; Liu, Xu; Guo, Rui; Sun, Ying; Lin, Ai-Hua; Chen, Lei; Ma, Jun

    2015-01-01

    This study is to evaluate the efficacy of additional concurrent chemotherapy for intermediate risk (stage II and T3N0M0) NPC patients treated with intensity-modulated radiotherapy (IMRT).440 patients with intermediate risk NPC were studied retrospectively, including 128 patients treated with IMRT alone [radiotherapy group (RT group)] and 312 paitents treated with IMRT plus concurrent chemotherapy [chemoradiotherapy group (CRT group)]. Propensity score matching was carried out to create RT and CRT cohorts equally matched for host and tumor factor. Significantly more severe acute toxicities were observed in the CRT group than in the RT group. Multivariate analyses of 440 patients failed to demonstrate concurrent chemotherapy as an independent prognostic factor for FFS, LR-FFS, and D-FFS. Between the well-matched RT cohort and the CRT cohort, no significant difference was demonstrated in all survival endpoints (FFS: 92.8% versus 91.2%, P = 0.801; LR-FFS: 95.2% versus 94.4%, P = 0.755; D-FFS: 96.4% versus 96.3%, P = 0.803; OS: 98.2% versus 98.9%, P = 0.276). Our results demonstrated that for patients with intermediate risk NPC treated with IMRT, additional concurrent chemotherapy did not provide any significant survival benefit but significantly more severe acute toxicities. However, prospective randomized trials are warranted for the ultimate confirm of our findings. PMID:26611462

  4. SU-E-T-17: A Comparison of Forward and Field in Field Intensity Modulation Radiotherapy Planning for Breast Cancer

    SciTech Connect

    Liu, T; Sun, T; Chen, J; Zhang, G

    2015-06-15

    Purpose: To compare the dosimetric difference in forward intensity modulation radiotherapy(fIMRT) and field in field IMRT (FIF IMRT)planning for breast cancer. Methods: Ten patients received radiotherapy are selected.For each patient,two treatment plans(fIMRT and FIF IMRT) were designed with Varian Eclipse ver11.0 treatment planning system.Evaluate the dose parameters of targets, organs at risk (OAR), monitor units and treatment time, using dose-volume histogram (DVH). Results: There were no significant difference were found in conformal index (CI), homogeneity index (HI) of PTV,V5,V10,V20,V30,V40,V50 of heart, lung and monitor unit(MU)(P>0.05).The differences were significant in the treatment time(fIMRT=8.3min,FIF IMRT=2.5,p<0.05). Conclusion: FIF IMRT is equal to fIMRT in dosimetril evaluation. Due to much less delivery time,FIF IMRT is an efficient technique in treating patients by reduceing the uncomfortable influnce which could effect the treatment.

  5. Dose reconstruction for intensity-modulated radiation therapy using a non-iterative method and portal dose image

    NASA Astrophysics Data System (ADS)

    Yeo, Inhwan Jason; Jung, Jae Won; Chew, Meng; Kim, Jong Oh; Wang, Brian; Di Biase, Steven; Zhu, Yunping; Lee, Dohyung

    2009-09-01

    A straightforward and accurate method was developed to verify the delivery of intensity-modulated radiation therapy (IMRT) and to reconstruct the dose in a patient. The method is based on a computational algorithm that linearly describes the physical relationship between beamlets and dose-scoring voxels in a patient and the dose image from an electronic portal imaging device (EPID). The relationship is expressed in the form of dose response functions (responses) that are quantified using Monte Carlo (MC) particle transport techniques. From the dose information measured by the EPID the received patient dose is reconstructed by inversely solving the algorithm. The unique and novel non-iterative feature of this algorithm sets it apart from many existing dose reconstruction methods in the literature. This study presents the algorithm in detail and validates it experimentally for open and IMRT fields. Responses were first calculated for each beamlet of the selected fields by MC simulation. In-phantom and exit film dosimetry were performed on a flat phantom. Using the calculated responses and the algorithm, the exit film dose was used to inversely reconstruct the in-phantom dose, which was then compared with the measured in-phantom dose. The dose comparison in the phantom for all irradiated fields showed a pass rate of higher than 90% dose points given the criteria of dose difference of 3% and distance to agreement of 3 mm.

  6. Dose distribution analysis of physical and dynamic wedges by using an intensity-modulated radiotherapy MatriXX

    NASA Astrophysics Data System (ADS)

    Lee, Hae-Kag; Cho, Jae-Hwan; Cho, Dae-chul

    2013-05-01

    This study investigated differences between the physical wedge and the dynamic wedge distributions of radiation by using an intensity-modulated radiotherapy (ImRT) MatriXX. The linear accelerator used X-rays with energy levels of 6 MV and 10 MV to adjust the collimator by motoring the independent jaws (X1, X2, Y1, Y2) for setting wedge angles of 15, 30, 45, and 60 degrees. The collimator field size was set as 10 × 10 cm2 or 20 × 20 cm2 at the maximum dose point. The dose distribution for each wedge had ±5% and ±11% errors for field sizes of 10 × 10 cm2 and 20 × 20 cm2, respectively. The error was greatest at a wedge angle of 45 degrees and was pronounced at the end of the dynamic wedge where Y1 and Y2 met. Consequently, concluded that the dose distributions were similar for both wedges for the field size of a small beam profile. The beam dose was greatly increased at the end of the dynamic wedge. A more precise estimate of the therapeutic dose of radiation for a dynamic wedge that nearly matches that of the physical wedge can be achieved by correcting of the increasing part of the beam dose. The findings imply that a heavy wedge filter should not be used when calculating the isodose distribution and the therapeutic dose.

  7. Intensity-Modulated Continuous-Wave Lidar at 1.57 Micrometer for Atmospheric CO2 Measurements

    NASA Technical Reports Server (NTRS)

    Lin, Bing; Ismail, Syed; Browell, Edward; Meadows, Byron; Nehrir, Amin; Harrison, Wallace F.; Dobler, Jeremy; Obland, Michael

    2014-01-01

    Understanding the earth's carbon cycle is essential for diagnosing current and predicting future climates, which requires precise global measurements of atmospheric CO2 through space missions. The Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission will provide accurate global atmospheric CO2 measurements to meet carbon science requirements. The joint team of NASA Langley Research Center and ITT Exelis, Inc proposes to use the intensity-modulated, continuous-wave (IM-CW) lidar approach for the ASCENDS mission. Prototype instruments have been developed and used to demonstrate the power, signal-to-noise ratio, precision and accuracy, spectral purity, and stability of the measurement and the instrument needed for atmospheric CO2 observations from space. The ranging capability from laser platform to ground surfaces or intermediate backscatter layers is achieved by transmitted range-encoded IM laser signals. Based on the prototype instruments and current lidar technologies, space lidar systems and their CO2 column measurements are analyzed. These studies exhibit a great potential of using IM-CW lidar system for the active space CO2 mission ASCENDS.

  8. Recurrence in Region of Spared Parotid Gland After Definitive Intensity-Modulated Radiotherapy for Head and Neck Cancer

    SciTech Connect

    Cannon, Donald M.; Lee, Nancy Y.

    2008-03-01

    Purpose: To discuss the implications of three examples of periparotid recurrence after definitive intensity-modulated radiotherapy (IMRT) for head and neck cancer (HNC). Methods and Materials: We present 3 patients with HNC who underwent definitive IMRT with concurrent chemotherapy and later had treatment failure in or near a spared parotid gland. Two patients had bilateral multilevel nodal disease, and all had Level II nodal disease ipsilateral to the site of recurrence. The patients were treated using dose-painting IMRT with a dose of 70 Gy to the gross tumor volume and 59.4 Gy or 54 Gy to the high-risk or low-risk clinical tumor volume, respectively. The parotid glands were spared bilaterally. The patients had not undergone any surgical treatment for HNC before radiotherapy. Results: All patients had treatment failure in the region of a spared parotid gland. Failure in the 2 patients with bilateral multilevel nodal involvement occurred in the periparotid lymph nodes. The third patient developed a dermal metastasis near the tail of a spared parotid gland. On pretreatment imaging, the 2 patients with nodal failure had small nonspecific periparotid nodules that showed no hypermetabolic activity on positron emission tomography. Conclusion: For HNC patients receiving definitive IMRT, nonspecific positron emission tomography-negative periparotid nodules on pretreatment imaging should raise the index of suspicion for subclinical disease in the presence of multilevel or Level II nodal metastases. Additional evaluation of such nodules might be indicated before sparing the ipsilateral parotid gland.

  9. Retrospective evaluation of dosimetric quality for prostate carcinomas treated with 3D conformal, intensity modulated and volumetric modulated arc radiotherapy

    SciTech Connect

    Crowe, Scott B; Kairn, Tanya; Middlebrook, Nigel; Hill, Brendan; Christie, David R H; Knight, Richard T; Kenny, John; Langton, Christian M; Trapp, Jamie V

    2013-12-15

    This study examines and compares the dosimetric quality of radiotherapy treatment plans for prostate carcinoma across a cohort of 163 patients treated across five centres: 83 treated with three-dimensional conformal radiotherapy (3DCRT), 33 treated with intensity modulated radiotherapy (IMRT) and 47 treated with volumetric modulated arc therapy (VMAT). Treatment plan quality was evaluated in terms of target dose homogeneity and organs at risk (OAR), through the use of a set of dose metrics. These included the mean, maximum and minimum doses; the homogeneity and conformity indices for the target volumes; and a selection of dose coverage values that were relevant to each OAR. Statistical significance was evaluated using two-tailed Welch's T-tests. The Monte Carlo DICOM ToolKit software was adapted to permit the evaluation of dose metrics from DICOM data exported from a commercial radiotherapy treatment planning system. The 3DCRT treatment plans offered greater planning target volume dose homogeneity than the other two treatment modalities. The IMRT and VMAT plans offered greater dose reduction in the OAR: with increased compliance with recommended OAR dose constraints, compared to conventional 3DCRT treatments. When compared to each other, IMRT and VMAT did not provide significantly different treatment plan quality for like-sized tumour volumes. This study indicates that IMRT and VMAT have provided similar dosimetric quality, which is superior to the dosimetric quality achieved with 3DCRT.

  10. Retrospective evaluation of dosimetric quality for prostate carcinomas treated with 3D conformal, intensity modulated and volumetric modulated arc radiotherapy

    PubMed Central

    Crowe, Scott B; Kairn, Tanya; Middlebrook, Nigel; Hill, Brendan; Christie, David R H; Knight, Richard T; Kenny, John; Langton, Christian M; Trapp, Jamie V

    2013-01-01

    Introduction This study examines and compares the dosimetric quality of radiotherapy treatment plans for prostate carcinoma across a cohort of 163 patients treated across five centres: 83 treated with three-dimensional conformal radiotherapy (3DCRT), 33 treated with intensity modulated radiotherapy (IMRT) and 47 treated with volumetric modulated arc therapy (VMAT). Methods Treatment plan quality was evaluated in terms of target dose homogeneity and organs at risk (OAR), through the use of a set of dose metrics. These included the mean, maximum and minimum doses; the homogeneity and conformity indices for the target volumes; and a selection of dose coverage values that were relevant to each OAR. Statistical significance was evaluated using two-tailed Welch's T-tests. The Monte Carlo DICOM ToolKit software was adapted to permit the evaluation of dose metrics from DICOM data exported from a commercial radiotherapy treatment planning system. Results The 3DCRT treatment plans offered greater planning target volume dose homogeneity than the other two treatment modalities. The IMRT and VMAT plans offered greater dose reduction in the OAR: with increased compliance with recommended OAR dose constraints, compared to conventional 3DCRT treatments. When compared to each other, IMRT and VMAT did not provide significantly different treatment plan quality for like-sized tumour volumes. Conclusions This study indicates that IMRT and VMAT have provided similar dosimetric quality, which is superior to the dosimetric quality achieved with 3DCRT. PMID:26229621

  11. Optimal matching of 3D film-measured and planned doses for intensity-modulated radiation therapy quality assurance.

    PubMed

    Shin, Dongho; Yoon, Myonggeun; Park, Sung Yong; Park, Dong Hyun; Lee, Se Byeong; Kim, Dae Yong; Cho, Kwan Ho

    2007-01-01

    Intensity-modulated radiation therapy (IMRT) is one of the most complex applications of radiotherapy that requires patient-specific quality assurance (QA). Here, we describe a novel method of 3-dimensional (3D) dose-verification using 12 acrylic slabs in a 3D phantom (30 x 30 x 12 cm(3)) with extended dose rate (EDR2) films, which is both faster than conventionally used methods, and clinically useful. With custom-written software modules written in Microsoft Excel Visual Basic Application, the measured and planned dose distributions for the axial, coronal, and sagittal planes were superimposed by matching their origins, and the point doses were compared at all matched positions. Then, an optimization algorithm was used to correct the detected setup errors. The results show that this optimization method significantly reduces the average maximum dose difference by 7.73% and the number of points showing dose differences of more than 5% by 8.82% relative to the dose differences without an optimization. Our results indicate that the dose difference was significantly decreased with optimization and this optimization method is statistically reliable and effective. The results of 3D optimization are discussed in terms of various patient-specific QA data obtained from statistical analyses.

  12. High dose chemoradiation for unresectable hilar cholangiocarcinomas using intensity modulated external beam radiotherapy: a single tertiary care centre experience

    PubMed Central

    Mehta, Shaesta; Kalyani, Nikhil; Chaudhari, Suresh; Dharia, Tejas; Shetty, Nitin; Chopra, Supriya; Goel, Mahesh; Kulkarni, Suyash; Shrivastava, Shyam Kishore

    2017-01-01

    Background We present results of patients diagnosed with unresectable hilar cholangiocarcinomas treated with high dose radiotherapy and concurrent chemotherapy. Methods From Aug 2005 to Dec 2012, 68 consecutive patients were treated. Fifty patients (group 1) presenting to us with obstructive jaundice were planned for endobiliary brachytherapy (EBBT 14 Gy) followed external beam radiotherapy (EBRT 45 Gy). Twenty-two patients (group 2) who had previously undergone biliary drainage underwent EBRT (57 Gy). All patients received injection Gemcitabine 300 mg/m2/weekly along with EBRT. Results Twenty-nine patients in group 1 and 22 patients in group 2 completed the treatment. Twenty-six (55%) patients achieved complete radiological response, 16 (64%) belonging to group 1 and 8 (44%) of group 2 (P=0.05). The median overall survival (MOS) was 17.5 and 16 months for group 1 and 2 respectively (P=0.07). The 1- and 2-year survival was 63%, and 18% for group I and 61% and 22% for group II respectively. The MOS was 5 months and 1 year survival was 14% for patients receiving EBBT only. MOS was significantly better after complete response (P=0.001). Conclusions Intensity modulated radiotherapy (IMRT) modulated high dose radiotherapy used either alone or with brachytherapy demonstrates potential to prolonged overall survival in unresectable hilar cholangiocarcinomas. PMID:28280622

  13. Whole-brain hippocampal sparing radiation therapy: Volume-modulated arc therapy vs intensity-modulated radiation therapy case study

    SciTech Connect

    Lee, Katrina Lenards, Nishele; Holson, Janice

    2016-04-01

    The hippocampus is responsible for memory and cognitive function. An ongoing phase II clinical trial suggests that sparing dose to the hippocampus during whole-brain radiation therapy can help preserve a patient's neurocognitive function. Progressive research and advancements in treatment techniques have made treatment planning more sophisticated but beneficial for patients undergoing treatment. The aim of this study is to evaluate and compare hippocampal sparing whole-brain (HS-WB) radiation therapy treatment planning techniques using volume-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT). We randomly selected 3 patients to compare different treatment techniques that could be used for reducing dose to the hippocampal region. We created 2 treatment plans, a VMAT and an IMRT, from each patient's data set and planned on the Eclipse 11.0 treatment planning system (TPS). A total of 6 plans (3 IMRT and 3 VMAT) were created and evaluated for this case study. The physician contoured the hippocampus as per the Radiation Therapy Oncology Group (RTOG) 0933 protocol atlas. The organs at risk (OR) were contoured and evaluated for the plan comparison, which included the spinal cord, optic chiasm, the right and left eyes, lenses, and optic nerves. Both treatment plans produced adequate coverage on the planning target volume (PTV) while significantly reducing dose to the hippocampal region. The VMAT treatment plans produced a more homogenous dose distribution throughout the PTV while decreasing the maximum point dose to the target. However, both treatment techniques demonstrated hippocampal sparing when irradiating the whole brain.

  14. Dosimetric evaluation of a simple planning method for improving intensity-modulated radiotherapy for stage III lung cancer

    PubMed Central

    Lu, Jia-Yang; Lin, Zhu; Zheng, Jing; Lin, Pei-Xian; Cheung, Michael Lok-Man; Huang, Bao-Tian

    2016-01-01

    This study aimed to evaluate the dosimetric outcomes of a base-dose-plan-compensation (BDPC) planning method for improving intensity-modulated radiotherapy (IMRT) for stage III lung cancer. For each of the thirteen included patients, three types of planning methods were applied to obtain clinically acceptable plans: (1) the conventional optimization method (CO); (2) a split-target optimization method (STO), in which the optimization objectives were set higher dose for the target with lung density; (3) the BDPC method, which compensated for the optimization-convergence error by further optimization based on the CO plan. The CO, STO and BDPC methods were then compared regarding conformity index (CI), homogeneity index (HI) of the target, organs at risk (OARs) sparing and monitor units (MUs). The BDPC method provided better HI/CI by 54%/7% on average compared to the CO method and by 38%/3% compared to the STO method. The BDPC method also spared most of the OARs by up to 9%. The average MUs of the CO, STO and BDPC plans were 890, 937 and 1023, respectively. Our results indicated that the BDPC method can effectively improve the dose distribution in IMRT for stage III lung cancer, at the expense of more MUs. PMID:27009235

  15. Anatomic and dosimetric changes during the treatment course of intensity-modulated radiotherapy for locally advanced nasopharyngeal carcinoma.

    PubMed

    Wang, Xin; Lu, Jiade; Xiong, Xiaopeng; Zhu, Guopei; Ying, Hongmei; He, Shaoqin; Hu, Weigang; Hu, Chaosu

    2010-01-01

    Many patients with nasopharyngeal carcinoma (NPC) have marked anatomic change during intensity-modulated radiation therapy (IMRT). In this study, the magnitude of anatomic changes and its dosimetric effects were quantified. Fifteen patients with locally advanced NPC treated with IMRT had repeated computed tomography (CT) after 18 fractions. A hybrid plan was made to the anatomy of the second computed tomography scan. The dose of the original plan, hybrid plan, and new plan were compared. The mean volume of left and right parotid decreased 6.19 mL and 6.44 mL, respectively. The transverse diameters of the upper bound of odontoid process, the center of odontoid process, and the center of C2 vertebral body slices contracted with the mean contraction of 8.2 mm, 9.4 mm, and 7.6 mm. Comparing the hybrid plan with the treatment plan, the coverage of target was maintained while the maximum dose to the brain stem and spinal cord increased by 0.08 to 6.51 Gy and 0.05 to 7.8 Gy. The mean dose to left and right parotid increased by 2.97 Gy and 2.57 Gy, respectively. A new plan reduced the dose of spinal cord, brain stem, and parotids. Measurable anatomic changes occurring during the IMRT for locally advanced NPC maintained the coverage of targets but increased the dose to critical organs. Those patients might benefit from replanning.

  16. Intensity-Modulated Continuous-Wave Laser Absorption Spectrometer at 1.57 Micrometer for Atmospheric CO2 Measurements

    NASA Technical Reports Server (NTRS)

    Lin, Bing

    2014-01-01

    Understanding the earth's carbon cycle is essential for diagnosing current and predicting future climates, which requires precise global measurements of atmospheric CO2 through space missions. The Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission will provide accurate global atmospheric CO2 measurements to meet carbon science requirements. The joint team of NASA Langley Research Center and ITT Exelis, Inc. proposes to use the intensity-modulated, continuous-wave (IM-CW) laser absorption spectrometer (LAS) approach for the ASCENDS mission. Prototype LAS instruments have been developed and used to demonstrate the power, signal-to-noise ratio, precision and accuracy, spectral purity, and stability of the measurement and the instrument needed for atmospheric CO2 observations from space. The ranging capability from laser platform to ground surfaces or intermediate backscatter layers is achieved by transmitted range-encoded IM laser signals. Based on the prototype instruments and current lidar technologies, space LAS systems and their CO2 column measurements are analyzed. These studies exhibit a great potential of using IM-CW LAS system for the active space CO2 mission ASCENDS.

  17. Flattening Filter-Free Beams in Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Therapy for Sinonasal Cancer

    PubMed Central

    Huang, Bao-Tian

    2016-01-01

    Purpose To evaluate the dosimetric impacts of flattening filter-free (FFF) beams in intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) for sinonasal cancer. Methods For fourteen cases, IMRT and VMAT planning was performed using 6-MV photon beams with both conventional flattened and FFF modes. The four types of plans were compared in terms of target dose homogeneity and conformity, organ-at-risk (OAR) sparing, number of monitor units (MUs) per fraction, treatment time and pure beam-on time. Results FFF beams led to comparable target dose homogeneity, conformity, increased number of MUs and lower doses to the spinal cord, brainstem and normal tissue, compared with flattened beams in both IMRT and VMAT. FFF beams in IMRT resulted in improvements by up to 5.4% for sparing of the contralateral optic structures, with shortened treatment time by 9.5%. However, FFF beams provided comparable overall OAR sparing and treatment time in VMAT. With FFF mode, VMAT yielded inferior homogeneity and superior conformity compared with IMRT, with comparable overall OAR sparing and significantly shorter treatment time. Conclusions Using FFF beams in IMRT and VMAT is feasible for the treatment of sinonasal cancer. Our results suggest that the delivery mode of FFF beams may play an encouraging role with better sparing of contralateral optic OARs and treatment efficiency in IMRT, but yield comparable results in VMAT. PMID:26734731

  18. A simple optimization approach for improving target dose homogeneity in intensity-modulated radiotherapy for sinonasal cancer

    PubMed Central

    Lu, Jia-Yang; Zhang, Ji-Yong; Li, Mei; Cheung, Michael Lok-Man; Li, Yang-Kang; Zheng, Jing; Huang, Bao-Tian; Zhang, Wu-Zhe

    2015-01-01

    Homogeneous target dose distribution in intensity-modulated radiotherapy (IMRT) for sinonasal cancer (SNC) is challenging to achieve. To solve this problem, we established and evaluated a basal-dose-compensation (BDC) optimization approach, in which the treatment plan is further optimized based on the initial plans. Generally acceptable initial IMRT plans for thirteen patients were created and further optimized individually by (1) the BDC approach and (2) a local-dose-control (LDC) approach, in which the initial plan is further optimized by addressing hot and cold spots. We compared the plan qualities, total planning time and monitor units (MUs) among the initial, BDC, LDC IMRT plans and volumetric modulated arc therapy (VMAT) plans. The BDC approach provided significantly superior dose homogeneity/conformity by 23%–48%/6%–9% compared with both the initial and LDC IMRT plans, as well as reduced doses to the organs at risk (OARs) by up to 18%, with acceptable MU numbers. Compared with VMAT, BDC IMRT yielded superior homogeneity, inferior conformity and comparable overall OAR sparing. The planning of BDC, LDC IMRT and VMAT required 30, 59 and 58 minutes on average, respectively. Our results indicated that the BDC optimization approach can achieve significantly better dose distributions with shorter planning time in the IMRT for SNC. PMID:26497620

  19. Early Outcome of Prostate Intensity Modulated Radiation Therapy (IMRT) Incorporating a Simultaneous Intra-Prostatic MRI Directed Boost

    PubMed Central

    Schild, Michael H; Schild, Steven E; Wong, William W; Vora, Sujay A; Silva, Alvin C; Silva, Annelise M; Daniels, Thomas B; Keole, Sameer R

    2015-01-01

    This study assessed the feasibility and outcomes of treating prostate cancer with intensity modulated radiotherapy (IMRT) incorporating a Magnetic Resonance Imaging (MRI) directed boost. Seventy-eight men received IMRT for localized prostate cancer. The entire prostate received 77.4Gy in 43 fractions and simultaneous intra-prostatic boosts (SIB) of 83Gy were administered to increase the dose to the MRI identified malignancy. In 16 (21%) patients, the MRI didn't detect a neoplasm and these patients received an SIB of 81Gy to the posterior prostate. Androgen Deprivation Therapy (ADT) was also administered to 32 (41%) patients. The 3-year rates of biochemical control, local control, distant control, and survival were 92%, 98%, 95%, and 95% respectively. While grade 1-2 toxicities were common, there were only 2 patients who suffered grade 3 toxicity. These patients developed strictures which were dilated resulting in improvement in symptoms such that both had grade 1-2 toxicity at last follow up examination. The results of this program of IMRT incorporating a MRI directed intra-prostatic boost suggest this technique is feasible and well tolerated. This technique appears to shift the therapeutic index favorably by boosting the malignancy to the highest dose without increasing the doses administered to the bladder and rectum. PMID:25717423

  20. Analysis of measurement deviations for the patient-specific quality assurance using intensity-modulated spot-scanning particle beams

    NASA Astrophysics Data System (ADS)

    Li, Yongqiang; Hsi, Wen C.

    2017-04-01

    To analyze measurement deviations of patient-specific quality assurance (QA) using intensity-modulated spot-scanning particle beams, a commercial radiation dosimeter using 24 pinpoint ionization chambers was utilized. Before the clinical trial, validations of the radiation dosimeter and treatment planning system were conducted. During the clinical trial 165 measurements were performed on 36 enrolled patients. Two or three fields of particle beam were used for each patient. Measurements were typically performed with the dosimeter placed at special regions of dose distribution along depth and lateral profiles. In order to investigate the dosimeter accuracy, repeated measurements with uniform dose irradiations were also carried out. A two-step approach was proposed to analyze 24 sampling points over a 3D treatment volume. The mean value and the standard deviation of each measurement did not exceed 5% for all measurements performed on patients with various diseases. According to the defined intervention thresholds of mean deviation and the distance-to-agreement concept with a Gamma index analysis using criteria of 3.0% and 2 mm, a decision could be made regarding whether the dose distribution was acceptable for the patient. Based measurement results, deviation analysis was carried out. In this study, the dosimeter was used for dose verification and provided a safety guard to assure precise dose delivery of highly modulated particle therapy. Patient-specific QA will be investigated in future clinical operations.

  1. A miniaturized compact open-loop RFOG with demodulation signal compensation technique to suppress intensity modulation noise

    NASA Astrophysics Data System (ADS)

    Ying, Diqing; Mao, Jianmin; Li, Qiang; Jin, Zhonghe

    2016-01-01

    A miniaturized compact open-loop resonator fiber optic gyro (RFOG) prototype with main body size of about 10.4 cm×10.4 cm×5.2 cm is reported, and a demodulation signal compensation technique is proposed, aiming to suppress the drift arising from accompanying intensity modulation induced by semiconductor laser diode (LD). The scheme of how to establish this miniaturized RFOG prototype is specifically stated. The linear relationship between the first-harmonic and second-harmonic demodulated signals respectively for the two counter propagating beams in the resonator is verified by theory and experiment, and based on this relationship, the demodulation signal compensation technique by monitoring the second-harmonic demodulated signal is described in detail. With this compensation technique, the gyro output stability under 1°/s rotation rate is effectively improved from 0.12°/s to 0.03°/s, and especially, an about 0.36°/s peak-to-peak fluctuation due to tuning current reset is significantly suppressed. A long term bias stability of about 4.5°/h in 1 h for such a small-sized RFOG prototype is demonstrated, which is of the same magnitude as that of currently reported large-sized RFOG systems utilizing LD as the laser source as well.

  2. A system for intensity modulated dose plan verification based on an experimental pencil beam kernel obtained by deconvolution.

    PubMed

    Azcona, Juan Diego; Burguete, Javier

    2008-01-01

    The number of intensity modulated radiation therapy (IMRT) procedures is continuously growing worldwide and it is necessary to develop tools for patient specific quality assurance (QA) that avoid using machine time that could be employed in treating additional patients. One way of achieving this goal is to perform a multileaf collimator quality assurance periodically in the linear accelerator and check the treatment planning system (TPS) calculation by employing an independent calculation system. Within the work frame of the pencil beam kernel approach, a new system was developed for obtaining an experimental kernel. This new technique is based on a deconvolution procedure using the Hankel transform. The resulting kernel is obtained in a way completely independent of those employed in commercial treatment planning systems, usually calculated by Monte Carlo simulations. Also provided are comparisons between calculated and measured doses with radiographic film, linear array of diodes, and ionization chamber. Measurements taken in polystyrene and water for clinical IMRT plans demonstrate that this method can calculate IMRT dose distributions, as well as treatment times, with great accuracy. Apart from other applications, it can be used as a double-check algorithm for IMRT QA.

  3. Intensity-modulated radiation therapy for early-stage breast cancer: is it ready for prime time?

    PubMed Central

    Chan, Tabitha Y; Tan, Poh Wee; Tang, Johann I

    2017-01-01

    Whole breast external beam radiotherapy (WBEBRT) is commonly used as an essential arm in the treatment management of women with early-stage breast cancer. Dosimetry planning for conventional WBEBRT typically involves a pair of tangential fields. Advancement in radiation technology and techniques has the potential to improve treatment outcomes with clinically meaningful long-term benefits. However, this advancement must be balanced with safety and improved efficacy. Intensity-modulated radiation therapy (IMRT) is an advanced technique that shows promise in improving the planning process and radiation delivery. Early data on utilizing IMRT for WBEBRT demonstrate more homogenous dose distribution with reduction in organs at risk doses. This translates to toxicities reduction. The two common descriptors for IMRT are forward-planning “fields in field” and inverse planning. Unlike IMRT for other organs, the aim of IMRT for breast planning is to achieve dose homogeneity and not organ conformality. The aim of this paper was to evaluate whether IMRT is ready for prime time based on these three points: 1) workload impact, 2) the clinical impact on the patient’s quality of life, and 3) the appropriateness and applicability to clinical practice. PMID:28360536

  4. Aspiration pneumonia after chemo–intensity-modulated radiation therapy of oropharyngeal carcinoma and its clinical and dysphagia-related predictors

    PubMed Central

    Hunter, Klaudia U.; Lee, Oliver E.; Lyden, Teresa H.; Haxer, Marc J.; Feng, Felix Y.; Schipper, Mathew; Worden, Francis; Prince, Mark E.; McLean, Scott A.; Wolf, Gregory T.; Bradford, Carol R.; Chepeha, Douglas B.; Eisbruch, Avraham

    2014-01-01

    Background The purpose of this study was to assess aspiration pneumonia (AsPn) rates and predictors after chemo-irradiation for head and neck cancer. Methods The was a prospective study of 72 patients with stage III to IV oropharyngeal cancer treated definitively with intensity-modulated radiotherapy (IMRT) concurrent with weekly carboplatin and paclitaxel. AsPn was recorded prospectively and dysphagia was evaluated longitudinally through 2 years posttherapy by observer-rated (Common Toxicity Criteria version [CTCAE]) scores, patient-reported scores, and videofluoroscopy. Results Sixteen patients (20%) developed AsPn. Predictive factors included T classification (p = .01), aspiration detected on videofluoroscopy (videofluoroscopy-asp; p = .0007), and patient-reported dysphagia (p = .02–.0003), but not observer-rated dysphagia (p = .4). Combining T classification, patient reported dysphagia, and videofluoroscopy-asp, provided the best predictive model. Conclusion AsPn continues to be an under-reported consequence of chemo-irradiation for head and neck cancer. These data support using patient-reported dysphagia to identify high-risk patients requiring videofluoroscopy evaluation for preventive measures. Reducing videofluoroscopy-asp rates, by reducing swallowing structures radiation doses and by trials reducing treatment intensity in patients predicted to do well, are likely to reduce AsPn rates. PMID:23729173

  5. Prognostic Value of Subclassification Using MRI in the T4 Classification Nasopharyngeal Carcinoma Intensity-Modulated Radiotherapy Treatment

    SciTech Connect

    Chen Lei; Liu Lizhi; Chen Mo; Li Wenfei; Yin Wenjing; Lin Aihua; Sun Ying; Li Li; Ma Jun

    2012-09-01

    Purpose: To subclassify patients with the T4 classification nasopharyngeal carcinoma (NPC), according to the seventh edition of the American Joint Committee on Cancer staging system, using magnetic resonance imaging (MRI), and to evaluate the prognostic value of subclassification after intensity-modulated radiotherapy (IMRT). Methods and Materials: A total of 140 patients who underwent MRI and were subsequently histologically diagnosed with nondisseminated classification T4 NPC received IMRT as their primary treatment and were included in this retrospective study. T4 patients were subclassified into two grades: T4a was defined as a primary nasopharyngeal tumor with involvement of the masticator space only; and T4b was defined as involvement of the intracranial region, cranial nerves, and/or orbit. Results: The 5-year overall survival (OS) rate and distant metastasis-free survival (DMFS) rate for T4a patients (82.5% and 87.0%, respectively), were significantly higher than for T4b patients (62.6% and 66.8%; p = 0.033 and p = 0.036, respectively). The T4a/b subclassification was an independent prognostic factor for OS (hazard ratio = 2.331, p = 0.032) and DMFS (hazard ratio = 2.602, p = 0.034), and had no significant effect on local relapse-free survival. Conclusions: Subclassification of T4 patients, as T4a or T4b, using MRI according to the site of invasion, has prognostic value for the outcomes of IMRT treatment in NPC.

  6. Anatomic and Dosimetric Changes During the Treatment Course of Intensity-Modulated Radiotherapy for Locally Advanced Nasopharyngeal Carcinoma

    SciTech Connect

    Wang Xin; Lu Jiade; Xiong Xiaopeng; Zhu Guopei; Ying Hongmei; He Shaoqin; Hu Weigang; Hu Chaosu

    2010-07-01

    Many patients with nasopharyngeal carcinoma (NPC) have marked anatomic change during intensity-modulated radiation therapy (IMRT). In this study, the magnitude of anatomic changes and its dosimetric effects were quantified. Fifteen patients with locally advanced NPC treated with IMRT had repeated computed tomography (CT) after 18 fractions. A hybrid plan was made to the anatomy of the second computed tomography scan. The dose of the original plan, hybrid plan, and new plan were compared. The mean volume of left and right parotid decreased 6.19 mL and 6.44 mL, respectively. The transverse diameters of the upper bound of odontoid process, the center of odontoid process, and the center of C2 vertebral body slices contracted with the mean contraction of 8.2 mm, 9.4 mm, and 7.6 mm. Comparing the hybrid plan with the treatment plan, the coverage of target was maintained while the maximum dose to the brain stem and spinal cord increased by 0.08 to 6.51 Gy and 0.05 to 7.8 Gy. The mean dose to left and right parotid increased by 2.97 Gy and 2.57 Gy, respectively. A new plan reduced the dose of spinal cord, brain stem, and parotids. Measurable anatomic changes occurring during the IMRT for locally advanced NPC maintained the coverage of targets but increased the dose to critical organs. Those patients might benefit from replanning.

  7. Comparison of intensity-modulated radiotherapy with three-dimensional conformal radiation therapy planning for glioblastoma multiforme

    SciTech Connect

    Chan, Maria F.; Schupak, Karen; Burman, Chandra; Chui, C.-S.; Ling, C. Clifton

    2003-12-31

    This study was designed to assess the feasibility and potential benefit of using intensity-modulated radiotherapy (IMRT) planning for patients newly diagnosed with glioblastoma multiforme (GBM). Five consecutive patients with confirmed histopathologically GBM were entered into the study. These patients were planned and treated with 3-dimensional conformal radiation therapy (3DCRT) using our standard plan of 3 noncoplanar wedged fields. They were then replanned with the IMRT method that included a simultaneous boost to the gross tumor volume (GTV). The dose distributions and dose-volume histograms (DHVs) for the planning treatment volume (PTV), GTV, and the relevant critical structures, as obtained with 3DCRT and IMRT, respectively, were compared. In both the 3DCRT and IMRT plans, 59.4 Gy was delivered to the GTV plus a margin of 2.5 cm, with doses to critical structures below the tolerance threshold. However, with the simultaneous boost in IMRT, a higher tumor dose of {approx}70 Gy could be delivered to the GTV, while still maintaining the uninvolved brain at dose levels of the 3DCRT technique. In addition, our experience indicated that IMRT planning is less labor intensive and time consuming than 3DCRT planning. Our study shows that IMRT planning is feasible and efficient for radiotherapy of GBM. In particular, IMRT can deliver a simultaneous boost to the GTV while better sparing the normal brain and other critical structures.

  8. The radiobiological effect of intra-fraction dose-rate modulation in intensity modulated radiation therapy (IMRT)

    NASA Astrophysics Data System (ADS)

    Bewes, J. M.; Suchowerska, N.; Jackson, M.; Zhang, M.; McKenzie, D. R.

    2008-07-01

    Intensity-modulated radiation therapy (IMRT) achieves optimal dose conformity to the tumor through the use of spatially and temporally modulated radiation fields. In particular, average dose rate and instantaneous dose rate (pulse amplitude) are highly variable within a single IMRT fraction. In this study we isolate these variables and determine their impact on cell survival. Survival was assessed using a clonogenic assay. Two cell lines of differing radiosensitivity were examined: melanoma (MM576) and non-small cell lung cancer (NCI-H460). The survival fraction was observed to be independent of instantaneous dose rate. A statistically significant trend to increased survival was observed as the average dose rate was decreased, for a constant total dose. The results are relevant to IMRT practice, where average treatment times can be significantly extended to allow for movement of the multi-leaf collimator (MLC). Our in vitro study adds to the pool of theoretical evidence for the consequences of protracted treatments. We find that extended delivery times can substantially increase the cell survival. This also suggests that regional variation in the dose-rate history across a tumor, which is inherent to IMRT, will affect radiation dose efficacy.

  9. Proposal of DCS-OFDM-PON upstream transmission with intensity modulator and collective self-coherent detection

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Yang, Heming; Zhao, Difu; Qiu, Kun

    2016-07-01

    We introduce digital coherent superposition (DCS) into optical access network and propose a DCS-OFDM-PON upstream transmission scheme using intensity modulator and collective self-coherent detection. The generated OFDM signal is real based on Hermitian symmetry, which can be used to estimate the common phase error (CPE) by complex conjugate subcarrier pairs without any pilots. In simulation, we transmit an aggregated 40 Gb/s optical OFDM signal from two ONUs. The transmission performance with DCS is slightly better after 25 km transmission without relative transmission time delay. The fiber distance for different ONUs to RN are not same in general and there is relative transmission time delay between ONUs, which causes inter-carrier-interference (ICI) power increasing and degrades the transmission performance. The DCS can mitigate the ICI power and the DCS-OFDM-PON upstream transmission outperforms the conventional OFDM-PON. The CPE estimation is by using two pairs of complex conjugate subcarriers without redundancy. The power variation can be 9 dB in DCS-OFDM-PON, which is enough to tolerate several kilometers fiber length difference between the ONUs.

  10. The Dosimetric Consequences of Intensity Modulated Radiotherapy for Cervix Cancer: The Impact of Organ Motion, Deformation and Tumour Regression

    NASA Astrophysics Data System (ADS)

    Lim, Karen Siah Huey

    Hypothesis: In intensity modulated radiotherapy (IMRT) for cervix cancer, the dose received by the tumour target and surrounding normal tissues is significantly different to that indicated by a single static plan. Rationale: The optimal use of IMRT in cervix cancer requires a greater attention to clinical target volume (CTV) definition and tumour & normal organ motion to assure maximum tumour control with the fewest side effects. Research Aims: 1) Generate consensus CTV contouring guidelines for cervix cancer; 2) Evaluate intra-pelvic tumour and organ dynamics during radiotherapy; 3) Analyze the dose consequences of intra-pelvic organ dynamics on different radiotherapy strategies. Results: Consensus CTV definitions were generated using experts-in-the-field. Substantial changes in tumour volume and organ motion, resulted in significant reductions in accumulated dose to tumour targets and variability in accumulated dose to surrounding normal tissues. Significance: Formalized CTV definitions for cervix cancer is important in ensuring consistent standards of practice. Complex and unpredictable tumour and organ dynamics mandates daily soft-tissue image guidance if IMRT is used. To maximize the benefits of IMRT for cervix cancer, a strategy of adaptation is necessary.

  11. Intensity modulation and direct detection Alamouti polarization-time coding for optical fiber transmission systems with polarization mode dispersion

    NASA Astrophysics Data System (ADS)

    Reza, Ahmed Galib; Rhee, June-Koo Kevin

    2016-07-01

    Alamouti space-time coding is modified in the form of polarization-time coding to combat against polarization mode dispersion (PMD) impairments in exploiting a polarization diversity multiplex (PDM) gain with simple intensity modulation and direct detection (IM/DD) in optical transmission systems. A theoretical model for the proposed IM/DD Alamouti polarization-time coding (APTC-IM/DD) using nonreturn-to-zero on-off keying signal can surprisingly eliminate the requirement of channel estimation for decoding in the low PMD regime, when a two-transmitter and two-receiver channel is adopted. Even in the high PMD regime, the proposed APTC-IM/DD still reveals coding gain demonstrating the robustness of APTC-IM/DD. In addition, this scheme can eliminate the requirements for a polarization state controller, a coherent receiver, and a high-speed analog-to-digital converter at a receiver. Simulation results reveal that the proposed APTC scheme is able to reduce the optical signal-to-noise ratio requirement by ˜3 dB and significantly enhance the PMD tolerance of a PDM-based IM/DD system.

  12. Phase II study to assess the efficacy of conventionally fractionated radiotherapy followed by a