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modulated arc therapy (VMAT) vs. serial tomotherapy, step-and-shoot IMRT and 3D-conformal RT for treatment of prostate cancer. Radiother Oncol 2009; 93: 226-33. 12. Wu QJ, Yoo S, Kirkpatrick JP, Thongphiew D, Yin FF. Volumetric arc intensity–modulated therapy for spine body radiotherapy: comparison with static intensity-modulated treatment. Int J Radiat Oncol 2009; 75: 1596-604. 13. Clivio A, Fogliata A, Franzetti-Pellanda A, Nicolini G, Vanetti E, Wyttenbach R, et al. Volumetric-modulated arc radiotherapy for carcinomas of the anal canal: A treatment planning

Introduction Volumetric modulated arc therapy (VMAT) demands high level of precision and reliability from the linear accelerator (LINAC) control system because the gantry rotation is synchronized with multi-leaf collimator (MLC) movement for accurate dose delivery. 1 , 2 Highly modulated dose distribution commonly requires MLC leaves of high speed moving along the whole arc. 3 – 5 However, fast leaf motion during gantry rotation may be affected by interleaf friction or MLC motor problems that result in leaf position errors. 6 Wijesooriya et al and Ling et al

References [1] Verbakel WF, Cuijpers J P, Hoffmans D, et al. Volumetric intensity-modulated arc therapy versus conventional IMRT in head-and-neck cancer: a comparative planning and dosimetric study. Int J Radiat Oncol Biol Phys. 2009;74(1):252–259. [2] Wolff D, Stieler F, Welzel G, et al. Volumetric modulated arc therapy (VMAT) versus serial tomotherapy, step-and-shoot IMRT and 3D-conformal RT for treatment of prostate cancer. Radiother Oncol. 2009;93(2):226–233. [3] Otto K. Volumetric modulated arc therapy: IMRT in a single gantry arc. Med Phys. 2008

. Rekonstrukcja rozkładu dawki w technikach dynamicznych: IMRT i VMAT [PhD dissertation]. Katowice: Uniwersytet Śląski; 2013. [15] Osewski W, Dolla Ł, Radwan M, et al. Clinical examples of 3D dose distribution reconstruction, based on the actual MLC leaves movement, for dynamic treatment techniques. Rep Pract Oncol Radiother. 2014;19(6):420-427. [16] Lin YW, Lin KH, Ho HW, et al. Treatment plan comparison between stereotactic body radiation therapy techniques for prostate cancer: non-isocentric CyberKnife versus isocentric RapidArc. Physica Medica. 2014;30(6):654-661. [17

nasopharyngeal carcinoma. Int J Radiat Oncol Biol Phys., 2000;48(2):329–337. 7. Otto K. - Volumetric modulated arc therapy: IMRT in a single gantry arc. Med Phys., 2008;35(1):310-317. 8. Zhao N., Yang R., Jiang Y., Tian S., Guo F., Wang J. - A Hybrid IMRT/VMAT Technique for the Treatment of Nasopharyngeal Cancer. BioMed Research International, 2015;(2015). Article ID 940102. 9. Verbakel W.F., Cuijpers J.P., Hoffmans D., Bieker M., Slotman B.J., Senan S. - Volumetric intensity-modulated arc therapy vs. conventional IMRT in head-and-neck cancer: a Comparative Planning and

Abstract

Background. The aim of the study was to evaluate the dosimetric benefit of applying volumetric modulated arc therapy (VMAT) on the post-mastectomy left-sided breast cancer patients, with the involvement of internal mammary nodes (IMN).

Patients and methods. The prescription dose was 50 Gy delivered in 25 fractions, and the clinical target volume included the left chest wall (CW) and IMN. VMAT plans were created and compared with intensity-modulated radiotherapy (IMRT) plans on Pinnacle treatment planning system. Comparative endpoints were dose homogeneity within planning target volume (PTV), target dose coverage, doses to the critical structures including heart, lungs and the contralateral breast, number of monitor units and treatment delivery time.

Results. VMAT and IMRT plans showed similar PTV dose homogeneity, but, VMAT provided a better dose coverage for IMN than IMRT (p = 0.017). The mean dose (Gy), V30 (%) and V10 (%) for the heart were 13.5 ± 5.0 Gy, 9.9% ± 5.9% and 50.2% ± 29.0% by VMAT, and 14.0 ± 5.4 Gy, 10.6% ± 5.8% and 55.7% ± 29.6% by IMRT, respectively. The left lung mean dose (Gy), V20 (%), V10 (%) and the right lung V5 (%) were significantly reduced from 14.1 ± 2.3 Gy, 24.2% ± 5.9%, 42.4% ± 11.9% and 41.2% ± 12.3% with IMRT to 12.8 ± 1.9 Gy, 21.0% ± 3.8%, 37.1% ± 8.4% and 32.1% ± 18.2% with VMAT, respectively. The mean dose to the contralateral breast was 1.7 ± 1.2 Gy with VMAT and 2.3 ± 1.6 Gy with IMRT. Finally, VMAT reduced the number of monitor units by 24% and the treatment time by 53%, as compared to IMRT.

Conclusions. Compared to 5-be am step-and-shot IMRT, VMAT achieves similar or superior target coverage and a better normal tissue sparing, with fewer monitor units and shorter delivery time.

these studies show no clear benefit to using higher energy photons. Volumetric Modulated Arc Therapy (VMAT) has now begun to replace IMRT for treating prostate cancer, and numerous studies show that using VMAT instead of IMRT for prostate cancer results in dosimetric benefits, such as reduced treatment time and more dose sparing to OAR. 15 - 20 Therefore, it is relevant to investigate if using higher energy photons has greater potency than using the traditional 6 MV for VMAT. To deal with the issue of neutron contamination, 10 MV photons were used for this work since

algorithm for IMRT and VMAT dose calculations with the Radiological Physics Centre’s head and neck phantom. Med Phys. 2012;39(4):2193-2202. [13] Shaw E, Kline R, Gillin M, et al. Radiation therapy oncology group: Radiosurgery quality assurance guidelines. Int J Radiat Oncol Biol Phys. 1993;27(5):1231-1239. [14] Aly MOMA, Glatting G, Jahnke L, et al. Comparison of breast simultaneous integrated boost (SIB) radiotherapy techniques. Radiat Oncol. 2015;10:139. [15] Cilla S, Deodato F, Digesù C, et al. Assessing the feasibility of volumetric modulated arc therapy using

Abstract

Aim: To study the dosimetric advantages of the jaw tracking technique in intensity-modulated radiotherapy (IMRT) and volumetric modulated arc radiotherapy (VMAT) for carcinoma of cervix patients.

Materials and Methods: We retrospectively selected ten previously treated cervix patients in this study. All the ten patients underwent CT simulation along with immobilization and positional devices. Targets and organ at risks (OARs) were delineated slice by slice for all the patients. All the patients were planned for IMRT and VMAT with intend to deliver 50 Gy in 25 fractions. All the plans were planned with 6 MV photon beam using millennium-120 multi leaf collimator (MLC) using the TrueBeam linear accelerator. IMRT and VMAT plans were performed with jaw tracking (JT) and with static jaw (SJ) techniques by keeping the same constraints and priorities for the target volumes and critical structures for a particular patient. For standardization, all the plans were normalized to the target mean of the planning target volume. All the plans were accepted with the criteria of bladder mean dose < 40 Gy and rectum mean dose < 40 Gy without compromising the target volumes. Target conformity, dose to the critical structures and low dose volumes were recorded and analyzed for IMRT and VMAT plans with and without jaw tracking for all the patients.

Results: The conformity index average of all patients followed by standard deviation (̄x± σ̄x) for JT-IMRT, SJ-IMRT, JT-VMAT and SJ-VMAT were 1.176 ± 0.139, 1.175 ± 0.139, 1.193 ± 0.220 and 1.228 ± 0.192 and homogeneity index were 0.089 ± 0.022, 0.085 ± 0.024, 0.102 ± 0.016 and 0.101 ± 0.016. In low dose volume J,T-IMRT shows a 5.4% (p-value < 0.001) overall reduction in volume receiving at least 5 Gy (V5) compared to SJ-IMRT, whereas 1.2% reduction was observed in V5 volume in JT-VMAT compared to SJ-VMAT. JT-IMRT showed mean reduction in rectum and bladder of 1.34% (p-value < 0.001) and 1.46% (p-value < 0.001) compared to SJ-IMRT, while only 0.30% and 0.03% reduction were observed between JT-VMAT and SJ-VMAT. JT-IMRT plans also showed considerable dose reduction to inthe testine, right femoral head, left femoral head and cauda compared to the SJ-IMRT plans.

Conclusion: Jaw tracking resulted in decreased dose to critical structures in IMRT and VMAT plans. But significant dose reductions were observed for critical structures in the JT-IMRT compared to SJ-IMRT technique. In JT-VMAT plans dose reduction to the critical structures were not significant compared to the JT-IMRT due to relatively lesser monitor units in the VMAT plans.

Abstract

Background: Cholangiocarcinoma is a locally extending tumor with a high incidence in Thailand. Most patients are diagnosed when the tumor is unresectable, which requires concurrent chemotherapy and/or radiation. Volumetric modulated arc therapy (VMAT) and conventional intensity-modulated radiotherapy (cIMRT) are advanced techniques that improve survival and reduce radiation-induced complications.

Objectives: To compare conformity, homogeneity, and treatment time between VMAT and cIMRT in unresectable cholangiocarcinoma.

Methods: Between September 2004 and December 2010, CT images of 11 unresectable cholangiocarcinoma patients were retrieved and replanned by VMAT and cIMRT. Comparison was made in conformation number, homogeneity index, and monitor units using a Wilcoxon signed-rank test. Dose constraints for critical organs such as the liver, kidneys, and spinal cord were restricted by Quantitative Analyses of Normal Tissue Effects in the Clinic criteria.

Results: Mean conformation number was 0.91 in both the VMAT and cIMRT plans (p = 0.477). Mean homogeneity index was 2% different, 1.11 in VMAT plans and 1.09 in cIMRT plans (p = 0.008). Mean monitor units was 529 in VMAT plans and 1,279 in cIMRT plans (p = 0.003).

Conclusion: This study is the first VMAT study in unresectable cholangiocarcinoma. Conformity was not different, but treatment time was shorter by VMAT as reported in other cancer studies. Homogeneity was 2% statistically higher by VMAT; however, clinical differences should be evaluated.