Dosimetric advantage and clinical implication of a micro-multileaf collimator in the treatment of prostate with intensity-modulated radiotherapy

Journal Article · Thu Jun 30 00:00:00 EDT 2005 · Medical Dosimetry

DOI:https://doi.org/10.1016/j.meddos.2005.03.002· OSTI ID:20696213

Lu, Wang ^[1]; Hoban, Peter ^[2]; Paskalev, Kamen ^[1]; Jie, Yang ^[1]; Jinsheng, Li ^[1]; Lili, Chen ^[1]; Weijun, Xiong ^[1]; Ma, Charlie ^[1]

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1. Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA (United States)
2. Siemens Medical Solution, Oncology Care Systems, Concord, CA (United States)

This paper investigates the dosimetric benefits of a micro-multileaf (4-mm leaf width) collimator (mMLC) for intensity-modulated radiation therapy (IMRT) treatment planning of the prostate cancer and its potential application for dose escalation and hypofractionation. We compared treatment plans for IMRT delivery using 2 different multileaf collimator (MLC) leaf widths (4 vs. 10 mm) for 10 patients with prostate cancer. Treatment planning was performed on the XknifeRT2 treatment planning system. All beams and optimization parameters were identical for the mMLC and MLC plans. All of the plans were normalized to ensure that 95% of the planning target volume (PTV) received 100% of the prescribed dose (74 Gy). The differences in dose distribution between the 2 groups of plans using the mMLC and the MLC were assessed by dose-volume histogram (DVH) analysis of the target and critical organs. Significant reductions in the volume of rectum receiving medium to higher doses were achieved using the mMLC. The average decrease in the volume of the rectum receiving 40, 50, and 60 Gy using the mMLC plans was 40.2%, 33.4%, and 17.7%, respectively, with p-values less than 0.0001 for V{sub 40} and V{sub 50} and 0.012 for V{sub 60}. The mean dose reductions for D{sub 17} and D{sub 35} for the rectum were 20.0% (p < 0.0001) and 18.3% (p < 0.0002), respectively, when compared to those with the MLC plans. There were consistent reductions in all dose indices studied for the bladder. The target dose inhomogeneity was improved in the mMLC plans by an average of 32%. In the high-dose range, there was no significant difference in the dose deposited in the 'hottest' 1 cc of the rectum between the 2 MLC plans for all cases (p > 0.78). Because of the reduction of rectal volume receiving medium to higher doses, dose to the prostate target can be escalated by about 20 Gy to over 74 Gy, while keeping the rectal dose (either denoted by D{sub 17} or D{sub 35}) the same as those with the use of the MLC. The maximum achievable dose, derived when the rectum is allowed to reach the tolerance level, was found to be in the range of 113-172 Gy (using the tolerance value of D{sub 17}). We conclude that the use of the mMLC for IMRT of the prostate may facilitate dose hypofractionation due to its dosimetric advantage in significantly improving the DVH parameters of the prostate and critical organs. When used for conventional fractionation scheme, mMLC for IMRT of the prostate may reduce the toxicity to the critical organs.

• OSTI ID: 20696213
• Journal Information: Medical Dosimetry, Vol. 30, Issue 2; Other Information: DOI: 10.1016/j.meddos.2005.03.002; PII: S0958-3947(05)00048-8; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0958-3947
• Country of Publication: United States
• Language: English

Related Subjects

61 RADIATION PROTECTION AND DOSIMETRY
BLADDER
CARCINOMAS
COLLIMATORS
CRITICAL ORGANS
FRACTIONATION
OPTIMIZATION
PATIENTS
PROSTATE
RADIATION DOSE DISTRIBUTIONS
RADIATION DOSES
RADIOTHERAPY
RECTUM
TOLERANCE
TOXICITY