title: Stereotactic IMRT for prostate cancer: dosimetric impact of multileaf collimator leaf width in the treatment of prostate cancer with IMRT.
abstract: The focus of this work is the dosimetric impact of multileaf collimator (MLC) leaf width on the treatment of prostate cancer with intensity-modulated radiation therapy (IMRT). Ten patients with prostate cancer were planned for IMRT delivery using two different MLC leaf widths--4mm and 10mm--representing the Radionics micro-multileaf collimator (mMLC) and Siemens MLC, respectively. Treatment planning was performed on the XKnifeRT2 treatment-planning system (Radionics, Burlington, MA). All beams and optimization parameters were identical for the mMLC and MLC plans. All the plans were normalized to ensure that 95% of the planning target volume (PTV) received 100% of the prescribed dose. The differences in dose distribution between the two different plans were assessed by dose-volume histogram (DVH) analysis of the target and critical organs. We specifically compared the volume of rectum receiving 40 Gy (V40), 50 Gy (V50), 60 Gy (V60), the dose received by 17% and 35% of rectum (D17 and D35), and the maximum dose to 1 cm3 of the rectum for a prescription dose of 74 Gy. For the urinary bladder, the dose received by 25% of bladder (D25), V40, and the maximum dose to 1 cm3 of the organ were recorded. For PTV we compared the maximum dose to the "hottest" 1 cm3 (Dmax1 cm3) and the dose to 99% of the PTV (D99). The dose inhomogeneity in the target, defined as the ratio of the difference in Dmax1 cm3 and D99 to the prescribed dose, was also compared between the two plans. In all cases studied, significant reductions in the volume of rectum receiving doses less than 65 Gy were seen using the mMLC. The average decrease in the volume of the rectum receiving 40 Gy, 50 Gy, and 60 Gy using the mMLC plans was 40.2%, 33.4%, and 17.7%, respectively, with p < 0.0001 for V40 and V50 and p < 0.012 for V60. The mean dose reductions for D17 and D35 for the rectum using the mMLC were 20.4% (p < 0.0001) and 18.3% (p < 0.0002), respectively. 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 29%. In the high-dose range, there was no significant difference in the dose deposited in the "hottest" 1 cm3 of the rectum between the two plans for all cases (p > 0.78). In conclusion, the use of the mMLC for IMRT of the prostate resulted in significant improvement in the DVH parameters of the prostate and critical organs, which may improve the therapeutic ratio.
authors.affiliation: Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA. L_wang@fccc.edu
authors.forename: L
authors.initials: L
authors.lastname: Wang
authors.forename: B
authors.initials: B
authors.lastname: Movsas
authors.forename: R
authors.initials: R
authors.lastname: Jacob
authors.forename: E
authors.initials: E
authors.lastname: Fourkal
authors.forename: L
authors.initials: L
authors.lastname: Chen
authors.forename: R
authors.initials: R
authors.lastname: Price
authors.forename: S
authors.initials: S
authors.lastname: Feigenberg
authors.forename: A
authors.initials: A
authors.lastname: Konski
authors.forename: A
authors.initials: A
authors.lastname: Pollack
authors.forename: C
authors.initials: C
authors.lastname: Ma
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods; D007103:Immobilization / Q000295:instrumentation* / Q000379:methods; D008297:Male; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011856:Radiographic Image Enhancement / Q000295:instrumentation / Q000379:methods; D011874:Radiometry / Q000295:instrumentation / Q000379:methods*; D016634:Radiosurgery / Q000295:instrumentation* / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D020266:Radiotherapy, Conformal / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods
references.citation: Med Phys. 1999 Jan;26(1):65-70
references.pmid: 9949399
references.citation: Int J Radiat Oncol Biol Phys. 2001 Mar 1;49(3):685-98
references.pmid: 11172950
references.citation: Int J Radiat Oncol Biol Phys. 1998 Jun 1;41(3):491-500
references.pmid: 9635694
references.citation: Int J Radiat Oncol Biol Phys. 1993 Jan 15;25(2):181-92
references.pmid: 8420867
references.citation: Int J Radiat Oncol Biol Phys. 1996 May 1;35(2):415-6
references.pmid: 8635953
references.citation: Int J Radiat Oncol Biol Phys. 2002 Feb 1;52(2):461-8
references.pmid: 11872293
references.citation: Int J Radiat Oncol Biol Phys. 2002 Dec 1;54(5):1314-21
references.pmid: 12459352
references.citation: Int J Radiat Oncol Biol Phys. 1993 Jun 15;26(3):551-7
references.pmid: 8514551
references.citation: Med Phys. 1999 May;26(5):729-33
references.pmid: 10360533
references.citation: Radiother Oncol. 1999 Mar;50(3):325-36
references.pmid: 10392819
references.citation: Int J Radiat Oncol Biol Phys. 2000 Sep 1;48(2):507-12
references.pmid: 10974469
references.citation: Int J Radiat Oncol Biol Phys. 2000 Apr 1;47(1):103-13
references.pmid: 10758311
references.citation: Int J Radiat Oncol Biol Phys. 1995 May 15;32(2):465-71
references.pmid: 7751187
references.citation: Int J Radiat Oncol Biol Phys. 1993 Jan 15;25(2):161-70
references.pmid: 8420865
references.citation: Int J Radiat Oncol Biol Phys. 1986 Apr;12(4):539-47
references.pmid: 3009368
references.citation: Int J Radiat Oncol Biol Phys. 1993 Jan 15;25(2):171-9
references.pmid: 8420866
references.citation: Int J Radiat Oncol Biol Phys. 1999 Jul 1;44(4):937-45
references.pmid: 10386653
references.citation: Phys Med Biol. 2001 Apr;46(4):1039-60
references.pmid: 11324950
references.citation: Int J Radiat Oncol Biol Phys. 2000 Jan 15;46(2):391-402
references.pmid: 10661346
references.citation: Int J Radiat Oncol Biol Phys. 1988 Dec;15(6):1299-305
references.pmid: 3198435
references.citation: Int J Radiat Oncol Biol Phys. 1992;24(4):781-7
references.pmid: 1429105
references.citation: Int J Radiat Oncol Biol Phys. 1997 Jan 1;37(1):3-11
references.pmid: 9054871
references.citation: Med Phys. 2003 Jul;30(7):1758-67
references.pmid: 12906193
references.citation: Phys Med Biol. 1990 Oct;35(10):1423-34
references.pmid: 2243845
references.citation: Med Phys. 2002 Jun;29(6):1116-9
references.pmid: 12094981
references.citation: J Clin Oncol. 2000 Dec 1;18(23 ):3904-11
references.pmid: 11099319
references.citation: Int J Radiat Oncol Biol Phys. 1996 Oct 1;36(3):721-30
references.pmid: 8948358
references.citation: Radiologe. 1998 Mar;38(3):228-34
references.pmid: 9577869