Email this article 
Post a Comment 
Hide
Show all
Stereotactic IMRT for prostate cancer: Dosimetric impact of multileaf collimator leaf width in the treatment of prostate cancer with intensity modulated radiotherapy
Abstract
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, 4 and 10 mm, 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 of 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 40Gy (V40), 50Gy (V50), 60Gy (V60), the dose received by 17% and 35% of rectum (D17 and D35), and the maximum dose to 1cc of the rectum for a prescription dose of 74Gy. For the urinary bladder, the dose received by 25% of bladder (D25), V40, and the maximum dose to 1cc of the organ were recorded. For PTV we compared the maximum dose to the ?hottest?1 cc (Dmax1cc) and the dose to 99% of the PTV (D99). The dose inhomogeneity in the target, defined as the ratio of the difference in Dmax1cc 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-values less than 0.0001 for V40 and V50 and 0.012 for V60. The mean dose reductions for D17 and D35 for the rectum using the mMLC were 20.4% (p
Ten patients with prostate cancer were planned for IMRT delivery using two different MLC leaf widths, 4 and 10 mm, 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 of 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 40Gy (V40), 50Gy (V50), 60Gy (V60), the dose received by 17% and 35% of rectum (D17 and D35), and the maximum dose to 1cc of the rectum for a prescription dose of 74Gy. For the urinary bladder, the dose received by 25% of bladder (D25), V40, and the maximum dose to 1cc of the organ were recorded. For PTV we compared the maximum dose to the ?hottest?1 cc (Dmax1cc) and the dose to 99% of the PTV (D99). The dose inhomogeneity in the target, defined as the ratio of the difference in Dmax1cc 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-values less than 0.0001 for V40 and V50 and 0.012 for V60. The mean dose reductions for D17 and D35 for the rectum using the mMLC were 20.4% (p
Keywords
IMRT, prostate cancer, multileaf collimator, radiation dosimetry