TY - JOUR
T1 - Comparison of dose distributions around the pulsed-dose-rate Fletcher-Williamson and the low-dose-rate Fletcher-Suit-Delclos ovoids
T2 - A Monte Carlo study
AU - Price, Michael J.
AU - Gifford, Kent A.
AU - Horton, John
AU - Lawyer, Ann
AU - Eifel, Patricia
AU - Mourtada, Firas
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2006/8/21
Y1 - 2006/8/21
N2 - We performed a Monte Carlo study to compare dose distributions for a Fletcher-Suit-Delclos (FSD) ovoid used with 137Cs low-dose-rate (LDR) sources with those for a Fletcher-Williamson (FW) ovoid used with an 192Ir pulsed-dose-rate (PDR) source for intracavitary brachytherapy of cervical cancer. We recently reported on extensive validation of Monte Carlo MCNPX models of these ovoids using radiochromic film measurements. Here, we compared these models assuming identical loading of 10, 15 and 20 mgRaEq (72, 108 and 145 cGy cm2 h-1, respectively) in three dose mesh planes: one perpendicular to the ovoid long axis bisecting the ovoid, one parallel to and displaced 2 cm medially from the long axis of the ovoid, and a 'rectal' plane perpendicular to the long axis located 1 cm distal to the distal face of the ovoid cap. The FW ovoid delivered slightly higher doses (within 10%) over all loadings to regions away from the bladder and rectal shields when compared to the FSD ovoid. However, the FW ovoid delivered much higher doses (>50%) in regions near these shields. In the rectal plane, the FW ovoid delivered a slightly higher dose, but within the region directly behind the rectal shield, the FW ovoid delivered a dose ranging from +35% to -35% of the FSD dose distribution. We attribute these differences to intrinsic differences in source characteristics (radial dose function and anisotropy factors) and extrinsic factors such as the solid-angle effect between sources and shields and applicator design.
AB - We performed a Monte Carlo study to compare dose distributions for a Fletcher-Suit-Delclos (FSD) ovoid used with 137Cs low-dose-rate (LDR) sources with those for a Fletcher-Williamson (FW) ovoid used with an 192Ir pulsed-dose-rate (PDR) source for intracavitary brachytherapy of cervical cancer. We recently reported on extensive validation of Monte Carlo MCNPX models of these ovoids using radiochromic film measurements. Here, we compared these models assuming identical loading of 10, 15 and 20 mgRaEq (72, 108 and 145 cGy cm2 h-1, respectively) in three dose mesh planes: one perpendicular to the ovoid long axis bisecting the ovoid, one parallel to and displaced 2 cm medially from the long axis of the ovoid, and a 'rectal' plane perpendicular to the long axis located 1 cm distal to the distal face of the ovoid cap. The FW ovoid delivered slightly higher doses (within 10%) over all loadings to regions away from the bladder and rectal shields when compared to the FSD ovoid. However, the FW ovoid delivered much higher doses (>50%) in regions near these shields. In the rectal plane, the FW ovoid delivered a slightly higher dose, but within the region directly behind the rectal shield, the FW ovoid delivered a dose ranging from +35% to -35% of the FSD dose distribution. We attribute these differences to intrinsic differences in source characteristics (radial dose function and anisotropy factors) and extrinsic factors such as the solid-angle effect between sources and shields and applicator design.
UR - http://www.scopus.com/inward/record.url?scp=33746798150&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33746798150&partnerID=8YFLogxK
U2 - 10.1088/0031-9155/51/16/014
DO - 10.1088/0031-9155/51/16/014
M3 - Article
C2 - 16885626
AN - SCOPUS:33746798150
SN - 0031-9155
VL - 51
SP - 4083
EP - 4094
JO - Physics in medicine and biology
JF - Physics in medicine and biology
IS - 16
M1 - 014
ER -