Dosimetric Comparison Of Manchester System And Paris System Planar Implants

The three dimensional dose distributions of Manchester system planar implants were compared to Paris system planar implants using the dose nonuniformity ratio. Single-plane implants and double-plane implants with equal as well as unequal implant planar areas were configured according to the implantation rules of Manchester and Paris systems. The three dimensional dose distributions were analyzed using cumulative dose volume curves and the dose nonuniformity ratio. The dose nonuniformity ratio was calculated as the quotient of the high dose volume (defined as the volume receiving dose rates greater than 1.5 times the reference dose rate) divided by the reference dose volume (defined as the volume receiving dose rates greater than or equal to the reference dose rate). The dose uniformity of the double-plane implants from both dosimetry systems were found to be comparable. Using the examples presented, we cannot continue to advocate the generalization that a dosimetry system that uses nonuniform sources produces a uniform dose distribution while a dosimetry system that uses uniform sources produces a nonuniform dose distribution.