A phantom study for the reconstruction defects of moving target volume decision by spiral CT / 中华放射肿瘤学杂志

ABSTRACT

Objective To investigate reasonable method of deciding internal target volume (ITV) by comparing physical phantom volumes (including moving volume) with reconstruction volumes of spiral CT scanning.Methods The various-volume wax blocks which were labeled No.1-9 were made and put on the respiratory motion simulator.The range of motion was set 2.5 cm and frequency 18 beats/min.All blocks were scanned 10 times continuously and imported into the Eclipse TPS.All blocks volumes were calculated and then compared with the true physical volumes and paired t-test.Results The reconstruction volumes of 1-9 blocks were bigger than their stationary volumes (121.77 cm3 vs.103.14 cm3,P =0.038),but significantly smaller than their moving volumes (121.77 cm3 vs.161.75 cm3,P =0.045).The results can be gotten in different volume block scanning.The relative deviation of reconstruction volumes and the moving volumes tends to increase as the stationary physical volume decreases.Conclusions As to moving targets,conventional spiral CT scanning speed is too fast to collect all volume information of targets.So the one-time-scanning volume does not represent the ITV.