FBCT与CBCT水模体模拟膀胱体积的准确性研究

目的 基于FBCT、CBCT水模体模拟膀胱显示体积的准确性和稳定性。方法 用已知体积的硬壁水模体和软壁水模体模拟膀胱。FBCT由2排Hispeed dual CT、64排Lightspeed VCT螺旋CT扫描,各自据螺距或床速分别扫描。CBCT据曝光条件分别pelvis、pelvis spotlight、high quality head扫描。每种扫描5次后于TPS重建分析体积差异并与真实值对比,对两种模体结果行独立样本t检验。结果 重建体积与真实值偏差硬壁模体FBCT为－(1.5~0.2)%,CBCT为－(5.1~2.9)%,软壁模体FBCT为－(4.2~0.1)%,CBCT为－(4.0~0.3)%。FBCT重建体积随螺距或床速增加而减小,Hispeed 重建体积大于Lightspeed (硬壁水模体和软壁水模体的P=0.010和0.004)。CBCT扫描pelvis模式重建体积最小(硬壁水模体和软壁水模体的P=0.020、0.013和0.006、0.008)。结论FBCT和CBCT扫描体积相近且均有良好重复性。对于活动性器官(呼吸、充盈等运动) FBCT扫描推荐少排慢扫描模式,CBCT扫描推荐pelvis spotlight和high quality head模式。

Analysis of accuracy of bladder volume by simulating water mold based on Computed Tomography and kilovoltage cone-beam computed tomography images

Objective To study accuracy and stability of bladder mold volume using fan beam CT (FBCT) and kilovoltage cone-beam CT (CBCT). Methods The water bladder molds in 2 categories:hard and soft water wall molds (1 group and 3groups), scanned by FBCT and CBCT. FBCT was scanned by 2 rows of Hispeed dual and 64 rows of Lightspeed VCT spiral scan, then it was divided into two groups according to the pitch/speed of bed. CBCT was scanned by pelvis, pelvis spotlight and high quality head scan. Every scan repeated 5 times, then compared reconstruction volume with the real volume, analyzing stability and repetition by treatment planning system and the results of two phantoms by using independent sample t test. Results The deviation which compared the hard wall phantom with the real value was FBCT:－(1.5-0.2)%, CBCT:－(5.1-2.9)%.The deviation of soft wall molds, FBCT:－(4.2-0.1)%, CBCT:－(4.0-0.3)%.Reconstruction volume of FBCT decreases with the increase of motion speed and pitch of bed,the volume of Hispeed was greater than the Lightspeed (hard wall molds, P=0.010 and soft wall molds, P=0.004).Among CBCT modes, the pelvis one had the smallest reconstruction volume (hard wall molds:CBCTH vs. CBCTP,P=0.020, CBCTP vs. CBCTPS P=0.013 and soft wall molds:CBCTH vs. CBCTP,P=0.006, CBCTP vs. CBCTPS P=0.008.). Conclusions Reconstruction volume of FBCT and CBCT have no statistical difference, and both of them have a good repeatability. Slow scan mode is recommended when using FBCT for active organ (respiration, filling and so on). Pelvis spotlight and high quality head protocols are recommended when using CBCT scanning.