基于水模体验证自主设计新型阴道宫颈固定系统的位置准确性和重复性

Verification of position accuracy and repeatability of a self-designed vaginal cervical immobilization device:a water phantom study

目的:基于水模体,用KVKV和CBCT验证自主设计的新型阴道宫颈固定系统的位置准确性和重复性。方法:新型阴道宫颈固定系统由体内和体外系统组成,体外系统由与底板固定的刻度尺、真空袋和腹部热缩膜构成;体内系统由圆柱形阴道固定器+宫腔管组成,内含4个钛合金标记点。水模体(40 cm×30 cm×20 cm)CT扫描层厚为1.25 cm,图像导入Monaco(v5.11)计划系统,分别以4个标记点为摆位等中心,在加速器分别行KVKV和CBCT验证,每个标记点两种模式各扫描5组(各20组图像),验证其位置准确性和重复性,并比较两种验证模式差异。结果:KVKV和CBCT总的垂直、头脚、左右方向位移分别为(0.10±0.05)cm vs(0.09±0.06)cm、(0.11±0.06)cm vs(0.10±0.05)cm、(-0.10±0.06)cm vs(-0.10±0.05)cm,两种验证模式的差异无统计学意义(P>0.05)。位置偏差的绝对值最大值为0.2 cm(频率≤17.5%),其余的偏差绝对值均≤±0.1 cm。KVKV与CBCT偏差的差值均≤±0.1 cm。结论:自主设计的新型阴道宫颈固定系统具有良好的位置准确性和重复性。KVKV验证相对于CBCT验证具有分辨率高、伪影小和时间短的优势,推荐优先使用KVKV进行验证,若需再行CBCT局部验证。

Objective To verify the position accuracy and repeatability of a novel self-designed vaginal cervical immobilization device using KVKV and CBCT based on water phantom.Methods The novel vaginal cervical immobilization device consists of in vivo and in vitro systems.The in vitro one consists of a scale fixed with the base plate,a vacuum bag and an abdominal heat shrinkable film,and the in vivo consists of a cylindrical vaginal fixator and a vaginal tube containing 4 titanium alloy marker.The CT image obtained with a scanning thickness of 1.25 cm and a 40 cm×30 cm×20 cm phantom was imported into the Monaco(v5.11)system.Four marked points were taken as isocentric to perform KVKV and CBCT verifications at the linac accelerator.Each marked point was scanned in 5 groups of two modes(20 images each)to verify its position accuracy and repeatability.The differences between the two verification modes were compared.Results The total vertical,longitudinal,lateral displacements of KVKV and CBCT were(0.10±0.05)cm vs(0.09±0.06)cm,(0.11±0.06)cm vs(0.1±0.05)cm,(-0.10±0.06)cm vs(-0.10±0.05)cm,respectively,and there was no statistical difference between the two verification modes(P>0.05).The maximum absolute value of the setup deviation was 0.2 cm(frequency≤17.5%),and the absolute values of the rest of the deviation were≤±0.1 cm.The difference of setup deviation between KVKV and CBCT was≤±0.1 cm.Conclusion The self-designed vaginal cervical immobilization device has good position accuracy and repeatability.KVKV verification has the advantages of higher resolution,smaller artifacts and shorter time as compared with CBCT.It is recommended to use KVKV for verification.If necessary,CBCT should be used for local assistant verification.