Salyapongse Aria M, Rose Sean D, Pickhardt Perry J, Lubner Meghan G, Toia Giuseppe V, Bujila Robert, Yin Zhye, Slavic Scott, Szczykutowicz Timothy P
Department of Radiology, University of WisconsinâMadison, Madison, WI.
Department of Diagnostic and Interventional Imaging, University of Texas Health Science Center, Houston, TX.
J Comput Assist Tomogr. 2025;49(2):297-307. doi: 10.1097/RCT.0000000000001670. Epub 2025 Jan 6.
Patient positioning during clinical practice can be challenging, and mispositioning leads to a change in CT number. CT number fluctuation was assessed in single-energy (SE) EID, dual-energy (DE) EID, and deep silicon photon-counting detector (PCD) CT over water-equivalent diameter (WED) with different mispositions.
A phantom containing five clinically relevant inserts (Mercury Phantom, Gammex) was scanned on a clinical EID CT and a deep silicon PCD CT prototype at vertical positions of 0, 4, 8, and 12 cm. EID scans used 120 kV and rapid kV-switching DE techniques. CT number was calculated for air, water, polystyrene, iodine 10 mg/mL, and bone. Ideal CT numbers were calculated using the NIST XCOM database toolkit. Comparison of measured to ideal CT number utilized relative root mean square error (RMSE). Trends in CT number versus WED were compared using linear regression and statistical comparisons to test for differences in slope.
No statistical difference of CT number with mispositioning was seen between acquisition modes. CT number fluctuation was larger due to WED than mispositioning for all material inserts. Water, iodine, and bone, for deep silicon PCD CT had statistically significant ( P < 0.05) smaller slopes compared to EIDof CT number over WED for all tested mispositions. The accuracy of deep silicon PCD CT was higher than either SE or DE EID CT for all materials at all mispositions except for polystyrene.
WED (ie, patient size) contributes to CT number fluctuation more than mispositioning. The change in CT number was significantly smaller, and CT number accuracy was higher for deep silicon PCD CT in this phantom study.
临床实践中的患者体位摆放可能具有挑战性，且体位摆放不当会导致CT值发生变化。在单能量（SE）能谱成像（EID）、双能量（DE）EID和深硅光子计数探测器（PCD）CT中，针对不同体位摆放不当情况，评估了水等效直径（WED）上的CT值波动。
在一台临床EID CT和一台深硅PCD CT原型机上，对一个包含五个临床相关插入物的体模（汞体模，Gammex）在垂直位置0、4、8和12 cm处进行扫描。EID扫描采用120 kV和快速kV切换DE技术。计算空气、水、聚苯乙烯、10 mg/mL碘和骨的CT值。使用美国国家标准与技术研究院（NIST）XCOM数据库工具包计算理想CT值。将测量的CT值与理想CT值进行比较，采用相对均方根误差（RMSE）。使用线性回归比较CT值与WED的趋势，并进行统计比较以检验斜率差异。
采集模式之间未观察到体位摆放不当导致的CT值存在统计学差异。对于所有材料插入物，由于WED导致的CT值波动大于体位摆放不当导致的波动。对于所有测试的体位摆放不当情况，深硅PCD CT的水、碘和骨的CT值在WED上的斜率与EID相比具有统计学显著差异（P < 0.05），斜率更小。除聚苯乙烯外，在所有体位摆放不当情况下，深硅PCD CT对所有材料的准确性均高于SE或DE EID CT。
WED（即患者体型）对CT值波动的影响大于体位摆放不当。在该体模研究中，深硅PCD CT的CT值变化明显更小，CT值准确性更高。
