Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390-9178, USA.
UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX, 75390-9178, USA.
Abdom Radiol (NY). 2017 Mar;42(3):702-709. doi: 10.1007/s00261-016-1036-9.
To assess virtual non-contrast (VNC) images obtained on a detection-based spectral detector CT scanner and determine how attenuation on VNC images derived from various phases of enhanced CT compare to those obtained from true unenhanced images.
In this HIPAA compliant, IRB approved prospective multi-institutional study, 46 patients underwent pre- and post-contrast imaging on a prototype dual-layer spectral detector CT between October 2013 and November 2015, yielding 84 unenhanced and VNC pairs (25 arterial, 39 portal venous/nephrographic, 20 urographic). Mean attenuation was measured by one of three readers in the liver, spleen, kidneys, psoas muscle, abdominal aorta, and subcutaneous fat. Equivalence testing was used to determine if the mean difference between unenhanced and VNC attenuation was less than 5, 10, or 15 HU. VNC image quality was assessed on a 5 point scale.
Mean difference between unenhanced and VNC attenuation was <15 HU in 92.6%, <10 HU in 75.2%, and <5 HU in 44.4% of all measurements. Unenhanced and VNC attenuation were equivalent in all tissues except fat using a threshold of <10 HU difference (p < 0.05). No significant variation was seen between phases. In fat, VNC overestimated the HU relative to unenhanced images. VNC image quality was rated as excellent or good in 84% of arterial phase and 85% of nephrographic phase cases, but only 40% of urographic phase.
VNC images derived from novel dual layer spectral detector CT demonstrate attenuation values similar to unenhanced images in all tissues evaluated except for subcutaneous fat. Further study is needed to determine if attenuation thresholds currently used clinically for common pathology should be adjusted, particularly for lesions containing fat.
评估基于检测的光谱探测器 CT 扫描仪上获得的虚拟非对比（VNC）图像，并确定从增强 CT 的不同相位得出的 VNC 图像的衰减与从真实未增强图像获得的衰减相比如何。
在这项符合 HIPAA 规定、IRB 批准的前瞻性多机构研究中，46 名患者在 2013 年 10 月至 2015 年 11 月期间在原型双层光谱探测器 CT 上进行了增强前后成像，产生了 84 对未增强和 VNC（25 个动脉期，39 个门静脉/肾造影期，20 个尿路造影期）。由三位读者之一测量肝脏、脾脏、肾脏、腰大肌、腹主动脉和皮下脂肪中的平均衰减。等效性检验用于确定未增强和 VNC 衰减之间的平均差异是否小于 5、10 或 15 HU。VNC 图像质量采用 5 分制进行评估。
在所有测量中，92.6%的未增强和 VNC 衰减之间的平均差异<15 HU，75.2%的<10 HU，44.4%的<5 HU。除脂肪外，在所有组织中，未增强和 VNC 衰减均等效，差异<10 HU（p<0.05）。在各期之间未观察到明显变化。在脂肪中，VNC 相对于未增强图像高估了 HU。84%的动脉期和 85%的肾造影期病例的 VNC 图像质量被评为优秀或良好，但仅 40%的尿路造影期病例如此。
从新型双层光谱探测器 CT 获得的 VNC 图像在评估的所有组织中显示出与未增强图像相似的衰减值，除了皮下脂肪。需要进一步研究以确定是否应调整目前用于常见病理的临床衰减阈值，特别是对于含有脂肪的病变。
