Institute of Diagnostic Radiology, University Hospital Zurich, Ch-8091 Zurich, Switzerland.
Acad Radiol. 2010 Apr;17(4):526-34. doi: 10.1016/j.acra.2009.11.007.
To assess the performance of dual-energy computed tomography (DECT) equipped with the new tin filter technology to classify phantom renal lesions as cysts or enhancing masses.
Forty spherical lesion proxies ranging in diameter from 6 to 27 mm were filled with either distilled water (n = 10) representing cysts or titrated iodinated contrast solutions with a concentration of 0.45 (n = 10), 0.9 (n = 10), and 1.8 mg/mL (n = 10) representing enhancing masses. The lesion proxies were placed in a 12-cm diameter renal phantom containing minced beef and submerged in a 28-cm water bath. DECT was performed using the new dual-source CT system (Definition Flash, Siemens Healthcare, Forchheim, Germany) allowing for an improved energy separation by using a tin filter. DECT was performed at tube voltages of 140/80 kV without the tin filter (protocol A) and with tin filter (protocol B). The tube current time product was selected in each protocol to achieve a constant CTDI (computed tomography dose index) with both protocols of 19 mGy (full dose), 9.5 mGy (half dose), and 4.8 mGy (quarter dose). Two blinded readers classified each lesion as a cyst or enhancing mass by using iodine overlay (IO) images. One reader measured the CT numbers of each lesion at 120 kV, in the IO, linear blending (LB), and virtual noncontrast (VNC) images.
The CT numbers of the lesions at 120 kV were 0.1 +/- 0.7 HU (0 mg iodine/mL), 9.1 +/- 0.7 HU (0.45 mg/mL), 18.1 +/- 1.4 HU (0.9 mg/mL), and 37.6 +/- 1.6 HU (1.8 mg/mL). Mean diameter of the lesion proxies filled with water or different iodine concentrations was similar (P = 0.38). Image noise was not significantly different in protocols A and B at the corresponding dose levels. At full dose, protocol A had a sensitivity of 93% and a specificity of 60% for discriminating renal lesions. Sensitivity and specificity declined to 84% and 38% at quarter dose. In protocol B, sensitivity was 100% and specificity was 90% at full dose and 93% and 70% at quarter dose. All misclassifications occurred in cyst or low iodine concentration (0.45 mg/mL) lesion proxies. The differences between CT numbers at 120 kV and in the IO, VNC, and AW (average weighted) images were significantly lower in protocol B compared to protocol A (each P < .05).
DECT using the tin filter results in an improved sensitivity and specificity for discriminating renal cysts from enhancing masses in a kidney phantom model and demonstrates higher dose efficiency as compared to former dual energy technology without tin filters.
评估配备新型锡滤器技术的双能计算机断层扫描（DECT）对肾占位病变进行分类的性能，以区分囊肿或增强肿块。
使用直径为 6 至 27 毫米的 40 个球形病变模拟物，用蒸馏水（n=10）或浓度为 0.45（n=10）、0.9（n=10）和 1.8mg/mL（n=10）的碘造影剂填充，以代表囊肿或增强肿块。病变模拟物置于含有肉末的 12 厘米直径肾模型中，并浸没在 28 厘米深的水浴中。使用新型双源 CT 系统（Definition Flash，西门子医疗，Forchheim，德国）进行 DECT，该系统采用锡滤器可实现更好的能量分离。DECT 以 140/80kV 管电压进行，无锡滤器（方案 A）和有锡滤器（方案 B）。每个方案中，均选择管电流时间乘积以实现两种方案的 CT 剂量指数（CTDI）相同，均为 19mGy（全剂量）、9.5mGy（半剂量）和 4.8mGy（四分之一剂量）。两名盲法读者使用碘覆盖（IO）图像对每个病变进行囊肿或增强肿块的分类。一名读者在 120kV 时测量每个病变的 CT 值，在 IO、线性混合（LB）和虚拟非对比（VNC）图像中。
在 120kV 时，病变的 CT 值为 0.1±0.7HU（0mg 碘/mL）、9.1±0.7HU（0.45mg/mL）、18.1±1.4HU（0.9mg/mL）和 37.6±1.6HU（1.8mg/mL）。水或不同碘浓度填充的病变模拟物的平均直径相似（P=0.38）。在相应剂量水平下，方案 A 和 B 的图像噪声无显著差异。在全剂量时，方案 A 对区分肾占位病变的敏感性为 93%，特异性为 60%。在四分之一剂量时，敏感性和特异性分别下降至 84%和 38%。在方案 B 中，全剂量时敏感性为 100%，特异性为 90%，四分之一剂量时敏感性为 93%，特异性为 70%。所有误分类均发生在囊肿或低碘浓度（0.45mg/mL）病变模拟物中。与方案 A 相比，方案 B 中在 120kV 时的 CT 值与 IO、VNC 和 AW（平均加权）图像之间的差异显著较低（均 P<.05）。
使用新型锡滤器的 DECT 可提高在肾模型中区分肾囊肿和增强肿块的敏感性和特异性，并显示出比以前的无锡滤器双能技术更高的剂量效率。
