分次团注对比增强能谱CT成像:肾透明细胞癌的显示及辐射剂量研究

Assessment of radiation dose and renal cell carcinoma conspicuity with split-bolus spectral multidetector CT

目的评价分次团注对比剂单期增强能谱CT成像对肾透明细胞癌的显示及辐射剂量。方法本研究经医院伦理委员会的批准和患者的知情同意。收集经腹部彩超及超声造影诊断怀疑肾恶性肿瘤患者90例,随机将患者分为实验组和对照组。实验组采用分次团注单期增强扫描能谱成像,对照组采用单次注射对比剂双期动态增强扫描。实验组扫描方案:先团注70 ml对比剂,注入对比剂后25 s再注射50 ml对比剂并以相同流率跟注40 ml生理盐水。在第一次注射对比剂开始后70 s行能谱CT扫描。利用后处理软件,计算显示肿物、肾动脉和肾静脉的最佳单能量keV,并重组图像。对照组扫描方案:一次性注入对比剂120 ml,行多层螺旋CT双期扫描,于动脉CT值达到100 HU时扫描动脉期,延迟60 s扫描静脉期。测量肿瘤组织和相邻肾皮质间的比值LKR(LKR越远离1肿瘤显示越好)和对比噪声比CNR,肾动脉、肾静脉的CT值。记录患者BMI指数和辐射剂量。统计学分析采用t检验,Fisher精确检验和Mann-Whitney检验。结果实验组中肾透明细胞癌43例,嫌色细胞和乏脂肪血管平滑肌脂肪瘤各1例。对照组肾透明细胞癌44例,肾乳头状癌1例。两组患者在年龄、体重、性别和BMI指数无统计学差异。显示肾肿物、肾动脉的最佳单能量为58 keV,显示肾静脉最佳单能量为67 keV。实验组58 keV单能量图肿瘤显示力和CNR(0.7±0.02和10.3±3.2)优于常规组动脉期(1.08±0.04和5.3±2.2)(P<0.01);实验组58 keV单能量图肾动脉CT值198±20.3 HU与常规组动脉期肾动脉CT值203±14.5 HU无明显差异(P>0.05)。实验组67 keV单能量图肾静脉CT值200±34.0 HU高于常规组静脉期肾静脉CT值140±12.6 HU(P<0.05)。实验组扫描剂量长度乘积[(735±162)mGy·cm]明显小于常规组[(1032±324)mGy·cm](P<0.01)。结论分次团注对比剂单期增强能谱成像在肾透明细胞癌、肾动脉、肾静脉的显示等同于或优于常规双期增强扫描,同时辐射剂量明显减少。

Objective To evaluate the radiation dose and renal cell carcinoma （RCC） conspicuity on split-bolus spectral multidetector CT. Methods 90 patients with suspectedRCC were randomly divided into two groups and evaluated with spectral CT （45） or conventional contrast-enhanced CT （45）. Spectral CT was performed 70 seconds after first intravenous bolus injection of 70 ml followed by a second 50 mL bolus of iodinated contrast agent 25 seconds later. Multiplanar reconstruction was performed on the single energy images that most clearly demonstrated the tumor , renal artery and renal vein. Conventional contrast-enhanced 64-slice CT was acquired in the corticomedullary and nephrographic phases. The ratios of tumors to adjacent renal cortices （LKR）, contrast-to-noise ratios （CNR）, and CT values of the renal arteries and veins were measured and compared. The body mass indices and radiation doses were recorded. Results On spectral CT, 58 keV wasthe best single energy for showing the tumor and renal artery and 67 keVwas best for demonstrating the renal vein. Tumor depiction （LKR=0.70±0.02, CNR=10.30±3.20） at 58 keV was significantly better than that of conventional CT in the corticomedullary phase （1.08±0.04,5.30±2.20）. There was no significant difference in CT values of the renal arteries between the 58 keV spectral CT （198.00±20.30 HU） and conventional CT （203.00± 14.50 HU） in the corticomedullary phase whereas the CT values of renal veinson 67 keV spectral CT （200.00±34.00 HU） were significantly higher than that on conventional CT （140.00±12.60 HU） in the nephrographic phase. The radiation dose （735±162 mGy·cm） of spectral CT was significantly less than thatof conventional CT （1032±324 mGy·cm）. Conclusion Split-bolus spectral multidetector CT is better than or equal to the conventional dual-phase enhanced CT for depicting RCC , renal artery and renal vein with 28.8%reduction in radiation dose.