Mitsuzaki K, Yamashita Y, Ogata I, Nishiharu T, Urata J, Takahashi M
Department of Radiology, Kumamoto University School of Medicine, Japan.
AJR Am J Roentgenol. 1996 Sep;167(3):753-7. doi: 10.2214/ajr.167.3.8751695.
Helical CT scanners allow multiple-phase sequential scans of the entire liver to be obtained during a single bolus injection of contrast material. The purpose of this study was to compare two injection protocols and to establish timing that would optimize detection of hepatomas less than 3 cm in diameter.
Triple-phase helical CT of the liver was evaluated in 217 patients who had liver cirrhosis and were referred for known or suspected hepatomas. Proof of individual neoplasms was based on biopsy results, surgical findings, or findings of other imaging studies. Sixty percent nonionic contrast material, infused at 2 or 4 ml/sec, was followed by sequential arterial-phase, portal-venous phase, and equilibrium-phase helical scans of the liver. Aortic and hepatic enhancement curves were constructed by measuring CT attenuation. The CT attenuation values of individual tumor lesions were also measured. We compared the degree of enhancement of normal structures and tumors obtained with four scan protocols (injection at 2 ml/sec with a 30-sec scan delay [n = 54], injection at 2 ml/sec with a 35-sec scan delay [n = 47], injection at 4 ml/sec with a 20-sec scan delay [n = 56], and injection at 4 ml/sec with a 25-sec scan delay [n = 60] and determined the optimal injection protocol and timing for CT acquisition.
Peak aortic and hepatic enhancement was obtained earlier with the 4-ml/sec protocol (at 24 sec and 61 sec versus 36 sec and 90 sec for the 2-ml/sec protocol). The peak attenuation value of the aorta was higher with the 4-ml/sec protocol (330 H versus 186 H for the 2-ml/sec protocol). However, peak hepatic attenuation was similar for both protocols (98 H for the 4-ml/sec protocol versus 92 H for the 2-ml/sec protocol). Liver-tumor contrast was highest in the arterial phase with both protocols. The next highest contrast was obtained during the equilibrium phase. Liver-tumor contrast in the portal-venous phase was significantly lower than that in the other two phases. Tumor enhancement was significantly higher in scans obtained using the 4-ml/sec protocol with a delay time of 25 sec than those obtained with a delay time of 20 sec. In 109 hepatomas, 35 tumors were only seen or were most conspicuous during the arterial phase, four tumors were most conspicuous during the equilibrium phase, and one tumor was most conspicuous during the portal-venous phase.
Arterial-phase helical CT of the liver after 4-ml/sec injection of contrast material significantly improves detection of hepatomas less than 3 cm in diameter when performed in addition to delayed scanning. Portal-venous phase helical CT is of limited value in detecting small hepatomas.
螺旋CT扫描仪能够在单次团注造影剂期间对整个肝脏进行多期连续扫描。本研究的目的是比较两种注射方案，并确定能优化直径小于3cm肝癌检测的扫描时间。
对217例肝硬化且因已知或疑似肝癌前来就诊的患者进行肝脏三期螺旋CT检查。通过活检结果、手术所见或其他影像学检查结果来确诊个体肿瘤。以2或4ml/秒的速度注入60%的非离子型造影剂，随后对肝脏进行连续的动脉期、门静脉期和平衡期螺旋扫描。通过测量CT衰减值构建主动脉和肝脏增强曲线。同时也测量各个肿瘤病灶的CT衰减值。我们比较了四种扫描方案（2ml/秒注射、扫描延迟30秒[n = 54]；2ml/秒注射、扫描延迟35秒[n = 47]；4ml/秒注射、扫描延迟20秒[n = 56]；4ml/秒注射、扫描延迟25秒[n = 60]）所获得的正常结构和肿瘤的强化程度，确定CT采集的最佳注射方案和时间。
4ml/秒方案能更早获得主动脉和肝脏的峰值强化（分别为24秒和61秒，而2ml/秒方案为36秒和90秒）。4ml/秒方案的主动脉峰值衰减值更高（330H，而2ml/秒方案为186H）。然而，两种方案的肝脏峰值衰减相似（4ml/秒方案为98H，2ml/秒方案为92H）。两种方案下肝脏肿瘤的对比度在动脉期最高，其次是平衡期。门静脉期的肝脏肿瘤对比度显著低于其他两个时期。使用4ml/秒方案且延迟时间为25秒所获得的扫描中肿瘤强化显著高于延迟时间为20秒的扫描。在109个肝癌中，35个肿瘤仅在动脉期可见或最为明显，4个肿瘤在平衡期最为明显，1个肿瘤在门静脉期最为明显。
除延迟扫描外，以4ml/秒的速度注射造影剂后进行肝脏动脉期螺旋CT显著提高了直径小于3cm肝癌的检测率。门静脉期螺旋CT在检测小肝癌方面价值有限。
