Sheiman R G, Raptopoulos V, Caruso P, Vrachliotis T, Pearlman J
Department of Radiology, Beth Israel Hospital, Harvard Medical School, Boston, MA 02215, USA.
AJR Am J Roentgenol. 1996 Sep;167(3):725-9. doi: 10.2214/ajr.167.3.8751690.
Scan delays for CT angiography of the abdomen are currently individualized by matching a scan delay to the transit time of a test bolus of IV contrast material to the abdominal aorta. We sought to determine whether this procedure improves the extent and uniformity of aortic enhancement when compared with the use of a standard scan delay that is determined empirically.
CT angiography of the upper abdomen (either the entire abdominal aorta or the aorta spanning the length of both kidneys for dedicated renal studies) was obtained in 48 patients who were considered to have normal cardiac function as determined by their referring physicians. Patients were randomized to undergo CT angiography that used either a standard scan delay of 20 or 22 sec (group 1, n = 26) or a tailored scan delay (group 2, n = 22), all other imaging parameters being identical. Tailored delays were determined by measuring contrast transit time to the abdominal aorta with software from the SmartPrep system. For each patient, aortic attenuation was measured at three different anatomic levels, and a lower threshold of 160 H was considered optimal. The number of attenuation values above this threshold, the mean attenuation, and the attenuation changes for each unit length along the abdominal aorta were then compared for the two groups of patients.
Fifty-eight (74%) of 78 aortic attenuation values in group 1 and 55 (88%) of 69 in group 2 were above 160 H. Mean attenuation values were 192.2 H +/- 8.1 (+/-SE) in group 1 and 199.2 H +/- 10.1 in group 2. These values and the attenuation changes for each unit length along the abdominal aorta-3.7 H/cm +/- 1.7 for group 1 and 2.2 H/cm +/- 2.0 for group 2- were not significantly different.
Tailoring the scan delay for CT angiography of the abdomen in patients considered to have normal cardiac function requires additional IV contrast agent, time, and patient imaging and does not improve the extent or uniformity of aortic enhancement over that obtained with a standard, empiric scan delay.
目前，腹部CT血管造影的扫描延迟是通过将扫描延迟与静脉注射造影剂试验团注至腹主动脉的通过时间相匹配来个体化确定的。我们试图确定与使用凭经验确定的标准扫描延迟相比，该方法是否能改善主动脉强化的程度和均匀性。
对48例经转诊医生判定心功能正常的患者进行上腹部CT血管造影（要么是整个腹主动脉，要么是专门针对肾脏研究的跨越双肾长度的主动脉）。患者被随机分为两组，一组接受采用20或22秒标准扫描延迟的CT血管造影（第1组，n = 26），另一组接受定制扫描延迟（第2组，n = 22），所有其他成像参数均相同。定制延迟通过使用SmartPrep系统软件测量造影剂至腹主动脉的通过时间来确定。对每位患者，在三个不同解剖层面测量主动脉衰减，将160 H的较低阈值视为最佳值。然后比较两组患者高于该阈值的衰减值数量、平均衰减以及腹主动脉沿线每单位长度的衰减变化。
第1组78个主动脉衰减值中有58个（74%），第2组69个中有55个（88%）高于160 H。第1组平均衰减值为192.2 H±8.1（±标准误），第2组为199.2 H±10.1。这些值以及腹主动脉沿线每单位长度的衰减变化——第1组为3.7 H/cm±1.7，第2组为2.2 H/cm±2.0——无显著差异。
对于被认为心功能正常的患者，定制腹部CT血管造影的扫描延迟需要额外的静脉造影剂、时间和患者成像，并且与标准的经验性扫描延迟相比，并未改善主动脉强化的程度或均匀性。
