Department of Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215.
Radiology. 2013 Oct;269(1):139-48. doi: 10.1148/radiol.13121409. Epub 2013 May 14.
To assess tumor conspicuity and radiation dose with a new multidetector computed tomography (CT) protocol for pancreatic imaging that combines spectral CT and split-bolus injection.
This study was approved by the institutional review board and compliant with HIPAA. The requirement for informed consent was waived. One hundred sixty-three consecutive patients referred for possible pancreatic mass underwent CT with either a standard or split-bolus spectral CT protocol depending on scanner availability. Split-bolus spectral CT (CT unit with spectral imaging) combines pancreatic and portal venous phases in a single scan: 70 seconds before CT, 100 mL of contrast material is injected for the portal venous phase followed approximately 35 seconds later by injection of 40 mL of contrast material to boost the pancreatic phase. Bolus tracking after the second bolus initiates scanning 15 seconds after aorta enhancement reaches 280 HU. Images were reconstructed at 60 and 77 keV. The standard protocol (64-detector row unit) included unenhanced and pancreatic and portal venous phase imaging, with a single contrast material injection timed with bolus tracking 15 seconds after aortic enhancement of 300 HU for the pancreatic phase and 32 seconds later for the portal venous phase. Tumor conspicuity (difference in attenuation between tumor and pancreatic parenchyma) and contrast-to-noise ratio (CNR) were determined. Attenuation of aorta, main portal vein, and liver were measured. Patient size and per-examination radiation dose were recorded. The heteroscedastic t test, Fisher exact test, and Mann-Whitney test were used for statistical analysis.
There were no significant differences in age, weight, and body mass index between patients in the standard CT (46 of 80 patients had lesions) and split-bolus spectral CT (39 of 83 patients had lesions) groups; however, there were significantly more women in the split-bolus group (P = .02). Tumor conspicuity and CNR were higher with the 60-keV split-bolus protocol (89.1 HU ± 56.6 and 8.8 ± 6.2, respectively) than with the pancreatic or portal venous phase of the standard protocol (43.5 HU ± 28.4 and 4.5 ± 3.0, and 51.5 HU ± 30.3 and 5.6 ± 4.0, respectively; P < .01 for all comparisons). Dose-length product was 1112 mGy · cm ± 437 with the standard protocol and 633 mGy · cm ± 105 with the split-bolus protocol (P < .001).
Split-bolus spectral multidetector CT resulted in vascular, liver, and pancreatic attenuation and tumor conspicuity equal to or greater than that with multiphase CT, with a 43% reduction in radiation dose.
评估一种新的多排 CT（MDCT）胰腺成像协议的肿瘤显影和辐射剂量，该协议结合了光谱 CT 和分裂团注。
本研究经机构审查委员会批准，并符合 HIPAA 规定。豁免了知情同意的要求。根据扫描仪的可用性，将 163 例连续就诊的胰腺肿块患者分为标准或分裂团注光谱 CT 方案组。分裂团注光谱 CT（具有光谱成像的 CT 机）在单次扫描中结合胰期和门静脉期：在 CT 前 70 秒，注射 100ml 对比剂进行门静脉期，大约 35 秒后再注射 40ml 对比剂增强胰期。第二次团注后启动跟踪，主动脉增强达到 280HU 后 15 秒开始扫描。图像在 60keV 和 77keV 重建。标准方案（64 排 CT 机）包括平扫、胰期和门静脉期成像，使用单对比剂团注，在主动脉增强达到 300HU 后 15 秒进行胰期团注，32 秒后进行门静脉期团注。测量肿瘤的显影（肿瘤与胰腺实质之间的衰减差异）和对比噪声比（CNR）。测量主动脉、主门静脉和肝脏的衰减。记录患者的体型和每次检查的辐射剂量。采用异方差 t 检验、Fisher 确切检验和曼-惠特尼检验进行统计学分析。
在标准 CT（46/80 例有病变）和分裂团注光谱 CT（39/83 例有病变）组患者中，年龄、体重和体重指数无显著差异；然而，分裂团注组女性明显较多（P=.02）。60keV 分裂团注方案的肿瘤显影和 CNR 均高于标准方案的胰期或门静脉期（89.1HU±56.6 和 8.8±6.2，分别）；51.5HU±30.3 和 5.6±4.0，P<.01）。标准方案的剂量长度乘积为 1112mGy·cm±437，分裂团注方案为 633mGy·cm±105（P<.001）。
分裂团注光谱多排 CT 可获得与多期 CT 相等或更高的血管、肝脏和胰腺衰减及肿瘤显影，同时辐射剂量降低 43%。
