Lell Michael M, Fleischmann Ulrike, Pietsch Hubertus, Korporaal Johannes G, Haberland Ulrike, Mahnken Andreas H, Flohr Thomas G, Uder Michael, Jost Gregor
Department of Radiology and Nuclear Medicine, Paracelsus Medical University, Nuernberg, Germany.
Department of Radiology, Friedrich-Alexander University Erlangen, Erlangen, Germany.
PLoS One. 2017 Mar 20;12(3):e0173592. doi: 10.1371/journal.pone.0173592. eCollection 2017.
Very short acquisition times and the use of low-kV protocols in CTA demand modifications in the contrast media (CM) injection regimen. The aim of this study was to optimize the use of CM delivery parameters in thoraco-abdominal CTA in a porcine model.
Six pigs (55-68 kg) were examined with a dynamic CTA protocol (454 mm scan length, 2.5 s temporal resolution, 70 s total acquisition time). Four CM injection protocols were applied in a randomized order. 120 kV CTA protocol: (A) 300 mg iodine/kg bodyweight (bw), IDR = 1.5 g/s (flow = 5 mL/s), injection time (ti) 12 s (60 kg bw). 70 kV CTA protocols: 150 mg iodine/kg bw: (B) IDR = 0.75 g/s (flow = 2.5 mL/s), ti = 12 s (60 kg bw); (C) IDR = 1.5 g/s (flow = 5 mL/s), ti = 12 s (60 kg bw); (D) IDR = 3.0 g/s (flow = 10 mL/s), ti = 3 s (60 kg bw). The complete CM bolus shape was monitored by creating time attenuation curves (TAC) in different vascular territories. Based on the TAC, the time to peak (TTP) and the peak enhancement were determined. The diagnostic window (relative enhancement > 300 HU), was calculated and compared to visual inspection of the corresponding CTA data sets.
The average relative arterial peak enhancements after baseline correction were 358.6 HU (A), 356.6 HU (B), 464.0 HU (C), and 477.6 HU (D). The TTP decreased with increasing IDR and decreasing ti, protocols A and B did not differ significantly (systemic arteries, p = 0.843; pulmonary arteries, p = 0.183). The delay time for bolus tracking (trigger level 100 HU; target enhancement 300 HU) for single-phase CTA was comparable for protocol A and B (3.9, 4.3 s) and C and D (2.4, 2.0 s). The scan window time frame was comparable for the different protocols by visual inspection of the different CTA data sets and by analyzing the TAC.
All protocols provided sufficient arterial enhancement. The use of a 70 kV CTA protocol is recommended because of a 50% reduction of total CM volume and a 50% reduced flow rate while maintaining the bolus profile. In contrast to pulmonary arterial enhancement, the systemic arterial enhancement improved only slightly increasing the IDR from 1.5 g/s to 3 g/s because of bolus dispersion of the very short bolus (3s) in the lungs.
CTA中极短的采集时间以及低千伏扫描方案的应用要求对造影剂（CM）注射方案进行调整。本研究的目的是在猪模型中优化胸腹部CTA中CM给药参数的使用。
对6头猪（体重55 - 68 kg）采用动态CTA方案（扫描长度454 mm，时间分辨率2.5 s，总采集时间70 s）进行检查。以随机顺序应用四种CM注射方案。120 kV CTA方案：（A）300 mg碘/千克体重（bw），注射速率（IDR）= 1.5 g/s（流速 = 5 mL/s），注射时间（ti）12 s（60 kg bw）。70 kV CTA方案：150 mg碘/千克bw：（B）IDR = 0.75 g/s（流速 = 2.5 mL/s），ti = 12 s（60 kg bw）；（C）IDR = 1.5 g/s（流速 = 5 mL/s），ti = 12 s（60 kg bw）；（D）IDR = 3.0 g/s（流速 = 10 mL/s），ti = 3 s（60 kg bw）。通过在不同血管区域创建时间 - 衰减曲线（TAC）来监测整个CM团注的形态。基于TAC，确定峰值时间（TTP）和峰值强化。计算诊断窗口（相对强化> 300 HU），并与相应CTA数据集的视觉检查结果进行比较。
基线校正后的平均相对动脉峰值强化分别为358.6 HU（A）、356.6 HU（B）、464.0 HU（C）和477.6 HU（D）。TTP随着IDR的增加和ti的减少而降低，方案A和B无显著差异（体动脉，p = 0.843；肺动脉，p = 0.183）。单相CTA的团注追踪延迟时间（触发水平100 HU；目标强化300 HU），方案A和B相当（3.9、4.3 s），方案C和D相当（2.4、2.0 s）。通过对不同CTA数据集的视觉检查以及分析TAC，不同方案的扫描窗口时间框架相当。
所有方案均提供了足够的动脉强化。推荐使用70 kV CTA方案，因为在保持团注形态的同时，总CM体积减少了50%，流速降低了50%。与肺动脉强化不同，由于极短团注（3 s）在肺内的团注扩散，将IDR从1.5 g/s增加到3 g/s时，体动脉强化仅略有改善。
