Aldosari Sultan, Jansen Shirley, Sun Zhonghua
Discipline of Medical Radiation Sciences, School of Molecular and Life Sciences, Curtin University, Perth, Western Australia, Australia.
Department of Vascular and Endovascular Surgery, Sir Charles Gairdner Hospital, Perth, Western Australia, Australia.
Quant Imaging Med Surg. 2019 Jan;9(1):53-62. doi: 10.21037/qims.2018.09.15.
Three-dimensional (3D) printing has been shown to accurately replicate anatomical structures and pathologies in complex cardiovascular disease. Application of 3D printed models to simulate pulmonary arteries and pulmonary embolism (PE) could assist development of computed tomography pulmonary angiography (CTPA) protocols with low radiation dose, however, this has not been studied in the literature. The aim of this study was to investigate optimal CTPA protocols for detection of PE based on a 3D printed pulmonary model.
A patient-specific 3D printed pulmonary artery model was generated with thrombus placed in both main pulmonary arteries to represent PE. The model was scanned with 128-slice dual-source CT with slice thickness of 1 and 0.5 mm reconstruction interval. The tube voltage was selected to range from 70, 80, 100 to 120 kVp, and pitch value from 0.9 to 2.2 and 3.2. Quantitative assessment of image quality in terms of signal-to-noise ratio (SNR) was measured in the main pulmonary arteries and within the thrombus regions to determine the relationship between image quality and scanning protocols. Both two-dimensional (2D) and 3D virtual intravascular endoscopy (VIE) images were generated to demonstrate pulmonary artery and thrombus appearances.
PE was successfully simulated in the 3D printed pulmonary artery model. There were no significant differences in SNR measured in the main pulmonary arteries with 100 and 120 kVp CTPA protocols (P>0.05), regardless of pitch value used. SNR was significantly lower in the high-pitch 3.2 protocols when compared to other protocols using 70 and 80 kVp (P<0.05). There were no significant differences in SNR measured within the thrombus among the 100 and 120 kVp protocols (P>0.05). For low dose 70 and 80 kVp protocols, SNR was significantly lower in the high-pitch of 3.2 protocols than that in other protocols with different pitch values (P<0.01). 2D images showed the pulmonary arteries and thrombus clearly, while 3D VIE demonstrated intraluminal appearances of pulmonary wall and thrombus in all protocols, except for the 70 kVp and pitch 3.2 protocol, with visualization of thrombus and pulmonary artery wall affected by artifact associated with high image noise. Radiation dose was reduced by up to 80% when lowering kVp from 120 to 100 and 80 kVp with use of 3.2 high-pitch protocol, without significantly affecting image quality.
Low-dose CT pulmonary angiography can be achieved with use of low kVp (80 and 100) and high-pitch protocol with significant reduction in radiation dose while maintaining diagnostic images of PE. Use of high pitch, 3.2 in 70 kVp protocol should be avoided due to high image noise and poorer quality.
三维（3D）打印已被证明能够精确复制复杂心血管疾病中的解剖结构和病变。应用3D打印模型来模拟肺动脉和肺栓塞（PE）有助于开发低辐射剂量的计算机断层扫描肺动脉造影（CTPA）方案，然而，这在文献中尚未得到研究。本研究的目的是基于3D打印肺模型研究检测PE的最佳CTPA方案。
构建一个患者特异性的3D打印肺动脉模型，在两条主肺动脉中放置血栓以模拟PE。使用128层双源CT对模型进行扫描，层厚为1mm，重建间隔为0.5mm。管电压选择范围为70、80、100至120kVp，螺距值为0.9至2.2以及3.2。在主肺动脉和血栓区域测量图像质量的定量指标信噪比（SNR），以确定图像质量与扫描方案之间的关系。生成二维（2D）和三维虚拟血管内镜（VIE）图像以展示肺动脉和血栓的表现。
在3D打印肺动脉模型中成功模拟了PE。无论使用何种螺距值，100和120kVp CTPA方案在主肺动脉中测量的SNR无显著差异（P>0.05）。与使用70和80kVp的其他方案相比，高螺距3.2方案的SNR显著更低（P<0.05）。100和120kVp方案在血栓内测量的SNR无显著差异（P>0.05）。对于低剂量70和80kVp方案，高螺距3.2方案的SNR显著低于其他不同螺距值的方案（P<0.01）。2D图像清晰显示了肺动脉和血栓，而3D VIE在所有方案中均展示了肺动脉壁和血栓的腔内表现，但70kVp和螺距3.2方案除外，该方案中血栓和肺动脉壁的可视化受到与高图像噪声相关的伪影影响。当将管电压从120kVp降至100kVp和80kVp并使用3.2高螺距方案时辐射剂量降低了高达80%，且未显著影响图像质量。
使用低管电压（80和100）和高螺距方案可实现低剂量CT肺动脉造影，在保持PE诊断图像的同时显著降低辐射剂量。70kVp方案中应避免使用高螺距3.2，因为图像噪声高且质量较差。
