Corredoira Eva, Vañó Eliseo, Alejo Luis, Ubeda Carlos, Gutiérrez-Larraya Federico, Garayoa Julia
Hospital Universitario La Paz.
J Appl Clin Med Phys. 2016 Jul 8;17(4):357-376. doi: 10.1120/jacmp.v17i4.5828.
The aim of this study was to assess image quality and radiation dose of a biplane angiographic system with cone-beam CT (CBCT) capability tuned for pediatric cardiac procedures. The results of this study can be used to explore dose reduction techniques. For pulsed fluoroscopy and cine modes, polymethyl methacrylate phantoms of various thicknesses and a Leeds TOR 18-FG test object were employed. Various fields of view (FOV) were selected. For CBCT, the study employed head and body dose phantoms, Catphan 504, and an anthropomorphic cardiology phantom. The study also compared two 3D rotational angiography protocols. The entrance surface air kerma per frame increases by a factor of 3-12 when comparing cine and fluoroscopy frames. The biggest difference in the signal-to- noise ratio between fluoroscopy and cine modes occurs at FOV 32 cm because fluoroscopy is acquired at a 1440 × 1440 pixel matrix size and in unbinned mode, whereas cine is acquired at 720 × 720 pixels and in binned mode. The high-contrast spatial resolution of cine is better than that of fluoroscopy, except for FOV 32 cm, because fluoroscopy mode with 32 cm FOV is unbinned. Acquiring CBCT series with a 16 cm head phantom using the standard dose protocol results in a threefold dose increase compared with the low-dose protocol. Although the amount of noise present in the images acquired with the low-dose protocol is much higher than that obtained with the standard mode, the images present better spatial resolution. A 1 mm diameter rod with 250 Hounsfield units can be distinguished in reconstructed images with an 8 mm slice width. Pediatric-specific protocols provide lower doses while maintaining sufficient image quality. The system offers a novel 3D imaging mode. The acquisition of CBCT images results in increased doses administered to the patients, but also provides further diagnostic information contained in the volumetric images. The assessed CBCT protocols provide images that are noisy, but with very good spatial resolution.
本研究的目的是评估具有针对儿科心脏手术进行优化的锥束CT（CBCT）功能的双平面血管造影系统的图像质量和辐射剂量。本研究结果可用于探索剂量降低技术。对于脉冲荧光透视和电影模式，使用了不同厚度的聚甲基丙烯酸甲酯体模和Leeds TOR 18-FG测试物体。选择了各种视野（FOV）。对于CBCT，该研究采用了头部和身体剂量体模、Catphan 504以及一个拟人化心脏病体模。该研究还比较了两种三维旋转血管造影协议。与电影和荧光透视帧相比，每帧的体表空气比释动能增加了3至12倍。荧光透视和电影模式之间信噪比的最大差异出现在视野为32 cm时，因为荧光透视是以1440×1440像素矩阵大小且在未合并模式下采集的，而电影是以720×720像素且在合并模式下采集的。电影的高对比度空间分辨率优于荧光透视，视野为32 cm时除外，因为视野为32 cm的荧光透视模式是未合并的。使用标准剂量协议用16 cm头部体模采集CBCT系列时，与低剂量协议相比，剂量增加了两倍。尽管低剂量协议采集的图像中的噪声量远高于标准模式下获得的噪声量，但这些图像具有更好的空间分辨率。在8 mm层厚的重建图像中可以分辨出直径为1 mm、亨氏单位为250的棒。儿科专用协议在保持足够图像质量的同时提供较低剂量。该系统提供了一种新颖的三维成像模式。CBCT图像的采集导致给予患者的剂量增加，但也提供了容积图像中包含的进一步诊断信息。评估的CBCT协议提供的图像有噪声，但具有非常好的空间分辨率。
