Horinouchi Hiroki, Sekitani Toshinori, Nishii Tatsuya, Negi Noriyuki, Sofue Keitaro, Fukuda Tetsuya, Takahashi Satoru
Radiology, National Cerebral and Cardiovascular Center, Suita, JPN.
Radiological Technologist, Osaka College of High Technology, Osaka, JPN.
Cureus. 2025 Apr 7;17(4):e81849. doi: 10.7759/cureus.81849. eCollection 2025 Apr.
Adaptive four-dimensional (4D) spiral computed tomography (CT) scans facilitate the acquisition of volume perfusion data for organs or long-range vessels; however, optimizing image quality and reducing noise while minimizing radiation doses remains challenging. Thus, image-processing techniques such as temporal maximum intensity projection (MIP) and average intensity projection (AIP) are crucial in this context. This ex vivo study aimed to compare the image noise, spatial resolution, and measurements of temporal MIP and AIP images generated from low radiation dose 4D CT scans data with those of conventional CT images using phantoms. Three phantoms were scanned with equivalent radiation doses using single helical and adaptive 10-phase 4D spiral scans using a third-generation dual-source CT scanner. Temporal MIP and AIP images of 4D CT scans were generated by summing varying numbers of phases, incorporating automatic motion correction with non-rigid registration and noise reduction algorithm. The CT values and image noise of the temporal MIP and AIP images were compared to conventional CT images. The task transfer function (TTF) was calculated using static phantoms. Vessel diameters of the phantoms for each image dataset were evaluated using motion phantoms. Temporal AIP images showed comparable CT values with those of the reference image. In contrast, the CT values of the temporal MIP images were significantly higher than those of the reference images (p<0.01). The image noise of temporal AIP images with six or more phases was equal to or lower than that of the reference images. In contrast, temporal MIP images exhibited consistently high noise levels regardless of the number of summed phases. The TTF of temporal AIP images was comparable to that of the reference CT images. However, the TTF of temporal MIP images gradually decreased as the number of summed phases increased. No significant differences were observed in vessel diameter measurements among the three groups or with varying numbers of summed phases (p>0.05). In conclusion, temporal MIP and AIP images generated from low radiation dose 4D CT scans could effectively reduce noise while preserving measurement reliability in the motion phantom, achieving performance comparable to conventional CT images.
自适应四维（4D）螺旋计算机断层扫描（CT）有助于获取器官或长距离血管的容积灌注数据；然而，在将辐射剂量降至最低的同时优化图像质量并降低噪声仍然具有挑战性。因此，诸如时间最大强度投影（MIP）和平均强度投影（AIP）等图像处理技术在这种情况下至关重要。本离体研究旨在使用体模比较低辐射剂量4D CT扫描数据生成的时间MIP和AIP图像与传统CT图像的图像噪声、空间分辨率以及测量结果。使用第三代双源CT扫描仪，通过单螺旋扫描和自适应10期4D螺旋扫描，以等效辐射剂量对三个体模进行扫描。通过对不同数量的期相求和，结合使用非刚性配准和降噪算法的自动运动校正，生成4D CT扫描的时间MIP和AIP图像。将时间MIP和AIP图像的CT值及图像噪声与传统CT图像进行比较。使用静态体模计算任务传递函数（TTF）。使用运动体模评估每个图像数据集的体模血管直径。时间AIP图像的CT值与参考图像相当。相比之下，时间MIP图像的CT值显著高于参考图像（p<0.01）。具有六个或更多期相的时间AIP图像的图像噪声等于或低于参考图像。相比之下，无论求和期相的数量如何，时间MIP图像的噪声水平始终较高。时间AIP图像的TTF与参考CT图像相当。然而，时间MIP图像的TTF随着求和期相数量的增加而逐渐降低。三组之间或不同求和期相数量之间在血管直径测量方面未观察到显著差异（p>0.05）。总之，低辐射剂量4D CT扫描生成的时间MIP和AIP图像能够在运动体模中有效降低噪声，同时保持测量可靠性，实现与传统CT图像相当的性能。
