Reynolds Tess, Ma Yiqun, Wang Tianyu, Mei Kai, Noël Peter B, Gang Grace J, Stayman J Webster
The University of Sydney, Australia.
Johns Hopkins University, United States of America.
Proc SPIE Int Soc Opt Eng. 2023 Feb;12466. doi: 10.1117/12.2652980. Epub 2023 Apr 3.
As the expansion of Cone Beam CT (CBCT) to new interventional procedures continues, the burdensome challenge of metal artifacts remains. Photon starvation and beam hardening from metallic implants and surgical tools in the field of view can result in the anatomy of interest being partially or fully obscured by imaging artifacts. Leveraging the flexibility of modern robotic CBCT imaging systems, implementing non-circular orbits designed for reducing metal artifacts by ensuring data-completeness during acquisition has become a reality. Here, we investigate using non-circular orbits to reduce metal artifacts arising from metallic hip prostheses when imaging pelvic anatomy. As a first proof-of-concept, we implement a sinusoidal and a double-circle-arc orbit on a CBCT test bench, imaging a physical pelvis phantom, with two metal hip prostheses, housing a 3D-printed iodine-filled radial line-pair target. A standard circular orbit implemented with the CBCT test bench acted as comparator. Imaging data collection and processing, geometric calibration and image reconstruction was completed using in-house developed software programs. Imaging with the standard circular orbit, image artifacts were observed in the pelvic bones and only 33 out of the possible 45 line-pairs of the radial line-pair target were partially resolvable in the reconstructed images. Comparatively, imaging with both the sinusoid and double-circle-arc orbits reduced artifacts in the surrounding anatomy and enabled all 45 line-pairs to be visibly resolved in the reconstructed images. These results indicate the potential of non-circular orbits to assist in revealing previously obstructed structures in the pelvic region in the presence of metal hip prosthesis.
随着锥形束CT（CBCT）在新的介入程序中的应用不断扩展，金属伪影这一棘手的挑战依然存在。视野内金属植入物和手术工具造成的光子饥饿和束硬化，可能导致感兴趣的解剖结构被成像伪影部分或完全遮挡。利用现代机器人CBCT成像系统的灵活性，通过在采集过程中确保数据完整性来设计非圆形轨道以减少金属伪影已成为现实。在此，我们研究使用非圆形轨道来减少在对骨盆解剖结构成像时金属髋关节假体产生的金属伪影。作为首个概念验证，我们在CBCT试验台上实现了正弦轨道和双圆弧轨道，对带有两个金属髋关节假体的物理骨盆模型进行成像，该模型内置一个3D打印的充碘径向线对靶标。CBCT试验台实现的标准圆形轨道用作对照。使用内部开发的软件程序完成成像数据采集与处理、几何校准和图像重建。采用标准圆形轨道成像时，在骨盆骨中观察到图像伪影，重建图像中径向线对靶标45对线对中只有33对部分可分辨。相比之下，采用正弦轨道和双圆弧轨道成像均减少了周围解剖结构中的伪影，并使所有45对线对在重建图像中均可清晰分辨。这些结果表明，在存在金属髋关节假体的情况下，非圆形轨道有助于揭示骨盆区域先前被遮挡的结构。
