基于相衬 CT 的相位恢复技术在微泡造影剂血管成像中的应用。
Phase retrieval-based phase-contrast CT for vascular imaging with microbubble contrast agent.
机构信息
Department of Radiology, Rui Jin Hospital, Shanghai Jiao Tong University, and School of Medicine, Shanghai, China.
Department of Neurology, Rui Jin Hospital, Shanghai Jiao Tong University, and School of Medicine, Shanghai, China.
出版信息
Med Phys. 2021 Jul;48(7):3459-3469. doi: 10.1002/mp.14819. Epub 2021 May 9.
PURPOSE
The introduction of microbubble contrast agent into tissues can create significant phase shifts. Phase retrieval (PR)-based phase-contrast computed tomography (PCCT) is an imaging method for retrieving and reconstructing the phase shifts within an object. This study aimed to evaluate the feasibility of PR-based PCCT with microbubble contrast agent for vascular imaging.
METHODS
Projection phase-contrast images of individual microbubbles and a cluster of microbubbles were captured and compared. Contrast enhancement from microbubbles was evaluated by comparing to the gold standard iodine-based contrast agent in vitro. The arterial systems of 14 Sprague-Dawley rats were perfused with microbubbles or saline. The rat hearts and the arterial systems were excised and imaged ex vivo. CT imaging was performed at the energy of 22 keV. PR was performed using the phase-attenuation duality (PAD) method with different δ/β values (PAD property). The contrast-to-noise ratio (CNR) was used for quantitatively assessing the contrast enhancement.
RESULTS
Individual microbubbles functioned as a lens to focus the x rays, whereas, a cluster of microbubbles scattered the x rays. In the in vitro experiment, the contrast enhancement from iodine was significantly greater than that from microbubbles (P < 0.05). In the heart samples, the CNRs for microbubbles on PR-based PCCT were significantly greater than those on absorption-contrast CT (ACCT) and PR-free PCCT (both P < 0.001). The CNRs for microbubbles were also significantly greater than those for saline on PR-based PCCT in the samples (P < 0.001). Although they provided weaker contrast enhancement than that from iodine, microbubbles could still provide sufficient contrast enhancement to clearly show the 3D architecture of rat aortas and their main branches.
CONCLUSION
The imaging modality can currently be used as a complement or alternative to absorption-based microCT for imaging vessels in biological samples.
目的
将微泡造影剂引入组织会产生显著的相位偏移。基于相位恢复（PR）的相衬计算机断层扫描（PCCT）是一种用于获取和重建物体内部相位偏移的成像方法。本研究旨在评估基于 PR 的微泡造影剂 PCCT 用于血管成像的可行性。
方法
采集并比较了单个微泡和微泡簇的投影相衬图像。通过与金标准碘基造影剂进行比较，评估了微泡的对比增强效果。将微泡或生理盐水灌注到 14 只 Sprague-Dawley 大鼠的动脉系统中。离体切除大鼠心脏和动脉系统并进行成像。CT 成像在 22keV 的能量下进行。使用相位衰减对偶性（PAD）方法和不同的 δ/β 值（PAD 属性）进行 PR。使用对比噪声比（CNR）定量评估对比增强效果。
结果
单个微泡可以作为聚焦 X 射线的透镜，而微泡簇则会散射 X 射线。在体外实验中，碘的对比增强明显大于微泡（P<0.05）。在心脏样本中，基于 PR 的 PCCT 中微泡的 CNR 明显大于吸收相衬 CT（ACCT）和无 PR 的 PCCT（均 P<0.001）。基于 PR 的 PCCT 中微泡的 CNR 也明显大于生理盐水样本（P<0.001）。虽然微泡的对比增强效果不如碘，但仍足以清晰显示大鼠主动脉及其主要分支的 3D 结构。
结论
目前该成像方式可作为吸收基微 CT 成像生物样本中血管的补充或替代方法。
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