The University of Melbourne, Parkville, 3010, Australia.
The University of Sydney, Lidcombe, 2141, Australia.
Med Phys. 2019 Dec;46(12):5478-5487. doi: 10.1002/mp.13842. Epub 2019 Oct 20.
Propagation-based phase-contrast computed tomography (PB-CT) is a method for three-dimensional x-ray imaging that utilizes refraction, as well as absorption, of x rays in the tissues to increase the signal-to-noise ratio (SNR) in the resultant images, in comparison with equivalent conventional absorption-only x-ray tomography (CT). Importantly, the higher SNR is achieved without sacrificing spatial resolution or increasing the radiation dose delivered to the imaged tissues. The present work has been carried out in the context of the current development of a breast CT imaging facility at the Australian Synchrotron.
Seven unfixed complete mastectomy samples with and without breast cancer lesions have been imaged using absorption-only CT and PB-CT techniques under controlled experimental conditions. The radiation doses delivered to the mastectomy samples during the scans were comparable to those approved for mammographic screening. Physical characteristics of the reconstructed images, such as spatial resolution and SNR, have been measured and compared with the results of the radiological quality assessment of the complete absorption CT and PB-CT image stacks.
Despite the presence of some image artefacts, the PB-CT images have outperformed comparable absorption CT images collected at the same radiation dose, in terms of both the measured objective image characteristics and the radiological image scores. The outcomes of these experiments are shown to be consistent with predictions of the theory of PB-CT imaging and previous reported experimental studies of this imaging modality.
The results presented in this paper demonstrate that PB-CT holds a high potential for improving on the quality and diagnostic value of images obtained using existing medical x-ray technologies, such as mammography and digital breast tomosynthesis (DBT). If implemented at suitable synchrotron imaging facilities, PB-CT can be used to complement existing imaging modalities, leading to more accurate breast cancer diagnosis.
基于相位对比的计算机断层扫描（PB-CT）是一种三维 X 射线成像方法，它利用 X 射线在组织中的折射以及吸收来提高图像的信噪比（SNR），与等效的传统仅吸收 X 射线断层扫描（CT）相比。重要的是，在不牺牲空间分辨率或增加对成像组织的辐射剂量的情况下，可以实现更高的 SNR。本工作是在澳大利亚同步加速器正在开发乳腺 CT 成像设备的背景下进行的。
在受控实验条件下，使用仅吸收 CT 和 PB-CT 技术对 7 个带有和不带有乳腺癌病变的未固定完整乳房切除术样本进行了成像。扫描过程中对乳房切除术样本的辐射剂量与批准用于乳房 X 线照片筛查的剂量相当。已测量并比较了重建图像的物理特性，如空间分辨率和 SNR，以及完整吸收 CT 和 PB-CT 图像堆栈的放射学质量评估结果。
尽管存在一些图像伪影，但 PB-CT 图像在相同辐射剂量下，在测量的客观图像特性和放射图像评分方面，均优于可比的吸收 CT 图像。这些实验的结果与 PB-CT 成像理论和以前报道的这种成像方式的实验研究的预测一致。
本文介绍的结果表明，PB-CT 有可能提高现有医学 X 射线技术（如乳房 X 线照片和数字乳腺断层合成术（DBT））获得的图像的质量和诊断价值。如果在合适的同步加速器成像设施中实施，PB-CT 可用于补充现有的成像方式，从而更准确地诊断乳腺癌。
