Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA 02114, United States of America. Department of Radiology, Harvard Medical School, Boston, MA 02115, United States of America.
Phys Med Biol. 2018 Jul 6;63(13):135019. doi: 10.1088/1361-6560/aacc2f.
Myocardial perfusion imaging (MPI) using rest/stress single photon emission computed tomography (SPECT) allows non-invasive assessment of reversible cardiac perfusion defects. Conventionally, reversible defects are identified using a difference image, called reversible map, obtained by subtracting the stress image from the rest image after registration and normalization of the two images. The identification of reversible defects using the conventional subtraction method is however limited by noise. We propose to jointly reconstruct rest and stress projection data to directly obtain the reversible map in a single reconstruction framework to improve the detectability of reversible defects. To evaluate the performance of the proposed method, we performed phantom studies to mimic reversible defects with different levels of severity and doses. As compared to the conventional subtraction method, the joint method yielded reversible maps with much lower noise and improved defect detectability. At a normal clinical dose level, the joint method improved the signal to noise ratio (SNR) of defect contrast in reversible maps from 13.2 to 66.4, 9.7 to 35.0, 6.1 to 13.2, and 3.1 to 6.5, for defect to normal myocardium concentration ratios of 0%, 25%, 50%, and 75%, respectively. The SNRs obtained using the joint method were improved from 6.1 to 13.2, 3.9 to 9.4, 3.0 to 8.0, and 2.1 to 7.1, for 100%, 75%, 50%, and 25% of the normal clinical dose as compared to the conventional subtraction method. To access clinical feasibility, we applied the joint method to a rest/stress SPECT MPI patient study. The joint method yielded a reversible map with much lower noise, translating into a much higher defect detectability as compared to the conventional subtraction method. Our results indicate that the joint method has the potential to improve radiologists' performance for assessing defects in rest/stress SPECT MPI. In addition, the joint method can be used to reduce dose or imaging time.
心肌灌注成像（MPI）使用静息/负荷单光子发射计算机断层扫描（SPECT）可以无创评估可逆性心肌灌注缺陷。传统上，通过减去静息图像和负荷图像的差异图像（称为可逆图）来识别可逆性缺陷，该差异图像是在对两幅图像进行配准和归一化后获得的。然而，使用传统的减法方法识别可逆性缺陷受到噪声的限制。我们建议联合重建静息和负荷投影数据，以便在单个重建框架中直接获得可逆图，从而提高可逆性缺陷的检测能力。为了评估所提出方法的性能，我们进行了模拟不同严重程度和剂量的可逆性缺陷的体模研究。与传统的减法方法相比，联合方法生成的可逆图噪声更低，缺陷检测能力更高。在正常临床剂量水平下，联合方法将可逆图中缺陷对比度的信噪比（SNR）从 13.2 提高到 66.4、9.7 提高到 35.0、6.1 提高到 13.2、3.1 提高到 6.5，对于缺陷与正常心肌浓度比分别为 0%、25%、50%和 75%。与传统的减法方法相比，联合方法将 SNR 从 6.1 提高到 13.2、3.9 提高到 9.4、3.0 提高到 8.0、2.1 提高到 7.1，用于 100%、75%、50%和 25%的正常临床剂量。为了评估临床可行性，我们将联合方法应用于静息/负荷 SPECT MPI 患者研究。与传统的减法方法相比，联合方法生成的可逆图噪声更低，因此缺陷检测能力更高。我们的结果表明，联合方法有可能提高放射科医生评估静息/负荷 SPECT MPI 中缺陷的能力。此外，联合方法可以用于减少剂量或成像时间。
