Mawlawi Osama, Erasmus Jeremy J, Pan Tinsu, Cody Dianna D, Campbell Rachelle, Lonn Albert H, Kohlmyer Steve, Macapinlac Homer A, Podoloff Donald A
Department of Imaging Physics, M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Box 56, Houston, TX 77030, USA.
AJR Am J Roentgenol. 2006 May;186(5):1458-67. doi: 10.2214/AJR.05.0255.
Discrepancy between fields of view (FOVs) in a PET/CT scanner causes a truncation artifact when imaging extends beyond the CT FOV. The purposes of this study were to evaluate the impact of this artifact on measurements of 18F-FDG activity concentrations and to assess a truncation correction algorithm.
Two phantoms and five patients were used in this study. In the first phantom, three inserts (water, air, bone equivalent) were placed in a water-filled cylinder containing 18F-FDG. In the second phantom study, a chest phantom and a 2-L bottle fitted with a bone insert were used to simulate a patient's torso and arm. Both phantoms were imaged while positioned centrally (baseline) and at the edge of the CT FOV to induce truncation. PET images were reconstructed using attenuation maps from truncated and truncation-corrected CT images. Regions of interest (ROIs) drawn on the inserts, simulated arm, and background water of the baseline truncated and truncation-corrected PET images were compared. In addition, extremity malignancies of five patients truncated on CT images were reconstructed with and without correction and the maximum standard uptake values (SUVs) of the malignancies were compared.
Truncation artifact manifests as a rim of high activity concentration at the edge of the truncated CT image with an adjacent low-concentration region peripherally. The correction algorithm minimizes these effects. Phantom studies showed a maximum variation of -5.4% in the truncation-corrected background water image compared with the baseline image. Activity concentration in the water insert was 6.3% higher while that of air and bone inserts was similar to baseline. Extremity malignancies showed a consistent increase in the maximum SUV after truncation correction.
Truncation affects measurements of 18F-FDG activity concentrations in PET/CT. A truncation-correction algorithm corrects truncation artifacts with small residual error.
当PET/CT扫描仪的成像范围超出CT视野（FOV）时，视野之间的差异会导致截断伪影。本研究的目的是评估这种伪影对18F-FDG活性浓度测量的影响，并评估一种截断校正算法。
本研究使用了两个体模和五名患者。在第一个体模中，将三个插入物（水、空气、骨等效物）放置在装有18F-FDG的充水圆柱体中。在第二个体模研究中，使用胸部体模和装有骨插入物的2升瓶子来模拟患者的躯干和手臂。两个体模在位于CT视野中心（基线）和CT视野边缘时进行成像，以诱导截断。使用来自截断和截断校正CT图像的衰减图重建PET图像。比较在基线截断和截断校正PET图像的插入物、模拟手臂和背景水上绘制的感兴趣区域（ROI）。此外，对五名CT图像截断的患者的四肢恶性肿瘤进行了有校正和无校正的重建，并比较了恶性肿瘤的最大标准摄取值（SUV）。
截断伪影表现为截断CT图像边缘的高活性浓度边缘，其周围有相邻的低浓度区域。校正算法可将这些影响降至最低。体模研究表明，与基线图像相比，截断校正后的背景水图像的最大变化为-5.4%。水插入物中的活性浓度高6.3%，而空气和骨插入物中的活性浓度与基线相似。截断校正后，四肢恶性肿瘤的最大SUV持续增加。
截断会影响PET/CT中18F-FDG活性浓度的测量。截断校正算法可校正截断伪影，残留误差较小。
