Lonneux M, Borbath I, Bol A, Coppens A, Sibomana M, Bausart R, Defrise M, Pauwels S, Michel C
Position Emission Tomography Laboratory, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.
Eur J Nucl Med. 1999 Jun;26(6):591-8. doi: 10.1007/s002590050426.
Whole-body fluorine-18 fluoro-2-d-deoxyglucose positron emission tomography (FDG-PET) is widely used in clinical centres for diagnosis, staging and therapy monitoring in oncology. Images are usually not corrected for attenuation since filtered backprojection (FBP) reconstruction methods require a 10 to 15-min transmission scan per bed position on most current PET devices equipped with germanium-68 rod transmission sources. Such an acquisition protocol would increase the total scanning time beyond acceptable limits. The aim of this work is to validate the use of iterative reconstruction methods, on both transmission and emission scans, in order to obtain a fully corrected whole-body study within a reasonable scanning time of 60 min. Five minute emission and 3-min transmission scans are acquired at each of the seven bed positions. The transmission data are reconstructed with OSEM (ordered subsets expectation maximization) and the last iteration is reprojected to obtain consistent attenuation correction factors (ACFs). The emission image is then also reconstructed with OSEM, using the emission scan corrected for normalization, scatter and decay together with the set of consistent ACFs as inputs. The total processing time is about 35 min, which is acceptable in a clinical environment. The image quality, readability and accuracy of uptake quantification were assessed in 38 patients scanned for various malignancies. The sensitivity for tumour detection was the same for the non-attenuation-corrected (NAC-FBP) and the attenuation-corrected (AC-OSEM) images. The AC-OSEM images were less noisy and easier to interpret. The interobserver reproducibility was significantly increased when compared with non-corrected images (96.1% vs 81.1%, P<0.01). Standardized uptake values (SUVs) measured on images reconstructed with OSEM (AC-OSEM) and filtered backprojection (AC-FBP) were similar in all body regions except in the pelvic area, where SUVs were higher on AC-FBP images (mean increase 7.74%, P<0. 01). Our results show that, when statistical reconstruction is applied to both transmission and emission data, high quality quantitative whole-body images are obtained within a reasonable scanning (60 min) and processing time, making it applicable in clinical practice.
全身氟-18氟代-2-脱氧葡萄糖正电子发射断层扫描（FDG-PET）在临床中心被广泛用于肿瘤学的诊断、分期和治疗监测。由于在大多数配备锗-68棒状透射源的当前PET设备上，滤波反投影（FBP）重建方法需要在每个床位进行10至15分钟的透射扫描，因此图像通常不进行衰减校正。这样的采集协议会使总扫描时间增加到超出可接受的限度。这项工作的目的是验证在透射和发射扫描中使用迭代重建方法，以便在60分钟的合理扫描时间内获得完全校正的全身研究。在七个床位位置分别采集5分钟的发射扫描和3分钟的透射扫描。透射数据用有序子集期望最大化（OSEM）进行重建，最后一次迭代被重投影以获得一致的衰减校正因子（ACF）。然后，发射图像也用OSEM重建，使用经过归一化、散射和衰变校正的发射扫描以及一致的ACF集作为输入。总处理时间约为35分钟，在临床环境中是可以接受的。对38例因各种恶性肿瘤进行扫描的患者评估了图像质量、可读性和摄取定量的准确性。未进行衰减校正（NAC-FBP）和进行了衰减校正（AC-OSEM）的图像对肿瘤检测的敏感性相同。AC-OSEM图像噪声更小且更易于解读。与未校正的图像相比，观察者间的可重复性显著提高（96.1%对81.1%，P<0.01）。除盆腔区域外，在使用OSEM（AC-OSEM）重建的图像和滤波反投影（AC-FBP）重建的图像上测量的标准化摄取值（SUV）在所有身体区域相似，在盆腔区域，AC-FBP图像上的SUV更高（平均增加7.74%，P<0.01）。我们的结果表明，当对透射和发射数据都应用统计重建时，能在合理的扫描（60分钟）和处理时间内获得高质量的定量全身图像，使其适用于临床实践。
