Nowak B, Zimny M, Schwarz E R, Kaiser H J, Schaefer W, Reinartz P, vom Dahl J, Buell U
Department of Nuclear Medicine, University Hospital, Aachen University of Technology, Germany.
Eur J Nucl Med. 2000 Oct;27(10):1501-8. doi: 10.1007/s002590000316.
This study assessed a dual-head coincidence gamma camera (hybrid PET) equipped with single-photon transmission for myocardial fluorine-18 fluorodeoxyglucose (FDG) imaging by comparing this technique with conventional positron emission tomography (PET) using a dedicated ring PET scanner. Twenty-one patients were studied with dedicated FDG ring PET and FDG hybrid PET for evaluation of myocardial glucose metabolism, as well as technetium-99m tetrofosmin single-photon emission tomography (SPET) to estimate myocardial perfusion. All patients underwent transmitted attenuation correction using germanium-68 rod sources for ring PET and caesium-137 point sources for hybrid PET. Ring PET and hybrid PET emission scans were started 61+/-12 and 98+/-15 min, respectively, after administration of 154+/-31 MBq FDG. Attenuation-corrected images were reconstructed iteratively for ring PET and hybrid PET (ac-hybrid PET), and non-attenuation-corrected images for hybrid PET (non-ac-hybrid PET) only. Tracer distribution was analysed semiquantitatively using a volumetric vector sampling method dividing the left ventricular wall into 13 segments. FDG distribution in non-ac-hybrid PET and ring PET correlated with r=0.36 (P<0.0001), and in ac-hybrid PET and ring PET with r=0.79 (P<0.0001). Non-ac-hybrid PET significantly overestimated FDG uptake in the apical and supra-apical segments, and underestimated FDG uptake in the remaining segments, with the exception of one lateral segment. Ac-hybrid PET significantly overestimated FDG uptake in the apical segment, and underestimated FDG uptake in only three posteroseptal segments. A three-grade score was used to classify diagnosis of viability by FDG PET in 136 segments with reduced perfusion as assessed by SPET. Compared with ring PET, non-ac-hybrid PET showed concordant diagnoses in 80 segments (59%) and ac-hybrid PET in 101 segments (74%) (P<0.001). Agreement between ring PET and non-ac-hybrid PET was best in the basal lateral wall and in the apical-septal segment (80%-100%), and lowest in the apical, supra-apical and posteroseptal segments (41%-55%). Ac-hybrid PET showed highest agreement in the lateral wall (89%-100%), and lowest agreement in the apical and the basal septal segments (59%-67%). In conclusion, non-uniform attenuation correction with singles transmission significantly improves the diagnostic accuracy of myocardial dual-head gamma camera coincidence imaging with FDG. However, results equivalent to those obtained with ring PET cannot yet be attained, even if attenuation correction is applied. New rebinning algorithms for three-dimensional data may further improve the performance of ac-hybrid PET and should be evaluated in future studies.
本研究通过将配备单光子发射的双头符合伽马相机（混合型正电子发射断层显像，即PET）用于心肌氟-18氟脱氧葡萄糖（FDG）成像技术与使用专用环形PET扫描仪的传统正电子发射断层显像（PET）进行比较，对该技术进行了评估。21例患者接受了专用FDG环形PET和FDG混合型PET检查，以评估心肌葡萄糖代谢情况，同时还接受了锝-99m替曲膦单光子发射断层显像（SPET）以评估心肌灌注。所有患者均使用锗-68棒源对环形PET进行透射衰减校正，使用铯-137点源对混合型PET进行透射衰减校正。分别在给予154±31MBq FDG后61±12分钟和98±15分钟开始环形PET和混合型PET发射扫描。对环形PET和混合型PET（衰减校正后的混合型PET，即ac-hybrid PET）进行迭代重建衰减校正图像，仅对混合型PET（未进行衰减校正的混合型PET，即non-ac-hybrid PET）重建未衰减校正图像。采用体积向量采样方法将左心室壁分为13个节段，对示踪剂分布进行半定量分析。未进行衰减校正的混合型PET和环形PET中FDG分布的相关性r = 0.36（P<0.0001），衰减校正后的混合型PET和环形PET中FDG分布的相关性r = 0.79（P<0.0001）。未进行衰减校正的混合型PET显著高估了心尖和心尖上节段的FDG摄取，低估了其余节段（除一个侧壁节段外）的FDG摄取。衰减校正后的混合型PET显著高估了心尖节段的FDG摄取，仅低估了三个后间隔节段的FDG摄取。对于通过SPET评估灌注减少的136个节段，采用三级评分法对FDG PET的存活诊断进行分类。与环形PET相比，未进行衰减校正的混合型PET在80个节段（59%）诊断结果一致，衰减校正后的混合型PET在101个节段（74%）诊断结果一致（P<0.001）。环形PET与未进行衰减校正的混合型PET之间的一致性在基底侧壁和心尖-间隔节段最佳（80%-100%），在心尖、心尖上和后间隔节段最低（41%-55%）。衰减校正后的混合型PET在侧壁的一致性最高（89%-100%），在心尖和基底间隔节段的一致性最低（59%-67%）。总之，采用单光子发射进行的不均匀衰减校正显著提高了心肌双头伽马相机符合FDG成像的诊断准确性。然而，即使应用了衰减校正，仍无法获得与环形PET相同的结果。用于三维数据的新重排算法可能会进一步提高衰减校正后的混合型PET的性能，应在未来研究中进行评估。
