van der Weerdt Arno P, Boellaard Ronald, Knaapen Paul, Visser Cees A, Lammertsma Adriaan A, Visser Frans C
Department of Cardiology, Room 6N120, Institute for Cardiovascular Research-VU, VU University Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands.
J Nucl Med. 2004 Feb;45(2):169-75.
The aim of the present study was to evaluate the effect of postinjection transmission scanning (Post-Tx) on both the qualitative interpretation and the quantitative analysis of cardiac (18)F-FDG PET images. Furthermore, the accuracy of 2 different methods to correct for emission contamination was studied. An additional aim of this study was to compare images reconstructed with both standard filtered backprojection (FBP) and an iterative reconstruction algorithm (ordered-subset maximization expectation [OSEM]).
Sixteen patients underwent dynamic (18)F-FDG imaging. Both before injection of (18)F-FDG and after completing the emission scan, a 10-min transmission scan was performed (Pre-Tx and Post-Tx, respectively). Images were reconstructed using both FBP and OSEM. The emission study reconstructed with Pre-Tx was considered to be the gold standard. Emission studies were also reconstructed with Post-Tx, with and without correction for emission contamination. Correction for emission contamination was performed with either transmission image segmentation (TIS) or by estimating the emission bias from the last emission frame (dwell profile [DP] method). All images were then compared by calculating ratios of (18)F-FDG activity between corresponding myocardial segments in each patient. Furthermore, qualitative grading of (18)F-FDG uptake was compared between the studies.
The mean ratio of (18)F-FDG activity between segments from FBP-Post and FBP-Pre was 0.78 +/- 0.08. When TIS and DP were used, the mean ratios were 0.80 +/- 0.07 and 0.94 +/- 0.06, respectively. The use of OSEM resulted in, on average, 2% lower values for (18)F-FDG activity as compared with FBP. The mean normalized (18)F-FDG uptake was higher in FBP-Post, especially in segments with decreased (18)F-FDG activity. Only in the case of DP were no significant differences observed as compared with FBP-Pre. In general, qualitative analysis of the images showed that the agreement between the reconstruction methods was comparable with the reproducibility of FBP-Pre.
Post-Tx for attenuation correction in cardiac (18)F-FDG PET scans resulted in substantial underestimation of (18)F-FDG activity. More accurate results were obtained with correction for emission contamination using DP. Differences in visual assessment of (18)F-FDG images were small. Finally, iterative reconstruction could be used as an alternative to FBP in static (18)F-FDG imaging of the heart.
本研究的目的是评估注射后透射扫描（Post-Tx）对心脏（18）F-FDG PET图像的定性解读和定量分析的影响。此外，还研究了两种不同的发射污染校正方法的准确性。本研究的另一个目的是比较用标准滤波反投影（FBP）和迭代重建算法（有序子集最大化期望[OSEM]）重建的图像。
16例患者接受了动态（18）F-FDG成像。在注射（18）F-FDG之前和完成发射扫描之后，分别进行了10分钟的透射扫描（分别为Pre-Tx和Post-Tx）。使用FBP和OSEM重建图像。用Pre-Tx重建的发射研究被视为金标准。发射研究也用Post-Tx重建，有和没有发射污染校正。发射污染校正是通过透射图像分割（TIS）或通过从最后一个发射帧估计发射偏差（驻留剖面[DP]方法）来进行的。然后通过计算每个患者相应心肌节段之间的（18）F-FDG活性比值来比较所有图像。此外，还比较了各研究之间（18）F-FDG摄取的定性分级。
FBP-Post和FBP-Pre节段之间的（18）F-FDG活性平均比值为0.78±0.08。当使用TIS和DP时，平均比值分别为0.80±0.07和0.94±0.06。与FBP相比，使用OSEM导致（18）F-FDG活性平均降低2%。FBP-Post中平均标准化（18）F-FDG摄取较高，尤其是在（18）F-FDG活性降低的节段。仅在DP的情况下，与FBP-Pre相比未观察到显著差异。总体而言，图像的定性分析表明，重建方法之间的一致性与FBP-Pre的可重复性相当。
心脏（18）F-FDG PET扫描中用于衰减校正的Post-Tx导致（18）F-FDG活性严重低估。使用DP进行发射污染校正可获得更准确的结果。（18）F-FDG图像视觉评估的差异较小。最后，在心脏的静态（18）F-FDG成像中，迭代重建可作为FBP的替代方法。
