RT Journal Article SR Electronic T1 The Effects of Misregistration between CT Attenuation and Emission PET Images in 13N-Ammonia Myocardial PET/CT JF Journal of Nuclear Medicine Technology JO J. Nucl. Med. Technol. FD Society of Nuclear Medicine SP jnmt.116.172742 DO 10.2967/jnmt.116.172742 A1 Tomita, Yoya A1 Ishida, Masaki A1 Ichikawa, Yasutaka A1 Suzawa, Naohisa A1 Kobayashi, Shigeki A1 Maeda, Hisato A1 Takeda, kan A1 Sakuma, Hajime YR 2016 UL http://tech.snmjournals.org/content/early/2016/04/21/jnmt.116.172742.abstract AB Previous studies using two-dimensional (2D) PET/CT demonstrated that image misregistration between PET and CT due to respiratory and cardiac motion results in substantial reduction of tracer uptake. The resolution and quality of cardiac PET/CT images have been considerably improved with recent three-dimensional (3D) PET acquisition techniques. In the current study, we investigated the impact of misregistration between PET and CT on myocardial 13N-ammonia uptake uptake by using 3D PET/CT images reconstructed with 3D ordered-subset expectation maximization (OSEM) combined with time of flight (TOF) and point-spread function (PSF) modeling. Methods: Eight normal volunteers (7 men, 53 ± 19 years) underwent 13N-ammonia cardiac PET/CT study at rest. Firstly misregistration of PET/CT images was manually corrected to generate reference images. Then, 13N-ammonia PET/CT images were misregistered by shifting PET images by 1-, 2-, 3-, 4-, 5-, 10- and 15-mm along both the x-axis (left) and z-axis (cranial) from the reference. PET images were reconstructed using the attenuation CT images in each setting. Left ventricle (LV) short-axis PET/CT image was divided into 4 segments (anterior, septum, inferior, lateral). Degree of erroneous reduction of LV myocardial 13N-ammonia uptake was visually graded using a 4-point scale (0: none, 1: mild, 2: moderate, 3: severe) on basal, mid and apical slices. Uptake ratios of anterior, lateral and inferior walls to the septum (A/S, L/S, I/S) were evaluated on basal, mid and apical segments. Results: Statistically significant reduction of regional myocardial 13N-ammonia uptake in anterior (P < 0.01) and lateral walls (P < 0.05) was observed when the misregistration was greater than 10 mm. The uptake ratios of A/S, L/S and I/S were 1.00 ± 0.04, 0.96 ± 0.08 and 0.91 ± 0.03 in the reference images, respectively. The A/S and L/S ratios significantly decreased when misregistration exceeded 10 mm (A/S, 0.80 ± 0.06, P < 0.0001; L/S, 0.82 ± 0.07, P < 0.01), while the decrease of I/S was relatively small throughout 7 different misregistration conditions (I/S, 0.86 ± 0.05 at 15-mm misregistration, P = 0.06). Conclusion: In the current study employing 3D PET/CT with 3D OSEM, TOF and PSF algorithms, statistically significant artifactual reduction in tracer uptake was observed in the heart regions that extended into the lung on misregistered CT when the amount of misregistration exceeds 10 mm.