Simultaneous dual-radionuclide myocardial perfusion imaging with a solid-state dedicated cardiac camera

Abstract

Purpose: We compared simultaneous dual-radionuclide (DR) stress and rest myocardial perfusion imaging (MPI) with a novel solid-state cardiac camera and a conventional SPECT camera with separate stress and rest acquisitions.

Methods: Of 27 consecutive patients recruited, 24 (64.5+/-11.8 years of age, 16 men) were injected with 74 MBq of (201)Tl (rest) and 250 MBq (99m)Tc-MIBI (stress). Conventional MPI acquisition times for stress and rest are 21 min and 16 min, respectively. Rest (201)Tl for 6 min and simultaneous DR 15-min list mode gated scans were performed on a D-SPECT cardiac scanner. In 11 patients DR D-SPECT was performed first and in 13 patients conventional stress (99m)Tc-MIBI SPECT imaging was performed followed by DR D-SPECT. The DR D-SPECT data were processed using a spill-over and scatter correction method. DR D-SPECT images were compared with rest (201)Tl D-SPECT and with conventional SPECT images by visual analysis employing the 17-segment model and a five-point scale (0 normal, 4 absent) to calculate the summed stress and rest scores. Image quality was assessed on a four-point scale (1 poor, 4 very good) and gut activity was assessed on a four-point scale (0 none, 3 high).

Results: Conventional MPI studies were abnormal at stress in 17 patients and at rest in 9 patients. In the 17 abnormal stress studies DR D-SPECT MPI showed 113 abnormal segments and conventional MPI showed 93 abnormal segments. In the nine abnormal rest studies DR D-SPECT showed 45 abnormal segments and conventional MPI showed 48 abnormal segments. The summed stress and rest scores on conventional SPECT and DR D-SPECT were highly correlated (r=0.9790 and 0.9694, respectively). The summed scores of rest (201)Tl D-SPECT and DR-DSPECT were also highly correlated (r=0.9968, p<0.0001 for all). In six patients stress perfusion defects were significantly larger on stress DR D-SPECT images, and five of these patients were imaged earlier by D-SPECT than by conventional SPECT.

Conclusion: Fast and high-quality simultaneous DR MPI is feasible with D-SPECT in a single imaging session with comparable diagnostic performance and image quality to conventional SPECT and to a separate rest (201)Tl D-SPECT acquisition.

Figure 1

A combined energy spectrum for ^99mTc and ²⁰¹Tl is plotted together with the energy windows selected for the dual radionuclide acquisition (N1-N6). These correspond to photopeaks for the two radionuclides (N1, N3, N5) and energy windows that estimate scatter and cross-talk (N2, N4, N6). Note that the algorithm can accommodate overlapping windows (e.g. N1, N2).

Figure 2

Correlation between DR D-SPECT and conventional SPECT for (A) summed rest score (r=0.9657, p<0.0001) and (B) % total perfusion defect at rest (r=0.9665, p<0.0001). Bland-Altman graphs showing good agreement between SRS (C) and % total perfusion defect (D) of DR D-SPECT and conventional SPECT with a mean difference of 0.79, 95% confidence interval −2.459-0.428 for SRS; mean difference 1.16, 95% confidence interval −3.54-0.627 for %TPD rest. DR=dual radionuclide; SRS= summed rest score; %TPD= % total perfusion defect.

Figure 3

66 year old male with atypical angina and shortness of breath. Known occluded RCA. Conventional SPECT images (top) showed absent uptake in the basal inferior wall and a stress induced infero-apical defect. Rest images showed infero-apical improvement. DR D-SPECT (bottom) showed similar findings. RCA = right coronary artery; DR = dual radionuclide

Figure 4

Correlation between DR D-SPECT and conventional SPECT for (A) summed stress score (r=0.9790, p<0.0001) and (B) % total perfusion defect at stress (r=0.9784, p<0.0001). Bland-Altman graphs showing good agreement between SSS (C) and % total perfusion defect (D) of DR D-SPECT and conventional SPECT with a mean difference of −2.0, 95% confidence interval −2.392-1.991 for SSS; mean difference −3.0, 95% confidence interval −3.42-3.076 for % TPD stress. DR=dual radionuclide; SSS= summed stress score; %TPD= % total perfusion defect.

Figure 5

39 year old male with previous history of inferior wall infarction, RCA and LAD PCI. In addition there is a known LCX lesion. Conventional SPECT (top) showed a stress induced inferior and apical perfusion defect with a possible stress induced defect in the septum, while DR D-SPECT showed the same abnormalities but more prominently and added a stress induced perfusion defect in the inferolateral wall. Coronary angiography 80 days after MPI showed 70% LAD in-stent restenosis, short focal 80% LCX stenosis and proximal occlusion of RCA. The patient was referred for CABG. RCA= right coronary artery; LAD=left anterior descending artery; PCI= percutaneous intervention; LCX= left circumflex artery; DR = dual-radionuclide; MPI= myocardial perfusion imaging; CABG = coronary artery bypass graft surgery.