Quantification of myocardial 99mTc-labeled bisphosphonate uptake with cadmium zinc telluride camera in patients with transthyretin-related cardiac amyloidosis

Abstract

Purpose We aimed to compare different methods for semi-quantitative analysis of cardiac retention of bone tracers in patients with cardiac transthyretin amyloidosis (ATTR). Methods Data from 67 patients with ATTR who underwent both conventional whole-body scan and a CZT myocardial SPECT (DSPECT, Spectrum Dynamics) 3 h after injection of 99mTc-labeled bone tracer were analyzed. Visual scoring of cardiac retention was performed on whole-body scan according to Perugini 4-point grading system from 0 (no uptake) to 3 (strong cardiac uptake with mild/absent bone uptake). A planar heart-to-background (H:B) ratio was calculated using whole-body scan (wb-H:B). CZT SPECT was quantified using three methods: planar H:B ratio calculated from anterior reprojection (ant-H:B), left anterior oblique reprojection (LAO-H:B), and 3D-H:B ratio calculated from transaxial slices as mean counts in a VOI encompassing the heart divided by background VOI in the contralateral lung. Interventricular septal thickness was obtained using echocardiography. Results H:Bs obtained from planar and reprojected data were not statistically different (wb-H:B, 2.05 ± 0.64, ant-H:B, 1.97 ± 0.61, LAO-H:B, 2.06 ± 0.64, all p = ns). However, 3D-H:B was increased compared to planar H:Bs (3D-H:B, 4.06 ± 1.77, all p < 0.0001 vs. wb-H:B, ant-H:B, and LAO-H:B). Bland-Altman plots demonstrated that the difference between 3D and planar H:Bs increased with the mean value of myocardial uptake. 3D-H:B was best correlated to septal thickness (r = 0.45, p < 0.001). Finally, abnormal right ventricular uptake was associated with higher values of cardiac retention. Conclusion 3D semi-quantitative analysis of CZT SPECT optimized the assessment of 99mTc-labeled bone tracer myocardial uptake in patients with cardiac amyloidosis.

Quantitative SPECT/CT parameters of myocardial 99mTechnetium-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) uptake in suspected cardiac transthyretin amyloidosis

“…Novel therapeutic agents recently introduced may require precise assessment of disease burden at diagnosis and during follow up [ 1 , 17 – 19 ].…”

“…Feasibility of quantitative SPECT/CT with Tc-DPD/HDP/PYP in patients with suspected ATTR was recently assessed using CZT-based SPECT/CT scanners [ 19 – 21 ] with overall similar results to conventional SPECT/CT. Bone activity showed no significant differences between the scores, whereas lung and soft tissue activity was significantly higher in grade 2 and 3 [ 20 ].…”

Quantification of amyloid deposition using bone scan agents

“…Amyloid bone scan agents imaging has already been attempted using CZT camera. 14,15 However, the majority of these studies used the H/CL method originally introduced by Bokuhari. 11 The value of SUV, which was used in the present study, was originally developed for use in FDG PET in oncology.…”

Variability in bone-seeking tracers and imaging protocols for the diagnosis of cardiac amyloidosis: The more the merrier?

“…Masri et al showed comparable diagnostic performance in 233 patients who had planar and SPECT imaging at 1 h and 3 h. 17 For planar images grades 1-2, SPECT was needed to make the diagnosis. SPECT/CT enables quantitation 19,20 and localization of uptake in soft tissue. 21,22 Another variation of the protocol is timing of the imaging, from 10 min as suggested by Santarelli et al in this issue, 4 to 3 h after the injection, the most validated time point.…”