Dual versus single energy cardiac CT to measure extra cellular volume in cardiac amyloidosis: Correlations with cardiac MRI.

Rationale and objectives: Determine in cardiac amyloid (CA) patients, whether cardiac CT derived extracellular volume (ECV) correlates with that obtained by MRI. Perform this correlation with single (SECT) versus dual energy (DECT) CT and evaluate whether a single sample volume ECV-measure was as reliable as a global (16 segment) assessment. Materials and methods: CA patients who had undergone a clinical cardiac MRI (CMR) were recruited prospectively. SECT and DECT cardiac scans were performed. Three ECG-triggered prospective SECT scans were acquired: non-contrast, arterial-phase contrast and 5-minute delayed images. A DECT scan was performed at 7 min. Post processing was used to determine ECV. Analyses of SECT or DECT global ECV versus CMR were performed using the Pearson correlation coefficient, Bland Altman analysis and Intraclass correlation coefficient (ICC). Similar analyses were performed to examine the performance of single-segment sampling by SECT or DECT versus CMR. Results: 25 patients were recruited, mean age was 80.0 ± 7.1 years, 80 % were male, 21 patients had transthyretin- CA, 4 had light chain- CA. Correlations were close with both SECT or DECT global ECV versus CMR (r = 0.79 and 0.88 respectively, p < 0.001 for both). Reliability of both SECT and DECT to assess global ECV in comparison to CMR was good: ICC for SECT was 0.88 (95 % CI 0.73-0.95) and 0.93 (95 % CI 0.82-0.97) for DECT. For single volume sampling techniques: correlations were close with both SECT or DECT versus CMR (r = 0.60 and 0.72 respectively, p < 0.01 for both) There was no difference in ICC for SECT (0.74, 95 %CI 0.41-0.88) versus DECT (0.84, 95 % CI 0.63-0.93). Wider confidence intervals were noted for ICC with single versus global CT derived ECV assessment. Mean effective radiation dose was for SECT was 5.49 ± 8.04 mSv and 6.90 ± 3.01 mSv for DECT dual energy CT (p = 0.75). Conclusions: Global ECV values derived by both DECT or SECT correlated with those obtained by CMR and demonstrated good reliability by ICC in a population of CA patients. DECT and SECT single sampling derived ECV values also demonstrated close correlation and good reliability but the ICCs for single sampling had wider confidence intervals than global ECV assessment.