TY - JOUR
T1 - Absolute Quantitation of Cardiac 99mTc-Pyrophosphate Using Cadmium-Zinc-Telluride-Based SPECT/CT
AU - Dorbala, Sharmila
AU - Park, Mi Ae
AU - Cuddy, Sarah
AU - Singh, Vasvi
AU - Sullivan, Kyle
AU - Kim, Sirwoo
AU - Falk, Rodney H.
AU - Taqueti, Viviany R.
AU - Skali, Hicham
AU - Blankstein, Ron
AU - Bay, Camden
AU - Kijewski, Marie F.
AU - Di Carli, Marcelo F.
N1 - Funding Information:
This observational study included a small number of patients with ECV, the current reference standard for amyloid burden. Previously studied 99mTc-pyrophosphate metrics, that is, heart-–to–whole-body retention index and heart-to-contralateral ratio, were not evaluated in this study, as early imaging and planar imaging data, respectively, were not available. A high SUVmax in patients with visual grade 0 or 1 could represent excess blood-pool activity, but that possibility is less likely because the duration Sharmila Dorbala has received consul-ting fees from Pfizer and GE Healthcare; an investigator-initiated grant from Pfizer; and research support from the U.S. National Institutes of Health/National Heart, Lung, and Blood Institute (grants R01 HL130563 and HL150342) and the American Heart Association (grant AHA 16 CSA 28880004) for amyloidosis. Sarah Cuddy has received an investigator-initiated research grant from Pfizer. Rodney Falk has received consulting fees from Ionis Pharmaceuticals, Alnylam Pharmaceuticals, and Caelum Biosciences; research funding from GlaxoSmithKline and Akcea; and research support from the U.S. National Institutes of Health/National Heart, Lung, and Blood Institute (grant R01 HL130563). Marcelo Di Carli has received a research grant from Spectrum Dynamics and Gilead and consulting fees from Sanofi and GE. No other potential conflict of interest relevant to this article was reported.
Publisher Copyright:
© 2021 by the Society of Nuclear Medicine and Molecular Imaging.
PY - 2021/5/10
Y1 - 2021/5/10
N2 - The primary aims of this study were to determine the correlation between absolute quantitative 99mTc-pyrophosphate metrics and traditional measures of cardiac amyloid burden and to measure the intraobserver repeatability of the quantitative metrics. Methods: We studied 72 patients who underwent 99mTc-pyrophosphate SPECT/CT using a novel general-purpose cadmium-zinc-telluride- based SPECT/CT system. The clinical standard for these studies is visual grading (with grades of 0, 1, 2, and 3 indicating myocardial uptake absent, less than rib uptake, equal to rib uptake, or more than rib uptake, respectively). A visual grade of 2 or more was considered positive. For 72 patients, SUVmax, SUVmean, cardiac amyloid activity (CAA; i.e., SUVmean left ventricular [LV] volume), and percentage injected dose (%ID) were calculated, and visual grading was performed. The correlation was determined between the 4 quantitative metrics or visual grades and the LV mass index (LVMI) (indexed to body surface area on echocardiography, 67 patients). For a subset of 11 patients, the correlation was determined between the visual or quantitative metrics and the extracellular volume (ECV) on cardiac MRI. Normal linear regression was used to compare the standardized association of each of the 4 quantitative metrics with LVMI, as a surrogate for amyloid burden. Receiver-operatingcharacteristic curve analysis was used to determine the diagnostic accuracy of quantitative metrics, using visual grading as the reference standard. The intraobserver repeatability of generating quantitative metrics was also determined. Results: All 4 quantitative metrics were highly accurate, with an area under the receiver-operatingcharacteristic curve of more than 0.96 for diagnosis of transthyretin cardiac amyloidosis. SUVmax, SUVmean, CAA, %ID, and visual grade were moderately positively correlated with LVMI (r 5 0.485 for %ID) and strongly positively correlated, albeit in a small cohort, with ECV (r 5 0.873, SUVmax). Intraobserver repeatability was excellent, with less than a 2%coefficient of variation for SUVmax, %ID, and CAA and 3.8%for SUVmean. All 4 quantitative metrics had a standardized effect of more than 0.324 on LVMI; the largest standardized effect was 0.485, for %ID. Conclusion: In this first (to our knowledge) study of 99mTc-pyrophosphate cardiac imaging using a novel cadmiumzinc- telluride SPECT/CT scanner, SUVmax, SUVmean, CAA, and %ID measured by absolute quantitation of 99mTc-pyrophosphate were moderately correlated with LVMI and strongly correlated, albeit in a small cohort, with ECV. The intraobserver repeatability of generating the quantitative metrics was excellent.
AB - The primary aims of this study were to determine the correlation between absolute quantitative 99mTc-pyrophosphate metrics and traditional measures of cardiac amyloid burden and to measure the intraobserver repeatability of the quantitative metrics. Methods: We studied 72 patients who underwent 99mTc-pyrophosphate SPECT/CT using a novel general-purpose cadmium-zinc-telluride- based SPECT/CT system. The clinical standard for these studies is visual grading (with grades of 0, 1, 2, and 3 indicating myocardial uptake absent, less than rib uptake, equal to rib uptake, or more than rib uptake, respectively). A visual grade of 2 or more was considered positive. For 72 patients, SUVmax, SUVmean, cardiac amyloid activity (CAA; i.e., SUVmean left ventricular [LV] volume), and percentage injected dose (%ID) were calculated, and visual grading was performed. The correlation was determined between the 4 quantitative metrics or visual grades and the LV mass index (LVMI) (indexed to body surface area on echocardiography, 67 patients). For a subset of 11 patients, the correlation was determined between the visual or quantitative metrics and the extracellular volume (ECV) on cardiac MRI. Normal linear regression was used to compare the standardized association of each of the 4 quantitative metrics with LVMI, as a surrogate for amyloid burden. Receiver-operatingcharacteristic curve analysis was used to determine the diagnostic accuracy of quantitative metrics, using visual grading as the reference standard. The intraobserver repeatability of generating quantitative metrics was also determined. Results: All 4 quantitative metrics were highly accurate, with an area under the receiver-operatingcharacteristic curve of more than 0.96 for diagnosis of transthyretin cardiac amyloidosis. SUVmax, SUVmean, CAA, %ID, and visual grade were moderately positively correlated with LVMI (r 5 0.485 for %ID) and strongly positively correlated, albeit in a small cohort, with ECV (r 5 0.873, SUVmax). Intraobserver repeatability was excellent, with less than a 2%coefficient of variation for SUVmax, %ID, and CAA and 3.8%for SUVmean. All 4 quantitative metrics had a standardized effect of more than 0.324 on LVMI; the largest standardized effect was 0.485, for %ID. Conclusion: In this first (to our knowledge) study of 99mTc-pyrophosphate cardiac imaging using a novel cadmiumzinc- telluride SPECT/CT scanner, SUVmax, SUVmean, CAA, and %ID measured by absolute quantitation of 99mTc-pyrophosphate were moderately correlated with LVMI and strongly correlated, albeit in a small cohort, with ECV. The intraobserver repeatability of generating the quantitative metrics was excellent.
KW - 99mTc-pyrophosphate
KW - pyrophosphate;
KW - quantitative SPECT
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U2 - 10.2967/jnumed.120.247312
DO - 10.2967/jnumed.120.247312
M3 - Article
C2 - 32887756
AN - SCOPUS:85106539351
SN - 0161-5505
VL - 62
SP - 716
EP - 722
JO - Journal of Nuclear Medicine
JF - Journal of Nuclear Medicine
IS - 5
ER -