Key result
SPECT/CT quantification outperforms planar techniques for diagnosing cardiac amyloidosis with a 0.999 AUC.
Why the study?
Noninvasive diagnosis of transthyretin-related cardiac amyloidosis typically relies on planar bone scintigraphy, prompting investigation into whether SPECT/CT quantification improves diagnostic accuracy and quantifies amyloid burden.
Does SPECT/CT quantification of DPD scans improve diagnostic accuracy compared to planar imaging in patients evaluated for cardiac amyloidosis?
Observational (n=100)
No
Does SPECT/CT quantification of DPD scans improve diagnostic accuracy compared to planar imaging in patients evaluated for cardiac amyloidosis?
Absolute Event Rate: 0.999% vs 0.987%
SPECT/CT quantification of DPD scintigraphy, particularly using a composite SUV retention index, outperforms planar techniques for diagnosing cardiac amyloidosis and overcoming soft tissue uptake confounding.
May improve DPD scan accuracy for cardiac amyloidosis; hypothesis-generating and requires prospective validation before practice change.
To assess whether single-photon emission computed tomography (SPECT/CT) quantification of bone scintigraphy would improve diagnostic accuracy and offer a means of quantifying amyloid burden. Transthyretin-related cardiac amyloidosis is common and can be diagnosed noninvasively using bone scintigraphy; interpretation, however, relies on planar images. SPECT/CT imaging offers 3-dimensional visualization. This was a single-center, retrospective analysis of 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) scans reported using the Perugini grading system (0 = negative; 1 to 3 = increasingly positive). Conventional planar quantification techniques (heart/contralateral lung, and heart/whole-body retention ratios) were performed. Heart, adjacent vertebra, paraspinal muscle and liver peak standardized uptake values (SUVpeak) were recorded from SPECT/CT acquisitions. An SUV retention index was also calculated: (cardiac SUVpeak/vertebral SUVpeak) × paraspinal muscle SUVpeak. In a subgroup of patients, SPECT/CT quantification was compared with myocardial extracellular volume quantification by CT imaging (ECVCT). A total of 100 DPD scans were analyzed (patient age 84 ± 9 years; 52% male): 40 were Perugini grade 0, 12 were grade 1, 41 were grade 2, and 7 were grade 3. Cardiac SUVpeak increased from grade 0 to grade 2; however, it plateaued between grades 2 and 3 (p < 0.001). Paraspinal muscle SUVpeak increased with grade (p < 0.001), whereas vertebral SUVpeak decreased (p < 0.001). The composite parameter of SUV retention index overcame the plateauing of the cardiac SUVpeak and increased across all grades (p < 0.001). Cardiac SUVpeak correlated well (r2 = 0.73; p < 0.001) with ECVCT. Both the cardiac SUVpeak and SUV retention index had excellent diagnostic accuracy (area under the curve [AUC]: 0.999). The heart to contralateral lung ratio performed the best of the planar quantification techniques (AUC: 0.987). SPECT/CT quantification in DPD scintigraphy is possible and outperforms planar quantification techniques. Differentiation of Perugini grade 2 or 3 is confounded by soft tissue uptake, which can be overcome by a composite SUV retention index. This index can help in the diagnosis of cardiac amyloidosis and may offer a means of monitoring response to therapy.
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Scully et al. (2020) conducted an observational in Transthyretin-related cardiac amyloidosis (n=100). SPECT/CT quantification (cardiac SUVpeak and SUV retention index) vs. Conventional planar quantification techniques was evaluated on Diagnostic accuracy (Area Under the Curve). SPECT/CT quantification using cardiac SUVpeak and SUV retention index yielded excellent diagnostic accuracy for cardiac amyloidosis (AUC 0.999), outperforming planar quantification techniques.
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