Verification of reprojected planar images generated from a ring-configured cadmium zinc telluride gamma camera in scintigraphy for diagnosing transthyretin cardiac amyloidosis

Abstract

Background Non-invasive diagnosis of amyloid transthyretin (ATTR) cardiac amyloidosis using planar scintigraphy and single-photon emission computed tomography – computed tomography (SPECT-CT) with 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) has high specificity and sensitivity. However, the introduction of ring-configured cadmium zinc telluride (CZT) gamma cameras warrants an update in the acquisition method since these systems are not able to perform planar scintigraphy. We aimed to verify the use of reprojected anterior planar images generated from reconstructed SPECT-CT to replace planar scintigraphy. Methods and Results The study examined 30 patients referred for clinically indicated 99mTc-DPD scintigraphy who were scanned with both a conventional camera and a ring-configured CZT camera. Planar images from the conventional system were compared to reprojected planar images from the ring-configured CZT system. The images were evaluated in regard to image quality and Perugini score in a blinded fashion by three nuclear medicine physicians. Heart-to-contralateral (H/CL) ratios were calculated. There were 27 patients who had an identical Perugini scores in planar and reprojected planar images, yielding a strong level of agreement and inter-rater reliability among the three readers (κ=0.85, R< 0.001). For the three patients scored differently (scored as Perugini 0 or Perugini 1), SPECT-CT was requested for full assessment. The H/CL ratios showed a strong correlation ratio (r=0.98, p < 0.0001). A shift towards lower image quality was seen for the reprojected images. Conclusions Reprojected planar images generated from 99mTc-DPD SPECT-CT scintigraphy can be used to score ATTR amyloidosis and extract H/CL ratios in the same way as planar images.