PT - JOURNAL ARTICLE AU - Kenneth Nichols AU - Se-Young Yoon AU - Christopher Palestro TI - Added value of SPECT/CT compared to SPECT in<sup>99m</sup>Tc-PYP cardiac ATTR amyloidosis imaging DP - 2021 May 01 TA - Journal of Nuclear Medicine PG - 1639--1639 VI - 62 IP - supplement 1 4099 - http://jnm.snmjournals.org/content/62/supplement_1/1639.short 4100 - http://jnm.snmjournals.org/content/62/supplement_1/1639.full SO - J Nucl Med2021 May 01; 62 AB - 1639Objectives: 99mTc-PYP imaging accurately diagnoses cardiac ATTR amyloidosis (AT). Both planar imaging &amp; SPECT can be performed. SPECT eliminates overlying skeletal activity, distinguishes blood pool from myocardial activity, &amp; assesses the distribution of 99mTc-PYP myocardial uptake. There are few if any data, however, on the use of SPECT/CT. This investigation was undertaken to test the hypothesis that SPECT/CT, by virtue of its anatomic component &amp; attenuation correction, would improve image quality, assessment of radiopharmaceutical localization &amp; distribution &amp; the certainty of diagnosis. Methods: We performed a retrospective analysis of data collected for 71 pts (46 male pts, 25 female pts, mean age = 74±11 yrs) who underwent SPECT/CT 1 hr &amp; 3 hrs after I.V. injection of 555 MBq 99mTc-PYP. SPECT &amp; SPECT/CT were reconstructed by iterative reconstruction, while SPECT/CT reconstruction also included CT-generated attenuation correction. Non-attenuation-corrected SPECT studies were read with a maximum intensity projection cine displayed simultaneously with transaxial, sagittal &amp; coronal tomographic sections. SPECT/CT displays also included CT sections alone &amp; CT sections fused with attenuation-corrected SPECT tomographic sections. One experienced physician read 1 &amp; 3 hr SPECT &amp; SPECT/CT studies, all independently of one another, &amp; without knowledge of the results of the other readings. Left ventricular myocardial uptake was compared to rib uptake &amp; graded as 0: no uptake (negative), 1: uptake &lt; rib (equivocal), 2: uptake ≥ rib (positive). Right ventricular (RV) uptake was graded as 0: negative (no uptake), 1: equivocal, 2: positive (definite uptake). SPECT &amp; SPECT/CT were graded for image quality as 1: poor, 2: satisfactory, 3: excellent. Results: There were significantly fewer equivocal SPECT/CT’s than SPECT’s at both 1 &amp; 3 hrs. Of the 30 studies that were equivocal on 1 or 3 hr SPECT, 21(70%) became negative, 7 (23%) were still equivocal &amp; 2 (7%) became positive on 1 or 3 hr SPECT/CT. Consequently, studies were read as either definitely negative or definitely positive more frequently by SPECT/CT than by SPECT. Right ventricular uptake was appreciated significantly more often on SPECT/CT at both time points. Image quality was significantly better for SPECT/CT than for SPECT at both time points, &amp; was the only parameter that was better for 3 hr SPECT/CT than for 1 hr SPECT/CT (Table). Conclusions: The use of attenuation-corrected 99mTc-PYP tomographic information, in conjunction with the anatomic certainty afforded by the fused CT with SPECT images, resulted in superior image quality, fewer equivocal results, &amp; more confident readings. Consequently, SPECT/CT at either 1 or 3 hrs post-injection is preferable to SPECT in the evaluation of AT. View this table:Test results (* p &lt; 0.05 versus 3 hr SPECT/CT)