^99mTc-DPD scintigraphy and SPECT/CT in patients with AL and ATTR type amyloidosis: Potential clinical implications

Although pathological confirmation is the gold standard for diagnosis of amyloidosis, there is a need for a relevant imaging modality to identify involved organs and evaluate disease extent. Thus, we prospectively investigated imaging findings of ^99mTc-DPD scintigraphy in AL and ATTR amyloidosis.A total of 21 subjects with pathologically confirmed AL or ATTR amyloidosis were included. Pretreatment whole body ^99mTc-DPD planar scanning and regional SPECT/CT were performed in all subjects. For allegedly involved organs, ^99mTc-DPD uptake was visually and semi-quantitatively evaluated on a 4-point scale (grade 0: no uptake, 1: uptake less than spine, 2: uptake similar to spine, and 3: uptake greater than spine).There were 29 organs involved in AL and 12 in ATTR. Significant ^99mTc-DPD uptake was found in 24 organs (sensitivity = 82.8%) in AL and 9 organs (sensitivity = 75.0%) in ATTR. Additional SPECT/CT was helpful to ensure abnormal DPD uptake in the involved organs, which was uncertain by attenuation in planar imaging. Degree of ^99mTc-DPD uptake was significantly higher in ATTR compared with AL amyloidosis (P = .017). Diffuse soft tissue uptake with photon defects in the liver area was found only in ATTR amyloidosis.This study showed that ^99mTc-DPD scintigraphy might have capacity to differentiate between AL and ATTR subtypes with good sensitivity in various organs involving primary systemic AL and ATTR amyloidosis. Additional SPECT/CT significantly improved the diagnostic efficacy of ^99mTc-DPD scintigraphy.