Imaging findings of Tc-99m DPD scan in patients with primary systemic AL amyloidosis

Objectives Although there were several studies that Tc-99m DPD uptake was increased in cardiac amyloidosis, Tc-99m DPD uptake in other organs was not known. We prospectively investigated the imaging findings of Tc-99m DPD scan in primary systemic AL amyloidosis.

Methods Subjects were 9 patients (M:F = 6:3; age, 59±11 yr) with histologically and immunochemically confirmed primary systemic AL amyloidosis who underwent Tc-99m DPD scan before treatment. Whole body planar and regional SPECT/CT images were acquired in all subjects. For involved organs, Tc-99m DPD uptake was visually and semiquantitatively evaluated with a 4-point scale (grade 0: no significant uptake or no difference from physiologic uptake, grade 1: uptake less than spines, grade 2: uptake similar to spines, and grade 3: uptake more than spines).

Results There were no other underlying malignancies or inflammation except multiple myeloma in 5 patients. There were 11 organs with histologically confirmed amyloidosis (heart in 4, kidney in 4, lung in 1, and liver in 2). Significant Tc-99m DPD uptake was found in 7 of the 11 organs (63.6%); 75.0% in heart (3/4; grade 1 in 3), 50.0% in kidney (2/4; grade 2 in 1, and grade 3 in 1), 100% in liver (2/2; grade 1 in 1 and grade 3 in 1), and 0% in lung (0/1). In 8 of 11 organs (72.7%; 4 in kidney and 4 in heart), additional SPECT/CT images were helpful to decide whether Tc-99m DPD uptake was related to amyloidosis or not.

Conclusions Significant Tc-99m DPD uptake may be observed in various organs with primary systemic AL amyloidosis. SPECT/CT images may provide additional diagnostic information to planar images. However, moderate sensitivity and variable degree of uptake suggests that it is difficult for Tc-99m DPD scan to be used as primary diagnostic imaging tool. Further studies for disease severity and prognosis evaluation are needed to evaluate the role of Tc-99m DPD scan in patients with primary systemic AL amyloidosis.