Soft-Tissue Uptake of ^99mTc-Diphosphonate and ^99mTc-Pyrophosphate in Systemic AA and AL Amyloidosis

Abstract

Reviewing the literature it is difficult to assess the significance of soft-tissue uptake on scanning with ^99mTc-labeled phosphates in amyloidosis, because of differences with regard to the radiopharmaceutical and the scanning technique used, and because of lack of information concerning the type of amyloid involved.

A comparative, prospective study was made to determine the efficacy of ^99mTc-methylene-diphosphonate (Tc-MDP) and ^99mTc-pyrophosphate (Tc-PYP) in demonstrating soft-tissue uptake in AA and AL amyloidosis. The results of scintigraphic imaging with Tc-MDP and Tc-PYP were compared with the clinical pattern of organ involvement in 6 patients with systemic AA and 6 patients with systemic AL amyloidosis. Image quality (contrast) was generally better with Tc-MDP than with Tc-PYP, although there was no difference in the extend or the intensity of the soft-tissue uptake. Tc-MDP can play an important role in evaluating amyloid disease with regard to involvement of the thyroid gland, the oropharyngeal region, the nervous system, the liver, the spleen, and the intestinal tract. In contrast with previous reports we found echocardiography to be more sensitive for demonstrating cardiac involvement than scintigraphy. Although nephropathy dominates the clinical scene in AA amyloidosis the scintigraphic pattern of organ involvement was compatible with the histological, multi-systemic, distribution of amyloid.