TTR and AL amyloidosis: Nuclear imaging with 99mTc- labeled 3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) or 99mTc- labeled pyrophosphate (PYP) bone tracer scintigraphy is helpful to evaluate suspected cardiac transthyretin (ATTR) amyloidosis in the absence of a detectable monoclonal protein, but is not relevant to the evaluation of suspected ALL and cannot be used to reliably distinguish cardiac ATTR from AL amyloidosis in the presence of a detectable monoclonal protein (42, 43).