Imaging of systemic amyloidosis

In systemic amyloidosis, several imaging techniques can be used to detect the presence, extent, and localization of amyloid deposits, to monitor their progression and regression, and to assess organ involvement and dysfunction. The presence of heart involvement is the main prognostic determinant and most efforts have been directed to the evaluation of cardiac amyloidosis. Heart involvement is classically diagnosed based on increased ventricular wall thickness and myocardial echogenicity (often referred to as “granular sparkling”) at echocardiography. However, more refined echocardiographic techniques, such as myocardial integrated backscatter, tissue Doppler, and strain imaging can provide evidence of early heart involvement and add functional and prognostic information. Magnetic resonance imaging (MRI) and cardiac scintigraphy with radiolabeled phosphate derivatives showed good sensitivity and specificity in the detection of heart involvement. In particular, scintigraphy with radiolabeled aprotinin can detect early amyloid deposits in the heart. Scintigraphy has the advantage of specific tissue characterization. The prototype of a specific amyloid tracer is iodinated serum amyloid P component (I-SAP). Scintigraphy with I-SAP is a useful complement for the diagnosis and provides an estimation of amyloid load, and serial studies can reveal disease progression and regression. However, I-SAP scintigraphy cannot image the heart. Anatomo-functional imaging, via ultrasound, computed tomography, and MRI scanning, is useful in the diagnosis and follow-up of localized amyloidosis. Accurate imaging of amyloid deposits can now be combined with the biochemical assessment of organ, particularly cardiac, damage and with reliable measurement of the circulating precursors. This will improve the care of patients with amyloidosis and shed light on the pathogenesis of organ damage