Visualization of multiple organ amyloid involvement in systemic amyloidosis using 11C-PiB PET imaging

Purpose To investigate the utility of Pittsburgh compound B (PiB) positron emission tomography (PET) imaging for evaluating whole-body amyloid involvement in patients with systemic amyloidosis. Methods Whole-body 11 C-PiB PET was performed in seven patients with systemic immunoglobulin light-chain (AL) amyloidosis, seven patients with hereditary transthyretin (ATTRm) amyloidosis, one asymptomatic TTR mutation carrier and three healthy controls. The correlations between clinical organ involvement, radiological 11 C-PiB uptake and histopathological findings were analysed for each organ. Results Organ involvement on 11 C-PiB PET imaging showed good correlations with the clinical findings for the heart and stomach. Abnormal tracer uptake was also observed in the spleen, lachrymal gland, submandibular gland, sublingual gland, lymph node, brain, scalp, extraocular muscles, nasal mucosa, pharynx, tongue and nuchal muscles, most of which were asymptomatic. Physiological tracer uptake was universally observed in the urinary tract (kidney, renal pelvis, ureter and bladder) and enterohepatic circulatory system (liver, gallbladder, bile duct and small intestine) in all participants. Most of the patients and one healthy control subject showed asymptomatic tracer uptake in the lung and parotid gland. The peripheral nervous system did not show any tracer uptake even in patients with apparent peripheral neuropathy. Histological amyloid deposition was confirmed in biopsied myocardium and gastric mucosa where abnormal 11 C-PiB retention was observed. Conclusions 11 C-PiB PET imaging can be used clinically in the systemic evaluation of amyloid distribution in patients with AL and ATTRm amyloidosis. Quantitative analysis of 11 C-PiB PET images may be useful in therapy evaluation and will reveal whether amyloid clearance is correlated with clinical response.