Extra-cardiac abnormalities on 82-Rubidium cardiac PET/CT

Objectives The role of 82-Rubidium in recognizing extra-cardiac diseases is minimally investigated. Our aim was to evaluate the frequency and incremental added value of clinically significant extra-cardiac findings from 82-Rb cardiac PET/CT studies.

Methods The study included all consecutive patients, who were referred from July 2008 to June 2010 for 82-Rb cardiac PET/CT. A blinded reader reviewed the images to assess for any areas of abnormal extra-cardiac uptake, i.e. not corresponding to expected physiologic distribution of Rubidium. Confirmatory imaging studies or clinical, laboratory and pathological confirmation for extra-cardiac findings were used as reference standard.

Results The images of four hundred six patients (142male;264female) with a mean age±SD of 59.7±12.9years were reviewed. Incidental extra-cardiac abnormalities were found in 67 out of 406 patients (16.5%). Among them, 8 patients had malignant etiologies (1.9%),including 3 breast cancers,2 multiple myeloma, 2 lung cancers and 1 lymphoma. Benign etiologies of extracardiac 82-Rb uptake were Bronchitis/pneumonitis, breast fibrocystic change, diffuse breast uptake in nursing mother, Hydradenitis Suppurativa, post-CABGs sternal uptake, Sarcoidosis, chronic thyroiditis, liver uptake in a patient with SVC obstruction and adrenal adenoma. Forty one patients (23 males and 12 females; mean age:64.6±9.2years) indicated abnormal diffuse bone marrow uptake, which could be explained by previously diagnosed anemia (35 patients) or unknown etiology (6 patients).

Conclusions Incidental extra-cardiac findings are present in a significant portion of Rb-82 PET/CT studies. The spectrum of pathologies visualized by extra-cardiac uptake of 82-Rb was wide. Although most of the extra-cardiac findings represent clinically known pathologies, these coincidental findings in routine 82-Rb cardiac PET/CT scans may have significant clinical impact, and offer the referring physician the chance to obtain added clinically relevant information. 82-Rb is a promising radiotracer for PET scanning beyond cardiac imaging