Incremental value of SPECT-CT to 67Ga studies

Abstract

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Objectives: To assess the incremental value of SPECT-CT in patients undergoing 67Ga studies. Methods: 40 consecutive patients had a 67Ga study for evaluation of lymphomas (n=34), osteomyelitis (n=4), and inflammatory diseases (n=2). The routine protocol included a planar whole-body scan followed by a low-dose SPECT-CT (Infinia-Hawkeye 4, GE Healthcare) covering the entire body in oncological indications or the body region of interest in inflammatory or infectious indications. Data processing and analysis was performed on the Xeleris 2.0 version. Two readers (R1 and R2) separately interpreted the planar and SPECT-CT images following a pre-defined template. Results: Overall, a 92.5% concordance (37/40) was obtained between the 2 readers interpretation. In the lymphoma group, 10 patients had a supra and infra-diaphragmatic disease, 10 patients had a supra-diaphragmatic disease only, 4 patients had an infra-diaphragmatic disease only, and 10 patients had no evidence of active disease. In the non-lymphoma group, 4 patients had no evidence of osteomyelitis, and 2 patients had a positive scan suggestive of inflammatory or infectious disease. In comparison to planar whole-body scan, SPECT-CT allowed better anatomic localization in 98% (R1) and 75% (R2) of cases, as well as differentiation between physiological and pathological uptakes in 100% (R1) and 45% (R2) of cases. In comparison to SPECT alone, SPECT-CT was found of incremental value in 75% (R1) and 70% (R2) of cases, with a concordant analysis in 58% of cases. The low-dose CT from SPECT-CT allowed detection of concordant morphological lesions in 48% of cases, which suggested a diagnosis in 35% of cases. Based on a concordant inter-reader interpretation, a final or faster diagnosis was obtained in 48% of cases. Conclusions: In 67Ga studies, SPECT-CT significantly improves the interpretation quality compared to whole-body and SPECT alone.