Can dual isotope SPECT/CT scan be a gold imaging standard for diabetic foot (DF) evaluation?

Abstract

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Objectives: We recently introduced a new comprehensive dual isotope (Tc-99m HDP/In-111 WBC) SPECT/CT (DI) protocol for DF evaluation. This protocol is not only practical & conserving of patient (pt) & camera time, but also helps precise registration of all images in a single acquisition. This study explores DI clinical utility in routine DF evaluation.

Methods: 3-phase blood flow & pool images were obtained followed by WBC reinjection & next day dual energy bone (BS) & WBC (WBCS) SPECT/CT acquisition. Additional Tc-99m sulfur colloid bone marrow/In-111 SPECT/CT (step 2 DI) was obtained on the following day in 16 pt with suspected mid/hindfoot osteomyelitis (OM) & WBC uptake confined only to bone. BS, WBCS, DI & step 2 DI were separately reviewed by 2 observers for diagnosis (Dx) & Dx confidence (uncertain, probable, certain) based on each scan. Final Dx was determined as OM, soft tissue infection (STI), OM/STI or other pathology by surgical/pathological &/or up to 17 months clinical follow-up.

Results: 85 pt (age 58 ± 14 years, 55 men) were evaluated. There was higher accuracy of final Dx prediction by DI than WBCS or BS alone, assessed by Lambda (0.88, 0.57, 0.1, respectively) & uncertainty coefficient error reduction (80%, 52%, 5%, respectively). Of 247 lesions identified, Dx confidence was higher (p < 0.001) in DI than WBCS (100 Vs 60/119) or BS (168 Vs 11/186) alone. All 16 pt with probable Dx by DI were confirmed by step 2 DI, achieving perfect prediction of final Dx.

Conclusions: DI is a highly accurate imaging protocol that considerably improves detection & discrimination of STI & OM while providing precise anatomic localization of DF infection. When needed, step 2 DI can further yield a comprehensive DF imaging for definitive Dx.