Maximum standardized uptake value of foot SPECT/CT using Tc-99m HDP in patients with accessory navicular bone as a predictor of surgical treatment

Quantitative bone SPECT/CT (single- photon emission computed tomography/computed tomography) using Tc- 99m hydroxymethylene diphosphonate is emerging as a useful imaging modality for skeletal diseases. Accessory navicular bone (ANB) has been evaluated by bone scintigraphy only qualitatively and semiquantitatively. However, a truly objective quantitative assessment of ANB is lacking. Here, we measured the maximum standardized uptake value (SUVmax) of the ANB and investigated its usefulness as an imaging biomarker for ANB. Consecutive quantitative bone SPECT/CT studies that had been performed on the foot were retrospectively analyzed. One hundred five patients (male: female =44: 61; median age=32.0 [range, 11- 81] years old; 31 negative controls without ANB and 74 patients with ANB [7 unilateral and 67 bilateral]) and their 210 feet were investigated. The ANBs were classified into types I, II, III (Geist classification), and 0 (contralateral navicular of unilateral ANB). Type II ANBs were subclassified into II- 1 (with bony abnormality) or II- 0 (without bony abnormality). The treatment modality was observation, conservative treatment, or surgical removal. The associations between the SUVmax and clinical findings, including surgery, were investigated. Patients with type II- 1 ANB had the highest SUVmax among all ANB types (P<. 001). The SUVmax of symptomatic ANB was greater than that for asymptomatic ANB (P<. 001), and the SUVmax for the surgically resected ANB group was also significantly higher than that for the observation only or conservative treatment group (P<. 001). Subtype II- 1 had a significantly higher SUVmax compared with subtype II- 0 (P<. 001). Logistic regression analyses in type II ANB showed that young age (P=. 020) and SUVmax (P=. 031) were significant predictors for surgery. Receiver operating characteristic curve and survival analyses revealed an optimal SUVmax cutoff of 5.27g/mL for predicting final surgical treatment. SUVmax derived from quantitative bone SPECT/CT was strongly associated with symptom, surgical treatment, and a known highrisk type of ANB. Risk stratification for final surgical treatment of ANB can be achieved using the SUVmax from quantitative bone SPECT/CT.