Comparison of SPECT/CT and MRI in diagnosing symptomatic lesions in ankle and foot pain patients: diagnostic performance and relation to lesion type

Abstract

Purpose: The purpose of this study was to compare the diagnostic performance of SPECT/CT and MRI in patients with ankle and foot pain, with regard to the lesion types.

Materials and methods: Fifty consecutive patients with ankle and foot pain, who underwent 99mTc-MDP SPECT/CT and MRI, were retrospectively enrolled in this study. Symptomatic lesions were determined based on clinical examination and response to treatment. On MRI and SPECT/CT, detected lesions were classified as bone, ligament/tendon, and joint lesions. Uptake on SPECT/CT was assessed using a 4-grade system. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of SPECT/CT and MRI were evaluated in all detected lesions and each lesion type. Diagnostic value of uptake grade was analyzed using receiver-operating characteristics (ROC) curve analysis, and diagnostic performance was compared using Chi-square or McNemar tests.

Results: In overall lesions, the sensitivity, PPV and NPV of SPECT/CT for symptomatic lesions were 93%, 56%, 91%, and they were 98%, 48%, 95% for MRI. There was no significant difference between SPECT/CT and MRI. However, the specificity of SPECT/CT was significantly higher than that of MRI (48% versus 24%, P = 0.016). Uptake grade on SPECT/CT was significantly higher in symptomatic lesions (P < 0.001), and its area under curve on ROC analysis was 0.787. In the analysis of each lesion type, the specificity of SPECT/CT was poor in joint lesions compared with other lesion types and MRI (P < 0.001, respectively). MRI exhibited lower specificity than SPECT/CT in bone lesions (P = 0.004) and ligament/tendon lesions (P < 0.001).

Conclusions: SPECT/CT has MRI-comparable diagnostic performance for symptomatic lesions in ankle and foot pain patients. SPECT/CT and MRI exhibit different diagnostic specificity in different lesion types. SPECT/CT may be used as a complementary imaging method to MRI for enhancing diagnostic specificity.

Fig 1. Images of representative cases.

(A) Axial MRI (left) of a19-year-old woman revealed an osteochondral lesion in the right medial talar dome area. SPECT/CT (middle and right) also exhibited focal intense uptake in the same area, concordant with MRI. The lesion was diagnosed with symptomatic osteochondral lesion of talus, and her ankle pain improved after arthroscopic multiple drilling of the talus. (B) Sagittal fat-saturated MRI (left) of a 65-year-old woman with posterior heel pain revealed an osteochondral lesion in the right medial talar dome area, whereas SPECT/CT showed no abnormal uptake in the same area. The pain improved after surgical removal of a right calcaneal bony fragment, and the talar dome lesion was determined to be asymptomatic.

Fig 2. Representative images of lesion types.

CT-axial (left), SPECT-axial (middle), and fusion-axial (right) images of SPECT/CT are shown; a bone lesion (contusion) involving the medial malleolus (A), a joint lesion (arthritis) involving the left talocrural joint (B), and a ligament/tendon lesion (tendinitis) involving the Achilles tendon insertion site of calcaneus (C).

Fig 3. ROC curve analysis of uptake grade for diagnosing symptomatic lesions.

The area under curve was 0.787, and the optimal cutoff was grade 3 with 60% sensitivity and 91% specificity.