Prospective comparison of WBC SPECT/CT and conventional MRI for diagnosing osteomyelitis and monitoring treatment response in diabetic foot infections.
By: O.K. Öz, A.M. Sherwood, P.A. Crisologo, A.L. Killeen, K. Bhavan, J. La Fontaine, K.L. Rubitschung, H. Hwang, R.W. Haley, L.A. Lavery | Published in: Diabetologia | January 2026
[No openly-licensed figure was available for this post.]
Bone infection in the diabetic foot — diabetic foot osteomyelitis, or DFO — is one of the trickiest calls a clinician makes. Get it wrong in either direction and patients suffer: over-diagnosis means unnecessary surgery or prolonged antibiotics; under-diagnosis means the infection smoulders and the bone disintegrates, raising amputation risk. In routine practice, MRI is the default non-invasive imaging tool, valued for its soft-tissue resolution and wide availability. But MRI in the setting of a diabetic foot is notoriously prone to false positives — inflammation, oedema and Charcot changes can all mimic the signal of osteomyelitis on T1 and T2 sequences. A better test has been needed for some time, and a prospective study from UT Southwestern Medical Center in Dallas now makes a strong case for radiolabelled white blood cell SPECT/CT stepping into that role.
The study enrolled 47 patients with foot wounds clinically suspicious for DFO, submitting each to both 99m-Tc-labelled WBC SPECT/CT and conventional MRI, followed by bone biopsy as the reference standard. For the initial diagnosis, WBC SPECT/CT delivered a sensitivity of 85% and specificity of 79%, with a positive predictive value of 90%. MRI lagged behind: sensitivity 73%, specificity just 43%, positive predictive value 75%. In plain terms, MRI missed more infections and — especially — generated far more false alarms. After antibiotic treatment, 20 patients returned for follow-up imaging and repeat biopsy to see how well each modality could confirm infection clearance. At that point the two methods performed identically: both achieved 75% sensitivity, 75% specificity, and a shared negative predictive value of 92%, suggesting that either tool can reasonably confirm treatment response once therapy is underway.
The clinical message is nuanced but important. When a patient first arrives with a suspicious foot wound and the question is “is there bone infection?”, WBC SPECT/CT appears to give a more reliable answer than MRI — particularly by reducing the number of false positives that lead to unnecessary surgery. Once a diagnosis has been made and antibiotics are running, MRI is perfectly adequate for monitoring. The main practical barrier is access: radiolabelled WBC imaging requires nuclear medicine facilities that are not available at every institution, and the scan process takes hours. This is a single-centre prospective study with a modest sample size, so replication at other centres is warranted. But for hospitals with nuclear medicine capacity, the data are compelling enough to shift the conversation about which scan to order first.
📌 Source: Öz OK, Sherwood AM, Crisologo PA, Killeen AL, Bhavan K, La Fontaine J, Rubitschung KL, Hwang H, Haley RW, Lavery LA. Prospective comparison of WBC SPECT/CT and conventional MRI for diagnosing osteomyelitis and monitoring treatment response in diabetic foot infections. Diabetologia. 2026;69(4):1049–1059. https://doi.org/10.1007/s00125-025-06652-8 | PubMed PMID: 41549141
Tags: diabetic foot osteomyelitis, bone infection, SPECT CT, MRI, imaging diagnosis, white blood cell scan, diabetic foot infection, amputation prevention
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