Staging diabetic foot infection using Tc- WBC and high resolution SPECT- CT imaging

Objectives Determine the ability of SPECT-CT to differentiate soft tissue infection from osteomyelitis in both the forefoot and hindfoot of diabetic patients.

Methods Retrospective review of 57 scans for diabetic foot infection/ulceration. Thin slice (1.25 mm) diagnostic quality CT images fused with SPECT (Siemens Symbia T2) were staged as follows: Negative (no abnormal WBC accumulation), Stage 0: soft tissue infection only (abnormal WBC accumulation in the soft tissues whose epicenter does not extend to the cortex of the bone), Stage I: periosteal osteomyelitis (abnormal WBC accumulation in the soft tissues whose epicenter extends to the cortex of the bone but does not cause CT abnormality of the cortex), Stage II: cortical osteomyelitis (abnormal WBC accumulation in the soft tissues whose epicenter extends to the cortex of the bone and causes cortical erosion on CT). Stage III: corticomedullary osteomyelitis (abnormal WBC accumulation in the soft tissues whose epicenter extends through the cortex of the bone and into the marrow space with erosion of cortical bone on CT).

Results Negative (no infection): 14 patients, Stage 0 (soft tissue only): 27 sites, Stage I (periosteal osteomyelitis): 6 sites, Stage II (cortical osteomyelitis): 9 sites, Stage III (corticomedullary osteomyelitis): 15 sites. Location/stage: hindfoot 19 sites- 8/19 (42%)stage 0, forefoot 38 sites- 17/38 (45%) stage 0.

Conclusions Thin slice diagnostic quality Tc WBC SPECT- CT fusion differentiates soft tissue, periostial, cortical, and corticomedullary infection equally well in the forefoot and hindfoot.