Abstract
1494
Aim: To evaluate the added value of single-photon emission computerized tomography/computerized tomography (SPECT/CT) during technetium-99m-methyl diphosphonate (Tc-99m MDP) triple phase bone scan (TPBS) in assessment of underlying osteomyelitis in patients with stage IV pressure ulcers.
Material and Methods: Retrospective review of TPBS in patients with stage IV pressure ulcers who had SPECT/CT imaging during scan late phase. We included 21 patients (mean age of 64.2±25.2 years; 16 males). Data included patients’ demographics, clinical findings, laboratory results as leukocytic count and ESR as well as biopsies or tissue cultures and other imaging modalities if available. Image interpretation was performed to assess early vascular phase activity and to compare extent and intensity of uptake in late planar and SPECT/CT images. A 4 point semiquantitative visual score was used to assess the intensity of radiotracer uptake (no uptake =0, mild =1, moderate =2, severe =3). Lesions were interpreted independently on both planar and SPECT/CT images based on: uptake intensity, location in relation to overlying ulcer and presence of other pathologies as heterotopic ossification (HO), fracture sites, internal fixation or joint prosthesis as: positive (unequivocal uptake related to overlying soft tissue ulcer site), negative (no uptake or uptake not related to ulcer site) or equivocal (faint uptake close to ulcer site). We used paired student T-test to compare mean values of planar and SPECT scores. McNemar test was used to test the change in proportions of negative, positive and equivocal results as well as equivocal versus definitive results between planar and SPECT/CT images as paired data and Pearson correlation was used to assess correlation between planar and SPECT uptake scores.
Results: Study population included 13/21 (62%) diabetics, 2/21 (9.5%) traumatic brain injury, 6/21 (28.6%) spinal injury, 7/21 (33%) post road traffic accident, 6/21 (28.6%) post stroke and 7/21 (33%) with dementia. We studied 38 pressure ulcer sites (14 sacrococygeal, 20 femoral trochanteric, 3 calcaneal and 1 elbow). Tissue cultures were available for 32 (84.2%) sites and all were positive but 3. Biopsies were available for 6 lesions in 5 patients with evidence of chronic osteomyelitis in 1 site, acute osteomyelitis in 2 sites and mixed acute and chronic in 3 sites. The mean lesional uptake score for SPECT images was higher compared to planar images (2.47 vs 1.65; p<0.0001). Planar and SPECT uptake scores were positively correlated (r=0.557; p<0.001). Based on the overall planar and SPECT/CT images there were 29/38 (76.3%) positive sites, 7/38 (18.4%) negative sites and 2/38 (5.3%) equivocal sites. SPECT/CT compared to planar images significantly reduced equivocal sites to only 2 (5.3%) compared to 16/38 (42%); p<0.001. From 16 equivocal lesions on planar 12 were positive and 2 were negative on SPECT/CT and out of 19 positive lesions 3 were negative on SPECT/CT while 1 out of 3 negative lesions on planar became positive on SPECT/CT. Adding SPECT/CT reduced equivocal results by accurate localization of uptake sites, differentiating areas of osteomyelitis related to the overlying pressure ulcers from non-related uptake sites due to other causes as HO or around internal fixation or hip prostheses hardware hence reducing false positive rate and reducing false negative rate by better detecting sites not well seen on planar images due to urinary bladder overlap or difficult patient positioning. Conclusion: SPECT/CT imaging has a significant added diagnostic value over planar imaging in accurately detecting osseous involvement with stage IV pressure ulcers. It significantly reduced equivocal results by accurate uptake localization, reducing false positive results due to other associated pathologies and reducing false negative results due to overlap by other structures or difficult patient positioning.