Leukocyte scintigraphy, SPECT/CT and PET/CT in prosthetic joint infection

Abstract: Background: A known complication of arthroplasty is prosthetic joint infection (PJI). It can be challenging to diagnose and treat PJI due to the formation of a biofilm protecting the bacteria in chronic infections from the innate immune system and antibiotics. The reference standard of PJI imaging is dual time point 99mTc-HMPAO-WBC scintigraphy, where a gamma camera detects the activity of radiolabelled leukocytes which migrate towards infection locations. Purpose: This thesis aims to evaluate the performance of different types of 99mTc- HMPAO-WBC imaging techniques and 18F-FDG-WBC PET/CT to detect infectious activity in patients with suspected chronic PJ. Study I, a retrospective cohort study, evaluated the sensitivity and specificity of a combination of dual time point 99mTc-HMPAO-WBC scintigraphy, 99mTc-HMPAOWBC SPECT/CT and 99mTc-Nanocolloid (bone marrow) scintigraphy in a clinical setting for treatment evaluation and detection of chronic PJI. It showed a worse performance of the method than is reported in the literature for PJI in general but is consistent with studies on chronic PJI. Study II, a subset analysis of the cohort in study I, compared visual and semi-quantitative evaluation of dual time point 99mTc-HMPAO-WBC scintigraphy, visual evaluation of single time point 99mTc-HMPAO-WBC scintigraphy combined with 99mTc-Nanocolloid (bone marrow) scintigraphy and visual evaluation of single time point 99mTc-HMPAOWBC SPECT/CT combined with 99mTc-Nanocolloid (bone marrow) SPECT/CT for treatment evaluation in patients with on-going antibiotic therapy. No method was shown superior. Study III, a prospective study, evaluated hip prostheses after uneventful primary arthroplasty without any signs of infection with 18F-FDG-WBC PET/CT and found a remaining uptake surrounding the prosthesis stem for at least 24 months. It seemed to decline over time. Study IV, a prospective study, compared single time point 99mTc-HMPAO-WBC SPECT/CT and 18F-FDG-WBC PET/CT, both combined with 99mTc-Nanocolloid SPECT/CT, in the diagnosis of PJI. Both methods had a poor performance, with no method being superior. Conclusions: In chronic PJI and treatment evaluation, dual time point 99mTc-HMPAOWBC scintigraphy is the preferred method out of the ones tested in these studies as no other method showed itself superior to all other methods result in an increased cost and radiation dose to the patient. Its performance is worse in chronic PJI than reported for PJI in general. 18F-FDG-WBC PET/CT does not seem to be a superior alternative.

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