# Diagnostic Performance of Integrated 18 F FDG PETMR in the Diagnosis of Recurrent Foot Infection—Comparison with 18 F FDG PETCT and Conventional 99m Tc MDP Bone Scan

## TL;DR

This study shows that integrated 18F FDG PETMR is more accurate than PETCT and bone scans for diagnosing recurrent foot infections and related bone issues in diabetic patients.

## Contribution

The study demonstrates the superior diagnostic performance of integrated PETMR for foot infections compared to existing imaging techniques.

## Key findings

- 18F FDG PETMR showed 99.4% sensitivity, 100% specificity, and 98.6% accuracy for diagnosing soft tissue infections.
- PETMR outperformed PETCT and bone scans in differentiating osteomyelitis from Charcot's foot in post-surgery cases.
- The study highlights PETMR's ability to delineate infection depth and guide surgical planning in complex foot cases.

## Abstract

Introduction
 Ulcerated foot is a forerunner for amputations among diabetics. Early detection of foot complications is imperative for guiding management; more so in recurrent foot infections.

Purpose
 The objective of this study was first, to determine the diagnostic performance of integrated Fluorodeoxyglucose (FDG) Positron emission tomography (PET) magnetic resonance (MR) in suspected soft tissue infections (STIs)/osteomyelitis (OM) in patients presenting with recurrent foot infections. Second, to compare regional [
18
F] fluoro-2-deoxy-2-d-glucose (
18
F FDG) PET Computed tomography (CT) and conventional three-phase
99m
Tc methylene diphosphonate (MDP) bone scan (BS) in this group of patients along with integrated PETMR.

Materials and Methods
 A total of 21 adult patients with suspected recurrent foot infections were prospectively enrolled from March 2020 until September 2023 in our tertiary care center. All patients were primarily referred for a regional PETMR (foot) study. We instituted a protocol to combine three-phase
99m
Tc MDP BS followed by PET imaging the next day (PETMR followed by PETCT). Images were correlated with patients' foot symptoms and clinical examination.

Results
 Diagnostic performance of
18
F FDG PETMR was superior compared with other two imaging modalities for STIs and OM. Using
18
F FDG PETCT, sensitivity, specificity, and accuracy for diagnosing soft tissue (ST) foot infections was 91, 71, and 79%, respectively, while for PET MR, it was 99.4, 100, and 98.6% versus 74.4, 31.2, and 62% for BS.

Conclusion
 Our study recommends the use of integrated
18
F FDG PETMR for podiatry-related problems, as it provides excellent ST demarcation and information on associated bone involvement, if any. It helps in accurately differentiating OM versus Charcot's foot; more so in surgically intervened or previously debrided foot when compared with the other two modalities.
18
F FDG PETMR clearly demarcates the depth and extent of surgery one must perform to get a reprieve from occult pockets of infection so as to attain a disease-free status. Given the paucity of evidence for integrated PETMR usage in foot-related indications, our small sample study highlights its superiority for clearly delineating and diagnosing various foot pathologies, infections, especially in the clinical setting of postsurgery/debrided foot.