Spondylodiscitis following endovascular abdominal aortic aneurysm repair: imaging perspectives from a single centre's experience.

OBJECTIVE: Very few reports have previously described spondylodiscitis as a potential complication of endovascular aortic aneurysm repair (EVAR). We present to our knowledge the first case series of spondylodiscitis following EVAR based on our institution's experience over an 11-year period. Particular attention is paid to the key imaging features and challenges encountered when performing spinal imaging in this complex patient group. MATERIALS AND METHODS: Of 1,847 patients who underwent EVAR at our institution between January 2006 and January 2017, a total of 9 patients were identified with imaging features of spondylodiscitis (0.5%). All cross-sectional studies before and after EVAR were assessed by a Consultant Musculoskeletal Radiologist and a Musculoskeletal Radiology Fellow to evaluate for features of spondylodiscitis. RESULTS: All 9 patients had single-level spondylodiscitis involving lumbosacral levels adjacent to the aortic/iliac stent graft. Eight out of nine patients had an extensive anterior paravertebral phlegmon/abscess that was contiguous with the infected stent graft and native aneurysm sac ± anterior vertebral body erosion. Epidural disease was present in only 3 out of 9 patients and was a minor feature. MRI was non-diagnostic in 3 out of 9 patients owing to susceptibility artefact. 18F-FDG PET/CT accurately depicted the spinal level involved and adjacent paravertebral disease in patients with non-diagnostic MRI and was adopted as the follow-up modality in 3 out of 5 surviving patients. CONCLUSION: Spondylodiscitis is a rare complication post-EVAR. Imaging features of disproportionate anterior paravertebral disease and anterior vertebral body bony involvement suggest direct spread of infection posteriorly to the adjacent vertebral column. Use of MRI versus 18F-FDG PET/CT as the optimal imaging modality should be directed by the type of stent graft deployed

Reduction of artefacts caused by hip implants in CT-based attenuation-corrected PET images using 2-D interpolation of a virtual sinogram on an irregular grid

Metallic prosthetic replacements, such as hip or knee implants, are known to cause strong streaking artefacts in CT images. These artefacts likely induce over- or underestimation of the activity concentration near the metallic implants when applying CT-based attenuation correction of positron emission tomography (PET) images. Since this degrades the diagnostic quality of the images, metal artefact reduction (MAR) prior to attenuation correction is required

[18F]FDG-6-P as a novel in vivo tool for imaging staphylococcal infections

Background Management of infection is a major clinical problem. Staphylococcus aureus is a Gram-positive bacterium which colonises approximately one third of the adult human population. Staphylococcal infections can be life-threatening and are frequently complicated by multi-antibiotic resistant strains including methicillin-resistant S. aureus (MRSA). Fluorodeoxyglucose ([18F]FDG) imaging has been used to identify infection sites; however, it is unable to distinguish between sterile inflammation and bacterial load. We have modified [18F]FDG by phosphorylation, producing [18F]FDG-6-P to facilitate specific uptake and accumulation by S. aureus through hexose phosphate transporters, which are not present in mammalian cell membranes. This approach leads to the specific uptake of the radiopharmaceutical into the bacteria and not the sites of sterile inflammation. Methods [18F]FDG-6-P was synthesised from [18F]FDG. Yield, purity and stability were confirmed by RP-HPLC and iTLC. The specificity of [18F]FDG-6-P for the bacterial universal hexose phosphate transporter (UHPT) was confirmed with S. aureus and mammalian cell assays in vitro. Whole body biodistribution and accumulation of [18F]FDG-6-P at the sites of bioluminescent staphylococcal infection were established in a murine foreign body infection model. Results In vitro validation assays demonstrated that [18F]FDG-6-P was stable and specifically transported into S. aureus but not mammalian cells. [18F]FDG-6-P was elevated at the sites of S. aureus infection in vivo compared to uninfected controls; however, the increase in signal was not significant and unexpectedly, the whole-body biodistribution of [18F]FDG-6-P was similar to that of [18F]FDG. Conclusions Despite conclusive in vitro validation, [18F]FDG-6-P did not behave as predicted in vivo. However at the site of known infection, [18F]FDG-6-P levels were elevated compared with uninfected controls, providing a higher signal-to-noise ratio. The bacterial UHPT can transport hexose phosphates other than glucose, and therefore alternative sugars may show differential biodistribution and provide a means for specific bacterial detection

Diagnosis and Management of Infected Total Knee Arthroplasty§

Infection following total knee arthroplasty can be difficult to diagnose and treat. Diagnosis is multifactorial and relies on the clinical picture, radiographs, bone scans, serologic tests, synovial fluid examination, intra-operative culture and histology. Newer techniques including ultrasonication and molecular diagnostic studies are playing an expanded role. Two-stage exchange arthroplasty with antibiotic cement and 4-6 weeks of intravenous antibiotic treatment remains the most successful intervention for infection eradication. There is no consensus on the optimum type of interval antibiotic cement spacer. There is a limited role for irrigation and debridement, direct one-stage exchange, chronic antibiotic suppression and salvage procedures like arthrodesis and amputation. We examine the literature on each of the diagnostic modalities and treatment options in brief and explain their current significance

Pyogenic spondylitis

Pyogenic spondylitis is a neurological and life threatening condition. It encompasses a broad range of clinical entities, including pyogenic spondylodiscitis, septic discitis, vertebral osteomyelitis, and epidural abscess. The incidence though low appears to be on the rise. The diagnosis is based on clinical, radiological, blood and tissue cultures and histopathological findings. Most of the cases can be treated non-operatively. Surgical treatment is required in 10–20% of patients. Anterior decompression, debridement and fusion are generally recommended and instrumentation is acceptable after good surgical debridement with postoperative antibiotic cover

Optical Imaging of Bacterial Infections

The rise in multidrug resistant (MDR) bacteria has become a global crisis. Rapid and accurate diagnosis of infection will facilitate antibiotic stewardship and preserve our ability to treat and cure patients from bacterial infection. Direct in situ imaging of bacteria offers the prospect of accurately diagnosing disease and monitoring patient outcomes and response to treatment in real-time. There have been many recent advances in the field of optical imaging of infection; namely in specific probe and fluorophore design. This combined with the advances in imaging device technology render direct optical imaging of infection a feasible approach for accurate diagnosis in the clinic. Despite this, there are currently no licensed molecular probes for clinical optical imaging of infection. Here we report some of the most promising and interesting probes and approaches under development for this purpose, which have been evaluated in in vivo models within the laboratory setting