Positron emission tomography (PET) has historically been an afterthought in musculoskeletal imaging for many logical reasons, but authors of a new investigation believe the method should play a larger role in managing these patients.
“With improvements in PET/CT and PET/MRI over the last decade, as well as increased understanding of the pathophysiology of musculoskeletal diseases, there is an emerging potential for PET as a primary or complementary modality in the management of rheumatologic and orthopedic conditions,” wrote Ali Gholamrezanezhad, with the Keck School of Medicine’s department of radiology at the University of Southern California. and colleagues.
In the literature review in the American Journal of Roentgenology, researchers looked at the role PET can have in nononcologic musculoskeletal disorders, including inflammatory and infection conditions, along with postoperative complications.
Traditional imaging methods such as ultrasound and MRI are often first- up when diagnosing bone inflammation or osseous infections, but Gholamrezanezhad et al. found nuclear medicine exams helpful for localizing or confirming infections.
They found several studies that utilized single-photon-emitting radiotracers as evidence of this, including gallium and bone scans. PET, using a variety of radiotracers such as Fluorodeoxyglucose (FDG) and 18F-NaF, have similarly improved the assessment of osteomyelitis, they wrote.
“Early diagnosis of osteomyelitis is important, because antibiotic therapy can be curative and may prevent amputation,” wrote the team. “In patients with equivocal findings for infection on conventional studies, nuclear medicine examinations can be used for further evaluation.”
Joint replacements and postoperative complications
Diagnosing the often-heard complaint of pain in orthopedic implant and prosthetic device patients is difficult for MRI and CT, but FDG imaging has adequately taken on the role. However, the diagnostic accuracy of this method compared to conventional nuclear medicine techniques has provided mixed results.
The authors examined studies that looked at varying reports and determined FDG PET/CT “seems to be an appropriate approach for diagnostic imaging in patients with possible hardware infection.”
“Despite the conflicting data about the diagnostic performance of FDG PET in peri-prosthetic infection relative to imaging with single-photon emitters, PET offers multiple advantages, including time savings (compared with dual-tracer techniques, which need dual-image acquisition), higher spatial resolution, and an improved cost and safety profile when compared with the complexity and risks of labeled [white blood cell scan] use, including direct handling of blood products,” Gholamrezanezhad et al. wrote.
This group of autoimmune disorders is associated with varying clinical features and prognoses, but the limited sensitivity of x-ray and MRI often miss these diseases. With modern agents now able to limit the progression of these conditions, authors argued “early diagnosis of inflammatory disorders of bones and joints is all the more critical.”
In rheumatoid arthritis, FDG PET/CT has been suggested as an aid in diagnosis and measuring response to treatment. PET provides information about deeper joints that are difficult to evaluate. The authors suggested the method may be best used to detect response to treatment.
Additionally, certain radiotracers such as 68Ga- or 8F-labeled Siglec-9 may be effective for in vivo imaging of inflammation in the synovitis membrane—a symptom of rheumatoid arthritis and other inflammatory arthropathies. However, the researchers cautioned further study is necessary to solidify the clinical value of PET with non-FDG radiotracers.
The group reaffirmed PET’s potential positive contributions to joint disease patients, but warned further research is needed to ultimately decide its clinical application.
“Inflammatory or infectious arthropathies have long posed a diagnostic dilemma, with significant potential morbidity and complications for patients with delayed or incorrect diagnosis,” researchers wrote.
“PET can aid in the early diagnosis of inflammatory or infectious arthropathies and may also be used for the longitudinal monitoring of disease activity for both clinical and research purposes. Potential musculoskeletal applications of PET/MRI remain in the realm of research and need to be expanded in future clinical studies,” they added.