Fluoride PET/MR could be ideal for finding root cause of foot pain

The origins of foot pain are often unclear and present a challenge for clinicians seeking to treat the underlying cause. PET/MR with F-18 fluoride may turn out to be the best modality to solve the mystery, the Society of Nuclear Medicine and Molecular Imaging announced this month.             

A preliminary human study published in the March issue of the Journal of Nuclear Medicine provides a thorough investigation of how the technique comes out ahead when compared to PET/CT.

“This is the first study evaluating foot pathologies in PET/MR using 18F-Fluoride,” co-author Isabel Rauscher from Technische Universität München Radiology Institute in Munich, Germany, told Health Imaging. “We hypothesize that the use of F-18 Fluoride PET/MR can provide additional therapeutically relevant information in patients with unclear foot pain.”

Such pain can be caused by a wide range of pathologies, from fractures, infections, osteoarthritis, deformities and cancerous tumors. While conventional radiography can spot a broken bone with ease, molecular bone scans can show signs of elusive stress fractures and early signs of malignancy.

In this prospective study, researchers compared F-18 fluoride PET/MR with PET/CT using comparable reconstruction and attenuation algorithms and enlisted two blinded interpreters to randomly assess both scans based on agent uptake and image quality. Results of the study revealed that PET/MR, while about as sensitive as PET/CT, led to superior image quality and definitive diagnoses due to the bone visualization and soft-tissue contrast provided by MR.

The readers scored up to three points for image quality. PET/MR received a score of 3/3, whereas PET/CT only got a 2.3/3.

The authors wondered if the improved image quality could be attributed to the extended PET/MR scan time, which may warrant dose reduction in additional research. With further validation, patients could get an effective diagnosis at a lower dose.

“However, this has to be proven in prospective studies also evaluating the contribution both of MR and F-18 fluoride to the final diagnosis and therapeutic management, as well as cost-effectiveness in a large patient cohort,” adds Rauscher.

Still, the application of PET/MR is limited by hospital resources. This modality is most often used in research and teaching hospitals. “PET/MR is a relatively new hybrid modality which is therefore not available in every hospital and this limits its broader application and evaluation in patients with benign pathologies such as unclear foot pain,” says Rauscher.