Speakers to Detail Effects of Imaging Modalities on Diagnosis of Crystal-Induced Arthropathies

Arthropathies induced by crystalline deposits have been a large part of rheumatology practice since the specialty’s earliest days. But recent advances in imaging are bringing dramatic change to the diagnosis and classification of gout (monosodium urate crystal deposition), calcium pyrophosphate deposition disease (CPPD), and basic calcium phosphate deposition (BCPD).

“As a radiologist, the key feature in this context is to look for crystals and, if we can with different imaging modalities, identify the crystals in the symptomatic joint,” said Fabio Becce, MD, Deputy Physician and Medical Senior Lecturer, Lausanne University Hospital, Switzerland. “The challenge is to identify the crystal as early as we can. By choosing the right exam, and by optimizing its protocol, you can improve the diagnostic performance of imaging techniques to identify crystals as early as possible to treat the patient correctly and not wait for weeks or months.”

Dr. Becce will discuss the latest imaging approaches during Not So Crystal Clear: The Changing Landscape of Crystalline Arthritis Diagnosis on Monday, Nov. 18, from 10–11:30 a.m. ET in Room 103AB of the Walter E. Washington Convention Center. He will share the podium with Sara Tedeschi, MD, MPH, Head of Crystal-Induced Arthritic Diseases at Brigham and Women’s Hospital, and Assistant Professor of Medicine, Harvard Medical School, and Nicola Dalbeth, MD, Professor and Head of the Department of Medicine at the University of Auckland, New Zealand.

“We all see a lot of crystal diseases in clinical practice, and there have been significant advances in both diagnosis and classification,” Dr. Dalbeth said. “Ultrasound and dual-energy CT are certainly useful and, in the context of calcium crystal diseases, plain radiography is still a good option. The real question is, when do we use advanced imaging tools in the clinical diagnosis and classification setting?”

Ultrasound and dual-energy CT are more sensitive, Dr. Dalbeth noted, but aspiration and microscopic examination is often the best approach. A trial of treatment may be needed if there is diagnostic uncertainty.

Spatial image resolution is the challenge.

Individual monosodium urate or calcium pyrophosphate crystals range from about 1 to 20 microns, Dr. Becce explained. A single crystal in precisely the wrong spot can generate symptomatic inflammation and pain, although symptoms more often result from larger crystal aggregates.

Ultrasound offers the highest spatial resolution, at about 50–100 microns at best, while conventional or dual-energy CT resolution tops out at around 250 microns. The newest technique, photon-counting CT, can resolve down to 100–150 microns, but is not widely available outside of a few academic centers.

None of the current imaging modalities can resolve single crystals.

“You need a cluster of crystals, an aggregate, for them to be visible with clinical imaging, and also at relatively high crystal concentration,” Dr. Becce said. “If the crystals are at low concentration, contrast on the image is not good enough to be sure it is a true crystal deposition, and crystals can be misidentified.”

Dr. Dalbeth will outline the 2023 EULAR recommendations on imaging in diagnosis and management of crystal-induced arthropathies in clinical practice. The guidelines offer evidence-based recommendations for the most common imaging modalities, including conventional radiography, ultrasound, CT, dual-energy CT, and MRI. Different crystal diseases are best identified using different imaging techniques.

“Rheumatologists can diagnose gout and CPPD in most clinical settings without difficulty,” Dr. Dalbeth said. “However, for complex presentations, advanced imaging and microscopy provide important additional information. People should come away from this session with a better understanding of diagnostic approaches and the latest classification criteria.”

Dr. Tedeschi will discuss new technologies in synovial fluid analysis.