Ari Polachek, MD, on Comparing Ultrasound and MRI for PsA

Dr Ari Polachek, a rheumatologist with the Department of Rheumatology at Tel Aviv Sourasky Medical Center, met with us to talk about his research comparing ultrasound (US), magnetic resonance imaging (MRI), and radiography for detection of inflammatory lesions and destructive changes in psoriatic arthritis.

RALN: Thank you for joining us, Dr Polachek. First, how are ultrasound (US), radiography, and MRI currently used in diagnosing and monitoring PsA? How do the 3 modalities differ in patient experience and utilization?

Dr Ari Polachek: The evaluation of PsA patients starts with clinical assessment, including history taking and physical examination, and imaging modalities should serve as ancillary tools.  Radiography, US, and MRI are the main imaging modalities for assessment of these patients. Radiography is the basic and most ubiquitous imaging tool that shows mainly chronic structural changes as bone proliferations and erosions, and accordingly is used for monitoring disease progression. US and MRI have the ability to demonstrate both acute inflammatory activity and chronic structural findings. Hence, US and MRI can be used for monitoring disease activity and progression.

RALN: Are there any benefits to radiography and ultrasound that MRI does not have? Does MRI have any negative effects not present in radiography or ultrasound?

Dr Polachek: The main benefits of radiography and US compared to MRI are lower cost and higher availability. In addition, US offers accessible bedside utilization and ability to examine multiple joints during the same assessment. In contrast, MRI has a restricted field of imaging and hence patients may need more than one assessment. Finally, closed MRI machines may pose a problem for claustrophobic patients.  

RALN: Why is MRI considering the gold standard in imaging for PsA rather than radiography or ultrasound?

Dr Polachek: MRI is considered by many as the leading imaging modality. MRI has high resolution for both acute inflammatory lesions, such as synovitis, tenosynovitis, as well as for structural lesions. Furthermore, the main advantage of MRI over US and radiography is to identify bone marrow edema (BME). Previous studies suggested that BME could differentiate between PsA and RA and be used as a prognostic marker for the development of structural damage (erosions).

RALN: What were the most important findings of this study?

Dr Polachek: The main findings of this study were: (1) US and MRI had very good agreement for detection of inflammatory lesions in PsA, and (2) US, MRI, and conventional radiography had good-to-very good agreement for detection of destructive changes. 

RALN: What does the relatively good agreement between these technologies, particularly ultrasound and MRI, mean for providers treating these patients?

Dr Polachek: Thank you for this important question. The good agreement between US and MRI imply that US can be the first option for disease activity evaluation in the finger joints of PsA patients. MRI could be left for cases where the US assessment is not clear or there is controversy.

RALN: Is there any cost difference to consider when it comes to these imaging technologies?

Dr Polachek: There are cost differences between these imaging modalities. Radiography is the cheapest option. Ultrasound is more expensive due to the price of the US machine and the time needed for scanning and interpretation. MRI is the most expensive modality, owing to the very high price of the MRI machine and amount of time for interpretation. Furthermore, the MRI examination field is limited, and hence additional MRI evaluations might be needed.

RALN: What are the next steps for this research?

Dr Polachek: The next step is to explore the differences between clinical assessment, including physical examination and disease activity indices, and US and MRI. In addition, to examine the sensitivity and specificity of physical examination compared to US and MRI. A possible future direction will be to establish a longitudinal cohort that will examine the role of these tools in the prediction of disease flare and remission.

Reference:
Polachek A, Furer V, Zureik M, et al. Ultrasound, magnetic resonance imaging and radiography of the finger joints in psoriatic arthritis patients. Rheumatology (Oxford). 2022;61(2):563-571. doi:10.1093/rheumatology/keab272
 

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