E1045. Green is the New Grayscale: A Pictorial Review of Typical and Atypical Gout on Dual-Energy CT
  1. Mohammadali Saffarzadeh; University of British Columbia
  2. Syed Haydar; University of British Columbia
  3. Shamir Rai; University of British Columbia
  4. Savvas Nicolaou; University of British Columbia
  5. Nicolas Murray; University of British Columbia
  6. Hugue Ouellette; University of British Columbia
Gout is the most common crystal arthropathy globally that can mimic septic arthritis, osteoarthritis, rheumatoid arthritis, pseudogout or tumors. The co-presentation of gout alongside other types of arthropathies can make the diagnosis more challenging. The utility of Dual-Energy CT (DECT) as a noninvasive investigational modality has emphasized its role in gout diagnosis, progression, and response to treatment. The aim of this educational exhibit is to highlight the unique potential role of DECT as a point-of-care imaging modality in typical and atypical presentations of urate arthropathies.

Educational Goals / Teaching Points
The goal of this exhibit is to describe an approach to radiological identification of typical and atypical presentation of gout on DECT. The potential role of point-of-care DECT for monitoring gout progression and mapping treatment response will be explored given DECT’s unique advantage in detection and quantification of monosodium urate (MSU) deposits in the joints. Additionally, the limitations of DECT that can lead to under- or over-estimation of disease burden will be discussed, with an emphasis on pitfalls and clinical pearls in radiological identification of gouty lesions.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
In addition to identifying MSU crystals in peripheral joints as seen in typical gout, DECT becomes advantageous for diagnosis in anatomical locations that are not easily accessible for joint fluid aspiration, such as the vertebrae, clavicle, and hip. There will be example cases of typical and atypical gout disease burden assessment using DECT in this educational exhibit. DECT can also be used to plan treatment and assess response for gout therapeutic management. This exhibit will portray the pre- and posttreatment DECT findings in a case of a patient with multiarticular gout. Familiarity with potential pitfalls and artifacts in DECT gout application would allow for better interpretation of disease distribution. This exhibit will describe the DECT findings of certain material such as skin, nail beds, costal cartilage, vascular calcification, and areas of beam hardening that have similar dual energy indices to uric acid. These materials can mistakenly be mapped as urate color (green) leading to an overestimation of urate burden. This exhibit will also discuss examples of gout burden being underestimated due to areas of mineralization falling outside of the DECT field of view.

DECT is utilized in diagnosis of both common and uncommon gout presentations by providing radiological evidence of MSU in various anatomical locations. DECT can also be used as a point-of-care imaging modality to evaluate gout disease burden for mapping and assessing treatment response. Familiarity with pitfalls and mimics of gout on DECT can prevent under- and over-estimation of disease severity.