Letter to the Editor (other) doi:10.1093/rheumatology/kes308

Potential interest of dual-energy computed tomography in gout: focus on anatomical distribution and clinical association SIR, Gout is a chronic inflammatory arthritis resulting from long-standing hyperuricaemia, and is characterized by monosodium urate (MSU) crystal deposits in joints and periarticular soft tissues [1]. Recently dual-energy CT (DECT) techniques have been introduced as a sensitive, non-invasive and reproducible imaging technique for de-tecting MSU deposits in clinical studies of gout patients [24]. The newly developed imaging modality, DECT, can provide more extensive information about the location of gouty MSU deposits and their association with clinical variables. The main goals of our study were to identify the anatomical distribution of urate crystals in affected foot and ankle joints and to define the relationships be-tween MSU crystal deposits and clinical parameters in gout patients using DECT. We consecutively enrolled a total of 101 gout patients (male, n = 96) who fulfilled the preliminary criteria for the classification of primary gout proposed by the ACR [5]. Patients with present symptoms or a previous history of gout in the ankles and feet were included in the study sample. The study was approved by the Institutional Review Board/Ethics Committee at the Catholic University of Daegu. Informed consent was obtained at the time of study enrolment. Seventeen arbitrary locations were defined to identify anatomical locations of urate crystal deposits in the foot and ankle (see Fig. 1A). The most clinically affected foot/ankle region was scanned in each patient. DECT scans were performed following Nicolaou et al. [3]. We identified 39 patients (38.6%) among a total of 101 gouty patients with urate crystal deposits in affected feet and ankles. Regardless of the volume or size of the de-posited crystals, a total of 82 urate crystal deposits from 39 gouty patients with crystals were identified (Fig. 1B). The most frequent locations for urate crystal deposits were at the first MTP joint of the great toe (n = 18, 22.0%), around or at the junction of the ankle (n = 16, 19.5%), around the first IP joint (n = 12, 14.6%) and in the transverse tarsal joint (n = 12, 14.6%). Among the total study sample (n = 101), the presence of urate crystals by DECT was increased in patients wit