Influence of contrast medium on tophus detection using dual-energy CT: phantom study and clinical illustration

Abstract

Background To investigate the influence of iodinated contrast medium (ICM) on detection of monosodium urate (MSU) with dual-energy computed tomography (DECT) in two types of phantoms and demonstrate an example patient for clinical illustration. Methods Approval is by the institutional review board, and written informed consent was obtained. A grid-like and a biophantom with 25 suspensions containing different concentrations of ICM (0 to 2%) and MSU (0 to 50%) were prepared and scanned with sequential single-source DECT using established methodology. Ascending orders of tube currents were applied at 80 kVp (16.5 to 220.0 mAs) and 135 kVp (2.75 to 19.25 mAs). Volume and mass measurements were performed using clinical gout software (dual-energy decomposition analysis). Numbers of true-positive and false-positive MSU detections were recorded and compared for different ICM concentrations. We demonstrate a patient with gouty arthritis for clinical illustration. Results Effects of ICM on MSU detection varied with the amount of iodine. Lower ICM concentrations (0.25 and 0.50%) improved detection of small uric acid concentrations of 35 to 45% in comparison to scans without ICM. However, high ICM concentrations (1 and 2%) almost completely precluded MSU detection for all MSU concentrations investigated. In a patient with gouty arthritis, tophi in the wrist were only detected after intravenous ICM administration. Conclusions Exploring multimodal DECT for arthritis imaging, enhancement of ICM influences tophus detection. It can help in visualizing previously undetected MSU depositions but, with too strong enhancement, also obscure tophi. Relevance statement Use of iodinated contrast media in dual-energy CT might help in visualizing previously undetected uric acid depositions but, with too strong enhancement, obscure gouty tophi. Key points • Iodine significantly influences the uric acid crystal detection in systematic phantom studies. • Lower iodine concentrations improved detection of low and medium uric acid concentrations. • High concentrations of iodine hampered detection of all uric acid concentrations. Graphical abstract

Virtual noncontrast images reveal gouty tophi in contrast-enhanced dual-energy CT: a phantom study

“…Five sets of suspensions containing MSU concentrations of 0%, 35%, 40%, 45%, and 50% mixed with varying ICM concentrations of 0%, 0.25%, 0.5%, 1%, and 2% (0.925, 1.85, 3.7, and 7.4 mg/mL of iodine, respectively) were prepared. The five MSU concentrations were selected based on previous work [ 7 – 9 ]. The suspensions were filled in 25 individual syringes.…”

“…The calculated sets of two VNC images at 80 and 135 keV were processed in the same way as conventional DECT scans using a two-material decomposition analysis algorithm (Dual-Energy Composition Analysis, version 6.0, Canon Medical Systems) for the detection of uric acid using clinical standard settings established in previous studies [ 7 – 12 ].…”

“…A single contrast-enhanced DECT scan in patients with an unclear arthritis etiology can thus provide objective evidence for active inflammation or rule out differential diagnoses. A recent phantom study of gouty arthritis has shown that DECT images acquired after administration of iodinated contrast medium (ICM) can improve the detection of tophi with a lower density that would remain undetected in unenhanced CT images [ 7 ]. At the same time, however, high ICM almost completely hampered tophus detection.…”

Advanced Imaging of Gout and Other Inflammatory Diseases Around the Knee

“…13 Also, postcontrast intrinsic vascularization of tophi can increase its density, thus helping make low-concentration tophi visible. 33 DECT may be used to stage patients with gout, especially in established disease, because 50% of patients have abnormal DECT scans with normal serum urate levels and no clinical tophi. 30 Other applications of DECT include prediction of disease flares at 6 months and 2 years and excess cardiovascular and all-cause mortality.…”

Updates on the Applications of Spectral Computed Tomography for Musculoskeletal Imaging

“…In a small series of 11 patients with non-tophaceous gout, DECT only detected deposits in 3 of 12 joints noted to have monosodium urate crystals at joint aspiration [24]. Using iodinated contrast media can partially overcome these limitations and improve the detection of small uric acid deposits, though higher contrast concentrations can obscure tophi and complicate monosodium urate crystal detection [25]. Still, further research is necessary to improve the sensitivity of DECT in patients with early-onset disease and non-tophaceous gout.…”