Assessing the Sensitivity of Dual-Energy Computed Tomography 3-Material Decomposition for the Detection of Gout

Abstract

ObjectivesThe aim of this study was to assess the accuracy and precision of a novel application of 3-material decomposition (3MD) with virtual monochromatic images (VMIs) in the dual-energy computed tomography (DECT) assessment of monosodium urate (MSU) and hydroxyapatite (HA) phantoms compared with a commercial 2-material decomposition (2MD) and dual-thresholding (DT) material decomposition methods.Materials and MethodsMonosodium urate (0.0, 3.4, 13.3, 28.3, and 65.2 mg/dL tubes) and HA (100, 400, and 800 mg/cm3 tubes) phantoms were DECT scanned individually and together in the presence of the foot and ankle of 15 subjects. The raw data were decomposed with 3MD-VMI, 2MD, and DT to produce MSU-only and HA-only images. Mean values of 10 × 10 × 10–voxel volumes of interest (244 μm3) placed in each MSU and HA phantom well were obtained and compared with their known concentrations and across measurements with subjects' extremities to obtain accuracy and precision measures. A statistical difference was considered significant if P < 0.05.ResultsCompared with known phantom standards, 3MD-VMI was accurate for the detection of MSU concentrations as low as 3.4 mg/dL (P = 0.75). In comparison, 2MD was limited to 13.3 mg/dL (P = 0.06) and DT was unable to detect MSU concentrations below 65.2 mg/L (P = 0.16). For the HA phantom, 3MD-VMI and 2MD were accurate for all concentrations including the lowest at 100 mg/cm3 (P = 0.63 and P = 0.55, respectively). Dual-thresholding was not useful for the decomposition of HA phantom. Precision was high for both 3MD-VMI and 2MD measurements for both MSU and HA phantoms. Qualitatively, 3MD-VMI MSU-only images demonstrated reduced beam-hardening artifact and voxel misclassification, compared with 2MD and DT.ConclusionsThree-material decomposition-VMI DECT is accurate for quantification of MSU and HA concentrations in phantoms and accurately detects a lower concentration of MSU than either 2MD or DT. For concentration measurements of both MSU and HA phantoms, 3MD-VMI and 2MD have high precision, but DT had limitations. Clinical implementation of 3MD-VMI DECT promises to improve the performance of this imaging modality for diagnosis and treatment monitoring of gout.

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

“…Tse, Kondro, and Kuczynski compared quantification of MSU with DECT in a phantom setting using different decomposition approaches. In this setting, three-material decomposition with virtual monochromatic images detected a lower concentration of MSU than either two-material decomposition or dual-thresholding methods [ 28 ].…”

Computed Tomography

“…116 Similarly, an exploration of varying DECT decomposition methods demonstrated the utility of 3D virtual monochromatic acquisitions in quantification and detection of monosodium urate deposits in a phantom-controlled study of subjects' feet and ankles. 117 Limitations of DECT in diagnosing gout have also been described in current literature. Dual-energy CT does not perform as well as ultrasound in patients in the early stage of the disease.…”

“…Recent efforts to distinguish crystal deposition types were successful in differentiating monosodium urate deposits (prevalent in gout) from calcium pyrophosphate (prevalent in pseudogout) or calcium hydroxyapatite deposits in a phantom study 116 . Similarly, an exploration of varying DECT decomposition methods demonstrated the utility of 3D virtual monochromatic acquisitions in quantification and detection of monosodium urate deposits in a phantom-controlled study of subjects' feet and ankles 117 …”

Updates on the Applications of Spectral Computed Tomography for Musculoskeletal Imaging

“…Three-material decomposition is a postprocessing technique that decomposes images into sets of three materials, allowing for their differentiation and quantification [16]. In a phantom study by Tse et al, the authors reported that the combined use of three-material decomposition and VMI allowed for the detection of monosodium urate crystals at lower concentrations [14].…”