Value of dual energy spectral CT for detecting uric acid deposition in tophaceous gout with base material mapping

Abstract

Objective To assess the feasibility and diagnostic value in detecting uric acid deposition among patients with tophaceous gout by using Gemstone spectral imaging(GSI)-based qualitative analysis technique.Methods Thirty-one patients with clinical obvious tophaceous gout and 10 healthy volunteers underwent Discovery CT 750 HD scan with GSI mode.Uratoma more than 10 mm in diameter,muscles,cortical bone,and cancellous bone were analyzed and compared between patients and controls by using CT imaging spectroscopy quantitative parameters [uric acid (Ca) concentration,calcium (uric acid) concentration,calcium (water) concentration,and water (Ca) concentration].Univariate analysis of variance was applied within the patient group,and independent samples t test was used to compare the abovedmentioned quantitative parameters between patient group and control group.Results Base substance concentration in patients was as follows:uric acid (Ca) concentration (1 268.8 ± 32.2) mg/cm3,calcium (uric acid) concentration (19.4 ± 9.5) mg/cm3,calcium (water) concentration (10.8 ± 9.5) mg/cm3,and water (calcium) concentration (1 171.0 ± 26.8) mg/ cm3.The cortical bone of the base substance concentration was as follows:uric acid (Ca) concentration (1 333.6 ± 83.8) mg/ cm3,calcium (uric acid) concentration (271.1 ± 85.0) mg/cm3,calcium (water) concentration (262.6 ± 85.4) mg/cm3,and water (calcium) concentration (1 230.8 ± 77.0) mg / cm3.The muscles of the base substance concentration was as follows:uric acid (Ca) concentration (1 143.5 ± 15.7) mg / cm3,calcium (uric acid) concentration (12.3 ± 5.0) mg /cm3,calcium (water) concentration (4.4 ± 1.9) mg / cm3,and water (calcium) concentration (1 054.1 ± 14.6) mg / cm3.The cancellous bone of the base substance concentration was as follows:uric acid (Ca) concentration (1 070.9 ± 26.4)mg / cm3,calcium (uric acid) concentration (85.1 ± 46.9) mg/cm3,calcium (water) concentration (77.4 ± 46.7) mg/cm3,and water (calcium) concentration (988.0 ± 23.4) mg / cm3.There were significant differences(F value were 665.04,646.13,642.10,and 692.41,respectively,P ＜ 0.01).The uric acid (Ca) concentration and water (calcium) concentration in tophi,muscle,cortical and cancellous bone showed differences between the two groups (P ＜ 0.05),while calcium (uric acid) concentration and calcium (water) concentration showed significant differences between tophi and cortical bone or cancellous bone (P ＜ 0.05).Between patient group and control group,cortical and cancellous bone calcium (uric acid) concentration and calcium (water) concentration showed significant difference (P ＜ 0.05),and muscle uric acid (Ca) concentration and water (calcium) concentration also showed significant difference (P ＜ 0.05).Conclusion Dual-energy spectral CT can detect the gout tophi within the peripheral joints in patients quantify the concentrations of the base materials,thus providing a new imaging method for the quantitative monitoring of clinical outcomes. Key words: Hyperuricemia; Tomography,X-ray computed; Comparative study