A clinical study on the application of spectral CT post-processing technology for distinguishing gouty arthritis from calcium pyrophosphate deposition disease

XU Wen-jing; XU Jian-ming; WANG Yi; JI Jing; SUN Ting; TIAN Jin-jie

doi:10.3969/j.issn.2095-252X.2025.08.010

Abstract：Objective To identify the nature of loose bodies in joints affected by gouty arthritis and calcium pyrophosphate deposition disease by spectral CT uric acid and Z Effective post-processing techniques.Methods The clinical and spectral CT raw data(SBI)of 31 patients diagnosed as gouty arthritis and 15 patients diagnosed as calcium pyrophosphate deposition disease were collected from Suzhou Hospital affiliated to Medical School of Nanjing University between September 2020 and November 2023.The spectral raw image data were imported into the spectral CT viewer software on the workstation for analysis.Utilizing the uric acid and Z Effective post-processing reconstruction techniques of spectral CT,the spectral data were obtained for further analysis.The differences in spectral data between patients with gouty arthritis and those with calcium pyrophosphate deposition disease were analyzed using an independent sample t-test.Results(1)There were significant differences in terms of gender[(28/3)vs.(8/7)],age[(55.02±24.34)vs.(64.15±13.72)]and serum uric acid levels[(540±96)μmol/L vs.(240±41)μmol/L]between the gouty arthritis group and the calcium pyrophosphate deposition disease group(gender t=3.227,P=0.031;age t=1.953,P=0.047;serum uric acid levels t=2.119,P=0.027).(2)Compared to conventional CT scans,spectral CT uric acid demonstrated higher sensitivity and specificity to detect the uric acid crystals associated with gout.It accurately identified a greater number of smaller uric acid crystals.Additionally,the uric acid map generated by spectral CT uric acid allowed color overlay visualization on a three-dimensional VR map,providing a more intuitive display of the location and quantity of uric acid crystal deposits.The Z Effective atomic number diagram showed that the atomic number value of urate crystals was significantly lower than that of calcium pyrophosphate crystals[(7.69±1.26)vs.(10.17±2.08)],enabling quantitative differentiation between these two types of crystals(t=2.262,P=0.043).Conclusions The spectral CT uric acid technique enables the visualization of uric acid crystals in the joint cavity,while the atomic number map allows the quantitative differentiation between uric acid crystals and calcium pyrophosphate crystals.The application of spectral CT post-processing technique holds promise to achieve painless and non-invasive diagnosis of gouty arthritis.