Prediction of chemical composition of urinary calculi in-vivo based on ct attenuation values – An analytical study
Keywords:Computed tomography, Calcium oxalate monohydrate, Calcium oxalate dihydrate, Uric acid.
Introduction: Chemically, stones are of various types including calcium stones, uric acid stones, struvite stones and cystine stones among others. Each pathophysiological group has a predisposition to form certain kind of stones. Hence, knowledge of the chemical composition of the stone that a patient forms can and does direct the management of the patient. Objectives: To evaluate if the chemical composition of urinary stones can be predicted with mean Hounsfield Unit (HU) value on computed tomography (CT). Methods: This is prospective and analytical study conducted in the Department of Radiology of a tertiary care teaching hospital in India. Patients diagnosed with urinary stones who had a non-contrast CT done and had stone retrieved were included in the study. The predominant chemical composition of the stone was analysed by X-ray diffraction crystallography. Results: Fifty-one stones of four types were studied. Statistically significant (p<0.001) differences were seen in the mean HU, maximum HU and median HU values between all the four types. No significant difference was observed in the difference between periphery and core HU values. Hierarchy of density among the stone types correlated with previous studies but absolute measurements varied among different studies. Conclusion: Mean HU of urinary stones correlates with their chemical composition. Calcium oxalate monohydrate, calcium oxalate dihydrate, uric acid and hydroxyapatite stones can be differentiated on their CT attenuation parameters if a database of attenuation characteristics for stones of known composition is built for given scanner and protocol.
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Copyright (c) 2022 Aravind Murugesan, Mossadeq A, Govardhanan R, Ratna Vasanthan S
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