Non-Invasive characterisation of renal stones using dual energy CT: A method to differentiate calcium stones

Abstract

Background: Non-invasive DECT based characterization of renal stones using their effective atomic number (Z_eff) and the electron density (ρe) in patients.

Aim: This paper aims to develop a method for in-vivo characterization of renal stone. Differentiation of renal stones in-vivo especially sub types of calcium stones have very important advantage for better judgement of treatment modality.

Materials and methods: 50 extracted renal stones were scanned ex-vivo using dual energy CT scanner. A method was developed to characterize these renal stones using effective atomic number and electron density obtained from dual energy CT data. The method and formulation developed in ex-vivo experiments was applied in in-vivo study of 50 randomly selected patients of renal stones who underwent dual energy CT scan.

Results: The developed method was able to characterize Calcium Oxalate Monohydrate (COM) and the combination of COM and Calcium Oxalate Dihydrate (COD) stones non-invasively in patients with a sensitivity of 81% and 83%respectively. The method was also capable of differentiating Uric, Cystine and mixed stones with the sensitivity of 100, 100 and 85.71% respectively.

Conclusion: The developed dual energy CT based method was capable of differentiating sub types of calcium stones which is not differentiable on single energy or dual energy CT images.

Keywords: Calcium Oxalate; Calcium Oxalate Monohydrate; Dual Energy CT; Effective atomic number; Electron density; Monohydrate and Calcium Oxalate Dihydrate.