MRI based Kidney Radiomics analysis during chronic lithium treatment: validation of a texture index associated with decreased kidney function.

Background. Chronic lithium therapy is associated with an increased risk of chronic kidney disease (CKD). Lithium nephrotoxicity is slowly progressive and difficult to detect at early stages. The aim of this study was to identify specific image texture changes of kidneys as possible imaging biomarkers of decreased measured glomerular filtration rate (mGFR) using radiomic analysis of T2 weighted imaging magnetic resonance imaging. 
 Methods. One hundred and nine patients treated with lithium carbonate were evaluated including mGFR and Kidney MRI, with T2 weighted sequence single-shot fast spin-echo. Computed radiomic analysis was performed after a manual kidney segmentation. Significant features were selected to build a radiomic signature using multivariable Cox analysis to detect a decreased mGFR <60 ml/min/1.73m2. The texture index was internally validated using a training and a validation cohort. Results. Texture analysis index was able to detect a decrease in mGFR, with an Area Under the Curve (AUC) of 0.85 in the training cohort and 0.71 in the validation cohort. Patients with a texture index below the median were older (59 [42-66] versus 46 [34-54] years, p=0.001), with longer treatment duration (10 [3-22] versus 6 [2-10] years, p=0.02), and a lower mGFR (66 [46-84] versus 83 [71-94] ml/min/1.73m2, p<0.001). Texture analysis index was independently and negatively associated with age (beta= -0.004 +/- 0.001, p<0.001), serum vasopressin (-0.005 +/- 0.002, p=0.02), lithium treatment duration (-0.01 +/- 0.003, p=0.001), with a significant interaction between lithium treatment duration and mGFR (p=0.02). Conclusion. A renal texture index was developed and validated among patients treated with lithium carbonate associated with a decreased mGFR. This index might be relevant in the diagnosis and prognosis of lithium-induced renal toxicity.