The relationship of apparent diffusion coefficient values of renal cell carcinoma before and after cryotherapy ablation

Abstract

IntroductionThe diagnosis of renal cell carcinoma (RCC) is increasing due to incidental findings with more frequent use of cross-sectional imaging. Therefore improvements to diagnostic and follow up imaging techniques is necessary. MRI diffusion weighted imaging (DWI) is a recognised method of measuring the diffusion of water within lesions using the apparent diffusion coefficient (ADC), and may have a role in monitoring the efficacy of cryotherapy ablation of RCC. MethodsA retrospective cohort study of 50 patients was approved to investigate if the ADC value can determine the success of cryotherapy ablation treatment for RCC. DWI was performed at a single centre using 1.5 T MRI before and after cryotherapy ablation to the RCC. The control group was considered as the unaffected kidney. The ADC value of the RCC tumour and normal kidney tissue prior to and after cryotherapy ablation was measured, and compared to the result of the MRI. ResultsA statistically significant change in the ADC values was observed, pre ablation (1.562 × 10¯mm2/sec) to the post ablation (1.126 × 10¯³mm2/sec), p < 0.0005. There was no statistical significance in any of the other outcomes measured. ConclusionAlthough a change of ADC value occurred this is likely due to cryotherapy ablation causing coagulative necrosis at the site, and does not determine the success of the cryotherapy ablation. This can be considered a feasibility study for future research. Implications for practiceDWI is a quick addition to routine protocols, does not require intravenous gadolinium based contrast agent, and provides qualitative and quantitative data. Further research is required to establish the role of ADC for treatment monitoring.