Abstract
ObjectiveADC (Apparent Diffusion Coefficient) derived from Diffusion-Weighted Imaging (DWI) has shown promise as a non-invasive quantitative imaging biomarker in Wilms’ tumours. However, many non-Gaussian models could be applied to DWI. This study aimed to compare the suitability of four diffusion models (mono exponential, IVIM [Intravoxel Incoherent Motion], stretched exponential, and kurtosis) in Wilms’ tumours and the unaffected contralateral kidneys.Materials and methodsDWI data were retrospectively reviewed (110 Wilms’ tumours and 75 normal kidney datasets). The goodness of fit for each model was measured voxel-wise using Akaike Information Criteria (AIC). Mean AIC was calculated for each tumour volume (or contralateral normal kidney tissue). One-way ANOVAs with Greenhouse–Geisser correction and post hoc tests using the Bonferroni correction evaluated significant differences between AIC values; the lowest AIC indicating the optimum model.ResultsIVIM and stretched exponential provided the best fits to the Wilms’ tumour DWI data. IVIM provided the best fit for the normal kidney data. Mono exponential was the least appropriate fitting method for both Wilms’ tumour and normal kidney data.DiscussionThe diffusion weighted signal in Wilms’ tumours and normal kidney tissue does not exhibit a mono-exponential decay and is better described by non-Gaussian models of diffusion.
Highlights
Wilms’ tumour is the most common paediatric renal tumour [1], and in Europe patients are treated with chemotherapy prior to surgery to reduce tumour size [2]
A total of 110 Wilms’ tumours were included for diffusion model comparison analysis; consisting of 49 pre-chemotherapy and 61 post-chemotherapy tumours (38 of the prechemotherapy tumours were included as part of the 61 postchemotherapy cohort)
This study compared four models of diffusion based on how well they fit to the Diffusion-Weighted Imaging (DWI) signal decay, according to Akaike Information Criteria (AIC)
Summary
Wilms’ tumour is the most common paediatric renal tumour [1], and in Europe patients are treated with chemotherapy prior to surgery to reduce tumour size [2]. Following a full or partial nephrectomy, histological analysis classifies the tumour as a subtype depending on the predominant cell type [3]. Patients will often have multiple MRI scans to monitor response to treatment, with Diffusion Weighted Imaging (DWI) being frequently acquired. The Apparent Diffusion Coefficient (ADC) can be derived from DWI by applying a mono-exponential fit (Eq 1) to the diffusion data. Where S(b) is the signal at a given b value, and S0 is the signal with no diffusion weighting. ADC has shown great promise as a quantitative imaging tool in Wilms’ tumour. ADC has been used to distinguish benign from malignant tumours
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