ESTRO 36 Abstract Book

S501 ESTRO 36 _______________________________________________________________________________________________

Purpose or Objective MR has the ability to assess numerous physiological and biochemical tumour characteristics. Fractal analysis may provide a better insight into the biology and behaviour of prostate tumour than simplistic comparisons of multiparametric data. In this pilot study, we aim to determine whether fractal and lacunarity analysis can characterize the properties of radio-recurrent prostate cancer, using Apparent Diffusion Coefficient (ADC) MR Images. Material and Methods Retrospective analysis of eight patients with recurrent prostate cancer after previous radical radiotherapy (mean age: 71.25 years), underwent MRI examination for re- staging prior to consideration of salvage therapy. ADC images of the prostate were manually segmented from surrounding tissue and a region of interest (ROI) drawn to distinguish between restrictive diffusion and non- restrictive tissue (figure 1b). Low, medium and high ADC value maps were generated by intensity thresholding the respective restrictive and non-restrictive ROIs. These were processed and converted to 8-bit black and white images (figure 1c, low intensity in restricted diffusion) for application to in-house textural analysis software (image 1d) to estimate (a) fractal dimension (b) fractal abundance and (c) lacunarity Curve1 Figure 1: (a) an ADC image of the prostate gland (b) an ADC image showing areas of restricted diffusion (red) and non-restricted diffusion (blue) (c) shows a binary image used for fractal and lacunarity analysis (d) lacunarity curves from restricted areas (red) and non-restricted areas (blue)

Results The average fractal characteristics are summarised in table 1 with the fractal dimension between areas of restricted diffusion and non-restrictive diffusion of the low and medium intensity images being of significant difference (p=0.0014 and 0.0023 respectively). The fractal abundance of the medium intensity image between the restricted diffusion and non-restrictive diffusion was also significant (p=0.0012).

Conclusion Automatic propagated contours for target and OARs need manual adjustments for clinical acceptance. Mesorectum and OARs adjustments can be made by an experienced technologist and are not clinically relevant different from the manual contours of an experienced radiation oncologist. This semi-automatic contouring strategy can be used in an online workflow for rectal boost treatment, however further speed-optimisation is desirable. PO-0906 Textural analysis of MR images to improve the characterisation of recurrent prostate cancer J. Stirling 1 , R. Alonzi 2 , P.J. Hoskin 2 , N.J. Taylor 1 , W.L. Wong 1 , A.R. Padhani 1 , B. Sanghera 1 1 Paul Strickland Scanner Centre, Research, Northwood, United Kingdom 2 Mount Vernon Hospital, Academic Oncology Unit, Northwood, United Kingdom