By: Dan Sperling, MD
The use of multiparametric MRI (mpMRI) for the detection of prostate cancer is increasingly validated by published studies that compare mpMRI performance against transperineal mapping biopsies and prostatectomy specimens. The four MRI parameters most studied (T2-Weighted, Diffusion-Weighted, Dynamic Contrast Enhanced and Spectroscopy) differentiate malignancy from normal or inflamed prostate tissue with upward ranges of specificity and sensitivity well over 90% depending on the combinations of parameters and experience of readers.[i]
However, the application of mpMRI for revealing identifiable tissue changes following focal laser ablation (FLA) is less well studied. A recent study retrospectively analyzed the pre-treatment and post-treatment multiparametric image data of five FLA cases in order to determine imaging sensitivity to changes.[ii] To the best knowledge of the research team, it was “the first attempt at examining focal treatment-related changes on a per-voxel basis via quantitative comparison of MRI features” before and after FLA. They identified computerized MRI features that were highly sensitive and specifc to changes within the ablation zone after treatment. (According to wikipedia, the term voxel is a combination of “volume” and “pixel” wherein each voxel represents a “value on a regular grid in three-dimensional space… Voxels are frequently used in the visualization and analysis of medical and scientific data.”[iii]
The team utilized T2-weighted MRI and diffusion-weighted MRI. As part of their analysis, they quantified the information captured by the two parameters according to texture and intensity features. The close comparisons of voxels allowed the researchers to distinguish specific changes to the texture of the MRI image at the site of laser ablation.
According to the authors, “Our preliminary results thus indicate great potential for non-invasive computerized MRI imaging features for determining focal treatment related changes, informing image-guided interventions, as well as predicting long- and short-term patient outcome.” Sharing these results will allow researchers and practitioners to track a patient’s treatment response over time by evaluating the degree to which the MRI texture changes over several years.
[i] Johnson L, Turkbey B, Figg W, and Choyke P. Multiparametric MRI in prostate cancer management. Nat Rev Clin Oncol. 2014;11:346-53.
[ii] Viswanath S, Toth R, Rusu M, Sperling D, et al. Identifying quantitative in vivo multi-parametric MRI features for treatment related changes after laser interstitial thermal therapy of prostate cancer. Neurocomputing. 2014 Nov 20;144:13-23.