BERKELEY, CA (UroToday.com) - There is growing interest in the use of prostate MRI, prior to prostate biopsy, in order to determine who should undergo prostate biopsies and how the biopsies should be performed. Our article provides readers important information about the utility of MR imaging in patient selection and of MR-guided targeted biopsy with cognitive registration. At present, MR-guided targeted biopsy includes transrectal US-guided biopsies and in-bore MR-guided biopsies. The former approach has two registration methods of MR and US images, including cognitive and software-fusion registry. MR-guided targeted biopsies with cognitive registry, which has been used in our current study, is very simple and feasible in almost all the hospitals where standard transrectal US-guided biopsies have been performed. Our results show that this MR-guided targeted biopsy approach would be well capable of detecting cancers wherever they may be in the prostate.
It is important to envisage high-quality MR images as minimal requirements for reporting MR results about whether the patient should undergo targeted biopsies, and if so, how the biopsies should be performed and how many biopsy cores should be taken from the targets. In the prostate MR imaging, acquisition protocols of minimum requirements were reported as ESUR prostate MR guidelines 2012 by Barentsz JO, et al. (Eur Radiol 2012; 22:746-757). We suggest that a combination of ADC-map with T2-weighted images is clinically sufficient to select patients and to detect target lesions for the subsequent biopsy. Dynamic contrast-enhanced imaging might have marginal significance in the detection of prostate cancer, especially in the peripheral zone. High-quality ADC map should be crucial to detect and localize small-sized cancer foci, and we recommend several technical considerations in diffusion-weighted imaging for ADC-map including thin section thickness, high spatial resolution, short TE as possible, high number of signal acquisition, and relatively small b-value (b=600 s/mm2). For T2-weighted imaging, a variety of techniques are now available. To obtain high-quality images with thin section thickness, we recommend three-dimensional T2-weighted TSE images, which allows for multiplanar reformations to provide anatomical details of the prostate gland. Heavily T2-weighted images using TE of 150 msec can offer high contrast between tumor and normal tissues.
Regarding sampling methods, we have taken several biopsy cores focused on the lesion itself, or the segment in the direction (as a time of the clock) of a low-ADC lesion, based on the ADC map information, which allowed us to detect even 5 mm-sized cancer foci.
We suppose further investigation is necessary to establish standard prostate MR imaging and to refine the biopsy strategy in order to maximize the detection of clinically significant prostate cancer, while reducing the burden of biopsy and the healthcare system.
Written by:
Yuji Watanabe, MD, PhD as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.
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