Images from the planning software used for targeted biopsy. The tumor is drawn in blue on anatomic imaging overlaid with A) perfusion data and B) RSI-MRI data. The H&E stained histology after prostatectomy D) shows the true boundary of the tumor outline in blue. A 3-D rendering C) of the whole prostate (green) and the tumor (yellow) shows the spatial position of the tumor within the prostate. RSI-MRI identified a suspicious area which after biopsy and prostatectomy was proven to be high grade tumor. As shown, the tumor is barely visible in conventional imaging. Multimodal Imaging Laboratory, UC San Diego
Prostate cancer can spread beyond the prostate gland and become an extraprostatic extension (EPE). Currently, contrast enhanced magnetic resonance imaging (MRI) is used to detect and diagnose prostate cancer. This technique involves injecting patients with a contrast agent to identify where blood flows. This is important because cancerous tissues often undergo angiogenesis. However, there is a problem in that tumors are sometimes indistinguishable from the surrounding healthy tissue and therefore avoid detection. Now researchers and doctors at UC San Diego and UCLA have developed a novel approach to imaging these tumors using diffusion MRI while getting rid of the distortions that come with the technique.
RSI-MRI imaging showing biopsy proven high-grade cancer with extension into the right seminal vesicle (arrow). There is also a region of enhanced RSI signal in the right pubic bone showing a likely focus of metastatic cancer. The extension into the right seminal vesicle and likely metastatic bone disease has implications for subsequent treatment. Multimodal Imaging Laboratory, UC San Diego
Diffusion MRI measures the diffusion of water in biological tissue. Tumors are denser than healthy tissue and thus restrict the flow of water. The downside to diffusion MRI is that it is susceptible to magnetic artifacts which are distortions in the MR image due to inhomogeneities in the field. Water is an inhomogeneity because it is considered a diamagnetic substance. These distortions can place tumors as much as a half inch (1.2 centimeters) away from the actual location, which can be a major problem. To correct the error, the researchers developed a new imaging method called RSI-MRI, or restriction spectrum imaging-MRI. This approach adjusts for the magnetic field distortions and measures the water diffusion in cancer cells. This technique can also predict tumor grade. In the study, RSI-MRI was able to successfully identify eight out of nine patients with EPE whereas the standard MRI used currently only identified two out of nine.
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