Imaging Prostate Cancer with SQUID-Detected Microtesla MRI

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DESCRIPTION (provided by applicant): Conventional magnetic resonance imaging (MRI) at 1.5 tesla and above is used increasingly for the detection, diagnosis and staging of cancer. In the case of prostate cancer, however, conventional MRI does not provide sufficient specificity for detection of prostate tumors. To take advantage of the enhanced T1 (longitudinal relaxation time) contrast available at low magnetic fields, a novel MRI system has been developed at LBNL which acquires MR images at microtesla fields, comparable to the Earth's field. In this technique, prepolarization of the proton spins in a much higher magnetic field is combined with detection of the nuclear magnetic resonance signal using a Superconducting QUantum Interference Device (SQUID) to enhance the signal-to-noise ratio. Preliminary data on ex vivo prostate specimens indicate that there is significantly enhanced contrast between prostate tumors and healthy prostate tissue. The goal of the proposed project is to assess the potential of this novel MR imaging method for the diagnosis and staging of prostate cancer. In a blinded study on ex vivo prostate specimens we will determine the T1 contrast in images of specimens containing different types of benign prostate tissue and tumors with various Gleason grades and compare the results with those from histopathology performed at the UCSF Comprehensive Cancer Center. In addition, we will improve the sensitivity of the SQUID detector and increase the magnitude of the polarizing field in our current imaging system to assess the spatial resolution and the signal to noise and contrast to noise ratios achievable with a future in vivo imaging system. To attain these goals we propose the following specific aims: Aim 1. Upgrade the detector sensitivity. Aim 2. Determine T1 contrast in images of ex vivo prostate tissue containing tumors and other prostate tissue types to determine the sensitivity and specificity for detecting prostate cancer. Aim 3. Design and build a polarizing coil suitable for in vivo imaging. Aim 4. Image three-dimensional (3D) prostate phantoms and compare the resolution with results predicted by calculations; image 2D ex vivo prostate specimens at a distance corresponding to that for in vivo imaging. Provided these experiments confirm the preliminary measurements, a prototype system could subsequently be constructed for in vivo studies of prostate cancer. This system would potentially be less expensive and more open than conventional MRI systems, and could significantly impact the diagnosis and staging of prostate cancer. Possible applications include: (i) Imaging the prostate before a biopsy to determine the location and extent of the cancer. (ii) More accurate mapping of the location of tumors to guide biopsy. (iii) Serial imaging to determine the progression of tumors during treatment or active surveillance. (iv) In situ monitoring of focal therapies, such as placement of the seeds during brachytherapy. PUBLIC HEALTH RELEVANCE: A magnetic resonance imaging (MRI) system will be developed to demonstrate the feasibility of imaging prostate tumors in very low magnetic fields. This technique offers much higher contrast between healthy and cancerous tissue compared to conventional high-field MRI, and the system is both less confining and less expensive. Clinical applications are expected to include serial monitoring of tumors during treatment or active surveillance, image guided biopsy, and monitoring of focal therapies like brachytherapy.