Professor John Clarke from the University of California at Berkeley will be giving a talk on an ultra-low field MRI system with potential for imaging prostate cancer and possibly other types of traditionally difficult-to-image cancers.
Date: Monday 6 September 2010
Time: 10:00 - 11:00
Location: Lecture Hall Kammaren, Sahlgrenska Universitetssjukhuset (between sections J and K of main hospital building entrance floor)
Magnetic Resonance Imaging in Microtesla Fields: A Potential Modality for Imaging Cancer
John Clarke
Department of Physics, University of California, Berkeley
and
Materials Sciences Department, Lawrence Berkeley National Laboratory
Clinical magnetic resonance imaging (MRI) machines operate typically at 1.5 or 3 T. Recently, there has been growing interest in systems that operate at magnetic fields four orders of magnitude lower using a Superconducting Quantum Interference Device (SQUID) to detect the nuclear magnetic resonance (NMR) signal. Such systems are lower in weight and, potentially, in cost than conventional machines, require only modest homogeneity in the imaging field, are insensitive to variations in the magnetic susceptibility of the specimen being imaged, and have an enhanced contrast in the longitudinal relaxation time T1 for different tissue types. The decrease in the polarization of the proton spins and hence in the NMR signal amplitude due to the low field is compensated partly by prepolarization of the spins in a field much higher than the imaging field and partly by frequency-independent SQUID-detection. Our current MRI machine operates at 0.132 mT, corresponding to a proton frequency of 5.2 kHz. The system is constructed from wood, and contains copper wire coils to enable us to perform MRI pulse sequences. Images show an in-plane spatial resolution of about 1mm for phantoms and 2 mm for in vivo images of the arm. Measurements of T1 in phantoms containing different concentrations of agarose gel in water show a much higher contrast than in fields even as low as a few millitesla. Measurements of T1 in surgically removed prostate tissue have an average value of about 80 ms in healthy tissue and 50 ms in tumor tissue. Provided similar values are found for in vivo tissue, microtesla MRI has the potential to image prostate cancer and possibly other kinds of cancer. Research in other institutions as well as challenges and future prospects are discussed.
