Researchers at Case Western Reserve University and University Hospitals (UH) Case Medical Center have developed a new MRI acquisition method that could greatly speed up the making of a scan. Normally scans are acquired in a very orderly fashion, with many parameters set to specific values generating a radiofrequency pulse which causes the protons to spin in a certain way, and one or more echos are generated and captured that make up the signal which is translated to images. Images are produced depending on different tissue characteristics, but each of these needs their own specific scanning sequence which typically lasts several minutes.
While you still need the same basic steps, the researchers threw most of the order out of the window and used a chaotic sequence of semi-random pulses and parameters to generate a signal that contains much more information than the normal MR signal, essentially acquiring several scans at once. The combination of these signals results in a very specific ‘fingerprint’ that is unique depending on the type of tissue imaged. The research team demonstrated that this could differentiate between gray and white matter, and cerebrospinal fluid (shown above, in gray a single captured frame and in color the complete information reconstructed), but many other tissues could in theory be discerned.
After the MRI signal is acquired, it is compared to a dictionary of possible patterns that can be generated by a computer based on knowledge of the exact used sequences. In the current study the researchers determined four different physical properties that vary from tissue to tissue from a single scan (T1, T2, proton density and off-resonance frequency), but in the end they expect to be able to assess a total of eight or nine physical properties all at once. As a further advantage, these properties can easily be quantified using this technique.
Another advantage of the technique is that it does not need any new hardware, and in theory it could be applied to current scanners with just a software update. The technique should be adaptable to several MRI data acquisition types. Patients will not notice much, other than that a scan will last a lot shorter, by up to a factor 50-fold with further optimizations. MR fingerprinting could also be used to identify the presence of a specific target material or tissue, and potentially lead to new diagnostic testing methodologies. In combination with pattern-recognition algorithms, it could even facilitate computer-aided diagnosis, or, in the far future, cut the radiologist out of the loop altogether.
Press release: New MRI method fingerprints tissues and diseases…
Article in Nature: Magnetic resonance fingerprinting… and editorial…
