The Magnetic Resonance Laboratory is currently engaged in several projects to identify new techniques for clinical use. Advances in acquisition and reconstruction speed, as well as greater resolution of resulting images, are investigated.
In the U.S., prostate cancer is the most common and second-most deadly noncutaneous cancer in men, but five-year survival rates approaching 100% are possible if the cancer is detected early. Prostate MRI has become increasingly important in cancer detection and localization.
The goal of this project is to view multislice imaging from a different mindset and transform the acquired data into kZ-space. With modest oversampling of acquired slices, correction for the slice profile can be made, and the corrected data transformed back to Z-space. Preliminary results have demonstrated sub-mm through-plane resolution and significant improvement in sharpness of structures relevant to prostate MRI.
These results have identified technical areas for further improvement:
- Acquisition and reconstruction strategies
- High-resolution T2-weighted spin-echo (T2SE) prostate MRI
- Application to diffusion-weighted imaging (DWI) prostate MRI
For over three decades, the Magnetic Resonance Laboratory has been developing methods applicable to imaging of the cardiovascular system. These include initial development of the technique of view sharing, segmented k-space sampling, use of real-time navigator echoes, centric and elliptical centric view orders, fluoroscopic triggering, continuous table motion magnetic resonance angiography (MRA), and more recently high spatial-temporal resolution contrast-enhanced MRA with Cartesian k-space sampling, or Cartesian acquisition with projection reconstruction-like (CAPR) sampling.
Current research projects are directed toward improved speed, reduced contrast dose, and extension of the high image quality over an extended field of view.
Fast scan research
Fast scanning techniques under study in the Magnetic Resonance Laboratory include single- and multi-shot echo planar imaging (EPI), gradient echo methods, and rapid acquisition with relaxation enhancement (RARE) fast spin-echo (FSE) techniques. Additionally, research is being done in the development of high-speed reconstruction methods and interactive scanner control, or MR fluoroscopy. As these techniques are developed, they are applied clinically in various ways, including abdominal, cardiovascular and neurological imaging.
The purpose of this project is to develop a rapid, interactive method for providing images that have high spatial resolution and high immunity to inhomogeneity artifact in exchange for some reduction of the image formation rate into the range of 0.5 to 1.0 Hz. This is done by using single-shot fast spin-echo (SSFSE) methods. With this approach the effective time can be adjusted by variation of the phase encoding order, and echo times from 60 msec to 500 msec or more are permitted. The image generation rate can be controlled in two ways. In the first, the frame rate is fixed; selected by the operator at 1.0 Hz or slower.
The second approach uses on-demand acquisition in which an image is acquired only when the operator specifies acquisition with a mouse click or when the plane of section is modified. This method allows fuller recovery of magnetization and thus higher signal-to-noise ratio (SNR) as well as fewer unnecessary images than a fixed rate approach. With both techniques the operator can interactively adjust parameters such as the field of view and oblique angulation. The principal applications of this method thus far have been for imaging of the pelvic floor and fetal imaging.
MRI of an extended field of view
This technique is helpful in situations in which the anatomy in question extends beyond the maximum field of view (FOV) allowed by the MR scanner. This maximum has historically been approximately 45 cm or less. One example necessitating a larger FOV is in angiographic peripheral runoff imaging. For this situation, an MR contrast agent is injected intravenously and the vasculature is imaged upon the passage of that contrast agent.
- MR fluoroscopy
- Centric view orders in MRI