Stephen G. Hushek

MR systems for MRI‐guided interventions

The field of MR imaging has grown from diagnosis via morphologic imaging to more sophisticated diagnosis via both physiologic and morphologic imaging and finally to the guidance and control of interventions. A wide variety of interventional procedures from open brain surgeries to noninvasive focused ultrasound ablations have been guided with MR and the differences between diagnostic and interventional MR imaging systems have motivated the creation of a new field within MR. This review discusses the various systems that research groups and vendors have designed to meet the requirements of interventional MR and suggest possible solutions to those requirements that have not yet been met. The common requirements created by MR imaging guidance of interventional procedures are reviewed and different imaging system designs will be independently considered. The motivation and history of the different designs are discussed and the ability of the designs to satisfy the requirements is analyzed. J. Magn. Reson. Imaging 2008;27:253–266.

Dynamic T1-weighted magnetic resonance imaging of interstitial laser photocoagulation in the liver: Observations on in vivo temperature sensitivity

Magnetic resonance imagings (MRI) potential to monitor interstitial laser photocoagulation (ILP) has been previously demonstrated and is further tested here with improved spatial and temporal resolution.

Dynamic weight-bearing cervical magnetic resonance imaging: technical review and preliminary results.

Background: Conventional magnetic resonance imaging (MRI) of complex cervical spine disorders may underestimate the magnitude of structural disease because imaging is performed in a nondynamic non-weight-bearing manner. Myelography provides additional information but requires an invasive procedure. Methods: This was a prospective review of the first 20 upright weight-bearing cervical MRI procedures with patients in the flexed, neutral, and extended positions conducted in an open-configuration MRI unit. Results: This technique clearly illustrated the changes in spinal cord compression, angulation, and spinal column alignment that occur during physiologic movements with corresponding changes in mid-sagittal spinal canal diameter (P < 0.05). Image quality was excellent or good in 90% of the cases. Conclusions: Dynamic weight-bearing MRI provides an innovative method for imaging complex cervical spine disorders. This technique is noninvasive and has adequate image quality that may make it a good alternative to cervical myelography.

Thermal contours from magnetic resonance images of laser irradiated gels

The ability of MRI to non-invasively monitor energy deposition with high spatial and temporal resolution provides the critical feedback required to make laser therapy procedures safe and efficacious. We have previously proposed the use of polyacrylamide gelatin as a phantom material whose optical and MR properties can be controlled independently by adding different dopants to the base gel. We have also begun to investigate the most effective imaging strategies for measuring temperature variations within this material. In this paper we further characterize the gels, delineate the temperature dependance of their MR properties and show how imaging can be used to determine thermal contours within an interstitially laser-irradiated gel.