Radiology

Magnetic Resonance Therapy (MRT)
 

Principal Investigators:
Clare MC Tempany-Afdhal, MD
Daniel Kacher, Jr

In 1989, the MR division of the Department of Radiology of Brigham and Women's Hospital and Harvard Medical School initiated a project to develop MR-guided interventional procedures and intraoperative guidance for surgeries.

The main components of this project have been the development of

• a new kind of MRI scanner, providing access to the patient during imaging, and
• the computerized processing methods necessary for efficient presentation and analysis of data generated in such an environment.

General Electric Medical Systems has participated in the project and has built an open magnet for surgical applications. This MRT (magnetic resonance therapy) system is a complete environment including MR-compatible instruments and MR-compatible anesthesia and monitoring equipment. The first machine was installed at Brigham and Women's Hospital in December 1993. Since then, close to 1,200 procedures have been performed in the MRT system.

Intraoperative MRI

For correct localization of tumor margins, particularly for low-grade gliomas in the brain, MRI is superior to any other imaging method. Intraoperative MRI was first introduced into clinical practice in neurosurgery at Brigham and Women’s Hospital in 1993. It provides accurate targeting for small, intracerebral lesions and avoids errors caused by the brain deformations and magnetic field inhomogeneities that are characteristic of stereotactic methods based on preoperative images. During surgery, direct visual definition of tumor boundaries by the neurosurgeon is not possible, and preoperatively defined margins are displaced. Therefore, intraoperative MRI is the most effective way to guide resections. The importance of well-defined tumor boundaries is especially convincing in cases of low-grade gliomas, in which the completeness of tumor removal relates directly to survival. Finally, continuous image update and navigational support will eventually result in the modification of surgical approaches, the adjustment of surgical techniques, and the transformation of conventional neurosurgery.

More recently, direct image guidance of lumpectomies has been tested with IMRI (intraoperative MRI). In breast cancer, like glioma, it is sometimes difficult to recognize tumor margins on visual inspection. Contrast-enhanced, fat-suppressed intraoperative MR images can provide effective guidance for more complete removal of tumors, especially those with a high degree of infiltration.

For image-guided surgeries, MRI’s high sensitivity for tumor detection can be fully exploited without suffering from the consequences of its relatively low specificity. Therefore, IMRI may have a substantial impact in oncologic surgeries. With the use of advanced contrast agents, image-detectable tumor markers, or tumor-specific genes, the usefulness of IMRI will be even more obvious.

In addition to oncologic applications, we are currently testing intraoperative MRI for various spine surgeries.

Interventional MRI

MRI has been used to guide various percutaneous, minimally invasive interventional procedures performed by radiologists at Brigham and Women’s Hospital.

MRI-guided prostate brachytherapy was developed in our department, and its feasibility has been proven in more than 50 cases. Using intraoperative MRI, the surgeon can more easily (and more reliably) differentiate tumor from healthy tissue and target a more specific area for treatment. Interactive, computerized analysis of the intraoperative images results in real-time targeting, dosimetry, and volumetric tumor treatment. This procedure has been shown to improve tumor treatment and reduce the complication rate.

The use of intraoperative MRI guidance has revived interest in thermal ablation techniques, such as cryoablation, interstitial laser therapy (ILT), radiofrequency (RF) and microwave ablation, and focused ultrasound surgery (FUS). Originally, the role of image-guidance was limited to the initial deployment of probes. And although this achieved correct initial positioning of the probes within the lesions, treatments were often less than satisfactory. As energy was delivered through the probes, tissue changes could result deformations that altered the ideal placement. The monitoring and control afforded by heat sensitive, advanced MRI-guidance methods have led to a resurgence in the use of these local tissue-killing techniques. We are currently treating brain tumors with interstitial laser therapy and liver cancer and other soft tissue tumors with cryoablation. We are developing protocols for the application of cryoablation to treat uterine fibroids and renal and adrenal tumors.

For further information contact:
Clare Tempany-Afdhal, MD at ctempanyafdhal@partners.org.