MSCT and MR compete for intraoperative imaging

Intraoperative guidance with multislice CT could prove advantageous where intraoperative MR imaging falters. Researchers might benefit from applying each modality's capabilities where they prove most useful, according to Florida researchers.

Intraoperative guidance with 1.5T and 3T MR scanners overcomes most limitations of low-field systems and has already proved its worth in neurosurgical settings. But these scanners are complex, expensive to run, and require MR-compatible operation rooms. In contrast, MSCT adapts easily to the OR environment and provides significant speed and visualization. With MSCT guidance, surgeons can perform thoracoabdominal interventions in minutes without compromising image quality, said Dr. Gary M. Onik, an interventional radiologist and director of surgical imaging at the Center for Surgical Advancement's Celebration Health/Florida Hospital.

In an ongoing study, Onik and colleagues have thus far prospectively enrolled 30 patients who have undergone abdominal, chest, and brain surgeries under intraoperative guidance and monitoring with a 16-slice scanner. The fully OR-integrated system includes a mechanized arm that guides several surgical instruments, a table specially designed to serve as a patient-immobilization device and respiratory-gating platform, and fluoroscopy and ultrasound equipment for simultaneous multimodality scanning and monitoring.

The Center for Surgical Advancement's system can guide laparoscopic and thoracoscopic procedures to remove occult pathology and to displace organs to protect them from thermal injury or bleeding during cryo- or radiofrequency ablation procedures. It also allows simultaneous monitoring and control of outcomes and complications. The CSA team presented their preliminary findings at the American Roentgen Ray Society meeting last month.

The researchers have developed ways to minimize the system's shortcomings. Alternative guidance and monitoring with ultrasound reduces the need for CT. They have also developed patient-protective pads to cut radiation exposure and are designing a special device that will allow manipulation of surgical instruments outside the scan's gantry. Several institutions have already expressed interest in the CSA's intraoperative MSCT setup, and plans are under way to implement it in a mobile operating room for smaller hospitals, Onik said.

"We have been able to monitor lesions and guide the laparoscopic surgeon down to the pathology to remove it minimally invasively. Intraoperative MSCT has had a major impact on the ability of our surgeons to take patients who otherwise would have been candidates for open surgery," he said.

Harvard researchers plan to install a PET/CT scanner in their OR for similar purposes and expect to benefit from PET's specificity to detect tumors, said Dr. Ferenc A. Jolesz, director of the MRI and image-guided therapy program at Brigham and Women's Hospital.

In spite of MSCT's perceived advantages, only MR can provide intraoperative imaging without interrupting surgery, Jolesz said.