Nonstandard patient positioning shows promise in intraoperative breast MRI

Intraoperative MRI for breast-tumor resection following presurgical MRI with the patient in the supine (“face up”) position can be used to effectively plan the extent of resection, detect residual tumor immediately after the first attempt at definitive lumpectomy and provide feedback to the surgeon within the surgical suite during a breast-conserving operation.

That’s according to the authors of a small study published online June 22 in Radiology.

Eva Gombos, MD, and colleagues at Harvard affiliate Brigham and Women’s Hospital found that this nonstandard approach works because it enables the surgeon to quantify breast tumor deformation and displacement caused by varying shifts in healthy and cancerous tissue.

The researchers looked at 12 patients who underwent lumpectomy and postsurgical intraoperative supine MR imaging.

Six of the 12 underwent both pre- and postsurgical supine MR imaging. The other six received pre-surgical MR in the standard prone position.

The team computed geometric, structural and heterogeneity metrics of the cancer and distances of the tumor from the nipple, chest wall and skin. They also computed, from tumor models, mean and standard deviations of the changes in volume, surface area, compactness, spherical disproportion, sphericity and distances from key landmarks.

The mean differences in tumor deformation metrics between prone and supine imaging were:

• Volume, 23.8 percent (range, −30 percent to 103.95 percent);
• Surface area, 6.5 percent (range, −13.24 percent to 63 percent);
• Compactness, 16.2 percent (range, −23 percent to 47.3 percent);
• Sphericity, 6.8 percent (range, −9.10 percent to 20.78 percent); and
• Decrease in spherical disproportion, −11.3 percent (range, −60.81 percent to 76.95 percent).

All tumors were closer to the chest wall on supine images than on prone images.

As for time differences, the mean duration of pre- and postoperative supine MR imaging was 25 minutes and 19 minutes, respectively.

“Supine MR imaging may aid in improving surgical planning by accounting for tumor displacement and deformation occurring between standard positioning for MR imaging and that for surgery to potentially allow for more complete tumor resection,” Gombos et al. write in summarizing their study’s implications for patient care.

“If validated in future large studies,” they add, “intraoperative supine MR imaging could be expected to help detect a remnant tumor immediately after breast-conserving surgery to ensure negative surgical margins.”