Prone-to-Supine Breast MRI for Tumor Margin Visibility and Surgical Guidance

Supine breast MRI reproduces the surgical position during breast-conserving surgery, with early studies reporting the benefit of decreased positive margin rates. However, acquiring an additional contrast-enhanced supine breast MRI after a prone breast MRI in a second imaging session is clinically and financially challenging. The aim of this study was to evaluate the tumor-to-fibroglandular tissue contrast ratios and the ability to visualize tumor margins in a double-bolus prone-to-supine breast MRI obtained in a single imaging session.

Thirty-nine patients with breast cancer had a standard prone breast MRI followed immediately by a second contrast injection in the supine position to obtain supine breast MRI (double-bolus prone-to-supine MRI protocol [P2S2]). A control group of 35 patients received a prone examination and an independent supine examination in 2 separate imaging sessions. Tumor-to-fibroglandular tissue contrast ratios (TFRs), a measure of tumor enhancement that informs the ability to visualize tumor margins, were statistically compared between cohorts. Two radiologists independently rated the ability to visualize tumor margins in the independent and double-bolus supine breast MRIs.

No significant differences were found in the mean TFR between the independent and P2S2 supine examinations (P = .79). Excellent agreement occurred between both readers regarding the ability to visualize the tumor margins in the independent and P2S2 supine MRIs with κ scores of 1.00 and 0.95, respectively.

A supine breast MRI obtained in a single imaging session after a second contrast injection provided adequate tumor enhancement for tumor margin visualization and preoperative surgical guidance comparable with independent supine breast MRI.