Contrast enhanced breast MRI : Spatial displacement from prone to supine patient's position : Preliminary results

Objective: To estimate the spatial displacement of breast lesions and nipples in MR images when the patient is moved from the standard prone to a supine position close to ultrasound (US) or surgical setting. Materials and methods: Eleven patients underwent breast MRI in prone position with dynamic 3D T1-weighted sequences using 0.1 mmol/kg gadobenate dimeglumine. Subsequently, the patient was repositioned in supine position and a 3D volumetric interpolated breathhold examination sequence was acquired using a thoracic surface coil. For both positions we measured the following minimal distances: (A) from lesion margin to the coronal plane passing through the anterior surface of the sternum, antero-posterior, on native axial images; (B) from lesion margin to the medial sagittal plane, on native axial images, latero-medial; (C) from lesion margin to the axial plane passing through the tracheal bifurcation, cranio-caudal; (D) from lesion margin to the thoracic wall/pectoral muscle, on native axial images; (E) from lesion margin to the skin, on native axial images; (F) from lesion margin to the base of the nipple, on oblique reconstructions. Measurements from A to D were also obtained for each nipple. The prone-to-supine spatial displacement was calculated as the absolute difference between the measurement obtained in supine position and the same measurement obtained in prone position. Displacements were presented as mean ± standard deviation and median in parenthesis. Results: Lesion displacements were (mm): A = 60 ± 38 (55); B = 40 ± 26 (41); C = 41 ± 33 (34); D = 32 ± 31 (27); E = 6 ± 5 (7); and F = 8 ± 6 (7). Nipple displacements were (mm): A = 84 ± 44 (91); B = 54 ± 24 (56); C = 27 ± 15 (24); and D = 48 ± 20 (48). Conclusion: These preliminary results show that preoperative breast MRI in prone position implies a median lesion displacement of about 3-6 cm along the three orthogonal directions in comparison with supine MRI. Conversely, median lesion-to-skin and lesion-to-nipple displacements were less than 1 cm, even though nipple displacements were similar to or larger than those of lesions. The lesion-to-nipple distance may be the most reliable measure to be used for second look breast US. Larger studies are warranted in order to define an optimized breast MRI protocol in the preoperative setting.