ABSTRACT
METHODS: A retrospective analysis was conducted on 75 lesions in 50 patients with pathologically proven breast cancer who underwent MRI in prone and supine positions between December 2019 and December 2020. The transverse, anteroposterior, and craniocaudal dimensions (in millimeters) of the tumor in the x -, y -, and z -axes were measured. Distances from the center of the tumor to the chest wall and the adjacent skin were measured on transverse and reformatted sagittal images. In cases where multifocal lesions were present, the transverse, anteroposterior, and craniocaudal distances between the tumor centers in the x -, y -, and z -axes were measured. Differences between measurements in supine and prone MRI were evaluated with the Mann-Whitney U and the Wilcoxon tests. P values of less than 0.05 were considered to indicate a statistically significant difference. RESULTS: The analysis revealed 31 MRIs with 1 and 20 with multifocal lesions. The x -axis dimension of the lesions in prone and supine positions did not significantly differ ( P = 0.198) between the 2 positions. A significant difference in the y - and z -axes dimensions was observed between the prone and supine position ( P = 0.00 for both). The distance from the tumor to the chest wall and the adjacent skin showed significant difference ( P = 0.00 for both). For multifocal lesions, the distance between the lesions showed a significant difference on the y -axis ( P = 0.00). CONCLUSIONS: This study showed a significant difference in the tumor size, location, and tumor-to-tumor distances due to change of patient position, from the standard prone MRI to the supine position in the operating room, resulting in distortion, spatial repositioning, and convergence of the lesions. Supine MRI may be considered in providing a less extensive surgery.