[Quantitative assessment of therapy related effects after breast conserving therapy with dynamic MRI of the breast].

Purpose: To quantify therapy related effects after breast conservation therapy (BCT) with dynamic MRI of the breast.

Methods: Twenty patients (median age 51 years) with breast conserving tumor excision were included. Contrast enhanced dynamic MRI was performed before and 3, 6 and 12 months after adjuvant radiation therapy (RT) with a total dose of 50.0 to 50.4 Gy. The following sequences were applied: axial fat-suppressed T(2)-weighted; coronal contrast enhanced 3D spoiled gradient-echo (first measurement prior to the administration of 0.16 mmol/kg Gd-DTPA, six repetitive measurements); sagittal T(1)-weighted Flash3D. Enhancement data were obtained using a computer software with automated segmentation of regions of interest (ROIs). After defining ROIs for skin, parenchyma and pectoral muscle of each breast the early enhancement after the first post contrast measurement (E(1)) and the slope of enhancement between the second and last postcontrast measurement (SE(2-L)) were calculated. The edema was quantified by assessing the signal intensities (SI) in the T(2)-weighted images. The thickness of the skin was measured in the sagittal T(1)-weighted images.

Results: Three months after RT statistically significant increases between 51 and 179 % of the SI and E(1) quotients were detected for all tissues compared to the examinations prior to RT. Six months after RT the skin still presented a by 102 % significantly higher E(1) quotient, and a by 140 % significantly increased SI quotient. No significant differences for SI and E(1) quotients could be observed 12 months after RT compared to the examinations prior to RT. A significant increase of the SE(2-L) difference for the skin from 0.0225 to 0.0691 and 0.0665 was found 3 and 6 months after RT, respectively. No significant differences between the initial MR examination and the follow-up examinations 3, 6 and 12 months could be detected for the SE(2-L) differences of the parenchyma.

Conclusion: Early therapy related effects after BCT can be exactly quantified with dynamic MRI using an automated ROI-segmentation and whole breast analysis software. Both edema formation and early enhancement show peaks 3 months after RT, and after 12 months there is no statistically significant difference compared with baseline.