Room: Exhibit Hall | Forum 8
Purpose: To investigate changes seen dynamic contrast-enhanced (DCE)MRI imaging after neoadjuvant single fraction (21 Gy) external beam radiotherapy for early stage breast cancer.
Methods: DCE-MRI images (spatial/time resolution of 1.0x2.1x1.2mm/18s) of five patients were acquired on a 3T-PET/MRI (Siemens Biograph mMR), with one pre- and 28 post-contrast images in five patients before and seven days after a single radiation dose of 21Gy. Patient motion was corrected using deformable registration. A rectangular volume-of-interest (VOI) encompassing the tumour was drawn for each patient in both the pre- and post- radiotherapy data, using the same sized VOI. Voxel-wise signal enhancement (SE) at three minutes was calculated and progressively thresholded from one (post-contrast signal = pre-contrast signal) to five (post-contrast signal = 5*pre-contrast) in increments of 0.05. The volume of voxels was calculated for each SE threshold. Changes between pre and post radiotherapy images were determined using the fractional change in the area under the volume-SE curve (AUC). In addition, the maximum SE threshold that contained 5% of the volume of voxels at SE = 1 was calculated.
Results: For every patient at all SE thresholds there was a greater volume of tissue that was enhancing post radiotherapy. On average, the AUC increased by (2.8 Â± 1.70), with all ratios greater than one. There was an increase in the maximum SE threshold from (1.94 Â± 0.25) to (2.3 Â± 0.36), indicating an overall greater signal enhancement.
Conclusion: Following high dose radiotherapy, there is a large increase in the volume of voxels that enhance, as well as an increase in the maximum SE threshold in the VOI. Further work will correlate the spatial distribution of radiotherapy dose and the degree of SE on a voxel-wise basis.