Evaluation of distortion correction of diffusion-weighted MR images of human cervix

Diffusion-weighted images are increasingly being employed in conjunction with T2-weighted images for accurate diagnosis of cervical cancer. However, these images suffer from eddy-current related and magnetic field inhomogeneity induced distortions. This paper presents an investigation into the reverse gradient technique to correct distortions in diffusion-weighted echo-planar images of human cervix. We hypothesize that the correction aligns the diffusion-weighted images with the T2-weighted images. To allow for any misalignments and to evaluate the correction, a normalized cross-correlation driven template matching strategy was employed to assess the correlation between the corrected image and the T2-weighted image. For b = 0 smm^-2 images, mean correlation values of 0.72±0.14 for regions-of-interest drawn around the cervix for 10 patients were achieved. We also found that our hypothesis was most valid in regions encompassing the cervix with a misalignment of 4.4±3.4mm. Results are presented for images acquired at a field-of-view of 100mm using an endovaginal coil developed in-house for cervix imaging at 3T which is the first of its kind in the world.