Purpose: Recently a spiral FLAIR MRI technique has been developed for treatment planning in stereotactic radiosurgery of trigeminal neuralgia, providing good delineation of the nerve root, adequate suppression of CSF, improved contrast, and insensitivity to field disturbance due to the metal frame. This study aims to determine the geometric accuracy of spiral FLAIR for treatment planning.
Methods: A CIRS MR distortion and image fusion head phantom 603A was used. CT images were acquired as reference. The phantom was scanned on a 3T research MRI scanner with a metal frame using SPGR, FIESTA, and the proposed spiral FLAIR (only available on the 3T research scanner), and on a 1.5T clinical MRI scanner without the metal frame using SPGR and conventional FLAIR.To measure the geometric accuracy, all MRI images were registered to CT images in Leksell GammaPlan. The coordinates of 13 points were measured from CT and all MRI images, 4 corner markers and 1 center marker at the middle slice, 4 corners at a superior and an inferior slice, respectively. The point-to-point deviation in each coordinate direction and corresponding distance between CT and each MRI data set were computed. Mean error in each direction, and mean and standard deviation of distance, are derived.
Results: Mean errors in (X, Y) (mm) at 3T are (0.19, 0.32), (0.37, 0.40), (0.68, 0.56) for SPGR, FIESTA, spiral FLAIR, respectively, (0.60, 0.24) and (0.56, 0.18) at 1.5T for SPGR and conventional FLAIR, respectively. Mean and standard deviation of distance at 3T are (0.40±0.26), (0.59±0.25), (0.98±0.56), for SPGR, FIESTA, spiral FLAIR, respectively, (0.66±0.38) and (0.61±0.25) at 1.5T for SPGR and conventional FLAIR, respectively. The error in Z is 0 in all measurements.
Conclusion: This study demonstrated that spiral FLAIR achieves good geometric accuracy, providing a potential tool for stereotactic radiosurgery treatment planning of trigeminal neuralgia.
Funding Support, Disclosures, and Conflict of Interest: Barrow Neurological Institute has a master research agreement with Philips Healthcare.