Reliability of Stereotactic Coordinates of 1.5-Tesla and 3-Tesla MRI in Radiosurgery and Functional Neurosurgery

Abstract

ObjectiveThe aims of this study are to identify interpersonal differences in defining coordinates and to figure out the degree of distortion of the MRI and compare the accuracy between CT, 1.5-tesla (T) and 3.0T MRI.MethodsWe compared coordinates in the CT images defined by 2 neurosurgeons. We also calculated the errors of 1.5T MRI and those of 3.0T. We compared the errors of the 1.5T with those of the 3.0T. In addition, we compared the errors in each sequence and in each axis.ResultsThe mean difference in the CT images between the two neurosurgeons was 0.48±0.22 mm. The mean errors of the 1.5T were 1.55±0.48 mm (T1), 0.75±0.38 (T2), and 1.07±0.57 (FLAIR) and those of the 3.0T were 2.35±0.53 (T1), 2.18±0.76 (T2), and 2.16±0.77 (FLAIR). The smallest mean errors out of all the axes were in the x axis : 0.28-0.34 (1.5T) and 0.31-0.52 (3.0T). The smallest errors out of all the MRI sequences were in the T2 : 0.29-0.58 (1.5T) and 0.31-1.85 (3.0T).ConclusionThere was no interpersonal difference in running the Gamma Plan® to define coordinates. The errors of the 3.0T were greater than those of the 1.5T, and these errors were not of an acceptable level. The x coordinate error was the smallest and the z coordinate error was the greatest regardless of the MRI sequence. The T2 sequence was the most accurate sequence.

Technical feasibility of integrating 7 T anatomical MRI in image-guided radiotherapy of glioblastoma: a preparatory study

“…The larger range of MAD-values is related to the increase in measurable distance between grid-intersection points and the residual system-related geometrical distortion factors, such as eddy currents and B 0 inhomogeneity, which were not corrected for. Others have used a similar method, as applied in this study to estimate the reliability of stereotactic coordinates on 1.5 and 3 T MR images [37]. They reported a range of mean errors of 0.30-1.20 and 0.43-1.78 mm in T 1 w-images at 1.5 and 3 T, respectively.…”

In phantom evaluation of targeting accuracy in MRI-based brain radiosurgery

“…The source of distortions can usually be found in nonlinearities of the gradient coils and inhomogeneities in the main magnetic field caused by main magnet imperfections and the magnetic effect of varying susceptibility of patient tissues. Once MRI acquisition settings are optimized to minimize the extent of distortions while maintaining a sufficient signal-to-noise ratio for brain radiosurgery, residual distortions are usually measured with geometric phantoms consisting of regular 3D grids of markers [2,3,6,[8][9][10][11][12][13][14][15]. Gamma Knife treatments are planned directly on MR images, and dose calculation is performed assuming the presence of a water-equivalent tissue inside an external contour through a tissue-to-maximum-ratio (TMR10) algorithm [16,17].…”

Deep Brain Stimulation: The Perspective of Brain Connectivity

“…At this time, T2-weighted axial and coronal images are fused if these are available. The author feels that this work may minimize the distortion error of the MRI images even though the distortion error of a 1.5 T MRI image is within the acceptable boundary [45]. The targets, such as the STN and GPi, may be easily visualized on T-2 weighted MRI images (Figure 1).…”