The Application Accuracy of Stereotactic Frames

Abstract

The purpose of incorporating stereotactic methodology into neurosurgical operations is to achieve a consistently high degree of accuracy in localizing intracranial targets. Therefore, the limits of resolution for the operation are a function of the accuracy of the particular stereotactic frame system. The total clinically relevant error (application accuracy) comprises errors associated with each procedural step, including imaging, target selection, vector calculations, and the mechanical errors of stereotactic frames. To evaluate these parameters, a systematic error analysis was carried out with four commonly used stereotactic devices: the Brown-Roberts-Wells, the Cosman-Roberts-Wells, the Kelly-Goerss COMPASS (modified Todd-Wells), and the Leksell frames. Over 21,500 independent accuracy test measurements were made with 11,000 computed tomograms. The results suggest a potentially significant degree of error in the application accuracy of all stereotactic instruments, which is accentuated by but not entirely due to imaging-associated errors. Clinically encountered levels of weightbearing by stereotactic frames may have a pronounced effect on their mechanical accuracy. Both the reapplication of aiming arc assemblies and the use of phantom base units introduce independent sources of mechanical inaccuracy into stereotactic procedures. The scope of individual error values and their determining factors must be considered with every clinical use of stereotactic frame systems.

The Impact of the Reference Imaging Modality, Registration Method and Intraoperative Flat-Panel Computed Tomography on the Accuracy of the ROSA® Stereotactic Robot

“…The accuracy of stereotactic procedures has been extensively studied [2,3,4,5,6,7,8,9,10,11,12]. However, technology is evolving rapidly in terms of both the surgical equipment and imaging techniques.…”

Evaluation of the stability of the stereotactic Leksell Frame G in Gamma Knife radiosurgery

“…The difference reported by Karlsson and colleagues is considerably lower than that observed in our study and this is explained by the methodological differences. The comparison between the pre‐ and post‐GKR scans in their study was done using the calculated mean of repeated observations (mean position of localization), rather than each individual localization attempt, and this could result in erroneously favorable outcomes (2) . Also, we used a different imaging technique before and after GKR, and the imaging slices were also thicker in our study (1.5 vs. 0.7 mm), which explains the increased uncertainty of our measurements.…”

“…The application accuracy of four commonly used stereotactic devices, including the Leksell frame, was challenged by Maciunas et al (2) in an attempt to evaluate the total accuracy conveyed by the entire visualization, calculation, and surgical systems working together. The study suggested a significant degree of error in the application accuracy of all the stereotactic instruments tested, but failed to specifically address the question of stability of the frame itself.…”

“…The paper by Maciunas et al (2) also claimed to evaluate the effect of frame weight‐bearing on the accuracy of the stereotactic systems and concluded that a mean displacement of 1.62 mm occurs if a weighting of 25 Kg is added to the Leksell Frame G. This is a significant weight unlikely to represent any clinical scenario and it is not possible to determine from the study report how the Leksell frame was fixed to the phantom's acrylic plastic base. Their results are more likely to reflect a technical fault on the specific experimental design rather than any clinically relevant instability of the frame.…”

“…The overall application accuracy of GKR, also referred to as the total clinically relevant error, (2) is the result of individual inaccuracies associated with each step in the procedure and they can be grouped into three categories. First is the difference between the radiation delivered to the patient and that defined in the treatment plan in terms of magnitude, location or distribution.…”