Yen Jun Roger Lai MD, Presenter: Nothing to Disclose

Wan-Yuo Guo MD, Abstract Co-Author: Nothing to Disclose

Hsiu-Mei Wu MD, Abstract Co-Author: Nothing to Disclose

Jiing-Feng Lirng, Abstract Co-Author: Nothing to Disclose

Cheng-Yen Chang MD, Abstract Co-Author: Nothing to Disclose

Stereotactic procedure of the brain has its advantage of managing deep-seated lesions with minimal invasion. In stereotactic radiosurgery, MRI or multi-platform stereotactic neuroimaging (combined MRI and X-ray angio-suite) have been proved a reliable modality in geometry accuracy and reproducibility. However, sparse reports, concerning geometry accuracy of stereotactic MDCT, are found in the literatures. In this study, we used the Leksell stereotactic system to evaluate the geometry accuracy of a 16-MDCT, focusing on different collimation and pitch settings.

A Leksell CT stereotactic indicator box, with N-shaped radiopaque fiducial markers on side plates, was used as a standard length. The indicator box was scanned in a 16-MDCT (Sensation-16, Siemens) with different pitches and collimations. All available pitches are 0.50, 0.75, 1.00, 1.25 & 1.50, and the collimations are 0.75 mm & 1.5 mm. Other imaging parameters are unchanged. Ten groups of axial source images were obtained with different pitch & collimation. Source images of different groups were sent to a workstation (AW, ver. 4.2, GE) & a Leksell Gamma Plan (LGP, ver. 4.12, Elekta Instruments). In the AW, length measurement is done on 3D multple plane reformatted images. In the LGP, mean errors are obtained directly by a default program. Differences in length measurement among groups are assessed by a two-way analysis of variance (ANOVA).

In the AW, the mean errors of length measurement on XY-plane are from 0.3 mm to 0.7 mm and from 0.3 mm to 1.2 mm on Z-plane. In the LGP, the mean errors read 0.3 mm. The overall mean errors are within sub-millimeter range, regardless of different pitches and collimations. No statistically significant difference in length measurement among those groups both on xy-plane and z-plane (P> 0.05).

This study validates the geometry accuracy of stereotactic 3D images by 16-MDCT, independent of all available default pitches and collimations. Patients, who needs stereotactic radiosurgery but have contraindication of undergoing MR study, may have an alternative imaging modality with 16-MDCT.

In stereotactic radiosurgery, 16-MDCT is also a reliable modality in geometry accuracy.

Lai, Y, Guo, W, Wu, H, Lirng, J, Chang, C, Evaluating Geometry Accuracy of Stereotactic 3D 16-MDCT.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5007349.html