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Anatomical evaluation of CT-MRI combined femoral model.

Lee YS, Seon JK, Shin VI, Kim GH, Jeon M - Biomed Eng Online (2008)

Bottom Line: Statistical analysis to assess any significant difference between accuracies of those two methods was performed using univariate repeated measures ANOVA with the Turkey post hoc test.The global 3D contour matching deviation of the landmark-based matching was 1.1 +/- 0.3 mm, but local 2D contour deviation through anatomical inspection was much larger as much as 3.0 +/- 1.8 mm.Even with human-factor derived errors accumulated from segmentation of MRI images, and limited image quality, the matching accuracy of CT-&-MRI combined 3D models was 0.5 +/- 0.3 mm in terms of local anatomical inspection.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Information and Mechatronics, Gwangju Institute of Science and Technology, Gwangju, Korea. biomechanics.yslee@gmail.com

ABSTRACT

Background: Both CT and MRI are complementary to each other in that CT can produce a distinct contour of bones, and MRI can show the shape of both ligaments and bones. It will be ideal to build a CT-MRI combined model to take advantage of complementary information of each modality. This study evaluated the accuracy of the combined femoral model in terms of anatomical inspection.

Methods: Six normal porcine femora (180 +/- 10 days, 3 lefts and 3 rights) with ball markers were scanned by CT and MRI. The 3D/3D registration was performed by two methods, i.e. the landmark-based 3 points-to-3 points and the surface matching using the iterative closest point (ICP) algorithm. The matching accuracy of the combined model was evaluated with statistical global deviation and locally measure anatomical contour-based deviation. Statistical analysis to assess any significant difference between accuracies of those two methods was performed using univariate repeated measures ANOVA with the Turkey post hoc test.

Results: This study revealed that the local 2D contour-based measurement of matching deviation was 0.5 +/- 0.3 mm in the femoral condyle, and in the middle femoral shaft. The global 3D contour matching deviation of the landmark-based matching was 1.1 +/- 0.3 mm, but local 2D contour deviation through anatomical inspection was much larger as much as 3.0 +/- 1.8 mm.

Conclusion: Even with human-factor derived errors accumulated from segmentation of MRI images, and limited image quality, the matching accuracy of CT-&-MRI combined 3D models was 0.5 +/- 0.3 mm in terms of local anatomical inspection.

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Local 2D contour-based measurement of matching deviation in the femoral condyle. The final value of local 2D contour-based measure of matching deviation was obtained as the average of all the deviation measured at all the intersection pixels on all the sagittal images.
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Figure 5: Local 2D contour-based measurement of matching deviation in the femoral condyle. The final value of local 2D contour-based measure of matching deviation was obtained as the average of all the deviation measured at all the intersection pixels on all the sagittal images.

Mentions: Local 2D contour-based measurement of matching deviation in the femoral condyle was executed on the sagittal MRI images (Fig. 5). On a sectional image at every 2.4 mm along the same medial-to-lateral direction as the CT or MRI scanners followed, 2D contour-based measurement of matching deviation was locally performed. First, in the sagittal view of the femoral condyle, a center line vector was determined. The center line vector was defined as the vector passing the centers of reference spheres that were numerically determined by picking points on the articulation surfaces of the medial and lateral condyles. Subsequently, the anteroinferior vector (the C-AB line), the inferior vector (the C-B line), and the posteroinferior vector (the C-PB line) were drawn in; anteroinferiorly 45°, distally 90°, and posteroinferiorly 45° in the sagittal view, respectively. Each MRI sagittal image was divided by those three vectors. At the points that the matched CT-derived contours intersect with the MRI-derived contour, the local 2D contour deviations were measured. In this way, the final value of local 2D contour-based measure of matching deviation was obtained as the average of all the deviation measured at all the intersection pixels on all the sagittal images.


Anatomical evaluation of CT-MRI combined femoral model.

Lee YS, Seon JK, Shin VI, Kim GH, Jeon M - Biomed Eng Online (2008)

Local 2D contour-based measurement of matching deviation in the femoral condyle. The final value of local 2D contour-based measure of matching deviation was obtained as the average of all the deviation measured at all the intersection pixels on all the sagittal images.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2265715&req=5

Figure 5: Local 2D contour-based measurement of matching deviation in the femoral condyle. The final value of local 2D contour-based measure of matching deviation was obtained as the average of all the deviation measured at all the intersection pixels on all the sagittal images.
Mentions: Local 2D contour-based measurement of matching deviation in the femoral condyle was executed on the sagittal MRI images (Fig. 5). On a sectional image at every 2.4 mm along the same medial-to-lateral direction as the CT or MRI scanners followed, 2D contour-based measurement of matching deviation was locally performed. First, in the sagittal view of the femoral condyle, a center line vector was determined. The center line vector was defined as the vector passing the centers of reference spheres that were numerically determined by picking points on the articulation surfaces of the medial and lateral condyles. Subsequently, the anteroinferior vector (the C-AB line), the inferior vector (the C-B line), and the posteroinferior vector (the C-PB line) were drawn in; anteroinferiorly 45°, distally 90°, and posteroinferiorly 45° in the sagittal view, respectively. Each MRI sagittal image was divided by those three vectors. At the points that the matched CT-derived contours intersect with the MRI-derived contour, the local 2D contour deviations were measured. In this way, the final value of local 2D contour-based measure of matching deviation was obtained as the average of all the deviation measured at all the intersection pixels on all the sagittal images.

Bottom Line: Statistical analysis to assess any significant difference between accuracies of those two methods was performed using univariate repeated measures ANOVA with the Turkey post hoc test.The global 3D contour matching deviation of the landmark-based matching was 1.1 +/- 0.3 mm, but local 2D contour deviation through anatomical inspection was much larger as much as 3.0 +/- 1.8 mm.Even with human-factor derived errors accumulated from segmentation of MRI images, and limited image quality, the matching accuracy of CT-&-MRI combined 3D models was 0.5 +/- 0.3 mm in terms of local anatomical inspection.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Information and Mechatronics, Gwangju Institute of Science and Technology, Gwangju, Korea. biomechanics.yslee@gmail.com

ABSTRACT

Background: Both CT and MRI are complementary to each other in that CT can produce a distinct contour of bones, and MRI can show the shape of both ligaments and bones. It will be ideal to build a CT-MRI combined model to take advantage of complementary information of each modality. This study evaluated the accuracy of the combined femoral model in terms of anatomical inspection.

Methods: Six normal porcine femora (180 +/- 10 days, 3 lefts and 3 rights) with ball markers were scanned by CT and MRI. The 3D/3D registration was performed by two methods, i.e. the landmark-based 3 points-to-3 points and the surface matching using the iterative closest point (ICP) algorithm. The matching accuracy of the combined model was evaluated with statistical global deviation and locally measure anatomical contour-based deviation. Statistical analysis to assess any significant difference between accuracies of those two methods was performed using univariate repeated measures ANOVA with the Turkey post hoc test.

Results: This study revealed that the local 2D contour-based measurement of matching deviation was 0.5 +/- 0.3 mm in the femoral condyle, and in the middle femoral shaft. The global 3D contour matching deviation of the landmark-based matching was 1.1 +/- 0.3 mm, but local 2D contour deviation through anatomical inspection was much larger as much as 3.0 +/- 1.8 mm.

Conclusion: Even with human-factor derived errors accumulated from segmentation of MRI images, and limited image quality, the matching accuracy of CT-&-MRI combined 3D models was 0.5 +/- 0.3 mm in terms of local anatomical inspection.

Show MeSH