doi: 10.3174/ajnr.A0934
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
American Journal of Neuroradiology 29:e5, March 2008
© 2008 American Society of Neuroradiology
Letter
Reply:
a Department of Diagnostic Imaging and Nuclear Medicine
Kyoto University
Kyoto, Japan
We appreciate the interest and comments regarding our article.1 In it, we reported the successful visualization of the optic radiations in 20 of the 24 hemispheres by diffusion tensor (DT) tractography. However, we did not evaluate the visualization of the variations of the anterior limit of the Meyer loop in this article because we aimed to evaluate the difference in visualization of the optic radiation due to the number of motion-probing gradients and because the anterior limit of the Meyer loop was beyond the scope of the article.
As mentioned by the authors, the anterior limit of the Meyer loop is important for anterior temporal lobe (ATL) resections, and we were also aware of the anatomic variations of the Meyer loop.2 We agree with the suggestion by the authors that evaluation of intersubject variability in the anterior limit of the Meyer loop is beneficial for ATL resection. However, it is challenging for DT tractography because of its acutely curved course around the anterior limit, as we stated in our article,1 and the crossing-fiber problem.3
DT tractography has some limits, which come from its technical aspects; however, it is currently the only method to evaluate the structures of the neuronal trajectories in vivo.4 Validation of DT tractography data with results of surgical resection may reinforce its limits and the feasibility of this technique.
DT tractography has been applied in preoperative planning for cranial surgery near eloquent areas, including temporal lobe surgery.5 Regarding the crossing-fiber problem, several approaches, such as multitensor tractography,3 are going to be developed. Therefore, we believe that DT tractography is a promising technique that will more constantly visualize the full trajectory of the optic radiation in the near future.
References
- Yamamoto A, Miki Y, Urayama S, et al. Diffusion tensor fiber tractography of the optic radiation: analysis with 6-, 12-, 40-, and 81-directional motion-probing gradients—a preliminary study. AJNR Am J Neuroradiol 2007;28:92–96
[Abstract/Free Full Text] - Ebeling U, Reulen HJ. Neurosurgical topography of the optic radiation in the temporal lobe. Acta Neurochir (Wien) 1988;92:29–36[CrossRef][Medline]
- Yamada K, Sakai K, Hoogenraad FG, et al. Multitensor tractography enables better depiction of motor pathways: initial clinical experience using diffusion-weighted MR imaging with standard b-value. AJNR Am J Neuroradiol 2007;28:1668–73. Epub 2007 Sep 20
[Abstract/Free Full Text] - Mori S, van Zijl PC. Fiber tracking: principles and strategies—a technical review. NMR Biomed 2002;15:468–80[CrossRef][Medline]
- Okada T, Miki Y, Kikuta K, et al. Diffusion tensor fiber tractography for arteriovenous malformations: quantitative analyses to evaluate the corticospinal tract and optic radiation. AJNR Am J Neuroradiol 2007;28:1107–13
[Abstract/Free Full Text]
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||