Optimized 3D Magnetization-Prepared Rapid Acquisition of Gradient Echo: Identification of Thalamus Substructures at 3T

Bender, Benjamín; Mänz, Constantin; Korn, A.; Nägele, Thomas; Klose, Uwe

doi:10.3174/ajnr.a2705

Cited by 21 publications

(24 citation statements)

References 21 publications

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“…Previous attempts to visualize thalamic nuclei required challenging data post-processing, or did at least rely on non-commercial in-house software solutions [11,12,13]. A recently published work of Bender et al [17] describes the identification of the four large thalamic nuclei groups (including the anterior group) by means of an optimized MPRAGE sequence. Their images show a good demarcation between the medial and the lateral group of thalamic nuclei whereas the image examples given here are supposed to allow a more precise targeting of the AV.…”

Section: Discussionmentioning

confidence: 99%

Direct Targeting of the Thalamic Anteroventral Nucleus for Deep Brain Stimulation by T<sub>1</sub>-Weighted Magnetic Resonance Imaging at 3 T

Buentjen

Kopitzki

Schmitt

et al. 2013

Stereotact Funct Neurosurg

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Background: The thalamic anteroventral nucleus (AV) is a promising target structure for deep brain stimulation (DBS) in patients suffering from refractory epilepsy. Direct visualization of the AV would improve spatial accuracy in functional stereotactic neurosurgery for treatment of this disease. Methods: On 3-tesla magnetic resonance imaging (MRI), acquisition parameters were adjusted for optimal demarcation of the AV in 1 healthy subject. Reliability of AV visualization was then evaluated in 5 healthy individuals and 3 patients with refractory epilepsy. Results: In all individuals, an adjusted T₁-weighted sequence allowed for demarcation of the AV. It was clearly distinguishable from hyperintense myelin-rich lamellae surrounding it ventrally and laterally and appeared hypo-intense compared to the adjacent thalamic nuclei. Image resolution and contrast facilitated direct stereotactic targeting of the AV prior to DBS surgery in all 3 patients. Conclusions: Direct targeting of the AV can be achieved, which has immediate implications for the accuracy of MRI-guided DBS in patients with refractory epilepsy.

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Section: Discussionmentioning

confidence: 99%

Direct Targeting of the Thalamic Anteroventral Nucleus for Deep Brain Stimulation by T<sub>1</sub>-Weighted Magnetic Resonance Imaging at 3 T

Buentjen

Kopitzki

Schmitt

et al. 2013

Stereotact Funct Neurosurg

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“…Hence inversion recovery (IR) T1-weighted pulse sequences (Deichmann et al, 2000; Deichmann et al, 2004) where contrast is mostly dependent on the presence of myelin, could be particularly suitable for high resolution and high contrast 3D imaging of the thalamus. In line with this reasoning, modifications of the magnetization-prepared rapidly-acquired gradient echo (MPRAGE) sequence have been suggested to visualize some intra-thalamic structures (Bender et al, 2011; Sudhyadhom et al, 2009; Vassal et al, 2012). In particular, intra-thalamic T1 contrast seems to be enhanced through the use of different inversion times (TI) than commonly used, specifically to null either white matter (WM) (Sudhyadhom et al, 2009; Vassal et al, 2012) or grey matter (GM) (Bender et al, 2011; Magnotta et al, 2000).…”

Section: Introductionmentioning

confidence: 98%

Visualization of intra-thalamic nuclei with optimized white-matter-nulled MPRAGE at 7T

et al. 2014

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Novel MR image acquisition strategies have been investigated to elicit contrast within the thalamus, but direct visualization of individual thalamic nuclei remains a challenge because of their small size and the low intrinsic contrast between adjacent nuclei. We present a step-by-step specific optimization of the 3D MPRAGE pulse sequence at 7T to visualize the intra-thalamic nuclei. We first measured T1 values within different sub-regions of the thalamus at 7T in 5 individuals. We used these to perform simulations and sequential experimental measurements (n=17) to tune the parameters of the MPRAGE sequence. The optimal set of parameters was used to collect high-quality data in 6 additional volunteers. Delineation of thalamic nuclei was performed twice by one rater and MR-defined nuclei were compared to the classic Morel histological atlas. T1 values within the thalamus ranged from 1400ms to 1800ms for adjacent nuclei. Using these values for theoretical evaluations combined with in vivo measurements, we showed that a short inversion time (TI) close to the white matter null regime (TI=670ms) enhanced the contrast between the thalamus and the surrounding tissues, and best revealed intra-thalamic contrast. At this particular nulling regime, lengthening the time between successive inversion pulses (TS=6000ms) increased the thalamic signal and contrast and lengthening the α pulse train time (N*TR) further increased the thalamic signal. Finally, a low flip angle during the gradient echo acquisition (α=4°) was observed to mitigate the blur induced by the evolution of the magnetization along the α pulse train. This optimized set of parameters enabled the 3D delineation of 15 substructures in all 6 individuals; these substructures corresponded well with the known anatomical structures of the thalamus based on the classical Morel atlas. The mean Euclidean distance between the centers of mass of MR- and Morel atlas-defined nuclei was 2.67mm (±1.02mm). The reproducibility of the MR-defined nuclei was excellent with intraclass correlation coefficient measured at 0.997 and a mean Euclidean distance between corresponding centers of mass found at first versus second readings of 0.69mm (±0.38mm). This 7T strategy paves the way to better identification of thalamic nuclei for neurosurgical planning and investigation of regional changes in neurological disorders.

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“…Urgent interest to subdivisions of the thalamus inspired Bender et al [16] to optimize and modernize protocols trying to enable direct visualization of the main nuclear groups of the thalamus and to improve targeting with coordinates from classic anatomical atlases. However,…”

Section: Discussionmentioning

confidence: 99%

Stereotactic Characteristics of the Thalamus Subject to Shape of the Skull: An MRI Study

Kornieieva¹

2017

OARA

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Introduction: The thalamus is a nuclear complex located in the dorsal part of the diencephalon. The wide implementation of deep brain stimulation into minimally invasive neurosurgical practice requires accurate localization of the thalamus. The present study is designed to assess the influence of the individual shape of the skull in relation to the stereotactic characteristics of the thalamus. Materials and methods:A total of 140 Arab patients underwent routine MRI examination of the head. The perpendicular distances from the outer surface of the skull bones to anterior, lateral and superior borders of the thalamus were analyzed in patients with dolichocephalic, mesocephalic, and brachycephalic shapes of the skull. The maximum-likelihood estimation of the observed variables was generalized to the studied population with the method of robust regression. Results:The distance from the anterior end of the thalamus to the outer surface of the frontal bone varies from the 81.92mm in the group of subjects with the dolichocephalic shape of the skull to 77.92mm in the brachiocephalic group, with the middle value obtained in the mesocephalic group. The opposite tendency concerns the distance from the midpoint of the lateral border of the thalamus to the outer surface of the temporal bone. Conclusion:The distances between the counter sides of the thalamus and the outer surfaces of overlaying bones do correlate with the shape of skull, and may contribute to personalization of preoperative stereotactic analysis and approach.

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Optimized 3D Magnetization-Prepared Rapid Acquisition of Gradient Echo: Identification of Thalamus Substructures at 3T

Cited by 21 publications

References 21 publications

Direct Targeting of the Thalamic Anteroventral Nucleus for Deep Brain Stimulation by T<sub>1</sub>-Weighted Magnetic Resonance Imaging at 3 T

Direct Targeting of the Thalamic Anteroventral Nucleus for Deep Brain Stimulation by T<sub>1</sub>-Weighted Magnetic Resonance Imaging at 3 T

Visualization of intra-thalamic nuclei with optimized white-matter-nulled MPRAGE at 7T

Stereotactic Characteristics of the Thalamus Subject to Shape of the Skull: An MRI Study

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