MRI Scanning Technique of Brain

T2 axial sequence of brain is planned in sagittal localizer so that the center of the slice group passes through line joining the inferior border of genu and splenium of the corpus callosum (upper dotted line) or use a plane parallel to a line linking the floor of the sella turcica to the fastigium of the fourth ventricle -the highest point in the roof of the fourth ventricle (lower dotted line). The third alternative solution is to position slices parallel to the bicommisural line, which links the anterior tothe posterior commisure line (yellow line).

 Drawing shows the hypothalamus (outlined with a dashed line) lying below an imaginary line between the anterior commissure (AC) and the posterior commissure (PC). The anterior boundary of the hypothalamus is the lamina terminalis (LT), which extends between the optic chiasm (OC) and the anterior commissure. The posterior boundary is imprecise; it is indicated by a line that extends between the mamillary bodies (MB) and the posterior commissure. The floor of the hypothalamus is formed by the infundibular stalk (IS), the tuber cinereum (TC), and the mamillary bodies. The major tracts related to the hypothalamus, the mamillothalamic tract (MT) and the postcommissural fornix (PF), are also shown. (b) Sagittal T1-weighted MR image clearly demonstrates the anatomy of the hypothalamus. Note the high-signal-intensity area (arrowhead) representing the posterior pituitary gland. AC = anterior commissure, IS= infundibular stalk, LT = lamina terminalis, MB = mamillary bodies, OC= optic chiasm, PC = posterior commissure, TC = tuber cinereum. (c)On a sagittal contrast material–enhanced MR image, the infundibular stalk and pituitary gland show normal homogeneous enhancement, which reflects their lack of a blood-brain barrier.

 Drawing shows the hypothalamus (outlined with a dashed line) lying below an imaginary line between the anterior commissure (AC) and the posterior commissure (PC). The anterior boundary of the hypothalamus is the lamina terminalis (LT), which extends between the optic chiasm (OC) and the anterior commissure. The posterior boundary is imprecise; it is indicated by a line that extends between the mamillary bodies (MB) and the posterior commissure. The floor of the hypothalamus is formed by the infundibular stalk (IS), the tuber cinereum (TC), and the mamillary bodies. The major tracts related to the hypothalamus, the mamillothalamic tract (MT) and the postcommissural fornix (PF), are also shown. (b) Sagittal T1-weighted MR image clearly demonstrates the anatomy of the hypothalamus. Note the high-signal-intensity area (arrowhead) representing the posterior pituitary gland. AC = anterior commissure, IS= infundibular stalk, LT = lamina terminalis, MB = mamillary bodies, OC= optic chiasm, PC = posterior commissure, TC = tuber cinereum. (c)On a sagittal contrast material–enhanced MR image, the infundibular stalk and pituitary gland show normal homogeneous enhancement, which reflects their lack of a blood-brain barrier.

 Anatomic landmarks for positioning of axial slices. Axial slices should be positioned parallel to the bicommisural line, which links the anterior to the posterior commisure (yellow line). Alternatively, axial slices can be oriented parallel to a line linking the floor of the sella turcica to the fastigium of the fourth ventricle (lower dotted line). A third alternative solution is to position slices parallel to a line linking the inferior borders of the genu and splenium of the corpus callosum (upper dotted line). In most (adult) patients, these imaging planes differ by only a few degrees. For coronal scans, we prefer a plane parallel to the posterior surface of the brainstem (blue dotted line).

In axial localizer, the epicenter of the FOV is centered at the middle of the image more often just above the heart shaped structure i.e. pons. The FOV box can be angled according to the rotation of the localizer image.

In coronal localizer, the scan lines are made parallel with the inferior surface of the brain parenchyma more often the hippocampal part of the temporal lobe. This makes the axial image free from rotation.
T1 axial sequence of brain is planned by copying the scan lines of T2 axial sequence.
This is how we perform axial sequence in MRI Brain.

For sagittal scanning of brain, the epicenter of FOV is centered at mass intermedia in sagittal localizer and the mid scan line is passed through the interhemispheric fissure in axial localizer and in coronal localizer, the scan lines are made parrallel to the interhemispheric fissure so that the sagittal images cover whole brain parenchyma from  right sylvian fissure to the left sylvian fissure.


 
For coronal scanning of brain, we typically choose a tilted plane, perpendicular to the long axis of the temporal lobes. This can be obtained by positioning the coronal slices on a midsagittal image, parallel to the posterior part of the brain stem. The epicenter of FOV is centered at third ventricular level in coronal localizer and the scan lines are made parallel to the posterior surface of the brain stem in sagittal localizer (blue dotted line) but make sure that the scan lines cover the whole brain parenchyma from frontal lobe to the posterior aspect of cerebellum. In axial localizer, the mid scan line is made parallel to the the line joining the right and left internal auditory meatus. This gives symmetrical coronal images.

Thin slice coronal scanning of brain may be required in case of pituitary gland pathology. To perform this, the mid scan line is made parallel to the pituitary stalk and make sure that the whole pituitary gland with associated pathology is scanned.

Thin slice coronal scanning of brain may also be required in case of epilepsy where, the scan lines are made perpendicular to the temporal lobe in sagittal localizer. We need to angle scan lines perpendicular to the hippocampal and hippocampal area and make sure whole temporal lobe is included.

Thin slice coronal scanning of brain may also be required in case of vestibular schwannoma. The scan lines are made parallel to the line joining right and left internal auditory canal. The main purpose is to obtain involvement of vestibulo-cochlear nerve, facial nerve, trigeminal nerve and probably other cranial nerves as well in the tumor formation.

The routine sequences in MRI scanning of Brain are:
T2 Axial
T1 Axial
Flair Axial
T2 Coronal
T1 Sagittal

Diffusion axial images at b=0 and b=800 can be obtained in case of stroke and tumor cases.

Filming of the images of T2 Axial, Flair Axial and T2 Coronal is done in 4x5 format. First of all, text is send for filming and then scanogram image in mid T2 Sagittal plane is send and the remainings are filled with the series of the images. One useless image at the vertex or the image of the skull base is cut from the 19 slices of the series to fulfil the remaining 18 slices.

T1 Sagittal sequence is filled in 4x6 format. First of all, text, then scanogram image in mid T2 coronal plane is send in filming layout. Then, the series of images are send. The most parasagittal image either of right or left side may be cut if the images are more than the remaining squares.

T1 Axial sequence is filled in 5x6 format. First of all, text, then scanogram image in mid T1 sagittal plane and the series of images of T1 Axial sequence is send in filming layout. The images at the vertex or the skull base may be cut if the images are more than the remaining squares.

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