 Hello everyone, I am Dr. Reina Tenbe and in today's lecture we shall be having a look at the normal angiography of the brain and neck on MRI. The most common indication of MRI angiography is when a patient presents with stroke. The other common indications are to look for an aneurysm or a vascular malformation. The advantages of MRI angiography are that there is no radiation involved and that also it can be done without contrast. There are various techniques to acquire the images. In today's lecture, we shall be having a look at the non-contrast time of light sequences. We shall identify the vessels, trace their course and have a look at their branches. So let us begin now. We have here the source images of the angiography of the neck. This is the arch of aorta. We first look at the origin of the arch vessels. So when we scroll through the images we can see the origin of brachiocephalic artery, left common carotid and left subclavian artery. The left common carotid arises directly from the aortic arch. The brachiocephalic artery then divides into the right subclavian and right common carotid artery. The common carotid artery then terminates by dividing into the external and internal carotid arteries. Let us have a look at this on the sagittal images. So we have here the sagittal image of the neck angiography. We can see the arch of aorta and we can see the origin of our arch vessels. We can see a common carotid artery and its division into the external and internal carotid artery. The internal carotid artery arises at approximately C3 to C4 vertebral level. There is a small fusiform dilatation at its origin which is the carotid sinus. This is concerned with the regulation of blood pressure. The cervical ICA can be tortuous at times forming a consular loop. There are no constant branches of the cervical segment of the ICA. The ICA then enters the cranial cavity. Let us have a look at its intracranial course now. So we have here the angiographic images of the brain. We can see our internal carotid artery. Let us trace this ICA now. We can see that the ICA enters the cranial cavity via the carotid canal in the petrous bone. It runs almost horizontally passing anterior medially in the carotid canal. It then crosses the foramen lacerum and turns upwards and medially to enter the cavernous sinus. In the cavernous sinus it runs forwards and upwards to enter the subaric moite space and then turns posteriorly, laterally and superiorly to terminate into its major divisions those are the anterior and middle cerebral arteries. Let us have a look at the branches of the ICA. Meningo-hypofacial trunk arises from the ICA just before it enters the cavernous sinus. This branch is not visualized on the angiography unless it is hypertrophied. The next branch that we see is the ophthalmic artery which is the first supraclinoid branch of the ICA. So we can see our ophthalmic artery over here which arises from the ICA in the subaric moite space and it goes through the optic foramen within the optic nerve sheath. The next branch that we are going to see is the posterior communicating artery which arises from the ICA posteriorly and which connects to the ipsilateral PCA. It forms an anastomotic link between the anterior and posterior circulation. The next vessel that we see is the anterior coroidal artery which arises from the ICA posteriorly lateral to the optic chiasm and distilled to the pico. It has a first part or the cisternal segment which passes between the optic tract and anchors. It then passes across the medial wing of the ambient cistern to enter the coroidal fissure where it becomes the plexus segment. It runs within the coroid plexus of the temporal horns and continues around the trigonal lateral ventricle into the coroid plexus of posterior horn and body and sometimes as far anteriorly as foramen of monro. After giving rise to the anterior coroidal artery, the ICA terminates by dividing into the anterior and middle cerebral arteries. The anterior cerebral arteries or the ACAs run anteriorly onto the medial surface of the hemisphere and in the inter hemispheric fissure. The two ACAs are linked together by the ACOM or the anterior communicating artery which lies in the cistern of laminar terminalis. The ACA has a A1 segment or the pre-communicating or a horizontal segment which lies between the ICA bifurcation and the origin of ACOM. The A2 segment extends from the ACOM to the origin of the callosomarginal artery. Let us have a look at this vessel on the sagittal images. So we have here the sagittal image of the brain. We can see our paired anterior cerebral arteries or the ACA. There is a small branch communicating the two which is the anterior communicating artery. Our A2 segment extends from this ACOM up to the origin of the callosomarginal artery. Let us now have a look at the branches of the A2 segment. The orbitofrontal artery is usually the first cortical branch of the A2 segment arising from the sub-callosal segment. The frontopolar artery runs from the genu of corpus callosum to the frontal pole. So when we trace this we can see that this vessel arises from the genu and runs up to the frontal pole. This is the frontopolar artery. The next branch that we see is the callosomarginal artery which runs through the singulate sulcus and gives rise to the internal frontal branches. The peri-callosal artery is the continuation of ACA beyond the origin of the callosomarginal artery. So we can see our peri-callosal artery here which is the continuation of ACA beyond the origin of the callosomarginal artery. So this is our peri-callosal artery which arches over the genu of the corpus callosum and goes posteriorly over the surface of the corpus callosum. It can go as far posteriorly as the splenium. The cortical branches of the ACA are the same as those of the MCA and PCA. Let us now have a look at the middle cerebral artery or the MCA. So we have our coronal images over here where we identify the ICA and its division into ACA and MCA. So this is our M1 segment of the MCA which lies in the horizontal limb of the sylvian fissure. At the antero inferior aspect of the insula it curves upwards forming its genu. The branches then course over the surface of the insula and at the superior limit of the insula they turn inferiorly and laterally to emerge from the lateral aspect of the sylvian fissure and then course along the cortical surfaces of the frontal, parietal, temporal and occipital lobes. Let us have a look at this MCA again in the axial plane. So this is our axial images where we see the anterior and the middle cerebral arteries. We can see our M1 segment which lies between the frontal and the temporal lobes in the horizontal limb of the sylvian fissure. At the sylvian fissure it bifurcates into groups of anterior and posterior branches. The anterior group includes orbitofrontal, operculofrontal and central sulcus arteries. The posterior group is generally made up of three major branches posterior parietal, angular and posterior temporal arteries. Let us now have a look at the external carotid artery. We have the neck angiographic images here. We can see our common carotid artery and when we scroll this we can see its division into the external carotid and the internal carotid artery. The ECA usually lies anteriorly and medially to the ICA. Traditionally eight branches of ECA have been described but variations are quite common and there can be between four to twelve branches. There is a lot of anastomosis between various branches of ECA between ICA and ECA and between vertebral arteries and ECA. Let us now have a look at these branches. We shall be going to the sagittal images. So we have here the sagittal image of the neck. We can see our common carotid artery and its division into external and internal carotid artery. We shall first look at the anterior branches and then have a look at the posterior branches. So we have our ECA here and we can see the first branch which arises anteriorly and which descends towards the superior pole of the thyroid gland is the superior thyroid artery. The next branch that we see is the lingual artery which arises anteriorly. It has a U-shaped upward curves and then it goes anteriorly again. This can have a common origin with the facial artery forming a lingual facial trunk. The next branch that arises superior to the lingual artery is the facial artery. This anastomosis with the ophthalmic artery of the ICA. Now let us have a look at the posterior branches. So this is our ECA. We can see a small branch which arises from it and travels between the ECA and ICA along the posterior lateral wall of the pharynx. We can see that it is travelling along the posterior lateral wall of the pharynx. This is the ascending pharyngeal artery. This has an extensive anastomosis with the other branches of the ECA. With cavernous branches of ICA and meningeal branches of vertebral artery this vessel is commonly involved in the craniofacial vascular anomalies. The next branch that we can see is the occipital artery which arises posteriorly. We can see this is our occipital artery. This may anastomose with the branches of the vertebral artery. The next posterior branch is the posterior auricular artery which arises superior to the occipital artery. The ECA then divides into the maxillary artery and the superficial temporal artery. Let us now have a look at the vertebro-basilar system. We have the neck angiographic images here. We scroll through the images. We identify the arch vessels. We can see our left subclavian artery. When we trace this vessel we can see the vertebral artery arising from it as its first branch. The vertebral artery travels through the foramen transversarium of the sixth to the third cervical vertebrae. It then goes superiorly and laterally. We can see here that it is going superiorly and laterally to enter the foramen transversarium of the axis vertebra. Then superiorly again to enter the foramen transversarium of the atlas vertebra. It then passes posteriorly around the atlantooccipital joint and then goes anteriorly, superiorly and medially to enter the skull through the foramen magnum. We have here the brain images where we can see the intracranial course of the vertebral artery. There is a vessel which arises from it as its largest and most distilled branch. This is the posterior inferior cerebellar artery or the paica. The paica binds around the olive of the medulla and comes near the biventric lobule of the cerebellum. This is the anterior medullary segment. The vessel then courses along the lateral aspect of the brainstem and comes to lie inferior to the tonsil, forming the lateral medullary segment. The vessel then ascends towards the superior part of the tonsil where it gives branches which supply the coroid complexes of the fourth ventricle and the cerebellar hemispheres. Let us now have a look at this vessel on the sagittal images. So we have here the sagittal image of the brain. We can identify our vertebral artery and the posterior inferior cerebellar artery. This vessel usually arises above the foramen magnum but may at times arise below it. We can see the anterior medullary segment of the paica which binds around the olive. Next is the lateral medullary segment which curves around the brainstem laterally and goes to the inferior part of the tonsil where it forms a chordal loop. It then ascends forming the posterior medullary segment and when it goes to the superior part of the tonsil it forms a cranial loop where it gives branches to the coroid complexes and the cerebellar hemispheres. The vertebral arteries then fuse to form the basilar artery. So we see here that the basilar artery is formed by the confluence of the vertebral arteries and the quantum medullary junction. It ascends approximately in the midline in the quantine system. Superiorly, we can see that it curves a little posteriorly before dividing into its posterior cerebral arteries. Along the length of the basilar artery are multiple small penetrating branches which pass posteriorly into the brainstem. Let us now have a look at these branches. So we can see here the basilar artery and we can see the anterior inferior cerebellar artery or the aika arising from the lateral aspect. This traverses the cerebellar quantine angle system usually anteriorly and medially to the neural bundle. It has a lateral branch which courses over the floculus of the cerebellum and a medial branch which supplies the biventric lobule cerebellar hemispheres. The next vessel that we can see which arises from the basilar artery and goes into the inner ear is the labyrinthine artery. We shall now have a look at the superior cerebellar artery. The superior cerebellar artery or the SCA arises from the basilar artery near its terminal division. It runs laterally around the brainstem and comes to lie inferior to the oculomotor nerve. The oculomotor nerve separates it from the PCA. At the lateral border of the pons the artery turns posteriorly over the middle cerebellar peduncle to form the ambient segment. In the ambient segment it parallels the course of the trochlear nerve. The vessel then approaches the midline in the quadrageminal plate system. The basilar artery then terminates by dividing into the posterior cerebral arteries or the PCAs. The PCAs have a P1 segment or a pre-communicating segment which extends between the basilar bifurcation to the PCOM. So we can see our posterior communicating artery here and we can see our basilar termination. So this segment is the P1 segment of the PCA which lies in the interpedentular fossa. Thelamic perforating arteries arise from the P1 segment and PCOM. The next is the P2 segment or the ambient segment which runs around the brainstem in the ambient system. So this is our P2 segment. This runs parallel to the basal vein of Rosenthal and optic tract. It curves around the cerebral peduncles to lie above the tentorium. This P2 segment can get compressed against the tentorial edge in case of ankle herniation which may lead to occipital lobe infarction. The P3 segment extends from the quadrigeminal plate system to the calcarene fissure. We can see here that this is our P3 segment. There are two major branches of the P3 segment. The parieto-oxcipital branch which we can see here and the calcarene branch which runs within the calcarene fissure. Let us now have a quick look at the circle of Willis. The branches of the internal carotid and basilar arteries form an epistemotic circle on the surface of the brain known as the circle of Willis. It is formed by the terminal internal carotid arteries. The A1 segment of the ACA, ACOM, the PCOM, the P1 segment of the PCA and the basilar termination. We can see that in this eczine plane the circle of Willis has a stellate configuration within the supracellar system. Hypoplasia and aplasia of its component now it says Moon. Thank you.