 Hello everyone welcome to Indian Radiologist.com. I am Dr. Sanjeev Mani and this is part of the five part web series called Time is Brain. This is a basic tutorial for residents and students who are just entering radiology and is a precursor to the 19th MRI teaching course that is run by Dr. Deepak Patkar every year. This year however it is going online and the dates are very conveniently placed on Saturday and Sunday which is on 9th August as well as on the 15th and 16th of August. So we would like you to see the link in the bio and consider registering for this event. We would also like to thank Ognito the leading mobile speech software that has been part of the Indian Radiologist series of educational videos and especially being part of the Time is Brain series. If you find the content on this channel useful to you and for your education in radiology and generally in medicine consider subscribing to our YouTube channel or any of our social media. Most casualty officers make do with a CT head plane scan mainly to rule out subarachnoid hemorrhage. So CT still does have a role to play and what we are going to do today is a study and review of the anatomy of the brain on CT scan. So before we start seeing the anatomy let us understand the HU values of the structures in the brain. The HU goes from minus 1000 to plus 1000 in which minus 1000 to minus 100 is air like we have all around minus 100 to 0 is fat. We can see this as fat 0 to 10 is usually fluid. So CSF will be basically between 0 and 10. Then we have white matter and gray matter. So white matter is usually between 22 and 32 while gray matter is usually between 32 to 42. So this is usually the first picture that comes to us and what we need to start is from base to top and then go back down back and forth. You got to do this at least three four times until you are very sure of your findings whether normal or abnormal. So let's just get started. Let's see some basic imported structures that you must know when you are reporting CT scans. This is the foramen magnum, medulla, the right and the left vertebral artery. As we move up you can see the cerebellar tonsils. Further up the cerebellar hemispheres, the right and the left cerebellar hemisphere. This happens to be the fourth ventricle right here. This is the pons. The pons is connected to the cerebellum by the middle cerebellar peduncles. Right in front of the pons you see this dark area. So these are CSF spaces or cisterns. So the cistern in front of the pons is called the pre-pontine cistern. You can see a round structure there that happens to be the basilar artery. As we're moving further up you can see the fourth ventricle again the right and the left cerebellar hemispheres and now this is the midbrain. The midbrain has two peduncles, the right and the left cerebral peduncles and it has also the inferior as well as the superior colicular. You can see the temporal lobes have now come up. You can see the right temporal lobe and the left temporal lobe. We can see again a sliver of black which is CSF value. So this happens to be the temporal horn of the right and the left lateral ventricles. Further up you see a very important cistern. This is known as the supracella cistern or the star-shaped cistern. This cistern communicates with the silvan fisher on either side here on the right as well as on the left. Antirel it moves towards the inter hemispheric fisher and on either side over here it goes and communicates with the perimidzen catholic cistern. You can see the two cerebral peduncles that we saw here. So you see a little notch forming here and this happens to be the inter peduncular corsa. As we go up this is another vital area of the brain and the anatomy of which you must know. We can see gray matter out here all around. We can see white matter right here and we can see the deep gray matter structures right here. So like I told you earlier the white matter is between 22 and 32 HU. Gray matter usually falls between 32 and 42 HU value. The deep gray matter is made up of the coordinate nucleus right here. This is the thalamus. This happens to be the lentiform nucleus this triangular structure. The lentiform nucleus is made up of the globus pallidus as well as the putamen. Immediately lateral to that you see again a strip of black which happens to be the external capsule. So where is the internal capsule? Media to the lentiform nucleus. This is the lentiform nucleus and you can see the anterior limb of the internal capsule the genu which is the knee and the posterior limb of the internal capsule. These structures are the areas where infarcts and bleeds commonly occur in hypertensives and it's an area that you must know. We go back once again through this. This is the corded nucleus. This is the thalamus. This happens to be the anterior limb of the internal capsule the genu and the posterior limb of the internal capsule. The lentiform nucleus which is made up of the globus pallidus as well as the putamen. We have the external capsule out here. This is the salient fissure and just in front of the salient fissure is the insular cortex. As we go further up you can see it's much more clearly you can see the corded nucleus, the thalamus, anterior limb, genu and the posterior limb and the lentiform nucleus. Structures you see here are both the frontal horns of the left as well as the right lateral ventricles. Still further up we start seeing the fibers of the corona radiator right here and when the ventricles disappear this area is known as the centrum semi-ovil. Let's have a look at the ventricles. Now the ventricles basically contains CSF as we can see from the HU value of these structures and what we can see are these slightly iso-to-hyperdense areas inside the ventricles. These are the coroid plexus on either side. We can see the lateral ventricles right here. These happen to be the frontal horns of the lateral ventricles. These are the occipital horns of the lateral ventricles. Please understand that the occipital horn stretches right at the back and this is a good area to see small areas of intraventricular bleed. Coming back you can see from the frontal horns you can see these little slim channels on either side the foramen of one row. We have the right and the left foramen of one row that culminates into the third ventricle. This happens to be the third ventricle and as we move down you can see a little round structure there a little small channel this is the cerebral aqueduct that communicates and leads up to the fourth ventricle and as we go still further down we can see the foramen of Lushka on either side and the foramen of Magenty. In the anatomy of the brain I'd like to show you a couple of commonly seen artifacts that are seen almost on every scan. The first one is this you see a lot of beam hardening artifacts coming out of dental fillings as well as this one. What you can see right here is a hypodense area going right across the pons. In fact not allowing us to see the pons very clearly. This is nothing but beam hardening artifacts that are coming because of the dense features on. So now we're going to have a quick look at the cranial forse. So the cranial forse are as follows we have the anterior cranial forsa that accommodates the anterior part of the frontal lobes right here. We have the middle cranial forsa if we go a bit down back again and we can see the middle cranial forsa is right here on the right and the left and these accommodate the temporal lobes. We have the posterior cranial forsa right here that accommodates the cerebellum as well as the brainstem and of course we have the pituitary forsa that accommodates the pituitary gland. On this window we can also see sinuses so if we have a good look especially during trauma patients you end up catching a lot of hemosinus especially when there are cranial facial injuries. So we can see the maxillary sinuses right here as we go a little higher we can see the sphenoid sinuses, the ethmoid sinuses and then the frontal sinuses. Let's have a look at the tables of the brain. This is the inner table of the brain, this is the outer table of the brain and these are the diploid spaces right here. The importance of seeing the bone windows cannot be reiterated further than on this example. We have here a CT scan of a young patient and as we scroll through these images we see normal structure of the brain but as soon as we switch to a bone window like we do now you can see that the mastoids are sclerotic on either side with some element of auto mastoid it is noted. So it's always a good idea to look at the bone windows while completing your evaluation of the brain. Another important point to remember is to make it a habit to see the images in all planes that is do a reformatting in the coronal and the sagittal planes as we can see here in this case it is always useful in patients who have lesions that have extra cranial extension or intra-orbital extension or even midline shift. It gives you a better perspective and you can have a lot more additional findings that you can add in your report. A word about the managers. They are known as covering of the brain and they are actually thin layers of tissue found between the brain and the inner table of the skull. They are very slim normally and hence we cannot see them on CT very clearly however there are two areas of thickened foldings of the managers that are visible on CT imaging. One of them is the phak cerebrine so as we can see here this happens to be the phak cerebrine right here and the other one is the tentorium cerebellar. If we go down a bit and you can see this linear slightly bright structure which comes up to the pitris bone right here this happens to be the tentorium cerebellar. So these are thickened foldings of the managers that are visible on CT scan. So the tentorium cerebellar actually is an unfolding of the duramatter and forms a tent-like sheet which separates the cerebrum from the cerebellum which is seen in the posterior fossa. The brain surface is formed by folds of the cerebral cortex known as gyri. Between these gyri are seen furrows called salsae like these which contain CSF. We also have fissures so they're two important fissures that you should know one is the inter hemispheric fissure right here and as we go down a little bit again you can see the sylvan fissure right here on either side. Now look at the cisterns now the pre-pontine cistern right here. This is the midbrain we see the supracella cistern here. These are the perimidzen Catholic cisterns that hosts the P1 segment of the posterior cerebellar tree. This happens to be the quadrigermal plate system and as we move a little naturally this as well as this are the ambient cisterns. This we'll dip over here again is the inter peduncular fossa, arterial anatomy or the circulophilus. So we've picked up a CT scan of a patient in whom contrast has been given and we can see here the right as well as the left vertebral arteries. They come together usually there's a bit of variation in the vertebral arteries and they may be ecstatic in elderly patients or even patients who have hypertension. Now they've joined up here and they form the basilar artery. The basilar artery runs in the pre-pontine system in front of the pons and as it goes up you can see it's splitting right here so you can see the right PC here the right posterior cerebellar tree as well as the left posterior cerebellar tree. Both these arteries will curve around the perimidzen Catholic cistern and run posterior you can see it here on the right and you can see it here on the left. This constitutes the posterior circulation that supplies most of the brainstem cerebellum, a part of the temporal lobe as well as the posterior aspect of the telangus. Now we're looking at the anterior circulation which comprises of both the right as well as the left internal carotid artery. You see the internal carotid here it happens to be the segment above the clenoid so the supra-clenoid segment and you can see it's splitting into the MCA that runs in the sylvanes fissure right here and the ACA that runs towards the inter hemispheric fissure right here. We have to see this nicely on both sides so now we're coming to the left and we can see the ICA bifurcation right here the left MCA going running towards the sylvanes fissure as well as the left ACA which is running alongside the right ACA in the inter hemispheric fissure. Venous anatomy will start from the top you can see these small superficial cortical veins that drain towards the superior surgical sinus which is here in all the way down absolutely in the midline of the brain run the internal cerebral veins which are formed from the thalamus striate vein to join together from the vein of gallin that drains into the straight sinus. You can see the thalamus striate veins forming the internal cerebral veins and join together to form the vein of gallin eventually runs towards the straight sinus. You see on either side the transverse sinus the left as well as the right you see there's a very bright structure which runs towards the sigmoid sinus right there and then into the internal cerebral veins. I want to look at a few changes that we see in the brain. Not all brains are like and as we age the certain changes which come which are basically just variations and not that it's abnormal and this is of a 91 year old leading. As you can see the ventricles are distended and you can see the sulci very very prominent. The gyri still reach up to the edge but you can see the sulci much more prominent compared to the patient that we saw earlier. So this is nothing but a mind cortical circulatory that we see very commonly as one ages. Now many a time you will see certain structures that are calcified in the brain commonly being the vertebral arteries like the internal carotid artery, the globus pallidus right here you can see bilateral calcification, the pineal gland that lies posterior to the third ventricle, the choroid plexus in the lateral ventricles as well as sometimes in the fourth ventricle and the pharx. You can see the pharx calcified out here. Now on this tutorial we are not going to go into the various types of in pharx and the appearances that we see that will be taken by Dr. Patkar in the lecture on stroke but suffice to say that this is one important sign you need to look for that is the hyper dense MCA sign and this is a sign of an hyper acute in fact and ranging from the hyper acute in fact to the acute to the sub acute and you get the chronic in pharx where the brain becomes N-cafillomalaceic and you can see X vacuodilitation of the lateral ventricle due to the atrophy of the brain.