this talk is intended to serve as a good introduction to CT head if you're a new radiology resident you must understand the basic concepts presented here so that you have a strong base to build on moving forwards if you're a generalist whether you be an emergency medicine internal medicine or whatever this will give you more than enough to start looking at CT heads right away will also give you more than enough to be way ahead of your peers and we know how important that is to internal medicine residents either way the focus of this talk is the basics but there will be pearls and some subtlety here which is going to become must know for future radiologists before we get started I strongly suggest that you watch the first talk in this series called a practical introduction to CT many concepts introduced in this talk will build on a basic understanding of what was discussed in the previous talk in more detail to start off we will briefly review some key concepts discuss some basic relevant anatomy and then we're going to get right into it by introducing you to a conceptual approach to CT scan we will then introduce some basic key concepts really just what you need to know to start looking at CT scans right away and efficiently next we will discuss windowing windowing is of utmost importance when looking at CT heads it's very easy to miss key findings if you don't window appropriately after that we will learn by repetition we will go through multiple cases with our approach and directly apply the things that we just learned for those that are interested the last five minutes or so will involve a demonstration of a more complete approach including blind spots this is mainly for those going into radiology quick review again I can't emphasize how important it is to know the basic radiographic densities and know some ballpark figures the hounds per unit scale is a measure of density from negative a thousand the least dense to beyond positive a thousand the most dense structures by convention zero is water and negative a thousand is air everything else is calculated based that cortical bone and metal are very dense structures near positive a thousand soft tissues are above zero will simplify and use a ballpark figure of positive 50 for now and fat is less dense than water we'll give a ballpark number to remember of negative 100 now let's focus on the main densities that we're going to deal with in the brain in the skull we have the brain itself sitting in a pool of CSF the brain is made up of mainly gray matter and white matter in the simplest terms the grey matter is the thinking part of the brain found mainly in the cortex or outer part of the brain and some deep gray matter structures gray matter consists of mostly neuronal cell bodies white matter is made up of mainly myelinated axon tracts the normal densities of these structures is important CSF is low density it's mainly water it measures around 15 hounds per units white matter measures approximately 25 pounds per units gray matter measures approximately 40 pounds per units knowing these actual numbers is not really that important instead understand the basic principle here CSF is near water density gray matter is slightly more dense than white matter a simple way to remember the relationship between gray and white matter is that white matter is mainly made up of myelinated tracts myelin is a fatty substance and fatty things have a lower density lastly we'll introduce acutely clotted blood which measures about positive eighty Hounds per units the principle to remember here is that acutely clotted blood is more dense than the rest of the brain the last thing to take away from this slide is that all of the densities we're looking at here are in a tiny range of densities and that's why windowing is so important when we look at CT scans of the brain I'll tell you right away there is a lot of anatomy that one can learn in the brain and how much you should know depends on your goal this introduction to basic anatomy is not meant to be comprehensive but it is more than enough to get you started you may know most of this already and can treat this is a review but if you don't you can watch this portion over again to learn the basics if you're going into radiology you're going to need to know way way way more anatomy than this I strongly suggest subscribing to e Anatomy also known as ima iOS you can take your time learning the cross-sectional and anatomy in detail so here is a normal CT scan of the head this is the right side of the patient here this is the left side of the patient this is the anterior portion this is the patient's forehead and this is the posterior portion of the head we've marked some of the major densities that we've discussed already this here is CSF it's the ventricles filled with CSF the average density here comes out to be about five pounds four units we said it's about water this is a white matter marked here the average density in that selected area is about 27 pounds four units and the gray matter is selected here with an average house for unit number of around 39 house per units again the numbers aren't so important but CSF is near water density and the grey matter is slightly more dense than the white matter okay let's move on to basic anatomy don't get bogged down with memorizing any specific names for now just listen and take in whatever is relevant to your current level in the midline here we have the Fox this is an imagination of Dura that separates the two hemispheres as we scroll down it's continuous with the tentorium which we can follow down here sanitorium looks like a tent everything above the tentorium is considered super tutorial brain and everything inferior is considered in for tutorial the superinten toriel brain is separated into lobes which many of you guys know the frontal lobes here the parietal lobes back here the occipital lobes back here and the temporal lobes over here the specific divisions between the lobes is beyond the scope here but I do want to touch on a couple first these here are the Sylvian fissure z' so in fissures operate the temporal lobe below from the frontal and parietal lobes above second this here is the central sulcus the central sulcus separates the frontal lobe anteriorly from the parietal lobe posteriorly in front of the central sulcus we have the precentral gyrus which is where motor control sits and posterior to the central sulcus we have the post central gyrus which is mainly sensory control there are a couple ways to look for the central sulcus actually there are many ways to look for it I'll only talk about a couple very quickly you're looking for this reverse omega sign it looks like Omega flipped upside down when you look for that this little bulb of tissue here is the motor control area of the hand or more specifically the thumb second way to find the central sulcus or another way to find the central sulcus that's practical is looking for this in the midline just in fearly call it mustache sign it kind of looks like a mustache these are the marginal sauce-i if i scroll up the sulcus anteriorly to that is going to be the central sulcus and it is here as well if you aren't going into radiology don't worry too much about these details just know the basic lobes for now the gray matter structures you're going to need to know are as follows I windowed it differently so that they pop a little bit more firstly within each of the lobes there is cortex or the outer portion is made up of mainly gray matter for example this here in the frontal lobe is all part of the frontal cortex this is a grey matter structure then you're going to need to know the deep gray matter structures as well and this slice right here is going to be very important I want you to burn it into your brains okay these are the deep gray matter structures that you're going to look for when you're looking for stroke on any CT head this here is the caudate or the head of the caudate this is the putamen and the Globus pallidus which is a little bit more inconspicuous here this here is the thalamus there are a few white matter structures you're going to also want to on this same slice this here is the internal capsule this is the external capsule over here as I scroll up this here is the corona radiata and this as I scroll up is the centrum Semyon Valley just above the ventricles the cerebellum is inferred tutorial or below the tent here for now just know that in the midline we have the vermis and we have the the right and left cerebellum here is the cerebellar tonsils inferior lis notice the normal location on a normal scan this here in the midline where my mouse is is the brainstem the brainstem is separated from most superiorly to inferiorly into the midbrain the pons and the medulla ok the way is the easy way to recognize these are by recognizing their shape so the midbrain is commonly referred to as a Mickey Mouse head with these being the Mickey Mouse ears over here the Mickey Mouse ears represent the cerebral peduncles okay as I scroll down this is the pons the easy way to recognize the pons is people refer to it looking like Darth Vader more inferior Lee we have the medulla and then the spinal cord this here is frame and magnum notice that there are CSF surrounding the spinal cord here and that the cerebellar tonsils don't crowd this area on a normal CT scan that'll be key next the CSF spaces are very very high yield first the ventricular system most basically these here are the lateral ventricles this is the third ventricle here sit like in the midline this is the fourth ventricle here behind the pons the basic CSF flow is as follows CSF is made by choroid plexus we'll talk about that a little bit more later CSF flows from the lateral ventricles to the third ventricle through the foramen of Monro can visualize right here the third ventricle CSF flows through this spot here which is called the cerebral aqueduct and into the fourth ventricle okay from the fourth ventricle there's communication with the subarachnoid space through the framing of Luca bilaterally and the foramen of Magendie don't worry about all the names for now just understand the principle of the flow of CSF any blockage of flow of CSF within the system is going to cause dilatation to the ventricular system approximately for example blockage of the aqueduct here is going to cause delectation of the third ventricle and the lateral ventricles next we talk about the basal cisterns these are just the CSF pools that sit at the bottom of the brain these pools are assigned names that are important to know I won't discuss all of them but just the most high-yield ones for now in front of the pons here there's the pre pontine cistern if I scroll up you guys will know that this is where the pituitary sits is the pituitary fossa / sella turcica as I scroll up we have this cistern here which is known as a super cellar cistern this is a very important cistern to keep in your minds it's that famous star-shaped cistern we already described this structure here as the midbrain these are the cerebral peduncles here this is the interpretative fossa on the sides of the midbrain here are the ambient cisterns and posteriorly we have the quadrigemina cistern lastly we talked about the vascular structures you can see on plane CT head you often look here for signs of acute clot we already said that acute clot is going to look bright because it is more dense than the other structures in the brain so very dense vessel might signify an acute thrombus first we discuss the arterial structures start with the anterior circulation for now no the internal carotid arteries can be seen beneath the skull base they pass into the skull eventually they split into the MCA and the ACA this is the MCA or the middle cerebral artery you're going to look here for a cute clot and stroke the MCA splits into uh branches that run in the Sylvian fissure so you can also look here for signs of acute clot or a cue clot in the more distal MCA branches you can also follow the distribution of the ACA it might be hard to see on plain CT head but they should run in this region here and then up here you're going to look for areas of clot there too but that's more advanced lastly these are the vertebral arteries here this is the Basra ER here it separates here the pca arteries again these might be hard to see especially when you're not using thin slices you're actually interrogating vascular structures you're going to do a CTA anyways but plane CT head it's important to know where to look for acute hyper dense vessel sign for a stroke and we'll talk about that more later blood drains from the brain parenchyma into veins and that eventually gets into the venous sinuses the basic venous sinuses that you're going to look at on CT headers follows this here is a superior sagittal sinus okay superior sagittal sinus separates down here into the transverse sinuses and the transverse sinuses become the sigmoid sinus is here and eventually the jugular vein beneath the skull base again acute clot within these sinuses is going to show up as bright clot in the venous sinus is known as venous sinus thrombosis it can cause Venus in furs are gonna look for an extra bright sinus so I know that was a lot of information especially if this is new for you if you're not going into radiology this is more than enough for now watch this as many times as you need to don't bog yourself down with too many names if you keep looking at CT scans you're going to pick up things as you go along you can also go to head neck brain spine comm where you can practice scrolling through images and identifying basic anatomy when you first start the best way to approach a CT head is by thinking of things conceptually based on the things that you never want to miss those are radiology do this too but the list of things gets much longer for now let's keep this list shorter and more practical first take a couple Scrolls through the head and look for anything big you're going to get better at identifying things as you move forward but you need to do more than just this foremost emerge physicians I've seen this is the end of their approach they look for anything big on a couple of Scrolls and call it day that can be dangerous especially if you're in the community and won't get a read on the CT scan until the next day once you've taken a few scrolls through the head to look for anything big you need to specifically look for signs of Mass Effect and herniation I put this first because this is the thing that beginners forget to look for and most commonly miss it's easy to miss subtle herniation you don't look for it then you specifically look for blood then specifically look for signs of stroke and then you're going to look at soft tissues and bones but for now especially for generalists focusing on remember the start points look for mass and Mass Effect slash herniation rule out a bleed and rule out a stroke there's some basic material that you're going to need to understand first about bleed stroke and mass effect in order to look for these adequately let's start with bleeds we mentioned that acutely clotted blood is denser than everything else in the brain so cuteee bleeds will look bright so when you're trying to reload a cube bleed you're looking for things that are bright I'm sure most of you guys know this but the major basic types of bleeds are as follows an epidural hematoma which is a biconvex or lenticular shape because it looks like a lens and it doesn't cross the suture lines a subdural hematoma over here it's Crescent Eric and it crosses sutures but generally not the mid like subarachnoid hemorrhage here is high density material in the subarachnoid space this is blood on a super cellar cistern looks like a star which we talked about earlier you have an intracerebral hemorrhage which is blood in the actual paren comma itself let's take this one step further there are two more concepts that are crucial to understand about the density of blood products firstly as we mentioned acute clotted blood is high density it's about positive eighty hotspur units so it's going to show up as bright as the blood progresses over time to sub acute and then chronic the density decreases over time in the sub acute phase at some point the density is going to be similar to the brain parenchyma so it can be difficult to see sub acute subdural sometimes but looking for Mass Effect is going to help you with that we'll talk about that later this here is an acute subdural notice the blood is brighter than the paren coma in this image this is a sub acute subdural notice the density is lower but it's not quite CSF density eventually a chronic subdural will approach the SF density like this one over here the second concept to understand is the density of hyper acute blood we know that acute clotted blood is dense but before it has a chance to clot it's going to have a lower density this is an example of a patient with an epidural hematoma it is mainly high density as you can see here the areas of high density represent acute clotted blood but there are also areas of lower density within like here and here and here these areas represent hyper acute blood that is not yet clotted some people refer to this appearance here as a swirl sign but the name of the sign doesn't matter so much do you understand the basic principle that the areas of low density here represent hyper acute or ongoing bleeding you'll be fine if we apply this further here we have a picture of a subdural hematoma along the that is mainly low density but also high density inferiorly this is a mixed density subdural haematoma this is the classic appearance of an acute on chronic subdural haematoma this is the acute component here and the rest of it was the chronic component however what we just learned this could also be a cute blood that for some reason hasn't completely clotted so it won't be completely bright the inferior part is the part of the blood that was able to clot and the superior part is the not yet clotted blood if a patient is on a blood thinner for example you can get this appearance and acute trauma keep this in mind as an alternative explanation for this appearance very quickly you should just be aware that not everything that's bright in the brain is blood a lot of structures commonly calcify normally and you shouldn't call them bleeds when you see them firstly choroid plexus is often calcified cord prep plexus as we mentioned produces CSF it is found mainly in the ventricular system here it's in the lateral ventricles in a sulcus adjacent to the thalamus it is not found in the frontal horns or the occipital horn of the lateral ventricles in the fourth ventricle sometimes you can see it sticking out of the frame of Luschka bilaterally and you shouldn't be alarmed when you see that secondly the pineal gland in the midline which is calcified here very commonly calcified thirdly the Globus pallidus is very commonly calcified and is calcified bilaterally here again this is not blood and lastly I'll mention one more which is not as common but the dentate nucleus in the cerebellum here something bilateral here it's mainly unilateral so we can't be 100% sure whether this is calcification or hemorrhage given its appearance and unilateral T you might have also heard the term pseudo subarachnoid hemorrhage which occurs when the entire brain is a diminished dark and the vessels in the sulci appear bright and can be mistaken blood again you don't need to worry about the details for now just understand the Cybil not everything that looks bright in the brain is going to be blood these are some common fake outz okay let's move on to ischemic strokes for now there are three major things that you need to understand and remember about ischemic strokes on plane CT head the first two are signs of acute stroke the first thing to look for is the hyper dense vessel sign as we know acute clot is bright on CT ischemic stroke is caused by acute thrombus including a vessel so the earliest sign of acute stroke on plane CT is actually visualizing that acute thrombus this is the case of a hyper dense vessel in a right MCA branch we will talk about where to look for hyper dense vessels when we go through our approach later but for now understand the basic principle the second main thing to look for is loss of gray white differentiation as we have mentioned many times the gray matter is slightly more dense than the white matter in acute ischemic stroke the cells in the gray matter distal to the occlusion are deprived of blood supply as a result they can't function they can't make ATP and their sodium potassium ATPase stops working as a result the cells themselves swell up what we call cytotoxic edema in other words their water content increases we know water is less dense so the density of the gray matter in the area is going to go down and look similar to the white matter you couldn't follow the physiology all you have to know is this when the cells are deprived of blood supply the cells themselves swell up and as a result look less dense and you lose the gray white differentiation it can be extremely subtle early on and then look more obvious later this is the same patient corresponding to the vessel clot we just saw there is an area here with subtle blurring of the gray white differentiation compared to the other side notice how crisp the gray white differentiation is here and it also is anteriorly on the right as well but in this area here you've lost the gray white differentiation this is a subtle case the third concept to know about ischemic stroke is the evolution of stroke over time and it's very important to know competently calling a stroke old versus something acute or subacute obviously has clinical implications in the simplest terms in general the infarcted tissue decreases in density over time so here we have an example of an acute stroke in the left MCA territory notice the blurring of the gray white differentiation on the left and compared to the other side which is very crisp this here is the insular ribbon and notice how it's lost here as well so that's an acute stroke as we said in general the infarcted tissue decreases in density over time so here two days later the infarcted tissue has in fact decreased in density over time the second thing to know is that the Mass Effect is worst at around 3 to 5 days post infarct and then decreases thereafter this is the same patient on day 5 you can see how much worse the Mass Effect is got lastly old strokes will eventually have negative mass effect often seen as dilatation of the ventricle close by is called X vacuole dilatation here's different patient with a left old MCA in fart notice the density here is near CSF and there is negative Mass Effect there is X vacuole dilatation of the left lateral ventricle now I covered this superficially so you can understand the basics I suggest further reading or watching the radio PDF is on evolution of stroke if you want to understand this in greater detail but this is more than enough for now so we've talked about bleeds and strokes the third big thing that I want to stress in this talk is looking for Mass Effect and brain herniation the reason I stress this is firstly because seeing Mass Effect can help you find more subtle pathology like a tumor on non-contrast CT or a sub acute subdural and even more importantly it may be a critical finding that requires neurosurgical intervention ASAP in my opinion forgetting to specifically look for mass effect is the most common mistake that beginners make and it can have massive consequences we can't go through it all but here are the basic concepts one look for Sokolov Faceman when you scroll through an image first you should be looking at the salsa and notice when they are faced like they are here in this case we know that there's going to be something on the left side that's exerting mass effect to cause this Dunkel of Faceman t' secondly look for midline shift this is a case of sub acute stroke that we just showed that demonstrates severe swelling in the left brain tissue we measure the midline shift by drawing a line from the attachments of the fox anteriorly and posteriorly and then measure the distance from that line to a midline structure most commonly we use a septum pellucidum the third thing we look for is evidence of other brain herniation this is an extremely important slide again if I get one thing across in this lecture it is this specifically looking for herniation syndrome is on every CT is unbelievably important I'll repeat myself in my opinion is the single most clinically significant thing that is missed or overlooked by beginners significant herniation can be easy to miss if you don't specifically look for it and it's something that may require immediate intervention the most basic herniation syndromes are as follows the first is sub foul scene herniation called sub falestine because it refers to displacement of brain underneath the free edge of the fox here in simplest terms when you have midline shift you're going to probably have a little bit of sub tossing herniation as we do in this case here the second place you're going to look for for herniation is the super cellar cistern so we know this is super cellar cistern here and this here is the uncus on the left as you can see there's displacement of the uncas slightly towards the contralateral side or towards the right the group of more severe herniation here are called DC trans tutorial herniation named because it refers to supratentorial structures descending through the tenth or trans 10th or early this is another case if you have bilateral uncle herniation you can get complete effacement of the super cellar sister again if you don't specifically look at the super cellar system for signs of uncle herniation you might scroll right by this it's harder to see something that's not there rather than something that is this is another case here we talked about tonsil herniation this can be subtle and is probably the most often missed on axial slices tonsil herniation refers to the downward herniation of the tonsils through foramen magnum on every scan you need to look at Freeman magnum which is right here to make sure that it's not crowded if there is even a question you need to get sagittal reform asked to assess further this patient has tonsil herniation and requires urgent decompression of the posterior fossa I've only mentioned the three most common and important herniation syndromes but there are more to know for example a sending trans tutorial' herniation occurs when there is mass effect causing in 4/10 toriel brain to herniate upwards through the 10th as in this example here notice that the quadrigemina cistern here that should sit behind the midbrain is completely a face as a result other herniation syndromes include trans calvarial which is through the calvarium and trans a lar which is herniation across the sphenoid Ridge if that demonstration was too much detail for you for now take away only these three some fala seen uncle or descending trans central herniation and tonsil herniation the next step mainly if you're going to go into radiology is to know the complications of these herniation syndromes which you should specifically look for I'll list them here quickly but won't belabor the point if you're going into radiology you need to know these cold so learn them the rad primer slash that DX article is a good reference it's actually not that difficult to remember these complications if you learn the anatomy for sub thousand herniation the foramen of Monro that drain each of the lateral ventricle sits right there the brain gets pushed over the contralateral foramen of Monro gets compressed and you get you to lateral hydrocephalus the anterior cerebral arteries or ACA is also run here with severe sub bouncing herniation these can be compressed against the Fox and you can get a CA in farms for descending transom toriel herniation think anatomically to figure out what's going to be compressed the third nerve runs here so you can get third cranial nerve palsy which causes a blown pupil the cerebral peduncles of the midbrain or ears of the Mickey Mouse right here as well compressing the ipsilateral cerebral peduncle would cause contralateral weakness if you remember your basic neurological pathways however the contralateral cerebral peduncles can also be pushed against the tentorium on the other side so you can often get its lateral weakness referred to as the false localizing sign or Curnow hands notch other complications of descending trans tutorial' herniation include hemorrhage in the midbrain known as direct hemorrhages or DeRay hemorrhages and PCA infarct the posterior cerebral arteries run here as well for tonsil herniation you can get obstruction of the fourth ventricle which causes dilatation of the other ventricles also known as hydrocephalus tonsillar herniation can also push in the brainstem where you have structures that are important for respiratory and cardiac control and this can cause respiratory or cardiac failure aka death okay so take a deep breath pause if you need to but that's it for the real hard content that we're going to cover here the rest of the talk focuses on practical knowledge that you're going to need to know to look at cts and then some examples of cases as I mentioned before for non radiologists the best way to approach is CT is by thinking of things conceptually based on the things you absolutely never want to miss we already went through this once before but let's go through it quickly again first take a couple Scrolls through the head and look for anything big then you need dedicated searches to allow big pathologies the first thing you should look for is any big mass or mass effect and I put this first again because it's easy to forget to look for this and the consequences can be huge then we do run specifically to look for bleeds and then for signs of stroke that we discussed looking at the soft tissues and the bones are also important but findings can be more subtle you're not going into radiology focus on the start pathologies in order to search for these management changing findings adequately it's critical that you understand windowing if you don't window it's very easy to miss things the basic concept of windowing is discussed in the first video in short our eyes can only detect a finite number of shades of gray if we were to distribute all these shades are grayed across the entire scale of densities that we might see for example from air and negative a thousand two very dense structures at paws of a thousand like this most of the tissues that we're interrogating in the brain in this region here will look like one or two shades of grey so we're looking for blood or a stroking like that we're not able to see it the principle of windowing is playing around with this distribution of shades of gray so that we can actually see with our eyes clinically important density differences there are two numbers that define any window the window width which is 2,000 here and the window level which is where the window is centered here it is zero when we open a CT head the default is a basic brain window this allows us to look at the anatomy evaluate for any large masses Mass Effect see if there's anything in the CSF etc this is the default window and many abnormalities will present themselves on this basic brain window but they can often be relatively subtle or even impossible to see on brain window is a relatively narrow window with a width of 70 and a senator centered at about 30 near the main structures that were evaluated here the CSF the white matter and the gray matter all are represented by different shades of gray within this range anything above positive 65 pounds four units will be completely white anything below negative five pounds finners will be completely black so you had acute clotted blood which is around positive eighty it's going to look bare right almost completely white and it's going to stick out like a sore thumb what if you have acute subdural haematoma later along the bone the blood as we can see here will be completely white and the bones surrounding it will also be completely white despite such a huge difference in density both are represented by white and it's difficult to tell them apart it's going to be super difficult to know if there's any blood layering along the skull so how do we solve this we use a blood window here the width is 180 and the level is 80 centred at where we expect clot of blood to be that way clotted blood appears grayish and bone appears completely white leaving no question whether or not a subtle subdural is present so let's look at the brain window again as we discussed when looking for stroke a key finding indicative of stroke is the loss of gray white differentiation so in evaluating for stroke we really have to compare the densities with our eyes of the gray matter and the white matter if we do that on this window the gray matter and the white matter are represented by different shades of gray but if you looked at CT before you know that gray white differentiation can be hard to evaluate well on basic brain window let's introduce the stroke window by narrowing the window here the difference between the gray matter and the white matter is accentuated making it way easier to compare the gray matter and white matter to look for signs of stroke the gray matter is represented by a shade of gray that's more bright and the white matter is represented by a shade of gray that's darker again when we use different windows we're looking at the same density information windowing is the principle of playing around with the distribution of shades of gray to help us see pathologies better then we use our soft tissue window to look at the orbits and other soft tissues a more detailed approach for radiologists will be included at the end of this talk and then we look at the bone window to look for fractures again this will be discussed more on the detailed portion of the talk at the end let's go through a CT scan and demonstrate our conceptual approach that we just learned and then we will practice our simplified conceptual approach on a few illustrative cases okay so I stress this is a conceptual approach it's very simplified if you're going into radiology your approaches gonna be more detailed and we'll talk about that approach in a few minutes at the end of the talk so conceptual approach take a couple Scrolls through the brain look for anything big as you look at more you're going to notice more okay there's nothing big here next my first of three star pathologies is looking for our Mass Effect so you take your first few Scrolls down looking at the sole side bilaterally and comparing them you're looking for any circle effacement and there is no significant Sauckel basement here as I scroll more inferiorly you're going to look for any midline shift or sub bouncing herniation look at the super cellar cistern look for any signs of uncle herniation this is the uncas here then go down to the friend magnum and look for signs of crowding here to suggest tonsil herniation you have any question gets a jewelry format next you'll assess for bleed so starting starting again at frame and magnum you want to scroll up and you're looking at all the CSF spaces so all the basal cisterns we talked about putting pre pontine supra cellar etc then you want to look at all the salsa up here for any hyper densities in there to suggest believe and there's none here as well blind spots for blood are more subtle and often dependent in the often in the dependent portions the brain such as the interpret ocular fossa right here you can often see very subtle hemorrhage there and trauma in the Sylvian fissure is here in the most dependent portion you can often see every density there representing subtle blood and also in the occipital horns of the lateral ventricles you can see in two particular blood then we look for signs of extracts you'll hemorrhage so when we scroll up we're looking at the anterior portion here to look for any extra axial blood we can come back down and look at the lateral side here on the left then go back up on the right and then look posteriorly and again we're looking for extra axial but as we mentioned because the bone is bright and acute blood is going to be bright as well it can be very easy to miss blood layering on the bone so we need to put on our blood window we do the same thing so look anteriorly first for any extra axial blood laterally on the right laterally on the left and then posteriorly and there's no extra axial blood here then you assess for stroke first start by looking for hybrid and vessel so I start in my simplified conceptual approach by looking at the M ones bilaterally and I'm looking at a Sylvian fissure for any hyper dense vessel there and looking at the basilar artery for a bright basilar suggesting clock there then I look for great white differentiation so put on the stroke window and then I sit back far off my computer or I just split it into four here so you can see the great white differentiation better so in a simplified approach you can just take a couple scroll through and look in the ACA territory here the great differentiation and the MCA territories here bilaterally and then most importantly we look at the instance for signs of early stroke the putamen the caudate and the phthalimide a more detailed approach you look for PCA strokes well because cerebellum the brainstem but that's beyond this right now then you look at the bones for any fractures or any bone lesions we'll talk about that more in a bit and look at the soft tissues and to include the orbits etc and again that's more in the detailed approach okay now let's practice our approach we're going to review the concepts that we learned today in these cases this is the first case let's say you're in the emergency department you get a CT head or a confused patient and you open it up you scroll down here quickly take a couple scrolls I don't really see much okay oftentimes if you were just to leave it alone you might miss some big things okay let's go through our conceptual Pro we took a few Scrolls now let's look for big Mass Effect so all set look okay there's no midline shift there's no uncle herniation the super stellar systems patent there's no tonsil herniation here okay I don't see any hyperdensity in the sauce I'm looking specifically for bleeds and certain locations as well and your bronchial foss okay I don't see any hyper density and a sauce I so I don't see any blood here guys make sure I remember to put on blood window put on blood window here you're looking for any extracts so hemorrhage along the right side here I don't see anything and tearily over here I don't see anything laterally here I don't see anything posteriorly here I don't see anything so there's no big bleed at least let's move on to look for a stroke to put our brain window look at the EM ones I don't see anything look at the end choose some questionable things over here but nothing that's definite look at the buzzer already looks okay don't really see any hyper dense vessels I don't look for more subtle signs of stroke I'm looking for loss of great white differentiation so change the window to stroke window split it into four so it's easier to see and I scroll down from the top okay it all looks preserved here it could be ACA territory first it's great look at the MC chair on the left it's very crisp great white differentiation notice how crisp and how bright the gray matter is compared to the white matter and look along the right side here and I notice this kind of looks a little bit blurred we've actually seen this case before so I'm concerned that this area has lost grammar differentiation and this is a sign of an acute stroke so again very easy to miss if I don't go through and know how to window appropriately and even subtle when I went and I want to do a new appropriately so even with our quick conceptual approach we caught this it also demonstrates the point that the hypertense vessel can often be very subtle so you don't really see it here on the thick slices but when you put it on thin slices this is again a non-contrast but in thin slices and we look at the m2 branches in this area here you actually see evidence vessel here compare this we kind of thought this is a hyper dense vessel that was not well appreciated thick slices so sometimes you can put the thin slices look for it but again this is a subtle case the point here is not a pathology but the fact that they go through our quick conceptual approach we can catch things that are more subtle and we won't miss important pathology ok case to this patient comes in with a bad headache and some neurologic symptoms you take a couple Scrolls through so first scroll through you're just looking pretty big and wow there's a big hemorrhage here centered in the right basal ganglia and you still want to go through your full approach we won't do it here for time sake but in this case this is a classic hypertensive hemorrhage now other things can cause blood in this area but this patient was hypertensive and we did vascular imaging to make sure there's no vascular malformation the most common location for a hypertensive hemorrhage is right here this is the third case this is a patient who fell and we want to rule out a bleed so again a couple scrolls through don't really see much on the first scroll through let's go back don't see much case rolling down looking for subtle signs of mass effect no software Faceman here no significant midline shift slash sub boston herniation super sheller cistern is patent no tonsil herniation now looking for blood looking for some regular blood person looking the basal cisterns pre pontine supercell ER into production the ambience in quadrant NOLs look at the Sylvian fissure is bilaterally dependently looking at the ventricles looking at the dependent ventricles look at all the salsa up here to see if there's any signs of it signs of blood and there's not and I look for extracts your blood so I look anteriorly first I don't see anything here look laterally here entry see anything laterally don't really see much posteriorly don't really see much there's really no blood on this window but remember to put on your blood windows so for my blood windows and again I look for extract so hemorrhage so I look anteriorly on the right here laterally again nothing on the left here laterally and look there's a decently sized subdural hemorrhage right here that was nearly impossible to see on normal brain windows but because we windowed it it sticks out so again very important to know how to window so you don't miss this it can be bigger and still blending in with the bone if you just use a normal brain window so this really reinforces the concept of the purpose of looking at blood windows okay then we look at signs of strokes we look for look at the M one's in the M choose front a hyper dense vessel sign look at the basilar artery and then look for lots of great white differentiation on the stroke windows and all the vascular territories again a CA MCA is included deep grand mater structures PCAs cerebellum okay case for this is a trauma first take a couple scroll through it look for anything big and then take our dedicated runs our first run again is Mass Effect as I scrolled down I noticed the salsa a little bit tight bilaterally there's no significant midline shift I look for the super cellar cistern and I can't really see it the reason is because this brain is a demo dis a few sullen face mint and obliteration of the super seller sister as I scroll more inferiorly still looking for mass effect and there is fullness at the Furman Magnum suggesting tonsillar herniation as a bonus point here there's also a sending transitory herniation the imprint tutorial brain is herniating superiorly through the tenth and causing a face mint of the quadrigemina cistern here next step I look for bleed and there is scattered blood on in this brain most importantly the posterior fossa it's kind of difficult to see on this window but if I use blood window you can see blood layering posteriorly in the posterior cranial fossa here this was causing the Mass Effect that is causing constant herniation and this patient needs urgent decompression I finish off my approach by going through to look for signs of stroke but there was nothing on this case and to save time we'll skip that for now okay so this is the end of the introductory CT head talk after the slide I will demonstrate a more complete approach to CT head on a more subtle case you can listen to this if you wish but the focus of this talk which is a more conceptual approach for non radiologists is complete so take-home points know your basic concepts of stroke bleed and mass effect they were introduced here know them well and always look for those three things on CT head number to understand the basic densities you don't need to know the numbers just know that CSF is basically water grey matter is slightly denser than white matter clotted blood is denser than everything else in the brain do you understand the densities of the different ages of blood it can really help you interpret scans accurately three use the conceptual approach if you're working in the ER especially in the community looking at the brain a few times isn't enough make it a point to go look for the big things that we just discussed start with Mass Effect look for the salk LaFace mint look at the super cellar sister and look for midline shift and look for tall slow herniation look for blood specifically specifically using blood window and then use a stroke window to rule strokes lastly window appropriately understand how to window appropriately on your pack system so you can go through your conceptual approach relatively quickly well at the same time making it more likely that you won't miss pathology that is going to change management we gave a couple good examples of situations where windowing well helped us identify the pathology accurately if you're going to go into radiology or you're already a radiology resident it's very important to have a good detailed approach that looks at everything this can serve as a good example and you can modify it as you get more practice and see what you prefer but this is a good starting point okay for the future radiology residents and the radiology residents out there let's go through a more complete approach that's a little bit more detailed and looking for more subtle findings this is a subtle case this is a patient who came in with a trauma okay so again similar principles to what we talked about in our conceptual approach we'll start by looking for anything big take one scroll down one scroll up don't see anything big next we're going to look for signs of Mass Effect's we look at the sole side bilaterally you look okay no significant midline shift superstellar cisterns patent with no uncle herniation and no tonsillar herniation then we're going to look for signs of bleed and we start by looking at all the CSF spaces again but in more detail we scroll up here looking at all the basal cisterns including the pre pontine cistern the super cellar cistern the ambient cisterns and the quadrigemina cisterns are all paitent there's no hyper density within them we scroll superiorly and look at the ventricles bilaterally looking for hydrocephalus or signs of hemorrhage as well and specifically we're looking at the in the most dependent portions of the ventricles for more subtle signs of hemorrhage in the lateral ventricles we don't see any looking at the third ventricle the aqueduct and then the fourth ventricle here okay then we're going to take a scroll through to look at the sulci specifically again for subtle locations of blood like the posterior portion of the Sylvian fissure is here and any subtle blood in the salsa more superiorly and we don't see any hemorrhage then we're going to look for extra axial blood you can do it on brane window first a blind spot for extra extra blood is also along the falx and along the tentorium here so always look at the tentorium the falx for extra actual blood as well always have to remember to look at the blood window so here we look anteriorly first and we don't see anything posteriorly next we don't see anything we look around along the right side here there's no extract still blood call them blind spot is just anterior to the temporal lobes here for extra axial blood similarly on the left look in the same location as well as along the left side of the skull here and we don't see anything so there's no signs of extracts your blood the next thing we look for signs of stroke and a more detailed approach involves looking at all the vasculature that we can see so starting posteriorly looking at the vertebral arteries scrolling up looking at the buzzer arteries looking at the PCAs we see the branch off looking at the m1 branches bilaterally looking at the m2 branches here in the Sylvian fissure bilaterally and looking at where we expect the ACA s to be we can kind of see them there as well there's no hyper dense vessel sign as well so now that we've looked at all their intracranial arterial vessels we can look at the venous sinuses venous thrombosis can cause a venous infarct so we want to look for hyper density in the superior sagittal sinus and the transverse sinus is bilaterally follow them down to the sigmoid sinuses and the jugular veins as well and then we look for signs of great white differentiation so we put on stroke window zoom out and again look at the same location so the ACA territory the mca territories bilaterally in the cortex all the way up to the top and then looking at the deep gray matter structures to putamen caudate the Falla my looking at the insular ribbon bilaterally never forget to look at the pca territory here it's a very commonly missed location for loss of great white differentiation and then the cerebellum as well lastly look at the brainstem be aware that there is a lot of artifact going through here as a result of this as a result of the skull base we can catch subtle strokes if you look here every time then I look at these soft tissues so I'm looking at the soft tissues I start superiorly and look along the anterior portion of the soft tissues here looking for any signs of trauma or any lesions and look laterally here posteriorly looking for any lymph nodes back here as well and then laterally as well on the left I don't see anything next I look at the orbits always look at the orbits slowly look through each of them compare them for symmetry as well I look at the retrobulbar fat look for any haziness or hemorrhage behind the globe look for any air behind the globe look at the globe itself is the lens I look at the optic nerves bilaterally and compare them and the extra extra ocular muscles to see if they're thickened and the last thing I look for is the superior ophthalmic veins I compare them bilaterally and look to see if they're dilated they can be dilated in cases of carotid cavernous fistula or cavernous sinus thrombosis then scroll inferiorly and there are five pairs of fat that you always want to look at at the skull base the first is the retro maxillary fat here it's relatively clean I look at ergo paletine fossa bilaterally to see if they're filled they're relatively clean I look at the superior orbital fissure x' posteriorly here that should be clean fat as well which it is this is the pharynx here I look at the para pharyngeal fat over here bilaterally for anything filling it and they look normal here then look at the stylo mastoid foramen posteriorly here and the fat beneath this area here should also be clean and look at the nasal pharynx itself for any asymmetry and then lastly but definitely sleep I look at the carotid arteries beneath the skull base okay and the carotid arteries beneath the skull base can be hard to find on an individual slice the best way to find them is to find the carotid canal itself here and scroll inferior lis from that location and naturally the carotid artery will be able to be followed beneath that point then we look at the bones looking for fractures or any big lesions to make your life easier most fractures are associated with either soft tissue changes overlying them or blood in the sinuses adjacent to them if you see soft tissue changes look at the bones beneath or in that region closely if you see blood and a sinus or in the mastoid air cells then look more closely at these bones with that in mind here's my approach to bones on a routine CT head you've already looked for soft tissue swelling if you see any focused or search in that reason region to start if not move on to the sinuses starting with the frontal sinuses here the eath moines air cells here the maxillary sinuses bilaterally here and the sphenoid sinuses here next look at the mastoid air cells here and on the left as well if you see any fluid or blood in any of these structures you need to focus on the walls and look for fractures closely once you've done that there are a few checkpoints that you need to look at look for calvarial fractures anteriorly laterally and posteriorly scrolling down from the top make sure you follow each of the bones down to the skull base so when you scroll when you're looking at the lateral bones make sure you follow it down to the greater ringless p9 and the skull base bilaterally when you're following it down posteriorly make sure you follow it down to the posterior cranial fossa until you reach frame and Magnum then I look at the orbits specifically looking at the lateral orbital wall superiorly and then the medial orbital wall and I look at the other side looking up the medial wall and then down lateral wall then look at the zygomatic arches bilaterally look at the pterygoid plates bilaterally all the Fort fractures or the four type fractures involved the pterygoid plates then look at the nasal bone the nasal bone is the most commonly fractured bone so always look at the nasal bone make sure you look at the clivus always always always look at the mandibles make sure they're congruent and then follow them down as far as you can you can always see part of the spine this is c1 it looks okay and then you can also see c2 and the dens here as well so always look for that you can see subtle signs of fractures there as well so that's it for a more detailed approach there are always other blind spots and things you can look for but that's a similar detailed approach the one that I use this case was subtle is pretty much normal there was nothing abnormal in the brain that was traumatic however if you notice when we're looking at the soft tissues beneath the skull base I didn't mention at the time all the pairs of fat looked okay but if you look at the carotid artery on the left here it looks okay we've looked at the credit artery on the right notice the hyper density of the walls here as I scroll down is more obvious here as we know acute clot or acute blood is bright this is a case of a dissection when you have an acute dissection you get acute mural hematoma or an intramural hematoma and this is the most subtle sign of an internal carotid artery dissection a CTA was done thereafter and confirmed that this was in fact a dissection an interesting case with no other findings except for this okay that's it for this talk thanks for listening I hope it helped