 All right. Hello and welcome to the fifth of many live stream noon conferences hosted by MRI online is just now 12 o'clock and I see the number is still rising. So I want to give it a few more minutes seconds really and just wanted to say welcome and in response to the changes happening around the world right now and the Shutting down of in-person events. We have decided to provide free daily noon lectures to all radiologists worldwide Today, we are joined by Dr. Mikesh Harrison Donnie He is a professor of radiology at Harvard Medical School and director of abdominal MRI at the Massachusetts General Hospital in Boston, Massachusetts. In addition, he serves as director of the clinical discovery program Center for Molecular Imaging Research at Mass Gen And has been the section editor of GU radiology for the AJR He has been practicing in the field of abdominal radiology for over 20 years has published over a hundred Pure reviewed papers and has edited five textbooks in the field of radiology Reminder that there will be time at the end of this hour for a Q&A session Please use the Q&A feature and we will get to as many of these questions as we can before our time is up That being said, thank you so much for joining us today. Dr. Harrison Donnie. I'll let you take it from here Thank you Ashley and welcome everyone. I hope everybody's staying safe and Taking the new precautions so that we can overcome this crisis in a healthy manner So having said that the topic of discussion today is going to be looking at how MR can be helpful in patients with rectal cancer and if you look at the The indications for MR specifically in the abdomen and pelvis There are a couple of indications like prostate and rectum where MR has suddenly become front and center in terms of what Information is gathered prior to therapy and the modality of choice So MR is certainly becoming the modality of choice and and what we are going to do today is Talk about these or cover these specific points. The first is why MR? Why do we need to do MR in rectal cancer? The second is how do we do the MR talk a little bit about technique and Kind of give you some pointers in terms of what the ideal protocol ought to be And then the most important thing is once you do the MR The question is what do you look for and how do you put that in a comprehensive report? And while we are discussing the content of our report We're going to talk about a few anatomical concepts, which are key to remember when one is looking at rectal MR Talk about standardized reporting why that is very important and I'll show you Or provide you with resources that you can use to download free templates for for the rectal MR and then talk about imaging pointers or You know that that predict worse prognosis in these in these patients So the first question is why and if you look at this is you know a year old in 2018 Rectal cancer gets clumped with with colonic tumors. So if you look at colorectal, they are the fourth most Common type of cancer and about one-third of these patients are rectal cancers So it's not a trivial number. It certainly is a significant number of cancer cases that we see in a year and If you look at this particular Distribution of what the five-year survival is it shows you that when the tumor is localized to the lumen and Gets and that patient gets appropriate therapy. There is a very good chance of a five-year Disease-free survival, but as the disease progresses and becomes regional or distant than the five-year survival drops And that's the reason why we have to be very diligent in accurately staging these patients so from a very simplistic perspective if the Tumor is confined to the lumen which means it stays inside the lumen of the rectum and doesn't extend out the treatments are primary surgical and you know, the standard is what we refer to as Transmissory rectal excision or TME surgery Whereas if it extends beyond the confines of the wall and extends into the surrounding fat or adjacent pelvic parenchymal organs and then those patients typically get new adjuvant chemo radiation therapy and Then they get subsequently followed up and if things seem to be progressing in the right direction and looks like the tumor is regressing and and Shrinking away, then those patients ultimately go for surgery. So again, this is a simplified grid. It's just to kind of highlight what some of the Mechanisms of how the tumor is treated Irrespective of what Or how you treat the disease the goal both for the folks that treat the patient and for us is to prevent recurrence and Here is a patient who had a mucinus type of adenocarcinoma in the Pelvis and came back after surgery with a local pelvic recurrence as you're seeing in this particular instance in the pre-sacral Region and when the disease comes back or the patient gets local recurrence that is a very difficult disease to get a Handle on these patients typically have bad prognosis. They have poor very poor quality of life And so we have to do whatever is in our You know, whatever is available to us use that to the best of our ability to prevent this Specific scenario from happening and so accurate staging and appropriate treatment are the key things that will end up preventing local recurrence And so with that said in mind what we are trying to do why we are doing MR is basically you try and distinguish those patients Into this into into those that have early lumen confined disease Which means the disease is not extended beyond the wall and those can you know, as I said get surgical modes of therapy and Distinguish those from local spread and and those with distant Pelvis spread because those require more aggressive modes of therapy prior to surgery and Then this is another important point of imaging is you know, when you look at the primary tumor you have to find Those specific imaging markers that can predict that this patient is going to do worse Or going to have adverse prognostic outcome and we will be discussing what these points are but this is sort of more or less in a nutshell what the Role of MR is in rectal cancer So then then comes the question of how do we do the MR and you know, I think like most other MRs in the abdomen and pelvis attention to detail in terms of technique is very critical if you Use a generic protocol that you use all the pelvis is it's not going to suffice for accurate stadium You have to spend some time in optimizing the protocol so that you get the necessary information that is required And so you use this, you know, the again, you can use a 1.5 or 3d use The phasor a coils that are available with your system to the best Of your ability and so let's look at what the protocol is the first thing you do is you do what is referred to as the Localizers or the scout images and this basically gives the technologies an idea of what is the area of anatomy that needs to be covered? generally you want to be Covering an anatomy that extends from the L5 S1 junction Down to the level of the anal words or perhaps a little bit lower than that because that will give you an entire coverage for You know where the rectum and the anal canal lie and give you will give you all the necessary information that you desire So that's in terms of coverage than the next sequence the technologies ought to run is the sagittal T2 weighted sequence and typically you like it to be a fast spin echo or a turbo spin echo T2 And this goes from one pelvic side wall to the other so that you cover the entire breadth of The viscera containing pelvis and the and the rectum more or less resides in the center as you're seeing in this instance The reason for doing a sagittal first is so that you get a lay of the land of where the You know where the rectum is what defines the rectum where is the cancer because based on You know where the tumor lies you are going to be prescribing some other planes And that's why it's important and critical to do the size of the sequence first After you do the saddle you do a true axial and again the extent is from the level of a little below the level of the Anal words up to the level of L5 S1 or the aortic biparcation And the reason for doing the true axial is you're trying to look take a look at the anatomy and you know there are There are anatomical features in the anal canal There are nicely laid out on the axial images that can help you in staging lower rectal cancers And this is just showing you if you take an axial slice Muscle which is this u-shaped muscle. That's where traditionally, you know the the columnar epithelium of the rectum becomes the squamous epithelium of the anal canal and that's where anatomically or histologically you would Locate the transition of the anal canal to the rectum or sorry the rectum to the anal canal Now once you're below this level in the level of the anal canal what there are two essential sphincters You're looking for internal sphincter and you're looking for external sphincter And so if you look here on this image the the green color is the internal sphincter The internal sphincter is an involuntary muscle And it's the continuation of the circular smooth muscle of the rectum. So it is a relatively Has relatively T2 bright Signal compared to the external sphincter which you see right here. The external sphincter is darker It has similar signal intensity as the skeletal muscle because this is a striated Muscle which is different from the internal sphincter and so You know I you need whenever you look at a pelvis whether it's for rectum prostate You know keep sort of emphasizing this anatomy because it helps one other way that you can distinguish the internal from the External sphincter is that the internal sphincter will show earlier enhancement after gathering and compared to the external sphincter So that's in terms of anatomy axiom now after axiom we do what is referred to as the This is sort of the money sequence. It is the high-resolution and T2 added oblique axiom Images these are the key Money sequences In terms of staging and what do you mean by that? So remember you acquired your sagittal and in this instance, there is a very long Segment of tumor and what you're doing is Scanning perpendicular to the plane or axis of the cancer as you see in this particular instance. That is the reason why You know that is the reason why you sort of angle it to the axis of the tumor So these are the key sequences for staging and why do we pay such? close attention and Pay a lot of emphasis on this is basically is because of this if you look at this particular case there is a tumor right here on the sag and and here is a true axial image without any Angulation and when you look at the true axial image if you look at from six o'clock to You know about nine o'clock in position there appears to be relatively Unsharpness and if someone asked you is the tumor confined to the lumen or do you think the tumor is extending out? It can be very difficult and challenging. No, that's the case Whereas if you look at the oblique perpendicular oblique axial, you can see the tumor is confined to the lumen and it's not extending beyond So it could mean in you know difference in accurate staging and that's why I cannot emphasize enough you have to spend some time in terms of Making sure that these sequences are adequately performed and they are more they are higher in resolution than the conventional axial T2 where it sequence so they have more detail that you can look for in terms of an atomic delineation and staging of the tumor after you do the Oblique axial you do the coronal T2 weighted and again the coronal sequence is To emphasize the anatomy particularly for the lower rectal cancer where you're looking for Involvement of the sphincter complex and so this is what the coronal looks like And just to kind of blow it up a little bit You see the the lavera muscle on either side the lavera muscles That form the pelvic floor are like hammers on either side These lavera muscles come down and insert into the pubo rectalis, which is this muscle that is Shown by the turquoise arrows and Then below the pubo rectalis you have the external sphincter the external sphincter typically has three fascicles Which you are seeing right here. We have the upper the mid and the lower fascicle and then you have the green arrows Which are pointing to the internal sphincter. That's this between the internal and the external sphincter is this bright fat containing space and that is referred to as an inter sphincteric space Again, you know, you need to kind of keep looking at this and reinforcing the anatomy when you're looking at You know images where patients don't have cancers and other pelvic so that you know When you do have a patient with low rectal cancer, you're Accurately depicting the anatomy and trying to figure out what's involved or not So pay attention to the anatomy in terms of in the coronal images Then we do DWI now the money sequences truly in terms of staging are the T2 error sequence There is a school of thought that the diffusions and the gadolin and enhanced images are really not required. I Can tell you in our practice They can be extremely helpful and beneficial and they can complement the information that you get from the T2 error sequence So typically you do a low B value a high B value around 800 to a thousand and then calculate an ADC from that and then you we also do gadolin and enhanced images and More so than the primary staging these can be very critical when you're looking at post treatment scans And so here is an example of a patient who has a tumor in the in the on the right wall and You can see that there is restricted diffusion and abnormal enhancement and after therapy on the T2 It's very difficult to know whether there is any real cancer But on the ADC of the DWI based on the enhancement, you can see that there is some residual cancer in that location. So Certainly of benefit in terms of follow-up And like I said, it's it doesn't hurt to do that in the regular Staging protocol as well because you certainly end up getting useful information So that is the how we do it now we come to what do we look for now before we talk about Looking at the specific features for the rectal cancer. We need to re-emphasize some Anatomic facts and also go through some of the terms that are critical for you to Know before you actually start looking at the rectal cancer patients So the first is anatomy and the question is how do we define the rectum on MR? and and what what are the boundaries that we use on MR to Truly say, you know, where the rectum begins and then and so on a mark. Excuse me. We follow the The the perspective of the endoscopies and from an endoscopy perspective The the rectum is the most distal part of the GI tract that extends 15 centimeters from the anal verge So this is what the endoscopies looks for and and and characterizes as the rectum So here is the anal verge and they go 15 centimeters from there and then they they break it up into upper Rectum, which is upper 5 centimeters mid rectum mid 5 centimeters and lower rectum. That is the lower 5 centimeters and this is what we follow and here is a sagittal T2-way that MR showing you how you go along the Lumen of the rectum and draw 15 centimeters and that's what is Classified as the as a rectum now You will see here that Based on this definition, you are actually including the most distal part, which is the anal canal within the rectum You know, that's what the endoscopy is doing. That's what we follow. So that's something for you to keep in the back of your mind now The question is what defines the anal verge? Typically, it's where the external sphincter ends. So the external sphincter is a little bit Extends a little bit lower than the internal sphincter There are some institutions that take the most distal part of the internal sphincter as the anal verge there are some institutions that take the most Distal part of the anal canal, which is where the external sphincter is as the anal verge I mean the difference between those two is about point five centimeters. So you really are not You know accounting for a lot of difference But the key is to talk to the surgical colleagues and oncologists and your respective institutions and see You know, which which definition of the anal words they would like to use But irrespective of that make sure that you know, it's it's the 15 centimeter accounting from the the anal verge as the definition of the rectum Now because This definition of the rectum includes the anal canal It means that if there are tumors primarily arising in the anal canal, which are primarily squamous cell carcinomas You know are also included in this in this supposed definition and so the question that begs the question is if you're looking at a pelvic MR Are you trying to distinguish an anal cancer from rectal cancer? And so if I show you these two coronal images, you know, one of them is a rectal cancer and one of them is an anal cancer and ask you What is the Which one is which it's very difficult to predict if you look on histopathology It's the one on the left was rectal on one on the right was anal cancer So as radiologists, we are not in the business of distinguishing anal from rectal cancer so even before you sit down and open the MR and Apply everything I tell you today. It is very very very important I can't emphasize that enough that you look and make sure that from an histopathologic perspective what you're looking at has been biopsy-proven to be a rectal cancer Because if what you are doing or what you're looking at is a biopsy-proven anal cancer Then none of what I tell you is going to apply to anal cancer because the staging and the treatment is totally different And so, you know again The take-home point here is do not try and distinguish rectum from anal based based on imaging You need to know that a priori before you look at the exam to apply whatever I tell you You need to be sure that what you're looking for is rectal cancer and not anal cancer before you Before you You know start applying the rules that we talked about today One more anatomic fact that you need to keep in mind is that Not the entire part of the rectum is extra peritoneum the peritoneum inserts in the upper part of the mid rectum and So in men it's typically here You can see the tip of the seminal vesicle this black line that you see going towards the rectum is a peritoneal reflection And in women who have their uteruses is typically at the junction of the uterus and cervix You see this thin black line extending on to the anterior part of the Antieta part of the rectum. So that is the peritoneal insertion above this level the anterior part of the rectum is lined by peritoneum and Why is that an important point? It becomes important from a staging perspective and it also becomes important from a Few of the imaging features that we will be talking on on Axial if you take an axial slice at this level, this is what it looks like. It has this sort of a gullwing pattern of Tin black line that is inserted and anteriorly on to the rectum So when you're looking at your MRs, please make sure that you identify this landmark because this is going to be a key landmark for force not only for staging but also for assessing Assessing some of the other features that we'll be talking about This is what the specimen looks like So here is the anterior part of the TME specimen where you can see this glistening surface of the rectum That's what is lined by peritoneum, whereas posteriorly there is no peritoneal line So, you know, just keep in mind that now the next point is the appearance of the The rectal wall on T2 weighted sequence because that's what governs the a lot of the staging information that we will be talking about So here is an anatomic depiction of the wall of the rectum and this is what we see on an axial T2 weighted sequence. So we look at two bands essentially The inner bright or hyper intense ring comprises of the mucosa and submucosa that you're seeing right here And then the outer ring, which is the dark ring Which is the most important part that we look for is the muscularis propria. So you see this dark line that extends all along that's the The muscularis propria and that is one very important structure that we pay attention to when we are looking at the MR's So here is a coronal In an oblique image you can see this is the dark line of the muscularis going all the way around And this is sort of the relatively brighter mucosa and submucosa Now there is another structure that you see on this T2 weighted sequence. That's this black line that extends all along In a circumferential manner surrounding the rectum And that's the other important landmark that we need to pay attention to and that is the mesorectal fascia It's a connective tissue sheet that encloses the the rectum also encloses the perirectal Fat perirectal vessels and small nodes that are in that location And so The reason why this is an important landmark because as we will see from a certain staging perspective as well as from a surgical perspective because typically when the surgeon does their surgery and does the Mesorectal excision they try and go along the plane of this mesorectal fascia Now they may not be very precise It could be a little bit to the inside a little bit to the outside, but this is more or less the They define surgical plane if you will Laterally for the TME and when the specimen does comes out. This is the plane of our resection that is You know that is defined by the mesorectal fascia now there are two Points to remember about the mesorectal fascia one is it is most Generous or capacious in the mid part of the rectum as you come to the lower part of the rectum It becomes very closely applied to the To the wall of the rectum in fact below the level of the levator muscle the mesorectal fascia is practically in close Attachment to the wall of the rectum and so that's important because you know if you have lower There is a chance that it's directly involving those are actually and we'll be talking about that a bit But this is an important an atomic Point to keep in mind and so that brings us to the next point What is total mesorectal excision? We have been talking about and this is you know This is the surgery that really Revolutionized the the treatment of rectal cancer and what was found is instead of just taking out the rectum along with the cancer if you dissect along the plane of the mesorectal fascia and not only removes the the rectum but also the fat and The and the lymph nodes and and structures that are present in the mesorectal fascia the outcome of Patience is much better in terms of reduced chance of local recurrence So these are diagrams showing you what essentially you are doing when you're doing a TME you are dissecting along the plane of the mesorectal Fascia and that's what defines the lateral extent. So then you will ask me if TME excision is Define laterally by the mesorectal fascia. How high does the surgeon go and how low does the surgeon go? so in terms of so this is what the specimen looks like there is the You know the the rectum rectal lumen with the cancer you can see right here You can see all the fat that comes out and this is the plane of dissection laterally along the mesorectal fascia Now superiorly they go up to the takeoff of the inferior mesentric archery So you can see this is a CT scan of a patient was undergone TME surgery and this is where the surgeon has left clips of how superiorly they work Now inferiorly depends on whether the cancer involves the sphincter muscle in the anal canal or not If the cancer does not involve the anal canal, then the surgeon does what is referred to as a LAR where they basically The inferior margin is at the level of the the leviators or the the pubal rectalis and and they spare the sphincter muscle Whereas if the tumor involves the The sphincter mechanism, then they do what is referred to as an APR or abdomen or abdomen of perineal resection Where they have to sacrifice the the sphincter mechanism and these patients get left with a permanent colostomy So that's sort of in a nutshell at the what we are looking for the couple of anatomic facts Now in terms of standardized reporting, I'm not going to go through the template, but I will point you to this website It's The society of abdominal radiology website and anybody can go to this website is www.obdominalradiology.org When you go to the website, there is a tab for dfp's which stands for disease focused Panels and if you click on the rectal and anal cancer panel It brings you to the various templates that are there So you don't have to kind of create these on your own. You can just take the templates You know if you click on when you any one of these for instance, if you click on the rectal cancer staging rectal cancer staging template it brings the For some reason the link is not active, but it will bring the the template that is available in a pdf format that you can then import into your respective reporting reporting You know software, so you don't have to sort of Reinvent the the the template so keep an eye I mean, you know use this as a resource and it gets continuously updated and and and the the dfp panel in sar has done an excellent job at at providing the the most up-to-date recommendations as well as A lot of other resources that one can use when looking at these templates So having said that Let's talk about now On the imaging side of things. Yes, you will use a template, but you have to pay particular attention to those imaging features that predict that the rectal cancer is going to behave in a in a adverse prognostic way in other words the the prognosis of the tumor is worse Then when these factors are not present and the key factors that we are looking for in terms of adverse prognostic indicators are Mucinous pathology And when you do have mucinous pathology, you have a very specific imaging appearance We talk about the t-stage and the crm which stands for the circumferential resection margin positivity And we'll go into what that means You need to know the presence or absence of emvi or extramural venous invasion this is again, relatively a new addition to I mean, it's it's been around but you know particular emphasis is being paid to this because this is Considered to be a harbinger for worse prognosis patients who have emvi typically behave In a in a worse manner with having large number of nodal meds and also being predisposed to distant metastases And then looking at close proximity to the anal sphincter complex, obviously the anal sphincter complex is involved then As I said, the surgeon has to do an APR and these patients are also difficult to get a get a You know get a surgically clear margin, especially the tumor is Is well beyond the confines of the sphincter complex. So let's look at each one of these five adverse prognostic indicators And the reason I'm doing this so that you know, I'm showing you the worst thing that you need to pay attention to when you're looking at that standardized reporting format And so if you look at the mucinus pathology as the name implies if you have mucinus ad mescarcinoma Mucin and the ad mescarcinoma can be extremely bright on t2 and that's what it looks like. So here is an example of a large mucinus tumor in the You know in the pelvis and you can see it's extremely bright When you do have this kind of signature of the tumor on the t2 weighted images It usually Means the tumors have a higher pathologic grade They have a greater tendency for metastases both in the lymph nodes and beyond And they typically have an unfavorable prognosis And so here's another example. You can see this is a bright lesion inside the lumen and it seems to be confined to the wall, but there is a A lymph node that has near total replacement by the mucinus deposit within it. So You know, despite being a small lesion, it does have a large nodal metastasis in the mesorectal space So if you do see features suggestive of mucinus A composition of the adenocarcinoma you make sure you put that in the report Then the next point is looking at the t-stage and looking at the circumferential resection margin positivity And so let's look at what this means. So if you look at The local staging the t-staging basically the t1 is confined to the mucosa T2 disease is confined to the by the muscularis. It doesn't extend beyond the muscularis T3 disease is when the disease has spread beyond the muscularis into the surrounding mesorectal fat And then t4 is when the disease invades adjacent pelvic organs or it invades into the peritoneal cavity So that's sort of in a nutshell the t-staging of You know of rectal cancer Now detection of locally advanced which means T3 that is, you know, the tumor has gone beyond the muscularis and extends into the mesorectal fat Typically those patients are treated with presurgical chemo radiation therapy So that is the first point to remember that essentially, you know, our goal is to identify the t3 and and above With mr We don't do a good job of distinguishing t1 from t2 and you shouldn't even make an attempt to because you will Be wrong most of the time and so, you know one way would be is just to sort of Say that the the tumor appears to be confined to the wall by or by the muscularis not extending beyond And once it does then you call it a t3. Now. Let's look at t3 disease in a little bit more Detailed so as I said t3 disease is when the when the tumor extends beyond the muscularis into the adjacent mesorectal fat So here is an anatomic depiction where you see the Outline of the mesorectal fascia. These are small normal size nodes Here is the rectum and this is the tumor That is extending through the muscularis into the adjacent mesorectal fat Now t3 is divided into four distinct categories. The first is t3a where the tumor is extending beyond the The muscularis into the fat but that extension is less than one millimeter And in this case you can see the dark line here But as you come to this part you can see that there is relative lack of that black line of the muscularis And there is a very subtle less than a millimeter or practically You know the tumor is it's sort of invading the muscularis and just stops Right there and it's less than a millimeter of extension into the Into the mesorectal fat Now t3b is when it is between one and five millimeters and in this case you can see here is a deposit right here That is going to less than five millimeters into the adjacent mesorectal fat T3c is when the tumor is greater than five but less than 15 millimeters And then finally t3d is when the tumor is greater than 15 millimeters extending into the mesorectal fat And so the question is why are we Taking the t3 and breaking it up into abc and d The first fundamental reason why we do that is Is the five millimeter cutoff which means that Tumors once they extend beyond the muscularis into the adjacent fat If they are five millimeters or less their overall survival is pretty good But it drops precipitously if it is if it extends beyond five millimeters And so you can see that you know essentially the goal of the abcd is to try and find those that are less than five millimeters Where there is a good five year survival versus those that are greater than five millimeters and then the survival drops to under 50 percent So then you will ask me well if it's if it's five millimeters Why don't you just have a and b where it's less than five and greater than five millimeters The whole purpose of having a and b that is less than a millimeter or between one and five millimeters Is because there are certain institutions That still treat early t3 disease as t2 which means they go for surgical resection And that's the reason why you have that subtle distinction of t3a and t3b But the take-home point for you guys, you know in terms of t3 diseases Remember if it is less than five millimeter extension beyond into the fat It usually is good prognosis. Whereas if it is beyond five millimeters into the meso-retal fat prognosis is very bad Then comes the next point which is the circumferential resection margin. Now, this is a CRM In short is a actually a pathologic term which means once the surgeon dissects along the plane of the Meso-retal fashion gives the specimen over to the pathologist the pathologist then looks at the The extent of the tumor in terms of involvement of this resection margin or circumferential resection margin So it's essentially a pathologic term the other important point to remember is although it is referred to as a circumferential resection margin It's not circumferential in the sense that it portrays circumferential resection only below the level of the peritoneal reflection Above the level of the peritoneal reflection It is non circumferential because you cannot assign a CRM status to that part of the rectum That is anteriorly covered by peritoneal. So please keep those two points in mind when you are reading and staging these tumors So let's look at the equivalent of CRM that we need to put in our reports and the equivalent is You measure the shortest distance From the tumor to the non peritonealized part of the meso-retal fascia. So in this case you are Below the level of the peritoneal insertion and you're going to measure this distance Which is the shortest distance Now the earlier descriptors actually included not only the shortest distance from the primary tumor but also to positive nodes But in the current consensus and you know going forward It's recommended that you only put the shortest distance to the primary tumor if you do have nodes And and and you are you are pretty sure the nodes are positive You can mention it in the in the in the report and let the You know let the oncologists and the surgeon decide what they would like to to do with that information and so What are the criteria if the tumor? Reaches and touches the meso-retal fascia Or within one millimeters of the meso-retal fascia the CRM is considered to be positive If it is very close, but between one and two millimeters CRM is considered threatened And if it is more than two millimeters CRM is considered to be negative Again, why are we doing this exercise? We are doing this exercise because If there is involvement of the circumferential resection margin That usually means there is a higher likelihood that patient is going to local and occur and do worse And that is the whole reason why we are trying you know, we are We are taking the next effort to do and measure this distance So in this in this particular example, you're seeing I have outlined the meso-retal fascia And you can see that there is a large tumor extension that is Involving it's less than a millimeter. So in this case it is Reaching and in this case the CRM is positive And so that's what you will put in your in your report Now In terms of CRM positivity as I mentioned, we do not consider the involvement of the peritoneal lining That is a separate category in terms of descriptor and a separate category in terms of assessing prognosis. So remember it was a thin black line that we saw extending Um from the utero cervical junction posteriorly into the rectum In these two different patients, you can see that the tumor is clearly extending to involve that peritoneal reflection And when you see that you need to put that in the report and that indicates t4a disease So it's no longer t3. It's t4a disease And you know, again, it requires pre surgical radiation therapy and also it indicates worse prognosis because what it tells the referring oncologist is that the tumor has involved the peritoneum and has shed cells into the peritoneal space and thus there is a higher risk of local recurrence So make sure that you you mention that Again, the pitfall alert is the peritoneum involvement is not equivalent to the CRM involvement. Remember the The CRM corresponds to the cut surgical resection margin and does not Cover the anterior aspect of the upper rectum The surgeon cannot influence the free peritoneal surface The surgical resection margin will be negative since the whole rectum will be excised. So That's an important point to distinguish when you do have peritoneum involvement It is t4a and it is reported as CRM negative, but you will mention that there is a peritoneal involvement. I hope that point is clear so that you know, that's one potential source of confusion and error and when when reading these cases Moving on to the next adverse prognostic indicator and that is the extramural venous invasion And what it essentially means is, you know, you have these very rectal veins that arise from the rectal wall and extend into the adjacent pad If you have tumor that extends into these veins, then that is considered to be An independent predictor of worse prognosis. These patients typically have local intestine recurrences, nodal disease and the overall survival is worse. MR is extremely good at detecting EMVI and also stratifying patients. So here are two examples You can clearly see that there is a bifurcating vessel where there is similar signal intensity as a tumor extending into the vein And here is another example where you can clearly see that there is tumor extension into the venous radical similar in signal intensity as the primary cancer One word of caution and also to look for is, you know, sometimes the extent of involvement in the vein may not be similar in terms of size. In other words, you can have a vein take off from the wall and you can have a larger tumor deposit distally compared to proximal and just to show you the example here is a patient where you can see this is the rectal wall right here and here is a vein that is emanating from the posterior wall of the rectum and as we scroll you can see that there is clearly tumor involvement here but as you go further there is a larger deposit somewhere in the mid portion of the lumen. So keep in mind that, you know, you can have this nodular deposits along the course of the vessel and that's something you need to pay attention to and call it appropriately EMVI. So lastly looking at close proximity to the anal sphincter complex and as I mentioned you have to pay close attention to the anatomy. The anatomy is what is going to help you in terms of, you know, in terms of defining whether there is extension into the sphincter complex or not and so if you have involvement of the laverums that is considered T4 disease and again it is treated as such and then once it extends lower down into the anal canal what you're doing is you're trying to look for involvement of three distinct structures. The first is the internal sphincter, the second is the inter sphincter space and third is the external sphincter and so you have to be descriptive in your outline and need to let the surgeons know if the inter sphincter space or the external sphincter is involved because these two factors are what will sway them towards doing an APR versus doing an LAR and so here is an example of a lower rectal tumor with the involvement of the inter sphincter space so you can see here is a circumferential lesion on the left the fact is maintained in the left inter sphincter space as we go as it scans through the corolla on the right side there is clearly tumor involving the inter sphincter space and it kind of aborts the external sphincter which appears to be relatively well maintained in this case so here there is involvement of the internal sphincter and extending into the inter sphincter space with relative sparing of the external sphincter and again one useful caveat is when the contralateral anatomy is spared it's good to you know compare and show what's going on and here is another example of a patient where there is external sphincter involvement two different patients here is a musinous lesion clearly there is extension into the external sphincter on the left side and beyond and here is another patient where you can clearly see there is involvement of the external sphincter on the left and extending beyond the the external sphincter complex and in this case these these patients clearly will have to undergo depending on what the features are after the argument they may still have to get their sphincter sacrificed and get a permanent cluster so I think that was in a nutshell you know covering more or less the important points for rectal cancer MR a couple of take home messages that I would like to re-emphasize do not skimp on the oblique axle plane please pay attention to you know to your technique to ensure that the oblique axle plane is performed properly if your texts don't have the ability to identify which in most cases you know it's very difficult for them to know where the cancer is it requires active participation from the radiologist to ensure that the plane is correctly selected then you have to pay close attention to those factors that contribute to local recurrence follow the template but within the template framework these are the you know key elements that you need to pay particular attention to looking for the t-stage presence or absence of peritonium involvement and then also looking at the CRM status in terms of extension to the mesorectal fascial margin you are looking for the presence or absence of EMVI and with low rectal cancers you're looking for extension into the sphincter complex vis-a-vis you know going into the internal sphincter intrasphincteric space or involving the external sphincter and then you know standardized reporting I can emphasize how important it is to have a standardized template so that everybody in your practice follows the same reporting guidelines and follows the same pattern of dictation with that I'm going to stop and say thanks again for listening and I will see if there are any questions that the audience would like to pose. So there are a couple of questions that I have already popped up I'm going to read through them and see about the rectum being divided into three portions each one measures about five centimeters a lower rectum extension the anal verge or from the inner rectal junction I think we have gone through that it's extension from the anal verge not you know not from the level of the pubo rectalis. Can we please see the reporting template I think I have given if you go to the society of abdominal radiology website you don't need a login you know you can pull it up without login information and it should be pretty straightforward to to look at that. What if the tumor involves the anterior peritonella again is T4A disease that does not count as CRM involvement. The next question is for T3 disease when measuring the distance from the tumor to mesoracil fascia and if the mass has speculation does one measure from the tip of the longest specular from the mass itself and the answer is you know I didn't cover this but one source of error between T2 and early T3 disease can be these spicules which are related to inflammation and what has been described in the literature is unless you see frank nodular extension of the tumor into the mesoracil fat you do not call it T3 disease. Subtle spicules can be seen with inflammation and I know in rectal cancer can be a fairly inflammatory disease and so if you have linear lines those don't classify as T3 disease. Again there is a difference of opinion between that because you know there are some groups which will call it a T3 disease or early T3 disease even if there are spicules and this is a dialogue that you need to have with your surgeon to you know to to figure out what's the best way to to do that. Can you can you please give us an example where contrast is helpful. Again I think you know like I said in our practice it's a useful complement sometimes when tumors are you know are fairly large or when tumors are fairly small and looking at the differential degree of enhancement between the wall and the and the tumor can be useful. I'm not saying that that is the primary means for staging but it can serve as a useful complement to actual detection and staging. Should we be reporting on CRM given that this is the pathologic term. I don't think you are reporting on the CRM what you're giving them is an indication of what they can perceive the status of the CRM to be should they operate on the patient so that is why you give the distance you don't call it CRM you give them the shortest distance between the tumor and the outline of the mesoractyl fascia is this. Let's see what else somebody has sent a link looks like. How do you treat desmoplastic inflammatory reaction in staging as post-treatment. It is very difficult to know the inflammatory changes adjacent to the tumor versus early T3. Again that's a very good point. I did not cover post-treatment assessment that itself is a very detailed topic to go through and I agree with the reviewer that it can be extremely challenging. There are certain indicators of how you could classify and describe the tumors one treatment has been given but again this is something that needs to be described separately. Can direct LMR on MR below 1.5T. My experience is limited to 1.5 and 3T. I am not so sure that for the kind of resolution you need on the T2 edit images if that will be possible on the lower field strength scanners but again if you are able to work with a physicist or the vendors and optimize your technique I think that should be I mean you should give it a try and if it's you're getting the kind of quality that is needed then I don't see any reason why that cannot be used. Somebody asked about lymph nodes again that's something that I didn't cover today you know it's given the time constraints but you know if you look at the most recent if you look at that SAR website it gives you in that template what should be done with the lymph nodes in terms of calling them positive versus negative. Let's see since MRI can distinguish between rectal and anal cancer is if I get such a case should I conclude features of inorectal cancer. As I said I don't think you should even make an attempt to start reading unless you are absolutely certain of the pathology before you start reading because the way rectal cancer stage and the way anal cancer stage is totally different and you don't want to confuse one for the other because it would sort of have profound differences in way the patients are managed so please do not make an attempt to distinguish the two do not attempt to start reading unless you have pathologic proof that you are reading a patient with rectal cancer. Does EMVI occur only anteriorly, posteriorly or all around? It can occur anywhere the vessels that arise from the rectum they don't follow a specific anatomy pattern so you have to pay close attention throughout the entire circumferential part to ensure that the EMVI is present or not. Should we report nodes in the meso rectal fat? Again yes if you think the nodes are positive and again there are two there are three sets of criteria used for nodes again I would suggest you go to the SAR website to get more information but if the nodes are above a certain size and or if the nodes are heterogeneous in signal intensity and or if the nodes are irregular in outline then in those instances you try and you know characterize those nodes as potentially positive and then you know you can what you need to do is say suspicious versus not and then give the total number of suspicious nodes. The other important point with nodes is also to distinguish the nodes that are within the meso rectal fascia versus those nodes that are in the pelvic sidewall. It's important because when the surgeon does the total meso rectal excision they do not dissect the nodes in the pelvic sidewall. So if you see pelvic adenopathy in the pelvic in the pelvic sidewall that you think are suspicious then that needs to be mentioned because that'll again alter what the surgeon plans to do with the with the patient. DWI is not very good for distinguishing benign from malignant nodes and I would refrain from you know to refrain from looking at the DWI for distinguishing or characterizing nodes as benign or malignant. Is there a large technical difference between 3T and 1.5T in terms of diagnostic capability should we only be doing them on 3T? I can tell you from our experience we scan on both 1.5 and 3T and you know as long as the protocols are optimized for the 1.5T you get comparable diagnostic information. Clearly the resolution can be a bit better but there are also sort of disadvantages of scanning on the 3T because bowel peristalsis can be accentuated on the higher field strength and so I think it's yin and yang you get you can get more resolution and time on the 3T but you can also get some artifact. So it's a balance and I would say that you know if protocols are optimized on each system then you are not going to have much difference in terms of what the difference is in the field strength. Let's see what happens. I think a lot of these are duplicate questions. Somebody has asked is there a need for endoretic coil for these exams and the answer is no, a very emphatic no because you know think about it unlike in the prostate with the rectal what you're trying to do is look for cancer in the lumen and if you use an endoretic coil and the coil pushes the tumor away from your coil you actually end up doing more harm than good to the patient and so you know we do not use an endoretic coil for for looking at rectal cancer cases and I would really refrain from doing that. It can be it can in fact totally mitigate the usefulness of the exam so be very careful if you you know if you are doing that I would discourage and you know ask you not to to do that. Let's see what do you think about endoretal ultrasound as a way of determining T1 from T2. That's a good question and I think EUS or endoluminal ultrasonography has a role for distinguishing T1 from T2. They are they can get very high resolution images of the rectal wall and are able to tell the difference. Clearly as I said on MR it's not it's not easy for us to do that. The problem with ultrasound is you know it's good at looking at the wall they can't see beyond the wall and that sometimes poses a challenge. The other issue with ultrasound is endoretal ultrasound is the experience of the reviewer so that's something also to keep in mind in terms of in terms of you know utility of. One last question is it important to use anti spasmolytic and again in the interest of time we didn't go into the specific you know details of the protocol but yes if you are if you have the ability to use anti spasmolytics in U.S. we don't have buscopan in you know in European countries and in Asian countries you do have buscopan. I would highly encourage you to use anti spasmolytics because it definitely helps in enhancing the quality of the images. There have also been instances where they do micro and emails. They don't it's not distention of the rectum but sort of putting minimal amount of fluid into the rectum to enable distention to get good quality images. I think that's the last question more or less we have answered most of the questions as there are duplicates. Ashley I'll hand it over back to you. Yep as we bring this to a close today I just wanted to thank you so much Dr. Harrison Ghani for your time today and thanks for all of you for participating in our noon conference. Just a reminder that this conference will be made available on demand within the next 24 hours on mrionline.com and please join us on Monday at 12 p.m eastern time. Dr. Jeanette Collins will be with us for a noon conference on the sea teen patterns of lung disease. Please visit mrionline.com to sign up for that one and all future noon conferences. Thanks so much and have a great day.