 So, we are welcoming here all of you to yet another session of Radiology Journal Club. This is a monthly event, a new endeavor by Indian radiologist, quite popular by now. This is the sixth session we are running and we have been doing a Radiology Journal Club since last September 2021 and we have covered important topics pertaining to neuroimaging, breast imaging, imaging of renal masses. Then last month we had a good session which was about pediatric neuro radiology. Also, they are shared on the YouTube channel of Indian radiologists and they are freely accessible to all our subscribers. So, do subscribe to our channel and you can revise all what we learned during these radiology journal clubs. We are thankful to the entire core team of Indian radiologists for these important events and keeping the education alive. Dr. Deepu Patkarsar, Dr. Sanjeev Mani, Dr. Jignesh Thakkar, Dr. Shalindra Singh and myself, Dr. Mithusha, my colleague Dr. Gauria Hoja and Mamta Patkar ma'am. So, as we all know it's difficult to keep in pace with all the upcoming advances and by these kinds of journal clubs we try to make it easier because these are something which we can on the go listen to and learn about. So, these articles are recent articles and our experts are the ones who have been using these articles as well as their day-to-day practice experience. So, bringing all of these together they can update us in quick 30 minutes about these upcoming advances and after this they also discuss about these important aspects with the help of two-three relevant cases. We are thankful to our education partners, Bayers as well as Fandom for their continued support because these are all events which are not possible without the support of these educational partners and we have shared their flyers as well as the leaflets and also they have shared a lot of educational materials that also will be shared on our channel soon. So, without further ado, we know that a lot of new upcoming webinars as well as hybrid events are coming from Indian ideologists. So, do subscribe to our channel for all these information and register for these upcoming conference. Sonobhas is March 19, 20th and now it's time to welcome the expert speaker for today Dr. Amit Chaudhary. Amit is assistant professor at Department of Ideology at Tata Memorial Hospital in Mumbai. He also worked as consultant ideologist at Nanavati Mac Super Speciality Hospital. He has completed his fellowship in neuroimaging from Nair College Mumbai and has several years of experience specifically to the field of oncorradiology. We welcome you Amit and over to you. Thank you Mithisha for your kind words. Let me dive straight into the today's journal club topic which is neuroimaging in the era of evolving WHO classification of brain tumors. So, as you all know recently WHO has revised the classification of CNS neoplasm in 2021 which builds on predominantly the molecular and genetic landscape of brain tumors which dictate their prognosis as well as management to large extent in addition to the histological features and then there can be certain imaging phenotypes which can be used to narrow the differentiates to certain molecular classification of these tumors. So, to begin with let me put across these two cases and all the participants can quickly vote for the diagnosis in the chat box. This is the first case wherein we have a plain T1 axial image, a T2 axial image and a post contrast T1 axial image and this is the next case. So, again a T2 axial image in the left bottom, a T2 flare image and a T1 post contrast image and audience can type in their answers in the chat box and we will discuss in these cases in further depth as we progress through the talk. Then this is another case, a case of a left frontal glioblastoma in our 53 years old lady who was operated and treated with chemotherapy of alkylating agent that is temozolomide. So, this is the first preoperative scan. This is the follow-up study in after about six months post treatment and when the patient has received chemotherapy and this is further follow-up. So, this is a response assessment scan and you can maybe in your minds make a response assessment and we will get back to these cases as we progress through the talk. Okay, moving on. So, the present article focuses mainly on 2016 CNS tumor WHO classification but at the same time it has included and incorporated the recommendations of the C impact now committee which was the committee who has recommended many of the guidelines for the new WHO 2022-2021 CNS tumor classification and these are now being practiced or incorporated into the practice of neuro oncology. So, moving on to adult gliomas mainly this article focuses on adult gliomas and their molecular landscapes. So, previously the gliomas were mainly differentiated into IDH mutant and IDH wild type based on immunohistochemistry and their histological features. So, typically a glioma was high grade if there were features of microvascular proliferation, necrosis, hemorrhage etc and then there was IDH mutation which was either detected to be positive when the tumor was IDH mutant or when it wasn't detected the tumor was considered to be a wild type the later being of pure prognosis compared to the former tumor type and in the recent context of 2021 classification this is the status. So, broadly they are classified into IDH mutant and IDH wild type tumors. So, if one encounters IDH mutation positive status then one would either do immunohistochemistry to look for what is known as ATRX which is a protein of the alpha thalassemia retardation X gene and this is detected by IHC. If the result of this test is inconclusive then one can go on to do genetic testing to look for co-deletion or non-co-deletion of 1P19Q. So, these two findings are mutually exclusive and one of these findings can be considered for this diagnosis. So, if this ATRX protein is retained or 1P19Q that is the short arm of chromosome 1 or long arm of chromosome 19 these are simultaneously deleted that is co-deleted in that case the diagnosis is oligodendroglioma and this is a typical case of oligodendroglioma wherein on this CT scan axial image which is actually borrowed from radiopedia one can see that there is this linear calcification which is related to the calcification of the vessels present in the oligodendroglioma. So, these are really fine capillaries which are present in the oligodendroglioma which is really the better tumor of all the tumors which we are going to see today and has a far better survival and outcome compared to the rest of the tumors with a 10 year overall survival of approximately 80 to 90 percent and on this axial T2-HMR image we can see that this is a particularly based tumor which is hyper intense on this T2 axial image is associated with some diaryl thickening and this hyper intensity perhaps which is related to calcification. Next we go on to see whether this protein is lost if it is lost and then there is either non-co-delation of 1P19Q then that would imply that this is an IDH mutant non-co-delated tumor. If that is the case one would further go on to assess what is known as cyclin-dependent kinase 2AB again this is a marker which implies that the tumor has poor prognosis. So, even though if that tumor might be IDH mutant this patient would carry a far more dismal prognosis or outflow compared to patients without this abnormality and without the presence of micro vascular proliferation, hemorrhage or necrosis. So, if this is non homozygous deleted or not deleted at all and then there is no micro vascular proliferation or necrosis then that would be an IDH mutant astrocytoma which would be either grade 2 or grade 3 and this is a typical example of the same. So, this is an IDH mutant 1P19Q non-co-deleted astrocytoma which again is having a relatively good prognosis because there is no CDKN2AB homozygous deletion and there is no micro vascular proliferation or necrosis. Now again in the context of WHO 2021 classification of tumor there is nothing called as grade 1 neoplasm as far as astrocytomas are concerned that classification now applies only to the well circumscribed neoplasms and not to diffuse gliomas. So, diffuse gliomas would be grade 2 to grade 4. Then if this is homozygous deleted and or associated with micro vascular proliferation with or without necrosis that would imply that this is a higher grade IDH mutant neoplasm. On the wild side that is IDH wild or absence of IDH mutation there can be association with micro vascular proliferation again and there can be necrosis which would help in histological grading of this tumor as a high grade neoplasm. Then again there are other molecular markers like third mutation, EGFR amplification, combined gain of chromosome 7 and loss of chromosome 10. In the presence of these mutations the tumor would be a IDH wild type tumor and the classic example being glioblastoma and this is the tumor where in on T2 weighted image and this X-ray T1 post contrast image one can see that there is a tumor which is epicentered in the sphenium of corpus callosum showing certain areas of image with areas of necrosis within on this post contrast T1 weighted image showing thick irregular peripheral rind of enhancement. Moving on, so the article also describes the molecular landscape of medulloblastoma and ependymoma really briefly stating it as being beyond the scope of this article but just to give you a brief overview of these tumors. So WHO 2016 classified medulloblastomas predominantly into four subgroups that is WNT or wingless subgroup of medulloblastoma which had excellent premises amongst all the medulloblastomas then SHH or the sonic hijab mutated subgroup of medulloblastoma. Again in the infantile form or age group this has a better prognosis compared to the adult patients then there was the worst form of medulloblastoma which was earlier classified as group 3 or group 4 depending on molecular and genetic analysis and these usually had bad prognosis because of presentation with metastasis in the first diagnosis or visit. So the WHO 2021 has revised this classification wherein WNT medulloblastoma stage SHH medulloblastoma continues to be similar just that this has been further subclassified into TP53 mutant and TP53 wild and the group 3 and group 4 medulloblastomas have both been grouped together into non-WNT and non-SHH type of medulloblastomas. Now for the sake of this article we wouldn't delve any further into medulloblastomas or even appendymomas. Appendymomas as per WHO 2016 classifications were classified into posterior fossa B and posterior fossa A posterior fossa A appendymomas typically were encountered at the Foramina of Lushka would extend into the CP angles and PFBA appendymoma was usually present at the obex of the fourth ventricle and was associated with better prognosis. As far as WHO 2021 classification of appendymomas is concerned it classifies appendymomas based on their anatomical location into supratentorial infratentorial or posterior fossa appendymomas and spinal appendymomas. Moving on to neuroimaging evaluation of tumor phenotype on imaging. So where can imaging help us in coming to a particular diagnosis? So these can be done by based of conventional MRI features that is T1 weighted imaging, T2 flare imaging, post contrast imaging and in addition we can use advanced techniques which can act as adherence which include diffusion weighted imaging and perfusion weighted imaging. Perfusion weighted imaging can be dynamic susceptibility contrast imaging or arterial spin labeling based perfusion techniques. So again we have seen this case in the question quiz to you before and what do we have in this first case? So this was again an elderly gentleman who had present with neurological disturbances and focal neurological deficits and we have here T1 weighted axial plane or an enhanced image that's the T2 axial image and this is the T1 post contrast image and we can see that there is a large heterogeneous mass or tumor which is epicenter in the genu of the corpus callus extending into both the cerebral hemispheres across the splemium of the corpus callus sorry it's not the genu but the splemium of the corpus callus and on T2 weighted images we can see that there are certain dark or high-pointed areas which are lining the cavity or necrotic portion of the tumor which is consistent with hemorrhage within the tumor. Again we can see that these areas are also T1 bright on the unenounced image implying that there are some areas of hemorrhage within the tumor and then on this post contrast image we can see that there is thick irregular rind of enhancement and on perfusion weighted imaging one would expect to see very high perfusion values in excess of RCBV of 1.75 where one would put an ROI on the tumor, preferentially in the enhancing portion of the tumor and in the contralateral unaffected white matter and take the ratio of these two. So this was an IDH white type of tumor that is a glioblastoma. Now this is the other end of the spectrum wherein on this T2 axial image we see a homogeneously hyper intense or bright tumor which is located along the Sylvian fissure involves the insula, the temporal lobe and the frontal lobe and on flare image we see that this tumor is suppressed partially or almost near completely and has some peripheral hyper intense rim. So what we can see over here is that there is a T2 flare mismatch that is the tumor is bright on T2 weighted images and is suppressed on flare images that is doesn't continue to be as hyper intense on flare images. So this is an important sign which has been discussed in this lower grade diffuse glioma that is the T2 flare mismatch sign and this has been shown to correlate very specifically with IDH mutant 1P19Q non-co-deleted astrocytomas which are relatively lower grade tumors than grade 4 IDH mutant astrocytomas or even glioblastomas and carry a very good prognosis and on post contrast imaging these tumors show mild to no enhancement at all. Moving on to tumor grading. Now tumor grading can be done again grossly by looking at morphological features and advanced techniques like diffusion weighted imaging and perfusion weighted imaging. On diffusion weighted imaging one can look into ADC values wherein higher grade tumors can have lower ADC values likewise lymphomas tend to show very low ADC values compared to glial neoplasms and tumors like glioblastoma which are really the highest grade tumors will show elevated perfusion value with the cutoff being an RCBV of 1.75 which has been widely explored in depth by Mengele et al in their 2003 book published in AJNR. So this is an example of a glioblastoma or high grade tumor wherein on this T1 an enhanced image you can see a heterogeneous tumor located in the right cerebral hemisphere in the right parietotemporal region. This is a susceptibility weighted image which is a form of gradient image which shows certain hypointense areas or foci which are also known as foci of blooming which represents hemorrhage within the lesion. On post-confrost T1 weighted image we can again see a thick rind of enhancement which is irregular with central non-enhancing necrotic area which is suggestive of a high grade tumor like glioblastoma and on RCBV map from dynamic susceptibility contrast perfusion we can see the ratio of the tumor to contralateral unaffected white matter is 3.5 implying this is a very high gradation. Again you can see that this the second signal intensity is that of the normal parenchyma and the ones in pink or red that is this curve number one represent the signal intensity of the first pass of contrast through the glioblastoma and what we can see here that because this is a very high grade tumor this doesn't show a complete baseline recovery that is the recovery doesn't go right up to that level rather it stops to somewhere around 50 percent because of presence of leaky channels of neo angiogenesis within the tumor. Next is the benign tumor which we have seen earlier tumor with T2 flare mismatch that is a low-grade IDH mutant 1P19Q non-co-deleted astrocytoma again here the tumor is bright on T2 my apologies for not presenting the flare image over here but on T1 post-contrast the tumor shows barely any enhancement or mild peripheral enhancement and on perfusion imaging we can see that the tumor is not very hyper perfused the ratio of rcpv of the tumor to the white matter is approximately 1.2 so this is a relatively lower grade tumor then the other perfusion technique which can be used for non-invasive assessment is arterial spin labeling based perfusion. Now this technique can be really good for patients with history of renal failure or patients with contrast allergies or in patients in home contrast administration is not possible perhaps because of our difficulty in getting venous access in such case one can do arterial spin labeling based perfusion provided the sequence is available on the scanner now the base modern 1.580 utility scanners come loaded with this sequence so this is a great sequence for doing a non-contrast perfusion study and it has been shown that cpf that is the cerebral blood flow measurements or matrix in arterial spin labeling correlate really well with the rcpv metric of the dynamic susceptibility contrast perfusion and again this was the case of glioblastoma which was showing very high or elevated rcpv value on dsc profusion technique and was showing corresponding elevated cbf values on the asl map this is the t2 actual image of the same case and these are the t1 post contrast images wherein again we can appreciate the thick irregular rind of enhancement with certain foci of enhancement within the tumor which can again be a case in a with glioblastomas moving on now there can be an exception to this rule of hyper perfusion one typical such exception is oligodendroglioma why so this is because oligodendrogliomas also demonstrate very high perfusion but in this scenario that elevated perfusion is related to the presence of network of capillaries within the oligodendroglioma deserving the presence of neo angiogenesis and related vessels in glioblastoma so again here we can see that the ratio of the relative cerebral blood volume of the tumor to counter lateral white matter is in excess of 1.75 obviously we can see it is about to the tune of six times roughly of that of the tumor in this scenario and here again we can see on this gradient image there are these linear hypo intensities or foci or lines of blooming which corresponds to the chicken wire type of calcification in the capillaries present in the oligodendroglioma so again this is an exception to that rule wherein not really every case which is hyper perfused is glioblastoma but then we can look at other ancillary features wherein if one finds sugar while calcification which can be better appreciated on CT scan image a cortical based tumor which is associated with thickening of the gyral folds and with which usually doesn't show significant neck crosses or hemorrhage in such cases a possibility of oligodendroglioma can be put for prospectively. Moving on the another exception is meningiomas in meningiomas tumor grading cannot be done on perfusion values this is because all meningiomas from lower grade to higher grade express EGFR and vascular endothelial growth factor which is responsible for higher vascularity in these tumors and hence most and in fact all the meningiomas have very high perfusion values so for assessing rates of meningiomas it is usually the growth rate of meningiomas which helps in assessment of the grade of meningiomas again the location of meningiomas to certain important structures like dural sinuses would imply that these meningiomas are relatively aggressive in nature than the typical convexity meningiomas. Moving on to tumor characterization now that is differentiating a tumor a glioblastoma or glioma from meningioma or from a lymphoma or any other intracranial tumor so we can make some attempt on imaging for characterization of tumor again this can be based on conventional MRI findings or advanced imaging techniques like diffusion perfusion or even diffusion tensor imaging. So diffusion tensor imaging though has not been discussed in this article so we will limit our discussion to just conventional imaging findings and advanced techniques like diffusion perfusion imaging. So this is an example this is again a case from the article by the authors wherein in that article there is a large tumor which is present in the anterior cranial fossa arising from the floor of the anterior cranial fossa which shows extensive calcifications and by virtue of this calcification this is a meningioma or was rather a meningioma in rare example and then this is another case a convexity based case towards the calvarium on this anenous CT scan gauge which is hyperdense and which doesn't show calcification. So when one doesn't encounter calcification one should consider a possibility of hemangioperisitoma as a differential for a meningioma again this doesn't negate or obviate a finding of meningioma because again higher grade meningiomas may not calcify vis-a-vis lower grade meningiomas which tend to calcify again diffusion weighted imaging. So diffusion weighted imaging is a very important tool which can allow for characterization of tumor typical example being lymphomas. So lymphomas by virtue of their high cellularity cause restriction of movement of water molecules in the interstitial space and we can see here on this axial T2 weighted image there is a tumor which is of intermediate signal intensity or signal intensity which is almost similar to that of the gray matter and on diffusion weighted imaging on the left side we can see that the tumor is restricting and extending across the entire corpus callosum and kind of encasing the lateral ventricles or traversing along the roof of the lateral ventricles and corpus callosum. So this was the case of lymphoma and again we can see the perfusion values. Remember the perfusion values which we saw for the case of glioblastoma they were very high there was poor recovery of the signal intensity poor return to baseline and there was a very high or elevated rcb value. Contrast that in cases of lymphoma these rcb values are relatively lower compared to glial neoplasms. So that can be a one differentiating factor in for narrowing down the differentials between a lymphoma and a glial neoplasm. Next is dynamic susceptibility contrast perfusion typically its percentage signal recovery which can be used for characterization of tumors. So this was an article which was published back in 2011 wherein they had shown that based on the percentage signal recovery that is the amount of return of this contrast bolus based on the signal intensity time curve to the baseline can be used to judge or estimate the grade of tumor or rather to characterize a tumor. So typically in a glial neoplasm this baseline recovery tends to be better more than 50 percent above the baseline towards the baseline. In a lymphoma there has been shown to be a phenomenon which is known as baseline overshoot which is considered to be characteristic of lymphoma. So just resuming as to how we can differentiate tumors based on the percentage signal recovery the glial tumors usually tend to have good percentage signal recovery that is they tend to reach towards the baseline. Then lymphomas demonstrate a characteristic feature which is known as a baseline overshoot that is they go over and above the baseline. This is thought to be because of interstitial leakage of contrast in cases of lymphomas where in T1 effects predominate over the T2 star effects. Standard metastasis these you have poor baseline recovery that is the return of signal after the passage of contrast bolus is less than 50 percent of what had of the signal dip. So that is how percentage signal recovery can be used to differentiate between tumors. Moving on now we discuss evaluation of tumor genotype. So we had discussed this feature before the T2 flare mismatch sign which is quite a specific feature for identifying a tumor genotype based on MR morphology that is a tumor which is nearly homogeneously hyper intense of bright on T2 weighted axial images is here completely suppressed on flare images with a small peripheral rim of hyper intensity on flare. So that is the T2 flare mismatch sign and then again these tumors have very minimal enhancement or even no enhancement at times and barely show any elevated for fusion values. So these are the RCBB map from dynamic susceptibility weighted contrast imaging or perfusion imaging wherein we can see that there are no elevated areas of blood flow or blood volume in the tumor and on the diffusion weighted imaging these tumors don't restrict. So usually tumors with restrict are lymphoma and then in post treatment scenario wherein there is tumor recurrence there will be increased cellularity and there might be restriction of diffusion. So this is one such tumor entity which can be prospectively diagnosed based on imaging alone. The other tumor entities described earlier was oligodendro glioma which by virtue of presence of the chicken wire calcification can be prospectively characterized as IDH mutant 1P19 cube co-deleted tumor. Then we saw the IDH mutant astrocytoma and finally glioblastoma IDH wild type which has thick peripheral irregular rind of enhancement with central necrotic areas and hemorrhage which are really the gross imaging features of histopathology which would show microvascular proliferation necrosis and hemorrhage within the tumor. Moving on now we go on to assess the post treatment changes or rather response assessment in brain tumor. So recently the response assessment criteria for brain tumor was defined by RANO group that is the response assessment in neuroancology which involves measuring the tumor in two axial dimensions and adding those axial dimensions. So this has been formulated for clinical trial and has been inculcated into clinical practice to some extent but again because of its tedious nature it hasn't really found a prime time in the clinical radiology scene. So the next step was BT RAT that is the brain tumor reporting and data systems which is akin to the conventional or classic bi RAT for breast cancer imaging or for example bi RAT and prostate imaging, lyrat and liver imaging so on and so forth. So how does one assess post treatment changes? So classically the post treatment changes can be appreciated in the early to early delayed phase after administration of radiotherapy and chemotherapy in patient with operated case of brain tumor and what one can see here is that this was an operated case of blastoma and we can see that in the early period that is after about three to four months of radiotherapy the imaging showed this irregular feathery kind of enhancement or the so-called switch is pattern of enhancement which is which can be seen frequently with radio necrosis or radiation necrosis in tumor. Again this can also be a feature of pseudo preparation which can be encountered in patients receiving hemozolomide chemotherapy and radiotherapy and on DAC contrast imaging we can see some reassuring RGB values wherein in this tumor we can see the RGB value is lower it is about 0.4. So this is an inverted map wherein the red areas are really the hypo or reduced perfusion areas and the blue areas are hyper or increased perfusion areas. So that is the perfusion of the normal brain parenchyma in the left cerebral hemisphere and that is the abnormal or the tumor areas. So this is abnormal this was normal. Moving on so this is another case a case of in fact oligodendroglioma who was operated and in the postoperative and post radiotherapy period on this follow-up study we can see that there is this irregular post contrast enhancement with some increase in flare signal intensity or almost similar flare signal intensity and then at further follow-up we can see that the patient is having on MRI the flare signal intensity which has reduced or stayed similar but the contrast enhancement has vanished near completely. So this is suggestive of response and this interim imaging was really pseudo progression or rather enhanced reactivity of the tissues to the agents which were administered that is radiotherapy and alkylatic chemotherapy agent. So this is how pseudo progression can be assessed and it can be best assessed on serial follow-up scans. There have been studies done which have tried to give a certain cutoff for differentiating a pseudo progression from real or true progression and these cutoff values of RCB vary from 0.9 to 2. So that is really a wide range implying that there is a lot of overlap between features of pseudo progression and actual or real progression in the post treatment setting of gliomas. So these methods are still under evaluation that is dynamic susceptibility contrast for response assessment are still under evaluation and haven't been formally incorporated yet into any of the guidelines be it rhino criteria or be it BTRAT imaging. Then there is this another example again from the author's article wherein we can see on this T1 axial post contrast enhancement there is this irregularly enhancing area which is seen in the setting of post radiotherapy and chemotherapy and this is arterial spin labeling map this area is showing a liberated effusion implying that there is some residual tumor. So if there were a follow-up in such a scenario compared to the pretreatment imaging then based on the enhancement findings and flare abnormality one would be able to categorize this as either post treatment change or stable findings or tumor progression but then as discussed earlier these would require serial follow-ups and this is another patient who had received Deversus map which is an anti angiogenic agent which is used in the setting of recurrent glioblastomas wherein all the chemotherapy arrangement has been completed in such scenarios Deversus map is usually used to tide over the abnormalities or symptoms arising from the mass effect of the tumor in these patients and this is usually because of tumor progression and associated peritumeral edema and what can one see in patients receiving Deversus map is that this drastically reduces any peritumeral edema and enhancement because of its direct action on the tumor vascularity and gives a dramatic symptom relief. However no studies to date have been able to prove its efficacy as far as overall survival is concerned. Again this agent doesn't really work that great in the setting of primary management of lymphomas that is glioblastomas or glial tumors. This is usually reserved for patients with recurrence and on perfusion as well one can see that there is complete suppression of perfusion in the patient who has received Deversus map. So that is how progression versus response versus pseudo response can be assessed. Now this is this can be said to be almost a response because we are not seeing any elevated CBF values in case of ASL perfusion in this scenario. The other technique which can be used for assessment of tumor progression versus response is FET-PET. This is an amino acid technique which employs a radio tracer called Fluoroethyl tyrosine. So this agent is really good for brain tumor imaging. This is because this agent is typically taken up by the brain tumor cells unlike FDG which is taken up by the entire brain parenchyma. So in such a scenario the brain tumor can be masked in the setting of FDG scan vis-a-vis an FET-PET scan which can be a good agent in case wherein the patient has contraindications to PET scan or there are certain anomalies in the tumor. The patient has a lot of hemorrhage and tumor which can cause susceptibility artifacts and can render DSC contrast perfusion imaging uninterpretable. Again ASL can be another good technique in the setting of hemorrhage within the tumor. Let me see if I can stop this scrolling through. So yeah. So this was the case of glioblastoma again on this FET-PET and a fusion of FET-PET MRI. We can see that there is this area of avid FET tracer uptake which is showing a tumor to white matter ratio in excess of 2. So that FET-PET the ability ratio of tumor to white matter of 2 is usually used as a cutoff. 2 to 2.5 is usually used as a cutoff for differentiating between treatment response vis-a-vis any residual or recurrent tumor. Moving on to structured reporting. Now what is structured reporting? So structured reporting employs certain radiology template and this is an attempt towards standardization of the reporting of any scans be it in any of the body area. Then again this provides a better communication between the radiology standard treating physician or surgeon. This serves as a very good checklist so that none of the pertinent findings are missed and hence there are fewer misdiagnosis and because of all the above features there is increased confidence in surgeons and treating physicians regarding decision for tumor receptability or further management of these cases. BT-RAT has made one such attempt towards standardization of follow-up of glial neoplasms who in the post-treatment settings and this is a template which is available on their website btrats.com which can be accessed by anyone. This is available for free of charge. We look at an algorithm as to how response assessment can be done in the setting of chemotherapy and radiotherapy being received in a patient who has been operated for brain tumor. So this is a very busy slide showing that algorithm but let's break it down and make it somewhat simpler. So let's say there is a patient of brain tumor who has been operated and who has been put on chemotherapy and is on follow-up and the patient curbs at the first follow-up and let's say that there is no prior imaging available. In such case we can put this or use this as a baseline study and categorize it as BT-RAT 0. Again this category is typically used in patients who have prior imaging but those are only pre-operative imaging. In the post-operative settings this can serve as a new baseline and it will be categorized as BT-RAT 0 and will be used as a baseline for subsequent follow-up studies. Say for example another patient who has been operated case of brain tumor is on chemotherapy has a prior imaging and with that prior imaging and the present follow-up imaging if there is no change in findings that would imply this is a BT-RAT category 2 that is there is no change in findings. So this can imply that there is stable residual disease or this can imply that there is post-treatment change wherein the disease has perhaps been taken care of or has been gone, reduced. So next category of assessment is mainly for patients who have been put on Bavacism map predominantly. In such cases if there is no enhancement or no mass effect and there is complete regression of flare signal and peritumeral edema then these will be assigned a criteria called BT-RAT 1A which would imply a good response to therapy. If the patient has been put on steroids and there is improvement in patient condition and imaging findings that is lack of enhancement or reduction in tumor enhancement or peritumeral edema this would be categorized as BT-RATs 1B. Again if there is improvement post-Bavacism map therapy with only improvement in enhancement but persistence of but persistence of flare signal abnormality that would be categorized as BT-RATs 1B. Can somebody tell me if I am audible? Yeah I am audible. And slides are visible right? Yes. Okay thank you. Then if the condition has been stable or there is improvement for subsequent follow-up studies for over a month then it will be again assigned a BT-RATs criteria of 1A. Now let us say that the patient has undergone radiotherapy and has undergone an imaging for certain reasons say for follow-up reasons or for certain worsening of features and if that imaging falls within the period of 90 days after initiation of therapy it is considered to be treatment related effect that is worsening of imaging findings which can imply increase in enhancement in the post-treatment setting and or increase in the flare abnormality along the operative bed or the treated tumor bed and this would be assigned a criteria of BT-RATs 3A. Next is worsening of imaging findings wherein this is seen in the settings of more than 90 days post-administration of chemotherapy. If in such settings there is worsening in either flare or enhancement but not both that would be assigned a category BT-RATs 3B. On the other hand if there is worsening of both flare that is increasing signal on flare imaging and increasing post-contrast enhancement in the post-treatment settings post 90 days of starting of treatment and if this increase in the signal abnormalities on either flare or rather both flare and ANH is less than 25% then this would still be progression but this would be BT-RATs category 3C in case this is the first search finding on the follow-up after 90 days post-administration of therapy. But if this is over a period of more than one studies or this is second or third follow-up and there is further progression or worsening of imaging findings that is in further increase in contrast enhancement, new onset epindymal enhancement or presence of new enhancing areas which has come up at a site distant from the radiotherapy portal in such scenarios this would be categorized as tumor progression that is BT-RATs 4. Again if this increase in signal is more than 25% compared to a previous study this would be categorized as BT-RATs 4. Let us look do one's exercise to understand how BT-RATs work. So this was a patient a case of glioblastoma 53 years old lady who has been operated has undergone surgery and this was the first baseline imaging post surgery. So at this instance since this is the first post-operative scan this will serve as a baseline so this would be categorized as BT-RATs 0 this will be BT-RATs 0. Then the patient came for follow-up after institution of chemotherapy that is themosolomide therapy and administration of radiotherapy and at this follow-up we see that the flare signal is unchanged along the treatment bed but there is some enhancement which is somewhat prominent compared to the prior study. So this patient was assigned a category of BT-RATs 3p that is findings are indeterminate of progression of disease versus response to therapy and his patient was advised a further follow-up. So this is how the categories can be assigned. As discussed earlier we have a prior imaging here so this was the BT-RATs 0 or baseline imaging and then on the subsequent follow-up imaging that is after administration of chemotherapy post 90 days period we can see that there is somewhat worsening in terms of a enhancement but stable flare findings and this was assigned BT-RATs category 3b. Now the same patient at further follow-up and what we can see here there is more than 25 percent increase in the flare signal there is obvious increase in the contrast enhancement which corresponds to more than 25 percent increase compared to this previous follow-up study or even baseline for that matter and then another feature which increases our diagnostic confidence of calling this progression is the elevated RCBV values. Compare this RCBV value ROI in the tumor with the control lateral side and we can see that this is approximately 2.4 implying that there is underlying tumor and progression in this case. So let us look at how this assessment can be made. So then if you recall we had prior imaging which barely had any enhancement or flare abnormality which was stable compared to the February scan and now we are comparing the March 2021 study with the October 2020 study. So we have previous imaging yes and the time since administration of chemotherapy or starting chemotherapy is more than 90 days we had seen that this was the response assessment category which was assigned during the October follow-up scan and on the current follow-up what do we see? We have both increase in flare signal abnormality along the treatment bed as well as enhancement within the tumor which is showing elevated perfusion. So more than 25 percent of both flare abnormality and enhancement hence this is Frank tumor progression BT RATS category 4. So this was a small exercise to understand how BT RATS assessment can be done and this completes the talk and I thank you all for listening patiently and daring with me during the power outage.