 Good evening. It's my pleasure and honor to be part of this course. And I would like to thank Dr. Patko and Dr. Verma for inviting me to talk about characterization of renal masses with MRI. Unfortunately, incidence of renal cancer has increased by 30 to 40 percent over the last 30 years or so. And this is predominantly due to incidental lesions due to increased imaging with ultrasound and CT scan. Although most of these lesions are less than four centimeters, increase in diagnosis has not resulted in better clinical outcome. In fact, the reported increased mortality from 1.5 to 6.5 deaths per 100,000. And this is predominantly due to over diagnosis and surgeries and aggressive management, even slow-growing tumors which may or may not show growth over the time. As we know, ultrasound is very cost-effective. It is very diagnostic for simple cyst. However, it has its limitations with smaller lesions. Patients body have it as characterized in complex cystic masses, differentiating from complex cystic masses to solid lesions and cannot stage the disease. CT scan is very sensitive and specific for renal masses greater than two centimeters in diameter. However, it does have its own limitations in complex cysts, cyst-containing hemorrhage of protein, lesion size, intraparent camel lesions that cannot be measured accurately as far as harmful density is concerned because of volume averaging and misregistration artifacts. It can be limited with renal function. So that's where MR comes in. MR has got excellent soft tissue contrast due to which we can use multiple sequences and parameters to characterize the renal lesions. We do not need iodinated contrast. Some of the patients who have allergies can be still scanned with this. In cases of renal insufficiency, now with newer microcyclic agents, we can give IV contrast even in in-stage renal failures. First of all, technique. Technique is very important. Our MR protocol is same for all abdomens. It has coronal T2, axial T2 fat sat, gradient taker in and out of phase imaging, DWI and coronal and axial Dixon. Post contrast, we typically do all these sequences in in arterial venous, three-minute delay, five-minute delay in coronal, and for all we do subtractions as well. The many sequences that can really make difference in diagnosing renal as well as liver lesions is subtraction in and out of phase and fat sat. Remember that for renal tumors, fat is your friend and diffusion-veteran images. As far as subtraction technique is concerned, it is grossly underutilized. It drives me crazy when I see outside scans where subtraction is not done. This is very simple. You just have to push a button and machine does it for you. There is no extra table time or patient time. I think it's crime not to do subtraction sequences when it is so easily available and it makes a lot of difference in characterizing these lesions. So essentially in this, you are subtracting pre-contrast images from post-contrast images. So it will subtract out the hemorrhage, hyperintensity within the lesion and it will just give you a pure enhancement within the lesion, which helps you a lot. So for example, in this patient, this is a lesion with slightly hyperdensity. There's peripheral calcification following intravenous IV contras. There is no way of measuring how much this lesion is enhancing. Same thing with MRI. You can see on T2-rated images, it is slightly, it is hyperintense. So on pre-contrast even, it is markedly hyperintense indicating hemorrhage or protein-ish material with IV contrast. You cannot exactly determine whether this is contrast or the hemorrhage within the lesion. But when you do subtraction, you can see this ugly nodule within this cyst, which was a papillary renal cell carcinoma, which would have been difficult to diagnose either on the CT images or non-subtracted images. So subtraction technique is very important. Another lesion here on CT scan, without contrast, arterial phase, portal venous phase or nephrographic corticometallia nephrographic phase. We don't know what is whether this lesion is enhancing or not. But on MRI, you can see that on T2-rated images, there is some heterogeneity within the lesion. On pre-contrast images, there is area of hemorrhage. But with IV contrast, we don't know how much of it is enhancing. On subtraction, you can clearly see that it has got low-level enhancement. This was another papillary renal cell carcinoma. This was a 50-year-old patient. It shows an ugly-looking, bilabilated lesion with hyperintensity on T1 pre-contrast-rated images. Even on T2-rated images, the lesion looks extremely ugly. But with IV contrast, you don't know whether this lesion is enhancing or not. But on subtraction images, you can clearly see that this is just a hemorrhagic lesion. There is no abnormal enhancement within it. We followed this lesion for three years and you can see that there is hardly change in this lesion. There is still some hemorrhage. It is still looking ugly. But there is no enhancement on subtraction images which saved nephrectomy for this patient. This was a high-grade papillary renal cell carcinoma. You can see that this lesion has got extensive hemorrhage within the lesion. This area, we don't know what is happening with IV contrast without subtraction. We don't know whether this area is enhancing or not. On subtraction images, you can see really ugly-looking papillary renal cell carcinoma which can be easily diagnosed once we subtract that hemorrhage. So subtraction, very important for diagnosing tumors. How about in and out of phase imaging? This is especially diagnostic for angiomyelipomas and some of the clear cell renal cell carcinomas. Let's see how we can diagnose those. Angiomyelipomas come in different flavors. They can be very fatty like this where you are going to get this indian artifact at the fat water interface. This is diagnostic of angiomyelipoma. You can also see that there is fat here which is going to suppress on fat-side images. Another lesion intraperenchymal angiomyelipoma is going to show that indian artifact all around it as well as chemical shift artifact. Some of the lesions could be tiny which will completely show dropout on out of phase imaging. If there are lesions containing less fat, then that portion of the lesion is going to show dropout on out of phase imaging. However, the problem comes when there is a lipid poor AML or clear cell carcinomas in and out of phase imaging. However, it has been shown that the lipid poor angiomyelipoma is trained to follow signal of suase muscle on in phase and they will show areas of drop in signal on out of phase depending on how much fat contained is within the lesion. Whereas in renal cell carcinoma, they usually follow the perenchymal intensity on in phase and on out of phase due to intra cytoplasmic fat that is microscopic fat is going to show uniform drop in signal which is very characteristic of clear cell renal cell carcinoma. This is a clear cell renal cell carcinoma in phase, out of phase. Although this tumor looks slightly heterogeneous, you can see that on out of phase imaging there is uniform drop in signal and that's because of intra cytoplasmic flat seen in this lesion which is very typical. In lipid poor angiomyelipoma again we can see that it follows the signal of suase on in phase, on out of phase there are areas of drop in signal within it due to fatty tissue within the lesion but it really depends on how much fat is within the lesion. This is lipid rich angiomyelipoma which follows the signal of surrounding fat. You can see it is getting saturated on fat sequences and out of phase imaging it shows areas of drop in signal typical for lipid rich angiomyelipoma. How about diffusion ADC sequences? This is especially helpful in differentiating cystic benign lesions from cystic renal cell cancers, can differentiate benign from malignant renal tumors, may be helpful in differentiating histologic subtype or grading the severity of the tumor DWI is also useful in patients if you cannot give gadolinium and that might be your only chance to grade the tumor. So here is a low grade oncocytoma which shows hardly any restriction whereas this is a clear cell renal cell carcinoma you can see how much restriction is there and low ADC so very helpful. So let's go through a couple of scenarios to run through different types of tumors and where MR is going to be helpful in diagnosing this lesion. So scenario one MR can be helpful to further characterize lesion where initial CT protocol was not adequate. So this patient had CT scan without contrast and you can see that this patient has got multiple renal lesions except one probably rest of the lesions are not characterized on this non-contrast CT scan. You can go ahead and do CT protocol with arterial venous phase however still there are going to be some lesions which are not going to be characterized as you can see on this MRI that all these lesions look cystic some of this lesion for example this one is hemorrhagic lesion there is small hemorrhagic lesion here which would problem with CT scan with and without contrast but on MRI we can show that all these lesions are benign and this patient does not need to follow or any other study. This patient had CTA examination which showed an indeterminate lesion here we went ahead and did MRI in this patient and we can see there's this lesion which was not characterized on with contrast is in fact an angiomyloeperma we detected another angiomyloeperma here these two lesions showed gross fat within it so there was no additional examination necessary in this patient. Summarizing scenario one MRI can be helpful to further characterize lesions where the initial CT scan protocol was not adequate so let's see whether MRI can be helpful in indeterminate lesion despite of adequate CT protocol so here the protocol is adequate but still the lesions could be non-diagnostic because in homogeneous lesion if there is intermediate change in density that is increase in density less than 20 harmful unit but more than 10 harmful unit then those lesions are going to be indeterminate whereas if it is a heterogeneous lesion then it's going to be difficult to exclude smaller nodular areas within the lesion so this is a renal mass or renal lesion here you cannot see it on pre-contrast but there was a 90 harmful unit increase in density from pre-contrast to post-contrast which is non-diagnostic so this is indeterminate lesion we are also to remember that smaller cysts which are intraperin thymol in central in location can give false reading because of partial volumic artifact for those smaller lesions within the renal perinchama in this patient we went ahead and did MRI and we can see that on T2-8 images it's a cystic lesion there's some internal density on pre-contrast T1 but however on post-contrast images as well as on subtraction there is no enhancement this is a lesion containing mild hemorrhage so advantage of MRI in such patients is we don't have to worry about pseudo enhancement we have subtraction images to subtract out the protein or hemorrhage within the lesion and we got very sensitive fluid sequences which can help us diagnosing this cystic indeterminate lesions this was a indeterminate lesion as this lesion was kind of bioloped or triloped and we can see following administration of IV contras you can see some septations within it is there some nodularity within it so this was at least two effligions by Bosnay classification on MRI we can see this portion of the cyst has got dense hemorrhage the other portion of the cyst did not have any hemorrhage and is an enhancing nodule which was diagnostic of early cystic renal cell carcinoma in this in this patient so MR is sensitive for detection of enhancing nodules in cystic renal lesions it upgraded 73% of patients on this study it had 95% positive predictive value for malignancy with enhancing mural nodules scenario number three how about CT protocol is adequate lesion is enhancing but the diagnosis is uncertain so in this the lesion is not fully evaluated with CT scan for example this patient which was a fat poor AML but based on multiple sequences and enhancement pattern and diffusion weighted images as well as in and out of phase images MR can characterize many of these lesions so wrapping up MRI is indicated in evaluation of indeterminate renal masses on CT and ultrasound and provide additional diagnostic information which can be helpful in diagnosing and managing these patients MR imaging is particularly helpful in distinguishing solid from cystic lesions when enhancement of renal masses is questionable especially for those where net enhancement on CT is between 10 and 20 harmful units so we can either upgrade or downgrade basneq 2f lesions so that these patients do not have to go for for follow-up examination every six months to one year for two and a half to three years diffusion weighted imaging and dynamic contrast NES imaging can provide specific information regarding tumor histology and staging MR is especially useful for too small to characterize lesions there are not going to be any lesions which are too small to characterize on MRI lesions with low level of NES pet hemorrhagic lesions and complex cyst thank you