 Hello everyone. I am Dr. Vanti Gulhane and I specialize in cardiovascular imaging. Today I am going to discuss a somewhat new but a rather important topic and a technical advancement that is T1 mapping in cardiac MR. Let us begin by discussing this case. We had a few days back where T1 mapping helped establish the diagnosis and solve the diagnostic dilemma. This was a 60-year-old man with a history of acute chest pain, ventricular tachycardia and hypertension. ECHO was done and it showed regional wall motion abnormalities and a moderate decline in the ejection fraction. The clinical question was whether this patient has an ischemic versus a stress-induced cardiomyopathy. For this, a cardiac MR was obtained with all the routine sequences. The short axis cine in this patient showed thinning and achinosis of the lateral wall and there was mild thickening and hypokinosis of the septum. The PSIR sequence showed a transmural infarction of the lateral wall. Now there was no enhancement in the septum to explain the hypokinosis of the septum in this patient and hence a T1 mapping was obtained. The T1 map demonstrated elevated native T1 values in the septum as well as the lateral wall. Now the LG distribution obviously pointed to the most consistent diagnosis of a prior diagonal or an LCX infarction. However, it was the native T1 value which was the clencher of the diagnosis in this patient, its elevation representing myocardial edema and thus recent myocarditis which explained his symptoms of acute chest pain. The extracellular volume was elevated at 31% which further supports the diagnosis. ECHO showed a gradual improvement in the ejection fraction in this patient over a period of one week which sealed the deal that he in fact had acute myocarditis. And thus this case proves a point that T1 mapping can be used and helpful to identify and establish the diagnosis in patients with diagnostic dilemmas such as this patient. Now before we begin to discuss the detail of T1 mapping we need to know the types of myocardial fibrosis. There are two types one is the interstitial fibrosis, second is the replacement fibrosis. Replacement fibrosis occurs in patients of infarctions. Interstitial fibrosis has two subtypes reactive and infiltrative fibrosis. The reactive fibrosis is seen in patients with hypertension, dilated cardiomyopathy, volume and pressure overload conditions. Infiltrative fibrosis occurs in patients having amyloidosis and andes infibrates disease. Now it has been known that the diseases characterized by diffuse myocardial fibrosis cannot be evaluated by late gadolinium enhancement imaging as there are no reference regions of the normal myocardium. In this patient comes the role of T1 mapping. Now what is a T1 map? It is a parametric reconstructed image where each pixel's intensity directly corresponds to the T1 relaxation time of the myocardial voxel. This enables quantification of diffuse myocardial fibrosis in cases where LGE does not give an answer. The native T1 value reflects myocardial disease involving the myocyte and the interstitium. The use of gadolinium allows measurement of the extracellular volume fraction which reflects the interstitial space. T1 values can be obtained by different techniques. For example, the inversion recovery as well as the saturation recovery techniques. This is an example of an inversion recovery sequence where different T1 weighted source images were obtained and the pixel intensity of these images were fitted on the T1 recovery curve to obtain the final T1 map. The most popular sequence supplied by the vendors is the MOLI or the Modified Looklocker Inversion Recovery Sequence and its popular variation. Then there is MOLI or the Short-End MOLI where we reduce the time for acquisition. Sasha and Sapphire are saturation based recovery sequences. Extracellular volume fraction can be calculated by administration of gadolinium and obtaining the post-contrast T1 values but they can be influenced by number of factors. We optimize for hematocrit values by using the following formula of the extracellular volume estimation. We need to know what are the normal values of the ECV. It is average 0.25 in volunteers less than 40 years and 0.32 in those more than 60 years of age. Now how to obtain the T1 value? All you need to do is put an ROI in the myocardium in a native T1 map. In order to obtain an extracellular volume you need to put ROIs on the septum as well as the blood pool in the native T1 as well as the post-contrast T1 values and then put those values in the equation and obtain the extracellular volume for a particular patient. Now we need to know the conditions which affect the T1 mapping in ECV values in clinical practice. First being lipomatous metaplasia where there is severe reduction in the T1 values as well as the ECV. Then fibrous disease and iron overload conditions should drop in the T1 values but a normal extracellular volume. In patients with HCM and DCM there is mildly elevated T1 values and near normal ECV. Patients with acute myocarditis have moderate elevation of the T1 values as well as the ECV. Finally the most important to remember is that patients of amyloidosis show the highest increase in the T1 values as well as extracellular volumes and highest values of the T1 mapping will be seen in patients of acute myocardial infarction. Now coming to few more examples this is a patient with HCM who showed enhancement in the superior and inferior RV insertion points but not much in the septum but a T1 mapping showed an elevated T1 values in the septum as well identifying myocardial fibrosis. Another patient with acute myocardial infarction showed only a subendocardial infarct in the inferior RV. However the T1 mapping identified a rather larger area at risk in this patient. Another example of a patient with amyloidosis which shows a significantly increased native T1 values. Thus it may be implied that a non-contrast T1 mapping may be even more sensitive alternative to late gadolinium enhancement. It has been shown that native T1 performed better than post-contrast T1 and ECV measurements and compared with LGE T1 maps eliminate the influence of windowing and variations in the signal enhancement by directly measuring the underlying T1 relaxation times. We need to know the limitations of the T1 mapping. First of all T1 maps rely on anatomy being aligned between all the images hence the need for motion correction. Secondly it is important to standardize the T1 methodology at each institution and to determine the range of normal T1 values at your scanner. Finally we need to know what is a normal T1 value whether it is a 1.5 Tesla system or a 3 Tesla system it has been found that the normal native T1 value is in the range of 1 second or 1000 milliseconds it is a little lesser for 1.5T and a little more for 3T and the take home message. First is that the identification of diffuse mercurial fibrosis and edema is now possible with T1 mapping which may not be detected by late gadolinium enhancement. The technique is highly reproducible highly sensitive as compared to LGE to a point that now it is being called as a non-invasive myocardial biopsy technique. It also serves as a promising alternative to late gadolinium enhancement in chronic kidney disease. Thank you for your attention.