 Hello everyone. My topic is differentiating intracranial lesions by diffusion weighted imaging, presenting author Dr. K. Sujata Chandrasekhar, Medicity Institute of Medical Sciences, co-authors Dr. Toyaja, Dr. Swami Aupalpati and Dr. Shruti Subramanian. Introduction. Diffusion weighted imaging is a specialized magnetic resonance imaging technique that depends on the random movement of water molecules within and between the intracellular and extracellular spaces. Regents with restricted mobility of water molecules eat a greater DWMRA signal and appears bright. In apparent diffusion coefficient maps, regions that contain high water mobility appear bright. Aims and objectives. The objective of the study is to describe the imaging characteristics of intracranial lesions on diffusion weighted imaging and to compare the features of these lesions. Materials and methods. Patience. A descriptive retro-prospective study was undertaken on 50 subjects at our institution from 2019 to 2021. The MRI was done on the advice of the referring doctor and no patient was made to undergo MRI for the sole purpose of this study. Inclusion criteria. The criteria for inclusion of the patients in the study included those patients who were clinically referred for diffusion weighted MRI of the brain and were detected to have any of the following. Infarction and hypoxic ischemic injury, infective conditions, tumors like extra-axial and intraaxial demyelination, metabolic or toxic insults to the brain and degenerative disorders. Exclusion criteria. Patients who are detected to have intracranial bleed were excluded from the study. Data acquisition. Patients referred for diffusion weighted MRI of the brain underwent the examination after contraindication for MRI were excluded and consent was taken. All the MRI scans in this study were performed using a 1.5 Tesla MRI scanner. MRI protocol. MRI protocol consisted of the following. A head coil was used. Axial diffusion weighted images of the brain were obtained. Sagittal demon weighted images of the brain were obtained. Axial T2 weighted flare images of the brain were obtained. ADC images were reconstructed from the diffusion weighted image. Results. After 50 patients studied, 24 patients that's about 48% were female and 26 that's about 52% patients were male. The mean age among females was 50 years and the mean age among males was 44 years. Spectrum of intracranial lesions. Of the total cases included in this study, infarcts were the majority which constituted 30 cases, 4 cases of hypoxic ischemic encephalopathy were included, 6 cases of tumors of which 5 were intraaxial and 1 was extra-axial tumor, 3 infective conditions, 4 cases of demyelination, 2 cases of arachnoid cysts and 1 case of press. Imaging characteristics of intracranial lesions. Infarcts. In 50 cases of infarcts, acute infarcts constituted 10 cases, 10 were chronic infarcts and 10 were subacute infarcts. All cases of acute infarcts and 50% of subacute infarcts showed diffusion restriction. None of the chronic infarcts showed true diffusion restriction. So this is the image of an acute infarct showing true diffusion restriction on DWI and reversal on ADC. Tumors. Among intraaxial tumors, glioblastoma multiforme showed true diffusion restriction. None of the low-grade gliomas or anaplastic astrocytoma showed diffusion restriction. Thus DWI may help in grading gliomas. DWI also provides information of the cellularity of the tumors. 75% of medialoblastoma and 50% of lymphoma showed true diffusion restriction. These tumors are known to have high cellularity. This is the image of glioblastoma multiforme showing true diffusion restriction on DWI. Medialoblastoma showing diffusion restriction on DWI went to its high cellularity. Abscess. All cases of intracellular abscess showed true diffusion restriction. This feature of abscesses on DWI have been showed to help differentiate them from cystic or necrotic brain tumors. The cystic or necrotic component of none of the brain tumors included in this study showed diffusion restriction. So this is the image of an intracellular abscess showing diffusion restriction on DWI with areas of necrosis without showing any diffusion restriction. Cyst and cyst-like condition. Arachnoid cysts seen in this study had those signal on DWI. This helps differentiate them from epidermal cysts which are seen to have high signal on DWI. Hypoxic ischemic encephalopathy. All cases of HII showed true diffusion restriction. Thus DWI is the more sensitive imaging technique than T2-weighted imaging in the evaluation of HII. Others. Hypotensive encephalopathy, demyelination disorders and posterior reversible encephalopathy press did not show restricted diffusion reflecting absence of cytotoxic edema in these conditions. Discussion. DWI MRI provides image contrast that is different from that provided by conventional MRI sequences. It provides a technique for mapping proton contrast that reflects the microvascular environment. Thus imaging technique is sensitive to early ischemic insult. DWI is performed with a pulse sequence capable of measuring water translation over short distances. This water diffusion is much slower in certain pathological conditions as compared with normal brain. This sensitivity and specificity of DWI in detection of acute ischemia is 100%. The difference in sensitivity of DWI and conventional MRI sequences is more in the initial time period and decreased as time progresses and hence we do not see any kind of diffusion restriction in chronic infarcts. MRI imaging is the most sensitive method of detecting tumors of the brain. It is however not specific enough to determine the histological nature of most tumors. DWI can differentiate between tumor and infection and can provide information about the cellularity of the tumors thereby helping in characterization and grading of the tumors. Several studies have shown that DWI can differentiate necrotic tumors from abscesses as both can show rim-like enhancement on post-contrast images. However, it's seen that abscess cavity shows high signal intensity on DWI and a low signal on ADC image. This is not seen in the necrotic component of the brain tumors. Hypoxic ischemic injury. Diffusion weighted imaging has proved to be more sensitive than conventional MRI imaging sequences for early detection of hypoxic ischemic brain injury. Most demonetting plagues which may or may not be part of multiple sclerosis have been showed to have increased ADC values. It is very rare for a plaque to show restricted diffusion. DWI helps in differentiating arachnoid cysts from epidermis cysts by later showing diffusion restriction. These are the references I have taken for my study. Thank you.