T2* relaxation refers to decay of transverse magnetization caused by a combination of spin-spin relaxation and magnetic field inhomogeneity. T2* relaxation is seen only with gradient-echo (GRE) imaging because transverse relaxation caused by magnetic field inhomogeneities is eliminated by the 180 degrees pulse at spin-echo imaging. T2* relaxation is one of the main determinants of image contrast with GRE sequences and forms the basis for many magnetic resonance (MR) applications, such as susceptibility-weighted (SW) imaging, perfusion MR imaging, and functional MR imaging. GRE sequences can be made predominantly T2* weighted by using a low flip angle, long echo time, and long repetition time. GRE sequences with T2*-based contrast are used to depict hemorrhage, calcification, and iron deposition in various tissues and lesions. SW imaging uses phase information in addition to T2*-based contrast to exploit the magnetic susceptibility differences of the blood and of iron and calcification in various tissues. Perfusion MR imaging exploits the signal intensity decrease that occurs with the passage of a high concentration of gadopentetate dimeglumine through the microvasculature. Change in oxygen saturation during specific tasks changes the local T2*, which leads to the blood oxygen level-dependent effect seen at functional MR imaging. The basics of T2* relaxation, T2*-weighted sequences, and their clinical applications are presented, followed by the principles, techniques, and clinical uses of four T2*-based applications, including SW imaging, perfusion MR imaging, functional MR imaging, and iron overload imaging.

The inquisitiveness about what happens in the brain has been there since the beginning of humankind. Functional magnetic resonance imaging is a prominent tool which helps in the non-invasive examination, localisation as well as lateralisation of brain functions such as language, memory, etc. In recent years, there is an apparent shift in the focus of neuroscience research to studies dealing with a brain at 'resting state'. Here the spotlight is on the intrinsic activity within the brain, in the absence of any sensory or cognitive stimulus. The analyses of functional brain connectivity in the state of rest have revealed different resting state networks, which depict specific functions and varied spatial topology. However, different statistical methods have been introduced to study resting state functional magnetic resonance imaging connectivity, yet producing consistent results. In this article, we introduce the concept of resting state functional magnetic resonance imaging in detail, then discuss three most widely used methods for analysis, describe a few of the resting state networks featuring the brain regions, associated cognitive functions and clinical applications of resting state functional magnetic resonance imaging. This review aims to highlight the utility and importance of studying resting state functional magnetic resonance imaging connectivity, underlining its complementary nature to the task-based functional magnetic resonance imaging.

Susceptibility-weighted imaging is useful in differentiating and characterizing diverse brain pathologies.

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Combining PWI and DWI with conventional MR imaging increases the accuracy of pre-operative imaging grading of glial neoplasms. The rCBV measurements had the most superior diagnostic performance in predicting glioma grade. Absolute ADC values or ADC ratios were also helpful in preoperative grading of gliomas. Threshold values can be used in a clinical setting to evaluate tumors preoperatively for histologic grade and provide a means for guiding treatment and predicting postoperative patient outcome.

Endovascular treatment of direct CCFs is safe and effective and results in long-term cure.

Summary Purpose In contrast to the well‐recognized association between acute symptomatic seizures and neurocysticercosis, the association between antiepileptic drug (AED)–resistant epilepsy and calcified neurocysticercosis lesions (CNLs) is poorly understood. We studied the association between AED‐resistant epilepsy and CNLs, including the feasibility and outcome of resective surgery. Methods From the prospective database maintained at our epilepsy center, we reviewed the data of all patients with AED‐resistant epilepsy who underwent presurgical evaluation from January 2001 to July 2010 and had CNL on imaging. We used clinical, neuroimaging, and interictal, ictal, and intracranial electroencephalography (EEG) findings to determine the association between CNL and epilepsy. Suitable candidates underwent resective surgery. Key Findings Forty‐five patients fulfilled the inclusion criteria. In 17 patients, CNL was proven to be the causative lesion for AED‐resistant epilepsy (group 1); in 18 patients, CNL was associated with unilateral hippocampal sclerosis (HS; group 2); and in 10 patients, CNLs were considered as incidental lesions (group 3). In group 1 patients, CNLs were more common in frontal lobes (12/17), whereas in group 2 patients, CNLs were more commonly located in temporal lobes (11/18; p = 0.002). Group 2 patients were of a younger age at epilepsy onset than those in group 1 (8.9 ± 7.3 vs. 12.6 ± 6.8 years, p = 0.003). Perilesional gliosis was more common among patients in group 1 when compared to group 3 patients (12/17 vs. 1/10; p = 0.006). Fifteen patients underwent resective surgery. Among group 1 patients, four of five became seizure‐free following lesionectomy alone. In group 2, four patients underwent anterior temporal lobectomy (ATL) alone, of whom one became seizure‐free; five underwent ATL combined with removal of CNL (two of them after intracranial EEG and all of them became seizure‐free, whereas one patient underwent lesionectomy alone and did not become seizure‐free. Significance In endemic regions, although rare, CNLs are potential cause for AED‐resistant and surgically remediable epilepsy, as well as dual pathology. Presence of perilesional gliosis contributes to epileptogenicity of these lesions. For those patients with CNL and HS, resection of both lesions favors better chance of seizure‐free outcome.

The increased susceptibility arising out of increased deoxyhemoglobin to oxyhemoglobin ratio leads to visualization of prominent veins over the affected cerebral hemisphere on SWI.