|Brain blood flow is the blood supply by network of blood nerves to the brain. It is also known as cerebral blood flow (CBF). Arteries supplies oxygenated blood, nutrients and glucose to brain whereas veins remove lactic acid, metabolic products and carbon dioxide by carrying deoxygenated blood back to the heart. The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information. The impact factor of a journal is evaluated by dividing the number of current year citations to the source items published in that journal during the previous two years.