The calculation of brain mean transit time (t-bar) using IADSA and its clinical application

It is important to know cerebral blood dynamics of cerebral infarcts. Intra-arterial Digital Subtraction Angiography (IADSA) is widely used in cerebrovascular diseases because of its superority in high sensitivity of time and contrast medium, and time-density curves of any area can be given easily at real time by A/D converter. Brain mean transit time (t-bar) (which means time from internal carotid artery to internal jugular vein) and partial brain mean transit time (t-bar p) (which means time from internal carotid artery to cortical area in the middle cerebral artery) were calculated in the damaged hemisphere and non-damaged one by time-density curves using Hamilton's dye dilution method in 84 middle cerebral artery infarcts. We discussed clinical application of t-bar and t-bar p to CT groups divided by lesion and low density area, and Activity of Daily Living (ADL). The larger the low density area is, the longer t-bar becomes prolonged both in the damaged hemisphere and the opposite one. t-bar was mutually correlated in all CT groups and was measured over 6.0 sec except normal group that showed 4.32 ± 0.45 sec. However t-bar p wasn't mutually correlated in CT groups and ADL ones. t-bar is clinically useful compared to t-bar p because of the former reflecting physical conditions of arterial and venous vessels. The better ADL is, the shorter t-bar becomes. Excellent prognostic group and bad ones can be classified whether t-bar indicates below 6.0 sec or not. We concluded that t-bar is one of the valuable parameters which reflects cerebral blood flow and can be useful to determine prognosis of cerebrovascular patients. (author)