CTPerfusion

CT perfusion (CTP) is a dynamic CT imaging technique that evaluates cerebral blood flow by tracking an iodinated contrast bolus as it traverses the brain’s vasculature. After rapid intravenous contrast injection, a series of CT scans is acquired over roughly 60 to 90 seconds. The resulting time-attenuation curves for each voxel are analyzed with deconvolution to produce functional maps of cerebral perfusion.

The major perfusion parameters typically displayed are cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), and time to maximum (Tmax). Together, these maps reflect tissue hemodynamics and help distinguish regions of irreversibly damaged tissue from potentially salvageable tissue. In practice, CTP results are used to assess the extent of ischemic core versus penumbra and to inform treatment decisions.

In the setting of acute ischemic stroke, CT perfusion is used to identify the ischemic core (often defined by markedly reduced CBF, with CBV changes varying by methodology) and the surrounding penumbra (typically prolonged Tmax with preserved CBV). This information supports decisions about reperfusion therapy, such as intravenous thrombolysis or mechanical thrombectomy, and in some centers guides eligibility beyond standard time windows.

Limitations include radiation exposure, risk of contrast-induced nephropathy, and variability between post-processing software and thresholds. Image quality can be affected by patient motion and anatomical factors. CT perfusion should be interpreted alongside non-contrast CT and CT angiography findings, and clinical assessment.