Computed Tomography (CT) Angiography and Perfusion

Computed Tomographic Angiography (CTA) provides angiographic like images of the cerebral blood vessels using an intra venous contrast injection and thin-section dynamic CT scanning. Various 3-dimensional display techniques, including shaded surface display, volume rendering, and maximal intensity projection, are used to complement the conventional transaxial images. Such studies provide multiple projections of anatomically complex vascular lesions and delineate their relationships to adjacent structures.

CT Perfusion is a relatively new technique that allows the evaluation of cerebral blood perfusion by generating maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) following the injection of a small amount of intravenous contrast media. CT acquisition over time through a section of the brain is used to construct perfusion maps. CT Perfusion is useful in the non-invasive diagnosis of early stroke, evaluation of vasospasm in patients not suited to Trans Cranial Doppler (TCD) and in tumour/ radiation necrosis changes.

NIISwa advocates the ALARA principle (As Low as Reasonably Achievable) in all cases involving radiation i.e. many dose reduction strategies in both CT and angiography procedures are implemented whilst maintaining image quality.