Digital subtraction angiography (DSA) is a recently developed non-invasive intravenous angiography which has become possible through real time digital subtraction of x-ray transmission data from an image intensifier and television system. The output signals of the image intensifier-television camera system are digitized by an analogdigital converter. The digital information, 512×512 pixels and 9 bits deep, is fed into the image processing assembly after logarithmic amplification, where 2-8 frames are added and subtracted from mask images for the final digital images. Intravenous digital subtraction angiography was performed in 21 patients with intractable dizzy spells of central origin resistant to treatment. These patients showed some signs of CNS disturbance, although there were no significant findings on CT scans.
DSA results
Cases Percentage
normal 7 33.3
abnormal 14 66.7
unilateral vertebral obstruction 4 19.0
stenosis 6 28.6
reduced flow 2 9.5
bilateral vertebral stenosis 2 9.5
Surprisingly, findings were abnormal in 14 of 21 patients (66.7%).
DSA is, therefore, considered to be an important aid in the diagnosis of vertigo of the central type.