Digital Subtraction Angiography Technique


DSA is a way of taking images of arteries, veins and organs of the body  using complex computerised x-ray equipment. This usually requires an injection of a special ‘dye’ to highlight the blood supply to the legs, heart or other organ.  The ‘dye’ is a clear liquid which shows on x-rays due to its high density.  This ‘dye’ is harmless and will pass out of your body in your urine over the hours following your test.


In traditional angiography, we acquire images of blood vessels on films by exposing the area of interst with time-controlled x-ray energy while injecting contrast medium into the blood vessels.

The images thus obtained would also record other structure besides blood vessels as the x-ray beam passes through the body. In order to remove these distracting structures to see the vessels better, we need to acquire a mask images for subtraction. The mask image is simply an image of the same area without contrast administration. So, using manual darkroom technique, clear pictures of blood vessels are obtained by taking away the overlying background.

In DSA, the images are acquired in digital format through the computer. With the help of the computer, all images would be recorded into the computer and subtracted automatically. As a result, we can have a near-instanteous film show of the blood vessels alone after x-ray.


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