Question

Regarding digital subtraction angiography (DSA):

a. It is a high-dose technique with a lower dose of contrast medium

b. Misregistration is more prominent at the boundaries between low-contrast details

c. Pixel shifting can be done for each movement in the field of view

d. The signals of the contrast and mask images are converted into their logarithms prior to subtraction because of the exponential nature of the attenuation

e. Taking several mask and contrast images, with later subtraction according to the table position, will need less examination time but more contrast medium

Answer 1

a. True.

b. False. Misregistration is caused by movement, particularly at the boundaries between high-contrast details, e.g. bone edges.

c. False. Pixel shifting can be done over the full area of the image and does not allow for differential movement within the field of view.

d. True.

e. False. Most DSA allows acquisition of several mask and contrast images along the full length by table movement. The table position is recorded for each contrast image. The system will subtract the appropriate mask image according to the table position. The advantages of this method are less contrast medium and less time required for examination.