(c) If the examination is localized to any specified region lying distal to
the proximal third of arm, again digital images are captured and digital subtraction is
applied to the images.
(d) If the object of the examination is to demonstrate the venous
channels of the upper portion of the arm, axillary, shoulder girdle, or upper thoracic
regions, then the position of the patient should be adjusted in relation to the midline of
the x-ray table so that the desired coverage will be obtained. Digital subtraction images
are captured. Identification markers are preferably placed on the tabletop.
The site of injection is rendered aseptic and local anesthesia is
(f) The injection needle is then inserted into a vein (for example, the
antecubital vein or the basilic vein for views of the hand).
(a) From 20 to 40 cc of the contrast solution, similar to that used for
arteriography, is injected at a rate of from 5 to 20 cc per second.
(b) When given the signal by the examiner, the specialist makes the
first exposure. The exact time at which this exposure is made may vary from the instant
the injection is completed to 5 or more seconds afterwards.
Additional exposures are made by direction of the examiner.
Control of respiration during exposure of films.
(a) In some cases, the patient may be instructed to suspend respiration
while the exposure is made. In other cases, he may be allowed to breathe naturally.
(b) Under certain conditions, special methods of respiration control
may be employed. For example, the patient may be instructed to inhale against the
closed glottis (Muller's maneuver) or to execute forced expiration against the closed
glottis (Valsalva's maneuver) while the exposure is being made.
(5) Digital subtraction radiography. Digital subtraction radiography is used
with automatic exposure control. With digital technology, a highly sophisticated
computer "subtracts" or removes certain anatomic structures so that the resultant image
demonstrates only the vessel(s) of interest containing contrast media. A subtracted
image appears as a reversed image and may visualize diagnostic information not
apparent on a conventional non-subtracted image.