(3) With all participants alerted and the x-ray unit in readiness for instant
exposure (the rotating anode must be at exposure speed), the examiner gives the
"Ready," signal to the specialist and injects the contrast solution at a rate of
approximately 10 cc per second. Just as the final cubic centimeter leaves the syringe,
the examiner gives the signal "Shoot," and the specialist makes the first exposure.
(4) In the absence of rapid-sequence serializing exposure apparatus, the
specialist (or an assistant) will rapidly exchange cassettes and then expose the second
film as quickly as possible. The pressure on the opposite side of the injection site is
now released. The second exposure, when executed 3 to 5 seconds after injection, will
represent the radiopaque medium passing through the venous phase of circulation.
This film is actually a type of cerebral venogram.
(5) The manner in which the next step of the procedure is carried out
depends largely upon the decision of the examiner. For example, he may order that
fronto-occipital and/or lateral projections be made addition to the AP.
(6) Exposure time should not exceed 1/4 second. The timing of the
exposures in relation to the time of injection is a vitally important point.
(7) All exposed films should be processed immediately and placed in an
illuminator for viewing by the examiner before the patient is removed from the table.
d. Variations. When direct percutaneous injection of the contrast substance is
made into the vertebral artery, the procedure is called vertebral arteriography. With
certain exceptions, the procedure is similar to that for cerebral arteriography by carotid
injection (supine position). In this case, the patient does not lie directly on the table
surface. Instead, a firm cushion (approximately 6 inches high) is placed beneath the
thoracic and pelvic regions and the head is hyperextended so that vertex of the skull
rests on the table surface. Submentovertical projections are exposed during the first
injection and such other projections as the examiner may direct during subsequent
e. Cerebral Arteriography by Use of Special Equipment. Special equipment
is used in various installations throughout the Army, such as automatic biplane C-arm
image intensifiers, with a digital subtraction capability used to demonstrate any part of
the cerebral anatomy. Notwithstanding the complexity of this type of apparatus, the
procedural principles are basically the same as when conventional equipment is used.