(6) Precautions. To obtain the best results, the patient must be properly
immobilized and must suspend respiration during exposure of the films. The positioning
of the head and the centering of the CR must be done with extreme care and
exactness. The mAs selected should be such as to allow use of the shortest possible
exposure time. Arrangements must be made for the films to be processed immediately
and presented to the radiologist for reading before the patient leaves the x-ray
department. The entire procedure must be under aseptic conditions.
d. Variations of Technique.
(1) Ventriculo-encephalography. This technique is used to demonstrate
structures in the posterior fossa that cannot be shown clearly by regular
ventriculography. A certain amount of cerebrospinal fluid is withdrawn by spinal
puncture (spinal tap) and replaced with air or other suitable gas. As soon as the
required amount of fluid has been drained off and replaced with air, the various
exposures are made at the direction of the examiner.
(2) Radiopaque contrast ventriculography. In this method, a radiopaque
contrast medium is introduced into selected portions of the ventricular system of the
brain and a series of radiographs made utilizing several positions. If indicted, this
procedure is usually performed immediately following gas ventriculography.
(a) The patient is seated in the erect position in front of a vertical
fluoroscopic table unit for lateral viewing of the skull by the examiner.
(b) The patient's neck and body are flexed so that the foramen
magnum is at higher level than the vertex of the skull. The head is then rotated so that
one of the trephine openings is uppermost.
(c) Using a syringe with needle attached, the examiner introduces
approximately 2 cc of contrast medium (for example, Pantopaque) into the lateral
ventricle via the upper trephine opening.
(d) The examiner signals the specialist to engage the fluoroscopic unit
and then proceeds to maneuver the contrast agent into the third ventricle by postural
manipulation of the patient's head, neck, and body.
(e) When the contrast agent is in the third ventricle, the examiner will
signal the specialist to prepare for the required radiography.
(f) Usually, the prescribed sagittal and lateral projections are made
without changing the position of the patient's head or body. Additional projections may
be made in various other positions according to the directions of the examiner.