Skull views Flashcards
In AP/PA projections how do you prevent rotations of the head?
(with permission) Place finger tips on mastoid processes & lateral rims of orbits & check each side is equidistant from tabletop / grid cassette.
Align patient so that vertical centering line goes center of spinous processes
Touch your mentomeatal line
yup
What are the relative exposure factor changes from AP/PA skull exposure (which is similar to?) to lateral and AP/PA to townes?
Relative changes
AP/PA to Towne’s increase 8-10 kVp
AP/PA to lateral decrease 5-8 kVp
AP/PA skull exposure is similar to hip
What are the clinical indications for skull x-rays?
Skull fractures Gunshot wounds Metastases Multiple myeloma Paget’s disease
Glasgow Coma Scale (GCS)
neurological scale that aims to give reliable, objective way of recording conscious state of a person & assess status of CNS (central nervous system)
Used to assess level of consciousness after head injury
Lowest possible GCS is deep coma or death
Highest is fully awake person.
What are the three parts that the Glasgow Coma scale made up of?
is composed of three parts:
Best Eye Response,
Best Verbal Response,
Best Motor
When is GCS invalid?
When patients have ingested alcohol, mind altering drugs, have hypoglycemia or shock with a systolic BP of 80 or less and when they are under 4 years old.
What are the 3 X-rays done for a skull trauma series?
- HCR Lateral
- AP (Reverse Caldwell) OMBL15° - 25°
- AP Towne 30° caudal
What are the 3 x-rays done for a routine skull x-ray?
- AP axial (Towne method) 30° caudal , 411
- Lateral, 412
- PA (which one depends on clinical site protocols)
PA axial 15° or 25° to 30° (Caldwell method)
or PA 0°, 414
What do we have to do before a skull trauma x-ray?
In true trauma a LATERAL C.SPINE image is required before skull imaging to exclude cervical injury.
Imaging series may be on a stretcher or trolley with a stationary grid.
How is a trauma skull HCR performed?
elevate occiput on sponge (if ? C SP trauma place IR inferior to mattress)
side of injury closest to IR
IR & grid supported vertically
CR: horizontal (HCR)
CP: 5cm superior to EAM to include entire cranium
CR: 90 to film plane
CP: 5cm superior to EAM
You see:
Walls of cranium,
Superimposition of orbital roofs, EAMs mandibular rami.
Sphenoid sinuses and sella turcica.
MSP = parallel to IR plane
IPL = perpendicular to IR plane
IOML = perpendicular to front edge of cassette
Pad placed under chin may assist in maintaining lateral position
TRAUMA AP Axial 25o (Reverse Caldwell)
ensure no rotation or side tilt of skull
OMBL as near to 25o as possible
CR is perpendicular to IR
CP is glabella
ORBITS WILL MAGNIFY DUE TO INCREASED OID Frontal sinus Anterior Ethmoid Maxillary sinus – behind nasal septum EXPOSURE Density (mA) & contrast (algorithm & kV) allow visualisation of frontal & ethmoid sinus and bony trabeculae
TOWNES (30 degrees AP Axial)
Patient positioned as for AP skull
CR is 30 caudal (ie forms angle of 30 with OMBL)
Positioning Patient supine or erect facing tube Chin tucked so OMBL: 90 to IR plane (may need to use NOP) MSP: 90 degrees to IR plane
CR is 30 caudad
CP: 5-6cm above glabella
(approx at hairline)
IR Cassette
24x30cm placed portrait
upper border level with vertex of skull
Demonstrates
occipital bone
petrous ridges
dorsum sellae seen within foramen magnum
What are the neurological - general skull imaging?
PA O degree Projection –
AP - Townes (30o caudal CR)
Lateral
PA O degree PROJECTION
Patient skull position is OMBL 90 to IR
CR: 90 to IR plane (either HCR if pt erect or VCR if pt prone) to exit at the glabella
Demonstration
Frontal bone, anterior and lateral wall of cranium
Petrous ridges fill orbits
Posterior ethmoid air cells
Caldwell/PA 15 degrees
Position
Informed & prepared pt sits facing vertical table/bucky, with forehead & nose resting IR
Arms relaxed by side or holding bucky for support
MSP central to & at 90o to table
OMBL ZERO
Centre Point
Through the occiput to pass thru the nasion
Central ray
CR 15 degrees caudal
- IR Size
24x30cm portrait
Respiration
Arrested
Demonstration
Anterior & lateral walls of cranium, frontal bone & frontal sinuses, superior orbital margins.
Petrous ridges should fill lower third of orbit.
Frontal sinus
Anterior Ethmoid
Maxillary sinus – behind nasal septum
EXPOSURE
Density (mA) & contrast (algorithm & kV) allow visualisation the frontal & ethnoid sinus
Bony trabeculae seen
How do you do a submentovertical x-ray?
Patient faces x-ray tube with chin & neck extended. (If supine, supports are placed under back, knees flexed & head resting on vertex)
MSP: 90 degree to IR plane
OMBL: parallel to film plane
CR: 5 cephalad
NB. This is more practical than Bontrager - IOML parallel and CR = 90 degrees
Centring point is along midline, midway between the angles of mandible
Cassette
24x30cm placed portrait
Demonstration
Base of skull, petrous pyramids, mastoids, sphenoid sinuses, mandible, foramen magnum
Acromegaly
enlarged occipital protuberance prognathism (elongation of mandible), some have enlarged paranasal sinuses (esp. frontal):
75%sellar enlargement & erosion
Gigantism and acromegaly are syndromes of excessive secretion of growth hormone that are nearly always due to a pituitary adenoma. Before closure of the epiphyses, the result is gigantism. Later, the result is acromegaly, which produces distinctive facial and other features.
Diagnosis is clinical & by skull and hand imaging & measurement of growth hormone levels.
Treatment involves removal or destruction of the responsible adenoma.
