Radiography Its Role in Diagnosis

Question 1

what are exposure factors

Answer 1

1. quality = kV –> penetrating power = photon energy
2. quantity = mA –> quantity = number of photons

• increase with patient/area thickness
• will depend on body area
• exposure chart (set distance between machine and cassette/plate)

Question 2

what are the considerations when adjusting kV

Answer 2

high kV might decrease the contrast of the image

Question 3

what are the considerations of milliamperage (mA)

Answer 3

high mAs can improve the contrast

Question 4

what is compensation

Answer 4

mAs = kV + 10 divided by 2

maintains image quality

Question 5

what needs to be considered in equine radiography

Answer 5

important to keep film focal distance constant

cassette must be perpendicular to tube

Question 6

what occurs if the kV is too low or too high

Answer 6

too low: chalk bones, lack of detail, grainy

too high: over exposed, toast

Question 7

what occurs if mAs too low

Answer 7

background pale, not enough photons to darken image

Question 8

what is the focal spot size

Answer 8

x-rays don’t come from a point source –> produces penumbra (unsharpness or blurring of edges)

Question 9

how can penumbra be reduced

Answer 9

1. object to film distance (OFD) –> keep organ as close to plate as possible
2. maximize focus to film distance (FFD) –> 100cm (powerful machines), 70cm (low power), inverse square law *further away from plate the more sharp the image will be

Question 10

what is the nomenclature of radiographs

Answer 10

direction of beam

where beam enters –> exits (anatomic terms)

ex. lat-medial, cranial-caudal, dorso-ventral, rostro-caudal
ex. carpus/hock & distal –> dorsal/palmar/plantar

Question 11

what are orthogonal views

Answer 11

90 degrees to eachother

ex. lat & DV/VD or lat & CrCd

Question 12

how are teeth radiographed

Answer 12

parallel technique –> film parralel to tooth, beam perpindicular to tooth long axis

Question 13

what are oblique views in equine

Answer 13

typically 4 views

LM

DP

DPLMO

DMPLO

convention –> marker on lateral aspect

Question 14

what are the keys to good quality views

Answer 14

1. film focus distance consistent
2. plate perpindicular to primary beam
3. area of interest in centre of beam
4. area of interest parallel to plate
5. repeat radiographs increase radiation risks

Question 16

What is movement unsharpness

Answer 16

prevent movement of patient

GA, sedate, restraint

Question 18

what are the 3 conventions for viewing

Answer 18

1. if lateral view: head points to the left
2. DV/VD: of trunk are shown right side on the left
3. equine: the side marker is placed on the lateral aspect of the limb

Question 20

what are the reasons to take oblique views

Answer 20

1. very thick tissues (poor penetration ex. equine spine)
2. skyline views: specific features (ex. mandible)
3. project tissue out of the way: ventro 20° rostral-dorsocaudal oblique