MAS

Question 1

o What is kV?

Answer 1

 is the energy difference applied across the tube, affecting the energy of exiting X-ray photons

Question 2

o How can you tell if an image has an appropriate kV?

Answer 2

 Good contrast (0.5), told by the fact that cortical bone and trabecular bone can be differentiated, and the retrocardiac silhouette/ behind the heart (0.5)

Question 3

o What does “p” stand for in kVp? And what is the difference between kV and kVp?

Answer 3

 P in kVp stands for peak, indicating the highest energy photon’s energy level in the exposure.

Question 4

o What is mA ?

Answer 4

 is the current applied to the cathode, affecting the amount of electrons produced by thermionic emission and thus number of exiting X-ray photons

Question 5

o How can you tell if an image has an appropriate mA?

Answer 5

 Sufficient photons have reached the image receptor (0.5),
 Indicated by minimal signs of burn out or noise (0.5)

Question 6

o What does “s” stand for in mAs?

Answer 6

 S in mAs stands for seconds, indicating the duration of the exposure.

Question 7

o How can you tell if an image has an appropriate brightness?

Answer 7

 visualise anatomical structures.

Question 8

o How can you tell if an image has an appropriate sharpness?

Answer 8

 sharp cortical outlines shown (1)

Question 9

• What is the effect of this on the image?
  o High kVp

Answer 9

too much penetration, image burn

Question 10

o Low kVp

Answer 10

lack of penetration, lack of contrast

Question 11

o High mAs

Answer 11

increases dose

Question 12

o Low mAs

Answer 12

low signal to noise ratio (SNR)

Question 13

PA chest

Answer 13

Horizontal central beam: at the level of the eighth thoracic vertebrae (i.e. spinous process of T7). Vertical beam: midline.
kvp- 125
mAs- 2.5

Question 14

AP abdomen

Answer 14

approximately at the level of a point located 1 cm below the line joining the iliac crests. This will ensure that the symphysis pubis is included on the image.
kvp - 75
mAs- 25

Question 15

DP hand

Answer 15

centred over the head of the third metacarpal.
kvp - 55-60
mAs- 1.6

Question 16

Oblique hand

Answer 16

centred over the head of the fifth metacarpal.
kvp - 55-60
mAs- 1.6

Question 17

DP wrist

Answer 17

central ray is centred to a point midway between the radial and ulnar styloid processes.
kvp- 60
mAs- 1.6-2

Question 18

lateral wrist

Answer 18

centred over the styloid process of the radius.

kvp - 60
mAs- 1.6-2

Question 19

AP elbow

Answer 19

vertical central ray is centred through the joint space 2.5 cm distal to the point midway between the medial and lateral epicondyles of the humerus.

kvp - 65
mAs- 2

Question 20

Lateral elbow

Answer 20

centred to the lateral epicondyle of the humerus.
kvp- 65
mAs- 2

Question 21

AP knee

Answer 21

Centre 2.5 cm below the apex of the patella through the joint space, with the central ray at 90 degrees to the long axis of the tibia.

kvp- 65
mAs- 4

Question 22

Lateral knee

Answer 22

2.5 cm inferior and medial to the apex of the patella

kvp 68
mAs 4

Question 23

AP ankle

Answer 23

perpendicular to the midpoint between the lateral and medial melleoli
kvp - 63
mAs - 2.5

Question 24

Lateral ankle

Answer 24

Centre over the medial malleolus, with the central ray at right-angles to the axis of the tibia.
kvp- 63
mAs- 2.5

Question 25

DP foot

Answer 25

central ray is directed over the cuboid-navicular joint, midway between the palpable navicular tuberosity and the tuberosity of the fifth metatarsal.

kvp- 60
mAs- 1.8

Question 26

Oblique foot

Answer 26

central ray is directed over the cuboid-navicular joint.