Viewing Radiographs

Question 1

What is computed radiography?

Answer 1

• use digital cassettes
• label with patietn data
• reusable (thousands of time)

Question 2

What is PACS?

Answer 2

picture archieving and communicating system

Question 3

What is direct digital radiography?

Answer 3

• detectors convert xrays into electrical charges
• enables portable radiographs
• no need for fixinf etc.

Question 4

What is photographic density?

Answer 4

• degree of BLACKENING
• metal is low photographic density
• over exposed rads are HIGH photo density

Question 5

What difference does photographic density make to manual and digital rads?

Answer 5

• Film screen: under/over exposures

- digital: Little effect on darkening, Noise ^ with LOW density (computer working with little data)

Question 6

How does contrast affect rads?

Answer 6

• high contrast -> loss of image data

- need some otherwise everythng would be grey

Question 7

What is resolution?

Answer 7

• degree of detail
• low resolution images described as BLURRED (not necessarily motion blur)
• double sided film -> paralax of the 2 images created on the 2 films and ^ blur

Question 8

What are the Rontgen signs?

Answer 8

• number (eg. digits)
• position (eg. retroflexed bladder in perineal hernia)
• size (indicates uniformly affected organs, eg. hypertrophy/plasia, infiltration, congestion, dilation; hypoplasia/atrophy esp. endocrine, fibrosis, hypovolaemia)
• shape (eg. scarring)
• opacity (metal/Iiodine-bone-soft tissue-fat-air)
• margination (abdomen only seen d/t fat interfaces, in young/skinny/ascites animals abdo appears grey)

Question 9

What are the 4 classical stages of film processing?

Answer 9

• development
• fixing
• washing
• drying

Question 10

What are direct (DR) and computed (CR) radiogaphy?

Answer 10

• computed cassettes still have to be read by a machine to get onto computer
• direct (eg. mobile xray units) convert xrays into electrical charges directly so instantaneous readout possible

Question 11

how does fluoroscopy differ to normal radiographs?

Answer 11

• read as a positive images (bones are black)

Question 12

Define density

Answer 12

• blackness

- black areas are radiodense, white areas are radiolucent

Question 13

Define contrast

Answer 13

• range of grey shades
• high contrast = few grey shades between black and white
• low contrast = many gray shades -> smooth gradation from black to white

Question 14

Define resolution

Answer 14

• ^ res image shows small sructures clearly
• v res = blurred
  > blur can be d/t movement, scattered radiation, fogging, cassette damage, other technical factors

Question 15

How is a film screen radiograph made?

Answer 15

• film surrounds middle bit
• middle bits fluoresce when xrays hit
• fluorescent light affects film
• latent image produced
• needs to be developed and fixed