Contrast Radiography & Modalities

Question 1

Why is contrast radiography used and provide an example:

Answer 1

on plain radiographs two organs of simialr densities cannot be disti guished between….
E.g. different in contrast of adjacent structures in areas such as GI tract is low, so not easy to distinguish on radiograph.

Question 2

Positive - seen as…………?

Answer 2

White image

Question 3

Negative - seen as……?

Answer 3

Black image

Question 4

Is barium suplhate a positive or negative contrast media?

Answer 4

Positive contrast media

Question 5

Radio-opaque means?

Answer 5

appears white on an x-ray

Question 6

Radiolucent means…?

Answer 6

appears black on an x-ray

Question 7

What is double contrast media and why is it used?

Answer 7

• This is negative and positive contrast media together.
• usually used in bladder/GI tract
• provides excellent muscosal detail

Question 8

Explain how double contrast media works.

Answer 8

A small amount of positive contrast agent is used to coat the inner lining of the organ, which is then distended using negative contrast agent (such as air).

Question 9

What drug classification is contrast media, and what checks should be made?

Answer 9

POM-V
date and type of contrast, quantity and concentration, administartion route, warm medium, check foreign particles, aseptic procedures, record type and amount on patient record, nursing considerations (procedure specific)

Question 10

Three…..

Examples of negative contrast media:

Answer 10

• air
• carbon dioxide
• oxygen

Question 11

What does MRI stand for?

Answer 11

Magnetic resonance imaging

Question 12

What contrast media can be used for MRI?

Answer 12

Gadolinium (Gd)

Question 13

Outline the process of an MRI

Answer 13

• body tissues become magnetized-alligning proton and hydrogen atoms.
• radiofrequency coil (RF) emits pulses of radiowaves - atoms become disoriented.
• atoms emit small radiowaves themselves as they return to their normal alignment.
• emitted radiowaves detected by RF coil and transformed into image by complex algorithms.

Question 14

Patient prep for MRI

Answer 14

• GA
• patients screened for presence of metal implants and pacemakers
• collars, leads etc… removed (incl horse shoes)
• only trained staff to use MRI/monitor GA

Question 15

Advantages of MRI

Answer 15

• better for soft tissue scans (brain, spinal cord, ligaments, tendons…)
• does not use ionising radiation
• uses magnetism and radio energy
• thought to be completely safe (tho GA still needed)
• planes: transverse, sagittal, oblique, dorsal
• produces cross-sectional slices through patient tissues

Question 16

Disadvantages of MRI:

Answer 16

• high purchase and running cost
• non-ferrous GA machines, drip stands etc…
• animal must be anaesthetised as they need to be really still

Question 17

What does CT stand for?

Answer 17

Computed Tomography

Question 18

Outline CT and what it’s used for:

Answer 18

• used a computer and rotating x-ray device to create detailed, cross-sectional images, or slices of organs/body parts.
• ionising radiation is used.
• used for orthopaedic and body cavity details

Question 19

Patient Prep - CT

Answer 19

• Heavy sedation or GA
• conventual GA machine sufficient
• remote monitoring
• ## no personnel allowed to reassess patient whilst CT in use

Question 20

Why is scintigraphy used?

Answer 20

• detection of focal disease
• diagnoses abnormal conditions
• gamma camera allows hot spots of activity to be identified

Question 21

Define: acoustic window

Answer 21

area over which sound waves are applied

Question 22

Define: acoustic impedance

Answer 22

The degree of resistance to the passage of ultrasound waves

Question 23

Define: acoustic interface

Answer 23

The junction between two tissues with different impedences, waves are reflected back as echoes

Question 24

Explain how an ultrasound image is produced:

Answer 24

1. when probe is applied to skin, sound waves pass through soft tissue as pressure waves
2. at acoustic interfaces between organs a % of sound waves are reflected back to transducer
3. returning sound waves lead to deformation of the crystal
4. the change in shape is detected and converted into an electrical signal which is converted to an image on the screen.

Question 25

Define the terms: anechoic, hypoechoic, hyperechoic…

Answer 25

• anechoic - without an echo (black)
• hypoechoic - darker than usual
• hyperechoic - brighter than usual