MRI, CT, scintigraphy, ultrasonography and endoscopy

Question 1

Describe computed tomography

Answer 1

Uses x-radiation to produce highly detailed cross sectional images of patient tissues and skeletal structures

Question 2

What is the basis of CT?

Answer 2

X-radiation. Previously it had very high dose rates, but these have been reduced with advancements and the level of exposure is now similar to that of conventional xrays

Question 3

What is the Hounsfield scale?

Answer 3

A quantitative measure of radiographic density that can be applied to medical CT scanning. It is based on the radiodensity of both water and air at standard temperature and pressure

Question 4

Describe magnetic resonance imaging

Answer 4

Combines the use of magnetism and radio energy. Very sensitive and good for picking up minute changes in tissues that could indicate the start of tumours. Patients lie in the middle of a large circular magnetised tube and the machine emits radio waves. These radiowaves disorientate the body’s protons and disrupts them . This can then be picked up by the MRI machine and an image can be formed

Question 5

What is the basis of MRI?

Answer 5

Magnets and radiowaves

Question 6

What is a vital part of MRI in terms of patients?

Answer 6

The patient must be fully anaesthetised

Question 7

What percentage of a neonate’s body is made up of water?

Answer 7

80%

Question 8

What percentage of an adult’s body is made up of water?

Answer 8

60%

Question 9

What are some of the key uses of MRI?

Answer 9

• very good for soft tissue
• monitoring progression of brain tumours
• monitoring the success of radiotherapy
• planning surgery
• identifying soft tissue lesions

Question 10

What are some drawbacks of MRI?

Answer 10

The patient must be fully anaesthetised for the procedure and it is very expensive

Question 11

Define SCINTIGRAPHY

Answer 11

A technique in which a detector substance is used with a radioactive tracer to obtain an image of an organ or a record of its functioning. The pictures are not detailed, and instead it relies on use of the bodies normal physiology to produce an image

Question 12

What type of radiation is used in scintigraphy?

Answer 12

Gamma radiation - further down the electromagnetic spectrum than x-radiation and potentially more dangerous

Question 13

Define ISOTOPE

Answer 13

One of two or more atoms with the same atomic number but with different numbers of neutrons (they may have different weights)

Question 14

Define RADIOACTIVE ISOTOPE

Answer 14

An isotope with an unstable nucleus that decomposes spontaneously (radioactive decay) by emission of radiation until it is stable. Alpha, beta and gamma radiation may be produced

Question 15

Define HALF LIFE

Answer 15

The time taken for half of the nuclei within an isotope to undergo radioactive decay

Question 16

What is the half life of iodine 131?

Answer 16

8.02 days, meaning the substance will not fully leaving the patient’s system for over 16 days, which can cause problems

Question 17

Define GAMMA RADIATION

Answer 17

A member of the electromagnetic spectrum that is similar to x-radiation but with shorter wavelengths, meaning it is higher frequency and higher energy

Question 18

Define a RADIONUCLIDE

Answer 18

The radioactive isotope which can be used within medical procedures Iodine 131 and Technetium 99m are examples

Question 19

What is a common radionuclide for thyroid studies?

Answer 19

Iodine 131

Question 20

Define a RADIOPHARMACEUTICAL

Answer 20

The combination of a radionuclide with a marker. This is the substance injected into the patient in order to conduct scintigraphy

Question 21

Define a MARKER in relation to scintigraphy

Answer 21

A compound that is combined with the radionuclide - it is attracted toward certain tissues in the body e.g. HDP will target bone

Question 22

What are some of the key safety precautions that must be considered with scintigraphy?

Answer 22

• the premises must be registered for the holding and use of radioactive material
• specific areas are required for the storage and preparation of radioactive materials
• personnel should only enter radioactive areas where necessary
• waterproof gloves must be worn to avoid ingestion and the radionuclides should be drawn up behind a lead barrier, into lead lined syringes
• patient’s must be isolated for at least 24 hours following treatment. They should have a dedicated nurse and no contact

Question 23

How should solid radioactive waste be disposed of?

Answer 23

Put into marked bags for incineration
Used bedding can be stored in a safe area until radioactive material has sufficiently depleted (usually at least 3 days, radionuclide dependent)

Question 24

How should liquid radioactive waste be disposed of?

Answer 24

Must be diluted with water.

Question 25

How should gaseous radioactive waste be disposed of?

Answer 25

Ventilation should be good. Gaseous waste can be vented into the atmosphere around the building

Question 26

How long should a patient be isolated for following scintigraphy?

Answer 26

24 hours, with a dedicated nurse and no contact

Question 27

What are the applications of nuclear medicine?

Answer 27

Assesses the physiological function or activity of a particularly organ system, with very limited information of the morphology and anatomy

Question 28

Define METASTESES

Answer 28

The spread of cancer cells

Question 29

Define PRIMARY BONE TUMOUR

Answer 29

The first tumour, which will then release satellite tumours, which become metastases once they are embedded

Question 29

Define OSTEOMYELITIS

Answer 29

The bacterial inflammation of bone

Question 30

What are some specific uses of scintigraphy?

Answer 30

• viewing the GI tract, specifically oesophageal ulceration
  -motility studies (although BIPS do the same thing and are much safer)
• detection of portosystemic shunts
• early detection of osteosarcoma
• detection of osteomyelitis
• assessment of thyroid function

Question 31

What are some treatment options for cats with hyperthyroid?

Answer 31

• surgical removal (a thyroidectomy - can be difficult to remove the entire gland and prevent it from coming back)
• medication (often ineffective)
• radioactive iodine treatment

Question 32

What is used to detect radiation from isotope decay?

Answer 32

A gamma camera

Question 33

What are some requirements for using a radioactive isotope?

Answer 33

• a good, patent IV catheter
• sufficient PPE –> at least two pairs of gloves and a lead apron with a disposable one over the top
• a designated, well signed area for patients
• minimal handling of patients during and after the procedure
• isolation facilities
• a lot of operator training
• correct disposal of radioactive waste