week 3, lec 2- patient prep and contrast

Question 1

what are 3 types of contrast

Answer 1

oral
intravenous
intra articular

Question 2

when is ooral contrast mainly used

Answer 2

abdominal scans

- occasionally neck and chest when looking at upper GIT

Question 3

why is contrast used in CT

Answer 3

to better delineate between anatomical structures and make interpretation easier
-Contrast is a vital tool in optimally visualising many anatomical structures

Question 4

what is an ionic contrast agent?

Answer 4

molecules will separate into charged particles (ions) when placed in an aqueous solution.

Question 5

what is a non-ionic contrast agent

Answer 5

will not separate and form ions when placed in an aqueous solution

Question 6

how should contrast be stored?

Answer 6

• In a cupboard away from direct sunlight and other sources of radiation
• Temperature: 20 degrees
• Stock should be kept in its original packaging until ready to use
• As new stock arrives place it to the back and move older stock forward. Contrast has an exp date so use the older ones first

Question 7

how and why is contrast warmed

Answer 7

Contrast media warmers:
- kept at a stable 37 deg C
This decreases the viscosity allowing for easier injection, lower pressures and a reduced risk of extravasation

Question 8

what should be included in the ‘before the scan checklist’?

Answer 8

• Do we have the right patient?
• Does the request match the symptoms?
• Does the patient consent to the test?
• What area of the body is being scanned?
• What pathology is being queried?
• Is contrast required?
• What contrast timing is required?
• Is this the best test?

Question 9

what are the patient considerations when administering contrast

Answer 9

• Fast the patient
• informed patient consent
• Pt must complete contrast questionnaire
• Check renal function
• Explain potential risks
• Explain common sensations
• Post procedure leave cannula in for 15-30 min in case of delayed reaction
• Let pt go to toilet and give them water to drink
• Inpatients should be monitored on the ward post contrast

Question 10

patient prep for head/ neck examinations

Answer 10

removal of all jewellery and hair accessories

Question 11

patient prep for chest, abdo and spine examinations

Answer 11

change into patient gown if not appropriately dressed
removal of all body piercings
belts and zippers

Question 12

patient prep for extremity examinations

Answer 12

removal of shoes and socks

removal of orthopaedic splints or braces

Question 13

pre scan checklist

Answer 13

• Request form correct
• Contrast form filled in
• Check for previous imaging
• Informed consent
• Procedure explanation
• Remove metal from area to be scanned if possible
• Check with patient that prep has been carried out
• Cannulate patient if contrast required

Question 14

what is needed to perform cannulation

Answer 14

• Correct training and certification
• Understanding aseptic technique
• Choosing the correct size cannula for the examination
• Knowing where to cannulate; cubital fossa, wrist

Question 15

what size cannulas are used for what

Answer 15

24g: paeds, chemo
22g: small veins, chemo, IVDU, elderly
20g: stock standard
18g: any CT requiring a high flow rate (CT angio)

Question 16

what are the two methods of IV contrast delivery

Answer 16

manual hand injection

motorised pressure injectors

Question 17

when do we use contrast?

Answer 17

Use of contrast may be indicated any time it increases the diagnostic value of the scan to answer the clinical question

Question 18

contraindications to administering contrast

Answer 18

allergic to iodine
renal failure (if not on dialysis)
previous contrast reactions
hyperthyroidism
myasthenia gravis

Question 19

what happens in a non-anaphylactic hypersensitivity reaction (8)

Answer 19

• Warmth
• Metallic taste
• Nausea
• Vomiting
• Bradycardia
• Hypotension
• Vasovagal reactions
• Neuropathy

Question 20

what happens in a moderate anaphylactic hypersensitivity reaction

Answer 20

• Persistence of mild symptoms
• Facial or laryngeal oedema
• Bronchospasm
• Dyspnoea
• Tachycardia
• Bradycardia

Question 21

what happens in a severe anaphylactic hypersensitivity reaction (8)

Answer 21

• Life-threatening arrhythmias
• Hypotension
• Overt bronchospasm
• Laryngeal oedema
• Pulmonary oedema
• Seizure
• Syncope
• Death

Question 22

what is extravasation of a vein and how is it treated

Answer 22

where contrast is administered into the sub cutaneous tissues and not into the blood stream
-Treated with cold packs and elevation

Question 23

technical considerations when using contrast

Answer 23

• Understand why you’re using contrast
• What anatomical structures are you trying to enhance
• What stage will optimal enhancement occur
• This will determine timing of scan post contrast
• Are multiple phases required
• Are multiple types of contrast required for optimal scan
• Automatic vs Hand injection
• Flow rate
• Always consider Risk vs Benefit

Question 24

steps to consider when performing a scan

Answer 24

• Position patient in gantry
• Cannulate and set up contrast if required
• Select patient from worklist / type in details
• Select patient orientation
• Select protocol
• Contrast? Rate, volume, timing?
• Scout for planning
• Plan then perform scan.

Question 25

artefacts seen in CT

Answer 25

patient motion
metal
partial volume
beam hardening
noise induced

Question 26

post scan check

Answer 26

• Is the patient OK?
• Have we covered all the required anatomy?
• Are there any obvious artefacts?
• If so will they hinder diagnosis?
• If contrast used, was the bolus and timing of the scan adequate? Any sign of contrast reaction?
• Wait for any sign of delayed reaction
• Remove cannula and ensure any bleeding stops
• Process images
• Prepare room for next patient