Lecture 23- Contrast Media & Radiology

Question 1

What is contrast media ?

Answer 1

A substance used to increase the contrast of structures or fluids within the body in medical imaging.

Question 2

Which imaging techniques can contrast media be used ?

Answer 2

• CT scans
• X-rays
• ultrasounds
• MRI scans
• fluoroscopy ( most common one)

Question 3

What would be considered a negative contrast ?

Answer 3

• black on film

- this would indicate Air or Co2 or water

Question 4

What would be considered a positive contrast ?

Answer 4

• white on film

-

Question 5

What are the advantages of using contrast media ?

Answer 5

• biologically inert
• cost effective
• safe when you use a low osmolality and viscosity
• heat and chemically stable

Question 6

What is the half life of contrast media ?

Answer 6

30-60 minutes

Question 7

How is contrast media excreted ?

Answer 7

95% of it is glomerular filtered in the kidney

-

Question 8

What are the side effects of using contrast media ?

Answer 8

• reactions due to high osmolality
• endothelial damage
• vasodilation
• vascular pain
• thrombosis and thrombophlebitis

Question 9

What are the two types of reactions patients can experience due to contrast media ?

Answer 9

1) idiosyncratic reactions ( occurs within 20 minutes) - this can be classified into either a)mild b)moderate c)severe
2) non-idiosyncratic reactions which is delayed (30mins-7 days)

Question 10

Idiosyncratic reactions

Answer 10

• an unpredictable reaction which generally occurs within 20 minutes.
• they are unrelated to the dose of the contrast medium.
• the mechanism by which it is caused is ‘ anaphylactoid reaction’

Question 11

Non-idiosyncratic reactions

Answer 11

These are dose related reactions and depend on the physiological properties of the contrast medium ( eg osmolality, concentration of injected substance, volume)

• often are delayed reactions ( 30 mins -7 days)

Question 12

What to assess before you administer contrast media ?

Answer 12

1) whether the patient has had previous reactions to contrast media
2) whether they have renal disease
3) identifying any risk factors eg diabetes , dehydration , over age of 70, hypertension, sepsis .

Question 13

What is a posterior - anterior x ray ?

Answer 13

The most common projection used to take a chest x ray.

• this is where the x ray beams hit the posterior part r the chest before the anterior part.
• the patient is asked to stand with their chest against the film.
• the image viewed is like looking at the patient face to face.

Question 14

What is an anterior-posterior x ray ?

Answer 14

This is where x ray beams hit the front of the chest before they hit the back of the chest.

• patients back is placed on the film.
• the image produced is as if you are looking at the patient face to face.

Question 15

POsterior - anterior projection image of the chest

Answer 15

Insert image

Question 16

Anterior -posterior projection image

Answer 16

Insert image

Question 17

CT/MRI scan image produced

Answer 17

It is as if you are looking through the patients feet upwards

Question 18

Define nuclear medicine

Answer 18

• involves the administration of radio pharmaceuticals labelled with radioactive tracer into the patient.
• these substances have a specific affinity for body tissues.
• anatomical details is limited in these studies , nuclear medicine is useful in displaying physiological function.
• devices used : Gamma camera and the PET scanner which detects the radiation emitted by the tracer in the body.

Question 19

What are the risks of nuclear medicine ?

Answer 19

Small doses of radiation which actually have little risk.

Question 20

What are the benefits to nuclear medicine ?

Answer 20

• detect diseases in their earliest stages
• PET scans can tell whether a tumour is malignant or benign.
• prevents a patient from getting dangerously worse

Question 21

When can nuclear medicine be used ?

Answer 21

• look at the excretory function of the kidneys , blood flow to the heart muscle , iodine concentrating ability of the thyroid

Question 22

AP or PA would give a larger appearance of the heart ?

Answer 22

AP