Imaging of cancer

Question 1

What structure in the body are barium contrasts primarily used to show?

Answer 1

Gastro-intestinal tract

Question 2

How do contrasts, such as barium sulphate, appear on a radiograph?

Answer 2

White

unless inversed image

Question 3

Although they’re rarely used, what are barium enema’s used to study?

Answer 3

Large bowel

Question 4

What are the types of cross-sectional imaging methods?

Answer 4

MRI
CT
PET

Question 5

In what plane do CT, MRI and PET scanners take images?

Answer 5

Axial (usually)

Question 6

What are Hounsfield’s units?

Answer 6

Attenuation values for x-rays, of different substances

Relative to that of water

Question 7

Air has a Hounsfield unit of:

a) +1000
b) -1000

Answer 7

b ( -1000 )

If it’s easy to pass through, it’s negative

If it is denser/better at absorbing - positive

Question 8

What natural substance in the body has the highest Hounsfield unit?

Answer 8

Bone

+700 to +3000

Question 9

What is the difference between a pixel and a voxel, and what are voxels used for?

Answer 9

Voxel is in the 3D plane, pixel is 2D

Used in 3D constructions of images taken from CT scans etc

Question 10

Describe the oral contrast that is used in CT scanning.

Answer 10

Dilute iodine based contrast

Called gastrografin

Outline gastrointestinal tract

Not used much nowadays - scanners more effective

Question 11

What contrast agent is used intravenously in CT scanning?

Describe it’s effectiveness

Answer 11

Iodine based contrast

Called omnipaque

Shows blood vessels and vascularity of different tissues

Question 12

What risk is associated with the IV contrasts in CT’s?

Answer 12

Risk of allergic/anaphylactic reaction

Question 13

What is the difference between a T1 and a T4 tumour?

Dont really need to know this in much detail

Answer 13

T1 is small and hasn’t really invaded/spread to much tissue

T4 has spread to adjacent tissues

Question 14

Different sites of malignancy can be imaged using different techniques, for a variety of reasons.

What two sites of malignancy can only be imaged using MRI scanners, and not CT?

Answer 14

Spinal chord

Lymphomas of the CNS/MSK (not a ‘site’ but you get the point)

Question 15

Aside from diagnosis, how is CT imaging used (in relation to cancers)?

Answer 15

Response to treatment

Checking for relapse

Checking progression of disease

Question 16

What does ALARA stand for, and what is the ALARA principle used for?

Answer 16

‘As Low As Reasonably Possible’

CT = fuck ton of x-rays = bad

To minimise risk of causing more harm (cancer) to the patient - examination should only be when:

• Necessary
• More information essential for appropriate protocol

Repeat examinations should be avoided

Question 17

In MRI imaging, protons (H+) have their poles lined up with a strong magnetic field.

When they relax from this fixed alignment (and release energy), different molecules take a different amount of time to ‘relax’.

What is the trend in the time taken to relax, and the molecular ‘size’?

Answer 17

Heavier molecules - quick to relax

Lighter molecules - take longer

(Fat people are quicker to relax than fit, lighter people)

Question 18

Describe the positives of MRI scanning?

Answer 18

Show bone and soft tissue in great detail

Show blood vessels

Imaging of the brain, spine, muscoloskeletal, abdomen, pelvis and cardiac

Question 19

What is the main contrast used in MRI imaging?

Answer 19

Gadolinium DTPA

Question 20

What cancers are screened for in the UK?

Answer 20

Breast
Colon
Cervical