Imaging in Cancer

Question 1

Name 5 Imaging techniques used in cancer

Answer 1

PET, CT, MRI, Barium studies and radiographs

Question 2

What is usually used for cancer imaging

Answer 2

Endoscopy and biopsy or barium examination

Question 3

What does barium sulphate do

Answer 3

Outline GI tract and does not react with tissues

High atomic number absorbs more xrays and appears white

Question 4

Barium swallow

Answer 4

Oesophagus

Question 5

Barium meal

Answer 5

Stomach and duodenum (1.5mSv) and fast for 4-6 hours

Question 6

Barium follow through/ small bowel study

Answer 6

Small bowel

Question 7

Barium enema

Answer 7

Large bowel (7mSv) and have a low residue diet for 48 hours and lie on left hand side

Question 8

CT

Answer 8

Xray Produce slice of tissue in axial plane

Fan shape beam of xray

Question 9

Hounsfield (HU)

Answer 9

Attenuation coefficient measurement

Question 10

HU of distilled water

Answer 10

0HU

Question 11

Sate some HU values

Answer 11

lung = -700
Fat = -100
blood = 40
muscle = 40
Calcium = 150

Question 12

Voxel

Answer 12

Value on a regular grid in 3D and position relative to other voxel

Question 13

Pixel

Answer 13

Physical point on an image (2D)

Question 14

Contrast agent

Answer 14

Oral ( dilute iodine to outline GI) or IV ( iodine for vascularity of tissues) but IV can have problems with anaphylaxis

Question 15

Explain the ways in which imaging can help with the diagnosis and staging of cancer

Answer 15

• Presence of distant metastases and spread to lymph nodes
• Relationship to adjacent structure
• Position and depth of tumour and penetration

Question 16

CT radiation dose for chest

Answer 16

8mSv

Question 17

CT radiation dose for abdomen and pelvis

Answer 17

10mSv

Question 18

MRI and H+

Answer 18

Align H+ by strong magnetic fields in one direction

Radio frequency displaces protons and images created during the time protons take to relax and realign

Question 19

What is MRI used to see

Answer 19

Bone and fat
Soft tissue
Vessels and heart

Question 20

Drawback of MRI

Answer 20

Loud, noisy and claustrophobic
Can create a “ghost” due to fluid movement which can mimic pathology
Cannot image patients with pacemakers or aneurysm clips

Question 21

MRI contrast agent

Answer 21

Gadolinium DTPA (IV)
Changes local magnetic field and allows vascularisation and tumours to be seen easier

Question 22

Screening

Answer 22

Diagnose at earlier stage when asymptomatic eg cervix, lung, breast - mammography before lump felt but can give false positives

Question 23

WHO principles

Answer 23

The condition should be a important health problem and used at latent stage of disease

Question 24

Screening principles

Answer 24

Detect at early stage with no harm caused and should be highly sensitised and specific