imaging in cancer

Question 1

Explain the scientific basis of magnetic resonance imaging (MRI).

Answer 1

MRI uses a magnetic field to align the H+ of carbon, oxygen, nitrogen and phosphorus in the body.
When the H+ bounce back into position an image is displayed based on the time it takes the protons to bounce back into position.

Question 2

Explain the indications, contraindications and application of MRI-specific contrast agents

Answer 2

Advantages:
-Excellent bone and soft tissue detail
-Vessels can be seen
-Cardiac imaging
-Brain, spine and musculoskeletal system can be seen
Disadvantages:
-Claustrophobic and noisy machine
-Patients with metal implants and pacemakers cannot have MRI taken
Contrast:
-Gatolinium DTPA is used as a contrast agent as it is able to alter the magnetic field of the cells in the body
-very safe
-vascular legions and some tumours can be seen very well

Question 3

Describe patient safety issues specific to MRI.

Answer 3

ALARA: as low as reasonable possible.
As with most of these scans there is exposure to radiation to patients as well as staff.
The test must be clinically significant:
-It should cause no harm
-It should outweigh the costs
-it should have high specificity and sensitivity

Question 4

Barium studies

Answer 4

-Mainly used in diagnosis of cancer.
-Radio-opaque contrast used to line the GI tract. It appears white of scan
-The high atomic number of barium allows it to absorb more X-rays than the tissues surrounding it
1-Barium swallow and meal- oesophagus, stomach, duodenum
2-Barium follow- through- small intestine
3-Barium enema- Large intestine
1+2:
-fast for 4-6 hours
-radiation 1.5 msv
3:
-low residue diet for 48 hours
-radiation 7msv

Question 5

CT scans

Answer 5

-Xray of digital slice in axial place
-contrast:
for GI tract: oral dilute iodine-based gastrografin
for blood vessels : IV iodine based omnipaque

Question 6

Outline the clinical application of imaging for the diagnosis, staging and treatment of cancer.

Answer 6

• Position of tumour
• Depth of tumour
• Relationship compared to adjacent structures
• Spread-metastases
• Involvement of blood vessels and the lymphatic system.

Question 7

Describe the pros and cons of population screening with radiological testing, using breast screening as an example.

Answer 7

Pros:

• Helps diagnose cancer at earlier stage and therefore improves chances of cure
• High sensitivity and specificity

Cons:
-exposure to radiation which can reduce life expectancy of both patients and medical staff

Question 8

Explain that guidelines can inform the judicious use of imaging.

Answer 8

• There should be treatment and facilities available for the treatment of the disease
• The test should be acceptable to the population
• The test should be an important health problem