Cancer Detection: Imaging

Question 1

What are the types of medical imaging techniques?

Answer 1

• X-rays
• Catheter angiography
• Ultrasound
• CT (computer tomography)
• MRI (magnetic resonance imaging)
• Scintigraphy and SPECT
• PET (Positron emission tomography)

Question 2

What are the most common types of imaging for cancer patients?

Answer 2

• Ultrasound
• CT
• MRI
  -PET

Question 3

What questions does imaging answer in cancer diagnosis?

Answer 3

• Where is it?
• Is it a cancer or something else?
• If it is a cancer, what type of cancer is it?
• Has it invaded the nearby structures?
• Has it spread further afield?

Question 4

Describe the role of X-rays in cancer diagnosis/treatment

Answer 4

• limited information as further cross-sectional imaging required
• useful in detecting abnormalities of lungs and bones

Question 5

Describe the positives and negatives of ultrasounds in cancer diagnosis

Answer 5

Positives:
- can be performed bedside
- good evaluation of
solid abdominal organs
and superficial
structures (breast,
thyroid, etc)
- Good spatial resolution
- no ionising radition

Negatives:
- User dependent
- Limited penetration
- ‘Blind spots’

Question 6

Describe the positives and negatives of CTs in cancer diagnosis

Answer 6

Positives:
- Quick, good for unstable
patients
- Good for hollow organs,
bones, blood
- Reasonable soft tissue
contrast– improved IV
contrast agents, asp.
multiphasic acquisition
- Excellent spatial resolution

Negatives:
- Limited evaluation of
tissue properties
- ionising radiation

Question 7

Describe the positives and negatives of MRIs in cancer diagnosis

Answer 7

Positives:
- Excellent soft tissue
contrast
- Excellent evaluation of
tissue properties e.g.
cellularity, perfusion,
chemical composition
etc
- Spatial resolution can
be very good
- no ionising resolution

Negatives:
- Long acquisition times
- Enclosed space

Question 8

Describe the positives and negatives of PETs in cancer diagnosis

Answer 8

Positives:
- High sensitivity for
detection of
metabolically active
tumour

Negatives:
- Poor spatial
resolution
- False positives
- ionising radiation

Question 9

What are the main uses of radiology in cancer?

Answer 9

• finding cancers
• staging cancers
• detecting changes (either in response to treatment or in progression)

Question 10

studying tissues with MRI

Answer 10

• post contrast scans: enhancement suggest increased capillary density and permeability
• diffusion weighted imaging: reflects cellularity of tumour, low diffusion indicates densely cellular tumours (lymphoma, PNET, germinomas)
• diffusion tensor imaging (BRAIN): changes in white matter integrity due to tumour

Question 11

magnetic resonance spectroscopy

Answer 11

• chemical signature of tissue
• increase in choline, inositol and mobile lipids
• decrease in NAA
• changes in lactate
• useful for tumour grade
• helps find very specific features for certain tumours
• point to other diagnoses, eg. inflammatory lesions

Question 12

medulloblastoma

Answer 12

• elevated taurine
• only present in group 4, not SHH or WNT subtypes

Question 13

MDT in cancer

Answer 13

• radiologist
• surgeon
• pathologist
• oncologist
• specialist nurses
• therapists
• patient makes ultimate decision

Question 14

staging tumours by imaging

Answer 14

• TNM staging (body tumours)
• T = size of original tumour and local invasion
• N = regional lymph node involvement
• M = distant mets
• put together to create stage (between 1 and 4)

Question 15

detecting progression/treatment response

Answer 15

• RECIST criteria (body tumours)
• Progressive disease: >20% increase
• Stable disease: neither sufficient increase or decrease
• Partial response: >30% decrease
• Complete response: disappearance of all lesions
• RANO criteria (brain tumours)
• different thresholds but same principle
• beware pseudoprogression (aggressive appearing treatment affects) and pseudoregression (anti-angiogenic agents)