Cancer Imaging

Question 1

Function of imaging in cancer

What makes a good diagnostic test

Answer 1

Detect, stage, treat cancers

• can be used as an adjunct to histology
• aids in staging

Sensitivity - true positives
Specificity - true negatives
Accuracy - proportion of correct test results
Negative predictive value - proportion of negative tests who are unaffected
Positive predictive value - proportion of positive tests who are affected

Question 2

Xrays

• abilities
• pros and cons

Answer 2

2D rep of 3D

Widely available
Cheap
Low radiation dose

Not suitable for soft tissue
Poor detail in comparison to CT/MRI

Question 3

Ultrasound

• abilities
• pros and cons

Answer 3

Imaging of soft tissues

Widely available
Cheap
No radiation
Interventions possible

Limited by patient factors
-very large patients affects depth of penetration
Limited by operator factors
-needs high level of skill

Question 4

CT

• abilities
• pros and cons

Answer 4

Can see body from multiple angles in more detail

High spatial resolution
Rapid

Moderately expensive
Increased radiation dose
Less soft tissue contrast than MRI

Question 5

MRI

• abilities
• pros and cons

Answer 5

Can get very detailed imaging of soft tissue
Can highlight different features with different contrasts (T1, 2)

Excellent soft tissue contrast
High spatial resolution
No radiation

Time consuming
Capacity is limited
Expensive
Claustrophobic 
Implants CI

Question 6

Hybrid imaging (PET/CT)

• abilities
• pros and cons

Answer 6

FDG PET to highlight metabolically active tissue
Can use this to find abnormal areas of high metabolism

High spatial resolution

Lower availability
Higher cost
Increased radiation dose

Question 7

What is the function of screening

How does this differ from cancer detection

Answer 7

Detect early disease in asymptomatic patients

• high sensitivity
• low false positives
• high positive predictive value

Confirm disease in symptomatic patients

• high specificity
• low false negatives
• high negative predictive value

Question 8

How would you assess for bony mets

Answer 8

CT - IV contrast enhanced

Bone scintigram - Tc99 , more sensitive