Imaging in Cancer COPY Flashcards

1
Q

What is the basic principle of barium studies?

A

Barium sulphate is a contrast used for outlining the gastro-intestinal tract, the high atomic number of barium absorbs more X-ray photons than surrounding tissues.

Administered through barium meal or barium enema.

Barium appears white in the rasiograph

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2
Q

How are CT scans produced?

A

X-rays produce a digital image of a slice of tissue, computer creates the image

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3
Q

What is the hounsfield unit?

A

Expresses CT numbers in a standard form.

CT numbers express attenuation values of voxels

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4
Q

What can be used as an oral contrast agent for a CT scan?

A

Oral - dilute iodine based contrast - outlines the gastrointestinal tract.

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5
Q

What can be used as an intravenous contrast agent for a CT scan?

A

Iodine based contrast - omnipaque - demonstrate blood vessels or the vascularity of different tissues

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6
Q

How does an MRI scan work?

A

Strong magnetic field aligns the H+ protons in the body in one direction

Radio pulse is applied and turns the nuclei 90 degrees away from the direction of the magnetic field.

Time is taken for the protons to relax and resume their initial alignment with the magnetic field

Image is created by measuring the time taken for the protons to relax to their original position

Lighter molecules take longer to come back to the rest state, higher mass returns to natural alignment quicker

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7
Q

What are the MRI indications?

A

Excellent bone soft tissue detail
Vessels can be demonstrated
Brain, spine and musculoskeletal, abdomen pelvis can all be clearly observed.

Cardiac imaging possible

Does not involve exposure to ionizing radiation

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8
Q

What MRI contraindications?

A

Claustrophobic and noisy

Cannot image patients with pacemakers

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9
Q

Name a MRI contrast agent

A

Gadolinium

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10
Q

What is the effect of Gadolinium

A

Causes changes in local magnetic field and so alters the tissue signal.

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11
Q

What is the effect of contrast agents in MRI?

A

Reduces the time of relaxation of atoms within the body

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12
Q

What is the purpose of screening?

A

Diagnose disease at an earlier stage before symptoms start and where treatment can alter the outcome

Cancer is therefore likely to be easier to treat

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13
Q

What does the NHS have screening programmes for?

A

Bowel
Breast
Cervix

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14
Q

What are the WHO principles of screening?

LIT FAT

A

There should be a latent stage of the disease
The condition should be an important health problem
There should be a test or examination for the condition

Facilities for the diagnosis and the treatment should be available
Test acceptable to the population
There should be a treatment for the condition

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15
Q

What are the Limitations of screening?

A

Test should cause no harm
Test should have high specificity and sensitivity
Benefit to the individual should outweigh the cost

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16
Q

What is used to screen for breast cancer in women?

A

Mammograms (x-ray of the breast)

17
Q

What are the pros and cons of population breast screening?

A

Pros: Early diagnosis and resulting successful treatment. So increased rates of successful treatment since more cancers are found at curable stages

Cons: Overdiagnosis - finding tumours that would never have normally caused harm to the individual - unnecessary cancer treatment
Exposure to harmful radiation
Unnecessary anxiety

18
Q

What can a CT scan be used to see?

A

The precise location of a tumor, its shape, and whether it is solid or hollow. Although it can give clues as to whether or not a tumor is cancerous, only a biopsy can tell for sure. Unfortunately ,a CT scan is not reliable in helping to find tumors that are less than 2 cm.

19
Q

What is it hard to differentiate between on an MRI scan?

A

Inflammation and scar tissue from tumors

20
Q

What does a PET scan detect?

A

Differences in metabolic and chemical activity in the body

LOOKS AT FUNCTION NOT STRUCTURE

Cancer cells divide rapidly and have a very high metabolic activity

Scar tissue has a very low metabolic activity

21
Q

What is the added benefit of the CAT/PET scan combo?

A

You can clearly see the anatomical detail of the CT and the ability to find small clumps of cancer cells of the PET

22
Q

CT imaging in cancer

A

diagnosis: lung, pancreatic, renal, adrenal, retropetitoneal and brain tumours
staging - lymph nodes and adjacent organs

23
Q

monitoring disease using CT

A

response to treatment
relapse
progression of disease
2D measurements

24
Q

chest CT radiation dose

A

8mSv

25
Q

abdominal CT radiation dose

A

10mSv

26
Q

pelvis CT radiation dose

A

10mSv