Positron Emission Tomography Scans

By: Ahmed Haleem

Points Of Discussion

What is a P.E.T scan What it does/ brief explanation on how Benefits Drawbacks Operation process Issues(social, ethical, political &

general) Societal benefits Canadian data on the use of the scan

What is a P.E.T Scan?

P.E.T stands for Positron Emission Tomography

It is performed by a nuclear medicine or radiologic technologist (Specially trained/certified to operate PET scanners)

Then interpreted by nuclear medicine physician or a radiologist(trained to interpret scans)

What does it do?

A P.E.T scan does not show body structures.

It shows concentration of radioactive tracers which are placed in the body before the test.

These tracers are called “radiopharmaceuticals”.

Theses tracers are absorbed by organs, tissue and cancer cells the most.

Benefits

Much lower exposure to radiation compared to other scans. The tracer is only in your body for a short time (1-3 hours) and drinking water helps wash it away.

Radiation is measured in millisieverts (mSv)

Average exposure is 3 mSv per year. (many variables however)

Benefits Continued

Goes through bloodstream (tracer) so it goes where ever the cancer does. (can see tumors in whole body)

Good image of where tumor is/where its spreading

Can be used to check effectiveness of treatment

Benefits continued

Relatively quick, 30-90 minutes Can be combined with CT scan to show

body structures and position of tracer (high detail cross sectional view can be achieved)

Drawbacks

Cannot tell the difference between malignant and benign tumors

Very expensive (Ontario average is 1,000 to 1,200 per scan)-is covered partially or fully by OHIP however

Certain cancers do not absorb tracer leading to a negative scan.

If chemical balances are not normal it may lead to false results.

Operation Procedure

Patient will be asked not to eat anything 3-5 hours before the test so results are clearer. (glucose use of organs is lower so tumors will stand out more)

A short lived radioactive tracer (radiopharmaceutical) will be injected into the blood stream

Usually FDG (Fluorodeoxyglucose) –small amount of radioactive isotope mixed with glucose.

Operation Procedure

Tissues and organs absorb radiopharmaceuticals based on rate of division. (because they use more glucose to divide)

Cancer sells have very high rate of division so radiopharmaceuticals are absorbed by cancer cells

Patient will then be asked to stay still (not talk or move much)

Operation procedure

Talking a lot would blur image of lung and movement (excessive) would blur image of body

Patient will wait like this for up to an hour so radiopharmaceutical can reach or be absorbed by organs.

The scan is then done for areas of very high concentration of radiopharmaceuticals.

Operation Procedure

Areas with very high concentration are areas of high division. (I.e. tumors)

A CT scan or MRI may be done at the same time to give more detailed image

Other scans are done without the patient moving to different machine and with little time added on

Issues

SOCIAL Can’t tell if it is benign or malignant,

may worry people unnecessarily ETHICAL Considered ethically incorrect because

misdiagnoses happen occasionally. Doctors say it is not right because it may have big impact on the patient mentally/ emotionally and turn out to be incorrect.

Issues

Also because it may waste time and resources on someone who doesn’t need it.

Another ethical issue: it is possible (not yet proven) that the radiation in radiopharmaceuticals can cause cancer. It is in small amounts but some say it isn’t right to be using them.

Issues

POLITICAL Government pays for it in Canada but

in U.S some say that we (the government) shouldn’t be paying for it.

In Ontario scans are only paid for if considered necessary, people and government may not see eye-to-eye on what is necessary and what is not

Canadian Data

29 PET scans in Canada. Ontario has 9 (second most) Quebec has 12 World health organization recommends

2 scanners/million people. Canada has fewer than half of that.

Cost of scan in Ontario is $1,000-$1,200

Thank You For Watching.

Hopefully this presentation has explained to you what a P.E.T scan is, how it works and why/when one would use it. Bibliography is provided on next slide.

Bibliography

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