Positron Emission Tomography (PET) is used as an imaging technique in a wide
range of biomedical research applications in human patients and volunteers.
Millions of PET scans are performed worldwide. Radio-tracer is introduced to the
patient and its movement or deposition in the body is followed through a PET
scan. A typical nuclear medicine procedure results in a radiation dose of
around 25 mSv to a patient, while a CT scan using X-rays gives a dose of 5-8
mSv per scan, depending on which part of the body is scanned. To put risks in a
proper perspective, natural background radiation dose is in the range of 2 to 3
mSv in year.
Radiation protection principle recommends
optimization of the procedure to minimise patient dose. Some of possible ways
of minimization of the dose is:
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Use highly sensitive and faster scanners for the procedure so that time
spent is minimum for scanning so that the system can detect and perform scans
at very low levels of emissions
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Optimise the radio-tracer dose to the patient to get a good scan
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Select a most suitable short-lived low energy photon emitting radiotracer
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Minimise radiation exposures of the healthy tissues/organs which are
adjacent to the tissue/organ being scanned or treated.
The procedures results in radiation dose
(occupational exposures) to the medical, para-medical staff and technicians who
are handling the radioactive material and who operate the machines for
scanning. Scattered radiation from the primary beam is of concern, particularly
to the eye lens, and needs to be monitored. Suitable radiation dosimetry
technique should be used for the purpose. The hospital health physicist should
ensure that the occupational exposures should be controlled and kept as low as
reasonably achievable (ALARA).
Finally, the hospitals, the physicians/radiologist
should avoid misuse of this technology for financial gains alone. In addition
to the benefits to the patient from the procedure, the patients should be thoroughly
briefed about the possible health effects from the exposure to radiation. Benefits
should outweigh the risks of the exposures.
