Simple measures can minimize tech’s exposure time. Holbrook avers, “It’s important to reiterate that the patient is where the tech can receive the most exposure.” Classic agrees. She adds, “Let’s face it. The patients are most technologists’ primary source of exposure. Reducing time spent close to patients reduces dose on the basis of time and distance.”
In all hospitals, a radioisotope is carefully shielded before it is injected into a patient in order to prevent accidental exposure. Once the isotope is injected into the patient, it becomes an unshielded source of radiation. So a tech cannot opt to sit next to a patient for reassurance after injecting radioisotopes, or he or she will receive an undesirable exposure.
A typical PET scan requires anywhere from 30 minutes to 90 minutes of uptake time after injection. A tech can be potentially exposed during this span of time. The patient should be isolated in a shielded area during the uptake phase.
Nevertheless, a few sites designed their PET facility incorrectly and failed to account for technologists’ safety during the uptake phase. Jeff Clanton, DPH, director of radiopharmacy services and manager of the cyclotron facility for Vanderbilt University (Nashville, Tenn.), notes, “I’ve seen a few PET facilities that aren’t designed correctly. A PET site should have an isolated holding area for patients during the uptake phase. The holding area should be away from staff and other patients.”
So once I am injected with the isotope I could be a source of radioactive contamination? Hmmm I don't like that at all. I found another reference that said the exposure is equivalent to two chest x-rays. Well I don't really want any more x-rays period and this is why I don't want to do any more mammograms. This concerns me and I don't trust the facilities who give the test to tell me the truth. I really want to see the results of this test BUT is it really worth the risk of certain radiation exposure? They try to assure you that the isotope is "short-lived" but exposure is exposure.. period.
I even found a reference in the same article that says it is more dangerous to be a PET scan technician than a "medical radiologist" meaning the ones that dose people with radiation therapy.
How can a facility insure the safety of its staff as it implements a PET scanner? The same general principles of time, distance and shielding that apply in nuclear medicine are used but in a much more stringent manner. The difference is a matter of simple physics. The gamma emitters used for diagnostic nuclear medicine are actually fairly low-energy — 135 to 150-keV, which means there isn’t much exposure from the patient. PET, however, is a whole different ball of wax.
Mary Anne Dell, vice president of manufacturing and health physicist for Capintec, Inc. (Pittsburgh, Pa.), explains, “All PET isotopes, by definition, are positron emitters and have an energy of 511-keV.” The reality of high-energy emitters is that the radiation exposure coming from the patient is much higher for PET than nuclear medicine. Consequently, the room for error is smaller and some concerns that might be taken for granted in nuclear medicine cannot be overlooked in PET or the tech will be overexposed.
Ok I found this now - it seems air travel exposes us to radiation also:
One drawback for PET scans is that PET centers must be located near a particle accelerator device that produces the short-lived radioisotopes used in the technique. Another drawback, of course, is that the technique involves exposing people to radiation, though the level is only about as high as exposure due to taking a cross-country air flight.So that isn't so bad really.. is it? Just something about having something radioactive in my blood that could *expose* a PET technician to dangerous radiation doesn't sit well with me. Still searching...
This information is specific to PEM Flex procedures:
PEM involves the injection of the radiopharmaceutical FDG. A patient needs to fast for four hours before the procedure. Afterward, a serum blood sample is taken to determine blood glucose level. Then FDG is injected intravenously. Tumor cells will take up much more glucose than normal cells, and PEM imaging will reveal the FDG concentrations that suggest malignancy.
The imaging is acquired one hour after the FDG injection, when the patient’s body has had enough time to absorb the radiopharmaceutical. Images are obtained in a manner similar to mammography. Both breasts are imaged, with mediolateral oblique and craniocaudal views taken. Each view takes approximately 10 minutes to accomplish; thus imaging requires roughly 40 to 45 minutes.
What is FDG?
Carbon-11, Nitrogen-13, Oxygen-15, Fluorine-18:These are positron emitters used in PET for studying brain physiology and pathology, in particular for localising epileptic focus, and in dementia, psychiatry and neuropharmacology studies. They also have a significant role in cardiology. F-18 in FDG has become very important in detection of cancers and the monitoring of progress in their treatment, using PET.
Found this consent form regarding the use of PET scans in University Research which I find interesting:
The consent form must include the following information:
- "I understand that FDG, the imaging material used in the PET scanning procedure is not burned up normally by the body, but in this study only very small doses will be administered, less than one-ten thousandths of the amount required to show any drug, behavior or mood effects. It will be passed in my urine within 48 hours after administration and most of it will be eliminated from my body in the first 7 hours."
- "Injection of the radioisotope (FDG) will expose me to a small dose of radiation, so that my risk of developing cancer in the future will be slightly increased."
- "If I have had a PET scan or been exposed to radiation while participating in other research during the past year, I will inform the investigator(s). This will enable the investigator(s) to assure that my total radiation exposure does not exceed accepted safety limits. If I participate in future studies that involve the use of x-rays or radioisotopes, I should discuss the safety limits of radiation exposure with the investigator who is performing the study."
More information that instead casts a positive light on the use of FDG for breast cancer TREATMENT!
Moadel et al. published the results of the FDG study in the August 22 issue of Breast Cancer Research (2003;5:R199–R205). The notion that the “workhorse” radiopharmaceutical of PET imaging may also provide therapeutic effects was both surprising and thought provoking
for many nuclear medicine specialists.
Moadel and her colleagues first determined radiotoxicity levels for FDG in healthy mice and then treated polyoma middle T antigen and mouse mammary tumor virus-NeuT mice and control mice with 2–4 mCi 18F-FDG. Tumors and control mammary glands were analyzed at 10 days after therapy.
The uptake in tumor showed an average tumor-to-liver ratio of 1.6 and resulted in apoptotic cell death in small tumors (0.15–0.17 cm). Cell death through the necrotic pathway was seen in large tumors (>1 cm) and was accompanied by tumor fragmentation and infiltration with leukocytes. Mammary tissues from the control mice were not damaged.
Another reference to consider:
Appendix 3: Theories of Radiation Risk
The traditional linear no-threshold (LNT) model assumes that there is a linear relationship between radiation dose and risk. This means that even at very low doses, there is a deleterious effect. Linear-quadratic and quadratic models have also been proposed, but the LNT model assumes the worse outcome for low doses, and therefore provides the greatest protection. On these grounds, in 1960, the International Commission on Radiation Protection (ICRP) and the US National Council on Radiation Protection and Measurements (NCRP) decided to adopt the LNT model. This model has been developed in ICRP Publication 26 (1977) and ICRP Publication 60 (1991).(9) The ICRP and NCRP have recently reiterated their belief that there is no safe radiation dose threshold.(127, 128)
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