Humans have evolved under a field of low level radiation, and continue to be exposed
to ubiquitous levels from natural and man-made sources including diagnostic radiology. The
computerized tomography scan, in particular, plays an important role in the investigation of
disease and its use increased dramatically over the years. This raises the concern that
elevation in radiation exposure from x-ray modalities may increase an individual's risk for
cancer. The purpose of this study is to help address this issue by measuring biological
changes in lymphocytes before and after a CT scan. Venous blood was collected from eight
prostate cancer patient:> before and after their scan and delivered to McMaster University at
room temperature. For the dicentric assay, 0.5 ml whole blood/tube was irradiated with 3 Gy
gamma rays using a 0 ;137 source and then incubated at 37°C for 46 hours. Metaphases were
scored by microscopy. For apoptosis and y-H2AX, lymphocytes in media were irradiated on
ice with 8 Gy and analyzed by flow cytometry. Biological effects in vivo from the CT scan
were minimal for all endpoints when averaged between all donors. Overall, there was a high
degree of inter-individual variation for each effect, although no correlation was found
between dose (dose length product) from CT and apoptosis as well as the induction of yH2AX
foci. The adaptive response also showed patient variation, and the frequency of
dicentrics was the only endpoint that was lower overall following CT + 3Gy in comparison to
3 Gy alone. This research presents a challenge to current linear models of radiation
associated genetic risk, and shows that individuals respond to radiation differently depending
on biological factors. / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/21016 |
| Date | 01 1900 |
| Creators | Asis, Angelica |
| Contributors | Boreham, D. R., Radiation Sciences (Medical Physics/Radiation Biology) |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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