Physics and Radiobiology of Nuclear Medicine

15 Radiation Biology 226 The subject of radiation biology deals with the effects of ionizing radiations on living systems. Durin ...

The Cell 227 Fig. 15.1. Structure of a typical mammalian cell. DNA Gene Chromosome Nucleus Fig. 15.2. Structural relationship of ...

cellular metabolic activities. Ribosomes are made up of protein and ribo- nucleic acid (RNA) and are responsible for protein syn ...

The Cell 229 Telophase Prophase Metaphase Anaphase Fig. 15.3. Different phases of mitosis. See text for details. Fig. 15.4. The ...

Effects of Radiation DNA Molecule The nucleus of the cell is the part most sensitive to radiation and this sen- sitivity has bee ...

cule on the strands on both sides, and are paired to each other by hydro- gen bonds. These four bases are arranged in a very spe ...

232 15. Radiation Biology A T G C T A G C T A A A T G C T A G C T A B A T G C A G C T A C A T G C T A G C T A D E A T G C G C G ...

Effects of Radiation 233 A Replication Dicentric Fragment Acentric Fragment B Fig. 15.7.(A)Illustration of restitution, in which ...

234 15. Radiation Biology A B Dicentric Acentric Translocation Fig. 15.8. Single-strand breaks in one arm of each of two separat ...

Direct and Indirect Actions of Radiation 235 Deletion A Inversion B Fig. 15.9. Two breaks in one arm of a chromosome producing t ...

In the indirect action, the radiation hits the water molecules, the major constituent of the cell, and other organic molecules i ...

H 2 O +energy →H 2 O++e− H 2 O +e−→HOH− H 2 O+→H++OH• (free radical) HOH−→OH−+H• (free radical) H++OH−→H 2 O H• +OH• →H 2 O OH• ...

are highly resistant to radiation. The tissue or organ that contains more radiosensitive cells will be highly radiosensitive and ...

ductive activity in undifferentiated cells. It should be noted that thousands of grays are needed to kill differentiated cells, ...

after irradiation, and cell killing is minimal, which is due to very limited radiation damage to the cell. D 0 is determined fro ...

Factors Affecting Radiosensitivity As already mentioned, various factors affect the radiation damage in the cell and hence the s ...

Linear Energy Transfer High-LET radiations do not exhibit a dose-rate effect on the survival curve. Also at high-dose rates (abo ...

lar components to repair the cell, RO• 2 is an altered chemical entity and cannot help in cell repair. The oxygen effect is most ...

of the blood vessels find themselves closer to the blood supply and so reoxygenate. Pyrimidines Halogenated pyrimidines such as ...

these products concentrate more in normal cells and less in tumor cells. As a result, normal cells are protected better than tum ...