CHAPTER 6

Molecular and Cellular Radiation biologyIonizing Radiation and the Human body

From x-rays, gamma, or high energy particulate radiation◦ ALPHA, BETA◦ Alpha=two protons and two neutrons attracts

negatively charged electrons

Ionized atoms will not bond properly in molecules

LET

RBE

OER

X-ray/gamma rays Streams of particles

with no mass or charge

Penetrating Sparsely ionizing Interacts randomly Damage via indirect

action Sublethal damage

Particles of mass and charge

Alpha, neutrons What other

characteristics?

Low◦ Risk of damage to

DNA/Probability of interaction with DNA

◦ What radiations are considered low LET?

High◦ Risk of damage to

DNA/ DNA/Probability of interaction with DNA

◦ Internal contamination◦ What radiations are

considered high LET?

250 kVp of known radiation (usually x-ray) over dose of test radiation=biologic effect (Box 5-2)

Used in animals Weighting factor of

radiation used to determine biologic damage

DOSE REQUIRED TO PRODUCE AN EFFECT IN AN OXYGEN DEPRIVED ENVIRONMENT VS A NORMAL OXYGEN ENVIRONMENT

OER IS HIGH FOR LOW LET THE OPPOSITE FOR HIGH LET THE DIFFERENCE IS DUE TO DIRECT AND

INDIRECT EFFECT

BOTTOM LINE…..IF IONIZATION FROM EITHER EFFECTS DISTURBS THE CHEMICAL BALANCE OF THE CELL, THE

CELLULAR ACTIVITY BECOMES ABNORMAL OR THE CELL CAN EVEN CEASE TO FUNCTION

IMPACTS THE DNA

OCCURS MORE OFTEN WITH HIGH LET

INTERACTS WITH WATER

OCCURS MORE OFTEN WITH LOW LET

RADIOLYSIS OF WATER/FREE RADICALS

SINGLE STRAND BREAK figure 6.6 DOUBLE STRAND BREAK figure 6-7/IN SAME

RUNG figure 6-8 MUTATION figure 6-9 COVALENT CROSS LINKS figure 6-10 CHROMOSOME BREAKS CHROMOSOMAL FRAGMENTS CHROMOSOME ANOMALIES Structural changes

HIGHLY MITOTITIC ABNORMALLY DIVIDE LARGE NUCLEUS

Relate this to Bergonie and Tribondeau (pg 102) and direct/indirect effects

THE MASTER MOLECULEPG 125