Cellular Effects of Radiation

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Cellular Effects of Radiation

• Linear Nonthreshold Dose Response

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Introduction

• Radiobiologists were conducting research to have
  a similar result in radiation and dose- response
  relationship.
• This result is needed so it can be used to
  predict the risk of malignancy in human
  populations that have been exposed to low levels
  of ionizing radiation or Low LET radiation.
• Dose- response relationship is also called the
  dose- response curves which are graph or maps
  relationship between observed effects (response)
  from radiation and dose of radiation received by
  the patient.

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Dose Response Curves

• Dose- response curves differ in two ways
• they are either linear or nonlinear.
• they are either threshold or nonthreshold.

Linear Nonthreshold Curve
Linear Threshold Curve
Linear Quadratic Curve
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Dose Response Relationship

• Linear means that an observed response is
  directly proportional to the dose.
• Example Doubling the dose of radiation would
  double the response
• Nonlinear means that an observed response is
  not directly proportional to the dose.
• Example Doubling the dose of radiation does not
  double the response

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Dose Response Relationship

• Threshold assumes that there is a radiation level
  reached below which there would be no effects
  observed.
• Nonthreshold assumes that any radiation dose
  produces an effect.

• Linear Quadratic Dose Response
• Linear Nonthreshold Dose Response
• Linear Threshold Dose Response
• Nonlinear Dose Response (sigmoid curve)

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Linear Nonthreshold Dose Response

• A Linear nonthreshold dose response means that
  any radiation dose will produce a biologic
  effect.
• No radiation dose is believed to be absolutely
  safe.
• Diagnostic radiology is primarily concerned with
  linear nonthreshold dose response relationship.
• Hypothesis of LNDR is basis for setting
  radiation- protection standards worldwide.

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Linear Nonthreshold Dose Response

• Stochastic (probabilistic) Health Effects are
  effects that which is occur by chance, generally
  occurring without a threshold level of dose.
• Leukemia, breast cancer, and other genetic damage
  are believed to follow the linear nonthreshold
  dose response relationship.

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Linear Nonthreshold Dose Response

• The principal basis for the LNDR is theoretical,
  and very simple. A single particle of radiation
  hitting a single DNA molecule in a single cell
  nucleus of a human body can initiate a cancer
  (direct action).

Direct Action Effect
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Factors Effecting the Dose Models and Theories

• The time period over which the dose is delivered
• Age of the exposed individual
• State of health of the exposed individual
• The time period between multiple exposures

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Conclusion

• People misunderstand everything about low level
  radiation if its safe or not. Public are scared
  having an x-ray procedure or nuclear scan when
  radiation is mentioned. Everybody in mind is
  cancer producing ray that will hit and absorb
  their body, that there are factors to consider
  for the biological damage happen.

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Questions

• 1. ________ which are graph or maps relationship
  between observed effects (response) from
  radiation and dose of radiation received by the
  patient.
• Answer Dose Response Relationship Curve
• 2. Dose Response Curve differ in two ways, what
  are they?
• Answer They are either linear or nonlinear and
  they are either threshold or nonthreshold.
• 3. List the 4 Dose Response Relationship Curve.
• Answer Linear Quadratic Dose Response,Linear
  Nonthreshold Dose Response,Linear Threshold Dose
  Response,and Nonlinear Dose Response (sigmoid
  curve)
• 4. No radiation dose is believed to be absolutely
  ______.
• Answer Safe
• 5. Identify Linear Nonthreshold Dose Response
  Curve in the picture.
• Answer Line B