Cellular Effects of Radiation

							Cellular Effects of Radiation

     Linear Nonthreshold Dose
             Response
                          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.
          Dose Response Curves
                                 Linear
   Dose- response               Nonthreshold
    curves differ in two         Curve
    ways:
       they are either linear   Linear Threshold
        or nonlinear.            Curve


        they are either
                                 Linear Quadratic
        threshold or             Curve
        nonthreshold.
    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
    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.
                            A. Linear Quadratic Dose
                               Response
                            B. Linear Nonthreshold Dose
                               Response
                            C. Linear Threshold Dose
                               Response
                            D. Nonlinear Dose Response
                               (sigmoid curve)
        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.
      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.
        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      Direct Action Effect
    cell nucleus of a
    human body can
    initiate a cancer
    (direct action).
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
                  Conclusion
   People misunderstand everything about
    low level radiation if it’s 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.

                       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