Lab 9 Radiation Measurement We use different terms depending on whether The radiation is coming from a radioactive source The radiation dose absorbed by a person The risk that a person will suffer health effects from exposure to radiation ID: 558125
Download Presentation The PPT/PDF document "Internal Radiation Dosimetry" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Internal Radiation Dosimetry
Lab 9Slide2
Radiation Measurement
We use different terms depending on whether:The radiation is coming from a radioactive sourceThe radiation dose absorbed by a person
The risk that a person will suffer health effects from exposure to radiationSlide3
Radiation Dosimetry
Radiation can cause deleterious effects in living systems. It is therefore essential to assess these effects in humans for a given nuclear medicine procedure involving the administration of a radiopharmaceutical.Slide4
Radiation Dosimetry
The activity of the administered radiopharmaceutical
The physical and biological half-lives of the radiopharmaceutical
The distribution and metabolic fate of the radiopharmaceutical in the body
The fraction of energy released per disintegration from a source region that is absorbed in the particular target volume
The shape, composition, and location of the source and target organs
The damaging effects arise from the absorption of energy in tissues and depend on a number of factors:Slide5
Radiation Units
There are three basic units related to radiation: The roentgen
(R) for exposure
The
rad
(radiation absorbed dose) for absorbed dose
The
rem
(roentgen equivalent man) for dose equivalent.Slide6
Units and Terminology
Two systems of measurementConventional
roentgen
rad
rem
SI (Systeme Internationale)
exposure
gray
sievertSlide7
Conversion between various units used in radiation Slide8
Calculation of Radiation Absorbed Dose
Radiopharmaceuticals administered to patients are distributed in various regions of the body. These regions can be considered points, lines, surfaces, or volumes. In internal dosimetry calculations:
‘‘
target
’’ a region of interest for which the absorbed dose is to be calculated.
‘‘
source
’’ All other regions contributing to the radiation dose to the target are considered. Slide9
1st
Definition: ExposureDefinition:
Charge per unit mass of air
One of the earliest radiation measurements
Unit:
Rontegen (R)Slide10
2nd
Definition: Absorbed Dose
Definition:
It is a measure of the energy deposited in unit mass of any material by any type of radiation (i.e., energy per gram)
Conventional units
rad
100 ergs of energy per 1 gm of material
Systeme Internationale
Gray (abbreviated Gy) 1 joule/kg
1 Gy = 100 radSlide11
Absorbed Dose, continued
Used for any and all types of ionizing radiation Neutrons, gammas, alpha particles, x-rays
Internal and external exposure.
Absorbed dose
rate
is given in rad/s, Gy per hr,...etc.Slide12
3rd
Definition: Relative Biological Effectiveness
Relative biological effectiveness (RBE)
is a measure of these differences in living tissue
The higher the number, the more damaging the radiation is, for the same amount of absorbed energy.
Radiation damage depends on
Type of material
Type of radiationSlide13
3rd
Definition: Relative Biological Effectiveness
Peak kilovoltage (
kVp
)
is the maximum voltage applied across an X-ray tube.Slide14
Biological Effects, continued
Conventional system:
Rem (“Roentgen equivalent man”)
Systeme Internationale:
Sievert (Sv)Slide15
4th Dose Equivalent Unit
The dose equivalent unit (Hr) has been developed to account for the differences in effectiveness of different radiations in causing biological damage.
Defined
as the ratio of the dose of a standard radiation to produce a particular biological response to the dose of the radiation in question to produce the same biological response.
Unit
:
Rontegen Equivalent Man (rem)
Sievert (Sv)Slide16
4th Definition Dose Equivalent Unit
For a particular radiation is defined as
Where rad = absorbed dose in rad
(RBE)r is the relative biological effectiveness of the radiation. Slide17
Thank You