7-8. units for measuring radiation
DESCRIPTION
its all about measuring the radiation.TRANSCRIPT
![Page 1: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/1.jpg)
1
UNITS FOR MEASURING RADIATION
![Page 2: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/2.jpg)
Learning objective:
At the end of this session, student should be able to:
- explain the quantity involved in ionizing radiation
- define and state the value of the annual dose limit involved.
- apply the unit conversion
2
![Page 3: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/3.jpg)
3
Several forms of ionizing radiation are used in medical imaging.
Even though the risk is low, or if there is a risk at all, it is appropriate to manage the radiation delivered to patients being imaged and to use only sufficient radiation to produce the necessary image quality.
![Page 4: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/4.jpg)
4
How much radiation is delivered to a patient's body?
![Page 5: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/5.jpg)
5
Physical Quantity
SI Unit Non-SI Unit Relationship
Activity Becquerel (Bq)
Curie (Ci) 1Ci = 3.7 x 1010 Bq
Exposure Coulomb per kg (C/kg)
Roentgen (R) 1R = 2.58 x 10-4 C/kg
Absorbed Dose
Gray (Gy) Rad (rad) 1 rad = 0.01 Gy1 Gy = 100 rad
Dose Equivalent
Sievert (Sv) Rem (rem) 1 rem = 0.01 Sv1 Sv = 100 rem
Effective Dose
Sievert (Sv) Rem (rem) 1 rem = 0.01 Sv1 Sv = 100 rem
![Page 6: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/6.jpg)
6
Activity (Bq) Rate of decay.
no of atoms that decay and emit radiation in one second.
Exposure (C/kg) ionization produced in air by photons per unit mass.
Radiation quantity that expresses the concentration of
radiation delivered to a specific point, such as the surface of the human body
![Page 7: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/7.jpg)
7
Absorbed dose (Gy) energy imparted by ionizing radiation per unit mass of irradiated material. This is the quantity that is most directly related to
biological effects.
Equivalent dose (Sv) the product of the absorbed dose and effective quality
factor (Q) equivalent dose = absorbed dose x Q
![Page 8: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/8.jpg)
8
Type of ionising radiation Quality factor (Q)
X-rays or gamma raysElectrons or beta-particlesThermal neutronsFast neutrons (or neutrons of unknown energy)ProtonsAlpha-particlesRecoil nuclei (eg. In alpha-decay)Fission fragment
11
2.310
10202020
![Page 9: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/9.jpg)
9
Effective dose-equivalent (Sv)
the sum of the weighted dose-equivalent of all organs
or tissues of interest.
It is used to compare radiation doses on different body parts on an equivalent basis because radiation does
not affect different parts in the same way
![Page 10: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/10.jpg)
10
The effective dose (H) to an individual is found by calculating a weighted average of the equivalent dose (E) to different body tissues, with the weighting factors (W) designed to reflect the different radiosensitivities of the tissues:
H = ∑i Ei Wi
![Page 11: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/11.jpg)
11
![Page 12: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/12.jpg)
12
![Page 13: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/13.jpg)
13
DOSE LIMIT
![Page 14: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/14.jpg)
14
ANNUAL DOSE LIMIT Annual dose – the dose received over a period of 1
calendar year. Annual dose limit – the value of the annual dose
that must not be exceeded. Every licensee shall ensure that no worker or
member of the public receives exposure exceeding the annual dose limits.
The annual dose limits shall not apply to medical exposure or exposure due to natural background radiation.
![Page 15: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/15.jpg)
15
DOSE LIMIT IN OCCUPATIONAL EXPOSURE
Effective dose limit (had dose berkesan) for whole body radiation 20 mSv per calendar year averaged over a defined periods of 5 years, and with the provision that the effective dose shall not
exceed 50 mSv in any single year. Additional restriction (pengehadan) applies to the
occupational exposure for pregnant women.
![Page 16: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/16.jpg)
16
Occupational dose limit
Limit on equivalent dose:
In a calendaryear
Eye -150 mSv Skin -
500 mSv
Hand & feet -500 mSv
![Page 17: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/17.jpg)
17
Dose limits are similar for men and women, except for pregnant women.
When a female worker is confirmed to be pregnant the foetus shall, from the date of confirmation, be afforded the level of protection so that the dose to the foetus shall not exceed 1 mSv for the remaining period of the pregnancy.
=
![Page 18: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/18.jpg)
18
DOSE LIMIT FOR MEMBERS OF THE PUBLIC
There are dose limits allowed for members of the public. BSS regulation recommend 1 mSv per year.
Effective dose limit for whole body exposure
1 mSv
Equivalent effective dose limit for the lens shall not exceed
15 mSv
Average equivalent effective dose limit to the skin (averaged over any 1 cm2)
50 mSv
![Page 19: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/19.jpg)
19
Effective dose limit for a person who knowingly assists in the support of a patient during the period of diagnostic examination or treatment of the patient.
<5 mSv
Effective dose limit for a person below the age of 16 years visiting patient undergoing treatment or diagnostic examination involving radioactive material during the period of the treatment or examination of the patient.
< 1 mSv
![Page 20: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/20.jpg)
20
PLANNED SPECIAL EXPOSURE
Also known as dose limit in special circumstances (keadaan).
Means voluntary (sukarela) exposure during normal operation whereby 1 or more of the annual dose limits for a worker are likely to be exceeded, permitted (dibenarkan) only in situations when alternative techniques which do not involve normal exposure cannot be used.
![Page 21: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/21.jpg)
21
Shall only carried out when approved by the appropriate authorities (AELB @ Ministry of Health of Malaysia).
The dose received over a period of 1 calendar year does not exceed twice the annual dose limits, and in a lifetime, five times those limits.
![Page 22: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/22.jpg)
22
In choosing volunteers, the following shall be taken into account:- Previous experience; State of health; Special skill; Social and economic responsibilities.
![Page 23: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/23.jpg)
23
Person who is forbidden to participate in planned special exposure:-
If during the previous 12 months, such worker has received an exposure giving rise to the annual dose limit (whole body and partial body exposures).
If such worker has previously received accidental or emergency exposures which exceeds 5 times the annual dose limit (whole body and partial body exposures).
If such worker is a female of reproductive capacity.
![Page 24: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/24.jpg)
24
ANNUAL LIMIT ON INTAKE (ALI)
The derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year.
Ways of intake – oral (ingestion), inhalation, injection or skin absorption
![Page 25: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/25.jpg)
25
The ALI of any radionuclide depends on all of the following factors: - The type of radiation emitted. - Energy of the radiation and that of any
radioactive progeny. - The selective deposition in specific body tissue. - The effective half-life .
![Page 26: 7-8. Units for Measuring Radiation](https://reader035.vdocument.in/reader035/viewer/2022062409/55cf9035550346703ba3e930/html5/thumbnails/26.jpg)
26