MODULE 2 (Part 3) UNITS, DETECTION AND MEASUREMENT

Radiation Monitoring

• To assess workplace conditions and individual exposures;

• To ensure acceptably safe and satisfactory radiological

conditions in the workplace;

• To keep records of monitoring, over a long period of time,

for the purposes of regulation or good practice.

Radiation monitoring instruments

used both for area monitoring and for individual

monitoring.

Area survey meters or area monitors

instruments used for measuring radiation levels are

referred to as?

Personal dosimeters or individual dosimeters

instruments used for recording the equivalent doses

received by individuals working with radiation are

referred to as?

Radiation detectors

1. Personnel or Personal

2. Area monitoring

Dosimetry

Measurement of ionizing radiaiton doses to personnel

when you are working with radiation,

radioactive materials or are in an area where work is

performed with radionuclides or radioactive waste storage

areas.

When to wear dosimetry?

RSO

Notify the ____ if your badge or ring has been damaged or lost

On the chest. (Torso, facing source)

For radiographer (Gen. Diagnostic X-ray/ CT), where to wear dosimetry if there’s no apron?

Wear badge at collar level on the outside of the apron

For radiographer (Gen. Diagnostic X-ray/ CT), where to wear dosimetry if there’s an apron?

• Badge on the collar, outside lead apron

• Badge on the wrist, under lead apron

Location of dosimetry for dual badges (Radiographer)

Nuclear Medicine Technologist

Main exposure: from unsealed radionuclides (Injection, dispensing, patient contact)

Records whole-body dose

Dosimeter: Torso (Chest outside apron NMT)

Monitors extremity dose (hands usually highest exposed)

Ring dosimeter(s) on dominant hand, base of finger

Second torso badge front & back

What is needed for therapy cases involving I-131, Lu-177, etc.?

Interventional Radiographer (Fluoro / Cath lab)

Always apron-wearing due to high scatter exposure

Under apron, at waist or chest level

Dosimeter (IR): whole body effective dose

Head, neck, and lens dose

IR Dosimeter on collar, outside apron

Hand dosimeter

IR dosimeter if hands is close to primary beam

Radiotherapist (Radiation Therapist / Radiotherapy Technologist)

Main exposure: scattered/leakage radiation from linac during patient setup (much lower than diagnostic staff)

Torso/chest level, outside apron (RadThera)

Dosimeter for Radthera:

Usually not worn since linacs have built-in shielding

Ring dosimeter

Only if doing brachytherapy source handling (direct contact with sealed/unsealed sources)

Extremity badges

In modern external beam radiotherapy ____ is rarely needed

1. Film badges

2. Pocket ionization chambers

3. Thermoluminescent dosimeters (TLDs)

4. Extremity dosimeters (TLD ring badges)

5. Optically stimulated luminescent (OSL) dosimeters

Types of personnel monitoring

Film Badges

- An economical type of personnel monitoring device

- Record whole-body radiation exposure accumulated at a

low rate over a long period of time

Film badges

Most common type of personnel monitor

Aluminum, cadmium, lead and copper

Metal filters inside the film badge

Film metal filters

Allows determination of posterior exposure and backscatter

Every months

How often should film badges be changed?

They are easily affected by temperature and humidity changes.

Why should the film badges be changed every month?

10 mrem and most sensitive to an energy of 50 keV

Sensitivity level of film badges

Forward

Film badges mus be worn with the correct side of the badge facing ____

Shallow and deep doses

__ and __ can be calculated according to the amount of darkening of the film after processing

Control badge

• serves as a baseline when compared with the rest of the film badges after processing by the monitoring company

• Kept in a radiation-free area

• Companies who supplies institutions with film badges

• inexpensive

• Simple to use

• Readily processed by commercial laboratories

• Provide a permanent record by laboratory and in radiology department

Advantages of film badges

• must wait for reading

• Low limit of sensitivity (approx. 10 mrem)

• Susceptible to heat, humidity, and light leaks

• Not reusable

Disadvantages of film badges

Philippine Nuclear Research Institure (PNRI)

• provides personnel monitoring services (whole body, extremity)

• Maintains the philipine dose registry (PhilDose) which tracks occupational exposure records for workers

• Under the Department of Science and Technology, specifically its radiation protection services section

Radiation Protection Services Section

RPSS meaning

Philippine Dose Registry

PhilDose meaning

Nagase Philippine Corporation

• authorized distributor of landuaer’s OSL technology in the Philippines

• Runs a dosimtery laboratory that provides radiation dose monitoring services (personnel dosimetry) using OSL badges

SGS Philippines Inc. (Societe Generale de Surveillance in French)

• translates to general society of surveillance in english

• Offers “Personal Radiation Monitoring Services” including TLD, CR-39, etc. as well as radiation consultancy and analytical services

TUV Rheinland Philippines, Inc. - Life Care Services

• Private provider; offers OSL dosimetry services

• Accredited / authorized for dosimetry testing udner DTI / national regulatory frameworks

Plastic film holder

Made of a plastic material of a low atomic number to filter low-energy x-radiation, gamma radiation, and beta radiation

Plastic film

Metal filters

A film packet

3 parts film badge

Metal filters

Aluminum or copper that are secured in a permanent position

Open window of the film badge

Allows all incident radiation that can penetrate the film wrapping to interact with the film.

Thin plastic filter

Attenuates beta radiation but passes all other radiations

Thick plastic filter

Passes all but the lowest energy photon radiation and absorbs all but the highest beta radiation

Dural filter

Progressively absorbs photon radiation at energies below 65keV as well as beta radiation

Tin/lead filter

Allows an energy independent dose response of the filmm over the photon energy range 75keV to 2Mev

Cadmium lead filter

Where the capture of neutrons by cadmium produces gamma rays which blacken the film thus enabling assessment of exposure to neutrons

Pocket ionization chamber

Also called self-reading pocket dosimeter, self-indicating

pocket dosimeter, and quartz-fiber dosimeter.

Pocket ionization chamber

very sensitive type of personnel monitoring device.

Pocket ionization chamber

Consists of one positive and one negative electrode

Stationary; hair or fiber

One electrode is ; one moves and is called ___