Radiation Protection in Nuclear Medicine
PRACTICAL SESSION 4
DECONTAMINATION
BACKGROUND
All work with unsealed sources in a nuclear medicine facility will result in contamination of surfaces, equipment and workers. Through regular monitoring, any significant
contamination will be detected and a decontamination procedure can then be initiated.
The decontamination procedure can be a simple removal of a surface
cover or protective clothing, but sometimes it might be necessary to clean the contaminated work area, equipment or person using a suitable method and cleaning
agent.
Nuclear medicine staff should be familiar with the techniques for decontamination of the body, dry and wet surfaces, equipment and clothing. The decontamination should always be done to the lowest level possible and well below the derived
limits for surface contamination given in Table 1. If a contamination can not be removed, the contaminated area should be marked and covered to prevent spread.
Table 1. Derived limits for surface contamination
Derived Limit (Bq∙cm2)
Surface and Equipment
In Controlled Areas
Surfaces of
Body
Radionuclide
Se, 89Sr, 125I, 131I
Supervised and Public
Areas, Personal Clothing,
Hospital Bedding
75
30
3
3
51
300
30
30
Cr, 99mTc, 201Tl
AIM
The aim of this practical session is to demonstrate, practise and compare decontamination methods on different surfaces with different agents.
MATERIAL
Different surface materials:
 Plastic flooring material
 Stainless steel
 Laminate (workbench surface)
 Glass
 Wood
 Skin of animal (e.g. pig)
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Radiation Protection in Nuclear Medicine
PRACTICAL SESSION 4
Decontamination agents:
 Distilled water
 70 % ethanol
 Soap solution
 Commercial decontamination agent
 10 % NaOH
Radiopharmaceutical
 Tc99m-pertechnetate
Instrumentation
 Contamination monitor (measuring count rate)
Other equipment
 Protective clothing (laboratory coat or plastic apron, gloves and overshoes)
 Tray
 Paper tissues or swabs
 Plastic bags
 Forceps
 Marker pen
PROCEDURE
Use protective clothing. Place the surface materials (plates) in the tray. Mark 5 (number of cleaning agents) circular areas on each plate. Make a background measurement. Put about 100 kBq (small volume) of Tc99m-pertechnetate in the middle of
each circle and let dry.
Measure the count rate. Start cleaning the contaminated area using the
different agents, working inwards from the periphery. Make another measurement
after the cleaning procedure. Calculate the remaining fraction of activity. Repeat the
cleaning procedure.
CONCLUSIONS
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Radiation Protection in Nuclear Medicine
PRACTICAL SESSION 4
Decontamination of dry surfaces
Detector:
Radiopharaceutical: 99mTc-pertechnetate
Surface:
Surface:
Agent:
Agent:
Background:
Background:
Number of
Measured
Net
Remaining
Number of
Measured
Net
Remaining
washings
count rate
count rate
activity
washings
count rate
count rate
activity
(%)
(%)
0
0
1
1
2
2
3
3
4
4
5
5
Surface:
Surface:
Agent:
Agent:
Background:
Background:
Number of
Measured
Net
Remaining
Number of
Measured
Net
Remaining
washings
count rate
count rate
activity
washings
count rate
count rate
activity
(%)
(%)
0
0
1
1
2
2
3
3
4
4
5
5
3
Radiation Protection in Nuclear Medicine
PRACTICAL SESSION 4
Surface:
Surface:
Agent:
Agent:
Background:
Background:
Number of
Measured
Net
Remaining
Number of
Measured
Net
Remaining
washings
count rate
count rate
activity
washings
count rate
count rate
activity
(%)
(%)
0
0
1
1
2
2
3
3
4
4
5
5
4