Dose Calibrator
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•
Accuracy
• Done on installation and annually
thereafter
• Usually 57Co and 137Cs
• Should document Zero and BKG
• Test reading needs to exceed 140 mV
• Also evaluate other channels
• National Bureau of Standards (NBS)
Accuracy Test Results
Accuracy
Linearity
Geometry
Constancy
Accuracy Results
• All accuracy measurements are repeated three
times to obtain an average value and assess the
unit's reproducibility.
• A percent error of ± 5.0% may indicate a need for
repair or adjustment.
• A percent error of ± 10.0% requires repair or
replacement of the unit.
Geometry
• Done at installation or after repair
• Use a syringe that is normally used for
injections
• Use a vial similar in size, shape, and
construction to the radiopharmaceutical kit
vials
1
Geometry - Results
Geo Variance Plot
• If any correction factors are greater than
1.1 or less than 0.9 or if any data points lie
outside the 10 percent error lines, it will be
necessary to make a correction table or
graph that will allow you to convert from
"indicated activity" to "true activity."
Geometric Variance - 5 cc Syringe
1.06
1.04
1.02
1.00
0.98
0.96
0.94
1.0
2.0
3.0
4.0
5.0
Volume (cc)
M easured
Lo wer Limit
Up p er Limit
Linearity
Linearity Test
• At installation and quarterly thereafter.
• Linearity means that the calibrator is able to
indicate the correct activity over the range of use
of that calibrator.
• This test is done using a vial or syringe of
activity which is at least as large as the highest
dosage that will be administered to a patient, in a
unit dosage syringe, or as a therapeutic
radiopharmaceutical (whichever is largest).
• Decay Method
• Shield Method
• If the worst deviation is more than ± 0.10, the
dose calibrator should be repaired or adjusted. If
this cannot be done, it will be necessary to make
a correction table or graph that will allow you to
convert from activity indicated by the dose
calibrator to "true activity".
Constancy
Linearity Test
8:29 AM
0.65625
5.00
4.00
• Daily
Ln Activity (mCi)
3.00
2.00
1.00
0.00
-1.00
-2.00
-3.00
-4.00
-5.00
0.00
0.50
1.00
1.50
2.00
Fractional Days
2.50
3.00
3.50
– Assay the reference source(s) using a
frequently used setting (i.e., Tc-99m may be
the most frequently used setting).
– Measure background at the same setting, and
subtract or confirm the proper operation of the
automatic background subtract circuit if it is
used.
2
Constancy
Date
1-Jan-10
2-Jan-10
3-Jan-10
4-Jan-10
5-Jan-10
6-Jan-10
7-Jan-10
8-Jan-10
9-Jan-10
10-Jan-10
11-Jan-10
12-Jan-10
13-Jan-10
14-Jan-10
15-Jan-10
16-Jan-10
17-Jan-10
18-Jan-10
Tc-99m Range (uCi)
Lowe r
Uppe r
604
603
601
600
598
596
595
593
592
590
589
587
586
584
583
581
580
578
-
Source Use d = Co-57 E-Vial
Me asure d
BKG
Ze ro
668
666
664
662
661
659
657
656
654
652
651
649
647
646
644
642
641
639
Weekly Constancy
Constancy
Initials
• Weekly
– Weekly, using one of the sources, repeat the
above procedure for all commonly used
radioisotope settings.
– If the value does not agree, within ± 10%, the
dose calibrator must be repaired or replaced.
• Daily and Weekly tests must be
documented
Frequency
• Test for the following at the indicated frequency and for
the suggested tolerance:
• Constancy at least once each day prior to assay of
patient dosages ( ±10 percent).
• Linearity at installation and at least quarterly
thereafter ( ±10 percent).
• Geometry dependence at installation ( ±10 percent).
• Accuracy at installation and at least annually
thereafter ( ±10 percent).
• After repair, relocation or adjustment, repeat the above
tests as appropriate.
NaI Well Counter
• Assess accuracy at installation and
annually.
• Evaluate Resolution FWHM
• Estimate MDA for swipe methods
– Package Receipts
– Daily & Weekly swipes
– Therapy room clearance surveys
• Chi Square Test semi-annually
Reporting Results
Rs < Lc reported as
Rs + 1.65[Rgross/tgross + Rbkg/tbkg]½
Rs > Lc reported as
Rs + 1.96[Rgross/tgross + Rbkg/tbkg]½
Lc = 1.65[ctsbkg/t2bkgs [1 + tbkg/tgross]½
MDA = 2.72/tgross + 3.30[Rbkg/tbkg [1 + tbkg/tgross]]½
3
Chi Square Test
NaI Uptake Probe
• Assess accuracy at installation and
annually.
• Evaluate Resolution FWHM
• Estimate MDA for Bioassays
• Chi Square Test semi-annually
70000
60000
50000
40000
30000
20000
10000
0
1
2
3
4
5
6
7
8
9
10
Survey Meters
• Calibrated Annually/Check Source
• Should be check for functionality with a
check source whenever used.
• Should be checked for battery leakage at
least semi-annually.
• Replace batteries that are getting low.
Package Receipt
• All radioactive packages received displaying a
Radioactive White I, Yellow II or Yellow III
labels which are equal to or greater than Type A
quantities
• Monitor the exposure levels at 3' from the
package and at the surface of the package.
• If the exposure rate exceeds 10 mR/hr at 3 feet,
or 200 mR/hr at the surface immediately notify
the Radiation Safety Officer.
Package Receipt
• All radioactive packages received displaying a
Radioactive White I, Yellow II or Yellow III
labels which are less than Type A quantities
• Wipe the external surface of the package (not
required for gases). If there is contamination
>2,200 dpm/100 cm2, stop and immediately
notify the Radiation Safety Officer.
Daily Surveys
• All radiological elution, preparation, and
administration areas, will be surveyed at the end
of each day of use with a low-range survey
meter.
• If diagnostic administrations are occasionally
made in patients' rooms and special care is taken
to remove all paraphernalia, those rooms need
not be surveyed.
4
Weekly Surveys
Survey Records
• All radiopharmaceutical use, storage and waste
storage areas will be surveyed weekly with a
low-range survey meter for exposure levels and
by swipe for removable contamination.
• The swipe sample assay procedure should be
sufficiently sensitive to detect the presence of
2,000 dpm per swipe of removable
contamination.
• The record must include the date of
the survey, the results of the survey,
the instrument used to make the
survey, and the name of the individual
who performed the survey.
• It is appropriate to set trigger levels at
which actions are required.
Survey Map
Waste Disposal
• All radioactive materials with a physical half-life
of less than 120 days will be held for decay-instorage before being disposed of in the ordinary
trash.
• Monitor all waste at the surface of the container,
with no interposed shielding, at the time of
disposal, and determine that its radioactivity
cannot be distinguished from background
radiation levels. This will be done with a
radiation detection survey meter set on the most
sensitive scale.
Waste Disposal
• Generally recommended that waste be held for 10
Half-lives of longest lived material.
• Make a record of the above steps including initial
date placed into storage, radionuclides, general
description of the materials, date of disposal,
survey meter used, background reading,
measured dose rate, ultimate disposition and the
initials of the individual performing the survey.
Sealed Source Inventory
• Sealed source inventory required in 6
months.
• Must include nuclide, activity, serial
number, location
5
Sealed Source Leak Tests
Leak Test Results
• Test the source for leakage before its first
use unless the licensee has a certificate from
the supplier indicating that the source was
tested within 6 months before transfer to the
licensee; and
• Test the source for leakage at intervals not to
exceed 6 months
• Sources containing 3.7 MBq (100 µCi) or less
of beta or gamma-emitting material or 0.37
MBq (10 µCi) or less of alpha-emitting
material
DOT Returns
• Sealed Sources
• Radiopharmaceuticals
– Unused doses
– Contaminated syringes
• Monitoring
– Contamination
– Exposure
LIMITED QUANTITY SHIPMENTS
• The radiation level at any point on the external
surface of the package must not exceed 0.5
millirem per hour.
• Removable contamination on the external surface
of the package must not exceed 2,200 dpm/100
cm2(3.7 Bq/100 cm2) for beta/gamma emitting
radionuclides.
• Individual shipping must receive DOT Training.
Spill Kits
Posting
Name and telephone
number of RSO or an
alternate person(s) should
be posted conspicuously in
areas of use, so that it is
readily available to
workers in case of
emergencies. Licensee
should have emergency
equipment readily
available for handling
spills.
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Disposable gloves
Housekeeping gloves
Disposable lab coats
Disposable head coverings
Disposable shoe covers
Roll of absorbent paper with plastic backing
Masking tape
Plastic trash bags with twist ties
“Radioactive Material” labeling tape
Marking pen
Pre-strung “Radioactive Material” labeling tags
Box of Wipes
Instructions for “Emergency Procedures”
Clipboard with a copy of the Radioactive Spill Report Form for the facility
Pencil
Appropriate survey instruments, including batteries (for survey meters).
6
Patient Release
• A licensee may authorize the release
from its control of any individual who
has been administered unsealed
byproduct material or implants
containing byproduct material if the
total effective dose equivalent to any
other individual from exposure to the
released individual is not likely to
exceed 5 mSv.
Documentation
• A licensee shall retain a record of the basis for
authorizing the release of an individual in
accordance with § 35.75, if the total effective
dose equivalent is calculated by-(1) Using the retained activity rather than the activity
administered;
(2) Using an occupancy factor less than 0.25 at 1
meter;
(3) Using the biological or effective half-life; or
(4) Considering the shielding by tissue.
Record of Release Calculation for I-131 Therapy
Bioassay - RSO
This record is intended to provide the information required by 10 CFR 35.75 for the release of patients treated
with therapeutics level of radioactive iodine-131. In order to be released the total effective dose equivalent to an
other individual from exposure to the releases individual must not be likely to exceed 5 millisieverts (0.5 rem).
Patient Name:
• Personnel monitoring program, including
determining the need for and evaluating
bioassays, monitoring personnel exposure
records, and developing corrective actions
for those exposures approaching maximum
permissible limits.
• Regulatory Guide 8.20 “Applications of
Bioassay for I-125 and I-131”
D.O.B.
Uptake Fractions and Effective Half-Lives
Extrathyroidal
Thyroidal
Component
Component
Medical
55
Condition
Uptake F1
T1eff
Uptake F2 T2eff
Hyperthyroidism
0.2
0.32
0.8
5.2
Postthyroidectomy
0.95
0.32
0.05
7.3
D(∞ ) =
34.6τ Q0
2 E T ( 0.8) 1 − e
(
(100cm) {
Factor
F1
F2
E1
E2
T1eff
T2eff
Qo
Compartment
Uptake
Body
Thyroid
Total
1 p
− .693( 0 .33 )/ T p
)+ e
E
0.75
0.25
0.125
− .693 ( 0.33 ) / Tp
Patient Specific Data
Definition
Extrathyroidal uptake fraction
Thyroidal uptake fraction
Occupancy factor for first 8 hours
Occupancy factor 8 hours to decay
Extrathyroidal effective half-life (day)
Thyroidal effective half-life (day)
Patient Dose (mCi)
External Dose Contribution
Dose
Dose
Time to Deliver
(rem)
(mSv)
90% of Dose
0.057
0.566
8.0
hours
0.007
0.065
1.1
days
0.423
4.231
17.3
days
0.486
4.862
5.8
days
Occupancy Factors
Condition
Tp, Teff or t < 1 day
Teff > 1 day (sleep alone)
Teff > 1 day
(live alone first 2 days)
E 2 F 1T 1eff + e
Value
0.20
0.80
0.75
0.25
0.32
5.2
55
− .693( 0.33 )/ T p
E 2 F 2 T 2 eff
}
Comment
Live alone 2 days
Internal Dose Contribution
D i = Qo 10
(
−5
)( DCF )
DCF
53
rem/mCi
Dose
0.02915
rem
Internal dose need not be considered
TEDE =
0.486
rem
* TEDE Below 500 mrem. Patient may be released.
Activity to be administered:
mCi of I-131
Date:
Date:
Authorized Physician User:
f
f
“
f
Breast Feeding
• If the total effective dose equivalent to a
nursing infant or child could exceed 1 mSv
(0.1 rem) assuming there were no
interruption of breast-feeding, the
instructions must also include-(1) Guidance on the interruption or discontinuation
of breast-feeding; and
(2) Information on the potential consequences, if
any, of failure to follow the guidance.
• The licensee shall maintain a record of
instructions provided to a breast-feeding
female in accordance with § 35.2075(b).
7
Duties and responsibilities of the RSO include:
• Oversight of ordering, receipt, surveys, and
delivery of byproduct material
• Monitoring and surveys of all areas in which
radioactive material is used
• Packaging, labeling, surveys, etc., of all
shipments of byproduct material leaving the
institution
• Personnel monitoring program, including
determining the need for and evaluating
bioassays, monitoring personnel exposure
records, and developing corrective actions for
those exposures approaching maximum
permissible limits
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•
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•
•
Training of all personnel
Waste disposal program
Inventory and leak tests of sealed sources
Decontamination
Investigating any incidents and responding to any
emergencies
• Maintaining all required records.
The RSO performs audits of all areas of use and
individuals who are authorized to use byproduct
material to ensure work is done in accordance with
the license, regulations, and user permit conditions.
8