biodex ATOMLAB 500 - Page 236

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236 ATOMLAB 500 DOSE CALIBRATOR
Dial Value Settings and Source Containers (Glass Vial, Glass Syringe, etc.)
The Atomlab Dial Value (DV) settings
enable the software to convert ion
chamber current into a displayed
activity value for the isotope
corresponding to the DV selected. The
displayed activity value is directly
proportional to the DV.
The isotope’s “source container” is
either a vial or syringe; the composition
of the vial or syringe MAY influence the
accuracy of the activity measurement.
The DV supplied in the Atomlab User
Guide (Instruction Manual), or pre-
programmed into the isotope buttons,
are calibrated for use with the source
material in an un-shielded plastic
syringe (nominal 1mm wall), while
hanging in the supplied “source dipper”
syringe support. For isotopes contained
in sealed long lived QA sources (Cs-
137, etc.), the DV supplied are
calibrated for use with type Vial E epoxy
sources or equivalent.
Accurate measurement of unsealed
sources in any other configuration must
be with a new Container Dial Value
“CDV”, determined by the USER with
the following procedure.
NOTE: This is important to determine
the appropriate Dial Value for Beta and
low energy gammas when the container
(syringe or vial) changes.
During following steps, set DV to the
Atomlab published value.
Container with no source material
1 Assay a quantity of isotope source
material in a plastic syringe, nomi-
nal wall thickness of 1mm, record as
(Plastic Syringe Activity)
1
.
2 Transfer part or all of the source
material from the plastic syringe into
the empty Container.
3 Assay the Container with the iso-
tope source material, record as
(Container Activity).
4 Assay the partial or “empty” plastic
syringe for residual activity, record
as (Plastic Syringe Activity)
2
.
5 Calculate the Container Dial Value for
type of container use with isotope
assayed in that type of container,
Container with source material
1 Assay Container with the isotope
source material, record as (Con-
tainer Activity)
1
.
2 Transfer part or all of the source
material from the Container into a
plastic syringe, nominal wall thick-
ness of 1mm.
3 Assay the plastic syringe with the
isotope source material, record as
(Plastic Syringe Activity).
4 Assay the partial or “empty” Con-
tainer for residual activity, record as
(Container Activity)
2
.
5 Calculate the Container Dial Value
for use with isotope assayed,where
PSA = Plastic Syringe Activity and CA
= Container Activity.
Typically, for glass wall source
Containers, CDV will be higher than DV
when the isotope has a significant
portion of low energy photons in its
emission spectrum.
where PSA = Plastic Syringe Activity.