Radiopharmaceutical Production
Radionuclidic identity
STOP
Radionuclidic identity
Radiopharmaceutical
Production
QC Tests
Radionuclidic Purity
Contents
Requirements
Discussion
Procedure
STOP
•
The radionuclidic identity and
purity tests show that the
radiopharmaceutical does not
contain radionculides other
than the one desired.
Contents
• Requirements
• Discussion
• Procedure
Requirements
Radiopharmaceutical
Production
•
Requirement: The measured physical half-life of the test
sample must be between 105 and 115 minutes. The test should
be completed prior to release of product.
•
The gamma spectrum of the test sample should show the major
peak at 511 KeV, and a sum peak at 1022 KeV depending on
geometry and detector efficiency. Not less than 99% of the
gamma emissions should correspond to 18F. This test should be
performed periodically.
QC Tests
Radionuclidic Purity
Contents
Requirements
Discussion
Procedure
STOP
Discussion
Radiopharmaceutical
Production
•
QC Tests
Radionuclidic Purity
Contents
Requirements
Discussion
Procedure
•
STOP
Discussion: Half-life: Half life can be determined within the
acceptable limits using counting equipment, such as dose
calibrator or a well counter by measuring radioactivity of the test
sample at two or more time points, and the decay calculations.
In practical consideration for the short half-life of 18F and need
to release the product the soonest, a precisely measured
counting time of at least 10 minutes is generally sufficient to
determine the physical half-life of 18F. The measured half life
will be lower if 13N impurity is present in FDG. During validation
studies, the time interval between measurements may be
increased for improved assurance of radionuclidic purity.
Gamma Spectrum: It must be realized that the mere presence
of 511 KeV or 1022 KeV peak in γ-ray spectrum is not sufficient
to determine radionuclidic identity. Impurity such as 13N (arising
from 16O impurity in the target) and/or other positron emitters
will not be detected as the gamma peaks with energy of 511
KeV and 1022 KeV sum peak are a common feature of positron
emitters. Therefore, a combination of gamma spectrum and the
half-life measurement together provide the best assurance of
radionuclidic identity and purity.
Half-Life Procedure
Radiopharmaceutical
Production
•
QC Tests
Radionuclidic Purity
Contents
Procedure: For half-life measurement, place a small aliquot of
the test sample in a dose calibrator or in a well counter. Record
the initial radioactivity (A0). Record the radioactivity again after
at least 10 minutes (measured precisely) (A10). Calculate the
half-life from the two measured values as per the formula:
Requirements
Discussion
T1/2 = 0.693 x t / [2.03 x [Log A0-Log A10]:
Procedure
where T1/2 and t are in minutes.
•
STOP
Record the gamma spectrum (NaI or HPGe) of a test sample
that has been diluted appropriately (and quantitatively) to
provide optimum number of counts.
Half-Life Procedure
Radiopharmaceutical
Production
•
QC Tests
Radionuclidic Purity
Contents
Requirements
•
Discussion
Procedure
•
•
STOP
Demonstration Procedure – In this demonstration, the test
is done using a well counter and software written to
calculate the half-life.
– A sample taken from the final product containing between
10,000 – 300,000 cpm. This particular program will record
the number of counts in the sample 100 times, and run an
algorithm that determines the half-life of the sample. It
reports the half-life and the percent deviation.
Half-life Values
– If the half-life values are not within the range specified in the
Table, a common cause is that the amount radionuclide
used was too high or too low, so this should be taken into
account when repeating the determination. As an example,
if the analysis gives an incorrect half-life, the amount of
fluorine-18 sample should be reduced by a factor of 5 and
the test repeated
Radionuclide Half-life
Acceptance Range
– Nitrogen-13
9 – 11 min
– Carbon-11
18 - 22 min
– Fluorine-18
105 - 115 min
Demonstration
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