Regulatory Commission (NRC) regulations,the permissible limit for^99 Mo
breakthrough is 0.15mCi (5.5 kBq) per millicurie (37 MBq) of 99mTc at
the time of injection. The^99 Mo breakthrough is determined by the
detection of high-energy photons (740 keV and 780 keV) of^99 Mo in a dose
calibrator after stopping 140-keV photons of 99mTc in a lead container
(6-mm thick).
Aluminum is also likely to be eluted with 99mTc activity and must be
checked. The presence of aluminum interferes with the preparation of
99mTc-labeled sulfur colloid by forming larger particles, which are trapped
in the lungs. It also agglutinates the red blood cells during labeling. Its
acceptable limit is 10mg/ml of 99mTc solution. Aluminum ion (Al^3 +) is
checked by the colorometric test using a paper strip impregnated with a
coloring agent and comparing the intensity of the color developed by the
sample solution with that by a standard test solution (10mg/ml).
Questions
- Describe the different methods of production of radionuclides.
Which method gives relatively more proton-rich and neutron-rich
radionuclides? - What is the average number of neutrons emitted in fission?
- What is the difference between carrier-free and no-carrier-added
radionuclides? - Why are cadmium rods and graphite used in the reactor?
- If^68 Zn is bombarded with protons in a cyclotron and three neutrons are
emitted from the nucleus, what is the product of the nuclear reaction?
Write the nuclear reaction. - (a) What are the primary requirements for a radionuclide generator?
(b) How long does it take to reach transient equilibrium in a^99 Mo–99mTc
generator?
(c) What is the permissible limit of^99 Mo breakthrough in the 99mTc
eluate?
(d) A 20-mCi (740-MBq) 99mTc eluate is found to contain 10mCi
(0.37 MBq) of^99 Mo. Can this preparation be injected into a patient? - Why is Al^3 +undesirable in the 99mTc eluate? What is the permissible limit
of Al^3 +in the 99mTc eluate? - A 2-Ci (74-GBq)^99 Mo–99mTc generator calibrated for Thursday noon
was eluted at 10 a.m. on the following Monday. Calculate the 99mTc activ-
ity assuming 80% yield and 87% of^99 Mo decays to 99mTc. - Calculate the activity in millicuries (MBq) of^111 In produced by irradia-
tion of 1 g of pure^111 Cd for 3 hr with 12-MeV protons having a beam
intensity of 10^13 particles/(cm^2 · sec). The cross section for formation of
(^111) In(t =2.8 days) is 200 millibarns (1 millibarn = 10 − (^27) cm (^2) ).
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54 5. Production of Radionuclides