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Technetium Tc 99m Generator


Sodium Pertechnetate Tc 99m Injection, as eluted according to the elution instructions with Lantheus Medical Imaging, Inc. TECHNELITE®, Technetium Tc 99m Generator, is in Sodium Chloride 0.9% as a sterile, non-pyrogenic, diagnostic radiopharmaceutical suitable for intravenous injection, and direct instillation. The pH is 4.5-7.5. The eluate should be clear, colorless, and free from visible foreign material. Each eluate of the TECHNELITE®, Technetium Tc 99m Generator should not contain more than 0.0056MBq (0.15 microcuries) of Molybdenum Mo99 per 37MBq (1 millicurie) of Technetium Tc 99m per administered dose at the time of administration, and not more than 10 micrograms of aluminum per milliliter of the Technetium Tc 99m Generator eluate, both of which must be determined by the user before administration. Since the eluate does not contain an antimicrobial agent, it should not be used later than one (1) working day after the elution (12 hours).

Lantheus Medical Imaging, Inc. TECHNELITE®, Technetium Tc 99m Generator consists of a column containing fission produced Molybdenum Mo99 adsorbed on alumina. The terminally sterilized and sealed column is enclosed in a lead shield; the shield and other components are sealed in a cylindrical plastic container with an attached handle. Built into the top surface are two recessed wells marked SALINE CHARGE and COLLECT. Needles protruding from these two wells accommodate supplied sterile eluant charge vials and sterile eluate collection vials. The eluting solvent consists of Sodium Chloride 0.9%, prepacked into septum-sealed vials.

The eluate collection vial is evacuated, sterile and non-pyrogenic. A sterile 0.22 micrometer bacteriological filter is incorporated between the column outlet and the collection vials. During and subsequent to elution, the eluate collection vial should be kept in a radiation shield. The Generator is shipped with a silicone needle seal over the charge needle and a vented needle cover over the collect needle. A sterile vial containing bacteriostat is supplied for the customer to aseptically reseal the collect needle after each elution.

Physical Characteristics

Technetium Tc 99m decays by isomeric transition with a physical half-life of 6.02 hours.1 Photons that are useful for imaging studies are listed in Table 1.

Table 1: Principal Radiation Emission Data -Technetium Tc 99m

Radiation Mean %/Disintegration Mean Energy (keV)
Gamma-2 89.07 140.5

External Radiation

The specific gamma ray constant for Technetium Tc 99m is 5.4 microcoulombs/Kg-MBq-hr (0.795 R/mCi-hr) at 1cm. The first half-value thickness is 0.023cm of lead (Pb). To facilitate control of radiation exposure from millicurie amounts of Technetium Tc 99m, for example, the use of a 0.27 cm thick standard radiation elution lead shield will attenuate the radiation emitted by a factor of about 1000. A range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of lead is shown in Table 2.

NOTE: Because the generator is well contained and essentially dry, there is little likelihood of contamination due to damage in transit.

Table 2: Radiation Attenuation of Technetium Tc 99m by Lead Shielding

Shield Thickness lead (Pb) cm Coefficient of Attenuation
0.023 0.5
0.09 10-1
0.18 10-2
0.27 10-3
0.33 10-4

Molybdenum Mo99 decays to Technetium Tc 99m with a Molybdenum Mo99 half-life of 66 hours. This means that only 78% of the activity remains after 24 hours; 60% remains after 48 hours, etc. (see Table 3). All units have a minimum of 38 mm, 1.5 inches (~ 6 half-value layers) of lead surrounding the activity. (See Table 3.)

Table 3: Molybdenum Mo99 Decay Chart Half-Life 66.0 Hours

Days Percent Remaining Days Percent Remaining
0 100 10 8
1 78 11 6
2 60 12 5
3 47 13 4
4 37 14 3
5 28 15 2
6 22 20 0.6
7 17 25 0.2
8 13 30 0.05
9 10    

The physical decay characteristics of Molybdenum Mo99 are such that approximately 88% of the decaying Molybdenum Mo99 atoms form Technetium Tc99m. Since the Molybdenum Mo99 is constantly decaying to fresh Technetium Tc99m, it is possible to elute the generator at any time. However, the total amount of Technetium Tc99m available will depend on the time interval from the previous elution, the quantity of Molydenum Mo99 remaining and the efficiency of the elution. Approximately 47% of maximum Technetium Tc 99m is reached after 6 hours and 95% after 23 hours.

The elution vial shield has a wall thickness of 7.9 mm, 0.31 inches, and reduces transmitted Technetium Tc 99m radiation essentially to zero. To correct for physical decay of Tc 99m, the fractions that remain at selected intervals of time are shown in Table 4.

Table 4: Physical Decay Chart: Technetium Tc 99m Half-Life 6Hours

Hours Percent Remaining Hours Percent Remaining
0* 100.0 9 35
1 89 10 32
2 79 11 28
3 71 12 25
4 63 14 20
5 56 16 16
6 50 18 13
7 45 24 6
8 40    
*Calibration Time

Last reviewed on RxList: 9/29/2014
This monograph has been modified to include the generic and brand name in many instances.

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