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Chemical Characteristics
CardioGen-82 contains accelerator-produced Sr-82 adsorbed on stannic oxide in a lead-shielded column and provides a means for obtaining sterile nonpyrogenic solutions of rubidium Rb 82 chloride injection. The chemical form of Rb-82 is 82RbCl.
The amount (millicuries) of Rb-82 obtained in each elution will depend on the potency of the generator. When eluted at a rate of 50 mL/minute, each generator eluate at the end of elution should not contain more than 0.02 microcurie of Sr-82 and not more than 0.2 microcurie of Sr-85 per millicurie of rubidium Rb 82 chloride injection, and not more than 1 microgram of tin per mL of eluate.
Physical Characteristics
Rb-82 decays by positron emission and associated gamma emission with a physical half-life of 75 seconds.4 Table 4 shows the annihilation photons released following positron emission which are useful for detection and imaging studies.
The decay modes of Rb-82 are: 95.5% by positron emission, resulting in the production of annihilation radiation, i.e., two 511 keV gamma rays; and 4.5% by electron capture, resulting in the emission of “prompt” gamma rays of predominantly 776.5 keV. Both decay modes lead directly to the formation of stable Kr-82.4
TABLE 4 : Principal Radiation Emission Data
| Radiation | Mean Percent Per Disintegration | Mean Energy (keV) |
| Annihilation photons (2) | 191.01 | 511 (each) |
| Gamma rays | 13-15 | 776.5 |
| aRb-82 doses are averages of rest and stress dosimetry data
(see Senthamizhchelvan et al.1,2). To calculate organ doses (mrem)
from Rb-82, multiply the dose coefficient for each organ by the administered
activity in mCi. bSr-82 and Sr-85 doses are calculated using software package DCAL and ICRP dose coefficients. To calculate organ doses (mrem) attributable to Sr-82, and Sr-85, multiply the dose coefficients by the calculated amounts of strontium in ?Ci.3 cTo convert to SI units, insert the dose coefficient into the formula in parentheses, e.g. for adrenals 7.56 mrem/mCi = 7.56 ?Sv/37 MBq = 2.04 x 10-13Sv/Bq . dCalculated from ICRP 66 eCalculated from ICRP 60 fStress phase only |
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The specific gamma ray constant for Rb-82 is 6.1 R/hour-millicurie at 1 centimeter. The first half-value layer is 0.7 centimeter of lead (Pb). Table 5 shows a range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of lead.5 For example, the use of a 7.0 centimeter thickness of Pb will attenuate the radiation emitted by a factor of about 1,000.
TABLE 5 : Radiation Attenuation
by Lead Shielding
| Shield Thickness (Pb) cm | Attenuation Factor |
| 0.7 | 0.5 |
| 2.3 | 10 -1 |
| 4.7 | 10-2 |
| 7.0 | 10-3 |
| 9.3 | 10-4 |
Sr-82 (half-life of 25 days (600 hrs)) decays to Rb-82. To correct for physical decay of Sr-82, Table 6 shows the fractions that remain at selected intervals after the time of calibration.
TABLE 6 : Physical Decay
Chart: Sr-82 half-life 25 days
| Days | Fraction Remaining | Days | Fraction Remaining | Days | Fraction Remaining |
| 0* | 1.000 | 15 | 0.660 | 30 | 0.435 |
| 1 | 0.973 | 16 | 0.642 | 31 | 0.423 |
| 2 | 0.946 | 17 | 0.624 | 32 | 0.412 |
| 3 | 0.920 | 18 | 0.607 | 33 | 0.401 |
| 4 | 0.895 | 19 | 0.591 | 34 | 0.390 |
| 5 | 0.871 | 20 | 0.574 | 35 | 0.379 |
| 6 | 0.847 | 21 | 0.559 | 36 | 0.369 |
| 7 | 0.824 | 22 | 0.543 | 37 | 0.359 |
| 8 | 0.801 | 23 | 0.529 | 38 | 0.349 |
| 9 | 0.779 | 24 | 0.514 | 39 | 0.339 |
| 10 | 0.758 | 25 | 0.500 | 40 | 0.330 |
| 11 | 0.737 | 26 | 0.486 | 41 | 0.321 |
| 12 | 0.717 | 27 | 0.473 | 42 | 0.312 |
| 13 | 0.697 | 28 | 0.460 | ||
| 14 | 0.678 | 29 | 0.448 | ||
| *Calibration time | |||||
To correct for physical decay of Rb-82, Table 1 shows the fraction of Rb-82 remaining in all 15 second intervals up to 300 seconds after time of calibration [see DOSAGE AND ADMINISTRATION].