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Cardiogen-82

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Cardiogen-82

CARDIOGEN-82 ®
(rubidium Rb 82 generator)

WARNING

UNINTENDED STRONTIUM-82 (Sr-82) AND STRONTIUM-85 (Sr-85) RADIATION EXPOSURE

Unintended radiation exposure occurs when the levels of Sr-82 or Sr-85 in the rubidium Rb 82 chloride injection exceed specified limits [see WARNINGS AND PRECAUTIONS]

Perform generator eluate tests:

1) Record each generator eluate volume, including waste and test volumes, and keep a record of the cumulative eluate volume [see DOSAGE AND ADMINISTRATION].

2) Determine Rb-82, Sr-82, Sr-85 in the generator eluate:

  • Once a day, prior to any drug administrations, and
  • At additional daily tests after detection of an Alert Limit. Alert Limits are:
    • 14 L for the generator's cumulative eluate volume, or
    • An eluate Sr-82 level of 0.002 μCi/ mCi Rb-82, or
    • An eluate Sr-85 level of 0.02 Sr-85 μCi/ mCi Rb-82.
    • Perform the additional daily tests at time points determined by the day's elution volume; tests are performed every 750 mL [see DOSAGE AND ADMINISTRATION].

3) Stop use of a generator at an Expiration Limit of:

    • 17 L for the generator's cumulative eluate volume, or
    • 42 days post generator calibration date, or
    • An eluate Sr-82 level of 0.01 μCi /mCi Rb-82, or
    • An eluate Sr-85 level of 0.1 μCi /mCi Rb-82 [see DOSAGE AND ADMINISTRATION].

DRUG DESCRIPTION

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 μCi.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 μSv/37 MBq = 2.04 x 10-13Sv/Bq .
dCalculated from ICRP 66
eCalculated from ICRP 60
fStress phase only

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].

REFERENCES

1. Senthamizhchelvan S. et al. Human biodistribution and radiation dosimetry of 82Rb. J Nucl Med, 2010; 51:1592 – 99.

2. Senthamizhchelvan S. et al. Radiation dosimetry of 82Rb in humans under pharmacologic stress. J Nucl Med 2011; 52: 485-91

3. Eckerman, K. F. et al. User's Guide to the DCAL System, ORNL/TM-2001-190; Oak Ridge National Laboratory, Oak Ridge, TN, August, 2006.

4. Lederer, M and Shirley, V. Table of Isotopes, 7th Edition.

5. Judge, S et al. Applied radiation and isotopes (1987); vol 38, no. 3: pp 185-90.

Last reviewed on RxList: 2/15/2012
This monograph has been modified to include the generic and brand name in many instances.

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