RATIONALE FOR PERFORMING QUALITY CONTROL For certain procedures, 
IT'S THE LAW.

Non-Diagnostic Study ==> Procedure must be repeated increased radiation dose and patient discomfort.

CRITERION: You must be able to answer "yes" to the question, "Would I inject this into my mother?"

CLASSIFICATION OF IMPURITIES

Type of Impurity Example Effect
Radionuclidic Mo-99 Increased Radiation Dose; Poor Image Quality
Radiochemical HR Tc Poor Image Quality; Increased Radiation Dose
Chemical Al3+ Poor Image Quality due to labeling problems

DETECTION OF IMPURITIES

METHOD TYPE OF IMPURITY
Dose Calibrator/Multichannel Analyzer Radionuclidic
Thin Layer Chromatography Radiochemical
Colorimetric Chemical

REQUIRED QC TESTING OF A Mo/Tc GENERATOR

TEST FREQUENCY SPECIFICATIONS
Mo Breakthrough Every Elution <0.15 µCi Mo/mCi Tc at time of injection
Al3+ Ion Breakthrough Every Elution <10 ppm of Al3+; may be expressed as µg/ml

OPTIONAL QC TESTING OF A Mo/Tc GENERATOR

TEST FREQUENCY SPECIFICATIONS
Hydrolyzed Reduced Tc Every Elution  < 2% (Reasonable Limit) (presently no legal limit)

1. Mo-99 Breakthrough: Mo-99 is assayed directly in the special lead pig supplied by the manufacturer of your dose calibrator. Tc-99m is then assayed directly in the plastic sleeve in your dose calibrator. Activity (uCi) of Mo-99 is divided by activity (mCi) of Tc-99m to obtain a ratio. If this ratio is <0.15 µCi Mo-99 per mCi of Tc-99m at time of injection, the generator eluate has passed the Mo-99 Breakthrough Test. As a rule of thumb, if the ratio is <0.038 at time of elution, the material will be suitable for injection for at least 12 hours.

2. Aluminum Ion Breakthrough: Al3+ ion is measured colorimetrically. A drop of the eluate is placed on one end of a special test paper; a drop of a standard solution of Al3+, concentration 10 ppm, is placed on the other end of the test strip. If the color at the center of the drop of eluate is less red than that of the standard solution, the eluate has passed the Aluminum Ion Breakthrough Test. Units may be expressed as ug/ml.

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Radiochemical Impurities in Tc-99m Radiopharmaceuticals

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THIN LAYER CHROMATOGRAPHY SYSTEMS OF Tc-99m COMPOUNDS
For Tc-99m DTPA, MDP, GH, PYP, HDP, MAA, MIAA, SULFUR COLLOID:
SYSTEM   IMPURITY MEASURED
Silica Gel/0.9% saline Hydrolyzed Reduced Tc
Paper/acetone or Paper/MEK Free Tc (Pertechnetate)

Tc-99m HEPATOBILIARY AGENTS
ITLC-SA/20% saline Free Tc (Pertechnetate)
ITLC-SG/water Hydrolyzed Reduced Tc

EXCEPTION TO THE RULE:

For insoluble Tc-99m Radiopharmaceuticals (e.g., Tc-MAA, Tc-MIAA, Tc-SC), it is only necessary to test for the presence of free Tc. No simple system can effectively separate colloidal HR Tc from an insoluble product, so HR Tc cannot be measured in these products. We therefore ignore its presence.

Tc-99m RADIOPHARMACEUTICALS: SEPARATION ON STRIP
SYSTEM SEPARATION OF RADIOCHEMICAL SPECIES
Silica Gel/saline HR Tc in bottom half; all other species in top half
Paper/acetone or Paper/MEK Free Tc in top half; all other species in bottom half
ITLC-SA/20% saline HR Tc in bottom half; all other species in bottom half
ITLC-SG/water  Free Tc in top half; all other species in bottom half

CALCULATIONS

% IMPURITY = (CPM IN HALF OF STRIP / CPM IN WHOLE STRIP ) X 100%

LABELING EFFICIENCY = 100% - % HR Tc - % Free Tc

FULL WIDTH/HALF-MAXIMUM TEST

This test measures the energy resolution capabilities of a NaI detector. It does NOT measure sensitivity, only energy resolution. Following display of the energy spectrum of the isotope, the width of the peak at half the maximum height is determined and then divided by the photopeak energy in keV. The ratio (usually 0.06-0.10, is then ultipled by 100% and the value reported as % full width at half maximum height. Values >10% indicate a crystal is near the end of its useful life.

The figure below indicates a FWHM value of 9.06%, indicating normal crystal energy resulution ability.

 

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