TThe Pharmaceutics and Compounding Laboratory
Radiopharmaceuticals:
TC-99M Sulfur Colloid

Laboratory Procedure

A. Preparation of Tc-99m Sulfur Colloid Injection

Video View a video demonstration on making a technetium-99m sulfur colloid

  1. Put on disposable gloves.

  2. Cover the work bench with plastic backed adsorbent paper.

  3. Prepare a boiling water bath (200 ml water in a 400 ml beaker) containing a lead shield. (The water level must be sufficient to cover the lead shield).

Video View a video demonstration on a rolling, boiling water bath

  1. In a 3 ml syringe, aseptically obtain 1 ml of sodium pertechnetate Tc-99m solution and sign the log out sheet. Assay the dose in the syringe with the radionuclide dose calibrator. Record the activity and time the dose was measured, as well as the activity and time of calibration of the original sample from the generator. Calculate the activity that should be present using the decay table provided and compare the calculated activity with the assayed activity.

  2. Swab the rubber closure of the sulfur colloid reaction vial. Place the reaction vial containing the lyophilized sodium thiosulfate, disodium EDTA, and gelatin into a lead pig.

  3. Inject the 1 ml of sodium pertechnetate Tc-99m solution into the reaction vial. DO NOT PRESSURIZE THE VIAL. Swirl vial to dissolve powder.

  4. Swab the rubber closure of vial A. Remove 1.5 ml of 0.148 N hydrochloric acid from vial A and aseptically inject the entire contents into the reaction vial. DO NOT PRESSURIZE THE VIAL. Swirl reaction vial to mix.

  5. Transfer the reaction vial to the lead shielded boiling water bath and heat for 5 minutes. The vial will float in the water bath.

  6. At the end of heating, remove the reaction vial and place it into a lead pig to cool for 3 minutes. Swab the reaction vial closure again.

  7. Swab the rubber closure of vial B. Remove 1.5 ml of phosphate buffer from vial B and aseptically transfer its contents into the reaction vial. DO NOT PRESSURIZE THE VIAL. Swirl reaction vial to mix.

  8. Calculate the radioconcentration (C) of the final 99mTc-SC using the following formula:
    radioconcentration equation
    where:
      A = Tc-99m activity added to the reaction vial at the time indicated on the label (Assayed Activity).
      V = Total volume in the reaction vial


  9. Complete the information on the pressure-sensitive label and place this label on the lead pig.

B. Radiochromatography (for radiochemical purity)

Video View a video demonstration on determining the radiopurity of a sulfur colloid

  1. Obtain three, Whatman 3-MM paper strips. Make a very light pencil mark 1 cm from one end of each strip to mark the origin. Place an ink mark with a water-based flair pen 2 mm from the opposite end to mark the solvent front. Number the top and bottom of each strip with the pencil as follows:

    strips image

  2. Using a clean 1 ml syringe and 27 gauge needle obtain a 0.1 ml sample of your 99mTc-SC preparation. Place a one drop sample (2 - 3 mm diameter spot) on the pencil line at the origin on strip 1.

  3. Repeat Step 2 using 99mTc pertechnetate dilution on strip 2 and the unknown 99mTc-SC on strip 3.

  4. Place each strip, origin end down, into a scintillation vial containing 0.9% Sodium Chloride Solution which is 2 - 3 mm deep. Be sure spot is above the level of liquid as follows:

    elution strips image

  5. Develop each strip until the solvent reaches the top, indicated by spreading of the ink spot.

  6. Remove the developed strips with forceps and blot dry on a paper towel. Cut each strip into two equal pieces.

  7. Obtain 30 second background count before counting your samples. Place each strip half onto a counter tray and count for 30 seconds with a gamma scintillation counter.

  8. Determine the net count per minute (CPM) per strip by subtracting the background CPM from each sample CPM. Record the data in your handout.

Comments: Radiochemical purity of a radiopharmaceutical is defined as the fraction of the total radioactivity present in the desired chemical form. Strip number 2 demonstrates the migration characteristics of the impurity, Tc-99m pertechnetate. It migrates to the solvent front, whereas 99mTc-SC remains at the origin.

 


Experimental Data and Results

A. Preparation of Tc-99m Sulfur Colloid Injection

Calibration time for sample from generator __________________
Calibrated activity at this time for sample from generator __________________ µCi
Time your sample's activity was assayed in lab __________________
Assayed activity (from 1 ml sample) __________________ µCi
Calculated activity in 1.0 ml of sodium
pertechnetate Tc-99m solution
__________________ µCi
Total volume of the final 99mTc-SC product __________________ ml
The radioconcentration (C) of the final 99mTc-SC
product (from assayed activity)
__________________ µCi/ml

DISPOSE OF ALL MATERIALS IN SPECIALLY MARKED SAFETY CONTAINERS. DO NOT PLACE IN TRASH.

B. Radiochromatography

Background CPM _________________

Sample Counts/30 sec Total CPM Net CPM % of Total Activity
1. Product
O
       
SF
       
O + SF
XXX
XXX
 
100%
2. Pertechnetate ion
O
       
SF
       
O + SF
XXX
XXX
 
100%
3. Unknown product
O
       
SF
       
O + SF
XXX
XXX
 
100%

O = Origin, SF = Solvent Front

What is the radiochemical purity of your product?___________________

What is the radiochemical purity of the unknown? ___________________

Inspection of Final Product/Label ___________________________________

 

Discussion Questions

  1. Would you dispense your 99mTc-SC product for patient use? The 99mTc-SC unknown product? Explain.

  2. You have just received the following order in the pharmacy. What volume of your 99mTc-SC preparation is required to fill the order if the dose is prepared 3 hours after the product calibration time? Half life for Tc-99m is 6 hours. Show your calculations!

    For: John Jones
    Rx: Tc-99 Sulfur Colloid 5 µCi for liver scan
    Sig: Dispense one dose