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Xenon Effluent Monitoring

January 23, 2014, 10:25am
Ann Marie Alessi, BS, CNMT, NCT, RT(N), FSNMMI-TS, Product Sales Manager, Nuclear Medicine, Biodex Medical Systems, Inc.
Xenon Trap Monitor
Xenon Trap Monitor

Did you know State and Federal regulations require the routine monitoring of trap effluent gas? Noble gases such as xenon in the air present an external source of radiation exposure that must be calculated

The charcoal traps of the Biodex Pulmonex can significantly reduce air contamination. However, they can also become saturated or ineffective by improper use, humidity, chemicals, or inadequate maintenance.

Trap effluent testing is quite in depth and time consuming. The new Atomlab Xenon Trap Monitor (136-755) is designed to monitor the trap effluent during Xe-133 Lung Ventilation procedures and provide an audio/visual alarm to indicate a trap is near failure and should be replaced. The addition of the Xenon Trap Monitor to your Pulmonex, makes meeting requirements a breeze.

Do you have a Xenon Trap Monitor on your Pulmonex?

 


 

Table of Contents

U.S. Nuclear Regulatory Commission - Regulatory Guide 10.8
Model Procedure for Monitoring, Calculating, and Controlling Air Concentrations

A. Pulmonex Charcoal Trap Effluent Monitoring Procedure for Users without Xenon Trap Monitor
B. Using the Atomlab Xenon Trap Monitor

 

U.S. Nuclear Regulatory Commission
Regulatory Guide 10.8 - APPENDIX O
Model Procedure for Monitoring, Calculating, and Controlling Air Concentrations

1. Did you know State and Federal regulations require the routine monitoring of trap effluent gas? Noble gases such as xenon in the air present an external source of radiation exposure that must be calculated
2. If you do not monitor the trap effluent, check it on receipt and once each month. Collect the effluent from the trap during one patient study in a plastic bag and then monitor the activity in the bag by holding the bag against a camera, with the camera adjusted to detect the noble gas, and compare its counts per minute (cpm) to background cpm with no other radioactivity in the area. Keep a record of the date, background cpm, and bag cpm.
3. The RSO will establish an action level based on cpm or a multiple of background cpm. If you measure a significant increase in the bag cpm, the trap is breaking down and must be replaced.
4. Follow the trap manufacturer's instructions for replacing the trap.

 

A.  Pulmonex Charcoal Trap Effluent Monitoring Procedure for Users without Xenon Trap Monitor

  Trap exhaust is monitored by using the gamma camera without a collimator. The following technique is used:
     
  1. Remove the collimator from the camera.
  2. With a five percent window, calibrate for Xe-133.
  3. Fill a large plastic bag with a known volume of air (example, 25 liters).
  4. Inject a known quantity of Xe-133 (such as 100 μCi) into the bag. The concentration will be 4 x 10-3 μCi/cm3.
  5. Place the bag in front of the crystal and count for a known period of time. The counts per minute (cpm) obtained is a measure of the efficiency.
  6. Collect the exhaust of a typical study in another bag of the same volume (25 liters) and count as defined in step #5.
  7.

Ratio the count rates to the standard taken to determine exhaust concentration.

Example: If 4 x 10-3 μCi/cm3 yields 600,000 cpm above the background and collected effluent from the patient study was 150 cpm above the background, then:

Ratio = 1.5x 102 cpm = 2.5 x 10-4
             6 x 105 cpm

Exhaust Concentration = r (2 x 10-3 μCi/cm3)
                                      = (2.5 x 10-4) (4 x 10-3 μCi/cm3)
                                      = 1 x 10-6 μCi/cm3


B.   Using the Atomlab Xenon Trap Monitor

 

Following the background and check source measurements, the Xenon Trap Monitor should be fully functional. Follow the procedure below to begin operation.

NOTE: Remove the check source from the holder and put it away.

     
  1. Press, then release the <Next/Mute> button until count LED light turns blue. If you are unable to select the count function, make sure that you have already done the background and check source functions as outlined above. You cannot run the count function until both the background and check source functions have passed.
  2. After two seconds the LED light will turn green and the unit will begin measuring. When the measurement is above the background level it will be displayed numerically in units of pCi/ml. Otherwise the numeric display will show four dashes “----”.
  3. If a measurement is made which exceeds the threshold value of 99 pCi/ml, the device will go into alarm mode. The alarm will continue to sound until either the <Next/Mute> button is pressed to mute the alarm for five minutes, or the power is turned off. Measurements will continue to take place and the peak value detected will be displayed until power is removed. The count LED light will blink red as long as measurements are above the threshold, but will be a steady red when they go below the threshold.


Trap Monitoring Test Results 

 

References:

NRC Regulatory Guide 10.8: Guide for the Preparation of Applications for Medical Use Programs; Revision 2, August 1987; APPENDIX O: Model Procedure for Monitoring, Calculating, and Controlling Air Concentrations.

PULMONEX II DOUBLE-TRAP XENON SYSTEM (132-503), OPERATION MANUAL;   FN: 07-151 Rev A 10/09; page 11.
ATOMLAB XENON TRAP MONITOR (136-755), OPERATION AND INSTALLATION MANUAL; FN: 12-148 5/12; page 10 and Appendix B page 14

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