Venti-Scan Physics Test Reports
Shielding Evaluation for the Venti-Scan IV Canister
Report prepared by: Lucian Wielopolski, Ph.D.
Date: 6/15/01
Method
Venti-Scan Physics Test Reports
Shielding Evaluation for the Venti-Scan IV Canister
Report prepared by: Lucian Wielopolski, Ph.D.
Date: 6/15/01
Method
A small, 0.5 cc, plastic syringe containing a 30 mCi Tc-99m source was measured in a shielded and unshielded environment. The syringe was housed in a lead pig, on contact the reading outside the pig was 0.2 mR/hr, slightly above background conditions that were <0.2 mR/h. The unshielded syringe measured gamma on contact of 1400 mR/h and at about 1″ 60 mR/h.
The instrument used for these and subsequent measurements was an Eberline Model RO-2 Ion Chamber Survey Meter. The syringe with the source was placed inside the Venti-Scan IV canister. Gamma and gamma plus beta readings were taken in contact with the outside of the canister and about 12″ away.
Conclusion
The Venti-Scan canister provides complete patient and technologist shielding for use as a delivery system for performing lung ventilation studies in a nuclear medicine environment. As noted in this study at a distance of 12″ virtually no radiation reading was recorded, except in the obvious case 7 with the top cover open. Thus, this canister provides minimal exposure to both patient and technologist.
Measurements Points
The following nine points were used to determine the effectiveness of the shielding of the canister:
Above opening of patient delivery tube.
- At the same level as above 90 degrees away from the opening
- At the same level as above 180 degrees away from the opening
- In center of the patient delivery tube
- Below patient delivery tube opening
- Top center of the canister with vent door in closed position
- Top center of the canister with vent door in open position
- Center of air inlet opening
- Bottom center of the canister
Table 1. Summary of the canister shielding readings.
| Location Point | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| Contact: | |||||||||
| Gamma: | 0.5 | <0.2 | <0.2 | 1.0 | 0 | 0 | 14 | 0.2 | 0.8 |
| Gamma + Beta: | 1.0 | <0.2 | <0.2 | 5.0 | 0 | 0 | 30 | 0.2 | 0.8 |
| 12″ Away: | |||||||||
| Gamma: | <0.2 | 0 | 0 | 0.2 | 0 | 0 | 8 | <0.2 | 0.2 |
| Gamma + Beta: | <0.2 | 0 | 0 | 0.3 | 0 | 0 | 10 | <0.2 | 0.2 |
* Somewhat elevated readings in position 4 stem from the fact that the source was held in a plastic syringe that was inserted in a place that normally is occupied by a plastic nebulizer. Consequently, the source was located somewhat higher and less spaced out than it would be when using a nebulizer resulting in a larger solid angle toward the opening of the delivery tube.
Trapping Efficiency of Venti-Scan Filters
Lucien Wielopolski, PhD.
Introduction
The purpose of this evaluation was to test and compare the trapping efficiencies of the filters used in the Venti-Scan II, and the Venti-Scan III or Venti-Scan IV Radioaerosol Disposables. The Venti-Scan III and Venti-Scan IV use the same pleated HEPA filters for a trap.
The Venti-Scan III and Venti-Scan IV filter uses a pleated HEPA filter and the Venti-Scan II uses a traditional flat filter media. The primary filter is the filter that is normally supplied with the Venti-Scan disposable. The secondary test filter was always a HEPA filter placed onto the exhaust port of the primary filter. All secondary filters were from the same manufacturing lot to eliminate variation of filter media.
Method
Venti-Scan II disposable assemblies were used for testing the filters. The primary filter was mounted in the standard position for each test. The tests were performed using either the Venti-Scan II or III and IV filter as the primary filter.
A blower was connected to the hose where the mouthpiece normally is located to simulate a patient. A constant rate was set for the blower during all tests.
The oxygen flow of 5 liters/minute was maintained through the nebulizer. The same nebulizer, filled with approximately 6cc of 6 mCi of Tc-99m labeled DTPA, was used for all measurements thus eliminating any potential variability in the nebulizers.
The filters, both primary and secondary, were exposed for 5 minutes to the nebulized Tc-99m DTPA.
For counting purposes the whole filter was inserted into a dose calibrator. The background count was 0.03 µCi. Results are listed in µCI read in the dose calibrator.
Test Set A used the Venti-Scan II filter/trap as the primary filter and Test Set B used the Venti-Scan III and Venti-Scan IV filter/trap as the primary filter.
Results
Set A (Venti-Scan II)
| Primary Filter Activity in µCI |
Secondary Filter Activity in µCI |
Ratio | % of Activity Trapped in Primary Filter | % of Activity Trapped in Secondary Filter |
| 237 | 0.20 | 1185 | 99.916% | .084% |
| 257 | 0.13 | 1977 | 99.949% | .051% |
| 261 | 0.20 | 1305 | 99.923% | .077% |
| 321 | 0.15 | 2140 | 99.953% | .047% |
| 251 | 0.12 | 2092 | 99.952% | .048% |
| Mean: S.D.: |
1740 458 |
| Primary filter activity | |
| Ratio = |
|
| Secondary filter activity |
| Primary filter activity – Secondary filter activity | ||
| % of Activity Trapped in Primary Filter = |
Primary activity |
X 100 |
Set B (Venti-Scan III and Venti-Scan IV)
| Primary Filter Activity in µCI | Secondary Filter Activity in µCI |
Ratio | % of Activity Trapped in Primary Filter | % of Activity Trapped in Secondary Filter |
| 260 | 0.06 | 4333 | 99.977% | .023% |
| 248 | 0.05 | 4958 | 99.98% | .020% |
| – | – | – | – | – |
| 245 | 0.06 | 4083 | 99.976% | .024% |
| 238 | 0.08 | 2975 | 99.966% | .034% |
| Mean: SD: |
4087 827 |
Conclusion
These are relative evaluations of the filters. It appears that the Venti-Scan III and Venti-Scan IV filter/trap is slightly better than the Venti-Scan II filter/trap. Both filters had greater than 99.9% trappings. It should be noted that the secondary filter readings are close to the background readings which fluctuates, and the primary filter retensions are all similar. Thus it can be concluded that both filters have similar trapping efficiencies with the Venti-Scan IV filter possibly slightly better. Note the small sample size.
Venti-Scan III Particle Size Test
| Robert J. Perry, B.S. Department of Medicine Pulmonary Disease Division SUNY Stony Brook HSC T-17 Rm 040 Stony Brook, NY 11794-8172 |
Jonathan S. Ilowite, M.D. Winthrop University Hospital Pulmonary & Critical Care Medicine Director, Pulmonary Rehabilitation Medical Director, Respiratory Therapy 222 Station Plaza North Suite 400 Mineola, NY 11501 |
Introduction
The following report summarizes our analysis of the Biodex Venti-Scan III (#177-080) disposable radioaerosol system for ventilation scanning studies. Using an Andersen cascade impactor we determined the mean particle size of the technetium 99m-DTPA aerosol produced by six units from lot #014504 under the following testing parameters.
NOTE: The Venti-Scan IV uses the same nebulizer Tee filter and tubing configuration as the Venti-Scan III.
Method
Nebulizer solution: 2 cc’s Tc-99m DTPA
Nebulizer flow: 10 liters/minute @50 psi
System ventilation: 15 bpm via Harvard pump @ 600 cc’s
Results
All six systems produced essentially the same size Tc-99m DTPA aerosol as illustrated in the average graph of aerosol diameter vs. cumulative percent.
Mean MMAD: 0.50 microns ±0.01 (S.D.)
Range: 0.48-0.52
Mean GSD: 1.8 (polydispersed)
This highly reproducible aerosol particle size is desirable for the deep lung penetration required in nuclear medicine lung ventilation studies.
In addition, one system was tested for filter efficiency in trapping the Tc-99m DTPA aerosol. With the T-piece plugged, aerosol was run through the HEPA filter followed by an absolute filter for a total of 5 minutes. There was no Tc-99m activity detected on the absolute filter indicating a HEPA filter efficiency of 100% in the one unit tested. It is not known however if this preliminary result can be extrapolated to represent a group of this type of filter without further confirmation in a formal study. Depending on the quality control during production of these filters it seems likely that they are very efficient.
Vent-Scan III
Biodex Medical Systems