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Radiological Protection of Patients |
Objective: Patient dose reduction through change of image intensifying screens
Many risk reduction possibilities are predictive and speculative in nature, and so are the numbers of dose reduction approaches. However, there are some definite approaches with clear impact on dose reduction. One of these is the replacement of the conventional image intensifying (II) screens in the X ray cassette (calcium tungstate) with the rare earth screens. This has been shown to reduce patient doses to half or still more in a very cost-effective manner.
Even though this technology had been introduced nearly 2 decades ago and has been implemented in most industrialised countries, not many developing countries have switched over to rare earth screens. The reasons for non-adoption are a) all the film cassettes of the department have to be replaced simultaneously, b) the films used have to match the spectral emission from the screen and thus the department has to switch over to new films. Both these factors involve financial inputs and require strong administrative and management commitments. It is also possible to use the conventional X ray films (blue sensitive ones) as some rare earth screens emit light in the blue region rather than the green region typical for many earlier rare earth screens. This reduces the burden of change to only II screen rather than both II screens plus film and dark room lamp of appropriate colour. Since the magnitude of the dose reduction with a switchover to rare earth screens is very significant, it is deemed appropriate for the IAEA to coordinate this action, as also demanded in the International Action Plan on the Radiological Protection of Patients.
In most cases the Member States will have technical capability to implement switch over. MS will need to assess if the existing cassettes are in good shape and if new screens are provided, they shall be able to replace themselves. Support for only one hospital may be provided by IAEA for few cases.
Outcome: Assured significant patient dose reduction in general radiographic examination
| IAEA’s Inputs | Action by Member State |
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A country where at present only calcium tungstate screens are used is eligible. Depending upon funds, screens/cassettes for one hospital in a country may be supplied on the condition that the facility has the capability to effect the change. |
1. Select one hospital 2. Estimate the number and sizes of a) screens or b) new cassettes needed 3. Inform exact requirement to IAEA and also if there is any local supplier with commitment to insert new screens and find new exposure factors without external help. |
Additional requirement by Member State, if any.