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Location: Aluminium Filter Techniques in Radiography
Discussion: Effect of Aluminium Filters on Radiation Dose
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junior_radiographer |
Effect of Aluminium Filters on Radiation Dose
Nov 6 2008, 2:48 AM EST
Hello all,With the advancement of Computed Radiography and the ability to "window" image, some Radiographers believe that using Aluminium filters is no longer necessary. I wanted to find out more about the effects on radiation dose caused by using Aluminium filters. For example, would the area covered by the aluminium receive a lower dose because the beam is attenuated, or would this result in more photons being deposited in the patient? Also, would the filter cause more scattered radiation, possibly reaching areas away from the primary beam. I have nearly graduated university and would like to refine my technique before entering practice. Any advice would be greatly appreciated. 2 out of 2 found this valuable. Do you? |
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Posted Anonymously |
1. RE: Effect of Aluminium Filters on Radiation Dose
Dec 11 2008, 3:19 AM EST
Aluminium when placed in the useful beam hardens the beam. The 1st half value layer increases and the dose equivalent delivered to the patient is reduced. Aluminium itself generates 1.5keV photons and dependind on the thickness of aluminium placed in the useful beam, allphotons below about 8-10keV photons are completely attenuated by the aluminium filter. Even digital imaging is aided by aluminium graded filters.
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Posted Anonymously |
2. RE: Effect of Aluminium Filters on Radiation Dose
Dec 16 2008, 8:06 PM EST
Regardless of the image receptor, filters produce the same effects on dose to patient and quality of the beam. I haven't seen the use of filters much in recent years, however, but I really wish I had some compensating filters! Any time you add an absorbant material between the tube and the patient, some of it will be attenuated, and adding filtration might require an increase in technique depending on how much you are using. The idea is to still reduce skin dose/absorbed dose to the patient by removing all of those low-energy rays. As for the ability to "window", we still have to be responsible and use the lowest amount of radiation possible to acquire optimum images. Current research suggests that with CR/DR systems, the scale of contrast is primarily controlled by the algorithm selected for processing (chest, c-spine, x-tbl hip, etc) and kVp is only a secondary controller of contrast. Hospitals in the US are expected to start using 10-20 kVp higher for all studies within the next few years to reduce the required mAs for images... I think that filtration would help even more to reduce exposure if it's available to you. 2 out of 2 found this valuable. Do you? |
