I followed a thread some time ago on the Health Physics Society website on where the half apron (used for patient shielding) should be placed for an erect chest x-ray and why? (i.e at the back of the patient for protection from primary beam or front of the patient to protect from backscatter from adjacent structures). It was then concluded that the half apron used during an erect chest x-ray for patient shielding only serve to re-assure the patient. I need further explanation on this from experts in the house please. Thank you
It is common practice to place a half apron behind the patient during an erect chest radiograph to reduce potential dose from tube leakage and room scatter. For all practical purposes, the dose from these sources is not measurable in modern chest x-ray rooms, thus the apron has minimal value. Protection from the primary beam is not necessary since it is collimated to the size of the film or image intensifier. Most of the backscatter is from the patient, thus any dose to the gonads and other tissues outside the beam results from internal scatter. Consequently, the half apron has minimal effect on patient dose, but it does reassure patients that precautions are taken to protect them from unnecessary radiation exposure.
https://hps.org/publicinformation/ate/faqs/leadgarmentsfaq.html
Hi,
can you post a link to this thread?
In Italy there is interest in a similar issue but concerning radiography in dentistry.
Actually, when using up to date X-ray machines, it should not be suprisingly that the patient dose outside the target is negligible, therefore the use of shields for patients could be unnecessary.
An old italian work dated in the 90's, even suggested that, in dentistry, the apron could even have resulted in increased dose due to scattered radiation.
Actually that work was based on phantom measurements near to the sensitivity thresholds of dosimeters, it could be interesting repeating test with upgraded material and methods
A protective device such as a lead apron aims to help reduce external exposure, but not internal scattering. The use of a half apron for an erect chest X-rays is not needed from the viewpoint of dose (unless irradiation field includes gonads), but may be reasonable as per a request from the patient. FYI, a diagnostic reference level for an erect PA chest X-ray in Japan is an entrance surface dose of 0.3 mGy (0.2 mGy for infants), which is similar to the IAEA guidance level of 0.4 mGy.
Thank you for your insightful contributions @Mushtaq, Francesco and Nobuyuki. I found them quite helpful.
@Francesco the link to the thread you requested for has already been provided by @Mushtaq's first response to this question.
@Mushtaq please I still have another question from your first answer. Just as you rightly said "Most of the backscatter is from the patient, thus any dose to the gonads and other tissues outside the beam results from internal scatter". Now how do we control internal scatter in the case of a pregnant patient?
Thank you for your insightful contributions @Mushtaq, Francesco and Nobuyuki. I found them quite helpful.
@Francesco the link to the thread you requested for has already been provided by @Mushtaq's first response to this question:
https://hps.org/publicinformation/ate/faqs/leadgarmentsfaq.html
@Mushtaq please I still have another question from your first answer. Just as you rightly said "Most of the backscatter is from the patient, thus any dose to the gonads and other tissues outside the beam results from internal scatter". Now how do we control internal scatter in the case of a pregnant patient?
The are only a few things that you can do to minimize internal scatter. By far, the most important one is to collimate the primary beam as much as posssible, since the more volume you irradiate, the more volume you have acting as a scatterer. You could also modify the kV, looking to minimize scatter, but that has a much smaller effect.
Using the Japanese guidline of 3 mGy entrance exposure, the corresponding effective dose is around 0.015 mGy. That’s roughly equivalent using the LNT model to winning the Massachusetts lottery, or 5-10 hours of background exposure (in the US). Is it useful to wear a half apron? I wouldn’t think so.
Thank you so much for you contributions @ Keran, Miguel and Robert.
Just to add that “the Japanese guidline of 3 mGy entrance exposure, the corresponding effective dose is around 0.015 mGy” mentioned above by Dr Robert Zamenhof may be “the Japanese guideline of 0.3 mGy entrance surface dose, the corresponding effective dose is around 0.05 or 0.06 mSv”.
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