Simo Saarakkala MSc, Presenter: Nothing to Disclose

Erna Kaleva, Abstract Co-Author: Nothing to Disclose

Eero Kauppinen MSc, Abstract Co-Author: Nothing to Disclose

Juha Töyräs PhD, Abstract Co-Author: Nothing to Disclose

To evaluate X-ray scattering field in examination room during routine radiography.

The Alderson Radiation Therapy Phantom was used as a patient equivalent in the measurements. The phantom was imaged in a standing position using a field size similar to that of a routine Thorax-PA projection (29.5 cm x 30.5 cm). Imaging parameters were as follows: focus-skin-distance (FSD) = 150 cm, tube voltage = 90 kV, tube current = 10 mAs, additional filtration = 1 mmAl + 0.1 mmCu. The entrance air kerma (EAK) was measured at 46 points inside the examination room and at 5 points at the doorway using an Unfors Xi meter (Unfors Instruments AB, Sweden). Based on the EAK measurements, a graphical X-ray scattering map (isodose curves) for the examination room was calculated. Furthermore, by assuming that 40 exposures are taken daily with the same parameters, effective dose of an individual person standing on the doorway (e.g. radiographer) during examination was estimated.

EAK at the surface of the phantom was 233.4 μGy. EAK values inside the room varied typically between 30 nGy and 2.7 μGy. EAK values at the doorway ranged between 20 and 30 nGy. The isodose curves revealed fine details of X-ray scattering field inside the examination room, especially near different obstacles and items. The effective dose for a person standing on the doorway during examination was estimated to be around 0.2 mSv per year.

According to Radiation and Nuclear Safety Authority of Finland (STUK), the average effective dose of a single Thorax-PA examination is 0.02 mSv. Based on the present estimation, the annual dose of a radiographer standing always on the doorway equals the dose accumulated to patient from ten Thorax-PA examinations. It is therefore recommended that the door of the examination room should always be closed during imaging.

The results are useful for the design of radiation protection in native examination rooms, e.g. when planning a proper location for assistant or radiographer operating in the imaging room or doorway.

Saarakkala, S, Kaleva, E, Kauppinen, E, Töyräs, J, Evaluation of X-ray Scattering in Examination Room during Routine Radiography.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5007714.html