Answer to Question #4110 Submitted to "Ask the Experts"

I'm a radiography student of the College of Radiography, University of Malaysia Medical Centre in Malaysia. I'm doing my final project titled "Scattered radiation measurements in conventional radiography, portable and fluoroscopy using survey meter in variety distances from the x-ray source."  I've been asking a radiation protection officer about my project, but I just want to  confirm the procedures/protocols. I put the survey meter at about one meter, two meters, three meters, and behind the control panel area of the x-ray tube. I used a bones or water contents phantom (10 cm thickness and width) in the primary beam. I collimated the beam for the phantom sizes. Then, I made exposures.I collected the reading from the survey meter in a table. All the readings are in microsieverts/hour (μSv/h).Then I'll do the same technique for the rest of the modalities. Am  I proceeding in the correct way for the scattered radiation measurements?

It sounds like you're doing the measurements correctly.  The reading you obtain should be small so microsieverts seems reasonable.  I am making the assumption that the survey meter you are using for measurements has been properly calibrated.

You probably already know this as well but to make the final numbers useful, you would want to take the reading (μSv/h) and put it in terms of a particular exam.  For instance, if you measured the scatter at one meter to be 1,200 μSv/h for fluoroscopy and the average fluoroscopy operating time at organizations in your area are one minute, the potential occupational exposure would be 20 μSv for someone needing to be in the room during a procedure.

A quick way to "test" your measurements is that the reading at two meters should be about four times less than the reading at one meter; the reading at three meters should be about nine times less than the reading at one meter (for the same set-up and x-ray beam factors).  It won't be exact but it should be close.

The information you are collecting will be useful not only from an occupational exposure perspective but also from a patient perspective when a family member, for instance, is asked to remain in the room with the patient while an x ray is being taken.  Now you will know what the magnitude of their exposure could be.

Kelly Classic
Certified Medical Health Physicist