South Australian Consolidated Regulations

RADIATION PROTECTION AND CONTROL (IONISING RADIATION) REGULATIONS 2000 - SCHEDULE 9

Schedule 9—Error distances for automatic collimation to an image intensifier

1         For the purposes of this Schedule—

area being imaged means the area of the input phosphor which produces an image on the television monitor;

error distance means the lack of alignment between the X-ray field and the area being imaged, where the X-ray field lies outside the area being imaged.

2         For a polygonal X-ray field, measurements of the error distance are taken perpendicularly from the mid-point of each side of the X-ray field, which is outside of the area being imaged, to the corresponding boundary of the area being imaged.

3         For an X-ray field with a curved boundary (eg a circular X-ray field) the error distance is defined for all points on the boundary of the X-ray field which lie outside of the area being imaged. For any such point the error distance is measured perpendicularly from the tangent to the boundary at that point to the corresponding boundary of the area being imaged.

4         In no case must the error distance, measured in the way described above, exceed 1 per cent of the focal spot to image receptor distance.