x ray

What is SID in X-ray imaging? Also why does it matter

The distance between the X-ray tube focal spot and the image receptor (detector).

For a standard chest X-ray, the typical SID is 180 cm (1.8 metres) for an erect PA projection.

Why it matters: A longer SID reduces magnification of the heart and helps produce a more accurate image of its size.

What is the difference between parallel and perpendicular lines?

Parallel lines: Lines that stay the same distance apart and never meet.

Perpendicular lines: Lines that intersect at a 90° angle (a right angle).

What is a projection?

A projection describes the direction the X-ray beam travels through the patient's body to reach the image receptor (detector).

What is a posteroanterior (PA) chest X-ray?

A PA chest X-ray is when the X-ray beam enters through the posterior (back) of the patient and exits through the anterior (front), reaching the detector.

Why is a PA projection preferred for an erect chest X-ray?

It reduces magnification of the heart compared with an AP projection, helping show its true size more accurately.

What are the pre examinations steps?

1. Room clean

2. Ask what scan they are here for

3. Request card checked - is it justified

4. Computer/ ô