In X-ray tubes, the heel effect or, more precisely, the anode heel effect is a variation of the intensity of X-rays emitted by the anode depending on the direction of emission along the anode-cathode axis.

What is the heel effect in xray?

Introduction. The anode heel effect in radiography is a well-described physical phenomenon,1,2 whereby radiation intensity varies along the anode–cathode axis of the X-ray tube, decreasing towards the anode. Photons emitted towards the tube’s anode side are attenuated more than those emitted towards the cathode.

Why is it called the heel effect?

The anode heel effect is the variation in x-ray intensity along the longitudinal axis of the tube. It’s called the anode heel effect because photons formed deeper in the anode must first pass through the “heel” of the anode which causes that “side” to lose intensity before reaching the object or image receptor.

What does the heel effect result in?

The Heel effect causes a Gaussian distribution around the anode–cathode axis and a logarithmic distribution parallel to this axis.