Heel Effect, Complete Physics Guide (Radiologic Technologists)

The heel effect in x-ray imaging leads to changes in the x-rays coming out of the anode. On the heel side of the tube there will be lower intensity x-rays and higher average energy. Likewise on the non heel side of the tube there will be higher intensity x-rays with lower average energy.
Chapters:
00:00 Introduction and Brian's Heel Effect
01:19 What is Beam Hardening
03:45 Heel Effect: Beam Hardening within tube
06:00 Heel effect illustrated
07:28 Compensate for heel effect
In order to understand the heel effect we first need to know the mechanism behind beam hardening. Beam hardening occurs when an x-ray beam passes through attenuating material such as a pre-patient collimator, the x-ray table or the patient themselves. After x-rays pass through the object the x-ray spectrum has a higher average energy. This is referred to as a harder x-ray beam as the lower energy photons are preferentially attenuated.
The heel effect is caused by beam hardening with the anode of the x-ray tube. The electrons are accelerated into the anode (i.e. the heavy metal) and will interact at some depth within the anode. The x-rays then pass through the anode on the way out of the anode.
The x-rays that need to pass through more metal on the way out have more beam hardening and this is referred to as the heel effect.
This is why on the heel side of the x-ray beam the x-ray spectrum has lower intensity and a higher average energy.
The heel effect can be compensated for using a physical filter. This filter would look like a wedge where there is more filter material on the non anode side and less filtration on the heel side.
X-ray technologists and radiographers can also use the heel effect to their advantage in positioning the anatomy such that the more attenuating regions of anatomy are placed in the non heel side. For example in the pelvis is more attenuating than the upper abdomen so if these two regions are imaged at once it is preferable to have the pelvis be on the non heel side of the x-ray tube. In this manner extra attenuation in the patient can help compensate for the fact that there is higher x-ray flux on the non heel side of the x-ray beam.

[@lynnbrown5242]

This was a very helpful explanation, thank you so much!

[@TheNettforce]

Thanks Lynn

[@monicasenese2839]

amazing explanation!

[@TheNettforce]

Thanks Monica, glad it helped

[@mariamhb3318]

Why would you want to the heal side towards the abdomen? I thought we want to heal effect on the thicker side in general? 8:38

[@HowRadiologyWorks]

The non heel side has more flux so we want to use that for the one that is more attenuating.

[@yaoyu7221]

Hi excuse me, May I know where can I purchase the X-ray tube regularly because we are a Chinese CT manufacturer. thanks in advance!

[@HowRadiologyWorks]

Sorry I don’t have any inside info on tube purchasing but if you do a web search companies like Varex will come up

[@abdovitamins6331]

Hello Mr Brian
Which side heel effect is going to be pronounced on , anode side or cathode side?!
Some books answer it anode side because of less intensity
Other books says it us more prominent at the cathode side because of high intensity so could you clarify this please?!

[@HowRadiologyWorks]

Even in the thumbnail I do try to get that point across that energy goes up on the anode side and the flux goes down on the anode side. So if you say which side is more affected by heel effect I believe it is the anode side

[@abdovitamins6331]

@@HowRadiologyWorks that’s it. Thanks a lot 🌸

[@lkfakjhqw3u4ijrt]

so in a way we are trying to reduce the intensity, then how would noise be compensated ...

[@HowRadiologyWorks]

We are trying to make the intensity more similar which will make the noise more similar and the density more similar if you are using film

[@abdovitamins6331]

This is the third time I watch this Video and every time I get more informations.
But I have a question
Does an increase in tube kilo voltage increase mean photon energy?
Does an increase in the tube voltage affect affect the energy of the X ray beam ?
A little bit confused!

[@HowRadiologyWorks]

Yes Abdo an increase in kVp does increase the mean photon energy.

[@abdovitamins6331]

@@HowRadiologyWorks thanks a lot