Anode Heel Effect Lecture Notes

Introduction

Overview of the lecture topic: Anode Heel Effect
Key areas of focus:
- Causes of the anode heel effect
- Factors to reduce the effect
- Utilizing the effect in radiography

Topic: Focal Spot
Key points:
- Reducing anode angle decreases field size and effective focal spot size
- Effective focal spot varies across the field:
  - Smaller on the anode side
  - Larger on the cathode side

Describes variation in x-ray beam intensity between the anode and cathode sides
Due to x-rays traveling through different lengths of the anode:
- Cathode side: shorter travel distance
- Anode side: longer travel distance, leading to attenuation
Myth: X-rays are formed on the surface of the anode
- Reality: X-rays are formed within the anode

Anode Angle
- Larger angles reduce the distance x-rays travel through the heel of the anode
- Smaller angles increase the heel effect
- To reduce the heel effect, increase the anode angle
Source to Image Distance (SID)
- Refers to the distance between the x-ray source and detector
- Increasing SID decreases the intensity variation across the detector
- To reduce the heel effect, increase the source to image distance
Field Size
- Achieved through collimation
- Collimation limits the x-ray beam size, reducing intensity variation
- To reduce the heel effect, collimate the field size

Can be utilized to enhance image quality
Example: In radiography of the pelvis:
- Higher intensity x-rays penetrate denser pelvic bones
- Lower intensity x-rays interact with less dense abdominal organs
Similar applications in other areas:
- Foot: Cathode side over the ankle (denser)
- Mammography: Cathode side over denser chest wall

Anode heel effect leads to varying x-ray intensities, attributed to differential distances through the anode
Important to understand for exam preparation:
- Common exam questions on definition, reduction methods, and advantages
Next lecture topic: Filtration in x-ray physics