X-ray cassettes are essential tools in the field of radiology, used to capture images of the body’s internal structures. These rigid holders are designed to house the screen film system or imaging plate in both conventional and computed radiography. The composition of an x-ray cassette is carefully engineered to ensure optimal image quality and patient safety.
Front and Back Layers
The front of the x-ray cassette is made of a low atomic number material, such as plastic or carbon, to enable easy passage of x-rays. This ensures that the x-rays can penetrate the cassette and reach the film or imaging plate without significant obstruction. On the other hand, the back of the cassette is made of a high atomic number material, typically lead, to reduce backscatter. Backscatter occurs when x-rays bounce off the cassette and return to the patient’s body, potentially causing additional radiation exposure. The lead backing helps to absorb these scattered x-rays, minimizing the amount of radiation that reaches the patient.
Rubber or Felt Lining
The back side of the x-ray cassette is lined with rubber or felt to ensure proper contact between the screen film system and the imaging plate. This intimate contact is crucial for accurate image capture and minimizing distortion. The rubber or felt material helps to create a smooth surface for the film or plate to rest against, ensuring consistent contact across the entire area.
Cassette Formats
X-ray cassettes come in various sizes to accommodate different imaging needs. The most common formats used in conventional radiology are:
13 x 18 cm
18 x 24 cm
24 x 30 cm
20 x 40 cm
30 x 40 cm
35 x 35 cm
35 x 43 cm
30 x 90 cm
These standardized sizes allow for efficient storage, handling, and processing of x-ray films. In computed radiography (CR), the cassettes are loaded with imaging plates instead of film, but the overall design remains similar.