Collimation of Radiation Field In radiography; restricting and shaping the X ray beam to cover only

Описание: Collimation of the Radiation Field in Radiography
Collimation refers to the restriction of the X-ray beam to the area of clinical interest by using adjustable shutters or diaphragms in the X-ray tube housing. It is one of the most important radiation protection and image quality practices in radiography.

Purpose of Collimation
Radiation Protection

Limits patient exposure to unnecessary radiation.

Reduces scatter radiation, lowering dose to both patient and staff.

Image Quality

Improves contrast by reducing scatter reaching the image receptor.

Prevents unnecessary anatomy from being included in the image.

Professional Standards

Required by regulations and ethical practice (ALARA principle).

Demonstrates radiographer’s responsibility in minimizing exposure.

Types of Collimators
Fixed Aperture Diaphragm – simple opening, rarely used today.

Cones and Cylinders – attach to tube housing to restrict beam to circular/rectangular areas.

Variable-Aperture Collimator (Light Beam Collimator) – most common; uses adjustable shutters and a light field to match the X-ray field.

Steps in Collimation During a Radiographic Exam
Position the patient correctly.

Align the central ray to the area of interest.

Adjust collimator shutters to restrict the beam to just beyond the anatomy of interest.

Verify that the light field matches the intended exposure area.

Recheck before exposure to ensure no unnecessary tissue is included

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