Lesson 1, Topic 1
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Introduction to Radiographic Equipment

April 11, 2024

Introduction to Radiographic Equipment

Learning Objective: Examine radiographic equipment.

Radiographic equipment is used to create the x-ray beam and produce the image. Typical equipment in an x-ray room includes the IR system, x-ray tube, radiographic table, upright IR, control console, and the transformer cabinet.

Image Receptor System

Learning Objective: Explain the image receptor system.

For computed radiography systems, the IR consists of an image receptor that contains a phosphor imaging plate. The x-ray image is produced in digital format using computer technology. After the exposure is made, the IR is inserted into a computed radiography reader. A laser beam in the reader scans the phosphor on the plate, and the final image appears on a computer monitor. Then, the image can be manipulated and stored. The image will be sent to the radiologist for interpretation.
For digital radiography (DR) systems, a flat panel detector is used. Flat-panel detectors (FPDs) consist of a scintillation screen for a photoconductor, which converts the x-ray photons directly to electrical signals. The FPD is wired into the x-ray table or upright unit. Once the exposure is made, the image appears on the computer monitor in seconds. Then, the image can be manipulated, stored, and sent to the radiologist and possible treating provider for interpretation.

FIGURE 37.7  Diagram of typical collimator demonstrating a beam-defining system: Anode focal spot, x-ray tube window, upper lead shutters, aluminum filter, mirror, light source, and lower lead shutters. The metal shutters collimate the x-ray beam, so that is no larger than the image receptor. From Sherer MAS, Visconti PJ, Ritenour ER, Haynes KW: Radiation protection in medical radiography, ed 8, St. Louis, 2018, Mosby.

FIGURE 37.8  The path and attenuation of a beam of x-radiation. (1) The primary beam exits the x-ray tube. (2) The beam enters the patient, where the individual ex-ray photons’ energies are altered (attenuated) by their passage through body tissues of varying characteristics. (3) The attenuated, or remnant, beam exits the patient, carrying energy representation of the body tissues traversed and striking the image receptor. (4) Some x-ray photons interact with matter and continue in a different direction, producing scatter radiation, which is nondiagnostic. From Adler AM, Carlton RR: Introduction to radiologic and imaging sciences and patient care, ed 7, St. Louis, 2020, Saunders.

TABLE 37.2

Summary of Primary, Remnant, and Scatter Radiation

Type of RadiationDefinitionDescription
Primary radiationThe x-ray beam that leaves the tube and travels into spaceIts direction and location are predictable and controllable.
Remnant (exit) radiationWhat remains of the primary beam after it has been attenuated by matter (the patient)Tissue of different density, or atomic number, in the body absorbs x-rays differently and therefore emits x-rays differently. The remnant beam contains a varied pattern of x-ray energies that reflects the different absorption characteristics. The pattern of the remnant radiation creates the x-ray image.
Scatter radiationRadiation from the primary beam that is randomly scattered within or outside of the bodyScatter radiation travels in all directions from the patient and is difficult to control.
In general, it has less energy than the primary beam.

X-Ray Room

Learning Objective: Describe the components of the x-ray room.

FIGURE 37.9 shows a typical x-ray room, including the x-ray equipment and a protective control booth. The x-ray machine consists of the x-ray tube, the tube support, the control console (located in the control booth), and the transformer cabinet. There is also a radiographic table and a wall-mounted IR for upright studies.

X-ray Machine

The x-ray machine consists of the transformer cabinet, x-ray tube, and collimator. Each of these is described in more depth in the following sections.

Transformer Cabinet

The transformer is an essential component of the x-ray machine. The function of the transformer is to produce the high voltage required for x-ray production and the low milliamperage (mA) needed in the x-ray tube. The transformer is located inside a cabinet in the x-ray room. The operator does not adjust or control the transformer.

X-Ray Tube

The x-ray tube is enclosed in a tube housing. The housing is lead-lined for radiation control. The housing protects the tube and the user. The housing may be mounted to the floor of the ceiling and is supported by a rail system. The rails allow for tube movement. Typical tube movement allows the following:

• Longitudinal: Along the long axis of the table
• Transverse: Across the table, at right angles to longitudinal
• Vertical: Up and down, increasing or decreasing the distance between the tube and table
• Rotational: Allows the entire x-ray tube to turn on its axis, changing the angle at which the tube arm is extended

FIGURE 37.9  The generic components of diagnostic radiographic equipment include the x-ray tube (A), collimator (B), radiographic table (C), and image receptor tray (Bucky) (D). The overhead tube crane support (E) is suspended from the ceiling, and the generator console is behind the leaded control booth (F). From Adler AM, Carlton RR: Introduction to radiologic and imaging sciences and patient care, ed 7, St. Louis, 2020, Saunders.

• Angular (tilt, roll): Permits angulation of the tube along the longitudinal axis of the table and allows the x-ray tube to be aimed at the wall rather than at the table

A system of locks holds the tube in place. To move the tube in any direction, a lock must be released. The detent is a special mechanism that allows the operator to position the tube at standard distances and when the x-ray tube and IR are correctly aligned.

Collimator

The collimator is a square-shaped device attached under the tube housing. It allows the operator to vary the size of the radiation field by adjusting the length and width of the primary beam. A centering light is used to align the CR to the Bucky tray.

Radiographic Table

The radiographic table is a support for the patient. The table typically has a floating tabletop and can be tilted and moved vertically. Mounted under the tabletop surface is a grid device used to absorb scatter radiation from the patient and prevent it from reaching the IR. For the CR, the IR is placed in the Bucky. For DR, the IR is housed below the grid.

Upright Image Receptor

The upright IR holds the IR in a vertical position for upright radiography. All rooms contain an upright IR because many x-rays are done with the patient standing or sitting upright. This unit is referred to as the upright Bucky.

Control Console

The control console is located in the control booth. This area is separated from the x-ray room by a lead barrier to protect the operator from scatter radiation exposure. There is usually a lead glass window so the operator can observe the patient from the control booth. The control console, or control panel, is the access point where the operator selects the exposure factors and initiates the exposure. A typical console has buttons for adjusting the milliamperage, exposure time, kilovoltage, Bucky, manual or automatic exposure control (AEC) , and anatomically programmed radiography control.