Chapter 1: Preliminary Steps in Radiography

Detailed Chapter Overview

Chapter 1 serves as the bedrock for the practice of radiography, establishing the essential link between professional responsibility and technical execution. It moves beyond a simple checklist of tasks to instill a comprehensive understanding of the radiographer's multifaceted role. This foundational chapter emphasizes that producing a diagnostic image is the culmination of a process rooted in ethical conduct, meticulous patient care, and a deep respect for radiation safety. It covers the governing bodies that define a radiographer's scope of practice and ethical obligations, ensuring that every action is both professional and legally sound. Furthermore, it details the critical pre-procedural steps, from rigorous infection control and patient communication to the art of obtaining a relevant clinical history. The chapter thoroughly explores the technical parameters that a radiographer controls—such as SID, collimation, and motion control—and explains how each decision directly impacts image quality and, most importantly, patient dose. Mastering these preliminary steps is not merely about following rules; it is about developing the professional judgment necessary to ensure every radiographic examination is safe, effective, and of the highest diagnostic value.

In-Depth Study Guide

The Radiographer & Professional Standards

A radiographer is more than a technician; they are a highly skilled medical professional responsible for creating medical images through the administration of ionizing radiation. This role requires a strong foundation in ethics, professionalism, and adherence to established standards.

Governing Bodies and Standards:

• ASRT (American Society of Radiologic Technologists): This is the premier professional association for medical imaging technologists. The ASRT's most crucial contribution is the development and maintenance of the Radiography Practice Standards. These standards are not merely suggestions; they define the acceptable level of performance and professional conduct for radiographers, covering clinical, quality, and professional responsibilities.
• ARRT (American Registry of Radiologic Technologists): This organization is responsible for credentialing and certifying radiographers. The ARRT writes and maintains the Standards of Ethics, which are divided into two parts:
  • Code of Ethics: An aspirational guide of professional conduct. It outlines the principles and values that radiographers should strive to uphold, such as acting with integrity, providing compassionate care, and maintaining patient confidentiality.
  • Rules of Ethics: These are mandatory, enforceable rules. A violation of these rules can result in sanctions, including the revocation of a radiographer's certification. They cover topics like fraud, performing procedures without an order, and working while impaired.

Patient Care, Safety, and Preparation

Before any exposure is made, the radiographer must ensure the environment and patient are properly prepared. This is a critical aspect of both safety and image quality.

Infection Control:

• Handwashing: The single most important and convenient method of preventing the spread of infection. Hands must be washed before and after every patient interaction.
• Equipment Cleaning: All equipment that comes into contact with the patient, especially the radiographic tabletop and image receptor, must be cleaned after every use with an approved disinfectant. This follows guidelines set by the CDC (Centers for Disease Control and Prevention).

Patient Interaction and History:

• Communication: Clear, calm, and concise instructions are paramount. The radiographer must explain the procedure to the patient, answer their questions, and ensure they are as comfortable as possible. This builds trust and improves cooperation.
• Clinical History: It is the radiographer's responsibility to obtain a relevant clinical history. This is not a diagnosis but a crucial step to ensure the correct exam is being performed for the right reason. Key questions might include, "What symptoms are you having?" and "Have you had surgery or injuries to this area before?" The presence of swelling, masses, scars, or tattoos should also be noted, as they can sometimes create artifacts on the image.

Motion Control:

Motion is the enemy of diagnostic detail. It creates blur (penumbra) and degrades spatial resolution. It is categorized into two types:

• Involuntary Motion: Motion that the patient cannot control, such as heartbeats, peristalsis (digestive movement), and muscle spasms. The primary method to combat involuntary motion is to use a very short exposure time.
• Voluntary Motion: Motion that the patient can control, often resulting from nervousness, discomfort, fear, or age. The best methods to control voluntary motion are:
  1. Providing clear instructions.
  2. Ensuring the patient is comfortable and supported.
  3. Using immobilization devices (e.g., sponges, sandbags) when necessary.
  4. For pediatric patients, decreasing exposure time is also highly effective.

Radiation Protection (ALARA)

The guiding principle of radiation safety is ALARA: As Low As Reasonably Achievable. This means using the lowest amount of radiation necessary to obtain a diagnostic-quality image.

• Collimation: This is the most important aspect of producing an optimal image and a cornerstone of ALARA. By restricting the x-ray beam to only the anatomy of interest, collimation achieves two critical goals:
  1. It significantly reduces the patient's radiation dose by limiting the volume of tissue exposed.
  2. It improves image quality by reducing the amount of scatter radiation produced, which in turn enhances contrast resolution.
• Gonadal Shielding: Historically, routine shielding of the gonads was standard practice. However, the AAPM (American Association of Physicists in Medicine) issued a position statement recommending the discontinuation of routine shielding. This is because modern equipment has highly effective automatic exposure control (AEC) systems and lower scatter, making the benefit from shields negligible. Furthermore, a shield can obscure relevant anatomy or interfere with AEC, potentially leading to a repeated exposure and a higher overall dose. Shielding should still be considered upon patient request or if required by state law.

Technical Factors & Image Quality

The radiographer directly controls several key technical factors that determine the final quality of the image.

• Image Receptor (IR): The device that captures the x-ray image. This can be a DR flat-panel detector, a CR cassette with a photostimulable phosphor plate, or a fluoroscopic IR. The IR must be positioned correctly (lengthwise or crosswise) to include all required anatomy.
• Central Ray (CR): The center point of the x-ray beam. The CR should generally be directed perpendicular to the structure of interest and the IR to minimize shape distortion.
• Source-to-Image Receptor Distance (SID): The distance from the x-ray tube's anode to the IR. SID has a profound effect on the image:
  • Magnification: Increasing the SID decreases magnification, making the image appear closer to the object's true size.
  • Spatial Resolution: Increasing the SID improves the sharpness and detail of the image (spatial resolution).
  • Patient Dose: Increasing the SID allows the beam to spread out, requiring a higher mAs to maintain exposure but decreasing the patient's entrance skin exposure (ESE).
  • Standard SIDs are 40 inches (102 cm) for general radiography and 72 inches (183 cm) for chest radiography to minimize heart magnification.
• Anatomic Markers: These are legal requirements. An "R" or "L" marker must be placed on every image, correctly identifying the patient's right or left side. The marker must be placed within the collimated field and should never obscure essential anatomy.
• Display of Radiographs: With few exceptions, radiographs are displayed in the anatomic position—as if the patient is standing upright and facing the viewer. The exceptions are hands, wrists, feet, and toes, which are displayed with the digits pointing toward the ceiling.