Preliminary Steps in Radiography

Introduction to Radiography and Professional Practice

• Definitions and Professional Roles:

  • Radiologic Technology: A healthcare profession encompassing all diagnostic imaging technologists and radiation therapists.
  • Radiographer: A radiologic technologist who administers ionizing radiation to perform radiographic procedures, producing diagnostic images at the request of a licensed medical practitioner.
  • Required Knowledge & Skills: Effective clinical practice requires combining technical skills with extensive knowledge of physics, anatomy, physiology, and pathology.

• Radiography Practice Standards:

  • Formulated, maintained, and published by the American Society of Radiologic Technologists (ASRT).
  • Define the scope of practice for radiography, detail educational and credentialing requirements, and set clear professional benchmarks.
  • Section Components:
  • Clinical Performance Standards: Define activities regarding patient care, operational procedures, and diagnostic evaluation.
  • Quality Performance Standards: Define activities regarding equipment operation, safety, and quality assurance.
  • Professional Performance Standards: Define expectations for professional conduct, ethics, and ongoing education.
  • The current version is maintained on the ASRT website (ASRT.org).

• Ethics in Radiologic Technology:

  • Definition: Ethics represents a health professional's moral responsibility and the science of appropriate conduct toward patients and healthcare team members.
  • ARRT Standards of Ethics: Developed and maintained by the American Registry of Radiologic Technologists (ARRT) to translate professional values into concrete practice.
  • Code of Ethics: Composed of 10 statements serving as an aspirational guide for professional behavior.
  • Rules of Ethics: Composed of 22 mandatory, enforceable rules defining minimally acceptable professional conduct.
  • CAMRT Code of Ethics: Developed by the Canadian Association of Medical Radiation Technologists (CAMRT) to delineate ethical expectations for practitioners in Canada (CAMRT.ca).

• Advanced Clinical Practice:

  • Advanced practice roles enable experienced radiographers to act as a "radiologist extender" to perform or assist with:
  • Patient care activities.
  • Selected radiologic procedures.
  • Initial image observations.
  • Professional Titles:
  • Radiologist Assistant (RA)
  • Radiology Practitioner Assistant (RPA)
  • Credentialing Requirements: Achieving RA or RPA status requires ARRT radiography certification, completion of advanced formal education, and supervised clinical experience under a radiologist preceptor, followed by passing an advanced-level certification examination.

Room Preparation and Infection Control

• Care of the Examination Room:

  • Radiographer Responsibility: Maintaining strict cleanliness of the examination room and equipment (X-ray tube housing, tabletop, and accessories) to minimize pathogen transmission and promote patient confidence.
  • Room Preparation Protocols:
  • Disinfect all contact surfaces prior to patient arrival.
  • Ensure the room is clean, organized, and stocked with necessary positioning aids.
  • Place a fresh pillowcase on positioning pillows.

• Control of Pathogen Contamination:

  • The Centers for Disease Control and Prevention (CDC) provides guidelines for infection control, with Standard Precautions for All Patient Care serving as the foundation.
  • Core Standard Precautions:
  • Hand Hygiene: Perform hand hygiene before and after each patient interaction.
  • Personal Protective Equipment (PPE): Use PPE (gloves, gowns, masks, eye protection) whenever exposure to infectious material is anticipated.
  • Respiratory Hygiene / Cough Etiquette: Implement measures to contain respiratory secretions.
  • Patient Placement: Ensure appropriate isolation or bed assignment based on infection transmission risks.
  • Equipment Disinfection: Properly clean and disinfect patient-care instruments, equipment, and environmental surfaces.
  • Textiles & Laundry: Handle contaminated linens carefully to prevent pathogen dispersion.
  • Safe Injection Practices: Follow strict aseptic technique; wear a surgical mask during lumbar punctures.
  • Sharps Safety: Ensure safe handling and disposal of needles and sharp devices.
  • Transmission-Based Precautions: Applied in addition to Standard Precautions for patients with known or suspected airborne, droplet, or contact transmissible infections.

• Handwashing Practices:

  • Handwashing is the single easiest and most convenient method to prevent the spread of microorganisms.
  • Mandatory Handwashing Indications:
  • Before and after caring for every individual patient.
  • After examining patients with known communicable diseases.
  • After coming into contact with blood, bodily fluids, secretions, or excretions.
  • Prior to starting any invasive procedure.
  • Prior to touching high-risk, immunocompromised, or vulnerable patients.

Patient Care, Communication, and Motion Management

• Basic Patient Care & Communication:
  • Patient Explanation: Technologists must provide coherent patients with a clear explanation of the procedure, detailing what to expect, potential discomfort, and instructions to ensure comfort and compliance.
  • Clinical History Collection:
  • Verifying the correct exam was ordered against clinical indications.
  • Observing physical conditions or anatomical abnormalities to relay to the radiologist.

• Types and Control of Motion:
  • Uncontrolled motion during exposure severely degrades recorded image detail and spatial resolution.

• Involuntary Motion:
  • Causes: Heartbeat, chills, peristalsis, muscle tremors, spasms, and severe pain.
  • Primary Control Mechanism: Utilizing the shortest possible exposure time ($\text{seconds}$).
• Voluntary Motion:
  • Causes: Nervousness, discomfort, excitability, mental illness, fear, age (pediatric or geriatric), and uncontrolled breathing.
  • Control Mechanisms: Giving clear instructions, providing patient comfort, adjusting positioning support devices, and applying physical immobilization.
  • Uncooperative Patients: For patients unable to cooperate (e.g., young children, confused elderly, or patients with severe mental illness), decreasing exposure time is the primary method of motion control.
• Equipment Motion: Unintended movement originating from the X-ray tube mount, table, or cassette tray.

Image Receptors and Accessory Equipment

• Image Receptor (IR) Definition & Types:
  • An Image Receptor is defined as a device that receives the energy of the remnant X-ray beam and forms the diagnostic image of the body part.
  • Four Primary Types:
  1. Solid-State Digital Detectors: Flat-panel digital radiography (DR) detectors utilizing amorphous silicon or amorphous selenium, available as fixed tabletop/bucky units, tethered panels, or wireless plates.
  2. Photostimulable Storage Phosphor Image Plate (PSP IP): Computed Radiography (CR) plates coated with photostimulable phosphor that store latent image energy until read by a laser scanner inside a CR reader.
  3. Fluoroscopic Image Receptor: Real-time imaging systems using either an image intensifier tube coupled to a television camera/monitor or a flat-panel digital fluoroscopy detector.
  4. Cassette with Film: Traditional screen-film cassettes requiring chemical film processing.

• Accessory Equipment:
  • Positioning Aids: Radiolucent sponges, sandbags, and specialized leg holders (e.g., Ferlic leg holder) used to stabilize the body part.
  • Grids: Precision devices composed of lead strips placed between the patient and the IR to absorb scattered radiation, enhancing contrast.
  • Compensating Filters: Absorptive devices placed in the X-ray beam path to compensate for variations in tissue thickness and density, yielding uniform image brightness.

Radiographic Technical Factors and Exposure Technique Charts

• Prime Technical Factors:

  • Milliamperage (mA): Controls X-ray photon quantity and rate of exposure.
  • Kilovolt Peak (kVp): Controls X-ray beam energy, quality, and penetrability.
  • Exposure Time (seconds): Duration of beam activation; multiplied by mA to determine total milliampere-seconds ($\text{mAs}$).
  • Control Systems: Manual technical factor selection or Automatic Exposure Control (AEC) chambers.

• Technique Charts:

  • Standardized charts must be available in every examination room and attached to all mobile units.
  • Foundation Parameters Required for Technique Chart Establishment:
  • Milliampere-seconds ($\text{mAs}$)
  • Kilovolt peak ($\text{kVp}$)
  • Automatic Exposure Control ($\text{AEC}$) chamber selection and sensitivity
  • Source-to-Image Receptor Distance ($\text{SID}$)
  • Relative patient or part thickness ($\text{cm}$)
  • Grid selection and ratio
  • CR/DR exposure indicators
  • IR or collimated field dimensions
  • Electrical supply characteristics (generator phase and frequency)

• Essential Projections Technical Reference Data (Thoracic Viscera):
  • Chest: Lungs and Heart — PA Projection: Part thickness: $22\,\text{cm}$; $120\,\text{kVp}$; $72''\,\text{SID}$; Collimation: $14'' \times 16''$ ($35 \times 40\,\text{cm}$); CR: $2.8\,\text{mAs}$, Dose: $0.188\,\text{mGy}$; DR: $1.4\,\text{mAs}$, Dose: $0.089\,\text{mGy}$.
  • Chest: Lungs and Heart — Lateral Projection: Part thickness: $33\,\text{cm}$; $120\,\text{kVp}$; $72''\,\text{SID}$; Collimation: $14'' \times 17''$ ($35 \times 43\,\text{cm}$); CR: $7.1\,\text{mAs}$, Dose: $0.550\,\text{mGy}$; DR: $3.6\,\text{mAs}$, Dose: $0.273\,\text{mGy}$.
  • Chest: Lungs and Heart — PA Oblique Projection: Part thickness: $25\,\text{cm}$; $120\,\text{kVp}$; $72''\,\text{SID}$; Collimation: $14'' \times 17''$ ($35 \times 43\,\text{cm}$); CR: $3.6\,\text{mAs}$, Dose: $0.255\,\text{mGy}$; DR: $1.8\,\text{mAs}$, Dose: $0.124\,\text{mGy}$.
  • Chest: Lungs and Heart — AP Projection (Nongrid, 40'' SID): Part thickness: $22\,\text{cm}$; $90\,\text{kVp}$; $40''\,\text{SID}$; Collimation: $16'' \times 14''$ ($40 \times 35\,\text{cm}$); CR: $4.0\,\text{mAs}$, Dose: $0.655\,\text{mGy}$.
  • Chest: Lungs and Heart — AP Projection (DR Nongrid, 40'' SID): Part thickness: $22\,\text{cm}$; $105\,\text{kVp}$; $40''\,\text{SID}$; Collimation: $16'' \times 14''$ ($40 \times 35\,\text{cm}$); DR: $1.6\,\text{mAs}$, Dose: $0.340\,\text{mGy}$.
  • Chest: Lungs and Heart — AP Projection (Bucky/Grid, 72'' SID): Part thickness: $22\,\text{cm}$; $120\,\text{kVp}$; $72''\,\text{SID}$; Collimation: $14'' \times 16''$ ($35 \times 40\,\text{cm}$); CR: $3.2\,\text{mAs}$, Dose: $0.217\,\text{mGy}$; DR: $1.6\,\text{mAs}$, Dose: $0.104\,\text{mGy}$.
  • Pulmonary Apices — AP Axial Projection: Part thickness: $23\,\text{cm}$; $120\,\text{kVp}$; $72''\,\text{SID}$; Collimation: $14'' \times 11''$ ($35 \times 28\,\text{cm}$); CR: $4.0\,\text{mAs}$, Dose: $0.198\,\text{mGy}$; DR: $2.0\,\text{mAs}$, Dose: $0.097\,\text{mGy}$.
  • Lungs and Pleurae — Lateral Decubitus Projection: Part thickness: $22\,\text{cm}$; $120\,\text{kVp}$; $72''\,\text{SID}$; Collimation: $17'' \times 14''$ ($43 \times 35\,\text{cm}$); CR: $4.0\,\text{mAs}$, Dose: $0.271\,\text{mGy}$; DR: $2.0\,\text{mAs}$, Dose: $0.133\,\text{mGy}$.
  • Lungs and Pleurae — Dorsal / Ventral Decubitus Projection: Part thickness: $33\,\text{cm}$; $120\,\text{kVp}$; $72''\,\text{SID}$; Collimation: $17'' \times 14''$ ($43 \times 35\,\text{cm}$); CR: $9.0\,\text{mAs}$, Dose: $0.697\,\text{mGy}$; DR: $4.5\,\text{mAs}$, Dose: $0.344\,\text{mGy}$.

Radiation Protection, Geometry, and Beam Alignment

• Gonad Shielding Guidelines:
  • AAPM position statements, endorsed by the ACR and other professional bodies, indicate routine gonadal shielding can negatively impact examination efficacy (e.g., obscuring anatomy or interfering with AEC).
  • State regulations may still mandate gonadal shielding; technologists must remain aware of institutional and regulatory guidelines.

• Image Receptor Placement Configurations:
  • Lengthwise Position: Long axis of the IR aligned parallel with the long axis of the body (most commonly used, e.g., AP Abdomen).
  • Crosswise Position: Long axis of the IR aligned perpendicular to the long axis of the body (e.g., AP Pelvis).
  • Diagonal Position: IR rotated diagonally to cover long bones (e.g., AP Leg including knee and ankle joints).
  • Built-in Flat-Panel Detectors: Typically $17 \times 17\,\text{inches}$ ($43 \times 43\,\text{cm}$), movable lengthwise along the bucky track.

• Central Ray (CR) Alignment:

  • The central or principal photon beam is termed the Central Ray (CR).
  • The CR is centered to the anatomy of interest and the IR.
  • Standard goal: CR perpendicular to the part and IR to prevent distortion.
  • Reasons for Angling the CR:
  • Avoid superimposition of structures.
  • "Straighten out" curved structures.
  • Align the beam through an angled joint space.
  • Avoid distortion of an angled structure.

• Source-to-Image Receptor Distance (SID):

  • Distance from the anode focal spot inside the X-ray tube to the IR surface.
  • Key factor affecting magnification, spatial resolution, and patient dose.
  • Standard Operating SIDs:
  • $40\,\text{inches}$ ($102\,\text{cm}$): Traditional standard for general examinations.
  • $48\,\text{inches}$ ($122\,\text{cm}$): Modern standard adopted across many facilities to reduce magnification.
  • $72\,\text{inches}$ ($183\,\text{cm}$): Standard for chest and cervical spine imaging to minimize Object-to-Image Receptor Distance (OID) magnification.
  • Specialized projections in Merrill's Atlas range from $30\,\text{inches}$ ($76\,\text{cm}$) to $120\,\text{inches}$ ($305\,\text{cm}$); a minimum of $40\,\text{inches}$ ($102\,\text{cm}$) is recommended if unspecified.

• Source-to-Skin Distance (SSD):

  • Distance from the X-ray tube focal spot to the patient's skin surface.
  • Influences patient entrance exposure dose.
  • NCRP Guidelines: SSD shall not be less than $12\,\text{inches}$ ($<30\,\text{cm}$) and should not be less than $15\,\text{inches}$ ($<38\,\text{cm}$).

• Collimation and Shuttering Rules:
  • Restricting the radiation field size to include only the anatomy of interest.
  • Two Primary Purposes:
  1. Minimizes patient radiation dose.
  2. Reduces scatter radiation, improving contrast resolution.
  • Ethical Mandate: Collimating larger than the required field size violates the ARRT Code of Ethics and ASRT Practice Standards.

• Shuttering (Electronic Cropping):
  • Software process adding a dark border around a collimated field in DR systems for viewing aesthetics.
  • Prohibition against Misuse: Electronic shuttering must never be used to replace physical beam collimation. Post-exposure cropping increases patient dose and creates legal liability if cropped diagnostic information leads to a missed diagnosis.

Anatomic Markers, Image Display, and Evaluation

• Anatomic Side Markers:

  • Medicolegal requirements mandate physical lead Right ($\text{R}$) or Left ($\text{L}$) markers on all radiographs prior to exposure.
  • Rules for Marker Placement:
  • Must be visible on the image without obscuring anatomy.
  • Placed within the collimation field border.
  • Positioned outside of lead shielding.
  • Post-acquisition digital annotation is discouraged due to the risk of lateral site identification errors.

• Image Display Standards:

  • Radiographs are viewed in standard anatomic position.

• Standard Display Exceptions: Images of extremities—specifically hands, fingers, wrists, feet, and toes—are displayed as seen from the perspective of the X-ray tube, with digits pointing upward toward the ceiling.

• Required Image Identification:
  1. Date of examination.
  2. Patient name or identification number.
  3. Anatomic side marker ($\text{R}$ or $\text{L}$).
  4. Healthcare institution name.

• Image Evaluation Criteria:
  • Technologists must evaluate every image for acceptability, safety compliance, and procedural goals.
  • Criteria include verifying patient ID, marker placement, collimation, shielding, and absence of technical artifacts.

Radiographic Considerations for Obese Patients

• Obesity Demographics and Definitions:

  • Obesity prevalence has doubled in the last 15 years; $71\%$ of American adults are overweight, obese, or morbidly obese.
  • Body Mass Index (BMI) Classifications:
  • Obese: $\text{BMI} = 30 \text{ to } 39.9$
  • Morbidly Obese: $\text{BMI} \ge 40$
  • Body weight and diameter determine whether radiographic procedures can be performed.

• Equipment Considerations:

  • Weight limits on radiographic tables; older tables held $350 \text{ to } 450\,\text{lbs}$, while redesigned modern tables support up to $700\,\text{lbs}$.
  • Diameter limits on fluoroscopy towers, CT scanners, and MRI units.
  • Mobile DR detectors facilitate positioning by providing greater tube-to-table clearance.

• Patient Transfer and Positioning:

  • Utilization of larger wheelchairs, heavy-duty stretchers, team movement, proper body mechanics, transfer boards, air mattresses, and ceiling-mounted power lifts.

• Communication Guidelines:

  • Use empathetic communication, avoid mentioning weight, and clearly explain movement and positioning steps.

• Landmark Location in Morbidly Obese Patients:

  • Most surface bony landmarks are unpalpable due to adipose tissue.
  • Jugular Notch Landmark Method: Locate the palpable jugular notch and measure inferiorly along the midline to locate the pubic symphysis plane based on height:
  • Height under $5\,\text{feet}$ ($<152\,\text{cm}$): Pubic symphysis is $21\,\text{inches}$ ($53\,\text{cm}$) inferior to jugular notch.
  • Height $5 \text{ to } 6\,\text{feet}$ ($152 \text{ to } 183\,\text{cm}$): Pubic symphysis is $22\,\text{inches}$ ($56\,\text{cm}$) inferior to jugular notch.
  • Height over $6\,\text{feet}$ ($>183\,\text{cm}$): Pubic symphysis is $24\,\text{inches}$ ($61\,\text{cm}$) inferior to jugular notch.

Questions & Discussion

• Question 1: What is the easiest method to control the spread of pathogens?

  • Options: A. Use of mask on patients | B. Radiographers wearing masks | C. Wearing gloves for all procedures | D. Hand hygiene
  • Answer: D. Hand hygiene
  • Explanation: Hand hygiene is the simplest and most effective method to prevent cross-contamination and pathogen transmission in medical environments.

• Question 2: All of the following are examples of involuntary motion, except:

  • Options: A. Peristalsis | B. Heartbeat | C. Breathing | D. Chills
  • Answer: C. Breathing
  • Explanation: Respiration is under voluntary patient control and can be stopped with clear breathing instructions. Peristalsis, heartbeat, and chills are involuntary movements.

• Question 3: How do radiographers help reduce the risk of imaging involuntary motion?

  • Options: A. Use immobilization | B. Appropriate patient instructions | C. Clear communications | D. Use the shortest possible exposure time
  • Answer: D. Use the shortest possible exposure time
  • Explanation: Involuntary motion cannot be controlled by verbal instructions or immobilization. Decreasing exposure time to the minimum achievable duration is required.

• Question 4: All of the following are required identification on a radiographic image, except the:

  • Options: A. Side marker | B. Patient name or ID number | C. Referring physician's name | D. Name of the facility
  • Answer: C. Referring physician's name
  • Explanation: Standard legal image identification requires examination date, patient name/ID number, side marker ($\text{R}$ or $\text{L}$), and institution name. The referring physician's name is not required on the image.

• Question 5: A technique chart must include all of the following, except:

  • Options: A. Pathology type | B. $\text{kVp}$ | C. $\text{AEC}$ | D. Grid
  • Answer: A. Pathology type
  • Explanation: Exposure technique charts detail technical factors ($\text{kVp}$, $\text{mAs}$, $\text{AEC}$, grid, $\text{SID}$) for specific anatomical projections, not pathology classifications.

• Question 6: Which of the following will affect whether a radiographic examination can be performed on an obese patient?

  • Options: A. Height | B. Weight | C. BMI | D. Communication skills
  • Answer: B. Weight
  • Explanation: Patient weight and body diameter directly determine equipment compatibility due to table load limits and gantry/aperture clearance dimensions.

• Question 7: Which guideline is used to locate the pubic symphysis on an obese patient who is approximately $5\,\text{feet}, 5\,\text{inches}$ tall?

  • Options: A. $15\,\text{inches}$ from the jugular notch | B. $21\,\text{inches}$ from the jugular notch | C. $22\,\text{inches}$ from the jugular notch | D. $24\,\text{inches}$ from the jugular notch
  • Answer: C. $22\,\text{inches}$ from the jugular notch
  • Explanation: For patients between $5\,\text{feet}$ and $6\,\text{feet}$ tall, the pubic symphysis plane lies $22\,\text{inches}$ inferior to the jugular notch.