Terminology, Positioning and Imaging Principles Study Notes

Terminology, Positioning and Imaging Principles

Unit 1

Instructor: A. Montalvo

Anatomic Position

  • Anatomic Position:
      - The person is upright.
      - Facing forward.
      - Upper limbs along the sides of the body with palms facing forward.
      - Feet firmly on the ground and parallel to each other.
      - This position serves as a standard reference point for describing all positions, movements, and anatomical planes.

Body Planes

  • Major body planes:
      - Sagittal (also referred to as midsagittal or median)
      - Horizontal (also called axial or transverse)
      - Coronal (also known as frontal or midcoronal)

  • Imaginary flat surfaces that divide the body:
      - Sagittal Plane: Divides body into right and left sides.
      - Midsagittal Plane (MSP): Divides the body into equal right and left halves.
      - Transverse Plane (Axial or Horizontal): Divides the body into upper and lower portions.
      - Coronal Plane (Frontal): Divides the body into anterior (front) and posterior (back) portions.
      - Midcoronal Plane (MCP): Divides the body into equal anterior and posterior halves.

Body Cavities

  • Two main types of cavities: Ventral and Dorsal.
      - Ventral Cavity (front half): Includes:
        - Thoracic Cavity: Contains the pleural cavities, mediastinum, and pericardial cavity.
        - Abdominopelvic Cavity: Contains the abdominal cavity and pelvic cavity.
      - Dorsal Cavity (back half): Includes:
        - Cranial Cavity: Contains the brain.
        - Spinal Cavity: Contains the spinal cord.

Anterior and Posterior Surfaces of Hands and Feet

  • Hands:
      - Dorsal (dorsum manus): Back or posterior aspect of the hand.
      - Palmar: Palm of the hand, anterior or ventral surface of the hand.

  • Feet:
      - Dorsal (dorsum pedis): Top or anterior surface of the foot.
      - Plantar: Sole or posterior surface of the foot.

Body Habitus

  • Definition: Refers to the build, physique, and general shape of the human body.

  • Impact on Positioning: The size, dimensions, and shape of the patient's body affect how specific regions, like the respiratory, gastrointestinal, and biliary systems, are positioned.

  • Classifications: Four general body styles:
      1. Sthenic: Approximately 50% of the population, average shape and organ location.
      2. Hyposthenic: A thin body style, more slender than sthenic, about 35% of the population.
      3. Asthenic: Very thin and slender with a long, narrow body build, about 10% of the population.
      4. Hypersthenic: A massive body style, large frame, about 5% of the population.

Anatomical Directions

  • Superior: Towards the head, above, upper.

  • Inferior: Towards the feet, below, lower.

  • Medial: Towards the midline of the body.

  • Lateral: Away from the midline.

  • Proximal: Towards/nearest the trunk or point of origin.

  • Distal: Away from/farthest from the trunk.

  • Superficial: Closer to the surface.

  • Deep: Farther away from the body surface.

  • Cephalad/Cephalic/Cranial: Tube angled towards the head.

  • Caudad/Caudal: Tube angled towards the feet.

Movement Terms

  • Flexion: Bending of a joint, decreasing the joint angle.

  • Extension: Straightening of a joint, increasing the joint angle.

  • Hyperflexion: Excessive or forced flexion of a limb or joint.

  • Hyperextension: Excessive or forced extension of a limb or joints.

Abduction vs. Adduction

  • Abduction: Movement away from the body.

  • Adduction: Movement toward the body.

Deviation

  • Deviation: Turning away from the regular standard or course.
      - Ulnar and Radial Deviation: Refers to the deviation of the wrist towards the ulna or radius, respectively.

Dorsiflexion vs. Plantar Flexion

  • Dorsiflexion: Flexion of the foot toward the leg, creating a 90-degree angle with the leg.

  • Plantar Flexion: Flexion of the foot toward the sole (pointing the toes).

Movements and Stress of Ankle Joint

  • Eversion: Outward turning of the foot at the ankle.

  • Inversion: Inward turning of the foot at the ankle.

  • Valgus Stress: Abnormal positioning forcing a limb outward from the midline of the body.

  • Varus Stress: Abnormal positioning forcing a limb inward towards the midline of the body.

Supination vs. Pronation

  • Supination: Rotation of the forearm placing the palm surface up.

  • Pronation: Rotation of the forearm placing the palm surface down.

Medial vs. Lateral Rotation

  • Medial Rotation: Turning of a body part inward about its axis.

  • Lateral Rotation: Turning of a body part outward about its axis.

Circumduction

  • Definition: Movement in a circular motion around a joint.

Protraction vs. Retraction

  • Protraction: Moving a part forward from its normal position.

  • Retraction: Moving a part backward from its normal position.

General Terms in Radiography

  • Radiography: The process and procedures of producing a radiograph.

  • Radiograph: An image of a patient’s anatomic parts produced by x-rays on an image receptor.

  • Film: Traditional Film-screen (Analog).

  • Computed Radiography: Viewed on a computer screen.

  • Digital (DR): Viewed on a computer screen.

  • Image Receptor (IR): The device that captures radiographic images exiting the patient.

  • Central Ray (CR): Centermost portion of the x-ray beam emitted from the x-ray tube, where divergence is least.

Positioning Terms in Radiography

  • Main Terms:
      - Projection: Path of the CR through the patient.
      - Position: Overall posture or general body position.
      - View: Describes the body part as seen by the IR (only used when referring to a finished radiograph).
      - Method: Some positions are named after individuals who created them (e.g., Waters or Towne methods for the skull).

Radiographic Projections

  • Definition: Direction or path of the CR as it passes through the patient, often defined by entrance and exit points.

  • Types of Projections:
      - AP Projection: Beam enters anterior, exits posterior.
      - PA Projection: Beam enters posterior, exits anterior.
      - Oblique Projection: Beam enters at an angle, between AP/PA and lateral views.
      - Lateral Projection: 90-degree angle to the body from the anatomic position.
      - Axial Projection: Angled CR to the longitudinal aspect of the body (often cephalad or caudal).
      - Tangential Projection: Beam directed to skim a body part and project it into profile.

Positioning Terms by General Body Position

  1. Upright/Erect: Patient is standing.

  2. Recumbent: Lying down in any position.

  3. Supine: Lying on the back.

  4. Prone: Lying on the stomach.

  5. Trendelenburg: Supine with head lower than feet.

  6. Fowler: Supine with feet lower than head.

  7. Modified SIMS: Recumbent, semi-prone, left leg extended, right leg/hip flexed.

  8. Lithotomy: Supine, knees and hips flexed, thighs abducted.

Positioning and Body Part Relation to IR

  • Lateral Position: Named for the side closest to the IR (e.g., left lateral position).

  • Oblique Position: Entire body rotated between 0-90 degrees, named according to part closest to IR (e.g., RAO, LAO, RPO, LPO).

  • Decubitus Position: Patient lying down with a horizontal beam. Includes three types:
      - Lateral Decubitus: Patient lying on either side with the beam entering anterior/posterior.
      - Dorsal Decubitus: Patient lying on back, beam enters side.
      - Ventral Decubitus: Patient lying on stomach, beam enters side.

Positioning Principles

  • Positioning Accuracy Criteria:
      - Anatomy demonstrated: Specific parts should be clearly visualized.
      - Position: Correct placement of body part and alignment with IR.
      - Exposure: Correct exposure factors (kVp and mAs).
      - Motion control: Ensuring no motion blurs the image.

Motion Control

  • Types of muscles involved:
      - Smooth (involuntary)
      - Skeletal (voluntary)
      - Cardiac (involuntary)

  • Ways to control voluntary motion:
      - Clear communication with patients.
      - Patient comfort measures.
      - Use of support devices and immobilization techniques.

Evaluation Criteria of Radiographs

  • Anatomy demonstrated: Include specific joints/structures (e.g., elbow and wrist).

  • Position: Confirm no rotation at joints.

  • Exposure: Ensure optimal exposure settings.

  • Image Markers: Should be visible, placed on the lateral side where possible.

Professional Ethics and Patient Care

  • Code of Ethics: Guidelines for acceptable conduct towards patients and fellow healthcare professionals.

  • Patient Care Priority: Emphasis on moral responsibility and ethics in treatment.

  • ASRT ACE Campaign:
      - Announce your name.
      - Communicate your credentials.
      - Explain procedures to the patient.

Radiographic Examination Steps

  1. Positioning body part and aligning with IR and CR.

  2. Applying radiation protection measures.

  3. Selecting exposure factors for radiographic technique.

  4. Communicating instructions for respiration and initiating x-ray exposure.

  5. Processing the IR and reviewing the resulting image.

Identification of Radiographs

  • Radiographs should include:
      - Date.
      - Patient’s name and MRN (Medical Record Number).
      - Right or left markers.
      - Institution identity.

  • Radiographs do not require the technologist’s name or initials.

Radiographic Room Preparation

  • Responsibilities include:
      - Ensuring the room is stocked (supplies, sheets, gowns, tape, gloves, etc.).
      - Cleaning x-ray room after each patient using disinfectant wipes.
      - Proper disposal of used materials.
      - Preparing room before patient arrival.

COVID-19 Precautions for Technologists

  • Hand Washing: Treat all patients as potentially infectious, wearing gloves always, and washing hands before and after each exam.

  • Masks: Mandatory usage during patient interactions, changing masks when necessary.

  • Room Protocol: Follow facility protocols for personal protective equipment (PPE)l

Image Receptor (IR) Placement

  • Long Axis Alignment: Ensure the long axis of IR is parallel to the long axis of the part being examined.

  • Generally, the CR is perpendicular to the IR.

  • Plate Usage: The term "plate" can also refer to IR, with placement as:
      - Portrait: Lengthwise position.
      - Landscape: Crosswise position.

Direction of the CR

  • The CR should be centered on the anatomy of interest and IR. Ideal placement is perpendicular, while angling is done when necessary:
      - To separate superimposed structures.
      - When imaging curvatures (e.g., sacrum).
      - For angled joints (such as knee).
      - To overcome foreshortening and self-superimposition.

SID and SSD

  • SID (Source-to-Image Receptor Distance): Distance between the x-ray tube and IR. Common values are 40 inches and 72 inches.

  • SSD (Source-to-Skin Distance): Distance between the x-ray tube and patient's skin.

Collimation

  • Purpose: Restricting the beam to reduce patient dose and scatter radiation.

  • Implementation: Adjust the light field size to improve image quality and recorded detail.

Gonadal Shielding

  • Usage criteria:
      - If gonads lie within 5 cm of the primary field.
      - If shielding does not compromise the study.
      - If the patient possesses reasonable reproductive potential.

  • Types: Include shadow shields placed on the x-ray tube.

Proper Display of Radiographs

  • AP or PA Images: Displayed in anatomical position as if patient is facing the viewer.

  • Chest Images: Must be displayed the same regardless of projection type.

  • Hands/Fingers and Toes: Displayed with digits pointing upwards towards the ceiling.

  • Lateral Radiographs: Viewed from the perspective of the x-ray tube or technologist’s view.

Positioning Routines Principles

  • Minimum Projections: A general rule requires a minimum of two projections (90 degrees apart) for most procedures.

  • Single Projections: Can include AP mobile chest, AP abdomen (KUB - Kidneys, Ureter, and Bladder), and AP pelvis.

Homework

  1. Bontrager’s Workbook: Refer to handouts for specific questions across pages 7 to 10.

  2. Video Viewing: Watch "x-ray room 101" (11 minutes).

  3. Reading Assignment: Review the chest chapter in Bontrager’s textbook.