Chapter 1 Notes: Terminology, Positioning, and Imaging Principles (Comprehensive Bullet Notes)

Levels of Structural Organization and Terminology

  • Focus of the beginning of the lecture: review of basic anatomy/physiology concepts and terminology related to positioning and imaging.
  • Levels of human structural organization mentioned: foundational concepts leading into osteology and arthrology.
  • Skeletal system basics are introduced as a core topic for radiologic positioning.

Osteology and Arthrology: Core Disciplines

  • Osteology: the study of the skeletal system.
  • Arthrology: the study of joints.
  • Quick recap: bones constitute the framework; joints connect bones allowing movement.

Major Organ Systems (Brief Functional Overview)

  • Digestive system: responsible for absorption and elimination.
  • Respiratory system: supplies oxygen and eliminates carbon dioxide.
  • Urinary system: regulates blood and eliminates waste.
  • Reproductive system: enables reproduction.
  • Nervous system: regulates body activities.
  • Muscular system: enables movement (skeletal, visceral, cardiac).
  • Endocrine system: ductless glands; regulates via hormones.
  • Integumentary system: protects the body and eliminates waste (via processes like perspiration).

The Skeleton: Axial vs Appendicular

  • Two main sections: axial skeleton and appendicular skeleton.
  • Axial skeleton: 80 bones; located along the central axis of the body (skull, vertebral column, ribs, sternum).
  • Appendicular skeleton: 126 bones; includes limbs (arms and legs) and girdles (shoulder and pelvic girdles).
  • For this course (Positioning One): focus primarily on the appendicular skeleton this semester.
  • When discussing chest and abdomen in upcoming weeks, note that ribs and sternum are in the region but rib/sternum positioning will not be studied in detail until next semester.

Bone Counts (Key Figures)

  • Axial skeleton: 80 bones.
  • Appendicular skeleton: 126 bones.
  • Total adult skeleton: 206 bones.

Classification of Bones

  • Long bones: e.g., humerus, femur.
  • Short and flat bones: e.g., wrist (carpal) bones, foot (tarsal) bones; skull calvarium.
  • Irregular bones: e.g., certain facial bones and vertebrae; usually peculiar shapes.
  • The skull (calvarium) is noted as an example of short/flat or irregular bones depending on region.

Pediatric Skeletal Development and Growth Plates

  • In pediatrics, radiographs show growth plates.
  • Primary center: diaphysis (the shaft of a long bone).
  • Secondary centers: metaphysis and epiphyseal plate (growth plate).
  • As bones grow, diaphysis meets metaphysis and forms the epiphyseal plate.
  • Pediatric radiographs can appear as growth plates rather than fractures; these are normal in growing children.
  • Growth centers and epiphyseal plates become important when discussing pediatrics in the spring semester.

Joints: Arthrology and Joint Classifications

  • Joints are categorized by structure (fibrous, cartilaginous, synovial).
  • Functional classifications: synarthrodial (immovable), amphiphrodial (slightly movable), diarthrodial (freely movable).
  • Synovial joints (seven types) are generally freely movable and contain a joint cavity with synovial fluid.
    • Plane (gliding) joints: e.g., between carpals; minor gliding movements.
    • Hinge joints: e.g., fingers and elbows; flexion/extension.
    • Trochoid (pivot) joints: e.g., C1-C2 (atlas/axis) and proximal/distal radioulnar joints.
    • Condyloid (ellipsoidal) joints: e.g., radiocarpal joint; allows biaxial movement.
    • Saddle joints: e.g., first carpometacarpal (thumb); concave/convex surfaces that fit like a saddle.
    • Ball-and-socket joints: e.g., shoulder, hip; multiaxial freedom of movement.
    • Additional terms referenced: sometimes referred to as spheroidal joints in some texts.

Body Habitus/Biotype Classifications and Their Relevance to Positioning

  • Four principal body habitus classifications (plus bariatric):
    • Sphenic
    • Hypostenic
    • Hyperphysic (often described as hypersthymic in texts)
    • Ascenic (often described as asthenic in texts)
    • Bariatric (obese patients)
  • Practical implications:
    • These classifications are used to anticipate organ location and soft tissue distribution for radiographic positioning, especially in the chest and abdomen.
    • About one-half of patients are considered average (example given: Figure 1.33 Hispanic patient).
    • Approximately 35% described as hypocenic (very slender).
    • Approximately 10% described as asenic (very slender or slender with specific features).
    • Hypersthymic (broad frame) patients are wider than average; bariatric patients are obese and more challenging to image due to landmarks and limb palpation.
  • Equipment and technique adaptations for bariatric patients:
    • Modern radiography equipment is capable of accommodating higher weights (e.g., up to around 650 pounds).
    • Palpation of landmarks can be difficult due to excess soft tissue.
    • Adjustments may be needed in technique and positioning to account for tissue distribution.
  • Important teaching point:
    • In obesity, emphasis is often on organ location and soft tissue distribution rather than bone placement alone; keep the “tiny inner ballerina” concept in mind for relative skeletal positions within soft tissue.
  • Classroom example discussion:
    • A bariatric patient may present with varying body habitus types; it’s not always strictly tied to a single category—adapt positioning based on actual anatomy and landmarks.
  • Summary takeaway:
    • The four non-bariatric body habitus concepts focus on organ placement and tissue distribution, which guides radiographic positioning decisions for chest and abdomen imaging.

Positioning, Planes, and Projections: Foundational Concepts

  • Anatomic position: establishes a baseline for positioning and orientation.
  • Body planes and terms:
    • Sagittal plane: divides body into left and right halves. Mid-sagittal (median) plane runs down the center.
    • Coronal (frontal) plane: divides body into anterior (front) and posterior (back) portions. Mid-coronal plane divides equally.
    • Horizontal (axial) plane: divides body into superior (top) and inferior (bottom).
  • Directional terms (based on anatomic position):
    • Superior / Inferior: top / bottom.
    • Anterior / Posterior: front / back.
    • Medial / Lateral: toward the midline / away from the midline.
  • Projections vs views:
    • Projection: the path of the X-ray beam as it enters and exits the body (e.g., AP, PA, oblique, lateral, axial, tangential).
    • View: the image as seen on the image receptor; a description of the body part’s appearance in the image.
  • Common projections and orientations:
    • AP (Anteroposterior): beam travels from front to back.
    • PA (Posteroanterior): beam travels from back to front.
    • Oblique: body part rotated at an angle relative to the IR; still described with anterior/posterior relationships (e.g., RAO, LAO, RPO, LPO).
    • Lateral: beam travels from the side; can be left or right lateral projection.
    • Mediolateral / Lateromedial: beam approaches from medial or lateral side of the limb.
    • Upright (erect) vs recumbent (supine or prone): upright/erect is standing; recumbent means lying down.
    • Sims position: a lateral position with patient on their side, often used for certain procedures (e.g., an enema technique) and discussed in relation to barium enema placement.
  • Specific positioning terms and examples from the lecture:
    • RAO (Right Anterior Oblique): person standing; left side closest to IR in some contexts; specimen examples discussed.
    • LPO (Left Posterior Oblique): standing with left posterior side contacting the IR.
    • AP/PA oblique entries in hands and feet examples; identification of projection by anatomical landmarks and which side is closest to the IR.
    • Upright lateral vs recumbent lateral distinctions; the difference between a left lateral recumbent and a left lateral upright position.
  • Decubitus positions (horizontal beam):
    • Decubitus describes a horizontal beam, with the body lying on a horizontal surface.
    • Left decubitus: left side down; right decubitus: right side down.
    • Dorsal decubitus: patient lies on back with X-ray beam directed horizontally; ventral decubitus would be with patient on stomach.
    • The term cubitus (elbow area) is noted separately as a special region; for certain exams the beam can be directed perpendicularly or at angles (axial) depending on the anatomy.
  • Central Ray (CR) orientation and anatomy awareness:
    • The central ray enters and exits at specific points; orientation relative to the IR is critical for accurate imaging.
    • If a beam is angled, we refer to an axial or oblique projection depending on whether the angle is along the long axis or between anatomical planes.
    • Axial projection vs oblique projection distinction:
    • Axial: central ray aligned with the long axis or at a significant angle (often > 10°) along the body part.
    • Tangential: projection that skim the body part rather than penetrating through it.
    • Oblique: body part rotated ~45°; anterior aspect closest to IR indicates specific labeled obliques.
  • Special body region examples and terminologies:
    • Dorsoplantar: projection for foot with the dorsal surface facing toward the IR and the plantar surface toward the detector.
    • Axial superior-to-inferior projections: central ray oriented from superior to inferior through a region such as the armpit (axilla) or nearby structures.
    • Inferior axial terminology: sometimes described as inferior or superior directional trajectories depending on anatomy and exam.
    • Dorsal decubitus and ventral decubitus terminologies reflect patient side and surface relationships.
  • Image receptor alignment and marker use:
    • Image receptor alignment can be portrait (vertical) or landscape (horizontal).
    • Markers and left/right indicators are essential for identifying sides and orientation on the radiograph.
  • Practical notes on positioning practice:
    • Positioning accuracy is emphasized as essential; always reference the anatomy and the anatomic position baseline.
    • The lab will include palpation to locate landmarks; consent and patient notification must precede touch.
    • Palpation involves gentle pressure to identify landmarks; you must obtain patient permission before touching.
    • The use of a phantom or skeletal models helps students practice left-right orientation and positioning before working with live patients.
  • Equipment and exposure considerations:
    • Image receptor alignment, patient positioning, and landmark palpation all influence exposure factors and image quality.
    • There are typical minimum projection requirements for imaging most body parts; some bones/joints require more than two projections.

Projections, Views, and Minimum Projections: Practical Imaging Rules

  • Minimum projections:
    • Generally, a minimum of two projections is required for most body parts.
    • Some bones or joints require three or more projections for adequate evaluation.
    • Examples mentioned: multiple projections for the hand (three), certain knee or pelvis examinations (two), but many joints may require three or more injections (projections).
  • Exceptions and considerations:
    • Pediatric exams (e.g., pediatric hand/wrist) may require different projection strategies due to growth plates.
    • Certain joints or clinical indications may mandate additional projections beyond the minimum.
  • The role of palpation and landmarks in projection planning:
    • Landmarks guide where to place the CR and how to angle the beam; palpation is essential for accuracy.
    • Consent and communication with the patient are essential before palpation.
  • Central ray and projection terminology recap:
    • AP vs PA: direction of beam entry (anterior vs posterior entry).
    • Lateral: beam enters from the side.
    • Oblique: beam angled with the patient rotated.
    • Axial: beam angled along the long axis of the body part.
    • Tangential: beam just skim or touch the superficial aspect without penetrating deeply.
  • The concept of “view” in radiology practice:
    • A view describes how the body part appears on the image receptor; a projection describes the beam direction used to obtain that view.

Ethical, Practical, and Professional Practice Considerations

  • Palpation safety and consent:
    • Always ask for permission before touching a patient and explain the purpose of palpation.
  • Professionalism and patient dignity:
    • Respect patient modesty and comfort throughout positioning and imaging.
  • Left-right orientation and marker use:
    • Proper labeling with left/right markers is essential to avoid misinterpretation.
  • Continuous practice and lab readiness:
    • Use phantoms and models to practice before working with real patients.
  • Summary reminder:
    • Mastery of anatomy, planes, projections, and positioning accuracy underpins quality radiographic images and patient safety.

Quick References and Key Terms to Remember

  • 206 bones in the adult skeleton: 206.
  • Axial skeleton: 80 bones; central axis.
  • Appendicular skeleton: 126 bones; limbs and girdles.
  • Growth centers: diaphysis (primary), metaphysis and epiphyseal plate (secondary).
  • Joint classifications: fibrous, cartilaginous, synovial.
  • Synovial joints types (7): plane, hinge, trochoid, condyloid, saddle, ball-and-socket, plus related terms.
  • Projections and directions: AP, PA, oblique, lateral, mediolateral, lateromedial, axial, tangential.
  • Planes: sagittal (mid-sagittal), coronal (mid-coronal), horizontal/axial.
  • Positions: erect/upright, recumbent (supine/prone), Sims, decubitus (left/right, dorsal/ventral).
  • IR: image receptor.
  • ROE: not explicitly defined in notes; ensure you understand its use in imaging workflow and orientation.

End of Chapter 1 Notes

  • The instructor encourages ongoing practice and application of these concepts in upcoming labs and imaging scenarios.
  • Look ahead to cross-sectional anatomy and CT orientation in later chapters, building on the planes and positioning fundamentals established here.