Week One Flashcards
Dimensional Thinking in Medical Imaging
2D vs 3D:
2D imaging adds height and width to the image plane.
3D imaging includes height, width, and length; all anatomical structures have 3 dimensions.
Accurate spatial relationships require incorporating the 3rd dimension.
Ultrasound interpretation:
Ultrasound uses 2D slices; 3D information is gleaned by viewing structures in more than one plane.
Sonographers routinely interpret anatomy in 3D by acquiring multiple 2D images in different planes.
Planes and orientation in imaging:
Sagittal plane (length and height): longitudinal view opening to assess length/depth.
Transverse plane (width and height): cross-sectional view.
Coronal plane (width and depth): front-to-back perspective.
Analogies and visualization aids (illustrative):
Conceptual analogies like slicing bread to view “slices” of a loaf from different angles help in understanding sectional views.
Note: All planes are analyzed in relation to the anatomical position and scanning orientation to preserve consistent interpretation.
Anatomy: Gross, Microscopic, and Sectional Concepts
Gross anatomy:
Study of anatomy without magnification.
Emphasizes body systems; focuses on shape, location, and function of structures visible to the naked eye.
Microscopic anatomy:
Study of cells and tissues under a microscope.
Sectional anatomy:
Regions of the body are studied instead of just systems.
Emphasizes 3D relationships within a region via sequential slices.
Relationship to physiology:
Structure (anatomy) underpins function (physiology); sectional views help relate anatomy to clinical imaging findings.
Anatomical Planes and Orientation
Anatomical planes (three major orthogonal planes):
Sagittal (longitudinal): a vertical plane that divides the body into right and left portions.
Midsagittal (midline): passes through the midline, creating equal right and left sides.
Parasagittal: divides the body into unequal right/left sections.
Transverse (axial, short axis): a horizontal plane dividing the body into superior and inferior portions; often used in cross-sectional imaging.
Coronal (frontal): a vertical plane dividing the body into anterior and posterior sections.
Additional related planes:
Midaxillary plane: a vertical plane passing through the midaxillary line.
Oblique: a plane angled between sagittal and/or transverse and/or coronal planes (not strictly orthogonal).
Key concept:
Anatomical relationships vary with the plane of view; imaging may use oblique planes to reflect natural organ orientation.
Planes vs. acoustic window:
Planes are mathematical constructs; acoustic window refers to where the ultrasound beam can interrogate tissue in the patient.
Acoustic Window, Scanning Planes, and Image Standardization
Acoustic window:
The location from which an ultrasound transducer scans; corresponds to the transducer position on the patient.
Only structures directly beneath the beam can be investigated.
The window is controlled by the sonographer (transducer manipulation).
Scanning planes:
2D ultrasound images are created; structures are typically viewed in multiple planes to obtain 3D information.
Sagittal/longitudinal planes show length and height/depth.
Transverse/short axis planes show width and height/depth.
Oblique scans are used to demonstrate the natural orientation of organs when standard planes do not optimally display structure.
Image standardization:
Standardization of ultrasound image display is essential for accuracy and consistency.
The sonographer controls probe orientation, which determines image orientation and displayed relationships.
Incorrect orientation can lead to misinterpretation and affect patient management.
Transducer orientation:
Each transducer has a marker used to orient on the patient; the marker's direction determines what side of the monitor displays the structure.
Typical orientation rules (dependent on position):
Sagittal (patient supine): marker directed toward the patient’s head.
Transverse (patient supine): marker directed toward the patient’s right side (the side of contact with the transducer).
Coronal (patient on side): marker directed toward the patient’s head.
Directional Terminology
Right and Left: always refer to the patient’s right/left, not the observer.
Superior (cranial/cephalic): toward the head or above another part.
Inferior (caudal): toward the feet or below another structure.
Anterior (ventral): toward the front of the body/structure.
Posterior (dorsal): toward the back of the body/structure.
Medial: toward the midline of the body or structure.
Lateral: toward the side of the body or structure.
Proximal: closer to the trunk or point of attachment.
Distal: farther from the trunk or point of attachment.
Superficial (external): toward or near the body surface.
Deep (internal): away from the body surface.
Ipsilateral: structures on the same side.
Contralateral: structures on opposite sides.
Visceral: related to the viscera (internal organs).
Parietal: related to the wall of the body.
Patient Positioning Terminology
General concept: patient position is described relative to anatomical position during a scan.
Common positions:
Prone: patient lying face down.
Supine: patient lying face up.
Lateral: patient lying on the right or left side (lateral decubitus).
True lateral: body at 90° from supine or prone; position named by the side touching the table (e.g., Left lateral).
Lateral oblique: body angled less than 90° from supine/prone; position named for surface/side nearest the table (e.g., Left posterior oblique, LPO).
Erect: standing or sitting upright.
Semi-erect: partially upright (usually partial sitting with back between supine and erect).
Trendelenburg: feet higher than the head.
Reverse Trendelenburg: feet lower than the head.
Body Cavities: Dorsal and Ventral
Body cavities: natural spaces containing internal organs; they protect, support, and allow organ movement/expansion.
Dorsal (posterior) cavity:
Associated with the central nervous system.
Contains cerebrospinal fluid (CSF) in its cavities.
Subdivided into cranial cavity (brain) and spinal (vertebral) cavity (spinal cord and nerves).
Ventral (anterior) cavity:
Larger than the dorsal cavity.
Contains viscera (internal organs).
Subdivided into thoracic cavity and abdominopelvic cavity by the diaphragm.
Thoracic Cavity (Ventral Cavity subdivision)
Thoracic cavity components:
Pleural cavities: right and left, containing the lungs; lined with pleura to reduce friction.
Mediastinum: central compartment between the pleural spaces; contains the heart, great vessels, thymus, trachea, esophagus, nerves, and lymph nodes.
Pericardial cavity: anterior compartment within the mediastinum; contains the heart.
Boundaries: thoracic boundaries formed by ribs, sternum, vertebrae, diaphragm, and associated muscles.
Abdominopelvic Cavity
Location: large cavity extending from the diaphragm to the pelvis; lined with a serous membrane.
Subdivisions:
Abdominal cavity: upper portion; from the inferior surface of the diaphragm to the superior bony pelvis.
Pelvic cavity: lower portion; within the pelvic bones, extending from the iliac crests to the pelvic floor.
Abdominal contents and retroperitoneal positioning:
Organs include liver, pancreas (part), stomach, spleen, gallbladder, small intestine, and most of the large intestine.
Some organs lie retroperitoneally along the posterior abdominal wall (e.g., kidneys, adrenal glands, part of pancreas).
Pelvic contents:
Bladder, distal ureters, reproductive organs, distal small bowel, rectum, sigmoid colon, vessels, lymph nodes, etc.
True vs False pelvis (pelvic regions):
True pelvis: area below the pelvic brim; contains bladder and reproductive organs.
False pelvis: area above the pelvic brim; contains parts of small intestine and colon.
Dividing lines in the pelvis:
An oblique plane from the sacral promontory to the superior surface of the pubic symphysis divides true and false pelvis.
Methodologies for Body Mapping
Purpose: identify specific areas and locate structures within the large abdominopelvic cavity.
Quadrant method:
Simple method for generalized location of symptoms or pain.
Two perpendicular lines intersect at the umbilicus (approximately at the level of the vertebral bodies L3-L4).
Four quadrants created: RUQ, LUQ, RLQ, LLQ.
Regional method:
Provides more precise descriptions of location for systems, pain, or pathology.
Regions formed by four planes: two vertical (right and left midclavicular) and two horizontal (subcostal and transtubercular).
Nine distinct regions created, smaller in area than the quadrant system.
Surface landmarks (easily palpable):
Sternal notch, xiphoid process, subcostal margin, iliac crest, symphysis pubis.
Exercise prompt (from slides): identify structures in each region and name one organ per region.
1) Right hypochondriac: e.g., liver, gallbladder.
2) Epigastric: e.g., stomach, part of pancreas.
3) Left hypochondriac: e.g., spleen.
4) Right lumbar: e.g., kidney (right), portions of colon.
5) Umbilical: e.g., small intestine.
6) Left lumbar: e.g., kidney (left), descending colon.
7) Right iliac (inguinal): e.g., appendix.
8) Hypogastric (pubic): e.g., bladder, reproductive organs.
9) Left iliac (inguinal): e.g., sigmoid colon.
Regional Anatomy and Key Organs (Nine-Region System)
Right hypochondriac region: liver and gallbladder commonly located here; portion of the right kidney may be nearby.
Epigastric region: stomach; portions of the pancreas; liver may extend into this region.
Left hypochondriac region: spleen; parts of stomach; tail of pancreas.
Right lumbar region: ascending colon; right kidney.
Umbilical region: parts of small intestine (jejunum/ileum); portions of transverse colon.
Left lumbar region: descending colon; left kidney.
Right iliac (inguinal) region: appendix commonly.
Hypogastric (pubic) region: bladder; reproductive organs (e.g., uterus in females).
Left iliac (inguinal) region: sigmoid colon; parts of ileum.
Practical Implications and Exam-Relevant Details
Orientation and imaging accuracy:
Correct orientation of the transducer marker and image display is critical to prevent misinterpretation.
Different scanning planes must be used to obtain complementary views for accurate 3D understanding.
Regional anatomy mapping supports clinical reasoning:
Quadrant and nine-region systems aid in localizing pain, symptoms, or injury.
Knowledge of surface landmarks improves the ability to locate underlying structures on imaging.
Common pitfalls:
Assuming planes align perfectly with anatomy; real anatomy is often oblique relative to standard planes.
Misinterpreting right/left due to patient positioning or observer perspective.
Ethical/practical considerations:
Adhere to standardized orientation to reduce diagnostic errors.
Ensure patient comfort and safety while positioning for imaging.
Formulas and notations used in the course:
Planes are orthogonal with a right-angle relationship: 90^{\circ} between sagittal, transverse, and coronal planes.
Quadrant division: two perpendicular lines intersecting at the umbilicus at around the level L3-L4 form RUQ, LUQ, RLQ, LLQ.
True vs False pelvis plane-based separation uses an oblique line from sacral promontory to the superior surface of the pubic symphysis.
References and Administrative Notes
Primary reference: Curry, R. A., & Prince, M. (2021). Sonography: Introduction to normal structure and function (5th ed.). Saunders.
Material is copyrighted by SAIT; use is governed by SAIT Fair Dealing Policy and related copyright notices.
Additional figures and diagrams referenced are for educational illustration and may be sourced from public domains or course materials.
Quick Glossary of Key Terms
Anatomical position: standard reference posture used to describe locations.
Planes: sagittal, midsagittal, parasagittal, transverse, coronal, oblique.
Acoustic window: transducer position/location from which the scan is obtained.
Quadrants: RUQ, LUQ, RLQ, LLQ.
Regions: nine-region abdominal division (right hypochondriac, epigastric, left hypochondriac, right lumbar, umbilical, left lumbar, right iliac, hypogastric, left iliac).
Cavities: dorsal (cranial, spinal) and ventral (thoracic, abdominopelvic).
Subdivisions of thorax: pleural cavities, mediastinum, pericardial cavity.
Subdivisions of abdomen/pelvis: abdominal cavity, pelvic cavity; true vs false pelvis.
Orientation markers: right/left refer to patient; head vs feet, anterior vs posterior, etc.