chapter 2

Key Words in Sonography

  • Angle of Incidence: The angle at which the sound beam strikes a surface. A 90-degree angle is optimal to capture all echoes and determine true amplitude. Incorrect angles can cause reflection issues, leading to missed structures or grayscale inaccuracies.

  • Axial Views: Images showing width and depth; often referred to as transverse views. Obtained by turning the transducer 90 degrees from the sagittal plane.

  • Coronal Planes: Divides the body into anterior and posterior sections. Achieved by scanning along the side of the patient or with specialized imaging techniques like transvaginal and 3D imaging.

    • scanning along the side of the patient, with the transducer pointing to the opposite side of the body when scanning abdominally.

  • Focal Zone: The area where the sound beam is narrow, improving resolution (in older transducers). Newer transducers use different technologies that do not rely on focal zones.

  • Long Axis: The maximum length of a structure, important for accurate measurements. Organs often lie in oblique planes, requiring careful transducer manipulation to align with the structure's orientation.

  • Longitudinal Views: Images showing a structure’s length and depth. Obtained when the ultrasound beam enters the body from an anterior or posterior approach, typically perpendicular to the floor.

  • Measurement: Accurate and reproducible measurements are critical for good patient care; needs to be correctly measured. Measurements are affected by the transducer's angle relative to the organ.

  • scanning planes are used to establish the direction from which the ultrasound beam enters the body and the anatomic portion of anatomy being visualized from that direction.

    • Oblique Orientation: Slanted or angled scanning planes, achieved by twisting/rotating the transducer. Useful for visualizing the longest length of a structure.

    • Orientation: The position of an organ in the body. Requires understanding anatomical relationships and variations.

    • Positional Orientation: Ensuring the transducer is correctly aligned with the image on the screen. Manufacturers provide marks on the transducer to ensure correct orientation.

  • Pressure: Applying the correct amount of pressure can help improve image quality. Communicate with the patient when and why pressure adjustments are needed.

  • Sagittal Planes: Divides the body into right and left sections. Can be mid-sagittal (dividing the body equally) or para-sagittal (parallel to the midline).

    • planes would be obtained by moving the transducer to the right or left side of patient’s body

  • Short Axis: The width of a structure, measured at its widest margins. Obtained by rotating 90 degrees from the long axis.

  • Transverse Planes: Divides the body into superior and inferior sections. Perpendicular to the sagittal plane, achieved by turning the transducer 90 degrees.

    • the transducer is turned 90 degress and is moved up toward the head or down toward the feet on the patient’s body.

Evaluating Sonographic Images

  • Plane Identification: Determine the plane used to obtain the image (e.g., supine, coronal). Crucial for proper interpretation and correlation with anatomical landmarks.

  • Scanning Plane Identification: Know the scanning plane (longitudinal, transverse). Impacts the visualized anatomical relationships and measurements.

  • Transducer as Flashlight: The transducer only visualizes what's in the sound beam's path. Understand the limitations of the technology; structures outside the beam's path will not be visible.

  • Normal Appearance: Understanding normal sonographic appearance is crucial for identifying pathology. Requires extensive knowledge of anatomy and variations.

Objectives of Scanning Planes and Methods

  • Define key words.

  • Explain how ultrasound uses body and scanning planes to image the body.

  • Differentiate between scanning planes and views.

  • Interpret scanning planes.

  • Apply scanning methods and manipulate the transducers.

  • Produce accurate measurements.

  • Identify surface landmarks.

Anatomic Planes in Sonography

  • Scanning planes in sonography align with anatomic body planes.

  • Image plane depends on transducer location and sound beam orientation.

Sagittal Planes

  • Mid-Sagittal Plane: Divides the body into equal right and left sections.

    • Often labeled as midline (ML) on images.

  • Para-Sagittal Planes: Parallel to midline, to the right or left.

    • Achieved by moving the transducer to either side of the body.

    • Unless noted, sagittal refers to parasagittal.

Transverse Planes

  • Divides the body into superior and inferior sections.

  • Perpendicular to the sagittal plane.

  • Transducer turned 90 degrees and moved up/down the body.

Coronal Planes

  • Divides the body into anterior and posterior sections.

  • Obtained by scanning along the side of the patient, transducer pointing to the opposite side during abdominal scans.

  • Also obtained with transvaginal and 3D imaging.

Scanning Planes Overview

  • Scanning planes determine the direction of the ultrasound beam entering the body.

  • They indicate the anatomic portion being visualized from that direction.

  • Often from an oblique orientation (slanted/angled).

  • Degree of obliquity depends on the structure’s orientation in the body.

  • Oblique scanning often visualizes the longest length of a structure.

  • Body structures viewed in longitudinal and axial planes.

  • Longitudinal views show length and depth.

  • Axial views show width and depth (often termed transverse).

  • Sagittal and longitudinal terms used interchangeably (e.g., Long Aorta).

Ultrasound Scanning Planes

Sagittal Scanning

  • Ultrasound beam enters the body from anterior (supine) or posterior (prone) approach.

  • Transducer usually perpendicular to the floor.

  • Evaluates structures in:

    • Anterior direction.

    • Posterior direction.

    • Superior direction.

    • Inferior direction.

    • NOTE: Medial and lateral aspects not seen on sagittal scans. Move transducer to parasagittal planes to visualize adjacent anatomy.

Transverse Scanning

  • 90 degrees to the sagittal plane.

  • Beam enters from anterior or posterior direction.

  • Sound beam perpendicular to the floor or slightly angled.

  • Evaluates structures in:

    • Anterior direction.

    • Posterior direction.

    • Medial direction.

    • Lateral direction.

    • NOTE: Superior and inferior aspects are not seen on a transverse scan. Move the transducer superiorly or inferiorly to visualize adjacent anatomy.

Coronal Scanning Plane

  • Ultrasound beam enters from right or left lateral direction.

  • Transducer placed along the side of the patient’s body.

  • Both longitudinal and transverse images can be obtained in this plane.

  • Used to scan under bowel or between ribs.

  • Most liver images are variations of a coronal plane to see more liver parenchyma.

Scanning Planes and Anatomy Visualization

  • Longitudinal/Long Axis Approach:

    • Anterior aspect.

    • Posterior aspect.

    • Superior aspect.

    • Inferior aspect.

  • Transverse Approach:

    • Medial aspect.

    • Lateral aspect.

    • Superior aspect.

    • Inferior aspect.

Scanning Skills and Techniques

  • Primary Role: Provide interpretable images for diagnosis.

  • Requires practice, good scanning methods, image optimization, critical thinking, and anatomical/pathological knowledge.

Transducers

  • Advances in transducer design offer better penetration, resolution, and Doppler sensitivity.

  • Ergonomic designs protect sonographer’s joints.

  • Shapes determine the field of view.

  • Frequency (MHz) determines penetration depth and resolution.

  • Low-frequency transducers:

    • Most penetration.

    • Less resolution.

  • High-frequency transducers:

    • Less penetration.

    • Better resolution, used for superficial structures.

  • Transducer types and frequencies:

    • Curved linear array:

    • Abdominal, obstetric, gynecologic imaging.

    • Frequencies: 2-10 MHz.

    • Example: C5-2 (curved, 2-5 MHz range).

    • Vector/sector array:

    • Low frequency for scanning between ribs, pediatrics.

    • Examples: V4-1 (low frequency), S12-4 (newborn/infant).

    • Linear array:

    • Largest tissue amount displayed.

    • Superficial structures: thyroid, breast, scrotum.

    • Doppler exams: carotid, lower extremity vessels.

    • Examples: L12-5 (carotid), L18-5 (thyroid).

    • Transvaginal/Transrectal:

    • Small scanning head on a long shaft.

    • Better resolution of pelvic organs or prostate.

    • Examples: C9-3 (endovaginal), C12-5 (prostate), EV9-3 (endovaginal).

    • Hockey stick:

    • Small size for intraoperative imaging and musculoskeletal studies.

    • Example: L12-5 (carotid endarterectomy).

    • Three-dimensional imaging (3D):

    • Obstetrics, gynecology, liver masses, thyroid, arterial disease.

    • Designated as 3D transducer (e.g., 3D9-3).

    • Newer models are all electronic with no moving parts.

  • Focal Zone (older transducers):

    • Sound beam is narrow to improve resolution.

    • Indicated by a mark on the image; area of interest should be positioned in this zone.

    • Newer transducer technologies don’t use focal zones.

Scanning Techniques

  • Transducer held in various ways (e.g., like a pencil).

  • Fluid motions combining angling, rotating, and moving the transducer.

  • Angle of incidence: Angle at which the sound beam strikes the structure’s surface.

    • 90-degree angle ensures all echoes are received, and true amplitude is determined.

    • Incorrect angles cause some echoes to reflect away, resulting in missing structures or incorrect grayscale.

  • Applying correct pressure improves images; tell the patient when and why you need to apply pressure.

  • Positional orientation needed to align the transducer with the image on the screen.

    • Manufacturers provide marks on the transducer to ensure correct orientation.

    • If the image appears reversed, rotate the transducer 180 degrees.

Accurate Measurements

  • Critical for good patient care, especially in follow-up exams.

  • Organs often lie in an oblique plane; scan according to the structure’s orientation.

  • Long axis: Maximum length of a structure.

    • Pancreas: Lies obliquely, long axis seen in a transverse oblique plane. Rotate the transducer counterclockwise to visualize the entire length.

    • Kidney: Lies obliquely; sagittal plane must be oblique to match the kidney’s angle. Rotate the transducer clockwise to see the entire length.

    • Gallbladder: Long axis is variable, seen in any plane. Rotate transducer to view the long axis.

  • Short axis: Rotate 90 degrees from the long axis for width measurements at the widest margins.

  • Tilt the transducer to be perpendicular to the organ; otherwise, measurements will be inaccurate.

  • Accurate measurements affect patient care and skills as a sonographer.

Transducer Positions and Motions

  • Perpendicular: Transducer straight up and down.

  • Sliding: Fluid motion, slowly slide the transducer along