Search our site 
 
Advanced Search
 
Home | Exam dates | Contact us | About us | Testimonials |
 
 

map
You are in Home >> Resources >> Physics and equipment >> Ultrasound


Present Ultrasound Techniques and Application Tips

Created: 13/7/2004
 

- Realtime 2D B-mode (brightness) utrasound
- M-mode (motion) ultrasound
- Doppler and colour Duplex ultrasound
- What defines good colour/CPD?
- What defines a good Doppler display?
- Clinical challenges with Doppler
- Key Doppler clinical applications
- Advances in imaging
- Ultrasound vs other imaging technologies


Realtime 2D B-mode (brightness) ultrasound

  • Two dimensional grey-scale display of anatomy (solid areas in "white" and fluid areas in "black")
  • Currently the most common form of imaging
  • Allows the physician to assess both motion and anatomy, including the motion of heart valves, the movement of intestines and lungs and also to guide needle biopsies in various organs
  • To produce a visual of motion, the ultrasound beam is swept repeatedly over the area being examined (this generates a rapid series of individual 2-D images which show motion)

Image Character


M-mode (motion) ultrasound

  • One-dimensional with very high sample rate (1000/s)

  • Display changes in the position of sound-reflecting structures over time

  • Can produce a picture in which movement of a structure (such as a heart valve) can be depicted in a wave-like manner

  • Useful in assessing rates and motion of these structures, particularly in cardiac structures such as the various valves and the chamber walls

 

M LineFetal M Mode


Doppler and colour duplex ultrasound

  • One-dimensional (spectral) or two-dimensional (colour)
  • Colour shades represent variations in blood flow
  • Power-mode Doppler estimates the power of the Doppler signal
  • Directional colour power Doppler (DCPD) incorporates velocity information to encode direction and variations in blood flow
  • Displays information that is not readily visualised with other techniques
  • Used most widely in analysis of blood flow to assess blood vessel or vascular function
  • Power-mode Doppler is more sensitive to low blood flow and allows more complete visualisation of detailed vascular (blood) structure.


What defines good colour/CPD?

Colour fills the entire vessel or chamber to the wall
Colour does not overwrite the wall
Good spatial resolution/colour dot size
Frame rates adequate to accurately display flow
Good colour flash suppression
Ability to display very slow flow states (colour sensitivity)
Easy to use!
 
 
Lymph Node Power


What defines a good Doppler display?

  • No background noise
  • Clean window/envelope in normal flow states
  • Clear audible signal
  • Accurate display of velocities

 


Clinical challenges with Doppler

  • Obtaining the appropriate Doppler angle
  • Doppler in deep vessels/large patients
  • Displaying high pulse repetition frequencies without aliasing, found in abnormal flow states (PW Doppler)
  • Exact site for sampling
Key Doppler clinical applications

Abdominal
  • Renal, celiac, mesenteric artery stenoses
  • Portal vein flow
  • Aorta
OB/Gyn
  • Ovarian cancer screening
  • Placental, circle of Willis, umbilical cord for fetal growth disorders
  • Fetal heart abnormalities
Vascular
  • Carotid artery stenosis
  • Peripheral artery and vein disease (legs & arms)
  • Transcranial Doppler
Cardiology
  • Valve disease, stenosis, regurgitation
  • Congenital heart diseas

Additional colour/power clinical applications

General

  • Qualitative flow assessment and localisation for spectral Doppler sample placement
  • Vessel/non-vessel or arterial/venous differentiation

Abdominal

  • Organ flow
    • liver, pancreas, spleen, kidneys
  • Aorta
  • Flow to tumours

Small parts

  • Thyroid, testicle, breast, prostate
  • Flow to tumours
  • Assess functionality

OB/Gyn

  • Ovarian flow
  • Placental flow
  • Fetal circulation
      • Circle of Willis
      • Kidneys
      • Umbilical cord
      • Heart

Advances in imaging

Scientists are continuing to research ways to improve ultrasound imaging and utility, to enable physicians to better read and understand ultrasound information/images. Specifically, researchers are examining how to better characterise tissue and differentiate between tissues through use of contrast agents, speckle-reduction techniques and improvements in colour flow imaging.

A very good example of such an advance is EXTENDED RESOLUTION HARMONICS. This is a technology which enables a dramatic reduction in image artifacts, reduces haze and clutter and significantly increases contrast resolution.

With EXTENDED RESOLUTION HARMONICS, the fundamental ultrasound signal is transmitted at a broad band of low frequencies. The signal resonates off tissue in the body at twice the transmitted frequency. Because higher-frequency signals travel one way from the tissue to the transducer, they are not attenuated by round-trip travel through tissue. Moreover, since the signals do not include fundamental frequencies, they are virtually free of artifacts.

EXTENDED RESOLUTION HARMONICS demonstrates significant improvements in greyscale imaging, especially in patients considered to be technically difficult, and provides a new level of patient-independent performance that can salvage examinations initially deemed undiagnostic.


LV no ERH

LV with ERH

Clinical benefits

  • Provides better visualisation of tissue interfaces
  • Dramatically reduces haze, clutter and image artifacts
  • Provides incremental improvements in diagnostic confidence and patient throughput

Ultrasound vs other imaging technologies

Medical imaging has been an important part of medical diagnostics since the discovery of the X-ray in 1895. As imaging technology has advanced in recent decades, applications of medical imaging have expanded to address increasingly complex disease states and conditions involving soft tissues and internal body organs.

Two-dimensional X-ray is the most widely used medical imaging technology; however, the patient is exposed to harmful radiation, and improved technologies are now available that can provide more information. Examples of these newer technologies include ultrasound, computer assisted tomography (CAT) scans, magnetic resonance imaging (MRI) and nuclear medicine. Each imaging method requires different, specialised equipment and has certain benefits in assessing different body functions and organs.

Ultrasound has become the most accepted means of conducting fetal assessment, in part because it does not expose the patient (or fetus) to any radiation and also because it is relatively painless and less expensive than other tests. Ultra-portable ultrasound is pioneering the use of ultrasound in gynaecology to augment every pelvic examination, and in cardiology to provide a qualitative 2-D assessment of the heart.

CAT scans are the preferred method for detecting tumours, cysts and abscesses because they can be highly sensitive and specific. For example, they can sometimes distinguish between benign and malignant tumours. CAT scans are not recommended for pregnant women due to the risk of radiation exposure to the fetus.

MRI scans are the best method for examining the brain because they show the brain's white and gray matter in greater detail; however, they are not as good for visualising motion. Again, MRIs are not recommended for pregnant women due to exposure to strong magnetic fields.

Nuclear medicine can show the size, shape, position and some functions of an organ; however, due to the exposure to radioactivity, this procedure is not recommended for pregnant women.


ArticleDate:20040713
SiteSection: Article
 
   
    
                                            
  Posting rules

     To view or add comments you must be a registered user and login  




Login Status  

You are not currently logged in.
UK/Ireland Registration
Overseas Registration

  Forgot your password?








 
All rights reserved © 2020. Designed by AnaesthesiaUK.

{Site map} {Site disclaimer} {Privacy Policy} {Terms and conditions}

 Like us on Facebook 

vp