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Result : Searchterm 'Reflection' found in 1 term [] and 25 definitions [])
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ReflectionMRI Resource Directory: - UltraSound Physics -
 
Reflection of the sound beam occurs when it hits a boundary between materials having different acoustic impedance. The reflection (echo) is the portion of a sound that is returned from the boundary. The reflection time (the time taken for the wave to return to the probe) can be used to determine the depth of the object.
The reflection within the body produces the ultrasound image, but should be minimized at an ultrasound couplant to skin boundary where the couplant acts as an acoustic window through which the image is seen. The amount of sound waves, which are reflected back at the interface between two tissues is depend on the angle of incidence and the difference between the acoustic impedance values of the two tissues.
If the difference is great, a large part of the sound waves will be reflected back. If too much sound is reflected back and not enough waves are remaining to be able to penetrate the tissue, the imaging will be poor.
If the difference is small, a small amount will be reflected back. Enough sound signal remains to continue with ultrasound imaging.
If the ultrasound beam meets a rough surface or small object, the beam is scattered in all directions and only a small amount will be received by the probe.
See also False Distance Artifact, Target Strength, and Snells Law.
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 Further Reading:
  Basics:
Reflection and Refraction of Waves (Explanation by Huygens' Principle)Open this link in a new window
   by www.sciencejoywagon.com    
  News & More:
Ultrasound in diagnostic and therapyOpen this link in a new window
   by www.anst.uu.se    
US Resources  
Developers - Universities - Education pool - Preferential Sites - PACS - Artifacts
 
A-ModeInfoSheet: - Modes - Intro, Overview, Types of, etc.MRI Resource Directory: - Modes -
 
A-mode (Amplitude-mode) ultrasound is used to judge the depth of an organ, or otherwise assess an organ's dimensions. A-mode technology has been used in midline echoencephalography for rapid screening of intracranial mass lesions and ophthalmologic scanning. A-mode ultrasound imaging is now obsolete in medical imaging. The A-mode scan had also been used for early pregnancy assessment (detection of fetal heart beat), cephalometry and placental localization.
When the ultrasound beam encounters an anatomic boundary, the received sound impulse is processed to appear as a vertical reflection of a point. On the display, it looks like spikes of different heights (the amplitude). The intensity of the returning impulse determined the height of the vertical reflection and the time it took for the impulse to make the round trip would determine the space between verticals. The distance between these spikes can be measured accurately by dividing the speed of sound in tissue (1540 m/sec) by half the sound travel time.
To make an echoencephalography scan, the first A-mode scan is obtained from the right side of the head and the image captured on film. Then the probe is placed at the corresponding point on the left side. The second exposure is made on the same film with inverted spikes. The A-mode ultrasound could be used to identify structures normally located in the midline of the brain such as the third ventricle and falx cerebri. The midline structures would be aligned in normal patients but show displacement in patients with mass lesion such as a subdural, epidural, or intracranial hemorrhage.
See also Ultrasound Biomicroscopy, A-scan, B-mode and the Infosheet about ultrasound modes.
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    ••    There is 1 news about 'A-Mode'.
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 Further Reading:
  Basics:
A-Mode EchoencephalographyOpen this link in a new window
   by www.obgyn.net    
A-Mode Area RatioOpen this link in a new window
   by www.wildultrasound.com    
  News & More:
Module 1: Basic A-scan Biometry Section 1: Basic ConceptsOpen this link in a new window
   by www.eyetec.net    
Searchterm 'Reflection' was also found in the following service of US-TIP.com:  
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Acoustic MismatchInfoSheet: - Artifacts - Intro, Artifacts, ReductionMRI Resource Directory: - Artifacts -
 
Acoustic mismatch arise at the boundary between two different media where reflection and refraction occurs.
See also Snells Law.
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 Further Reading:
  Basics:
The influence of acoustic impedance mismatch on post-stenotic pulsed-Doppler ultrasound measurements in a coronary artery model.Open this link in a new window
1996   by www.ncbi.nlm.nih.gov    
US Resources  
Education - Portals - Contrast Agents - Portable UltraSound - Veterinary UltraSound - General
 
Acoustic WindowMRI Resource Directory: - UltraSound Physics -
 
The acoustic window or field is the area defined by the pathway of the ultrasound beam between the transducer and the acoustic reflector. The sound reflection to skin boundary should be minimized with an ultrasound gel where this gel acts as an acoustic window through which the image is seen.
Acoustic window refers also to the optimal placing of the transducers so that the areas of interest are clearly imaged.
See also Transforaminal Window, Transcranial Window, Transorbital Window and Transtemporal Window.
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 Further Reading:
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Ultrasound renal anatomyOpen this link in a new window
   by rad.usuhs.mil    
Searchterm 'Reflection' was also found in the following service of US-TIP.com:  
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ArtifactInfoSheet: - Artifacts - Intro, Artifacts, ReductionMRI Resource Directory: - Artifacts -
 
An image artifact is any image attribute, which is not present in the original imaged object. An image artifact is sometime the result of an improper operation of the imager, and in other times a consequence of natural processes or properties of the human body.
Artifacts in diagnostic ultrasound are a reflection or an echo, which appears on the display and represents the real anatomical structure not correctly. An artifact can be a false, multiple or misleading information introduced by the imaging system or by interaction of ultrasound with the adjacent tissue.

Artifacts in ultrasound can be classified as to their source like e.g.:
point physiologic (motion, different sound velocities, acoustical impedances of tissue);
point hardware (dimension of the ultrasound beam and the transducer array);
point imaging technique (B-mode, spectral Doppler, color Doppler, 3D ultrasound).
Image artifacts can occur in each medical ultrasound. Then an interpretation of the image is complicated and can eliminate the structural information of objects looking for.
See also Ultrasound Imaging Procedures.
Radiology-tip.comImage Quality
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Radiology-tip.comArtifact
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 Further Reading:
  Basics:
Types of ultrasound artifacts?Open this link in a new window
   by www.frca.co.uk    
  News & More:
Ultrasonographic fata morganaOpen this link in a new window
2003   by ndt.oxfordjournals.org    
US Resources  
Calculation - Breast - Pelvic - Probes Transducers - Fetal - UltraSound Reimbursement
 
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