UltraSound - Technology Information PortalTuesday, 21 February 2017
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FahrenheitMRI Resource Directory:
 - UltraSound Physics -
 
This unit of temperature is still used customarily in the United States.
Definition: 0° is the coldest temperature achieved by using an ice and salt mixture, and 100° is set at the temperature of the human body. On this scale, the freezing point of water turned out to be about 32 °F and the boiling point about 212 °F.
1°F equals 5/9 °C. To convert a temperature in °F to the Celsius scale, first subtract 32° and then multiply by 5/9. In the other direction, to convert a temperature in °C to the Fahrenheit scale, multiply by 9/5 and then add 32°. The unit was defined by the German physicist Fahrenheit.
See also Thermal Units Per Hour.
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Welcome to NODC Unit Conversion GuideOpen this link in a new window
Monday, 4 August 2003   by www.nodc.noaa.gov    
False Distance ArtifactInfoSheet: - Artifacts -
Intro, 
Artifacts, 
ReductionMRI Resource Directory:
 - Artifacts -
 
Different sound velocities in tissues are causing false distance artifacts. Ultrasound beams can suffer multiple reflections or specular reflections away from the sensor, giving false distance readings.
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• View the DATABASE results for 'False Distance Artifact' (3).Open this link in a new window.

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Safety - Calculation - Artifacts - UltraSound Reimbursement - Carotid - Quality Advice
 
Far FieldMRI Resource Directory:
 - UltraSound Physics -
 
The far field (also called Fraunhofer zone) is the distal part of an ultrasound beam characterized by a diverging shape and continuous loss of ultrasound intensity with distance from the transducer. The angle of divergence increases with lower transducer frequency and with smaller transducer diameter.
See also Sonographic Features.
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• View the DATABASE results for 'Far Field' (8).Open this link in a new window.

 Further Reading:
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Physics, instrumentation and basic technique.Open this link in a new window
   by dynamicultrasound.org    
Fast Fourier TransformationMRI Resource Directory:
 - UltraSound Physics -
 
(FFT) The fast Fourier transformation is a particularly fast and efficient computational method of performing a Fourier transformation, which is the mathematical process by which raw data is processed into a usable image.
The fast Fourier transform analyzer is a common device that performs spectral analysis in ultrasound instruments. In this case, it displays different quadrature Doppler frequencies or reflector velocities when a sample volume cursor is used along time. The Doppler frequency is proportional to the spectral reflector velocity.
See also Proportionality Constant, and Sampling Rate.
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• View the DATABASE results for 'Fast Fourier Transformation' (5).Open this link in a new window.

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Ultrasound and k-space K-space transforms of elementary geometriesOpen this link in a new window
   by dukemil.egr.duke.edu    
Fetal UltrasoundMRI Resource Directory:
 - Fetal -
 
The FDA ultrasound regulations allow an eight-fold increase in ultrasound intensity to be used in fetal ultrasound examinations. They place considerably responsibility on the user to understand the output measurements, the mechanical index (MI), the thermal index (TI) and to use them in their scanning. The primary safety concern in prenatal diagnostic imaging is temperature rise. It is known that hyperthermia is teratogenic. The efforts of investigators have concentrated on defining the temperature increases and exposure times which may give rise to biological effects and on determining the ultrasound levels which might, in turn, lead to those temperature rises.
In fetal ultrasound, the highest temperature increase would be expected to occur at bone and the thermal index with bone at/near the focus (TIB) would give the ‘worst case’ conditions. The mechanical index and thermal index must be displayed if the ultrasound system is capable of exceeding an index of 1. The displayed indices are based on the manufacturer’s experimental and modeled data. However, an independent study has demonstrated significant discrepancies over declared spatial peak time averaged intensity (I-SPTA) output of up to 400%.
See also ALARA Principle, Pregnancy Ultrasound and Doppler Fluximetry in Pregnancy.
Radiology-tip.comRadiation Safety
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Radiology-tip.comFetal MRI
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• View the NEWS results for 'Fetal Ultrasound' (3).Open this link in a new window.

• View the DATABASE results for 'Fetal Ultrasound' (7).Open this link in a new window.

 Further Reading:
  Basics:
Pelvic ultrasoundOpen this link in a new window
   by www.surgeryencyclopedia.com    
Guidelines for the Safe Use of Diagnostic Ultrasound(.pdf)Open this link in a new window
   by folk.ntnu.no    
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UltraSound Reimbursement - UltraSound Technician and Technologist Career - Preferential Sites - Image Quality - Image Libraries - Examinations
 
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