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 'Center Frequency' 
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General - Kidney - Gynecology - Ultrasound Gel - Rental - Obstetric
 
Center FrequencyMRI Resource Directory:<br> - UltraSound Physics -
 
The center frequency is the median frequency of the transmitted pulse. This pulse contains a range of frequencies in pulsed ultrasound systems.
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US Resources  
Fetal - Equipment and Parts - PACS - UltraSound Reimbursement - Heart - Journals
 
Harmonic ImagingInfoSheet: - Modes - 
Intro, 
Overview, 
Types of, 
etc.MRI Resource Directory:<br> - Modes -
 
Harmonic imaging relies on detection of harmonics of the transmitted frequency produced by bubble oscillation. This method is widely available on ultrasound scanners and uses the same array transducers as conventional imaging. A major limitation of the use of ultrasound contrast agents is the problem that signals from the microbubbles are mixed with those from tissue. Echoes from solid tissue and red blood cells are suppressed by harmonic imaging.
In harmonic mode, the system transmits at one frequency, but is tuned to receive echoes preferentially at double that frequency, and the second harmonic echoes from the place of the bubble. Typically, the transmit frequency lies between 1.5 and 3 MHz and the receive frequency is selected by means of a bandpass filter whose center frequency lies between 3 and 6 MHz.
Color Doppler and real-time harmonic spectral Doppler modes have also been implemented and show a level of tissue motion suppression not available in conventional modes.
See also Harmonic B-Mode Imaging, and Harmonic Power Doppler.
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• View the news results for 'Harmonic Imaging' (2).



 Further Reading:
  Basics:
Harmonic ImagingOpen this link in a new window
   by www.imasonic.com    
  News & More:
Combination of contrast with stress echocardiography: A practical guide to methods and interpretationOpen this link in a new window
2004   by www.cardiovascularultrasound.com    
US Resources  
Doppler UltraSound - Used and Refurbished UltraSound Equipment - Thyroid - Abdominal - Preferential Sites - Gall Bladder
 
Liver SonographyMRI Resource Directory:<br> - Liver -
 
A liver sonography is a diagnostic tool to image the liver and adjoining upper abdominal organs such as the gallbladder, spleen, and pancreas. Deeper structures such as liver and pancreas are imaged at a lower frequency 1-6 MHz with lower axial and lateral resolution but greater penetration. The diagnostic capabilities in this area can be limited by gas in the bowel scattering the sound waves.
The application of microbubbles may be useful for detection of liver lesions and for lesion characterization. Some microbubbles have a liver-specific post vascular phase where they appear to be taken up by the reticuloendothelial system (RES). Dynamic contrast enhanced scans in a similar way as with CT or MRI can be used to studying the arterial, venous and tissue phase.
After a bolus injection, early vascular enhancement is seen at around 30sec in arterialized lesions (e.g., hepatocellular carcinomas (HCC), focal nodular hyperplasia (FNH)). Later enhancement is typical of hemangiomas with gradually filling towards the center. In the late phase at around 90sec, HCCs appear as defects against the liver background. Most metastases are relatively hypovascular and so do not show much enhancement and are seen as signal voids in the different phases.
Either with an intermittent imaging technique or by continuous scanning in a nondestructive, low power mode, characteristic time patterns can be used to differentiate lesions.
See also Medical Imaging, B-Mode, High Intensity Focused Ultrasound, Ultrasound Safety and Contrast Medium.
Radiology-tip.comAbdomen CT
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Radiology-tip.comLiver Imaging
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 Further Reading:
  Basics:
Optimizing Doppler and Color Flow US: Application to Hepatic Sonography(.pdf)Open this link in a new window
   by radiographics.rsna.org    
Cirrhosis, Ultrasound findingsOpen this link in a new window
   by rad.usuhs.mil    
  News & More:
Continuous Infusion Versus Bolus Injection Of Ultrasound Contrast Agents in Vascular Doppler Flow Imaging Response(.pdf)Open this link in a new window
Friday, 1 September 2000   by stroke.ahajournals.org    
Noninvasive ways to assess liver diseaseOpen this link in a new window
Friday, 1 February 2008   by www.eurekalert.org    
High-energy Ultrasound Sharpens View Of Liver TumorsOpen this link in a new window
Friday, 11 January 2008   by www.sciencedaily.com    
US Resources  
Developers - Kidney - Manufacturers - Hospitals - Pregnancy - Vascular
 
Artemis 2InfoSheet: - Devices -
Intro, 
TypesMRI Resource Directory:<br> - Devices Machines Scanners Systems -
 
www.arcscan.com/products.html

From Ultralink LLC;
'Artemis is a very high frequency (VHF) ultrasound eye scanner. In use, the patient leans forward placing their head onto an adjustable headrest. The headrest's unique design permits the patient to pull away quickly from the scanner if desired. An eyecup filled with a saline-based interface fluid couples the ultrasound signal to the eye, while a precision mechanism moves the transducer past the front of the eye. During the accurately controlled arc motion of the transducer, which lasts less than one second, many thousands of ultrasound samples are digitized. Following a scan, signal analysis is performed on a PC-compatible microcomputer, and the data are available for immediate viewing on an LCD monitor or disk storage. Artemis is very flexible; many adjustments to the scanning parameters are possible to customize the scan to your clinical needs. Functions are provided for centering the scan about the optical axis of the eye. The starting location of the scans as well as the extent can be varied as desired, to view image planes through the eye at different angles.'

Specifications for this system will be available soon.

See also Ultrasound Biomicroscopy, A-Mode and A-Scan.

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 Further Reading:
  News & More:
Module 1: Basic A-scan Biometry Section 1: Basic ConceptsOpen this link in a new window
   by www.eyetec.net    
ULTRASOUND MEASUREMENT OF THE EFFECT OF TEMPERATURE ON MICROPERFUSION IN THE EYEOpen this link in a new window
Thursday, 25 April 2002   by www.ncbi.nlm.nih.gov    
US Resources  
Service and Repair - Renal - Calculation - - Obstetric - 4d UltraSound
 
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