Ultrasonography handling and interpreta...

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Information about Ultrasonography handling and interpreta...

Published on February 11, 2009

Author: azamahk2000

Source: authorstream.com

:  Dr.Abdelazim Hussein Khalafalla Ribat universty hospital Khartoum - Sudan Feb 2007 Ultrasonography Handling and interpretation Handling : Operation panel Handling Menu key : This key is used together with Control knob Set key Next key For setting of built-in functions. contrast FRM-CO (frame correlations) PUNC- (Puncture guide line display) Sweep DISP (automatic display off/on) Menu key Menu key : Setup IP set (change of IP registration data) CHAR (character of size in comment) Date (seting of date and time) Menu key Measurement ,Next ,Set and Print key : Measurement key DIST to measure the distance MEASURE to measure dimension Next key to select menu page, or caliper mark Set key to set menu items, or to position the caliper mark when making measurement Print key for printing Measurement ,Next ,Set and Print key Frequency keys : Frequency - the number of cycles per unit of time. Frequency and wavelength are inversely related. The higher the frequency the smaller the wavelength. Frequency selection: change US frequency High freq. (backspace) Low freq. Three different transmission frequency available for the probe ,and any one frequency can be selected Frequency keys BS Frequency : Frequency & Depth of Penetration Higher frequencies are attenuated by tissue more than lower frequencies. This means that the higher the frequency the greater the resolution but the lower the depth of penetration. User lower frequencies for adults and higher frequencies for children. The advent of harmonic imaging allows the use of a lower frequency pulse to be picked up and sampled at a higher frequency (the second harmonic) where the low frequency allows greater penetration and high frequency provides better resolution. Frequency Frequency : Frequencies for adult imaging - 2.0mHz to 3.0mHz. Frequencies for pediatric imaging - 5.0mHz to 7.5mHz to 12mHz.Effect of higher frequencies on penetration - the higher the frequency the less penetration, the lower the frequency the greater the penetration. Frequency Control knob : Change in display magnification by control tab clockwise (magnification) anticlockwise (minimize) Control knob Control knob : Select menu items Rotate the probe mark Control knob Gain knob : Gain knob to adjust the echo intensity (image brightness) clockwise enhance brightness anticlockwise reduce brightness Near gain knob adjust the intensity of US echo in shallow area Far gain knob adjust the intensity of US echo in deep area Both knobs when turn it clockwise image become brighter Gain knob Image direction keys : the display of the image is inverted in left/right direction the display of the image is inverted in up/down direction Image direction keys 5 6 Trackball : Used to move: M-cursor is displayed Caliper mark Probe mark (it displayed in body mark) Trackball Transducer Selection : The upper abdomen is scanned with the highest-resolution transducer possible for the size of the patient. The transducer may be a sector or curved linear array, or in many cases, a combination of the two. The transducer frequency depends on: the size muscle fat composition of the patient. Generally a 3-MHz transducer is used on most normal sized adult patients, with variations of 2.25 to 7.5 MHz, depending on image resolution and beam penetration through the deeper structures in the liver. Transducer Selection Transducer Selection : Most transducers today actually are multi-focal with multiple frequencies available in one transducer; therefore, the liver may be scanned with the lower frequency, the pancreas and gallbladder may be scanned with the higher frequency transducer. The lower-frequency transducers are often necessary in patients with fatty infiltration or cirrhosis of the liver. Transducer Selection Space key : Space key: used to change the display angle of visibility. For 40% or 60% (not for linear probe) *track ball can move the scan area. Space key Slide 17: Interpretation General Scanning Guidelines : The baseline upper abdominal ultrasound examination includes a survey of the liver and porta hepatis, vascular structures, biliary system, pancreas, kidneys, spleen, and paraaortic area. If variations in anatomy or pathology are seen, multiple views are obtained over the area of interest. General Scanning Guidelines image planes : Ultrasound of the abdomen is generally performed in at least two image planes, transverse longitudinal. It is not unusual for the sonographer to alter these imaging planes or change the patient position if adequate visualization is not obtained. image planes Reflection and Propagation: : Effect of propagation through gaseous zones - poor propagation, inadequate imaging. Effect of propagation through dense zones - nearly all of the US is reflected. Structures below dense zones are poorly imaged.Examples of dense materials - bone, calcium, metal Reflection and Propagation: Reflection and Propagation: : Material Speed of Propagation bone 4080 m/s blood 1570 m/s tissue 1540 m/s fat 1450 m/s air 330 m/s Attenuation - the decrease in amplitude and intensity as a sound wave travels through a medium. Reflection and Propagation: Transverse Plane : The transverse sectional images are presented in descending order from the dome of the diaphragm to the umbilicus. The sonographer should review the relationship of each organ to it's neighboring structures as one proceeds in a caudal direction towards the umbilicus: Transverse Plane Longitudinal Plane : The longitudinal sectional images are presented from the midline of the abdomen to the right abdominal border. Images of the spleen and left kidney are made with the patient in a left lateral decubitus position. Longitudinal Plane Scanning Techniques : Ultrasound can distinguish interfaces among soft tissue structures of different acoustic densities. The strength of the echoes reflected depends on the acoustic interface and the angle at which the sound beam strikes the interface. The sonographer must determine which "window" on the patient is the best to record optimal ultrasound images and which transducer will best fit into that window. The curved array transducer provides a large field of view, but may be difficult to scan between intercostal patient ribs in some examinations. The small-diameter sector transducer allows the sonographer to go in between intercostal spaces from a supine, coronal, decubitus, or upright position. Scanning Techniques Basic abdominal US protocol : The transducer should be angled from the diaphragm to the inferior border of the right lobe of the liver. The diaphragm should be well defined as a linear bright line superior to the dome of the liver. The liver parenchyma should be homogeneous and uniform throughout. If the overall gain is at the maximum limit without good uniform penetration, a lower-frequency transducer should be used to provide increased sensitivity. Vascular structures should be outlined with the patient in deep inspiration. This allows the inferior vena cava to dilate slightly and thus become easier to image. Basic abdominal US protocol Criteria for an Adequate Scan : With the use of real time ultrasound, it is sometimes difficult to become oriented to all of the anatomic structures on a single frozen image; therefore it is critical to obtain as many anatomical landmarks as possible. With careful scanning technique and experience, the sonographer will be able to determine the appropriate transducer and instrumentation settings necessary to perform a high-quality ultrasound examination Criteria for an Adequate Scan Criteria for an Adequate Scan : Avoiding rib interference is important to eliminate artifact "ring-down" reverberation that may destroy information. The small-diameter real time transducers allow the sonographer to scan in between the ribs but limit the near field visualization. Variations in the patient's respiration may also help eliminate rib interference and improve image quality. Criteria for an Adequate Scan Conclusion : Correlation of ultrasound images with sectional anatomy is a critical talent that must be mastered by every sonographer in order to produce consistent, quality images. The abdominal protocol presented is a generic one that may be adapted to your particular lab situation. Careful manipulation of the instrumentation and recognition of adequate scanning windows will allow the sonographer to obtain quality images for interpretation Conclusion

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