practical us
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Basic physics of USSound is a mechanical wave,it is a series of pressure waves propagating through a medium.
Audible range of sound frequency for humans is 20 Hzto 20 kHz , so ultrasound By Definition is greater than20 kHzMedical ultrasound is performed in the range of 2 20
MHz
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Basic physics of USSound waves are expressed as sine waves with thefollowing properties:
1- Wavelength ( )2- Frequency (f) : The higher the frequency, the better theresolution and the lower the penetration .
3- Propagation Velocity (v) : expressed by the Wave Equation v= f In soft tissue propagation velocity is relatively constant at 1540m/sec. Hence wavelength is inversely proportional to frequency
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Basic physics of US4- Amplitude : is the height above the baseline andrepresents maximal compression. It is expressed indecibels.
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US Modes A mode :a display of ultrasonicechoes in which thehorizontal axis of the
cathode ray tube display represents the timerequired for the return of the echo and the verticalaxis represents thestrength of the echo. Themode is used inechoencephalography
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US ModesM Mode : M-mode stands formotion mode. Itcaptures returningechoes in only one lineof the B-mode image butdisplays them over a timeaxis. Movement of structures positioned inthat line can now be visualized. Often M-mode and B-mode aredisplayed together onthe ultrasound monitor
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US modesB Modes :B-mode stands forbrightness mode andprovides structuralinformation utilizingdifferent shades of gray (or different brightness)
in a two-dimensionalimage
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US modesDoppler Mode :the Doppler mode examines thecharacteristics of direction andspeed of tissue motion andblood flow and presents it inaudible, color or spectraldisplays
Pulsed (spectral) doppler
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US modesColor doppler modeDirection and velocity of
tissue motion and bloodflow are color coded andsuperimposed on thecorresponding B-modeimage
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US modesPower dopplerNon directionalMore sensitive formeasure blood flow
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US modesDuplex and triplex
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Interaction with matter Absorption, reflection,refraction. Scatter
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Abdomen USPt. preprationFasting 6 hrs to reduce bowel gases and gallbladder
shown distended .Transducer : Curve linear , 3-5 MHzUse aqueous gel as coupling material to minimizereflection of US
Mostly use B mode .
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Abdomen USGeneral points for imaging upper abdomen :1-Always scan any organ in at least two planes ,
to reduces the risk of missing pathology and helps todifferentiate artifact from true pathology.2- Use a combination of sub- and intercostal .3- never limit the scan to longitudinal andtransverse sections.4- Deep inspiration can be useful.
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liver pathology
Simple cyst
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Liver pathology
Liver cirrhosis
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GallbladderThe normal gallbladder is best visualized after fasting for around sixhours, it should be distended withbile into an elongated pear-shapedsac.It should have a hyperechoic, thin
wall and contain anechoic bile Wall thickness of gallbladder notmore than 3 mm.(GB wall ismeasured at the most narrow pointof the anterior wall in the short-axis)GB diameter 4- 5 cm and the longaxis from 8-12 cm
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GallbladderDuodenum mimicking gallbladder pathologyThe close proximity of the duodenum to theposterior gallbladder wall often causes it toinvaginate the gallbladder turn the patient to causethe duodenal contents to move.
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Gallbladder
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GB pathology
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GB pathology
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Pathology
acute cholecystitisContracted GB
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Common bile ductThe internal diameter of the common duct is reported tobe In adults, the average diameter o 4 mm. less than 6 mmis considered to be normal, 6 to 7 mm is equivocal, andmore than 7 mm is dilated. may be more than 8 mm ineldery pt .Patients with a cholecystectomy CBD is dilated, but non-obstructed 10 mm .
CBD dilated if there obstruction due to formation of stonesin the duct.
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CBD
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CBD
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CBD
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pathology
Stone in CBD
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PancreasThe most useful technique is to start by scanning theepigastrium in transverse plane, using the left lobe of theliver as an acoustic window. In adult , the pancreas is
hyperechoic compared to normal liver.The normal stomach or duodenum can mimic pancreaticpathology if the patient is insufficiently fasted , Giving thepatient a drink of water usually differentiates the
gastrointestinal tract from a collection.
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Pancreas
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SpleenThe normal spleen has a fine, homogeneous withsmooth margins and a pointed inferior edge. It hassimilar echogenicity to the liver but may be slightly hypo- or hyperechoic . A splenic length of below 12 cm is generally considerednormal .
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Spleen
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KidneysThe right kidney is readily demonstrated through theright lobe of the liverThe left kidney is not usually demonstrable sagittally because it lies posterior to the stomach and splenicflexure. The spleen can be used as an acoustic window tothe upper pole by scanning coronally, from the patientsleft side, with the patient supine or decubitus (left side
raised) . Normal ultrasound appearances of the kidneysThe cortex of the normal kidney is slightly hypoechoic when compared to the adjacent liver parenchym
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kidneysThere is gooddifferentiation of therenal capsule ,cortex,
medulla, and renalsinus complex. Thelongitudinal plane.
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kidneysNormal renal value :Renal length: 9-12 cmRenal width :4-6 cmCortex width : 1.3-2.5 cm
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pathology
Renal cyst
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pathology
Renal stone
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pathology
Mild HN
Moderate HN
Severe HN
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Urinary bladderPt. preparation :Full bladder .
To show bladder outline ,window for prostate anduterus .When the bladder is distended with urine, the wallsare thin, regular and hyperechoic. The walls may
appear thickened if the bladder is insufficiently distended, making it impossible to exclude a bladderlesion.
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Urinary bladderHypoechoic with smooth outline.The wall thickness of 4 to 6mmthree perpendicularmeasurements and multiplyingby 0.56:Bladder volume (ml) = length * width * anteroposterior diameter (cm) * 0.56post micturition residue of lessthan 20 cc in an adult is regardedas normal
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patholgy
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Vascular USR/O DVTNo preparation
Linear transducer 7-10 MHZPopilital and femoral veinSpectral ( pulsed ) doppler used to differentiate artery and vein
differences between artery and vein :Pulsation and compressepility
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DVT
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DVT
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3D /4D US
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