Ultrasound Physics PDF

Terms to know Ultrasound Physics Frequency sound waves with frequencies that are of times a higher than range of human hearing cycle or wave is Beyond 20,000 Hz epeated per second sound emitted From transducer into...

Terms to know Ultrasound Physics Frequency sound waves with frequencies that are of times a higher than range of human hearing cycle or wave is Beyond 20,000 Hz epeated per second sound emitted From transducer into the body expressed in at one or multiple Frequencies Hertelitz images are created when echoes are Wavelength reflected back to transducer istance traveled oy the sound waves expressed in millimeter mm Velocity speed at which sound ravels throug medium travels Fastest in solid objects closeness of molecules Transducer Slowest in gases molecules Further apart  increased frequency and short a elect resolution 2 structures wavelength decreased Frequency and longer eparately located wave length penetration resolution n a parallel beam Penetration tow For sound waves are allowed to travel Attenuation oss of sound waves strength s they travel through medium Absorption on version of sound energylowto in heat ultrasound Very Reflection Oundwaves encountering tissues 7 differing acoustic mpedence only sound waves that get back to transducercontribute to image  Attenuation Scattering creased with ound waves encounter increased distance From transduce mall and uneven more heterogenous medium with urfaces and increased acoustic impedence egenerate weak mismatch echoes parenchymal Higher Frequency transducer appearance of organs Refraction Acoustic impedence Product of the tissue density and the of the beam ending velocity of the sound within that hen encountering tissue change in medium when the beam Changes impedence From one in trikes the interface tissue to the next determines 7 an oblique angle the amount of sound that is Bending of beam reflected back to the transducer leaves shadow and how much is transmitted at edges of curved structures to the next tissue gallbladder or large acoustic impedence cyst much sound reflected Small acoustic impedence little sound reflected no differences no reflection air and Bone hashongest interface Image Based on display pulse echo principle Sound emitted 1 of the time transducer listens 99 of the time Electrical signals from returning echoes enhanced to display image to Transit time directly related depth amount ofreflected sound depends on tissue impedence Ultrasound machine is at a constant speed in tissue at 1540 m s Artifacts Assumptions made by ultrasound Sound waves travel in a straight line All echoes originate from objects in beam axis Echoes return to trans ducer after single reflection speed of sound in tissueconstant is Strength of echoes is directly related to the reflecting scattering properties of the object Depth to the reflecting or scattering object is proportional to the round trip time of the sound wave strength of the sound wave is attenuated evenly Artifacts can be helpful or confusing maybe present in Ultrasound study 1 Acoustic shadowing 2 acousticenhancement 3 Edge shadowing 4 slice thickness artifact 5 mirror image artifact Acoustic shadowing Cleanacoustic result of sound being absorbed or shadowing reflected no reverberation artifact Anechoic orBlack Dirty acoustic Tends to happen at tissue shadowing gas interface Bowel most sound is reflected shadow is more gray as a result of reverberation inhomogenous artifact Acoustic enhancement sound waves are less attenuated when transmittingthrough Fluid machine processing compensates and overcompensa hyperchoic area distal to Hold filled structure Edge shadowing small shadows on the edge of rounded structures Slice thickness artifact Sound beam hits gall bladder wall and bile within The ultrasound machine combines the two False sludgeimage which is curved real sludge creates a straight edge mirror image artefact Some sound is reflected From the liver back to the diaphragm lung interface before going to the transducer increased time travel computer places artificial image distal to origin Transducers Do NOT DROP converts electrical current into sound waves and vice versa Piezo electrical crystals expensive Emits sound waves less than 1 of the time and receives sound waves about 99 ofthetime Different shapes and sizes selection depends on properties of the transducer and anatomical a lineartransduce c rMm Emits highest Frequency Used for small parts b convextransducer 7,1 IE faYiIrfo8eece C sectortransducer pie shaped image Echocardiology multifrequency General rule choose the highest Frequency that will penetrate the area of the patient during your exam Small dogs and cats 7.5 10MHz medium sized dogs 5 7 5MHz large breed dogs 5MHz large animals 2 5MHz Tendons and small parts 10MHz Ultrasound machine controls Power intensity of sound output Absolute gain amplification of returning echoes Time gain depth compensation Focus mode measurement Freeze Power gain controls increased gain power Increased brightness of the image  Time gain compensation TGC can selectively amplify weakened echoes from deeper structures and from different image Fields increased far field gain FOCUS Soundwaves can be focused can be adjusted on the imagemanually the area of sharpest sound Place focus at the level of the organ that is to be scanned modes of echo display B mode brightness mode Echoes are displayed as dots in proportion to the amplitude of the returning echo M mode motion mode Used in echocardiograph records images in respect to time B mode M mode Doppler mode measures blood Flow velocity with in a blood vessel Color How doppler measures direction of blood Flow Color assigned for direction Blue How away from the transducer Rede Flow towards the transducer BART Scanning patient tasted Stress avoided For should be shaved Dorsal recumbency ultrasound machine and examiner on the right side of the patient Patients head in the direction of the machine Acoustic gel medium for sound waves to travel Scan planes Sagittal or dorsal plane transducer pointed cranial Transverse plane transducer turned towards the examiner or the patients right cross section  Evaluation of structures size Shape number location margination Echogenicity Opacity on radiograph Anechoic Homogenously black Pure Fluids w o cellular content very low intensity of echoes returning to transduce Hypoechoic relative to other tissues Dark gray tones low intensity 07 returning signals Iso echoic same echogenicity as another structure Hyper echoic relative white structures Anechoic high intensity of signals going back to the transducer diaphragm is hyperechoic compared to the liver Normoechoic expected echogenicity for a certain structure Expected returning signal ypoechoic  urethra O O O O Hyperenoic HYPE Lnone Hypo echoic echoic Hyper