12951721
Beschreibung
Karteikarten von Alinta Kalns, aktualisiert more than 1 year ago
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Erstellt von Alinta Kalns
vor mehr als 6 Jahre
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| Frage | Antworten |
| What are sound waves? | Longitudinal waves of compression and rarefaction |
| What is the normal velocity of sound in tissue? | 1540 m/s |
| How does an ultrasound transducer work? | Piezoelectric crystals convert electrical energy to sound energy |
| What is attenuation? | Weakening of sound waves due to reflection and absorption Denser tissue = more attenuation |
| How does wave frequency influence sound depth? | Higher frequency = less depth - more pixels hitting/reflecting off the tissue increases attentuation |
| How does wave frequency influence image resolution? | Higher frequency = more pixels hitting/reflecting off the tissue = higher resolution |
| How does amplitude influence brightness? | Higher amplitude = poorer far-field brightness and visibility |
| Define acoustic impedance | Difference in densities between two tissue types Shown by an acoustic interface between each tissue |
| List tissue types in descending order of density | Bone > Muscle > Liver > Blood > Water > Fat > air |
| How much attenuation do sound waves go in fluid? | NONE - anechoic, transmits waves 30% acoustic interface reflection with soft tissue |
| What artifact does fluid produce? | Acoustic enhancement |
| How much attenuation do sound waves undergo in bone? | 80% reflection 20% absorbance |
| What artifact can be seen with bone? | Anechoic acoustic shadowing - only see edge of structure |
| How much attenuation do sound waves undergo in air? | None, 100% reflection of sound waves |
| What artifact is produced by air? | Reverberation artifact |
| What types of resolution are there? | Lateral - 2 structures adjacent, perpendicular to sound beam Axial - 2 structures behind one another, parallel to sound beam |
| What factors influence lateral resolution? | Beam width Focal zone Transducer type Thinner width + linear transducer = better resolution |
| What does a curved beam do in lateral resolution? | Produce merging artifact |
| What factors influence axial resolution? | Pulse length Pulse frequency Shorter wavelength + higher frequency = better resolution |
| What are the ultrasonic modes? | A-mode - Amplitude B-mode - Brightness M-mode - Motion Doppler - Velocity (spectral, colour, power) |
| What are the different transducer types? | Liner - wide near-field Curvilinear/Convex - sector Phased array - sector Annular array - sector |
| What types of focus are there, and what does using more than 1 focal zone do to the image? | Broad focus Multi-point focus (1-4) More focal zones decreases image quality |
| Track Ball Cursor movement +/- zoom | |
| Power gain Changes amplitude of sound beam Creates whole-screen artificial enhancement | |
| Time gain Left = echo suppression Right = echo enhancement Up is near-field, down is far-field | |
| When would you use time gain? | Pancreatitis is highly hyperechoic Near-field suppression needed to see far-field structures |
| When would you use split screen? | To compare structures To measure a long structure |
| Image direction Changes left and right direction of the image | |
| What is often used to set initial depth of an ultrasonic image? | Magnification Liver is often used to start with |
| What ID do you need to include in an ultrasonic image? | Patient ID and case number Organ ID Probe orientation Practice and date |
| Where could you stored ultrasonic images digitally? | PACS system Hard drive Personal computer |
| Define anechoic. | No returning echoes - homogenous E.g. fluid |
| Define hypoechoic | Low intensity returning echoes Low reflection E.g. organs with high fluid content (kidneys) |
| Define hyperechoic | High intensity returning echoes Large acoustic impedance |
| Isoechoic | Two adjacent structures have the same echogenicity |
| Normoechoic | A structure returning the expected echo intensity |
| How would you describe echoes? | Homogenicity Artifact Borders/walls Adjacent echo patterns |
| Describe acoustic enhancement. | Sound waves that travel through fluid and undergo no attenuation, causing the structure after the fluid to appear hyperechoic |
| Describe acoustic shadowing. | Produced if sound waves encounter tissue with high reflection and absorption Anechoic area after said tissue |
| Describe edge shadows | Narrow hypoechoic shadows produced by walls of cystic structures |
| What influences edge shadows? | Refraction - difference in speed of sound in a structure vs surround tissue Reflection - angled incident beam |
| What is reverberation? | 100% reflection - sound waves bouncing to and from transducer Multiple equidistant hyperechoic lines produced |
| What are 2 forms of reverberation? | Comet-tail - solid hyperechoic streak due to metallic objects Ring-down - similar to comet-tail, produced by bugle-shaped fluid trapped between air |
| What can cause ring-down reverberation artifact? | Pleural/interstitial disease Gas trapped in bladder |
| Describe mirror-image artifact | Highly reflective, curved structure rebounds sound waves at an angle and tricks transducer into believing structures those waves hit are deep to the curved structure Positions it on a linear axis + the real image |
| Describe slice thickeness. | Lateral resolution artifact Soft tissue included in fluid - average of both echoes taken, simulates sediment in fluid |
| How do you check whether slice thickness or true sediment? | Ballottement of the structure |
| What are 4 operator artifacts? | Poor patient preparation Poor transducer contact Incorrect gain settings Off-incidence artifact (not perpendicular to structure) |
| What factors would you use to describe a lesion? | Radioopacity/echogenicity Size, shape, number, location, margination Homogenicity Useful artifact present Edge regularity + definition Surround tissues (effect on structure) Vascularity |
| How would you describe tissues on ultrasound? | Tissue type + echogenicity Artifact Foreign bodies |
| What does gas produce when it moves over other structures? | Curtain sign - incomplete acoustic shadowing |
| What would you expect if fluid become hypoechoic or hyperechoic? | Crystalline or cellular content increase Suspended gas Food in lumen of GIT |
| What echogenicity is cartilage? | Anechoic |
| How would you recognise musculature and tendons? | Striated appearance Wavy/hypoechoic if not engaged |
| Name organs in descending organ of echogenicity | Prostate > spleen > liver > kidney |
| Which organ is used as a reference for parenchymatous ultrasonography? | Spleen - most homogenous + hyperechoic |
| What artifact does metal produce? | Comet tail |
| What echogenicity is wood? | Hyperechoic until absorbs fluid from body Acoustic shadowing if recent |
| What are echogenicities of the small intestinal wall layers? | Mucosa - thick hyperechoic Submucosa - hyperechoic Muscular - hypoechoic Serosa - hyperechoic |
| What scanning planes would you normally adhere to? | Sagittal Parasagittal Transverse |
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