STEEPLECHASE ULTRASONOGRAPHY Flashcards
Frequency
No. diff sound waves that pass through point at any given time
High freq
- Good axial resolution
- More rapid beam attenuation - lose energy from beam quicker
- Poor penetration
- Cardiac scanning- better resolution, low penetration
Low freq
- Poor axial resolution
- Less rapid beam attenuation
- Better penetration
- E.g. Large dog w/ deep abdo
Depth
Should be set so image takes up 2/3 of screen - centimetre markers
Gain
- Overall brightness of image
- Further from the probe, more gain required to achieve same level of brightness
- Time gain compensation (TGC) - controls brightness at diff levels through tissue
Focus/focal zone
- Improves lateral resolution - targets perpendicular to beam distinguished from each other
Echogenicity
- Due to beam attenuation - reflects normal tissue back to transducer, fluid e.g. cysts = attenuation
- Normal organs + tissues displayed as shades of grey
Isoechoic
Structures same shade of grey
Hypoechoic
Darker shade of grey
Hyperechoic
Lighter shade of grey
Anechoic
- Black structure
- E.g. Fluid, cyst
Describing US image
- L - location - normal/displaced?
- E - echotexture - anechoic, hypoechoic, isoechoic, hyperchoic; homo/heterogeneous
- M - measurement/size
- O - outline/margin - disruption/capsule of organ - smooth, well-defined?
- N - No. organs correct, lesions etc
- S - shape/size - reference to another organ
Artefacts
- Reverberation - gas/parallel reflective surfaces -> hyperechoic parallel bright lines e.g. in lungs
- Mirror image - highly reflective curved surfaces e.g. diaphragm
- Acoustic enhancement - US beam not attenuated by fluid + passes straight through -> bright acoustic area distal to fluid filled structure e.g. bladder/gall bladder
- Acoustic shadowing - highly attenuating structure e.g. calculi/bone/gas (get comet tail) - all waves reflected -> hypoechoic shadow below structure
- Edge shadowing - beam changes direction at fluid/tissue interface -> hypoechoic streaks from curved structure edge
- Poor probe contact - insufficient clipping/not enough gel -> air trapping
- Slice thickness - pseudo-sludge e.g. bladder/gallbladder, part of beam is wider than cystic (circular structure), mimics tissue interface within fluid-filled structure
Distal acoustic enhancement
- Spleen heterogenous compared to liver; liver more homogenous, only in comparison!
- If spleen itself was heterogenous, tumour within spleen, more epitexture
Heterogenous - haemangiosarcoma/lymphoma, tumour
Acoustic enhancement
Indications - POCUS SCAN (point of care US) - emergency (abdo)
- Identify and sample free fluid
- Identify free gas
- Evaluation the intestines for obstruction
- Evaluate pancreas region for signs of inflammation
- Evaluation the biliary tract for signs of obstruction or perforation
- Evaluation of the urinary tract for obstruction or rupture
Indications - elective (abdo)
- Medical + Sx work-up
- Staging of neoplasia
- Abdo organ/mass sampling
- Intra-abdo biopsy
- System specific investigation e.g. pyo, PD, ascites
Equipment + patient prep
- Microconvex transducer
- 5 - 8 MHz
- Withhold food for 12 hours
- Appropriate environment - quiet, low lighting, animal comfortable
- Abdominal hair clipping - from xiphoid to pubis
- Dorsal or lateral recumbency - don’t place unstable in dorsal
- Assistants for restraint
Approaching US exam checklist
- 1). Number – correct number organs / single or multiple abnormalities
- 2). Location – does an abnormality displace an organ
- 3). Function – is the heart beating/the GI tract peristalsis etc.
- 4). Size – can you compare to breed ‘normal’
- 5). Echogenicity – focal or diffuse changes
- 6). Architecture – disruptions often marked in chronic disease
- 7). Shape – very subjective, although can be affected by masses
- 8). Margins – normally smooth and well defined
POCUS abdo protocol
- Logical approach
- Each organ evaluated in all planes + fanning probe
- Identify abnormalities
- R lateral = xiphoid process -> liver -> stomach -> spleen -> L kidney -> SI -> colon -> urinary bladder -> +/- prostate
POCUS - AFAST - sites
- DH = diaphragmatic-heptic view
- CC = cystocolic view
- SR = splenorenal view
- HR = hepatorenal view
- Each site in two planes at 90 degrees
- Give abdo fluid score - 0 - 4 for no. fluid +ive areas, inc score w/ ongoing fluid accum, dec score = resorption of fluid
DH - Diaphragmatic hepatic view
- Diaphragm
- Fluid
- Cranial
CC - cystocolic view
- Back of abdo (caudal)
- Bladder
- Colon
SR - splenorenal view
- Spleen
- Kidney
- LHS