📝 STANDARD DESCRIPTION:
Ultrasound Basics:
• Uses high-frequency sound waves (2-10 MHz).
• Probe (transducer) sends sound + receives echoes.
• Echoes reflect off tissue interfaces → image.
• SAFE — no ionising radiation; can be done on pregnant animals.
Echogenicity terms:
• Anechoic (BLACK): Pure fluid (urine, bile, blood).
• Hypoechoic (DARKER): Less reflective than surroundings.
• Isoechoic: Same density as a reference organ.
• Hyperechoic (BRIGHT): Strong reflectors (fat, gas-bubbles, calcified).
• Acoustic shadowing: Stones, gas, bone block deeper view.
Uses: Pregnancy diagnosis (cattle, mare, bitch), abdominal organs (liver, spleen, kidneys, bladder), heart (echocardiography), eye, soft-tissue masses.
📚 DETAILED DESCRIPTION:
ULTRASONOGRAPHY (USG) — PRINCIPLES & APPLICATION
Ultrasound uses pulsed high-frequency sound waves (2-15 MHz) generated by piezoelectric crystals in the transducer (probe). The probe both emits sound and receives the echoes; transit times and intensities are reconstructed into a 2-D grey-scale image.
HOW IT WORKS:
1. Probe emits a pulse of ultrasound.
2. Sound travels through tissues; reflects at acoustic interfaces (tissue boundaries with different acoustic impedance).
3. Echoes return to probe.
4. Computer maps depth (from echo time) + intensity (from echo amplitude) into pixels.
ECHOGENICITY (relative brightness):
• Anechoic (BLACK) — fluid (urine, bile, simple cyst, fluid in bladder/uterus).
• Hypoechoic (DARKER GREY) — relatively less reflective (kidney medulla, lymph nodes).
• Isoechoic — same brightness as adjacent reference (e.g., spleen vs liver).
• Hyperechoic (BRIGHT) — fat, fibrous tissue, calcifications, gas-fluid interfaces.
USEFUL ARTEFACTS:
• Acoustic shadowing — bone, stone, gas reflects all sound; black 'shadow' beyond.
• Posterior enhancement — fluid transmits sound well → tissues beyond appear brighter.
• Reverberation — repeated reflections from gas (lung).
• Mirror image — at strong reflector (diaphragm).
FREQUENCIES (Trade-off: penetration vs resolution):
• 2-5 MHz — deep abdomen of cow/horse.
• 5-7.5 MHz — small animal abdomen.
• 7.5-15 MHz — superficial structures (eye, tendons).
VETERINARY APPLICATIONS:
• Pregnancy Diagnosis: Cow ~28 days; mare 14-15 d; bitch 28 d. Check fetal HR (>120 bpm = healthy).
• Reproductive: Ovarian follicles + corpus luteum (cattle/horse breeding management).
• Abdominal: Liver (FNA-guided biopsy), spleen, kidneys (PKD, hydronephrosis), bladder (stones, tumours), GI tract (intussusception, foreign body).
• Cardiac (Echocardiography): Chamber dimensions, valves, contractility, pericardial effusion.
• Ocular: Retinal detachment, lens luxation.
• Tendon/Ligament: Tendinitis (e.g., bowed tendon in horse SDF), suspensory ligament desmitis.
• Pleural: 'Sliding lung sign' for pneumothorax exclusion.
• FAST scan in trauma cases (fluid in abdomen / thorax).
ADVANTAGES over Radiography: No radiation, real-time, can image fluids and soft tissues, portable, can guide biopsies.
LIMITATIONS: Bone & gas block penetration. Operator-dependent.
// COMPARATIVE ANALYSIS
| CATTLE |
Trans-rectal USG is daily practice for reproductive monitoring (CL, follicles, early pregnancy). |
| HORSE |
Trans-rectal USG for ovarian follicle tracking. Tendon USG (B-mode + Doppler) routine for performance horses. |
| DOG/CAT |
|
CLINICAL RELEVANCE
USG-Guided FNA / Biopsy: Standard for liver, kidney, spleen, lymph node sampling. Doppler USG: For blood flow (tumour vascularity, fetal viability). Trans-rectal USG: Most economic test for pregnancy in cow.
