Ultrasound Imaging (US)
Diagnosis: Prostate, urinary bladder, uterus
Components of ultrasound machine
· Transducer probe
· Central processing unit (CPU)
· Transducer pulse controls
· Disk storage device
· piezoelectric crystal
ü Non-invasive and painless.
ü Without using ionizing radiation (particular advantage in pregnancy & paediatrics)
ü Real time information.
ü Sensitive to detect flow changes
ü Possible control of respiratory phases.
ü Colour Doppler shows blood flowing towards the transducer as red, blood flowing away as blue – particularly useful in echocardiography and identifying very small blood vessels
ü low equipment price, mobility
ü Interactive modality, operator dependent (relies on operator to produce and interpret images at the time of examination)
ü US cannot penetrate gas or bone. Ultrasound waves are greatly reflected by air-soft tissue and bone-soft tissue interfaces, thus limiting its use in the head, chest and musculoskeletal system
ü flowing blood alter frequency of sound waves returning to the ultrasound probe
ü Cannot perform global view of the veins.
ü Influenced by hydration status
1. The ultrasound transducer is placed against the skin of the patient near the region of interest.
2. A piezoelectric transducer is used to create high frequency sound waves (3-10 MHz) when electric current is applied to it.
3. The ultrasonic sound wave emitted travel through human tissues.
4. Wave is being reflected when it reach an object or surface with different texture or acoustic nature.
5. Reflected wave will travel back to the piezoelectric transducer to create electric current and a 2d image is produced.
The image formed will be based on how strong the returning signal is:
• The stronger the returning signal, the more white it will be on image (Hyperechoic = white or light grey e.g. fat-containing tissues)
(Hypoechoic = dark grey e.g. lymphoma, fibro adenoma of the breast)
•Pure fluid gives no echoes, appearing black (anechoic)
•Acoustic shadow is the opposite effect where tissues distal to e.g. gas containing areas, gallstones, renal stones receive little sound and thus appear as black