Each step up multiplies by 10. Each step down divides by 10.
A shorthand for very large or small numbers. Write a number between 1 and 10, then multiply by a power of 10.
The decimal moved 3 places left, so the exponent is positive 3.
The decimal moved 2 places right, so the exponent is negative 2.
Positive exponent = big number (decimal moved left).
Negative exponent = small number (decimal moved right).
Four prefixes you will use constantly in sonography physics. These appear in every chapter going forward.
Ultrasound lives in the Megahertz range. A 12 MHz transducer reveals exquisite surface detail. A 2 MHz transducer reaches deep into the body. The tradeoff between resolution and penetration is the central tension of your craft.
Axial resolution is measured in fractions of a millimeter. It determines whether your image shows two structures or smears them into one. At the milli scale, the difference between seeing and missing is everything.
The kilohertz range is the rhythm of motion. Doppler shift and Pulse Repetition Frequency live here. When you track a thousand pulses per second to watch blood move through a vessel, you are counting at the kilo scale.
A microsecond is the period of one ultrasound wave cycle at 1 MHz. Double the frequency and the period halves to 0.5 μs. Pulse duration, spatial pulse length, and duty factor are all measured at this scale.
Test your understanding of metric prefixes.