Instrumentation: Pulser and Power Control

What are the ultrasound’s system components? (8)

• Pulser

• Power Control

• Beam Former

• Transducer

• Receiver

• Memory

• Display

• Recording Device

What is the pulser?

It sets the PRF (pulse repetition frequency).

One AC voltage burst creates how many pulses?

One.

The pulser is also known as the master…? Why?

Synchronizer. This is because it times all events.

What are the two types of driving voltages for the pulser?

• Spike voltage which uses DC current (@ 200+ volts)

• Burst voltage which uses AC current (@ ~100 volts)

What is output power?

It controls the output power strength.

Does output power effect patient exposure?

Yes.

When determining the amount of output power to use, what is the rule of thumb?

ALARA (always low as reasonably achievable).

What are some synonyms for output power?

• Acoustic power

• Output

• Output Power

• Power

What is the output power labelled as in the ultrasound machine?

• dB

• %

• max-min

What is the max dB output power?

0 dB

What is ½ dB output power?

-3 dB

100% power into dB?

0 dB

50% power into dB?

-3 dB

25% power into dB?

-6 dB

10% power into dB?

-10 dB

What is the beamformer?

A small digital chip that all transmit and receive circuits use to produce, optimize, focus, and steer the beam.

What makes up the beamformer? (6)

• Transmit focus

• Dynamic aperature

• Dynamic apodization

• Beam steering and switching

• Receive focus

• Coded excitation

What is coded excitation?

Newer technology that digitally encodes the driving voltage into pieces (breaks it up).

What does coded excitation help to improve?

SNR (signal-to-noise ratio) and penetration.

What is B Flow?

An option on some machines that allows us to see flowing blood.

B Flow is possible due to what?

Coded excitation.

What is the advantage of B Flow over colour Doppler?

It prevents overwriting (showing flow in tissue when its not really there).

What is the echo signal also known as?

The Rf signal.

What is the Rf signal?

Radio frequency (low megahertz range)