Standard scanners allow visualizing microbubbles on conventional gray scale imaging in large vascular spaces. In the periphery, more sensitive techniques such as Doppler or non-linear gray scale modes must be used because of the dilution of the microbubbles in the blood pool. Harmonic power Doppler (HPD) is one of the most sensitive techniques for detecting ultrasound contrast agents.
Commonly microbubbles are encapsulated or otherwise stabilized to prolong their lifetime after injection. These bubbles can be altered by exposure to ultrasound pulses. Depending on the contrast agent and the insonating pulse, the changes include deformation or breakage of the encapsulating or stabilizing material, generation of free gas bubbles, reshaping or resizing of gas volumes.
High acoustic pressure amplitudes and long pulses increase the changes. However, safety considerations limit the pressure amplitude and long pulses decrease spatial resolution. In addition, lowering the pulse frequency increases destruction of contrast bubbles. However, at low insonation power levels, contrast agent particles resist insonation without detectable changes. Newer agents are more reflective and will usually allow gray scale imaging to be used with the advantages of better spatial resolution, fewer artifacts and faster frame rates.

Feasible imaging methods with advantages in specific acoustic microbubble properties:
Resonating microbubbles emit harmonic signals at double their resonance frequency. If a scanner is modified to select only these harmonic signals, this non-linear mode produces a clear image or trace. The effect depends on the fact that it is easier to expand a bubble than to compress it so that it responds asymmetrically to a symmetrical ultrasound wave. A special array design allows to perform third or fourth harmonic imaging. This probe type is called a dual frequency phased array transducer.

See also Bubble Specific Imaging.

Usually, multiple probes are used because most transducers are only able to emit one frequency because the piezoelectric ceramic or crystals within it have a certain inherent frequency.
Multi-frequency probes have multiple crystals with different frequencies and the desired specific frequency can be selected. Advanced probes can emit sound waves at different frequencies for the near and far fields. The disadvantage is that multi-frequency (multifrequency) probes have slower frame rates and therefore they are only useful for imaging of static structures.

See also Dual Frequency Phased Array Transducer and Tri-Frequency Probe.

Pulsed ultrasounds are cycles of ultrasound separated in time with gaps of no signal. Pulsed sound waves are generated by short, strong pulses of sound from a phased array of piezoelectric crystals. The transducer, though emitting ultrasound in rapid pulses, acts as a receiver most of the time. In sonography, pulsed ultrasound is used to perform diagnostic or therapeutic procedures.

See also Pulse Average Intensity, Release Burst Imaging.

Most usual ultrasound machines are 2D real-time systems. This types of ultrasound scanners allow to assess both motion and anatomy, including the motion of heart valves, the movement of intestines and lungs and also to guide interventions, like for example a biopsy or a laparoscopic ultrasound.
A standard real-time scanner consists of a mobile console with the monitor on the top and rows of small containers at the bottom to accommodate a variety of scanner probes. The linear, curved or phased array transducers are usually equipped with multiple crystals or in some cases with a moving crystal. A real-time scanner may be e.g., a mechanical scanner or electronic array scanner.

See also Musculoskeletal and Joint Ultrasound.

From Philips Medical Systems;
'The perfect practice system...
The SD 240E is a compact and ergonomically designed system, standard equipped with two probe connectors. The user has a choice out of more than 12 linear, curved and annular phased array probes which can be used with this perfect office unit. Total Image Focus and cine memory technology are just the icing on the cake.'
This product is not available in the US, Australia, or New Zealand from Philips Medical Systems.'

Specifications for this system will be available soon.