The frequency of an ultrasound machine determines how deep its waves are capable of travelling within the body tissues. A general rule here is:
Higher frequency (10-16MHz) = Lesser Penetration (superficial Imaging)
Lower frequency (1-2Mhz) = More Penetration (deep Imaging)
Refers to the amount of sound energy released during its operation. High power output can be detrimental to body tissues (burns may result). Hence, lower power settings are preferred.
Pulsed Wave & Continuous Wave Doppler
In PW Doppler, the probe releases pulsed ultrasound waves to the desired depth and then becomes quiet. During this quiescence, it receives the wave that reflects back after passing through body tissues. This cycle is repeated multiple times per second. In CW Doppler, the probe never remains quiet. It emits and receives ultrasound waves simultaneously.
The efficiency of PW Doppler is limited due to ‘interruptions’ in its functioning pattern; hence it can measure blood flow velocity up to a certain level and not beyond that. CW Doppler on the other hand works in a continuous fashion, thereby allowing interrogation of high velocity flows accurately.
DICOM refers to “Digital Imaging and Communications in Medicine”, which is a standard developed and implemented by American College of Radiology and the NEMA (National Electrical Manufacturers Association). By providing a protocol the defines network communications and a file format that enables storage and transmission of imaging related data, DICOM serves to bridge the gap that arises due to differences in hardwares and softwares of different manufacturers’ equipment.
2D, 3D and 4D
A conventional ultrasound scan provides a two-dimensional images (2D).
Three-dimensional images are obtained by using 3D scanning; but these images are “static”.
The images produced by 3D scan can be seen in “motion”; this “motion” is regarded as being the fourth-dimension i.e. 4D. Hence, a 4D-scan is in essence a “3D scan in motion”.
Doppler technology & Color Doppler
Using the ‘Doppler effect’, the direction and speed of flowing blood is determined. Echocardiography works on this principle.