Question

list at least two weaknesses of using sound to image an object. can these weaknesses be overcome, how?

Answer 1

The weaknesses of the sound to image an object (also called as ultrasound / sonography) are:

(1) Poor resolution of the image compared to other methods such as CT and MRI scans. (2) The use of the equipment and quality of results depends on skills of user or operator. (3) Images can be difficult to interpret and it needs skilled operators or specialist such as radiologist..

One of the limits to the detail obtainable with sonography is the frequency of the sound. The laws of physics defines that the smallest objects we can see are about the size of the wavelength of the sound waves. Normally in such cases evanescent waves are captured. These waves waves are bouncing off an object to reconstruct detail as small as one-fiftieth of the wavelength of the sound waves.Evanescent sound waves are vibrations near the object that damp out within a very short distance, as opposed to propagating waves, which can travel over a long distance. With the help of an advanced device, we can pick up and transmit the evanescent waves, which contain a substantial fraction of the ultra-subwavelength information from the object, so that we can realize super-resolution acoustic imaging. With this device, resolution is only limited by the size of the holes. Where as for ultrasound detection, the image resolution is generally in the millimeter range.

The weakness (2) and (3) as mentioned above an be overcome by providing specialised training to the operators or radiologists and certifying them before they can use the actual device in real life.