PHY 211 Net Research Project for 12/1/03

Sound Outside Hearing

NOTE: I was just made aware that there was a problem with the submission text field being erased when returning from a link. I now have all the links targeted to a new window. Please let me know if the problem persists.

Sonograms

Sonograms have become as common place a method of investigating inside the body as are x-rays. While sonograms cannot produce images as clear as x-rays in most cases, they have the advantage of being much safer and able to produce real time images, as opposed to still images. Sonograms use ultrasound, sound at frequencies well above human hearing. These very short wavelength rays penetrate the body and reflect off organs and tissue to varying degrees. The level of the reflected ultrsound energy is used to create the picture. Imaginis has a some more information on ultrasound imaging.

While the standard sonogram produces a 2-D image, there is a new 3-D imaging technology. The 3-D images are sharper and have the advantage that the computer generated image can be rotated 360^o to allow a view of the target area from all directions. The Dannish Sonace company has some nice graphics, but you'll have to excuse the translation. While 3-D sonograms look nice, there is some controversy concerning whether they are an improvement in diagnostic poetential or just a high-priced toy that is being marketed as commercial venture. Check out the Washington Post article on 3-D sonograms controversy.
3D sonogram image

Lithotripsy

Anyone who has passed a kidney stone can attest to the immense pain. Some women have compared it to giving birth. (Some men have also compared it to giving birth, but what do they know!) Until recently, there were only two methods for removing kidney stones. The first is to drink lots of fluids to flush out the stones. This is viable if the stones are not too large. The second option is surgery. More recently, there has evolved a third option.

High intensity sound wave pulses are now being used destroy those unwanted renal stones in a process called lithotripsy. The great advantage to using sound waves is that there is no surgery and little chance of infection. While there is a bruise to deal with (more like a localize skin burn), the post procedural pain is considerably less than with surgery.

Essentially, high energy pulsed sound waves literally pulverize the brittle kidney stone. The "sand" resulting from the pulverization is passed through the urinary system over the next day or so. The clever trick is how to bring the sound energy to bear on the stone and not the surrounding tissue. The secret is focusing the sound energy.

First, normal ultrasound imaging locates the stones. It is critical that location of the stone is known as precisely as possible. Then, the high intensity sound pulses are brough to bear on the target. The sound pulse enters the body as a diffuse, but converging/concave wavefront that comes to a focus at the stone. (See the diagram to the right.) It is very similar to using a magnifying glass to focus light to a small point for roasting annoying insects. For more details, check out the Conier lithotripsy tutorial offered by Global Lithotripsy Services.

Courtesy of yoursurgery.com

Questions:

Does ultrasound penetrate bone material?
About what percentage of mothers-to-be have prenatal ultrasound?
Which uses a wider frequency band for imaging, 2-D or 3-D sonograms?
What is the major advantage of 2-D sonograms over 3-D?
What is the focus volume for the Dornier Compact S lithotripsy machine?

Be sure to enter your full name. Enter your email address ONLY if you want the number of points awarded e-mailed to you. Responses should be brief but complete. You must click the SUBMIT button to submit your entry. Entries are due by noon on Monday of next week.