There was a study recently that showed that ultrasound scanning late on in pregnancy is related to the infant being left-handed. Make of that what you will!!!! There are a number of possible explanations! Ben ----- Original Message ----- From: "techhead" To: Sent: Sunday, November 24, 2002 12:58 PM Subject: Re: [EE]:Physiological effects of ultrasound transducers > If you look at the medical studies of ultrasound exposure there are too > many to even count. Let me just give the basics. > Medical ultrasound is limited by law to exposure levels of 100mw to the > square CM. At that level there has never been any proof of tissue > damage. This is for imaging ultrasound. Studies DO show however that for > fetal imaging the fetus is aware of the scan taking place. There is just > no damage. There is another variety used for medical purposes which is > in physical therapy. Their levels are much higher than used for imaging. > The physical damage done to tissue by high levels of ultrasound is, in > order, heating, cavitation. Imaging does not want either of these to > occur. Physical therapy wants the heating to occur. Diagnostic > ultrasound uses the range of 1 MHz to 7.5 MHz transducers for their > purpose. Lower freqs give lower resolution but better penetration. > Higher freqs, higher resolution but lower penetration. Most diagnostic > equipment today does not use a single transducer but a phased array so > that they can steer the beam to acquire the image. Many ultrasound > technologists report that their hands feel better than their non > ultrasound imaging counterparts which tends to lend credence to the fact > that although there is no damage(?) some long term exposure effects are > taking place. The effects taking place are akin to the physical therapy > properties desired in the other ultrasound modality. In imaging it is > essential that a coupling gel be used between the patient and the > transducer to lessen the impact of the difference in impedance between > the human skin and the transducer. High impedance interfaces disperse > the ultrasound beam (attenuate it actually) to such an extent as to > render imaging unusable without the gel. The gel is a very sophisticated > formula and made explicitly for imaging taking into account the > impedance of human flesh, transducer freqs, etc. Free air is a very good > attenuator of diagnostic ultrasound also. Hope this helps > Gary B. > > -----Original Message----- > From: pic microcontroller discussion list > [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Chris Hunter > Sent: Sunday, November 24, 2002 5:18 AM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [EE]:Physiological effects of ultrasound transducers > > > The only physiological effects I've ever seen are those in cats and dogs > - most of them hate bursts of ultrasound! The levels attainable with > the little ultrasonic transducers (like the Murata ones from Maplin) are > pretty low - there's no need to be concerned. > > Incidentally, ordinary electret microphone inserts work very well at > ultrasonic frequencies, though you usually have to highpass filter the > signal to prevent lower frequency sounds obliterating the ultrasonics. > > Chris > > ----- Original Message ----- > From: "Steve Russell" > To: > Sent: Saturday, November 23, 2002 10:05 PM > Subject: [EE]:Physiological effects of ultrasound transducers > > > I'm about to start playing with some ultrasound transducers (for > measuring distance). Is anyone aware of any studies, research, or other > information about the physiological effects of ultrasound from these > transducers? I know they are used in a variety of equipment, but I've > found nothing that talks about possible hazards from exposure to > ultrasound. > > I know ultrasound is used for foetal scanning, physiotherapy, Polaroid > cameras, and so on, but there is no information about the levels used in > such equipment, versus the output from transducers available from places > such as Maplin in the UK. > > Thanks, Steve. > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics