Physical Therapy Technical Reports http://www.ptjournal.org Physical Therapy RSS feed -- recent Technical Reports articles 1538-6724 Physical Therapy 0031-9023 Physical Therapy http://www.ptjournal.org/icons/banner/title.gif http://www.ptjournal.org <![CDATA[Variability in Effective Radiating Area at 1 MHz Affects Ultrasound Treatment Intensity]]> http://www.ptjournal.org/cgi/content/short/88/1/50?rss=1 Background and Purpose: Previous research has indicated that not all ultrasound transducers heat at equal rates; however, the cause of this disparity is unclear. Variability in spatial average intensity (SAI) has been implicated in this disparity at 3 MHz. This variability has not been explored at 1 MHz.

Methods: Sixty-six 5-cm2 ultrasound transducers were purchased from 6 different manufacturers. Transducers were calibrated and assessed for effective radiating area (ERA), total output power, and SAI using standardized measurement techniques.

Results: Total output power values fell within US Food and Drug Administration guidelines, but there were large variations in ERA. The resulting SAI values showed large deviations (–43% to +61%) from the digitally displayed value. Intra-manufacturer SAI values varied up to 53%.

Discussion and Conclusion: Spatial average intensity can vary largely from the values displayed on these ultrasound generators; in a calibrated cohort, this difference is primarily attributable to differences in measured ERA. Patterns of SAI variability within the manufacturer at 1 MHz do not follow previous reports of variability at 3 MHz.

]]> 2007-12-31 info:doi/10.2522/ptj.20060358 American Physical Therapy Association 1 88 57 2008-01-01 50 Technical Reports <![CDATA[Invited Commentary]]> http://www.ptjournal.org/cgi/content/short/88/1/58?rss=1 2007-12-31 info:doi/10.2522/ptj.20060358.ic American Physical Therapy Association 1 88 61 2008-01-01 58 Technical Reports <![CDATA[Author Response]]> http://www.ptjournal.org/cgi/content/short/88/1/61?rss=1 2007-12-31 info:doi/10.2522/ptj.20060358.ar American Physical Therapy Association 1 88 62 2008-01-01 61 Technical Reports