Johns Lennart D, Straub Stephen J, Howard Samuel M
Quinnipiac University, Hamden, CT 06518, USA.
J Athl Train. 2007 Jan-Mar;42(1):22-8.
Spatial average intensity (SAI) is often used by clinicians to gauge therapeutic ultrasound dosage, yet SAI measures are not directly regulated by US Food and Drug Administration (FDA) standards. Current FDA guidelines permit a possible 50% to 150% minimum to maximum range of SAI values, potentially contributing to variability in clinical outcomes.
To measure clinical values that describe ultrasound transducers and to determine the degree of intramanufacturer and intermanufacturer variability in effective radiating area, power, and SAI when the transducer is functioning at 3 MHz.
A descriptive and interferential approach was taken to this quasi-experimental design.
Measurement laboratory.
Sixty-six 5-cm(2) ultrasound transducers were purchased from 6 different manufacturers.
INTERVENTION(S): All transducers were calibrated and then assessed using standardized measurement techniques; SAI was normalized to account for variability in effective radiating area, resulting in an nSAI.
MAIN OUTCOME MEASURE(S): Effective radiating area, power, and nSAI.
All manufacturers with the exception of Omnisound (P = .534) showed a difference between the reported and measured effective radiating area values (P < .001). All transducers were within FDA guidelines for power (+/-20%). Chattanooga (0.85 +/- 0.05 W/cm(2)) had a lower nSAI (P < .05) than all other manufacturers functioning at 3 MHz. Intramanufacturer variability in SAI ranged from 16% to 35%, and intermanufacturer variability ranged from 22% to 61%.
Clinicians should consider treatment values of each individual transducer, regardless of the manufacturer. In addition, clinicians should scrutinize the power calibration and recalibration record of the transducer and adjust clinical settings as needed for the desired level of heating. Our data may aid in explaining the reported heating differences among transducers from different manufacturers. Stricter FDA standards regarding effective radiating area and total power are needed, and standards regulating SAI should be established.
临床医生常使用空间平均强度（SAI）来衡量治疗性超声剂量，但SAI测量值并未直接受美国食品药品监督管理局（FDA）标准的监管。当前FDA指南允许SAI值的最小到最大范围可能在50%至150%之间，这可能导致临床结果的变异性。
测量描述超声换能器的临床值，并确定当换能器在3MHz频率下工作时，有效辐射面积、功率和SAI在制造商内部和制造商之间的变异程度。
对该准实验设计采用描述性和干预性方法。
测量实验室。
从6个不同制造商处购买了66个5平方厘米的超声换能器。
所有换能器均经过校准，然后使用标准化测量技术进行评估；SAI进行了归一化处理，以考虑有效辐射面积的变异性，得出归一化空间平均强度（nSAI）。
有效辐射面积、功率和nSAI。
除Omnisound外（P = 0.534），所有制造商报告的和测量的有效辐射面积值之间均存在差异（P < 0.001）。所有换能器的功率均在FDA指南范围内（±20%）。Chattanooga（0.85±0.05W/cm²）的nSAI低于所有其他在3MHz频率下工作的制造商（P < 0.05）。SAI在制造商内部的变异范围为16%至35%，在制造商之间的变异范围为22%至61%。
临床医生应考虑每个换能器的治疗值，而不论其制造商如何。此外，临床医生应仔细检查换能器的功率校准和重新校准记录，并根据所需的加热水平进行必要的临床设置调整。我们的数据可能有助于解释不同制造商的换能器之间所报告的加热差异。需要更严格的FDA关于有效辐射面积和总功率的标准，并且应制定规范SAI的标准。
