Surface areas in ultrasound therapy. Evaluation of seven methods for measuring the treated skin area in physiotherapeutic application of ultrasound

Abstract

Recent articles on ultrasound (US) do not contain information about precise dosage, thus risking a non-valid conclusion of possible effects. To ensure safer standards in treatment-time, the present study compared 7 methods for the calculation of areas. Measurement by eye had a median relative difference (MRD) from the true reading of 22% (lower quartile (l.q.) = -14%, upper quartile(u.q) = -+46%), with large intraindividual variation, the span of MRD being -46% to +53%. Measuring with the transducer showed a systematic error: MRD was -48% (l.q. = -55%, u.q.= -35%), which is unacceptable. Areas were measured with satisfactory accuracy with 5 methods that require little training and use accessories some of which are inexpensive. Plates with ellipses of known size had a MRD of 0.1%, (l.q. = -3%, u.q. = +2%), while rulers showed MRD of -2%, (l.q. = -0.6%, u.q. = +5%) both on selected material. The most accurate and versatile instruments were a planimeter (MRD = -0.1%; l.q. = -0.6%; u.q. = +0.5%), a Mettler weighing apparatus (MRD = 3%; l.q. = 2%; u.q. = 6%), and a digitizer (MRD = -0.1%; l.q. = -0.4%; u.q. = +0.3%).