IEC\/TR 62799:2013(E), which is a technical report, provides background information for users of IEC 62359 to understand the relative merits of several of the potential replacements for the thermal index as described in IEC 60601-2-37 and IEC 62359. The report discusses parameters related to thermal aspects of diagnostic ultrasonic fields; and methods for the determination of an exposure parameter relating to temperature rise in theoretical tissue-equivalent models, resulting from absorption of ultrasound. The report is intended to be used: – by those involved in the development and maintenance of IEC 62359; – manufacturers of medical electrical equipment for risk assessment; – and health care regulatory authorities, test houses and other organizations responsible for implementing standards for medical electrical equipment.<\/p>\n
| PDF Pages<\/th>\n | PDF Title<\/th>\n<\/tr>\n | ||||||
|---|---|---|---|---|---|---|---|
| 4<\/td>\n | CONTENTS <\/td>\n<\/tr>\n | ||||||
| 6<\/td>\n | FOREWORD <\/td>\n<\/tr>\n | ||||||
| 8<\/td>\n | 1 Scope 2 Normative references 3 Terms and definitions <\/td>\n<\/tr>\n | ||||||
| 12<\/td>\n | 4 Background 4.1 General <\/td>\n<\/tr>\n | ||||||
| 13<\/td>\n | 4.2 Limitations of the existing standard 4.2.1 Linear display <\/td>\n<\/tr>\n | ||||||
| 14<\/td>\n | 4.2.2 Equilibrium temperature 4.2.3 Tissue parameters 4.2.4 Transducer self-heating 4.2.5 Safety limits <\/td>\n<\/tr>\n | ||||||
| 15<\/td>\n | 5 Options for improvement of the existing standard 5.1 General 5.2 Exponential display of the current TI 5.2.1 Theory <\/td>\n<\/tr>\n | ||||||
| 17<\/td>\n | 5.2.2 Illustrative results for the new thermal index display 5.2.3 Advantages of the new display Figures Figure 1 \u2013 Comparison of the values of thermal index that would be displayed under the proposed definition, TInew, with that displayed currently, TIcur Figure 2 \u2013 Expanded view of the comparison of Figure 1 for smaller values of TIcur <\/td>\n<\/tr>\n | ||||||
| 18<\/td>\n | 5.2.4 Shortcomings of the new display 5.3 Replacement of the TI with the thermally equivalent time index (TETI) 5.3.1 Theory <\/td>\n<\/tr>\n | ||||||
| 20<\/td>\n | Figure 3 \u2013 Thermal-equivalent core temperature elevations vs time <\/td>\n<\/tr>\n | ||||||
| 21<\/td>\n | Figure 4 \u2013 Temperature-time curve (solid line) that represents a conservative boundary for non-foetal exposure durations, particularly for exposure durations of less than 5 s <\/td>\n<\/tr>\n | ||||||
| 22<\/td>\n | 5.3.2 Illustrative results for the TETI Tables Table 1 \u2013 Thermally equivalent time thresholds for chronic damage in various tissues, t43; see [21]. <\/td>\n<\/tr>\n | ||||||
| 23<\/td>\n | Figure 5 \u2013 Thermally equivalent time index (solid curves) vs foetal exposure duration for TI = 1, 2, 3 and 4 <\/td>\n<\/tr>\n | ||||||
| 24<\/td>\n | 5.3.3 Advantages of the TETI 5.3.4 Shortcomings of the TETI Table 2 \u2013 Foetal exposure durations for a thermally equivalent time index value of 1 Table 3 \u2013 Non-foetal exposure durations for a thermally equivalent time index value of 1 <\/td>\n<\/tr>\n | ||||||
| 25<\/td>\n | 5.4 Replacement of the TI with the time to threshold (TT) 5.4.1 Theory <\/td>\n<\/tr>\n | ||||||
| 26<\/td>\n | 5.4.2 Illustrative results for the TT <\/td>\n<\/tr>\n | ||||||
| 27<\/td>\n | Figure 6 \u2013 Temperature rise for distance (z0 > 3 cm) for four models \nas a function of US exposure time <\/td>\n<\/tr>\n | ||||||
| 28<\/td>\n | Figure 7 \u2013 Relation between TT (time to threshold) and power parameters that give a \ntemperature rise of \u0394Tthr = 4 \u00b0C <\/td>\n<\/tr>\n | ||||||
| 29<\/td>\n | 5.4.3 Advantages of the TT 5.4.4 Shortcomings of the TT Figure 8 \u2013 The ratio of temperature rise to acoustic absorption coefficient, \u0394T\/\u03bc , vs exposure duration for the non-scanning soft tissue model with Pa = 100 mW <\/td>\n<\/tr>\n | ||||||
| 30<\/td>\n | 5.5 Replacement of the TI with the safe use time (SUT) 5.5.1 Theory <\/td>\n<\/tr>\n | ||||||
| 31<\/td>\n | Figure 9 \u2013 A typical example of temperature rise due to diagnostic ultrasound <\/td>\n<\/tr>\n | ||||||
| 32<\/td>\n | 5.5.2 Illustrative results for the SUT <\/td>\n<\/tr>\n | ||||||
| 33<\/td>\n | Figure 10 \u2013 Values of temperature rise as a function of insonation time <\/td>\n<\/tr>\n | ||||||
| 34<\/td>\n | Figure 11 \u2013 The thermal load as a function of time and f-number Table 4 \u2013 SUT values when including and ignoring the contribution of \ntemperatures lower than \u0394Tmax for the four exposure conditions and \nthe corresponding values of \u0394Tmax <\/td>\n<\/tr>\n | ||||||
| 35<\/td>\n | 5.5.3 Advantages of the SUT 5.5.4 Shortcomings of the SUT Table 5 \u2013 Values of W, Wa, and \u0394Tmax for the case of SUT = 500 s. <\/td>\n<\/tr>\n | ||||||
| 36<\/td>\n | 5.6 Replacement of the TI with the thermally equivalent time displayed (TETD) 5.6.1 Theory <\/td>\n<\/tr>\n | ||||||
| 37<\/td>\n | 5.6.2 Illustrative results for the TETD <\/td>\n<\/tr>\n | ||||||
| 38<\/td>\n | Figure 12 \u2013 A comparison of thermally equivalent times (t43) for the temperature profiles shown in Figure 6 <\/td>\n<\/tr>\n | ||||||
| 39<\/td>\n | Figure 13 \u2013 Probability of birth defect or kidney necrosis as a function of thermally equivalent time (t43) <\/td>\n<\/tr>\n | ||||||
| 40<\/td>\n | 5.6.3 Advantages of the TETD Figure 14 \u2013 Probabilities of kidney necrosis estimated for the thermally equivalent times (t43) shown in Figure 12 <\/td>\n<\/tr>\n | ||||||
| 41<\/td>\n | 5.6.4 Shortcomings of the TETD Figure 15 \u2013 Probabilities of birth defect estimated for the thermallyequivalent times (t43) shown in Figure 12 <\/td>\n<\/tr>\n | ||||||
| 42<\/td>\n | 6 Summary Table 6 \u2013 Comparison of significant characteristics of the possible replacements for the TI. <\/td>\n<\/tr>\n | ||||||
| 43<\/td>\n | 7 Recommendations 7.1 General 7.2 Thermally equivalent time index 7.3 Other models <\/td>\n<\/tr>\n | ||||||
| 44<\/td>\n | Bibliography <\/td>\n<\/tr>\n<\/table>\n","protected":false},"excerpt":{"rendered":" Models for evaluation of thermal hazard in medical diagnostic ultrasonic fields<\/b><\/p>\n |