Recommended Maximum Scanning Times for Displayed Thermal Index (TI) Values

The following two tables contain recommended maximum times for the duration of an ultrasound exposure at a given setting of the Thermal Index (TI).These recommendations for maximum scanning time vs. TI are intended to provide reasonable assurance that an ultrasound examination can be conducted without risk of producing an adverse effect due to a thermal mechanism under any scanning conditions. If it is necessary to exceed the recommendations, the occurrence of an adverse thermal effect is still unlikely under most scanning situations due to mitigating factors such as transducer movement and perfusion. However, the principle of ALARA should be followed so that examination times are only as long as necessary to produce a useful diagnostic result. See the AIUM Statement “As Low as Reasonably Achievable (ALARA) Principle.”

Table1. Recommended maximum scanning time and TI ranges for obstetric (including gynecologic when pregnancy is possible), neonatal transcranial, and neonatal spinal examinations. For obstetric exams, monitoring the TIS is recommended up to 10 weeks from the last menstrual period (LMP) and TIB thereafter.

 

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TI range                                                Max Scanning Time

                                                                (minutes)

_____________________________________________________________

3.0 < TI                                                 Not recommended

2.5 < TI <=3.0                                                                       <1

2.0 < TI <= 2.5                                                                       <4

1.5 < TI <= 2.0                                                                       <15

1.0 < TI <= 1.5                                                                       <30

0.7 < TI <= 1.0                                                                       <60

TI <= 0.7                                                  No time limit

 

 

 

Table2. Recommended maximum scanning time and TI ranges for adult transcranial, general abdominal, peripheral vascular, neonatal (except head and spine), and other scanning examinations (except the eye).

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TI range                                                Max Scanning Time

                                                                (minutes)

___________________________________________________________

6.0 < TI                                                 Not recommended

5.0 < TI <= 6.0                                                       <0.25 (15 s)

4.0 < TI <= 5.0                                                                       <1

3.0 < TI <= 4.0                                                                       <4

2.5 < TI <= 3.0                                                                       <15

2.0 < TI <= 2.5                                                                       <60

1.5 < TI <= 2.0                                                                       <120

TI <= 1.5                                                  No time limit

 
  1. Harris GR, Church CC, Dalecki D, Ziskin MC, Bagley JE. Comparison of thermal safety practice guidelines for diagnostic ultrasound exposures.Ultrasound Med Biol 2016; 42:345-357.

Approved: 10/30/2016;

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