Title
Time to threshold (TT), a safety parameter for heating by diagnostic ultrasound
Author
Lubbers, J.
Hekkenberg, R.T.
Bezemer, R.A.
TNO Preventie en Gezondheid
Publication year
2003
Abstract
Activities in the standardisation of medical ultrasonic imaging and monitoring devices have been undertaken to ensure the safe application and to provide the user with tools to perform risk-to-benefit analysis. Internationally, agreement has not been reached to implement a system based on a physical quantity such as temperature rise. Therefore, recently, the IEC Standard 60601-2-37 has adopted the thermal index (TI) as a safety parameter. TI indicates conditions that are more likely than others to produce thermal effects. The models used to calculate TI are based on the equilibrium temperature rise for a stationary transducer. Ultrasound (US) is often applied during a short time at one place. To characterise the situation before equilibrium is reached, this study proposes a new parameter: TT (time to threshold). TT indicates the time after which a threshold temperature rise is exceeded. TT is calculated for some tissue models to illustrate the meaning of TT. TT indicates how long one piece of tissue can be insonated safely, provided the safe threshold is known. Using TT, higher intensities can be applied safely during a limited time. This paper illustrates the effects of short insonation times and the influence of the beam diameter. Questions that are critical to the introduction of TT as a safety parameter are discussed. © 2003 World Federation for Ultrasound in Medicine & Biology.
Subject
Biology
Heating
Safety
Temperature
Thermal index
TI
Time to threshold
TT
Ultrasound
Codes (standards)
Diagnosis
High temperature effects
Tissue
Transducers
Thermal index (TI)
Ultrasonic imaging
article
echography
equilibrium constant
heating
mathematical computing
priority journal
risk benefit analysis
safety
standardization
temperature
thermal analysis
time
Algorithms
Heat
Humans
Models, Biological
Risk Assessment
Safety Management
Temperature
Ultrasonography
To reference this document use:
http://resolver.tudelft.nl/uuid:fd8608db-9bd2-4a12-bbb8-dfd4ae25e3a3
DOI
https://doi.org/10.1016/s0301-5629(02)00790-1
TNO identifier
237080
ISSN
0301-5629
Source
Ultrasound in Medicine and Biology, 29 (5), 755-764
Document type
article