Time-resolved radiation beam profiles in water obtained by ultrasonic tomography

Published

December 31, 2010

Author(s)

Eugene Malyarenko, Joseph Heyman, Heather H. Chen-Mayer, Ronald Tosh

Abstract

This paper presents a practical ultrasonic system for near real-time imaging of spatial temperature distributions in water caused by absorption of radiation. Initial testing with radiation from a highly attenuated infrared lamp demonstrates that the system is able to map sub-milliKelvin temperature changes, thus making it suitable for characterizing dose profiles of therapy-level ionizing radiation beams. The system uses a fan-beam tomographic reconstruction algorithm to invert time-of-flight data derived from ultrasonic pulses produced and detected by a circular array of transducers immersed in water. Temperature dependence of the speed of sound in water permits the conversion of these measured two-dimensional velocity distributions into temperature distributions that indicate the absorbed radiation dose. The laboratory prototype, based on a 128-element transducer array, is used to acquire temperature maps of a 230 mm x 230 mm area every 4 seconds with sub-milliKelvin resolution in temperature and about 5 mm resolution in space. Earlier measurements with a single-channel version of this prototype suggest refinements in signal-conditioning electronics and signal-processing algorithms that would allow the present instrument to resolve temperature changes as low as a few microKelvin. Possible applications include real-time intensity profiling of radiation beams and three-dimensional characterization of the absorbed dose.

Citation

Medical Physics

Volume

47

Pub Type

Journals

Download Paper

Local Download

Keywords

absorbed dose, standard reference dosimetry, ultrasonic tomography, water calorimeters

Citation

Malyarenko, E. , Heyman, J. , Chen-Mayer, H. and Tosh, R. (2010), Time-resolved radiation beam profiles in water obtained by ultrasonic tomography, Medical Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=902937 (Accessed October 8, 2025)