Premium
The effect of electronically steering a phased array ultrasound transducer on near‐field tissue heating
Author(s) -
Payne Allison,
Vyas Urvi,
Todd Nick,
Bever Joshua,
Christensen Douglas A.,
Parker Dennis L.
Publication year - 2011
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3618729
Subject(s) - transducer , phased array , beam steering , materials science , acoustics , imaging phantom , main lobe , clutter , beam (structure) , optics , raster scan , side lobe , physics , computer science , engineering , electrical engineering , radar , telecommunications , antenna (radio)
Purpose: This study presents the results obtained from both simulation and experimental techniques that show the effect of mechanically or electronically steering a phased array transducer on proximal tissue heating. Methods: The thermal response of a nine‐position raster and a 16‐mm diameter circle scanning trajectory executed through both electronic and mechanical scanning was evaluated in computer simulations and experimentally in a homogeneous tissue‐mimicking phantom. Simulations were performed using power deposition maps obtained from the hybrid angular spectrum (HAS) method and applying a finite‐difference approximation of the Pennes' bioheat transfer equation for the experimentally used transducer and also for a fully sampled transducer to demonstrate the effect of acoustic window, ultrasound beam overlap and grating lobe clutter on near‐field heating. Results: Both simulation and experimental results show that electronically steering the ultrasound beam for the two trajectories using the 256‐element phased array significantly increases the thermal dose deposited in the near‐field tissues when compared with the same treatment executed through mechanical steering only. In addition, the individual contributions of both beam overlap and grating lobe clutter to the near‐field thermal effects were determined through comparing the simulated ultrasound beam patterns and resulting temperature fields from mechanically and electronically steered trajectories using the 256‐randomized element phased array transducer to an electronically steered trajectory using a fully sampled transducer with 40 401 phase‐adjusted sample points. Conclusions: Three distinctly different three distinctly different transducers were simulated to analyze the tradeoffs of selected transducer design parameters on near‐field heating. Careful consideration of design tradeoffs and accurate patient treatment planning combined with thorough monitoring of the near‐field tissue temperature will help to ensure patient safety during an MRgHIFU treatment.