Multi-Focus Beamforming for Thermal Strain Imaging Using a Single Ultrasound Linear Array Transducer.
Ultrasound-induced thermal strain imaging (TSI) has been used successfully to identify lipid- and water-based tissues in atherosclerotic plaques in some research settings. However, TSI faces several challenges to be realized in clinics. These challenges include motion artifacts and displacement tracking accuracy, as well as limited heating capability, which contributes to low thermal strain signal-to-noise ratio, and a limited field of view. Our goal was to address the challenge in heating tissue in TSI. Current TSI systems use separate heating and imaging transducers, which require physical alignment of the heating and imaging beams and result in a bulky setup that limits in vivo operation. We evaluated a new design for heating beams that can be implemented on a linear array imaging transducer and can provide improved heating area and efficiency as compared with previous implementations. The heating beams designed were implemented with a clinical linear array imaging transducer connected to a research ultrasound platform. In vitro experiments using tissue-mimicking phantoms with no blood flow revealed that the new design resulted in an effective heating area of approximately 0.85 cm2and a 0.3°C temperature rise in 2 s of heating, which compared well with in silico finite-element simulations. With the new heating beams, TSI was found to be able to detect a lipid-mimicking rubber inclusion with a diameter of 1 cm from the water-based gelatin background, with a strain contrast of 2.3 (+0.14% strain in the rubber inclusion and -0.06% strain in the gelatin background). Lastly, lipid-based tissue in a 1-cm-diameter human carotid endarterectomy (CEA) sample was identified in good agreement with histology.
Center for Ultrasound Molecular Imaging and Therapeutics, Department of Medicine, University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center (UPMC), Pittsburgh, Pennsylvania, USA.
Man M
MM
Nguyen
Center for Ultrasound Molecular Imaging and Therapeutics, Department of Medicine, University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center (UPMC), Pittsburgh, Pennsylvania, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Medical Scientist Training Program, University of Pittsburgh and Carnegie Mellon University, Pittsburgh, Pennsylvania, USA.
Xuan
X
Ding
Heart and Vascular Institute, University of Pittsburgh School of Medicine and UPMC, Pittsburgh, Pennsylvania, USA.
Steven A
SA
Leers
Center for Ultrasound Molecular Imaging and Therapeutics, Department of Medicine, University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center (UPMC), Pittsburgh, Pennsylvania, USA; Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Heart and Vascular Institute, University of Pittsburgh School of Medicine and UPMC, Pittsburgh, Pennsylvania, USA; McGowan Institute of Regenerative Medicine, University of Pittsburgh and UPMC, Pittsburgh, Pennsylvania, USA. Electronic address: kangkim@upmc.edu.
Kang
K
Kim
D002339:Carotid Arteries / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D055119:Elastic Modulus / Q000502:physiology*; D054459:Elasticity Imaging Techniques / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D013817:Thermography / Q000295:instrumentation*; D014159:Transducers; D000069453:Ultrasonic Waves
Apodization; Beamforming; Carotid plaque characterization; Linear array; Multiple foci; Thermal strain imaging