Remote temperature estimation in intravascular photoacoustic imaging

Area of Science:

• Biomedical Optics
• Medical Imaging
• Ultrasound Technology

Background:

• Intravascular photoacoustic (IVPA) imaging detects laser-induced acoustic waves in arteries.
• Established safety standards for IVPA laser use are lacking.
• Monitoring temperature changes is crucial for IVPA thermal safety.

Purpose of the Study:

• To develop and validate an ultrasound-based method for estimating laser-induced temperature increases during IVPA imaging.
• To assess the thermal safety of IVPA imaging in phantom and ex vivo arterial tissues.

Main Methods:

• Utilized intravascular ultrasound (IVUS)-based strain measurements to estimate temperature increases.
• Employed a cross-correlation-based time delay estimator to assess temperature-induced strains.
• Applied the technique to a phantom model and ex vivo rabbit aorta samples.

Main Results:

• IVUS measurements showed temperature increases of 0.7°C, 2.9°C, and 5.0°C at laser radiant energies of 30, 60, and 85 mJ/cm², respectively.
• In rabbit aorta, a 1.1°C temperature elevation was observed at 60 mJ/cm², with less than 1°C at lower energies.
• Arrhenius thermal damage model analysis indicated no thermal injury.

Conclusions:

• The developed ultrasound technique effectively monitors temperature during IVPA imaging.
• IVPA imaging, at tested energy levels, appears safe for arterial tissues with no observed thermal injury.
• This method supports the establishment of safety standards for IVPA procedures.