Hemispherical photoacoustic imaging of myocardial infarction: in vivo detection and monitoring.

OBJECTIVES

This study aimed to demonstrate the capacity for noninvasive localisation and characterisation of myocardial infarction (MI) in vivo using a hemispherical photoacoustic imaging (PAI) system. MI remains a leading cause of morbidity and mortality worldwide. To enable optimal treatment of patients, timely and accurate diagnosis and longitudinal monitoring is critical.

METHODS

Ischaemia was induced in Balb/c mice by ligation of the left anterior descending artery. The hemispherical PAI system, equipped with 128 ultrasonic transducers spirally distributed on the surface, along with parallel data acquisition, was applied for imaging of the mouse heart.

RESULTS

Our study showed that hemispherical PAI can delineate thoracic vessels and the morphology of the entire heart. Longitudinal PAI images revealed gradual expansion of the infarcted area along with necrosis and fibrosis, which were quantitatively validated by triphenyltetrazolium chloride staining. After MI modelling, the photoacoustic (PA) signal intensity decreased by 399.1 ± 56.3 (p < 0.001), a ~2.5-fold reduction compared to that of healthy cardiac tissue. The calculated size of the enlarged heart, 10.4 ± 6.0 mm (p < 0.001), represents an increase of ~18% versus that of a healthy heart.

CONCLUSIONS

PAI enables MI diagnosis and injury localisation with its capabilities for both deep organ imaging and lesion region differentiation.

KEY POINTS

• Photoacoustic imaging (PAI), combining optical absorption and ultrasonic resolution, can delineate cardiac anatomy. • PAI can diagnose myocardial infarction lesions with 10 mm imaging depth in vivo. • Quantified results are in excellent agreement with enzyme and histological examinations. • PAI can serve as a complementary modality to SPECT and ultrasound imaging. • This study will encourage further PAI development for clinical use.