Multiangle Long-Axis Lateral Illumination Photoacoustic Imaging Using Linear Array Transducer

Abstract

Photoacoustic imaging (PAI) combines optical contrast with ultrasound spatial resolution and can be obtained up to a depth of a few centimeters. Hand-held PAI systems using linear array usually operate in reflection mode using a dark-field illumination scheme, where the optical fiber output is attached to both sides of the elevation plane (short-axis) of the transducer. More recently, bright-field strategies where the optical illumination is coaxial with acoustic detection have been proposed to overcome some limitations of the standard dark-field approach. In this paper, a novel multiangle long-axis lateral illumination is proposed. Monte Carlo simulations were conducted to evaluate light delivery for three different illumination schemes: bright-field, standard dark-field, and long-axis lateral illumination. Long-axis lateral illumination showed remarkable improvement in light delivery for targets with a width smaller than the transducer lateral dimension. A prototype was developed to experimentally demonstrate the feasibility of the proposed approach. In this device, the fiber bundle terminal ends are attached to both sides of the transducer’s long-axis and the illumination angle of each fiber bundle can be independently controlled. The final PA image is obtained by the coherent sum of subframes acquired using different angles. The prototype was experimentally evaluated by taking images from a phantom, a mouse abdomen, forearm, and index finger of a volunteer. The system provided light delivery enhancement taking advantage of the geometry of the target, achieving sufficient signal-to-noise ratio at clinically relevant depths.

Dual-Modal Photoacoustic Imaging and Optical Coherence Tomography [Review]

“…In addition, custom transducers and new materials have been explored to develop different illumination geometries and improve the quality of the PA image [173,174]. However, these methods require significant modification of the system and cannot be readily integrated into standard clinical scanners [175].…”

Photoacoustic imaging as a highly efficient and precise imaging strategy for the evaluation of brain diseases

“…According to the anatomy of the target sample, commonly configured US transducers can be divided into three categories: circular (47,48), spherical (49), and planar geometry (50). These transducers have been implemented for imaging in both smallanimals and humans (40)(41)(42)(43), and are shown in Figure 1B.…”

“…Planar array-based PACT can be implemented by taking advantage of commercial linear acoustic transducer arrays (43). Because of their cost-effectiveness, hand-held probes, and co-registered PA/US imaging characterization, the linear scanner arrays have been widely applied in PACT with much higher clinical availability than circular or spherical detectors.…”

Biomedical Photoacoustic Imaging and Sensing Using Affordable Resources

“…Conventionally, hand-held linear-array-based PA imaging systems operate in the reflection mode using a dark-field illumination scheme, where the illumination is on both sides of the elevation plane (short-axis) of the US probe. Uliana et al reported and demonstrated a novel multiangle long-axis lateral illumination approach with several advantages [ 9 ]. Phantom, animal, and human in vivo results in this work demonstrate a remarkable improvement of the new illumination approach in light delivery for targets with a width smaller than the transducer’s lateral dimension.…”