High-resolution photoacoustic endoscope through beam self-cleaning in a graded index fiber

Abstract

Intravascular photoacoustic imaging can potentially improve the identification of lipid-laden atherosclerotic plaque. Most intravascular photoacoustic endoscopes use multimode fibers, which do not allow tight focusing of photons. Recent experiments on pulse propagation in multimode graded-index fibers have shown a nonlinear improvement in beam quality. Here, we harness this nonlinear phenomenon for fiber-delivery of nanosecond laser pulses. We built a photoacoustic catheter 1.4 mm outer diameter, offering a lateral resolution as fine as 30 μm within a depth range of 2.5 mm. Such resolution is one order of magnitude better than current multimode fiber-based intravascular photoacoustic catheters. At the same time, the delivered pulse energy can reach as high as 20 μJ, which is two orders of magnitude higher than that of an optical resolution photoacoustic endoscope built with a single mode fiber. These improvements are expected to promote the biomedical application of photoacoustic endoscopes which require both high resolution and high pulse energy.

Combined Ultrasound and Photoacoustic Image Guidance of Spinal Pedicle Cannulation Demonstrated With Intact ex vivo Specimens

“…The acoustic pressure is then received by an ultrasound probe, and beamforming is applied to create a photoacoustic image. Applications of photoacoustic imaging to surgical guidance include visualization of tool tips such as a neurosurgical drill tip [22], a needle tip [23]- [26], or a cardiac catheter tip [27], visualization of underlying structures such as blood vessels [28], and photoacoustic-based guidance during a range of surgeries, such as fetal surgeries [29], endonasal surgeries, [30]- [32], hysterectomy procedures [33], [34], and prostate surgeries [35]. The incorporation of robotics with teleoperated surgery [33] and robotic visual servoing [36], [37] has also been demonstrated.…”

Spatiotemporal Beam Self-cleaning for High-resolution Nonlinear Fluorescence Imaging With Multimode Fiber

“…For instance, MMFs may provide a solution to the data capacity bottleneck of optical communication links via spatial-division-multiplexing [1][2], and scale-up the output energy of fiber lasers sources [3][4][5][6]. Linear and nonlinear imaging in microscopy and endoscopy configurations [7][8] also provide an interesting application of MMFs. Several systems have already been proposed, which all require a careful control of multimode beam propagation [9][10].…”

“…In the recent experiment of photoacoustic endoscopy [8], the resolution improvement, obtained by replacing a step-index with a GRIN multimode fiber, was ascribed to the presence of spatial BSC [26][27][28][29][30][31][32][33][34]. However, the spatial reshaping of the pump beam as a function of the pump power was not proven.…”

GPU implementation of photoacoustic short-lag spatial coherence imaging for improved image-guided interventions

“…5,17,18 One or more optical fibers may be coupled to the tool, catheter, or needle tips to transmit the light pulses. 11,[19][20][21] Alternatively, a fiber or fiber bundle may be operated independently to provide photoacoustic-based anatomical guidance in the absence of surgical tools. [22][23][24] With the rise of robotic surgery, [25][26][27][28] we can reasonably envision photoacoustic system components that are robotically controlled to enable more successful surgeries and interventions.…”

“… 5 , 17 , 18 One or more optical fibers may be coupled to the tool, catheter, or needle tips to transmit the light pulses. 11 , 19 – 21 Alternatively, a fiber or fiber bundle may be operated independently to provide photoacoustic-based anatomical guidance in the absence of surgical tools. 22 – 24 …”