Photoacoustic microscopy: Seeing More with a Needle-Shaped Laser

Good news! This seems to be a considerable improvement!

"... However, one limitation of high-resolution (i.e., optical-resolution) PAM has been its narrow depth of field, meaning that it can only focus on a thin layer (approximately 30 micrometers, or about the length of one skin cell, with one to two micrometers of resolution) of tissue at a time. To see something above or below the plane that the device is viewing, it needs to refocus above or below that plane. ...
developed a new variant of PAM called needle-shaped beam photoacoustic microscopy, or NB-PAM, which that has a depth of field nearly 14 times greater than what was achievable before. This means NB-PAM can create 3-D imagery of samples without refocusing and better image samples with uneven surfaces. ..."

From the abstract:

"Optical-resolution photoacoustic microscopy can visualize wavelength-dependent optical absorption at the cellular level. However, this technique suffers from a limited depth of field due to the tight focus of the optical excitation beam, making it challenging to acquire high-resolution images of samples with uneven surfaces or high-quality volumetric images without z scanning. To overcome this limitation, we propose needle-shaped beam photoacoustic microscopy, which can extend the depth of field to around a 28-fold Rayleigh length via customized diffractive optical elements. These diffractive optical elements generate a needle-shaped beam with a well-maintained beam diameter, a uniform axial intensity distribution and negligible sidelobes. The advantage of using needle-shaped beam photoacoustic microscopy is demonstrated via both histology-like imaging of fresh slide-free organs using a 266 nm laser and in vivo mouse-brain vasculature imaging using a 532 nm laser. This approach provides new perspectives for slide-free intraoperative pathological imaging and in vivo organ-level imaging."

Seeing More with a Needle-Shaped Laser | www.caltech.edu Photoacoustic microscopy (PAM) is a relatively new imaging technique that uses laser light to induce ultrasonic vibrations in tissue. These ultrasonic vibrations, along with a computer that processes them, can then be used to create an image of the structures of the tissue in much the same way ultrasound imaging works.

Optical-resolution photoacoustic microscopy with a needle-shaped beam (no public access)

Traditional photoacoustic microscopy (PAM) (left) compared to needle-shaped photoacoustic microscopy (NB-PAM) (right). In traditional PAM, only objects near the focal point of the laser are imaged sharply. In NB-PAM, the longer, narrower beam allows objects over a greater range of depth to be clearly imaged.