Sentinel lymph node biopsy (SLNb) plays an important role in determining whether breast cancer has metastasized. The current standard method for SLNb is to use radioactive material and blue dye to detect sentinel lymph nodes (SLNs). However, this method has limitations such as radiation exposure, radioactive material disposal, and subjective evident interpretation of the blue dye. To overcome these limitations, we developed a non-radioactive detector, the photoacoustic finder (PAF), which utilizes the photoacoustic (PA) signal from the SLN's blue dye to identify SLNs instead of radioactive material. For evaluating the PAF, in this ex vivo clinical study, we compared the detection rate of standard SLN detection methods and PAF in resected SLNs from breast cancer patients. A total of 92 breast cancer patients were enrolled in the study, and 164 SLNs resected from the patients were analyzed. The detection rate was similar for gamma probe (85%, 139 of 164 SLNs) and PAF (85%, 139 of 164 SLNs), while the detection rate using blue dye visual inspection was 74% (122 of 164 SLNs), which was lower than gamma probe and PAF. These results affirm the validity of PAF as a non-radioactive alternative for detecting SLNs, indicating the potential feasibility of non-radioactive SLNb in future applications.
Optical resolution photoacoustic microscopy (OR-PAM) provides high optical contrast and lateral resolution. However, the resolution of a typical OR-PAM using an objective lens is limited to not exceeding Abbe's optical diffraction limit. In this study, a lensless shear force scanning PAM is presented. Instead of a lens, the system uses an imaging probe that combines a non-coated tapered fiber with a quartz tuning fork (QTF). A shear force feedback mechanism is used to maintain a tens of nm (near-field) distance between the fiber tip and the sample. With the system, PA signals generated in the near field of a gold sputtered glass sample were successfully acquired. We also performed 2D PA scanning experiments and obtained PA images of gold cube samples with high lateral resolution. This study demonstrates the existence of a near field PA signal and shows its potential for super-resolution scanning PAM.
Excessive bleaching can cause changes in the amino acid composition as well as the surface structure of the hair. Thus, proper hair bleaching and quantification is important to achieve cosmetic purposes while maintaining the healthy properties of the hair. Here, we propose a novel method to quantify the degree of hair bleaching at the nanoscale resolution using a photoactivated atomic force microscopy (pAFM). We demonstrated that acquiring and quantifying pAFM images of hair according to bleaching time can help determine the appropriate bleaching time. We believe that this result will help to prevent unwanted hair damage due to bleaching.
Peripheral vascular disease (PVD) is a narrowing of the arteries in the extremities that might result in amputation when left untreated. The conventional ways to diagnose PVD are vascular imaging techniques such as ultrasound (US) Doppler, computed tomography (CT) angiography, and magnetic resonance angiography, which generally can only visualize large vessels or require contrast agents. Photoacoustic (PA) imaging could be a promising agent-free, highresolution modality to visualize vessels and be applied in various clinical studies. We have previously demonstrated an agent-free multi-structural photoacoustic (PA) and US peripheral angiography technique using contour scanning. To reduce the effect of the optical fluence, we compensated the PA images using the background PA signals that represent optical attenuation in the tissue. To evaluate its capability to provide functional information of the vasculature, we demonstrated an intentional blood flow occlusion with a pressure cuff and observed the changes in the quantification metrics. From the experiments, we confirmed the potential of the technique for providing a diagnostic evaluation of the peripheral vasculature.
We developed a handheld photoacoustic signal detector for sentinel lymph node (SLN) localization. The detector consists of a solid-state dye laser and a transparent ultrasound transducer (TUT). The TUT was designed as a focused-type. The TUT had an 8 MHz center frequency with a 30% bandwidth. Using the detector, we confirmed photoacoustic signals in a tube filled with methylene blue (MB) below 10-mm thick chicken tissues. We successfully performed in vivo photoacoustic detection for MB injected SLN localization and subcutaneously injected melanoma assessments. We believe that our detector will play an effective role in SLN localization and biopsy.
We developed a photoacoustic imaging (PAI) system based on a solid-state dye laser. Using the system, PA images of a tube filled with methylene blue (MB) below 3.9 cm chicken tissue were successfully obtained. After injecting MB into a rat, MB dyed sentinel lymph node (SLN) under chicken tissue was well described. In addition, it was confirmed the change in PA amplitude of the SLN over time in the PA images. Additionally, lymph vessels, SLN, and blood vessels were also successfully identified in multispectral PA images. These results demonstrate the clinical potential of the system in SLN detection.
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