Percutaneous entry is the initial and most important part of percutaneous nephrolithotomy (PNL). Needle puncture directly into the fornix of a calyx is the safest route of percutaneous entry into the renal collecting system. When the pelvicalyceal system is not dilated, localization and puncture of the specific calyx may require special expertise. Ho:YAG laser lithotripsy was performed to carve a channel to allow the ureteroscope to be passed into the desired calyx occupied with stone. At this point, percutaneous antegrade access to the calyx of interest was obtained using a 21-gauge nephrostomy needle under ultrasonic guidance with a biopsy attachment. Vapor bubbles and fragmented calculi were visualized as hyperechoic moving particles like powder snow in the aimed calyx on the B-mode gray-scale ultrasound monitor during laser firing. The needle was safely inserted into the desired calyx. This novel technique of needle puncture to the renal calyx using laser-assisted ultrasound scanning (LAUS) method is safe and effective, even when the pelvicalyceal system is not dilated. Greater experience and comparison to standard technique are required to determine if this method will be a useful technique in the future.

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Ultrasound and optical medical imaging are both widely used in clinical medicine since they share common advantages: noninvasive, real-time and easy-to-use. On the other hand, considering their strong and weak points, optical imaging has merits of being able to visualize superficial structure with high resolution and contrast, and obtain biochemical data using fluorescence analysis and absorbance spectrum. However, optical imaging is unsuitable to the visualization of deep area due to strong scattering property of tissues. Ultrasound imaging can measure morphological and dynamical information of even deep area because ultrasound is easy to be focused and can penetrate deep into tissues. By integrating two medical imaging technologies and covering for each other’s weaknesses, it is expected to create novel modalities for advanced functional information. Photoacoustic imaging and ultrasound-modulated optical imaging are representative examples of optics-ultrasound integration technologies. Recently, research toward practical application of photoacoustic imaging has proceeded at a rapid rate. Here I give an outline of these technologies to be benefit to considering their future direction.

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Photoacoustic imaging based on optical absorption as a contrast mechanism is a promising imaging modality enabling depth-resolved diagnosis of tissue.In this paper, we report a newly developed prototype photoacoustic imaging system for real-time burn depth diagnosis.

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Photoacoustic imaging is a novel imaging technique which can offer a high contrast tomographic image with ultrasound like resolution in depth of centimeters. Additionally, it has been studied well as functional imaging modality using absorption spectra. In this report, the evaluation results of technical potential were shown as a hybrid imaging which combined morphological image and functional image. Finally, I described research trend and future expectation about medical applications of photoacoustic imaging.

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Recently, photoacoustic microscopy(PAM)has attracted attention to visualize deep structures in living tissues. However, it is difficult to improve the spatial resolution of PAM without using high-frequency components of photoacoustic waves, which are not suitable for deep imaging. To overcome this drawback, we developed two-photon absorption-induced photoacoustic microscopy(TP-PAM). The spatial resolution in TP-PAM is determined by two-photon absorption(TPA). The use of low-frequency ultrasonic components generated by TPA enables PAM to visualize deeper structures while preserving the high spatial resolution.

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Photoacoustic microscopy is being established not only for the in vivo imaging but for the in vitro cellular imaging. Especially, to obtain of the internal information of 3D cell culture cluster by using photoacoustic microscopy should be useful tools for in vitro imaging study. In this article, we summarize recent reports regarding to photoacoustic microscopy for cell imaging and future perspects.

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