Yasufumi Asao

NOVEL FERROELECTRIC LIQUID CRYSTAL MODE FOR ACTIVE MATRIX LIQUID CRYSTAL DISPLAY USING CHOLESTERIC-CHIRAL SMECTIC C PHASE TRANSITION MATERIAL

We propose a novel ferroelectric liquid crystal (FLC) mode which is capable of gray-scale display with an active device such as a thin-film transistor (TFT). This technology is based on the monostable FLC mode, which is obtained from a material with cholesteric–chiral smectic C (Ch–SmC*) phase transition sequences and by applying a low DC voltage only near the phase transition temperature from Ch to SmC* for making the layer normal direction uniform. The electrooptical response of liquid crystal molecules under AC voltage is asymmetric between plus and minus voltages. It shows characteristics such as low spontaneous polarization (PS) value, short response time, small temperature dependence and wide tolerance to cell gap nonuniformity. Furthermore, we made TFT prototype panels using this mode. We could confirm this mode, realizing high-quality moving pictures without blurring based on the nonholding display and good color reproducibility based on the field sequential color method.

Model-Based Reconstruction Integrated With Fluence Compensation for Photoacoustic Tomography

Photoacoustic (PA) tomography (PAT) is a rapidly developing imaging modality that can provide high contrast and spatial-resolution images of light-absorption distribution in tissue. However, reconstruction of the absorption distribution is affected by nonuniform light fluence. This paper introduces a reconstruction method for reducing amplification of noise and artifacts in low-fluence regions. In this method, fluence compensation is integrated into model-based reconstruction, and the absorption distribution is iteratively updated. At each iteration, we calculate the residual between detected PA signals and the signals computed by a forward model using the initial pressure, which is the product of estimated voxel value and light fluence. By minimizing the residual, the reconstructed values converge to the true absorption distribution. In addition, we developed a matrix compression method for reducing memory requirements and accelerating reconstruction speed. The results of simulation and phantom experiments indicate that the proposed method provides a better contrast-to-noise ratio (CNR) in low-fluence regions. We expect that the capability of increasing imaging depth will broaden the clinical applications of PAT.

Visualization of tumor-related blood vessels in human breast by photoacoustic imaging system with a hemispherical detector array

Noninvasive measurement of the distribution and oxygenation state of hemoglobin (Hb) inside the tissue is strongly required to analyze the tumor-associated vasculatures. We developed a photoacoustic imaging (PAI) system with a hemispherical-shaped detector array (HDA). Here, we show that PAI system with HDA revealed finer vasculature, more detailed blood-vessel branching structures, and more detailed morphological vessel characteristics compared with MRI by the use of breast shape deformation of MRI to PAI and their fused image. Morphologically abnormal peritumoral blood vessel features, including centripetal photoacoustic signals and disruption or narrowing of vessel signals, were observed and intratumoral signals were detected by PAI in breast cancer tissues as a result of the clinical study of 22 malignant cases. Interestingly, it was also possible to analyze anticancer treatment-driven changes in vascular morphological features and function, such as improvement of intratumoral blood perfusion and relevant changes in intravascular hemoglobin saturation of oxygen. This clinical study indicated that PAI appears to be a promising tool for noninvasive analysis of human blood vessels and may contribute to improve cancer diagnosis.

Clinical Report on the First Prototype of a Photoacoustic Tomography System with Dual Illumination for Breast Cancer Imaging.

Photoacoustic tomography is a recently developed imaging modality that can provide high spatial-resolution images of hemoglobin distribution in tissues such as the breast. Because breast cancer is an angiogenesis-dependent type of malignancy, we evaluated the clinical acceptability of breast tissue images produced using our first prototype photoacoustic mammography (PAM) system in patients with known cancer. Post-excisionally, histological sections of the tumors were stained immunohistochemically (IHC) for CD31 (an endothelial marker) and carbonic anhydrase IX (CAIX) (a marker of hypoxia). Whole-slide scanning and image analyses were used to evaluate the tumor microvessel distribution pattern and to calculate the total vascular perimeter (TVP)/area for each lesion. In this clinical study, 42 lesions were primarily scanned using PAM preoperatively, three of which were reported to be benign and were excluded from statistical analysis. Images were produced for 29 out of 39 cancers (visibility rate = 74.4%) at the median depth of 26.5 (3.25–51.2) mm. Age, menopausal status, body mass index, history of neoadjuvant treatment, clinical stage and histological tumor angiogenesis markers did not seem to affect the visibility. The oxygen saturation level in all of the measured lesions was lower than in the subcutaneous counterpart vessels (Wilcoxon test, p value<0.001), as well as in the counterpart contralateral normal breast region of interest (ROI) (Wilcoxon test, p value = 0.001). Although the oxygen saturation level was not statistically significant between CAIX-positive vs. -negative cases, lesional TVP/area showed a positive correlation with the oxygen saturation level only in the group that had received therapy before PAM. In conclusion, the vascular and oxygenation data obtained by PAM have great potential for identifying functional features of breast tumors.

Photoacoustic mammography capable of simultaneously acquiring photoacoustic and ultrasound images

Abstract. We have constructed a prototype photoacoustic mammography system (PAM-02) capable of simultaneously acquiring photoacoustic (PA) and ultrasound (US) images. Each PA, US, and fused PA/US image can be acquired over a wide area of the breast using the scanning module of a US transducer, a PA detector, and optical prisms. The resolution of the PA images exhibits improvement from 2 to 1 mm compared to images acquired using our previous prototype. The maximum scan area of PAM-02 is 90 mm along the horizontal axis and 150 mm along the vertical axis. In a phantom experiment, the available depth was at least 45 mm. A representative example of the application of the PAM-02 prototype in clinical research at Kyoto University is presented and shows S-factor images, which are considered an approximation parameter related to hemoglobin saturation of tumor-related blood vessels. We confirmed the applicability of the system for anatomical and biological research.

Label-free photoacoustic imaging of human palmar vessels: a structural morphological analysis

We analysed the vascular morphology of the palm using a photoacoustic tomography (PAT) instrument with a hemispherical detector array. The three-dimensional (3D) morphology of blood vessels was determined noninvasively. Overall, 12 females and 11 males were recruited as healthy volunteers. Their ages were distributed almost evenly from 22 to 59 years. In all cases, many vascular networks were observed just beneath the skin and were determined to be veins anatomically. To analyse the major arteries, the layer containing the subcutaneous venous network was removed from the image. The analysis focused on the common and proper palmar digital arteries. We used the curvature of these arteries as a parameter to analyse their morphologies. There was no significant difference in the curvature between genders when comparing the subjects as a whole. The blood vessel curvature increased with age. Good agreement was found between the 3D numerical analysis results and the subjective evaluation of the two-dimensional (2D) projection image. The PAT system enabled visualization of the 3D features of blood vessels in the palm and noninvasive analysis of arterial tortuousness.

Adaptive and quantitative reconstruction algorithm for photoacoustic tomography

Photoacoustic (PA) tomography is a rapidly developing imaging modality which can provide high contrast and spatial-resolution images of light absorption distribution in tissue. However, the quantitative reconstruction of absorption distribution is still a challenge. In this study, we propose an adaptive and quantitative reconstruction algorithm for reducing amplification of noises and artifacts in deep position due to light fluence compensation. In this method, the quantitative processing is integrated into the iterative reconstruction, and absorption coefficient distribution is iteratively updated. At each iteration step, the residual is calculated from detected PA signals and the signals calculated from a forward model by using the initial pressure which is calculated from the production of voxel value and the light fluence. By minimizing the residual, the reconstructed values are converged to the true absorption coefficient distributions. Since this method uses a global optimized compensation, better CNR can be obtained. The results of simulation and phantom experiment indicate that the proposed method provide better CNR at deep region. We expect that the capability of increasing imaging depth will broaden clinical applications.

34.3: Quasi- and Analog-Full-Color Displaying Methods with High Light Efficiency in Super-High-Resolution LCDs

A new coloring method of LCD (liquid crystal display) using the hybrid structure of CF (color filter) method and the interference coloration of ECB (electrically controlled birefringence) effect is presented. One unit pixel is divided into at least two sub-pixels, and the one sub-pixel is equipped with a green CF and the other one a magenta CF. As for the green coloration of the highest luminosity property, a green CF is used in order to display the analogue gray scale. The interference coloration of ECB effect with a magenta CF is used for red and blue binary coloration as well as analogue gray scale of the magenta color. Monochrome gray scale can be realized by the additive color mixing of green and magenta sub-pixels. The VA (vertical alignment) mode is adopted for suppressing the temperature dependence of the optical retardation. We can achieve much better light efficiency than that of the conventional color LCDs with both an RGB-CF and a polarizer. This mode has the features of quasi-full color and wide color space for red and blue color by the subtractive color mixing effect between interference coloration and magenta CF. Furthermore, the present LCD can be fabricated without changing the conventional LCD process and materials. We also present the analog-full-color method, which can be realized by using small additive sub-pixels of red and blue colors.

Dot Inversion Spontaneous Polarization Structure in the Half-V-shaped Switching Ferroelectric Liquid Crystal Mode

The half-V shaped switching ferroelectric liquid crystal mode (half-V FLC mode) can easily yield excellent moving pictures based on the nonholding display by simple AC driving. However, the AC driving in the entire area of the liquid crystal display (LCD) panel (i.e. the field-inversion drive method) raises a concern of the cross talk problem in large-size LCD panels. In this paper, we propose a novel alignment method that is controlled to yield alternating layer directions between neighboring pixels. Such layer structures correspond to the structure of dot inversion spontaneous polarization, and a nonholding display can be realized by the dot-inversion drive method. By this method, we can simultaneously obtain a cross-talk-free display, excellent moving pictures and wider viewing angle. The contrast ratio is expected to be improved by further liquid crystal development and/or the multi-domain process technology.

Abstract P1-02-01: Evaluation of second-generation photoacoustic mammography in detecting the breast cancer vasculature and hypoxic status; a preliminary study

Background: Functional imaging of tumor vasculature and oxygenation status is essential for monitoring the therapeutic response to the manipulation of abnormal vasculature. Moreover, it could be also applicable for the detection and risk assessment of breast lesion with borderline malignancy since hypoxia and angiogenesis is known to be associated with the malignant potential of precursor lesion of solid tumor. Photoacoustic mammography (PAM) is a novel optical imaging technology that can visualize the hemoglobin distribution and its oxygen saturation (SO2) noninvasively. We have previously reported a promising clinical result of a prototype model of PAM (Canon Inc., Tokyo, Japan) in breast cancer patients. However, the improvement of spatial resolution and the identification of signal origin are still big challenges when considering its application for clinical settings. Materials and methods: We developed the second-generation model of PAM (PAM-02). This instrument has achieved the improved spatial resolution (1.3mm) and enhanced detectability by carrying a high-sensitive detector. Moreover, it is equipped with B-mode ultrasound, which enables us to identify the tumor location in PAM images more precisely. The distribution of hemoglobin within breast tissue carrying solid tumor was evaluated by using PAM-02 under the approval of the ethics committee in Kyoto University Hospital, Japan. Contralateral breast without tumor was also evaluated as a control if possible. Calculated SO2 from photoacoustic (PA) signals were illustrated by using color scale. Results: Seventeen breast lesions from 15 patients were analyzed including 4 ductal carcinoma in situ (DCIS), 12 invasive ductal carcinoma (IDC) and one usual ductal hyperplasia. Tumor locations were successfully identified in 14 out of 17 lesions (82.3%) by B-mode ultrasound imaging. The location of 3 lesions undetectable by B-mode ultrasound imaging could be identified by comparing with corresponding MRI images. B-mode ultrasound imaging made it easy to distinguish intra-tumoral PA signals from peri-tumoral PA signals. Intra-tumoral PA signals were detectable in 68.7% of malignant lesions (11 out of 16 lesions). Peri-tumoral PA signals, which were suggested to be from feeding vessels, were detectable in 81.3% of malignant lesion (13 out of 16 lesions). In the case of benign UDH, PA signals were not detected in either intra- or peri-tumoral region. Intra-tumoral SO2 was estimated to be lower than peri-tumoral SO2 in malignant lesion. While peri-tumoral PA signals were often described as continuous vasculature, intra-tumoral PA signals often showed the spotty patterns. In addition, PA signal density was relatively higher in DCIS compared with IDC. These findings was supposed to reflect the decreased hemoglobin perfusion within solid structure of breast cancer. The minimum detectable lesion was DCIS with a diameter of 8mm. Conclusion: Improved spatial resolution and combination with B-mode ultrasound imaging facilitate the region-specific evaluation of PAM imaging. PAM-02 was supposed to be feasible for evaluating the hypoxic status within small breast tumor and its microenvironment. Citation Format: Masahiro Kawashima, Iku Yamaga, Masae Torii, Mariko Tokiwa, Fakhrejahani Elham, Masako Kataoka, Shotaro Kanao, Masahiro Takada, Yasufumi Asao, Tsuyoshi Shiina, Masakazu Toi. Evaluation of second-generation photoacoustic mammography in detecting the breast cancer vasculature and hypoxic status; a preliminary study [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-02-01.