羽石 秀昭

© 2019 SPIE. In open surgery, observing organ blood circulation and distinguishing artery and vein are important to improve precision of surgery. However, there are some difficulties in this judgement and distinction because there are only slight color differences in the color of ischemic or healthy organs. Peripheral vessels between artery and vein also have subtle difference in their color. The difference in absorption coefficients between oxygenated and deoxygenated hemoglobin mainly affects these characteristics. Therefore, if the illuminant spectrum can be optimized based on the optical properties, there is a possibility to enhance the difference between the two types of vessels and blood-oxygenation levels. To achieve these purposes, we conducted a spectroscopic design of a surgical illuminant combining 14 kinds of commercially available light-emitting diode (LED) spectra by maximizing color differences between blood samples. Spectral reflectance of the blood samples whose oxygen saturation (SO2) measured in advance were employed for computer simulation. In this study, we prototyped a spectrally tunable light source which contains the same LED sets used in the simulation of the surgical illuminant. A conventional illuminant and the designed illuminant spectrum were spectrally adjusted by the spectrally tunable light source to evaluate the effectiveness of the optimal illuminant. Two kinds of cattle blood samples that have different SO2 were enclosed in glass cells and covered with cattle artery for subjective evaluation. Research participants were instructed to compare the color of samples and to sort these blood samples in a SO2 order under the two illuminant conditions. The percentage of correct answers under the designed illuminant was superior to that under the conventional illuminant. This results showed the effectiveness of the designed illuminant.

Microcirculation plays an important role in maintaining our lives. Observing the microcirculation has been considered important in understanding the disease mechanisms and diagnosing diseases. Sidestream dark-field (SDF) imaging is one of the methods to observe the microcirculation. However, the SDF imaging has several problems for instance artifacts caused by pressure and heat. Measurement points is under pressure because SDF imaging requires direct contact with measurement points, which may affect hemodynamics. Therefore, we construct a non-contact setup. Furthermore, at the early stage of sepsis, it is known that the microcirculation is impaired. To investigate the relationship between the flow of red blood cells (RBCs) and septic shock, we conducted an experiment using the setup to observe septic model rats and sham rats. Moreover, we calculated the blood velocity to estimate the flow of RBCs by using acquired motion pictures. We confirmed that the sham rats showed slight change in lactate value during the observation and improved the blood velocity compared with just after abdominal closure. However, lactate value of the septic model rats increased and the blood velocity of septic model rats decreased. This finding suggests that microcirculatory alteration may be a sign of sepsis and septic shock progression.

In the medical field, visual diagnosis is one of the most important ways for evaluation. Observing tissue structure is effective for improving precision of surgery. We focused on an emphatic illuminant which brought a fine view of micro blood vessel structures. In this paper, we simulated the illuminant and evaluated it by subjective evaluation. In an evaluation experiment, to compare two illuminant conditions, a conventional and the emphatic illuminant, 14 LEDs fixed to the light unit were spectrally adjusted to demonstrate the two illuminants, We set a rat cecum as a target to observe the structure of micro blood vessels. The effectiveness of the emphatic illuminant was confirmed by ratio of detected blood vessel region to the ground truth.

In open surgery, observing organ blood circulation and distinguishing artery and vein are important to improve precision of surgery. However, there are some difficulties in this judgement and distinction because there are only slight color differences in the color of ischemic or healthy organs. Peripheral vessels between artery and vein also have subtle difference in their color. The difference in absorption coefficients between oxygenated and deoxygenated hemoglobin mainly affects these characteristics. Therefore, if the illuminant spectrum can be optimized based on the optical properties, there is a possibility to enhance the difference between the two types of vessels and blood-oxygenation levels. To achieve these purposes, we conducted a spectroscopic design of a surgical illuminant combining 14 kinds of commercially available light-emitting diode (LED) spectra by maximizing color differences between blood samples. Spectral reflectance of the blood samples whose oxygen saturation (SO2) measured in advance were employed for computer simulation. In this study, we prototyped a spectrally tunable light source which contains the same LED sets used in the simulation of the surgical illuminant. A conventional illuminant and the designed illuminant spectrum were spectrally adjusted by the spectrally tunable light source to evaluate the effectiveness of the optimal illuminant. Two kinds of cattle blood samples that have different SO2 were enclosed in glass cells and covered with cattle artery for subjective evaluation. Research participants were instructed to compare the color of samples and to sort these blood samples in a SO2 order under the two illuminant conditions. The percentage of correct answers under the designed illuminant was superior to that under the conventional illuminant. This results showed the effectiveness of the designed illuminant.

We investigated a non-contact imaging method to evaluate plethysmogram and vasomotion with a digital color camera. Monte Carlo simulation for light transport in skin tissue is used to specify a relation among the red-green-blue-values and hemoglobin contents. Applying the FFT band pass filters to each pixel of the sequential images for the total hemoglobin concentration along the time line, two-dimentional plethysmogram and vasomotion can be reconstructed. In vivo experiments with human skin before, during, and after auditory stimulation demonstrated the feasibility of the method to evaluate the activities of autonomic nervous systems.

© 2019 SPIE. We investigated a method to visualize transcutaneous bilirubin, hemoglobin, and melanin based on hyperspectral imaging. In the method, the Monte Carlo simulation-based multiple regression analysis for an absorbance spectrum in the visible wavelength region is used to specify the concentrations of bilirubin, oxygenated hemoglobin, deoxygenated hemoglobin, and melanin. Bile duct ligation in rats demonstrated the remarkable change in bilirubin concentration whereas rats under varying fraction of inspired oxygen showed well-known hemodynamic changes in skin tissue. The results in this study indicate potential of the method for simultaneous imaging of multiple chromophores in skin tissue.

© 2019 SPIE. In this study, the examination results of speed of sound of sliced rat organs analyzed with multi-frequency ultrasound (80 and 250 MHz) from the acquiring radiofrequency (RF) echo signals observed by our self-made scanning acoustic microscopy (SAM) system is reported. The frequency dependence of SoS was evaluated by analysis method involving filtering considering spatial resolution at each frequency.

In order to analyze the relationship between ultrasonic signal and tissue structure, accurate image registration is required. However, spatial resolution and image features are different between pathological and ultrasonic images. Thus, this paper proposed an image feature conversion method including downscale process using convolutional neural network. The proposed method was applied to the pathological images and we confirmed that the converted pathological images were similar to the ultrasonic images from visual assessment and image registration was also successfully conducted.

Catheter-based therapy is typically performed under fluoroscopic image observation. However, the vessel structure cannot be visualized on fluoroscopic images. To overcome this limitation, angiographic images are captured with a contrast agent, and digital subtraction angiography (DSA) images are acquired during the intervention. In thoracoabdominal DSA, patients have to hold their breath to match the respiratory phase during DSA acquisition. However, breath holding is difficult for some patients, including the elderly. If the organs move during DSA acquisition, artifacts can occur on DSA images, and the DSA acquisition must be performed again. In the present study, we describe and characterize a new respiratory phase matching method for respiratory-synchronized DSA acquisition under natural respiration. Preoperative angiographic and intra-operative fluoroscopic images were collected under natural respiration during the operation. For each fluoroscopic image, we used a pattern matching to select an angiographic image in the most similar respiratory phase. We then examined whether the method could be applied to both the free breathing DSA and the respiratory-synchronized roadmap. We found that our proposed respiratory phase matching method produced acceptable DSA images without breath holding, and that the processing could be performed in real time.

Relation analysis between physical properties and microstructure of the human tissue has been widely conducted. In particular, the relationships between acoustic parameters and the microstructure of the human brain fall within the scope of our research. In order to analyze the relationship between physical properties and microstructure of the human tissue, accurate image registration is required. To observe the microstructure of the tissue, pathological (PT) image, which is an optical image capturing a thinly sliced specimen has been generally used. However, spatial resolutions and image features of PT image are markedly different from those of other image modalities. This study proposes a modality conversion method from PT image to ultrasonic (US) image including downscale process using convolutional neural network (CNN). Namely, constructed conversion model estimates the US from patch image of PT image. The proposed method was applied to the PT images and we confirmed that the converted PT images were similar to the US images from visual assessment. Image registration was then performed with converted PT and US images measuring the consecutive pathological specimens. Successful registration results were obtained in every pair of the images.

Near-infrared spectroscopy (NIRS) is a noninvasive method for monitoring tissue oxygen saturation (StO2). Many commercial NIRS devices are presently available. However, the precision of those devices is relatively poor because they are using the reflectance-model with which it is difficult to obtain the blood volume and other unchanged components of the tissue. Human webbing is a thin part of the hand and suitable to measure spectral transmittance. In this paper, we present a method for measuring StO2 of human webbing from a transmissive continuous-wave nearinfrared spectroscopy (CW-NIRS) data. The method is based on the modified Beer-Lambert law (MBL) and it consists of two steps. In the first step, we give a pressure to the upstream region of the measurement point to perturb the concentration of deoxy-And oxy-hemoglobin as remaining the other components and measure the spectral signals. From the measured data, spectral absorbance due to the components other than hemoglobin is calculated. In the second step, spectral measurement is performed at arbitrary time instance and the spectral absorbance obtained in the step 1 is subtracted from the measured absorbance. The tissue oxygen saturation (StO2) is estimated from the remained data. The method was evaluated on an arterial occlusion test (AOT) and a venous occlusion test (VOT). In the evaluation experiment, we confirmed that reasonable values of StO2 were obtained by the proposed method.

Systolic blood pressure (SBP) is highly sensitive to various factors such as psychological stress, and hence its continuous monitoring is essential to evaluate different health conditions. However, conventional sphygmomanometers cannot continuously measure SBP given the time-consuming setup based on a pressure cuff. Moreover, continuous biological signal monitoring is more comfortable when no sensors are attached. A solution for continuous SBP estimation is based on pulse transit time (PTT), which determines the time difference between two pulse waves at different body parts. In previous studies, we successfully measured the PTT using a contactless setup composed by two digital color cameras recording the face and hand of subjects. Then, the acquired images were transformed into blood volume by combining multiple regression analysis and a Monte Carlo method. As a result, the delay among images allowed to determine the PPT from pulse waves. In this study, we simultaneously measured SBP and PTT by using a sphygmomanometer and the two cameras, respectively. We evaluated SBP increases (i.e., stressful situations) and the corresponding PPT by asking participants to either grasp a handgrip or momentarily interrupting breath. We also determined the SBP and PTT without asking for such exercises. Comparison results show that the mean PTT under stress was significantly lower than that without stress, which is consistent with an increased SBP. Finally, we related the SBP and PTT by a nonlinear formula with a coefficient of determination of 0.59, thus confirming the effectiveness of the proposed system.

We propose a method to estimate transcutaneous bilirubin, hemoglobin, and melanin based on the diffuse reflectance spectroscopy. In the proposed method, the Monte Carlo simulation-based multiple regression analysis for an absorbance spectrum in the visible wavelength region (460-590 nm) is used to specify the concentrations of bilirubin (Cbil), oxygenated hemoglobin (Coh), deoxygenated hemoglobin (Cdh), and melanin (Cm). Using the absorbance spectrum calculated from the measured diffuse reflectance spectrum as a response variable and the extinction coefficients of bilirubin, oxygenated hemoglobin, deoxygenated hemoglobin, and melanin, as predictor variables, multiple regression analysis provides regression coefficients. Concentrations of bilirubin, oxygenated hemoglobin, deoxygenated hemoglobin, and melanin, are then determined from the regression coefficients using conversion vectors that are numerically deduced in advance by the Monte Carlo simulations for light transport in skin. Total hemoglobin concentration (Cth) and tissue oxygen saturation (StO2) are simply calculated from the oxygenated hemoglobin and deoxygenated hemoglobin. In vivo animal experiments with bile duct ligation in rats demonstrated that the estimated Cbil is increased after ligation of bile duct and reaches to around 20 mg/dl at 72 h after the onset of the ligation, which corresponds to the reference value of Cbil measured by a commercially available transcutaneous bilirubin meter. We also performed in vivo experiments with rats while varying the fraction of inspired oxygen (FiO2). Coh and Cdh decreased and increased, respectively, as FiO2 decreased. Consequently, StO2 was dramatically decreased. The results in this study indicate potential of the method for simultaneous evaluation of multiple chromophores in skin tissue.

Plethysmogram is the periodic variation in blood volume due to the cardiac pulse traveling through the body. Photo-plethysmograph (PPG) has been widely used to assess the cardiovascular system such as heart rate, blood pressure, cardiac output, vascular compliance. We have previously proposed a non-contact PPG imaging method using a digital red-green-blue camera. In the method, the Monte Carlo simulation for light transport is used to specify a relationship among the RGB-values and the concentrations of oxygenated hemoglobin (CHbO) and deoxygenated hemoglobin (CHbR). The total hemoglobin concentration (CHbT) can be calculated as a sum of CHbO and CHbR. Applying the fast Fourier transform (FFT) band pass filters to each pixel of the sequential images for CHbT along the time line, two-dimentional plethysmogram can be reconstructed. In this study, we further extend the method to imaging the arterial oxygen saturation (SaO2). The PPG signals for both CHbO and CHbR are extracted by the FFT band pass filter and the pulse wave amplitudes (PWAs) of CHbO and CHbR are calculated. We assume that the PWA for CHbO and that for CHbR are decreased and increased as SaO2 is decreased. The ratio of PWA for CHbO and that for CHbR are associated to the reference value of SaO2 measured by a commercially available pulse oximeter, which provide an empirical formula to estimate SaO2 from the PPG signal at each pixel of RGB image. In vivo animal experiments with rats during varying the fraction of inspired oxygen (FiO2) demonstrated the feasibility of the proposed method.

We developed a modified, more practical four-layered depth-of-interaction (DOI) detector based on the light sharing method. Reflectors, which are inserted in every two lines of crystal segments and shifted differently depending on each layer, project 3-D crystal positions onto a 2-D position histogram without any overlapping after applying an Anger-type calculation. The best crystal separation we have ever made based on this method was the 4-layered 32 × 32 array of LYSO crystals sized at 1.45 × 1.45 × 5 mm3. However, assembling crystals of a tiny size tends to cost a lot, and fine tuning of the light guide and the front-end circuit is required to have fine crystal identification from photo sensor signals of coarser pixel pitch. In this paper, therefore, we proposed a more practical 4-layered DOI detector. The key idea is that the crystals in the top layer, which have the highest detection efficiency, mostly contribute to PET spatial resolution. We applied two new ideas: (1) use of 1/4 size crystals only for the 1st (top) layer and (2) inserting a thin light guide between the 1st and the 2nd layers of crystal array. In the developed prototype detector, the 1st layer used 32 × 32 LYSO crystals of quarter size (1.4 × 1.4 × 5.0 mm3) compared with the other layers (16 × 16 arrays of crystals of 2.8 × 2.8 × 5.0 mm3). For better crystal identification of small crystals in the 1st layer, we optimized the optical condition between crystals such as use of an optical glue or air. Also, a thin light guide was inserted between the 1st and the 2nd layers for improvement of crystal identification of the 1st layer. With the appropriate insertion of the light guide, all crystals of the 1st layer were identified as well as the crystals in the other layers.

Tomosynthesis is attracting attention as a low-dose tomography technology compared with X-ray CT. However, conventional tomosynthesis imaging devices are large and stationary. Furthermore, there is a limitation in the working range of the X-ray source during image acquisition. We have previously proposed the use of a portable X-ray device for tomosynthesis that can be used for ward rounds and emergency medicine. The weight of this device can be reduced by using a flat panel detector (FPD), and flexibility is realized by the free placement of the X-ray source and FPD. Tomosynthesis using a portable X-ray device requires calibration of the geometry between the X-ray source and detector at each image acquisition. We propose a method for geometry calibration and demonstrate tomosynthesis image reconstruction by this method. An image processing-based calibration method using an asymmetric and multilayered calibration object (AMCO) is presented. Since the AMCO is always attached to the X-ray source housing for geometry calibration, the additional setting of a calibration object or marker around or on the patients is not required. The AMCO's multilayer structure improves the calibration accuracy, especially in the out-of-plane direction. Two experiments were conducted. The first was performed to evaluate the calibration accuracy using an XY positioning stage and a gonio stage. As a result, an accuracy of approximately 1 mm was achieved both in the in-plane and out-of-plane directions. An angular accuracy of approximately was confirmed. The second experiment was conducted to evaluate the reconstructed image using a foot model phantom. Only the sagittal plane could be clearly observed with the proposed method. We proposed a tomosynthesis imaging system using a portable X-ray device. From the experimental results, the proposed method could provide sufficient calibration accuracy and a clear sagittal plane of the reconstructed tomosynthesis image.

Background: The aims of this study were to reveal the characteristics of the meniscal shape at each knee osteoarthritis (OA) severity level and to predict trends or patterns of the meniscal shape change as associated with knee OA progression. Methods: Fifty-one patients diagnosed with knee OA based on X-ray and magnetic resonance (MR) images were evaluated. They were divided into three groups based on the Kellgren-Lawrence (KL) grade: normal group (KL grade of 0 or 1), mild group (KL grade of 2 or 3), and severe group (KL grade of 4). We measured the patients' meniscal size and meniscal extrusion using MR images. In addition, semiquantitative measurement was performed using MR images to determine the arthritic status of the corresponding compartment using a whole-organ magnetic resonance imaging score (WORMS). Results: The longitudinal diameter and posterior wedge angle of the medial meniscus were significantly larger, and the posterior wedge width of the medial meniscus was significantly smaller in the severe group than in the normal group. The WORMS scores for cartilage and osteophytes in the medial region were significantly different among the groups. The WORMS score of each region was strongly correlated with the longitudinal diameter. The WORMS scores of the lateral region were lower than those of the medial region. Conclusion: Our observation of the shape change of the medial meniscus in the posterior region was roughly consistent with that in many previous studies of meniscal degeneration. On the other hand, we saw that the most relevant relation between the progression of the knee OA and the deformation of the meniscus was in the longitudinal direction.

The sidestream dark-field (SDF) imaging allows direct visualization of red blood cells in microvessels near tissue surfaces. We have developed an image-based oximetry method using two-band images obtained by SDF imaging (SDF oximetry) and a trial SDF device with light-emitting diodes to obtain band images. In this study, we propose a technique of producing oxygen saturation (SO2) maps from SDF images and perform animal experiments in vivo. To produce SO2 maps, we use spectral analysis using two band images obtained with our SDF device. As an image processing, the combination of both the Hessian-based and pixel value-based techniques as blood vessel extraction from an SDF image is used. From the experiment with the surface of rat small intestines, we can produce SO2 maps and find that the map represents arterioles and venules those were determined based on the blood flow from SDF images. Moreover, we find the variation of SO2 along a blood vessel running direction.

The sidestream dark-field (SDF) imaging allows direct visualization of red blood cells in microvessels near tissue surfaces. We have developed an image-based oximetry method using two-band images obtained by SDF imaging (SDF oximetry) and a trial SDF device with light-emitting diodes to obtain band images. In this study, we propose a technique of producing oxygen saturation (SO2) maps from SDF images and perform animal experiments in vivo. To produce SO2 maps, we use spectral analysis using two band images obtained with our SDF device. As an image processing, the combination of both the Hessian-based and pixel value-based techniques as blood vessel extraction from an SDF image is used. From the experiment with the surface of rat small intestines, we can produce SO2 maps and find that the map represents arterioles and venules those were determined based on the blood ow from SDF images. Moreover, we find the variation of SO2 along a blood vessel running direction.

Septic shock induces organ dysfunction by microcirculatory disturbance. Observation and quantification of microcirculation are expected to be effective for the diagnosis of septic shock. Sidestream dark-filed (SDF) imaging is a suitable technique for observation of microcirculation. It can noninvasively visualize red blood cells (RBCs) of microcirculation. We are developing early diagnostic criteria for septic shock from microcirculation SDF images. As an initial study, we use the blood flow velocity estimated from the images as a diagnostic criteria. However, low contrast quality and subject's movement disturb the blood flow velocity estimation. In this paper, we present a procedure of image processing for a stable estimation of the blood flow velocity. In the procedure, we first perform a robust principal component analysis (RPCA) as a preprocessing. RPCA decomposes a motion picture into a low-rank (L) component and a sparse (S) component. The S component images clearly expresses RBCs flow and is used for the velocity estimation. The temporal change of the intensity profile along the vessel was analyzed by Hough transform to estimate the blood flow velocity is. The proposed procedure was examined with dorsal microcirculation of septic model rats and a sham rat. As a result, the decrease in blood flow velocity of the septic rats after 17 hours was greater than that of the sham. It was also suggested that blood flow velocity might be faster index of septic shock reaction earlier than lactic acid value. These results suggest that the velocity estimation is reasonable for diagnosis of septic shock.

We have previously proposed an estimation method of intravascular oxygen saturation (SO2) from the images obtained by sidestream dark-field (SDF) imaging (we call it SDF oximetry) and we investigated its fundamental characteristics by Monte Carlo simulation. In this paper, we propose a correction method for scattering by the tissue and performed experiments with turbid phantoms as well as Monte Carlo simulation experiments to investigate the influence of the tissue scattering in the SDF imaging. In the estimation method, we used modified extinction coefficients of hemoglobin called average extinction coefficients (AECs) to correct the influence from the bandwidth of the illumination sources, the imaging camera characteristics, and the tissue scattering. We estimate the scattering coefficient of the tissue from the maximum slope of pixel value profile along a line perpendicular to the blood vessel running direction in an SDF image and correct AECs using the scattering coefficient. To evaluate the proposed method, we developed a trial SDF probe to obtain three-band images by switching multicolor light-emitting diodes and obtained the image of turbid phantoms comprised of agar powder, fat emulsion, and bovine blood-filled glass tubes. As a result, we found that the increase of scattering by the phantom body brought about the decrease of the AECs. The experimental results showed that the use of suitable values for AECs led to more accurate SO2 estimation. We also confirmed the validity of the proposed correction method to improve the accuracy of the SO2 estimation.

Although abdominal aortic aneurysms (AAAs) occur mostly inferior to the renal artery, the mechanism of the development of AAA in relation to its specific location is not yet clearly understood. The objective of this study was to evaluate the hypothesis that even healthy volunteers may manifest specific flow characteristics of blood flow and alter wall shear or oscillatory shear stress in the areas where AAAs commonly develop. Eight healthy male volunteers were enrolled in this prospective study, aged from 24 to 27. Phase-contrast magnetic resonance imaging (MRI) was performed with electrocardiographic triggering. Flow-sensitive four-dimensional MR imaging of the abdominal aorta, with three-directional velocity encoding, including simple morphological image acquisition, was performed. Information on specific locations on the aortic wall was applied to the flow encodes to calculate wall shear stress (WSS) and oscillatory shear index (OSI). While time-framed WSS showed the highest peak of 1.14 +/- A 0.25 Pa in the juxtaposition of the renal artery, the WSS plateaued to 0.61 Pa at the anterior wall of the abdominal aorta. The OSI peaked distal to the renal arteries at the posterior wall of the abdominal aorta of 0.249 +/- A 0.148, and was constantly elevated in the whole abdominal aorta at more than 0.14. All subjects were found to have elevated OSI in regions where AAAs commonly occur. These findings indicate that areas of constant peaked oscillatory shear stress in the infra-renal aorta may be one of the factors that lead to morphological changes over time, even in healthy individuals.

The single-ring OpenPET (SROP), for which the detector arrangement has a cylinder shape cut by two parallel planes at a slant angle to form an open space, is our original proposal for in-beam PET. In this study, we developed a small prototype of an axial-shift type SROP (AS-SROP) with a novel transformable architecture for a proof-of-concept. In the AS-SROP, detectors originally forming a cylindrical PET are axially shifted little by little. We designed the small AS-SROP prototype for 4-layer depth-of-interaction detectors arranged in a ring diameter of 250 mm. The prototype had two modes: open and closed. The open mode formed the SROP with the open space of 139 mm and the closed mode formed a conventional cylindrical PET. The detectors were simultaneously moved by a rotation handle allowing them to be transformed between the two modes. We evaluated the basic performance of the developed prototype and carried out in-beam imaging tests in the HIMAC using C-11 radioactive beam irradiation. As a result, we found the open mode enabled in-beam PET imaging at a slight cost of imaging performance; the spatial resolution and sensitivity were 2.6 mm and 5.1% for the open mode and 2.1 mm and 7.3% for the closed mode. We concluded that the AS-SROP can minimize the decrease of resolution and sensitivity, for example, by transforming into the closed mode immediately after the irradiation while maintaining the open space only for the in-beam PET measurement.

High-resolution 3D histology image reconstruction of the whole brain organ starts from reconstructing the high-resolution 2D histology images of a brain slice. In this paper, we introduced a method to automatically align the histology images of thin tissue sections cut from the multiple paraffin embedded tissue blocks of a brain slice. For this method, we employed template matching and incorporated an optimization technique to further improve the accuracy of the 2D reconstructed image. In the template matching, we used the gross image of the brain slice as a reference to the reconstructed 2D histology image of the slice, while in the optimization procedure, we utilized the Jaccard index as the metric of the reconstruction accuracy. The results of our experiment on the initial 3 different whole-brain tissue slices showed that while the method works, it is also constrained by tissue deformations introduced during the tissue processing and slicing. The size of the reconstructed high-resolution 2D histology image of a brain slice is huge, and designing an image viewer that makes particularly efficient use of the computing power of a standard computer used in our laboratories is of interest. We also present the initial implementation of our 2D image viewer system in this paper. (C) 2016 S. Karger AG, Basel

Computed tomography (CT) and magnetic resonance (MR) imaging have been widely used for visualizing the inside of the human body. However, in many cases, pathological diagnosis is conducted through a biopsy or resection of an organ to evaluate the condition of tissues as definitive diagnosis. To provide more advanced information onto CT or MR image, it is necessary to reveal the relationship between tissue information and image signals. We propose a registration scheme for a set of PT images of divided specimens and a 3D-MR image by reference to an optical macro image (OM image) captured by an optical camera. We conducted a fundamental study using a resected human brain after the death of a brain cancer patient. We constructed two kinds of registration processes using the OM image as the base for both registrations to make conversion parameters between the PT and MR images. The aligned PT images had shapes similar to the OM image. On the other hand, the extracted cross-sectional MR image was similar to the OM image. From these resultant conversion parameters, the corresponding region on the PT image could be searched and displayed when an arbitrary pixel on the MR image was selected. The relationship between the PT and MR images of the whole brain can be analyzed using the proposed method. We confirmed that same regions between the PT and MR images could be searched and displayed using resultant information obtained by the proposed method. In terms of the accuracy of proposed method, the TREs were 0.56 +/- 0.39 mm and 0.87 +/- 0.42 mm. We can analyze the relationship between tissue information and MR signals using the proposed method. (C) 2016 The Authors. Published by Elsevier GmbH.

Lung motion due to respiration causes image degradation in medical imaging, especially in nuclear medicine which requires long acquisition times. We have developed a method for image correction between the respiratory-gated (RG) PET images in different respiration phases or breath-hold (BH) PET images in an inconsistent respiration phase. In the method, the RG or BH-PET images in different respiration phases are deformed under two criteria: similarity of the image intensity distribution and smoothness of the estimated motion vector field (MVF). However, only these criteria may cause unnatural motion estimation of lung. In this paper, assuming the use of a PET-CT scanner, we add another criterion that is the similarity for the motion direction estimated from inhalation and exhalation CT images. The proposed method was first applied to a numerical phantom XCAT with tumors and then applied to BH-PET image data for seven patients. The resultant tumor contrasts and the estimated motion vector fields were compared with those obtained by our previous method. Through those experiments we confirmed that the proposed method can provide an improved and more stable image quality for both RG and BH-PET images.

We developed a modified, more practical four layered depth-of-interaction (DOI) detector based on the light sharing method. Reflectors, which are inserted in every two lines of crystal segments and shifted differently depending on each layer, project 3-D crystal positions onto a 2-D position histogram without any overlapping after applying an Anger-type calculation. The best crystal separation we have ever made based on this method was the 4-layered 32 x 32 array of LYSO crystals sized at 1.45 x 1.45 x 5 mm(3). However, assembling crystals of a tiny size tends to cost a lot, and fine tuning of the light guide and the front-end circuit is required to have fine crystal identification from photo sensor signals of coarser pixel pitch. In this paper, therefore, we proposed a more practical 4-layered DOI detector. The key idea is that the crystals in the top layer, which have the highest detection efficiency, mostly contribute to PET spatial resolution. We applied two new ideas: (1) use of 114 size crystals only for the st (top) layer and (2) inserting a thin light guide between the 1st and the 2nd layers of crystal array. In the developed prototype detector, the 1st layer used 32 x 32 LYSO crystals of quarter size (1.4 x 1.4 x 5.0 mm(3)) compared with the other layers (16 x 16 arrays of crystals of 2.8 x 2.8 x 5.0 mm(3)). For better crystal identification of small crystals in the 1st layer, we optimized the optical condition between crystals such as use of an optical glue or air. Also, a thin light guide was inserted between the 1st and the 2nd layers for improvement of crystal identification of the 1st layer. With the appropriate insertion of the light guide, all crystals of the Is' layer were identified as well as the crystals in the other layers.

To improve treatment workflow, we developed a graphic processing unit (GPU)-based patient positional verification software application and integrated it into carbon-ion scanning beam treatment. Here, we evaluated the basic performance of the software. The algorithm provides 2D/3D registration matching using CT and orthogonal X-ray flat panel detector (FPD) images. The participants were 53 patients with tumors of the head and neck, prostate or lung receiving carbon-ion beam treatment. 2D/3D-ITchi-Gime (ITG) calculation accuracy was evaluated in terms of computation time and registration accuracy. Registration calculation was determined using the similarity measurement metrics gradient difference (GD), normalized mutual information (NMI), zero-mean normalized cross-correlation (ZNCC), and their combination. Registration accuracy was dependent on the particular metric used. Representative examples were determined to have target registration error (TRE) = 0.45 +/- 0.23 mm and angular error (AE) = 0.35 +/- 0.18 degrees with ZNCC + GD for a head and neck tumor; TRE = 0.12 +/- 0.07 mm and AE = 0.16 +/- 0.07 degrees with ZNCC for a pelvic tumor; and TRE = 1.19 +/- 0.78 mm and AE = 0.83 +/- 0.61 degrees with ZNCC for lung tumor. Calculation time was less than 7.26 s.The new registration software has been successfully installed and implemented in our treatment process. We expect that it will improve both treatment workflow and treatment accuracy.

The in vivo kinematics of the knee joint has been analyzed by multiple approaches. In order to obtain the knee potion with the weight-bearing characteristic, a 2D/3D registration technique has been used. Whereas many studies have analyzed the femorotibial (FT) joint, only a few studies have reported a motion analysis for the patellofemoral (PF) joint. This paper focuses on the motions of both the FT and PF joints with the weight-bearing characteristic. An image acquisition test is conducted with weight-bearing for healthy subjects (n = 10) and patients with knee osteoarthritis (OA) (n = 10). The knee motions of the FT and PF joints are analyzed using the distribution area (DA) of a facet space map, percentage of short facet space (PS), weighted center position of the facet space map and average space distance (ASD) at 10 degree intervals of the flexion angle. In the case of knee OA patients, most ASDs of the PF joint were over 1 mm shorter than those of the healthy subjects. DAs of the PF facet space maps of the patient group were twice as large as those of the healthy group at 20 and 30 degree flexion angles. PSs of the PF joint of the patient group were over 2.5% from 10 to 40 degree flexion angles. This paper shows that the knee OA narrows the facet spaces of both FT and PF joints. In particular, the short facet space appears for the PF joint in knee OA patients.

We investigate the possibility of oxygen saturation estimation from images obtained by the sidestream dark-field (SDF) technique. The SDF technique is a method for microvascular imaging. In SDF imaging, light enters a tissue directly from illumination sources configured around a camera and then the camera captures the light scattered by the tissue. To advance the capability of the SDF imaging system, we develop a SDF oximetry method with LED illumination sources. In this paper, we evaluate some SDF oximetry methods from virtual SDF images obtained by the Monte Carlo photon propagation simulation. As a result, we verify that SDF imaging allows the estimation of oxygen saturation of the individual vessels from virtual images using the average extinction coefficients considering the bandwidth of the illumination and the effect of the integration of the camera. (C) 2015 Optical Society of America

We have previously proposed an intersection profile method for reconstructing four-dimensional (4-D) magnetic resonance imaging (MRI) consisting of one breathing cycle of the thoracoabdominal region. This method captures a set of temporal sequence images in a proper sagittal plane and sets of temporal sequence images in continuous coronal slices. The former set is used as a navigator slice and the latter sets are used as data slices. A 4-D MRI is reconstructed by synchronizing the respiratory pattern found in the navigator slice and the data slices. We propose a prospective method to reduce the acquisition time for data slices. During data slice acquisition, the synchronization process between the respiratory pattern found in the navigator slice and one data slice is monitored in real time. Data acquisition will be terminated and moved to the next data slice based on a threshold value. We used 14 data sets (seven patients with certain pulmonary disease and seven healthy volunteers) previously obtained for the original intersection profile method for a simulation using the proposed method to evaluate the time reduction and impact on image quality. Each of the data set was tested using three different threshold values and the acquisition time can be reduced up to 75%. Although the quantitative evaluation of image quality was slightly worse than that by the conventional method, the difference based on the visual inspection was subtle to human eyes.

We have developed a method called intersection profile method to construct a 4D-MRI (3D+time) from time-series of 2D-MRI. The basic idea is to find the best matching of the intersection profile from the time series of 2D-MRI in sagittal plane (navigator slice) and time series of 2D-MRI in coronal plane (data slice). In this study, we use 4D-MRI to semiautomatically extract the right diaphragm motion of 16 subjects (8 healthy subjects and 8 COPD patients). The diaphragm motion is then evaluated quantitatively by calculating the displacement of each subjects and normalized it. We also generate phase-length map to view and locate paradoxical motion of the COPD patients. The quantitative results of the normalized displacement shows that COPD patients tend to have smaller displacement compared to healthy subjects. The average normalized displacement of total 8 COPD patients is 9.4mm and the average of normalized displacement of 8 healthy volunteers is 15.3mm. The generated phase-length maps show that not all of the COPD patients have paradoxical motion, however if it has paradoxical motion, the phase-length map is able to locate where does it occur.

This paper presents two features to make neurosurgery with 5-ALA-induced fluorescent imaging more convenient and more reliable. The first one is the concept for a system that switches between white light and excitation light rapidly and allows surgeons to easily locate the tumor region on the normal color image. The second one is the way for color signal processing that yields a stable fluorescent signal without depending on the lighting condition. We developed a prototype system and confirmed that the color image display with the fluorescent region worked well for both the brain of a dead swine and the resected tumor of a human brain. We also performed an experiment with physical phantoms of fluorescent objects and confirmed that the calculated flurophore density-related values were stably obtained for several lighting conditions.

This paper describes a comparative study of the various color signals for non-contact heart rate (HR) measurement on a video sequence. The color signals include red, green, blue, hue, the principal components of the red, green, and blue signals from video data. Experimental results prove that hue and the 3rd principal component are the most effective signals for the HR measurement. Experimental results also show that the two signals behave differently to different lighting conditions. Thus, we have integrated the two signals and achieved an improved performance than those based on a single color signal.

We have developed a method called intersection profile method to construct a 4D-MRI (3D+time) from time-series of 2D-MRI. The basic idea is to find the best matching of the intersection profile from the time series of 2D-MRI in sagittal plane (navigator slice) and time series of 2D-MRI in coronal plane (data slice). In this study, we use 4D-MRI to semiautomatically extract the right diaphragm motion of 16 subjects (8 healthy subjects and 8 COPD patients). The diaphragm motion is then evaluated quantitatively by calculating the displacement of each subjects and normalized it. We also generate phase-length map to view and locate paradoxical motion of the COPD patients. The quantitative results of the normalized displacement shows that COPD patients tend to have smaller displacement compared to healthy subjects. The average normalized displacement of total 8 COPD patients is 9.4mm and the average of normalized displacement of 8 healthy volunteers is 15.3mm. The generated phase-length maps show that not all of the COPD patients have paradoxical motion, however if it has paradoxical motion, the phase-length map is able to locate where does it occur.