Identification of loss of the gray-white matter interface (GWMI) is important for the diagnosis of acute stroke in unenhanced CT. However, the identification is difficult due to the intrinsic presence of quantum noise on CT images. As a result, low sensitivity of detection of loss of the GWMI becomes a major issue in unenhanced CT. To cope with this issue, we have previously developed an adaptive partial median filter (APMF). In order to validate the usefulness of the APMF, we have evaluated the performance of the proposed filter using simulated images and clinical images. This report first describes the outline of the APMF and its performance. Next, the practically clinical usefulness of the APMF is presented based on experimental results.

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Medical displays are indispensable for picture archives and communication system in medical settings, and the performance of the displays have been improved day by day. Therefore, image quality evaluations of displays are still important, and continued effective improvements of display's performance are demanded by users. Author has been developed image quality evaluation methods for medical displays. For resolution measurement, a simple and accurate method using high-contrast bar-pattern images was developed. For noise property evaluation, a method which can elude problems caused by pixel structures and accurately measure random noise level was developed. Both methods can be performed by using a commercially available digital camera, and do not need complicated procedures for measurement, which were indispensable in previously reported methods. Author also developed super high-resolution medical liquid crystal displays (LCDs) using independent sub-pixel drive technology. The developed LCDs provide three times resolution enhancement, and have performances that can display high signal-to-noise ratio images of digital mammography and general radiography images.

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We evaluated the X-ray digital tomosynthesis (DT) reconstruction processing method for metal artifact reduction and the application of wavelet denoising to selectively remove quantum noise and suggest the possibility of image quality improvement using a novel application for chest. In orthopedic DT imaging, we developed artifact reduction methods based on a modified Shepp and Logan reconstruction filter kernel realized by taking into account additional weighing by direct current (DC) components in frequency domain space. Processing leads to an increase in the ratio of low-frequency components in an image. The effectiveness of the method in enhancing the visibility of a prosthetic case was quantified in terms of removal of ghosting artifacts. In chest DT imaging, the technique was implemented on a DT system and experimentally evaluated through chest phantom measurements, spatial resolution and compared with an existing post-reconstruction wavelet denoise algorithm by Badea et al. Our wavelet technique with balance sparsity-norm contrast-to-noise ratio (CNR) effectively decreased quantum noise in the reconstructed images with and improvement when applied to pre-reconstruction image for post-reconstruction. The results of our technique showed that although modulation transfer function (MTF) did not vary (preserving spatial resolution), the existing wavelet denoise algorithm caused MTF deterioration.

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In consideration of the requirement for global standardization and quality control of PET imaging, the present studies gave an outline of phantom study to decide both scan and reconstruction parameters based on FDG-PET/CT procedure guideline in Japan, and optimization of scan duration based on NEC_density was performed continuously. In the phantom study, scan and reconstruction parameters were decided by visual assessment and physical indexes (N_10mm, NEC_phantom, Q_H,_10mm/N_10mm) to visualize hot spot of 10mm diameter with SUV=4 explicitly. Simultaneously, RC was evaluated to recognize that PET images had enough quantifiably. Scan durations were optimized by Body Mass Index (BMI) based on retrospective analysis of NEC_density. Correlation between visual score in clinical FDG-PET images and NEC_density fell after the optimization of scan duration. Both Inter-institution and inter-patient variability were decreased by performing the phantom study based on the procedure guideline and the optimization of scan duration based on NEC_density which seem finally useful to practice highly precise examination and promote high-quality controlled study.

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In high precise conformal radiation therapy, patient's intrafraction motion decreases the accuracy of target coverage and organs at risk sparing. In our study, we designed and developed a new monitoring system for the motion. The system consisted of a web camera and a computer running our in-house software in which template matching algorithms with pre-image processing were implemented. The motion of a marker box on patient was tracked as a surrogate of the motion. The system accuracy was evaluated by employing a respiratory motion phantom. Additionally, the effectiveness of the system was investigated in healthy volunteers, in terms of the results from the differences in the intrafraction motion detectable between the marker positions. The monitoring system could achieve a 1 mm positional accuracy and also 50 msec temporal resolution. The system was found to be within AAPM Task Group 142 tolerance for respiratory-gated radiation therapy. The movement of the marker on the sternum was substantially decreased as compared with the abdomen. The measurement of the motion could be measured using the sternum as a position of the marker box. Our system can manage the intrafraction motion and also enables treatment irradiation to be undertaken with high accuracy.

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Volumetric modulated arc therapy (VMAT) is a rotational intensity-modulated radiotherapy (IMRT) technique capable of acquiring projection images for cone-beam computed tomography (CBCT). CBCT during treatment is expected to evaluate the actual tumor position and dose distribution. The goal of our research is to establish a new method of verification during treatment in stereotactic body radiotherapy. In this study, we evaluated the movement of the target “in treatment” using kilo volts X-ray beams for diagnosis (kV-CBCT) and mega volts X-ray beams for treatment (MV-CBCT). One patient with lung tumor underwent CT scans for radiotherapy planning and was treated by VMAT while acquiring projection images for kV and MV-CBCT. The datasets were reconstructed from the projection images using in-house programs. The position of the target in kV and MV-CBCT were detected using radiotherapy planning system and the movement of the targets between kV and MV-CBCT was similar. We have successfully evaluated the movement of the target “in treatment” using kV and MV-CBCT.

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Stereotactic radiosurgery is a non-invasive method for the treatment of tumors that employs a narrow, high-energy X-ray beam. In this form of therapy, the target region is intensively irradiated with the narrow beam, and any unexpected patient motion may therefore lead to undesirable irradiation of neighboring normal tissues and organs. To overcome this problem, we propose a contactless motion detection system with three USB cameras for use in stereotactic radiosurgery of the head and neck. In our system, the three cameras monitor images of the patient's nose and ears, and patient motion is detected using a template-matching method. If patient motion is detected, the system alerts the radiologist to turn off the beam. We reduced the effects of variations in the lighting in the irradiation room by employing USB cameras sensitive to infrared light. To detect movement in the acquired images, we use a template-matching method that is realized with general-purpose computing-on-graphics processing units. In this paper, we present an outline of our proposed motion detection system based on monitoring of images of the patient acquired with infrared USB cameras and a template-matching method. The performance of the system was evaluated under the same conditions as those used in actual radiation therapy of the head and neck.

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In order to diagnose osteoarthritis in its early stages, it is desirable to detect changes in the main components of the knee cartilage such as proteoglycan (PG) and collagen (CG). In the present study, we first fabricated physical phantoms containing different concentrations of PG or CG and then acquired MR images of these phantoms with a clinical MRI scanner using a variety of pulse sequences. The ratio of the MR signal intensity of each phantom to that of a reference object was then calculated. We also acquired MR images of the PG phantoms using an MR microscope and calculated the T1 relaxation time. The results showed a high correlation between the PG component concentration and the ratio of the MR signal intensity for the clinical scanner. A high correlation between the PG component concentration and the T1 relaxation time was also observed. The results of this study suggest that image acquisition of the knee joint together with a suitable reference object for calibration using a clinical MRI scanner may be a practical method for evaluating changes in PG in the knee cartilage.

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Architectural distortion is one of the most important findings in screening mammograms. Since this finding is related to the risk of malignancy and a poor prognosis, improvement of the detection rate is strongly desired. In this paper, we propose a novel method for detecting architectural distortion by analyzing mammary gland structure using multiple Gabor filters. In our method, multiple Gabor filters with different characteristics are applied, and the filter that matches the mammary gland structure is selected. Then, the degree of concentration is calculated using a filter output image, and a candidate region of spicula and traction of the mammary gland structure caused by the architectural distortion is obtained. In the experiments, we compared the results of the proposed method against interpretation by a physician using 22 images of 6 cases in a digital database of screening mammograms. The results showed a true positive rate of 80% with 1.06 false positives per image. We conclude that this initial candidate detection method for architectural distortion provides an acceptable level of performance.

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In a previous study, we developed a cylindrical filter for the detection of lung nodules in chest CT images. However, the detection rate of this method is reduced when nodules are adjacent to or overlap blood vessels or bronchi. The main objective of the present study was to develop a novel technique for improving the nodule detection capabilities of our method based on the anatomical structure of the bronchi and blood vessels obtained from CT images. In the proposed method, chest CT images are divided into a region consisting of normal lung structures (bronchi and blood vessels) and another region. Then, cylindrical filters with different characteristics are applied to the two regions. In order to evaluate the effectiveness of this method, the proposed method and the conventional method were applied to chest CT images, and their nodule detection capabilities were compared. The results showed that the true positive rate of the conventional method was 0.72, whereas that of the proposed method was 0.79. The number of false positives per case was 4.19 for both methods. These results indicate that the proposed method may be useful for improving nodule detection performance.

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A phase-contrast X-ray imaging technique using an X-ray interferometer that provides approximately 1000 times higher sensitivity than the conventional X-ray imaging method for low-atomic number elements based on the difference in the mass attenuation coefficient has recently been developed. In the present study, we compared rat kidneys fixed in 100% ethanol and in 10% formalin to evaluate the effects of ethanol in enhancing image contrast in phase-contrast imaging because ethanol causes significant dehydration of tissues and enhances density differences between tissue components. The experiments were conducted at the Photon Factory in Tsukuba, and the X-ray energy was set at 35 keV. Fine anatomical structures in the kidney such as the glomeruli, tubules, and vessels were observed. Particularly clear renal images were obtained with ethanol fixation. The pixel value ratio between the cortex and medulla was about 43% in ethanol-fixed kidneys and 21% in formalin-fixed kidneys. In other words, the contrast in ethanol-fixed kidneys was about two times higher than that in formalin-fixed kidneys. Histological examination showed significantly condensed features in the cortex. The results of this study suggest that the ethanol fixation technique may be useful for enhancing the image contrast of renal structures in the phase-contrast X-ray imaging technique.

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In this paper, we describe 3D shape construction, and rapid prototyping techniques using 3D printer. We also generate 3D surface models of brain, skin, muscle, and bone from the segmented 3D image obtained by X-ray CT and MRI devices, and show several replica models by 3D printer.

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