PubMed Health⌕ Search

Biomedical subjects

Shigeru Sanada

Publications and source records attributed to Shigeru Sanada.

At least 19 recordsLinked to original sources
PubMed2007

Sonographic appearance of the normal appendix in adults.

OBJECTIVE: To evaluate the sonographic visualization of the normal adult appendix, a large series of sonographic images from consecutive asymptomatic patients was analyzed. METHODS: A total of 788 consecutive adult patients (402 male and 386 female; median age +/- SD, 51.1 +/- 17.2 years; range, 16-91 years) were examined by appendiceal transabdominal sonography with tissue harmonic imaging. The detection rate, outer appendiceal diameter, intraluminal content, and location of the appendix were estimated. The overall normal appendix was separated into appendix-visualized and appendix-not-visualized groups, which were then examined for the relationship with abdominal wall thickness, body mass index (in kilograms per square meter), age, and sex. RESULTS: The normal appendix was detected in 388 (49.2%) of 788 patients. The outer appendiceal diameter +/- SD was 4.27 +/- 1.2 mm (range, 1.0-11.1 mm). In 291 (75%) of the 388 patients, appendices could be depicted in the intra-luminal gas during sonography. The location of the appendix was classified according to the appendiceal tip, which was found to be abdominal in 37 (9.5%), pelvic in 291 (75%), retrocecal in 23 (6.0%), and a midline extension in 37 (9.5%). In both body mass index and abdominal wall thickness, significant differences were found between appendix-visualized and appendix-not-visualized cases (P < .05). There was no significant difference in age (P = .37) or sex (P = .23) between appendix-visualized and appendix-not-visualized cases. CONCLUSIONS: The results show that the normal adult appendix can be revealed by sonographic visualization in a large series of asymptomatic patients.

Adolescent↗
PubMed2006

Psychophysical evaluation of calibration curve for diagnostic LCD monitor.

PURPOSE: In 1998, Digital Imaging Communications in Medicine (DICOM) proposed a calibration tool, the grayscale standard display function (GSDF), to obtain output consistency of radiographs. To our knowledge, there have been no previous reports of investigating the relation between perceptual linearity and detectability on a calibration curve. MATERIALS AND METHODS: To determine a suitable calibration curve for diagnostic liquid crystal display (LCD) monitors, the GSDF and Commission Internationale de l'Eclairage (CIE) curves were compared using psychophysical gradient delta and receiver operating characteristic (ROC) analysis for clinical images. RESULTS: We succeeded in expressing visually recognized contrast directly using delta instead of the just noticeable difference (JND) index of the DICOM standard. As a result, we found that the visually recognized contrast at low luminance areas on the LCD monitor calibrated by the CIE curve is higher than that calibrated by the GSDF curve. On the ROC analysis, there was no significant difference in tumor detectability between GSDF and CIE curves for clinical thoracic images. However, the area parameter Az of the CIE curve is superior to that of the GSDF curve. The detectability of tumor shadows in the thoracic region on clinical images using the CIE curve was superior to that using the GSDF curve owing to the high absolute value of delta in the low luminance range. CONCLUSION: We conclude that the CIE curve is the most suitable tool for calibrating diagnostic LCD monitors, rather than the GSDF curve.

Calibration↗
PubMed2006

Development of a method for reconstructing three-dimensional data from axial, sagittal, and coronal MR images.

Magnetic resonance (MR) imaging is useful for the diagnosis of brain atrophy and intracranial abnormalities. We have developed a method of automated volumetry to evaluate the degree of brain atrophy for the diagnosis of dementia. Whole-brain MR images with thin slices without gaps are required for segmentation and volumetry. However, obtaining such images requires that the patient remain at rest for a prolonged period, thereby reducing the throughput of MR imaging examinations. Therefore, a method is needed for the reconstruction of isotropic three-dimensional (3D) data using routine axial, sagittal, and coronal MR images with 30% gaps and measurement of brain volume. The method of reconstructing 3D data consists of four processes: 1) segmentation of the brain region on axial, sagittal, and coronal MR images using the region-growing technique; 2) setting data to a 3D domain; 3) registration by manual operation; and 4) interpolation between the data based on linear interpolation. In clinical MR images, the differences between this method and the conventional technique were less than 10%. These results demonstrate that this technique is able to construct 3D data from axial, sagittal, and coronal MR images.

Adult↗
PubMed2006

Computerized methods for determining respiratory phase on dynamic chest radiographs obtained by a dynamic flat-panel detector (FPD) system.

Chest radiography using a dynamic flat-panel detector with a large field of view can provide sequential chest radiographs during respiration. These images provide information regarding respiratory kinetics, which is effective for diagnosis of pulmonary diseases. For valid analysis of respiratory kinetics in diagnosis of pulmonary diseases, it is crucial to determine the association between the kinetics and respiratory phase. We developed four methods to determine the respiratory phase based on image information associated with respiration and compared the results in dynamic chest radiographs of 37 subjects. Here, the properties of each method and future tasks are discussed. The method based on the change in size of the lung gave the most stable results, and that based on the change in distance from the lung apex to the diaphragm was the most promising method for determining the respiratory phase.

Humans↗
PubMed2006

Evaluation of pulmonary function using breathing chest radiography with a dynamic flat panel detector: primary results in pulmonary diseases.

OBJECTIVES: Dynamic flat panel detectors (FPD) permit acquisition of distortion-free radiographs with a large field of view and high image quality. The present study was performed to evaluate pulmonary function using breathing chest radiography with a dynamic FPD. We report primary results of a clinical study and computer algorithm for quantifying and visualizing relative local pulmonary airflow. MATERIALS AND METHODS: Dynamic chest radiographs of 18 subjects (1 emphysema, 2 asthma, 4 interstitial pneumonia, 1 pulmonary nodule, and 10 normal controls) were obtained during respiration using an FPD system. We measured respiratory changes in distance from the lung apex to the diaphragm (DLD) and pixel values in each lung area. Subsequently, the interframe differences (D-frame) and difference values between maximum inspiratory and expiratory phases (D-max) were calculated. D-max in each lung represents relative vital capacity (VC) and regional D-frames represent pulmonary airflow in each local area. D-frames were superimposed on dynamic chest radiographs in the form of color display (fusion images). The results obtained using our methods were compared with findings on computed tomography (CT) images and pulmonary functional test (PFT), which were examined before inclusion in the study. RESULTS: In normal subjects, the D-frames were distributed symmetrically in both lungs throughout all respiratory phases. However, subjects with pulmonary diseases showed D-frame distribution patterns that differed from the normal pattern. In subjects with air trapping, there were some areas with D-frames near zero indicated as colorless areas on fusion images. These areas also corresponded to the areas showing air trapping on computed tomography images. In asthma, obstructive abnormality was indicated by areas continuously showing D-frame near zero in the upper lung. Patients with interstitial pneumonia commonly showed fusion images with an uneven color distribution accompanied by increased D-frames in the area identified as normal on computed tomography images. Furthermore, measurement of DLD was very effective for evaluating diaphragmatic kinetics. CONCLUSIONS: This is a rapid and simple method for evaluation of respiratory kinetics for pulmonary diseases, which can reveal abnormalities in diaphragmatic kinetics and regional lung ventilation. Furthermore, quantification and visualization of respiratory kinetics is useful as an aid in interpreting dynamic chest radiographs.

Adult↗
PubMed2005

Automated image-matching technique for comparative diagnosis of the liver on CT examination.

When interpreting enhanced computer tomography (CT) images of the upper abdomen, radiologists visually select a set of images of the same anatomical positions from two or more CT image series (i.e., non-enhanced and contrast-enhanced CT images at arterial and delayed phase) to depict and to characterize any abnormalities. The same process is also necessary to create subtraction images by computer. We have developed an automated image selection system using a template-matching technique that allows the recognition of image sets at the same anatomical position from two CT image series. Using the template-matching technique, we compared several anatomical structures in each CT image at the same anatomical position. As the position of the liver may shift according to respiratory movement, not only the shape of the liver but also the gallbladder and other prominent structures included in the CT images were compared to allow appropriate selection of a set of CT images. This novel technique was applied in 11 upper abdominal CT examinations. In CT images with a slice thickness of 7.0 or 7.5 mm, the percentage of image sets selected correctly by the automated procedure was 86.6+/-15.3% per case. In CT images with a slice thickness of 1.25 mm, the percentages of correct selection of image sets by the automated procedure were 79.4+/-12.4% (non-enhanced and arterial-phase CT images) and 86.4+/-10.1% (arterial- and delayed-phase CT images). This automated method is useful for assisting in interpreting CT images and in creating digital subtraction images.

Aged↗
PubMed2005

Development of a semi-automated superimposing image verification system using a template matching algorithm in radiotherapy.

To analyze shifts in the isocenter of images, we developed a semi-automated superimposing image-verification system that is capable of automatically quantifying shifts in the isocenter through image analysis with a personal computer (PC). The accuracy and usefulness of this software were examined through a comparison of nine portal images with a simulation image and by comparing nine portal images with a DRR image, using a human pelvic phantom. The difference between the known magnitude of shift and the magnitude of shift detected with this method was analyzed as detection error. When the portal images were compared with the simulation image, the 95% confidence interval (95% CI) of detection errors (mean+/-SD) was 0.57+/-0.36 mm (95% CI: 0.49-0.65 mm). When the portal images were compared with the DRR image, the respective figures were 0.68+/-0.38 mm (95% CI: 0.59-0.77 mm). No significant difference was noted between these two categories of comparison (N.S). The absolute detection error (mean+/-SD) in all directions was 0.34+/-0.34 mm for the comparison of portal images with the simulation image and 0.41+/-0.36 mm for the comparison of portal images with the DRR image. This system seems to be appropriate for verification of the treatment field by improving the accuracy of radiotherapy as a method of computer-assisted landmark recognition during image comparison.

Algorithms↗
PubMed2005

Development of computerized patient setup verification and correction system in radiotherapy.

Visual comparison of a reference image with a verification image is commonly used for setup verification in external beam radiation therapy. However, it sometimes lacks reproducibility and provides insufficient quantitative evidence. The present study was performed to develop computerized methods for determining landmarks to verify a portal image with digital reconstruction radiograph (DRR), and to investigate the clinical effectiveness of our method. Our computer algorithm consisted of three main procedures--preprocessing, determination of landmarks, and verification--none of which required manual operation. Finally, our system indicated the distance for setup correction. We evaluated the accuracy of our system using pelvic phantom images, and the maximum magnitude of error was shown to be 1.12 (n=9). The results indicated that the error range of our system was sufficiently small to examine patient positioning error, which should be less than 5 mm, as described in AAPM report TG40. Our system will aid operators in positioning patients accurately for external radiation therapy.

Algorithms↗
PubMed2005

[Evaluation of the perceptional performance of high resolution flat panel displays].

With the recent great advances in technology, the use of flat panel displays (FPD) is tending to increase. However, there is concern that the physical properties are not understood well enough by physicians to take advantage of the improved physical properties to assist them with diagnosis. Because displays of differing physical properties are being used in clinics, we have not seen enough research about the relationship between diagnostic ability and the physical properties of displays. The purpose of this study was to evaluate radiologists' performance in the diagnosis of nodules in chest radiographs with three kinds of flat panel displays: 3M- and 5M-pixel monochrome flat panel displays, and a 3M-pixel color flat panel display. Nine radiologists participated in this observer study. Sixty chest radiographs were used. Thirty-five images depicted malignant nodules, and 25 images were normal. We set for an 8-bit gray scale in advance. The radiologists' performance was evaluated with receiver operating characteristic (ROC) analysis by using a computer program (ROCKIT; Charles E. Metz, University of Chicago) . Observer performance for the diagnosis of nodules in chest radiographs was not significantly different using 3M- and 5M-pixel monochrome, and 3M-pixel color flat panel displays. Further investigation of frequent spatial patterns requiring higher resolutions such as the interstitial infiltrate pattern in chest images and the microcalcifications in mammographs will be needed.

Data Display↗
PubMed2005

[Study of automated segmentation of the cerebellum and brainstem on brain MR images].

MR imaging is an important method for diagnosing abnormalities of the brain. This paper presents an automated method to segment the cerebellum and brainstem for brain MR images. MR images were obtained from 10 normal subjects (male 4, female 6; 22-75 years old, average 31.0 years) and 15 patients with brain atrophy (male 3, female 12; 62-85 years of age, average 76.0 years). The automated method consisted of the following four steps: (1) segmentation of the brain on original images, (2) detection of an upper plane of the cerebellum using the Hough transform, (3) correction of the plane using three-dimensional (3D) information, and (4) segmentation of the cerebellum and brainstem using the plane. The results indicated that the regions obtained by the automated method were visually similar to those obtained by a manual method. The average rates of coincidence between the automated method and manual method were 83.0+/-9.0% in normal subjects and 86.4+/-3.6% in patients.

Adult↗
PubMed2004

Quantitative perfusion map of malignant liver tumors, created from dynamic computed tomography data.

RATIONALE AND OBJECTIVES: To apply perfusion computed tomography (CT) technique to variable malignant liver tumors, and to define the usefulness of quantitative color mapping. MATERIALS AND METHODS: Perfusion CT images were created for 36 malignant liver tumors in 28 patients (age, 66.4 +/- 10.1 years; range, 48-85) with metastatic liver tumors (n = 17; nine colorectal carcinomas, eight other malignant tumors) and hepatocellular carcinomas (n = 11). A single-slice dynamic CT was performed after an intravenous bolus injection of 40 mL of contrast material (320 mgI/mL) with 8 mL/sec. The parameters were calculated pixel-by-pixel using maximum slope method, and quantitative maps of arterial and portal perfusion were created. In four patients who underwent transcatheter arterial chemoembolization, perfusion CT was performed before and after transcatheter arterial chemoembolization. RESULTS: In all patients, liver tumors were shown as hypervascular lesions on arterial perfusion CT. The average arterial perfusion value of the metastatic tumors from the colorectal carcinomas was 0.67 +/- 0.33 mL/min/mL, and that of hepatocellular carcinomas was 0.94 +/- 0.26 mL/min/mL (P = .03). The other metastatic tumors from various primary tumors showed a wide range (0.19-1.45 mL/min/mL) of arterial perfusion. Arterial perfusion of the liver tumors was obviously decreased after successful transcatheter arterial chemoembolization. In 12 of 15 tumors, in which portal perfusion CT images could be created, region-of-interest analysis showed no portal perfusion in the tumors. In two cases, decreased portal perfusion in the segments, which malignant tumors involved, was demonstrated. CONCLUSION: Perfusion CT can provide quantitative information about arterial and portal perfusion of liver tumors, combined with good anatomic detail in one image. This technique has a potential to evaluate the angiogenesis of liver tumors, to show secondary changes in perfusion, such as decreased portal perfusion in apparently normal liver adjacent to metastases, and to monitor the therapeutic response in vivo.

Aged↗
PubMed2004

Breathing chest radiography using a dynamic flat-panel detector combined with computer analysis.

Kinetic information is crucial when evaluating certain pulmonary diseases. When a dynamic flat-panel detector (FPD) can be used for a chest examination, kinetic information can be obtained simply and cost-effectively. The purpose of this study was to develop methods for analyzing respiratory kinetics, such as movement of the diaphragm and lung structures, and the respiratory changes in x-ray translucency in local lung fields. Postero-anterior dynamic chest radiographs during respiration were obtained with a modified FPD, which provided dynamic chest radiographs at a rate of 3 frames/s. Image registration for correction of physical motion was followed by measurement of the distance from the lung apex to the diaphragm. Next, we used a cross-correlation technique to measure the vectors of respiratory movement in specific lung areas. Finally, the average pixel value for a given local area was calculated by tracing the same local area in the lung field. This method of analysis was used for six healthy volunteers and one emphysema patient. The results reported here represent the initial stage in the development of a method that may constitute a new method for diagnosing certain pulmonary diseases, such as chronic obstructive pulmonary disease, fibroid lung, and pneumonia. A clinical evaluation of our method is now in progress.

Humans↗
PubMed2003

[Hepatic perfusion CT imaging analyzed by the dual-input one-compartment model].

AIM: To improve liver-perfusion imaging by using the dual-input one-compartmental model. METHODS: Single-level dynamic computed tomography (dynamic CT) was taken at the height of the hepatic hilum after a rapid intravenous injection using 40 ml of iodinated contrast material. From the time-density curve of each pixel on CT, we calculated blood-flow rate constants of liver inflow and outflow. For inflow, two constants were calculated at arterial and portal veins. We postulated that blood flow between hepatic vessels and the hepatic parenchyma could be analyzed by using the calculated constants, and made equations for liver perfusion mapping. The perfusion images obtained by this method were compared with those made by the maximum slope method. RESULTS: We applied the method to a patient with hepatolithiasis. On dynamic CT, there was an abnormal enhancement pattern in the posterior segment of the liver. Perfusion CT images made by the dual-input one-compartment model demonstrated abnormal portal perfusion of the liver. In contrast, those made by the maximum-slope method did not represent the perfusion pattern well. CONCLUSION: The dual-input one-compartmental model makes it possible to obtain more detailed information on liver hemodynamics.

Bile Ducts, Intrahepatic↗
PubMed2003

[Kinetic radiography and functional analysis of the temporomandibular joint (TMJ)].

To develop a method of kinetic radiography and a computer-aided diagnosis (CAD) system for quantitative evaluation of the temporomandibular joint (TMJ), dynamic images of the TMJ from one healthy volunteer were obtained by fluoroscopy in the lateral view on the right and left sides. The accumulated image subtraction technique extracted the condyle in each image. A sequential similarity detection algorithm (SSDA) was employed to trace the movement path and the velocity of the condyle. The shape of the path of the right condyle was smoother than that of the left condyle. The size of the maximum vertical and horizontal movements of the condyle were 4.6+/-0.1 mm and 15.0+/-0.2 mm, respectively. The velocity of the movement of the condyle was higher in the area close to the articular eminence than in any other area during the opening and closing of the mouth. This CAD system will contribute to the kinetic analysis of the TMJ for screening, follow-up study, and informed consent, providing speed, quantitation, and cost-effectiveness.

Algorithms↗