Biomedical subjects

Takashi Ueguchi

Publications and source records attributed to Takashi Ueguchi.

12 recordsLinked to original sources

PubMed2006

Novel display technique for reference images for visibility of temporal change on radiographs--color digital summation radiography.

PURPOSE: The present study investigated color digital summation radiography (CDSR) as a novel display technique for reference images for the visibility of temporal change on radiographs. In CDSR, only the parts with temporal differences are displayed in color. Moreover, all other parts are displayed in gray scale. MATERIALS AND METHODS: CDSR was defined as "radiographs combined by the additive color mixture method". The visibility of simulated nodules located in the lung fields and mediastinum was evaluated by 12 radiologists (mean experience, 9.8 years; range, 1-26 years) for 24 conventional radiographs and CDSR for 6 color patterns. A five-point rating system (5, very good; 4, good; 3, adequate; 2, poor; 1, very poor) was used. RESULTS: The mean scores (average +/- standard deviation) for the visibility of simulated nodules were as follows: magenta, 3.88 +/- 0.90; blue, 3.08 +/- 0.72; green, 3.04 +/- 0.86; red, 3.00 +/- 0.98; cyan, 2.71 +/- 0.86; and yellow, 2.50 +/- 0.72. Compared to conventional radiography in gray scale, at 1.21 +/- 0.41, all six color patterns for CDSR displayed significantly improved scores (p<0.001). CONCLUSION: CDSR might represent a useful technique for reference images from chest digital radiography.

Angiography↗

PubMed2006

Evaluation of the usefulness of color digital summation radiography in temporally sequential digital radiographs: a phantom study.

PURPOSE: The purpose of this study was to assess the usefulness of color digital summation radiography (CDSR) for detection of nodules on chest radiographs by observers with different levels of experience. MATERIALS AND METHODS: A total of 30 radiographs of chest phantoms with abnormalities and 30 normal ones were arranged at random. Set A was conventional radiographs only. Set B consisted of both conventional radiographs and CDSR images, which were colored with magenta. Five chest radiologists and five residents evaluated both image sets on a TFT monitor. The observers were asked to rate each image set using a continuous rating scale. The reading time for each set was also recorded. RESULTS: In set A, the performance of chest radiologists was significantly superior to that of the residents (P < 0.05). However, in set B, there was no significant difference in the performance of the chest radiologists and the residents. In both observer groups, the mean reading time per case in set B was significantly shorter than that in set A (P < 0.01). CONCLUSION: By using CDSR, the detection capability of observers with little experience improves and is comparable to that of experienced observers. Moreover, the reading time becomes much shorter using CDSR.

Color↗

PubMed2006

Evaluation of usefulness of color digital summation radiography for solitary pulmonary nodules on chest radiographs.

PURPOSE: The aim of this study was to evaluate the usefulness of novel color digital summation radiography (CDSR) for detecting solitary pulmonary nodules on chest radiographs by observers with different levels of experience. MATERIALS AND METHODS: A total of 30 healthy controls and 30 patients with newly detected solitary pulmonary nodules were evaluated. Six radiologists and five residents evaluated three image sets: set A, current and prior radiographs only; set B, set A with temporal subtraction images; and set C, set A with CDSR. The observers were asked to rate each image set using a continuous rating scale. In addition, the reading time required for each set was recorded. RESULTS: The radiologists showed no significant differences in the mean A(z) value between set A, set B, and set C. However, the residents showed significant differences between set A and set B and between set A and set C. In addition, for set B and set C, the mean reading time per case of all readers was significantly shorter than that for set A. CONCLUSION: The detection capability of observers with little experience is comparable to that of experienced observers when reading radiographs with temporal subtraction images or with CDSR. The usefulness of CDSR is comparable to that of temporal subtraction.

Clinical Competence↗

PubMed2006

Air microbubbles as MR susceptibility contrast agent at 1.5 Tesla.

Air microbubbles have been investigated recently at high magnetic field strength (2 Tesla or greater) as potential MR susceptibility contrast agents. We used a phantom to measure their susceptibility at 1.5 T to clarify their usefulness for this purpose. The phantom, filled with fresh Levovist suspension at 4 different doses (67 to 125 mg/mL), was continuously scanned with a gradient-echo technique at a temporal resolution of 10 s. The transverse relaxation increase (R2*) by microbubbles demonstrated a time course of exponential decay at each dose (time-constant, 39 to 57 s). The dependency of R2* on microbubble volume fraction was linear, with a slope of 89 s-1 per percentage microbubble volume fraction. Our study represents the first step towards applying microbubbles as susceptibility contrast agents at 1.5 T.

Air↗

PubMed2005

Full-size digital storage phosphor chest radiography: effect of 4K versus 2K matrix size on observer performance in detection of subtle interstitial abnormalities.

PURPOSE: To compare observer performance in the detection of subtle interstitial abnormalities on 3,520 x 3,520 (4K) matrix and 1,760 x 1,760 (2K) matrix full-size digital storage phosphor (DSP) chest radiographs. MATERIALS AND METHODS: Thirty-five 4K DSP chest radiographs with subtle interstitial abnormalities (n=27) or normal lungs (n=8) were processed with a half-band low-pass filter to produce 2K DSP radiographs. Although the actual matrix size of the 2K DSP radiographs remained 4K, the effective matrix size was reduced to 2K. Four chest radiologists independently evaluated full-sized hard-copy of the 4K and 2K DSP radiographs, and scored the presence of interstitial abnormalities for both right and left lungs on a five-point confidence scale. With findings on high-resolution computed tomography as the reference standard, observer performance was evaluated using multireader-multicase receiver operating characteristic (ROC) analysis. RESULTS: The average area under the ROC curve (Az) values for 4K and 2K DSP radiographs were 0.791+/-0.055 and 0.804+/-0.050, respectively. Both individual and averaged Az values showed no statistically significant differences (p>0.05) between 4K and 2K DSP radiographs. CONCLUSION: Observer performance in the detection of subtle interstitial abnormalities on 4K full-size DSP chest radiographs was equivalent to that on 2K full-size DSP chest radiographs.

Humans↗

PubMed2005

Aortic compliance in patients with aortic regurgitation: evaluation with magnetic resonance imaging.

PURPOSE: To assess by means of cine magnetic resonance imaging (MRI) aortic compliance before and after aortic valve replacement (AVR with SJM valve) in patients with aortic regurgitation (AR). MATERIALS AND METHODS: Two groups (healthy controls and patients with severe isolated AR) of 10 subjects each were included in this study. Cine MRI was performed at three locations of the aorta, and aortic compliance was calculated by dividing the maximum change in the aortic area by pulse pressure. RESULTS: Cine MRI is useful to assess abnormalities of aortic compliance in patients with AR. Compared with the control group, aortic compliance in the AR group was significantly less in the ascending aorta (p<0.05), decreasing in order of aortic location. After AVR, aortic compliance improved for all locations. CONCLUSION: Cine MRI enables assessment of aortic biophysical properties such as a compliance for evaluating the progression of AR and the efficacy of treatment.

Adult↗

PubMed2005

Voxel dimensions required for micromorphologic evaluation of ground-glass opacity on lung high-resolution CT.

PURPOSE: To clarify the appropriate voxel dimensions required for pathologic evaluation of areas with ground-glass opacity on lung high-resolution computed tomography (HRCT). MATERIALS AND METHODS: Synchrotron radiation CT (SRCT) images of autopsied lung speci-mens (n=25) that showed ground-glass opacity on HRCT were reconstructed with 12 different voxel dimensions ranging from 0.006 to 0.6 mm. The specimens were micromorphologically categorized into one of three pathologic groups: alveolar, interstitial, and mixed abnormalities. Each SRCT image was independently diagnosed as one of three pathologic groups by six chest radiologists. The diagnostic accuracy required to estimate the appropriate voxel dimensions was compared among different voxel dimensions by means of the Tukey test. RESULTS: Diagnostic accuracy with voxel dimensions less than or equal to 0.06 mm was significantly higher than that with voxel dimensions of 0.18 mm or more (p<0.01). There was, however, no significance of difference in diagnostic accuracy with voxel dimensions of less than or equal to 0.06 mm. In addition, no significant difference in diagnostic accuracy was found with voxel dimensions of 0.18 mm or more. CONCLUSION: The appropriate voxel dimensions are approximately 0.06 mm for pathologic differentiation of areas with ground-glass opacity on HRCT.

Humans↗

PubMed2004

[PACS for multi-slice CT--seamless integration implementing 3D and 4D workstations].

A PACS system for data management in multi-slice CT examination was upgraded using interactive 3D and 4D workstations and network computing technology. We categorized the original PACS (CT-PACS) as follows: (1) a fault-tolerant system linked with the hospital information system (HIS) and radiology information system (RIS); (2) an interactive network system using a workstation with real-time 3D and 4D reconstruction; (3) a system for research and development of software for 3D image analysis on the CT-PACS system. Because of the use of cooperative diagnostic supporting tools, no major problems occurred in daily clinical practice or research and education. In conclusion, CT-PACS with real-time 3D and 4D workstations was found to be helpful to radiologists and researchers in reading and analyzing large volumetric data.

Computer Communication Networks↗

PubMed2003

Analysis of entrance surface dose in general radiographies using body mass index classification.

Dose audit is an important topic in radiology and variations in dose attributable to sex have not been fully investigated. The primary purpose of our study was to determine the entrance surface dose (ESD) for men and women, from which we established an easy estimation equation for ESD, using the body mass index (BMI) as a variable. From April 2000 to March 2002, 15424 patients (8586 men, 6838 women; mean age, 58 years old; age range, 20 to 90 years old) were recruited in this study. Estimated equation of ESD was obtained from the dispersion data of BMI and ESD. Welch's t-test was used as the test of significance. P values evaluated levels of significance at 5%. Analysis for correlation coefficients was used for Peason's correlation coefficient test. And, we also performed a simple regression analysis. The results of the simple regression equation with BMI as variable (y: ESD [mGy], x: BMI [kg/m(2)), and the median values of ESD were as follows: for chest PA, men, 0.22, y = 0.0145 x - 0.0876, women, 0.20, y = 0.0126 x - 0.0704; for abdomen AP, men, 2.12, y = 0.2707 x - 3.7206, women, 1.65, y = 0.2561 x - 3.7989; for pelvis AP, men, 1.87, y = 0.0517 x + 0.8753, women, 1.77, y = 0.0674 x + 0.4775; for lumbar spine AP, men, 3.08, y = 0.3462 x - 4.1416, women, 2.66, y = 0.2525 x - 2.8131; and for lumbar spine lateral, men, 9.31, y = 0.6012 x - 3.7216, women, 7.42, y = 0.3147 x + 0.3384. The results of ESD had a significant difference between sexes (P < 0.05). Chest PA, abdomen AP, lumbar spine AP, and lumbar spine lateral each had a good correlation between ESD and BMI (r: 0.4 to 0.8). We successfully obtained the estimation equation using BMI as variable.

Body Mass Index↗

PubMed2002

Reconstruction of time-varying 3-D left-ventricular shape from multiview X-ray cineangiocardiograms.

This paper reports on the clinical application of a system for recovering the time-varying three-dimensional (3-D) left-ventricular (LV) shape from multiview X-ray cineangiocardiograms. Considering that X-ray cineangiocardiography is still commonly employed in clinical cardiology and computational costs for 3-D recovery and visualization are rapidly decreasing, it is meaningful to develop a clinically applicable system for 3-D LV shape recovery from X-ray cineangiocardiograms. The system is based on a previously reported closed-surface method of shape recovery from two-dimensional occluding contours with multiple views. To apply the method to "real" LV cineangiocardiograms, user-interactive systems were implemented for preprocessing, including detection of LV contours, calibration of the imaging geometry, and setting of the LV model coordinate system. The results for three real LV angiographic image sequences are presented, two with fixed multiple views (using supplementary angiography) and one with rotating views. 3-D reconstructions utilizing different numbers of views were compared and evaluated in terms of contours manually traced by an experienced radiologist. The performance of the preprocesses was also evaluated, and the effects of variations in user-specified parameters on the final 3-D reconstruction results were shown to be sufficiently small. These experimental results demonstrate the potential usefulness of combining multiple views for 3-D recovery from "real" LV cineangiocardiograms.

Algorithms↗

PubMedDate not supplied

Quantitative analysis for computed tomography findings of various diffuse lung diseases using volume histogram analysis.

OBJECTIVES: : The aim of this study was to achieve the quantitative analysis of the characteristic computed tomography (CT) findings and course of interstitial pneumonia using the volume histogram method. METHODS: : Contrast (CNT), variance (VAR), and entropy (EPY) values from whole-lung volume data were compared between normal lungs and 5 diseases that have characteristic CT findings. Thirteen cases with nonspecific interstitial pneumonia (NSIP) were evaluated before and after treatment. RESULTS: : In cases with thickening of the bronchovascular bundles and interlobular thickening, ground-glass attenuation, airspace consolidation, and honeycombing, the values of VAR and EPY were greater than those in the normal cases (P < 0.05). In the cases with NSIP, the CNT value after treatment was significantly greater and the values of VAR and EPY after treatment were significantly lower than those before treatment (P < 0.05). CONCLUSIONS: : Volume histogram analysis is a promising method for the evaluation of diffuse lung diseases and the effectiveness of treatment.

Adolescent↗

PubMedDate not supplied

Real-time estimation system for mean glandular dose in mammography.

PURPOSE: The purpose of this study was to construct a system that calculates mean glandular dose (MGD) in mammography in real-time on the RIS network. MATERIALS AND METHODS: Measurement of the half-value layer (HVL) and exposure dose were measured according to the Japanese mammographic quality control manual. A parallel plate chamber (10X5-6M; soft X-rays only) was used for measurement. Exposure dose was measured from 26 to 32 kV. RESULTS: Effective energy (Eeff [keV]) could be determined from tube voltage (V [kV] ) using the measure of the HVL according to the following equations: for the Mo/Mo combination, Eeff = 0.1325V + 11.80; for the Mo/Rh combination, Eeff = 0.1435V + 12.20; for the Rh/Rh combination, Eeff = 0.1724V + 11.29. Exposure output (XmAs [mR/mAs]), which can be determined from dosimetry per 1 mAs, becomes the following equation if effective energy is expressed as a variable: for the Mo/Mo combination, XmAs = 2.1329 Eeff2 - 57.784 Eeff + 392.71; for the Mo/Rh combination, XmAs = 1.1919 Eeff2 - 31.924 Eeff + 212.23; and for the Rh/Rh combination, XmAs = 2.6929 Eeff2 - 82.831 Eeff + 643.54. The MGD conversion factor (DgN [mGy/mR]) can be determined from effective energy using the ACR protocol according to the following equation: for the Mo/Mo combination, DgN = (0.3962 Eeff- 4.3178) 10(-3); for the Mo/Rh combination, DgN = (0.3495 Eeff - 3.5479) x 10(-3); and for the Rh/Rh combination, DgN = (0.4498 Eeff - 5.0448) x 10(-3). However, in these cases, compression breast thickness (CBT) was 4.2 cm, and the ratio of adipose and glandular tissue was 50/50. CONCLUSION: MGD can be determined using mAs obtained from mammography, exposure output (XmAs), MGD conversion factor (DgN), and source-skin distance compensation factor (SSDcf) according to the following equation: MGD [mGy] = mAs x XmAs [mR/mAs] x DgN [mGy/mR] x SSDcf where SSDcf = (64/(64 - CBT [cm]))2.

Breast↗