Biomedical subjects

Mitsuru Ikeda

Publications and source records attributed to Mitsuru Ikeda.

At least 37 records · Page 2Linked to original sources

PubMed2005

Branch duct-type intraductal papillary mucinous tumor: diagnostic value of multiplanar reformatted images in multislice CT.

The object of this study was to evaluate the usefulness of high-resolution multiplanar reformatted (MPR) images obtained by multislice CT in demonstrating connection between pancreatic cystic lesions and the main pancreatic duct. The study included 27 lesions with connection to the main pancreatic duct and 12 lesions without. All but one of the former lesions were branch duct-type intraductal papillary mucinous tumors (IPMTs). Oblique and curved MPR images with 0.5 mm continuous slices were generated from pancreatic-phase axial images reconstructed with 0.5 mm or 1 mm thickness at 0.5 mm intervals over a 260 mm field of view. The diagnostic capabilities for demonstrating connection with the main pancreatic duct were compared among axial images, MPR images, and both axial and MPR images in combination using the Brier score. The diagnosis in MPR images for demonstrating connection was more certain than that in axial images (P<0.05). Compared with MPR images alone, the use of both axial and MPR images resulted in further improvements in diagnostic performance, although the difference was not statistically significant. The use of high-resolution MPR images significantly improves diagnostic performance for demonstrating connection between pancreatic cystic lesions and the main pancreatic duct, which is useful for the diagnosis of branch duct-type IPMT.

Adenocarcinoma, Mucinous↗

PubMed2005

Effects of monitor luminance change on observer detection performance.

To confirm that the dimming luminance change in the CRT monitor will have a detrimental effect on diagnostic performance, we performed the four-alternative forced choice experiments on the CRT monitor with the 11 luminance conditions simulating CRT degraded by long-term usage. Six radiologists and one pulmonary physician performed a detection task for 11,000 test areas on 110 test images. The 11 monitor conditions significantly affected the correct detection rates of simulated nodules in the four-alternative forced choice experiments. The gradual deterioration in CRT monitor luminance will have certainly a detrimental effect on detection performance.

Computer Terminals↗

PubMed2005

Multiphase contrast-enhanced CT of the liver with a multislice CT scanner: effects of iodine concentration and delivery rate.

PURPOSE: To determine whether or not high-concentration contrast material is useful in multiphase contrast-enhanced CT of the liver with a multislice CT scanner. MATERIALS AND METHODS: One hundred twenty-four examinations, in which first- and second-pass acquisitions (double arterial phase imaging) were performed during a single breath-hold followed by third-pass acquisition, were randomized into three protocols: contrast injection at 0.07 mL/kg body weight/sec over 30 sec at an iodine concentration of 300 mgI/mL in group 1, contrast injection at 0.06 mL/kg body weight/sec over 30 sec at an iodine concentration of 350 mgI/mL in group 2, and contrast injection at 0.07 mL/kg body weight/sec over 25.7 sec at an iodine concentration of 350 mgI/mL in group 3. Each group received an equivalent iodine dose per kg body weight (2.1 mL/kg of contrast material of 300 mgI/mL). Contrast enhancement in each acquisition was measured in the aorta, portal vein, and liver. RESULTS: No statistically significant differences were seen between groups 1 and 2 in any enhancement in any acquisition. In group 3, aortic enhancement in the first-pass acquisition was significantly more intense than in groups 1 and 2, while portal venous enhancement and hepatic enhancement were equivalent. CONCLUSION: Shortening the injection duration for a given iodine dose with high-concentration contrast material (group 3) can achieve improved arterial enhancement on arterial phase images.

Adult↗

PubMed2005

Three-phase CT examination of the pancreatobiliary region using multislice CT with 1-mm collimation.

PURPOSE: To evaluate the degree of contrast enhancement and accuracy of imaging of the circulatory phase in the first-pass, second-pass, and third-pass acquisitions in the pancreato-biliary region with 1-mm collimation obtained by multislice computed tomography (CT). MATERIALS AND METHODS: In 53 patients, two sequential acquisitions from the porta hepatis to the pancreas were performed during a single breath-hold, followed by a third-pass acquisition including the liver beginning 15 sec after the second-pass acquisition. Contrast enhancement in each acquisition was measured in the aorta, portal vein and its branches, and pancreas. Four experienced radiologists graded using four-point scoring whether or not each acquisition was appropriate for imaging of the arterial phase, pancreatic phase, and portal venous phase. RESULTS: Aortic enhancement was highest at the beginning of the second-pass acquisition. The portal and splenic veins and pancreas showed maximum enhancement in the second-pass acquisition, while the superior mesenteric vein showed maximum enhancement in the third-pass acquisition. In the visual assessment, significantly higher grades were achieved in the first-pass, second-pass, and third-pass acquisitions with regard to imaging of the arterial phase, pancreatic phase, and portal venous phase, respectively. CONCLUSION: Multislice CT permits the acquisition of three distinct circulatory phases (arterial, pancreatic, and portal venous phases) in the pancreatobiliary region with 1-mm collimation.

Adult↗

PubMed2004

Late-arterial and portal-venous phase imaging of the liver with a multislice CT scanner in patients without circulatory disturbances: automatic bolus tracking or empirical scan delay?

The value of automatic bolus tracking in late-arterial and portal-venous phase imaging of the liver with a multislice CT scanner as compared with fixed time-delay examination in patients without circulatory disturbances is evaluated. For the evaluation of known or suspected liver disease, 98 multiphase contrast-enhanced CT examinations including double late-arterial phase imaging were randomized into either scanning with a scan delay of 30 s from the beginning of contrast material injection or scanning with automatic bolus tracking. Contrast material was injected at 0.07 ml/kg body weight/s over 30 s. Contrast enhancement in each acquisition was measured in the aorta, portal vein, liver, pancreas and hepatocellular carcinomas. The density difference between hepatocellular carcinomas and the hepatic parenchyma was calculated. The mean time to the first-pass acquisition as determined by automatic bolus tracking was 29.6 s. No statistically significant difference was observed between the two groups either in any enhancement in any acquisition or in the lesion-to-liver density difference. The use of automatic bolus tracking in late-arterial and portal-venous phase hepatic CT does not significantly improve the degree of contrast enhancement in the aorta, portal vein, liver and pancreas or lesion-to-liver conspicuity in patients without circulatory disturbances.

Adult↗

PubMed2004

Long-term result of high dose-rate afterloading brachytherapy in squamous cell carcinoma of the cervix: relationship between facility structure and outcome.

OBJECTIVE: To compare outcome results for squamous cell carcinoma of the uterine cervix between patients treated in a single facility [single facility therapy: (SFT)] and others combined with external beam irradiation (EBRT) in a small facility and intracavitary brachytherapy in a central facility (combined facilities therapy: CFT). METHODS: This is a retrospective analysis of 155 patients with histologically proven squamous cell carcinoma of the cervix radically treated by EBRT and high dose-rate (HDR) intracavitary brachytherapy from August 1995 to May 2000. The overall survival and cause-specific survival rates were calculated by using the Kaplan-Meier method. The endpoint was defined as death due to cervical cancer for the cause-specific survival. The log-rank test and the generalized Wilcoxon test were used to compare the survival curves between the two treatment groups. RESULTS: Nine patients were lost, so 146 patients were retrospectively analyzed. There were 22 patients (15%) in stage I, 21 (14%) stage IIA, 51 (35%) stage IIB, 41 (28%) stage III, 11 (8%) stage IVA. The median age was 72 years (range, 30-89 years). The median follow-up time was 58 months. The proportion of patients treated with SFT was 23% (33/146) and CFT 77% (113/146). The overall survival rate was 62.3% and the cause-specific survival rate was 71.3%. The cause-specific survival rates for SFT and CFT were 87.9% and 66.4%, respectively; the difference between these two treatments was statistically significant (P = 0.024). The difference in the survival rate between these two treatments for stage III and IVA patients was also statistically significant (P = 0.021). However, no significant difference between these treatments was seen in the cause-specific survival rate for each stage. There was a significant difference between SFT and CFT in the incidence rate of severe late complications (grade 3-5) (P = 0.038). There was no significant difference in overall treatment times and total dose between the two groups; the applied photon beam energy showed a significant difference. CONCLUSION: Our results suggest that the survival outcome will be aggravated by CFT. If the treatment process of using a lower photon beam energy were to be improved by the installation of a high-energy linear accelerator, CFT can be applied to patients with cervical cancer.

Adult↗

PubMed2004

A telemedicine system for collaborative work on radiographic coronary video-images.

We designed a telemedicine system that supports collaborative work on video-images from coronary cine-angiograms and cine-ventriculograms. Two workstations were connected by ISDN at 128 kbit/s. Coronary cine-angiogram and cine-ventriculogram video-images were transmitted to an image examination workstation before the images were required for analysis (i.e. in a 'pre-fetch' operation). If one workstation changed even a single frame in a video-sequence, then the change was transmitted to the other workstation, rather than the entire video-sequence. To evaluate the performance of the system, the diagnoses made by five cardiology specialists were compared with those recorded in the original report. Coronary cine-angiogram and cine-ventriculogram video-images from 27 patients were used. The cardiologists, who were blinded to the patient information, regenerated the video-images on the workstation and assessed coronary arterial stenosis and wall motion. The kappa scores for clinician agreement with the original reports for ratings of stenosis were 0.54-0.66 and for wall motion were 0.41-0.69. The system performed reasonably reliably and it therefore appears likely to be useful in telemedicine work.

Cineangiography↗

PubMed2003

Influence of monitor luminance change on observer performance for detection of abnormalities depicted on chest radiographs.

RATIONALE AND OBJECTIVES: To investigate how changes in luminance affect the detection accuracy of radiologists viewing chest radiograph images on high-resolution CRT monitors. MATERIALS AND METHODS: Thirteen radiologists performed a detection task for 11 chest radiograph images with simulated nodules on a monitor with 11 luminance conditions (the maximum luminance ranges from 157.4-369.0 candela/m2) simulating CRT degraded by long-term usage, under the ambient illumination of 200 lux; the observation order was always from the darkest to the brightest. RESULTS: There was a statistically reliable effect of the 11 monitor display conditions on the detection of nodules (P < 0.001). In the conditions in which the maximum luminance of the CRT was 60.7% or below that of the standard display luminance, the correctly detected nodule number reliably deteriorated. CONCLUSIONS: The luminance change in CRT monitor display under long-term usage will have a detrimental effect on nodule detection performance in chest radiograph images.

Data Display↗

PubMed2003

Prospective analysis of mortality, morbidity, and risk factors in elderly diabetic subjects: Nagano study.

OBJECTIVE: To clarify mortality and morbidity of intensively managed elderly diabetic individuals and to explore factors predicting mortality and diabetes-related end points. RESEARCH DESIGN AND METHODS: A total of 390 elderly (>or=65 years of age) outpatients with type 2 diabetes ( 173 men and 217 women, mean age 73.0 years) were analyzed. The mean HbA(1c) upon entry was 6.8% (332 receiving oral hypoglycemics and/or insulin) and blood pressure upon entry was 136/74 mmHg (219 receiving antihypertensive drugs). The patients have been followed-up for 3 years with HbA(1c) <7.0% and blood pressure <145/80 mmHg as targets, with mortality and an aggregate of fatal and nonfatal diabetes-related events as end points. Mortality rate and causes of mortality, as well as risk factors for mortality and morbidity, were determined. RESULTS: The mortality rate, 2.9% per year, was comparable to that of the age- and sex-matched general population. Stroke was a leading cause of mortality after malignancy. By the univariate Cox proportional hazards model, only high serum creatinine and prior stroke were highly significant and strong risks for both end points. In those without prior stroke and receiving antihypertensive agents, the incidence of the diabetes-related end point based on their systolic blood pressure (SBP) quartile was U-shaped, with the nadir at the 3rd (SBP, 137-147 mmHg) and the peak at the 1st (SBP <or= 125 mmHg) quartile. CONCLUSIONS: In well-controlled elderly diabetic subjects, there was no excessive mortality compared to the age- and sex-matched general population. Renal dysfunction and prior stroke were independent risks for mortality and morbidity. In those without prior stroke, a risk of too much lowering of blood pressure was suggested.

Aged↗

PubMed2003

Relationship between exercise-induced myocardial ischemia and reduced left ventricular distensibility in patients with nonobstructive hypertrophic cardiomyopathy.

UNLABELLED: Many studies have demonstrated that reduced left ventricular (LV) diastolic distensibility plays a key role in the pathophysiology of hypertrophic cardiomyopathy (HCM). However, the relationship between myocardial ischemia and reduced LV distensibility in HCM remains unclear. We aimed to clarify the relationship between exercise-induced ischemia and reduced LV distensibility in patients with HCM. METHODS: Twenty patients with HCM and 5 age-matched control subjects underwent stress-redistribution (201)Tl myocardial scintigraphy and biventricular cardiac catheterization and echocardiography at rest and during exercise. Scintigraphic defect analysis was interpreted using Berman's 20-segment model. The summed stress score (SSS) was calculated as the sum of scores of the 20 LV segments and the summed difference score (SDS) was calculated as the sum of differences between each of the 20 LV segments on stress and rest images. RESULTS: Patients were divided into 2 groups according to the (201)Tl defect as follows: 9 patients with an SSS on (201)Tl of >or=10 and an SDS on (201)Tl of >or=5 (ischemic group) and 11 patients with an SSS of <10 or an SDS of <5 (nonischemic group). The absolute increases from rest to peak exercise in LV end-diastolic pressure (LVEDP) and pulmonary artery wedge pressure were significantly greater (15.5 +/- 5.2 vs. 7.6 +/- 5.5 mm Hg and 17.3 +/- 5.0 vs. 8.9 +/- 5.0 mm Hg, P < 0.01, respectively), and the percentage changes from rest to peak exercise in the maximum first derivative of LV pressure and LV pressure half-time were significantly smaller in the ischemic HCM group compared with the nonischemic HCM group (70% +/- 24% vs. 123% +/- 43% and -32% +/- 6.4% vs. -44% +/- 9.4%, P < 0.01, respectively). However, the end-diastolic dimensions did not differ between the 2 HCM groups. One of the 9 patients in the ischemic group, as revealed by fill-in on (201)Tl scintigraphy, showed increased (18)F-FDG uptake in the anteroseptal wall. CONCLUSION: Some HCM patients show a significant increase in LVEDP without chamber dilatation, indicating reduced LV diastolic distensibility. Myocardial ischemia may at least in part contribute to this condition.

Adult↗

PubMed2002

MMP-9 and EBA immunoreactivity after papaverine mediated opening of the blood-brain barrier.

Papaverine is a non-specific vasodilatory drug, which was found to unexpectedly cause opening of the blood-brain barrier (BBB). We studied the expression of two endothelial cell related markers, endothelial barrier antigen (EBA) as a marker of BBB intactness, and matrix metalloproteinase-9 (MMP-9), an extracellular matrix molecule, the activation of which results in BBB opening. Immunoreactivity was quantified after intra-carotid injection of papaverine in rats. BBB opening was identified at 1 h, but had been reversed by 24 h. Reduction in EBA-immunoreactivity occurred at 3 h, whereas MMP-9 was not observed until 24 h. The activation of MMP-9 thus occurred much later than BBB opening, which suggests a different role for MMP-9 when selective and reversible opening of the BBB is produced by pharmacological manipulation.

Animals↗

PubMed2002

Multiphase contrast-enhanced CT of the liver with a multislice CT scanner.

Our objective was to assess the effects of the injection rate of contrast material and of a 5% dextrose flush on enhancement in multiphase hepatic CT using a multislice CT scanner. Most patients had chronic hepatitis and/or liver cirrhosis. One hundred eighty examinations, in which two sequential acquisitions were performed during a single breath-hold followed by third- and fourth-pass acquisitions, were randomized into four protocols: contrast injection at 0.1 ml/kg body weight s(-1) over 21 s without and with a 30-ml flush in groups 1 and 2, respectively, and contrast injection at 0.07 ml/kg body weight s(-1) over 30 s without and with a flush in groups 3 and 4, respectively. Contrast enhancement in each acquisition was measured in the aorta, portal vein, and liver. The visualization of hepatic arterial branches was scored by visual assessment. The highest aortic enhancement was observed in the first-pass acquisition in all groups. At the higher injection rate (groups 1 and 2), aortic enhancement in the first-pass acquisition was significantly more intense, whereas portal venous and hepatic enhancement was significantly less intense. The use of a flush considerably improved aortic enhancement at the beginning of the second-pass acquisition. In the visual assessment of hepatic arterial branches, the protocols with the higher injection rate received significantly higher grades. Multislice CT permits the entire liver to be imaged during an almost exclusively arterial phase by shortening the injection duration for a given volume of contrast material.

Adult↗

PubMed2002

Assessment of the pancreatic and intrapancreatic bile ducts using 0.5-mm collimation and multiplanar reformatted images in multislice CT.

Our objective was to evaluate the ability of multiplanar reformatted (MPR) images combined with 0.5-mm axial images to depict the pancreatic and intrapancreatic bile ducts and compare the results with those of 0.5-mm axial, 2-mm axial, and 6-mm axial images alone. Seventy-seven patients without obstruction of the main pancreatic ducts (MPD) underwent dual-phase helical scanning of the pancreas using multislice computed tomography (MSCT). The MPR images were generated from 0.5-mm-thick images. Visualization of the pancreatic and intrapancreatic bile ducts and their confluence was graded on a four-point scale by a consensus of two radiologists. The results for 0.5-mm axial images in early-phase CT, 2-mm axial images in early-phase CT, MPR images combined with 0.5-mm axial images in early-phase CT, and 6-mm axial images in late-phase CT were then compared. The relationships of the focal pancreatic lesions with the pancreatic ducts were analyzed. The MPR images combined with 0.5-mm axial images were significantly superior to the other three types of images for the visualization of the pancreatic and intrapancreatic bile ducts and their confluence (p<0.01). The depiction rate of the MPD using MPR images combined with 0.5-mm axial images was 94, 94, 95, and 75%, respectively in the head, neck, body, and tail of the pancreas. Accessory pancreatic ducts, intrapancreatic bile ducts, and duct confluence were depicted in 48, 99, and 92%, respectively. In comparison with evaluation based on axial images alone, the use of MPR images more clearly demonstrated the relationship between the lesions and the pancreatic ducts in 14 of 19 lesions. The MPR images combined with 0.5-mm axial images improve the CT depiction of the pancreatic and intrapancreatic bile ducts in comparison with 0.5-mm axial, 2-mm axial, and 6-mm axial images alone.

Adult↗

PubMed2002

Interobserver agreement and performance score comparison in quality control using a breast phantom: screen-film mammography vs computed radiography.

Our objective was to evaluate interobserver agreement and to compare the performance score in quality control of screen-film mammography and computed radiography (CR) using a breast phantom. Eleven radiologists interpreted a breast phantom image (CIRS model X) by four viewing methods: (a) original screen-film; (b) soft-copy reading of the digitized film image; (c) hard-copy reading of CR using an imaging plate; and (d) soft-copy reading of CR. For the soft-copy reading, a 17-in. CRT monitor (1024x1536x8 bits) was used. The phantom image was evaluated using a scoring system outlined in the instruction manual, and observers judged each object using a three-point rating scale: (a) clearly seen; (b) barely seen; and (c) not seen. For statistical analysis, the kappa statistic was employed. For "mass" depiction, interobserver agreement using CR was significantly lower than when using screen-film ( p<0.05). There was no significant difference in the kappa value for detecting "microcalcification"; however, the performance score of "microcalcification" on CR hard-copy was significantly lower than on the other three viewing methods ( p<0.05). Viewing methods (film or CR, soft-copy or hard-copy) could affect how the phantom image is judged. Paying special attention to viewing conditions is recommended for quality control of CR mammograms.

Female↗

PubMed2002

Synergistic effect of cold mannitol and Na(+)/Ca(2+) exchange blocker on blood-brain barrier opening.

The precise mechanism of reversible opening of the blood-brain barrier (BBB) is elusive. Hyperosmotic mannitol at 1.4 to 1.6 M is commonly used for this purpose but intraarterial injection of such a hyperosmotic solution is known to have possible side effects on the brain. Cooling of the solution has recently been reported to have potential to open the BBB. The in situ brain perfusion technique with [(14)C]-sucrose was used first to quantify BBB permeability in rats after intraarterial injection of 1.1 M mannitol, which is less hyperosmotic than commonly used mannitol, at room temperature and at 4 degrees C. Mannitol at 4 degrees C produced an opening of the BBB but the duration of the opening was less than 30 min. We then investigated the effect of an Na(+)/Ca(2+) exchange blocker (KB-R7943) on this hypothermic BBB opening. KB-R7943 extended the BBB opening to 30 min without affecting the peak level of BBB permeability at 5 min. Simple manipulation of temperature can thus enhance the reversible BBB opening in mannitol and pharmacological manipulation of calcium dynamics works synergistically with hypothermic mannitol.

Animals↗

PubMed2002

Relationship between Brier score and area under the binormal ROC curve.

If we consider the Brier score (B) in the context of the signal detection theory and assume that it makes sense to consider the existence of B as a parameter for the population (let B be this B), and if we assume that the calibration in the observer's probability estimate is perfect, we find that there is a theoretical relationship between B and the area under the binormal receiver operating characteristic (ROC) curve, A(Z). We have derived this theoretical functional relationship between B and A(Z), by using the parameter a and b in the binormal ROC model and the prior probability of signal events (alpha); here, the two underlying normal distributions are N and N; and, a= and b=. We empirically found that, if parameters b and alpha are constant, B values in relation to given A(Z) values monotonically decrease as A(Z) values increase, and these relationship curves have monotonically decreasing slopes.

Data Interpretation, Statistical↗

PubMed2002

Use of an artificial neural network to differentiate between ECGs with IRBBB patterns of atrial septal defect and healthy subjects.

Atrial septal defect (ASD) is one of the most commonly recognized congenital cardiac anomalies in adults, but its diagnosis is easily missed because about half of the patients are asymptomatic early in life. Although an electrocardiogram (ECC) diagnosis with an incomplete right bundle branch block (IRBBB) pattern is of major importance for this disease, an RSR' complex similar to an IRBBB pattern is also found in some healthy individuals. A feed-forward artificial neural network was constructed to distinguish between ASD and healthy subjects using 12-lead ECGs with IRBBB. A total of 106 clinically validated subjects, including 58 with ASD and 48 healthy subjects were used in this study. QRS and T wave measurements from I, II, and all precordial leads were used as the input parameters to a back propagation network. The leave-one-out method revealed that in the test data (106 cases), the overall accuracy, sensitivity and specificity of the artificial neural network were 91.5, 91.4, and 91.7%, respectively. This study demonstrates that the neural network technique may offer higher accuracy than computerized ECG diagnosis of IRBBB from the viewpoint of ASD.

Bundle-Branch Block↗

PubMed2002

Lung: feasibility of a method for changing tube current during low-dose helical CT.

A method for changing the tube current during helical scanning was applied to low-dose computed tomography (CT) in the lung. The changing method resulted in significant equalization of image noise in various lung sections compared with that at scanning with constant tube current. Detectability of nodules was equivalent between 60 mA and the changing method, whereas degradation occurred at 20 mA. This method seems feasible for the low-dose CT of lung cancer screening.

Humans↗