Biomedical subjects

Mitsuru Ikeda

Publications and source records attributed to Mitsuru Ikeda.

At least 19 recordsLinked to original sources

PubMed2006

Information loss in visual assessments of medical images.

We applied information theory to quantify information losses in assessing contrast-detail (C-D) analysis. Images of a C-D phantom were acquired with a flat panel detector (FPD) and a computed radiography (CR) by changing surface entrance doses. Six phantom radiographs (FPD: five images; CR: one image) were prepared for visual evaluations. Thirteen radiographers and two radiologists participated in the observation test. Detectability was defined as the shortest length of the cylinders of which border the observers could recognize from the background, and was recorded using row number. Information content was defined as the entropy summation operatorp(i)log(1/p(i)) with detection probabilities p(i), which were calculated from distribution of detection rate of the ith column. Information loss, in unit of bits, was calculated as the difference between information obtained and information content when all the columns were detected. The information losses decreased with the increase in cylinder diameters and with the increase in surface entrance dose. Because the information loss varies depending on distribution of detection rate, this method of using the information theory was expected to be more sensitive in evaluating the C-D image quality than using the averaged values of detectability.

Contrast Sensitivity↗

PubMed2006

Quantification of distension in rat cerebral perforating arteries.

We developed a novel cerebral angiography procedure for rodents using monochromatic synchrotron radiation X-rays and obtained images of rat cerebral perforating arteries for the first time. In normotensive rat, hypercapnia rapidly distended the perforators between 3 and 15 min after induction and major trunk vessels distended more rapidly in 3-6 min. Systemic hypotension made by stepwise hemorrhage distended the perforators up to 158% of control values but constricted most of the large cerebral trunk vessels. In spontaneous hypertensive rats, systemic hypotension-induced distension disappeared in perforators, indicating that perforators with chronic hypertension lose their autoregulatory distensibility.

Animals↗

PubMed2006

Diagnostic value of curved multiplanar reformatted images in multislice CT for the detection of resectable pancreatic ductal adenocarcinoma.

The purpose of this study was to assess the usefulness of curved multiplanar reformatted (MPR) images obtained by multislice CT for the depiction of the main pancreatic duct (MPD) and detection of resectable pancreatic ductal adenocarcinoma. This study included 28 patients with pancreatic carcinoma (size range 12-40 mm) and 22 without. Curved MPR images with 0.5-mm continuous slices were generated along the long axis of the pancreas from pancreatic-phase images with a 0.5- or 1-mm slice thickness. Seven blinded readers independently interpreted three sets of images (axial images, curved MPR images, and both axial and curved MPR images) in scrolling mode. The depiction of the MPD and the diagnostic performance for the detection of carcinoma were statistically compared among these images. MPR images were significantly superior to axial images in depicting the MPD, and the use of both axial and MPR images resulted in further significant improvements. For the detection of carcinoma, MPR images were equivalent to axial images, and the diagnostic performance was significantly improved by the use of both axial and MPR images. High-resolution curved MPR images can improve the depiction of the MPD and the diagnostic performance for the detection of carcinoma compared with axial images alone.

Adult↗

PubMed2006

Relationship between CT densitometry with a slice thickness of 0.5 mm and audiometry in otosclerosis.

The appropriate cutoff Hounsfield unit (HU) value for the diagnosis of otosclerosis was determined and the correlation between the bone conduction threshold and the findings of computed tomography (CT) densitometry investigated. CT images, 0.5-mm thick, were evaluated in 24 ears with otosclerosis and 19 control ears. Eight regions of interest were set around the otic capsule. The mean HU values in the area anterior to the oval window (A-OW) and anterior to the internal auditory canal (A-IAC) were significantly lower in otosclerosis than in controls. Based on receiver operating characteristic (ROC) analysis, the cutoff HU value in A-OW was determined to be 2,187.3 HU. The mean HU value in retrofenestral otosclerosis was significantly lower in the area A-OW, A-IAC and around the cochlea than in controls. Based on ROC analysis, the cutoff HU value in the latter was determined to be 2,045 HU. A statistically significant correlation was found between the density of the area A-OW and the hearing level at 500 and 1,000 Hz, and between the density of the area around the cochlea and the hearing level at most frequencies. These results suggest the semi-automated diagnosis of otosclerosis may be possible.

Absorptiometry, Photon↗

PubMed2006

Influence of rib structure on detection of subtle lung nodules.

PURPOSE: To access the influence of anatomic noise on the detectability of subtle lung nodules depicted on chest radiographs. MATERIAL AND METHODS: From normal chest radiography images, 132 square regions were extracted, of which the centers were on the upper margin of a rib, the inside of a rib, the lower margin of a rib, and the central region between two adjoining ribs. Simulated nodules were digitally superimposed at the centers of these extracted square images. Twelve radiologists viewed 50 soft-copy images consisting of these 792 processed images, including the noise-added images. The observer's confidence level for the square images containing single nodules was used as an index of observer performance. RESULTS: Results indicated statistically reliable effects of the relationship between rib structures and nodule positions on the detection performance (P < 0.001). The nodule detectability on the images with a center located between two adjoining ribs was significantly the best, whereas it was significantly the worst on the noise-added images with a center located between two adjoining ribs. CONCLUSION: The rib structures overlying a subtle lung nodule on chest X-ray images have a detrimental effect on nodule detection performance as anatomic noise, regardless of the nodule location on ribs.

Adult↗

PubMed2006

Intraarterial cisplatin/nedaplatin and intravenous 5-fluorouracil with concurrent radiation therapy for patients with high-risk uterine cervical cancer.

OBJECTIVE: The purpose of this study was to determine the effectiveness of the combination of intraarterial and intravenous concurrent chemoradiation therapy (CIAIV-CCRT) for the treatment of high-risk uterine cervical cancer. METHODS: Between January 2000 and November 2004, we reviewed 45 cervical cancer patients treated by CIAIV-CCRT. The numbers of patients with stage IB2, IIA, IIB, IIIA, IIIB, and IVA were 3, 6, 14, 1, 17, and 4, respectively. Patients with stage III and IVA or patients with tumors >3 cm in diameter were enrolled in this study. Two sessions of CCRT were administered every 3 weeks using a combination of 70 mg/m2 x h(-1) cisplatin or 50 mg/m2 x h(-1) nedaplatin via the bilateral uterine artery and 2800 mg/m2 x 96 h(-1) 5-fluorouracil intravenously. Patients concurrently received external beam radiation therapy and brachytherapy. A nonrandomized control group of 47 patients who underwent radiation therapy alone between 1993 and 2000 was used for comparison. RESULTS: Of the 45 patients, 28 (62%) exhibited complete response and 16 (36%) exhibited partial response. One IIIB patient (2%) did not show any response. The 5-year overall survival (OAS) rates in the CCRT group and control group were 80.6% and 54.9%, respectively. With regard to late toxicities, no statistically significant differences were observed between the two groups. In uni- and multivariate analyses, positive pelvic lymph node showed a statistically significant influence on the OAS in the CIAIV-CCRT group (P = 0.049). CONCLUSION: These preliminary results suggest that CIAIV-CCRT can improve the prognosis of patients with high-risk cervical cancer.

Adult↗

PubMed2006

[Evaluation of change in the optimal image reconstruction phase in retrospective ECG-gated reconstruction].

The purpose of this study was to optimize the reconstruction phase in order to improve depiction of the coronary artery in the relative delay method of the retrospective electrocardiogram (ECG)-gated reconstruction technique using a multi-slice computed tomography (MSCT) scanner with four channels. The following items were evaluated; 1) image quality of the coronary arteriogram, 2) degree of difference between the standard phase corresponding to the diastasis period and the selected phase, which was determined in each case to obtain the best image, and 3) the factors causing the phase difference. The image quality in the selected phase was better than that in the standard phase. A positive correlation was observed between the degree of phase difference and the median value and standard deviation of the heart rate. The degradation of image quality was remarkable in cases showing a large degree of phase difference. A negative correlation was observed between image quality in the selected phase and the degree of phase difference. Individualizing the reconstruction phase is required to improve the image quality of coronary arteriograms with MSCT. It should be noted that the condition of a low and stable heart rate results in reduction in the degree of phase difference, which is useful for the acquisition of better images.

Adolescent↗

PubMed2006

Magnetic resonance cholangiopancreatography: comparison of respiratory-triggered three-dimensional fast-recovery fast spin-echo with parallel imaging technique and breath-hold half-Fourier two-dimensional single-shot fast spin-echo technique.

PURPOSE: The aim of this study was to compare magnetic resonance cholangiopancreatography (MRCP) using respiratory-triggered (resp) three-dimensional Fourier transformation (3D) fast-recovery fast spin echo (FR-FSE) sequence with array spatial sensitivity technique (ASSET) for visualization of the pancreatobiliary system with breath-hold single thick-section and multiple thin-section MRCP using 2D single shot FSE (SSFSE) sequences. MATERIALS AND METHODS: Forty patients underwent MRCP for evaluation of pancreatobiliary abnormalities in a 1.5-T magnet. Imaging time for resp 3D FR-FSE was recorded. The ghosting and blurring artifacts, overall image quality, and delineation of the pancreatobiliary ducts were evaluated using a five-point scale. RESULTS: On multisection 2D SSFSE source images, there were the least ghosting artifacts (4.9 +/- 0.3, P < 0.05). Ghosting (3.4 +/- 0.6, P < 0.05) and blurring (4.4 +/- 0.8; P < 0.05) artifacts were the most prominent on resp 3D FR-FSE. 3D FR-FSE MRCP provided the highest rating of overall image quality (4.3 +/- 0.8, P < 0.05) and delineation of third- and second-order branches of the hepatic ducts (2.9 +/- 1.6 for third-order branches and 3.9 +/- 1.3 for second-order branches, P < 0.05). Extrahepatic bile ducts, including upper and middle portions and cystic and pancreatic ducts, were also better seen with resp 3D FR-FSE MRCP than others. CONCLUSION: MRCP with resp 3D FR-FSE using ASSET can be routinely used for acquiring information from the pancreatobiliary system.

Adult↗

PubMed2006

Cerebral glucose metabolism change in patients with complex regional pain syndrome: a PET study.

PURPOSE: The aim of this study was to examine abnormalities of the central nervous system in patients with chronic pain who were diagnosed with complex regional pain syndrome (CRPS). MATERIALS AND METHODS: Brain activity was assessed using (18)F-fluorodeoxyglucose positron emission tomography. The data collected from 18 patients were compared with data obtained from 13 normal age-matched controls. RESULTS: Our results showed that glucose metabolism was bilaterally increased in the secondary somatosensory cortex, mid-anterior cingulated cortex (ACC) or posterior cingulated cortex (PCC) (or both), parietal cortex, posterior parietal cortex (PPC), and cerebellum as well as in the right posterior insula and right thalamus in our patients. In contrast, glucose metabolism was reduced contralaterally in the dorsal prefrontal cortex and primary motor cortex. Glucose metabolism was bilaterally elevated in the mid-ACC/PCC and the PPC, which correlated with pain duration. CONCLUSION: These data suggested that glucose metabolism in the brains of patients with CRPS changes dramatically at each location. In particular, glucose metabolism was increased in the areas concerned with somatosensory perception, possibly due to continuous painful stimulation.

Adult↗

PubMed2006

The application of Markov theory to contrast-detail analysis.

RATIONALE AND OBJECTIVES: To improve the accuracy of contrast-detail (C-D) analysis, we have devised a new evaluation method of the detection performance in the C-D analysis by using the Markov process model. This article describes this new evaluation method and the results of applying it to the illustrative examples. MATERIALS AND METHODS: A commercially available C-D phantom was employed as a test object, and 20 phantom radiographs with an average background density of 0.8 were prepared. Thirty-five observers interpreted all phantom radiographs independently of each other with the room lights off. We assume the Markov model in which the selection of the smallest visible contrast for each row of disks with the same diameter depends only on the contrast selected as the smallest visible one for the same row in the just-before reading experiment. By using this Markov model, the contrast detectability for each disk diameter was calculated, and a C-D diagram was constructed based on these results. The conventional C-D diagram was also derived from the averages of contrast detectability obtained from the interpretations of all phantom radiographs. RESULTS: All C-D diagrams obtained from our devised method agreed well with each other and were in good accord with the conventional C-D diagram from the interpretations of all phantom radiographs. CONCLUSIONS: We have devised a new evaluation method of C-D analysis by using the Markov model and have shown this method will be consistent with the conventional evaluation method in the C-D analysis.

Analysis of Variance↗

PubMed2006

The effect of patient age on contrast enhancement during CT of the pancreatobiliary region.

OBJECTIVE: The objective of our study was to assess whether it is possible to reduce the dose and rate of contrast material injection in elderly patients in triple-phase contrast-enhanced CT of the pancreatobiliary region with an MDCT scanner. SUBJECTS AND METHODS: One hundred twelve patients were divided into three groups: contrast injection at 0.08 mL/kg body weight/s (an upper limit of 5 mL/s) over 30 seconds in patients 60 years old or younger (group 1, n = 49), the same contrast injection as group 1 in patients more than 60 years old (group 2, n = 32), and contrast injection at 0.07 mL/kg body weight/s (an upper limit of 4.5 mL/s) over 30 seconds in patients more than 60 years old (group 3, n = 31). Contrast enhancement in the aorta, portal venous system, pancreas, and liver was assessed quantitatively. Two radiologists blinded to the patients' clinical information and the injection protocol used to acquire the CT images graded the degree of contrast enhancement using a 5-point scoring system. The results for the different groups were statistically compared. RESULTS: Contrast enhancement in the main phases for all organs was significantly more intense in group 2 than in groups 1 and 3. Cases in which pancreatic enhancement in the pancreatic phase was graded as excessive were more frequently observed in group 2. No statistically significant differences were observed between groups 1 and 3 in either quantitative or visual assessment for enhancement of any organ in any phase. CONCLUSION: We recommend reducing the dose and rate of contrast material injection by at least 10% for elderly patients undergoing MDCT examination of the pancreatobiliary region.

Adult↗

PubMed2006

Low efficacy of 18F-FDG PET for detection of uveal malignant melanoma compared with 123I-IMP SPECT.

UNLABELLED: Earlier investigations showed that N-isopropyl-p-123I-iodoamphetamine SPECT (123I-IMP SPECT) is useful for the diagnosis of uveal malignant melanoma, whereas the feasibility and usefulness of 18F-FDG PET in uveal malignant melanoma have not yet been established. We compared the usefulness of 123I-IMP SPECT and 18F-FDG PET for the detection of uveal malignant melanoma on the same subjects. METHODS: Nineteen patients (10 men, 9 women) with suspected uveal malignant melanoma were examined by 123I-IMP SPECT. Thirteen of them were also examined by 18F-FDG PET. 123I-IMP SPECT was performed at 15 min or at 3 and 24 h after intravenous administration of 123I-IMP. RESULTS: In 12 of 19 study patients, 123I-IMP SPECT obtained at 24 h after intravenous administration of 123I-IMP delineated an area of increased uptake in the site corresponding to the ocular tumor. All of the ocular tumors in the 12 123I-IMP SPECT-positive patients were confirmed histopathologically and clinically to be uveal malignant melanoma. The other 7 123I-IMP-SPECT-negative patients have been monitored under the diagnosis of choroidal nevus, choroidal hemangioma, hyperplasia of the pigment epithelium of the retina, or idiopathic inflammatory lesions without any complications. In a total of 13 patients examined by 18F-FDG PET, 9 of whom were 123I-IMP SPECT positive and 4 were negative, only 1 patient showed abnormal uptake of 18F-FDG PET in the site corresponding to the ocular tumor. Therefore, 8 of 9 patients with uveal malignant melanoma showed false-negative results in 18F-FDG PET. The 18F-FDG PET-positive patient with uveal malignant melanoma had the largest tumor mass with a short diameter of 12 mm, a long diameter of 17 mm, and a height of 7 mm. In the other 8 18F-FDG PET-negative patients, the tumors had a dimension of 11 x 13 x 7 mm or less. CONCLUSION: 123I-IMP SPECT is a sensitive and accurate method for the detection of uveal malignant melanoma, whereas the efficacy of 18F-FDG PET for this purpose is low because of a high incidence of false-negative results. 123I-IMP SPECT is far more superior in comparison with 18F-FDG PET in detecting uveal malignant melanoma.

Adult↗

PubMed2006

Influence of monitor luminance and room illumination on soft-copy reading evaluation with electronically generated contrast-detail phantom: comparison of cathode-ray tube monitor with liquid crystal display.

The influence of monitor brightness and room illumination on soft-copy diagnosis by both cathode-ray tube (CRT) monitor and liquid crystal display (LCD) was evaluated and compared using a contrast-detail phantom. Nine observers (7 radiologists and 2 radiological technicians) interpreted six types of electronically generated contrast-detail phantom images using a 21-inch CRT (2,048x2,560) and a 21-inch LCD (2,048x2,560) under 6 kinds of viewing conditions, i.e. monitor brightness of 330 cd/m2 or 450 cd/m2, and room illumination of 20, 100 or 420 lux at the center of the display. Observers were requested to determine the visible borderline of the objects. Between 330 cd/m2 and 450 cd/m2, no significant difference in the visible area was found under any of the three lighting conditions. However, in two low-contrast phantom images, the visible area on the LCD was significantly larger than that on the CRT, independent of both monitor brightness and room illumination. (p<0.05). The effect of room illumination was not significant, suggesting that the use of LCD at high room illumination is acceptable.

Computers↗

PubMed2006

Evaluation of new image processing conditions for digital mammograms from Fuji computed radiography.

PURPOSE: A new processing parameter (T-type parameter) setting for gray scale was developed to improve the image quality of digital mammograms. To clarify the usefulness of this parameter setting, we have evaluated the image quality of digital mammograms (hard copy images) processed with this parameter, and compared it with S/F mammography. MATERIAL AND METHODS: Mammograms were made under the same radiographic conditions by the S/F and FCR systems (type 1, S/F; type 2 and 3, FCR with new T-type parameters; type 4 and 5, FCR with conventional parameters). A total of 49 images from 10 cases was selected for evaluation testing. Evaluation items were the contrast visibility of mammary glands and adipose tissues together with their granularity and sharpness. Eleven medical doctors participated in evaluating the images. RESULTS: The FCR hard copy images processed with the T-type parameter settings were significantly preferred over the conventional S/F images for the contrast visibility of mammary glands and adipose tissue. As for the other items (except for granularity), the FCR hard copy images processed with the T-type parameter settings were subjectively evaluated as slightly better than or equal to the S/F images. In contrast, the conventional S/F images were significantly preferred over the FCR hard copy images processed with the conventional parameter settings. CONCLUSION: The image quality of FCR hard copy images processed with the T-type parameter settings was preferred over that of conventional S/F images as evaluated by medical doctors who specialized in mammography interpretation.

Female↗

PubMed2006

Application of subsecond rotation scan to helical CT for lung cancer screening.

PURPOSE: To clarify whether the benefit of a reduced effective scan width obtained using a smaller pitch outweighs the disadvantage of increased noise in the application of a subsecond helical CT to mass screenings for lung cancer. MATERIALS AND METHODS: Twenty-two helical CT scans of the lung were obtained in 11 healthy subjects using the following parameters: 1) scan 1 was performed at 120 kVp, 50 mA, 10-mm collimation, 1-second/rotation, helical pitch of 2.0; and 2) scan 2 was performed at 120 kVp, 50 mA, 10-mm collimation, 0.75-second/rotation, helical pitch of 1.5. Computer-generated nodules measuring 10 mm and 6 mm in diameter showing ground-glass opacity were superimposed on these images. The detectability of each nodule was evaluated by six blinded readers using ROC analysis. RESULTS: Detectability of the 6-mm nodules was significantly higher in scan 2 than in scan 1. Detectability of the 10-mm nodules was not significantly different between scans 1 and 2. CONCLUSION: The use of a smaller pitch by employing a subsecond rotation scan in a helical CT for lung cancer screenings improves the detection of small lesions without increasing either the scanning time or radiation dose.

Adult↗

PubMed2006

Intra- and interobserver agreement and performance score of breast phantom image interpretation: influence of ambient room lighting levels.

The influence of ambient room lighting conditions on soft-copy breast phantom image interpretation was evaluated by comparing cathode ray tube (CRT) monitors with liquid crystal displays (LCDs). Nine observers were asked to use a three-point scale to rate the visibility of various phantom objects (masses, specks, and fibers) displayed on a 21-inch CRT (2,560 x 2,048) and a 21-inch LCD (2,560 x 2,048) under three different levels of ambient lighting (20, 100 and 420 lux at the display center). Each phantom image was interpreted twice, and the reproducibility of judgment and inter-observer agreement was evaluated using kappa statistics. Except for the "mass" score, the LCD score showed a significantly higher value (p<0.05) compared with that of CRT. Nevertheless, no significant differences were found among the three lighting levels. Furthermore, intra- and inter-observer agreement in judgments showed no effects of room illumination. Although the breast phantom objects were better visualized on LCDs than on CRT monitors, room illumination did not affect the performance score of soft-copy reading.

Breast Neoplasms↗

PubMed2005

Measurement of modulation transfer functions for liquid crystal displays by rectangular waveform analysis.

We measured modulation transfer functions (MTFs) of liquid crystal displays (LCDs) by rectangular waveform analysis. This method consists of taking a picture of the bar pattern on the display surface with a digital camera, and analyzing the picture with a personal computer. The displays used are LCDs of 1M (about 1 million pixels), 2M, 3M, and 5M, and a cathode ray tube (CRT) display with a pixel number of 5M. Two kinds of 2M displays were used, an in-plane switching (IPS) system and vertical alignment (VA) system, from which liquid crystal operation mode differs. MTFs increased as pixels increased. For the LCDs, MTFs in the horizontal direction were higher than those in the vertical direction except for the 2M VA system. For the LCD of the 2M VA system, MTF in a horizontal direction was equal to MTF in a vertical direction. For the displays with the same number of pixels (5M), MTF of a LCD was higher than that of a CRT display. MTFs of LCDs are influenced by the pixel form, pixel composition, and the liquid crystal operation mode.

Data Display↗

PubMed2005

A method of clustering observers with different visual characteristics.

Evaluation of observer's image perception in medical images is important, and yet has not been performed because it is difficult to quantify visual characteristics. In the present study, we investigated the observer's image perception by clustering a group of 20 observers. Images of a contrast-detail (C-D) phantom, which had cylinders of 10 rows and 10 columns with different diameters and lengths, were acquired with an X-ray screen-film system with fixed exposure conditions. A group of 10 films were prepared for visual evaluations. Sixteen radiological technicians, three radiologists and one medical physicist participated in the observation test. All observers read the phantom radiographs on a transillumination image viewer with room lights off. The detectability was defined as the shortest length of the cylinders of which border the observers could recognize from the background, and was recorded using the number of columns. The detectability was calculated as the average of 10 readings for each observer, and plotted for different phantom diameter. The unweighted pair-group method using arithmetic averages (UPGMA) was adopted for clustering. The observers were clustered into two groups: one group selected objects with a demarcation from the vicinity, and the other group searched for the objects with their eyes constrained. This study showed a usefulness of the cluster method to select personnels with the similar perceptual predisposition when a C-D phantom was used in image quality control.

Cluster Analysis↗