Biomedical subjects

Mitsuru Ikeda

Publications and source records attributed to Mitsuru Ikeda.

43 records · Page 3Linked to original sources

PubMed2002

Statistical method in a comparative study in which the standard treatment is superior to others.

The statistical method in a comparative study in which the standard treatment is theoretically or practically superior to the others has been investigated for a matched-pairs design. We derived this statistical method from one based on the maximum likelihood and score methods. Here we have shown that the score test statistic is algebraically the same as the statistic from the maximum likelihood method. As an example of our method's applications, we have considered a study on the detection of nodules on chest X-ray images displayed on a CRT with low luminance.

Biometry↗

PubMedDate not supplied

Angiographic guidewire with measuring markers: design and clinical experience.

PURPOSE: We have developed an angiographic guidewire with measuring markers to determine accurately how far a guidewire is inserted within a catheter. We investigated whether use of this guidewire reduces the risk of vascular injury and the fluoroscopic time during guidewire manipulations. METHODS: Four markers were put on the surface of the guidewire at 80, 100, 110, and 120 cm from the tip. The actual lengths of 54 catheters from seven manufacturers were measured and compared with the nominal lengths. Sixty consecutive patients who underwent angiography were randomized into two groups: in one group guidewires with surface markers were used (marker group) and in the other group, conventional guidewires (control group). For each guidewire insertion, the fluoroscopic time before the guidewire was pushed forward into the vessel lumen was recorded. The number of occasions on which unintentionally the guidewire had already been pushed out of the catheter at the start of fluoroscopy was also evaluated. RESULTS: The actual lengths of all catheters were greater than the nominal lengths by 1.0-11.0 cm. Mean fluoroscopic time for each guidewire insertion was 3.3 sec in the marker group and 5.7 sec in the control group (p < 0.05). Guidewires were unintentionally pushed out of the catheters without fluoroscopy three times (3.6%), in each case in the control group. CONCLUSION: The guidewire with measuring markers is effective for enhancing safety and in reducing fluoroscopic radiation during angiographic procedures. It is recommended that operators be aware that actual lengths of catheters may vary significantly from the nominal lengths listed; they should be aware of this with any guidewire, but particularly with the angiographic measuring guidewire.

Aged↗

PubMedDate not supplied

CRT diagnosis of pulmonary disease: influence of monitor brightness and room illuminance on observer performance.

Using a 21-in. cathode ray tube (CRT) monitor (2048 x 2560 x 8bits), six radiologists interpreted 12 images with interstitial lung disease under six conditions of CRT luminance (50 and 400 cd/m(2)) and room illuminance (20, 120 and 480lx), and 10 radiologists interpreted 25 images with pulmonary nodules under nine conditions of CRT luminance (50, 200 and 500 cd/m(2)) and room illuminance (20, 120 and 480lx). Observer's performance for interstitial disease was relatively better at 120lx. Four hundred and eighty lux illuminance with 50 cd/m(2) CRT luminance, which degraded the detectability of pulmonary nodule significantly (p<0.05), should be avoided for clinical use.

Data Display↗

PubMedDate not supplied

Solitary pulmonary nodules: optimal slice thickness of high-resolution CT in differentiating malignant from benign.

The purpose of this study was to determine an optimal slice thickness that was efficient in differentiating malignant from benign solitary pulmonary nodules (SPNs) on high-resolution computed tomography (HRCT) images. For a total of 92 SPNs, four radiologist indicated their confidence level for the malignant or benign SPN on the CT images presented in 1-, 3-, and 5-mm slice thickness. HRCT could be used to differentiate more accurately the malignant nodules from the benign ones using 1-mm-thick sections than 3- or 5-mm-thick sections.

Adult↗

PubMedDate not supplied

Usefulness of a method for changing tube current during helical scanning in multislice CT.

PURPOSE: To determine whether employing a method for changing the tube current during helical scanning helps to adapt the image noise among various sections of the upper abdomen and chest in multislice computed tomography (CT). MATERIALS AND METHODS: One hundred CT examinations of the upper abdomen were assigned to one of two scanning protocols: standard scanning with a constant tube current and scanning with the changing method based on protocol 1. One hundred fifty CT examinations of the chest were assigned to one of three protocols: standard scanning with a constant tube current and scanning with the changing method based on protocols 1 and 2. In protocol 1, the tube current for each rotation was reduced in proportion to the water equivalent thickness based on the rotation showing the maximum value, while, in protocol 2, the tube current was increased in proportion to the water equivalent thickness based on the rotation showing the minimum value. The mean tube current, mean standard deviations (SDs) of the measured CT numbers, and dispersion of the SDs were compared between the different protocols. RESULTS: In the upper abdomen, the use of the changing method based on protocol 1 resulted in a significant reduction in the dispersion of the SDs of CT numbers, with no increase in mean tube current or mean SDs. In the chest, use of the changing method based on protocol 2 resulted in a significant reduction in the dispersion of the SDs of CT numbers, with a reduction in mean tube current and no increase in mean SDs. CONCLUSION: The method for changing tube current during helical scanning makes it possible to adapt the image noise among various sections of the upper abdomen and chest without increasing dose in multislice CT.

Adult↗

PubMedDate not supplied

Evaluation of abdominal aortic aneurysm for endovascular stent-grafting with volume-rendered CT images of vessel lumen and thrombus.

PURPOSE: To evaluate the accuracy of CT images of abdominal aortic aneurysm (AAA) with volume-rendered (VR) display of vessel lumen and thrombus and to evaluate its usefulness in the planning of stent-grafting. MATERIALS AND METHODS: Helical CT was performed in 11 patients with AAA. Volume data of the vessel lumen and thrombus were separately extracted, and the VR images were reconstructed. Vessel measurements were made by five radiologists and compared with the axial and multiplanar reconstruction (MPR) images. Angiography and intravascular ultrasonography were used as standard references. The relations of aneurysmal sac to the major arterial branches and the subjective overall diagnostic value were evaluated by using a continuous rating scale. RESULTS: Accuracy of measurements was higher on VR images than on axial/MPR in 7 of 13 regions. Interobserver variance of VR images was smaller in 7 of 14 regions. Detection of renal and internal iliac artery involvements was better on VR images (p<0.05). Overall diagnostic value was also higher on VR images (p<0.05). CONCLUSION: VR CT images of vessel lumen and thrombus are supportive of and supplementary to conventional axial/MPR images in planning stent-grafting for AAA.

Aged↗

PubMedDate not supplied

Multi-slice CT of thyroid nodules: comparison with ultrasonography.

PURPOSE: To evaluate the usefulness of multi-slice computed tomography (MSCT) in comparison with ultrasonography (US) for the differentiation of benign from malignant thyroid nodules and the evaluation of tumor extension. MATERIALS AND METHODS: Thirty patients with thyroid nodules (14 malignant, 16 benign) who underwent both MSCT and US participated in the present study. MSCT with contrast enhancement was performed, and 3D shaded volume rendering (SVR) and multiplanar reconstruction (MPR) were employed to differentiate benign from malignant nodules and to evaluate tumor extension. US images were obtained using a 7.5 MHz annular array probe. A three-point rating scale was used for image interpretation, and the kappa statistic was employed to evaluate agreement between MSCT and US. RESULTS: Sensitivity in differentiating benign from malignant nodules was found to be 85.7% for US and 78.6% for MSCT. Disagreement between MSCT and US occurred in assessing the homogeneity of the solid component and the presence of fibrous capsule. In two of seven T4 cases, MPR provided a more accurate diagnosis than US examination in detecting extracapsular invasion. CONCLUSION: For differential diagnosis of thyroid nodules, US was found to be better than MSCT. However, MSCT could be useful for the evaluation of advanced cases with suspicion of extracapsular extension.

Diagnosis, Differential↗