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Takeshi Johkoh

Publications and source records attributed to Takeshi Johkoh.

At least 19 recordsLinked to original sources
PubMed2007

Improvement of spatial resolution in the longitudinal direction for isotropic imaging in helical CT.

Experiments were conducted to confirm the isotropic spatial resolution of multislice CT with a 0.5 mm slice thickness. Isotropic spatial resolution means that the spatial resolution in the transaxial plane (X-Y plane) and that in the longitudinal direction (Z direction) are equivalent. To obtain point spread function (PSF) values in the X-Y-Z directions, three-dimensional voxel data were obtained by helical scanning of a bead phantom. The modulation transfer function (MTF) values were then obtained by three-dimensional Fourier transform of the PSF. Evaluation of the spatial resolution in the X-Y-Z directions by the MTF values showed that the spatial resolution in the Z direction does not depend on the reconstruction kernel used. It was also found that the spatial resolution in the Z direction, as compared with that in the X-Y plane, is superior with the standard kernel for the abdomen and is inferior with the high-definition kernel for the ears/bones. By performing sharpening filter processing in the Z direction with a high-definition kernel, comparable spatial resolution could be obtained in the X-Y-Z directions. It was confirmed that adjusting the spatial resolution in the Z direction with the reconstruction kernel used is an effective method for isotropic imaging.

Biophysical Phenomena↗
PubMed2006

Computer-assisted lung nodule volumetry from multi-detector row CT: influence of image reconstruction parameters.

PURPOSE: To investigate differences in volumetric measurement of pulmonary nodules caused by changing the reconstruction parameters for multi-detector row CT. MATERIALS AND METHODS: Thirty-nine pulmonary nodules less than 2 cm in diameter were examined by multi-slice CT. All nodules were solid, and located in the peripheral part of the lungs. The resultant 48 parameters images were reconstructed by changing slice thickness (1.25, 2.5, 3.75, or 5 mm), field of view (FOV: 10, 20, or 30 cm), algorithm (high-spatial frequency algorithm or low-spatial frequency algorithm) and reconstruction interval (reconstruction with 50% overlapping of the reconstructed slices or non-overlapping reconstruction). Volumetric measurements were calculated using commercially available software. The differences between nodule volumes were analyzed by the Kruskal-Wallis test and the Wilcoxon Signed-Ranks test. RESULTS: The diameter of the nodules was 8.7+/-2.7 mm on average, ranging from 4.3 to 16.4mm. Pulmonary nodule volume did not change significantly with changes in slice thickness or FOV (p>0.05), but was significantly larger with the high-spatial frequency algorithm than the low-spatial frequency algorithm (p<0.05), except for one reconstruction parameter. The volumes determined by non-overlapping reconstruction were significantly larger than those of overlapping reconstruction (p<0.05), except for a 1.25 mm thickness with 10 cm FOV with the high-spatial frequency algorithm, and 5mm thickness. The maximum difference in measured volume was 16% on average between the 1.25 mm slice thickness/10 cm FOV/high-spatial frequency algorithm parameters and overlapping reconstruction. CONCLUSION: Volumetric measurements of pulmonary nodules differ with changes in the reconstruction parameters, with a tendency toward larger volumes in high-spatial frequency algorithm and non-overlapping reconstruction compared to the low-spatial frequency algorithm and overlapping reconstruction.

Adolescent↗
PubMed2006

Usual interstitial pneumonia and chronic idiopathic interstitial pneumonia: analysis of CT appearance in 92 patients.

PURPOSE: To retrospectively analyze computed tomographic (CT) findings of chronic idiopathic interstitial pneumonia (IIP) and to determine which findings are most helpful for distinguishing IIP from usual interstitial pneumonia (UIP) with univariate and multivariate analyses. MATERIALS AND METHODS: Institutional review board approval and informed consent were not required for this retrospective review of patient records and images. Two observers working independently and without knowledge of the diagnosis evaluated the extent and distribution of various thin-section CT findings (ground-glass opacity, consolidation, reticulation, and honeycombing) in 92 patients (51 men, 41 women; mean age, 56 years; age range, 29-81 years) with a histologic diagnosis of UIP (n = 20), cellular nonspecific interstitial pneumonia (NSIP) (n = 16), fibrotic NSIP (n = 16), respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) (n = 11), desquamative interstitial pneumonia (DIP) (n = 15), or lymphoid interstitial pneumonia (LIP) (n = 14). Observers used univariate and multivariate statistical analyses to compare their findings with the extent and distribution of UIP. RESULTS: Observers made the correct diagnosis in 145 (79%) of 184 readings. Multivariate logistic regression analysis showed that the independent findings that distinguished UIP from cellular NSIP were the extent of honeycombing and the most proximal bronchus with traction bronchiectasis (odds ratio, 5.16 and 0.37, respectively); the finding that distinguished UIP from fibrotic NSIP was the extent of honeycombing (odds ratio, 2.10). CT features that distinguished UIP from RB-ILD and DIP included extent of ground-glass opacity (odds ratio, 0.76), thickening of bronchovascular bundles (odds ratio, 1.58), the most proximal bronchus with traction bronchiectasis (odds ratio, 0.22), and the number of segments with traction bronchiectasis (odds ratio, 3.64). CONCLUSION: UIP has a characteristic appearance that usually facilitates distinction from other types of chronic IIPs at thin-section CT. The most useful finding when differentiating UIP from NSIP was the extent of honeycombing.

Adult↗
PubMed2006

Acute exacerbation of interstitial pneumonia following surgical lung biopsy.

STUDY OBJECTIVES: Surgical lung biopsy (SLB) plays an important role in the diagnosis of interstitial pneumonia, however, the occurrence of acute respiratory failure following SLB remains largely unreported. We evaluated the incidence, clinical features, therapy and prognosis of acute exacerbation of interstitial pneumonia following SLB. DESIGN: Retrospective study of consecutive patients who underwent SLB to establish a diagnosis of diffuse lung disease between May 1989 and April 2000. Patients with an acute exacerbation following lung biopsy were studied, and the HRCT images of the chest before and after surgery were reviewed. MEASUREMENTS AND RESULTS: Among the 236 consecutive patients with interstitial pneumonia who underwent a surgical lung biopsy, five (2.1%) (IPF, 3; NSIP, 1; COP, 1) developed acute exacerbation of the diffuse lung disease in the course of 1-18 days after SLB. The extent of parenchymal involvement on HRCT before surgery was not significantly different between operated and contralateral nonoperated lung. Significantly increased regions of parenchymal involvement on HRCT were seen postoperatively compared with the preoperative CT in both the operated (20.7+/-12.5% versus 38.2+/-10.8%, P = 0.0431) and nonoperated lung (22.7+/-13.8% versus 70.5+/-24.4%, P = 0.0431), but the extent of the parenchymal involvement was significantly greater on the nonoperated side (P = 0.0251). Two of the 3 IPF patients died from the acute exacerbation. CONCLUSIONS: It is important to be aware of the possibility of acute exacerbation of interstitial pneumonia following SLB even after an apparently uneventful immediate postoperative course. The asymmetric image findings suggest that intraoperative respiratory management is a possible etiologic factor.

Acute Disease↗
PubMed2006

Imaging of gefitinib-related interstitial lung disease: multi-institutional analysis by the West Japan Thoracic Oncology Group.

Gefitinib (Iressatrade mark) is an epidermal growth factor receptor tyrosine kinase inhibitor that has been approved for the treatment of lung cancer in Japan, however, after marketing several cases of severe pulmonary toxicity were reported. The West Japan Thoracic Oncology Group conducted an independent survey of acute pulmonary toxicity and interstitial lung disease (ILD) caused by gefitinib in its member's institutions. The purpose of this study was to clarify the image characteristics of ILD caused by the molecular-targeting drug gefitinib. A total of 1976 patients had been treated with gefitinib between August and December 2002, and 102 of them were suspected of having acute pulmonary toxicity and ILD. A final definite diagnosis of gefitinib-induced ILD was made by at least three radiologists based on a review and analysis of the chest radiography and CT findings plus the clinical data in the medical records. The imaging findings were classified into four patterns: (A) a nonspecific area with ground-glass attenuation, (B) a multifocal area of airspace consolidations, (C) patchy distribution of ground-glass attenuation accompanied by interlobar septal thickening, and (D) extensive bilateral ground-glass attenuation or airspace consolidations with traction bronchiectasis. CT as well as chest radiography had been performed in 65 of the 102 patients at the onset of ILD, and chest radiography alone had been performed in 26. After excluding 11 cases with insufficient data and 21 cases concluded to be other pulmonary diseases, 70 patients were diagnosed with gefitinib-induced ILD. Finally, the diagnostic image findings were classified as pattern A in 29 cases, pattern B in 7 cases, pattern C in 3 cases, pattern D in 20 cases and others in 11 cases. The CT images were classified as pattern A, B, C, and D in 24, 7, 1, and 12 cases, respectively. The mortality rate was significantly higher in the patients with pattern D than the other patterns. Pattern D were thought to represent the features of diffuse alveolar damage. In conclusion, the molecular-targeting drug gefitinib induces pulmonary toxicity at a certain rate and the imaging findings of ILD induced by gefitinib are similar to those of pulmonary toxicity induced by conventional antineoplastic agents.

Adult↗
PubMed2006

Computational flow dynamics in abdominal aortic aneurysm using multislice computed tomography.

Following the introduction of a new multislice computed tomography (MSCT) scanner, it has become possible to produce high-speed CT angiography (CTA), the preferred method for imaging in emergent abdominal vascular conditions. Unlike catheter angiography, multislice CTA not only depicts the vessels but also allows perfusion in adjacent organs to be assessed. To make the most effective diagnostic use of multi-detector row CTA and three-dimensional image post-processing, radiologists must be familiar with the optimal CTA protocols and the typical CT findings in various emergent vascular conditions using computational flow dynamics (CFD). This article describes a technical approach to estimating the blood flow state of human abdominal aortic aneurysms (AAA) in more detail by constructing realistic three-dimensional (3D) vessel models using CFD methods, focusing on pre- and postoperative cases.

Aged↗
PubMed2006

Simulator-assisted setting of scan protocols for X-ray CT: development and clinical usefulness of the Scan Plan Simulator.

To assist in the selection of complicated computed tomography (CT) scan protocols and to obtain stable image SD values, prototype "Scan Plan Simulator" software with the following functions was developed and evaluated. 1) The image SD value that will be obtained in actual scanning is estimated by entering the patient's body size and scan protocol, after which a simulated image is displayed so that the estimated image SD value can be checked. The exposure dose can also be estimated in the Scan Plan Simulator. 2) The appropriate tube current is automatically set by entering the required image SD value. We evaluated the accuracy of the Scan Plan Simulator by comparing the simulation results with the image SD values and exposure dose obtained in actual scanning and assessed the usefulness of this method using Monte Carlo simulation based on body thickness data obtained in clinical examinations. The results showed that the Scan Plan Simulator not only stabilizes image SD by minimizing the effects of body size but also permits the exposure dose to be reduced by optimizing tube current.

Body Constitution↗
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 coronary artery bypass grafts using multidetector-row CT with Japanese patients.

PURPOSE: To evaluate the patency of coronary artery bypass grafting (CABG) with multidetector-row computed tomography (MDCT) in Japanese patients, who have narrower coronary arteries than Caucasians. MATERIALS AND METHODS: Nineteen patients (12 men and 7 women, mean age: 63 +/- 12 years) with 33 coronary bypass grafts were examined with three-dimensional volume rendering (3D-VR) and curved multiplanar reconstruction (MPR) of MDCT. All grafts were compared with those obtained with selective graft angiography. RESULTS: For the 19 patients with 33 grafts, the overall sensitivity and specificity, compared with those for selective bypass angiography, were 96.7% and 100%, respectively. CONCLUSION: The patency of CABG in Japanese patients can be effectively evaluated with 3D-VR and curved MPR of MDCT.

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

MR imaging of thymic epithelial tumors: correlation with World Health Organization classification.

PURPOSE: The aim of this study was to determine magnetic resonance imaging (MRI) features of various subtypes of thymic epithelial tumors based on the World Health Organization classification. MATERIALS AND METHODS: The study included 64 patients with histologically proven thymic epithelial tumors. Two observers evaluated the MRI findings in terms of tumor size, contour, lobulation, shape, homogeneity, the presence of intratumor high- and low-signal foci, enhancement degree and pattern, the presence of capsule and septum, and associated mediastinal lymphadenopathy and pleural effusion. RESULTS: Type A tumors were more likely to have a smooth contour, round shape, distinct capsule, and smaller size compared to any other type of thymic epithelial tumor. Thymic carcinomas demonstrated a higher prevalence of low-signal foci within the mass on T2-weighted images and mediastinal lymphadenopathy than any other types. The frequency of heterogeneous intensity on T2-weighted images increased from type A tumors to thymic carcinomas. CONCLUSION: The presence of a smooth contour, round shape, and capsule is highly suggestive of a type A tumor. Foci of low signal intensity in the mass on T2-weighted images and mediastinal lymphadenopathy are highly suggestive of thymic carcinomas.

Adult↗
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

Drug-associated organizing pneumonia: high-resolution CT findings in 9 patients.

OBJECTIVE: To assess the high-resolution computed tomography appearances of drug-associated organizing pneumonia (OP). MATERIALS AND METHODS: Nine patients with clinical and biopsy proven drug-associated OP were included in the study. High-resolution computed tomography exams were retrospectively reviewed by 2 observers for the presence, extent, and distribution of parenchymal abnormalities. RESULTS: The commonest findings consisted of air space consolidation (n = 8) and ground-glass opacification (n = 7). The air space consolidation was bilateral and asymmetric in 7 patients, symmetric in 1 patient and in all cases involved mainly the peribronchial or subpleural regions or both. The ground-glass opacities were predominantly bilateral and asymmetric in 6 patients and unilateral in 1 patient. They had a patchy distribution in 4 patients, were diffuse in 2 patients, and subpleural in 1 patient. CONCLUSION: Drug-associated OP most commonly presents with bilateral, asymmetrical air space consolidation in a predominantly peribronchial and subpleural distribution.

Adult↗
PubMed2006

Idiopathic interstitial pneumonias: prevalence of mediastinal lymph node enlargement in 206 patients.

OBJECTIVE: The purposes of our study were to determine the prevalence of mediastinal lymphadenopathy in idiopathic interstitial pneumonias, correlate their presence with high-resolution CT (HRCT) findings, and assess the potential value of mediastinal lymphadenopathy in the differential diagnosis of idiopathic interstitial pneumonias. MATERIALS AND METHODS: The study included 206 consecutive patients from three medical centers with pathologically proven idiopathic pulmonary fibrosis (n = 136), non-specific interstitial pneumonia (NSIP) (n = 47), cryptogenic organizing pneumonia (COP) (n = 16), respiratory bronchiolitis-interstitial lung disease (RB-ILD) (n = 5), and desquamative interstitial pneumonia (DIP) (n = 2). HRCT scans were retrospectively reviewed for the presence of mediastinal lymphadenopathy (short-axis diameter, >or= 10 mm), predominant parenchymal pattern, and extent of disease. RESULTS: Mediastinal lymphadenopathy was seen in 139 (67%) of 206 patients, including 90 (66%) of 136 with idiopathic pulmonary fibrosis, 38 (81%) of 47 with NSIP, six (38%) of 16 with COP, and five (71%) of seven with RB-ILD or DIP. The presence of enlarged nodes was less common in COP than in the other idiopathic interstitial pneumonias (p = 0.04). No significant difference was found in the prevalence of lymphadenopathy in patients with predominant ground-glass opacity (53%) or predominant reticulation (40%). The extent of parenchymal abnormalities was 25-50% in 74 patients (53%), 50-75% in 30 (22%), < 25% in 22 (16%), and > 75% in 13 (9%). A positive correlation between the extent of disease and presence of lymphadenopathy was seen in patients with NSIP (p = 0.01). CONCLUSION: Mediastinal lymphadenopathy is a common feature in idiopathic interstitial pneumonias, being slightly less common in COP than in the other idiopathic interstitial pneumonias. The presence of lymphadenopathy therefore has limited value in the differential diagnosis. In patients with idiopathic pulmonary fibrosis, the presence of lymph node enlargement did not correlate to any specific HRCT pattern or to the extent of disease.

Diagnosis, Differential↗
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

Prediction of prognosis for acute respiratory distress syndrome with thin-section CT: validation in 44 cases.

PURPOSE: To retrospectively evaluate whether the thin-section computed tomographic (CT) appearance has prognostic value for prediction of mortality, number of ventilator-free days (ie, days without mechanical ventilation), and 28-day risk of barotrauma in patients with a clinically early stage of acute respiratory distress syndrome (ARDS) from diverse causes. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. Two independent observers who were blinded to patient outcomes retrospectively evaluated the thin-section CT scans obtained within 7 days after clinical ARDS onset in 26 survivors and 18 nonsurvivors. Of 44 patients, there were 37 men and seven women (mean age +/- standard deviation, 61.8 years +/- 15.6). CT findings were graded on a scale of 1-6 that corresponded with consecutive pathologic phases: score of 1, normal attenuation; score of 2, ground-glass attenuation; score of 3, consolidation; score of 4, ground-glass attenuation associated with traction bronchiolectasis or bronchiectasis; score of 5, consolidation associated with traction bronchiolectasis or bronchiectasis; and score of 6, honeycombing. An overall CT score was obtained by adding the six averaged scores (three zones in each lung). Multivariate regression analysis was used to assess the independent predictive value of the CT score. RESULTS: The area of increased attenuation associated with traction bronchiolectasis or bronchiectasis (P = .002), as well as the overall CT score (P = .002), was smaller in survivors than in nonsurvivors. Results of multivariate regression analysis revealed that CT score was independently associated with mortality (P = .006). A CT score of less than 230 enabled prediction of survival with 73% sensitivity and 75% specificity and was associated with both a greater number of ventilator-free days (P = .018) and a lower incidence of barotrauma (P = .013) within 28 days after ARDS onset. CONCLUSION: Extensive thin-section CT abnormalities indicative of fibroproliferative changes were independently predictive of poor prognosis in patients with a clinically early stage of ARDS.

Chi-Square Distribution↗