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Shinagawa-ku, Japan

Sase S.,Anzai Medical Co. | Nakano H.,Toho University | Suzuki H.,Toho University | Honda M.,Toho University
Medical Physics | Year: 2010

Purpose: The goal of this work was to develop a method of transforming a xenon-enhanced CT (Xe-CT) image of the lung, so as to overlap well with its baseline CT image, and creating a subtraction image (enhanced image minus baseline image), and to demonstrate the possibility of evaluating pulmonary ventilation using the subtraction image. Methods: Eight healthy men (37.1±10.1 yr) underwent Xe-CT lung studies. In protocol 1 for five subjects, 30% nonradioactive xenon (Xe) was inhaled for 2 min (washin) followed by air breathing for 4 min (washout). In protocol 2 for three subjects, only washin (30% Xe) for 2 min was applied. In each study, a specific range of the thorax (30 mm) in the supine position was scanned craniocaudally three times in the helical mode: At the start and end of washin and at the end of washout in protocol 1 and at 1 min intervals from the start to end of washin in protocol 2. After each study, 10-mm-thick CT images were reconstructed to have similar anatomical structures throughout the study. Two-dimensional geometrical warping was performed on enhanced CT images so that they could geometrically overlap with the baseline CT image. Second to eighth degree polynomials were applied to the warping functions. Results: It was derived from the Kety model that subtraction images during washin would directly reflect pulmonary ventilation. Geometrical warping achieved an increase of 0.3%-22.0% in the area, for which ventilation could be evaluated in the subtraction image. In the cases in protocol 2 where the initial lung volume was well retained throughout the study, the ratios of the specific ventilation from the subtraction image to that from the specific ventilation map were 0.88±0.06 and 0.96±0.10 for the right and left lungs, respectively. Conclusions: A subtraction lung image during washin would provide quantitative information on pulmonary ventilation when the baseline and enhanced images could have close lung volume and these two images could overlap well. Image subtraction requires only two scans and therefore less radiation exposure compared to ordinary protocols in Xe-CT. The proposed Xe-CT subtraction method with the geometrical warping technique could be clinically utilized for evaluating pulmonary ventilation. © 2010 American Association of Physicists in Medicine. Source

Takahashi H.,St. Marianna University School of Medicine | Suzuki M.,St. Marianna University School of Medicine | Ikeda H.,St. Marianna University School of Medicine | Kobayashi M.,St. Marianna University School of Medicine | And 5 more authors.
Alcoholism: Clinical and Experimental Research | Year: 2010

Background/Aims: Xenon computed tomography (Xe-CT) is a noninvasive method of quantifying and visualizing tissue blood flow (TBF). For the liver, Xe-CT allows separate measurement of hepatic arterial and portal venous TBF. The present study evaluated the usefulness of Xe-CT as a noninvasive diagnostic procedure for measuring hepatic TBF in alcoholic liver cirrhosis (AL-LC), compared with liver cirrhosis related to nonalcoholic steatohepatitis (NASH), (NASH-LC), and hepatitis C virus (HCV), (C-LC). Methods: Xe-CT was performed on 22 patients with AL-LC, 7 patients with NASH-LC, and 24 patients with C-LC. Severity of LC was classified according to Child-Pugh classification. Correlations between hepatic TBF, Child-Pugh classification, and indocyanin green retention (ICG) rate after 15 minutes (ICG15R) were examined. Correlations of hepatic TBF in Child-Pugh class A to AL-LC, NASH-LC, and C-LC were also examined. Results: Portal venous TBF (PVTBF) displayed a significant negative correlation with Child-Pugh score and ICG15R (r =-0.432, p < 0.01, r =-0.442, p < 0.01, respectively). Moreover, ICG15R displayed a significant positive correlation with Child-Pugh score (r = 0.661, p < 0.001). Meanwhile, mean PVTBF and total hepatic TBF (THTBF) was significantly lower in AL-LC than in C-LC (p < 0.05). Mean PVTBF was significantly lower in Child-Pugh class A to AL-LC and NASH-LC than in that to C-LC (p < 0.05). Similarly, mean THTBF was significantly lower in Child-Pugh class A to NASH-LC than in that to C-LC (p < 0.05). Conclusions: Measurement of hepatic TBF using Xe-CT is useful as a noninvasive, objective method of assessing the state of the liver in chronic liver disease. © Copyright © 2008 by the Research Society on Alcoholism. Source

Takahashi H.,St. Marianna University School of Medicine | Suzuki M.,St. Marianna University School of Medicine | Shigefuku R.,St. Marianna University School of Medicine | Okano M.,St. Marianna University School of Medicine | And 17 more authors.
Journal of Gastroenterology | Year: 2013

Background: Xenon computed tomography (Xe-CT) provides quantitative information on tissue blood flow (TBF). In the present study, Xe-CT was performed in patients with esophagogastric varices (EGV) before and after endoscopic injection sclerotherapy (EIS) to evaluate hepatic blood flow (HBF), hepatic arterial TBF (HATBF) and portal venous TBF (PVTBF). Methods: Subjects comprised of 88 patients with EGV (49 men, 39 women, average age 65.8 ± 11.5 years, median age 68 years, 30-86 years) and liver cirrhosis related to either hepatitis C virus (C) (n = 33), hepatitis B virus (B) (n = 3), alcohol (AL) (n = 22), AL + C (n = 7), AL + B (n = 1), B + C + AL (n = 1), nonalcoholic steatohepatitis (NASH) (n = 4), autoimmune hepatitis (AIH) (n = 5), primary biliary cirrhosis (PBC) (n = 2), or cryptogenic (n = 10) were enrolled. All patients, who were enrolled in this study, were performed EIS for prophylaxis. Xe-CT and measurement of the retention rate of indocyanine green 15 min after administration (ICG R15) were performed before and after EIS. Total hepatic TBF (THTBF) and PVTBF/HATBF ratio (P/A) were also calculated. Results: PVTBF, HATBF, THTBF, P/A and ICG R15 before EIS were 28.3 ± 8.91, 22.5 ± 14.4 and 50.8 ± 17.6 ml/100 ml/min, 1.62 ± 0.71 and 28.8 ± 12.7 %, respectively and those after EIS were 31.9 ± 10.0, 19.3 ± 11.6, and 51.2 ± 17.0 ml/100 ml/min, 1.92 ± 0.84 and 23.6 ± 11.3 %, respectively. PVTBF and P/A after EIS were significantly higher than those before EIS (p = 0.00444, p = 0.0179, respectively), and HATBF and ICG R15 after EIS were significantly lower than those before EIS (p = 0.00129, p < 0.001, respectively). Conclusions: Xenon computed tomography showed that PVTBF increased after EIS for EGV and HATBF decreased in response to an increase in PVTBF. © 2013 Springer Japan. Source

Honda M.,Toho University | Sase S.,Anzai Medical Co. | Yokota K.,Toho University | Ichibayashi R.,Toho University | And 6 more authors.
Neurologia Medico-Chirurgica | Year: 2012

Subarachnoid hemorrhage (SAH) causes dynamic changes in cerebral blood flow (CBF), and results in delayed ischemia due to vasospasm, and early perfusion deficits before delayed cerebral vasospasm (CVS). The present study examined the severity of cerebral circulatory disturbance during the early phase before delayed CVS and whether it can be used to predict patient outcome. A total of 94 patients with SAH underwent simultaneous xenon computed tomography (CT) and perfusion CT to evaluate cerebral circulation on Days 1-3. Cerebral blood flow (CBF) was measured using xenon CT and the mean transit time (MTT) using perfusion CT and calculated cerebral blood volume (CBV). Outcome was evaluated with the Glasgow Outcome Scale (good recovery [GR], moderate disability [MD], severe disability [SD], vegetative state [VS], or death [D]). Hunt and Hess (HH) grade II patients displayed sig- nificantly higher CBF and lower MTT than HH grade IV and V patients. HH grade III patients displayed significantly higher CBF and lower MTT than HH grade IV and V patients. Patients with favorable out- come (GR or MD) had significantly higher CBF and lower MTT than those with unfavorable outcome (SD, VS, or D). Discriminant analysis of these parameters could predict patient outcome with a probability of 74.5%. Higher HH grade on admission was associated with decreased CBF and CBV and prolonged MTT. CBF reduction and MTT prolongation before the onset of delayed CVS might influence the clinical outcome of SAH. These parameters are helpful for evaluating the severity of SAH and predicting the outcomes of SAH patients. Source

Sase S.,Anzai Medical Co. | Sase S.,St. Marianna University School of Medicine | Takahashi H.,St. Marianna University School of Medicine | Shigefuku R.,St. Marianna University School of Medicine | And 4 more authors.
Medical Physics | Year: 2012

Purpose: The goal of this work was to develop a method of calculating blood flow and xenon solubility coefficient (λ) in the hepatic tissue by xenon-enhanced computed tomography (Xe-CT) and to demonstrate λ can be used as a measure of fat content in the human liver. Methods: A new blood supply model is introduced which incorporates both arterial blood and portal venous blood which join and together flow into hepatic tissue. We applied Ficks law to the model. It was theoretically derived that the time course of xenon concentration in the inflow blood (the mixture of the arterial blood and the portal venous blood) can be approximated by a monoexponential function. This approximation made it possible to obtain the time-course change rate (K I) of xenon concentration in the inflow blood using the time course of xenon concentration in the hepatic tissue by applying the algorithm we had reported previously. KI was used to calculate blood flow and λ for each pixel in the CT image of the liver. Twenty-six patients (49.2 ± 18.3 years) with nonalcoholic steatohepatitis underwent Xe-CT abdominal studies and liver biopsies. Steatosis of the liver was evaluated using the biopsy specimen and its severity was divided into ten grades according to the fat deposition percentage (severity 1) 10, 10 (severity 2) 20, , 90 (severity 10) 100. For each patient, blood flow and λ maps of the liver were created, and the average λ value (λ) was compared with steatosis severity and with the CT value ratio of the liver to the spleen (liverspleen ratio). Results: There were good correlations between λ and steatosis severity (r 0.914, P 0.0001), and between λ and liverspleen ratio (r -0.881, P 0.0001). Ostwald solubility for xenon in the hepatic tissue (tissue Xe solubility), which is calculated using λ and the hematocrit value of the patient, also showed a good correlation with steatosis severity (r 0.910, P 0.0001). λ ranged from 0.86 to 7.81, and tissue Xe solubility ranged from 0.12 to 1.16. This range of solubility is reasonable considering the reported Ostwald solubility coefficients for xenon in the normal liver and in the fat tissue are 0.10 and 1.3, respectively, at 37 °C. The average blood flow value ranged from 15.3 to 53.5 ml100 ml tissuemin. Conclusions: A method of calculating blood flow and λ in the hepatic tissue was developed by means of Xe-CT. This method would be valid even if portosystemic shunts exist; it is shown that λ maps can be used to deduce fat content in the liver. As a noninvasive modality, Xe-CT would be applicable to the quantitative study of fatty change in the human liver. © 2012 American Association of Physicists in Medicine. Source

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