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Biomedical subjects

Y Itai

Publications and source records attributed to Y Itai.

At least 109 records · Page 6Linked to original sources
PubMed1997

Fulminant hepatic failure: observation with serial CT.

PURPOSE: To determine the imaging characteristics of fulminant hepatic failure at serial computed tomography (CT) and to assess if any CT findings have prognostic value. MATERIALS AND METHODS: In 40 patients, 207 CT scans were analyzed retrospectively. Thirty-four patients had fulminant hepatic failure (acute in seven and subacute in 27), and six had late-onset hepatic failure. Twenty-one patients died of hepatic failure. CT was performed soon after the onset of coma and repeated weekly. Liver volume was measured by tracing the hepatic contour and summing the areas to estimate whole-liver volume. RESULTS: Liver volumes in survivors (n = 19) and nonsurvivors (n = 21), respectively, were 1,090 cm3 +/- 300 and 830 cm3 +/- 240 at initial CT and 1,130 cm3 +/- 310 and 700 cm3 +/- 280 at last CT (P = .0001). III-defined hypoattenuating areas were noted in 20 patients and were distributed in a solitary (n = 13), multiple (n = 6), or diffuse (n = 1) pattern. At follow-up CT, the area of hypoattenuation increased in six patients (five nonsurvivors) and disappeared or markedly decreased in four survivors. An increase in or late occurrence of ascites was noted in 15 patients (14 nonsurvivors, P = .0001). CONCLUSION: Liver volumes at the initial and last CT examinations and an increase in or late occurrence of ascites are useful prognostic findings.

Adolescent↗
PubMed1997

Changes in contrast enhancement of hepatocellular carcinoma and liver: effect of temporary occlusion of a hepatic vein evaluated with spiral CT.

PURPOSE: To assess the hemodynamics of the liver and of hepatocellular carcinomas (HCCs) with hepatic vein occlusion. MATERIALS AND METHODS: Selected hepatic veins were temporarily occluded with a balloon catheter in 21 patients with 28 nontreated nodular HCCs. Computed tomographic (CT) arteriography was performed without and with temporary occlusion of a hepatic vein that drained the blood from segmental liver parenchyma containing tumor by using a unified spiral CT and angiography system. The degree of enhancement and change in appearance of the HCC in each condition were compared. RESULTS: All HCCs were well-enhanced, almost round masses at CT arteriography. At CT arteriography with hepatic vein occlusion, however, HCCs were changed as follows: (a) the absolute attenuation of the HCC was decreased in 27 (96%) of 28 tumors compared with that at CT arteriography without hepatic vein occlusion, while attenuation of the surrounding liver parenchyma was increased; (b) the size of the highly enhanced area in HCC became smaller in 17 (61%) tumors (of these, two disappeared); and (c) the shape was changed in 12 (43%) tumors. CONCLUSION: Hepatic vein occlusion resulted in reciprocal hemodynamic changes in the liver parenchyma relative to HCCs: Enhancement of the liver increases and that of HCCs decreases.

Adult↗
PubMed1997

Dynamic intravenous coronary arteriography using synchrotron radiation and its application to the measurement of coronary blood flow.

We have developed dynamic intravenous coronary arteriography (IVCAG) using a monochromatic (33.3 keV), 2-dimensional X-ray beam (70 x 70 mm) generated from synchrotron radiation. To investigate its use to visualize the coronary arteries and to estimate coronary blood flow, we performed IVCAG in 10 dogs and 1 goat. The animals were irradiated with the synchrotron beam after intravenous injection of a contrast agent, and images were obtained using a TV camera and videorecorder. In the dogs, blood flow in the left anterior descending coronary artery (LAD) was also estimated from the images by applying a transit-time analysis. We obtained dynamic IVCAG images in the dogs and goat and could visualize even a deliberately created coronary stenosis about 1 mm in length. In addition, coronary blood flow could be estimated with an acceptable degree of accuracy. LAD flow calculated from IVCAG was 14.7 +/- 5.1 ml/min, whereas measured LAD flow was 16.6 +/- 4.8 ml/min. There was a close correlation between the estimated and measured LAD flows (r = 0.90, p < 0.01). Thus, dynamic IVCAG is minimally invasive, permits the simultaneous evaluation of coronary anatomy and blood flow, and may be feasible for clinical application.

Animals↗
PubMed1997

Multishot echoplanar MR imaging of the female pelvis: comparison with fast spin-echo MR imaging in an initial clinical trial.

OBJECTIVE: The purpose of this study was to apply multishot echoplanar MR imaging (EPI) to the female pelvis and compare image quality with that of fast spin-echo MR imaging. SUBJECTS AND METHODS: Twenty-one patients with suspected pelvic disease and five healthy female volunteers were prospectively examined. MR imaging was obtained using an EPI-capable 1.0-T imager and a pelvic phased-array coil. Axial EPI and fast Spin-echo sequences were obtained at identical image locations in each patient and volunteer. Spin-echo EPI images were obtained using a multishot number of 16. Acquisition time for each EPI sequence was 2 min 10 sec. Fat-suppressed T2-weighted fast spin-echo images were obtained in 2 min 12 sec. Paired EPI and fast spin-echo MR images were independently evaluated by three reviewers. RESULTS: Delineation of the perivaginal and parametrial venous plexus on EPI was rated superior to the fast spin-echo images in 62 (77%) of 81 cases. On EPI, uterine zone anatomy and ovary visualization were judged to be inferior in 44 (56%) of 78 cases and in 18 (33%) of 54 cases, respectively. For delineation of uterine abnormalities, including leiomyoma and adenomyosis, both sequences performed almost equally well. However, ovarian cystic lesions were revealed more precisely by the fast spin-echo sequence. An overall fat-suppression effect was seen on EPI images in 62 (77%) of 81 cases. CONCLUSION: Multishot EPI cannot replace fast spin-echo sequences for imaging the female pelvis; however, because EPI has a potent fat-suppression effect and heavily T2-weighted contrast, EPI sequences can be a valuable adjunct to routine examination.

Echo-Planar Imaging↗
PubMed1997

Bronchoarterial inversion: radiographic-CT correlation in combined right middle and lower lobe collapse.

Pulmonary arteries of the right middle (RML) and right lower (RLL) lobes lie toward the lung periphery relative to their corresponding bronchi, i.e., along their lateral or posterior aspects. In contrast, those of the right upper lobe (RUL) tend to be located along the medial or anterior aspect of the bronchi. We postulate that a reversal of the normal bronchoarterial relationship at the lung base may indicate combined RML and RLL collapse. We evaluated bronchoarterial relation by computed tomography (CT) and posteroanterior (PA) chest radiographs n patients with combined RML and RLL collapse. On PA chest radiographs, an inverse bronchoarterial relationship could be recognized in the lower perihilar region in seven of 10 patients. In the 10 patients with complete collapse of both the RML and RLL, CT disclosed that the normal bronchoarterial relationship of the RUL was preserved, despite caudal extension of the RUL. In no case were arteries visible along the lateral aspect of bronchi. Thus, on frontal radiographs, when the bronchoarterial relationship in the right lower lung is inverse to that of normal subjects, combined collapse is strongly suggested.

Bronchography↗
PubMed1997

[High resolution MR imaging of the hip using pelvic phased-array coil].

A pelvic phased-array coil was applied to obtain high resolution MR images of the hip. Three-mm-thick fast spinecho images were obtained in seven hips. Images with a pelvic coil enhanced delineation of acetabular labrum and articular cartilage more clearly than those with a body coil or flexible-surface coil. The use of a pelvic coil in imaging of the hip may be of diagnostic value because of its superior delineation.

Adult↗
PubMed1997

[Functional MRI employing diazepam; a proposal of neuropharmacological fMRI].

Employing the active benzodiazepine receptor (BZR) ligands, we have used BOLD fMRI to elucidate the effects of these drugs on brain function. The sequential MRI was performed with a 1.5T clinical scanner (Philips GYROSCAN) using a FLASH sequence with the following parameters: TR/TE, 100/45 msec; flip angle, 25 degrees; matrix size, 128*128; 2 averages; for 64 image acquisitions in 32 min. First, 2 mg of diazepam was administrated intravenously at the beginning of the 5th, 15th, 25th, and 35th acquisitions. Then, flumazenil was administrated at the beginning of the 45th (0.2 mg) and 55th (0.3 mg) acquisitions in order to reverse the effect of diazepam. Data processing was made employing Akaike Information Criterion to detect if there were intensity changes after the medication among the trends of intensity changes. Diazepam administration decreased the intensity for a while and flumazenil increased one. In the case of the left frontal glioma with focal epileptogenicity, intensity changes were detected around the tumor. Since the neuronal function consists of the trans-neuronal communications employing neurotransmitters, the result on the modulation of this passage depends on the neuronal function related to the transmitter: gamma-amino butyric acid (GABA) in this instance for the effects of these medications to epilepsy. The change in the local blood flow is the result of the local neuronal activity. Therefore, we speculate that this neuropharmacological functional MR image may reflect the neuronal function related to the GABAegic neurotransmitter system. In addition to elucidating basic neurotransmitter function mechanisms, we believe this technique may have clinical utility in the pre-surgical evaluation of patients with intractable seizure disorders. In this respect, this paper presents a new spectrum of fMRI that is capable to study a part of neurotransmitter function employing the BZR ligands, reversing the effect of the agonist with the competitive antagonist, for the first experience, to propose the neuropharmacological functional MR images to have clinical utility in patients with intractable epilepsy in the interictal state.

Anti-Anxiety Agents↗
PubMed1996

High-Spatial-Resolution Medical-Imaging System Using a HARPICON Camera Coupled with a Fluorescent Screen.

A high-sensitivity HARPICON camera was developed for medical X-ray imaging using a fluorescent screen. It is an avalanche-multiplication-type image pick-up tube and is 32 times more sensitive than conventional tubes. The camera also has a wider dynamic range than conventional medical-imaging cameras because a maximum output signal current of 2.3 muA is obtained and, in high-illumination-intensity regions, photocurrent is not proportional to illumination intensity. The fluorescent screen is an intensifying screen of the type used for radiographic screen-film combinations in medical examination. An X-ray image on the screen is focused on the photoconductive layer of the pick-up tube using a coupling lens with f/0.65. Experiments were performed using monochromated X-rays at the Photon Factory. An image of a spatial resolution test chart was taken in a 525 scanning-line mode of the camera. The chart pattern of 5 line-pairs mm(-1 )(spatial resolution of 100 mum) was observed at an X-ray input field of 50 x 50 mm. Real-time digital images of the heart of a 12 kg dog were obtained at a frame rate of 60 images s(-1) after injection of a contrast medium into an artery. The images were stored in digital format at 512 x 480 pixels with 12 bits pixel(-1). High-spatial-resolution and high-contrast images of coronary arteries were obtained in aortography using X-rays with energy above that of the iodine K edge; the image quality was comparable with that of conventional selective coronary angiography.

Journal Article↗
PubMed1996

Impact of biological clearance on tumor radioresponsiveness.

PURPOSE: To determine the capacity of biological clearance in tumor regression following radiotherapy by using metastatic brain tumors as a clinical model in which mechanical clearance is negligible. METHODS AND MATERIALS: Thirty-eight tumors (19 nonsmall cell lung cancer, 11 small cell lung cancer, and 8 nonlung cancer) in 23 patients were followed with computed tomography (CT) scans over 3 months or more following initiation of radiotherapy, with doses ranging between 34 and 66 Gy. The tumor regression rate (RR; mm3/day), which represented the capacity of biological clearance, was calculated for each CT observation period. The complete response (CR) rate was calculated. The relationship between RR and tumor diameter was determined with regression analysis in conjunction with the pattern of contrast enhancement and the type of primary disease. The change of the RR also was examined. RESULTS: The CR rate was 60.5% for the total group; it was lower for ring-enhanced tumors (41.7%) than diffusely enhanced tumors (69.2%), which included mostly small cell lung cancer metastases. The RR correlated significantly with the tumor diameter (D), with a regression curve of exponential function (RR = 0.035 *D2.5). The RR varied widely and was rather large until 40 days following initiation of radiotherapy, especially for the subgroups of diffusely enhanced tumors and the small cell lung cancer tumors, and became rather constant thereafter. CONCLUSION: A tumor diameter exponent in the regression curve of smaller than 3.0 indicates that the larger the tumor volume is, the smaller the capacity of biological clearance. The capacity of biological clearance also is dependent on vascularity and cellularity of the tumor components expressed by the pattern of contrast enhancement.

Adult↗
PubMed1996

Relationships between fiber composition and NMR measurements in human skeletal muscle.

The purpose of this study was to examine the relationships between the relative contents of phosphocreatine (PCr), inorganic phosphate (Pi), beta-adenosine triphosphate (ATP), and transverse relaxation time (T2) with fiber composition, which determined histochemically in the human skeletal muscle. The vastus lateralis muscles of 28 volunteers were subjected to phosphorus nuclear magnetic resonance (31P NMR) spectroscopy, magnetic resonance imaging (MRI) and muscle biopsy. Muscle fibers were divided into type I and type II fibers using myosin ATPase stain. A wide range of fiber composition levels were observed in the subjects (27.3-74.6% type I fibers). The PCr/ATP, Pi/ATP and (PCr + Pi)/ATP ratios were positively related to the percentage of type II fibers (r = 0.695, p < 0.001, r = 0.429, p < 0.05 and r = 0.773, p < 0.001, respectively). There was no correlation between fiber composition and the PCr/Pi ratio (r 0.127, n.s.) or intracellular pH (r = 0.305, n.s.). Moreover, no correlation was found between T2 and fiber type (r = 0.144, n.s.). These results suggest that 31P NMR can detect the differences in relative content of phosphates between type I and type II fibers, thereby noninvasively evaluating fiber composition in human skeletal muscle.

Adenosine Triphosphate↗
PubMed1996

MR imaging of non-cancerous hepatic lesions in Long-Evans cinnamon rats.

We measured MR images of the liver of Long-Evans Cinnamon (LEC) rats with pathologic correlation and assessed the effectiveness of MR imaging (MRI) for diagnosis of noncancerous hepatic lesions. T1- and T2-weighted images of their livers were obtained, and the dynamic and delayed studies after intravenous gadolinium injection were also performed. Cholangiofibrosis showed low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. The T2 relaxation time of cholangiofibrosis was significantly prolonged (p < .01), and the signal intensity ratio of this lesion to muscle on T1-weighted images was significantly lower than that of normal liver parenchyma to muscle (p < .01). The lesion was enhanced immediately after gadolinium injection and the enhancement was prolonged. Among three cases of peliosis hepatis identified, one showed heterogeneous intensities on both T1- and T2-weighted images and the other two showed similar intensity pattern to cholangiofibrosis. The characteristic MR appearance of cholangiofibrosis may be useful to distinguish it from hepatocellular carcinoma (HCC).

Animals↗
PubMed1996

Hyperattenuating rim on noncontrast CT of the liver: probable peritumoral sparing of fatty infiltration.

CT scans showing a hyperattenuating rim within the liver were retrospectively evaluated in 10 patients to clarify the character, aetiology and clinical significance. All patients had hepatic tumours (7 cavernous haemangiomas in 6 patients, 3 metastatic tumours and 1 hepatocellular carcinoma) as well as fatty infiltration of the liver. Typical features of the hyperattenuating rim on noncontrast CT of the liver included (1) attenuation similar to that of the spleen, (2) a circular or semicircular shape, (3) a width of a few millimeters, (4) peritumoral localization and (5) loss of visualization with contrast enhancement. No such rims were noted around hepatic tumours unassociated with fatty infiltration. Peritumoral sparing of fatty infiltration was inferred. A hyperattenuating rim on noncontrast liver CT, although rare, suggests the presence of a hepatic tumour in fatty liver.

Adult↗
PubMed1996

Clearance of parenchymal tumors following radiotherapy: analysis of hepatocellular carcinomas treated by proton beams.

Clearance of a parenchymal tumor following radiotherapy was determined by using follow-up CT scans of 18 hepatocellular carcinoma tumors treated with focused proton beams. Regression analysis of the daily decrement (DD) and the diameter (D) of a tumor mass in each CT observation interval, DD = a*Db, showed that the exponent b was 3.0 or larger in early periods and 2.0 or smaller in late periods. This suggests that the clearance depends initially on the tumor volume, subsequently on the tumor surface area, and then it becomes much more moderate, possibly due to radiation damage to the parenchymal tissues.

Aged↗