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Biomedical subjects

Y Itai

Publications and source records attributed to Y Itai.

At least 127 records · Page 7Linked to original sources
PubMed1996

Phase-contrast X-ray computed tomography for observing biological soft tissues.

Biological soft tissues are almost transparent to hard X rays and therefore cannot be investigated without enhancement with a contrast medium, such as iodine. On the other hand, phase-contrast X-ray imaging is sensitive to light elements (1-8). This is because the X-ray phase shift cross section is almost thousand times larger than the X-ray absorption cross section for light elements such as hydrogen, carbon, nitrogen and oxygen (4,5). Hence, phase-contrast X-ray imaging is a promising technique for observing the structure inside biological soft tissues without the need for staining and without serious radiation exposure. We have devised a means of observing biological tissues in three dimensions using a novel X-ray computed tomography (CT) by modifying the phase-contrast technique. To generate appropriate CT input data, we used phase-mapping images obtained using an X-ray interferometer (6) and computer analysis of interference patterns (9). Now, we present a three-dimensional observation result of a nonstained sample of a cancerous rabbit liver, using a synchrotron X-ray source. Phase-contrast X-ray CT was able to clearly differentiate the cancer lesion from the normal tissue. Moreover, fine structures corresponding to cancerous degeneration and fibrous tissues were clearly depicted.

Animals↗
PubMed1996

Magnetic resonance imaging of isolated skeletal muscles. Osmotic influence.

RATIONALE AND OBJECTIVES: The authors evaluate the contribution of intracellular water to the change of T2 relaxation time. METHODS: Magnetic resonance images of frog muscles (n = 16) were obtained in hypotonic, isotonic, and hypertonic solutions, and their leg weights and T2 relaxation times were measured. Likewise, these values were measured after electric stimulation for 2 to 10 minutes in isotonic solution (n = 5). RESULTS: The muscle weights increased in the hypotonic solutions, whereas they showed no change in isotonic solution. T2 relaxation times, however, showed little change in either isotonic or hypotonic solutions. In electrically stimulated muscles, T2 relaxation times increased, accompanying the increase in muscle weight in isotonic solutions. CONCLUSION: Muscle contraction results in increased T2 relaxation time, but intracellular water hardly contributes to the increase in this value. Therefore, an increase in extracellular water may be the main cause of the increase in T2 relaxation time seen in exercised muscles.

Animals↗
PubMed1996

Early squamous cell carcinoma of the lung: CT and pathologic correlation.

PURPOSE: To study the factors that influence computed tomographic (CT) visibility of early squamous cell carcinoma, which was defined as a lesion confined to the bronchial wall without lymph node metastasis. MATERIALS AND METHODS: CT was performed in 18 patients with 18 early squamous cell carcinoma lesions. The 5.0-mm or thinner sections were reviewed independently by three observers who were aware of the bronchoscopic findings, and the visibility of the lesions was correlated with histopathologic findings. RESULTS: Tumors consisted of 13 flat and five polypoid lesions. Three of the lesions were epithelial, eight were subepithelial, and seven were cartilaginous or extracartilaginous. Eleven lesions were visualized at CT as an endobronchial mass or focal bronchial wall thickening. Lesions with polypoid growth and/or cartilaginous or extracartilaginous invasion were all visualized, even on 5-mm-thick sections. Subepithelial lesions could be demonstrated when located at bronchi with craniocaudal orientation. CONCLUSION: CT is a valuable tool for diagnosis of early squamous cell carcinomas, particularly when lesions show polypoid growth and/or invade the cartilaginous layer.

Aged↗
PubMed1996

Cystic lesions of the maxillomandibular region: MR imaging distinction of odontogenic keratocysts and ameloblastomas from other cysts.

OBJECTIVE: Differentiating odontogenic keratocysts and ameloblastomas from other cystic lesions in the maxillomandibular region is important because of their high recurrence rates. Conventional radiography, CT, and fine-needle aspiration biopsy are limited for differential diagnosis. The purpose of this study was to review the MR findings in patients with odontogenic keratocysts, ameloblastomas, and other maxillomandibular cysts to determine the value of MR imaging in the differential diagnosis of these lesions. SUBJECTS AND METHODS: MR images were obtained in 38 patients with 43 cystic lesions of the maxillomandibular region. All the lesions (19 odontogenic keratocysts, 11 ameloblastomas, five primordial cysts, five radicular cysts, and three cysts of other types) were pathologically confirmed by surgery or biopsy. Contrast-enhanced MR studies were performed in 34 patients. Images were reviewed to determine various imaging parameters: locularity, solid or cystic pattern, thickness and contrast enhancement of the walls, and homogeneity and signal intensities of the fluids. T2 relaxation times of cystic components were calculated in 31 lesions. RESULTS: MR images of odontogenic keratocysts showed that the cyst were unilocular in 10 lesions and multilocular in nine. In 10 lesions the cysts wall was uniformly thin and had poor contrast enhancement. Seven cysts had thick walls and two had no definite walls. In 17 lesions, the cystic contents showed heterogeneous signal intensity on T1-weighted images, T2-weighted images, or both. Eight cysts had predominantly intermediate or high T1-weighted signal intensity, and six cysts had predominantly intermediate T2-weighted signal intensity. MR findings in ameloblastomas were different from those in odontogenic keratocysts: a mixed solid and cystic pattern (11 lesions), irregularly thick walls (11 lesions), papillary projections (seven lesions), and strong enhancement of solid components (nine lesions). T2 relaxation times of cystic components were significantly shorter in odontogenic keratocysts than in ameloblastomas, with no overlap. All other cysts showed a unilocular, purely cystic pattern, with homogeneous fluids, although the T2 relaxation times of four lesions overlapped those of odontogenic keratocysts. CONCLUSION: From the MR findings of the walls, solid components, and the fluid contents, odontogenic keratocysts could be differentiated from ameloblastomas in all cases, although some other cysts showed MR findings similar to those of odontogenic keratocysts.

Adolescent↗
PubMed1996

[Evaluation of reserved hepatic function in patients with hepatobiliary tumor by 99mTc-GSA: effect of hyperbilirubinemia and usefulness of regional reserved hepatic functional imaging].

The evaluation of the reserved hepatic function was performed by 99mTc-galactosyl serum albumin (99mTc-GSA) in seventy patients with hepatobiliary tumor. The dynamic study was performed to evaluate global reserved hepatic function following the intravenous bolus injection of 99mTc-GSA, and the hepatic single photon emission computed tomography (SPECT) was obtained to assess the regional reserved hepatic function. The functional hepatic index (LHL15) was derived from liver time-activity data, and it was compared with serum total-bilirubin level, serum albumin level and plasma disappearance rate of indocyanine green (ICG15). In the patients with hepatocellular carcinoma, LHL15 value agreed well with ICG15 value, serum total-bilirubin level, and serum albumin level. Moderate or severe hepatic dysfunction was observed at 65.4% of these patients. In the patients with cholangiocellular carcinoma, a discrepancy of LHL15 value and ICG15 value was observed. Increment of the ICG15 value was correlated with that of the serum total-bilirubin level, whereas the correlations was not observed between the LHL15 value and the serum total-bilirubin level. These results indicate that 99mTc-GSA scintigraphy can evaluate the reserved hepatic function without the embellishment of jaundice. This method is useful for assessing the global and regional reserved hepatic function.

Aged↗
PubMed1996

[Anomalous origin of the left coronary artery from the pulmonary trunk with myocardial infarction and severe left ventricular dysfunction in infancy--assessment of myocardial damage using SPECT studies with 201TlCl and 123I-BMIPP].

A 4-month-old male infant with Bland-White-Garland (BWG) syndrome complicated myocardial infarction was reported. Signs included tachypnea, coughing, and failure to thrive. However, there was no sign of myocardial infarction. A chest radiograph revealed cardiomegaly (CTR = 65%) and electrocardiogram showed abnormal Q waves in I, aVL, V6 leads. Cardiac catheterization and angiography revealed marked dilatation of left ventricle (end-diastolic volume = 384 ml/m2) and extremely depressed ejection fraction (16%), confirming the diagnosis of BWG syndrome. A 201TlCl-myocardial SPECT demonstrated apical defect and hypoperfusion in the anterolateral, inferoposterior walls, whereas 123I-beta-methyl-p-iodophenylpentadecanoic-acid (123I-BMIPP) SPECT showed a wider defect area. SPECT studies with 201TlCl and 123I-BMIPP, are useful to assess myocardial viability more accurately in BWG syndrome.

Coronary Vessel Anomalies↗
PubMed1995

31P NMR study of acute toxic effects of cadmium chloride on rat liver.

In this study, acute effects of cadmium ions (Cd2+) on energy metabolism in rat livers were analyzed in vivo after intravenous administration using 31P NMR. Both inorganic phosphate (Pi) and nucleotide triphosphate (NTP) peaks of in vivo Cd-treated livers gradually decreased over a 6-h period. In the extract, NTP peaks in Cd-treated livers were lower, as in the in vivo experiments, but the Pi peak was significantly higher than the control. The apparent decrease in Pi in in vivo liver treated with Cd could be caused by the reduced visibility of Pi because of its uptake into mitochondria from cytoplasm, accompanied by the uncoupling of oxidative phosphorylation by Cd2+. These results indicated that total Pi in the hepatocytes increases after Cd administration. However, only 10% of Pi was visible in Cd-treated livers in vivo, whereas 34% of Pi was visible in controls. Significant increases in phosphocholine and glycerophosphocholine were also observed in extracts of Cd-treated livers.

Acute Disease↗
PubMed1995

Control of the rate of phosphocreatine resynthesis after exercise in trained and untrained human quadriceps muscles.

We examined the effect of differences in exercise intensity on the time constant (tc) of phosphocreatine (PCr) resynthesis after exercise and the relationships between tc and maximal oxygen uptake (VO2max) in endurance-trained runners (n = 5) and untrained controls (n = 7) (average VO2max = 66.2 and 52.0 ml.min-1.kg-1, respectively). To measure the metabolism of the quadriceps muscle using phosphorus nuclear magnetic resonance spectroscopy, we developed a device which allowed knee extension exercise inside a magnet. All the subjects performed four types of exercise: light, moderate, severe and exhausting. The end-exercise PCr: [PCr+inorganic phosphate (P(i))] ratio decreased significantly with the increase in the exercise intensity (P < 0.01). Although there was little difference in the end-exercise pH, adenosine diphosphate concentration ([ADP]) and the lowest intracellular pH during recovery between light and moderate exercise, significant changes were found at the two higher intensities (P < 0.01). These changes for runners were smaller than those for the controls (P < 0.05). The tc remained constant after light and moderate exercise and then lengthened in proportion to the increase in intensity (P < 0.05). The runners had a lower tc at the same PCr and pH than the controls, particularly at the higher intensity (P < 0.05). There was a significant correlation between tc and [ADP] in light exercise and between tc and both end-exercise PCr and pH in severe and exhausting exercise (P < 0.05). The threshold of changes in pH and tc was a PCr: (PCr+P(i)) ratio of 0.5. There was a significant negative correlation between the VO2max and tc after all levels of exercise (P < 0.05). However, in the controls a significant correlation was found in only light and moderate exercise (P < 0.05). These findings suggest the validity of the use of tc at an end-exercise PCr: (PCr+P(i)) ratio of more than 0.5 as a stable index of muscle oxidative capacity and the correlation between local and general aerobic capacity. Moreover, endurance-trained runners are characterized by the faster PCr resynthesis at the same PCr and intracellular pH.

Adenosine Diphosphate↗
PubMed1995

Muscle metabolism during exercise using phosphorus-31 nuclear magnetic resonance spectroscopy in adolescents.

Very little has been reported on muscle energetics during exercise in adolescents. This is attributable to the difficulty of subjecting children to muscle biopsy. The purpose of this study was to investigate the characteristics of muscle metabolism during exercise in vivo in adolescents by comparing firstly, with adults and secondly, the differences resulting from physical activity using phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy. The subjects were boys aged 12 to 15 years, comprising 21 trained boys and 23 control boys, and 6 adults controls. The ratio of phosphocreatine (PCr):(PCr + P(i)), where P(i) is inorganic phosphate intracellular pH at exhaustion and the time constant of PCr during recovery were measured in all the subjects using 31P NMR. Both groups of children showed higher values of PCr:(PCr + P(i)) and intracellular pH at exhaustion than did the adult control group (P < 0.01 or P < 0.05). However, no significant differences were found between the trained boys and the control boys with respect to PCr:(PCr + P(i)) and intracellular pH at exhaustion. On the other hand, we found the same values for PCr time constant in all groups. This result suggested no differences of the muscle oxidative capacity between children and adults. We concluded that the adolescents, aged 12 to 15 years in both the trained and control groups, had less glycolytic ability during exercise than the adults.

Adolescent↗
PubMed1995

Study on the primary visual cortex of visually impaired subjects by means of 123I-IMP SPECT and MRI.

We conducted a study of rCBF in the primary visual cortex of visually impaired subjects who have not been subjected to external stimulation for a long period, by means of 123I-IMP SPECT and MRI. The four subjects had lost their sight due to brain tumors (n = 2), glaucoma (n = 1) and trauma (n = 1). 123I-IMP SPECT showed no differences between the visually impaired group and a visually sound control group on visual analysis as well as semiquantitative analysis. MRI of the visually impaired subjects showed no organic changes, such as atrophy, in the occipital cortex. In conclusion, visually impaired subjects have no decrease in rCBF and no anatomical changes in the primary visual cortex.

Adult↗
PubMed1995

The functional hepatic volume assessed by 99mTc-GSA hepatic scintigraphy.

The accuracy of measurement of the functional hepatic volume by single photon emission computed tomography (SPECT) with 99mTc-galactosyl serum albumin (99mTc-GAS) was evaluated. 99mTc-GSA planar scintigraphic images were obtained dynamically and the hepatic SPECT imaging was then performed in 25 patients with hepatobiliary tumors. The patients were divided into 4 groups with normal hepatic function, and mild, moderate and severe hepatic dysfunction. The functional hepatic volume determined by SPECT was compared with the morphological hepatic volume determined by compute tomography. The ratio of the hepatic volumes obtained by the two methods was calculated. The mean hepatic volume ratio was 96.6 +/- 2.3% in the normal hepatic function group and 95.9 +/- 2.2% in the mild dysfunction group (n.s.). In both the moderate and severe hepatic dysfunction groups, the hepatic volume ratio was smaller than that in the normal group (87.9 +/- 5.2%, p < 0.0001, and 71.9 +/- 7.6%, p < 0.0001, respectively). There was a linear correlation between the hepatic volume ration and various indices of reserve hepatic function, such as LHL15 (r = 0.83, p < 0.0001), HH15(r = 0.74, p < 0.0001), and ICG15 (r = 0.75, p < 0.0005). These results indicate that the hepatic volume ratio is proportional to the severity of hepatic dysfunction, and suggest that the functional hepatic volume measured with 99mTc-GSA faithfully reflects the functioning hepatocyte mass. 99mTc-GSA scintigraphy and hepatic SPECT therefore provide information regarding global and regional reserve hepatic function.

Adult↗
PubMed1995

Acute effects of exercise on muscle MRI in peripheral arterial occlusive disease.

The midcalf muscles of eight patients who had peripheral arterial occlusive disease were evaluated by exercise MRI before and after bypass surgery or percutaneous transluminal angioplasty. MRI showed a high intensity of these muscles, especially the posterior muscles, after exercise in all patients before intervention. The mean T2 relaxation time was maximal immediately after exercise (tibialis anterior, T2 = 30.8 ms; soleus, T2 = 36.2 ms; gastrocnemius, T2 = 32.8 ms) and then gradually decreased to the preexercise level. The difference in the T2 relaxation time of the soleus between immediately after exercise and at rest was smaller along with improvement of ankle pressure indices (API) after successful intervention (mean T2 difference: 4.91 and 0.72 ms (p < .001); mean API: 0.54 and 0.86 (p < .001) before and after intervention, respectively). The mean resting midcalf T2 relaxation time was significantly higher after intervention (tibialis anterior, T2 = 28.4 and 29.5 ms (p < .05); soleus, T2 = 31.4 and 32.9 ms (p < .05); gastrocnemius, T2 = 29.5 and 31.1 ms (p < .01) before and after intervention, respectively). T2 relaxation time may be a useful quantitative parameter in peripheral arterial occlusive disease as well as in other muscle studies.

Aged↗
PubMed1995

Contrast effect of blood on phase-contrast X-ray imaging.

RATIONALE AND OBJECTIVES: As a preliminary study for application of phase-contrast X-ray imaging to medicine, we measured the X-ray refractive index of human blood and its influence on image contrast. METHODS: Using an X-ray interferometer, the X-ray phase shifts caused by human blood and its ingredients were measured from the interval of interference fringes. RESULTS: The X-ray phase shift caused by blood was 3% larger than that caused by serum. CONCLUSION: The large phase shift caused by blood is due to red blood cells, which contain hemoglobin molecules with iron atoms. It is possible that blood produces a structure in a phase-contrast X-ray image.

Blood↗
PubMed1995

Two-dimensional intravenous coronary arteriography using above-K-edge monochromatic synchrotron X-ray.

RATIONALE AND OBJECTIVES: For intravenous (i.v.) coronary arteriography, a real-time two-dimensional (2D) imaging system is being developed using above-K-edge monochromatic X-rays alone. The potential diagnostic value of this system was examined in the current study. METHODS: The angiographic system consisted of an asymmetric silicon (311) monocrystal, an image intensifier, and a charged-coupled device camera. It was constructed at the beam line of the Tristan Accumulation Ring. Monochromatic X-rays of 33.32 keV were used, and each image was recorded over 2 msec. RESULTS: Ventricular wall motion and the anatomy of the coronary arteries could be seen in dogs by sequential images obtained without subtraction. The left anterior descending coronary artery, left circumflex coronary artery, and right coronary artery and the branches of these vessels were observed. The parts of the coronary arteries overlapping the aorta and left ventricle were revealed somewhat during washout of the contrast material. CONCLUSION: For a 2D imaging system, monochromatic i.v. coronary angiography using an energy above the iodine K-edge might be able to image the coronary arteries without subtraction. However, the image quality needs to be improved by increasing the X-ray flux, decreasing background radiation scatter from the object, and decreasing contamination with 99-keV X-rays.

Animals↗