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M Onomichi

Publications and source records attributed to M Onomichi.

13 recordsLinked to original sources
PubMed2001

Evaluation of the intracranial dural sinuses with a 3D contrast-enhanced MP-RAGE sequence: prospective comparison with 2D-TOF MR venography and digital subtraction angiography.

BACKGROUND AND PURPOSE: The diagnosis of dural sinus thrombosis is often difficult because of its variable and nonspecific clinical presentation and the overlapping signal intensities of thrombosis and venous flow on conventional MR images and MR venograms. We compared 3D contrast-enhanced magnetization-prepared rapid gradient-echo (MP-RAGE) sequences with 2D time-of-flight (TOF) MR venography, digital subtraction angiography (DSA), and conventional spin-echo (SE) MR imaging for the assessment of normal and abnormal dural sinuses. METHODS: In a phantom study, a plastic tube with pulsating flow was used to simulate the intracranial dural sinus. With 3D MP-RAGE, a variety of flow velocities, contrast material concentrations, and angulations between the phantom flow tube and the plane of acquisition were tested to measure their relationship to signal-to-noise ratio (SNR). In a clinical study, 35 patients, including 18 with suspected dural sinus thrombosis, were studied with both MR imaging and DSA. Receiver operating characteristic (ROC) analysis was performed in a blinded fashion using DSA as the reference standard. RESULTS: With the phantom, the SNR of flow increased with increasing contrast concentration, but was not affected by the angle between the tube and scan slab. There was no relationship between SNR and velocity when the contrast concentration was 1.0 mmol/L or greater. In the clinical study, dural sinus thrombosis as well as the normal anatomy of the dural sinuses were seen better with 3D contrast-enhanced MP-RAGE than with 2D-TOF MR venography. Three-dimensional contrast-enhanced MP-RAGE showed the highest diagnostic confidence on ROC curves in the diagnosis of thrombosis. CONCLUSION: Three-dimensional contrast-enhanced MP-RAGE is superior to 2D-TOF MR venography and conventional SE MR imaging in the depiction of normal venous structures and the diagnosis of dural sinus thrombosis, and is a potential alternative to DSA.

Adult↗
PubMed1999

Dynamic magnetic resonance imaging of head and neck lesions.

Dynamic magnetic resonance imaging (MRI) has been used to improve the detection of tumors, to determine the tumor extension, and to make differential diagnosis. Most malignant lesions of the head and neck show early enhancement and early washout of contrast media on dynamic MRI, but the tumor characterization remains unclear. Pharmacokinetic analysis of dynamic MRI can provide information about the permeability of Gd-DTPA in the tumor that may reflect the oxygen concentration of the tumor and the amount of drug delivered to the tumor. This information may be useful in the prediction of radiation and/or chemotherapy response of the tumor.

Algorithms↗
PubMed1998

Pulsatile cycle-specific data acquisition in carotid MR angiography with segmented FLASH sequence: experimental and clinical investigation.

RATIONALE AND OBJECTIVES: The authors evaluated the usefulness of diastolic data acquisition in magnetic resonance (MR) angiography of the carotid artery. MATERIALS AND METHODS: MR angiographic images of phantom models of 30%, 40%, and 50% stenosis were obtained at different pulsatile cycles by using variable delay times from the electrocardiogram triggering with segmented fast low-angle shot sequences (14/7.3 [repetition time msec/echo time msec]) with k-space segmentation. The degree of stenosis was measured on the MR angiographic images by three observers. Poststenotic signal intensity loss was analyzed by measuring the signal intensity on the axial image acquired 10 mm distal to the stenotic portion of the 50% stenosis phantom at variable delay time from triggering. Six patients with stenosis of the internal carotid artery also underwent conventional and MR angiography. The degree of stenosis depicted on diastolic- and systolic-phase MR angiographic images was measured by three observers and compared with that shown on the conventional angiographic images. RESULTS: The diastolic-phase images more accurately depicted the degree of stenosis than did the systolic-phase images in the phantom and all six patients, although the degree of stenosis tended to be overestimated on both images. The degree of stenosis was most overestimated with triggering that occurred at the time of peak flow velocity. In the phantom with 50% stenosis, the signal intensity 10 mm distal to the stenotic portion was decreased in the systolic phase. CONCLUSION: Diastolic data acquisition is a useful method of reducing intra- and poststenotic signal intensity loss in the carotid artery.

Aged↗
PubMed1998

[An analysis on a relationship between perinatal mortality and live births of low birthweight, in Kumamoto Prefecture, 1968-1994].

The aims of this investigation were to describe the relationship between perinatal mortality rates and the proportions of live births among low birth weight (LBW) infants from 1968 to 1994, and to determine risk factors in infants of low birth weight. Using vital statistics from 1968 to 1994 of the Japanese government and the Kumamoto Prefecture and Maternal and Child Health Statistics of Japan from 1968 to 1995, perinatal deaths and live births of infants of low birth weight were studied according to national statistics criteria. In Japanese and Kumamoto Prefecture, there was an association between perinatal deaths and live births of LBW. The significant decline of perinatal mortality rates from 1968 to 1976, of which the fetal death ratio at 28 weeks and over mostly declined, was closely related to the decline of live births of LBW. In this period, the improvement of socioeconomic conditions and the comprehensive health care provided by the government contributed in improving perinatal mortality rates. From 1977 to 1988, the annual variation of Kumamoto was different from that of all Japan. Both perinatal mortality rates continued to decline due to a general decrease in early neonatal mortality rates. The number of Live births of LBW infants in Kumamoto prefecture increased in 1977 and once again started to decline in 1982. In 1977, the insufficient maternal-child health care and the increase of female workers contributed to increasing rates of live births of LBW. Advances in neonatal medicine contributed to the increase in survival rates of infants of LBW. Although, after 1982, the improvement of maternal-child health care and the perinatal care system contributed to the declining rates of live births of LBW. On the other hand, those rates in all Japan continued to gradually increase from 1977 to 1988. After 1989, perinatal mortality rates continued to decline, and live births of LBW continued to increase in both Kumamoto prefecture and all Japan. These results were contrary to the above results from 1968 to 1976. It was considered that medical advances in the care of pregnant women and neonates increased survival rates of the LBW. In future, the perinatal mortality rates will appear to approach a minimum constant, that is, a minimum of fetal death rates. It is important to reduce the number of LBW infants, particularly birthweight of 2000 g-2499 g, with maternal-child health care.

Birth Weight↗
PubMed1995

[Recovered state of iron in female blood donors--after taking an iron supplement].

An iron supplement was given to female blood donors to prevent iron deficiency after blood donation. The levels of items related to red blood cells and serum ferritin (S-Fer) among 17 iron-takers and 31 non-iron-takers were analyzed continuously. In most of the non-iron-takers, the S-Fer levels did not recover within four weeks after the donation of 200ml or 400ml of blood. In the approximately half of the donors, hemoglobin (Hb) levels did not recover either. However, in 59% of those taking iron supplements three times the amount of iron lost by donation, the levels of Hb and S-Fer recovered within two weeks. In the remaining 41%, the Hb levels recovered within four weeks by taking the iron supplement. Four weeks after blood donation, the incidence of iron deficiency anemia among the non-iron-takers increased from 13% to 23% and the incidence of latent iron deficiency among the non-iron-takers increased from 32% to 42%. However, the incidence of iron deficiency anemia among the iron-takers remained 0% and the incidence of latent iron deficiency among the iron-takers decreased from 12% to 6%.

Adult↗
PubMed1993

[The states of recovery of blood counts and serum ferritin levels after blood donation].

Complete blood counts and levels of ferritin in serum (S-Fer) in 62 college students were analyzed continuously to clarify the effects of blood donation. In 14 (45%) of 31 females, hemoglobin (Hb) and S-Fer levels showed decrease of more than 5% and 30%, respectively, four weeks after donation of 200ml or 400ml of blood. In 11 (35%) of the males and 6% of the females, Hb levels increased over 5% during the same period. In 61% of the males and 45% of the females, S-Fer levels decreased. In only 19% of the males, the Hb and S-Fer levels were unchanged. Red blood cell (RBC) counts and Hb levels showed almost the same pattern. In 39% of the males and 48% of the females, the white blood cell (WBC) counts decreased more than 10%. In 10% of the males and 23% of the females, WBC counts increased more than 10% after blood donation. The WBC and RBC counts did not always show the same pattern of variation. After blood donation, the incidence of iron deficiency anemia among females increased from 13% to 23% and the incidence of latent iron deficiency among females increased from 10% to 42%.

Adult↗
PubMed1991

[Effects of long-term low dose radiation--relationship between chromosomal translocation and the cellular oncogenes].

To clarify the late effects of long-term exposure to low doses of radiation, chromosomal aberrations in the lymphocytes of radiological technologists (RT) were analyzed by the trypsin G-banding method. Structural aberrations were identified in 384 (2.5%) of 15,442 cells analyzed from 53 RT as compared to 177 (1.6%) of 11,136 cells from 36 healthy controls. Most of structural aberrations in both groups was translocations, and this frequency was significantly higher in the RT than in the controls. Translocations of chromosomes, such as Nos. 1, 2, 7 and 14 in RT and Nos. 1, 3, 7 and 14 in controls, was observed in over 7% of the cells. 7/14 translocations were the most frequent reciprocal translocations in RT. However, the frequency of 7/14 translocations was not significantly different between the RT and controls. In these cases, most of the break points were localized in band 14q11-12 and 7q32-36. At the chromosomal sites which were related to the sites of ski, abl, myb, mos, myc, N-myc oncogenes, very low incidences of translocation were detected in RT. However, none of the RT demonstrated abnormal clones of cells with identical chromosomal aberrations.

Chromosomes, Human↗
PubMed1990

Effects of long-term radiation exposure on chromosomal aberrations in radiological technologists.

Chromosomal aberrations in the lymphocytes of radiation technologists (RT) were analyzed by the trypsin G-banding method to study the late effects of long-term exposure to low doses of radiation. Structural aberrations were identified in 384 (2.5%) of 15,442 cells analyzed from 53 RT as compared to 177 (1.6%) of 11,136 cells from 36 healthy controls. Stable aberrations were the most frequent in both groups and were either translocations or deletions. Unstable aberrations were mainly acentric fragments in both groups. The frequency of translocations and acentric fragments was significantly higher in the RT than in the controls and was highest in the RT over 50 years. The highest frequency observed in the greater than 50 age group was attributed to the unknown for cumulative dose prior to introduction of film badges. Frequency of chromosomal aberrations correlated with the estimated dose from the film badges and years of experience of each RT based on the equation y = 0.22 + 0.37D + 4.35D2, where y is overall frequency of chromosomal aberrations and D is the estimated radiation dose in Sv.

Chromosome Aberrations↗
PubMedDate not supplied

Delineation of simulated vascular stenosis with Gd-DTPA-enhanced 3D gradient echo MR angiography: an experimental study.

PURPOSE: The purpose of this experimental study was to evaluate the influence of contrast material concentration and flow velocity on pulsatile flow in Gd-DTPA-enhanced 3D gradient echo MR angiographic sequence. METHOD: In vivo flow experiments were performed in Plexiglas phantoms with artificial stenosis (50% stenotic ratio and 20 mm stenotic length) attached to a cardiac pump that generated physiological pulsatile flow similar to that of the bloodstream in a closed circuit. We used a steady-state gradient echo sequence with different TEs (6, 3, and 1.4 ms). A TR of 15 ms was used for all parameters. The concentration of Gd-DTPA varied from 0 to 2.0 mmol/L and flow velocities from 25 to 80 cm/s. We measured the degree of stenosis and length of stenosis in comparison with the actual values. RESULTS: The degree and length of stenosis on 3D gradient echo MR angiographic images were markedly influenced by the velocity of the flow and concentration of Gd-DTPA. The degree of stenosis was overestimated when the flow was fast or when the concentration of Gd-DTPA was low. When the concentration of Gd-DTPA was low, stenosis was elongated. These effects were less prominent on short TE (1.4 ms) sequence. CONCLUSION: The stenotic lesions were markedly overestimated on MR angiographic images obtained with Gd-DTPA-enhanced fast 3D gradient echo sequence. Spin dephasing can be compensated for almost entirely by a high concentration of Gd-DTPA and/or a short TE sequence.

Arterial Occlusive Diseases↗
PubMedDate not supplied

Carbon-13 magnetic resonance spectroscopy of glucose metabolism in SCC-VII tumors.

We used 13C MR spectroscopy to follow the metabolism of [1-13C]glucose in SCC-VII tumors of C3H/HeN mice. Six different SCC-VII tumors and six muscles of normal legs were used. Spectroscopy was carried out with the intraperitoneal injection of 100 mg of [1-13C]glucose. Six distinct resonances were detected: the alpha and beta anomers of the C1 of glucose, C2,3,4 of glutamate and glutamine, and the C3 of lactate. Signals from [1-13C]glucose were first detected in the spectra of tumor 10 minutes after injection. Signals decreased faster in the SCC-VII tumors than the muscle of normal leg. The presence of 13C of glutamate/glutamine suggested the entry of pyruvate into the TCA cycle in SCC-VII tumor. The more rapid decrease of signals from [1-13C]glucose in the SCC-VII tumor may be attributed to the effects of blood flow volume and metabolic activity.

Animals↗
PubMedDate not supplied

Determination of the optimal pulses in MR imaging with magnetization transfer contrast at 7 Tesla.

OBJECTIVE: The magnetization transfer contrast (MTC) effect depends on the shape, duration, amplitude, and offset frequency of the saturation pulse. In the present study, we investigated optimal combinations of these four parameters in vitro. METHODS: All experiments were performed with a 7.05 Tesla MR system, and the spin echo technique (TR 500/TE 30) was adopted. We used a simple phantom composed of 1% agar and water, representing restricted and free proton pools, respectively. Signal intensity changes were measured in the agar (Ma) and water (Mw), when the shape, duration, magnitude, and offset frequency of the saturation pulses were varied. The MTC effect was examined with the Mw/Ma ratio. RESULTS: The suppression of Mw was less with the gauss pulse than with the square and sinc pulses. The gauss pulse had the best MTC effect. The suppression of both Ma and Mw was greatest with a saturating duration of 60 msec. The MTC effect was greatest with a longer saturation pulse. The larger the amplitude, the stronger the MTC effect obtained. Mw was suppressed with an offset frequency of less than 3 kHz, and the MTC effect was greatest with an offset frequency closer to the spectrum of the free proton pool. CONCLUSION: In the present study the optimal MTC pulse at 7 Tesla is the gauss pulse with longer duration, maximal amplitude, and approximately 3 kHz off resonance.

Contrast Media↗