Biomedical subjects

R Morita

Publications and source records attributed to R Morita.

At least 73 records · Page 4Linked to original sources

PubMed1997

Two optimal prefilter cutoff frequencies needed for SPECT images of myocardial perfusion in a one-day protocol.

OBJECTIVE: The purpose of this study was to determine if cutoff frequencies of two-dimensional Butterworth filters need to be changed, depending upon the amount of radiopharmaceutical administered in one-day protocols for reconstructing SPECT images of myocardial perfusion. METHODS: A scintilation camera and a phantom were used with 2.2 MBq and 10.6 MBq 99mTc. These activities corresponded to the approximate amounts used in our one-day myocardial perfusion imaging protocol. The projection data were collected in 30 positions spread over 180 degrees. Thirty- and 150-sec acquisitions per position were performed to obtain the study and the high-quality reference images. Thirteen cutoff frequencies of the filter were used to reconstruct the SPECT images. Optimal cutoff frequencies were determined by visual assessment and by calculating the normalized mean square error (n.m.s.e). These results were then compared. The same protocol was used to image three volunteers with no heart disease and the images were evaluated visually. RESULTS: In the phantom study, the optimal cutoff frequencies were 0.225 cycles/pixel for 2.2 MBq, and 0.275 cycles/pixel and 0.25 cycles/pixel for 10.6 MBq by visual inspection, and were 0.225 cycles/pixel and 0.275 cycles/pixel by calculating the n.m.s.e., respectively. In the patient study, the lower cutoff frequency of 0.20 cycles/pixel was optimal for the exercise study (low dose), while the higher cutoff frequencies of 0.275 cycles/pixel was optimal for the resting study (high dose). CONCLUSION: The optimal cutoff frequencies differed for the two activity levels. Cutoff frequencies should be changed according to the amounts of radiopharmaceuticals used for the first and the second examinations in one-day protocols.

Heart↗

PubMed1996

Coexistence of choriocarcinoma and adenocarcinoma in the rectum: molecular aspects.

Choriocarcinoma, a malignant tumor of usually placental origin, in divided into two groups; the gestational and non-gestational types, the latter being rare. Non-gestational choriocarcinoma occurs in the lung, mediastinum, kidney, stomach, and small intestine, but rarely appears in the large intestine. We treated a 29-year-old woman with choriocarcinoma of the rectum with adenocarcinoma. Despite the rarity of the condition and the obscurity of the histogenesis, reports of similar cases and the occurrence of the tumors in the digestive tract suggest that the condition constitutes a clinical entity of a digestive tumor.

Adenocarcinoma↗

PubMed1996

Peribronchovascular interstitium of the pulmonary hilum: normal and abnormal findings on thin-section electron-beam CT.

The peribronchovascular interstitium, including bronchial vessels and lymphatic channels, is an important anatomic component of the lung, especially the pulmonary hilum [1-3] (Fig.1). Various pathologic processes involve and spread along this interstitium [4, 5]. Although it has been difficult to accurately evaluate the morphologic changes occurring in the peribronchovascular interstitium with conventional CT or MR imaging [6], spiral CT and electron-beam CT can show these changes clearly and consistently [7, 8]. A judgement as to whether the peribronchovascular interstitium is normal or abnormal is necessary for the CT diagnosis of pulmonary hilar lesions. In this assay, the normal peribronchovascular interstitium and various pathologic processes involving this interstitium are shown as they appear on thin-section electron-beam CT scans.

Aged↗

PubMed1996

[Bone densitometry].

Recently, several methods for measurement of bone density have been developed. Among them, dual X-ray absorptiometry (DXA) is now considered to be a standard method in bone densitometry. In most cases, values by DXA measurement reflect bone strength and thus measurements of lumbar spine and femoral neck by DXA are used for diagnosis of osteopenia or osteoporosis. In several clinical trials of new drugs, measurement of DXA proved to be very useful. Other methods such as DXA for os radius or os calcaneus are also useful for screening of general osteopenia and quantitative ultrasound is widely used for mass-screening of osteoporosis because of its convenience. Radiographic absorptiometry is also a convenient method, which can be performed only by taking an X-ray photograph with an aluminum phantom. Quantitative computed tomography (QCT) is a method which enables measurement of trabecular true bone density as well as an analysis of trabecular structure and peripheral QCT, aimed for measurement of peripheral bones, is also expected to be a sensitive method to monitor therapeutic responses. Since several methods are now available, it is important to choose a method which is the most suitable for the purpose of each bone mineral measurement.

Absorptiometry, Photon↗

PubMed1996

[Detection of bone metastasis by serial measurement of C-terminal telopeptide of type I collagen in patients with malignancy].

Measurements of biochemical markers specific to bone resorption are known to be useful in evaluation of skeletal metastasis. However, most of previous studies were performed cross-sectionally and sensitivity for detection of early bone metastasis was not satisfactory. Since basal levels of bone markers differ significantly individually, longitudinal studies would be preferable to evaluate small metabolic changes such as in early skeletal metastasis. Thus, we performed serial measurements of serum c-terminal telopeptide of type I collagen (ICTP), a bone resorption marker, in patients with malignancy and evaluated its clinical significances for detection of bone metastasis, comparing with measurements of propeptide of type I procollagen (PICP) and tumor markers. In total, 43 patients (41 of them are breast cancer), serial serum samples were obtained during 0.5 to 2.4 years (mean 1.4 years). In all of nine patients, who developed bone metastasis, serum ICTP level increased, and by successful treatment to the metastatic lesions, ICTP level decreased, while in some cases, tumor markers remained to be elevated. PICP was less sensitive and specific for detection of bone metastasis. Thus, serial measurement of ICTP is suggested to be useful for detection and evaluation of therapeutic responses in patients with bone metastasis.

Biomarkers, Tumor↗

PubMed1996

[Evaluation of renal function using Gd-DTPA dynamic MR imaging].

To establish a new method for evaluating renal function using MRI, we performed dynamic Gd-DTPA enhanced MR imaging at 1.5 T in 68 subjects (71 examinations), including 23 normal volunteers, 19 patients with chronic renal failure, 22 with hydronephrosis, and 7 with renal vascular disorders. Thirty GRASS images [35/9/20 degrees /1 (TR/TE/Flip Angle/NEX)] were obtained after a bolus injection of Gd-DTPA (0.2 mmol/Kg) in each case, and were evaluated in the following respects. (1) Whether or not the initial signal increase and/or the following signal drop in cortex was observed. (2) Whether or not the signal drop in medulla and/or calyces was observed. (3) Time between initial signal increase in cortex and signal drop in medulla (Ta). (4) Time between signal drop in medulla and calyces (Tb). (5) Time between signal increase in cortex and signal drop in calyces (Tc). (6) Maximum ratio of signal intensity between cortex and medulla (Max. C/M). In normal subjects, the initial signal increase and the following signal drop in cortex, and the signal drop in medulla and calyces were observed. In patients with abnormal renal function, the characteristic signal changes described above were not seen clearly or disappeared in many cases. In normal subjects, Ta, Tb, Tc, and Max. C/M were 41.9 +/- 6.9 sec, 53.2 +/- 10.6 sec, 95.0 +/- 9.5 sec, and 1.10 +/- 0.05, respectively. In the patients, time parameters were significantly larger than those of normal subjects and C/M ratios were lower. This study suggested that dynamic Gd-DTPA renal MR imaging can serve as a new method for the evaluation of renal function.

Adolescent↗

PubMed1996

[Measurement of gastric emptying by magnetic resonance imaging].

The purpose of the study was to establish a new method of measuring gastric emptying using MR Imaging in human. Gastric emptying was measured in 6 healthy male volunteers aged from 28 to 43 years, using MR imaging and RI. The measurements were performed after the oral administration of liquid meal containing glucose, protein and fat. The MR imaging was performed with 0.5T superconducting magnet machine, and consecutive 12 transaxial T1 weighted spin echo images (TR/TE = 300/17) of the upper abdomen were recorded every 10 minutes for more than 1 hour. Gastric emptying curves and their T1/2 values obtained by MR imaging and RI method were correlated well in 5 of 6 cases. We concluded that a non invasive and radiation free method using MR imaging was proved to be a useful tool for measuring gastric emptying.

Adult↗

PubMed1996

CT of the pulmonary hilum: evaluation with thin-section ultrafast CT.

The recent progress of CT technology, such as spiral and ultrafast CT, has made it possible to obtain contiguous thin-section CT images of the pulmonary hilum during rapid injection of contrast material. These CT images consistently provide clear images of the pulmonary hilum, including normal peribronchovascular interstitium, bronchi, and pulmonary vessels, enabling a more precise and detailed evaluation of various pathological conditions than CT previously allowed. This article illustrates high-quality CT images in normal and abnormal conditions occurring in the pulmonary hilum and discusses the present CT diagnosis of various pulmonary hilar diseases.

Contrast Media↗

PubMed1996

Three-dimensional bone scintigraphy using volume-rendering technique and SPECT.

UNLABELLED: Three-dimensional bone scintigraphic images were made and their usefulness and limitations discussed. METHODS: After usual bone scan procedures, single-photon emission computed tomography (SPECT) data were taken and reconstructed into three-dimensional images. Volume rendering methods were used. RESULTS: Three cases of three-dimensional bone scintigraphy were obtained; one of a normal patient, one of a case of transplanted kidney and incomplete fracture of the left femoral head, and one of a case of degenerative joint disease (DJD) on the left temporomandibular joint (TMJ). The three-dimensional structure of the skeletal system was depicted more clearly by the three-dimensional images than by a conventional bone scan. CONCLUSION: Three-dimensional bone scintigraphs were thought to provide additional information for better understanding of the nature of bone lesions. Some technical improvements including automated threshold level determination and feature extraction for detecting abnormal high uptake are required before routine use can be envisaged.

Adult↗

PubMed1996

[Ultra-low-dose spiral (helical) CT of the thorax: a filtering technique].

To reduce the radiation dose from spiral (helical) CT, a custom-made aluminium filter was installed in the X-ray tube and a reduction of effective tube current was attempted. A pronounced reduction of effective tube current, namely, 6 and 3 mA, was achieved with 26 and 37 mm thick aluminium filters, respectively. Visualization of normal lung structure was accomplished with both 6 and 3 mA settings. However, images of 3 mA failed to delineate mediastinal structures because of marked beam hardening resulting from the bone structure of the thoracic inlet. Six mA was considered the lowest dose setting of spiral (helical) CT of the thorax that could be used for lung cancer screening.

Adult↗

PubMed1996

Lumbosacral nerve root enhancement with disk herniation on contrast-enhanced MR.

PURPOSE: To evaluate the clinical importance of nerve root enhancement associated with lumbar disk herniation. METHODS: Thirty-two patients with lumbar disk herniation were examined with unenhanced and contrast-enhanced MR imaging. We investigated the relationship between nerve root enhancement and location of herniated disk in the epidural space, onset pattern of symptoms, subsequent treatment, and surgical findings. RESULTS: Ten of the 32 patients had nerve root enhancement, and all belonged to the group with abrupt and severe nerve root compression with no residual space for the root between the herniated disk and the pedicle in the lateral recess. Tight compression of the root without mobility was seen in the four patients with nerve root enhancement who were treated surgically. CONCLUSION: Nerve root enhancement may indicate the existence of abrupt and severe compression of the nerve root as well as the presence of severe adhesion of the herniated disk and the nerve root. This finding does not necessarily determine the type of subsequent treatment.

Adolescent↗

PubMed1996

[Dynamic Gd-DTPA-enhanced MR imaging in evaluation of the function of transplanted kidneys].

The purpose of the study was to evaluate the potential of dynamic Gd-DTPA-enhanced MR imaging in assessing of the function of transplanted kidneys. Dynamic MR imaging was performed using the GRASS pulse sequence in 21 subjects (56 examinations), and in each examination 30 images were obtained after a bolus injection of Gd-DTPA. Imaging findings including signal increase and/or signal drop in cortex, signal drop in medulla, and signal drop in calyces were utilized for the evaluation of renal function. Renal function was also evaluated using the following parameters: Ta, time between the initial observation of signal increase in cortex and signal drop in medulla. Tb, time between the initial observation of signal drop in medulla and in calyces; Tc, Ta + Tb, and Max. C/M, maximum ratio of signal intensity between cortex and medulla among 30 images. In the group of patients with normal graft function (Ccr > or = 60ml/min), all imaging findings were observed. In the group of patients with mild graft dysfunction (30ml/min < or = Ccr < 60ml/min), all imaging findings but signal drop in cortex were observed. The time parameters of Ta, Tb, and Tc were significantly larger, and Max. C/M was significantly smaller than those observed in the group with normal graft function. In the group of patients with severe graft dysfunction (Ccr < 30ml/min), almost none of the findings were observed. The investigation in patients in the postoperative state revealed a close correlation of the imaging findings and the values of parameters with changes in graft function over time. The results indicated the usefulness of the method in semiquantitative evaluation of graft function, including that of patients in postoperative state. This study suggests that dynamic Gd-DTPA-enhanced MR imaging could be a valuable method for the management of transplanted kidneys.

Adolescent↗

PubMed1996

Age-related change of technetium-99m-HMDP distribution in the skeleton.

UNLABELLED: To understand age-related changes of whole-body and regional skeletal metabolism, it is important to investigate the mechanisms of age-related bone loss and to develop suitable treatments for it. Bone biopsies show metabolism of the particular site examined while biochemical markers for bone metabolism reflect total skeletal metabolism. Bone scintigraphy is a convenient and simple way to analyze whole-body and regional skeletal metabolism. We attempted to study and understand age-related changes in bone metabolism by quantifying the bone scan and correlating it with biochemical bone metabolic markers. METHODS: The whole-body skeletal uptake (WBSU) and tracer distribution pattern were studied in men and women by bone scintigraphy using 99mTc-hydroxy-methane-diphosphonate (HMDP). Bone scans were performed using a standard protocol and quantified by setting regions of interest (ROIs) on selected regions. WBSU and the skeletal distribution pattern were compared with simultaneously obtained serum biochemical markers. RESULTS: WBSU showed an increase with age in both sexes, but in women, uptake in the head and legs increased more relatively than in the thoracic region, while in men no such tendency was observed. Increase of WBSU and relative increase of uptakes in the head demonstrated a weak correlation with the serum levels of alkaline phosphatase and type 1 collagen metabolites. CONCLUSION: These results show an age-related increase of skeletal turnover and sex-dependent regional skeletal metabolism. The age-related changes seen in bone scintigrams might be a sign of progressive bone loss, reflecting changes in local bone metabolism.

Age Factors↗

PubMed1996

Evaluation of the pharyngeal airway in obstructive sleep apnea: study by ultrafast MR imaging.

To evaluate dynamic morphologic changes of the respiratory tract in patients with obstructive sleep apnea syndrome (OSAS), the cross section and the midline sagittal section of the upper respiratory tract of OSAS were examined using ultrafast MR imaging technique. In 10 men and 2 women diagnosed with OSAS, 30 images obtained in 30-90 s at each location of sagittal and multilevel transverse sections were observed with cineloop display in awake and sleeping status. No patients had complete pharyngeal obstruction while awake. On the other hand, 9 patients had at least one occluded site, and 3 patients had wider obstructed sites during sleep. We are convinced that ultrafast MR imaging is very useful in determining the indication and the method for surgical treatment for OSAS.

Adult↗

PubMed1995

Left atrial plication combined with mitral valve surgery in patients with a giant left atrium.

The benefits of performing left atrial plication during mitral valve surgery for patients with a giant left atrium were evaluated by analyzing the short- and long-term surgical results and changes in the left atrial dimension (LAD) and respiratory function of 30 patients. Of the 30 patients, 2 (7%) died of multiple organ failure on postoperative days 26 and 117, but no other deaths occurred during the mean follow-up of 5.9 +/- 2.1 years. Valve thrombosis was observed in one patient and cerebral complications with no residual deficit were observed in two patients, with a 9-year event-free rate of 87 +/- 7%. The LAD decreased significantly from 69.0 +/- 8.5 mm to 53.7 +/- 9.1 mm (P < 0.01) shortly after surgery, and this decreased was maintained even 5 years after surgery (53.3 +/- 11.4 mm). The cardiothoracic ratio decreased from 74.8 +/- 8.3% to 62.8 +/- 9.0% (P < 0.01) and the vital capacity of the lungs increased from 71.1 +/- 18.0% to 82.9 +/- 22.2% (P < 0.01). Thus, we conclude that performing left atrial plication during mitral valve surgery is safe and effective for patients with giant left atrium.

Adult↗

PubMed1995

Systolic and diastolic function after patch reconstruction of left ventricular aneurysms.

Left ventricular function after patch reconstruction for postinfarction left ventricular aneurysms is largely unknown. In this study, 16 patients with an anteroseptal-lateral left ventricular aneurysm were treated by reconstruction of the left ventricle using a Dacron patch. Coronary artery bypass grafting was performed concomitantly in 9 patients. The size of the patch used was 57% +/- 19% of the resected myocardial scar area, including the sewing cuff area to be sutured. In these patients, the ejection fraction increased significantly from 0.28 +/- 0.12 to 0.39 +/- 0.12 (p = 0.007) at rest and from 0.32 +/- 0.14 to 0.41 +/- 0.10 (p = 0.008) during exercise. The left ventricular end-diastolic pressure and left ventricular end-diastolic volume index were reduced significantly from 14 +/- 7.0 to 8 +/- 3.2 mm Hg (p = 0.032), and from 178 +/- 116 to 92 +/- 21 mL/m2 (p = 0.016). The peak filling rate was improved significantly from 1.2 +/- 0.47 to 1.8 +/- 0.6/s (p = 0.048) postoperatively. The ratio of the peak flow velocity during the atrial kick phase to the peak flow velocity in the rapid filling phase, at the level of the mitral valve, improved (p = 0.016) after operation and remained improved up to 16 to 24 months after operation. Patch reconstruction of the left ventricle resulted in the recovery of systolic and diastolic function soon after operation, which has persisted into the late postoperative period.

Blood Pressure↗

PubMed1995

Phosphatidylinositol-3 kinase in fission yeast: a possible role in stress responses.

A DNA fragment coding for a part of a putative phosphatidylinositol 3 kinase was cloned from Schizosaccharomyces pombe by cross-hybridization with Saccharomyces cerevisiae VPS34 gene, a yeast homologue of mammalian PI-3 kinase. The clone contained an open reading frame of 797 amino acids but lacked the initiation codon, ATG. The predicted amino acid sequence was homologous to those of S. cerevisiae VPS34 and mammalian PI-3 kinase genes. Disruption of the gene resulted in extremely low levels of PI-3-P and higher levels of PI-4-P, supporting the idea that the gene codes for the PI-3 kinase of S. pombe. The disruptants harbored large vacuoles and were sensitive to stresses such as high temperature or high concentration of monovalent and divalent cations.

Amino Acid Sequence↗

PubMed1995

Chronic intramedullary infusion of prostaglandin E2 stimulates bone formation both in the bone marrow and in the periosteum.

Prostaglandin E2 (PGE2) has a potent bone resorbing activity in vitro, but some recent studies have shown that PGE2 stimulates bone formation in vivo. The effects of PGE2 on the bone are therefore still controversial. We attempted to reveal the effects of PGE2 on bone in vivo more directly; we injected PGE2 continuously into the bone marrow and onto the periosteum and examined the local effects of PGE2 histologically or by bone densitometry. Following PGE2 infusion into the bone marrow, new bone was formed in the bone marrow around the infused site and following PGE2 infusion onto the periosteum, extensive periosteal bone formation was observed. Bone mineral content was also increased significantly in the PGE2 infused bones. The administration of cyclic AMP did not mimic the effects of PGE2. In contrast to in vitro experiments, the in vivo effect of PGE2 is predominantly to produce bone.

8-Bromo Cyclic Adenosine Monophosphate↗