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Biomedical subjects

K Okajima

Publications and source records attributed to K Okajima.

At least 181 records · Page 10Linked to original sources
PubMed1992

Quantitative assessment of digitized portal images: effect of sampling frequency on observer performance.

To investigate spatial resolution requirements for digitized portal images in radiation therapy, observer performance tests were performed. One hundred twenty portal images were digitized with sampling frequencies of 0.700, 0.350, and 0.175 mm for observation. Receiver operating characteristic analysis was used to determine the acceptable sampling frequency for clinical portal images. The detectability of setup errors was significantly better on the original images than on the digitized images with sampling frequencies of 0.700 mm (P = .005) and 0.350 (P = .046). Some clinical disadvantages might accrue with the use of a sampling frequency of 0.350 mm or larger.

Humans↗
PubMed1992

Cerebral infarction in a heterozygote with variant antithrombin III.

BACKGROUND: We report a heterozygous case of familial qualitative deficiency of antithrombin III associated with cerebral infarction. CASE DESCRIPTION: A 33-year-old man had a history of recurrent transient ischemic attacks from the age of 28. Cerebral computed tomography at age 29 disclosed a low-density area in the left frontal lobe, and an internal carotid angiogram showed branch occlusion of the right anterior cerebral artery and stenosis of the left middle cerebral artery. Occlusion of the right middle cerebral artery developed thereafter. The plasma antithrombin III antigen concentration and progressive antithrombin activity were normal, but plasma heparin cofactor activity was low in the patient and his father. Nucleotide sequence analysis of the proband's deoxyribonucleic acid showed no mutation in exons II and VI of antithrombin III. CONCLUSIONS: We conclude that abnormal antithrombin III with defective heparin binding, even though heterozygous, may cause ischemic stroke in young adults. We named this antithrombin III variant "Antithrombin III Nagasaki."

Adult↗
PubMed1991

Inhibitory effects of activated protein C and heparin on thrombotic arterial occlusion in rat mesenteric arteries.

Effects of human activated protein C (APC) and heparin on thrombus formation were examined using small mesenteric arteries of rats and video-recording system attached to a microscope. To induce thrombosis we damaged the vessel wall over a short segment by compression and exposed the damaged media to the blood stream. Platelet-rich thrombus enlarged gradually at the damaged site, occluded the vascular lumen for a short period and then flowed away. Such thrombus formation was observed several times after a compression damage. An intravenous administration of APC significantly decreased the total occlusion time from 6.4 +/- 0.7 min at control to 2.2 +/- 0.4 min at 0.9 mg/kg given over 1 min (mean +/- SEM, n = 6, p less than 0.01), and from 6.5 +/- 1.0 min to 1.0 +/- 0.3 min at 3.0 mg/kg (n = 6, p less than 0.01). An intravenous heparin (300 and 1000 U/kg) also decreased the total occlusion time significantly from 6.2 +/- 0.8 to 2.2 +/- 0.8 min (n = 6, p less than 0.05) and from 5.4 +/- 0.8 to 0.8 +/- 0.7 min (n = 6, p less than 0.01), respectively. APC prolonged APTT from 11 +/- 1 sec (n = 5) at control to 50 +/- 5 sec (n = 5) at 0.9 mg/kg and to 87 +/- 8 sec (n = 5) at 3.0 mg/kg, while heparin prolonged APTT to more than 120 sec in all 5 rats at both doses. APTT prolongation by APC was significantly attenuated by inhibiting its residual activity in the plasma samples using monoclonal antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Role of leukocytes in the activation of intravascular coagulation in patients with septicemia.

To elucidate the role of leukocytes in intravascular coagulation in patients with septicemia, plasma levels of thrombin-antithrombin III complex (TAT), soluble fibrin monomer complex (SFMC) and fibrinogen (Fbg) were determined in 33 patients with septicemia. Twenty of 33 patients revealed marked leukopenia caused by suppression of hematopoiesis by the administration of chemotherapeutic agents for the treatment of hematological malignancies; the total leukocyte count of these patients was less than 1,000/microliters. Thirteen of 33 patients showed normal or increased leukocyte counts. Plasma levels of TAT and SFMC in septicemic patients without leukopenia were significantly higher than in patients with leukopenia. Although plasma TAT and SFMC levels correlated well with the number of leukocytes, a more significant positive correlation was found between the number of monocytes and the levels of TAT and SFMC. Plasma levels of Fbg were significantly lower in patients without leukopenia than in patients with leukopenia. No significant correlation was found between the number of leukocytes and the levels of Fbg. However, a significant negative correlation was found between the number of monocytes and the levels of Fbg. TAT levels did not correlate with the number of platelets. The fibrinolytic system was activated only in septicemic patients without leukopenia, which may be explained by secondary fibrinolysis following leukocyte-activated coagulation. These findings suggest that leukocytes, in particular monocytes, may play a critical role in the pathogenesis of intravascular coagulation in septicemia.

Antithrombin III↗
PubMed1991

A recurrent system incorporating characteristics of the visual system: a model for the function of backward neural connections in the visual system.

A recurrent system is constructed in order to investigate the role of the backward neural connections found in the primate visual system. The system incorporates a layer to perform localized spatial frequency analysis of input images, a function which has been assumed to take place in the primary visual cortex. The function of the system is examined by simulation. The results show that the system can separate an object pattern from its background, irrespective of its precise position. The acceptable displacement range for input images is determined from the width of the window function used to calculate the local Fourier transform. A multilayer version of the above recurrent system is also constructed.

Animals↗
PubMed1991

Postnatal head growth in very premature infants with good outcome.

Postnatal head growth was examined retrospectively in 118 infants (male 60, female 58) born with a gestational age of from 24 to 29 weeks. Infants fulfilled the following criteria: (1) Those with hydrocephalus and small for dates (less than -1.5 standard deviation) were excluded. (2) Infants had normal intelligence and no cerebral palsy or epilepsy at 3 years of age or above. They were divided into four groups according to gestational ages: 24-26 wks (n = 21), 27 wks (n = 25), 28 wks (n = 41) and 29 wks (n = 31). The head circumference was measured at least twice monthly. The head growth curves in each group were obtained. After a transient decrease, head growth averaged 1.1-1.2 mm/day from day 21-30 to day 61-70 in all groups. From day 61-70 to 91-100 head growth averaged 1.2 mm/day at 24-26 wks and 0.8 mm/day at 27-29 wks, respectively.

Cephalometry↗
PubMed1991

Quantitative assessment of quality of digitized portal images: receiver operating characteristic analysis applied to imaging in radiation therapy.

An objective and quantitative method for the evaluation of the quality of megavoltage portal images was developed by applying receiver operating characteristic analysis. On the basis of therapeutic use of portal images, setup errors were employed as "signals" in this experimental study that compared the original portal films with digitized images. Six readers observed 104 portal images of a chest phantom, half of which were "abnormal" (ie, had setup errors). Digital images (2,048 x 2,048 matrix) were enhanced by means of histogram equalization and then printed with a laser printer for observation. The readers showed a higher discrimination capacity with the digitally enhanced images, although a statistically significant improvement was not demonstrated. The present method of assessment of image quality proved to be both simple and clinically reasonable.

Humans↗
PubMed1991

[Nuclear DNA content in breast cancer in relation to postoperative recurrence].

Nuclear DNA content in breast cancer patients who underwent extended radical mastectomy was investigated to evaluate its possible relation to postoperative recurrence. The most frequent site of the first recurrence in diploid type (D type) cases was the bone and the frequency was significantly higher than that in non-diploid type (N type) cases. On the other hand, the ploidy pattern in all cases associated with local or local lymph node recurrence was N type and the lung was the next frequent site of recurrence in N type case. The frequency of over 4c cells was the highest in the cases of local or local lymph node recurrence being significantly higher than in all cases of distant recurrence or of the bone recurrence. The cumulative disease-free survival rate in patients with D type breast cancer was significantly higher than that in patients with N type. These results suggest that nuclear DNA content provides important information for deciding therapy and the schedule of postoperative follow-up study based on the mode of recurrence.

Breast Neoplasms↗
PubMed1990

[The preoperative and postoperative carcinoembryonic antigen test in the diagnosis, staging, and prognosis of gastric cancer. Tumor Marker Committee, Japanese Foundation for Multidisciplinary Treatment of Cancer].

Preoperative and postoperative carcinoembryonic antigen (CEA) levels were studied in 3,532 patients with Surgically treated gastric cancer in 52 institutions from 1980 to 1981. These patients had disease resectable with curative intent and were followed for a minimum of 5 years or until death. Among 2,749 Stage I cases, 33 had recurrence and proved to be histologically stage I. A pair matching case control study between these 33 cases and matched 33 stage I controls without recurrence proved that the preoperative CEA level was relatively higher in cases with recurrence (p = 0.079). In Stage II and III cases, an analysis of variance using a cut off level as a block factor was performed. Among 315 Stage II cases, preoperative CEA levels were significantly higher in cases with recurrence than in cases without recurrence. In 468 Stage III cases, no correlations between preoperative CEA levels and high risks of cancer recurrence were detected. In Stage I and Stage II cases, CEA levels significantly increased at the time of recurrence. In conclusion, preoperative high serum CEA levels might be considered one of the risk factors for recurrence of Stage I and II gastric cancers, and monitoring the postoperative CEA levels might be useful in early detection of recurrence.

Analysis of Variance↗