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N Nohara

Publications and source records attributed to N Nohara.

At least 19 recordsLinked to original sources
PubMed1997

The local noise property in positron volume imaging and optimal conditions for the signal-to-noise ratio of the 3D reconstructed image.

The local noise property of a 3D PET reconstructed image is investigated for a uniform-activity sphere distributed in a constantly attenuating spherical object. The positional dependence of the statistical noise is approximately derived and calculated for some special cases. It is suggested that a larger diameter of the activity sphere causes noise amplification, and the noise property for the large attenuating sphere is close to that for a non-attenuating object with the same total number of measuring counts. By considering noise propagation of two spherical activity distributions, we suggest that the signal-to-noise ratio of the image depends on a set of projection directions and the sizes and intensities of the activity distributions. In a simple case, we derive an optimal value of the maximum acceptance angle for the projection directions to improve the signal-to-noise ratio of the image.

Humans↗
PubMed1991

[Response analysis for an approximate 3-D image reconstruction in cone-beam SPECT].

Cone-beam Single Photon Emission Computed Tomography (SPECT) offers the potential for a large increase in sensitivity as compared with parallel hole or fan-beam collimation. Three-dimensional image reconstruction was approximately accomplished by backprojecting filtered projections using a two-dimensional fan-beam algorithm. The cone-beam projection data were formed from mathematical phantoms as analytically derived line integrals of the density. In order to reduce the processing time, the filtered projections were backprojected into each planes parallel to the circle on which the focal point moved. Discrepancy of source position and degradation of resolution were investigated by computer simulation in three-dimensional image space. The obtained results suggest that, the nearer to the central plane or the axis of rotation, the less image degradation is performed. By introducing a parameter of angular difference between the focal point and fixed point in the image space during rotation, degradation of the reconstructed image can be estimated for any cone-beam SPECT system.

Algorithms↗
PubMed1989

Molecular characteristics and physical state of human papillomavirus DNA change with progressing malignancy: studies in a patient with epidermodysplasia verruciformis.

In order to establish the role of human papillomavirus (HPV) in carcinogenesis of epidermodysplasia verruciformis (EV), the presence, the molecular characteristics and the physical state of HPV DNA in a benign lesion, a primary carcinoma and a metastatic carcinoma developing in the same EV patient were studied and compared. Of the 2 HPV DNAs isolated from benign macular lesions, only one (a subtype of HPV 5) was detected in both primary and metastatic tumors. Only one normal species of viral DNA molecule was detected in the benign lesion, whereas most, if not all, viral DNA molecules present in the carcinoma (both primary and metastatic) were aberrant ones. The major viral DNA molecule in the primary carcinoma was a large HPV DNA with duplicated 40% subgenomic segments, and was present as free episomes. The major viral DNA molecule in the metastatic carcinoma was the 40% subgenomic segment itself, lacking the remaining 60% segment of the viral genome, and was integrated within cellular DNA. Thus, HPV DNA was present in tumors at any stage of malignancy, and its molecular characteristics and physical state changed not only with the development but also with the enhancement of malignancy, consistently conserving its defined 40% subgenomic segment as the predominant viral sequences. Our results suggest that HPV 5 may be actually involved in carcinogenesis in EV patients.

Carcinoma, Squamous Cell↗
PubMed1989

Cutaneous mucinosis associated with SLE--a case provoked by PUVA.

A patient with SLE which was complicated by a characteristic cutaneous mucinosis is reported. The skin lesions were composed of intradermal soft nodules, purple-red plaques, and alopecia of the scalp. Acid mucopolysaccharides accumulated in each lesion. PUVA provoked an infiltrated skin lesion in which acid mucopolysaccharides were deposited in the dermis. Deposition of immunoglobulins and complements were also observed at the dermo-epidermal junction and on the vascular walls. Some immunological processes which may stimulate the synthesis of acid mucopolysaccharides in the dermis were suggested.

Adult↗
PubMed1989

Two sisters with impetigo herpetiformis.

Two sisters (non-twins) had impetigo herpetiformis triggered by their first pregnancy. One sister treated with etretinate had good resolution of skin disease. Impetigo herpetiformis is probably a variant of pustular psoriasis and may be provoked or precipitated by factors, such as pregnancy. Both patients shared common HLA antigens (All, AW24, BW44, BW54 and DR6Y).

Adult↗
PubMed1989

[Comparative clinical study of roxithromycin and josamycin for suppurative skin and soft tissue infections by a double-blind method].

The clinical efficacy and safety of Roxithromycin (RU 28965, RU), a new macrolide preparation, were compared with those of Josamycin (JM) in superficial suppurative skin infections. The study was designed as double-blind controlled trial with daily dosages of 300 mg in RU group and 1200 mg in JM group. A total of 209 cases (RU:105; JM:104) was analyzed and the final global improvement rating was 82.9% in the RU group and 80.8% in the JM group; there was no significant difference between the two groups. Slight adverse reactions were observed in 3.6% (4 cases) of the RU group and in 4.6% (5 cases) of the JM group. In conclusion, RU at daily doses of 300 mg is as effective as JM at daily doses of 1200 mg in superficial suppurative skin infections.

Adult↗
PubMed1989

Computer system and software of POSITOLOGICA II: a whole body positron emission tomograph.

Since a whole body PET-scanner POSITOLOGICA II was installed at the National Institute of Radiological Sciences (NIRS) in 1982, improvements of the computer system and developments of new software have been continuously made to correspond to clinical requirements. As the result, POSITOLOGICA II possesses one of the most powerful systems and sophisticated software in Japan. This report describes the present status of the computer system and software of POSITOLOGICA II. It also discusses problems which still exist and proposes a future computer system for the PET study.

Brain↗
PubMed1988

Persistence of foam cells in rabbit xanthoma after normalization of serum cholesterol level.

Xanthoma was produced in diet-induced hypercholesterolemic rabbits by intradermal dextran sulfate injections. The serum cholesterol level returned to the normal range at about 10 weeks after ending the cholesterol diet. Gross observations after cessation of the cholesterol diet revealed a decrease in xanthomatous infiltrations. However, the dense foam cell infiltrations and cholesterol accumulations showed no signs of regression at even 9 months after ending the cholesterol diet. Signs of foam cell migration into the blood stream were not observed. The persistence of the xanthoma may be due to a lack of acceptors, such as high-density lipoproteins, that remove the cholesterol from the foam cells. During our 9-month observation period, some foam cells were degenerated and a few were fused with each other to transform into Touton-type giant cells. Nonfoamy histiocytes were infiltrated around these degenerating foam cells. The histiocytes may have transformed into foam cells by incorporating the lipids of the degenerated foam cells.

Animals↗
PubMed1987

[Count rate characteristics and count loss correction of Positologica II: a whole body positron emission tomograph].

This paper describes evaluation and correction of count rate characteristics of POSITOLOGICA II, a multi-slice whole body positron emission tomography system. The present study was performed using three phantoms; a 5 cm inner diameter, water-filled lucite cylinder, a 20 cm inner diameter, water-filled lucite cylinder and a chest phantom. After injection of high activity (about 1.85 GBq (50 mCi] of 13N ammonia into each phantom, rates of true coincidence, random coincidence and single photon detections were measured during decay of the isotope through more than two orders of magnitude of activity. At very high levels of activity, count rate characteristics of the system were saturated and limited to 660 kcps of total coincidence rate, which was the sum of rates in on-time and off-time windows, by the FIFO (first-in first-out) output frequency. Below those levels of activity the relationship between count loss and true coincidence rate was not unique but depended on the phantom configurations, suggesting that count loss correction using the above relationship was inadequate for quantitative study. However, the relationship between count loss and single rate was almost independent of the phantom configurations. Thus in conclusion count loss could be corrected using single rate for POSITOLOGICA II. A practical method of count loss correction was also proposed.

Models, Structural↗