Biomedical subjects

A Kojima

Publications and source records attributed to A Kojima.

352 records · Page 20Linked to original sources

PubMedDate not supplied

Correlation between CA19-9 production in vitro and histological grades of differentiation in vivo in clones isolated from a human pancreatic cancer cell line (SUIT-2).

The production of carcino-embryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) were investigated in 28 clones isolated from a human pancreatic cancer cell line (SUIT-2) and related to in vitro morphology of the clones and in vivo tumorigenicity. Clones of fusiform and polygonal cells could be morphologically distinguished in confluent cultures. There was no significant difference in CEA production between fusiform-cell clones (2.10 +/- 2.70 ng/L x 10(6) per 24 h) and polygonal-cell clones (6.01 +/- 7.30 ng/L x 10(6) per 24 h), but polygonal-cell clones had higher production of CA19-9 (1176.1 +/- 1628.4 U/L x 10(6) per 24 h) than fusiform (6.0 +/- 7.3 U/L x 10(6) per 24 h; P < 0.01). Production of CA19-9 in vitro correlated with the histological grade of differentiation in vivo in nude mice (r = 0.73, P < 0.001), but CEA production did not. The polygonal-cell clones developed well-differentiated carcinomas in vivo and produced significantly more CA19-9 (P < 0.001) than fusiform-cell clones, which generally developed into poorly differentiated tubular adenocarcinomas in vivo. This cell line may provide an appropriate system for further studies of the biology and therapy of pancreatic cancer.

Adenocarcinoma↗

PubMedDate not supplied

Effect of energy resolution on scatter fraction in scintigraphic imaging: Monte Carlo study.

The effect of energy resolution in detector systems on scatter fractions in scintigraphic imaging through Monte Carlo simulation is investigated. A 10-cm Tc-99m line source within a cylindrical water phantom 20 cm in diameter and 20 cm in length was modeled and energy spectra were calculated at three different line source positions. The energy resolution was changed from 8% to 16% FWHM at 140 keV and a symmetrical energy window width was varied from 8% to 23% on the photopeak of 140 keV in energy spectra corresponding to each energy resolution. The relationship between the scatter fraction and the symmetrical energy window width, and the relationship between the scatter fraction and the primary counts were presented for all energy resolutions investigated. Furthermore, the effect of the asymmetrical energy window on reducing the scatter fraction was also studied and compared with the narrow symmetrical energy window. The results quantitatively showed that improved energy resolution can considerably decrease the scatter fraction with a narrow symmetrical energy window or an asymmetrical energy window without significant primary count-loss compared to that obtained with lower quality energy resolution. The asymmetrical energy window could reduce scatter fraction as compared with the narrow symmetrical energy window when the same number of primary counts was required for both energy windows. Knowing the relationship between the scatter fraction and the primary counts is important in scintigraphic imaging to select the optimum energy window corresponding to the energy resolution.

Biophysical Phenomena↗

PubMedDate not supplied

A preliminary phantom study on a proposed model for quantification of renal planar scintigraphy.

A method for estimation of the absolute renal activity within background activity in renal planar scintigraphy will be presented. This method corrects for oversubtraction of background activity with consideration of background activity of the kidney volume, and employs the depth-independent buildup factor (DIBF) method for the correction of attenuation and scatter of photons. This method requires the depth and thickness of the organ and the thickness of background for a background activity correction. The transmission factor (TF) for a volume source is derived from integrating TF for a thin source over the thickness of the organ for the DIBF method. To validate this method, phantom studies with various uniform background activity concentrations were performed and the data were compared with conventional background subtraction that do not consider the organ's volume. The results showed that with the conventional background subtraction method at all depth activity was underestimated with errors of 5%-30% for organ/background concentration ratios of 5-40, while this method estimated the true count rate with errors of less than 5%. More accurate quantifications of renal functions such as renal uptake, glomerular filtration rate (GFR) and renogram may be obtained by this proposed method on the planar images.

Biophysical Phenomena↗

PubMedDate not supplied

Antrolithiasis in the frontal sinus.

A very rare case of sinusitis with antrolithiasis in the left frontal sinus of a 63-year-old male patient is reported. Various conservative treatments had no effect on the decrease of his left frontal pain and of postnasal drip. Neither bacteria nor fungus were detected in the discharge. Computed tomographic scanning revealed several high-dense spots in an isodense shadow in the left frontal sinus. At first, endoscopic sinus surgery (ESS) was employed and a stony mass was detected in the nasofrontal duct and sinus. Patency of the nasofrontal duct was insured and a sticky paste and small masses were removed as well as possible. However, the flow of discharge from the frontal duct continued after surgery. We performed a second operation with extranasal approach and additional stones in the sinus were successfully removed. Most cases of antrolithiasis are caused by a foreign body or caseous sinusitis with fungus. The maxillary sinus is the most common site of disease in antrolithiasis. It is unknown why the present case of antrolithiasis was in the frontal sinus. In such cases of antrolithiasis or cases having pastelike contents in the frontal sinuses, we conclude that ESS may be an unsuccessful treatment and a classical surgical approach may be required.

Endoscopy↗

PubMedDate not supplied

F-waves of the facial muscles in healthy control subjects and in patients with peripheral facial nerve disturbance.

F-waves were recorded from the mentalis muscles with surface electrodes following stimulation of the marginal mandibular branch of the facial nerve in healthy control subjects during wakefulness, non-REM (rapid eye movement) sleep and voluntary contraction and in patients with Bell's palsy and acoustic neurinoma. The F-wave of the facial muscles results from the backfiring of antidromically activated alpha motoneurons in the facial motonucleus. Therefore, first, the F-waves were not easily elicited in patients with any disturbance in the proximal segment of the facial nerve (Bell's palsy and acoustic neurinoma). Second, the F-waves were affected by excitability of the facial motonucleus; the F-waves were inhibited significantly during sleep and enhanced significantly during voluntary contraction compared with those at rest during wakefulness. When the stimulation strength was set submaximum for M-waves, F-waves were elicited but H-waves, which have lower threshold than M-waves, were not elicited in the facial muscles, unlike the case of the extremities. Measurement of the F-waves of facial muscles is a new method for estimating excitability of the facial motonucleus unless there is any disturbance of the proximal segment. Fundamental characteristics of the facial F-waves were shown in the present study and measuring facial F-waves is clinically applicable for investigation of both excitability of the facial motonucleus and facial peripheral nerve disturbance.

Adult↗

PubMedDate not supplied

Phantom evaluation of scatter and attenuation correction in thallium-201/technetium-99m acquisition in myocardial perfusion single-photon emission computed tomography.

PURPOSE: This phantom study was carried out to evaluate the usefulness of scatter correction combined with transmission-based attenuation correction in separate and simultaneous 201Tl/99mTc myocardial SPECT. METHODS: An anthropomorphic torso phantom was used in this study. We used the triple-energy-window (TEW) method for scatter correction and transmission computed tomography (TCT) images for attenuation correction. Images without corrections (UC) and images with corrections (SAC) for scatter and attenuation were reconstructed for the evaluation. RESULTS: The differences in defect size between 99mTc and 201Tl UC images led to interpretation errors in separate (separate protocol) and simultaneous dual-isotope studies (simultaneous protocol). These errors were more prominent in the infero-posterior wall in the simultaneous protocol. Improvement for overestimation in object size and underestimation in defect contrast was visually obtained, and increased contrast was also shown by the myocardium-to-defect count (MD) ratios on SAC images in the separate and simultaneous protocols. However, 201Tl SAC images in the simultaneous protocol still had less defect contrast than the corresponding 201Tl SAC images in the separate protocol. CONCLUSIONS: From the results of our phantom experiment, separate rest 201Tl/stress 99mTc-sestamibi acquisitions may be recommended in clinical practice. Further clinical and phantom studies will be needed to validate the method using scatter correction combined with transmission-based attenuation correction.

Exercise Test↗

PubMedDate not supplied

Single photon emission computed tomography in children with idiopathic seizures.

Single photon emission computed tomography (SPECT) with N-isopropyl-p[123I]-iodoamphetamine (IMP), X-ray computed tomography (X-CT), and magnetic resonance imaging (MRI) were performed in 20 children with idiopathic seizures. In children with idiopathic seizures, SPECT could detect the abnormal sites at the highest rate (45%) compared with CT (10%) and MRI (12%), but the abnormal sites on SPECT correlated poorly with the foci on electroencephalograph (EEG). Idiopathic epilepsy with hypoperfusion on SPECT was refractory to treatment and was frequently associated with mental and/or developmental retardation. Perfusion defects on SPECT scans probably affect the development and maturation of the brain in children.

Adolescent↗

PubMedDate not supplied

SPECT evaluation of simulated white matter lesions: experimental study using a brain phantom.

An experimental study using a brain phantom was performed to evaluate the detectability of simulated white matter lesions on two types of single photon emission computed tomography (SPECT) systems. A ring-type SPECT system with high spatial resolution was able to demonstrate these lesions in the white matter, while a widely used general-purpose single-head rotating gamma camera failed to show them. The detectability of white matter lesions was decreased by photons scattered from the highly radioactive gray matter and the poor spatial resolution of the SPECT system. In order to improve the detectability of white matter lesions it is important to apply scatter correction and improve the spatial resolution of the SPECT system. Brain phantom studies made it easier to interpret white matter lesions that were difficult to interpret on the basis of clinical images alone, and the knowledge acquired from the brain phantom study will contribute to the interpretation of clinical images.

Brain↗

PubMedDate not supplied

Quantitative measurement of high flow velocities by a spin echo MR technique.

A new method of flow measurement using a spin echo (SE) technique has been developed on the basis of the flow effect that at high velocities signal intensity decreases linearly with increasing flow velocity. Flow velocity is calculated from the signal intensity ratio of the flowing material in two images with the same imaging parameters but different echo times. The linear relationship between the signal intensity and flow velocity was examined with a steady flow phantom. When assessed with steady flows in the phantom, flow velocities calculated by this method were in good agreement with velocities measured by a flow meter. This method was used with ECG gating to measure the blood flow of the right common carotid artery of a healthy volunteer. The measured peak flow velocity and the pattern of flow velocities during systole correlated well with the results obtained by Doppler ultrasound.

Blood Flow Velocity↗

PubMedDate not supplied

Measurement of effective renal plasma flow (ERPF) with 123I-orthoiodohippurate (I-123-OIH).

We evaluated the necessity of attenuation correction for calculating effective renal plasma flow (ERPF) using I-123-orthoiodohippurate (OIH), an agent introduced recently to replace I-131-OIH. From a kidney phantom experiment, the attenuation coefficient (mu) for I-123-OIH in the human body was determined as 0.1262 cm-1. I-123-OIH renal scintigraphy was performed in 23 patients with urinary diseases with blood sampling for calculation of ERPF by Tauxe's method. Calculated renal uptake, with or without attenuation correction, was compared with ERPF determined by Tauxe's method. There was good correlation between renal uptake without attenuation correction and ERPF obtained by Tauxe's method (r = 0.737), while much better correlation was found between attenuation-corrected renal uptake and ERPF calculated by Tauxe's method (r = 0.816). In conclusion, attenuation correction for renal uptake is an important technique for estimating ERPF using I-123-OIH renal scintigraphy.

Adolescent↗