Calculation of personal dose equivalent for positron-emitting radionuclides using Monte Carlo code EGS5.

The conversion coefficients, H'(d,α)/Φ, for monoenergetic positrons and positron-emitting radionuclides were calculated by using the user code UCICRPM of the Monte Carlo code EGS5 to estimate the radiation dose for medical staff involved in positron emission tomography examinations. From these coefficients, the dose equivalent rates per unit activity at 0.07 and 10 mm depths in a soft tissue for a straight-line source of 2-deoxy-2-[(18)F]fluoro-d-glucose ((18)F-FDG) were calculated by using the developed user code UCF18DOSE. The dose equivalent rates per unit activity at 0.07 and 10 mm depths were measured by using a personal dosemeter (DOSE(3)) under the same conditions as those considered in the calculation. The calculated dose equivalent rates per unit activity at 0.07 and 10 mm depths were 0.116 and 0.0352 pSv min(-1) Bq(-1), respectively, at 20 cm from the (18)F-FDG injection tube.

Shape-memory alloy loop snare for endoscopic photodynamic therapy of early gastric cancer.

BACKGROUND AND STUDY AIMS: Photodynamic therapy (PDT) has proved effective in the treatment of gastric cancer, but there is room for improvement. To achieve the technical goal of carrying out endoscopic PDT, endoscopists need to determine the precise area for laser irradiation at adequate dosages. This report describes the use of a shapememory alloy (SMA) loop snare as a useful tool in endoscopic PDT. PATIENTS AND METHODS: Eleven patients with biopsy-proved early gastric cancer were treated with endoscopic PDT after intravenous injection of Photofrin II (2 mg/kg b.w.). Five patients underwent PDT using the SMA loop snare, and six underwent PDT without the use of the device. Cancer lesions smaller than 2 cm in diameter were irradiated with an excimer-dye laser (4 mJ, 80 Hz, 630 nm) for 20 min. RESULTS: All five patients (100%) treated with PDT using the SMA loop snare, and four of the six patients (67%) treated with PDT without use of the SMA loop snare, showed complete remission. CONCLUSIONS: The SMA loop snare routinely forms a circle 2 cm in diameter, covering an area of 3.14 cm2, and makes it possible to mark and calculate the precise area of cancerous lesions for irradiation at appropriate dosages. The findings of this study suggest that the SMA loop snare is an effective tool for PDT in early gastric cancer.

Early and delayed Tc-99m ECD brain SPECT in SLE patients with CNS involvement.

We compared early and delayed Tc-99m ECD SPECT scans in 32 SLE patients (Group 1, definite neuropsychiatric disorders; Group 2, minor neurologic symptoms or normal) with those of normal controls by visual inspection and semi-quantitative evaluation. With visual interpretation, 13 out of 14 patients in Group 1 (93%) and 7 out of 18 patients in Group 2 (39%) had diffuse uneven decrease in early scans. Seven patients in Group 2 (39%) who had normal early scans demonstrated focal decrease in the medial frontal lobe in delayed scans. With cerebral region to cerebellar ratios, in early scans, the medial frontal lobe in Group 1 and Group 2 was significantly lower than in normal controls, and lateral frontal lobe and occipital lobes in Group 1 were significantly lower than in normal controls. Nevertheless, in delayed scans, every cortical region except for the parietal lobe in Groups 1 and 2 was significantly lower than in normal controls. The retention rates in all regions in SLE patients were significantly lower than in normal controls. No case showed SPECT improvement on follow-up studies in either group in spite of clinical improvement. Delayed Tc-99m ECD brain SPECT of high sensitivity might be useful in detecting CNS involvement. Although the SPECT findings did not correlate with the neuropsychiatric symptoms, early and delayed Tc-99m ECD SPECT seems to provide useful objective diagnostic information in SLE patients.

Evaluation of asialoglycoprotein receptor imaging agent as a marker of hepatic ischemia-reperfusion injury and recovery.

Protection of hepatocytes from ischemia-reperfusion injury is a clinically important issue. The purpose of this study was to evaluate changes in acute liver damage and recovery after ischemia-reperfusion in rats with asialoglycoprotein receptor (ASGP-R) ligand. Ischemia was induced by clamping the hepatoduodenal ligament for 90 min. At 1, 3, 24, 48 hr, 1 and 2 wk after reperfusion, I-125-GSA was injected. Five min after injection, blood samples were obtained and the liver was removed. Several regions from each lobe were dissected, weighed and counted. Mean uptakes (% dose/g) in the liver and blood samples were calculated. Histologic sections stained with hematoxylin-eosin (H-E) stain showed ischemic damage at 1 and 3 hr, and focal hepatocyte necrosis at 24 hr. Predominant massive necrosis was not seen. The mitotic index with H-E stain and proliferating cell nuclear antigen (PCNA) labeling index were highest at 1 wk, indicating liver regeneration. At 1 and 3 hr, liver uptake was significantly decreased, and blood uptake was significantly increased, indicating decreased tissue blood flow and ischemic damage. Liver uptake showed significant increases at 48 hr and 1 wk, and was the highest at 1 wk, indicating liver regeneration during the convalescence stage. ASGP-R binding may provide valuable information on ischemia-reperfusion injury and recovery.

[Synchronization between preverbal vocal behavior and motor action in early infancy. II: An acoustical examination of the functional significance of the synchronization].

Normal infants start to produce canonical babbling (CB) at the age of 6 to 10 months. CB consists of reduplicated sequences of consonant-vowel syllables which have adult-like acoustical features. Therefore, onset of CB is considered to be a landmark in the development of spoken language. The previous study indicated that a behavioral synchronization of vocalizations with rhythmic actions occurred in infants before the onset of CB. The present study examined the function of synchronization. Acoustical analyses were conducted on vocalizations of four infants during three-months-period including the month when synchronization occurred most frequently. The results show that both utterance length and formant frequency transition duration of synchronized vocalizations are shorter than those of non-synchronized vocalizations. These acoustical features, which are required to produce CB, persisted even after the synchronization has disappeared. The present study suggests that synchronization of vocalizations with rhythmic actions has the function of prompting infants to produce CB.

Developmental changes of gene expression in heme metabolic enzymes in rat placenta.

Transcription levels of the non-specific delta-aminolevulinate synthase (ALAS-N) and heme oxygenase-1 (HO-1) in the placenta at the terminal stage of pregnancy were comparable to those in the female adult liver and in the spleen, respectively. Immunohistochemical studies demonstrated that both enzymes were exclusively expressed in the trophoblast. During gestation, transcript of ALAS-N slightly increased, while HO-1 mRNA significantly decreased. Induced acute fetal hypoxia resulted in an increase in ALAS-N mRNA and in a decrease in HO-1 mRNA. These findings indicate that placental heme metabolism is influenced by the oxygen supply.

[Synchronization between preverbal vocalizations and motor actions in early infancy. I: Pre-canonical babbling vocalizations synchronize with rhythmic body movements before the onset of canonical babbling].

This study reports the synchronization between vocal behaviors and motor actions in infants at the prelinguistic stage. Four Japanese infants were studied from the age of 4-6 months to 11 months. For all infants, a 40-min segment was selected from the 60-90 min observation recording taken on each month. All the vocalizations and motor actions recorded in the segment were transcribed. The results show that a behavioral synchronization occurred between vocalizations and rhythmic actions in infants at the prelinguistic stage. The synchronization was particularly obvious in the month immediately before the onset of canonical babbling. These findings suggest that the synchronization between vocalizations and rhythmic actions may have the function of promoting infants to produce canonical babbling, that is indispensable for the acquisition of spoken language.

Relationship between rhythmic behavior and canonical babbling in infant vocal development.

The onset of canonical babbling (CB) is a landmark event in infants' vocal development for spoken language. Previous research has suggested that the onset of CB coincides with the peak period of rhythmic activities. To examine this phenomenon in detail, 28 Japanese infants (14 girls, 14 boys) were observed longitudinally from the age of 5 to 9 months. In the experimental sessions, an audible or an inaudible rattle was placed into a hand of each tested infant. Then the number of times that the infant shook the rattle was counted. In the observational sessions, infants' spontaneous rhythmic activities under natural conditions were observed. The result shows that rhythmic activities reached their peak around the onset of CB. When the infants began to babble, they shook whichever rattle was in their hand, regardless of its audibility. After this period, they shook the audible rattles more frequently than the inaudible ones. These findings suggest that, around the onset of CB, infants learn to control their motor activities based on auditory feedback.

[Evaluation of the clinical usefulness of super dynamic 99mTc-HM-PAO SPECT in ischemic cerebrovascular disease--detection of hypo- and hyperperfusion area].

The purpose of this study is to assess the clinical usefulness of super dynamic SPECT of 99mTc-HM-PAO. Six patients with unilateral occlusion of middle cerebral artery (MCA) or internal carotid artery (ICA) in the chronic phase, and 5 patients with subacute cerebral infarction were studied. We used a ring-type SPECT "HEADTOME." Two types of collimator were used: a high sensitivity (HS) collimator for super dynamic scan and a high resolution (HR) collimator for static scan. First, the intravenous constant infusion of 99mTc-HM-PAO (925-1480 MBq) for 1 minute was started. After 30 seconds from the beginning of the injection, we performed the 12 seconds/frame super dynamic SPECT for 2 minutes. Then, the static SPECT for 10 minutes was done. For semiquantitative analyses, differential percentage of regional activity between affected and non-affected hemispheres was calculated in the 6th frame image of super dynamic SPECT and static SPECT image. In all 6 patients with unilateral occlusion of MCA and ICA, super dynamic SPECT images showed the better contrast of low perfusion areas in comparison with the static SPECT images. In 5 patients with subacute cerebral infarction who showed focal hyperactivities on static SPECT, focal hyperactivities (hyperperfusion or hyperemia) were displayed in 3 cases, whereas, focal hypo- or isoactivities (hypo- or isoperfusion) were shown in 2 cases on super dynamic SPECT. However, all patients with subacute cerebral infarction showed hyperfixation on static SPECT as compared with super dynamic SPECT. Although the image quality on super dynamic SPECT is not as high as that on static SPECT, cerebral hemodynamics would be detected with less backdiffusion of 99mTc-HM-PAO from the brain to blood, and with less accumulation of hydrophilic components in subacute infarct region. In conclusion, super dynamic SPECT in early distribution of 99mTc-HM-PAO using dedicated SPECT device might be helpful to detect cerebral perfusion close to true cerebral blood flow distribution.

Effect of intracellular free calcium mobilization on aggregation of umbilical cord blood platelets.

Aggregation activity of platelets in umbilical blood is lower than that in adult blood, but the reason for this is not well understood. It has recently been clarified that calcium plays a role as a second messenger of platelet aggregation, and that glycoproteins of platelet surface membrane such as glycoprotein I b and IIb/IIIa are receptors for agonists inducing aggregation. We examined the concentrations of intracellular calcium and the membrane glycoproteins of platelets in umbilical and adult blood. The increase of intracellular calcium in umbilical platelets was lower than that in adult platelets when the aggregation was induced by ADP, collagen, thrombin and epinephrine. Only calcium ionophore A23187 induced aggregation of both umbilical and adult platelets. On the other hand, there were no qualitative differences between glycoproteins I b and IIb/IIIa of these two groups. Therefore, the low aggregation activity of umbilical platelets seems to be due to low responsiveness of the intracellular calcium system, not to the disorder of functional surface membrane glycoprotein.

Developmental changes in P300 wave elicited during two different experimental conditions.

Age-related correlations on auditory event-related potentials were studied using a task-relevant oddball paradigm in 175 normal subjects aged 4-21 years and age-related correlations in the "ignore" condition were studied in 108 normal subjects aged 1-21 years. In the ignore condition, subjects more than 4 years of age were instructed to read a book to divert attention from the auditory stimulus. From 4 to about 17 years of age, the latencies of task-relevant P300 in event-related potentials (ERPs) gradually shortened. In the ignore condition experiment, the P300 latency shortened progressively, but stabilized at about 12 years of age. Whereas P300 in the ignore condition likely corresponds to P3a described previously (passive attention), the conventional P300 wave corresponds to P3b (active attention). The findings indicate a developmental difference between the P3a and P3b potential.

[Effectiveness of haloperidol in the treatment of chorea minor].

Chorea minor is the most curious manifestation of rheumatic fever, first described by Sydenham in 1686. Subsequent evidence showed that chorea could be a late manifestation of rheumatic fever, often occurring several months after a streptococcal infection in contrast to other major manifestations. During the ten-year period between 1984 and 1993, 11 children with rheumatic fever were seen at our hospital, two cases of these being accompanied with chorea minor. Case 1, a male aged 12, presented with involuntary movements. He was diagnosed as having rheumatic fever because of chorea and systolic ejection murmur at the apex of the heart. Plain cranial CT was normal. However, positron emission computed tomography revealed an increased 11C-glucose uptake in the caudate nucleus as compared with the cerebral cortex. Case 2, a female aged 14, presented with involuntary movements. Plain cranial CT was normal, but single photon emission CT showed a difference between the right and left brain. These two patients were given penicillin G (PCG), predonisolone (PSL) and haloperidol. Haloperidol was administered, because PCG and PSL had no effect to improve the clinical manifestations. After administer decreased to a half with a clinical improvement, but the level of GABA did not change. Haloperidol seemed to be an effective and useful agent for motor manifestations of the disease.

[The administered activity of radionuclides in nuclear medicine--rational reduction of medical radiation exposure].

A survey of 104 hospitals was conducted to determine the administered activity of radionuclides. Eighty-five hospitals responded, and reported a total of 119,614 examinations in one year. The examinations included: bone scintigraphy, 26.4%; Thallium-201 (201Tl) myocardial scintigraphy, 15.5%; Gallium-67 (67Ga) scintigraphy, 13.3%; N-isopropyl-p-[123I]iodoamphetamine (IMP) brain perfusion scintigraphy, 7.0%. The administered activity was corrected by body weight only for children at more than 80% of the responding hospitals. The number of hospitals that reported over-administration of radionuclide varied according to the type of scintigraphy performed: bone, 76%; inflammatory (67Ga), 93%; myocardial (201Tl), 89.2%; brain (IMP), 8.5%. The administered activity of IMP was closer to the upper limits specified in the Recommendations on Standardization of Radionuclide Imaging by the Japan Radioisotope Association (1987), because IMP is very expensive and is supplied as single vials. The highest average effective dose was for myocardial scintigraphy, the second-highest for inflammatory scintigraphy, and the third-highest for bone scintigraphy. In 201Tl and 67Ga scintigraphy, the entire contents of the vial may be administered two days before the expiration date, because the ratio of (true patient administered activity) to (declared patient administered activity) is similar to the ratio of (radioactivity on the day of supply) to (radioactivity on the day of expiration). The factors that influence administered activity are throughput, price of the radionuclide, and whether the radionuclide is sold as a single vial. In order to decrease the effective dose, it is necessary to establish a close cooperation between medical personnel, the makers of radiopharmaceuticals, and manufacturers of gammacameras.

[The study of mismatch negativity].

We studied age related correlations of mismatch negativity (MMN) auditory event-related potentials (ERPs) using odd ball paradigm in 121 normal subjects (from 6 months to 43 years) and 33 mentally retarded subjects (from 2 to 18 years). The subject was instructed to read a book in order to ignore the stimulus during the experiment, or no specific task was imposed on young child. The MMN wave form was clearly obtained in normal 6 month old subjects. As the age advanced from 6-months, the latencies of MMN progressively shortened till about 7 years, when the latency reached adult level. One-third of mentally retarded patients had prolonged MMN than that normal age-matched subjects. Reliable recording of P300 requires subject's cooperation and attentiveness, which are difficult to achieve in young children or mentally retarded patients. MMN may be utilized in children to evaluate the development of the cognitive function.

Effect of taurine concentration on platelet aggregation in gestosis patients with edema, proteinuria and hypertension.

To elucidate the relationship between the high concentration of taurine in platelets and platelet aggregation in patients with EPH gestosis (gestosis with edema, proteinuria and hypertension), platelet aggregation and the platelet release response (release of ATP and beta-thromboglobulin) were studied in the washed platelet suspension (PS) obtained from normal pregnant or non-pregnant women and EPH gestosis patients. Platelet aggregation and platelet release response were significantly lower in EPH gestosis patients than in normal pregnant and non-pregnant women. Platelet aggregation, platelet release response induced by ADP and collagen and the aggregation induced by A23187 were inhibited in taurine-loaded PS from non-pregnant women. These results suggest that the decrease of platelet aggregation in EPH gestosis patients was caused by high concentrations of taurine in platelets, which may inhibit the intracellular Ca2+ movement and platelet release response. Therefore, taurine appears to have a protective effect against the hyper-coagulative state in EPH gestosis.

Concentration and uptake of taurine in umbilical blood platelets.

The concentration and uptake of taurine in the umbilical and adult blood platelets were studied. Taurine was the most abundant free amino acid in both umbilical and adult blood platelets. The taurine concentration in umbilical blood platelets (2.30 pmoles/10(4) cells) was significantly lower than that of adult blood platelets (3.27 pmoles/10(4) cells) in contrast to the reverse relationship in taurine concentrations in umbilical and adult blood plasma. No other amino acid showed such significant difference in the concentrations between umbilical and adult blood platelets. Taurine uptake into umbilical blood platelets was temperature sensitive and sodium-dependent in a manner similar to that of adult blood platelets. The uptake conformed well to Hanes-plot. The Vmax of the uptake into adult blood platelets was about 3.6 times higher than that of umbilical blood platelets, but no significant difference was seen in the Km value between the two groups.

Platelet taurine concentration and uptake in gestosis patients with edema, proteinuria and hypertension.

The taurine concentration and uptake in platelets obtained from normal pregnant women and gestosis patients with edema, proteinuria and hypertension (EPH gestosis) were investigated. The taurine concentration in platelets showed a marked increase in severe EPH gestosis compared with normal pregnancy or mild and moderate EPH gestosis, while the plasma taurine concentration did not change significantly. Taurine uptake in platelets paralleled the severity of EPH gestosis. The Vmax of the uptake in severe EPH gestosis was about 2.4 times higher than that in normal pregnancy or mild and moderate EPH gestosis, but no significant difference was seen in the Km value among these groups.

Effect of the cooling rate on insulin release from frozen-thawed In-111 cells.

Cultured cells derived from hamster insulinoma (In-111 R1 cells) were placed in 1.4 M dimethyl sulfoxide (Me2SO)-containing RPMI 1640 at 20 degrees C for 20 min. They were frozen to -40 degrees C at a cooling rate of 1.0 or 0.5 degrees C/min, subsequently to -80 degrees C at 3 degrees C/min with a programmable freezer. After being maintained at -80 degrees C, they were rapidly thawed to 37 degrees C. Thawed cells were washed with 0.75 M sucrose for removal of Me2SO. Recovered cells were cultured in 2 ml of RPMI 1640 with 1.3 mM theophylline under a gas phase of 95% air -5% CO2 at 37 degrees C for 2 days. In both cooling rates, frozen-thawed cells discharged more insulin than the thawed in the absence of theophylline. However, this released insulin level was higher in the cells frozen at a cooling rate of 0.5 degrees C/min than that at 1.0 degrees C/min. Moreover, insulin released from frozen-thawed hamster insulinoma cells increased significantly with the addition of 1.3 mM theophylline. Considering that the higher insulin release level at 11.1 mM glucose alone might indicate cellular damage, it is suggested that the cooling rate of 1 degree C/min may be better for cryopreservation of the dispersed cells under the present protocol for the assessment of the function of insulin release.

[The influence of the time activity variation on dynamic SPECT images in camera based SPECT].

Image quality of dynamic single photon emission computed tomography (SPECT) using a rotating gamma camera is dependent on the time activity variation of the tracer such as accumulation and excretion in the object's organ. Especially at the early time after injection of radionuclide, artifacts may occur strongly in the SPECT images. Simulated and experimental projection data of line sources and Jaszczak phantom were altered by sequentially weighting the projections with a function that varied linearly with time. With a variation of object activity given by linearly decaying functions, the main effect observed on the SPECT images obtained from simulated line sources was an elliptical deformation on the object. If the changing rate (R (t + 1)-R(t))/R(t) x 100 remained within 20% during acquisition, this deformation of SPECT images of line sources was not noticeable visually and resolution (FWHM) of line sources scarcely was degraded. In renal dynamic SPECT study using 99mTc-DTPA, the image quality of the first scan (30 sec) was considerably degraded. However, the changing rates after the third scan were less than 20% on the mean of 10 kidneys and the image quality was not noticeable visually.

Photodynamic therapy for early gastric cancer using a pulsed gold vapor laser.

Endoscopic photodynamic therapy (PDT) using a pulsed gold vapor laser (wavelength 628 nm, LaserSonics Inc.) was performed on eight cases of early gastric cancer. Three patients refused to have surgery, and the others were in a high-risk group due to old age or complications with other diseases. Hematoporphyrin derivative (HpD I, 2.5-3 mg/kg, Photofrin Inc.) was injected intravenously, and 48-72 hours later, the entire cancer lesion and 5 mm width mucosa encircling it were irradiated with a gold vapor laser through a single quartz fiber. The irradiation was delivered at 300-330 mW for 5-20 minutes, which gave about 90 J/cm 2 dosage. In seven of eight cases, local cure was achieved. Recurrence was noted only in one patient. In one of eight patients, operation was carried out 1 month after PDT. Pathological examination of the resected stomach revealed that the effect of PDT extended into the tunica muscularis propria. Side effects of HpD, such as skin rash, were noted in two patients, but no serious complications of PDT were encountered. This suggests that PDT with a pulsed gold vapor laser is clinically useful in the treatment of early gastric cancer.