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Biomedical subjects

Koichi Maruyama

Publications and source records attributed to Koichi Maruyama.

At least 19 recordsLinked to original sources
PubMed2006

Evaluation of static physics performance of the jPET-D4 by Monte Carlo simulations.

The jPET-D4 is the first PET scanner to introduce a unique four-layer depth-of-interaction (DOI) detector scheme in order to achieve high sensitivity and uniform high spatial resolution. This paper compares measurement and Monte Carlo simulation results of the static physics performance of this prototype research PET scanner. Measurement results include single and coincidence energy spectra, point and line source sensitivities, axial sensitivity profile (slice profile) and scatter fraction. We use GATE (Geant4 application for tomographic emission) as a Monte Carlo radiation transport model. Experimental results are reproduced well by the simulation model with reasonable assumptions on characteristic responses of the DOI detectors. In a previous study, the jPET-D4 was shown to provide a uniform spatial resolution as good as 3 mm (FHWM). In the present study, we demonstrate that a high sensitivity, 11.3 +/- 0.5%, is provided at the FOV centre. However, about three-fourths of this sensitivity is related to multiple-crystal events, for which some misidentification of the crystal cannot be avoided. Therefore, it is crucial to develop a more efficient way to identify the crystal of interaction and to reduce misidentification in order to make use of these high performance values simultaneously. We expect that effective sensitivity can be improved by replacing the GSO crystals with more absorptive crystals such as BGO and LSO. The results we describe here are essential to take full advantage of the next generation PET systems that have DOI recognition capability.

Algorithms↗
PubMed2006

Development of an easy-to-handle range measurement tool using a plastic scintillator for proton beam therapy.

Proton beam therapy can concentrate the dose on a tumour. In order to offer high-precision proton beam therapy to the patient, it is important to confirm the range every day. At the National Cancer Center Hospital East (NCC), the range measurement tool consists of a water phantom and an ionization chamber. These large and heavy tools take a long time to set up. Therefore, we developed a simple and easy-to-handle range measurement tool for proton beam therapy. This tool consists of a plastic scintillator block and a CCD camera. We recorded visible scintillation light generated by proton irradiation on the scintillator, and could measure the range from the shape of light distribution by using a computer with automatic analysis software installed. We carried out proton irradiation experiments with this tool to examine its performance as a tool of daily range measurements. The precision of the range measurement is within 0.3 mm (sd). The tool can measure possible short-term range variation with 1 s sampling time during the time interval of a typical treatment in a few minutes. We conclude that this tool can measure the range with sufficient resolution in a short time, and is useful for range control in a clinical setting.

Dose-Response Relationship, Radiation↗
PubMed2006

X-ray magnetic circular dichroism of size-selected, thiolated gold clusters.

We report herein the X-ray magnetic circular dichroism (XMCD) at the Au L2,3 edges of a series of Au clusters protected by glutathione (GSH). The samples used here included AuN(SG)M with (N, M) = (10, 10), (15, 13), (18, 14), (22, 16), (25, 18), (29, 20), (39, 24) and a sodium gold(I) thiomalate (SGT) as a reference. Magnetic moments per cluster were found to be increased with size, whereas those per Au-S bond were nearly constant. This finding suggests that a localized hole created by Au-S bonding at the gold/glutathione interface, rather than the quantum size effect, is responsible for the spin polarization of gold clusters.

Journal Article↗
PubMed2006

Serial diffusion-weighted imaging of neonatal herpes encephalitis: a case report.

We reported a patient with neonatal herpes simplex encephalitis in whom diffusion-weighted imaging was performed repeatedly. Diffusion-weighted imaging at 20h after the onset of seizures revealed scattered small spotty high intensity lesions in both hemispheres and a high intensity area in the left fronto-temporal lobe. There was no abnormal finding on conventional magnetic resonance imaging. Second diffusion-weighted imaging 72h after the onset revealed expanded scattered high intensity lesions in the bilateral hemisphere, a high intensity area in the left fronto-temporal lobe, and a new high intensity area in the right temporal lobe. There was no report on neonatal herpes simplex encephalitis that showed scattered high intensities in diffusion-weighted imaging. Scattered small high intensities on diffusion-weighted imaging may suggest endothelial cell infection with swelling and small vessel necrosis. Early diffusion-weighted imaging will be valuable for early detection and diagnosis of neonatal herpes simplex encephalitis.

Brain↗
PubMed2006

Ictal EEG in patients with convulsions with mild gastroenteritis.

The aim of this study is to reveal detailed clinical manifestations and an evolution of ictal EEG discharges of convulsions with mild gastroenteritis (CwG). We recorded ictal EEGs of six patients with CwG. Clinical manifestations included loss of responsiveness, motion arrest, cyanosis, lateral eye deviation, and hemifacial convulsion. Automatism was not observed in any patients. A generalized tonic-clonic convulsion was observed in five of six patients. Ictal EEGs demonstrated that all seizures were of focal onset that evolved into a secondarily generalized seizure. The region of the onset of ictal discharge was the occipital area in three patients, parietal in one, central in one, and frontal in one, respectively. The seizure of patients with CwG is likely to be a partial seizure with secondary generalization.

Age Factors↗
PubMed2006

Antiepileptic treatment against clustered seizures in benign partial epilepsy in infancy.

We performed detailed review of clinical course of clustered seizures in patients with benign partial epilepsy in infancy in order to determine the optimal treatment during the acute period. We retrospectively investigated the details of antiepileptic treatment for clustered seizures in 20 patients with benign partial epilepsy in infancy. The temporal course of seizures and the use of antiepileptic drugs were investigated in each patient. Drugs were judged as effective when seizure cessation was achieved after administration of the drug. As the first drug, diazepam/bromazepam was effective in 14% and phenobarbital in 60%. As the second drug, diazepam/bromazepam was effective in 13% and phenobarbital in 40%. As the third drug, phenobarbital was effective in 56%. The efficacy rate of the first dose of phenobarbital was relatively higher than that of diazepam/bromazepam. Persistence of seizures after treatment was relatively shorter and the number of seizures after treatment was relatively smaller in patients treated with PB as the first 2 drugs. In conclusion, the efficacy of diazepam/bromazepam or phenobarbital was insufficient for the cessation of clustered seizures in benign partial epilepsy in infancy.

Anticonvulsants↗
PubMed2006

Single photon emission computed tomography and serial MRI in preterm infants with kernicterus.

Single photon emission computed tomography was performed in three preterm infants with athetoid cerebral palsy due to kernicterus. No clinical signs and symptoms of kernicterus, or ultrasonographic abnormalities were seen during the neonatal period in any patients. Although MRI during infancy revealed high intensity areas in bilateral globi pallidi in all of them, MRI abnormalities were mild in two of them. On later MRI, subtle high intensity areas in the globi pallidi were recognized in only one of them. Single photon emission computed tomography demonstrated hypoperfusion in the basal ganglia regions in all patients. Regions of interest analyses showed decreased blood flow in the basal ganglia related to the cortical areas. Single photon emission computed tomography will be useful for the diagnosis of kernicterus, whereas MRI abnormalities become less clear beyond infancy.

Basal Ganglia↗
PubMed2006

Effect of clonidine premedication on postoperative sore throat and hoarseness after total intravenous anesthesia.

To determine the effect of oral clonidine premedication on postoperative sore throat and hoarseness, we evaluated the incidence and severity of each of these complications in patients who underwent elective surgery in the supine position. The subjects were 82 patients, American Society of Anesthiologists (ASA) status I-III, aged 15-82 years. They were premedicated with either 150 microg oral clonidine and 20 mg raftidine (clonidine group; n = 41) or with 20 mg raftidine only (control group; n = 41) 2 h before anesthesia induction. General anesthesia was maintained with propofol, ketamine, fentanyl, and vecuronium, with or without epidural anesthesia. Postoperative sore throat and hoarseness were evaluated immediately after surgery and on the day after surgery. The incidences of sore throat and hoarseness tended to be higher in the clonidine group than in the control group; however, the difference did not reach statistical significance. There were no significant differences in the severity of these symptoms between the two groups. In conclusion, oral premedication with 150 microg clonidine did not prevent postoperative sore throat or hoarseness, and may have exacerbated these symptoms.

Adjuvants, Anesthesia↗
PubMed2006

Long-term follow-up of patients with benign partial epilepsy in infancy.

PURPOSE: The aim of this study was to investigate the long-term outcome of children with benign partial epilepsy in infancy (BPEI). METHODS: A telephone-interview survey using a structured questionnaire was conducted with patients who were diagnosed as having possible BPEI at age 2 years and who were 8 years or older at the time of the survey. The data from 39 of 48 patients were available. The median age at the time of the survey was 11.3 years; 18 boys and 21 girls were included. RESULTS: Three patients had a recurrence of unprovoked seizure beyond age 2 years. Four patients had cognitive problems (mild mental retardation in three and Asperger syndrome in one). An association of paroxysmal kinesigenic choreoathetosis was observed in three patients, and another three had experienced seizures associated with mild gastroenteritis. Major behavioral problems were not recognized in any patients. Four patients were excluded from having definite BPEI at age 5 years, and another two were excluded for having definite BPEI at the last follow-up. Eventually, 33 of 39 patients were categorized as having definite BPEI beyond 8 years of age. CONCLUSIONS: A large majority of patients diagnosed as possibly having BPEI at age 2 years did not have a recurrence of unprovoked seizures and cognitive problems beyond 8 years of age.

Age Factors↗
PubMed2006

[Elucidation of the energy absorption spectra of the (11)C beam in a plastic scintillator.].

Heavy ion therapy using the energetic (12)C beam is successfully under way at HIMAC, Japan. The method is more advantageous than traditional radiation therapy in dose concentration owing to the Bragg peak and high relative biological effectiveness. A research study using the (11)C beam for heavy ion therapy in the future has been carried out in order to develop the capability of monitoring the dose distribution. Our group has examined the total energy absorption spectrum of the (11)C beam in a plastic scintillator. We could clearly observe the total absorption peak of (11)C in the energy spectrum and, in addition, we found a broad bump structure was associated with the peak. The bump area occupies 37% of the total spectrum and it probably affects the dose calculation for an accurate treatment planning. We elucidated the mechanism that leads to the structure of the total energy absorption spectra given by (11)C and (12)C in a block of plastic scintillator. This paper describes the method in detail and gives experimental analysis results which deal with the bump structure. We could explain the bump structure using the energy spectra caused by the fragmentation reactions.

Heavy Ions↗
PubMed2006

[High incidence of fatal cytokine-related disease among children with sequelae of perinatal hypoxic-ischemic encephalopathy].

Children with sequelae of perinatal hypoxic-ischemic encephalopathy (HIE) occasionally suffer from cytokine-related disease. We investigated 12 children with perinatal HIE sequelae, who died in childhood, concerning (1) the incidence of cytokine-related disease as the cause of death, and (2) the characteristics of the cytokine-related disease. Six (50%) of the 12 patients died from cytokine-related disease:two had virus-associated hemophagocytic syndrome (VAHS) ; one had acute encephalopathy;one had systemic inflammatory response syndrome (SIRS); and two had severe pneumonia/acute respiratory distress syndrome (ARDS). These six patients presented with increased liver transaminase, LDH, and CK, and decreased platelet count and albumin. This study shows the high incidence of cytokine-related disease as the cause of death in children with perinatal HIE sequelae. Further investigation is needed to clarify the pathogenesis of this disease.

Basal Ganglia Diseases↗
PubMed2005

[A Generator of Mono-energetic Electrons for Response Test of Charged Particle Detectors.].

We designed and fabricated a generator of mono-energetic electrons for the response test of charged particle detectors, which is used to measure fragmented particles of the carbon beam for cancer therapy. Mono-energetic electrons are extracted from (90)Sr by analyzing the energy of beta rays in the generator with a magnetic field. We evaluated performance parameters of the generator such as the absolute energy, the energy resolution and the counting rates of extracted electrons. The generator supplies mono-energetic electrons from 0.5MeV to 1.7MeV with the energy resolution of 20% in FWHM at higher energies than 1.0MeV. The counting rate of electrons is 400cpm at the maximum when the activity of (90)Sr is 298kBq. The generator was used to measure responses of fragmented-particle detectors and to determine the threshold energy of the detectors. We evaluated the dependence of pulse height variation on the detector position and the threshold energy by using the generator. We concluded this generator is useful for the response test of general charged particle detectors.

Beta Particles↗
PubMed2004

On-clock non-paralyzable count-loss model.

This paper proposes a new count-loss model that is applicable to radiation detection systems in the field of nuclear medicine. The proposed model, represented by n = (1 - exp(-tau(n)0))/tau(n)0: input rate, n: output rate,tau: system clock duration), gives higher count rates than the well-known standard nonparalyzable (non-extensible) model represented by n = n0/(1 + tau(n)0) does, being equally simple. This model assumes that a part of the data processing is performed on a fixed system clock, requiring a data buffering function (latch) to retain digital event information temporarily, and that input timing is random. The model's simple interpretation and expression also offers an advantage over various other advanced count-loss models proposed so far. This model was found to be a better fit to a data-acquisition system for a positron emission tomography scanner.

Algorithms↗
PubMed2004

Laryngotracheal application of lidocaine spray increases the incidence of postoperative sore throat after total intravenous anesthesia.

PURPOSE: To determine the effect of laryngotracheal application of different doses of lidocaine spray on postoperative sore throat and hoarseness, we evaluated the incidence and severity of these complications in 168 ASA I-III patients aged 15-92 years in a placebo-controlled study. METHODS: After induction of anesthesia with propofol, ketamine, fentanyl, and vecuronium, the laryngotracheal area was sprayed immediately before intubation with lidocaine spray either 5 times (L5 group, n = 47) or 10 times (L10 group, n = 48) or with normal saline 1 ml (placebo group, n = 51). Postoperative sore throat and hoarseness were evaluated immediately after surgery and on the day after surgery. RESULTS: The incidence of sore throat was significantly higher in the L10 group than in the placebo group on both the day of and the day after surgery. The severity of sore throat was significantly higher in the L5 and L10 groups than in the placebo group on the day of surgery. On the day after surgery, the severity of sore throat remained significantly higher in the L10 group than in the placebo group. Although the incidence and severity of sore throat increased in a dose-dependent manner, these were not significantly different between the L5 and L10 groups. In addition, the incidence and severity of hoarseness did not differ at all among the three groups. CONCLUSION: We recommend that applications of lidocaine spray to the laryngotracheal area should be avoided to help eliminate unnecessary postoperative sore throat, thereby leading to improvement in patient satisfaction.

Adolescent↗
PubMed2004

Temporal structure of the apparent motion perception: a magnetoencephalographic study.

Humans perceive motion when numerous small dots pattern is followed by one of the same pattern but with all the dots shifted a little in one direction. When the amount of shift exceeds a level humans no more perceive motion even though physical visual information does not change. Using this stimulus, we addressed to elucidate the temporal structure of the neural activity related to this apparent motion perception. The magnetic responses to the random-dot patterns with various amounts of shift were measured while the subjects were performing a direction discrimination task. A significant magnetic response amplitude change occurred with three distinct peaks when the response inducing apparent motion was compared with those inducing no motion without change in the response latencies. The major difference occurred at about 110, 140, 210 ms after the stimulus onset. The response origin was always within the occipitotemporal area. The results indicate that the neural activity for the perception of apparent motion can be measured by MEG that occur at least 110 ms after the stimulus onset possibly in the human MT+. Three distinct peaks in the response difference may represent the sequential multiple neural process proposed theoretically though further study is necessary to prove.

Adult↗
PubMed2004

Treatment and outcome in patients with febrile convulsion associated with epileptiform discharges on electroencephalography.

The aim of this study is to determine the efficacy of prophylactic treatment for patients with febrile convulsions (FCs) in whom electroencephalograms (EEGs) revealed epileptiform discharges. We retrospectively investigated 43 patients who met the following criteria: (a) at least one FC during the study period; (b) epileptiform discharges were first recognized; (c) no unevoked seizures before epileptiform discharges were first seen; (d) normal psychomotor development and no neurological abnormality; and (e) follow-up >3 years. The clinical characteristics, treatment, and a later occurrence of FCs or unevoked seizures were studied. EEGs revealed focal epileptiform discharges in 25 patients and generalized ones in 18. There was no significant difference in the rate of recurrence of FC or occurrence of unevoked seizures between those with focal and generalized epileptiform discharges. No prophylaxis was performed in ten patients, 14 patients being treated with intermittent diazepam and 19 with a daily anticonvulsant. The rate of recurrence of FC was not significantly different between patients with and without prophylaxis. Unevoked seizures were only observed in two patients undergoing daily treatment. Intermittent or daily anticonvulsant therapy will not reduce the risk of recurrence of FCs or later development of unevoked seizures in patients with FC with epileptiform discharges.

Anticonvulsants↗
PubMed2004

Oral clonidine premedication exacerbates hypotension following tourniquet deflation by inhibiting noradrenaline release.

Clonidine premedication prevents tourniquet pain and reduces sympathetic nerve activity. We evaluated hemodynamic changes and catecholamine release following tourniquet deflation during spinal anesthesia in patients who received oral clonidine premedication. The final analysis included 24 otherwise healthy patients undergoing lower-limb surgery randomly assigned to two groups: those receiving approximately 5 micrograms/kg of oral clonidine 1 hr before anesthesia (clonidine group, n = 12), and those receiving no premedication (control group, n = 12). After lumbar anesthesia, a tourniquet was applied for approximately 60 minutes to each patient. Electrocardiogram, arterial blood pressure, and consumption of butorphanol for tourniquet pain were monitored. Blood samples were obtained at different times to measure serum concentration of catecholamine. In the clonidine group, mean blood pressure decreased from 87 +/- 7 mmHg at baseline to 65 +/- 10 mmHg after tourniquet deflation (P < 0.05). This peak reduction of mean blood pressure in the clonidine group was significantly lower than in the control group. After receiving clonidine premedication, the plasma noradrenaline concentrations in the clonidine group were significantly lower than those in the control group. Noradrenaline concentration increased in the control group from 162.3 +/- 89.2 pg/mL before tourniquet deflation to 199.3 +/- 95.7 pg/mL afterward (P < 0.01), but there was no significant change in noradrenaline concentration after tourniquet deflation in the clonidine group. We conclude that oral clonidine premedication exacerbated the reduction in mean blood pressure following tourniquet deflation by inhibiting noradrenaline release.

Administration, Oral↗