Development of a voxel phantom of Japanese adult male in upright posture

A Japanese voxel phantom in upright posture, JM2, has been developed on the basis of CT images of a healthy Japanese adult male. Body characteristics of JM2 were compared with those of the supine voxel phantom, JM, previously developed using CT images of the same person. Differences were found in the shapes of the spine and lower abdomen and the locations of several organs such as kidneys, liver and stomach between the two phantoms. Specific absorbed fractions (SAFs) for 24 target and 11 sources organs were calculated for monoenergetic photon ranging from 0.01 to 4 MeV. It was found that the SAFs for the kidneys as source organ and the lower large intestine wall as target organ in JM2 were significantly higher than those in JM for all photon energies. The differences of the SAFs between the two phantoms were attributed to the differences in the organ distance and organ geometry depending on the posture.

Darwin: dose monitoring system applicable to various radiations with wide energy ranges

A new radiation dose monitor, designated as DARWIN (Dose monitoring system Applicable to various Radiations with Wide energy ranges), has been developed for real-time monitoring of doses in workspaces and surrounding environments of high-energy accelerator facilities. DARWIN is composed of a phoswitch-type scintillation detector, which consists of liquid organic scintillator BC501A coupled with ZnS(Ag) scintillation sheets doped with (6)Li, and a data acquisition system based on a Digital-Storage-Oscilloscope. DARWIN has the following features: (1) capable of monitoring doses from neutrons, photons and muons with energies from thermal energy to 1 GeV, 150 keV to 100 MeV and 1 MeV to 100 GeV, respectively, (2) highly sensitive with precision and (3) easy to operate with a simple graphical user-interface. The performance of DARWIN was examined experimentally in several radiation fields. The results of the experiments indicated the accuracy and wide response range of DARWIN for measuring dose rates from neutrons, photons and muons with wide energies. It was also found from the experiments that DARWIN enables us to monitor small fluctuations of neutron dose rates near the background level because of its high sensitivity. With these properties, DARWIN will be able to play a very important role for improving radiation safety in high-energy accelerator facilities.

Extension of applicable neutron energy of DARWIN up to 1 GeV

The radiation-dose monitor, DARWIN, needs a set of response functions of the liquid organic scintillator to assess a neutron dose. SCINFUL-QMD is a Monte Carlo based computer code to evaluate the response functions. In order to improve the accuracy of the code, a new light-output function based on the experimental data was developed for the production and transport of protons deuterons, tritons, (3)He nuclei and alpha particles, and incorporated into the code. The applicable energy of DARWIN was extended to 1 GeV using the response functions calculated by the modified SCINFUL-QMD code.

Scatter radiation in cephalometric radiography: the effects of grid and collimation

OBJECTIVES

To measure the scatter fraction in cephalometric radiography with and without a grid and to estimate the patient's dose reduction by using a specially fabricated collimator without a grid.

METHODS

A 16 cm thick water-equivalent phantom was used to measure the scatter fraction. The projection geometry was the same as our conventional one, i.e. the distance from the X-ray source to the centre of the phantom was 200 cm. A photostimulable phosphor plate was used as an X-ray sensor and was 20 cm from the centre of the phantom. The measurements were performed in four combinations: with an antiscatter grid in place, with a specially fabricated collimator in place, with neither in place, and with both in place. The images of a human dried skull were obtained by using the above parameters and were subjectively assessed for a visibility of several reference points.

RESULT

The scatter fraction in the regularly collimated geometry with the antiscatter grid in place was 0.35 for a relative exposure of 1. With the antiscatter grid removed, the scatter fraction increased to 0.68, but the relative exposure was reduced to 0.3. With a special collimator, the scatter fraction was reduced to some extent in all instances, but the exposure was reduced to 0.45. The visibility of the reference points was acceptable in all conditions.

CONCLUSION

In cephalometric radiography, removal of the antiscatter grid yields a significant reduction in exposure with no significant loss of information.

Why do we help a micropreemie to live?

Helping a "micropreemie" to live by aggressive interventions may sometimes seem unnatural. However, utilitarian assessment of benefits derived from lifesaving efforts for a micropreemie is considered inappropriate. The goal in treating premature infants has advanced from fetal salvage to achieving "intact survival", which represents a new therapeutic target. In this way, the record for lifesaving in extremely low-birthweight infants is continually being broken. Why do we help a micropreemie to live? Moral and ethical emotions are the underlying reasons for the aggressive care devoted to premature infants, including micropreemies. Such human feelings might even be considered the purpose of life. Human emotion is the impetus for aggressive efforts to improve the survival prospects of premature infants. The beautiful and delicate nature of a newborn is compelling. The high-order emotion of empathy for another's misfortune is also important. Most human emotions are related to an awareness of death, and micropreemies are near death. In Oriental thought, a human being is a growing product of nature. Forces of nature and changes in a living being follow nature's rules. First and foremost, an individual life is part of the long chain of existence beginning before the self and continuing beyond it. An immature human being, even a newborn, is simultaneously a complete entity and part of nature's long chain of being, which has a wholeness of its own that affirms a micropreemie's right to life. A fetus is a member of human society in the sense that there is an overall reverence for life as a quality that lives on.

CONCLUSION

The limit that bioethics must not exceed is the sanctity of life. We believe that the birth of a micropreemie is an important and serious event. We profoundly wish that a micropreemie might live and thrive, because we on earth must live with the continual presence and imminence of death.

Dose assessment from activated sodium within a body in criticality accidents

Some data were derived using recent sophisticated methods to rapidly convert specific activity of induced 24Na to average dose over a whole body in criticality accidents. Monte Carlo calculations using the MCNP-4B code were performed to study energy spectra of neutrons and gamma rays for some criticality systems with fissile uranium. Absorbed dose to the human body and the activation of sodium were also analysed against external radiation by simulations using a MIRD-5 type phantom and the calculated energy spectra. It was found that the neutron dose assessment from induced 24Na would be important to give medical staff initial guidance for treatment of a victim. However, the energy distribution of incident neutrons to the human body did not significantly influence the conversion from the specific activity of 24Na to dose from gamma rays induced within a body. Analyses were made to clarify the dependence of conversion from 24Na specific activity to neutron dose on the orientation toward the source and the size of the human body. The total dose estimated based upon the obtained data ranged from 33 mGy to 514 mGy for a given specific activity of 1.4 kBq 24Na per g 23Na for some criticality assemblies. This study suggested that the size of uranium solution and material around the fuel should be defined to properly estimate the total dose, including the dose from external photons.

Development and assessment of a new radioactive decay database used for dosimetry calculation

The present paper discusses the technical issues and a scheme for their resolution before undertaking the development of a new radioactive decay database to succeed ICRP38. The scheme consists of the following procedures. (1) The consistency of nuclear structure data files used as input to the computer code EDISTR is established by referring to the latest nuclear parameters and by comparing the computed energies of emitted radiations with total decay energy. (2) A method for calculating detailed spectra of X rays and Auger electrons is incorported into EDISTR to enhance the treatment of atomic relaxation processes initiated by electron vacancies from internal conversion and electron capture. (3) Quality assurance of the compiled data is undertaken by comparisons with experimental data and other decay databases prepared from different computer codes and libraries. JAERI and ORNL are cooperating to implement the scheme in order to assemble a comprehensive radioactive decay database including over 1000 nuclides.

[Anesthetic management for elective cesarean section due to placenta previa in a patient with moyamoya disease]

We report the anesthetic management of a 31-year-old female patient with moyamoya disease using general anesthesia combined with epidural anesthesia for a cesarean section due to placenta previa. Epidural anesthesia with 10 ml of 2% lidocaine was first used. Then general anesthesia was induced with thiamylal 200 mg and succinylcholine 60 mg just before starting operation and was maintained with 60% nitrous oxide in oxygen. After the delivery, propofol was administered at 3-5 mg.kg-1.hr-1. Except for temporary hypotension due to massive bleeding, systolic blood pressure was maintained between 100 and 120 mmHg. Arterial carbon dioxide tension was maintained at about 40 mmHg. Intracranial blood velocity and regional oxygen saturation were also measured to monitor cerebral blood flow. There was no postoperative pain, and no postoperative neurological defects. On the basis of these findings, it was concluded that general anesthesia combined with epidural anesthesia for elective cesarean section due to placenta previa is effective for perioperative management of a patient with moyamoya disease.

Particle size analysis of radioactive aerosols formed by irradiation of argon using 65 MeV quasi-monoenergetic neutrons

The size distributions of 38Cl and 39Cl aerosols formed from the irradiation of argon gas containing di-octyl phthalate (DOP) aerosols by 65 MeV quasi-monoenergetic neutrons were measured to study the formation mechanism of radioactive aerosols in high-energy radiation fields. Both the number size distribution and the activity-weighted size distribution were measured using an electrical low-pressure impactor. It was found that the 35Cl and 39Cl aerosols are formed by attachment of the radioactive atoms generated by the neutron-induced reaction to the DOP aerosol particles.

Age related expression of Werner's syndrome protein in selected tissues and coexpression of transcription factors

AIMS

Werner's syndrome (WS) is an uncommon autosomal recessive disease resulting from mutational inactivation of human WRN helicase, Werner's syndrome protein (WRNp). Patients with WS progressively develop a variety of aging characteristics after puberty. The aim of this study was to determine the distribution of WRNp and the expression of the transcription factors regulating WRN gene expression in a variety of human organs in an attempt to understand the WS phenotype.

METHODS

Tissue specimens were obtained from 16 controls aged from 27 gestational weeks to 70 years of age and a 56 year old female patient with WS. The distribution of WRNp and the expression of the transcription factors regulating WRN gene expression-SP1, AP2, and retinoblastoma protein (Rb)- were studied in the various human organs by immunohistochemical and immunoblot analyses.

RESULTS

In the healthy controls after puberty, high expression of WRNp was detected in seminiferous epithelial cells and Leydig cells in the testis, glandular acini in the pancreas, and the zona fasciculata and zona reticularis in the adrenal cortex. In addition, the SP1 and AP2 transcription factors, which regulate WRNp gene expression, appeared in an age dependent manner in those regions where WRNp was expressed. In controls after puberty, SP1 was expressed in the testis and adrenal gland, whereas AP2 was expressed in the pancreas.

CONCLUSIONS

These findings suggest that the age specific onset of WS may be related to age dependent expression of WRNp in specific organs.

Prediction of extubation failure in preterm infants

OBJECTIVE

To identify whether the results of assessment of respiratory muscle strength or respiratory load were better predictors of extubation failure in preterm infants than readily available clinical data.

PATIENTS

Thirty six infants, median gestational age 31 (range 25-36) weeks and postnatal age 3 (1-14) days; 13 were < 30 weeks of gestational age.

METHODS

Respiratory muscle strength was assessed by measurement of maximum inspiratory pressure generated during airway occlusion, and inspiratory load was assessed by measurement of compliance of the respiratory system.

RESULTS

Overall, seven infants failed extubation-that is, they required reintubation within 48 hours. These infants were older (p < 0.01), had a lower gestational age (p < 0.01), and generated lower maximum inspiratory pressure (p < 0.05) than the rest of the cohort. Similar results were found in the infants < 30 weeks of gestational age. Overall and in those < 30 weeks of gestational age, gestational age and postnatal age had the largest areas under the receiver operator characteristic curves.

CONCLUSION

In very premature infants, low gestational age and older postnatal age are better predictors of extubation failure than assessment of respiratory muscle strength or respiratory load.

Measurement of neutron dose with an organic liquid scintillator coupled with a spectrum weight function

A dose evaluation method for neutrons in the energy range of a few MeV to 100 MeV has been developed using a spectrum weight function (G-function), which is applied to an organic liquid scintillator of 12.7 cm in diameter and 12.7 cm in length. The G-function that converts the pulse height spectrum of the scintillator into the ambient dose equivalent, H*(10), was calculated by an unfolding method using successive approximation of the response function of the scintillator and the ambient dose equivalent per unit neutron fluence (H*(10) conversion coefficients) of ICRP 74. To verify the response function of the scintillator and the value of H*(10) evaluated by the G-function. pulse height spectra of the scintillator were measured in some different neutron fields, which have continuous energy, monoenergetic and quasi-monoenergetic spectra. Values of H*(10) estimated using the G-function and pulse height spectra of the scintillator were compared with those calculated using neutron energy spectra. These doses agreed with each other. From the results, it was concluded that H*(10) can be evaluated directly from the pulse height spectrum of the scintillator by applying the G-function proposed in this study.

Structural features of a wheat plastome as revealed by complete sequencing of chloroplast DNA

Structural features of the wheat plastome were clarified by comparison of the complete sequence of wheat chloroplast DNA with those of rice and maize chloroplast genomes. The wheat plastome consists of a 134,545-bp circular molecule with 20,703-bp inverted repeats and the same gene content as the rice and maize plastomes. However, some structural divergence was found even in the coding regions of genes. These alterations are due to illegitimate recombination between two short direct repeats and/or replication slippage. Overall comparison of chloroplast DNAs among the three cereals indicated the presence of some hot-spot regions for length mutations. Whereas the region with clustered tRNA genes and that downstream of rbcL showed divergence in a species-specific manner, the deletion patterns of ORFs in the inverted-repeat regions and the borders between the inverted repeats and the small single-copy region support the notion that wheat and rice are related more closely to each other than to maize.

A case of pulmonary hypoplasia associated with intrauterine brainstem necrosis

An infant with intrauterine brain death accompanied by pulmonary hypoplasia is reported. The fetus was delivered after 36 weeks gestation, 5 weeks after fetal movements ceased. The child died 4 h after birth. Pulmonary hypoplasia and remote brainstem necrosis associated with multicystic encephalomalacia were found at autopsy.

CONCLUSION

These findings suggest that damage to brainstem respiratory centres had led to pulmonary hypoplasia through the absence of fetal respiratory movement.

Dose estimation based on a behavior survey of residents around the JCO facility

The NIRS staff interviewed the residents in the evacuated zone around the JCO facility in Tokai-mura on 19 and 20 November, 1999, to obtain the following parameters every 30 minutes starting from 10:35 A.M. on 30 September to 6:15 A.M. on 1 October: the distance from the precipitation tank, the type of the house, positions in the house, wall materials and their thickness in order to estimate individual doses due to the accident. The ambient dose equivalents were obtained based on monitoring data during the accident. In addition, computer calculations were conducted to evaluate the conversion factor from ambient dose equivalent to effective dose equivalent as well as the shielding effect of the house or factory to estimate the effective dose equivalent to the residents. The estimated individual doses based on the behavior survey were in the range from zero to 21 mSv. The individual doses were reported to the residents during the second visit to each house and factory at the end of January, 2000.

Calculation of the absorbed dose for the overexposed patients at the JCO criticality accident in Tokai-mura

The doses for the overexposed patients were estimated by the measurement result of specific activity of 24Na in blood. The present method is almost based on documents of the International Atomic Energy Agency (IAEA) and the Oak Ridge National Laboratory. The neutron energy spectrum obtained using the ANISN code (Multigroup One-Dimensional Discrete Ordinates Transport Code System with Anisotropic Scattering) was assumed. The values in ICRP Publication 74 were applied for the doses in each organ per unit neutron fluence. Gamma-ray dose was indirectly estimated based on (a) the result of environmental monitoring around the accident site and (b) a graph in IAEA manual, which gives the kerma ratio of neutrons and gamma-rays as a function of the critical volume or the atomic ratio of hydrogen to 235U. The estimated neutron doses were 5.4 Gy for patient A. 2.9 Gy for patient B and 0.81 Gy for patient C. The estimated gamma-ray doses were 8.5 or 13 Gy for patient A, 4.5 or 6.9 Gy for patient B, and 1.3 or 2.0 Gy for patient C.

Biosynthesis of acaterin: coupling of C(5) unit with octanoate

Acaterin (1), produced by Pseudomonas sp. A 92, is a secondary metabolite having a 2-penten-4-olide structure. Feeding experiments with (2)H- and (13)C-labeled decanoic acid, their 3-oxygenated congeners, and octanoic acid have suggested that 1 is biosynthesized via coupling of a C(5) unit with octanoate, rather than via introduction of a C(3) unit at the alpha position of a decanoate derivative. Further feeding study of [2,3-(13)C(2)]decanoic acid concluded that the former route is operating in the biosynthesis of 1.

Facial palsy associated with mumps parotitis

Peripheral facial nerve paralysis is relatively common in the pediatric age group. However, facial palsy rarely has been documented in patients with mumps parotitis. This case report describes the findings of a 3-year-old Japanese boy who developed facial palsy immediately after mumps parotitis. This work calls attention to a possible association between mumps parotitis and facial palsy.

Cardiac imaging in a patient with anomalous origin of the left coronary artery from the pulmonary artery--a case report

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is an uncommon congenital heart disease and has a high mortality rate in infancy. However, myocardial ischemia does not develop until adolescence or adulthood in about 10% of patients. Moreover, the diagnosis of ALCAPA is often difficult in cases without heart murmur or cardiac symptoms. The authors report the case of a 31-year-old man with ALCAPA. He was admitted to the hospital for evaluation of mild shortness of breath at exercise, but he had no typical chest symptoms due to myocardial ischemia or heart failure until age 31 and he had no heart murmur. Moreover, electrocardiogram did not show an old myocardial infarction or myocardial ischemia. Therefore, the authors did not suspect ALCAPA until they performed transthoracic echocardiography and exercise-stress single photon emission computed tomography (SPECT) with Tc-99m-tetrofosmin. The final diagnosis was established from the results of coronary arteriography. In the present case, a transthoracic echocardiogram showed abnormal coronary circulation, and exercise-stress SPECT revealed reversible myocardial ischemia. Transthoracic echocardiography and myocardial SPECT imaging could be a useful noninvasive tools for diagnosing the ALCAPA.

Spontaneous labor increases nitric oxide synthesis during the early neonatal period

BACKGROUND

This paper aimed to assess the influence of spontaneous labor upon endogenous nitric oxide (NO) and endothelin 1 (ET-1) during transition to extrauterine life.

METHODS

The serum levels of NO metabolites (the sum of nitrites and nitrates (NOx)) and the plasma level of ET-1 were determined in 53 healthy full-term infants (spontaneous labor group; n=40, cesarean delivery group; n=13). In both groups, blood samples were obtained from a cord vein at birth and from a peripheral vein at 5 days of age.

RESULTS

The differences in serum NOx concentrations between the spontaneous labor group and the elective cesarean group were not significant at birth. By the age of 5 days, serum NOx concentrations had risen significantly in the spontaneous labor group to become significantly higher in the elective cesarean group.

CONCLUSION

It is speculated that spontaneous labor might enhance endogenous NO synthesis at 5 days of age.