Comparison between Monte Carlo simulation and measurement with a 3D polymer gel dosimeter for dose distributions in biological samples.

In this research, we used a 135 MeV/nucleon carbon-ion beam to irradiate a biological sample composed of fresh chicken meat and bones, which was placed in front of a PAGAT gel dosimeter, and compared the measured and simulated transverse-relaxation-rate (R2) distributions in the gel dosimeter. We experimentally measured the three-dimensional R2 distribution, which records the dose induced by particles penetrating the sample, by using magnetic resonance imaging. The obtained R2 distribution reflected the heterogeneity of the biological sample. We also conducted Monte Carlo simulations using the PHITS code by reconstructing the elemental composition of the biological sample from its computed tomography images while taking into account the dependence of the gel response on the linear energy transfer. The simulation reproduced the experimental distal edge structure of the R2 distribution with an accuracy under about 2 mm, which is approximately the same as the voxel size currently used in treatment planning.

Quality of life of patients and medical cost of "half elemental diet" as maintenance therapy for Crohn's disease: secondary outcomes of a randomised controlled trial.

BACKGROUND/AIM: Quality of life (QOL) of the patients and medical costs are important in current medical treatments, especially those for chronic diseases. We have reported the effectiveness of 'half elemental diet (ED)' as maintenance therapy for patients with Crohn's disease (CD). The aim of this study was to evaluate the QOL of CD patients and medical costs of half-ED. METHODS: Fifty-one CD patients in remission were randomly assigned to a half-ED group (n=26) or a free diet group (n=25). The primary outcome measure was the occurrence of relapse during a 2-year period. This time, we investigated the QOL of the patients and medical costs of half-ED, as secondary outcomes. QOL was evaluated using the Japanese version of the IBDQ scoring system, and medical costs were calculated monthly from the receipts. RESULTS: IBDQ score was not significantly different between the two groups at 1 and 13 months after the start of maintenance treatment. Medical costs were not significantly different between them either. This study showed that half-ED therapy did not affect the treatment of CD patients, neither regarding their QOL nor medical costs. CONCLUSION: This study has confirmed this half-ED therapy is beneficial for patients with Crohn's disease.

Application of voxel phantoms and Monte Carlo method to whole-body counter calibration.

Voxel phantoms and Monte Carlo methods are of considerable interest in calibrating in vivo counting applications for radioactive body burden such as whole-body counters. At the Japan Atomic Energy Research Institute (JAERI), a calculation code--UCWBC code--for whole-body counter calibrations using voxel phantoms has been developed as an EGS4 Monte Carlo user code. To validate the UCWBC code for calibrating whole-body counters at JAERI, response functions and counting efficiencies of a p-type high-purity Ge (HPGe) semiconductor detector used for the whole-body counter were evaluated for a water-filled block-shape phantom by use of UCWBC code and were measured by experiments. The voxel version of the water-filled block-shape phantom based on an actual phantom was used for the calculations. Furthermore, counting efficiencies of the Ge semiconductor detector for the male and female voxel phantoms developed at JAERI were evaluated in the photon energy range from 60 to 1836 keV by the UCWBC code in order to examine the differences between the counting efficiencies for voxel phantoms. In conclusion, it was found that the response functions and counting efficiencies of the Ge semiconductor detector found by the UCWBC code for the water-filled block-shape phantom are in good agreement with measured data. The UCWBC code was validated by those comparisons. It was also found that the counting efficiencies of the Ge semiconductor detector depend on the size of the phantoms and the effective distance between phantom and detector. The calibration of whole-body counters using voxel phantoms and Monte Carlo methods would be quite useful for the improvement in the accuracy of measurement results.

Real-time measurement of low-energy-range neutron spectra on board the space shuttle STS-89 (S/MM-8).

We have developed a real-time, Bonner Ball-type (neutron energy range is from thermal to 15 MeV) neutron spectral measurement system (Bonner Ball Neutron Detector (BBND)) for use on board the International Space Station (ISS). From measurements taken inside STS-89 (S/MM-8), we successfully distinguished neutrons from protons and other particles in a mixed radiation field; a task hitherto considered difficult. Although the experimental period was short, only 3.5 days (January 24-27, 1998), we were able to obtain energy spectral data and the Earth's neutron dose-equivalent map for the ISS orbital conditions (altitude 400 km, orbit inclination angle 51.6 degrees). A method for calculating the neutron energy spectrum and compensating for the particle interaction with the sensors is also described in detail.

[PET evaluation of glucose metabolism in cancer].

Accelerated glycolysis is one of the biochemical characteristics of cancer cells. Based on this fact, positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) has been used in the diagnosis of various cancers. After intravenous injection of FDG and PET scans, most cancers are identified by high FDG accumulation. This metabolic tumor imaging method has been used successfully in the differentiation of benign and malignant tumors, in the diagnosis of metastasis or recurrence, in the detection of primary unknown cancers, and in cancer screening. Because the degree of FDG accumulation reflects tumor glucose consumption, quantification of FDG uptake by PET can be used in predicting biological malignancy and in monitoring treatment in both radiation and chemotherapy. The potential utility of Glut-1 and hexokinase, reported to be responsible for increased glucose metabolism, as biological markers of cancers is yet to be determined.

Quantitative assessment of the efficacy of amorphous calcium phosphate/methacrylate composites in remineralizing caries-like lesions artificially produced in bovine enamel.

Recent studies show that methacrylate-based composites with amorphous calcium phosphate (ACP) as a filler can release supersaturating levels of calcium and phosphate ions in proportions favorable for apatite formation. These findings suggest that such composites could be effectively used as coatings for remineralizing teeth damaged by tooth decay. To examine this hypothesis, we tested composites in vitro for their efficacy to remineralize artificially formed caries-like lesions in extracted bovine incisors. Single 120-microns-thick sagittal tooth sections were placed in holders that exposed only the carious enamel surface. The exposed surfaces were coated with a 1-mm- to 1.5-mm-thick layer of the composite containing, by mass, 40% apatite, silica, or P2O7(-4)-stabilized ACP and 60% photoactivated resin comprised of Bis-GMA, TEGDMA, HEMA, and ZrM. The photocured composite-coated sections were immersed either in a remineralizing solution for 4 weeks at 37 degrees C (static model) or cyclically immersed in demineralizing (0.5 h) and remineralizing solutions (11.5 h) for 2 weeks (dynamic model). Quantitative digital image analysis of matched 102 microns x 220 microns areas from contact microradiographs taken of the sections before and after immersion showed that lesions coated with ACP-filled composites fractionally recovered 71% +/- 33% of their lost mineral compared with 14% +/- 13% for apatite controls in the static model and 38% +/- 16% compared with -6% +/- 24% in the dynamic model. The results suggest that sealants based on ACP-filled methacrylate composites have the potential to remineralize carious enamel lesions.

[Assessment of pre-term uterine contractions by characterization of the power spectra of abdominal surface potentials (ASP)].

The prognosis of pre-term labor in the absence of complications such as PROM is dependent on the strength of the uterine contractions, which are dependent on the sensitivity of the myometrium, expressed in terms of bio-electric potentials. Our electromyography were obtained from pregnant ewes, and these were correlated with abdominal surface potentials (ASP) obtained from human volunteers, to see if impending premature labor could be detected and the prognosis predicted. 1) The EMG tracings obtained from pregnant ewes were submitted to a power spectrum analysis. 2) EMG tracings revealed an increase in power output with the advance of labor, but power spectra varied with the stage of labor. 3) Uterine contractions not leading to cervical ripening had a low power output with a low frequency range. 4) Ewes in true labor had EMG's at a high power output of low frequency waves. 5) Ewes in pre-term labor leading to cervical ripening had power outputs similar to ewes in true labor, but the power spectra of the former were wider in range. 6) ASP tracing revealed an increasing power output with increasing uterine contractile activity and power spectra correlated well with the EMGs obtained from ewes. In conclusion, since ASP findings were in good correlation with EMGs obtained directly from the myometrium, we hope that this method may be developed into a practical non-invasive method for detecting and assessing uterine contractions.

Assessment of loosely-bound and firmly-bound fluoride uptake by tooth enamel from topically applied fluoride treatments.

The amounts of loosely-bound fluoride (F) deposited on human enamel by two topical F treatments were measured with use of a constant-composition F washing method. Enamel biopsies conducted before treatment and after the washing were used for determination of the firmly-bound F uptake. The results showed that (1) the washing system did not remove F from untreated enamel surface, (2) a four-minute application of an acidulated phosphate fluoride (APF) gel deposited 27.2 (2.4) (mean, S.E.) micrograms of loosely-bound F per cm2 of enamel surface and 186 (111) ppm of firmly-bound F in the outer 10 microns of enamel, and (3) a four-minute application of a pH-2.1 dicalcium phosphate dihydrate (DCPD)-forming solution followed by APF produced 44.9 (3.1) micrograms/cm2 of loosely-bound F and 1280 (354) ppm of firmly-bound F in the outer 10 microns of enamel. The results showed that the DCPD pre-treatment effectively enhanced the enamel reactivity with F, so that the DCPD-APF treated enamel acquired greater amounts of both loosely-bound F and firmly-bound F than did samples treated with APF alone.