Aloe vera oral administration accelerates acute radiation-delayed wound healing by stimulating transforming growth factor-ß and fibroblast growth factor production.

BACKGROUND: Delayed wound healing is a significant clinical problem in patients who have had previous irradiation. This study investigated the effectiveness of Aloe vera (Av) on acute radiation-delayed wound healing. METHODS: The effect of Av was studied in radiation-exposed rats compared with radiation-only and control rats. Skin wounds were excised on the back of rats after 3 days of local radiation. Wound size was measured on days 0, 3, 6, 9, and 12 after wounding. Wound tissues were examined histologically and the expressions of transforming growth factor ß-1 (TGF-ß-1) and basic fibroblast growth factor (bFGF) were examined by immunohistochemistry and reverse-transcription polymerase chain reaction. RESULTS: Wound contraction was accelerated significantly by Av on days 6 and 12 after wounding. Furthermore, the inflammatory cell infiltration, fibroblast proliferation, collagen deposition, angiogenesis, and the expression levels of TGF-ß-1 and bFGF were significantly higher in the radiation plus Av group compared with the radiation-only group. CONCLUSIONS: These data showed the potential application of Av to improve the acute radiation-delayed wound healing by increasing TGF-ß-1 and bFGF production.

Neurobehavioral changes in mice exposed to fast neutrons in utero.

Epidemiological studies have revealed that radiation causes brain development abnormalities in atomic bomb survivors exposed in utero. Rat and mouse studies have also shown that prenatal exposure to low-linear energy transfer radiation induces developmental brain anomalies. Because the effects of prenatal irradiation on adult behavior patterns remain largely unknown, the present study investigated the effects of neutron exposure in utero on postnatal behavior patterns in mice. [C57BL/6J × C3H/He] hybrid (B6C3F1) mice were exposed to cyclotron-derived fast neutrons with peak energy of 10 MeV (0.02-0.2 Gy) or Cs-137 gamma-rays (0.2-1.5 Gy) on embryonic day 13.5. At 5.5-8 months of age, the neurobehavior of male offspring was examined by Rota-rod treadmill and locomotor activity. The accumulation of radio-labeled drug at muscarinic acetylcholine and serotonin receptors in mice from control and neutron-irradiated groups was determined by the tracer method. Locomotor activity during the dark period increased in the 0.02 Gy neutron-irradiated group. Furthermore, at 5.5 months of age, tracer binding in vivo to the muscarinic acetylcholine increased and to the serotonin receptors decreased in the 0.02 Gy neutron-irradiated group. In conclusion, the present study reveals that a certain "low-dose window" may exist for radiation-induced changes in neurobehavior and binding to neurotransmitter receptors, because there was correlation in neurobehavior and binding to neurotransmitter receptors in the 0.02 Gy neutron-irradiated group though there was not correlation in the neutron-irradiated groups more than 0.05 Gy.

[Evaluation of relative electrometer calibration factor with user beam.].

To establish traceability of absorbed dose to water, a cobalt calibration coefficient is transferred to a reference ionization chamber by the standard dosimetry laboratory in the radiotherapy field. In Japan, the calibration is done against a set of an ionization chamber and an electrometer as a system. Nowadays, solely electrometer calibration is desirable to measure absorbed dose with more than one combination of ionization chamber and electrometer. Unfortunately, there is no domestic electrometer calibration service for nano-ampere range appropriate for ionization current measurement in the radiotherapy field. In this report, a relative electrometer calibration factor was determined by comparison between a calibrated combination and a non-calibrated electrometer under identical irradiation conditions at the user site. To estimate uncertainties of user electrometer calibration, comparison was made between calibration factors obtained by ionization current under a linac photon beam and DC current with a precision DC source instrument. It was found that the variation of electrometer readings to pulse ionization current is negligible under the steady photon beam output and dose monitor system. Therefore relative electrometer calibration under identical irradiation conditions at the user site was judged valid until a domestic nano-ampere electrometer calibration service becomes available.

Production design and evaluation of a novel breast phantom with various breast glandular fractions.

The purpose of this study was to evaluate the production design of a novel breast phantom, which has adjustable breast glandular fractions and potential application in the mammography quality assurance/quality control system. The breast phantom was based on a urethane resin that was used to adjust the breast glandular fraction by varying the amount of plasticizer added. The resin was cured at constant temperature and humidity. Theoretical phantom properties, such as elemental composition, specific density, effective atomic number, electron density, and linear attenuation coefficients, at various energies were compared to those of breast tissue tabulated in the ICRU 44. These properties were also compared to polymethyl methacrylate resin and BR12. The novel breast phantom was made to represent breast glandular content calculated from breast tissue of the ICRU 44. We hypothesized that the breast phantom theoretical properties are approximately equal to those of the BR12, which is known for being an excellent substitute breast phantom. It was found that the phantom can be used to improve both mammography performance and dosimetry.

Dose-response and large relative biological effectiveness of fast neutrons with regard to mouse fetal cerebral neuron apoptosis.

To evaluate the relative biological effectiveness (RBE) of low doses of neutrons on fetal nervous development, [C57BL/6J x C3H/He] hybrid (B6C3F1) mice were exposed to cyclotron-derived fast neutrons with peak energy of 10 MeV (0.02-1.0 Gy) or 137Cs-generated gamma-rays (0.1-2.0 Gy) on embryonic day 13.5. We then evaluated the incidence of neuronal apoptosis in the cerebral cortex 24 hours after irradiation. Neuronal apoptosis increased in a dose-dependent manner in both neutron- and gamma-ray-irradiated groups: even at the lowest dose, a minimal increase in the apoptotic index was noted in response to both types of radiation. The dose-response curves were best fitted to linear quadratic models, and the evaluated RBE was 9.8, which was considered to be large for a prenatal effect and acute tissue injury induced by a low dose of neutrons.

[Polarity effects of commercial plane-parallel ionization chamber in therapeutic electron dosimetry-Results with C-134A ionization chamber.].

Plane-parallel ionization chambers that exhibit polar effects with low energy electron beams are recommended for therapeutic electron dosimetry. In this study, the polarity effects of a C-134A ionization chamber, a major commercially available plane-parallel ionization chamber in Japan, were characterized as a function of mean energy at various depths. Polarity effects were measured at representative depths along depth dose curves of nominal 4, 6, 9, 12 and 15 MeV electron beams, and were compared with previously reported results. Polarity errors for the ionization chamber studied were shown to monotonically increase with decreasing mean energy at a given depth and were maximal at about 1-2 MeV. It was also shown that polarity errors depended on the energy of the incident electron beam. The polarity error of the C-134A ionization chamber was larger than that of other previously investigated plane-parallel ionization chambers. Because the magnitude of polarity effects should be determined throughout the depth dose curve in therapeutic electron dosimetry, it is always necessary to measure ionization readings taken at both polarities.

[Absorbed dose measurement of photon beam with Farmer-type ionization chambers in Japanese dosimetry protocols].

The Japan Society of Medical Physics (JSMP) has published a new dosimetry protocol "JSMP-01" (standard dosimetry of absorbed dose in external beam radiotherapy) which conforms to the recommendations of the International Atomic Energy Agency (IAEA TRS-398) and the American Association of Physicists in Medicine (AAPM TG-51) protocols for the calibration of radiotherapy beams. Since the new protocol offers the physical data for the Famer-type ionization chambers of the various wall materials, the user can measure the absorbed dose at reference point (D(r)) using most of the commercially available Famer-type ionization chambers. In this paper, the six Famer-type ionization chambers of the various wall materials are examined for photon beam by two ways. To verify the JSMP-01 protocol as the first way, D(r) was cross-measured based on the JSMP-01 protocol using a Farmer-type ionization chamber of the acrylic wall material which is called "JARP-chamber" and the Farmer-type ionization chambers of the various wall materials, and compared. To compare the basic data in previous and new protocols as the second way, D(r) was measured based on the previous protocol (JSMP-86) and the JSMP-01 protocol using the Farmer-type ionization chambers of the various wall materials. Dose calculation was made using common exposure calibration factor for (60)Co gamma-rays (Nc) for each of the Farmer-type ionization chambers. Measurement was made with each ionization chamber for 6 and 10 MV photon beams in two facilities. D(r) were found to agree to that of JARP-chamber within about +/- 1% despite significant differences of ratio of calibration factor (k(D,X)) and beam quality conversion factor (k(Q)) for photon beams. The ratios JSMP-01/JSMP-86 of the reference dose were found to lie on between 0.999 and 1.004 for 6 MV and on between 0.999 and 1.005 for 10 MV depending upon the Farmer-type ionization chambers used. The largest discrepancies between the previous and new protocols arise from the use of different data of k(D,x) x k(Q) and C(lambda) for the absorbed dose conversion factors of each ionization chamber.

An accidental exposure by a medical linear accelerator under construction.

A radiation accident occurred at a medical linear accelerator facility under construction in Japan. The radiation source was a 3- and 6-MV potential drop accelerator designed to produce X-rays for radiation therapy. This accelerator was also capable of producing a 5 to14-MV swept electron beam. During setting up, an operator turned on the accelerator to test the beam not knowing that a man was working on the ceiling above the accelerator. Thus, an X-ray beam was emitted against the ceiling and the man was exposed to 10-MV of X-ray irradiation. However, no obvious physical symptoms were noted. Dose estimation was made from reconstruction of the accident and clinical examinations including chromosome analysis. Mean dose of the whole body ranged from 70 to 180 mSv. Estimated dose from his right foot to hand was between180 to 900 mSv.

Contribution of Cerenkov radiation in high-energy x-ray and electron beam film dosimetry using water-substitute phantoms.

The contribution of Cerenkov radiation in high-energy film dosimetry was investigated using commercially available water-substitute phantoms. Doses were evaluated using six phantoms: RMI-451, Mix-DP, WE-211, WE-Black, PMMA and PMMA-Black. The contribution of Cerenkov radiation was determined from the shielded and unshielded evaluation doses when a bare film was inserted into the phantom in a dark room and irradiated. For both x-ray and electron beams, Cerenkov radiation produced a phantom-dependent increase in the unshielded dose when compared with the shielded dose. We also found that the darker the phantom, the smaller the contribution of Cerenkov radiation. These results suggest that for film dosimetry using bare film, the accuracy of dose evaluation may be improved by using phantoms with high opacity.

[Trial production of water substitute phantom considering the effect of light].

We have produced a novel water substitute phantom suitable for film dosimetry, while retaining the radiological property of a conventional water substitute phantom. The novel phantom excludes the effect of light, which is known to affect the accuracy of results on conventional phantoms. The effect of light was eliminated by appropriately adjusting the quantum of the carbon black to that of a conventional phantom material. Through comparison of the novel phantom with a conventional phantom it was shown that the absorbed dose determined by conventional phantom was 15% higher for 10 MV X-rays and 18% higher for an 18 MeV electron beam, attributable to the contamination of Cerenkov light. Although the net optical density of the film increased with time owing to the optical permeability of the phantom, that of the novel phantom did not vary with time. The novel phantom was therefore shown to be unaffected by such local light and by the optical transmission of the phantom.