Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.3.1.51 (HDR)
 605 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Inoue applicator (3 channels) for endometrial cancer with a microSelectron-HDR was modified to enable both intrauterine and vaginal treatments to be done at the same time. The applicator is described together with a case report.
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PMID:Modified Inoue applicator for endometrial brachytherapy. 772 22

A modified ovoid applicator for intracavitary radiotherapy was developed for Japanese and other Asian women. It has more variations of smaller sized ovoids than the original rigid standard applicator of the Selectron-MDR and microSelectron-HDR. In addition, application of the ovoid pair and tandem flange is easy due to the flat surface of the inner aspect of the ovoid pairs, which prevents slippage of the ovoids and flange. The applicator is described together with source loading and dose distribution.
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PMID:Modified ovoid applicator for intracavitary radiation therapy with a Selectron-MDR or microSelectron-HDR. 772 23

Commercially available ovoid tubes for gynecological applications used in conjunction with the microSelectron-HDR (Nucletron International B.V., Waardegelder 1, 3905 TH Veenendaal, The Netherlands) for 192Ir sources, allow for shielding. Publications concerning the transmission properties of these 4.5-mm thick stainless steel (AISI number 303/304) shielding segments are scarce and not compatible for implementation in treatment planning. Therefore the effect of shielding on dose distribution is unknown. The effective transmission factor has been measured and implemented in the planning computations. Screening efficacy was evaluated on 20 actual treatment plans, analyzing dose reduction to critical tissue and comparing dose distribution in planes relevant for this particular application. Due to high transmission (effective transmission factor = 0.85), stainless steel screening segments only provide low, local dose reductions of maximum 15%. A new approach with regard to optimization and source configuration is needed to reduce dose to vulnerable tissue, exploiting the screening segments to a maximum extent. Better shielding, especially at the midline (plane bisecting the ovoids) could be expected by using shielding segments with other geometrical characteristics.
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PMID:On the determination of the effective transmission factor for stainless steel ovoid shielding segments and estimation of their shielding efficacy for the clinical situation. 789 27

The protraction of total body irradiation (TBI) to a continuous low dose-rate has been investigated for its effect on donor marrow engraftment in murine bone marrow transplant (BMT) models of varying histocompatibility. Three different BMT combinations were used: syngeneic [B6-Gpi-1a-->B6-Gpi-1b], H-2 compatible allogeneic [BALB.B (H-2b)-->B6 (H-2b)] and H-2 mismatched allogeneic [BALB/c (H-2d)-->B6 (H-2b)]. TBI was delivered over a range of doses at either a high (HDR, 40 cGy/min) or low (LDR, 2 cGy/min) dose rate followed by infusion of 10(7) bone marrow cells from syngeneic or allogeneic donors. The level of donor (Gpi-1a) engraftment was determined from blood Gpi-typing at different times after TBI and BMT. Radiation dose-response relationships corresponding to long-term haemopoietic engraftment at 20 weeks showed a dose-sparing effect of LDR that became more prominent with increasing genetic disparity between donor and host. For fully allogeneic (H-2 incompatible) BMT, a dose as high as 16Gy LDR was still not sufficient for achieving chimerism in all recipients. In many cases allogeneic BMT gave transient blood chimerism enabling the recipient to survive the acute effects of high dose TBI with full long-term repopulation from surviving stem cells of the host. Radiation cell survival curves were obtained for the frequency of alloreactive precursors of proliferating T-lymphocytes (pPTL) remaining in the spleen at 1 day after TBI. A radiation dose-sparing effect of LDR was also found for pPTL depletion. These data suggest that radiation damage repair during LDR irradiation in an immunocyte target cell population is mainly responsible for enhanced graft rejection thus rendering protracted TBI less effective for application in clinical allogeneic BMT.
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PMID:Compromising effect of low dose-rate total body irradiation on allogeneic bone marrow engraftment. 790 44

We investigated the effects of gamma-ray exposures at high dose-rate (HDR, 23.2 Gy/min) and low dose-rate (LDR, 0.47 Gy/min) on survival and the induction of DNA double-strand breaks (dsb) in a diploid wild-type (D7) and the repair-deficient mutant strain rad52/rad52 of Saccharomyces cerevisiae. Analysis by pulsed-field gel electrophoresis (PFGE) using a contour homogeneous electric field apparatus revealed that, at HDR, in the range 0-400 Gy, dsb are induced as a linear function of gamma-ray dose. Liquid holding recovery in non-nutrient medium (LHR) for 48 h of wild-type cells treated at HDR, significantly increased survival and reduced the yield of dsb. Such changes did not occur in rad52/rad52 cells defective in the repair of dsb. Thus, in gamma-irradiated wild-type cells, an efficient repair of dsb is taking place during LHR. Treatments of wild-type cells at LDR resulted in higher survival and an approximately two-fold lower yield of dsb than at HDR. Such a dose-rate effect was absent in rad52/rad52 cells suggesting that, in wild-type cells during LDR exposures, significant amounts of dsb can be repaired. This repair could be very much accentuated by 48-h LHR of wild-type cells treated at LDR. The relationship observed between gamma-ray survival and dsb repair clearly indicates that increases in survival of wild-type cells, during LDR as compared with HDR exposures and after LHR, are strongly related to the repair of dsb.
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PMID:Repair of DNA double-strand breaks induced in Saccharomyces cerevisiae using different gamma-ray dose-rates: a pulsed-field gel electrophoresis analysis. 790 9

The method for determination of the active pellets' position in the Selectron vaginal tube is shown. A special steel cap shielding with narrow window mounted above the Therados RFA-3 semiconductor detector was constructed. By scanning along the Selectron line vaginal tube in air and water, for an appropriate distance with mild dose gradient, the actual active pellets' positions can be determined. The resolution was higher during scanning in the air than in water. The minimum number of tries for checking the whole system depends on the total number of pellet sources in the main safe, and the number of active pellets used. Advantages of this method, compared to other conventional methods for determination of the Selectron-HDR source positions, are associated with high resolution and capability of repetition without movement of the tube during checking procedure.
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PMID:Determination of active pellets' position in the selectron-HDR vaginal tube using a therados RFA-3 water phantom system. 791 75

Calibrating Cs-137 and Ir-192 brachytherapy sources in a solid phantom has the advantage over calibration in air that the positioning of the sources is very accurate and straightforward. In order to determine the air kerma rate at the point of measurement it is, however, necessary to take the replacement of the phantom material by the ionization chamber into account. The replacement correction factor pr of a Farmer-type ionization chamber has been determined for a few types of 137Cs and 192Ir sources at a source to chamber distance of 5 cm. For spherical 137Cs sources the replacement correction was determined by means of measurements with chambers with decreasing diameter and length. Additional measurements were performed for some other source configurations in order to determine pr for 137Cs micro-seed trains. For an 192Ir-HDR source pr was determined for a source chamber configuration equal to that for spherical 137Cs sources by comparing measurements in-phantom with measurements free in-air. Finally, measurements were performed with source configurations that yielded pr values for 192Ir seed trains and 192Ir wires. The resulting replacement correction factors are all within +/- 2% of unity. It can be concluded that, although the dose nonuniformity over the chamber volume caused by each source is rather substantial, the replacement correction that has to be applied is rather small.
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PMID:Replacement corrections of a Farmer-type ionization chamber for the calibration of Cs-137 and Ir-192 sources in a solid phantom. 804

Our early experience using microSelectron HDR to treat cervical cancer patients at Osaka University Hospital is presented. From June 1991 through December 1992, a total of 20 patients (stage Ib, 6; stage IIa, 2; stage IIb, 5; stage IIIb, 6 and stage IVa, 1) with previously untreated invasive uterine cervical cancer and intact uterus were treated with high-dose rate intracavitary therapy administered with a microSelectron. For the treatment, a standard rigid applicator made of stainless steel for a microSelectron was used. Twenty to 30 Gy of external irradiation was administered to the whole pelvic field and 30 to 20 Gy to the central shielded field (total 50 Gy/5-6 weeks) for patients in stage II-IVa. For stage Ib, 40 Gy was delivered to the central shielded field. The 192Ir source had an activity of 370 GBq as of the measuring time. Source loading corresponded to the Manchester System for cervical cancer. Thirty-two or 30 Gy was administered at point A in four fractions over four weeks of intracavitary irradiation. Early primary tumor responses for all patients were complete. There have been two local recurrences in stage IIb and IIIb patients. Three patients in stages Ib, IIb, and IIIb developed para-aortic lymph node metastases, and two of them died from generalized metastasis. No acute radiation injury has been observed. One patient in stage IIb developed subileus five months after irradiation. From our early experience, it is concluded that microSelectron HDR can be used for cervical cancer patients as safely and effectively as our previously used high-dose rate machine.
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PMID:High-dose rate intracavitary therapy for cervical cancer with a microSelectron: a preliminary report. 815 67

Thirteen radiotherapy departments in The Netherlands and Belgium participated in an intercomparison of the calibration procedures in use for the quality control of iridium-192 high dose rate sources. A measuring device from 1 of the departments was taken to the 12 other participants, where 1-3 sources were measured by both the local and the visiting physicist's team. Also, 1 192Ir HDR reference source was taken to 7 other--Dutch--departments to serve as a stability check of the measuring device. The results of the local calibration were compared with the values obtained by the visiting team. A mean deviation of +1.3% was found in 19 observations, with values ranging from -0.4% to +3.0%. In total, 16 sources were checked. The measured reference air kerma rate of the available sources was compared with the value stated on the source calibration certificate: the values on the certificate were on the average +1.8% higher than the measured values, ranging from -4.2% to +6.8%. In 1 instance the reference source was also measured by The Netherlands Measurements Institute (NMI), the national standards laboratory in The Netherlands. A good agreement was found between the NMI calibration and the reference air kerma rate determined with the measuring device used in this project.
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PMID:Intercomparison of calibration procedures for Ir-192 HDR sources in The Netherlands and Belgium. 818 14

From Jan. 1981 to Dec. 1986, 1053 patients with cervical cancer were treated with Cobalt-60 high dose-rate afterloading therapy (Ralstron-20B). All cases have been followed up over 5 years. This paper analysed the 5-year survival rates and complications of cervical carcinoma treated with high dose-rate afterloading therapy. According to the point A dosage, the whole series was divided into four groups: group A 141 patients (65Gy/6 wks), group B 130 patients (60Gy/6 wks), group C 243 patients (55Gy/6 wks) and group D 539 patients (50Gy/5 wks). The dosage of external irradiation in four groups was the same. The 5-year survival rates of the four groups were little better than that of the conventional radium-treated group. The incidence of late rectal and bladder reactions in group D was lower than that in group A B C or radium-treated group. These results indicate that the point A dosage of 50Gy/5 wks (dose rate about 100cGy/min) is suitable in HDR intracavitary afterloading therapy of cervical cancer.
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PMID:[Long-term results of 60Co HDR after-loading in the treatment of cervical cancer]. 822 19


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