[en] Background and purpose: The potential risk of prolongation of treatment time in cervical cancer has been reported for many low-dose rate (LDR) studies, with an estimated loss of local control ranging from 0.3 to 1.6% per day of treatment prolongation. Since the treatment schedule for fractionated high-dose rate intracavitary brachytherapy (HDRICB) is not directly comparable with that for low-dose rate studies, this report aims to evaluate the adverse effect of treatment prolongation specifically for cervical cancer treated with HDRICB. Material and methods: From September 1992 to December 1997, 257 patients diagnosed with uterine cervical cancer (35 Ib, 26 IIa, 122 IIb, 10 IIIa, 57 IIIb, 7 IVa), who underwent external radiotherapy combined with between two and four courses of HDRICB and a minimum of 3 years of follow-up (median 57 months), were analyzed. Treatment consisted of irradiation of the whole pelvis with 44-45 Gy consisting of 22-25 fractions by 5 weeks, with the dose boosted to 54-58 Gy (with central shielding) for patients diagnosed as FIGO stage IIb-IVa bilateral parametrial disease. HDRICB was performed using an Ir-192 remote afterloading technique at 1-week intervals. The standard prescribed dose for each course of HDRICB was 7.2 Gy to point A for three insertions (before July 1995), or 6.0 Gy to point A for four insertions (after July 1995). Total prescribed point A doses (external beam radiotherapy+HDRICB) ranged from 58 to 71.6 Gy (median, 65.6 Gy) for stage IB-IIA, while analogous dosage for larger lesions (stage IIb-IVa) ranged from 59 to 75.6 Gy (median, 65.6 Gy). Kaplan-Meier and multivariate analyses were used to test the effect of treatment time on pelvic control rate (PCR) and cause-specific survival (CSS) at 5 years. Results: Median treatment time was 63 days. For all stages of disease, the 5-year CSS and PCR were significantly different comparing treatment times of less than and greater than or equal to 63 days [83% and 65% (P=0.004], 93% and 83% (P=0.02), respectively]. These associations were also significant for stage Ib/IIa [97% and 79% (P=0.01), and 100% and 87% (P=0.02), respectively), but not for stage IIb [75% and 72% (P=0.79), and 93% and 87% (P=0.83), respectively] or stage III [66% and 49% (P=0.2), and 83% and 72% (P=0.21), respectively]. Multivariate analysis identified three prognostic factors for CSS, stage (P<0.001), tumor response to external RT (P=0.001), and overall treatment time (OTT; P=0.006). Prognostic factors for pelvic failure were stage (P<0.001), tumor response to external RT (P=0.001), and OTT (P=0.03). Prolongation of treatment time resulted in a daily decrease in pelvic control rate of 0.67% overall, and 0.43% for stage Ib-IIa, 0.57% for stage IIb, and 0.73% for stage III patients. Conclusion: Analysis of the data from the current study demonstrates that the adverse effect of treatment prolongation was observed later in the treatment course for the high-dose rate (HDR) series compared to the LDR analog, however, treatment-time prolongation still negatively influenced the cause-specific survival and pelvic control rate for both dosage groups

[en] An on-line neutron moisture measuring system for discontinuous moving materials (such as ore) mounted over a conveyor is described. A gamma density gauge was used to provide density-corrected direct readout of water content in terms of weight percentage. Three groups of measuring signals coming from a slow neutron detector, a gamma ray detector and an electronic weigh system were together fed into a PC computer through a count card to realize data processing, recording and displaying. the prompt and average moisture content, as well as total material, pure dry material and water passing the measuring point at a certain time interval can be plotted or tabulated

[en] The neutron transmission of a T(d,n)⁴He fast neutron source shielded with iron of different thickness is simulated using Monte Carlo method. The pole of (n,2n) reaction on the slowing down of fast neutrons is studied in detail, and it caused accumulation of the lower energy neutron. The reflected neutrons entering into the shielding again are considered in the analysis. The reasonable thicknesses of the multi-layer shielding are recommended and they are in agreement with the data published

[en] The beam characteristic of 14 MeV neutron therapy facility is described, which includes neutron energy spectrum, interaction between fast neutron and organism, relation between absorption dose and depth, relation between absorption dose and biological effect and so on. The properties of this facility with other type facility are compared

[en] This study aimed to investigate the survival and complications of patients who received adjuvant radiotherapy for invasive cervical cancer following inadvertent simple hysterectomy. From September 1992 through to December 1998, 54 patients who had received simple hysterectomies for benign lesions, but were incidentally found with invasive carcinoma of the cervix in the surgical specimen, were referred to our department for postoperative irradiation. They were categorized into two groups according to pathological findings. Group A consisted of 25 patients whose specimen showed microinvasion alone, with the depth of stromal invasion <5 mm. Group B consisted of 29 patients whose pathological findings included deep stromal invasion, tumor emboli in cervix, lymphovascular permeation, positive or close resection margin, endometrial or myometrial invasion and vaginal involvement. After external beam irradiation dose of 44 Gy in 22 fractions over 4-5 weeks to the whole pelvis, the radiation field was reduced to true pelvis for a further 10 Gy in five fractions. Brachytherapy was performed using an Ir-192 remote after-loading technique for 1-2 courses. The prescribed dose for each treatment was 7.5 Gy to the vaginal surface. A retrospective analysis was conducted to compare radiation-therapy outcomes for these 54 patients. After 37-102 months of follow-up (median, 58 months), 47 patients were alive without evidence of disease; five patients in Group B died of the disease (three with distant metastasis, one with local relapse, one with both). Two patients died of other concurrent diseases. The 5-year actuarial survival (AS) and disease-free survival (DFS) rates for all patients were 88 and 90%, respectively. The respective 5-year AS and DFS rates for Group A/B were 95/82% (P=0.07) and 100/83% (P=0.03). Ten patients (18.5%) developed Radiation Therapy Oncology Group (RTOG) Grade 1-4 rectal complications. Five patients (9.3%) developed RTOG Grade 3-4 bladder complications. Eight patients (14.8%) had RTOG Grade 1-4 non-rectal gastrointestinal complications. For patients with invasive cervical cancer following inadvertent simple hysterectomy, external beam radiotherapy combined with one or two fractions of intravaginal brachytherapy could achieve satisfactory disease control. It is recommended to select a high-risk group for intensive adjuvant treatment. Further optimization of the irradiation strategy is also imperative to decrease the incidence of complications. (author)

[en] A design of the rotating target system used in an intense neutron generator is described. By simulating the temperature of target disc, some operating parameters of the intense neutron generator are also obtained. (authors)

[en] The author introduces the principle of PRC supply which gives high frequency large power sinusoidal wave. The parameters design method and the control system are given. The simulation and experimental results verify the effectiveness of this method

[en] The experimental values of γ ray linear absorption coefficient μ_exp under various experimental conditions are calculated. Various μ_exp values which vary with the thickness and moisture of matter in bulk under the conditions of wide and narrow γ ray beams are studied, and the measuring method of the thickness of matter in bulk is given. The μ_exp is compared with the μ_th which is obtained by theoretical calculation. In addition, the variation of the buildup factor B with the experimental conditions, such as the thickness and the moisture of matter in bulk, is studied

[en] A technology alteration was accomplished for the neutron generstor at Lanzhou University. A 2.5 kHz intermediate frequency power supplies and a Cockroft-Walto circuit with a maximum votage of 320 kV were developed. A control stand using computer was developed. The parameters of instrumentation and controls between the HV terminal and the ground were delivered by an optical fiber system. The key assemblys of duoplasmatron ion source were improved. The life-time of the filament is greater than 50 h. A associated particles measurement system was applied to monitor neutron yield. Preliminary test results show that the D beam current at the target is greater than 2 mA and the beam dot is about Φ20 mm. D-T and D-D neutron yields are greater than 1x10⁹ s^-1 and 1x10⁸ s^-1, respectively. A rotating target system is still in being developed stages. The goal is that the D beam current at the target is greater than 10 mA. D-T and D-D neutron yields are greater than 1 x 10¹² s^-1 and 1 x 10¹⁰ s^-1, respectively. (authors)

[en] This study aimed to assess the dose-rate effect of ¹⁹²Ir source activity on pelvic control and late complications following high-dose-rate intracavitary brachytherapy (HDRICB) for cervical cancer patients. Two hundred and twelve patients were enrolled in this study. They were treated with external beam radiotherapy to the pelvis, after which HDRICB was performed using ¹⁹²Ir remote after-loading at 1-week intervals for 4 or 5 sessions. Source activity was defined as the average of source activity in each HDRICB session. Dose-rate effect was analyzed after stratification of stage and biologically effective dose (BED). The 5-year pelvic relapse-free survival was 88% for all patients. Forty-two patients developed late rectal complications (13 grade 1, 23 grade 2, 6 grade 3-4). Twenty-seven patients had grade 2 and higher late bladder complications (14 grade 2, 13 grade 3-4). There was no dose-rate effect on pelvic control or complications when source activity was stratified. Multivariate analysis demonstrated a high risk of grade 2 and higher rectal sequelae in patients whose rectal BED≥110 Gy₃ (p=0.039, hazard ratio 2.05). The high risk factors for grade 2 and higher bladder complications were a bladder BED≥100 Gy₃ (p=0.03, hazard ratio 4.37). This study demonstrated no dose-rate effect of ¹⁹²Ir source in HDRICB for cervical cancer in terms of pelvic control or radiation injuries. Careful monitoring of the BED values for rectum and bladder is a scrutinizing factor for minimizing late sequelae. (author)