[en] Our recent research has shown that the main technical difficulties employing field emission arrays (FEAs) in electron guns of microwave power amplifiers could be attributed to the FEAs' insufficient emission current density, emission stability, and the defocusing of the electron beams. The investigation of these parameters and measures for performance improvement are described in this paper. The conditions for obtaining a current density of several A/cm² and a stable working point are studied and realized. An electron gun with the FEAs for traveling wave tubes (TWTs) was designed and simulated, which allows focusing of a 100 mA electron beam with a 30 deg. divergence angle

[en] Using local irradiation method, the migration principle of stromal progenitors (CFU-F) of the bone marrow in the circulating blood of mice was studied. CFU-F could be found in the circulating blood in 6 hours after a local irradiation at a dosage of 20 Gy, reaching the first peak in 24 hours. There was then a decrease of CFU-F, with a second peak of CFU-F exhibiting in 96 hours after irradiation. Then, CFU-F descended gradually and disappeared on the sixth day after the second peak. CFU-F were not found in the cirulatory blood under normal conditions or after a high dosage of systemic irradiation, because in the latter case the stromal progenitors in the bone marrow were heavily damaged so that their regeneration could no longer take place. It is obviously seen that CFU-F migration takes place from the shielded to the exposed places in order to promote hemopoietic regeneration. The stromal cell migration is a kind of stress in nature and some regularity in pattern exists

[en] Objective: To study the dosimetric comparison of split field and fixed jaw techniques for large IMRT target volumes in the rectum cancer. Methods: CT images of fifteen patients with rectum malignancies and regional target volumes were transferred into Eclipse planning system. SFT plan and FJT plan were performed on an Eclipse TPS using beam data generated for linear accelerator. A standard beam arrangement consisting of seven coplanar fields was used in both techniques.Institutional dose-volume constraints used in rectum cancer were kept the same for both techniques. Target and organs at risk were evaluated. Results: PTV₉₅ in FJT plan coverage was lower (t=-2.24, P<0.05). D_mean in FJT plan was increased (t=2.54, P<0.05), but D_max was not different. HI in FJT plan became inferior (t=3.09, P<0.05), while CI was not different. There was no difference in dose distribution among bladder, femoral head and cauda equina. The value of V₅ of small intestine increased in FJT plan (t=4.76, P<0.05), and the values of V₂₀ and V₅₀ of bone marrow were better than those in SFT plan (t=-2.66, -3.36, P<0.05), while D_max was higher than that in SFT plan (t=3.30, P<0.05). The value of V₂₀ of body was higher in FJT plan than that in SFT plan (t=2.48, P<0.05). The number of MU was significantly lower in FJT plan than that in SFT plan (t=-9.38, P<0.05). The average segments in FJT plan decreased by 39.4% compared with SFT plan (t=-6.46, P<0.05). Verification rate in FJT plan group was better than that in SFT plan (t=10.46, P<0.05), and the treatment time was shortened from 12 to 6 min. Conclusions: Compared to SFT technique, patients with rectal cancer who were treated with FJT could get better dose of target and organs, which can meet the clinical treatment requirements. The technique could shorten the treatment time and reduce the treatment MU. It also could increase the number of patients to be treated, reduce their waiting time and reduce the difficulty of QA. (authors)

[en] Para-aortic lymph node metastasis is one of the main prognostic factors for cervical cancer. The para-aortic lymph node metastatic rate increases with the progression of disease stage. Therefore, an important approach for improving the prognosis in cervical cancer patients with para-aortic lymph node metastasis is early diagnosis followed by proper therapy, as well as prophylactic para-aortic irradiation in high-risk patients. (authors)

[en] In recent years, along with the clinical exploration and application of magnetic resonance simulation localization and radiotherapy equipment, more and more studies have been performed to focus on the excellent ability of MRI in identifying soft tissues, aiming to explore the potential application value of magnetic resonance imaging (MRI) in radiotherapy for breast cancer patients. In this article, the research progress on MRI in radiotherapy after breast-conserving surgery was reviewed to provide certain ideas and references for subsequent research. (authors)

[en] Objective: To assess the coverage of pelvic lymph nodes in conventional pelvic radiation for cervical cancer. Methods: Between Jan. 2005 and Mar. 2008, 56 patients with cervical cancer receiving radiotherapy were enrolled in this study. The common iliac, external and internal iliac lymph nodes were delineated on the planning CT images of digital reconstruction. Anterior-posterior fields (AP): superior border were 15 mm lateral to The bone pelvic. Lateral fields (LAT): anterior border was anterior to the symphysis pubis; posterior border was the posterior border of the sacrum. Distances were measured between the bifurcation of the aorta and superior border, between the bifurcation of the common iliac artery and lateral border of the AP field, and between the external iliac artery and anterior border of the LAT field. The radiation fields were defined as adequate, undersize and oversize when the distances were 15-20 mm, less than 15 mm and more than 20 mm, respectively. Results: Superiorly, the common iliac lymph nodes were missed in 98% patients, oversize fields found in 2%, and at least one side of the internal or external iliac lymph nodes missed in 14%. Laterally, the external iliac lymph nodes were missed in 41% patients, and oversize fields found in 11%. Anteriorly, the external iliac lymph nodes were missed in 43% patients, and oversize fields found in 25%. Conclusions: Conventional pelvic radiation fields according to the bone markers may miss the pelvic lymph nodes, especially the internal iliac lymph nodes. The target nodes should be delineated individually based on CT or MRI to guarantee their coverage in radiotherapy. (authors)

[en] Objective: To study the image quality control system to ensure that equipment meet clinical needs. Methods: It was scanning the Catphan_5_0_4 phantom with models of high quality head, standard dose head and pelvis, we could get the results of CT numbers linearity, uniformity, spatial resolution, contrast resolution. Using T test to compare different scanning technique results. Results: The standard dose head scanning technique was better than the pelvis scanning technique in CT numbers linearity test, and gets the best result in uniformity test. The result of CT numbers uniformity was higher in the standard dose head scanning than the high quality head and the pelvis scanning (9.7 ±3.9 vs. 17.9 ±5.3, P=0.00 and 9.5 ± 4.0 vs. 31.1 ± 5.7, P=0.00). The result of contrast resolution was higher in the pelvis scanning than the high quality head and the pelvis scanning (5.6 ± 0.1 vs. 1.3 ± 0.5, P=0.00 and 6.0 ± 1.0 vs. 1.3 ± 0.5, P=0.00). The result of spatial linear distance was very accurate,the range was 4.98 -5.06 cm. Conclusions: The results of spatial linearity test are stable and accuracy, but CT numbers linearity and uniformity test are affected by the scanning technique significantly for device. To spatial resolution test and contrast resolution test, we need to set the standard and tolerance according to each linear accelerator specialty. (authors)

[en] Objective: To study the dosimetry characteristics of 9 equal spaced fields and 9 fields with beam angle optimization (BAO) process for cervix uteri. Methods: 12 cervix uteri cancer patients CT Images were transferred into Eclipse planning system. Each patient, the 9 equal spaced fields and 9 fields by BAO process were IMRT plan designed with the same CT image. Make a evaluation of dose distribution for target volume and OARs, and paired t test for them. Results: Comparing to 9 equal spaced fields IMRT plan, the quality of 9 fields IMRT plan with BAO process the the PTV V_95% was 99.31% vs 99.42%, P = 0.020, at the same time V₁₀₅%, V_110%, D_max, D_mean got 60.54% vs 47.92%, P = 0.013; 7.14% vs 0.37%, P = 0.000; 56.62 Gy vs 55.47 Gy, P = 0.000; 53.29 Gy vs 52.72 Gy, P = 0.000, the CI and HI was 0.85 vs 0.89, P = 0.000; 0.10 vs 0.13, P = 0.000. For organs at risk, bladder was increased by 4.7% (P = 0.013); the of rectum was 0.5 Gy higher (P = 0.004); the small bowels DVH showed that and D_max increased by 0.6% (F = 0.015) and 1.4 Gy (P = 0.000), D_mean of bone marrow were raised separately by 1.3 Gy (P = 0.000), the spinal cord's dose D_{0.1 cm³} was also increased by 2.0 Gy (P = 0.000). Conclusion: The quality of 9 equal spaced fields IMRT plan will be better than those achieved by BAO process optimized plans. (authors)

[en] Objective: To investigate the anatomical changes and dose variation of rectum during radiotherapy in patients with cervical cancer. Methods: Ten patients with cervical cancer underwent intensity-modulated radiotherapy using online cone beam computed tomography (CBCT) before each fraction. Rectum was contoured on each CBCT and projected onto the planning CT to analyze the changes of the rectal volume and position. The rectal volume receiving ≥ 45 Gy (V₄₅) was evaluated accordingly. Results: 227 CBCT images in 10 patients were collected. The rectal volume changed from (35.0 ± 7.3)cm³ to (97.7±14.7)cm³. The shift of rectal center was (0.14 ±0.06)cm in left and right direction, (0.24±0.10)cm in anterior and posterior direction, and (0.55±0.28)cm in superior and inferior direction. The V₄₅ of rectum varied from (9.19±2.46)% to (60.54 ±11.67)%. In 7 of the 10 patients,rectal volume and V₄₅ of the rectum had significant positive correlation (r =0.582 - 0.743, all P < 0.01). Among the 227 images, the V₄₅ of rectum was ≤50% in 68 images (30.0%). Conclusions: Significant changes in rectal volume and position occurred during fractionated radiotherapy in patients with cervical cancer, which results in variations in the dose rectum received. For most patients, rectal volume and the V₄₅ of rectum had significant positive correlation. (authors)

[en] Objective: To evaluate the feasibility and significance of CT image-based three-dimensional (3D) brachytherapy for cervical cancer. Methods: Three-dimensional (3D) plan and two-dimensional (2D) plan were designed for 55 CT images of brachytherapy from 12 cervical cancer patients who received radical radiotherapy in 2013. Dosimetric comparison was performed between the 3D plan and 2D plan, and paired t-test, Wilcoxon signed rank test, Pearson correlation analysis, and Spearman correlation analysis were performed. Results: A point dose, D₉₀, V₁₀₀, CI, and CI' in 3D plan were higher than those in 2D plan (F = 0.015, 0.016, 0.000, 0.000, 0.000). Bladder point dose, rectal point dose, and rectal D_{2 cm³} in 3D plan were slightly higher than those in 2D plan, but hot spot dose was significantly reduced in 3D plan (P = 0.140, 0.123, 0.214). Bladder D_{2 cm³} was significantly higher than bladder point dose (P = 0.000). Sigmoid colon D_{2 cm³} was more correlated with the average doses of the three highest rectal points than rectal D_{2 cm³} (r = 0.314, 0.630, P = 0.000, 0.000). V₁₀₀ showed a linear relationship with high-risk CTV (r = 0.981, P = 0.000). Bladder D_{2 cm³} was higher than 430 cGy when the bladder volume was more than 80 cm³; small intestinal D_{2 cm³} did not change significantly when the bladder volume was less than 115 cm³, but decreased significantly once the volume exceeded the value. Conclusions: Compared with the traditional 2D plan, the 3D plan for CT image-based cervical cancer brachytherapy significantly increases the target coverage and conformity index, but does not significantly increase the doses to organs at risk. Point dose evaluation is confirmed to be inaccurate. The doses to the bladder, rectum, and small intestine can be adjusted by controlling the bladder volume. (authors)