ABSTRACT
Compared with conventional radiotherapy, FLASH radiotherapy has advantages in protecting normal tissues, while the dose rate is increased by more than 100 times. If the shielding design of the treatment room is carried out according to the existing standard, the thickness and cost of the shielding wall will be significantly increased, or even hardly to meet the requirement of the standards, resultsing in the failure of the application of FLASH radiotherapy. By investigating the domestic and foreign standards and literature, this paper analyzes the challenges brought by FLASH radiotherapy technology to the shielding design of radiotherapy treatment room in China. Dose rate control standards adopted by different countries in the shielding design are emphatically compared as well. In several countries, the average dose rate under the actual treatment conditions was considered in the shielding design. In China, the method of instantaneous dose rate taking acount of occupancy factor is adopted. However, if FLASH radiotherapy technology is applied, the requirement of instantaneous dose rate will be difficult to meet. In order to improve the high dose rate radiotherapy technology such as FLASH radiotherapy, the revision of the existing standards is advised if the authorized limits are not changed. To use the average dose rate limit within a certain period of time for control, or to raise the control standard in the case of flash radiotherapy, are also avaliable.
ABSTRACT
Objective@#To obtain the high-resolution dose distribution for the single source channel of Leksell 4C gamma knife.@*Methods@#A parallel computing platform based on the Message Passing Interface (MPI) and Monte Carlo Code MCNPX was established. The ring-shaped detector and two pre-validated variance reduction techniques (emission direction-biased sampling of source and termination of electron tracking in partial structures) were adopted to derive the high-resolution dose distribution for the single source channel of Leksell 4C gamma knife. The effect of cut-off energy for both photon and electron on the accuracy of simulation outcomes was evaluated and statistically compared.@*Results@#Compared with previous findings, the spatial resolution of the dose distribution for the single source channel obtained in this study was higher (radial resolution=0.1 mm) with less statistical error (<1%). The calculation time was acceptable (approximately 24 h). For the 4-, 8-, 14-and 18-mm variable collimators, the penumbra and full width at the half maximum (FWHM) for single side were 1.0, 1.1, 1.2, 1.3 mm and 2.2, 4.3, 7.3, 9.3 mm, respectively, which were consistent with previous studies. The difference of the simulation results was extremely small between different cut-off energy for photon (1 keV vs.10 keV). However, the simulation results significantly differ between 1 and 521 keV electronic cut-off energy.@*Conclusions@#The MCNPX parallel computing platform based on the MPI environment can be utilized to derive highly accurate dose distribution with high resolution in acceptable calculation time. The cut-off energy of the photon and electron should be cautiously set up during simulation.
ABSTRACT
Objective To discuss the effect of low-frequency pulsed electromagnetic field (ELF-PEMFs) combined with-whole-body vibration(WBV) on the bone mineral density,bone microstructure and the biological mechanics performance inhindlimb unloading osteoporosis rats.Methods Forty female 4 months aged SD rats were randomly divided into five groups:blank group,control group,ELF-PEMFs group,WBV group,low-frequency pulsed electromagnetic field combined with wholebody-vibration(ELF-PEMFs + WBV) group.The blank group was the normal control which comprise the healthy rats.The controlgroup was the disused osteoporosis model.Except for the blank group,thehind limb unloading rats were kept for six weeks.No intervention were provided to the blank group and the control group,other three groups were treated with physical therapy.The bodyweight of rats in each group was record.Bone mineral density was measured by Dual energy X-ray absorptiometry.The right femurs was analyzed by Micro-CT and the left femur was tested through a biomechanical machine.Results After 8 weeks of continuous treatment,the ELF-PEMFs group,WBV group,ELF-PEMFs+WBV group were significantly increased in weight and bonedensity (PELF-PEMFs=0.015,PWBV=0.016,PELF-PEMFs+WBV=0.007),(tELF-PEMFs=5.956,PELF-PEMFs=0.000;tWBV=6.127,PWBV=0.000;tELF-PEMFs+WBV=4.639,PELF-PVMFs+WBV=0.000).The difference was statistically significant (F=0.091,P=0.018).The ELF-PEMFs +WBV group was significantly higher in bone formation index.The items of BV/TV,Tb.N,Tb.Th and SMI in Micro-CT analysis increased,while Tb.Sp and Conn.D index decreased significantly.Trabecular bone structure of all the three groups was improved,however the ELF PEMFs +WBV group was better than the other two groups (vs.ELF-PEMF group,PBV/TV=0.041,PTb.N=0.026,PTb.Th=0.009,PConn.D=0.030,PTb.Sp=0.045,PSMI=0.032;VS.WBV group,PBv/Tv=0.018,PTb.N=0.004,PTb.Th=0.022,PConn.D=0.042,PTb.Sp=0.039,PSMI=0.049).The maximum load,energy absorption and bone stiffness index in biomechanicalperformance test were improved.The combination treatment group were significantly improved (F=0.167,P=0.038).Conclusion Low-frequencypulsed electromagnetic field combined with whole body vibration therapy can improve bone mineral density,bone microstructureand the biological mechanics performance.They have synergistic effect and the combination therapy is better than single treatment.
ABSTRACT
Magnetic resonance imaging (MRI) simulator (MRI-Sim) can provide superior images for radiotherapy.Due to the complexity of MRI technology and the safety problem caused by strong magnetic field, the acquisition and implementation of MRI simulation is more complicated than CT simulation.In order to ensure the introduction of MRI-Sim, this paper reviews the selection, installation, and acceptance test of MRI-Sim, including the selection of host and auxiliary equipment, installation site preparation, and safety precautions,as well as MRI-Sim acceptance test and commissioning.
ABSTRACT
Objective To develop whole breast irradiation with volumetric-modulated arc therapy (VMAT)-based hybrid intensity-modulated radiotherapy (IMRT) after breast conserving surgery for breast cancer,and to evaluate its value in clinical application.Methods Ten patients with breast cancer undergoing breast conserving surgery were enrolled.Two radiotherapy plans were designed based on hybrid fixed-beam IMRT/IMRT technique and hybrid VMAT/IMRT technique,respectively.One group received whole breast irradiation with a prescribed dose of 50 Gy in 25 fractions.The other group received whole breast irradiation with a prescribed dose of 50 Gy in 25 fractions,as well as simultaneous integrated boost to the tumor bed with 60 Gy in 25 fractions.The dosimetric parameters and delivery efficiency were compared between the two plans using paired t test.Results For patients treated with whole breast irradiation alone,there were no significant differences in conformity index and homogeneity index of target volume between the two plans (P=0.866,0.056);however,compared with the hybrid fixed-beam IMRT/IMRT technique,the hybrid VMAT/IMRT technique significantly increased the doses to organs at risk (OARs) and the number of monitor units (MUs) in the intensity-modulated field (P=0.000-0.050,P=0.002).For patients treated with whole breast irradiation with a simultaneous integrated boost to the tumor bed;however,the hybrid VMAT/IMRT technique significantly reduced the doses to the lung and spinal cord,number of MUs in intensity-modulated field,and delivery time compared with the hybrid fixed-beam IMRT/IMRT technique (P=0.004,0.001,0.000,0.000).Conclusions For patients treated with whole breast irradiation with a simultaneous integrated boost to the tumor bed,the hybrid VMAT/IMRT technique is highly promising for clinical application due to better OAR sparing and higher delivery efficiency.
ABSTRACT
Objective To verify the dose delivery accuracy of volumetric-modulated arc therapy plan by log-file analysis of linear accelerator that can be created when a dynamic delivery occurs.Methods Accelerator log file in binary format recorded the accelerator execution plan for each control point corresponding to the gantry angle,multi-leaf collimator leave position,cumulative machine monitor units ( MU).These information were read from the accelerator log file with Matlab7.1,then the original control points in the plan file replaced the corresponding information for the log,which generated a new plan.New plan was exported into the planning system to reculculate the dose.The volume dose histogram (DVH) and dose distribution was contrasted to determine the accuracy of the accelerator plan of implementation between two plans.Results Compared with the original plan,antry angle difference over ± 1° accounted for about 35％ of the entire arc of control points in 4 of 12 arcs and the percentage of the leave error of ±0.5 mm was about 95％.MU error of a single control point was larger,but the cumulative MU for each are was small which was located between-0.09％ to 0.11％ in the selected 12 arcs.Between the targets,the maximum dose,minimum dose,the mean dose differences were from-0.07％ to 0.42％,-0.38％ to 0.40％,0.03％ to 0.08％,respectively.The maximum dose and mean dose differences of organs at risks were located from-1.16％ to 2.51％,-1.21％ to 3.12％,respectively.Conclusions Accelerator log-file analysis to verify the VMAT plan nan be supplyed to the experimental method supplement.
ABSTRACT
Objective To evaluate the efficacy and toxicity of fractionated stereotactic body radiotherapy in treating patients with liver metastases. Methods From January 1997 to January 2007, 22 patients with liver metastases of total 33 lesions were treated with fractionated stereotactic body radiation therapy (SBRT). All patients were confirmed as unresectable and resistant to chemotherapy. The most common primaries were breast cancer in 12 patients and colorectal cancer in 5. Fifteen patients had metastases in the liver alone and 7 had concurrent metastases in other sites. Eighteen patients received one course of SBRT, and 4 patients got two courses. The median total dose was 40 (range, 30 - 60) Gy in 3 (range, 2 -6) fractions. Results All patients were followed up. The median follow up was 13.9 months (range, 5.0 -36. 4 months). The median size of the irradiated lesions was 2. 0 cm (range 1.0 -4. 3 cm) and the target volume was 3. 68 cm~3 (range 0. 45 - 77. 29 cm~3). The 1- and 2-year local control rate, overall survival rate and progression-free survival rate were 100% and 90%, 73% and 49%, 94% and 28%, respectively. No grade 3/4 SBRT related toxicities occurred. Conclusions SBRT, with high local control and tolerable complications, is an effective and safe treatment for liver metastases.
ABSTRACT
Objective To compare the characteristics of dose distribution between hypofractionated intensity modulated radiotherapy (IMRT) and hypofractionated stereotactic radiotherapy (SRT) plans in lung tumor and to select an optimal clinical approach. Methods SRT plans were designed for 16 patients with lung tumors who had received IMRT between April 2007 and April 2008. The dose distribution of target volume and normal tissues, conformal index (CI) and heteregenous index (HI) were analyzed using the dose-volume histogram (DVH) for the IMRT and SRT plans. Results The mean dose and equivalent uni-form dose of planning target volume (PTV) in IMRT were similar to those in SRT. SRT had significantly better CI and HI than IMRT (t = 2.77, P < 0.05 and t = - 4.38, P < 0.01 ). The mean lung dose of IMRT and SRT was (492.4 ±368.5) cGy and ( 310.0 ± 73.1 ) cGy, respectively ( t = 1.68, P > 0.05 ). The lung V20 of IMRT and SRT was 6.9% ± 2.1% and 4.2%± 1.9%, respectively ( t = 3.30, P < 0.01 ). No sig-nificant differences were found in the mean dose to the heart or the spinal cord between IMRT and SRT. Conclusions When PTV is less than 57 cm3 or the long diameter of tumor is less than 4.7 cm, hypofrac-tionated SRT has similar dose distribution to hypofractionated IMRT, while the lung dose was lower in the former.
ABSTRACT
ObjectiveTo investigate the etiology, exacerbating factors and outcome of geriatric patients with acute renal failure (ARF) in emergency and critical internal medicine. MethodsClinical features of elderly inpatients with ARF who were diagnosed in internal medicine of our hospital during the past 10 years were retrospectively analyzed. Patients were divided into community-acquired ARF (CA-AFR) group and hospital-acquired ARF (HA-ARF) group. Comparisons between CA-ARF group and HA-ARF group, and between elderly patients and non-elderly patients with ARF in internal medicine were performed. ResultsAmong 381 elderly ARF patients in internal medicine, there were 218 (57.2%) CA-ARF patients and 163 (42.8%) HA-ARF patients. Most of the HA-ARF patients (153 cases) were distributed in medical intensive care. Compared with CA-ARF group, patients in HA-ARF group were older, with more underlying diseases, a higher ratio of infections and/or heart failure and more severe acute renal failure. Infection and heart failure/severe myocardial isehemia were the major exacerbating factors for HA-ARF. Of the 163 patients with HA-ARF, 146 patients died and 17 patients survived. Patients in the death group had more underlying diseases, a higher ratio of severe infections and heart failure/severe myocardial ischemia, a higher ratio of cases with multiple organ dysfunction syndrome(MODS) and a higher score of APACHE Ⅱ.When compared with non-elderly patients with ARF, the elderly patients had a higher proportion ofHA-ARF, a higher ratio of MODS, a higher score of APACHEⅡ and a higher mortality of ARF.ConclusionsThe elderly critical patients are susceptible to HA-ARF with more chronic underlying diseases. Infection and heart failure/severe myocardial ischemia are the major exacerbating factors.The prognosis depends on the treatment of predisposing diseases and removal of exacerbating factors.
ABSTRACT
Objective To improve the recognition of sarcoidosis in elderly patients.Methods Clinical data of 13 elderly patients with sarcoidosis were retrospectively analyzed.Results There were three cases without symptom and five cases with intra-pulmonary and extra-pulmonary manifestations respectively.Eight cases had atypical radiological appearances and five cases showed inflammatory changes through bronchofibercopy.There were three cases with increased percentage of lymphocytes and high ratio of CD4/CD8 in bronchoalveolar lavage fluid (BALF) respectively.Seven cases were diagnosed through biopsy.And the symptoms of all thirteen patients diminished after treatmeit.Conclusions The clinical symptom and radiologieal manifestation of sarcoidosis in elderly patients are varied and usually atypical.The diagnosis should be based on comprehensive analysis including clinical manifestation and examination.The elderly patients with indication of treatment can be given corticosteroid therapy with close clinical monitoring.
ABSTRACT
To investigate plasma N-terminal pro-brain natriuretic peptide (NT-BNP) levels and to assess their clinical significance in elderly patients with isolated diastolic dysfunction. Methods Plasma NT-BNP level were measured by electrochemiluminescence immunoassay in 34 symptomatic patients (Group 1), 34 asymptomatic patients (Group 2) with isolated diastolic dysfunction, and in 16elderly healthy subjects (control group, Group 3), serving controls. Colored Doppler echocardiography was performed to evaluate the patients' cardiac structures and functions. Results The plasma NT-BNP level in Group 1 was significantly higher than those in Group 2 and Group 3 and increased with the severity of heart failure. There was no significant difference of plasma NT-BNP levels between Group 2 and Group 3 (p＞0.05). A NT-BNP value of 102.75 pg/mL showed a sensitivity of 88.2%, a specificity of 87.5%, and an accuracy of 88.1% for diagnosing diastolic dysfunction. Patients with restrictive filling pattern on echocardiography had higher NTBNP levels than those of impaired relaxation pattern (1961.2±304.9 versus 460. 1±92.7pg/mL, p＜0.001). Conclusion The elevation of plasma NT-BNP level in elderly patients with isolated diastolic dysfunction correlates with the severity of their diastolic abnormalities.The level of plasma NT-BNP has an important clinical value in the diagnosis of elderly patients with isolated diastolic dysfunction.
ABSTRACT
Objective To investigate the relative relationship between the degrees of seriousness of obstructive sleep apnea hypopnea syndrome and the variation of blood pressure in exercise Methods 49 patients with obstructive sleep apnea hypopnea syndrome without using anti hypertension drugs, were used as our objectives We performed the exercise test with bicycle like instrument During the test, we measured the blood pressure, plasma lactic acid and arterial blood gases Then we analysed the blood pressure in exercise, BMI, clinical symptoms and the mean of the lowest SpO2 measured by over night polysomnography Results The variation of blood pressure in exercise was related to the clinical symptoms and the mean of the lowest SpO2, but not to the BMI Conclusion The degrees of seriousness of obstructive sleep apnea hypopnea syndrome may be related to the elevation of blood pressure