The dose verification methods in advanced radiotherapy are elaborated in this paper. The usage and application results for various dosimeters in dose verification are explained. As a theoretical method, Monte Carlo simulation, which has been developed greatly in recent years based on the technical progress in computer science, can be also used in dose verification with unique advantages. On the other hand, the principle of dose verification on proton and heavy-ion therapy is discussed briefly. Finally, the evaluation criteria for verification and the future development for dose verification are presented.
Humans ; Monte Carlo Method ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted

BACKGROUND: It is demonstrated that bone marrow stem cells (BMSCs) can generate neurosphere structures, which is similar to cloning sphere of neuron-specific enolase (NSE), in a specially induced system in vitro; therefore, BMSCs draw more and more attention as seed cells to repair central nerve injury.OBJECTIVE: To investigate the differentiation from BMSCs into neuron-like calls induced by fetal spinal cord tissue.DESIGN: Observational study.SETTING: Department of Spine Surgery, Second People's Hospital of Shenzhen.MATERIALS: SD rats (16 pregnant days old and 2 months old) were provided by Animal Center, Tongji Medical College,Huazhong University of Science and Technology. Single antibody of NSE, multi-antibody of glial fibrillary acidic protein (GFAP) and single antibody of neurofilament (NF200) were provided by Wuhan Boster Company.METHODS: The experiment was carried out in Immune Opening Laboratory and Central Laboratory, Basic Medical Department, Tongji Medical College, Huazhong University of Science and Technology in September 2006. Bones of lower extremities of rats were collected to centrifuge BMSCs. Fetal spinal cord tissue homogenate was extracted from 16 pregnant days old rats to make inducing solution and induce differentiation of BMSCs. Otherwise, embryo muscle tissue was used to make muscle tissue homogenate as the same way so as to regard as the controls.MAIN OUTCOME MEASURES: BMSCs underwent morphological observation after induction; in addition, anti-NSE, NF200 and anti-GFAP were used to label neurons and astrocytes, respectively. Ten non-overlapping sights were randomly selected from positive reactive-induced cells after immunohistochemical staining under optic microscope to calculate ratio of positive cells of NSE and NF200 counting for total numbers of cells.RESULTS: ① Morphological changes of BMSCs after induction: During early induction, optic microscope indicated that soma of partial cells rebounded; whose apophysis was long and thin; apophysis of differentiated cells grew gradually and intercrossed each other. It was similar to nerve cells and some branches were similar to dendrite branches. However,morphological changes of cells in the control group were not obvious. ② Expression of relevant antigens differentiated from BMSCs into neuron-like cells at one week after induction: Most cells in spinal cord homogenate group expressed as positive NSE and NF200; a few of cells expressed as GFAP. While, positive staining of nerve cell antibody was not observed in the control group; meanwhile, positive reaction of nerve cell antigen was not observed in the control group,too. Immunohistochemistry examination demonstrated that positive rates of NSE and NF200 expressions were (68±1.7)%and (76.2±2.9)%, respectively.CONCLUSION: Fetal spinal cord tissue homogenate can induce differentiation from BMSCs into neuron-like cells.

BACKGROUND: Pathophysiological mechanism of local microenvironment is complex after central nerve injury; especially,both inflammatory reaction at an acute phase and formation of secondary glial scar have tremendous effects on effective regeneration of axon, regeneration and arrangement of local nerve cells, proliferation and migration of local stem cells;therefore, it becomes a basic reason for blocking nerve repair in an early period. Thus, how to effectively resist inflammatory factors in injured region at an acute phase and how to optimize microenvironment of neural regeneration are the most important strategies for repairing spinal cord injury in recent years.OBJECTIVE: To design, establish and screen the best expression of interleukin-6 receptor (IL-6R) α to inhibit shRNA adenovirus expression vector by using spinal cord injury models.DESIGN: Duplicative measurement study.SETTING: Department of Spine Surgery, the Second People's Hospital of Shenzhen.MATERIALS: A total of 40 healthy Wistar rats, either gender, 8-10 weeks old, were selected in this study. Rabbit-anti-rat glial fibrillary acidic protein (GFAP) antibody Ⅰ was provided by Santa Cruz Compan; siRNA eukaryon expression plasmid pGenesil (cohtaining green fluorescent expression system) was provided by Wuhan Jingsai Bioengineering Company.METHODS: The experiment was carried out in ImmuneOpening Laboratory, Basic Medical Faulty, Tongji Medical College, Huazhong University of Science and Technology, and Medica Laboratory Center, the Second People's Hospital of Shenzhen in November 2006. Three pairs of shRNA template which composed of 19 bp reverse repeated motif of IL-6 receptor (IL-6R) α target sequence with 9 bp spacer were designed and synthesized, then the recombinant adenovirus expression vectors with green fluorescence protein were constructed in vitro respectively. The acute spinal cord injury models were completed, and the adenovirus recombinants were regionally injected post 12 hours after spinal cord injury;in addition, the inhibitory effect of RNA interference (RNAi) on expression of IL-6R in local region after spinal cord injury were detected by using real-time fluorescence quantitative reverse transcription polymerase chain reaction (RT-PCR) and Western blot so as to screen adenovirus expression vector which had the best inhibitory effect on expression of IL-6R.MAIN OUTCOME MEASURES: Inhibitory effect of RNAi on expressions of IL-6R RNA and protein in local region after spinal cord injury.RESULTS: Sequence analysis showed that IL-6R-shRNA recombinant adenovirus expression vector was successfully constructed, and optimal IL-6R-shRNA recombinant adenovirus expression vector was screened by using real-time fluorescence quantitative RT-PCR and Western blot. The IL-6R expressions were 49% and 56% at the levels of mRNA and protein, respectively.CONCLUSION: The IL-6R--shRNA recombinant adenovirus expression vector is successfully constructed and screened.The gene expression of IL-6R can be highly inhibited after acute spinal cord injury.

BACKGROUND: Glial cell-derived neurotrophic factor (GDNF) and transforming growth factor-beta 1 (TGF-β1)co-subordinate to TGF-β family. Both of them play very important roles in the development and differentiation of central and peripheral nervous system, and regulation of cell cycle in mammals.OBJECTIVE: To observe the differentiation of spinal cord-derived neural stem cells(NSCs) induced by GDNF combined with TGF-β1, and make a comparison of differentiation results with GDNF or TGF-β1 culture fluid.DESIGN: Controlled observation.SETTING: Central Laboratory, Shenzhen Hospital Affiliated to Southern Medical University.MATERIALS: Ten SD rats of clean grade, which were at conception for 16 days, were provided by the Experimental Animal Center, Tongji Medical College, Huazhong University of Science and Technplogy. Main reagents and materials:DMEM/F12,B27(GIBCO); basic fibroblast growth factor (bFGF), GDNF; TGF-β1(PeproTech);fetal bovine serum (FBS,Hyclone); nestin multiple antibody (Boster, Wuhan); glial fibrillary acidic protein (GFAP) multiple antibody; neurofilament protein (NF-200) monoclonal antibody (Sigma).METHODS: This experiment was carried out in the Central Laboratory, Shenzhen Hospital Affiliated to Southern Medcial University between October 2005 and September 2006. Under the aseptic condition, rat fetus was isolated for isolation and culture of spinal cord-derived neural stem cells. In this study, five groups were divided: basal medium group, control group, bFGF group, TGF-β1 group, GDNF+ TGF-β1 group. In the basal medium group, DMEM/F12 containing penicillin,streptomycin, amphotericin (AMPH) B and 0.02 volume fraction of B27 annex solution. At 1 week after primary culture, rat spinal cord-derived NSC clones proliferated in vitro stably were harvested. In the control group, 0.1 volume fraction of FBS was added into basal medium. In the later three groups, induced medium was exchanged, i.e. 20 μg/L bFGF, 2 μg/L TGF-β1, and 10 μg/L GDNF+2 μg/L TGF-β1 were added into the basal medium, respectively. ①The differentiation of spinal cord-derived NSCs induced by different factors were observed under the optical microscope. ②The expressions of neurons and astrocytes were detected by immunocytochemical staining labeling. ③ The differentiated cells were counted by sorting technique by means of fluorescence excitation flow cytometer, and the percentage of NSCs differentiating into neurons and astrocytes were detected under the different induction environments.MAIN OUTCOME MEASURES: ① Morphological feature of cell differentiation in each group. ② Immunohistochemical detection of NSCs in each group. ③ The percentage of NSCs differentiating into neurons and astrocytes in each group.RESULTS: ① Cell morphology during differentiation: At the early stage of differentiation, lots of cells creeped to all the directions, and one week later, most of the migrated cells adhered to the wall entirely. Neuron-like cells, astrocyte-like cells and oligodendrocyte-like cells could be identified in the low-density cell region. ②Immunohistochemical detection results: A lot of GFAP- positive astrocytes were found in the control group and TGF-β1 group; Many differentiated neurons and NF-200 staining positive were found in the bFGF group and GDNF+ TGF-β1 group. ③Percentage of stained neuron and astrocyte: at one week of induction, the percentage of stained neurons was higher in the GDNF+ TGF-β1 group than in the control group, bFGF group and TGF-β1 group (x2=24.15,19.56,25.32,P ＜ 0.05-0.01), and the percentage of stained astrocytes was lower in the GDNF+ TGF-β1 group than in the control group, bFGF group and TGF-β1 group (x2=24.45,23.79,P ＜ 0.01 ).CONCLUSION: The combined in vitro induction of GDNF and TGF-β1 contributes to the neuronal differentiation of spinal cord-derived NSCs, indicating that both of them have synergistic effect.

ObjectiveTo compare the calculation precision of the collapsed cone convolution (CCC) algorithm and pencil beam convolution (PBC) algorithm in TPS in heterogeneous tissue.Methods We made two virtual lung phantoms,one is single field phantom,In this case the photon beam incident into the phantom,the other is the two fields phantom and a cubic'tumor' was placed in the centre of the phantom.two opposite photon beams incident into the phantom.We calculated the dose of the'tumor' and the lung with the CCC and PBC algorithm.We compared the results in both case with if obtained from Monte Carlo (MC) method.ResultsIn the single field phantom,the photon beam incident from the high-density tissue to the low-density lung equivalent tissue,compared with the result of MC algorithm PBC algorithm overestimated the lung equivalent tissue dose (t =3.90,P =0.012) and the result of CCC algorithm is close to it ( t =2.25,P =0.087 ).In the two fields phantom,tumor boundary dose calculated by CCC algorithm and the MC algorithm are lower than that of the PBC algorithm (t =2.43,3.18,P =0.038,0.011 ),and the difference increase when the field size decrease, the beam energy increase and the density of the inhomogeneity decrease.ConclusionsWe had better use the CCC algorithm when calculating the dose of the tumor surrounded by low-density tissue or the tumor behind the low-density tissue,such as the lung cancer,esophageal cancer etc.

Objective The aim of this study was to evaluate the role of multicriteria optimization (MCO) in planning of intensity-modulated radiotherapy (IMRT).Methods Twenty IMRT patients (ten with prostate and ten with lung cancers) were randomly selected.For these patients,the treatment plans were designed with direct machine parameter optimization (DMPO).Based on these plans,new plans were designed with MCO,while keeping the setting conditions unchanged.Comparison was made between the two plans including the dose distribution,the dose volume histogram,the time of optimization and number of monitor unit (MU),but were play by pairing-t test.Results The plan designed in both optimizations satisfied all clinical requirements.For the same or better target coverage,rectum,bladder and small bowel were better with MCO compared with DMPO,MCO reduced 58％ of the time for optimization by average while MU increased 32％ by average for prostate cancer.For lung cancer,the whole lung,heart and spinal cord were better with MCO compared with DMPO,MCO reduced 59％ of the time for optimization by average while MU increased 11％ by average.Conclusions In comparison with DMPO,MCO reduces the dose of organs at risk,shorten the time of optimization.

Objective To calculate the effects of thermoplastic mask on X-ray surface dose.Methods The BEAMnrc Monte Carlo Code system, designed especially for computer simulation of radioactive sources, was performed to evaluate the effects of thermoplastic mask on X-ray surface dose.Thermoplastic mask came from our center with a material density of 1.12 g/cm2. The masks without holes,with holes size of 0. 1 cm× 0. 1 cm, and with holes size of 0. 1 cm × 0. 2 cm, and masks with different depth (0.12 cm and 0.24 cm) were evaluated separately. For those with holes, the material width between adjacent holes was 0. 1 cm. Virtual masks with a material density of 1.38 g/cm3 without holes with two different depths were also evaluated. Results Thermoplastic mask affected X-rays surface dose. When using a thermoplastic mask with the depth of 0. 24 cm without holes, the surface dose was 74. 9% and 57.0% for those with the density of 1.38 g/cm3 and 1.12 g/cm3 respectively. When focusing on the masks with the density of 1.12 g/cm3, the surface dose was 41.2% for those with 0.12 cm depth without holes;57.0% for those with 0. 24 cm depth without holes;44. 5% for those with 0. 24 cm depth with holes size of 0.1 cm ×0.2 cm;and 54.1% for those with 0.24 cm depths with holes size of 0.1 cm ×0.1 cm.Conclusions Using thermoplastic mask during the radiation increases patient surface dose. The severity is relative to the hole size and the depth of thermoplastic mask. The surface dose change should be considered in radiation planning to avoid severe skin reaction.

Objective To explore the elementary properties of LiF (Mg,Cu,and P) thermoluminescent dosimeter (TLD) in dosimetry for tumor radiotherapy,and to provide a reliable basis for thermoluminescent dosimetry in clinical radiotherapy.Methods 60Coγ-ray and 6 MV X-ray were used for evaluation of the dispersion,repeatability,and dose response of LiF TLD.To meet the requirement of clinical radiotherapy,the effects of energy,dose (50-600 cGy),radiation dose rate (50-600 MU/min),and the angle of incidence for accelerator gantry (0°-± 90°) on TLD were determined and the respective correction factors were calculated.Results The errors of repeatability and dispersion of TLD were less than ±3％.There was a linear relationship between readout and irradiation dose within a certain range of irradiation dose.The minimal relative deviation of 0.3％ was obtained when 6 MV X-ray was used with a dose rate of 300 MU/min and an angle of incidence of 0°.Conclusions LiF TLD shows excellent repeatability,low dispersion,high stability,and strong linear correlation.It meets the international criteria and can be used for dose measurement in tumor radiotherapy.

Objective To investigate the dose and mechanical properties of medical electron linear accelerators in grass-roots radiotherapy units in Sichuan Province,China via sampling and inspection.Methods A total of eight radiotherapy units in Sichuan Province were selected by sampling,and the tests were performed for the dose and mechanical properties of the medical electron linear accelerators in use.Among these accelerators,there were 5 imported accelerators and 3 domestic accelerators.The test items and methods were determined according to the requirements in GB15213-94.Results Among the 14 test items,the items related to the flatness,symmetry,and overlap of radiation field.The other tests of dose accuracy and mechanical precision achieved good results.Conclusions There is a need to strengthen the daily quality control work for dose and mechanical accuracy of medical electron linear accelerators in grass-roots radiotherapy units in Sichuan Province and perfect the allocation of professional equipment and personnel and training of related personnel.With the support of Sichuan Radiotherapy Quality Control Center,quality control supervision and guidance should cover the whole province.