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Objective Based on the lanthanum bromide scintillator detector, the calculation method of G(E) function was developed to measure the air absorbed dose rate. Methods Firstly, the gamma energy spectrumof the lanthanum bromide detector were simulated and the response functions with different energies were determined with Monte Carlo simulation method. Then, the G(E) function was calculated by the least square method. Finally, the air absorbed dose rate measured by the lanthanum bromide detector using G(E) function conversion method was compared with the theoretical calculation value based on the point source experiments. Results The experimental verification results showed that the relative deviation between thecalculated value with G(E) function and the theoretical calculation value wasmostly controlled within ± 6%, which verified the accuracy of G(E) function. Conclusion The results showed that the method of G(E) function could be applied to calculate the gamma radiation dose rate based on the in-situ the gamma spectrum with LaBr3 detector.
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Objective@#To evaluate the efficiency of preoperative Halo-gravity traction (HGT) in the treatment of severe kyphoscoliosis secondary to neurofibromatosis type Ⅰ (NF1).@*Methods@#A retrospective review was conducted on patients with severe kyphoscoliosis secondary to NF1 at Department of Spinal Surgery, Drum Tower Hospital, Medical School of Nanjing University between July 2007 and May 2016. A total of 29 patients including 17 males and 12 females were finally enrolled and the age was (13.7±2.9) years. The Cobb angle of major coronal curve and global kyphosis were measured before and after HGT. The forced vital capacity (FVC)and forced expiratory volume in 1 second (FEV1) before and after traction were also recorded. The paired t test was used for comparison analysis.@*Results@#The average maximum traction weight of HGT was (12.2±2.8) kg and the traction duration was (10.2±6.6) weeks. The coronal Cobb angle before HGT was (87.5±36.5)°, which improved to (68.4±25.9)° after HGT with a correction rate of (21.9±12.1)% (t=9.14, P<0.001); the average global kyphosis before HGT was (79.1±27.1)°, which improved to (59.9±19.4)° after HGT and the correction rate was (20.2±14.1)% (t=8.55, P<0.001). One patient had transient brachial plexus palsy which resolved completely after reducing the traction weight. After HGT treatment, FVC increased from (0.83±0.16) L to (0.89±0.19) L (t=1.48, P=0.12) and FEV1 increased from (0.72±0.16) L to (0.78±0.20) L (t=0.49,P=0.63). FVC predicted and FEV1 predicted improved from (42.9±20.1)% and (40.6±19.6)% to (46.9±20.5)% (t=0.98,P=0.33) and (43.6±25.8)% (t=1.24,P=0.22), respectively.@*Conclusion@#Preoperative HGT in the treatment of severe kyphoscoliosis secondary to NF1 can improve spinal deformity and pulmonary function to some extent, which can further benefit the patients by improving their surgical tolerance.
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Objective@#To evaluate the radiographic and clinical outcomes of Scoliosis Research Society(SRS)-Schwab Grade IV osteotomy in type I congenital kyphosis.@*Methods@#All of 28 patients with type I congenital kyphosis who underwent SRS-Schwab Grade 4 osteotomy from June 2015 to June 2017 were retrospectively reviewed,including 21 males and 7 females aged 10 to 28 years old, with an average of 13.6±8.5 years. On standing wholespinal X-rays at pre-operation, post-operation and each follow-up, global kyphosis(GK), thoracic kyphosis(TK), lumbar lordosis(LL) and sagittal vertical axis(SVA) were measured. The intra-operative and post-operative complications were recorded for each patient. The Scoliosis Research Society-22 questionnaires(SRS-22) and visual analog scale(VAS) for back pain were collected from patients elder than 12 years old at pre-operation and last follow-up. The comparison analysiswasperformed by paired samples t test.@*Results@#At pre-operation, the GK, TK, LL and SVA were 47.0°±4.9°, 16.8°±3.7°, 36.6°±7.7°, (-31.9±13.6) mm, respectively. At 3 months post-operation, the average values improved to 3.7°±2.3°, 36.8°±4.0°, 46.5°±4.4°, 4.0±19.1 mm, respectively. Significant differences were found in all parametersbetween pre- and post-operation. The post-operative follow-up was 12 to 24 months, with an average of 13.2±5.2 months. At the last follow-up, the GK, TK, LL and SVA were 4.0°±2.4°, 38.0°±6.0°, 45.9°±5.4°, 7.6±15.3 mm, and no significant correction loss was found during follow-up. The scores of each domain of SRS-22 questionnaire improved at different level during follow-up, of which the improvement in self-imagewas statistically significant (P<0.001). The scores of VAS for back pain improved significantly after operation (P<0.001). One patient hadabnormal intra-operative monitoringwhile no neurological defectwas detected at post-opera tion. Proximal junctional kyphosis occurred in 2 patients at 3 months follow-up while no patients needed revision surgery. There wereno implant-related complicationsduring follow-up.@*Conclusion@#The SRS-Schwab Grade 4 osteotomycould provide satisfying correction with relatively low rates of complications in type I congenital kyphosis. Thus, the SRS-Schwab Grade IV osteotomy is a safe strategy for type I congenital kyphosis.
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Objective To study the method of dose reconstruction in human body under the photon external radiation accident condition,and to verify the accuracy of the method for the local dose distribution.Methods Based on the open source Monte Carlo tool kit Geant 4 and using the human voxel phantom recommended by ICRP Publication 103,the dose reconstruction method under the condition of external radiation accident was studied to evaluate the average absorbed dose,organ absorbed dose and local dose distribution.To validate the code,several irradiation experiments were implemented in some standard radiation fields by putting TLDs in the tissue equivalent physical phantom ART.A voxel phantom was used to reconstruct the radiation doses,which was created based on the CT scan image of the ART phantom with resolution of 1.57 mm× 1.57 mm× 10.00 mm.The result of experiment were compared with those of dose reconstruction simulation.Results The relative uncertainty of the measured values was 10.9％.The relative uncertainty of the dose reconstruction simulation values was 7.10％ at the non-tissueinterface area and 16.6％ at the tissue-interface area.For 451 measuring points,the average of the simulated value divided by the measured value was 0.972,with the standard deviation of 0.083 8.In the range of 0.95-1.05,0.90-1.10 and 0.80-1.20,and the proportions were 49.2％,79.4％ and 96.4％,respectively.Conclusions The method of Monte Carlo dose reconstruction based on human voxel phantom meets the accuracy requirement of actual uses both at the whole body or organ level and at the local dose distribution level.It can be used as a powerful tool for dose assessment of the exposed people in an external radiation accidents and provide support for diagnosis and treatment.
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Objective To investigate the incidence and risk factors for rod fracture after correction surgery with satellite rod in severe spinal deformity.Methods A retrospective analysis was made including 234 cases who underwent correction surgery using satellite rod technique for severe spinal deformity in our hospital from July 2012 to June 2017.At the last follow-up,a total of 6 patients were found to have rod fracture.All the patients had complete clinical and imaging data at the time of preoperation,postoperation,rod fracture occurring,post-revision and the last follow-up.The Cobb angle,the Global kyphosis (GK),the coronal balance (distance between C7 plumb line and center sacral vertical line,C7PL-CSVL) and the sagittal vertical axis (SVA) were measured respectively in the 6 patients with rod fracture during the follow-up process.The time,incidence and position of the broken rod were recorded,and the reasons of rod fracture were analyzed for each patient.Results The incidence of rod fracture was 2.6％ (6/234) in the current study.The 6 patients included 3 males and 3 females with an average age of 34.5±15.4 years at initial surgery.The mean time of rod fracture was 24.0±17.7 months,of which 3 cases (50％) occurred within 1 years after operation.A total of 7 rods were broken,including 4 (57％) rods located at the single-rod-fixed side with stress concentration and 3 (50％) rods at the adjacent segment of the satellite rod.The average loss of correction was 20.8°±29.4° for Cobb angle and 34.0°±21.4° for GK.The potential reasons for rod fracture were listed as follows:3 cases for residual kyphosis;2 cases for pseudarthrosis;3 cases for long fusion construct crossing lumbosacral junction;1 case for trauma.Of the 6 patients with rod fracture,3 (43％) patients underwent revision surgery by replacing the broken rods,adding satellite rod at the opposite side of pre-existing satellite rod and bone graft at the rod-breakage area.The other 3 patients underwent observation and no deterioration was found during follow-up.Conclusion The incidence of rod fracture after correction for severe spinal deformity with satellite rod is 2.6％.The broken rods are mainly located at the single-rod-fixed side with stress concentration or the adjacent segment of the satellite rod.Residual kyphosis,pseudarthrosis,long fusion construct crossing lumbosacral junction and trauma are the significant risk factors of rod fracture.
