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Objective:To study the differences in the cumulative dose between deformable image registration (DIR) and simple dose-volume histogram (DVH) summation in the fractionated brachytherapy of cervical cancer, and to analyze the feasibility of the application of DIR in the dosimetry assessment of targets and organs-at-risk (OARs) in the brachytherapy.Methods:A retrospective analysis was conducted for 13 cases with primary cervical cancer treated with four fractions of interstitial brachytherapy guided by CT images. The four CT images of each cases were registered using an intensity-based DIR. Then, the cumulative doses (the D2 cm 3, D1 cm 3, and D0.1 cm 3 of the bladder, rectum, intestine, and colon and the D90for targets) after DIR were calculated and compared to those obtained using simple DVH summation. Afterward, the correlation between the dose difference and dice similarity coefficient (DSC) was analyzed. With the dose difference (the remaining dose of OARs caused by the DIR) as limits, a new plan was made for the latest CT to calculate the dose increase to targets. Results:Compared to simple DVH summation, DIR allowed the cumulative doses of the D2 cm 3 and D1 cm 3 of bladder to be decreased by (2.47±1.92) and (2.82±2.73) Gy, respectively on average ( t=-3.65, -2.93, P < 0.05), those of the D2 cm 3, D1 cm 3, and D0.1 cm 3 of rectum to be decreased by (2.05 ± 1.61) Gy, (1.51 ± 1.58), and (3.21 ± 2.50) Gy, respectively on average ( t=-4.02, -3.02, -4.06, P < 0.05), and those of the D2 cm 3, D1 cm 3, and D0.1 cm 3 to be decreased by (1.42 ± 0.99), (1.55 ± 1.28) Gy, and (2.43 ± 1.95) Gy, respectively on average ( t=-3.52, -2.96, -3.06, P < 0.05). There was no significant statistical difference in the D90 of targets, the D0.1 cm 3 of the bladder, and the D2 cm 3, D1 cm 3, D0.1 cm 3 of the colon ( P > 0.05) between both methods, and there was no distinct correlation between DSC and dose difference ( P > 0.05). The DIR increased the dose to targets, with a median value of 150 cGy. However, the accuracy of the DIR should be improved. Conclusions:In clinical practice of multiple fractions of brachytherapy for cervical cancer, it′s still recommended to adopt the simple dose summation method to assess the doses to targets and OARs.
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Objective:To establish a dosimetric method based on the well-chamber to verify the accuracy of the source positioning and dwelling time for the afterloading machine, aiming to provide a new method for the quality control of afterloading machine.Methods:The principle of this method was explained according to the hardware structure of the well-chamber. Then, the precision of this method was analyzed by the simulation test and data fitting. The feasibility test was also performed. And the advantages and disadvantages of this method were compared with those of the traditional method.Results:The precision of this method for detecting the source positioning was 0.07 mm and the dwelling time was 0.09 s, respectively. In the feasibility test, the standard deviation of the measure value was below 3%.Conclusions:The well-chamber method has high precision and convenient operation. It can be applied in the rapid verification of the relative accuracy of the source positioning and dwelling time of well-chamber.
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Objective To study the feasibility of using the PTW729 2D array ion-chamber to verify the relative dose distribution calculated with the Acuros BV algorithm.Both advantages and disadvantages of the method were analyzed to provide reference for practical clinical practices.Methods Based on self-built measurement phantoms,the dose distribution on the same slice of the phantom was measured with PTW729 and film,respectively,under the same measurement condition and plan.The dose distributions obtained by the two method were compared with the result calculated with Acuros BV,separately,by using γ analytical tool.And the stability of the PTW729 was tested.Results The γ comparison value was 95.9％ between the film and Acuros BV,98.9％ between the PTW729 and Acuros BV and 88.0％ between the film and PTW729,with 95.0％,i00.0％,and 100.0％,in their stability test respectively.Conclusions PTW729 2D array ion-chamber can be applied to the rapid verification of Acuros BV algorithm-calculated relative dose distribution.
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Objective@#To study the feasibility of using the PTW729 2D array ion-chamber to verify the relative dose distribution calculated with the Acuros BV algorithm. Both advantages and disadvantages of the method were analyzed to provide reference for practical clinical practices.@*Methods@#Based on self-built measurement phantoms, the dose distribution on the same slice of the phantom was measured with PTW729 and film, respectively, under the same measurement condition and plan. The dose distributions obtained by the two method were compared with the result calculated with Acuros BV, separately, by using γ analytical tool. And the stability of the PTW729 was tested.@*Results@#The γ comparison value was 95.9% between the film and Acuros BV, 98.9% between the PTW729 and Acuros BV and 88.0% between the film and PTW729, with 95.0%, 100.0%, and 100.0%, in their stability test respectively.@*Conclusions@#PTW729 2D array ion-chamber can be applied to the rapid verification of Acuros BV algorithm-calculated relative dose distribution.
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Objective To measure the total β radioactive background level in the urine of normal adults,and to establish the method which can be universally used and satisfy the needs of rapid screening of samples in large batch.Methods A total of 83 urine samples from healthy adults were prepared by evaporation.And the gross β activity in urine was detected by using low background measuring instrument.Results The optimal experimental conditions were in place.The sampled volume was 200 ml,and the samples were turned to nitric acid salinization,ashed at 300℃ for 2 h,and the measured time was 1000 min.To get a more stable result,the urine residues were put aside for 24 h before measurement.The radioactivity in urine of healthy adults was between 9.40-55.92 Bq/L,and showed no correlation with age and sex.Conclusions When the radioactivity in urine is detected under the conditions mentioned above,the sample preparation process is simple and quickly,which can satisfy the needs of large batch sample screening.
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Objective To investigate the effect of the histological changes on rat dorsal root ganglia (DRG) after 125I seed brachytherapy.Methods Twelve adult male Sprague-Dawley rats ( 150-180g each) were randomly divided into 6 groups,125I seeds with different activities of 0 (Titanium shell),14.8,18.5,22.2,25.9 and 29.6 MBq were implanted to 6 groups of rats respectively and the behavioral changes of rats were observed.The rats were killed in different periods after implantation,the morphological changes in DRG and surrounding muscle tissue were observed with an Olympus BX51 optical microscope and then the irradiation doses were estimated.Results After 125I seed implantation,the movement function of rats was not affected and the weight of rats gained after 7 days.After the titanium shell implantation,very few mild swelling was induced in neuroganglion cells that still had clear nucleolus and normal cytoplasm.At 14 days after 18.5 MBq seed implantation,cell swelling was more serious and cell dehydrating,nuclear condensation and nuclear fragmentation appeared after 30 days.At 60 days after 29.6 MBq of seed implantation,nuclear dissolution and cytoplasmic shrinkage were induced in a large number of cells.In general,the severity of fibrosis was aggravated with the time post-irradiation and the dose in the muscles around the ganglion.Conclusions After 125I seed implantation,the injury degree of DRG tissue is dose-dependent,and the 125I seed irradiation would have analgesic effect on releasing intractable pain.