ABSTRACT
Objective:To explore the application of ArcCheck system in the validation of Helical and Direct tomotherapy plans for esophageal cancer and summarize relevant experience.Methods:The Helical and Direct tomotherapy verification plans were established for 32 patients with esophageal cancer at different positions according to the doctor′s instructions, which were verified by the ArcCHECK system to compare the passing rate of the results.The correlation between the volume of the target area and the passing rate of the planned verification was analyzed. The therapeutic verification plan with a small target volume was made. The target area was placed at the center of ArcCHECK phantom and the area of detectors to statistically compare the verification passing rates.Results:Helical plan showed a significantly higher passing rate than the Direct plan ( P<0.01). The correlation coefficients between the target volume and the passing rate of the Helical and Direct plans were -0.364 and -0.042, and the P values were 0.041 and 0.819, respectively. For the Helical plan, when the 3%/2mm criterion was adopted, there was significant difference between placing the high-dose area at the center of the phantom and the area of detectors ( P=0.005), and the passing rate of the latter was higher. There was no significant difference in the other cases (all P>0.05). Conclusions:The passing rate of the Helical plan is generally higher than that of the Direct plan, which may be related to the angular response of the ArcCHECK detector and the fact that more reference points are not included for calculation due to low-dose radiation. In addition, it may also be related to the higher requirements of Direct plan for tomotherapy dose control system. In the Helical verification plan, when the 3%/3mm criterion is adopted, the larger the target volume, the higher the possibility of lower passing rate, whereas the correlation coefficient between them is relatively low. The high-dose area can be verified by the plans at the center of the phantom or the detection point. With the comprehensive consideration, we suggest putting it at the center of the phantom.
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Objective To simulate the biomechanical characteristics of pelvic-ligament-muscle during vaginal delivery and rest, and to explore the injury of levator ani muscles during vaginal delivery, pelvic organ prolapse and stress urinary incontinence. Methods The three-dimensional (3D) nonlinear finite element model of pelvis-ligament-muscle was established to calculate the stress and strain distributions and injury of levator ani muscles under different abdominal pressures and loads. The stress and strain distributions as well as damage of type I, Ⅱ, Ⅲ stress urinary incontinence and pelvic organ prolapse were also calculated. Results The highest equivalent stresses of levator ani were 14, 29, 43, 86, 144, 230 kPa, respectively, when the abdominal pressure was 1 kPa under the load of 3, 5, 8 kPa and the abdominal pressure was 1.5 kPa under the load of 3, 5, 8 kPa. The stresses of type I, Ⅱ, Ⅲ stress urinary incontinence and pelvic organ prolapse were 1.69, 1.01, 0.70, 1.58 MPa. Conclusions Vaginal delivery would result in the damage to the puborectalis and the middle of the pubococcipital muscle, which was consistent with the damage of the anal levator muscle with pelvic floor dysfunction. This study uses scientific method to find out the exact location of pelvic floor injury during vaginal delivery, which can provide references for clinicians to prevent pelvic floor disease and formulate post natal rehabilitation training.
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Objective To analyze setup errors and guide the calculation of margins from clinical target volume (CTV) and planning target volume (PTV) in esophageal cancer patients treated with tomothcrapy by the MVCT image-guided system.Methods Sixty-four esophageal canccr patients trcated with tomotherapy in our hospital in 2016 were randomly selected.MVCT images were acquired after patients' positioning and co-registered with KVCT images.The setup errors of x,y,and z translations and roll rotation were analyzed with the t-test or one-way ANOVA.Meanwhile,PTV margin was calculated based on the formula of M =2.5 Σ + 0.7δ Results According to the formula,the CTV-PTV margins in the x,y and z directions are slightly different between cancers located in the cervical,upper thoracic,middle thoracic,and lower thoracic segments.In patients with upper thoracic esophageal cancer,the average setnp error in the yaxis was lower when the head-neck-shoulder thermoplastic film fixation was used than when somatic thermoplastic film fixation (P=0.000);the setup errors of z-axis with somatic thermoplastic film fixation in the fifth and sixth weeks were slightly less than those in the first several weeks (P =0.036);the setup errors acquired by three image registration patterns were similar (x-axis P=0.868,y-axis P=0.491,z-axis P=0.169,roll P=0.985).Conclusions In the treatment of patients with esophageal cancer,the setup errors are large,but the MVCT in the TOMO HD system can greatly reduce the setup errors,ensuring the accuracy of each treatment.It is further recommended that in clinical practice,different CTV-PTV margins should be used for the treatments of esophageal cancers located in different segments.Patients with upper thoracic esophageal cancer are advised to use the head-neck-shoulder thermoplastic film fixation.