Objective To investigate the impact of immobilization devices and treatment couches on the planned dose in stereotactic body radiation therapy(SBRT).Methods A retrospective study was conducted involving 23 SBRT patients,all of whom underwent CT simulation with foam padding or vacuum bag immobilization.For each patient,two sets of contours were outlined on CT images:one encompassing only the patient's skin(Body),and the other including the skin plus immobilization devices(BodyF).Initially,a reference plan(noFC)meeting clinical requirements was generated based on the Body contour.Without altering the plan(noFC)parameters and field setups,plan calculations were performed separately based on three different contours:BodyF(with immobi-lization devices only),Body+C(with treatment couch only),and BodyF+C(with both immobilization devices and treatment couch),yielding plan(F),plan(C),and plan(FC),respectively.By comparing the target and skin dose parameters across these four plans,the effects of immobilization devices and treatment couches on the planned dose were evaluated.Results Compared to plans based solely on the patient's skin contour,plans incorporating immobilization devices showed reduced high-dose,prescription dose coverage,and average dose in the target volume.Notably,the difference in the percentage of the planning target volume(PTV)receiving 105%of the prescribed dose(PTV/V105%p(%))between plan(FC)and plan(noFC)could reach 61.86%.Conversely,plans with immobilization devices increased both the maximum and average skin doses.Specifically,the dose to 10 cc of skin within 2 mm of the surface(body 2 mm/D 10 cc(Gy))showed a 21.36%difference between plan(FC)and plan(noFC).For all target and skin parameters,no statistically significant differences were observed between plan(C)and plan(noFC).Among plans with immobilization devices,the minimum distance from the target to the skin correlated inversely with skin dose,indicating greater impact on skin dose with closer proximity.Conclusions Immobilization devices in SBRT lead to beam attenuation and altered build-up effects,significantly reducing target dose parameters while increasing skin dose.The closer the target is to the skin,the greater the impact of immobiliza-tion devices on skin dose.It is recommended to incorporate immobilization devices into the contour design during radiotherapy planning.

BACKGROUND:Currently,pedicle screw fixation technology is recognized as the gold standard for lumbar posterior fusion surgery.However,this technique is associated with several complications such as suboptimal screw placement,loosening,and fracture.Addressing these issues,it requires a thorough investigation into the mechanical properties of screw reinsertion to optimize surgical procedures and enhance success rates and safety.OBJECTIVE:By combining finite element analysis with biomechanical experiments,this study aims to compare and analyze the mechanical performance of traditional trajectory pedicle screws during multiple extraction processes.The goal is to reveal patterns in screw extraction strength over repeated withdrawals,providing scientific insights into the safety and effectiveness of pedicle screw reinsertion for clinicians.METHODS:Based on CT scan data,a three-dimensional reconstruction of the L4 vertebra model was performed.Three-dimensional printing technology was used to create biological experimental samples.A pull-out experiment was conducted according to a screw placement plan.Utilizing CT data and standard pedicle screw parameters,a finite element model of the L4 vertebra and a pedicle screw model(diameter 6.0 mm,length 45 mm)were established.The model was divided into five operating conditions based on screw placement angle and cycles.A finite element model was developed to simulate axial pull-out testing,analyzing stress distribution in the vertebral body and maximum axial pull-out strength of the screw.Mechanics experimental results of three-dimensional printing were compared and analyzed against simulation outcomes.RESULTS AND CONCLUSION:(1)A dedicated experimental setup for pedicle screw extraction from single vertebrae was designed and constructed.(2)In the three-dimensional printing experiment,our groups of models were compared between correctly placed screws and once improperly placed screws.The correctly placed screws group exhibited a maximum pull-out force of(1 422.63±23.80)N.Furthermore,with increasing deviation angles in screw placement,the maximum pull-out forces of each group gradually decreased.(3)Comparing the condition of a single improper nail placement with repositioning the nail correctly,when the offset angle of the improper placement exceeded that of Model 3,correctly repositioning the nail helps to increase the screw's pull-out resistance.(4)Comparing the scenario of two consecutive improper nail placements with repositioning correctly after two improper placements,correctly repositioning the nail reduced the screw's pull-out resistance.Without replacing the screw,it was not advisable to attempt a third nail placement.(5)Experimental pull-out strength of three-dimensional printing correlates significantly with finite element simulation results,with a correlation coefficient of 0.98.There is no significant difference in the outcomes between the two methods(P＞0.05).

Objective To investigate the impact of immobilization devices and treatment couches on the planned dose in stereotactic body radiation therapy(SBRT).Methods A retrospective study was conducted involving 23 SBRT patients,all of whom underwent CT simulation with foam padding or vacuum bag immobilization.For each patient,two sets of contours were outlined on CT images:one encompassing only the patient's skin(Body),and the other including the skin plus immobilization devices(BodyF).Initially,a reference plan(noFC)meeting clinical requirements was generated based on the Body contour.Without altering the plan(noFC)parameters and field setups,plan calculations were performed separately based on three different contours:BodyF(with immobi-lization devices only),Body+C(with treatment couch only),and BodyF+C(with both immobilization devices and treatment couch),yielding plan(F),plan(C),and plan(FC),respectively.By comparing the target and skin dose parameters across these four plans,the effects of immobilization devices and treatment couches on the planned dose were evaluated.Results Compared to plans based solely on the patient's skin contour,plans incorporating immobilization devices showed reduced high-dose,prescription dose coverage,and average dose in the target volume.Notably,the difference in the percentage of the planning target volume(PTV)receiving 105%of the prescribed dose(PTV/V105%p(%))between plan(FC)and plan(noFC)could reach 61.86%.Conversely,plans with immobilization devices increased both the maximum and average skin doses.Specifically,the dose to 10 cc of skin within 2 mm of the surface(body 2 mm/D 10 cc(Gy))showed a 21.36%difference between plan(FC)and plan(noFC).For all target and skin parameters,no statistically significant differences were observed between plan(C)and plan(noFC).Among plans with immobilization devices,the minimum distance from the target to the skin correlated inversely with skin dose,indicating greater impact on skin dose with closer proximity.Conclusions Immobilization devices in SBRT lead to beam attenuation and altered build-up effects,significantly reducing target dose parameters while increasing skin dose.The closer the target is to the skin,the greater the impact of immobiliza-tion devices on skin dose.It is recommended to incorporate immobilization devices into the contour design during radiotherapy planning.

BACKGROUND:Currently,pedicle screw fixation technology is recognized as the gold standard for lumbar posterior fusion surgery.However,this technique is associated with several complications such as suboptimal screw placement,loosening,and fracture.Addressing these issues,it requires a thorough investigation into the mechanical properties of screw reinsertion to optimize surgical procedures and enhance success rates and safety.OBJECTIVE:By combining finite element analysis with biomechanical experiments,this study aims to compare and analyze the mechanical performance of traditional trajectory pedicle screws during multiple extraction processes.The goal is to reveal patterns in screw extraction strength over repeated withdrawals,providing scientific insights into the safety and effectiveness of pedicle screw reinsertion for clinicians.METHODS:Based on CT scan data,a three-dimensional reconstruction of the L4 vertebra model was performed.Three-dimensional printing technology was used to create biological experimental samples.A pull-out experiment was conducted according to a screw placement plan.Utilizing CT data and standard pedicle screw parameters,a finite element model of the L4 vertebra and a pedicle screw model(diameter 6.0 mm,length 45 mm)were established.The model was divided into five operating conditions based on screw placement angle and cycles.A finite element model was developed to simulate axial pull-out testing,analyzing stress distribution in the vertebral body and maximum axial pull-out strength of the screw.Mechanics experimental results of three-dimensional printing were compared and analyzed against simulation outcomes.RESULTS AND CONCLUSION:(1)A dedicated experimental setup for pedicle screw extraction from single vertebrae was designed and constructed.(2)In the three-dimensional printing experiment,our groups of models were compared between correctly placed screws and once improperly placed screws.The correctly placed screws group exhibited a maximum pull-out force of(1 422.63±23.80)N.Furthermore,with increasing deviation angles in screw placement,the maximum pull-out forces of each group gradually decreased.(3)Comparing the condition of a single improper nail placement with repositioning the nail correctly,when the offset angle of the improper placement exceeded that of Model 3,correctly repositioning the nail helps to increase the screw's pull-out resistance.(4)Comparing the scenario of two consecutive improper nail placements with repositioning correctly after two improper placements,correctly repositioning the nail reduced the screw's pull-out resistance.Without replacing the screw,it was not advisable to attempt a third nail placement.(5)Experimental pull-out strength of three-dimensional printing correlates significantly with finite element simulation results,with a correlation coefficient of 0.98.There is no significant difference in the outcomes between the two methods(P＞0.05).

OBJECTIVE：To study the effects and potential mechani sm of deoxyschizandrin on the proliferation ，migration and invasion of nasopharyngeal carcinoma cell HONE- 1. METHODS ：HONE-1 cell was set as cell model ，while CCK- 8 test，wound healing assay and Transwell chamber test were used to detect the proliferation ，migration and invasion ability changes of HONE- 1 cells after treatment with different concentrations [ 0（blank control ），10，20，40 μmol/L] of deoxyschizandrin. Computer molecular docking was performed to analyze the binding ability between deoxyschizandrin and Met protein. Western blotting assay was used to detect the relative protein expressions of p-Met ，p-PI3K，p-Akt，Bcl-2 and N-cadherin in cells. RESULTS ：Compared with blank control ，the proliferation ，migration and invasion ability of cells after treated with 10，20，40 μmol/L deoxyschizandrin were all decreased significantly （P＜0.05）. Results of molecular docking revealed that deoxyschizandrin could stably bind with the activity pocket of Met protein. Results of Western blotting assay demonstrated that compared with blank control ，10，20，40 μmol/L deoxyschizandrin all decreased the relative protein expressions of p-Met ，p-PI3K，p-Akt，Bcl-2 and N-cadherin in cells significantly（P＜0.05）. CONCLUSIONS ：Deoxyschizandrin can inhibit the proliferation ，migration and invasion of HONE- 1 cell via inhibiting the activation of Met/PI 3K/Akt signaling pathway.