***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: PURPOSE Mobility of the seminal vesicles relative to the prostate challenges adequate dose coverage . The aim of this study was to assess the impact of tumour invasion on SV mobility . METHODS AND MATERIAL S Three groups of 30 prostate cancer patients with ( 1 ) no invasion on MR , ( 2 ) minimal invasion ( < 5 mm ) , and ( 3 ) extensive invasion ( > 5 mm ) were studied .  Translations and rotations of the SV were measured with CBCT and compared between the three groups . RESULTS In the extensive group the r and om SV translations were significantly lower in comparison with the no invasion group in the LR : 0.15 vs 0.16 cm ( p=0.015 ) , CC : 0.17 vs 0.23 cm ( p=0.004 ) and AP direction : 0.19 vs 0.26 cm ( p=0.002 ) . Also the r and om SV rotation on the LR axis was significantly lower : 5.2 vs 6.3 ° ( p=0.035 ) . In comparison with the minimal invasion group the r and om SV translations were significantly lower in the extensive group in the CC : 0.17 vs 0.24 cm ( p=0.001 ) and AP direction 0.19 vs 0.31 cm ( p=0.007 ) and for the rotation on the LR axis : 5.2 vs 6.5 ° ( p=0.043 ) . CONCLUSION Increasing tumour invasion in the SV reduces the mobility of the SV , however the mobility remains considerable BACKGROUND / AIM To assess intrafractional prostate and patient movement using intra-prostatic fiducials and stereoscopic kilovoltage ( kV ) X-ray imaging in a 6-dimensional ( 6D ) position correction protocol . To evaluate potential gains of intra-treatment repositioning with respect to treatment margins . PATIENTS AND METHODS In intensity-modulated radiotherapy of prostate cancer patients  were positioned according to internal fiducials in six dimensions by the use of ExacTrac/Novalis Body ™ ( ET/NB ) System and a robotic couch . Intrafractional displacement of both , prostate and patient were analyzed in 427 treatment fractions of 13 patients . Systematic and r and om components were specified and used for intra-treatment margin calculation . The potential reduction of treatment margins , and intrafractional repositioning by use of the ET Snap Verification presumed , was simulated . RESULTS The mean treatment duration was 14.2±2.6 min . St and ard deviations ( SDs ) of the effective intrafractional target displacement in superior-inferior ( SI ) and anterior-posterior ( AP ) axes were 2.4 mm and 2.1 mm , respectively . Systematic errors for patient were 1.8 and 1.7 mm , and for prostate movement were 2.1 and 2.0 mm in SI and AP , respectively . The SDs of intrafractional rotation errors of the prostate around SI and left right ( LR ) were on average 2.2 and 3.6 degrees , respectively . Margins covering intrafractional motion were 4.5 and 4.3 mm in SI and AP without intrafractional correction and were estimated to 2.9 mm and 2.8 mm in SI and AP , respectively for simulated intra-treatment intervention . CONCLUSION After positioning according to fiducials , intrafractional motion is significant for treatment margins . Despite correcting rotational deviations by couch angulation , the systematic error for the component of prostate motion was somewhat larger than that of patient displacement . Intrafractional correction could be useful in reducing treatment margins PURPOSE To evaluate the setup , interfraction , and intrafraction organ motion error distributions and simulate intrafraction intervention strategies for  prostate radiotherapy .  METHODS AND MATERIAL S A total of 17 patients underwent treatment setup and were monitored using the Calypso system during radiotherapy .  On average , the prostate tracking measurements were performed for 8 min/fraction for 28 fractions for each patient . For both patient couch shift data and intrafraction organ motion data , the systematic and r and om errors were obtained from the patient population . The planning target volume margins were calculated using the van Herk formula . Two intervention strategies were simulated using the tracking data : the deviation threshold and period . The related planning target volume margins , time costs , and prostate position " fluctuation " were presented . RESULTS The required treatment margin for the left-right , superoinferior , and anteroposterior axes was 8.4 , 10.8 , and 14.7 mm for skin mark-only setup and 1.3 , 2.3 , and 2.8 mm using the on-line setup correction , respectively . Prostate motion significantly correlated among the superoinferior and anteroposterior directions . Of the 17 patients , 14 had prostate motion within 5 mm of the initial setup position for ≥91.6 % of the total tracking time . The treatment margin decreased to 1.1 , 1.8 , and 2.3 mm with a 3-mm threshold correction and to 0.5 , 1.0 , and 1.5 mm with an every-2-min correction in the left-right , superoinferior , and anteroposterior directions , respectively . The periodic corrections significantly increase the treatment time and increased the number of instances when the setup correction was made during transient excursions . CONCLUSIONS The residual systematic and r and om error due to intrafraction prostate motion is small after on-line setup correction . Threshold-based and time-based intervention strategies both reduced the planning target volume margins . The time-based strategies increased the treatment time and the in-fraction position fluctuation PURPOSE To develop a method for margin evaluation accounting for all measured displacements during treatment of prostate cancer . METHODS AND MATERIAL S For 21 patients treated with stereographic targeting marker-based online translation corrections  , dose distributions with varying margins and gradients were created . Sets of possible cumulative delivered dose distributions were simulated by moving voxels and accumulating dose per voxel . Voxel motion was simulated consistent with measured distributions of systematic and r and om displacements due to stereographic targeting inaccuracies , deformation , rotation , and intrafraction motion . The method of simulation maintained measured correlation of voxel motions due to organ deformation . RESULTS For the clinical target volume including prostate and seminal vesicles ( SV ) , the probability that some part receives < 95 % of the prescribed dose , the changes in minimum dose , and volume receiving 95 % of prescription dose compared with planning were 80.5 % ± 19.2 % , 9.0 ± 6.8 Gy , and 3.0 % ± 3.7 % , respectively , for the smallest studied margins ( 3 mm prostate , 5 mm SV ) and steepest dose gradients . Corresponding values for largest margins ( 5 mm prostate , 8 mm SV ) with a clinical intensity-modulated radiotherapy dose distribution were 46.5 % ± 34.7 % , 6.7 ± 5.8 Gy , and 1.6 % ± 2.3 % . For prostate-only clinical target volume , the values were 51.8 % ± 17.7 % , 3.3 ± 1.6 Gy , and 0.6 % ± 0.5 % with the smallest margins and 5.2 % ± 7.4 % , 1.8 ± 0.9 Gy , and 0.1 % ± 0.1 % for the largest margins . Addition of three-dimensional rotation corrections only improved these values slightly . All rectal planning constraints were met in the actual reconstructed doses for all studied margins . CONCLUSION We developed a system for margin validation in the presence of deformations . In our population , a 5-mm margin provided sufficient dosimetric coverage for the prostate . In contrast , an 8-mm SV margin was still insufficient owing to deformations . Addition of three-dimensional rotation corrections was of minor influence Background The rapid adoption of image-guidance in  prostate intensity-modulated radiotherapy ( IMRT )  results in longer treatment times , which may result in larger intrafraction motion , thereby negating the advantage of image-guidance . This study aims to qualify and quantify the contribution of image-guidance to the temporal dependence of intrafraction motion during prostate IMRT . Methods One-hundred and forty-three patients who underwent conventional IMRT ( n=67 ) or intensity-modulated arc therapy ( IMAT/RapidArc , n=76 ) for localized prostate cancer were evaluated . Intrafraction motion assessment was based on continuous RL ( lateral ) , SI ( longitudinal ) , and AP ( vertical ) positional detection of electromagnetic transponders at 10 Hz . Daily motion amplitudes were reported as session mean , median , and root-mean-square ( RMS ) displacements . Temporal effect was evaluated by categorizing treatment sessions into 4 different classes : IMRTc ( transponder only localization ) , IMRTcc ( transponder + CBCT localization ) , IMATc ( transponder only localization ) , or IMATcc ( transponder + CBCT localization ) . Results Mean/median session times were 4.15/3.99 min ( IMATc ) , 12.74/12.19 min ( IMATcc ) , 5.99/5.77 min ( IMRTc ) , and 12.98/12.39 min ( IMRTcc ) , with significant pair-wise difference ( p<0.0001 ) between all category combinations except for IMRTcc vs. IMATcc ( p>0.05 ) . Median intrafraction motion difference between CBCT and non-CBCT categories strongly correlated with time for RMS ( t-value=17.29 ; p<0.0001 ) , SI ( t-value=−4.25 ; p<0.0001 ) , and AP ( t-value=2.76 ; p<0.0066 ) , with a weak correlation for RL ( t-value=1.67 ; p=0.0971 ) . Treatment time reduction with non-CBCT treatment categories showed reductions in the observed intrafraction motion : systematic error (Σ)<0.6 mm and r and om error (σ)<1.2 mm compared with ≤0.8 mm and < 1.6 mm , respectively , for CBCT-involved treatment categories . Conclusions For treatment duration s > 4 - 6 minutes , and without any intrafraction motion mitigation protocol in place , patient repositioning is recommended , with at least the acquisition of the lateral component of an orthogonal image pair in the absence of volumetric imaging Implanted radiofrequency transponders were used for real‐time monitoring of the intrafraction prostate displacement between patients in the prone position and the same patients in the supine position . Thirteen patients had three transponders implanted transperineally and were treated prone with a custom‐fitted thermoplastic immobilization device . After collecting data from the last fraction , patients were realigned in the supine position and the displacements of the transponders were monitored for 5–7 minutes . Fourier transforms were applied to the data from each patient to determine periodicity and its amplitude . To remove auto correlation from the stream of displacement data , the distribution of short‐term and long‐term velocity components were calculated from Poincaré plots of paired sequential vector displacements . The mean absolute displacement was significantly greater prone than supine in the superior – inferior ( SI ) plane ( 1.2±0.6 mm vs. 0.6±0.4 mm , p=0.015 ) , but not for the lateral or anterior – posterior ( AP ) planes . Displacements were least in the lateral direction . Fourier analyses showed the amplitude of respiratory oscillations was much greater for the SI and AP planes in the prone versus the supine position . Analysis of Poincaré plots confirmed greater short‐term variance in the prone position , but no difference in the long‐term variance . The centroid of the implanted transponders  was offset from the treatment isocenter by > 5 mm for 1.9 % of the time versus 0.8 % of the time for supine . These results confirmed significantly greater net intrafraction prostate displacement of patients in the prone position than in the supine position , but most of the difference was due to respiration‐induced motion that was most pronounced in the SI and AP directions . Because the respiratory motion remained within the action threshold and also within our 5 mm treatment planning margins , there is no compelling reason to choose one treatment position over the other . PACS number : The aim of this study was assess the patient setup errors for various tumor sites based on clinical data from a sufficient number of treatments with volumetric‐modulated arc therapy ( VMAT ) using daily pretreatment CBCT imaging guidance . In addition , we calculated and compared the planning target volume ( PTV ) margins for all disease sites based on an analysis of specific systematic and r and om errors in our institution . All patients underwent pretreatment kV‐CBCT imaging .  The various tumor sites were divided into four categories ; 21 brain ( 438 fractions ) , 35 head‐ and ‐neck tumors ( H&N , 933 fractions ) , 19 thorax and abdomen tumors ( T&A , 313 fractions ) , and 17 prostate cancer tumors ( 546 fractions ) . Overall distributions of setup corrections in all directions , frequencies of 3D vector lengths , institution‐specific setup error , and PTV margins were analyzed . The longitudinal distribution for the T&A site represented an asymmetric offset in the negative direction . Rotational distributions were comparable for all treatment sites , and the prostate site had the narrowest distribution of ≤±2∘. The cumulative frequencies of 3D vector length of ≥ 7 mm were rare for brain lesions and H&N , but more common for T&A and prostate lesions at 25.6 % and 12.1 % , respectively . The overall mean error for all treatment sites were within ±1 mm and ±0.1∘ , with the exception of the T&A site , which had overall 
    Output:
    
Dose escalated radiotherapy improves outcomes for men with prostate cancer .
A plateau for benefit from dose escalation using EBRT may not have been reached for some patients with higher risk disease .