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Objective:To establish the basic procedures of the application of optical surface monitoring system (OSMS) in the deep inspiration breath hold (DIBH) radiotherapy for patients with left sided breast cancer and compare the performance of OSMS and cone-beam CT (CBCT) in the determination of the set-up errors of DIBH radiotherapy for patients with left sided breast cancer.Methods:Twenty patients with left sided breast cancer received DIBH radiotherapy. Through the registration of CBCT images with the planning CT images, and the registration of OSMS radiography images with the outer contour of the body surface, translational set-up errors and rotational errors were determined along the lateral-medial ( Rx), superior-inferior ( Ry) and anterior-posterior ( Rz) directions. Pearson correlation analysis was performed to evaluate the correlation of the set-up errors determined by two methods, and Bland- Altman plot analysis was used to assess the coincidence of these two methods. Results:Two methods were positively correlated. The Rz volume was 0.84, 0.74 and 0.84 in the x, y and z directions, and 0.65, 0.41 and 0.54 in the Rx, Ry and Rz directions, respectively (all P<0.01). The 95% CI of agreement were within preset 5 mm tolerance (-0.37-0.42cm, -0.39-0.41cm, -0.29-0.49cm ) in x, y and z directions for two methods. The 95% CI of agreement were within preset 3 ° tolerance -2.9°-1.4°, -2.6°-1.4°, -2.4°-2.5°in Rx, Ry and Rz directions for two methods. The system errors of 20 patients with left sided breast cancer receiving DIBH radiotherapy were <0.18cm and the random errors were <0.24cm. Conclusions:OSMS is equivalent to CBCT in the determination and stimulation of set-up errors for patients with left sided breast cancer receiving DIBH radiotherapy. The combination of CBCT and OSMS is a safe and reliable method.
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Objective:To design and implement a plan data archiving system (PDAS) for radiotherapy treatment, in order to improve the efficiency of plan archiving and avoid plan data loss.Methods:The original plan file in the treatment planning system (TPS) was read and parsed, and the record and verification (R&V) system database was accessed to obtain the patient′s treatment record. PDAS processed all parameters involved in the plan archiving and saved the structured data into a local database. PDAS included two major modules, the plan archiving module and the plan loss detection module. The former could be divided into four parts, data sorting, data compression, archiving check and plan recovery. For different modules, we designed corresponding logic rules and wrote programs to realize the system. Compared with the plan data of manual archiving, the clinical application effect of PDAS was evaluated.Results:Each module of PDAS was developed and implemented. During 31 months of clinical application, the system was stable, and 17 614 plans were archived. Compared with manual archiving, PDAS improved the archiving efficiency significantly and reduced the plan loss rate from 0.004 or so to 0.Conclusions:PDAS can improve the efficiency of plan archiving and ensure the security and integrity of plan data.
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Objective To establish a novel method of describing the off-axis ratio (OAR) characteristics of the flattening filter-free (FFF) beam.Methods The OAR curves at a depth of 1.5,5,10 and 20 cm were measured for Varian Edge,Elekta VersaHD and Tomotherapy using the water tank.The second derivatives of the OAR in the positive and negative directions were calculated.The center of the line connecting the maximum and minimum second derivatives was defined as the field edge.The distance between the left and right field edges was defined as the dosimetric field size.The OAR curve within the 80％ of dosimetric field size was fitted using the gaussian function and the fitting parameters were adopted to describe the shape of OAR.Results The calculated field size error was less than 0.11 cm and the central axis position error was less than 0.05 cm.The fitting correlation coefficient was greater than O.998.The fitting maximum error of OAR curve did not significantly alter with the depth,whereas slightly increased over the increased field size.The maximum error for a field size of 10,20,30 and 40 cm was 0.49％,0.67％,1.25％ and 2.52％,respectively.Conclusions A method which can independently and accurately describe the OAR characteristics of FFF photon beam is established for the first time,which can calculate the field size of FFF beam and fit the OAR curve of FFF beam using the gaussian function.
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Objective To evaluate the effect of setup errors upon the target area and the organs at risk (OAR) during radiotherapy for prostate cancer.Methods Twelve prostate cancer patients receiving treatment in the recent 1 year were randomly recruited in this study.The position of each patient was verified by using cone beam CT (CBCT) for 6-10 times during the treatment.In treatment planning system (TPS),the isocenter position was moved along the setup errors with averaging error value (Plan_A) and each CBCT value (Plan_F).The dose distribution was recalculated without changing the beam setting,weight factors and monitor units (MUs).The dose difference was statistically compared between the simulation and original plans (Plan_O).Results For clinical target volume (CTV) D95,there was a significant difference between Plan_A and Plan_O (P =0.008),whereas no significant difference was observed between Plan_F and Plan_O.There were significant differences between Plan_F and Plan_O,Plan_A and Plan_O (P=0.004,and 0.041) for the planned target volume (PTV) D95.For OAR,rectal V60,Dmax,left femoral V20,Dmax and right femoral Dmax significantly differed between Plan_F and Plan_O (P=0.026,0.015,0.041,0.049,0.003).However,only left femoral Dmax significantly differed between Plan_A and Plan_O (P=0.045).The movement in the superior-inferior (SI) direction was significantly correlated with the changes in the rectal V40,V50 and V60 and PTV D95 (r=-0.785,-0.887,-0.833,0.682).The movement in the anterior-posterior (AP) direction was significantly associated with the variations in the bladder V20,V30,V40,V50 and V60(r=-0.945,-0.823,-0.853,-0.818,-0.774).The evaluation indexes of all normal tissues in the re-plan could meet the clinical requirements.However,the volume of target prescription volume had different levels of deficit,and the deficit of Plan_F was greater than that of Plan_A.Conclusions The simulation results of averaging into the TPS underestimates the effect of daily setup errors on the dose distribution.The effect of setup errors on the dose distribution in target area is greater than that of normal tissues.Y-direction errors are more likely to cause the variations of the rectal and PTV dose,and the errors in the z-direction are inclined to cause the changes in the bladder dose.
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Objective To retrospectively analyze the setup error in radiotherapy of somal tumors and body metastases using the ExacTrac X-ray portal image,and to evaluate the feasibility and effectiveness of 6D setup error correction in body radiotherapy.Methods The translational and rotational setup errors were calculated by registering the bony structures on the ExacTrac X-setup images to that of the digitally reconstructed setup images,and the corresponding residual errors were calculated together.Results The translational and rotational setup errors in the x (left-right),y (superior-inferior),z (anterior-posterior) and Rx (sagittal),Ry (transverse),Rz (coronal) directions were(2.27±2.02) mm,(4.49±2.52) mm,(2.27± 1.37) mm and (1.02 ± 0.73) °,(0.67 ± 0.68) °,(0.76 ± 0.84) °,respectively.The residual translational and rotational setup errors in the x(r),y(r),z(r) and Rx(r),Ry(r),Rz(r) directions were(0.27±0.48)mm,(0.37±0.45)mm,(0.22±0.30)mm and (0.17±0.33)°,(0.14±0.34)°,(0.16± 0.28) ° respectively.Conclusions Besides the translational setup errors,a certain amount of rotational setup errors exist in radiotherapy of somal tumors and body metastases.By using the 6D setup error correction of the ExacTrac system,a translational less than 0.4 mm and rotational setup errors less than 0.2° could be achieved.
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Objective To evaluate the effect of the tolerance table of different couch positions in the record and verify system (R&V system) upon the setup accuracy.Methods Clinical data of 715 patients (15 743 fractions of treatment) were extracted from the R&V system database and assigned into four categories including thorax and abdomen,head and neck,breast,and rectum based on the disease site and immobilization device.The first day couch position (FstD) and cumulative average couch position (CumA)were utilized as the references to analyze the couch setup of each faction of treatment,and to establish the tolerance tables of different sites.The sensitivity and specificity of two methods were evaluated by the actual clinical treatment record of the patients.Results For the FstD as the reference,the couch tolerance in the breast was significantly higher than those in other parts.When the CumA was used as the reference,the couch tolerance tended to be stable after a certain fractions of treatment,and the tolerance of all sites was less than that of the FstD.The tolerance tables significantly differed between these two methods (P=0.000).Both two methods possessed high specificity,whereas the CumA method yielded higher sensitivity than the FstD approach.Conclusion Setting a reasonable tolerance table of couch position can effectively improve the setup accuracy.
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Objective To evaluate the necessity of arc by arc setup verification in patients with brain metastases receiving stereotactic radiotherapy (SRT) by analyzing the inter-and intra-fraction setup errors and residual errors collected from the ExacTrac X-ray portal image.Methods Clinical data of brain metastases patients treated with SRT in the previous two years were retrospectively analyzed.The ExacTrac X-ray setup images were collected after the normal setup procedure.Setup errors were calculated by registering the cranial bony structures of the ExacTrac X-ray setup images to that of the digitally reconstructed setup images.The inter-and intra-fraction setup errors and residual errors were statistically analyzed.Results Seventy-five patients from 116 lesions received 337 cycles of SRT of the head.The inter-and intra-fraction translational setup errors in the x,y and z directions were (0.93±0.86) mm and (0.15±0.59) mm;(1.83± 1.27) mm and (0.25±0.73) mm;(0.96±0.80) mm and (0.14±0.56) mm,respectively.The inter-and intra-fraction rotational setup errors in the x,y,z directions were (0.65°± 0.62°) and (0.19°± 0.40°);(0.97°±0.94°) and (0.13°± 0.25°);(0.92°± 0.71°) and (0.10°± 0.29°),respectively.The residual translational setup errors in the x,y,z directions were (0.06±0.23) mm,(0.08±0.24) mm and (0.08±0.22)mm,and (0.12°± 0.27°),(0.09°± 0.18°) and (0.06°± 0.19°) for the residual rotational setup errors,respectively.For a reference setup error threshold of 0.7 mm/0.7°,99.1％ of the SRT exceeded the threshold and required setup correction.For 1 006 non-coplanar arcs,rotating the treatment couch from 0° to the treatment angle made 66.4％ of arcs exceed the threshold and require at least once setup correction.Conclusions During SRT for brain metastasis,the inter-and intra-fraction setup errors should be emphasized.It is necessary to perform arc by arc setup error verification.
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Objective A self-made tiltable treatment couch was adopted for CT simulation positioning and radiotherapy to evaluate the feasibility and effectiveness to minimize the setup errors. Methods Twenty-two patients with thoracic and abdominal tumors receiving radiotherapy in Department of Radiation Oncology,Peking Union Medical College between March and September 2016 were recruited in this study. All patients were randomly divided into the experimental(n=11)and control groups(n=11).In the study group,the tiltable treatment couch was adopted to switch the patients from the standing position to the supine position,and conventional supine position was utilized in the control group. All patients received CT positioning under spontaneous breathing. Image registration was performed according to the standard recommendations of IGRT group. The image registration data for the translational and rotation errors of CBCT were recorded and analyzed. The setup errors were calculated by four-parameter model between two groups. Results In the experimental group,the translational error of the x direction was(-0.012±0.128)cm with a variation range of(0.29-0.70 cm),(0.272±0.123)cm for the y direction(0.23-0.70 cm)and(0.089± 0.105)cm for the z direction(0.14-0.53 cm),respectively. In the control group,the translational error of the x direction was(0.006±0.198)cm(0.27-0.75 cm),(-0.108±0.396)cm for the y direction(0.56-2.08 cm)and(- 0.096± 0.176)cm for the z direction(0.34-0.89 cm), respectively. Conclusions Application of the self-made tiltable treatment couch can enhance the setup reproducibility and reduce the setup errors,especially in the y direction during radiotherapy for the thoracic and abdominal tumors.
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Objective To design and implement a planning backup and restore system and evaluate its clinical effectiveness.Methods The default TPS menu of data save (File-Save) and system exit (File -Exit) was replaced by user designed script (Script_Save and Script_Exit) which backup the current planning status in a special format besides performing the normal save and exit operation.The treatment plan can be rolled back to any previously saved backup status in case the data were damaged or,the plan quality was deteriorated in the try and error planning process.Results The save and exit operation was simplified by using the user designed script.An extra disk space of 59.4MB per patient was required to backup the planning process and the backup was performed with no impact to the normal planning operation.1.9％ of the plans were restored during the planning process.For all of the restoring operations,65％ were performed within 1 day,80％ were performed within 1 week,and 87.6％ were performed within 1 month.Some restoring operations were even performed 4 months after the planning.Conclusions The designed backup and restore system is clinical applicable and valuable.Clinical using of the system can improve the planning efficiency and patient data safety.
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Objective To investigate the correlation between setup error and couch position error in radiotherapy.Methods A total of 25 patients with thoracic and abdominal tumors who recently finished image-guided radiotherapy were randomly selected.The data on couch position during treatment were obtained through the record validation system, and then the couch position error was calculated.The Pearson correlation analysis was used to investigate the correlation between setup error and couch position error during treatment.Results In the ≥5 setup errors among the 25 patients, the correlation coefficient between random setup error and random couch position error was 0.83(P=0.00), and the correlation coefficient between systematic setup error and systematic couch position error was 0.36(P=0.11).Conclusions In radiotherapy, the random setup error is highly correlated with the random couch position error, while a moderate or low correlation exists between the systematic setup error and the systematic couch position error.
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Objective To design and develop a treatment unit selecting system in aim of enhancing work efficiency and safety,adjusting treatment unit workload,improving quality of medical care.Methods Various treatment techniques,immobilization devices and setup verification devices were modeled in software.Workload of treatment units were extract from the Record and Verify System.These two types of information were then combined with the unit's workload capability to calculate the optimal radiotherapy apparatus for tumor patient.Results The system had finished selecting radiotherapy apparatusv for more than 5 000 patients since its taking place of the old patient selecting methods.Maximum variation of daily treatment duration between treatment units had decreased from 4-5 hours (mean 4.22 hours) to 1-2 hours (mean 1.84 hours) since the system have been put into operation.Workload and device configuration of various units could be controlled by easily editing of the system configuration file.Conclusions The system developed not only accomplish patient selecting in an optimal and safe way,but also provide a way of easily control the treatment unit workload.
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Objective This study analyzes the effect of the shrinkage of thermoplastic mask on patient positioning. Methods Design of the two test. Test 1:thermoplastic film shrinkage test. Get some thermoplastic film by the size of 10 cm×5 cm, extrude it at a certain rate after heated. Measure the length of thermoplastic film on different time, and calculate the contraction. Test 2:phantom test. Take advantage of head and neck phantom, and simulate the procedure that from making mask for patients to radiation therapy. Measure the off set of isocenter which caused by the contraction of thermoplastic mask. Results The largest shrinkage of thermoplastic had happened in 20 minutes. Different tensile ratio had little effect on the shrinkage. The offset of isocenter which caused by the shrinkage of thermoplastic mask were:LR ( -0?? 1± 0?? 3) mm,SI (-0?? 2±0?? 2) mm, AP (0.6±0?? 4) mm,respectively. There was little change in the course of six weeks ( P= 0.185?0?? 961). Conclusions The cooling time should be more than 20 minutes, when making a mask for the patient. The setup errors which caused by the shrinkage of thermoplastic mask is at an acceptable level on this premise.
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Objective To investigate the impact of anatomical landmarks on registration in image?guided radiotherapy (IGRT) for central and peripheral lung cancer. Methods Twenty?five patients with central or peripheral lung cancer for IGRT were enrolled in this study. Kilo?voltage cone?beam CT ( kV?CBCT) scanning was acquired before irradiotion. Tumor coverage on CBCT was assessed using gross tumor volume (GTV), clinical target volume (CTV), and planning target volume (PTV) contours according to tumor alignment, carina registration, and spine registration, respectively. The grading analysiswas based on visual tumor assessment as follows:grade 0, tumor within GTV;grade 1, tumor outside GTV but inside CTV;grade 2, tumor outside CTV but inside PTV;and grade 3, tumor outside PTV. Results Totally 177 sets of kV?CBCT of 25 patients was collected. According to the registration landmarks of the tumor, carina and spine for central lung cancer, the percentages were 57?55%, 53?77% and 16?04% in grade 0, 39?62%, 45?28%and 58?49% in grade 1, and 1?89%, 0?94% and 25?47% in grade 2, respectively. For peripheral lung cancer, the percentages were 47?89%, 14?08% and 2?82% in grade 0, 43?66%, 29?58% and 45?07% in grade 1, and 8?45%, 40?85% and 35?21% in grade 2, respectively. Conclusions For central lung cancer,the tumor was recommended as the best registration landmark, and the carina was recommended as well, while the spine was not recommended. For peripheral lung cancer, the tumor was recommended as the best registration landmark, while the spine and the carina were not recommended.
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<p><b>OBJECTIVE</b>To investigate the dosimetric benefit of 4D-CT in the planning target volume (PTV) definition process compared with conventional PTV definition using general margin in radiotherapy of lung cancer.</p><p><b>METHODS</b>A set of 4D-CT images and multiphase helical CT scans were obtained in 10 patients with lung cancer. The radiotherapeutic plans based on PTV determined by 4D-CT and in addition of general margin were performed, respectively. The 3D motion of the centroid of GTV and the 3D spatial motion vectors were calculated. The differences of the two kinds of PTVs, mean lung dose (MLD), V5,V10,V15,V20 of total lung, mean heart dose (MHD), V30 and V40 of heart, D99 and D95 were compared, and the correlation between them and the 3D spatial motion vector was analyzed.</p><p><b>RESULTS</b>The PTV4D in eight patients were smaller than PTVconv, with a mean reduction of (13.0 ± 8.0)% (P = 0.018). In other two patients, whose respiration motion was great, PTV4D was larger than PTVconv. The mean 3D spatial motion vector of GTV centroid was (0.78 ± 0.72)cm. By using 4D-CT, the mean reduction of MLD was (8.6 ± 9.9)% (P = 0.037). V5, V10, V15, V20 of total lung were decreased averagely by (7.2 ± 10.5)%, (5.5 ± 8.9)%, (6.5 ± 8.4)% and (5.7 ± 7.4)%, respectively (P < 0.05 for all). There was a significant positive correlation between PTV4D/PTVconv and the 3D spatial motion vector of the GTV centroid (P = 0.008). A significant inverse correlation was found between D994D/D99conv and the 3D spatial motion vector of the GTV centroid (P = 0.002). D994D/D99conv, (MLDconv-MLD4D) /MLDconv, total lung (V5conv-V54D)/V5conv, total lung (V10conv-V104D)/V10conv, (MHDconv-MHD4D)/MHDconv, heart (V30conv-V304D)/V30conv were inversely correlated with PTV4D/PTVconv (P < 0.05 for all).</p><p><b>CONCLUSIONS</b>4D-CT can be used to evaluate the respiration motion of lung tumor accurately. The 4D-CT-based PTV definition and radiotherapeutic planing can reduce the volume of PTV in patients with small respiration motion, increase the intra-target dose, and decrease the dose of normal tissue sequentially. For patients with large respiration motion, especially those more than 1.5-2 cm, this method can avoid target miss, meanwhile, not increase the dose of normal tissue significantly.</p>
Subject(s)
Humans , Four-Dimensional Computed Tomography , Methods , Lung , Lung Neoplasms , Radiotherapy , Movement , Radiometry , Radiotherapy Planning, Computer-Assisted , Methods , Respiration , Tomography, X-Ray Computed , MethodsABSTRACT
Objective The aim of this study is to evaluate the feasibility of using orthogonal kilo voltage fluoroscopic imaging(OKVFI)for setup correction in image guided radiotherapy of the liver.Methods After positioned the patients with liver cancer implanted with silver rings on the accelerator equipped with kilo voltage X-ray volume imaging(XVI),averaged OKVFI and cone beam CT(CBCT) volumetric images were acquired.A total of 90 datasets of averaged OKVFI and 90 datasets of volumetric images for 10 patients were obtained.The couch shifts obtained by the matching between OKVFI and digitally reconstructed radiograph were compared tu those achieved by the registration between CBCT and 4D reference average CT.On the comparison of the two different matching metheds.the Pearson coefficient was used to analyzed the correlation and Bland-Altman analysis to discern the consistence.Results The Pearson coefficient of correlation for the patient position shifts were R2=0.821.0.771 and 0.909 in the left-right (LR),anterior-posterior(AP)and superior-inferior(SI)directions respectively.95% CI were-2.30 -1.53(LR),-2.06-3.01(AP)and-2.69-1.53(SI)respectively.Within a±3 mm tolerance were 97.78%.95.56%and 96.67%respectively.Conclusions OKVFI has hish correlation and consistence with CBCT image on the setup correction.It is feasible to implement position correction with OKVFI in clinic practice.
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Objective This study was to assess the three-dimensional gross tumor volume(GTV)motion of lung cancer caused by respiration using four-dimensional computed tomography(4DCT),and to analyze the influenee factors.Methotis Four-DCT scans of 22 lung focuses in 21 patients with lung cancer were analyzed.The gross tumor volume was contoured in all 10 respiration phases of 4DCT scans.The changes in volume of GTV,the 3D motion of the centroid,boundary of GTV and the 3D spatial motion vectors were calculated and the irdluenee factors were analyzed.Results The average change in volume of GTV was+14.3%(0.2%.42.5%)/-8.4%(0.4%-38.6%),the average movement amplitude of GTV centroid and GTV boundary were(0.18±0.12)cm,(0.20±0.16)cm,(0.53±0.59)cm and(0.42±0.23)cm,(0.41±0.22)cm,(0.57±0.70)cm in medio-lateral,vertro-dorsal,cranio-caudal(CC) direction,respectively.The CC movement was larger than other directions(Z=-2.12,P=0.034;Z:-2.10,P=0.035),and no significant difference was observed in 3D motion of GTV boundary(Z=-0.81.P=0.417;Z=-0.86,0.391).The CC motion of GTV eentroid in lower lobe was larger than that in upper lobe[(0.87±0.64)and(0.35±0.49)cm,(t=-2.12,P=0.047)],and no significant difference was found in other directions[(0.23±0.10)and(0.19±0.18)em(t=-0.49,P=0.629),(0.21±0.13)and(0.17±0.11)cm(t=0.76,P=0.460)].There was no correlation of the 3D movement and 3D spatial motion vector of GTV to the volume of GTV(r=-0.306,-0.062,-0.279,-0.300;P=0.189,0.796.0.234,0.199).Conclusions GTV motion of patients with lung cancer is individual,the CC movement is the moat obvious,using 4DCT to assess is comparatively accurate.The motion amplitude of lower lobe focuses is larger.No significant correlation of the GTV motion to the volume was observed.Larger sample study is needed to analyze the influence of adjacency to the GTV motion.
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Objective To analyze the influencing factors of cone-beam CT (CBCT) imagine registration in lung cancer. Methods From Mar. 2007 to Dec. 2007, 20 patients with lung cancer were treated with IGRT. The imagines of CBCT were collected from 6 to 19 fractions during the patients' radiotherapy. To compare the difference of set-up errors between the two groups according to the distance from the lesion in lung to the centrum. At the same time, CBCT imagines from the first, middle and the last fraction of these patients' radiotherapy were registrated in bone and grey methods by four doctors. The difference of set-up errors between different doctors and registrated methods were compared. Results The mean values of set-up errors were ＜2 mm in the two groups without significant difference (x:-1.31mm vs 0. 10 mm (t=0. 07,P=0.554);y:1.24 mm vs 1.37 mm (t=0. 05,P=0. 652);z: - 1.88mm vs -1.26mm (t= -0. 12,P=0.321)). The mean values of set-up errors were ＜ 1.3 mm in four doctors and registrated methods without significant difference, for bone registration,x: -0. 05 mm, -0. 01 mm,0. 05 mm, -0.12 mm and -1.31 mm ( F=-0.01,P=0.887) ;y:0.56 mm,0.35 mm,0.51 mm and 0.43 mm (F= -0.01,P=0.880);z: -1.16 mm, -1.20 mm, -0.88 mm and -1.03 mm (F= -0.04,P=0. 555 ), for grey registration ,x: -0.32 mm, -0.341 mm, -0.395 mm and - 0.37 mm(F=-0.01, P=0.874);y:0.34 mm,0.54 mm, -0.04 mm and 0.27 mm (F= -0.03,P=0.622);x:-1.12 mm,- 1.15 mm, - 1.13 mm and - 1.04 mm (F=0. 00,P=0. 812). Conclusions With the same registrated box and imagine quality, the location of the lesions in lung, registred methods and different doctors are not the influencing factors for CBCT imagine registration.
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Objective To study the variation of gross tumor volume (GTV) and clinical target volume (CTV) definition for lung cancer between different doctors.Methods Ten lung cancer patients with PET-CT simulation were selected from January 2008 to December 2009.GTV and CTV of these patients were defined by four professors or associate professors of radiotherapy independently.Results The mean ratios of largest to smallest GTV and CTV were 1.66 and 1.65, respectively.The mean coefficients of variation for GTV and CTV were 0.20 and 0.17, respectively.System errors of CTV definition in three dimension were less than 5 mm, which was the largest in inferior and superior (0.48 cm,0.37 cm,0.32 cm;F=0.40,0.60,0.15,P=0.755,0.618,0.928).Conclusions The variation of GTV and CTV definition for lung cancer between different doctors exist.The mean ratios of largest to smallest GTV and CTV were less than 1.7.The variation was in hilar and mediastinum lymphanode regions.System error of CTV definition was the largest (<5 mm) in cranio-caudal direction.
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Objective To study the value of image-guided radiotherapy (IGRT) in lung cancer. Methods From Mar. 2007 to Dec. 2007,58 patients with lung cancer were treated with IGRT. Set-up er-rors in each axial direction was calculated based on IGRT images of each patient. The change of GTV was e-valuated on both cone-beam CT and CT simulator images. Results Twenty-two patients with left lung cane-er,30 with right lung cancer,5 with mediastinal lymphanode metastasis and one with vertebra metastasis were included. The set-up error in x,y and z axes was (0.02±0.26) cm, (0.14±0.49) cm and ( -0. 13± 0.27) cm, respectively,while the rotary set-up error in each axis was -0.15°± 1.59°, -0.01°± 1.50° and 0.12°±1.08°, respectively. The set-up errors were siguifieantly decreased by using of IGRT. GTV movement was observed in 15 patients (25.9%) ,including 5 with left upper lung cancer. GTV moving to the anterior direction was observed in 9 patients,including 4 with]eft upper lung cancer. GTV reduced in 23 (44.2%) patients during treatment. Asymmetric GTV reduction of 22 lesions was observed,with a mean re-ductive volume of 4.9 cm3. When GTV began to shrink,the irradiation dose was 4 -46 Gy,with 20 -30 Gy in 9 patients. Conclusions The use of IGRT can significantly reduce set-up errors. GTV movement and reduction are observed in some cases. The time to modify the target volume needs to be further studied.
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Objective To commission a Mobetron intra-operative mobile accelerator and analyze the characteristics of its electron beams. Methods The dosimetrie characteristics of the electron beams genera-ted by Mobetron accelerator were measured and compared with those generated by conventional accelerator (Primus, Siemens). M oberton accelerator can generate electron beams of nominal energies of 4,6,9 and 12 MeV. The measurement items were as followings : percentage depth dose perpendicular to water phantom sur-face and beam profiles parallel to water phantom surface, output factors, applicator leakage, electron beam at-tenuation made by lead blocks,and machine output calibration. The measurement devices included a three-dimensional ( 3 D) water scanning phantom, an electrometer, a 0.6 cm3 Farmer ionization chamber, a parallel-plate ionization chamber and solid water slabs. During measurement, all applicators of different tilt angles and diameters were attached to the machine head,and their ends were adjusted to be tangent to the phantom surface. Results Except for the 12 MeV,skin dose for all energies was no more than 90%. The skin dose was higher for Mobetron accelerator electron beams than for regular electron beams. The Dmax depth in water for a 10 cm flat applicator were 0.7,1.3,2.0 and 2.2 cm for the 4 energies,respectively. The depths of 90% dose were 1.0,1.8,2.7 and 3.6 cm, respectively. The selected flat applicator was just 1 cm larger than the tumor bed. But for the beveled applicators,the field flatness and symmetry became worse,and con-sequently,the applicator size had to be selected based on the isodose distribution. The leakage dose at 1 cm outside the applicator was 1.2% ,5.1%, 10.0% and 9.1%, respectively. The lead thickness for full block was 1.5,3.0,4.5 and 6.0 mm,respectively. Conclusions Through the commissioning of Mobetron accel-erator, the machine characteristics are understood, and the data for clinical implementation and routine quality assurance are acquired.