Eclipse Ver Research Articles

Point dose verification in breast cancer radiotherapy: comparison between 3D conformal and IMRT technique

The aim of this work was to verify multi point dose of the 3D-CRT and IMRT in the case of breast cancer. The experiment was perfomed at Siloam Hospital using Linac Trilogy and TPS Eclipse ver. 11. For measurements, Gafchromic film EBT3 was employed in this work in which the EBT3 film was distributed at 5 different points (trachea, axilla, and mammari interna, nipple, mamme inferior). Then, the statistical comparison between the dose measurement between 3D-CRT and IMRT techniques was evaluated. Moreover, the comparison of dose measurement between the non mastectomy and mastectomy group was also carried out. The result of differences in dose shows the trachea dose in the 3D-CRT is smaller than the IMRT in both the non mastectomy and mastectomy patients. The dose at the axilla, internal mammary, nipple, and inferior mammae are greater in the 3D-CRT than IMRT techniques in both non mastectomy and mastectomy patients. The dosage difference between TPS and EBT3 film in the range of from 0.66% to 5.67% (3D-CRT) and -0.67% to -7.57% (IMRT). The statistical test showed there was no difference of mean dose (sig 2 tailed > 0,025) between non mastectomy and mastectomy patients group and 3D-CRT and IMRT.

SU-F-T-681: Does the Biophysical Modeling for Immunological Aspects in Radiotherapy Precisely Predict Tumor and Normal Tissue Responses?

Purpose: Recent advances in immunotherapy make possible to combine with radiotherapy. The aim of this study was to assess the TCP/NTCP model with immunological aspects including stochastic distribution as intercellular uncertainties. Methods: In the clinical treatment planning system (Eclipse ver.11.0, Varian medical systems, US), biological parameters such as α/β, D50, γ, n, m, TD50 including repair parameters (bi-exponential repair) can be set as any given values to calculate the TCP/NTCP. Using a prostate cancer patient data with VMAT commissioned as a 6-MV photon beam of Novalis-Tx (BrainLab, US) in clinical use, the fraction schedule were hypothesized as 70–78Gy/35–39fr, 72–81Gy/40–45fr, 52.5–66Gy/16–22fr, 35–40Gy/5fr of 5–7 fractions in a week. By use of stochastic biological model applying for Gaussian distribution, the effects of the TCP/NTCP variation of repair parameters of the immune system as well as the intercellular uncertainty of tumor and normal tissues have been evaluated. Results: As respect to the difference of the α/β, the changes of the TCP/NTCP were increased in hypo-fraction regimens. The difference between the values of n and m affect the variation of the NTCP with the fraction schedules, independently. The elongation of repair half-time (long) increased the TCP/NTCP twice or much higher in the case of hypo-fraction scheme. For tumor, the repopulation parameters such as Tpot and Tstart, which is immunologically working to the tumor, improved TCP. Conclusion: Compared to default fixed value, which has affected by the probability of cell death and cure, hypo-fractionation schemes seemed to have advantages for the variations of the values of m. The possibility of an increase of the α/β or TD50 and repair parameters in tumor and normal tissue by immunological aspects were highly expected. For more precise prediction, treatment planning systems should be incorporated the complicated biological optimization in clinical practice combined with basic experiments data.

SU‐E‐T‐410: Evaluation of Treatment Modalities for Stereotactic Lung Radiation Therapy: A Phantom Study

Purpose:To evaluate and verify the accuracy of alternative treatment modalities for stereotactic lung therapy with end‐to‐end testing. We compared three dimensional conformal therapy (3DCRT), dynamic conformal arc therapy (DCAT), intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) treatment using 6 MV, 6 MV flattening filter free (FFF) and 10 MV FFF photons.Methods:A QUASAR respiratory motion phantom was utilized with custom ion chamber and gafchromatic EBT2 film inserts. The phantom contained a low density lung medium with a cylindrical polystyrene tumor (35 cc). Pseudo representative structures for various organs at risk (OAR) were created. All treatment plans were created using Eclipse ver. 11 using the same image and structure sets, and delivered via Varian TrueBeam STx linear accelerator equipped with high definition MLC. Evaluation of plan quality followed ROTG 0813 criterion for conformity index (CI100%), high dose spillage, D2cm, and R50%.Results:All treatment plans met the OAR dose constraints per protocol and could be delivered without any beam hold offs or other interlocks and hence were deemed clinically safe. For equivalent beam energies, target conformity was improved for all modalities when switching to FFF mode. Treatment efficiency increased for VMAT FFF by a factor of 3–4 over IMRT, and up to factor of 7 when compared to 3DCRT. Pass rates were > 97% for all treatment using gamma criteria of 3%, 3mm. Absolute dose at iso‐center was verified with ion chamber, and found to be within 2% of the treatment planning system.Conclusion:The higher dose rate associated with FFF not only reduces delivery times, but in most cases enhances plan quality. The one modality with succeeding best results for all RTOG criterions was VMAT 6 MV FFF. This end‐to‐end testing provides necessary confidence in the entire dose delivery chain for lung SBRT patients.

SU‐E‐T‐810: Volumetric Modulated Arc Therapy and Conventional Intensity‐Modulated Radiotherapy for Non‐Small‐Cell Lung Cancer with Simultaneously Integrated Boost Radiation Therapy: A Planning Comparison Study

Purpose:To compare and analyze the characteristics of intensity‐modulated arc therapy(IMAT) versus fixed‐gantry intensity‐modulated radiotherapy(IMRT) in treatment of non‐small‐cell lung cancer.Methods:Twelve patients treated in our radiotherapy center were selected for this study. The patient subsequently underwent 4D‐CT simulation.Margins of 5mm and 10mm were added to the ITV to generate the CTV and PTV respectively. Three treatment plans (IMRT,one single arc (RA1),double arcs (RA2))were generated with Eclipse ver.8.6 planning systems. Using a dose level of 75Gy in 15fractions to the ITV,60Gy in 15fractions to the CTV and 45Gy in 15fractions to the PTV respectively. The target and normol tissue volumes were compared,as were the dosimetry parameters.Results:There were no significant differences in CI of ITV,PTV,HI of ITV,CTV and PTV, V5,V10,V15,V20,V25,V30,V45,V50 of total‐lung and mean lung dose (all p>0.05). However, the differences were significant in terms of CI of CTV,V5 of B‐P (all p<0.05). On the MU, IMRT=1540MU,RA1=1006 MU and RA2=1096 MU. (F=12.00,P=0.000).On the treatment time, IMRT= 13.5min,RA1= 1.5min,and RA2=2.5 min (F= 30.11,P=0.000 ).Conclusion:IMAT is equal to IMRT in dosimetril evaluation. Due to much less Mu and delivery time,IMAT is an ideal technique in treating patients by reduceing the uncomfortable influnce which could effect the treatment.

SU‐E‐J‐210: Thoracic Atlas Segmentation Model Based On Consensus Contours

Purpose:Generation of a thoracic segmentation atlas based on consensus contours obtained through input from individual expertsMethod and Materials:A cohort of 30 patients treated for lung disease was selected for this study. All patients had 4D‐CT studies with image segmentation based on respiration‐averaged images. For each subject, three experts delineated the eighteen agreed‐upon structures using tools available in Eclipse ver.10.0. Consensus structures were generated using CERR(4.0β2). The EM‐STAPLE method was chosen to generate the consensus contours based on published reports which state that iterative methods yield better results over analytical methods in medical imaging. Once the consensus contours were generated they were re‐imported in Eclipse for further processing and evaluation. For each structure, each expert's contour was scored against the consensus using two scoring indices: Dice similarity coefficient, DSC, and Dice‐Jaccard coefficient, DJC. Visual inspection was always performed to detect large segmentation errorsResults:The respiration‐averaged CT set proved to be adequate for all structures included in the thoracic atlas. As expected, anatomic variability between patients was larger than the variability due to the level of expertise. Across the entire cohort the smallest structure segmented was the brachial plexus with a 9.4cc (+/− 3.5) volume, while the chest wall was the largest (2933cc +/‐560). The DSC and DJC coefficients were smallest for Left Brachial Plexus 0.894 (+/−0.138) and 0.842 (+/− 0.138), respectively, while the largest were 0.992(+/−0.004) and 0.990(+/− 0.004), observed for the right lung.Conclusions:Consensus contours generated using expert input were analyzed using comparison indices and visual evaluation. With appropriate atlas selection (e.g. patient gender, arm position) a robust thoracic atlas segmentation tool can be set up and may be used in conjunction with an automatic segmentation algorithm.Project supported by Varian Medical System

SU-E-T-196: Commissioning for Volumetric Modulated Radiation Therapy on Varian Clinac 21EX.

Recently the volumetric arc therapy (VMAT) technology such as RapidArc is widely distributed in Japan. These technologies are normally provided by the high spec linear accelerator such as Trilogy, Novalis Tx, Synergy, et al. The specific DICOM-file is generally used for commissioning of these technologies. On the other hand, we had to apply RapidArc into historic linear accelerator. This title expresses an experience how we performed the commissioning of RapidArc with the old linear accelerator. Two Varian's linear accelerators "Clinac 21EX" equipped with Millenium multi-leaf collimator and a Varian's treatment planning system "Eclipse ver.8.9" were used for this study. The commissioning for RapidArc was performed in energy 4,6,10,15 MV (Max-DR: 250, 600, 400, 600 MU/min). Commissioning procedure composed two categories: the general machine QA for DMLC-IMRT procedure and the specific RapidArc QA procedure. In RapidArc QA procedure, we modified DICOM-file to apply into the potential spec of Clinac 21EX optimally. The specific MLC-motion sequence and the gantry rotation speed were created by the dedicated programs (Shaper and DicomEdit, Varian) for RapidArc QA procedure. Each tolerance value was defied by the data from daily/monthly QA and the paper by Ling et al. As the results of the general machine QA procedure, the variance of radiation output during static/dynamic gantry rotation was less than 1%. The deference of fence tests during static/dynamic gantry rotation and RapidArc were less than 1 mm in each. However, the results of the RapidArc QA were worse than the latest machine (especially variable gantry speed) and it was careful to define tolerance level. The procedure of commissioning for RapidArc on historic linear accelerator was proposed. Several minor revisions for DICOM-file should be required for suitable commissioning and it may ensure the tolerance limit for gantry/MLC-leaf motion speeds.

SU‐E‐T‐364: Verification of MLC Motion Error during IMRT/VMAT Delivery by Using an In‐House Program

Purpose: In intensity modulated radiation therapy (IMRT) and/or volumetric modulated arc therapy (VMAT), it is important to ensure the accuracy of multi‐leaf collimator (MLC) motion during delivery. However, the commercially available software can evaluate only summary of MLC motion during delivery as the error's root‐mean‐square (RMS). The purposeof this study is to construct the suitable procedure to evaluate MLC‐motion continuously with an in‐house program. Method: This study was composed into two sections. First, we created the in‐house program to import MLC‐log file during delivery. The in‐house program was built by using visual basic language. The in‐house program includes some additional: 1) visualization of MLC motion during delivery with an animation, 2) classification whether the MLC‐motion error was over the tolerance or not, and 3) visualization of the location of MLC‐motion error during delivery. Second, we evaluated the MLC‐log during VMAT delivery by using our in‐house program. The VMAT plan was created by Eclipse ver.8.9 (Varian). The Clinac 21EX linear accelerator (Varian) equipped with Millenium multi‐leaf collimator was used for this study. Results: We confirmed the functions of our in‐house program as follows. The in‐house software was available to import the Varian's formatted MLC‐log file. The animation of MLC motion during delivery was expressed in 2 fr/sec. The tolerance value of MLC motion error could be defined optimally. If the MLC motion error happened, the location became colored from default color to red color. For prostate VMAT, the MLC motion error in all cases passed the tolerance value. We defined the tolerance value based on AAPM TG‐119 and 142. Conclusion:We conclude that our in‐house program should be useful to evaluate the accuracy of MLC motion during IMRT and/or VMAT delivery because the users can analyze the MLC motion error simply.

SU-E-T-585: Application of IMAT in Non-Small-Cell Lung Cancer with Simultaneously Integrated Boost Radiation Therapy.

To compare and analyze the characteristics of intensity-modulated arc therapy(IMAT) versus fixed-gantry intensity-modulated radiotherapy(IMRT) in treatment of non-small-cell lung cancer. Twelve patients treated in our radiotherapy center were selected for this study. The patient subsequently underwent 4D-CT simulation.Margins of 5 mm and 10mm were added to the ITV to generate the CTV and PTV respectively. Three treatment plans (IMRT,one single arc (RA1),double arcs (RA2))were generated with Eclipse ver.8.6 planning systems. Using a dose level of75Gy in 15fractions to the ITV,60Gy in 15fractions to the CTV and 45Gy in 15fractions to the PTV respectively. The target and normol tissue volumes were compared, as were the dosimetry parameters. There were no significant differences in CI of ITV,PTV, HI of ITV,CTV and PTV, V5,V10,V15,V20,V25,V30,V45,V50 of total-lung and mean lung dose (all p>0.05). However, the differences were significant in terms of CI of CTV, V5 of B-P (all p<0.05). On the MU, IMRT=1540MU,RA1=1006 MU and RA2=1096 MU. (F=12.00,P=0.000).On the treatment time, IMRT= 13.5min,RA1= 1.5min, and RA2=2.5 min (F= 30.11,P=0.000). IMAT is equal to IMRT in dosimetril evaluation. Due to much less Mu and delivery time,IMAT is an ideal technique in treating patients by reduceing the uncomfortable influnce which could effect the treatment.

SU‐E‐T‐707: Clinical Evaluation of a New Commercial Dose Calculation Algorithm

Purpose: A new algorithm, Acuros® XB Advanced Dose Calculation, has been introduced by Varian Medical Systems in the Eclipse planning system for photon dose calculation in external beam radiotherapy. Acuros XB is based on the solution of the linear Boltzmann transport equation (LBTE). In this study we perform a clinical evaluation of the Acuros XB by comparison to other known and tested treatment planning systems and dose calculation algorithms. Methods: Twenty (n=20) patients previously planned with the Pinnacle ver.9.0 treatment planning system and calculated using the collapsed cone convolution superposition algorithm, were recalculated using the Eclipse ver. 10.0 with the Acuros XB dose calculation algorithm. A mixture of treatment sites were chosen, including brain, lung, liver, and pelvis. The metrics chosen for the evaluation were DVH, absolute dose difference, and profiles along the axial, sagital and coronal planes at the isocenter Results: Good agreement was observed between the dose calculations with Acuros and the ones from Pinnacle using the CCCS algorithm. Differences were mostly detected in inhomogeneous media. Maximum differences of 2.5% were observed for lung patients, while, smaller differences were detected for pelvic, brain, and abdominal cases. Conclusions: The new dose calculation algorithm Acuros XB available in Eclipse ver. 10 is in very good agreement with the widely tested and accepted CCCS dose calculation algorithm. More extensive testing of the algorithm might be necessary in order to further evaluate the accuracy of the calculations.

SU-FF-T-608: Planning Comparison Between IMRT and RapidArc in CGMH Experience

Purpose: To evaluate the dose performance and delivery efficiency for RapidArc plan. Material and methods: Fixed‐beam IMRT can deliver prescribed dose to target and spare dose to OAR. Because it had an ineffective beam on time, some patients would lie on treatment couch for a long time. A new technique‐ RapidArc‐ was developed for shortening treatment time to compare with fixed‐beam IMRT. A selected NPC case was involved in this study, and treatment plans were created with IMRT and RapidArc technique for evaluating dose performance and delivery efficiency. In this case, the prescribed dose of CTV was 46Gy in the first phase. Fixed‐beam IMRT plan with 7 fields was used and RapidArc plan was performed using two arcs with total 718 rotation angle. Both plans executed on Eclipse ver 8.6 planning system. CTV coverage and avoidance structures sparing are two major indexes to compare through DVH. Results: Compared DVH showed 46Gy covering 96% and 95% volume of CTV for fixed‐beam IMRT and RapidArc respectively. High dose did not exceed 110.5% of prescribed dose in both. RapidArc can have heterogeneity dose in CTV as IMRT. With more than received dose 23Gy in parotid glands, the former had 30%∼31% volume and the later had 40.5%∼42% volume. Other avoidance structures showed the former had lower mean dose than the later. The total MU was 627 MU and delivery time was 3.5 min. in RapidArc. But, IMRT had 1195 MU and around 10 min. treatment time. Conclusions: In this study, RapidArc provided better plan quality than fixed‐beam IMRT. The features of lower MU and lower delivery time are the clinical advantage in RapidArc.