Study of normal tissue dosimetric benefit using asymmetric margin-based biological fuzzy decision making: volumetric modulated arc therapy of prostate cancer

2020 ◽  
pp. 1-9
Author(s):  
Santosh Kumar Patnaikuni ◽  
Sapan Mohan Saini ◽  
Rakesh Mohan Chandola ◽  
Pradeep Chandrakar ◽  
Rajeev Jain ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Normal Tissue ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Normal Tissue Complication Probability ◽  
Fuzzy Decision Making ◽  
Inference System ◽  
Error Magnitude ◽  
Arc Therapy ◽  
Fuzzy Logic Technique

Abstract Aim: Radiation therapy has historically used margins for target volume to ensure dosimetric planning criteria. The size of margin for a given treatment site is still uncertain particularly for moving targets along with set-up variations leading to a fuzziness of target volume. In this study, we have estimated the dosimetric benefit of normal structures using biological-based optimal margins. The treatment margins are derived by knowledge-based fuzzy logic technique which is considering the radiotherapy uncertainties in treatment planning. Materials and methods: All treatment plans were performed using stepped increments of asymmetric margins to estimate prostate radiobiological indices such as tumour control probability (TCP) and normal tissue complication probability (NTCP). An absolute NTCP of 5% was considered to be the maximum acceptable value while TCP of 85% was considered to be the minimal acceptable limit for each volumetric modulated arc therapy (VMAT) plan of localised prostate cancer radiotherapy. Results were used to formulate rules and membership functions for Mamdani-type fuzzy inference system (FIS). In implementing the rules for the fuzzy system for ΔNTCP values above 10%, the PTV margin was not permitted to exceed 5 mm to avoid rectal complications due to margin selection. The new margins were applied in VMAT planning of prostate cancer for standard displacement errors. The dosimetric results of normal tissue predictors were estimated such as organ mean doses, rectum V60 (volume receiving 60 Gy), bladder V65 (volume receiving 65 Gy) and other clinically significant dose–volume indicators and compared with VMAT plans using current margin formulations. Results: Dosimetric results compared well to the results obtained by current techniques. Good agreement was obtained between proposed fuzzy model margins and currently used margins in lower error magnitude, but significant results were observed at higher error magnitude when organ toxicity concerned without compromising the target volumes. Findings: The new margins may be helpful to estimate possible outcomes of normal tissue complications and thus may improve complication free survival particularly when organ motion errors are inevitable, case by case.

scholarly journals Risk-Adaptive Volumetric Modulated Arc Therapy Using Biological Objective Functions for Subvolume Boosting in Radiotherapy

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Nicholas Hardcastle ◽  
Wolfgang A. Tome
Keyword(s):  
Prostate Cancer ◽  
Normal Tissue ◽  
Volumetric Modulated Arc Therapy ◽  
Simultaneous Integrated Boost ◽  
Tumor Control ◽  
Objective Functions ◽  
Arc Therapy ◽  
Integrated Boost ◽  
Dose Constraints ◽  
Biological Optimization

Objectives. Simultaneous integrated boost (SIB) for prostate cancer allows increases in tumor control probability while respecting normal tissue dose constraints. Biological optimization functions that optimize based on treatment outcome can be used to create SIB prostate plans. This study investigates the feasibility of biologically optimized volumetric modulated arc therapy (VMAT) for SIB prostate radiotherapy.Methods. Five prostate cancer patients with diffusion-weighted MR images were selected for analysis. A two-step VMAT optimization was performed, which consisted of an initial biological optimization of a static gantry angle delivery followed by conversion of the static delivery to a single arc VMAT plan. A dosimetric analysis was performed on the resulting plans.Results. The VMAT plans resulted in a ΔEUD between the prostate and the boost volume of between 15.1 Gy and 20.3 Gy. Rectal volumes receiving 75.6 Gy ranged from 4.5 to 9.9%. Expected rectal normal tissue complication probabilities were between 8.6% and 21.4%. Maximum bladder doses ranged from 73.6 Gy to 75.8 Gy. Estimated treatment time was 120 s or less.Conclusions. The presented biological optimization method resulted in deliverable VMAT plans that achieved sufficient modulation for SIB without violating rectal and bladder dose constraints.Advances in knowledge. This study presents a method for creating simultaneous integrated boost VMAT treatments using biological outcome objective functions.

Effect of translational couch shifts in volumetric modulated arc therapy (VMAT) plans and predicting its impact on daily dose delivery

2017 ◽  
Vol 17 (2) ◽  
pp. 230-243
Author(s):  
Noufal M. Padannayil ◽  
Kallikuzhiyil K. Abdullah ◽  
Pallimanhayil A. R. Subha ◽  
Sanudev Sadanadan
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Normal Tissue Complication Probability ◽  
Planning System ◽  
Treatment Planning System ◽  
Equivalent Uniform Dose ◽  
Tumour Control ◽  
Matlab Code ◽  
Arc Therapy ◽  
The Impact

AbstractAimTo evaluate the impact of couch translational shifts on dose–volume histogram (DVH) and radiobiological parameters [tumour control probability (TCP), equivalent uniform dose (EUD) and normal tissue complication probability (NTCP)] of volumetric modulated arc therapy (VMAT) plans and to develop a simple and swift method to predict the same online, on a daily basis.MethodsIn total, ten prostate patients treated with VMAT technology were selected for this study. The plans were generated using Eclipse TPS and delivered using Clinac ix LINAC equipped with a Millennium 120 multileaf collimator. In order to find the effect of systematic translational couch shifts on the DVH and radiobiological parameters, errors were introduced in the clinically accepted base plan with an increment of 1 mm and up to 5 mm from the iso-centre in both positive and negative directions of each of the three axis, x [right–left (R-L)], y [superior–inferior (S-I)] and z [anterior–posterior (A-P)]. The percentages of difference in these parameters (∆D, ∆TCP, ∆EUD and ∆NTCP) were analyzed between the base plan and the error introduced plans. DVHs of the base plan and the error plans were imported into the MATLAB software (R2013a) and an in-house MATLAB code was generated to find the best curve fitted polynomial functions for each point on the DVH, there by generating predicted DVH for planning target volume (PTV), clinical target volume (CTV) and organs at risks (OARs). Functions f(x, vj), f(y, vj) and f(z, vj) were found to represent the variation in the dose when there are couch translation shifts in R-L, S-I and A-P directions, respectively. The validation of this method was done by introducing daily couch shifts and comparing the treatment planning system (TPS) generated DVHs and radiobiological parameters with MATLAB code predicted parameters.ResultsIt was noted that the variations in the dose to the CTV, due to both systematic and random shifts, were very small. For CTV and PTV, the maximum variations in both DVH and radiobiological parameters were observed in the S-I direction than in the A-P or R-L directions. ∆V70 Gy and ∆V60 Gy of the bladder varied more due to S-I shift whereas, ∆V40 Gy, ∆EUD and ∆NTCP varied due to A-P shifts. All the parameters in rectum were most affected by the A-P shifts than the shifts in other two directions. The maximum percentage of deviation between the TPS calculated and MATLAB predicted DVHs of plans were calculated for targets and OARs and were found to be less than 0·5%.ConclusionThe variations in the parameters depend upon the direction and magnitude of the shift. The DVH curves generated by the TPS and predicted by the MATLAB showed good correlation.

scholarly journals A dosimetric study of volumetric modulated arc therapy planning techniques for treatment of low-risk prostate cancer in patients with bilateral hip prostheses

2014 ◽  
Vol 03 (01) ◽  
pp. 018-021 ◽  
Author(s):  
Suresh B. Rana ◽  
Shyam Pokharel
Keyword(s):  
Prostate Cancer ◽  
Cancer Patient ◽  
Prostate Cancer Patient ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Low Risk ◽  
Hip Prostheses ◽  
Arc Therapy ◽  
Risk Prostate Cancer ◽  
Low Risk Prostate Cancer

Abstract Background and Purpose: Recently, megavoltage (MV) photon volumetric modulated arc therapy (VMAT) has gained widespread acceptance as the technique of choice for prostate cancer patients undergoing external beam radiation therapy. However, radiation treatment planning for patients with metallic hip prostheses composed of high-Z materials can be challenging due to (1) presence of streak artifacts from prosthetic hips in computed tomography dataset, and (2) inhomogeneous dose distribution within the target volume. The purpose of this study was to compare the dosimetric quality of VMAT techniques in the form of Rapid Arc (RA) for treating low-risk prostate cancer patient with bilateral prostheses. Materials and Methods: Three treatment plans were created using RA techniques utilizing 2 arcs (2-RA), 3 arcs (3-RA), and 4 arcs (4-RA) for 6 MV photon beam in Eclipse treatment planning system. Each plan was optimized for total dose of 79.2 Gy prescribed to the planning target volume (PTV) over 44 fractions. All three RA plans were calculated with anisotropic analytical algorithm. Results : The mean and maximum doses to the PTV as well as the homogeneity index among all three RA plans were comparable. The plan conformity index was highest in the 2-Arc plan (1.19) and lowest in the 4-Arc plan (1.10). In comparison to the 2-RA technique, the 4-RA technique reduced the doses to rectum by up to 18.8% and to bladder by up to 7.8%. In comparison to the 3-RA technique, the 4-RA technique reduced the doses to rectum by up to 14.6% and to bladder by up to 3.5%. Conclusion: Based on the RA techniques investigated for a low-risk prostate cancer patient with bilateral prostheses, the 4-RA plan produced lower rectal and bladder dose and better dose conformity across the PTV in comparison with the 2-RA and 3-RA plans.

Two-arc volumetric modulated arc therapy to provide dosimetric advantages for pancreas stereotactic body radiotherapy.

2016 ◽  
Vol 34 (4_suppl) ◽  
pp. 445-445
Author(s):  
Jason K Molitoris ◽  
Christopher Brown ◽  
Shifeng Chen ◽  
Kimberly Marter ◽  
Kristin Spaeth ◽  
...  
Keyword(s):  
Normal Tissue ◽  
Locally Advanced ◽  
Volumetric Modulated Arc Therapy ◽  
Advanced Pancreatic Cancer ◽  
Intensity Modulated Radiotherapy ◽  
Target Volume ◽  
Breath Hold ◽  
Target Coverage ◽  
Delivery Time ◽  
Arc Therapy

445 Background: Stereotactic body radiation therapy(SBRT) is increasingly used in locally advanced pancreatic cancer (LAPC). SBRT can be delivered using 3D conformal, static intensity modulated radiotherapy (IMRT), and volumetric modulated arc therapy (VMAT) techniques. Prior data suggest advantages of using VMAT over IMRT for single-fraction pancreas SBRT. We performed the first dosimetric comparison of IMRT with one and two arc VMAT for 5-fraction pancreas SBRT, a more commonly used regimen. Methods: We generated 5-fraction SBRT plans for 12 LAPC patients who were previously treated at our institution with standard fractionation. The prescription dose was 33 Gy delivered in 6.6 Gy fractions. Assuming breath hold, 3 plans were generated for each patient: 9-beam static IMRT, 1-arc VMAT (VMAT1), and 2-arc VMAT (VMAT2) targeting the primary tumor. Target coverage and normal tissue doses were compared between the delivery techniques. Results: Each plan met target coverage planning goals. More VMAT2 plans (100%) were able to meet all normal tissue constraints than VMAT1 (83.3%) or IMRT (75%). Duodenal dose was most lowest for VMAT2 compared to VMAT1 and IMRT for mean dose (8.66 vs. 9.00 vs. 8.99 Gy); D4% (25.9 vs. 26.6 vs. 26.3 Gy); V10Gy (38.02 vs. 39.33 vs. 40.11%), V15Gy (23.98 vs. 25.88 vs. 25.97%), V20Gy (12.73 vs. 13.84 vs. 14.95%), and V25Gy (5.96 vs. 6.85 vs. 6.78%)(all p < 0.05). The tumors closest to the duodenum had statistically significantly improved V30Gy for VMAT2 compared to VMAT1 and IMRT (both p < 0.001). VMAT1 and VMAT2 reduced dose to the stomach, spinal cord, and liver compared to IMRT; kidney dose, however, was lowest using IMRT. VMAT2 plans had the highest conformity, but required the most monitor units to deliver. Delivery time was significantly longer with IMRT, compared to VMAT1 and VMAT2 (8.25 vs. 2.16 vs. 3.33 mins). Conclusions: These data suggest that VMAT2 should be strongly considered for 5-fraction pancreas SBRT because of superior normal tissue sparing, more conformal target volume coverage, and faster treatment delivery time (compared to IMRT). Further evaluation is needed to clarify whether the dosimetric advantages of VMAT2 are clinically significant.

Dosimetric comparison of RapidPlan and manually optimised volumetric modulated arc therapy plans in prostate cancer

2020 ◽  
pp. 1-8
Author(s):  
Loyce M. H. Chua ◽  
Eric P. P. Pang ◽  
Zubin Master ◽  
Rehena Sultana ◽  
Jeffrey K. L. Tuan ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Organs At Risk ◽  
Volumetric Modulated Arc Therapy ◽  
Target Volume ◽  
Plan Quality ◽  
Planning Time ◽  
Arc Therapy ◽  
Treatment Plans ◽  
The Mean ◽  
Time Required

Abstract Purpose: The aim of this study was to evaluate whether RapidPlan (RP) could generate clinically acceptable prostate volumetric modulated arc therapy (VMAT) plans. Methods: The in-house RP model was used to generate VMAT plans for 50 previously treated prostate cancer patients, with no additional optimisation being performed. The VMAT plans that were generated using the RP model were compared with the patients’ previous, manually optimised clinical plans (MP), none of which had been used for the development of the in-house RP prostate model. Differences between RP and MP in planning target volume (PTV) doses, organs at risk (OAR) sparing, monitor units (MU) and planning time required to produce treatment plans were analysed. Assessment of PTV doses was based on the conformation number (CN), homogeneity index (HI), D2%, D99% and the mean dose of the PTV. The OAR doses evaluated were the rectal V50 Gy, V65 Gy, V70 Gy and the mean dose, the bladder V65 Gy, V70 Gy and the mean dose, and the mean dose to both femurs. Results: D99% and mean dose of the PTV were lower for RP than for MP (p = 0·006 and p = 0·040, respectively).V50 Gy, V65 Gy and the mean dose to rectum were lower in RP than in MP (p < 0·001). V65 Gy, V70 Gy and the mean dose to bladder were lower in RP than in MP (p < 0·001). RP had enhanced the sparing of both femurs (p < 0·001) and significantly reduced the planning time to less than 5% of the time taken with MP. MU in RP was significantly higher than MP by an average of 52·5 MU (p < 0·001) and 46 out of the 50 RP plans were approved by the radiation oncologist. Conclusion: This study has demonstrated that VMAT plans generated using an in-house RP prostate model in a single optimisation for prostate patients were clinically acceptable with comparable or better plan quality compared to MP. RP can add value and improve treatment planning efficiency in a high-throughput radiotherapy department through reduced plan optimisation time while maintaining consistency in the plan quality.

scholarly journals Dosimetric comparison between volumetric modulated arc therapy planning techniques for prostate cancer in the presence of intrafractional organ deformation

2020 ◽  
Author(s):  
Maria Varnava ◽  
Iori Sumida ◽  
Michio Oda ◽  
Keita Kurosu ◽  
Fumiaki Isohashi ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Organs At Risk ◽  
Volumetric Modulated Arc Therapy ◽  
Normal Tissue Complication Probability ◽  
Conformity Index ◽  
Tumor Control ◽  
Tumor Control Probability ◽  
Planning Techniques ◽  
Dose Distributions ◽  
Arc Therapy

Abstract The purpose of this study was to compare single-arc (SA) and double-arc (DA) treatment plans, which are planning techniques often used in prostate cancer volumetric modulated arc therapy (VMAT), in the presence of intrafractional deformation (ID) to determine which technique is superior in terms of target dose coverage and sparing of the organs at risk (OARs). SA and DA plans were created for 27 patients with localized prostate cancer. ID was introduced to the clinical target volume (CTV), rectum and bladder to obtain blurred dose distributions using an in-house software. ID was based on the motion probability function of each structure voxel and the intrafractional motion of the respective organs. From the resultant blurred dose distributions of SA and DA plans, various parameters, including the tumor control probability, normal tissue complication probability, homogeneity index, conformity index, modulation complexity score for VMAT, dose–volume indices and monitor units (MUs), were evaluated to compare the two techniques. Statistical analysis showed that most CTV and rectum parameters were significantly larger for SA plans than for DA plans (P &lt; 0.05). Furthermore, SA plans had fewer MUs and were less complex (P &lt; 0.05). The significant differences observed had no clinical significance, indicating that both plans are comparable in terms of target and OAR dosimetry when ID is considered. The use of SA plans is recommended for prostate cancer VMAT because they can be delivered in shorter treatment times than DA plans, and therefore benefit the patients.

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