Dose homogeneity as a function of source strength in optimized treatment plans

2002 ◽  
Author(s):  
W.D. D'Souza ◽  
R.R. Meyer ◽  
B.R. Thomadsen
Keyword(s):  
Source Strength ◽  
Treatment Plans ◽  
Dose Homogeneity ◽  
Optimized Treatment

Interactively exploring optimized treatment plans

2005 ◽  
Vol 61 (2) ◽  
pp. 570-582 ◽  
Author(s):  
Isaac Rosen ◽  
H. Helen Liu ◽  
Nathan Childress ◽  
Zhongxing Liao
Keyword(s):  
Treatment Plans ◽  
Optimized Treatment

scholarly journals Quantification of plan robustness against different uncertainty sources for classical and anatomical robust optimized treatment plans in head and neck cancer proton therapy

2020 ◽  
Vol 93 (1107) ◽  
pp. 20190573 ◽  
Author(s):  
Macarena Cubillos-Mesías ◽  
Esther G C Troost ◽  
Fabian Lohaus ◽  
Linda Agolli ◽  
Maximilian Rehm ◽  
...  
Keyword(s):  
Robust Optimization ◽  
Head And Neck ◽  
Proton Therapy ◽  
Anatomical Variations ◽  
Target Volume ◽  
Target Coverage ◽  
Intensity Modulated Proton Therapy ◽  
Uncertainty Sources ◽  
Treatment Plans ◽  
Optimized Treatment

Objective: Classical robust optimization (cRO) in intensity-modulated proton therapy (IMPT) considers isocenter position and particle range uncertainties; anatomical robust optimization (aRO) aims to consider additional non-rigid positioning variations. This work compares the influence of different uncertainty sources on the robustness of cRO and aRO IMPT plans for head and neck squamous cell carcinoma (HNSCC). Methods: Two IMPT plans were optimized for 20 HNSCC patients who received weekly control CTs (cCT): cRO, using solely the planning CT, and aRO, including 2 additional cCTs. The robustness of the plans in terms of clinical target volume (CTV) coverage and organ at risk (OAR) sparing was analyzed considering stepwise the influence of (1) non-rigid anatomical variations given by the weekly cCT, (2) with fraction-wise added rigid random setup errors and (3) additional systematic proton range uncertainties. Results: cRO plans presented significantly higher nominal CTV coverage but are outperformed by aRO plans when considering non-rigid anatomical variations only, as cRO and aRO plans presented a median target coverage (D98%) decrease for the low-risk/high-risk CTV of 1.8/1.1 percentage points (pp) and −0.2 pp/−0.3 pp, respectively. Setup and range uncertainties had larger influence on cRO CTV coverage, but led to similar OAR dose changes in both plans. Considering all error sources, 10/2 cRO/aRO patients missed the CTV coverage and a limited number exceeded some OAR constraints in both plans. Conclusion: Non-rigid anatomical variations are mainly responsible for critical target coverage loss of cRO plans, whereas the aRO approach was robust against such variations. Both plans provide similar robustness of OAR parameters. Advances in knowledge: The influence of different uncertainty sources was quantified for robust IMPT HNSCC plans.

scholarly journals Impact of prescription isodose level and collimator selection on dose homogeneity and plan quality in robotic radiosurgery

2021 ◽  
Author(s):  
Alexandra Hellerbach ◽  
Markus Eichner ◽  
Daniel Rueß ◽  
Klaus Luyken ◽  
Mauritius Hoevels ◽  
...  
Keyword(s):  
Treatment Time ◽  
Target Dose ◽  
Dose Distributions ◽  
Robotic Radiosurgery ◽  
Treatment Plans ◽  
Dose Homogeneity ◽  
Physical Limitations ◽  
The Impact ◽  
Prescription Isodose ◽  
Selection Of

Abstract Purpose In stereotactic radiosurgery (SRS), prescription isodoses and resulting dose homogeneities vary widely across different platforms and clinical entities. Our goal was to investigate the physical limitations of generating dose distributions with an intended level of homogeneity in robotic SRS. Methods Treatment plans for non-isocentric irradiation of 4 spherical phantom targets (volume 0.27–7.70 ml) and 4 clinical targets (volume 0.50–5.70 ml) were calculated using Sequential (phantom) or VOLOTM (clinical) optimizers (Accuray, Sunnyvale, CA, USA). Dose conformity, volume of 12 Gy isodose (V12Gy) as a measure for dose gradient, and treatment time were recorded for different prescribed isodose levels (PILs) and collimator settings. In addition, isocentric irradiation of phantom targets was examined, with dose homogeneity modified by using different collimator sizes. Results Dose conformity was generally high (nCI ≤ 1.25) and varied little with PIL. For all targets and collimator sets, V12Gy was highest for PIL ≥ 80% and lowest for PIL ≤ 65%. The impact of PIL on V12Gy was highest for isocentric irradiation and lowest for clinical targets (VOLOTM optimization). The variability of V12Gy as a function of collimator selection was significantly higher than that of PIL. V12Gy and treatment time were negatively correlated. Plans utilizing a single collimator with a diameter in the range of 70–80% of the target diameter were fastest, but showed the strongest dependence on PIL. Conclusion Inhomogeneous dose distributions with PIL ≤ 70% can be used to minimize dose to normal tissue. PIL ≥ 90% is associated with a marked and significant increase in off-target dose exposure. Careful selection of collimators during planning is even more important.

SU-FF-T-124: Comparison of Eclipse Step-And-Shoot IMRT Plans with Direct Aperture Optimized Treatment Plans

2009 ◽  
Vol 36 (6Part10) ◽  
pp. 2548-2548
Author(s):  
M Weldon ◽  
D Zhang ◽  
T Korytko ◽  
J Radawski ◽  
N Gupta
Keyword(s):  
Treatment Plans ◽  
Step And Shoot ◽  
Optimized Treatment

Evaluation of three dimensional conformal radiation therapy of oesophageal cancer: a dosimetric study

2018 ◽  
Vol 18 (03) ◽  
pp. 246-250 ◽  
Author(s):  
Hafiz Muhibb ullah Zulkafal ◽  
Muhammad Mazhar Iqbal ◽  
Muhammad Waqas Akhtar ◽  
Khalid Iqbal ◽  
Muhammad Afzal Khan
Keyword(s):  
At Risk ◽  
Radiation Therapy ◽  
Oesophageal Cancer ◽  
Conformal Radiotherapy ◽  
Homogeneity Index ◽  
3D Conformal Radiotherapy ◽  
Treatment Plans ◽  
Oesophagus Cancer ◽  
Dose Homogeneity ◽  
Dosimetric Indices

AbstractAimsThe main objective of this research work is to compare the dosimertic effect on lower and upper oesophagus cancer treatment using 3D conformal radiotherapy as well as to evaluate the doses administered to the organs at risk.Materials and methodsIn this study, a cohort of 30 oesophageal cancer patients between the ages of 45 and 67 years registered during March 2017 to February 2018 was considered. These patients were treated through 3D conformal radiotherapy using four-field technique. Beam energy of 15 MV from Varian DHX linear accelerator was used. The given 30 patients were divided into two groups. The 1st group of 15 patients with upper oesophagus cancer was prescribed 5000 cGy doses, and the 2nd group of remaining 15 patients with lower oesophagus cancer was prescribed 4500 cGy. Computed tomography scans of every patient were obtained and then transmitted to Eclipse TPS for generating treatment plans. All radiotherapy plans were evaluated through various dosimetric indices. Statistical analysis software SPSS was utilised to get the values of means standard error and standard deviation of these indices for the treatment plan evaluation.ResultsUniformity index (UI) calculated for first group of patients showed difference of 7·4% from ideal value. A difference of 7% between ideal and calculated UI value was observed in 2nd group of patients. The values of other dosimetric indices like coverage, homogeneity, moderate dose homogeneity index (mDHI) and radical dose homogeneity index (rDHI) were found in limits specified by the Radiation Therapy and Oncology Group. The maximum difference of 6% was observed between the coverage mean values of 1stand 2ndgroup treatment plans.ConclusionFor oesophageal cancer, 3D conformal radiotherapy using four-field treatment plans shows homogeneous distribution of dose around the target and limits the dose to organ at risk.

scholarly journals Split Common Coincidence Point Problem: A Formulation Applicable to (Bio)Physically-Based Inverse Planning Optimization

Symmetry ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2086
Author(s):  
Charles E. Chidume ◽  
Lois C. Okereke
Keyword(s):  
Optimization Problem ◽  
Coincidence Point ◽  
Point Problem ◽  
Optimization Approach ◽  
Inverse Planning ◽  
Clinical Criteria ◽  
Planning Optimization ◽  
Physically Based ◽  
Treatment Plans ◽  
Optimized Treatment

Inverse planning is a method of radiotherapy treatment planning where the care team begins with the desired dose distribution satisfying prescribed clinical objectives, and then determines the treatment parameters that will achieve it. The variety in symmetry, form, and characteristics of the objective functions describing clinical criteria requires a flexible optimization approach in order to obtain optimized treatment plans. Therefore, we introduce and discuss a nonlinear optimization formulation called the split common coincidence point problem (SCCPP). We show that the SCCPP is a suitable formulation for the inverse planning optimization problem with the flexibility of accommodating several biological and/or physical clinical objectives. Also, we propose an iterative algorithm for approximating the solution of the SCCPP, and using Bregman techniques, we establish that the proposed algorithm converges to a solution of the SCCPP and to an extremum of the inverse planning optimization problem. We end with a note on useful insights on implementing the algorithm in a clinical setting.

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