scholarly journals Optimisation of a composite difference metric for prompt error detection in real-time portal dosimetry of simulated volumetric modulated arc therapy

2021 ◽  
Vol 94 (1120) ◽  
pp. 20201014
Author(s):  
James L Bedford ◽  
Ian M Hanson
Keyword(s):  
Real Time ◽  
Error Detection ◽  
Volumetric Modulated Arc Therapy ◽  
Portal Dosimetry ◽  
Arc Therapy ◽  
Aperture Opening ◽  
Treatment Plans ◽  
Portal Images ◽  
The Individual ◽  
Individual Metrics

Objectives: In real-time portal dosimetry, thresholds are set for several measures of difference between predicted and measured images, and signals larger than those thresholds signify an error. The aim of this work is to investigate the use of an additional composite difference metric (CDM) for earlier detection of errors. Methods: Portal images were predicted for the volumetric modulated arc therapy plans of six prostate patients. Errors in monitor units, aperture opening, aperture position and path length were deliberately introduced into all 180 segments of the treatment plans, and these plans were delivered to a water-equivalent phantom. Four different metrics, consisting of central axis signal, mean image value and two image difference measures, were used to identify errors, and a CDM was added, consisting of a weighted power sum of the individual metrics. To optimise the weights of the CDM and to evaluate the resulting timeliness of error detection, a leave-pair-out strategy was used. For each combination of four patients, the weights of the CDM were determined by an exhaustive search, and the result was evaluated on the remaining two patients. Results: The median segment index at which the errors were identified was 87 (range 40–130) when using all of the individual metrics separately. Using a CDM as well as multiple separate metrics reduced this to 73 (35–95). The median weighting factors of the four metrics constituting the composite were (0.15, 0.10, 0.15, 0.00). Due to selection of suitable threshold levels, there was only one false positive result in the six patients. Conclusion: This study shows that, in conjunction with appropriate error thresholds, use of a CDM is able to identify increased image differences around 20% earlier than the separate measures. Advances in knowledge: This study shows the value of combining difference metrics to allow earlier detection of errors during real-time portal dosimetry for volumetric modulated arc therapy treatment.

scholarly journals CT reconstruction from portal images acquired during volumetric-modulated arc therapy

2010 ◽  
Vol 55 (19) ◽  
pp. 5635-5651 ◽  
Author(s):  
G Poludniowski ◽  
M D R Thomas ◽  
P M Evans ◽  
S Webb
Keyword(s):  
Volumetric Modulated Arc Therapy ◽  
Ct Reconstruction ◽  
Arc Therapy ◽  
Portal Images

First clinical results of adaptive radiotherapy based on 3D portal dosimetry for lung cancer patients with atelectasis treated with volumetric-modulated arc therapy (VMAT)

2013 ◽  
Vol 52 (7) ◽  
pp. 1484-1489 ◽  
Author(s):  
Lucas C. G. G. Persoon ◽  
Ada G. T. M. Egelmeer ◽  
Michel C. Öllers ◽  
Sebastiaan M. J. J. G. Nijsten ◽  
Esther G. C. Troost ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Cancer Patients ◽  
Volumetric Modulated Arc Therapy ◽  
Clinical Results ◽  
Adaptive Radiotherapy ◽  
Lung Cancer Patients ◽  
Portal Dosimetry ◽  
Arc Therapy

scholarly journals Real-time interactive planning for radiotherapy of head and neck cancer with volumetric modulated arc therapy

2019 ◽  
Vol 9 ◽  
pp. 83-88 ◽  
Author(s):  
Lindsey Baker ◽  
Robert Olson ◽  
Taran Braich ◽  
Theodora Koulis ◽  
Allison Ye ◽  
...  
Keyword(s):  
Head And Neck Cancer ◽  
Head And Neck ◽  
Real Time ◽  
Neck Cancer ◽  
Volumetric Modulated Arc Therapy ◽  
Interactive Planning ◽  
Arc Therapy

Cherenkov imaging during volumetric modulated arc therapy for real-time radiation beam tracking and treatment response monitoring

2016 ◽  
Author(s):  
Jacqueline M. Andreozzi ◽  
Rongxiao Zhang ◽  
Adam K. Glaser ◽  
David J. Gladstone ◽  
Lesley A. Jarvis ◽  
...  
Keyword(s):  
Treatment Response ◽  
Real Time ◽  
Volumetric Modulated Arc Therapy ◽  
Response Monitoring ◽  
Radiation Beam ◽  
Arc Therapy ◽  
Beam Tracking ◽  
Cherenkov Imaging

scholarly journals Considerations for the verification of volumetric modulated arc therapy-planned dose distributions

2019 ◽  
Vol 3 ◽  
Author(s):  
Lourens Strauss ◽  
William Shaw
Keyword(s):  
Error Detection ◽  
Volumetric Modulated Arc Therapy ◽  
Standard Of Care ◽  
Target Volume ◽  
Pass Rates ◽  
Dose Distributions ◽  
Dose Volume ◽  
Multi Leaf Collimator ◽  
Arc Therapy ◽  
Verification Systems

Background: Volumetric modulated arc therapy (VMAT) is the standard of care for many clinical indications, but should only be considered with proper technical support and quality assurance (QA) in place. Despite the high accuracy of VMAT systems, errors can be present and adequate verification is required. Dosimetric VMAT verification systems have a broadly similar analysis philosophy. However, many factors influence the analyses and the subsequent QA outcome, based on which the plan will pass or fail.Aim: This study investigated various factors that influence the dosimetric impact and detectability of known linac component deviations on VMAT QA, including geometries, tissue densities, gamma criteria and dose–volume differences.Setting: Universitas Hospital (Annex), Bloemfontein, South Africa.Methods: Deliberate multi-leaf collimator (MLC)-bank offsets were introduced on four different VMAT plans of the prostate, nasopharynx and brain. Measured reference dose sets were compared to measured QA results, using the IBA Dolphin© detector and Compass© software for three dosimetric scenarios. Gamma pass rates over a range of criteria from 1%/2-mm to 4%/4-mm in the total volumes and per structure, as well as dose–volume differences were studied.Results: Gamma tests in the total patient/phantom did not sufficiently detect errors. The calculation media did not influence the QA outcome greatly. However, the detection geometry affected the results. Per structure gamma analyses provided superior error detection, although still missed some clinically relevant differences. The addition of dose–volume analyses highlighted several important errors.Conclusion: Volumetric modulated arc therapy using only total volume gamma analyses can easily overlook clinically relevant errors. The choice of gamma criterion is crucial. Verification with at least a per structure gamma test in combination with dose–volume checks is recommended, especially in small target volume cases.

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