Impact of daily anatomical changes on EPID-based in vivo dosimetry of VMAT treatments of head-and-neck cancer

Rozendaal, R.; Mijnheer, Ben J.; Hamming‐Vrieze, Olga; Mans, A.; Herk, Marcel van

doi:10.1016/j.radonc.2015.05.020

Cited by 31 publications

(27 citation statements)

References 17 publications

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“…It could also be used, if processed immediately, to identify the correctness of individual multileaf collimator (MLC) fields 32 and to identify significant anatomical changes such as those seen in H&N cancer patients experiencing weight loss during treatment. 33 After the DC software obtains the in-air fluence in RMU it is possible to independently calculate the dose delivered to a given patient using the original planning CT scan. Currently the DC software uses a PBC algorithm to calculate this dose while the Eclipse treatment planning system used the Analytical Anisotropic Algorithm (AAA).…”

Section: B | Radiotherapy Courses and Patientsmentioning

confidence: 99%

EPID‐based in vivo dosimetry using Dosimetry Check™: Overview and clinical experience in a 5‐yr study including breast, lung, prostate, and head and neck cancer patients

Nailon

Welsh

McDonald

et al. 2018

J Applied Clin Med Phys

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BackgroundIndependent verification of the dose delivered by complex radiotherapy can be performed by electronic portal imaging device (EPID) dosimetry. This paper presents 5‐yr EPID in vivo dosimetry (IVD) data obtained using the Dosimetry Check (DC) software on a large cohort including breast, lung, prostate, and head and neck (H&N) cancer patients.Material and MethodsThe difference between in vivo dose measurements obtained by DC and point doses calculated by the Eclipse treatment planning system was obtained on 3795 radiotherapy patients treated with volumetric modulated arc therapy (VMAT) (n = 842) and three‐dimensional conformal radiotherapy (3DCRT) (n = 2953) at 6, 10, and 15 MV. In cases where the dose difference exceeded ±10% further inspection and additional phantom measurements were performed.ResultsThe mean and standard deviation (normalμ±normalσ) of the percentage difference in dose obtained by DC and calculated by Eclipse in VMAT was: 0.19±3.89% in brain, 1.54±4.87% in H&N, and 1.23±4.61% in prostate cancer. In 3DCRT, this was 1.79±3.51% in brain, −2.95±5.67% in breast, −1.43±4.38% in bladder, 1.66±4.77% in H&N, 2.60 ± 5.35% in lung and −3.62±4.00% in prostate cancer. A total of 153 plans exceeded the ±10% alert criteria, which included: 88 breast plans accounting for 7.9% of all breast treatments; 28 H&N plans accounting for 4.4% of all H&N treatments; and 12 prostate plans accounting for 3.5% of all prostate treatments. All deviations were found to be as a result of patient‐related anatomical deviations and not from procedural errors.ConclusionsThis preliminary data shows that EPID‐based IVD with DC may not only be useful in detecting errors but has the potential to be used to establish site‐specific dose action levels. The approach is straightforward and has been implemented as a radiographer‐led service with no disruption to the patient and no impact on treatment time.

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Section: B | Radiotherapy Courses and Patientsmentioning

confidence: 99%

EPID‐based in vivo dosimetry using Dosimetry Check™: Overview and clinical experience in a 5‐yr study including breast, lung, prostate, and head and neck cancer patients

Nailon

Welsh

McDonald

et al. 2018

J Applied Clin Med Phys

View full text Add to dashboard Cite

show abstract

“…First, a characteristic limitation of using the planning CT to reconstruct dose via EPID images is that the CT may not reflect accurately the patient’s setup or anatomy at treatment, producing a dose calculation error. 29 As a result, dose differences should mainly be interpreted as flags warranting further investigation. Second, we make use of correlation ratios obtained through slab phantoms and thus do not model the differences in scatter due to inhomogeneities.…”

Section: Resultsmentioning

confidence: 99%

In vivo Portal Imaging Dosimetry Identifies Delivery Errors in Rectal Cancer Radiotherapy on the Belly Board Device

Peca

Sinha

Brown

et al. 2017

Technol Cancer Res Treat

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Purpose:We recently developed a novel, open-source in vivo dosimetry that uses the electronic portal imaging device to detect dose delivery discrepancies. We applied our method on patients with rectal cancer treated on a belly board device.Methods: In vivo dosimetry was performed on 10 patients with rectal cancer treated prone on the belly board with a 4-field box arrangement. Portal images were acquired approximately once per week from each treatment beam. Our dosimetry method used these images along with the planning CT to reconstruct patient planar dose at isocenter depth.Results:Our algorithm proved sensitive to dose discrepancies and detected discordances in 7 patients. The majority of these were due to soft tissue differences between planning and treatment, present despite matching to bony anatomy. As a result of this work, quality assurance procedures have been implemented for our immobilization devices.Conclusion: In vivo dosimetry is a powerful quality assurance tool that can detect delivery discrepancies, including changes in patient setup and position. The added information on actual dose delivery may be used to evaluate equipment and process quality and to guide for adaptive radiotherapy.

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“…In our anatomy‐based VMAT optimization strategy, the field shape always conform to the PTV outline, and this choice should avoid both target missing and possible interplay effect. Only a DVH‐analysis based on 3D IVD would allow a quantitative assessment of the clinical relevance of observed deviations . Secondly, as shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

Epid‐based in vivo dose verification for lung stereotactic treatments delivered with multiple breath‐hold segmented volumetric modulated arc therapy

Cilla

Ianiro

Craus

et al. 2019

J Applied Clin Med Phys

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We evaluated an EPID‐based in‐vivo dosimetry (IVD) method for the dose verification and the treatment reproducibility of lung SBRT‐VMAT treatments in clinical routine. Ten patients with lung metastases treated with Elekta VMAT technique were enrolled. All patients were irradiated in five consecutive fractions, with total doses of 50 Gy. Set‐up was carried out with the Elekta stereotactic body frame. Eight patients were simulated and treated using the Active Breath Control (ABC) system, a spirometer enabling patients to maintain a breath‐hold at a predetermined lung volume. Two patients were simulated and treated in free‐breathing using an abdominal compressor. IVD was performed using the SOFTDISO software. IVD tests were evaluated by means of (a) ratio R between daily in‐vivo isocenter dose and planned dose and (b) γ‐analysis between EPID integral portal images in terms of percentage of points with γ‐value smaller than one (γ%) and mean γ‐values (γmean) using a 3%(global)/3 mm criteria. Alert criteria of ±5% for R ratio, γ% < 90%, and γmean > 0.67 were chosen. 50 transit EPID images were acquired. For the patients treated with ABC spirometer, the results reported a high level of accuracy in dose delivery with 100% of tests within ±5%. The γ‐analysis showed a mean value of γmean equal to 0.21 (range: 0.04–0.56) and a mean γ% equal to 96.9 (range: 78–100). Relevant discrepancies were observed only for the two patients treated without ABC, mainly due to a blurring dose effect due to residual respiratory motion. Our method provided a fast and accurate procedure in clinical routine for verifying delivered dose as well as for detecting errors.

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Impact of daily anatomical changes on EPID-based in vivo dosimetry of VMAT treatments of head-and-neck cancer

Cited by 31 publications

References 17 publications

EPID‐based in vivo dosimetry using Dosimetry Check™: Overview and clinical experience in a 5‐yr study including breast, lung, prostate, and head and neck cancer patients

EPID‐based in vivo dosimetry using Dosimetry Check™: Overview and clinical experience in a 5‐yr study including breast, lung, prostate, and head and neck cancer patients

In vivo Portal Imaging Dosimetry Identifies Delivery Errors in Rectal Cancer Radiotherapy on the Belly Board Device

Epid‐based in vivo dose verification for lung stereotactic treatments delivered with multiple breath‐hold segmented volumetric modulated arc therapy

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