Is integrated transit planar portal dosimetry able to detect geometric changes in lung cancer patients treated with volumetric modulated arc therapy?

Persoon, L.; Podesta, Mark; Hoffmann, Lone; Sanizadeh, Abir; Schyns, Lotte E J R; Ruiter, Ben-Max de; Nijsten, S.; Muren, L.P.; Troost, Esther G.C.; Verhaegen, Frank

doi:10.3109/0284186x.2015.1061213

Cited by 16 publications

(16 citation statements)

References 25 publications

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“…The clinically relevant magnitude of change will vary with treatment site and technique and potentially even with each patient and as a result is more challenging to measure. Work by other groups have typically used gamma analysis with standard pass criteria (3%, 3 mm) to determine if measured transit images pass. One study using a 3%, 3 mm criteria had false positive alerts for 10 clinically irrelevant discrepancies, while in a separate clinical implementation, a gamma analysis with looser criteria of 4%, 4 mm for pixels above a 10% threshold was used but no patients in the trial ever had such large differences .…”

Section: Discussionmentioning

confidence: 99%

Evaluating the sensitivity of Halcyon’s automatic transit image acquisition for treatment error detection: A phantom study using static IMRT

Ray¹,

Bojechko²,

Moore³

2019

J Applied Clin Med Phys

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PurposeThe Varian Halcyon™ electronic portal imaging detector is always in‐line with the beam and automatically acquires transit images for every patient with full‐field coverage. These images could be used for “every patient, every monitor unit” quality assurance (QA) and eventually adaptive radiotherapy. This study evaluated the imager’s sensitivity to potential clinical errors and day‐to‐day variations from clinical exit images.MethodsOpen and modulated fields were delivered for each potential error. To evaluate output changes, monitor units were scaled by 2%–10% and delivered to solid water slabs and a homogeneous CIRS phantom. To mimic weight changes, 0.5–5.0 cm of buildup was added to the solid water. To evaluate positioning changes, a homogeneous and heterogeneous CIRS phantom were shifted 2–10 cm and 0.2–1.5 cm, respectively. For each test, mean relative differences (MRDs) and standard deviations in the pixel‐difference histograms (σRD) between test and baseline images were calculated. Lateral shift magnitudes were calculated using cross‐correlation and edge‐detection filtration. To assess patient variations, MRD and σRD were calculated from six prostate patients’ daily exit images and compared between fractions with and without gas present.ResultsMRDs responded linearly to output and buildup changes with a standard deviation of 0.3%, implying a 1% output change and 0.2 cm changes in buildup could be detected with 2.5σ confidence. Shifting the homogenous phantom laterally resulted in detectable MRD and σRD changes, and the cross‐correlation function calculated the shift to within 0.5 mm for the heterogeneous phantom. MRD and σRD values were significantly associated with the presence of gas for five of the six patients.ConclusionsRapid analyses of automatically acquired Halcyon™ exit images could detect mid‐treatment changes with high sensitivity, though appropriate thresholds will need to be set. This study presents the first steps toward developing effortless image evaluation for all aspects of every patient’s treatment.

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Section: Discussionmentioning

confidence: 99%

Evaluating the sensitivity of Halcyon’s automatic transit image acquisition for treatment error detection: A phantom study using static IMRT

Ray¹,

Bojechko²,

Moore³

2019

J Applied Clin Med Phys

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“…This reduction in volume in NSCLC has also been shown to occur as early as within the first 2 weeks of treatment and also correlates with outcome [30–32]. Additionally, changes in lung density, due to atelectasis and pleural effusions, are possible during treatment and require re-planning in about 10% of patients [33, 34].…”

Section: Adaptive Re-planningmentioning

confidence: 99%

The Practicality of ICRU and Considerations for Future ICRU Definitions

Shepherd

James

Rengan

2018

Seminars in Radiation Oncology

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The International Commission on Radiation Units and Measurements (ICRU) volumes are standardized volume definitions used in radiation oncology practice that have evolved over time to account for advancements in technology and radiation planning. The current definitions have strengths but also practical limitations. The main limitation is related to the process of accounting for tumor motion during treatment. As radiotherapeutic techniques become more precise, motion interplay effects and anatomical changes during treatment must be taken into account to ensure accurate and safe delivery of treatment. Adaptive replanning can help to mitigate the effect of these uncertainties and widen the therapeutic ratio by maximizing dose to the tumor and protecting critical normal structures. As adaptive replanning becomes more common, standardization of how adaptive therapy is implemented and reported will become necessary.

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“…15,16,22 We have shown that relevant dose differences can be hidden by ITPD. 22 Integrated transit planar dosimetry might show little to no failure, whereas with time-integrated 3D portal dosimetry, relevant dose differences are detected. Time-resolved planar dosimetry shows to be a promising method in detecting those cases.…”

Section: Np84mentioning

confidence: 99%

Time-Resolved Versus Integrated Transit Planar Dosimetry for Volumetric Modulated Arc Therapy

Persoon

Podesta

Nijsten

et al. 2016

Technol Cancer Res Treat

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Purpose: It is desirable that dosimetric deviations during radiation treatments are detected. Integrated transit planar dosimetry is commonly used to evaluate external beam treatments such as volumetric-modulated arc therapy. This work focuses on patient geometry changes which result in differences between the planned and the delivered radiation dose. Integrated transit planar dosimetry will average out some deviations. Novel time-resolved transit planar dosimetry compares the delivered dose of volumetric-modulated arc therapy to the planned dose at various time points. Four patient cases are shown where time-resolved transit planar dosimetry detects patient geometry changes during treatment. Methods: A control point to control point comparison between the planned dose and the treatment dose of volumetric-modulated arc therapy beams is calculated using the planning computed tomography and the kV cone-beam computed tomography of the day and evaluated with a time-resolved g function. Results were computed for 4 patients treated with volumetric-modulated arc therapy, each showing an anatomical change: pleural effusion, rectal gas pockets, and tumor regression. Results: In all cases, the geometrical change was detected by time-resolved transit planar dosimetry, whereas integrated transit planar dosimetry showed minor or no indication of the dose discrepancy. Both tumor regression cases were detected earlier in the treatment with time-resolved planar dosimetry in comparison to integrated transit planar dosimetry. The pleural effusion and the gas pocket were detected exclusively with time-resolved transit planar dosimetry. Conclusions: Clinical cases were presented in this proof-of-principle study in which integrated transit planar dosimetry did not detect dosimetrically relevant deviations to the same extent time-resolved transit planar dosimetry was able to. Time-resolved transit planar dosimetry also provides results that can be presented as a function of arc delivery angle allowing easier interpretation compared to integrated transit planar dosimetry.

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Is integrated transit planar portal dosimetry able to detect geometric changes in lung cancer patients treated with volumetric modulated arc therapy?

Abstract: This study showed that most cases with geometric changes caused by atelectasis could be captured by ITPD, however for other causes ITPD is not sensitive enough to detect the clinically relevant changes and no predictive power of ITPD was found.

Cited by 16 publications

References 25 publications

Evaluating the sensitivity of Halcyon’s automatic transit image acquisition for treatment error detection: A phantom study using static IMRT

Evaluating the sensitivity of Halcyon’s automatic transit image acquisition for treatment error detection: A phantom study using static IMRT

The Practicality of ICRU and Considerations for Future ICRU Definitions

Time-Resolved Versus Integrated Transit Planar Dosimetry for Volumetric Modulated Arc Therapy

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