Log file‐based dose reconstruction and accumulation for 4D adaptive pencil beam scanned proton therapy in a clinical treatment planning system: Implementation and proof‐of‐concept

Meijers, Artürs; Jakobi, Annika; Stützer, Kristin; Marmitt, Gabriel Guterres; Both, Stefan; Langendijk, Johannes A.; Richter, Christian; Knopf, Antje

doi:10.1002/mp.13371

Cited by 50 publications

(68 citation statements)

References 17 publications

(33 reference statements)

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“…We therefore can only suspect a small influence of baseline drifts on the 4DCBCT acquisitions for a part of the patient population. With respect to the observed large day-to-day motion variations in the 4DCBCTs, we recommended base treatment adaptation decisions on observed trends as proposed by Meijers et al 21 rather than on single day recalculations.…”

Section: Discussionmentioning

confidence: 99%

“…Ultimately, a 4D adaptive workflow could be the solution to obtain highly conformal dose distributions not compromised by motion and other anatomical variations occurring throughout the course of fractionated treatment. 21 Patient selection is a key element in the treatment of moving targets with PBS-PT. Literature states that NSCLC patients with gross tumor volume (GTV) motion amplitudes less than 5 mm can be safely treated using rescanning only to diminish interplay effects.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of inter‐fraction target motion variations in the context of pencil beam scanned proton therapy in non‐small cell lung cancer patients

et al. 2020

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For locally advanced-stage non-small cell lung cancer (NSCLC), inter-fraction target motion variations during the whole time span of a fractionated treatment course are assessed in a large and representative patient cohort. The primary objective is to develop a suitable motion monitoring strategy for pencil beam scanning proton therapy (PBS-PT) treatments of NSCLC patients during free breathing. Methods: Weekly 4D computed tomography (4DCT; 41 patients) and daily 4D cone beam computed tomography (4DCBCT; 10 of 41 patients) scans were analyzed for a fully fractionated treatment course. Gross tumor volumes (GTVs) were contoured and the 3D displacement vectors of the centroid positions were compared for all scans. Furthermore, motion amplitude variations in different lung segments were statistically analyzed. The dosimetric impact of target motion variations and target motion assessment was investigated in exemplary patient cases. Results: The median observed centroid motion was 3.4 mm (range: 0.2-12.4 mm) with an average variation of 2.2 mm (range: 0.1-8.8 mm). Ten of 32 patients (31.3%) with an initial motion <5 mm increased beyond a 5-mm motion amplitude during the treatment course. Motion observed in the 4DCBCT scans deviated on average 1.5 mm (range: 0.0-6.0 mm) from the motion observed in the 4DCTs. Larger motion variations for one example patient compromised treatment plan robustness while no dosimetric influence was seen due to motion assessment biases in another example case. Conclusions: Target motion variations were investigated during the course of radiotherapy for NSCLC patients. Patients with initial GTV motion amplitudes of < 2 mm can be assumed to be stable in motion during the treatment course. For treatments of NSCLC patients who exhibit motion amplitudes of > 2 mm, 4DCBCT should be considered for motion monitoring due to substantial motion variations observed.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation of inter‐fraction target motion variations in the context of pencil beam scanned proton therapy in non‐small cell lung cancer patients

et al. 2020

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“…However, their study did not take anatomical changes or treatment uncertainties into consideration as the target is always covered in the nominal scenario [4]. Changes in anatomy can have a large impact on the delivered dose distribution compared to the planned dose distribution [8][9][10]. These and other results show that uncertainty setting reduction is impactful on patient-reported toxicities.…”

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confidence: 99%

“…Previous studies in head and neck cancer (HNC) photon therapy reported toxicity reduction after changing the CTV-planning target volume (PTV) margin from 5 mm to 3 mm, but a further reduction to a 2 mm uncertainty setting might be possible without altering the physician prescribed dosimetric parameters [11,12]. By accumulating the dose on diagnostic quality verification CT images, the impact of interfractional anatomy changes can be evaluated and the delivered dose can be estimated more accurately [8][9][10]13]. Earlier studies focused on dose accumulation incorporating repeated imaging to study the effect of changing anatomy, but these neglected other treatment uncertainties such as inter-and intrafraction motion which could have a large effect on target coverage [8,9].…”

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confidence: 99%

Head and neck IMPT probabilistic dose accumulation: Feasibility of a 2 mm setup uncertainty setting

Wagenaar

Kierkels

Schaaf

et al. 2021

Radiotherapy and Oncology

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Objective: To establish optimal robust optimization uncertainty settings for clinical head and neck cancer (HNC) patients undergoing 3D image-guided pencil beam scanning (PBS) proton therapy. Methods: We analyzed ten consecutive HNC patients treated with 70 and 54.25 Gy RBE to the primary and prophylactic clinical target volumes (CTV) respectively using intensity-modulated proton therapy (IMPT). Clinical plans were generated using robust optimization with 5 mm/3% setup/range uncertainties (RayStation v6.1). Additional plans were created for 4, 3, 2 and 1 mm setup and 3% range uncertainty and for 3 mm setup and 3%, 2% and 1% range uncertainty. Systematic and random error distributions were determined for setup and range uncertainties based on our quality assurance program. From these, 25 treatment scenarios were sampled for each plan, each consisting of a systematic setup and range error and daily random setup errors. Fraction doses were calculated on the weekly verification CT closest to the date of treatment as this was considered representative of the daily patient anatomy. Results: Plans with a 2 mm/3% setup/range uncertainty setting adequately covered the primary and prophylactic CTV (V 95 ! 99% in 98.8% and 90.8% of the treatment scenarios respectively). The average organat-risk dose decreased with 1.1 Gy RBE /mm setup uncertainty reduction and 0.5 Gy RBE /1% range uncertainty reduction. Normal tissue complication probabilities decreased by 2.0%/mm setup uncertainty reduction and by 0.9%/1% range uncertainty reduction. Conclusion: The results of this study indicate that margin reduction below 3 mm/3% is possible but requires a larger cohort to substantiate clinical introduction.

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“…Recently, Pfeiler et al has shown the implementation of a 4D dose calculation routine for PBS using the time structure of the pencil beam spot delivery from a system log files with validation via 2D array ion chamber and motion platform. Fraction‐wise retrospective dose reconstruction and accumulation was investigated using machine log files in combination with the patient’s breathing patterns from a pressure belt system and 4D CT datasets through entire treatment course . The deforming grid 4D dose calculation techniques have been employed to predict and validate the pattern of 4D dose distribution and to evaluate different PBS rescanning techniques for moving targets .…”

Section: Introductionmentioning

confidence: 99%

Measurement‐based study on characterizing symmetric and asymmetric respiratory motion interplay effect on target dose distribution in the proton pencil beam scanning

Lee

Perry

Speth

et al. 2020

J Applied Clin Med Phys

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Pencil beam scanning proton therapy makes possible intensity modulation, resulting in improved target dose conformity and organ-at-risk (OAR) dose sparing. This benefit, however, results in increased sensitivity to certain clinical and beam delivery parameters, such as respiratory motion. These effects can cause plan degeneration, which could lead to decreased tumor dose or increased OAR dose. This study evaluated the measurements of proton pencil beam scanning delivery made with a 2D ion chamber array in solid water on a 1D motion platform, where respiratory motion was simulated using sine and cosine 4 waves representing sinusoidal symmetric and realistic asymmetric breathing motions, respectively. Motion amplitudes were 0.5 cm and 1 cm corresponding to 1 cm and 2 cm of maximum respiratory excursions, respectively, with 5 sec fixed breathing cycle. The treatment plans were created to mimic spherical targets of 3 cm or 10 cm diameter located at 5 cm or 1 cm depth in solid water phantom. A reference RBE dose of 200 cGy per fraction was delivered in 1, 5, 10, and 15 fractions for each dataset. We evaluated dose conformity and uniformity at the center plane of targets by using the Conformation Number and the Homogeneity Index, respectively. Results indicated that dose conformity as well as homogeneity was more affected by motion for smaller targets. Dose conformity was better achieved for symmetric breathing patterns than asymmetric breathing patterns regardless of the number of fractions. The presence of a range shifter with shallow targets reduced the motion effect by improving dose homogeneity. While motion effects are known to be averaged out over the course of multifractional treatments, this might not be true for proton pencil beam scanning under asymmetrical breathing pattern. K E Y W O R D S conformity index, homogeneity index, interplay effect, motion platform, proton pencil beam scanning, respiratory motion ---

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Log file‐based dose reconstruction and accumulation for 4D adaptive pencil beam scanned proton therapy in a clinical treatment planning system: Implementation and proof‐of‐concept

Cited by 50 publications

References 17 publications

Investigation of inter‐fraction target motion variations in the context of pencil beam scanned proton therapy in non‐small cell lung cancer patients

Investigation of inter‐fraction target motion variations in the context of pencil beam scanned proton therapy in non‐small cell lung cancer patients

Head and neck IMPT probabilistic dose accumulation: Feasibility of a 2 mm setup uncertainty setting

Measurement‐based study on characterizing symmetric and asymmetric respiratory motion interplay effect on target dose distribution in the proton pencil beam scanning

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