A margin recipe for the management of intra-fraction target motion in radiotherapy

Janssen, Tomas; Heide, Uulke A. van der; Remeijer, P.; Sonke, J.J.; Bijl, Erik van der

doi:10.1016/j.phro.2022.11.008

Cited by 6 publications

(1 citation statement)

References 25 publications

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“…Using the intrafraction motions from a 3D match of the post- and pre (simulated)treatment CBCTs, the intrafraction motion CTV-PTV margins were calculated using the systematic (Σ = standard deviation of the means per patient) and random (σ = mean of the standard deviations per patient) intrafraction motion parameters. The PTV margin formalism developed by Van Herk et al [35] was adjusted using Janssen et al [36] . The latter paper states that if the intrafraction motion is a continuous drift during the treatment, the required margin is well approximated by an average position of the target at ¾ of the drift.…”

Section: Methodsmentioning

confidence: 99%

Setup and intra-fractional motion measurements using surface scanning in head and neck cancer radiotherapy– A feasibility study

Essers,

Mesch,

Beugeling

et al. 2024

Physics and Imaging in Radiation Oncology

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Section: Methodsmentioning

confidence: 99%

Setup and intra-fractional motion measurements using surface scanning in head and neck cancer radiotherapy– A feasibility study

Essers,

Mesch,

Beugeling

et al. 2024

Physics and Imaging in Radiation Oncology

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Efficacy of a thermoplastic mask and pneumatic abdominal compression device for immobilization in stereotactic ablative radiotherapy of spine metastases

Walter,

Speir,

Burrell

et al. 2024

J Applied Clin Med Phys

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Stereotactic ablative radiotherapy (SABR) has become a key technique in management of spine metastases. With improved control over treatment plan dosimetry, there is a greater need for accurate patient positioning to guarantee agreement between the treatment plan and delivered dose. With serious potential complications such as fracture and myelopathy, the margins of error in SABR of the spine are minimal. In this study, we assessed the performance of two patient immobilization setups in SABR for spinal metastases. First, a Type‐S head and shoulders mask (CQ Medical, Avondale, PA), and second, the BPL1 setup, which includes a wing board, vacuum bag, and the Respiratory Belt for the Body Pro‐Lok ONE (CQ Medical, Avondale, PA). Immobilization was assessed using image‐guided intrafraction repositioning shifts. Required planning target volume (PTV) margins were calculated based on repositioning data for 172 treated fractions using 2 standard deviation (2SD) and analytic approaches. Overall, 91.7% and 74.1% of fractions treated had total 3D repositioning shifts ≤3.0 mm using the Type‐S and BPL1 setups, respectively. In the thoracic spine, 43.2% and 46.5% of fractions had shifts ≤1.5 mm for the respective setups. Suggested margins were under 3.5 mm in all directions and use cases. In the posterior‐anterior direction, the BPL1 setup had a 0.6 mm smaller suggested margin for the thoracic spine compared to the Type‐S setup, at 1.4 mm, calculated using the analytic approach. Both the Type‐S and BPL1 setups are effective for immobilization in spine SABR. The Type‐S demonstrated superior immobilization in the upper spine and remains the clinical standard for cervical and upper thoracic spine positioning. The BPL1 setup showed effective immobilization in use cases treating the mid‐to lower thoracic spine and lumbar spine and remains our clinical standard for those use cases. Results additionally demonstrate feasibility of potential PTV margin reduction.

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Intrafraction motion and impact of margin reduction for MR‐Linac online adaptive radiotherapy for pancreatic cancer treatments

Fasala,

Carr,

Surjan

et al. 2024

J of Medical Radiation Sci

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IntroductionOnline adaptive radiotherapy is well suited for stereotactic ablative radiotherapy (SABR) in pancreatic cancer due to considerable intrafractional tumour motion. This study aimed to assess intrafraction motion and generate adjusted planning target volume (PTV) margins required for online adaptive radiotherapy in pancreatic cancer treatment using abdominal compression on the magnetic resonance linear accelerator (MR‐Linac).MethodsMotion monitoring images obtained from 67 fractions for 15 previously treated pancreatic cancer patients were analysed. All patients received SABR (50 Gy in five fractions) on the MR‐Linac using abdominal compression. The analysis included quantification of intrafraction motion, leading to the development of adjusted PTV margins. The dosimetric impact of implementing the adjusted PTV was then evaluated in a cohort of 20 patients.ResultsIntrafraction motion indicated an average target displacement of 1–3 mm, resulting in an adjusted PTV margin of 2 mm in the right–left and superior–inferior directions, and 3 mm in the anterior–posterior direction. Plans incorporating these adjusted margins consistently demonstrated improved dose to target volumes, with improvements averaging 1.5 Gy in CTV D99%, 4.9 Gy in PTV D99% and 1.2 Gy in PTV‐high D90%, and better sparing of the organs at risk (OAR).ConclusionsThe improved target volume coverage and reduced OAR dose suggest potential for reducing current clinical margins for MR‐Linac treatment. However, it is important to note that decreasing margins may reduce safeguards against geographical misses. Nonetheless, the continued integration of gating systems on MR‐Linacs could provide confidence in adopting reduced margins.

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A margin recipe for the management of intra-fraction target motion in radiotherapy

Cited by 6 publications

References 25 publications

Setup and intra-fractional motion measurements using surface scanning in head and neck cancer radiotherapy– A feasibility study

Setup and intra-fractional motion measurements using surface scanning in head and neck cancer radiotherapy– A feasibility study

Efficacy of a thermoplastic mask and pneumatic abdominal compression device for immobilization in stereotactic ablative radiotherapy of spine metastases

Intrafraction motion and impact of margin reduction for MR‐Linac online adaptive radiotherapy for pancreatic cancer treatments

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