Impact of spot size on plan quality of spot scanning proton radiosurgery for peripheral brain lesions

Wang, Dongxu; Dirksen, B; Hyer, Daniel E.; Buatti, John M.; Sheybani, Arshin; Dinges, Eric; Felderman, Nicole; Tennapel, M.J.; Bayouth, John E.; Flynn, R

doi:10.1118/1.4901260

Cited by 40 publications

(50 citation statements)

References 57 publications

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“…Previous studies have indicated better organ sparing due to reduced PBS spot size for specific patient cases [25,26]. Chanrion et al [27] explored the consequences of unexpected spot size fluctuations on the target coverage in PBS.…”

Section: Introductionmentioning

confidence: 99%

Impact of Spot Size and Beam-Shaping Devices on the Treatment Plan Quality for Pencil Beam Scanning Proton Therapy

Moteabbed

Yock

Depauw

et al. 2016

International Journal of Radiation Oncology*Biology*Physics

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Purpose This study aims to assess the clinical impact of spot size and the addition of apertures and range compensators on the treatment quality of pencil beam scanning (PBS) proton therapy and to define when PBS could improve upon passive scattering proton therapy (PSPT). Methods and materials The patient cohort included fourteen pediatric patients treated with PSPT. Six PBS plans were created and optimized for each patient using three spot sizes (~12, 5.4, and 2.5 mm median sigma at isocenter for 90–230 MeV range), and adding apertures and compensators to plans with the two larger spots. Conformity and homogeneity indices, dose-volume histogram parameters, equivalent uniform dose (EUD), normal tissue complication probability (NTCP) and integral dose were quantified and compared with the respective PSPT plans. Results The results clearly indicated that PBS with the largest spots does not necessarily offer a dosimetric or clinical advantage over PSPT. With comparable target coverage, the mean dose (Dmean) to healthy organs was on average 6.3% larger than PSPT when using this spot size. However, adding apertures to plans with large spots improved the treatment quality by decreasing the average Dmean and EUD by up to 8.6 and 3.2% of the prescribed dose, respectively. Decreasing the spot size further improved all plans, lowering the average Dmean and EUD by up to 11.6% and 10.9% compared to PSPT, respectively, and eliminated the need for beam-shaping devices. The NTCP decreased with spot size and addition of apertures, with maximum reduction of 5.4% relative to PSPT. Conclusions The added benefit of using PBS strongly depends on the delivery configurations. Facilities limited to large spot sizes (>~8 mm median sigma at isocenter) are recommended to use apertures in order to reduce the treatment-related toxicities, at least for complex and/or small tumors.

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Section: Introductionmentioning

confidence: 99%

Impact of Spot Size and Beam-Shaping Devices on the Treatment Plan Quality for Pencil Beam Scanning Proton Therapy

Moteabbed

Yock

Depauw

et al. 2016

International Journal of Radiation Oncology*Biology*Physics

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“…On the other hand, recent studies on head and neck treatment and brain radiosurgery have demonstrated the benefit of further reduction in spot size in the sparing of normal tissues, e.g. salivary and parotid glands and normal brain [57, 58]. Thus, to achieve higher conformity, it is beneficial to generate beamlets of smaller σ, particularly for treatment sites with depths < 10–12 cm.…”

Section: Treatment Delivery Related Challenges and Potential Solutmentioning

confidence: 99%

Empowering Intensity Modulated Proton Therapy Through Physics and Technology: An Overview

Mohan

Das

Ling

2017

International Journal of Radiation Oncology*Biology*Physics

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Considering the clinical potential of protons attributable to their physical characteristics, interest in proton therapy has increased greatly in this century as has the number of proton therapy installations. Until recently, passively scattered proton therapy (PSPT) was used almost entirely. Notably, overall clinical results to date have not shown convincing benefit protons over photons. A rapid transition is now occurring with the implementation of the most advanced form of proton therapy, the intensity-modulated proton therapy (IMPT). IMPT is superior to PSPT and IMRT dosimetrically. However, numerous limitations exist in the present IMPT methods. In particular, compared to IMRT, IMPT is highly vulnerable to various uncertainties. In this overview we identify three major areas of current limitations of IMPT: treatment planning, treatment delivery, and motion management, and discuss current and future efforts for improvement. For treatment planning, we need to reduce uncertainties in proton range and in computed dose distributions, improve robust planning and optimization, enhance adaptive treatment planning and delivery, and consider how to exploit the variability in the relative biological effectiveness (RBE) of protons for clinical benefit. The quality of proton therapy also depends on the characteristics of the IMPT delivery systems and image-guidance. Efforts are needed to optimize the beamlet spot size for both improved dose conformality and faster delivery. For the latter, faster energy switching time and increased dose-rate are also needed. Real-time in-room volumetric imaging for guiding IMPT is in its early stages with CBCT and CT-on-rails, and continued improvements are anticipated. In addition, imaging of the proton beams themselves using, for instance, prompt gamma emissions, is being developed to determine the proton range and to reduce range uncertainty. With the realization of the advances described above, we posit that IMPT, thus empowered, will lead to substantially improved clinical results.

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“…However, lateral and distal target penumbra of noncollimated IMPT fields are not necessarily smaller than from double scattering delivery . Aside from optimization dependencies, the conformity and lateral penumbra of an IMPT system are proportional to the proton beamlet spot size . Hence, IMPT therapy system spot sizes have shown a continual developmental trend toward smaller since inception.…”

Section: Introductionmentioning

confidence: 99%

Development, commissioning, and evaluation of a new intensity modulated minibeam proton therapy system

et al. 2018

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Impact of spot size on plan quality of spot scanning proton radiosurgery for peripheral brain lesions

Cited by 40 publications

References 57 publications

Impact of Spot Size and Beam-Shaping Devices on the Treatment Plan Quality for Pencil Beam Scanning Proton Therapy

Impact of Spot Size and Beam-Shaping Devices on the Treatment Plan Quality for Pencil Beam Scanning Proton Therapy

Empowering Intensity Modulated Proton Therapy Through Physics and Technology: An Overview

Development, commissioning, and evaluation of a new intensity modulated minibeam proton therapy system

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