Feasibility study of utilizing Sphinx Compact for quality assurance in uniform scanning proton therapy

Rana, Suresh; Eckert, Colton; Tesfamicael, Biniam

doi:10.1016/j.ejmp.2022.10.001

Cited by 4 publications

(4 citation statements)

References 25 publications

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“…The in vivo monitoring was enabled by placing the scintillating sheet directly in the water bath adjacent to the mouse leg target. While scintillation imaging systems with a fixed closed configuration [4][5][6][7][8][9] allow universal corrections regarding flat field and geometry, these systems do not provide the necessary temporal resolution and are furthermore not compatible with in vivo application during the mouse irradiations. On the other hand, radiochromic films allow in vivo 2D profile measurements but they lack temporal resolution.…”

Section: Discussionmentioning

confidence: 99%

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Two‐dimensional time‐resolved scintillating sheet monitoring of proton pencil beam scanning FLASH mouse irradiations

Kanouta,

Bruza,

Johansen

et al. 2024

Medical Physics

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BackgroundDosimetry in pre‐clinical FLASH studies is essential for understanding the beam delivery conditions that trigger the FLASH effect. Resolving the spatial and temporal characteristics of proton pencil beam scanning (PBS) irradiations with ultra‐high dose rates (UHDR) requires a detector with high spatial and temporal resolution.PurposeTo implement a novel camera‐based system for time‐resolved two‐dimensional (2D) monitoring and apply it in vivo during pre‐clinical proton PBS mouse irradiations.MethodsTime‐resolved 2D beam monitoring was performed with a scintillation imaging system consisting of a 1 mm thick transparent scintillating sheet, imaged by a CMOS camera. The sheet was placed in a water bath perpendicular to a horizontal PBS proton beam axis. The scintillation light was reflected through a system of mirrors and captured by the camera with 500 frames per second (fps) for UHDR and 4 fps for conventional dose rates. The raw images were background subtracted, geometrically transformed, flat field corrected, and spatially filtered. The system was used for 2D spot and field profile measurements and compared to radiochromic films. Furthermore, spot positions were measured for UHDR irradiations. The measured spot positions were compared to the planned positions and the relative instantaneous dose rate to equivalent fiber‐coupled point scintillator measurements. For in vivo application, the scintillating sheet was placed 1 cm upstream the right hind leg of non‐anaesthetized mice submerged in the water bath. The mouse leg and sheet were both placed in a 5 cm wide spread‐out Bragg peak formed from the mono‐energetic proton beam by a 2D range modulator. The mouse leg position within the field was identified for both conventional and FLASH irradiations. For the conventional irradiations, the mouse foot position was tracked throughout the beam delivery, which took place through repainting. For FLASH irradiations, the delivered spot positions and relative instantaneous dose rate were measured.ResultsThe pixel size was 0.1 mm for all measurements. The spot and field profiles measured with the scintillating sheet agreed with radiochromic films within 0.4 mm. The standard deviation between measured and planned spot positions was 0.26 mm and 0.35 mm in the horizontal and vertical direction, respectively. The measured relative instantaneous dose rate showed a linear relation with the fiber‐coupled scintillator measurements. For in vivo use, the leg position within the field varied between mice, and leg movement up to 3 mm was detected during the prolonged conventional irradiations.ConclusionsThe scintillation imaging system allowed for monitoring of UHDR proton PBS delivery in vivo with 0.1 mm pixel size and 2 ms temporal resolution. The feasibility of instantaneous dose rate measurements was demonstrated, and the system was used for validation of the mouse leg position within the field.

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Section: Discussionmentioning

confidence: 99%

“…Scintillation imaging has been routinely utilized for proton beams with the use of commercial scintillatorbased systems for quality assurance 4,5 or in-house developed systems. [6][7][8][9][10][11] High temporal resolution can be obtained by using a fast camera.…”

Section: Introductionmentioning

confidence: 99%

Two‐dimensional time‐resolved scintillating sheet monitoring of proton pencil beam scanning FLASH mouse irradiations

Kanouta,

Bruza,

Johansen

et al. 2024

Medical Physics

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“…Several studies 23–28 have established daily QA checks and jigs procedures following AAPM TG‐224 recommendations 29 . However, a quantitative evaluation of the performance of the UHDR delivery system remains lacking.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the availability of a UHDR-compatible dosimeter and standard QA parameters is critical for successful translation from preclinical studies to clinical applications. Several studies [23][24][25][26][27][28] have established daily QA checks and jigs procedures following AAPM TG-224 recommendations. 29 However, a quantitative evaluation of the performance of the UHDR delivery system remains lacking.…”

Section: Introductionmentioning

confidence: 99%

A comprehensive pre‐clinical treatment quality assurance program using unique spot patterns for proton pencil beam scanning FLASH radiotherapy

Tsai,

Yang,

et al. 2024

J Applied Clin Med Phys

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BackgroundQuality assurance (QA) for ultra‐high dose rate (UHDR) irradiation is a crucial aspect in the emerging field of FLASH radiotherapy (FLASH‐RT). This innovative treatment approach delivers radiation at UHDR, demanding careful adoption of QA protocols and procedures. A comprehensive understanding of beam properties and dosimetry consistency is vital to ensure the safe and effective delivery of FLASH‐RT.PurposeTo develop a comprehensive pre‐treatment QA program for cyclotron‐based proton pencil beam scanning (PBS) FLASH‐RT. Establish appropriate tolerances for QA items based on this study's outcomes and TG‐224 recommendations.MethodsA 250 MeV proton spot pattern was designed and implemented using UHDR with a 215nA nozzle beam current. The QA pattern that covers a central uniform field area, various spot spacings, spot delivery modes and scanning directions, and enabling the assessment of absolute, relative and temporal dosimetry QA parameters. A strip ionization chamber array (SICA) and an Advanced Markus chamber were utilized in conjunction with a 2 cm polyethylene slab and a range (R80) verification wedge. The data have been monitored for over 3 months.ResultsThe relative dosimetries were compliant with TG‐224. The variations of temporal dosimetry for scanning speed, spot dwell time, and spot transition time were within ± 1 mm/ms, ± 0.2 ms, and ± 0.2 ms, respectively. While the beam‐to‐beam absolute output on the same day reached up to 2.14%, the day‐to‐day variation was as high as 9.69%. High correlation between the absolute dose and dose rate fluctuations were identified. The dose rate of the central 5 × 5 cm2 field exhibited variations within 5% of the baseline value (155 Gy/s) during an experimental session.ConclusionsA comprehensive QA program for FLASH‐RT was developed and effectively assesses the performance of a UHDR delivery system. Establishing tolerances to unify standards and offering direction for future advancements in the evolving FLASH‐RT field.

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Evaluation of a prototype array for daily quality assurance in spot scanning proton therapy

Flatten,

Devendranath,

Kroh

et al. 2024

J Applied Clin Med Phys

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BackgroundQuality assurance (QA) on a daily basis is an essential task in radiotherapy. In pencil beam scanning proton therapy (PBS), there is a lack of available practical QA devices for routine daily QA in comparison to conventional radiotherapy.PurposeThe aim was to characterize and evaluate a prototype for the task of daily QA routine for PBS with parameters recommended by the AAPM TG 224, that is, the dose output constancy, the spot position and the distal range verification. Furthermore, a time efficient calibration method for fast and reliable daily QA routine was established for the prototype.MethodsFirst, a calibration routine was designed and evaluated, which characterizes the array response and allows for a conversion of the measured signal to clinically needed QA parameters. Finally, a time and resource efficient daily QA routine was developed and tested.ResultsThe prototype array can distinguish spot position deviations with sub‐millimeter accuracy, as well as changes in the spot size in terms of FWHM with a 2 sensitivity. The range and thus the energy can be evaluated at different depths also with sub‐millimeter precision. After some training, the setup of the prototype device took roughly two minutes and the total beamtime was about one minute on cyclotron site and five minutes for synchrotrons.ConclusionsA prototype for daily QA in spot scanning proton therapy was evaluated, which features a fast and easy setup and allows for measuring relevant beam parameters, typically within less than a minute of beam time. All QA parameters as recommended by the AAPM TG 224 report can be analyzed with sufficient accuracy.

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Feasibility study of utilizing Sphinx Compact for quality assurance in uniform scanning proton therapy

Cited by 4 publications

References 25 publications

Two‐dimensional time‐resolved scintillating sheet monitoring of proton pencil beam scanning FLASH mouse irradiations

Two‐dimensional time‐resolved scintillating sheet monitoring of proton pencil beam scanning FLASH mouse irradiations

A comprehensive pre‐clinical treatment quality assurance program using unique spot patterns for proton pencil beam scanning FLASH radiotherapy

Evaluation of a prototype array for daily quality assurance in spot scanning proton therapy

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