Range resolution and reproducibility of a dedicated phantom for proton PBS daily quality assurance.

Placidi, Lorenzo; Togno, Michele; Weber, Damien Charles; Lomax, Antony J; Hrbacek, Jan (2018). Range resolution and reproducibility of a dedicated phantom for proton PBS daily quality assurance. Zeitschrift fur medizinische Physik, 28(4), pp. 310-317. Elsevier 10.1016/j.zemedi.2018.02.001

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PURPOSE Wedge phantoms coupled with a CCD camera are suggested as a simple means to improve the efficiency of quality assurance for pencil beam scanning (PBS) proton therapy, in particular to verify energy/range consistency on a daily basis. The method is based on the analysis of an integral image created by a pencil beam (PB) pattern delivered through a wedge. We have investigated the reproducibility of this method and its dependence on setup and positional beam errors for a commercially available phantom (Sphinx, IBA Dosimetry) and CCD camera (Lynx, IBA Dosimetry) system. MATERIAL AND METHODS The phantom includes 4 wedges of different thickness, allowing verification of the range for 4 energies within one integral image. Each wedge was irradiated with a line pattern of clinical energies (120, 150, 180 and 230MeV). The equipment was aligned to the isocenter using lasers, and the delivery was repeated for 5 consecutive days, 4 times each day. Range was computed using the myQA software (IBA Dosimetry) and inter- and intra-setup uncertainty were calculated. Dependence of range on energy was investigated delivering the same pencil beam pattern but with energy variations in steps of ±0.2MeV for all the nominal energies, up to ±1.0MeV. Possible range uncertainties, caused by setup and positional errors, were then simulated including inclination of the phantom, pencil beam and couch shifts. RESULTS Intra position setup (based on in-room laser system) shows a maximum in plane difference within 1.5mm. Range reproducibility (standard deviation) was less than 0.14mm. Setup and beam errors did not affect significantly the results, except for a vertical shift of 10mm which leads to an error in the range computation. CONCLUSION Taking into account different day-to-day setup and beam errors, day-to-day determination of range has been shown to be reproducible using the proposed system.

Item Type:

Journal Article (Original Article)

Division/Institute:

04 Faculty of Medicine > Department of Haematology, Oncology, Infectious Diseases, Laboratory Medicine and Hospital Pharmacy (DOLS) > Clinic of Radiation Oncology

UniBE Contributor:

Weber, Damien Charles

Subjects:

600 Technology > 610 Medicine & health

ISSN:

1876-4436

Publisher:

Elsevier

Language:

English

Submitter:

Beatrice Scheidegger

Date Deposited:

21 Jun 2018 11:06

Last Modified:

24 Dec 2018 01:30

Publisher DOI:

10.1016/j.zemedi.2018.02.001

PubMed ID:

29548595

Uncontrolled Keywords:

Daily quality assurance Dosimetry equipment Pencil beam scanning Range

BORIS DOI:

10.7892/boris.113621

URI:

https://boris.unibe.ch/id/eprint/113621

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