Dosimetric commissioning and quality assurance of scanned ion beams at the Italian National Center for Oncological Hadrontherapy. Issue 9 (18th August 2015)

• Record Type: Journal Article
• Authors: Mirandola, Alfredo; Molinelli, S.; Vilches Freixas, G.; Mairani, A.; Gallio, E.; Panizza, D.; Russo, S.; Ciocca, M.; Donetti, M.; Magro, G.; Giordanengo, S.; Orecchia, R.
• Is Part Of: Medical physics. Volume 42:Issue 9(2015)
• Page Start: 5287
• Page End: 5300
• Publication Date: 2015-08-18
• Subjects: carbon -- dosimetry -- ion beams -- ionisation chambers -- Monte Carlo methods -- proton beams -- quality assurance -- radiation therapy; Dose‐volume analysis -- Therapeutic applications, including brachytherapy -- Gas‐filled counters: ionization chambers, proportional, and avalanche counters -- Monte Carlo methods -- Dosimetry/exposure assessment; Radiation therapy -- Measurement of nuclear or x‐radiation -- Tubes for determining the presence, intensity, density or energy of radiation or particles -- Scintigraphy -- with scintillation detectors -- Ionisation chambers; light ion radiotherapy -- beam commissioning -- quality assurance -- dosimetry; Carbon -- Protons -- Ion beams -- Calibration -- Dosimetry -- Ionization chambers -- Monte Carlo methods -- Cancer -- Computed tomography; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4928397
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: To describe the dosimetric commissioning and quality assurance (QA) of the actively scanned proton and carbon ion beams at the Italian National Center for Oncological Hadrontherapy. Methods: The laterally integrated depth‐dose‐distributions (IDDs) were acquired with the PTW Peakfinder, a variable depth water column, equipped with two Bragg peak ionization chambers.fluka Monte Carlo code was used to generate the energy libraries, the IDDs in water, and the fragment spectra for carbon beams. EBT3 films were used for spot size measurements, beam position over the scan field, and homogeneity in 2D‐fields. Beam monitor calibration was performed in terms of number of particles per monitor unit using both a Farmer‐type and an Advanced Markus ionization chamber. The beam position at the isocenter, beam monitor calibration curve, dose constancy in the center of the spread‐out‐Bragg‐peak, dose homogeneity in 2D‐fields, beam energy, spot size, and spot position over the scan field are all checked on a daily basis for both protons and carbon ions and on all beam lines. Results: The simulated IDDs showed an excellent agreement with the measured experimental curves. The measured full width at half maximum (FWHM) of the pencil beam in air at the isocenter was energy‐dependent for both particle species: in particular, for protons, the spot size ranged from 0.7 to 2.2 cm. For carbon ions, two sets of spot size are available: FWHM ranged from 0.4 to 0.8 cm (for the smaller spot size) and from 0.8 to 1.1 cm (for the larger one). The spot position was accurate to within ±1 mm over the whole 20 × 20 cm 2 scan field; homogeneity in a uniform squared field was within ±5% for both particle types at any energy. QA results exceeding tolerance levels were rarely found. In the reporting period, the machine downtime was around 6%, of which 4.5% was due to planned maintenance shutdowns. Conclusions: After successful dosimetric beam commissioning, quality assurance measurements performed during a 24‐month period show very stable beam characteristics, which are therefore suitable for performing safe and accurate patient treatments.