A novel technique for measuring the low-dose envelope of pencil-beam scanning spot profiles

Lin, Liyong; Ainsley, C.; Mertens, T.; Wilde, Olivier De; Talla, Patrick Takoukam; McDonough, James E.

doi:10.1088/0031-9155/58/12/n171

Cited by 58 publications

(66 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While the proton fluence for a single proton spot can be measured by high resolution detectors such as film, diodes, pinpoint chambers, and scintillators [7, 13], these measurements are usually time consuming, sensitive to setup errors, or need post-processing. It is especially challenging to measure the low-dose tails directly because a large number of monitor units are needed to increase the low-dose signals to the measurable level.…”

Section: Discussionmentioning

confidence: 99%

Using field size factors to characterize the in-air fluence of a proton machine with a range shifter

Shen

Lentz

et al. 2017

Radiat Oncol

View full text Add to dashboard Cite

Introduction: The range shifter (RS) is used to treat shallow tumors for a proton pencil beam scanning system (PBS). Adding RS certainly complicates the commissioning of the treatment planning system (TPS) because the spot sizes are significantly enlarged with RS. In this work, we present an efficient method to configure a commercial TPS for a PBS system with a fixed RS. Methods: By combining a spiral delivery with customized control points, we were able to significantly improve measurement efficiency and obtain 250 field size factors (FSF) within three hours. The measured FSFs were used to characterize the proton fluence and fit the parameters for the double-Gaussian fluence model used in the TPS. Extensive validation was performed using FSFs measured in air and in water, absolute doses of spread-out Bragg peak (SOBP) fields, and the dose measurements carried out for patient-specific quality assurance (QA). Results: The measured in-air FSFs agreed with the model's prediction within 3% for all 250 FSFs, and within 2 for 94% of the FSFs. The agreement between model's prediction and measurement was within 2% for the in-air and in-water FSFs and the absolute doses for SOBP beams. The patient-specific QA of 113 fields showed an excellent gamma passing rates (96.95 ± 2.51%) for the absolute dose comparisons with gamma criteria of 2 mm and 2%. Conclusion: The excellent agreement between the model's prediction and measurements proved the efficiency and accuracy of the proposed method of using FSFs to characterize the proton fluence and configure the TPS for a PBS system with fixed RS.

show abstract

Section: Discussionmentioning

confidence: 99%

Using field size factors to characterize the in-air fluence of a proton machine with a range shifter

Shen

Lentz

et al. 2017

Radiat Oncol

View full text Add to dashboard Cite

show abstract

“…The film dosimetry software suite available in the Mephysto (PTW, Freiburg) software is used for scanning, calibrating, and analyzing the films. Film dosimetry is often considered as the reference detector for 2D dosimetry or at least as an independent device to cross‐check 2D fluence measurements obtained with other devices such as scintillating screens . Dosimetric characterization and uncertainty analysis of EBT films for proton and carbon ion beams has been presented elsewhere .…”

Section: Methodsmentioning

confidence: 99%

Implementation of dosimetry equipment and phantoms at the MedAustron light ion beam therapy facility

et al. 2017

View full text Add to dashboard Cite

Purpose: To describe the implementation of dosimetry equipment and phantoms into clinical practice of light ion beam therapy facilities. This work covers not only standard dosimetry equipment such as computerized water scanners, films, 2D-array, thimble, and plane parallel ionization chambers, but also dosimetry equipment specifically devoted to the pencil beam scanning delivery technique such as water columns, scintillating screens or multilayer ionization chambers. Method: Advanced acceptance testing procedures developed at MedAustron and complementary to the standard acceptance procedures proposed by the manufacturer are presented. Detailed commissioning plans have been implemented for each piece of dosimetry equipment and include an estimate of the overall uncertainty budget for the range of clinical use of each device. Some standard dosimetry equipment used in many facilities was evaluated in detail: for instance, the recombination of a 2D-array or the potential use of a microdiamond detector to measure reference transverse dose profiles in water in the core of the primary pencil beams and in the low-dose nuclear halo (over four orders of magnitude in dose). Results: The implementation of dosimetry equipment as described in this work allowed determining absolute spot sizes and spot positions with an uncertainty better than 0.3 mm. Absolute ranges are determined with an uncertainty comprised of 0.2-0.6 mm, depending on the measured range and were reproduced with a maximum difference of 0.3 mm over a period of 12 months using three different devices. Conclusion: The detailed evaluation procedures of dosimetry equipment and phantoms proposed in this work could serve as a guidance for other medical physicists in ion beam therapy facilities and also in conventional radiation therapy.

show abstract

“…This method can be translated to the other scintillator, such as Lynx (Ion Beam Applications, SA, Louvain‐la‐Neuve, Belgium). The 2D scintillator is used in our institute and other institutes for the quality assurance of the spot sizes and spot positions . These spot size and position measurements are not included in this paper because they are beyond the scope of this paper.…”

Section: Discussionmentioning

confidence: 99%

“…In this letter, we propose a novel analytic method using a large 2D scintillator of 30 cm × 40 cm combined with a customized wedge device to efficiently measure the proton range to 0.2 mm precision. Notably, the large 2D scintillator device also allows for simultaneous quality assurance for spot size and spot position . Other technologies discussed above do not currently offer such efficient and convenient all‐in‐one functionality for range, spot size, and spot position QA.…”

Section: Introductionmentioning

confidence: 99%

A novel and fast method for proton range verification using a step wedge and 2D scintillator

et al. 2017

View full text Add to dashboard Cite

Purpose: To implement and evaluate a novel and fast method for proton range verification by using a planar scintillator and step wedge. Methods: A homogenous proton pencil beam plan with 35 energies was designed and delivered to a 2D flat scintillator with a step wedge. The measurement was repeated 15 times (3 different days, 5 times per day). The scintillator image was smoothed, the Bragg peak and distal fall off regions were fitted by an analytical equation, and the proton range was calculated using simple trigonometry. The accuracy of this method was verified by comparing the measured ranges to those obtained using an ionization chamber and a scanning water tank, the gold standard. The reproducibility was evaluated by comparing the ranges over 15 repeated measurements. The sensitivity was evaluated by delivering to same beam to the system with a film inserted under the wedge. Results: The range accuracy of all 35 proton energies measured over 3 days was within 0.2 mm. The reproducibility in 15 repeated measurements for all 35 proton ranges was AE0.045 mm. The sensitivity to range variation is 0.1 mm for the worst case. This efficient procedure permits measurement of 35 proton ranges in less than 3 min. The automated data processing produces results immediately. The setup of this system took less than 5 min. The time saving by this new method is about two orders of magnitude when compared with the time for water tank range measurements. Conclusions: A novel method using a scintillator with a step wedge to measure the proton range was implemented and evaluated. This novel method is fast and sensitive, and the proton range measured by this method was accurate and highly reproducible.

show abstract

A novel technique for measuring the low-dose envelope of pencil-beam scanning spot profiles

Cited by 58 publications

References 16 publications

Using field size factors to characterize the in-air fluence of a proton machine with a range shifter

Using field size factors to characterize the in-air fluence of a proton machine with a range shifter

Implementation of dosimetry equipment and phantoms at the MedAustron light ion beam therapy facility

A novel and fast method for proton range verification using a step wedge and 2D scintillator

Contact Info

Product

Resources

About