A critical evaluation of the PTW 2D‐ARRAY seven29 and OCTAVIUS II phantom for IMRT and VMAT verification

Hussein, Mohammad; Adams, Elizabeth; Jordan, Thomas; Clark, Catharine H.; Nisbet, Andrew

doi:10.1120/jacmp.v14i6.4460

Cited by 54 publications

(59 citation statements)

References 38 publications

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“…During previous years, commercially available measurement devices for IMRT and VMAT QA have been tested for general performance and plan‐specific QA abilities2, 3, 10, 24, 25. Dose, dose rate and field size dependence as were described by these authors are supported by our data, even though the non‐linearity for very small doses in the linac ramp up was either not studied before or described to a different reference and also field sizes below 2 × 2 cm² we not studied.…”

Section: Discussionmentioning

confidence: 99%

“…On the one hand, using the popular method of gamma‐evaluation and subsequent pass rate analysis,26 one can argue about the correct distance‐to‐agreement and dose criteria or pass rate, that has to be used 2, 9, 10, 12, 13, 15, 18. On the other hand, one can question this method in general,27, 28 as there might be a lack of correlation between the results of the gamma‐analysis and the clinical implication 9, 11, 13, 14, 27, 29, 30, 31, 32.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, improvements in tests for the correct beam model parameters were proposed 5, 6, 7, 8. Nevertheless, the evaluation of treatment plan QA is still cumbersome as shown by ongoing discussions about the widely used gamma‐evaluation method itself, the optimal evaluation parameters and the comparison between different measurement devices 9, 10, 11, 12, 13, 14, 15, 16, 17, 18…”

Section: Introductionmentioning

confidence: 99%

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Practical implications for the quality assurance of modulated radiation therapy techniques using point detector arrays

Kantz

McDermott

Söhn

et al. 2017

J Applied Clin Med Phys

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PurposeLinac parameters potentially influencing the delivery quality of IMRT and VMAT plans are investigated with respect to threshold ranges, consequently to be considered in a linac based quality assurance procedure. Three commercially available 2D arrays are used to further investigate the influence of the measurement device.MethodsUsing three commercially available 2D arrays (Mx: MatriXXevolution, Oc: Octavius1500, Mc: MapCHECK2), simple static measurements, measurements for MLC characterization and dynamic interplay of gantry movement, MLC movement and variable dose rate were performed. The results were evaluated with respect to each single array as well as among each other.ResultsSimple static measurements showed different array responses to dose, dose rate and profile homogeneity and revealed instabilities in dose delivery and profile shape during linac ramp up. Using the sweeping gap test, all arrays were able to detect small leaf misalignments down to ±0.1 mm, but this test also demonstrated up to 15% dose deviation due to profile instabilities and fast accelerating leaves during linac ramp up. Tests including gantry rotation showed different stability of gantry mounts for each array. Including gantry movement and dose rate variability, differences compared to static delivery were smaller compared to dose differences when simultaneously controling interplay of gantry movement, leaf movement and dose rate variability.ConclusionLinac based QA is feasible with the tested commercially available 2D arrays. Limitations of each array and the linac ramp up characteristics should be carefully considered during individual plan generation and regularly checked in linac QA. Especially the dose and dose profile during linac ramp up should be checked regularly, as well as MLC positioning accuracy using a sweeping gap test. Additionally, dynamic interplay tests including various gantry rotation speeds and angles, various leaf speeds and various dose rates should be included.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Practical implications for the quality assurance of modulated radiation therapy techniques using point detector arrays

Kantz

McDermott

Söhn

et al. 2017

J Applied Clin Med Phys

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“…Currently, the electronic dosimetry system is still more popular in clinic use for patient‐specific QA because of its easy handling and the reproducibility. The electronic dosimetry systems with various geometry configurations and detector types introduced for routine patient‐specific QA for linac‐based treatments include planar ion chamber/diode arrays 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 (e.g., MatriXX, IBA Dosimetry; Octavius 729, PTW; MapCHECK, SunNclear Corp.), cylindrical diode arrays 16 , 17 , 18 , 19 , 20 , 21 , 22 (ArcCHECK, Sun Nuclear Corp), and two diode arrays embedded in a cross‐plane fashion in a cylindrical phantom (23) (Delta 4 , ScandiDos AB, Uppsala, Sweden). In contrast to the measurements for the linac delivery, which are mostly in a coplanar manner with larger field sizes, the measurements for the CyberKnife delivery can be more challenging since the delivery involves numerous narrow unflattened photon beams at a wide range of spatial angles.…”

Section: Introductionmentioning

confidence: 99%

Robotic radiosurgery system patient‐specific QA for extracranial treatments using the planar ion chamber array and the cylindrical diode array

Lin

Veltchev

Koren

et al. 2015

J Applied Clin Med Phys

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Robotic radiosurgery system has been increasingly employed for extracranial treatments. This work is aimed to study the feasibility of a cylindrical diode array and a planar ion chamber array for patient‐specific QA with this robotic radiosurgery system and compare their performance. Fiducial markers were implanted in both systems to enable image‐based setup. An in‐house program was developed to postprocess the movie file of the measurements and apply the beam‐by‐beam angular corrections for both systems. The impact of noncoplanar delivery was then assessed by evaluating the angles created by the incident beams with respect to the two detector arrangements and cross‐comparing the planned dose distribution to the measured ones with/without the angular corrections. The sensitivity of detecting the translational (1–3 mm) and the rotational (1°–3°) delivery errors were also evaluated for both systems. Six extracranial patient plans (PTV 7–137 cm3) were measured with these two systems and compared with the calculated doses. The plan dose distributions were calculated with ray‐tracing and the Monte Carlo (MC) method, respectively. With 0.8 by 0.8 mm2 diodes, the output factors measured with the cylindrical diode array agree better with the commissioning data. The maximum angular correction for a given beam is 8.2% for the planar ion chamber array and 2.4% for the cylindrical diode array. The two systems demonstrate a comparable sensitivity of detecting the translational targeting errors, while the cylindrical diode array is more sensitive to the rotational targeting error. The MC method is necessary for dose calculations in the cylindrical diode array phantom because the ray‐tracing algorithm fails to handle the high‐Z diodes and the acrylic phantom. For all the patient plans, the cylindrical diode array/ planar ion chamber array demonstrate 100%/>;92%false(3%/3 mmfalse) passing rates. The feasibility of using both systems for robotic radiosurgery system patient‐specific QA has been demonstrated. For gamma evaluation, 2%/2 mm criteria for cylindrical diode array and 3%/3 mm criteria for planar ion chamber array are suggested. The customized angular correction is necessary as proven by the improved passing rate, especially with the planar ion chamber array system.PACS number: 29.40.‐n

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“…The diode-detector-based MapCHECK (Sun Nuclear Corporation, US) [7], the ion-chamber based Seven29 2D array (PTW, Germany) [8,9], and MatriXX (IBA Dosimetry, Germany) [10][11][12][13][14] are commonly used commercial 2D detector arrays. The MatriXX array has a linear response with dose and it is independent of energy [12].…”

Section: Introductionmentioning

confidence: 99%

Study of impacts of different evaluation criteria on gamma pass rates in VMAT QA using MatriXX and EPID

Noufal

Abdullah

Puzhakkal

et al. 2017

Polish Journal of Medical Physics and Engineering

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Aim: This study evaluates the impacts of using different evaluation criteria on gamma pass rates in two commercially available QA methods employed for the verification of VMAT plans using different hypothetical planning target volumes (PTVs) and anatomical regions. Introduction: Volumetric modulated arc therapy (VMAT) is a widely accepted technique to deliver highly conformal treatment in a very efficient manner. As their level of complexity is high in comparison to intensity-modulated radiotherapy (IMRT), the implementation of stringent quality assurance (QA) before treatment delivery is of paramount importance. Material and Methods: Two sets of VMAT plans were generated using Eclipse planning systems, one with five different complex hypothetical three-dimensional PTVs and one including three anatomical regions. The verification of these plans was performed using a MatriXX ionization chamber array embedded inside a MultiCube phantom and a Varian EPID dosimetric system attached to a Clinac iX. The plans were evaluated based on the 3%/3 mm, 2%/2 mm, and 1%/1 mm global gamma criteria and with three low-dose threshold values (0%, 10%, and 20%). Results: The gamma pass rates were above 95% in all VMAT plans, when the 3%/3mm gamma criterion was used and no threshold was applied. In both systems, the pass rates decreased as the criteria become stricter. Higher pass rates were observed when no threshold was applied and they tended to decrease for 10% and 20% thresholds. Conclusion: The results confirm the suitability of the equipments used and the validity of the plans. The study also confirmed that the threshold settings greatly affect the gamma pass rates, especially for lower gamma criteria.

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A critical evaluation of the PTW 2D‐ARRAY seven29 and OCTAVIUS II phantom for IMRT and VMAT verification

Cited by 54 publications

References 38 publications

Practical implications for the quality assurance of modulated radiation therapy techniques using point detector arrays

Practical implications for the quality assurance of modulated radiation therapy techniques using point detector arrays

Robotic radiosurgery system patient‐specific QA for extracranial treatments using the planar ion chamber array and the cylindrical diode array

Study of impacts of different evaluation criteria on gamma pass rates in VMAT QA using MatriXX and EPID

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