Monitor unit calculations for external photon and electron beams: Report of the AAPM Therapy Physics Committee Task Group No. 71

Gibbons, John; Antolak, John A.; Followill, David S; Huq, M. Saiful; Klein, Eric E.; Lam, Kwok L.; Palta, Jatinder; Roback, Donald M.; Reid, M. J.; Khan, Faiz M.

doi:10.1118/1.4864244

Cited by 71 publications

(67 citation statements)

References 150 publications

(145 reference statements)

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“…An independent check of a treatment planning dose calculation process is a mandated component of the quality assurance in radiation therapy 1 , 2 , 3 . The goal of an independent second check of dose calculation is not to correct the primary calculation, but to ensure that the primary calculation has been done accurately for the safe and effective treatment of the patient.…”

Section: Introductionmentioning

confidence: 99%

Two‐year experience with the commercial Gamma Knife Check software

Bhatnagar

Bednarz

et al. 2016

J Applied Clin Med Phys

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The Gamma Knife Check software is an FDA approved second check system for dose calculations in Gamma Knife radiosurgery. The purpose of this study was to evaluate the accuracy and the stability of the commercial software package as a tool for independent dose verification. The Gamma Knife Check software version 8.4 was commissioned for a Leksell Gamma Knife Perfexion and a 4C unit at the University of Pittsburgh Medical Center in May 2012. Independent dose verifications were performed using this software for 319 radiosurgery cases on the Perfexion and 283 radiosurgery cases on the 4C units. The cases on each machine were divided into groups according to their diagnoses, and an averaged absolute percent dose difference for each group was calculated. The percentage dose difference for each treatment target was obtained as the relative difference between the Gamma Knife Check dose and the dose from the tissue maximum ratio algorithm (TMR 10) from the GammaPlan software version 10 at the reference point. For treatment plans with imaging skull definition, results obtained from the Gamma Knife Check software using the measurement‐based skull definition method are used for comparison. The collected dose difference data were also analyzed in terms of the distance from the treatment target to the skull, the number of treatment shots used for the target, and the gamma angles of the treatment shots. The averaged percent dose differences between the Gamma Knife Check software and the GammaPlan treatment planning system are 0.3%, 0.89%, 1.24%, 1.09%, 0.83%, 0.55%, 0.33%, and 1.49% for the trigeminal neuralgia, acoustic neuroma, arteriovenous malformation (AVM), meningioma, pituitary adenoma, glioma, functional disorders, and metastasis cases on the Perfexion unit. The corresponding averaged percent dose differences for the 4C unit are 0.33%, 1.2%, 2.78% 1.99%, 1.4%, 1.92%, 0.62%, and 1.51%, respectively. The dose difference is, in general, larger for treatment targets in the peripheral regions of the skull owing to the difference in the numerical methods used for skull shape simulation in the GammaPlan and the Gamma Knife Check software. Larger than 5% dose differences were observed on both machines for certain targets close to patient skull surface and for certain targets in the lower half of the brain on the Perfexion, especially when shots with 70 and/or 110 gamma angles are used. Out of the 1065 treatment targets studied, a 5% cutoff criterion cannot always be met for the dose differences between the studied versions of the Gamma Knife Check software and the planning system for 40 treatment targets.PACS number(s): 87.55.Qr, 87.56.Fc

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Section: Introductionmentioning

confidence: 99%

Two‐year experience with the commercial Gamma Knife Check software

Bhatnagar

Bednarz

et al. 2016

J Applied Clin Med Phys

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“…The irregular cutouts were not included in this work due to their variability and that their field sizes can be estimated using rectangular field sizes. [9] The criteria for the selection of these field sizes included approximations to clinical scenarios and tests of the limitations of the algorithm in small dimension and varying aspect ratio situations. Cerrobend cutouts were designed to fit in either a 10 cm × 10 cm or a 15 cm × 15 cm applicator.…”

Section: Methodsmentioning

confidence: 99%

“…71. [9] With inclusion of the electron dosimetry considerations mentioned in other TG reports,[101112] TG 71 explicitly proposed a unified definition for the dosimetric quantities in electron MU calculations and provided instructions to determine these quantities. It is beneficial to have such a well-established electron MU calculation protocol implemented in clinic.…”

Section: Introductionmentioning

confidence: 99%

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Clinical implementation of an electron monitor unit dosimetry system based on task group 71 report and a commercial calculation program

Xu¹,

Guerrero²,

Chen³

et al. 2016

J Med Phys

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Many clinics still use monitor unit (MU) calculations for electron treatment planning and/or quality assurance (QA). This work (1) investigates the clinical implementation of a dosimetry system including a modified American Association of Physicists in Medicine-task group-71 (TG-71)-based electron MU calculation protocol (modified TG-71 electron [mTG-71E] and an independent commercial calculation program and (2) provides the practice recommendations for clinical usage. Following the recently published TG-71 guidance, an organized mTG-71E databook was developed to facilitate data access and subsequent MU computation according to our clinical need. A recently released commercial secondary calculation program – Mobius3D (version 1.5.1) Electron Quick Calc (EQC) (Mobius Medical System, LP, Houston, TX, USA), with inherent pencil beam algorithm and independent beam data, was used to corroborate the calculation results. For various setups, the calculation consistency and accuracy of mTG-71E and EQC were validated by their cross-comparison and the ion chamber measurements in a solid water phantom. Our results show good agreement between mTG-71E and EQC calculations, with average 2% difference. Both mTG-71E and EQC calculations match with measurements within 3%. In general, these differences increase with decreased cutout size, increased extended source to surface distance, and lower energy. It is feasible to use TG71 and Mobius3D clinically as primary and secondary electron MU calculations or vice versa. We recommend a practice that only requires patient-specific measurements in rare cases when mTG-71E and EQC calculations differ by 5% or more.

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“…[47][48] This is typically done by comparing to the calculation of another system and is described in section 5.3.4 of AAPM TG-114. 49 The second category is the validation of IMRT dose distributions. AAPM TG-71, Monitor Unit Calculations for External Photon and Electron Beams, 49 and ESTRO booklet 6, Monitor Unit Calculation for High Energy Photon Beams: Practical Examples, 50 are also good references on MU verification.…”

Section: Patient-specific Qamentioning

confidence: 99%

Quality Assurance of Radiotherapy Dose Calculations

Dieterich

2016

Practical Radiation Oncology Physics

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Monitor unit calculations for external photon and electron beams: Report of the AAPM Therapy Physics Committee Task Group No. 71

Cited by 71 publications

References 150 publications

Two‐year experience with the commercial Gamma Knife Check software

Two‐year experience with the commercial Gamma Knife Check software

Clinical implementation of an electron monitor unit dosimetry system based on task group 71 report and a commercial calculation program

Quality Assurance of Radiotherapy Dose Calculations

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