Comparison of monitor unit calculations performed with a 3D computerized planning system and independent “hand” calculations: Results of three years clinical experience

Chan, Jackson; Russell, David; Peters, Victor; Farrell, Thomas J.

doi:10.1120/jacmp.v3i4.2553

Cited by 12 publications

(5 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Independent verification of the treatment planning system (TPS) calculations is an essential part of the quality assurance (QA) process in radiation therapy. This verification is traditionally based on manual monitor unit (MU) calculation methods for 3D conformal radiotherapy (3D CRT) treatments 3 , 4 , 5 , 6 , 7 . The complexity present in the modulated treatments requires an introduction of a comprehensive quality assurance program aimed at its implementation (8) .…”

Section: Introductionmentioning

confidence: 99%

Dosimetric validation and clinical implementation of two 3D dose verification systems for quality assurance in volumetric‐modulated arc therapy techniques

Clemente-Gutiérrez

Perez-Vara

2015

J Applied Clin Med Phys

View full text Add to dashboard Cite

A pretreatment quality assurance program for volumetric techniques should include redundant calculations and measurement‐based verifications. The patient‐specific quality assurance process must be based in clinically relevant metrics. The aim of this study was to show the commission, clinical implementation, and comparison of two systems that allow performing a 3D redundant dose calculation. In addition, one of them is capable of reconstructing the dose on patient anatomy from measurements taken with a 2D ion chamber array. Both systems were compared in terms of reference calibration data (absolute dose, output factors, percentage depth‐dose curves, and profiles). Results were in good agreement for absolute dose values (discrepancies were below 0.5%) and output factors (mean differences were below 1%). Maximum mean discrepancies were located between 10 and 20 cm of depth for PDDs (‐2.7%) and in the penumbra region for profiles (mean DTA of 1.5 mm). Validation of the systems was performed by comparing point‐dose measurements with values obtained by the two systems for static, dynamic fields from AAPM TG‐119 report, and 12 real VMAT plans for different anatomical sites (differences better than 1.2%). Comparisons between measurements taken with a 2D ion chamber array and results obtained by both systems for real VMAT plans were also performed (mean global gamma passing rates better than 87.0% and 97.9% for the 2%/2 mm and 3%/3 mm criteria). Clinical implementation of the systems was evaluated by comparing dose‐volume parameters for all TG‐119 tests and real VMAT plans with TPS values (mean differences were below 1%). In addition, comparisons between dose distributions calculated by TPS and those extracted by the two systems for real VMAT plans were also performed (mean global gamma passing rates better than 86.0% and 93.0% for the 2%/2 mm and 3%/3 mm criteria). The clinical use of both systems was successfully evaluated.PACS numbers: 87.56.Fc, 87.56.‐v, 87.55.dk, 87.55.Qr, 87.55.‐x, 07.57.Kp, 85.25.Pb

show abstract

Section: Introductionmentioning

confidence: 99%

Dosimetric validation and clinical implementation of two 3D dose verification systems for quality assurance in volumetric‐modulated arc therapy techniques

Clemente-Gutiérrez

Perez-Vara

2015

J Applied Clin Med Phys

View full text Add to dashboard Cite

show abstract

“…Jackson et al 23 . confirmed that the differences in MU between manual and TPS calculations for breast radiotherapy increase when these calculations require OAR(r) corrections, and compared 6 MV and Cobalt beams (the OAR correction is neglected for Co‐60) under similar conditions while neglecting influencing factors such as tissue heterogeneities in both calculations.…”

Section: Discussionmentioning

confidence: 93%

“…Thus, several mathematical formulas were developed to improve the accuracy of calculations for asymmetric fields based on the GESF concept, 12,18–21 the simplest of which is the area‐perimeter ratio 22 . According to these formulas, in order to calculate the S cp for asymmetric fields, the S c and S p of their GESF can be used 3,23–26 …”

Section: Introductionmentioning

confidence: 99%

Validation of the geometric equivalent field concept in total scatter factor calculations, for half‐, quarter‐ and off‐isocenter asymmetric square fields

Hmodi,

Nahili,

Tsalafoutas

et al. 2023

J Applied Clin Med Phys

View full text Add to dashboard Cite

ObjectiveMonitor unit (MU) verification for any symmetric or asymmetric field is performed using a total scatter factor (Scp), that is calculated based on the geometric equivalent square field (GESF) concept. In this study, we measured the Scp of various asymmetric square fields (ASFs) and their respective GESFs.MethodsSquare half‐fields (SHFs), square quarter‐fields (SQFs) and square off‐isocenter fields (SOFs), with sizes ranging from 3×3 cm2 to 20×20 cm2 were created, by varying the collimator jaws of two Varian iX Linacs (6/18 and 6/23 MV). A semi‐flex ion chamber was used to measure Scp at a depth of 10 cm within a water phantom, at the effective field center (EFC) of all ASFs, and at the isocenter (IC) of their respective GESFs. The later Scp values were corrected by the off‐axis ratio [OAR(r)] of the 40×40 cm2 field size, where r is the distance between EFC and IC.ResultsThe results show that the Scp (EFC) is independent of the type of the ASF (SHF, SQF, or SOF) and no significant difference exists between the 18 and 23 MV beams. Compared with the Scp (IC), the Scp (EFC) increased with increasing r, by up to 2% and 4% for 18/23 and 6 MV, respectively.ConclusionsThe GESF concept provides acceptable accuracy (< 2%) for the calculation of Scp of the ASFs used in most clinical situations (except from SOF with EFC at large r), and thus can be used in MU verification calculations.

show abstract

“…In order to prevent accidents in radiotherapy, the monitor unit recalculations are a prerequisite component of quality assurance (QA) in radiation therapy. Because errors and large uncertainties in dose calculations reduce the quality of a treatment, MU recalculations have been recommended as a routine quality assurance (QA) procedure when verifying individual treatment plans [1]. Even though the validity of the calculation algorithms can be passed during the commissioning of a TPS, verification of the monitor units calculated by the TPS is typically performed using a ''hand'' calculation based all of standard beam data.…”

Section: Introductionmentioning

confidence: 99%

Untitled

2017

CTOIJ

View full text Add to dashboard Cite

A comparison of the monitor unit calculations between a commercial treatment planning system (TPS) and ''hand'' calculations is extremely important in radiation therapy. In this paper, we will recalculate MU of the 3D-CRT plan for Lung and Rectal cancer on the treatment planning system supplied by Prowess Panther 4.6 at Dong Nai General Hospital, Vietnam. The monitor unit of each beams was recalculate by ''hand'' calculations and compared TPS. In general excellent overall agreement was found between calculations performed with the TPS and "hand" calculations. The MU difference between the monitor unit calculations of TPS and ''hand'' calculation was 0.144% with a standard deviation of 0.051% for rectal patients and 0.027 with a standard deviation of 0.008% for Lung patients. The result shows that there were no significant differences between recalculation and TPS.

show abstract

Comparison of monitor unit calculations performed with a 3D computerized planning system and independent “hand” calculations: Results of three years clinical experience

Cited by 12 publications

References 11 publications

Dosimetric validation and clinical implementation of two 3D dose verification systems for quality assurance in volumetric‐modulated arc therapy techniques

Dosimetric validation and clinical implementation of two 3D dose verification systems for quality assurance in volumetric‐modulated arc therapy techniques

Validation of the geometric equivalent field concept in total scatter factor calculations, for half‐, quarter‐ and off‐isocenter asymmetric square fields

Untitled

Contact Info

Product

Resources

About