Experimental validation of the Eclipse AAA algorithm

Abstract

The present study evaluates the performance of a newly released photon‐beam dose calculation algorithm that is incorporated into an established treatment planning system (TPS). We compared the analytical anisotropic algorithm (AAA) factory‐commissioned with “golden beam data” for Varian linear accelerators with measurements performed at two institutions using 6‐MV and 15‐MV beams. The TG‐53 evaluation regions and criteria were used to evaluate profiles measured in a water phantom for a wide variety of clinically relevant beam geometries. The total scatter factor (TSF) for each of these geometries was also measured and compared against the results from the AAA.At one institute, TLD measurements were performed at several points in the neck and thoracic regions of a Rando phantom; at the other institution, ion chamber measurements were performed in a CIRS inhomogeneous phantom. The phantoms were both imaged using computed tomography (CT), and the dose was calculated using the AAA at corresponding detector locations. Evaluation of measured relative dose profiles revealed that 97%, 99%, 97%, and 100% of points at one institute and 96%, 88%, 89%, and 100% of points at the other institution passed TG‐53 evaluation criteria in the outer beam, penumbra, inner beam, and buildup regions respectively. Poorer results in the inner beam regions at one institute are attributed to the mismatch of the measured profiles at shallow depths with the “golden beam data.”For validation of monitor unit (MU) calculations, the mean difference between measured and calculated TSFs was less than 0.5%; test cases involving physical wedges had, in general, differences of more than 1%. The mean difference between point measurements performed in inhomogeneous phantoms and Eclipse was 2.1% (5.3% maximum) and all differences were within TG‐53 guidelines of 7%. By intent, the methods and evaluation techniques were similar to those in a previous investigation involving another convolution–superposition photon‐beam dose calculation algorithm in another TPS, so that the current work permitted an independent comparison between the two algorithms for which results have been provided.PACS number: 87.53.Dq

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

“…However, common metrics may reduce the sensitivity of systems involved in patient‐specific QA processes 15 , 25 , 26 , 48 , 49 , 50 . A recent study by Nelms et al (50) suggested performing a more stringent gamma analysis, restricting traditional tolerances.…”

“…In addition, the pretreatment QA measurement‐based process must be considered to ensure the correct information flow from TPS plan calculation to treatment delivery in the linac by means of the record and verify system (R&V). The usual method to perform this QA consists of comparing dose distribution measurements acquired with phantoms/detectors of regular geometries with TPS calculations made under the same conditions 13 , 14 , 15 . Volumetric treatments have incorporated specifically developed solutions for these techniques 16 , 17 .…”

Evaluation of semiempirical VMAT dose reconstruction on a patient dataset based on biplanar diode array measurements

“…While reliable agreement between the calculated and measured/reconstructed dose in a geometrical phantom is the basis for the dosimetric commissioning of an IMRT system, its value for the meaningful patient‐specific, end‐to‐end testing is less clear. With the prevalent 3% globally normalized dose error and 3 mm DTA threshold criteria in particular, 3 , 4 , 5 y‐analysis passing rates for either per‐beam, single‐plane (6) or quasi‐3D (7) array geometries, had weak — and counter‐intuitive, if any — correlation with the conventional clinical DVH metrics. Instances of the $3\%/3\hspace{0.17em}\text{mm}$ passing rate metric's failure to detect systematic errors are numerous 6 , 7 , 8 , 9 .…”

Quantitative analysis of brass compensators for commissioning of the Pinnacle planning system for IMRT

“…A typical institutional criteria for gamma analysis 7 , 8 is to use values of $\text{DTA}=\pm \hspace{0.17em}3\hspace{0.17em}\text{mm}$ and % absolute dose difference $=\pm 3\%$. These values give very good passing rates (as expected), but also show little change in the number of failed points as the parameters MSF and ρ are varied.…”