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

A database of clinically approved stereotactic radiosurgery treatment plans was created. One hundred and seventy targets in the database were then retrospectively evaluated using conformity indices suggested by RTOG, SALT‐Lomax and Paddick. Relationships between the three alternative conformity indices were determined. The Paddick index combines the information provided by the RTOG and SALT‐Lomax indices into a single index. The variation in the geometric overlap ratio, which is related to the SALT‐Lomax index, was found to be not clinically relevant for our cohort of patients, and thus the Paddick and RTOG indices can be directly related. It was found that access to a dose volume histogram or dose distribution for a treatment plan renders the RTOG conformity index sufficient for plan quality evaluation.PACS number: 87.53.Ly

A modified sector-integration method has been developed that predicts electron beam output factor at any point on the beam central axis, for a given source to surface distance (SSD), as a function of the geometry of the irradiated field. The main concept of this method is that with the arbitrary field shape divided into small sectors, the individual contributions from each sector can be calculated based on the sector radius, using a dataset consisting of circular inserts of standard radii. A computer program was developed based on this algorithm. The program interfaces to a digital camera that is used to capture the shape of the electron insert. We compared the calculated and the measured output factors and per cent depth doses (PDDs) at different SSDs for various rectangular inserts and a typical irregularly shaped insert used in our clinic. To determine the geometric limitations of this algorithm, a series of rectangular inserts were designed with the long-to-short axis ratio between 1:1 and 7:1. The agreement between calculation and measurement for the electron output and PDD was generally within 2% (or 2 mm) for energies from 6 to 20 MeV.

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The Medical Physics departments of the Tom Baker Cancer Center (TBCC) and the Cross Cancer Institute (CCI) independently performed preliminary evaluation of the new Analytical Anisotropic Algorithm (AAA) implemented in Varian's Eclispe (v. 6.0) treatment planning system (TPS). The TPS was pre‐commissioned with “Golden Beam Data” from the vendor. We measured central and off‐axis profiles in several beam configurations including: open square, rectangular and asymmetric (half‐blocked) beams; wedged square and half‐blocked beams; square fields at three SSDs; open and wedged oblique beams; irregular field defined by MLC and cerrobend blocks. All measurements were performed on Varian 2100EX linear accelerators. Measurements were made to assess the dose in heterogeneous media at both the CCI (CIRS Thorax IMRT phantom) and at the TBCC (TLDs in a Rando phantom). Profiles were evaluated in the buildup, penumbra, inner and outer beam regions as per AAPM Task Group 53. Measured and calculated profiles agreement was very good in all regions except for the inner beam region at the CCI, attributed a difference in interpolation schemes at the two institutions and the large volume ion chamber used for measurements. The AAA penumbra was also found to be steeper than measured penumbra since AAA was pre‐commissioned using diode measurements. Total scatter factors for most measurements differed by less than 2% from the calculated ones except for the hard wedges where differences up to 4% were found. Anthropomorphic phantoms measurements differed from AAA by as much as 5.6%. Funding provided by Varian.