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We investigated the influence of random spot positioning errors (SPEs) on dosimetric outcomes of robustly optimized intensity-modulated proton therapy (RB-IMPT) plans in craniospinal irradiation (CSI). Six patients with CSI treated using the RB-IMPT technique were selected. An in-house MATLAB code was used to simulate a random SPE of 1 mm in positive, negative, and both directions for 25%, 50%, and 75% of the total spot positions in the nominal plan. The percentage dose variation (ΔD%) in the six nominal and 54 error-introduced plans was evaluated using standard dose-volume indices, line dose difference, and 3D gamma analysis method. The introduction of a random SPE of 1 mm resulted in a reduction in D99%, D98%, and D95% of both CTVs and PTVs by

We investigated the dynamic positioning accuracy of Agility (Elekta) for volumetric modulated arc therapy (VMAT). The accuracy of the multileaf collimator (MLC) leaf position during VMAT was evaluated using three different tests: (1) a dynamic multileaf collimator (DMLC) output test with various leaf speeds, and gantry angles; (2) a slit-fence test with and without gantry rotation; and (3) a complicated VMAT plans test with dose distributions compared with measurements using gamma analysis. The DMLC output was within 1.5 % under all test conditions. The agreement between the static and VMAT in the slit-fence test was within 0.5 mm. The pass rate of each complicated VMAT test plan was more than 93.9 % ± 0.36 for gamma analysis. We confirmed the dynamic positioning accuracy of Agility, which during VMAT delivery is within VMAT tolerances. The fastest MLC was found to have the potential to offer clinical advantages, such as high-quality rapid VMAT.

Our objective in this study was to create AAPM TG 119 test plans for intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) in the Monaco planning system. The results were compared with the published studies, and the performance of the Monaco planning system was analyzed. AAPM TG 119 proposed a set of test cases called multi-target, mock prostate, mock head and neck and C-shape to ascertain the overall accuracy of IMRT planning, measurement, and analysis. We used these test cases to investigate the performance of the Monaco planning system for the complex plans. For these test cases, we created IMRT plans with static multi-leaf collimator (MLC) and dynamic MLC by using 7-9 static beams as explained in TG-119. VMAT plans were also created with a 320° arc length and a single or double arc. The planning objectives and dose were set as described in TG 119. The dose prescriptions for multi-target, mock prostate, mock head and neck, and C-shape were taken as 50, 75.6, 50 and 50 Gy, respectively. All plans were compared with the results of TG 119 and the study done by Mynampati et al. Point dose and fluence measurements were done with a CC13 chamber and ArcCHECK phantom, respectively. Gamma analysis was done for the calculated and measured dose. Using the Monaco planning system, we achieved the goals mentioned in AAPM TG-119, and the plans were comparable to those of other studies. A comparison of point dose and fluence showed good results. From these results, we conclude that the performance of the Monaco planning system is good for complex plans.

Our purpose in this study was to implement three-dimensional (3D) gamma analysis for structures of interest such as the planning target volume (PTV) or clinical target volume (CTV), and organs at risk (OARs) for intensity-modulated radiation therapy (IMRT) dose verification. IMRT dose distributions for prostate and head and neck (HN) cancer patients were calculated with an analytical anisotropic algorithm in an Eclipse (Varian Medical Systems) treatment planning system (TPS) and by Monte Carlo (MC) simulation. The MC dose distributions were calculated with EGSnrc/BEAMnrc and DOSXYZnrc user codes under conditions identical to those for the TPS. The prescribed doses were 76 Gy/38 fractions with five-field IMRT for the prostate and 33 Gy/17 fractions with seven-field IMRT for the HN. TPS dose distributions were verified by the gamma passing rates for the whole calculated volume, PTV or CTV, and OARs by use of 3D gamma analysis with reference to MC dose distributions. The acceptance criteria for the 3D gamma analysis were 3/3 and 2 %/2 mm for a dose difference and a distance to agreement. The gamma passing rates in PTV and OARs for the prostate IMRT plan were close to 100 %. For the HN IMRT plan, the passing rates of 2 %/2 mm in CTV and OARs were substantially lower because inhomogeneous tissues such as bone and air in the HN are included in the calculation area. 3D gamma analysis for individual structures is useful for IMRT dose verification.

Our purpose in this study was to evaluate the accuracy of a new multi-planar dose measurement method. The multi-planar dose distributions were reconstructed at each depth by convolution of EPID fluence and dose kernels with the use of EPIDose software (SunNuclear). The EPIDose was compared with EPID, MapCHECK (SunNuclear), EDR2 (Kodak), and Monte Carlo-calculated dose profiles. The EPIDose profiles were almost in agreement with Monte Carlo-calculated dose profiles and MapCHECK for test plans. The dose profiles were in good agreement with EDR2 at the penumbra region. For dose distributions, EPIDose, EDR2, and MapCHECK agreed with that of the treatment-planning system at each depth in the gamma analysis. In comparisons of clinical IMRT plans, EPIDose had almost the same accuracy as MapCHECK and EDR2. Because EPIDose has a wide dynamic range and high resolution, it is a useful tool for the complicated IMRT verification. Furthermore, EPIDose can also evaluate the absolute dose.

Our purpose in this study was to evaluate the fundamental accuracy of reconstructed dose distributions from the COMPASS system using specific MLC test patterns and complicated IMRT neck plans. The COMPASS-reconstructed dose distributions were compared with those measured with EPID, MapCHECK, and EDR2 film and as well as Monte Carlo-calculated dose profiles with use of square-wave chart patterns of 20-, 10-, and 5-mm gaps and step and pyramid patterns. Additionally, the COMPASS dose distributions for clinical IMRT neck plans were tested. The COMPASS dose profiles were almost in agreement with the Monte Carlo-calculated dose profiles and point doses measured with MapCHECK for 20- and 10-mm gap patterns. The dose profile for a 5-mm gap pattern showed a narrow width due to the detector size in the penumbra region. For step and pyramid patterns, COMPASS agreed with MapCHECK and Monte Carlo calculation, except for EDR2 film. The COMPASS and MapCHECK dose distributions agreed with that of a treatment planning system by gamma analysis (criteria; 3 mm/3%). In comparisons of clinical IMRT neck dose distributions, COMPASS was measured with almost the same accuracy as MapCHECK, but slight deviations were found for large IMRT fields. These deviations could be minimized by improvement of the beam model of the COMPASS system. The COMPASS system can be expected to be used for traditional QA methods in clinical routine with the same accuracy as a MapCHECK diode detector.