IMRT quality assurance using a second treatment planning system.

We used a second treatment planning system (TPS) for independent verification of the dose calculated by our primary TPS in the context of patient-specific quality assurance (QA) for intensity-modulated radiation therapy (IMRT). QA plans for 24 patients treated with inverse planned dynamic IMRT were generated using the Nomos Corvus TPS. The plans were calculated on a computed tomography scan of our QA phantom that consists of three Solid Water slabs sandwiching radiochromic films, and an ion chamber that is inserted into the center slab of the phantom. For the independent verification, the dose was recalculated using the Varian Eclipse TPS using the multileaf collimator files and beam geometry from the original plan. The data was then compared in terms of absolute dose to the ion chamber volume as well as relative dose on isodoses calculated at the film plane. The calculation results were also compared with measurements performed for each case. When comparing ion chamber doses, the mean ratio was 0.999 (SD 0.010) for Eclipse vs. Corvus, 0.988 (SD 0.020) for the ionization chamber measurements vs. Corvus, and 0.989 (SD 0.017) for the ionization chamber measurements vs. Eclipse. For 2D doses with gamma histogram, the mean value of the percentage of pixels passing the criteria of 3%, 3 mm was 94.4 (SD 5.3) for Eclipse vs. Corvus, 85.1 (SD 10.6) for Corvus vs. film, and 93.7 (SD 4.1) for Eclipse vs. film; and for the criteria of 5%, 3 mm, 98.7 (SD 1.5) for Eclipse vs. Corvus, 93.0 (SD 7.8) for Corvus vs. film, and 98.0 (SD 1.9) for Eclipse vs. film. We feel that the use of the Eclipse TPS as an independent, accurate, robust, and time-efficient method for patient-specific IMRT QA is feasible in clinic.

Anjum MN ，Parker W ，Ruo R ，Aldahlawi I ，Afzal M ... -  《-》

Evaluation of the accuracy of 3DVH software estimates of dose to virtual ion chamber and film in composite IMRT QA.

Olch AJ 《MEDICAL PHYSICS》

Volumetric-modulated arc therapy: effective and efficient end-to-end patient-specific quality assurance.

To explore an effective and efficient end-to-end patient-specific quality-assurance (QA) protocol for volumetric modulated arc radiotherapy (VMAT) and to evaluate the suitability of a stationary radiotherapy QA device (two-dimensional [2D] ion chamber array) for VMAT QA. Three methods were used to analyze 39 VMAT treatment plans for brain, spine, and prostate: ion chamber (one-dimensional absolute, n = 39), film (2D relative, coronal/sagittal, n = 8), and 2D ion chamber array (ICA, 2D absolute, coronal/sagittal, n = 39) measurements. All measurements were compared with the treatment planning system dose calculation either via gamma analysis (3%, 3- to 4-mm distance-to-agreement criteria) or absolute point dose comparison. The film and ion chamber results were similarly compared with the ICA measurements. Absolute point dose measurements agreed well with treatment planning system computed doses (ion chamber: median deviation, 1.2%, range, -0.6% to 3.3%; ICA: median deviation, 0.6%, range, -1.8% to 2.9%). The relative 2D dose measurements also showed good agreement with computed doses (>93% of pixels in all films passing gamma, >90% of pixels in all ICA measurements passing gamma). The ICA relative dose results were highly similar to those of film (>90% of pixels passing gamma). The coronal and sagittal ICA measurements were statistically indistinguishable by the paired t test with a hypothesized mean difference of 0.1%. The ion chamber and ICA absolute dose measurements showed a similar trend but had disparities of 2-3% in 18% of plans. After validating the new VMAT implementation with ion chamber, film, and ICA, we were able to maintain an effective yet efficient patient-specific VMAT QA protocol by reducing from five (ion chamber, film, and ICA) to two measurements (ion chamber and single ICA) per plan. The ICA (Matrixx®, IBA Dosimetry) was validated for VMAT QA, but ion chamber measurements are recommended for absolute dose comparison until future developments correct the ICA angular dependence.

O'Daniel J ，Das S ，Wu QJ ，Yin FF ... -  《-》

Patient-specific IMRT verification using independent fluence-based dose calculation software: experimental benchmarking and initial clinical experience.

Georg D ，Stock M ，Kroupa B ，Olofsson J ，Nyholm T ，Ahnesjö A ，Karlsson M ... -  《PHYSICS IN MEDICINE AND BIOLOGY》

Biological consequences of MLC calibration errors in IMRT delivery and QA.

Moiseenko V ，Lapointe V ，James K ，Yin L ，Liu M ，Pawlicki T ... -  《MEDICAL PHYSICS》