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The purpose of this study was to test the feasibility of a patient specific phantom for patient specific dosimetric verification.Using the head and neck region of an anthropomorphic phantom as a substitute for an actual patient, a soft-tissue equivalent model was constructed with the use of a 3D printer. Calculated and measured dose in the anthropomorphic phantom and the 3D printed phantom was compared for a parallel-opposed head and neck field geometry to establish tissue equivalence. A nine-field IMRT plan was constructed and dose verification measurements were performed for the 3D printed phantom as well as traditional standard phantoms.The maximum difference in calculated dose was 1.8% for the parallel-opposed configuration. Passing rates of various dosimetric parameters were compared for the IMRT plan measurements; the 3D printed phantom results showed greater disagreement at superficial depths than other methods.A custom phantom was created using a 3D printer. It was determined that the use of patient specific phantoms to perform dosimetric verification and estimate the dose in the patient is feasible. In addition, end-to-end testing on a per-patient basis was possible with the 3D printed phantom. Further refinement of the phantom construction process is needed for routine use.

At our institution EPID (electronic portal imaging device) dosimetry is routinely applied to perform in vivo dose verification of all patient treatments with curative intent since January 2008. The major impediment of the method has been the amount of work required to produce and inspect the in vivo dosimetry reports (a time-consuming and labor-intensive process). In this paper we present an overview of the actions performed to implement an automated in vivo dosimetry solution clinically. We reimplemented the EPID dosimetry software and modified the acquisition software. Furthermore, we introduced new tools to periodically inspect the record-and-verify database and automatically run the EPID dosimetry software when needed. In 2012, 95% of our 3839 treatments scheduled for in vivo dosimetry were analyzed automatically (27,633 portal images of intensity-modulated radiotherapy (IMRT) fields, 5551 portal image data of VMAT arcs, and 2003 portal images of non-IMRT fields). The in vivo dosimetry verification results are available a few minutes after delivery and alerts are immediately raised when deviations outside tolerance levels are detected. After the clinical introduction of this automated solution, inspection of the detected deviations is the only remaining work. These newly developed tools are a major step forward towards full integration of in vivo EPID dosimetry in radiation oncology practice.

Dosimetry verification is an important step during intensity modulated radiotherapy treatment (IMRT). The verification is usually conducted with measurements and independent dose calculations. However, currently available independent dose calculation methods were developed for step-and-shoot beam delivery methods, and their uses for dynamic multi-leaf collimator (MLC) delivery methods are not efficient. In this study, a dose calculation method was developed to perform independent dose verifications for a dynamic MLC-based IMRT technique for Varian linear accelerators. This method extracts the machine delivery parameters from the dynamic MLC (DMLC) files generated by the IMRT treatment planning system. Based on the parameters a monitor unit (MU) matrix was separately calculated as two terms: direct exposure from the open MLC field and leakage contributions, where the leaf-end leakage contribution becomes more important in higher dose gradient regions. The MU matrix was used to compute the primary dose and the scattered dose with a modified Clarkson technique. The doses computed using the method were compared with both measurement and treatment planning for 14 and 25 plans respectively. An average of less than 2% agreement was observed and the standard deviation was about 1.9%.

This paper investigates a quality assurance (QA) phantom specially designed to verify the accuracy of dose distributions and monitor units (MU) calculated by clinical treatment planning optimization systems and by the Monte Carlo method for intensity-modulated radiotherapy (IMRT). The QA phantom is a PMMA cylinder of 30 cm diameter and 40 cm length with various bone and lung inserts. A procedure (and formalism) has been developed to measure the absolute dose to water in the PMMA phantom. Another cylindrical phantom of the same dimensions, but made of water, was used to confirm the results obtained with the PMMA phantom. The PMMA phantom was irradiated by 4, 6 and 15 MV photon beams and the dose was measured using an ionization chamber and compared to the results calculated by a commercial inverse planning system (CORVUS, NOMOS, Sewickley, PA) and by the Monte Carlo method. The results show that the dose distributions calculated by both CORVUS and Monte Carlo agreed to within 2% of dose maximum with measured results in the uniform PMMA phantom for both open and intensity-modulated fields. Similar agreement was obtained between Monte Carlo calculations and measured results with the bone and lung heterogeneity inside the PMMA phantom while the CORVUS results were 4% different. The QA phantom has been integrated as a routine QA procedure for the patient's IMRT dose verification at Stanford since 1999.

A three-dimensional dose verification with photographic emulsions (x-ray films) was realized within the tumour therapy project at GSI Darmstadt, using carbon ions. We present Bragg-peak measurements for 88, 100 and 200 MeV/u carbon ion beams as the simplest case of dose verification. An actual patient treatment plan, composed by the superposition of Bragg-peaks having different energies and intensities, was used to perform a three-dimensional dose verification of an irregularly formed target volume. The shape of the measured dose distribution from film closely matches the intended irradiation volume. Furthermore, the calculated and measured optical density distribution is in good agreement with a maximum deviation of less than 10%.

This study evaluates the performance of the Nikon Coolscan 9000 ED film scanner for high-gradient radiochromic film dosimetry. As a reference for comparison, analogue experiments were performed on the Epson Expression 10000XL flatbed scanner. Based on these results, a dosimetric protocol was established for the Nikon scanner and its overall performance for high-gradient dosimetry was evaluated. The Nikon scanner demonstrated a high sensitivity for radiochromic film dosimetry, resulting in more contrast in the digitized image. The scanner's optics also demonstrated excellent stability and did not necessitate warm-up scans prior to data acquisition. Moreover, negative effects of temperature changes of the film inside the scanner were shown to be limited. None of the digitized images showed significant disturbances by moire-patterns, by virtue of the absence of a glass plate for film positioning. However, scanner response was found to vary considerably across the reading area, requiring an optical density-dependent correction procedure to be incorporated into the scanning protocol. The main limitation of the Nikon Coolscan 9000 ED transmission scanner remains its film size restriction to 6.2 × 20 cm2. Nevertheless, its excellent characteristics render it the preferential tool for high-gradient radiochromic film dosimetry in applications limited to small film sizes, such as dosimetry in the build-up region.

We validate the dosimetric performance of COMPASS®, a novel 3D quality assurance system for verification of volumetric-modulated arc therapy (VMAT) treatment plans that can correlate the delivered dose to the patient's anatomy, taking into account the tissue inhomogeneity. The accuracy of treatment delivery was assessed by the COMPASS® for 12 VMAT plans, and the resulting assessments were evaluated using an ionization chamber and film measurements. Dose–volume relationships were evaluated by the COMPASS® for three additional treatment plans and these were used to verify the accuracy of treatment planning dose calculations. The results matched well between COMPASS® and measurements for the ionization chamber (≤3%) and film (73–99% for gamma(3%/3 mm) < 1 and 98–100% for gamma(5%/5 mm) < 1) for the phantom plans. Differences in dose–volume statistics for the average dose to the PTV were within 2.5% for three treatment plans. For the structures located in the low-dose region, a maximum difference of