In this work we compare doses from imaging procedures performed on today's state‐of‐the‐art integrated imaging systems using a reference radiochromic film dosimetry system. Skin dose and dose profile measurements from different imaging systems were performed using radiochromic films at different anatomical sites on a humanoid RANDO phantom. EBT3 film was used to measure imaging doses from a TomoTherapy MVCT system, while XRQA2 film was used for dose measurements from kilovoltage imaging systems (CBCT on 21eX and TrueBeam Varian linear accelerators and CyberKnife stereoscopic orthogonal imagers). Maximum measured imaging doses in cGy at head, thorax, and pelvis regions were respectively 0.50, 1.01, and 4.91 for CBCT on 21eX, 0.38, 0.84, and 3.15 for CBCT on TrueBeam, 4.33, 3.86, and 6.50 for CyberKnife imagers, and 3.84, 1.90, and 2.09 for TomoTherapy MVCT. In addition, we have shown how an improved calibration system of XRQA2 film can achieve dose uncertainty level of better than 2% for doses above 0.25 cGy. In addition to simulation‐based studies in literature, this study provides the radiation oncology team with data necessary to aid in their decision about imaging frequency for image‐guided radiation therapy protocols.PACS number: 87.53.Bn, 87.55.Qr, 87.56.Fc

Impact of the various kVp settings used during computed tomography (CT) simulation that provides data for heterogeneity corrected dose distribution calculations in patients undergoing external beam radiotherapy with either high‐energy photon or electron beams have been investigated. The change of the Hounsfield Unit (HU) values due to the influence of kVp settings and geometrical distribution of various tissue substitute materials has also been studied. The impact of various kVp settings and electron density (ED) distribution on the accuracy of dose calculation in high‐energy photon beams was found to be well within 2%. In the case of dose distributions obtained with a commercially available Monte Carlo dose calculation algorithm for electron beams, differences of more than 10% were observed for different geometrical setups and kVp settings. Dose differences for the electron beams are relatively small at shallow depths but increase with depth around lower isodose values.PACS numbers: 87.57.Q‐, 87.55.D‐

No abstract

Objective: To commission a grid block for spatially fractionated grid radiation therapy (SFGRT) treatments and describe its clinical implementation and verification through the record and verify (R&V) system. Methods: SFGRT was developed as a treatment modality for bulky tumours that cannot be easily controlled with conventionally fractionated radiation. Treatment is delivered in the form of open-closed areas. Currently, SFGRT is performed by either using a commercially available grid block or a multileaf collimator (MLC) of a linear accelerator. In this work, 6-MV photon beam was used to study dosimetric characteristics of the grid block. We inserted the grid block into a commercially available treatment planning system (TPS), and the feasibility of delivering such treatment plans on a linear accelerator using a R&V system was verified. Dose measurements were performed using a miniature PinPoint TM ion chamber (PTW, Freiburg, Germany) in a water phantom and radiochromic film within solid water slabs. PinPoint ion chamber was used to measure the output factors, percentage depth dose (PDD) curves and beam profiles at two depths, depth of maximum dose (z max ) and 10 cm.Film sheets were used to measure dose profiles at z max and 10-cm depth.Results: The largest observed percentage difference between output factors for the grid block technique calculated by the TPS and measured with the PinPoint ion chamber was 3.6% for the 5 3 5-cm 2 field size. Relatively significant discrepancies between measured and calculated PDD values appear only in the build-up region, which was found to amount to ,4%, while a good agreement (differences ,2%) at depths beyond z max was observed. Dose verification comparisons performed between calculated and measured dose distributions were in clinically acceptable agreements. When comparing the MLC-based with the grid block technique, the advantage of treating large tumours with a single field reduces treatment time by at least 3-5 times, having significant impact on patient throughput. Conclusion:The proposed method supports and helps to standardize the clinical implementation of the grid block in a safer and more accurate way. Advances in knowledge: This work describes the method to implement treatment planning for the grid block technique in radiotherapy departments.

Delivering accurate radiation dose to blood specimens during biological irradiations is essential in quantifying damage of ionizing radiation. To estimate dose to blood samples as accurately as possible, pieces of EBT2 model GAFCHROMIC™ film were placed within an approximately 10 mm finely ground rice layer that was used to simulate test specimens inside 40 mL plastic flasks. Irradiations of flasks were carried out using an X-RAD 320 irradiator with a beam quality of 320 kVp and a measured half value layer of 1.12 mm Cu, in air and in a full scattering setup which consisted of either rice or Solid Water™ (SW) surrounding flasks, filled to the same level at top of the flasks, together with a 5 cm thick SW slab beneath them. Outputs, per cent depth doses and beam profiles at different depths were measured and compared between setups. For the same setting, the dose delivered to the middle flask under the full scattering setup is 22% larger than with the in-air setup at the depth of the specimen and 9.2% more homogeneous across the specimen thickness of 10 mm (2.3% variation in comparison to the surface). Rice showed a fairly similar performance to SW within 1% at the same depth of 10 mm. Experimental setup based on full scattering conditions was shown to provide faster, more homogenous and fairly uniform dose delivery to biological specimens in comparison to conventionally used in-air setups.

PurposeThe aim of this work is to introduce the 2019 International Planning Competition and to analyze its results.Methods and materialsA locally advanced non-small cell lung cancer (LA-NSCLC) case using the simultaneous integrated boost approach was selected. The plan quality was evaluated by using a ranking system in accordance with practice guidelines. Planners used their clinical Treatment Planning System (TPS) to generate the best possible plan along with a survey, designed to obtain medical physics aspects information. We investigated the quality of the large population of plans designed by worldwide planners using different planning and delivery systems. The correlations of plan quality with relevant planner characteristics (work experience, department scale, and competition experience) and with technological parameters (TPS and modality) were examined.ResultsThe number of the qualified plans was 287 with a wide range of scores (38.61–97.99). The scores showed statistically significant differences by the following factors: 1) department scale: the mean score (89.76 ± 8.36) for planners from the departments treating >2,000 patients annually was the highest of all; 2) competition experience: the mean score for the 107 planners with previous competition experience was 88.92 ± 9.59, statistically significantly from first-time participants (p = .001); 3) techniques: the mean scores for planners using VMAT (89.18 ± 6.43) and TOMO (90.62 ± 7.60) were higher than those using IMRT (82.28 ± 12.47), with statistical differences (p <.001). The plan scores were negligibly correlated with the planner’s years of work experience or the type of TPS used. Regression analysis demonstrated that plan score was associated with dosimetric objectives that were difficult to achieve, which is generally consistent with a clinical practice evaluation. However, 51.2% of the planners abandoned the difficult component of total lung receiving a dose of 5 Gy in their plan design to achieve the optimal plan.ConclusionThe 2019 international planning competition was carried out successfully, and its results were analyzed. Plan quality was not correlated with work experiences or the TPS used, but it was correlated with department scale, modality, and competition experience. These findings differed from those reported in previous studies.

No abstract

No abstract