Accurate estimation of daily delivered radiotherapy dose with an external treatment planning system.
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ABSTRACT:
SUBMITTER: Kanehira T
PROVIDER: S-EPMC7807587 | biostudies-literature | 2020 Apr
REPOSITORIES: biostudies-literature
Publications
Accurate estimation of daily delivered radiotherapy dose with an external treatment planning system.
Kanehira Takahiro T Svensson Stina S van Kranen Simon S Sonke Jan-Jakob JJ
Physics and imaging in radiation oncology 20200401
Accurate estimation of the daily radiotherapy dose is challenging in a multi-institutional collaboration when the institution specific treatment planning system (TPS) is not available. We developed and evaluated a method to tackle this problem. Residual errors in daily estimations were minimized with single correction based on the planned dose. For nine patients, medians of the absolute estimation errors for targets and OARs were less than 0.2 Gy ( D mean ), 0.3 Gy ( D 1 ), and 0.1 Gy ( ...[more]
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Project description:Recent research efforts investigating dose escalation techniques for three-dimensional conformal radiation therapy (3D CRT) and intensity modulated radiation therapy (IMRT) have demonstrated great benefit when high-dose hypofractionated treatment schemes are implemented. The use of these paradigms emphasizes the importance of smaller treatment margins to avoid high dose to surrounding normal tissue or organs at risk (OARs). However, tighter margins may lead to underdosage of the target due to the presence of organ motion. It is important to characterize organ motion and possibly account for it during treatment delivery. The need for real-time localization of dynamic targets has encouraged the use and development of more continuous motion monitoring systems such as kilo-voltage/fluoroscopic imaging, electromagnetic tracking, and optical monitoring systems.This paper presents the implementation of an algorithm to quantify translational and rotational interfractional and intrafractional prostate motion and compute the dosimetric effects of these motion patterns. The estimated delivered dose is compared with the static plan dose to evaluate the success of delivering the plan in the presence of prostate motion. The method is implemented on a commercial treatment planning system (Pinnacle(3), Philips Radiation Oncology Systems, Philips Healthcare) and is termed delivered dose investigational tool (DiDIT). The DiDIT implementation in Pinnacle(3) is validated by comparisons with previously published results. Finally, different workflows are discussed with respect to the potential use of this tool in clinical treatment planning.The DiDIT dose estimation process took approximately 5-20 min (depending on the number of fractions analyzed) on a Pinnacle(3) 9.100 research version running on a Dell M90 system (Dell, Inc., Round Rock, TX, USA) equipped with an Intel Core 2 Duo processor (Intel Corporation, Santa Clara, CA, USA). The DiDIT implementation in Pinnacle(3) was found to be in agreement with previously published results, on the basis of the percent dose difference (PDD). This metric was also utilized to compare plan dose versus delivered dose, for prostate targets in three clinically acceptable treatment plans.This paper presents results from the implementation of an algorithm on a commercially available treatment planning system that quantifies the dosimetric effects of interfractional and intrafractional motion in external beam radiation therapy (EBRT) of prostate cancer. The implementation of this algorithm within a commercial treatment planning system such as Pinnacle(3) enables easy deployment in the existing clinical workflow. The results of the PDD tests validate the implementation of the DiDIT algorithm in Pinnacle(3), in comparison with previously published results.
| S-EPMC3261057 | biostudies-other
Project description:Background and purposeRadiotherapy dose painting is a promising technique which enables dose escalation to areas of higher tumour cell density within the prostate which are associated with radioresistance, known as dominant intraprostatic lesions (DILs). The aim of this study was to determine factors affecting the feasibility of radiotherapy dose painting in patients with high and intermediate risk prostate cancer.Materials & methodsTwenty patients were recruited into the study for imaging using a 3 T magnetic resonance imaging (MRI) scanner. Identified DILs were outlined and the scan registered with the planning computed tomography (CT) dataset. Intensity-modulated plans were produced and evaluated to determine the effect of the organ-at-risk constraints on the dose that could be delivered to the DILs. Measurements were made to verify that the distribution could be safely delivered.ResultsMRI scans were obtained for nineteen patients. Fourteen patients had one to two DILs with ten overlapping the urethra and/or rectum. The target boost of 86 Gy was achieved in seven plans but was limited to 80 Gy for five patients whose boost volume overlapped or abutted the urethra. Dosimetric measurements gave a satisfactory gamma pass rate at 3%/3 mm.ConclusionsIt was feasible to produce dose-painted plans for a boost of 86 Gy for approximately half the patients with DILs. The main limiting factor was the proximity of the urethra to the boost volumes. For a small proportion of patients, rigid registration between CT and MRI images was not adequate for planning purposes.
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Project description:Background and purposeConversion factors between dose to medium (Dm,m) and dose to water (Dw,w) provided by treatment planning systems that model the patient as water with variable electron density are currently based on stopping power ratios. In the current paper it will be illustrated that this conversion method is not correct.Materials and methodsMonte Carlo calculations were performed in a phantom consisting of a 2 cm bone layer surrounded by water. Dw,w was obtained by modelling the bone layer as water with the electron density of bone. Conversion factors between Dw,w and Dm,m were obtained and compared to stopping power ratios and ratios of mass-energy absorption coefficients in regions of electronic equilibrium and interfaces. Calculations were performed for 6 MV and 20 MV photon beams.ResultsIn the region of electronic equilibrium the stopping power ratio of water to bone (1.11) largely overestimates the conversion obtained using the Monte Carlo calculations (1.06). In that region the MC dose conversion corresponds to the ratio of mass energy absorption coefficients. Near the water to bone interface, the MC ratio cannot be determined from stopping powers or mass energy absorption coefficients.ConclusionStopping power ratios cannot be used for conversion from Dm,m to Dw,w provided by treatment planning systems that model the patient as water with variable electron density, either in regions of electronic equilibrium or near interfaces. In regions of electronic equilibrium mass energy absorption coefficient ratios should be used. Conversions at interfaces require detailed MC calculations.
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Project description:In this work we present a methodology able to use harmonized PET/CT imaging in dose painting by number (DPBN) approach by means of a robust and accurate treatment planning system. Image processing and treatment planning were performed by using a Matlab-based platform, called CARMEN, in which a full Monte Carlo simulation is included. Linear programming formulation was developed for a voxel-by-voxel robust optimization and a specific direct aperture optimization was designed for an efficient adaptive radiotherapy implementation. DPBN approach with our methodology was tested to reduce the uncertainties associated with both, the absolute value and the relative value of the information in the functional image. For the same H&N case, a single robust treatment was planned for dose prescription maps corresponding to standardized uptake value distributions from two different image reconstruction protocols: One to fulfill EARL accreditation for harmonization of [18F]FDG PET/CT image, and the other one to use the highest available spatial resolution. Also, a robust treatment was planned to fulfill dose prescription maps corresponding to both approaches, the dose painting by contour based on volumes and our voxel-by-voxel DPBN. Adaptive planning was also carried out to check the suitability of our proposal. Different plans showed robustness to cover a range of scenarios for implementation of harmonizing strategies by using the highest available resolution. Also, robustness associated to discretization level of dose prescription according to the use of contours or numbers was achieved. All plans showed excellent quality index histogram and quality factors below 2%. Efficient solution for adaptive radiotherapy based directly on changes in functional image was obtained. We proved that by using voxel-by-voxel DPBN approach it is possible to overcome typical drawbacks linked to PET/CT images, providing to the clinical specialist confidence enough for routinely implementation of functional imaging for personalized radiotherapy.
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Project description:PurposeAn accurate assessment of out-of-field dose is necessary to estimate the risk of second cancer after radiotherapy and the damage to the organs at risk surrounding the planning target volume. Although treatment planning systems (TPSs) calculate dose distributions outside the treatment field, little is known about the accuracy of these calculations. The aim of this work is to thoroughly compare the out-of-field dose distributions given by two algorithms implemented in the Monaco TPS, with measurements and full Monte Carlo simulations.MethodsOut-of-field dose distributions predicted by the collapsed cone convolution (CCC) and Monte Carlo (MCMonaco ) algorithms, built into the commercially available Monaco version 5.11 TPS, are compared with measurements carried out on an Elekta Axesse linear accelerator. For the measurements, ion chambers, thermoluminescent dosimeters, and EBT3 film are used. The BEAMnrc code, built on the EGSnrc system, is used to create a model of the Elekta Axesse with the Agility collimation system, and the space phase file generated is scored by DOSXYZnrc to generate the dose distributions (MCEGSnrc ). Three different irradiation scenarios are considered: (a) a 10 × 10 cm2 field, (b) an IMRT prostate plan, and (c) a three-field lung plan. Monaco's calculations, experimental measurements, and Monte Carlo simulations are carried out in water and/or in an ICRP110 phantom.ResultsFor the 10 × 10 cm2 field case, CCC underestimated the dose, compared to ion chamber measurements, by 13% (differences relative to the algorithm) on average between the 5% and the ≈2% isodoses. MCMonaco underestimated the dose only from approximately the 2% isodose for this case. Qualitatively similar results were observed for the studied IMRT case when compared to film dosimetry. For the three-field lung plan, dose underestimations of up to ≈90% for MCMonaco and ≈60% for CCC, relative to MCEGSnrc simulations, were observed in mean dose to organs located beyond the 2% isodose.ConclusionsThis work shows that Monaco underestimates out-of-field doses in almost all the cases considered. Thus, it does not describe dose distribution beyond the border of the field accurately. This is in agreement with previously published works reporting similar results for other TPSs. Analytical models for out-of-field dose assessment, MC simulations or experimental measurements may be an adequate alternative for this purpose.
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Project description:NeuMANTA is a new generation boron neutron capture therapy (BNCT)-specific treatment planning system developed by the Neuboron Medical Group and upgraded to an important feature, a Hounsfield unit (HU)-based material conversion algorithm. The range of HU values was refined to 96 specific groups and established corresponding to tissue information. The elemental compositions and mass densities have an important effect on the calculated dose distribution. The region of interest defined in the treatment plan can be converted into multiple material compositions based on HU values or assigned specified single material composition in NeuMANTA. Different material compositions may cause normal tissue maximum dose rates to differ by more than 10% in biologically equivalent doses and to differ by up to 6% in physically absorbed doses. Although the tumor has a lower proportion of BNCT background dose, the material composition difference may affect the minimum dose of biologically equivalent dose and physically absorbed dose by more than 3%. In addition, the difference in material composition could lead to a change in neutron moderation as well as scattering. Therefore, the material composition has a significant impact on the assessment of normal tissue side effects and tumor control probability. It is essential for accurate dose estimation in BNCT.
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Project description:Biological effect of radiation can be enhanced with hypofractionation, localized dose escalation, and, in particle therapy, with optimized distribution of linear energy transfer (LET). The authors describe a method to construct inhomogeneous fractional dose (IFD) distributions, and evaluate the potential gain in the therapeutic effect from their delivery in proton therapy delivered by pencil beam scanning.For 13 cases of prostate cancer, the authors considered hypofractionated courses of 60 Gy delivered in 20 fractions. (All doses denoted in Gy include the proton's mean relative biological effectiveness (RBE) of 1.1.) Two types of plans were optimized using two opposed lateral beams to deliver a uniform dose of 3 Gy per fraction to the target by scanning: (1) in conventional full-target plans (FTP), each beam irradiated the entire gland, (2) in split-target plans (STP), beams irradiated only the respective proximal hemispheres (prostate split sagittally). Inverse planning yielded intensity maps, in which discrete position control points of the scanned beam (spots) were assigned optimized intensity values. FTP plans preferentially required a higher intensity of spots in the distal part of the target, while STP, by design, employed proximal spots. To evaluate the utility of IFD delivery, IFD plans were generated by rearranging the spot intensities from FTP or STP intensity maps, separately as well as combined using a variety of mixing weights. IFD courses were designed so that, in alternating fractions, one of the hemispheres of the prostate would receive a dose boost and the other receive a lower dose, while the total physical dose from the IFD course was roughly uniform across the prostate. IFD plans were normalized so that the equivalent uniform dose (EUD) of rectum and bladder did not increase, compared to the baseline FTP plan, which irradiated the prostate uniformly in every fraction. An EUD-based model was then applied to estimate tumor control probability (TCP) and normal tissue complication probability (NTCP). To assess potential local RBE variations, LET distributions were calculated with Monte Carlo, and compared for different plans. The results were assessed in terms of their sensitivity to uncertainties in model parameters and delivery.IFD courses included equal number of fractions boosting either hemisphere, thus, the combined physical dose was close to uniform throughout the prostate. However, for the entire course, the prostate EUD in IFD was higher than in conventional FTP by up to 14%, corresponding to the estimated increase in TCP to 96% from 88%. The extent of gain depended on the mixing factor, i.e., relative weights used to combine FTP and STP spot weights. Increased weighting of STP typically yielded a higher target EUD, but also led to increased sensitivity of dose to variations in the proton's range. Rectal and bladder EUD were same or lower (per normalization), and the NTCP for both remained below 1%. The LET distributions in IFD also depended strongly on the mixing weights: plans using higher weight of STP spots yielded higher LET, indicating a potentially higher local RBE.In proton therapy delivered by pencil beam scanning, improved therapeutic outcome can potentially be expected with delivery of IFD distributions, while administering the prescribed quasi-uniform dose to the target over the entire course. The biological effectiveness of IFD may be further enhanced by optimizing the LET distributions. IFD distributions are characterized by a dose gradient located in proximity of the prostate's midplane, thus, the fidelity of delivery would depend crucially on the precision with which the proton range could be controlled.
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