bluuebunny/crossref_metadata_2025_split huggingface dataset:
SU‐G‐JeP3‐04: Estimating 4D CBCT from Prior Information and Extremely Limited Angle Projections Using Structural PCA and Weighted Free‐Form Deformation
Authors: Harris W , Yin F , Zhang Y , Ren L 
Published: July 2016

Purpose:To investigate the feasibility of using structure‐based principal component analysis (PCA) motion‐modeling and weighted free‐form deformation to estimate on‐board 4D‐CBCT using prior information and extremely limited angle projections for potential 4D target verification of lung radiotherapy.Methods:A technique for lung 4D‐CBCT reconstruction has been previously developed using a deformation field map (DFM)‐based strategy. In the previous method, each phase of the 4D‐CBCT was generated by deforming a prior CT volume. The DFM was solved by a motion‐model extracted by global PCA and a free‐form deformation (GMM‐FD) technique, using data fidelity constraint and the deformation energy minimization. In this study, a new structural‐PCA method was developed to build a structural motion‐model (SMM) by accounting for potential relative motion pattern changes between different anatomical structures from simulation to treatment. The motion model extracted from planning 4DCT was divided into two structures: tumor and body excluding tumor, and the parameters of both structures were optimized together. Weighted free‐form deformation (WFD) was employed afterwards to introduce flexibility in adjusting the weightings of different structures in the data fidelity constraint based on clinical interests. XCAT (computerized patient model) simulation with a 30 mm diameter lesion was simulated with various anatomical and respirational changes from planning 4D‐CT to onboard volume. The estimation accuracy was evaluated by the Volume‐Percent‐Difference (VPD)/Center‐of‐Mass‐Shift (COMS) between lesions in the estimated and “ground‐truth” on board 4D‐CBCT.Results:Among 6 different XCAT scenarios corresponding to respirational and anatomical changes from planning CT to on‐board using single 30° on‐board projections, the VPD/COMS for SMM‐WFD was reduced to 10.64±3.04%/1.20±0.45mm from 21.72±9.24%/1.80±0.53mm for GMM‐FD. Using 15° orthogonal projections, the VPD/COMS was further reduced to 1.91±0.86%/0.31±0.42mm based on SMM‐WFD.Conclusion:Compared to GMM‐FD technique, the SMM‐WFD technique can substantially improve the 4D‐CBCT estimation accuracy using extremely small scan angles to provide ultra‐fast 4D verification.This work was supported by the National Institutes of Health under Grant No. R01‐CA184173 and a research grant from Varian Medical Systems
SU‐G‐JeP3‐05: Geometry Based Transperineal Ultrasound Probe Positioning for Image Guided Radiotherapy
Authors: Camps S , Verhaegen F , de With P , Fontanarosa D 
Published: July 2016

Purpose:The use of ultrasound (US) imaging in radiotherapy is not widespread, primarily due to the need for skilled operators performing the scans. Automation of probe positioning has the potential to remove this need and minimize operator dependence. We introduce an algorithm for obtaining a US probe position that allows good anatomical structure visualization based on clinical requirements. The first application is on 4D transperineal US images of prostate cancer patients.Methods:The algorithm calculates the probe position and orientation using anatomical information provided by a reference CT scan, always available in radiotherapy workflows. As initial test, we apply the algorithm on a CIRS pelvic US phantom to obtain a set of possible probe positions. Subsequently, five of these positions are randomly chosen and used to acquire actual US volumes of the phantom. Visual inspection of these volumes reveal if the whole prostate, and adjacent edges of bladder and rectum are fully visualized, as clinically required. In addition, structure positions on the acquired US volumes are compared to predictions of the algorithm.Results:All acquired volumes fulfill the clinical requirements as specified in the previous section. Preliminary quantitative evaluation was performed on thirty consecutive slices of two volumes, on which the structures are easily recognizable. The mean absolute distances (MAD) between actual anatomical structure positions and positions predicted by the algorithm were calculated. This resulted in MAD of 2.4±0.4 mm for prostate, 3.2±0.9 mm for bladder and 3.3±1.3 mm for rectum.Conclusion:Visual inspection and quantitative evaluation show that the algorithm is able to propose probe positions that fulfill all clinical requirements. The obtained MAD is on average 2.9 mm. However, during evaluation we assumed no errors in structure segmentation and probe positioning. In future steps, accurate estimation of these errors will allow for better evaluation of the achieved accuracy.
SU‐G‐JeP3‐08: Robotic System for Ultrasound Tracking in Radiation Therapy
Authors: Kuhlemann I , Jauer P , Schweikard A , Ernst F 
Published: July 2016

Purpose:For safe and accurate real‐time tracking of tumors for IGRT using 4D ultrasound, it is necessary to make use of novel, high‐end force‐sensitive lightweight robots designed for human‐machine interaction. Such a robot will be integrated into an existing robotized ultrasound system for non‐invasive 4D live tracking, using a newly developed real‐time control and communication framework.Methods:The new KUKA LWR iiwa robot is used for robotized ultrasound real‐time tumor tracking. Besides more precise probe contact pressure detection, this robot provides an additional 7th link, enhancing the dexterity of the kinematic and the mounted transducer. Several integrated, certified safety features create a safe environment for the patients during treatment. However, to remotely control the robot for the ultrasound application, a real‐time control and communication framework has to be developed. Based on a client/server concept, client‐side control commands are received and processed by a central server unit and are implemented by a client module running directly on the robot's controller. Several special functionalities for robotized ultrasound applications are integrated and the robot can now be used for real‐time control of the image quality by adjusting the transducer position, and contact pressure. The framework was evaluated looking at overall real‐time capability for communication and processing of three different standard commands.Results:Due to inherent, certified safety modules, the new robot ensures a safe environment for patients during tumor tracking. Furthermore, the developed framework shows overall real‐time capability with a maximum average latency of 3.6 ms (Minimum 2.5 ms; 5000 trials).Conclusion:The novel KUKA LBR iiwa robot will advance the current robotized ultrasound tracking system with important features. With the developed framework, it is now possible to remotely control this robot and use it for robotized ultrasound tracking applications, including image quality control and target tracking.
SU‐G‐JeP3‐12: Use of Cone Beam CT and Deformable Image Registration for Assessing Geometrical and Dosimetric Variations During Lung Radiotherapy
Authors: Jurkovic I , Stathakis S , Markovic M , Papanikolaou N , Mavroidis P 
Published: July 2016

Purpose:To assess the value of cone beam CT (CBCT) combined with deformable image registration in estimating the accuracy of the delivered treatment and the suitability of the applied target margins.Methods:Two patients with lung tumor were selected. Using their CT images intensity modulated radiation therapy (IMRT) treatment plans were developed to deliver 66Gy to the 95% of the PTV in 2Gy fractions. Using the Velocity AI software, the planning CT of each patient was registered with the fractional CBCT images that were obtained through the course of the treatment. After a CT to CBCT deformable image registration (DIR), the same fractional deformation matrix was used for the deformation of the planned dose distributions, as well as of all the contoured volumes, to each CBCT dataset. The dosimetric differences between the planning target volume (PTV) and various organs at risk (OARs) were recorded and compared.Results:CBCT data such as CTV volume change and PTV coverage was analyzed. There was a moderate relationship between volume changes and contouring method (automatic contouring using the DIR transformation vs. manual contouring on each CBCT) for patient #1 (r = 0.49), and a strong relationship for patient #2 (r = 0.83). The average PTV volume coverage from all the CBCT datasets was 91.2% for patient #1 and 95.6% for patient #2.Conclusion:Daily setup variations, tumor volume motion and lung deformation due to breathing yield differences in the actual delivered dose distributions versus the planned ones. The results presented indicate that these differences are apparent even with the use of daily IGRT. In certain fractions, the margins used seem to be insufficient to ensure acceptable lung tumor coverage. The observed differences notably depend on the tumor volume size and location. A larger cohort of patient is under investigation to verify those findings.
SU‐G‐TeP3‐01: A New Approach for Calculating Variable Relative Biological Effectiveness in IMPT Optimization
Authors: Cao W , Randeniya K , Yepes P , Grosshans D , Mohan R 
Published: July 2016

Purpose:To investigate the impact of a new approach for calculating relative biological effectiveness (RBE) in intensity‐modulated proton therapy (IMPT) optimization on RBE‐weighted dose distributions. This approach includes the nonlinear RBE for the high linear energy transfer (LET) region, which was revealed by recent experiments at our institution. In addition, this approach utilizes RBE data as a function of LET without using dose‐averaged LET in calculating RBE values.Methods:We used a two‐piece function for calculating RBE from LET. Within the Bragg peak, RBE is linearly correlated to LET. Beyond the Bragg peak, we use a nonlinear (quadratic) RBE function of LET based on our experimental. The IMPT optimization was devised to incorporate variable RBE by maximizing biological effect (based on the Linear Quadratic model) in tumor and minimizing biological effect in normal tissues. Three glioblastoma patients were retrospectively selected from our institution in this study. For each patient, three optimized IMPT plans were created based on three RBE resolutions, i.e., fixed RBE of 1.1 (RBE‐1.1), variable RBE based on linear RBE and LET relationship (RBE‐L), and variable RBE based on linear and quadratic relationship (RBE‐LQ). The RBE weighted dose distributions of each optimized plan were evaluated in terms of different RBE values, i.e., RBE‐1.1, RBE‐L and RBE‐LQ.Results:The RBE weighted doses recalculated from RBE‐1.1 based optimized plans demonstrated an increasing pattern from using RBE‐1.1, RBE‐L to RBE‐LQ consistently for all three patients. The variable RBE (RBE‐L and RBE‐LQ) weighted dose distributions recalculated from RBE‐L and RBE‐LQ based optimization were more homogenous within the targets and better spared in the critical structures than the ones recalculated from RBE‐1.1 based optimization.Conclusion:We implemented a new approach for RBE calculation and optimization and demonstrated potential benefits of improving tumor coverage and normal sparing in IMPT planning.
SU‐G‐TeP3‐02: Determination of Geometry‐Specific Backscatter Factors for Radiobiology Studies
Authors: Viscariello N , Culberson W , Lawless M , Kunugi K , DeWerd L 
Published: July 2016

Purpose:Radiation biology research relies on an accurate radiation dose delivered to the biological target. Large field irradiations in a cabinet irradiator may use the AAPM TG‐61 protocol. This relies on an air‐kerma measurement and conversion to absorbed dose to water (Dw) on the surface of a water phantom using provided backscatter factors. Cell or small animal studies differ significantly from this reference geometry. This study aims to determine the impact of the lack of full scatter conditions in four representative geometries that may be used in radiobiology studies.Methods:MCNP6 was used to model the Dw on the surface of a full scatter phantom in a validated orthovoltage x‐ray reference beam. Dw in a cylindrical mouse, 100 mm Petri dish, 6‐well and 96‐well cell culture dishes was simulated and compared to this full scatter geometry. A reference dose rate was measured using the TG‐61 protocol in a cabinet irradiator. This nominal dose rate was used to irradiate TLDs in each phantom to a given dose. Doses were obtained based on TLDs calibrated in a NIST‐traceable beam.Results:Compared to the full scattering conditions, the simulated dose to water in the representative geometries were found to be underestimated by 12‐26%. The discrepancy was smallest with the cylindrical mouse geometry, which most closely approximates adequate lateral‐ and backscatter. TLDs irradiated in the mouse and petri dish phantoms using the TG‐61 determined dose rate showed similarly lower values of Dw. When corrected for this discrepancy, they agreed with the predicted Dw within 5%.Conclusion:Using the TG‐61 in‐air protocol and given backscatter factors to determine a reference dose rate in a biological irradiator may not be appropriate given the difference in scattering conditions between irradiation and calibration. Without accounting for this, the dose rate is overestimated and is dependent on irradiation geometry.
SU‐G‐TeP3‐06: Nanoparticle‐Aided External Beam Radiotherapy Leveraging the Cerenkov Effect
Authors: Ouyang Z , Liu B , Yasmin‐Karim S , Sajo E , Ngwa W 
Published: July 2016

Purpose:This study investigates the feasibility of exploiting the Cerenkov radiation (CR) present during external beam radiotherapy (EBRT) for significant therapeutic gain, using titanium dioxide nanoparticles (titania) delivered via a new design of radiotherapy biomaterials.Methods:Recently published work has shown that CR generated by radionuclides during PET imaging could substantially enhance damage to cancer cells in the presence of 0.625 µg/g titania. We hypothesize that equal or greater damage can be achieved during EBRT. To test this hypothesis, Monte Carlo simulation was done using GEANT4 in order to get the total CR yield inside a tumor volume during EBRT compared to that of the radionuclides. We considered a novel approach where a sufficiently potent concentration of the titania was delivered directly into the tumor using radiotherapy biomaterials (e.g. fiducials) loaded with the titania. The intra‐tumor distribution/diffusion of titania released from the fiducials was calculated. An in‐vitro MTS assay experiment was also carried out to establish the relative non‐toxicity of titania for concentrations of up to 1 µg/g.Results:For a radiotherapy biomaterial loaded with 15 µg/g of 2‐nm titania, at least 0.625 µg/g could be delivered through out a tumor sub‐volume of 2‐cm diameter after 14 days. This concentration level could inflict substantial damage to tumor cells during EBRT. The Monte Carlo results showed the CR yield in tumor by 6 MV radiation was higher than the radionuclides and hence potentially greater damage may be obtained during EBRT. No significant cell viability change was observed for 1 µg/g titania.Conclusion:Altogether, these preliminary findings demonstrate a potential new approach that can be used to take advantage of the CR present during megavoltage EBRT to boost damage to tumor cells. The results provide significant impetus for further experimental studies towards development of nanoparticle‐aided EBRT powered by the Cerenkov effect.
SU‐G‐TeP3‐08: Pre‐Clinical Radionuclide Therapy Dosimetry in Several Pediatric Cancer Xenografts
Authors: Marsh I , Otto M , Weichert J , Baiu D , Bednarz B 
Published: July 2016

Purpose:The focus of this work is to perform Monte Carlo‐based dosimetry for several pediatric cancer xenografts in mice treated with a novel radiopharmaceutical 131I‐CLR1404.Methods:Four mice for each tumor cell line were injected with 8–13 µCi/g of the 124124I‐CLR1404. PET/CT images of each individual mouse were acquired at 5–6 time points over the span of 96–170 hours post‐injection. Following acquisition, the images were co‐registered, resampled, rescaled, corrected for partial volume effects (PVE), and masked. For this work the pre‐treatment PET images of 124I‐CLR1404 were used to predict therapeutic doses from 131I‐CLR1404 at each time point by assuming the same injection activity and accounting for the difference in physical decay rates. Tumors and normal tissues were manually contoured using anatomical and functional images. The CT and the PET images were used in the Geant4 (v9.6) Monte Carlo simulation to define the geometry and source distribution, respectively. The total cumulated absorbed dose was calculated by numerically integrating the dose‐rate at each time point over all time on a voxel‐by‐voxel basis.Results:Spatial distributions of the absorbed dose rates and dose volume histograms as well as mean, minimum, maximum, and total dose values for each ROI were generated for each time point.Conclusion:This work demonstrates how mouse‐specific MC‐based dosimetry could potentially provide more accurate characterization of efficacy of novel radiopharmaceuticals in radionuclide therapy.This work is partially funded by NIH grant CA198392.
SU‐G‐TeP3‐09: Proton Minibeam Radiation Therapy Increases Normal Tissue Resistance
Authors: Prezado Y , Gonzalez‐Infantes W , Heinrich S , Labiod D , Juchaux M , Martinez‐Rovira I , Nauraye C , Patriarca A , Peucelle C , Sebrie C 
Published: July 2016

Purpose:The dose tolerances of normal tissues continue being the main limitation in radiotherapy. To overcome it, we recently proposed a novel concept: proton minibeam radiation therapy (pMBRT) [1]. It allies the physical advantages of protons with the normal tissue preservation observed when irradiated with submillimetric spatially fractionated beams (minibeam radiation therapy) [2]. The dose distributions are such that the tumor receives a homogeneous dose distribution, while normal tissues benefit from the spatial fractionation of the dose. The objective of our work was to implement this promising technique at a clinical center (Proton therapy center in Orsay) in order to evaluate the potential gain in tissue sparing.Methods:Dose distributions were measured by means of gafchromic films and a PTW microdiamond detector (60019). Once the dosimetry was established, the whole brain of 7 weeks old male Fischer 344 rats was irradiated. Half of the animals received conventional seamless proton irradiation (25 Gy in one fraction). The other rats were irradiated with pMBRT (58 Gy peak dose in one fraction). The average dose deposited in the same targeted volume was in both cases 25 Gy.Results:The first complete set of dosimetric data in such small proton field sizes was obtained [3]. Rats treated with conventional proton irradiation exhibited severe moist desquamation and permanent epilation afterwards. The minibeam group, on the other hand, exhibited no skin damage and no clinical symptoms. MRI imaging and histological analysis are planned at 6 months after irradiation.Conclusion:Our preliminary results indicate that pMBRT leads to an increase in tissue resistance. This can open the door to an efficient treatment of very radioresistant tumours. [1] Prezado et al. Med. Phys. 40, 031712, 1–8 (2013).[2] Prezado et al., Rad. Research. 184, 314‐21 (2015). [3] Peucelle et al., Med. Phys. 42 7108‐13 (2015).
SU‐G‐TeP3‐13: The Role of Nanoscale Energy Deposition in the Development of Gold Nanoparticle‐Enhanced Radiotherapy
Authors: Kirkby C , Koger B , Suchowerska N , McKenzie D 
Published: July 2016

Purpose:Gold nanoparticles (GNPs) can enhance radiotherapy effects. The high photoelectric cross section of gold relative to tissue, particularly at lower energies, leads to localized dose enhancement. However in a clinical context, photon energies must also be sufficient to reach a target volume at a given depth. These properties must be balanced to optimize such a therapy. Given that nanoscale energy deposition patterns around GNPs play a role in determining biological outcomes, in this work we seek to establish their role in this optimization process.Methods:The PENELOPE Monte Carlo code was used to generate spherical dose deposition kernels in 1000 nm diameter spheres around 50 nm diameter GNPs in response to monoenergetic photons incident on the GNP. Induced “lesions” were estimated by either a local effect model (LEM) or a mean dose model (MDM). The ratio of these estimates was examined for a range of photon energies (10 keV to 2 MeV), for three sets of linear‐quadratic parameters.Results:The models produce distinct differences in expected lesion values, the lower the alpha‐beta ratio, the greater the difference. The ratio of expected lesion values remained constant within 5% for energies of 40 keV and above across all parameter sets and rose to a difference of 35% for lower energies only for the lowest alpha‐beta ratio.Conclusion:Consistent with other work, these calculations suggest nanoscale energy deposition patterns matter in predicting biological response to GNP‐enhanced radiotherapy. However the ratio of expected lesions between the different models is largely independent of energy, indicating that GNP‐enhanced radiotherapy scenarios can be optimized in photon energy without consideration of the nanoscale patterns. Special attention may be warranted for energies of 20 keV or below and low alpha‐beta ratios.
SU‐G‐TeP3‐15: Radiation Dose Enhancement by Anatase TiO2NPs
Authors: Youkhana E , Geso M , Feltis B 
Published: July 2016

Purpose:This work investigates radiation dose enhancement caused by TiO2 nanoparticles covering entire X‐ray energy ranges used in radiation therapy.Methods:Anatase TiO2NPs crystal were synthesised and modified as hydrophilic and hydrophobic to disperse in culture‐medium and halocarbons (PRESAGE chemical composition) respectively. TiO2NPs were characterised using TEM, XPS, XRD, TGA and FTIR. Various Concentrations have been utilised for determination of radiation‐dose enhancement. This investigation is carried out in two ways; one using PRESAGE dosimeter/phantom and the other is radiobiological and based on in vitro study using two types of cell lines, Human Keratinocyte (HaCaT) and prostate cancer cell lines. The x‐ray used are both kilovoltage and megavoltage separately. The prepared PRESAGE dosimeters were scanned using optical CT scanner. Clonogenic and MTS assays were employed for cell cytotoxicity and viability measurements for determination of the levels of dose enhancement.Results:Significant about (50%, 45%) dose enhancement by TiO2‐NPs for kV x‐rays is measured in both ways (Presage and Cells study). Slightly more is detected with the cells. However, the dose enhancement with megavoltage beams was insignificant using Presage and under same conditions the cells survival curves indicates around 20% which is relatively high. This difference can only be attributed to some biochemical effects. Such as generation of reactive oxygen species (ROS), this can affect the cells while it can't be detected by Presage. Elevation of hydroxyl radicals (•OH) of many orders is observed with the inclusion of TiO2‐NPs in cells‐medium.Conclusion:Dose enhancement inflicted by TiO2‐NPs is proven to be significant with megavoltage beams and minimal with kV. The high dose enhancements obtained can be attributed to higher levels of ROS generated. Since MV beams are most commonly used, this research proves potential value for more efficient beam delivery. This has potential to be applied in future clinical radiotherapy applicationsThe research is supported and funded by RMIT university‐Melbourne/Australia