Publications

@article{Goodall2014,

title = {Technical Note: A method for improving the calibration reproducibility of an ionization chamber detector array},

author = {Simon Goodall and Steve Morgan},

doi = {10.1118/1.4892607},

issn = {2473-4209},

year  = {2014},

date = {2014-09-00},

journal = {Medical Physics},

volume = {41},

number = {9},

publisher = {Wiley},

abstract = {Purpose:This paper describes an extension to a wide field calibration method implemented on a commercial detector array in order to improve the reproducibility of the calibration procedure.Methods:Following the standard array calibration procedure, two additional 10 × 10 cm exposures were acquired for each array axis with the detector array shifted by ±10 cm in the transverse or axial axes, or by ±10 cm in the positive or negative diagonal axes. These exposures were compared with a final baseline 10 × 10 cm exposure captured with the detector repositioned at the isocenter. The measurements were used to calculate a linear off‐axis correction gradient which was then applied to the stored calibration factors.Results:The mean coefficient of variation between five repeat calibrations was reduced from 4.17% to 0.48% and the maximum percentage error in individual calibration factors was reduced from 6.46% to 0.77%.Conclusions:The reproducibility of the calibration factors of an ionization chamber array was increased by capturing a baseline exposure and two further off‐axis readings per calibration axis.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Colvill2014,

title = {DMLC tracking and gating can improve dose coverage for prostate VMAT},

author = {E. Colvill and P. R. Poulsen and J. T. Booth and R. T. O'Brien and J. A. Ng and P. J. Keall},

doi = {10.1118/1.4892605},

issn = {2473-4209},

year  = {2014},

date = {2014-09-00},

journal = {Medical Physics},

volume = {41},

number = {9},

publisher = {Wiley},

abstract = {Purpose:To assess and compare the dosimetric impact of dynamic multileaf collimator (DMLC) tracking and gating as motion correction strategies to account for intrafraction motion during conventionally fractionated prostate radiotherapy.Methods:A dose reconstruction method was used to retrospectively assess the dose distributions delivered without motion correction during volumetric modulated arc therapy fractions for 20 fractions of five prostate cancer patients who received conventionally fractionated radiotherapy. These delivered dose distributions were compared with the dose distributions which would have been delivered had DMLC tracking or gating motion correction strategies been implemented. The delivered dose distributions were constructed by incorporating the observed prostate motion with the patientˈs original treatment plan to simulate the treatment delivery. The DMLC tracking dose distributions were constructed using the same dose reconstruction method with the addition of MLC positions from Linac log files obtained during DMLC tracking simulations with the observed prostate motions input to the DMLC tracking software. The gating dose distributions were constructed by altering the prostate motion to simulate the application of a gating threshold of 3 mm for 5 s.Results:The delivered dose distributions showed that dosimetric effects of intrafraction prostate motion could be substantial for some fractions, with an estimated dose decrease of more than 19% and 34% from the planned CTVD99% and PTV D95% values, respectively, for one fraction. Evaluation of dose distributions for DMLC tracking and gating deliveries showed that both interventions were effective in improving the CTV D99% for all of the selected fractions to within 4% of planned value for all fractions. For the delivered dose distributions the difference in rectum V65% for the individual fractions from planned ranged from −44% to 101% and for the bladder V65% the range was −61% to 26% from planned. The application of tracking decreased the maximum rectum and bladder V65% difference to 6% and 4%, respectively.Conclusions:For the first time, the dosimetric impact of DMLC tracking and gating to account for intrafraction motion during prostate radiotherapy has been assessed and compared with no motion correction. Without motion correction intrafraction prostate motion can result in a significant decrease in target dose coverage for a small number of individual fractions. This is unlikely to effect the overall treatment for most patients undergoing conventionally fractionated treatments. Both DMLC tracking and gating demonstrate dose distributions for all assessed fractions that are robust to intrafraction motion.},

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pubstate = {published},

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}

@article{Grimes2014,

title = {Comparison of internal dose estimates obtained using organ‐level, voxel S value, and Monte Carlo techniques},

author = {Joshua Grimes and Anna Celler},

doi = {10.1118/1.4892606},

issn = {2473-4209},

year  = {2014},

date = {2014-09-00},

journal = {Medical Physics},

volume = {41},

number = {9},

publisher = {Wiley},

abstract = {Purpose:The authors’ objective was to compare internal dose estimates obtained using the Organ Level Dose Assessment with Exponential Modeling (OLINDA/EXM) software, the voxel S value technique, and Monte Carlo simulation. Monte Carlo dose estimates were used as the reference standard to assess the impact of patient‐specific anatomy on the final dose estimate.Methods:Six patients injected with99mTc‐hydrazinonicotinamide‐Tyr3‐octreotide were included in this study. A hybrid planar/SPECT imaging protocol was used to estimate 99mTc time‐integrated activity coefficients (TIACs) for kidneys, liver, spleen, and tumors. Additionally, TIACs were predicted for 131I, 177Lu, and 90Y assuming the same biological half‐lives as the 99mTc labeled tracer. The TIACs were used as input for OLINDA/EXM for organ‐level dose calculation and voxel level dosimetry was performed using the voxel S value method and Monte Carlo simulation. Dose estimates for 99mTc, 131I, 177Lu, and 90Y distributions were evaluated by comparing (i) organ‐level S values corresponding to each method, (ii) total tumor and organ doses, (iii) differences in right and left kidney doses, and (iv) voxelized dose distributions calculated by Monte Carlo and the voxel S value technique.Results:The S values for all investigated radionuclides used by OLINDA/EXM and the corresponding patient‐specific S values calculated by Monte Carlo agreed within 2.3% on average for self‐irradiation, and differed by as much as 105% for cross‐organ irradiation. Total organ doses calculated by OLINDA/EXM and the voxel S value technique agreed with Monte Carlo results within approximately ±7%. Differences between right and left kidney doses determined by Monte Carlo were as high as 73%. Comparison of the Monte Carlo and voxel S value dose distributions showed that each method produced similar dose volume histograms with a minimum dose covering 90% of the volume (D90) agreeing within ±3%, on average.Conclusions:Several aspects of OLINDA/EXM dose calculation were compared with patient‐specific dose estimates obtained using Monte Carlo. Differences in patient anatomy led to large differences in cross‐organ doses. However, total organ doses were still in good agreement since most of the deposited dose is due to self‐irradiation. Comparison of voxelized doses calculated by Monte Carlo and the voxel S value technique showed that the 3D dose distributions produced by the respective methods are nearly identical.},

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pubstate = {published},

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}

@article{Lee2014b,

title = {Dynamic keyhole: A novel method to improve MR images in the presence of respiratory motion for real-time MRI},

author = {Danny Lee and Sean Pollock and Brendan Whelan and Paul Keall and Taeho Kim},

doi = {10.1118/1.4883882},

issn = {0094-2405},

year  = {2014},

date = {2014-07-00},

journal = {Med. Phys.},

volume = {41},

number = {7},

publisher = {Wiley},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Connell2014,

title = {Delivery validation of an automated modulated electron radiotherapy plan},

author = {T. Connell and A. Alexander and P. Papaconstadopoulos and M. Serban and S. Devic and J. Seuntjens},

doi = {10.1118/1.4876297},

issn = {0094-2405},

year  = {2014},

date = {2014-06-00},

journal = {Med. Phys.},

volume = {41},

number = {6Part1},

publisher = {Wiley},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Freudenberg2014,

title = {On the dose calculation at the cellular level and its implications for the RBE of^{99m}Tc and^{123}I},

author = {R. Freudenberg and R. Runge and U. Maucksch and V. Berger and J. Kotzerke},

doi = {10.1118/1.4876296},

issn = {0094-2405},

year  = {2014},

date = {2014-06-00},

journal = {Med. Phys.},

volume = {41},

number = {6Part1},

publisher = {Wiley},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Tomic2014,

title = {Characterization of calibration curves and energy dependence GafChromic^{TM}

 XR-QA2 model based radiochromic film dosimetry system},

author = {Nada Tomic and Chrystian Quintero and Bruce R. Whiting and Saad Aldelaijan and Hamed Bekerat and LiHeng Liang and François DeBlois and Jan Seuntjens and Slobodan Devic},

doi = {10.1118/1.4876295},

issn = {0094-2405},

year  = {2014},

date = {2014-06-00},

journal = {Med. Phys.},

volume = {41},

number = {6Part1},

publisher = {Wiley},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Lee2014,

title = {Audiovisual biofeedback improves image quality and reduces scan time for respiratory-gated 3D MRI},

author = {D Lee and P B Greer and J Arm and P Keall and T Kim},

doi = {10.1088/1742-6596/489/1/012033},

issn = {1742-6596},

year  = {2014},

date = {2014-03-24},

journal = {J. Phys.: Conf. Ser.},

volume = {489},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Norris2014,

title = {A set of 4D pediatric XCAT reference phantoms for multimodality research},

author = {Hannah Norris and Yakun Zhang and Jason Bond and Gregory M. Sturgeon and Anum Minhas and Daniel J. Tward and J. T. Ratnanather and M. I. Miller and D. Frush and E. Samei and W. P. Segars},

doi = {10.1118/1.4864238},

issn = {2473-4209},

year  = {2014},

date = {2014-03-00},

journal = {Medical Physics},

volume = {41},

number = {3},

publisher = {Wiley},

abstract = {Purpose:The authors previously developed an adult population of 4D extended cardiac‐torso (XCAT) phantoms for multimodality imaging research. In this work, the authors develop a reference set of 4D pediatric XCAT phantoms consisting of male and female anatomies at ages of newborn, 1, 5, 10, and 15 years. These models will serve as the foundation from which the authors will create a vast population of pediatric phantoms for optimizing pediatric CT imaging protocols.Methods:Each phantom was based on a unique set of CT data from a normal patient obtained from the Duke University database. The datasets were selected to best match the reference values for height and weight for the different ages and genders according to ICRP Publication 89. The major organs and structures were segmented from the CT data and used to create an initial pediatric model defined using nonuniform rational B‐spline surfaces. The CT data covered the entire torso and part of the head. To complete the body, the authors manually added on the top of the head and the arms and legs using scaled versions of the XCAT adult models or additional models created from cadaver data. A multichannel large deformation diffeomorphic metric mapping algorithm was then used to calculate the transform from a template XCAT phantom (male or female 50th percentile adult) to the target pediatric model. The transform was applied to the template XCAT to fill in any unsegmented structures within the target phantom and to implement the 4D cardiac and respiratory models in the new anatomy. The masses of the organs in each phantom were matched to the reference values given in ICRP Publication 89. The new reference models were checked for anatomical accuracy via visual inspection.Results:The authors created a set of ten pediatric reference phantoms that have the same level of detail and functionality as the original XCAT phantom adults. Each consists of thousands of anatomical structures and includes parameterized models for the cardiac and respiratory motions. Based on patient data, the phantoms capture the anatomic variations of childhood, such as the development of bone in the skull, pelvis, and long bones, and the growth of the vertebrae and organs. The phantoms can be combined with existing simulation packages to generate realistic pediatric imaging data from different modalities.Conclusions:The development of patient‐derived pediatric computational phantoms is useful in providing variable anatomies for simulation. Future work will expand this ten‐phantom base to a host of pediatric phantoms representative of the public at large. This can provide a means to evaluate and improve pediatric imaging devices and to optimize CT protocols in terms of image quality and radiation dose.},

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pubstate = {published},

tppubtype = {article}

}

@article{Hansen2014,

title = {Improved proton computed tomography by dual modality image reconstruction},

author = {David C. Hansen and Jørgen Breede Baltzer Petersen and Niels Bassler and Thomas Sangild Sørensen},

doi = {10.1118/1.4864239},

issn = {2473-4209},

year  = {2014},

date = {2014-03-00},

journal = {Medical Physics},

volume = {41},

number = {3},

publisher = {Wiley},

abstract = {Purpose:Proton computed tomography (CT) is a promising image modality for improving the stopping power estimates and dose calculations for particle therapy. However, the finite range of about 33 cm of water of most commercial proton therapy systems limits the sites that can be scanned from a full 360° rotation. In this paper the authors propose a method to overcome the problem using a dual modality reconstruction (DMR) combining the proton data with a cone‐beam x‐ray prior.Methods:A Catphan 600 phantom was scanned using a cone beam x‐ray CT scanner. A digital replica of the phantom was created in the Monte Carlo code Geant4 and a 360° proton CT scan was simulated, storing the entrance and exit position and momentum vector of every proton. Proton CT images were reconstructed using a varying number of angles from the scan. The proton CT images were reconstructed using a constrained nonlinear conjugate gradient algorithm, minimizing total variation and the x‐ray CT prior while remaining consistent with the proton projection data. The proton histories were reconstructed along curved cubic‐spline paths.Results:The spatial resolution of the cone beam CT prior was retained for the fully sampled case and the 90° interval case, with the MTF = 0.5 (modulation transfer function) ranging from 5.22 to 5.65 linepairs/cm. In the 45° interval case, the MTF = 0.5 dropped to 3.91 linepairs/cm For the fully sampled DMR, the maximal root mean square (RMS) error was 0.006 in units of relative stopping power. For the limited angle cases the maximal RMS error was 0.18, an almost five‐fold improvement over the cone beam CT estimate.Conclusions:Dual modality reconstruction yields the high spatial resolution of cone beam x‐ray CT while maintaining the improved stopping power estimation of proton CT. In the case of limited angles, the use of prior image proton CT greatly improves the resolution and stopping power estimate, but does not fully achieve the quality of a 360° proton CT scan.},

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pubstate = {published},

tppubtype = {article}

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@article{Veiga2014,

title = {Toward adaptive radiotherapy for head and neck patients: Feasibility study on using CT‐to‐CBCT deformable registration for “dose of the day” calculations},

author = {Catarina Veiga and Jamie McClelland and Syed Moinuddin and Ana Lourenço and Kate Ricketts and James Annkah and Marc Modat and Sébastien Ourselin and Derek D'Souza and Gary Royle},

doi = {10.1118/1.4864240},

issn = {2473-4209},

year  = {2014},

date = {2014-03-00},

journal = {Medical Physics},

volume = {41},

number = {3},

publisher = {Wiley},

abstract = {Purpose:The aim of this study was to evaluate the appropriateness of using computed tomography (CT) to cone‐beam CT (CBCT) deformable image registration (DIR) for the application of calculating the “dose of the day” received by a head and neck patient.Methods:NiftyReg is an open‐source registration package implemented in our institution. The affine registration uses a Block Matching‐based approach, while the deformable registration is a GPU implementation of the popular B‐spline Free Form Deformation algorithm. Two independent tests were performed to assess the suitability of our registrations methodology for “dose of the day” calculations in a deformed CT. A geometric evaluation was performed to assess the ability of the DIR method to map identical structures between the CT and CBCT datasets. Features delineated in the planning CT were warped and compared with features manually drawn on the CBCT. The authors computed the dice similarity coefficient (DSC), distance transformation, and centre of mass distance between features. A dosimetric evaluation was performed to evaluate the clinical significance of the registrations errors in the application proposed and to identify the limitations of the approximations used. Dose calculations for the same intensity‐modulated radiation therapy plan on the deformed CT and replan CT were compared. Dose distributions were compared in terms of dose differences (DD), gamma analysis, target coverage, and dose volume histograms (DVHs). Doses calculated in a rigidly aligned CT and directly in an extended CBCT were also evaluated.Results:A mean value of 0.850 in DSC was achieved in overlap between manually delineated and warped features, with the distance between surfaces being less than 2 mm on over 90% of the pixels. Deformable registration was clearly superior to rigid registration in mapping identical structures between the two datasets. The dose recalculated in the deformed CT is a good match to the dose calculated on a replan CT. The DD is smaller than 2% of the prescribed dose on 90% of the bodyˈs voxels and it passes a 2% and 2 mm gamma‐test on over 95% of the voxels. Target coverage similarity was assessed in terms of the 95%‐isodose volumes. A mean value of 0.962 was obtained for the DSC, while the distance between surfaces is less than 2 mm in 95.4% of the pixels. The method proposed provided adequate dose estimation, closer to the gold standard than the other two approaches. Differences in DVH curves were mainly due to differences in the OARs definition (manual vs warped) and not due to differences in dose estimation (dose calculated in replan CT vs dose calculated in deformed CT).Conclusions:Deforming a planning CT to match a daily CBCT provides the tools needed for the calculation of the “dose of the day” without the need to acquire a new CT. The initial clinical application of our method will be weekly offline calculations of the “dose of the day,” and use this information to inform adaptive radiotherapy (ART). The work here presented is a first step into a full implementation of a “dose‐driven” online ART.},

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pubstate = {published},

tppubtype = {article}

}

@article{Belley2014,

title = {Toward an organ based dose prescription method for the improved accuracy of murine dose in orthovoltage x‐ray irradiators},

author = {Matthew D. Belley and Chu Wang and Giao Nguyen and Rathnayaka Gunasingha and Nelson J. Chao and Benny J. Chen and Mark W. Dewhirst and Terry T. Yoshizumi},

doi = {10.1118/1.4864237},

issn = {2473-4209},

year  = {2014},

date = {2014-03-00},

journal = {Medical Physics},

volume = {41},

number = {3},

publisher = {Wiley},

abstract = {Purpose:Accurate dosimetry is essential when irradiating mice to ensure that functional and molecular endpoints are well understood for the radiation dose delivered. Conventional methods of prescribing dose in mice involve the use of a single dose rate measurement and assume a uniform average dose throughout all organs of the entire mouse. Here, the authors report the individual average organ dose values for the irradiation of a 12, 23, and 33 g mouse on a 320 kVp x‐ray irradiator and calculate the resulting error from using conventional dose prescription methods.Methods:Organ doses were simulated in the Geant4 application for tomographic emission toolkit using the MOBY mouse whole‐body phantom. Dosimetry was performed for three beams utilizing filters A (1.65 mm Al), B (2.0 mm Al), and C (0.1 mm Cu + 2.5 mm Al), respectively. In addition, simulated x‐ray spectra were validated with physical half‐value layer measurements.Results:Average doses in soft‐tissue organs were found to vary by as much as 23%–32% depending on the filter. Compared to filters A and B, filter C provided the hardest beam and had the lowest variation in soft‐tissue average organ doses across all mouse sizes, with a difference of 23% for the median mouse size of 23 g.Conclusions:This work suggests a new dose prescription method in small animal dosimetry: it presents a departure from the conventional approach of assigninga single dose value for irradiation of mice to a more comprehensive approach of characterizing individual organ doses to minimize the error and uncertainty. In human radiation therapy, clinical treatment planning establishes the target dose as well as the dose distribution, however, this has generally not been done in small animal research. These results suggest that organ dose errors will be minimized by calibrating the dose rates for all filters, and using different dose rates for different organs.},

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pubstate = {published},

tppubtype = {article}

}

@article{O’Brien2014c,

title = {Respiratory motion guided four dimensional cone beam computed tomography: encompassing irregular breathing},

author = {Ricky T O’Brien and Benjamin J Cooper and John Kipritidis and Chun-Chien Shieh and Paul J Keall},

doi = {10.1088/0031-9155/59/3/579},

issn = {1361-6560},

year  = {2014},

date = {2014-02-07},

journal = {Phys. Med. Biol.},

volume = {59},

number = {3},

pages = {579--595},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{O’Brien2014,

title = {Respiratory motion guided four dimensional cone beam computed tomography: encompassing irregular breathing},

author = {Ricky T O’Brien and Benjamin J Cooper and John Kipritidis and Chun-Chien Shieh and Paul J Keall},

doi = {10.1088/0031-9155/59/3/579},

issn = {1361-6560},

year  = {2014},

date = {2014-02-07},

journal = {Phys. Med. Biol.},

volume = {59},

number = {3},

pages = {579--595},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Tehrani2013,

title = {Real-time estimation of prostate tumor rotation and translation with a kV imaging system based on an iterative closest point algorithm},

author = {Joubin Nasehi Tehrani and Ricky T O’Brien and Per Rugaard Poulsen and Paul Keall},

doi = {10.1088/0031-9155/58/23/8517},

issn = {1361-6560},

year  = {2013},

date = {2013-12-07},

journal = {Phys. Med. Biol.},

volume = {58},

number = {23},

pages = {8517--8533},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pareek2013,

title = {Prostate Tissue Characterization/Classification in 144 Patient Population Using Wavelet and Higher Order Spectra Features from Transrectal Ultrasound Images},

author = {Gyan Pareek and U. Rajendra Acharya and S. Vinitha Sree and G. Swapna and Ratna Yantri and Roshan Joy Martis and Luca Saba and Ganapathy Krishnamurthi and Giorgio Mallarini and Ayman El-Baz and Shadi Al Ekish and Michael Beland and Jasjit S. Suri},

doi = {10.7785/tcrt.2012.500346},

issn = {1533-0338},

year  = {2013},

date = {2013-12-00},

journal = {Technol Cancer Res Treat},

volume = {12},

number = {6},

pages = {545--557},

publisher = {SAGE Publications},

abstract = { In this work, we have proposed an on-line computer-aided diagnostic system called “UroImage” that classifies a Transrectal Ultrasound (TRUS) image into cancerous or non-cancerous with the help of non-linear Higher Order Spectra (HOS) features and Discrete Wavelet Transform (DWT) coefficients. The UroImage system consists of an on-line system where five significant features (one DWT-based feature and four HOS-based features) are extracted from the test image. These on-line features are transformed by the classifier parameters obtained using the training dataset to determine the class. We trained and tested six classifiers. The dataset used for evaluation had 144 TRUS images which were split into training and testing sets. Three-fold and ten-fold cross-validation protocols were adopted for training and estimating the accuracy of the classifiers. The ground truth used for training was obtained using the biopsy results. Among the six classifiers, using 10-fold cross-validation technique, Support Vector Machine and Fuzzy Sugeno classifiers presented the best classification accuracy of 97.9% with equally high values for sensitivity, specificity and positive predictive value. Our proposed automated system, which achieved more than 95% values for all the performance measures, can be an adjunct tool to provide an initial diagnosis for the identification of patients with prostate cancer. The technique, however, is limited by the limitations of 2D ultrasound guided biopsy, and we intend to improve our technique by using 3D TRUS images in the future. },

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ng2013,

title = {Estimation of effective imaging dose for kilovoltage intratreatment monitoring of the prostate position during cancer radiotherapy},

author = {J A Ng and J Booth and P Poulsen and Z Kuncic and P J Keall},

doi = {10.1088/0031-9155/58/17/5983},

issn = {1361-6560},

year  = {2013},

date = {2013-09-07},

journal = {Phys. Med. Biol.},

volume = {58},

number = {17},

pages = {5983--5996},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bjerre2013,

title = {Three-dimensional MRI-linac intra-fraction guidance using multiple orthogonal cine-MRI planes},

author = {Troels Bjerre and Sjoerd Crijns and Per Munck af Rosenschöld and Marianne Aznar and Lena Specht and Rasmus Larsen and Paul Keall},

doi = {10.1088/0031-9155/58/14/4943},

issn = {1361-6560},

year  = {2013},

date = {2013-07-21},

journal = {Phys. Med. Biol.},

volume = {58},

number = {14},

pages = {4943--4950},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Rottmann2013,

title = {Markerless EPID image guided dynamic multi-leaf collimator tracking for lung tumors},

author = {J Rottmann and P Keall and R Berbeco},

doi = {10.1088/0031-9155/58/12/4195},

issn = {1361-6560},

year  = {2013},

date = {2013-06-21},

journal = {Phys. Med. Biol.},

volume = {58},

number = {12},

pages = {4195--4204},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pommer2013,

title = {Dosimetric benefit of DMLC tracking for conventional and sub-volume boosted prostate intensity-modulated arc radiotherapy},

author = {Tobias Pommer and Marianne Falk and Per R Poulsen and Paul J Keall and Ricky T O'Brien and Peter Meidahl Petersen and Per Munck af Rosenschöld},

doi = {10.1088/0031-9155/58/7/2349},

issn = {1361-6560},

year  = {2013},

date = {2013-04-07},

journal = {Phys. Med. Biol.},

volume = {58},

number = {7},

pages = {2349--2361},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pollock2013,

title = {Audiovisual biofeedback improves motion prediction accuracy},

author = {Sean Pollock and Danny Lee and Paul Keall and Taeho Kim},

doi = {10.1118/1.4794497},

issn = {2473-4209},

year  = {2013},

date = {2013-04-00},

journal = {Medical Physics},

volume = {40},

number = {4},

publisher = {Wiley},

abstract = {Purpose:The accuracy of motion prediction, utilized to overcome the system latency of motion management radiotherapy systems, is hampered by irregularities present in the patients’ respiratory pattern. Audiovisual (AV) biofeedback has been shown to reduce respiratory irregularities. The aim of this study was to test the hypothesis that AV biofeedback improves the accuracy of motion prediction.Methods:An AV biofeedback system combined with real‐time respiratory data acquisition and MR images were implemented in this project. One‐dimensional respiratory data from (1) the abdominal wall (30 Hz) and (2) the thoracic diaphragm (5 Hz) were obtained from 15 healthy human subjects across 30 studies. The subjects were required to breathe with and without the guidance of AV biofeedback during each study. The obtained respiratory signals were then implemented in a kernel density estimation prediction algorithm. For each of the 30 studies, five different prediction times ranging from 50 to 1400 ms were tested (150 predictions performed). Prediction error was quantified as the root mean square error (RMSE); the RMSE was calculated from the difference between the real and predicted respiratory data. The statistical significance of the prediction results was determined by the Student'st‐test.Results:Prediction accuracy was considerably improved by the implementation of AV biofeedback. Of the 150 respiratory predictions performed, prediction accuracy was improved 69% (103/150) of the time for abdominal wall data, and 78% (117/150) of the time for diaphragm data. The average reduction in RMSE due to AV biofeedback over unguided respiration was 26% (p < 0.001) and 29% (p < 0.001) for abdominal wall and diaphragm respiratory motion, respectively.Conclusions:This study was the first to demonstrate that the reduction of respiratory irregularities due to the implementation of AV biofeedback improves prediction accuracy. This would result in increased efficiency of motion management techniques affected by system latencies used in radiotherapy.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Reynolds2013,

title = {Dose response of selected ion chambers in applied homogeneous transverse and longitudinal magnetic fields},

author = {M. Reynolds and B. G. Fallone and S. Rathee},

doi = {10.1118/1.4794496},

issn = {2473-4209},

year  = {2013},

date = {2013-04-00},

journal = {Medical Physics},

volume = {40},

number = {4},

publisher = {Wiley},

abstract = {Purpose:The magnetic fields of an integrated MR‐Linac system will alter the paths of electrons that produce ions in the ionization chambers. The dose response of selected ion chambers is evaluated in the presence of varying transverse and longitudinal magnetic fields. The investigation is useful in calibration of therapeutic x‐ray beams associated with MR‐Linac systems.Methods:The Monte Carlo code PENELOPE was used to model the irradiation of NE2571, and PR06C ionization chambers in the presence of a transverse and longitudinal (with respect to the photon beam) magnetic fields of varying magnitude. The long axis of each chamber was simulated both parallel and perpendicular to the incident photon beam for each magnetic field case. The dose deposited in each chamber for each case was compared to the case with zero magnetic field by means of a ratio. The PR06C chamber's response was measured in the presence of a transverse magnetic field with field strengths ranging from 0.0 to 0.2 T to compare to simulated results.Results:The simulations and measured data show that in the presence of a transverse magnetic field there is a considerable dose response (maximum of 11% near 1.0 T in the ion chambers investigated, which depends on the magnitude of magnetic field, and relative orientation of the magnetic field, radiation beam, and ion chamber. Measurements made with the PR06C chamber verify these results in the region of measurement. In contrast, a longitudinal magnetic field produces only a slight increase in dose response (2% at 1.5 T) that rises slowly with increasing magnetic field and is seemingly independent of chamber orientation. Response trends were similar for the two ion chambers and relative orientations considered, but slight variations are present from chamber to chamber.Conclusions:Care must be taken when making ion chamber measurements in a transverse magnetic field. Ion chamber responses vary not only with transverse field strength, but with chamber orientation and type, and can be considerable. Longitudinal magnetic fields influence ion chamber responses relatively little (2% at 1.5 T), and only at field strengths in excess of 1.0 T.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{O’Brien2013,

title = {Optimizing 4D cone beam computed tomography acquisition by varying the gantry velocity and projection time interval},

author = {Ricky T O’Brien and Benjamin J Cooper and Paul J Keall},

doi = {10.1088/0031-9155/58/6/1705},

issn = {1361-6560},

year  = {2013},

date = {2013-03-21},

journal = {Phys. Med. Biol.},

volume = {58},

number = {6},

pages = {1705--1723},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Cho2012,

title = {Experimental investigation of a general real-time 3D target localization method using sequential kV imaging combined with respiratory monitoring},

author = {Byungchul Cho and Per Poulsen and Dan Ruan and Amit Sawant and Paul J Keall},

doi = {10.1088/0031-9155/57/22/7395},

issn = {1361-6560},

year  = {2012},

date = {2012-11-21},

journal = {Phys. Med. Biol.},

volume = {57},

number = {22},

pages = {7395--7407},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Mizuta2012,

title = {A Mathematical Study to Select Fractionation Regimen Based on Physical Dose Distribution and the Linear–Quadratic Model},

author = {Masahiro Mizuta and Seishin Takao and Hiroyuki Date and Naoki Kishimoto and Kenneth L. Sutherland and Rikiya Onimaru and Hiroki Shirato},

doi = {10.1016/j.ijrobp.2012.01.004},

issn = {0360-3016},

year  = {2012},

date = {2012-11-00},

journal = {International Journal of Radiation Oncology*Biology*Physics},

volume = {84},

number = {3},

pages = {829--833},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Thibaudeau2012,

title = {Toward truly combined PET/CT imaging using PET detectors and photon counting CT with iterative reconstruction implementing physical detector response},

author = {Christian Thibaudeau and Philippe Bérard and Marc‐André Tétrault and Jean‐Daniel Leroux and Mélanie Bergeron and Réjean Fontaine and Roger Lecomte},

doi = {10.1118/1.4747265},

issn = {2473-4209},

year  = {2012},

date = {2012-09-00},

journal = {Medical Physics},

volume = {39},

number = {9},

pages = {5697--5707},

publisher = {Wiley},

abstract = {Purpose:This paper intends to demonstrate the feasibility of truly combined PET/CT imaging and addresses some of the major challenges raised by this dual modality approach. A method is proposed to retrieve maximum accuracy out of limited resolution computed tomography (CT) scans acquired with positron emission tomography (PET) detectors.Methods:A PET/CT simulator was built using the LabPET™ detectors and front‐end electronics. Acquisitions of energy‐binned data sets were made using this low spatial resolution CT system in photon counting mode. To overcome the limitations of the filtered back‐projection technique, an iterative reconstruction library was developed and tested for the counting mode CT. Construction of the system matrix is based on a preregistered raster scan from which the experimental detector response is obtained. PET data were obtained sequentially with CT in a conventional manner.Results:A meticulous description of the system geometry and misalignment corrections is imperative and was incorporated into the matrix definition to achieve good image quality. Using this method, no sinogram precorrection or interpolation is necessary and measured projections can be used as raw input data for the iterative reconstruction algorithm. Genuine dual modality PET/CT images of phantoms and animals were obtained for the first time using the same detection platform.Conclusions:CT and fused PET/CT images show that LabPET™ detectors can be successfully used as individual X‐ray photon counting devices for low‐dose CT imaging of the anatomy in a molecular PET imaging context.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Chen2012,

title = {Prognostic Value of Subclassification Using MRI in the T4 Classification Nasopharyngeal Carcinoma Intensity-Modulated Radiotherapy Treatment},

author = {Lei Chen and Li-Zhi Liu and Mo Chen and Wen-Fei Li and Wen-Jing Yin and Ai-Hua Lin and Ying Sun and Li Li and Jun Ma},

doi = {10.1016/j.ijrobp.2011.11.021},

issn = {0360-3016},

year  = {2012},

date = {2012-09-00},

journal = {International Journal of Radiation Oncology*Biology*Physics},

volume = {84},

number = {1},

pages = {196--202},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Huang2012b,

title = {Assessment of Vascular Contrast and Depiction of Stenoses in Abdominopelvic and Lower Extremity Vasculature},

author = {Steven Y. Huang and Rendon C. Nelson and Michael J. Miller and Charles Y. Kim and Jeffrey H. Lawson and Daniela B. Husarik and Daniel T. Boll},

doi = {10.1016/j.acra.2012.04.014},

issn = {1076-6332},

year  = {2012},

date = {2012-09-00},

journal = {Academic Radiology},

volume = {19},

number = {9},

pages = {1149--1157},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Pinnix2012,

title = {Topical Hyaluronic Acid vs. Standard of Care for the Prevention of Radiation Dermatitis After Adjuvant Radiotherapy for Breast Cancer: Single-Blind Randomized Phase III Clinical Trial},

author = {Chelsea Pinnix and George H. Perkins and Eric A. Strom and Welela Tereffe and Wendy Woodward and Julia L. Oh and Lisa Arriaga and Mark F. Munsell and Patrick Kelly and Karen E. Hoffman and Benjamin D. Smith and Thomas A. Buchholz and T. Kuan Yu},

doi = {10.1016/j.ijrobp.2011.09.021},

issn = {0360-3016},

year  = {2012},

date = {2012-07-00},

journal = {International Journal of Radiation Oncology*Biology*Physics},

volume = {83},

number = {4},

pages = {1089--1094},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Huang2012,

title = {Dose–Volume Analysis of Predictors for Gastrointestinal Toxicity After Concurrent Full-Dose Gemcitabine and Radiotherapy for Locally Advanced Pancreatic Adenocarcinoma},

author = {Jiayi Huang and John M. Robertson and Hong Ye and Jeffrey Margolis and Laura Nadeau and Di Yan},

doi = {10.1016/j.ijrobp.2011.09.022},

issn = {0360-3016},

year  = {2012},

date = {2012-07-00},

journal = {International Journal of Radiation Oncology*Biology*Physics},

volume = {83},

number = {4},

pages = {1120--1125},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Crocker2012,

title = {Measurement of patient imaging dose for real-time kilovoltage x-ray intrafraction tumour position monitoring in prostate patients},

author = {James K Crocker and Jin Aun Ng and Paul J Keall and Jeremy T Booth},

doi = {10.1088/0031-9155/57/10/2969},

issn = {1361-6560},

year  = {2012},

date = {2012-05-21},

journal = {Phys. Med. Biol.},

volume = {57},

number = {10},

pages = {2969--2980},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kang2011,

title = {Role of Extended Chemotherapy in Advanced Ovarian Cancer Patients with High Posttreatment Serum CA-125 Levels},

author = {Sokbom Kang and Tae-Joong Kim and Sang-Soo Seo and Byoung-Gie Kim and Duk-Soo Bae and Sang-Yoon Park},

doi = {10.1159/000322438},

issn = {1423-002X},

year  = {2011},

date = {2011-08-05},

journal = {Gynecol Obstet Invest},

volume = {72},

number = {1},

pages = {50--54},

publisher = {S. Karger AG},

abstract = {\textit{Background:} We aimed to determine whether the inclusion of additional cycles of carboplatin-paclitaxel is beneficial to patients with high posttreatment serum CA-125 levels. \textit{Methods:} Among patients who achieved remission after six cycles of carboplatin-paclitaxel chemotherapy, those with CA-125 of 10–35 U/ml at the time of remission were divided into two groups (group A: six cycles of standard chemotherapy vs. group B: two or more additional cycles) and were analyzed. \textit{Results:} Among the 436 patients with advanced epithelial ovarian cancer, 154 patients (46.8%) had CA-125 of 10–35 U/ml at the time of remission. Fifty-six patients (36.4%) received two or more cycles after the first six cycles of chemotherapy (group B). The addition of two or more cycles of chemotherapy did not improve the progression-free survival (p = 0.660). There was no statistical difference in the rates of CA-125 falling to <10 U/ml between the two groups (p = 0.256). Moreover, the degree of CA-125 decrease after six cycles of chemotherapy was similar regardless of the additional cycles (p = 0.656). \textit{Conclusion:} The addition of two or more cycles of standard chemotherapy based on posttreatment CA-125 levels was not beneficial.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Seitel2011,

title = {Computer-assisted trajectory planning for percutaneous needle insertions},

author = {Alexander Seitel and Markus Engel and Christof M. Sommer and Boris A. Radeleff and Caroline Essert-Villard and Claire Baegert and Markus Fangerau and Klaus H. Fritzsche and Kwong Yung and Hans-Peter Meinzer and Lena Maier-Hein},

doi = {10.1118/1.3590374},

issn = {0094-2405},

year  = {2011},

date = {2011-06-00},

journal = {Med. Phys.},

volume = {38},

number = {6Part1},

pages = {3246--3259},

publisher = {Wiley},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Schnoll2011,

title = {Predictors of smoking cessation among cancer patients enrolled in a smoking cessation program},

author = {Robert A. Schnoll and Elisa Martinez and Corey Langer and Curtis Miyamoto and Frank Leone},

doi = {10.3109/0284186x.2011.572915},

issn = {1651-226X},

year  = {2011},

date = {2011-06-00},

journal = {Acta Oncologica},

volume = {50},

number = {5},

pages = {678--684},

publisher = {MJS Publishing, Medical Journals Sweden AB},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kapanen2011,

title = {How can a cost/benefit ratio be optimized for an output measurement program of external photon radiotherapy beams?},

author = {Mika Kapanen and Ritva Bly and Petri Sipilä and Hannu Järvinen and Mikko Tenhunen},

doi = {10.1088/0031-9155/56/7/014},

issn = {1361-6560},

year  = {2011},

date = {2011-04-07},

journal = {Phys. Med. Biol.},

volume = {56},

number = {7},

pages = {2119--2130},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Miller2011,

title = {Mometasone Furoate Effect on Acute Skin Toxicity in Breast Cancer Patients Receiving Radiotherapy: A Phase III Double-Blind, Randomized Trial From the North Central Cancer Treatment Group N06C4},

author = {Robert C. Miller and David J. Schwartz and Jeff A. Sloan and Patricia C. Griffin and Richard L. Deming and Jon C. Anders and Thomas J. Stoffel and Robert E. Haselow and Paul L. Schaefer and James D. Bearden and Pamela J. Atherton and Charles L. Loprinzi and James A. Martenson},

doi = {10.1016/j.ijrobp.2010.01.031},

issn = {0360-3016},

year  = {2011},

date = {2011-04-00},

journal = {International Journal of Radiation Oncology*Biology*Physics},

volume = {79},

number = {5},

pages = {1460--1466},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Blessing2010,

title = {Breath-Hold Target Localization With Simultaneous Kilovoltage/Megavoltage Cone-Beam Computed Tomography and Fast Reconstruction},

author = {Manuel Blessing and Dzmitry Stsepankou and Hansjoerg Wertz and Anna Arns and Frank Lohr and Jürgen Hesser and Frederik Wenz},

doi = {10.1016/j.ijrobp.2010.01.030},

issn = {0360-3016},

year  = {2010},

date = {2010-11-00},

journal = {International Journal of Radiation Oncology*Biology*Physics},

volume = {78},

number = {4},

pages = {1219--1226},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Strassmann2010,

title = {Atlas-Based Semiautomatic Target Volume Definition (CTV) for Head-and-Neck Tumors},

author = {Gerd Strassmann and Soulimane Abdellaoui and Detlef Richter and Fayzal Bekkaoui and Marlene Haderlein and Emmanouil Fokas and Nina Timmesfeld and Birgitt Vogel and Martin Henzel and Rita Engenhart-Cabillic},

doi = {10.1016/j.ijrobp.2010.01.029},

issn = {0360-3016},

year  = {2010},

date = {2010-11-00},

journal = {International Journal of Radiation Oncology*Biology*Physics},

volume = {78},

number = {4},

pages = {1270--1276},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Barnett2010,

title = {No association between SNPs regulating TGF-β1 secretion and late radiotherapy toxicity to the breast: Results from the RAPPER study},

author = {Gillian C. Barnett and Charlotte E. Coles and Neil G. Burnet and Paul D.P. Pharoah and Jennifer Wilkinson and Catharine M.L. West and Rebecca M. Elliott and Caroline Baynes and Alison M. Dunning},

doi = {10.1016/j.radonc.2009.12.006},

issn = {0167-8140},

year  = {2010},

date = {2010-10-00},

journal = {Radiotherapy and Oncology},

volume = {97},

number = {1},

pages = {9--14},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Collen2010,

title = {Volumetric Imaging by Megavoltage Computed Tomography for Assessment of Internal Organ Motion During Radiotherapy for Cervical Cancer},

author = {Christine Collen and Benedikt Engels and Michael Duchateau and Koen Tournel and Mark De Ridder and Samuel Bral and Dirk Verellen and Guy Storme},

doi = {10.1016/j.ijrobp.2009.10.021},

issn = {0360-3016},

year  = {2010},

date = {2010-08-00},

journal = {International Journal of Radiation Oncology*Biology*Physics},

volume = {77},

number = {5},

pages = {1590--1595},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Rockne2010,

title = {Predicting the efficacy of radiotherapy in individual glioblastoma patients\textit{in vivo:}a mathematical modeling approach},

author = {R Rockne and J K Rockhill and M Mrugala and A M Spence and I Kalet and K Hendrickson and A Lai and T Cloughesy and E C Alvord and K R Swanson},

doi = {10.1088/0031-9155/55/12/001},

issn = {1361-6560},

year  = {2010},

date = {2010-06-21},

journal = {Phys. Med. Biol.},

volume = {55},

number = {12},

pages = {3271--3285},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Gemmel2010,

title = {Development and performance evaluation of a dynamic phantom for biological dosimetry of moving targets},

author = {A Gemmel and C Bert and N Saito and C von Neubeck and G Iancu and W K-Weyrather and M Durante and E Rietzel},

doi = {10.1088/0031-9155/55/11/001},

issn = {1361-6560},

year  = {2010},

date = {2010-06-07},

journal = {Phys. Med. Biol.},

volume = {55},

number = {11},

pages = {2997--3009},

publisher = {IOP Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{VanWaes2010,

title = {Molecular and Clinical Responses in a Pilot Study of Gefitinib With Paclitaxel and Radiation in Locally Advanced Head-and-Neck Cancer},

author = {Carter Van Waes and Clint T. Allen and Deborah Citrin and David Gius and A. Dimetrios Colevas and Nancy A. Harold and Susan Rudy and Liesl Nottingham and Christine Muir and Zhong Chen and Anurag K. Singh and Janet Dancey and John C. Morris},

doi = {10.1016/j.ijrobp.2009.05.037},

issn = {0360-3016},

year  = {2010},

date = {2010-06-00},

journal = {International Journal of Radiation Oncology*Biology*Physics},

volume = {77},

number = {2},

pages = {447--454},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Popescu2010,

title = {Volumetric Modulated Arc Therapy Improves Dosimetry and Reduces Treatment Time Compared to Conventional Intensity-Modulated Radiotherapy for Locoregional Radiotherapy of Left-Sided Breast Cancer and Internal Mammary Nodes},

author = {Carmen C. Popescu and Ivo A. Olivotto and Wayne A. Beckham and Will Ansbacher and Sergei Zavgorodni and Richard Shaffer and Elaine S. Wai and Karl Otto},

doi = {10.1016/j.ijrobp.2009.05.038},

issn = {0360-3016},

year  = {2010},

date = {2010-01-00},

journal = {International Journal of Radiation Oncology*Biology*Physics},

volume = {76},

number = {1},

pages = {287--295},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Chung2009,

title = {Radiosensitization Effect of STI-571 on Pancreatic Cancer Cells In Vitro},

author = {Hye Won Chung and Jing Wen and Jong-Baeck Lim and SeungMin Bang and Seung Woo Park and Si Young Song},

doi = {10.1016/j.ijrobp.2009.06.021},

issn = {0360-3016},

year  = {2009},

date = {2009-11-00},

journal = {International Journal of Radiation Oncology*Biology*Physics},

volume = {75},

number = {3},

pages = {862--869},

publisher = {Elsevier BV},

keywords = {},

pubstate = {published},

tppubtype = {article}

}