bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proton radiography and fluoroscopy of lung tumors: A Monte Carlo study using patient‐specific 4DCT phantoms
Authors: Han Bin , Xu X. George , Chen George T. Y. 
Published: April 2011

Purpose:Monte Carlo methods are used to simulate and optimize a time‐resolved proton range telescope (TRRT) in localization of intrafractional and interfractional motions of lung tumor and in quantification of proton range variations.Methods:The Monte Carlo N‐Particle eXtended (MCNPX) code with a particle tracking feature was employed to evaluate the TRRT performance, especially in visualizing and quantifying proton range variations during respiration. Protons of 230 MeV were tracked one by one as they pass through position detectors, patient 4DCT phantom, and finally scintillator detectors that measured residual ranges. The energy response of the scintillator telescope was investigated. Mass density and elemental composition of tissues were defined for 4DCT data.Results:Proton water equivalent length (WEL) was deduced by a reconstruction algorithm that incorporates linear proton track and lateral spatial discrimination to improve the image quality. 4DCT data for three patients were used to visualize and measure tumor motion and WEL variations. The tumor trajectories extracted from the WEL map were found to be within agreement with direct 4DCT measurement. Quantitative WEL variation studies showed that the proton radiograph is a good representation of WEL changes from entrance to distal of the target.Conclusions:MCNPX simulation results showed that TRRT can accurately track the motion of the tumor and detect the WEL variations. Image quality was optimized by choosing proton energy, testing parameters of image reconstruction algorithm, and comparing to ground truth 4DCT. The future study will demonstrate the feasibility of using the time resolved proton radiography as an imaging tool for proton treatments of lung tumors.
Dynamic gating window for compensation of baseline shift in respiratory‐gated radiation therapy
Authors: Pepin Eric W. , Wu Huanmei , Shirato Hiroki 
Published: April 2011

Purpose:To analyze and evaluate the necessity and use of dynamic gating techniques for compensation of baseline shift during respiratory‐gated radiation therapy of lung tumors.Methods:Motion tracking data from 30 lung tumors over 592 treatment fractions were analyzed for baseline shift. The finite state model (FSM) was used to identify the end‐of‐exhale (EOE) breathing phase throughout each treatment fraction. Using duty cycle as an evaluation metric, several methods of end‐of‐exhale dynamic gating were compared: Ana posteriori ideal gating window, a predictive trend‐line‐based gating window, and a predictive weighted point‐based gating window. These methods were evaluated for each of several gating window types: Superior/inferior (SI) gating, anterior/posterior beam, lateral beam, and 3D gating.Results:In the absence of dynamic gating techniques, SI gating gave a 39.6% duty cycle. The ideal SI gating window yielded a 41.5% duty cycle. The weight‐based method of dynamic SI gating yielded a duty cycle of 36.2%. The trend‐line‐based method yielded a duty cycle of 34.0%.Conclusions:Dynamic gating was not broadly beneficial due to a breakdown of the FSM's ability to identify the EOE phase. When the EOE phase was well defined, dynamic gating showed an improvement over static‐window gating.
Local and global 3D noise power spectrum in cone‐beam CT system with FDK reconstruction
Authors: Baek Jongduk , Pelc Norbert J. 
Published: April 2011

Purpose:The authors examine the nonstationary noise behavior of a cone‐beam CT system with FDK reconstruction.Methods:To investigate the nonstationary noise behavior, an analytical expression for the NPS of local volumes and an entire volume was derived and quantitatively compared to the NPS estimated from experimental air and water images.Results:The NPS of local volumes at different locations along the‐axis showed radial symmetry in theplane and different missing cone regions in thedirection depending on the tilt angle of rays through the local volumes. For local volumes away from the‐axis, the NPS of air and water images showed sharp transitions in theandplanes and lack of radial symmetry in theplane. These effects are mainly caused by varying magnification and different noise levels from view to view. In the NPS of the entire volume, theplane showed radial symmetry because the nonstationary noise behaviors of local volumes were averaged out. The nonstationary sharp transitions were manifested as a high‐frequency roll‐off.Conclusions:The results from noise power analysis for local volumes and an entire volume demonstrate the spatially varying noise behavior in the reconstructed cone‐beam CT images.
Calibration of GafChromic XR‐RV3 radiochromic film for skin dose measurement using standardized x‐ray spectra and a commercial flatbed scanner
Authors: McCabe Bradley P. , Speidel Michael A. , Pike Tina L. , Van Lysel Michael S. 
Published: April 2011

Purpose:In this study, newly formulated XR‐RV3 GafChromic® film was calibrated with National Institute of Standards and Technology (NIST) traceability for measurement of patient skin dose during fluoroscopically guided interventional procedures.Methods:The film was calibrated free‐in‐air to air kerma levels between 15 and 1100 cGy using four moderately filtered x‐ray beam qualities (60, 80, 100, and 120 kVp). The calibration films were scanned with a commercial flatbed document scanner. Film reflective density‐to‐air kerma calibration curves were constructed for each beam quality, with both the orange and white sides facing the x‐ray source. A method to correct for nonuniformity in scanner response (up to 25% depending on position) was developed to enable dose measurement with large films. The response of XR‐RV3 film under patient backscattering conditions was examined using on‐phantom film exposures and Monte Carlo simulations.Results:The response of XR‐RV3 film to a given air kerma depended on kVp and film orientation. For a 200 cGy air kerma exposure with the orange side of the film facing the source, the film response increased by 20% from 60 to 120 kVp. At 500 cGy, the increase was 12%. When 500 cGy exposures were performed with the white side facing the x‐ray source, the film response increased by 4.0% (60 kVp) to 9.9% (120 kVp) compared to the orange‐facing orientation. On‐phantom film measurements and Monte Carlo simulations show that using a NIST‐traceable free‐in‐air calibration curve to determine air kerma in the presence of backscatter results in an error from 2% up to 8% depending on beam quality. The combined uncertainty in the air kerma measurement from the calibration curves and scanner nonuniformity correction was ±7.1% (95% C.I.). The film showed notable stability. Calibrations of film and scanner separated by 1 yr differed by 1.0%.Conclusions:XR‐RV3 radiochromic film response to a given air kerma shows dependence on beam quality and film orientation. The presence of backscatter slightly modifies the x‐ray energy spectrum; however, the increase in film response can be attributed primarily to the increase in total photon fluence at the sensitive layer. Film calibration curves created under free‐in‐air conditions may be used to measure dose from fluoroscopic quality x‐ray beams, including patient backscatter with an error less than the uncertainty of the calibration in most cases.
Computer‐aided detection of lung nodules via 3D fast radial transform, scale space representation, and Zernike MIP classification
Authors: Riccardi Alessandro , Petkov Todor Sergueev , Ferri Gianluca , Masotti Matteo , Campanini Renato 
Published: April 2011

Purpose:The authors presented a novel system for automated nodule detection in lung CT exams.Methods:The approach is based on (1) a lung tissue segmentation preprocessing step, composed of histogram thresholding, seeded region growing, and mathematical morphology; (2) a filtering step, whose aim is the preliminary detection of candidate nodules (via 3D fast radial filtering) and estimation of their geometrical features (via scale space analysis); and (3) a false positive reduction (FPR) step, comprising a heuristic FPR, which applies thresholds based on geometrical features, and a supervised FPR, which is based on support vector machines classification, which in turn, is enhanced by a feature extraction algorithm based on maximum intensity projection processing and Zernike moments.Results:The system was validated on 154 chest axial CT exams provided by the lung image database consortium public database. The authors obtained correct detection of 71% of nodules marked by all radiologists, with a false positive rate of 6.5 false positives per patient (FP/patient). A higher specificity of 2.5 FP/patient was reached with a sensitivity of 60%. An independent test on the ANODE09 competition database obtained an overall score of 0.310.Conclusions:The system shows a novel approach to the problem of lung nodule detection in CT scans: It relies on filtering techniques, image transforms, and descriptors rather than region growing and nodule segmentation, and the results are comparable to those of other recent systems in literature and show little dependency on the different types of nodules, which is a good sign of robustness.
Evaluation of intersession 3D‐TRUS to 3D‐TRUS image registration for repeat prostate biopsies
Authors: Karnik V. V. , Fenster A. , Bax J. , Romagnoli C. , Ward A. D. 
Published: April 2011

Purpose:3D‐TRUS‐guided prostate biopsy permits a 3D record of biopsy cores, supporting the planning of targets to resample or avoid during repeat biopsy sessions. Image registration is required in order to map biopsy targets planned on a previous session's 3D‐TRUS image into the context of the current session. The authors evaluated the performance of surface‐ and intensity‐based rigid and nonrigid registration algorithms for this task using a clinically motivated success criterion of a maximum 2.5 mm target registration error (TRE).Methods:The authors collected two 3D‐TRUS images for each of 13 patients, where each image was collected in a separate biopsy session, and the sessions were 1 week apart. The authors tested the iterative closest point and thin‐plate spline surface‐based registration methods, and the block matching and B‐spline intensity‐based methods. Manually marked intrinsic fiducials (calcifications) were used to calculate a TRE for each of the tested methods. In addition, error ellipsoids, anisotropy, and variability due to image segmentation were analyzed. All analysis was performed separately for the peripheral zone since this area harbors up to 80% of all prostate cancer.Results:Only the intensity‐based nonrigid registration method met the success criterion for both the whole gland and the peripheral zone. Segmentation was a substantial contributor to registration error variability for the surface‐based methods, and the surface‐based methods resulted in greater error volumes and anisotropy.Conclusions:Intensity‐based rigid registration is clinically sufficient to register regions outside the peripheral zone, but nonrigid registration is required in order to register the peripheral zone with clinically needed accuracy. The clinical advantage of using nonrigid registration is questionable since the difference between the RMS TREs for rigid and nonrigid intensity‐based registration could be considered to be small (0.3 mm) and is statistically significant. If the added clinical value in performing a nonrigid registration is insufficient given the additional time required for this computation, rigid registration alone may be suitable.
Development and evaluation of a computer‐aided diagnostic scheme for lung nodule detection in chest radiographs by means of two‐stage nodule enhancement with support vector classification
Authors: Chen Sheng , Suzuki Kenji , MacMahon Heber 
Published: April 2011

Purpose:To develop a computer‐aided detection (CADe) scheme for nodules in chest radiographs (CXRs) with a high sensitivity and a low false‐positive (FP) rate.Methods:The authors developed a CADe scheme consisting of five major steps, which were developed for improving the overall performance of CADe schemes. First, to segment the lung fields accurately, the authors developed a multisegment active shape model. Then, a two‐stage nodule‐enhancement technique was developed for improving the conspicuity of nodules. Initial nodule candidates were detected and segmented by using the clustering watershed algorithm. Thirty‐one shape‐, gray‐level‐, surface‐, and gradient‐based features were extracted from each segmented candidate for determining the feature space, including one of the new features based on the Canny edge detector to eliminate a major FP source caused by rib crossings. Finally, a nonlinear support vector machine (SVM) with a Gaussian kernel was employed for classification of the nodule candidates.Results:To evaluate and compare the scheme to other published CADe schemes, the authors used a publicly available database containing 140 nodules in 140 CXRs and 93 normal CXRs. The CADe scheme based on the SVM classifier achieved sensitivities of 78.6% (110/140) and 71.4% (100/140) with averages of 5.0 (1165/233) FPs/image and 2.0 (466/233) FPs/image, respectively, in a leave‐one‐out cross‐validation test, whereas the CADe scheme based on a linear discriminant analysis classifier had a sensitivity of 60.7% (85/140) at an FP rate of 5.0 FPs/image. For nodules classified as “very subtle” and “extremely subtle,” a sensitivity of 57.1% (24/42) was achieved at an FP rate of 5.0 FPs/image. When the authors used a database developed at the University of Chicago, the sensitivities was 83.3% (40/48) and 77.1% (37/48) at an FP rate of 5.0 (240/48) FPs/image and 2.0 (96/48) FPs /image, respectively.Conclusions:These results compare favorably to those described for other commercial and noncommercial CADe nodule detection systems.
Characterization of lamina propria and vocal muscle in human vocal fold tissue by ultrasound Nakagami imaging
Authors: Tsui Po‐Hsiang , Huang Chih‐Chung , Sun Lei , Dailey Seth H. , Shung K. Kirk 
Published: April 2011

Purpose:A number of ultrasound techniques have been applied to identify the biomechanical properties of the vocal folds. These conventional ultrasound methods, however, are not capable of visually mapping the concentration of collagen and elastic fibers in the vocal folds in the form of a parametric image. This study proposes to use a statistical parameter, the Nakagami factor estimated from the statistical distribution of the ultrasonic signals backscattered from tissues, as a means for parametric imaging of the biomechanical properties of the vocal folds.Methods:The ultrasonic backscattered signals were acquired from four larynges (eight vocal folds) obtained from individuals without vocal fold pathology for constructing the Nakagami images. The textures of the Nakagami image in the lamina propria (LP) and the vocal muscle (VM) were observed and compared. The average and standard deviation of the Nakagami parameter for the LP and the VM were also calculated.Results:The results showed that the Nakagami parameter of the LP is larger than that of the VM. Moreover, the LP and the VM have different shading features in the Nakagami images. It was found that the Nakagami parameter may depend on the concentration of collagen and elastic fibers, demonstrating that the Nakagami imaging may allow visual differentiation between the LP and the VM in the vocal folds.Conclusions:Current preliminary results suggested that the high‐frequency Nakagami imaging may allow real‐time visual characterization of the vocal fold tissues in clinical routine examinations.
Comparative performance of multiview stereoscopic and mammographic display modalities for breast lesion detection
Authors: Webb Lincoln J. , Samei Ehsan , Lo Joseph Y. , Baker Jay A. , Ghate Sujata V. , Kim Connie , Soo Mary Scott , Walsh Ruth 
Published: April 2011

Purpose:Mammography is known to be one of the most difficult radiographic exams to interpret. Mammography has important limitations, including the superposition of normal tissue that can obscure a mass, chance alignment of normal tissue to mimic a true lesion and the inability to derive volumetric information. It has been shown that stereomammography can overcome these deficiencies by showing that layers of normal tissue lay at different depths. If standard stereomammography (i.e., a single stereoscopic pair consisting of two projection images) can significantly improve lesion detection, how will multiview stereoscopy (MVS), where many projection images are used, compare to mammography? The aim of this study was to assess the relative performance of MVS compared to mammography for breast mass detection.Methods:The MVS image sets consisted of the 25 raw projection images acquired over an arc of approximately 45° using a Siemens prototype breast tomosynthesis system. The mammograms were acquired using a commercial Siemens FFDM system. The raw data were taken from both of these systems for 27 cases and realistic simulated mass lesions were added to duplicates of the 27 images at the same local contrast. The images with lesions (27 mammography and 27 MVS) and the images without lesions (27 mammography and 27 MVS) were then postprocessed to provide comparable and representative image appearance across the two modalities. All 108 image sets were shown to five full‐time breast imaging radiologists in random order on a state‐of‐the‐art stereoscopic display. The observers were asked to give a confidence rating for each image (0 for lesion definitely not present, 100 for lesion definitely present). The ratings were then compiled and processed using ROC and variance analysis.Results:The mean AUC for the five observers was for mammography and for multiview stereoscopy. The difference of was statistically significant with a ‐value of 0.0148.Conclusions:The differences in the AUCs and the ‐value suggest that multiview stereoscopy has a statistically significant advantage over mammography in the detection of simulated breast masses. This highlights the dominance of anatomical noise compared to quantum noise for breast mass detection. It also shows that significant lesion detection can be achieved with MVS without any of the artifacts associated with tomosynthesis.
Water equivalent path length measurement in proton radiotherapy using time resolved diode dosimetry
Authors: Gottschalk B. , Tang S. , Bentefour E. H. , Cascio E. W. , Prieels D. , Lu H.‐M. 
Published: April 2011

Purpose:To verify water equivalent path length (WEPL) before treatment in proton radiotherapy using time resolvedin vivo diode dosimetry.Methods:Using a passively scattered range modulated proton beam, the output of a diode driving a fast current‐to‐voltage amplifier is recorded at a number of depths in a water tank. At each depth, a burst of overlapping single proton pulses is observed. The rms duration of the burst is computed and the resulting data set is fitted with a cubic polynomial.Results:When the diode is subsequently set to an arbitrary depth and the polynomial is used as a calibration curve, the “unknown” depth is determined within 0.3 mm rms.Conclusions:A diode or a diode array, placed (for instance) in the rectum in conjunction with a rectal balloon, can potentially determine the WEPL at that point, just prior to treatment, with submillimeter accuracy, allowing the beam energy to be adjusted. The associated unwanted dose is about 0.2% of a typical single fraction treatment dose.
Method for measuring the focal spot size of an x‐ray tube using a coded aperture mask and a digital detector
Authors: Russo Paolo , Mettivier Giovanni 
Published: April 2011

Purpose:The goal of this study is to evaluate a new method based on a coded aperture mask combined with a digital x‐ray imaging detector for measurements of the focal spot sizes of diagnostic x‐ray tubes. Common techniques for focal spot size measurements employ a pinhole camera, a slit camera, or a star resolution pattern. The coded aperture mask is a radiation collimator consisting of a large number of apertures disposed on a predetermined grid in an array, through which the radiation source is imaged onto a digital x‐ray detector. The method of the coded mask camera allows one to obtain a one‐shot accurate and direct measurement of the two dimensions of the focal spot (like that for a pinhole camera) but at a low tube loading (like that for a slit camera). A large number of small apertures in the coded mask operate as a “multipinhole” with greater efficiency than a single pinhole, but keeping the resolution of a single pinhole.Methods:X‐ray images result from the multiplexed output on the detector image plane of such a multiple aperture array, and the image of the source is digitally reconstructed with a deconvolution algorithm. Images of the focal spot of a laboratory x‐ray tube (W anode: 35–80 kVp; focal spot size of 0.04 mm) were acquired at different geometrical magnifications with two different types of digital detector (a photon counting hybrid silicon pixel detector with 0.055 mm pitch and a flat panel CMOS digital detector with 0.05 mm pitch) using a high resolution coded mask (type no‐two‐holes‐touching modified uniformly redundant array) with 480 0.07 mm apertures, designed for imaging at energies below 35 keV. Measurements with a slit camera were performed for comparison. A test with a pinhole camera and with the coded mask on a computed radiography mammography unit with 0.3 mm focal spot was also carried out.Results:The full width at half maximum focal spot sizes were obtained from the line profiles of the decoded images, showing a focal spot of at 35 kVp and , with a detector entrance exposure as low as 1.82 mR (0.125 mA s tube load). The slit camera indicated a focal spot of at 35 kVp and , with an exposure at the detector of 72 mR. Focal spot measurements with the coded mask could be performed up to 80 kVp. Tolerance to angular misalignment with the reference beam up to 7° in in‐plane rotations and 1° deg in out‐of‐plane rotations was observed. The axial distance of the focal spot from the coded mask could also be determined. It is possible to determine the beam intensity via measurement of the intensity of the decoded image of the focal spot and via a calibration procedure.Conclusions:Coded aperture masks coupled to a digital area detector produce precise determinations of the focal spot of an x‐ray tube with reduced tube loading and measurement time, coupled to a large tolerance in the alignment of the mask.