bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alanine/EPR dosimetry applied to the verification of a total body irradiation protocol and treatment planning dose calculation using a humanoid phantom
Authors: Schaeken B. , Lelie S. , Meijnders P. , Van den Weyngaert D. , Janssens H. , Verellen D. 
Published: December 2010

Purpose:To avoid complications in total body irradiation (TBI), it is important to achieve a homogeneous dose distribution throughout the body and to deliver a correct dose to the lung which is an organ at risk. The purpose of this work was to validate the TBI dose protocol and to check the accuracy of the 3D dose calculations of the treatment planning system.Methods:Dosimetry based on alanine/electron paramagnetic resonance (EPR) was used to measure dose at numerous locations within an anthropomorphic phantom (Alderson®) that was irradiated in a clinical TBI beam setup. The alanine EPR dosimetry system was calibrated against water calorimetry in a Co‐60 beam and the absorbed dose was determined by the use of “dose‐normalized amplitudes”. The dose rate of the TBI beam was checked against a Farmer ionization chamber. The phantom measurements were compared to 3D dose calculations from a treatment planning system (Pinnacle®) modeled for standard dose calculations.Results:Alanine dosimetry allowed accurate measurements which were in accordance with ionization chamber measurements. The combined relative standard measurement uncertainty in the Alderson phantom was. The humanoid phantom was irradiated to a reference dose of 10 Gy, limiting the lung dose to 7.5 Gy. The ratio of the average measured dose midplane in the craniocaudal direction to the reference dose was 1.001 with a spread of ±4.7% (1 sd). Dose to the lung was measured in 26 locations and found, in average, 1.8% lower than expected. Lung dose was homogeneous in the ventral‐dorsal direction but a dose gradient of was observed in the craniocaudal direction midline within the lung lobe. 3D dose calculations (Pinnacle®) were found, in average, 2% lower compared to dose measurements on the body axis and 3% lower for the lungs.Conclusions:The alanine/EPR dosimetry system allowed accurate dose measurements which enabled the authors to validate their TBI dose protocol. Dose calculations based on a collapsed cone convolution dose algorithm modeled for regular treatments are accurate within 3% and can further be improved when the algorithm is modeled for TBI.
Comparison of radiation exposure and associated radiation‐induced cancer risks from mammography and molecular imaging of the breasta)
Authors: O'Connor Michael K. , Li Hua , Rhodes Deborah J. , Hruska Carrie B. , Clancy Conor B. , Vetter Richard J. 
Published: December 2010

Purpose:Recent studies have raised concerns about exposure to low‐dose ionizing radiation from medical imaging procedures. Little has been published regarding the relative exposure and risks associated with breast imaging techniques such as breast specific gamma imaging (BSGI), molecular breast imaging (MBI), or positron emission mammography (PEM). The purpose of this article was to estimate and compare the risks of radiation‐induced cancer from mammography and techniques such as PEM, BSGI, and MBI in a screening environment.Methods:The authors used a common scheme for all estimates of cancer incidence and mortality based on the excess absolute risk model from the BEIR VII report. The lifetime attributable risk model was used to estimate the lifetime risk of radiation‐induced breast cancer incidence and mortality. All estimates of cancer incidence and mortality were based on a population of 100 000 females followed from birth to age 80 and adjusted for the fraction that survives to various ages between 0 and 80. Assuming annual screening from ages 40 to 80 and from ages 50 to 80, the cumulative cancer incidence and mortality attributed to digital mammography, screen‐film mammography, MBI, BSGI, and PEM was calculated. The corresponding cancer incidence and mortality from natural background radiation was calculated as a useful reference. Assuming a 15%–32% reduction in mortality from screening, the benefit/risk ratio for the different imaging modalities was evaluated.Results:Using conventional doses of 925 MBq Tc‐99m sestamibi for MBI and BSGI and 370 MBq F‐18 FDG for PEM, the cumulative cancer incidence and mortality were found to be 15–30 times higher than digital mammography. The benefit/risk ratio for annual digital mammography was for both the 40–80 and 50–80 screening groups, but dropped to 3:1 for the 40–49 age group. If the primary use of MBI, BSGI, and PEM is in women with dense breast tissue, then the administered doses need to be in the range 75–150 MBq for Tc‐99m sestamibi and 35 MBq–70 MBq for F‐18 FDG in order to obtain benefit/risk ratios comparable to those of mammography in these age groups. These dose ranges should be achievable with enhancements to current technology while maintaining a reasonable examination time.Conclusions:The results of the dose estimates in this study clearly indicate that if molecular imaging techniques are to be of value in screening for breast cancer, then the administered doses need to be substantially reduced to better match the effective doses of mammography.
Evaluation of a multi‐atlas based method for segmentation of cardiac CTA data: a large‐scale, multicenter, and multivendor study
Authors: Kirişli H. A. , Schaap M. , Klein S. , Papadopoulou S. L. , Bonardi M. , Chen C. H. , Weustink A. C. , Mollet N. R. , Vonken E. J. , van der Geest R. J. , van Walsum T. , Niessen W. J. 
Published: December 2010

Purpose:Computed tomography angiography (CTA) is increasingly used for the diagnosis of coronary artery disease (CAD). However, CTA is not commonly used for the assessment of ventricular and atrial function, although functional information extracted from CTA data is expected to improve the diagnostic value of the examination. In clinical practice, the extraction of ventricular and atrial functional information, such as stroke volume and ejection fraction, requires accurate delineation of cardiac chambers. In this paper, we investigated the accuracy and robustness of cardiac chamber delineation using a multiatlas based segmentation method on multicenter and multivendor CTA data.Methods:A fully automatic multiatlas based method for segmenting the whole heart (i.e., the outer surface of the pericardium) and cardiac chambers from CTA data is presented and evaluated. In the segmentation approach, eight atlas images are registered to a new patient's CTA scan. The eight corresponding manually labeled images are then propagated and combined using a per voxel majority voting procedure, to obtain a cardiac segmentation.Results:The method was evaluated on a multicenter/multivendor database, consisting of (1) a set of 1380 Siemens scans from 795 patients and (2) a set of 60 multivendor scans (Siemens, Philips, and GE) from different patients, acquired in six different institutions worldwide. A leave‐one‐out 3D quantitative validation was carried out on the eight atlas images; we obtained a mean surface‐to‐surface error of and an average Dice coefficient of 0.93 was achieved. A 2D quantitative evaluation was performed on the 60 multivendor data sets. Here, we observed a mean surface‐to‐surface error of and an average Dice coefficient of 0.91 was achieved. In addition to this quantitative evaluation, a large‐scale 2D and 3D qualitative evaluation was performed on 1380 and 140 images, respectively. Experts evaluated that 49% of the 1380 images were very accurately segmented (below 1 mm error) and that 29% were accurately segmented (error between 1 and 3 mm), which demonstrates the robustness of the presented method.Conclusions:A fully automatic method for whole heart and cardiac chamber segmentation was presented and evaluated using multicenter/multivendor CTA data. The accuracy and robustness of the method were demonstrated by successfully applying the method to 1420 multicenter/multivendor data sets.
ACCOMP: Augmented cell competition algorithm for breast lesion demarcation in sonography
Authors: Cheng Jie‐Zhi , Chou Yi‐Hong , Huang Chiun‐Sheng , Chang Yeun‐Chung , Tiu Chui‐Mei , Yeh Fang‐Cheng , Chen Kuei‐Wu , Tsou Chi‐Hsuan , Chen Chung‐Ming 
Published: December 2010

Purpose:Fully automatic and high‐quality demarcation of sonographical breast lesions remains a far‐reaching goal. This article aims to develop an image segmentation algorithm that provides quality delineation of breast lesions in sonography with a simple and friendly semiautomatic scheme.Methods:A data‐driven image segmentation algorithm, named as augmented cell competition (ACCOMP) algorithm, is developed to delineate breast lesion boundaries in ultrasound images. Inspired by visual perceptual experience and Gestalt principles, the ACCOMP algorithm is constituted of two major processes, i.e., cell competition and cell‐based contour grouping. The cell competition process drives cells, i.e., the catchment basins generated by a two‐pass watershed transformation, to merge and split into prominent components. A prominent component is defined as a relatively large and homogeneous region circumscribed by a perceivable boundary. Based on the prominent component tessellation, cell‐based contour grouping process seeks the best closed subsets of edges in the prominent component structure as the desirable boundary candidates. Finally, five boundary candidates with respect to five devised boundary cost functions are suggested by the ACCOMP algorithm for user selection. To evaluate the efficacy of the ACCOMP algorithm on breast lesions with complicated echogenicity and shapes, 324 breast sonograms, including 199 benign and 125 malignant lesions, are adopted as testing data. The boundaries generated by the ACCOMP algorithm are compared to manual delineations, which were confirmed by four experienced medical doctors. Four assessment metrics, including the modified Williams index, percentage statistic, overlapping ratio, and difference ratio, are employed to see if the ACCOMP‐generated boundaries are comparable to manual delineations. A comparative study is also conducted by implementing two pixel‐based segmentation algorithms. The same four assessment metrics are employed to evaluate the boundaries generated by two conventional pixel‐based algorithms based on the same set of manual delineations.Results:The ACCOMP‐generated boundaries are shown to be comparable to the manual delineations. Particularly, the modified Williams indices of the boundaries generated by the ACCOMP algorithm and the first and second pixel‐based algorithms are, , and , respectively. If the modified Williams index is greater than or equal to 1, the average distance between the computer‐generated boundaries and manual delineations is deemed to be comparable to that between the manual delineations.Conclusions:The boundaries derived by the ACCOMP algorithm are shown to reasonably demarcate sonographic breast lesions, especially for the cases with complicated echogenicity and shapes. It suggests that the ACCOMP‐generated boundaries can potentially serve as the basis for further morphological or quantitative analysis.
High‐rate x‐ray spectroscopy in mammography with a CdTe detector: A digital pulse processing approach
Authors: Abbene L. , Gerardi G. , Principato F. , Del Sordo S. , Ienzi R. , Raso G. 
Published: December 2010

Purpose:Direct measurement of mammographic x‐ray spectra under clinical conditions is a difficult task due to the high fluence rate of the x‐ray beams as well as the limits in the development of high resolution detection systems in a high counting rate environment. In this work we present a detection system, based on a CdTe detector and an innovative digital pulse processing (DPP) system, for high‐rate x‐ray spectroscopy in mammography.Methods:The DPP system performs a digital pile‐up inspection and a digital pulse height analysis of the detector signals, digitized through a 14‐bit, 100 MHz digitizer, for x‐ray spectroscopy even at high photon counting rates. We investigated on the response of the digital detection system both at low (150 cps) and at high photon counting rates (up to 500 kcps) by using monoenergetic x‐ray sources and a nonclinical molybdenum anode x‐ray tube. Clinical molybdenum x‐ray spectrum measurements were also performed by using a pinhole collimator and a custom alignment device.Results:The detection system shows excellent performance up to 512 kcps with an energy resolution of 4.08% FWHM at 22.1 keV. Despite the high photon counting rate (up to 453 kcps), the molybdenum x‐ray spectra, measured under clinical conditions, are characterized by a low number of pile‐up events. The agreement between the attenuation curves and the half value layer values, obtained from the measured spectra, simulated spectra, and from the exposure values directly measured with an ionization chamber, also shows the accuracy of the measurements.Conclusions:These results make the proposed detection system a very attractive tool for both laboratory research and advanced quality controls in mammography.
Acoustic radiation force contrast in MRI: Detection of calcifications in tissue‐mimicking phantoms
Authors: Mende Jessica , Wild Judith , Ulucay Deniz , Radicke Marcus , Kofahl Anna‐Lisa , Weber Bernd , Krieg Robert , Maier Karl 
Published: December 2010

Purpose:Mammography is a widely used tool for the screening of breast cancer, and calcifications are a common finding in most mammograms. The location, size, number, morphology, and distribution of calcifications are an important information to differentiate a benign lesion from probably malignant pathologies. Calcifications are not detectable with a standard dynamic contrast enhanced breast MRI. The authors present a novel method for the detection and imaging of calcifications in breast tissue without ionizing radiation or contrast agents.Methods:Measurements of localized tissue displacement in phantoms due to applied acoustic radiation force were performed. This displacement was imaged with a displacement sensitive spin‐echo MRI sequence. Pieces of eggshell that represent calcifications were embedded in tissue‐mimicking agarose phantoms. The sizes of the calcifications were, , and . The calcifications were scanned with ultrasound (U.S.) at 2.5 MHz and intensities up to . The U.S. beam was moved inside the phantom by a computer‐controlled three‐dimensional hydraulic positioning system. The U.S. beam was scanned over the two smaller calcifications with the displacement sensitivity of the MRI sequence parallel to the U.S. beam path. Grayscale coded maps of the displacement scans are presented. For the calcification, the U.S. intensities were varied. Finite element simulations were performed to verify if the experiments complied with theory.Results:The authors found that the displacement caused by the U.S. is increased at the position of the calcification. The area of increased displacement is at least twice as large as the calcification itself. The simulations show this increase in displacement and area at the position of the calcification. When changing the displacement sensitivity direction to perpendicular to the U.S. beam, a crossed black and white four‐leaf clover is visible at the position of the calcification.Conclusions:The U.S. is scattered and reflected by the calcifications. This leads to the increased displacement which is transmitted to the surrounding material because of the elastic coupling between the calcification and the agarose material. Due to the high differences in acoustic impedance and elastic properties between the surrounding tissue and the calcification, even the detection of pieces smaller than the resolution of the MRI scanner is possible. The acoustic radiation force contrast in MR phase‐difference images offers a positive signal for calcifications from a smooth background in phantoms. This method offers a possibility of differentiating qualitatively and quantitatively hard calcifications from stiffer inclusions such as tumors.
A novel off‐axis scanning method for an enlarged ellipse cone‐beam computed tomography field of view
Authors: Li Tianfang , Li Xiang , Yang Yong , Heron Dwight E. , Huq M. Saiful. 
Published: December 2010

Purpose:Current on‐board imaging systems commonly used by modern linear accelerators (LINACs) have a limited field of view (FOV) for a cone‐beam CT (CBCT) scan, which is typically less than 50 cm. Consequently, truncation artifacts often occur for large patients. The goal of this work is to investigate a novel method to increase the FOV for current on‐board CBCT systems.Methods:When a large patient is scanned with CBCT, any region outside the FOV is only partially sampled within a short range of projection angles, and at other angles no x‐ray beams may pass through that region. To increase the sampling rate for the region outside the FOV, we have designed a new source trajectory by shifting the center of rotation during a CBCT scan. This resulted in a reduced sampling rate at the central area and increased sampling rate at the edges. The tradeoff led to a more balanced sampling for an enlarged FOV. An iterative algorithm was also developed to reconstruct the CT image under the new sampling scheme using a compressed sensing technique.Results:The method was validated by numerical simulations mimicking a Varian Trilogy CBCT system, and it was found that artifact‐free images could be obtained with the FOV as large as 80 cm.Conclusions:The new CT scanning trajectory can be easily realized under current clinical setup with little modification of the control system, and this can be useful for treating obese patients.
Combining registration and active shape models for the automatic segmentation of the lymph node regions in head and neck CT images
Authors: Chen Antong , Deeley Matthew A. , Niermann Kenneth J. , Moretti Luigi , Dawant Benoit M. 
Published: December 2010

Purpose:Intensity‐modulated radiation therapy (IMRT) is the state of the art technique for head and neck cancer treatment. It requires precise delineation of the target to be treated and structures to be spared, which is currently done manually. The process is a time‐consuming task of which the delineation of lymph node regions is often the longest step. Atlas‐based delineation has been proposed as an alternative, but, in the authors' experience, this approach is not accurate enough for routine clinical use. Here, the authors improve atlas‐based segmentation results obtained for level II–IV lymph node regions using an active shape model (ASM) approach.Methods:An average image volume was first created from a set of head and neck patient images with minimally enlarged nodes. The average image volume was then registered using affine, global, and local nonrigid transformations to the other volumes to establish a correspondence between surface points in the atlas and surface points in each of the other volumes. Once the correspondence was established, the ASMs were created for each node level. The models were then used to first constrain the results obtained with an atlas‐based approach and then to iteratively refine the solution.Results:The method was evaluated through a leave‐one‐out experiment. The ASM‐ and atlas‐based segmentations were compared to manual delineations via the Dice similarity coefficient (DSC) for volume overlap and the Euclidean distance between manual and automatic 3D surfaces. The mean DSC value obtained with the ASM‐based approach is 10.7% higher than with the atlas‐based approach; the mean and median surface errors were decreased by 13.6% and 12.0%, respectively.Conclusions:The ASM approach is effective in reducing segmentation errors in areas of low CT contrast where purely atlas‐based methods are challenged. Statistical analysis shows that the improvements brought by this approach are significant.
Three‐dimensional tracking of cardiac catheters using an inverse geometry x‐ray fluoroscopy system
Authors: Speidel Michael A. , Tomkowiak Michael T. , Raval Amish N. , Van Lysel Michael S. 
Published: December 2010

Purpose:Scanning beam digital x‐ray (SBDX) is an inverse geometry fluoroscopic system with high dose efficiency and the ability to perform continuous real‐time tomosynthesis at multiple planes. This study describes a tomosynthesis‐based method for 3D tracking of high‐contrast objects and present the first experimental investigation of cardiac catheter tracking using a prototype SBDX system.Methods:The 3D tracking algorithm utilizes the stack of regularly spaced tomosynthetic planes that are generated by SBDX after each frame period (15 frames/s). Gradient‐filtered versions of the image planes are generated, the filtered images are segmented into object regions, and then a 3D coordinate is calculated for each object region. Two phantom studies of tracking performance were conducted. In the first study, an ablation catheter in a chest phantom was imaged as it was pulled along a 3D trajectory defined by a catheter sheath (10, 25, and 50 mm/s pullback speeds). SBDX tip tracking coordinates were compared to the 3D trajectory of the sheath as determined from a CT scan of the phantom after the registration of the SBDX and CT coordinate systems. In the second study, frame‐to‐frame tracking precision was measured for six different catheter configurations as a function of image noise level ( mean detected x‐ray fluence at isocenter).Results:During catheter pullbacks, the 3D distance between the tracked catheter tip and the sheath centerline was (mean standard deviation). The electrode to centerline distances were comparable to the diameter of the catheter tip (2.3 mm), the confining sheath (4 mm outside diameter), and the estimated SBDX‐to‐CT registration error . The tip position was localized for all 332 image frames analyzed and 83% of tracked positions were inside the 3D sheath volume derived from CT. The pullback speeds derived from the catheter trajectories were within 5% of the programed pullback speeds. The tracking precision of ablation and diagnostic catheter tips ranged from at the highest image fluence to at the lowest fluence. Tracking precision depended on image fluence, the size of the tracked catheter electrode, and the contrast of the electrode.Conclusions:High speed multiplanar tomosynthesis with an inverse geometry x‐ray fluoroscopy system enables 3D tracking of multiple high‐contrast objects at the rate of fluoroscopic imaging. The SBDX system is capable of tracking electrodes in standard cardiac catheters with approximately 1 mm accuracy and precision.