bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multilevel analysis of spatiotemporal association features for differentiation of tumor enhancement patterns in breast DCE‐MRI
Authors: Lee Sang Ho , Kim Jong Hyo , Cho Nariya , Park Jeong Seon , Yang Zepa , Jung Yun Sub , Moon Woo Kyung 
Published: July 2010

Purpose:Analyzing spatiotemporal enhancement patterns is an important task for the differential diagnosis of breast tumors in dynamic contrast‐enhanced MRI (DCE‐MRI), and yet remains challenging because of complexities in analyzing the time‐series of three‐dimensional image data. The authors propose a novel approach to breast MRI computer‐aided diagnosis (CAD) using a multilevel analysis of spatiotemporal association features for tumor enhancement patterns in DCE‐MRI.Methods:A database of 171 cases consisting of 111 malignant and 60 benign tumors was used. Time‐series contrast‐enhanced MR images were obtained from two different types of MR scanners and protocols. The images were first registered for motion compensation, and then tumor regions were segmented using a fuzzy c‐means clustering‐based method. Spatiotemporal associations of tumor enhancement patterns were analyzed at three levels: Mapping of pixelwise kinetic features within a tumor, extraction of spatial association features from kinetic feature maps, and extraction of kinetic association features at the spatial feature level. A total of 84 initial features were extracted. Predictable values of these features were evaluated with an area under the ROC curve, and were compared between the spatiotemporal association features and a subset of simple form features which do not reflect spatiotemporal association. Several optimized feature sets were identified among the spatiotemporal association feature group or among the simple feature group based on a feature ranking criterion using a support vector machine based recursive feature elimination algorithm. A least‐squares support vector machine (LS‐SVM) classifier was used for tumor differentiation and the performances were evaluated using a leave‐one‐out testing.Results:Predictable values of the extracted single features ranged in 0.52–0.75. By applying multilevel analysis strategy, the spatiotemporal association features became more informative in predicting tumor malignancy, which was shown by a statistical testing in ten spatiotemporal association features. By using a LS‐SVM classifier with the optimized second and third level feature set, the CAD scheme showed of 0.88 in classification of malignant and benign tumors. When this performance was compared to the same LS‐SVM classifier with simple form features which do not reflect spatiotemporal association, there was a statistically significant difference (0.88 vs 0.79, ), suggesting that the multilevel analysis strategy yields a significant performance improvement.Conclusions:The results suggest that the multilevel analysis strategy characterizes the complex tumor enhancement patterns effectively with the spatiotemporal association features, which in turn leads to an improved tumor differentiation. The proposed CAD scheme has a potential for improving diagnostic performance in breast DCE‐MRI.
Fundamental properties of the delivery of volumetric modulated arc therapy (VMAT) to static patient anatomy
Authors: Rangaraj D. , Oddiraju S. , Sun B. , Santanam L. , Yang D. , Goddu S. , Papiez L. 
Published: July 2010

Purpose:The primary goal of this article is to formulate volumetric modulated arc therapy (VMAT) delivery problem and study interdependence between several parameters (beam dose rate, gantry angular speed, and MLC leaf speed) in the delivery of VMAT treatment plan. The secondary aim is to provide delivery solution and prove optimality (minimal beam on time) of the solution. An additional goal of this study is to investigate alternative delivery approaches to VMAT (like constant beam dose rate and constant gantry angular speed delivery).Method:The problem of the VMAT delivery is formulated as a control problem with machine constraints. The relationships between parameters of arc therapy delivery are derived under the constraint of treatment plan invariance and limitations on delivery parameters. The nonuniqueness of arc therapy delivery solutions is revealed from these relations. The most efficient delivery of arc therapy is then formulated as optimal control problem and solved by geometrical methods. A computer program is developed to find numerical solutions for deliveries of specific VMAT plan.Results:Explicit examples of VMAT plan deliveries are computed and illustrated with graphical representations of the variability of delivery parameters. Comparison of delivery parameters with that of Varian's delivery are shown and discussed. Alternative delivery strategies such as constant gantry angular speed delivery and constant beam dose rate delivery are formulated and solutions are provided. The treatment times for all the delivery solutions are provided.Conclusion:The investigations derive and prove time optimal VMAT deliveries. The relationships between delivery parameters are determined. The optimal alternative delivery strategies are discussed.
Robust optimization based upon statistical theory
Authors: Sobotta B. , Söhn M. , Alber M. 
Published: July 2010

Purpose:Organ movement is still the biggest challenge in cancer treatment despite advances in online imaging. Due to the resulting geometric uncertainties, the delivered dose cannot be predicted precisely at treatment planning time. Consequently, all associated dose metrics (e.g., EUD and maxDose) are random variables with a patient‐specific probability distribution. The method that the authors propose makes these distributions the basis of the optimization and evaluation process.Methods:The authors start from a model of motion derived from patient‐specific imaging. On a multitude of geometry instances sampled from this model, a dose metric is evaluated. The resulting pdf of this dose metric is termed outcome distribution. The approach optimizes the shape of the outcome distribution based on its mean and variance. This is in contrast to the conventional optimization of a nominal value (e.g., PTV EUD) computed on a single geometry instance. The mean and variance allow for an estimate of the expected treatment outcome along with the residual uncertainty. Besides being applicable to the target, the proposed method also seamlessly includes the organs at risk (OARs).Results:The likelihood that a given value of a metric is reached in the treatment is predicted quantitatively. This information reveals potential hazards that may occur during the course of the treatment, thus helping the expert to find the right balance between the risk of insufficient normal tissue sparing and the risk of insufficient tumor control. By feeding this information to the optimizer, outcome distributions can be obtained where the probability of exceeding a given OAR maximum and that of falling short of a given target goal can be minimized simultaneously.Conclusions:The method is applicable to any source of residual motion uncertainty in treatment delivery. Any model that quantifies organ movement and deformation in terms of probability distributions can be used as basis for the algorithm. Thus, it can generate dose distributions that are robust against interfraction and intrafraction motion alike, effectively removing the need for indiscriminate safety margins.
Tissue typing using ultrasound RF time series: Experiments with animal tissue samples
Authors: Moradi Mehdi , Abolmaesumi Purang , Mousavi Parvin 
Published: July 2010

Purpose:This article provides experimental evidence to show that the time series of radiofrequency (RF) ultrasound data can be used for tissue typing. It also explores the tissue typing information in RF time series. Clinical and high‐frequency ultrasound are studied.Methods:Bovine liver, pig liver, bovine muscle, and chicken breast were used in the experiments as the animal tissue types. In the proposed approach, the authors record RF echo signals backscattered from tissue, while the imaging probe and the tissue are stationary. This sequence of recorded RF data generates a time series of RF echoes for each spatial sample of the RF signal. The authors use spectral and fractal features of ultrasound RF time series averaged over a region of interest, along with feedforward neural networks for tissue typing. The experiments are repeated at ultrasound frequency of 6.6 and also 55 MHz. The effects of increasing power and frame rate are studied.Results:The methodology yielded an average two‐class classification accuracy of 95.1% when ultrasound data were acquired at 6.6 MHz and 98.1% when data were collected with a high‐frequency probe operating at 55 MHz. In four‐class classification experiments, the recorded accuracies were 78.6% and 86.5% for low and high‐frequency ultrasound data, respectively. A set of 12 texture features extracted from the B‐mode image equivalents of the RF data yields an accuracy of only 77.5% in typing the analyzed tissues. An increase in acoustic power and the frame rate of ultrasound results in an improvement in classification results.Conclusions:The results of this study demonstrate that RF time series can be used for ultrasound‐based tissue typing. Further investigation of the underlying physical mechanisms is necessary.
Temporal resolution improvement in cardiac CT using PICCS (TRI‐PICCS): Performance studies
Authors: Tang Jie , Hsieh Jiang , Chen Guang‐Hong 
Published: July 2010

Purpose:The recently proposed prior image constrained compressed sensing (PICCS) method has been applied in cardiac MDCT to improve the temporal resolution by approximately a factor of 2, by using projection data acquired from half of the standard short‐scan angular range to reconstruct images with improved temporal resolution. The method was referred to as temporal resolution improvement using PICCS (TRI‐PICCS). The primary purpose of this article is to study (1) the relationship between the performance of the TRI‐PICCS algorithm and the angular range of projection data used in image reconstruction; (2) the relationship between the performance of the TRI‐PICCS algorithm and the motion orientations and motion patterns of moving objects; and (3) the relationship between the performance of the TRI‐PICCS algorithm and various heart rates.Methods:A hybrid phantom consisting of realistic cardiac anatomy and eight moving objects with known motion profiles to simulate coronary arteries was constructed by superimposing the analytical projection data of eight simulated moving vessels to thein vivo projection data from a cardiac MDCT scan. The motion profiles of the moving objects may independently change orientations, period, and amplitude. A prior image was reconstructed using a short‐scan filtered backprojection method from a gated short‐scan data set for each given motion profile. The TRI‐PICCS method was applied to improve temporal resolution for each configuration of given motion profiles of moving objects and given active angular range specified by the target temporal resolution. To quantitatively study the performance, figures of merit were introduced to quantify signal intensity deficit, image distortion, and residual motion artifacts, respectively.Results:The performance of the TRI‐PICCS method is the same when the projection data are taken from 100° to 120°. The performance of the TRI‐PICCS method is independent of location and motion orientations. The performance of the TRI‐PICCS method does not significantly degrade for heart rates up to 100 bpm with a gantry rotation speed of 350 ms per rotation.Conclusions:The TRI‐PICCS method can be used to systematically improve temporal resolution for MDCT cardiac imaging by a factor of 2–2.3 and the performance of the TRI‐PICCS method is insensitive to motion locations and motion orientations. The TRI‐PICCS method enables a single‐source MDCT scanner with 350 ms or faster gantry speed to scan patients with heart rates as high as 100 bpm.
A method to evaluate the dose increase in CT with iodinated contrast medium
Authors: Amato Ernesto , Lizio Domenico , Settineri Nicola , Di Pasquale Andrea , Salamone Ignazio , Pandolfo Ignazio 
Published: July 2010

Purpose:The objective of this study is to develop a method to calculate the relative dose increase when a computerized tomography scan (CT) is carried out after administration of iodinated contrast medium, with respect to the same CT scan in absence of contrast medium.Methods:A Monte Carlo simulation inGEANT4 of anthropomorphic neck and abdomen phantoms exposed to a simplified model of CT scanner was set up in order to calculate the increase of dose to thyroid, liver, spleen, kidneys, and pancreas as a function of the quantity of iodine accumulated; a series of experimental measurements of Hounsfield unit (HU) increment for known concentrations of iodinated contrast medium was carried out on a Siemens Sensation 16 CT scanner in order to obtain a relationship between the increment in HU and the relative dose increase in the organs studied. The authors applied such a method to calculate the average dose increase in three patients who underwent standard CT protocols consisting of one native scan in absence of contrast, followed by a contrast‐enhanced scan in venous phase.Results:The authors validated theirGEANT4 Monte Carlo simulation by comparing the resulting dose increases for iodine solutions in water with the ones presented in literature and with their experimental data obtained through a Roentgen therapy unit. The relative dose increases as a function of the iodine mass fraction accumulated and as a function of the Hounsfield unit increment between the contrast‐enhanced scan and the native scan are presented. The data shown for the three patients exhibit an average relative dose increase between 22% for liver and 74% for kidneys; also, spleen (34%), pancreas (28%), and thyroid (48%) show a remarkable average increase.Conclusions:The method developed allows a simple evaluation of the dose increase when iodinated contrast medium is used in CT scans, basing on the increment in Hounsfield units observed on the patients’ organs. Since many clinical protocols employ multiple scans at different circulatory phases after administration of contrast medium, such a method can be useful to evaluate the total dose to the patient, also in view of potential clinical protocol optimizations.
Influence of skull conductivity perturbations on EEG dipole source analysis
Authors: Chen Fangmin , Hallez Hans , Staelens Steven 
Published: July 2010

Purpose:Electroencephalogram (EEG) source analysis is a noninvasive technique used in the presurgical of epilepsy. In this study, the dipole location and orientation errors due to skull conductivity perturbations were investigated in two groups of three‐dimensional head models: A spherical head model and a realistic head model.Methods:In each group, the head model had a brain‐to‐skull conductivity ratio within the range of 10–40. Solving the forward problem in the head model with skull conductivity perturbations along with the inverse problem in the baseline head model with permitted the derivation of the dipole estimation errors.Results:Perturbations in the skull conductivity generated dipole location and orientation errors: The larger the perturbations, the larger the errors and the error ranges. The dipole orientation error due to skull conductivity perturbations was not great (maximal mean of) in this study, but the dipole location error was notable (maximal mean of ).Conclusions:Therefore, the influence of skull conductivity perturbations on EEG dipole source analysis cannot be neglected. This study suggests that it is necessary to measure the skull conductivity of the individual patients in order to achieve accurate EEG source analysis.
Dosimetric characteristics of a single use MOSFET dosimeter for in vivo dosimetry in proton therapy
Authors: Cheng Chee‐Wai , Wolanski Mark , Zhao Q. , Fanelli Leia , Gautam Archana , Pack Daniel , Das Indra J. 
Published: July 2010

Purpose:Entrance dose (or skin dose) is an important part of patient quality assurance in external beam radiation therapy. However, entrance dose verification in proton beam is not routinely performed. In this study, the OneDose single use MOSFET detector system forin vivo dosimetry measurement in proton therapy is investigated.Methods:Using a solid water phantom, several fundamental dosimetric characteristics of the OneDose system are studied with a proton beam: The reproducibility (consistency) of the dosimeter, the linearity with dose and dose rate, energy dependence, directional dependence, LET dependence, and fading (delay readout with time) is studied.Results:OneDose detectors show dose and dose rate linearity but exhibit pronounced energy dependence at depth and a large variation in dose response with LET. On the other hand, the detector response remain relatively constant (within 3%) at surface over a wide range of energies. There is also a slight angular dependence (about 2%) up to 60° angle of incidence. However, detector orientation such that incidence along the long axis of the detector should be avoided as the proton beam will have to traverse a large amount of the copper backing. Since mostin vivo dosimetry involves entrance dose measurement, the OneDose at surface appears to be well suited for such application. OneDose exhibits small intrabatch variation ( at one SD) indicating that it is only necessary to calibration a few detectors from each batch. The interbatch variation is generally within 3%.Conclusions:The small detector size and its relatively flexible design of OneDose allow dose measurement to be performed on a curved surface or in small cavities that is otherwise difficult with the conventional diode detectors. The slight drawback in its angular dependence can be easily handled by angular dependence table. However, since OneDose is a single use detector, the intrabatch consistency must be verified before the remaining detectors from the same batch could be used forin vivo dosimetry. It is advisable that the detectors from the same batch be taken for the same application to reduce the dosimetric uncertainty. For detectors from different batches, interbatch consistency should also be verified to obtain reliable results. OneDose provides an opportunity to measure in vivo dose with proton beam within acceptable clinical criterion of ±(5.0%–6.5%).
Technical note: Optimization for improved tube‐loading efficiency in the dual‐energy computed tomography coupled with balanced filter method
Authors: Saito Masatoshi 
Published: July 2010

Purpose:This article describes the spectral optimization of dual‐energy computed tomography using balanced filters (bf‐DECT) to reduce the tube loadings and dose by dedicating to the acquisition of electron density information, which is essential for treatment planning in radiotherapy.Methods:For the spectral optimization of bf‐DECT, the author calculated the beam‐hardening error and air kerma required to achieve a desired noise level in an electron density image of a 50‐cm‐diameter cylindrical water phantom. The calculation enables the selection of beam parameters such as tube voltage, balanced filter material, and its thickness.Results:The optimal combination of tube voltages was 80 kV/140 kV in conjunction with Tb/Hf and Bi/Mo filter pairs; this combination agrees with that obtained in a previous study [M. Saito, “Spectral optimization for measuring electron density by the dual‐energy computed tomography coupled with balanced filter method,” Med. Phys. 36, 3631–3642 (2009)], although the thicknesses of the filters that yielded a minimum tube output were slightly different from those obtained in the previous study. The resultant tube loading of a low‐energy scan of the present bf‐DECT significantly decreased from 57.5 to 4.5 times that of a high‐energy scan for conventional DECT. Furthermore, the air kerma of bf‐DECT could be reduced to less than that of conventional DECT, while obtaining the same figure of merit for the measurement of electron density and effective atomic number.Conclusions:The tube‐loading and dose efficiencies of bf‐DECT were considerably improved by sacrificing the quality of the noise level in the images of effective atomic number.
Elevated D-dimers are also a marker of underlying malignancy and increased mortality in the absence of venous thromboembolism
Authors: Knowlson L , Bacchu S , Paneesha S , McManus A , Randall K , Rose P 
Published: July 2010

BackgroundD-dimers are used in conjunction with clinical probability scores in the assessment of venous thromboembolism (VTE), and they are elevated in other conditions, including malignancy, infection and arrhythmias. High levels of D-dimers in VTE are associated with adverse outcomes, including increased mortality. Their significance in patients without VTE has not previously been established.AimsTo establish the clinical significance of elevated D-dimer levels in patients without VTE.MethodsThis prospective study included 2263 patient episodes of suspected deep vein thrombosis, which were excluded radiologically. Patients were followed up for survival and adverse events for a median of 22 months.ResultsD-dimer levels greater than 4000 ng FEU/ml (4.9% of patients), and greater than 8000 ng FEU/ml (1.8%) were associated with a reduced overall survival. D-dimer levels greater than 8000 ng FEU/ml and age over 60 years were independent poor prognostic factors for overall survival (p<0.001.). D-dimer levels greater than 8000 ng FEU/ml were associated with an increased incidence of malignancy (p=0.003).ConclusionsThis study provides evidence of very high D-dimer levels in patients with cancer who do not have VTE. This suggests that elevated D-dimer levels in patients with VTE and malignancy are not solely due to presence of thrombus. High D-dimer levels in malignancy are likely to reflect the biology of the underlying tumour, with higher levels observed in breast, prostate and bowel cancers.
Comparative validation of the SP6 antibody to Ki67 in breast cancer
Authors: Zabaglo Lila , Salter Janine , Anderson Helen , Quinn Emma , Hills Margaret , Detre Simone , A'Hern Roger , Dowsett Mitch 
Published: July 2010

AimTo compare SP6 and MIB1 antibodies for Ki67 staining in breast cancer.BackgroundImmunohistochemical detection of Ki67 has been widely used to assess the proliferative fraction in breast cancer. Ki67 is used prognostically and is the primary end-point for some presurgical trials. MIB1 has been the preferred antibody, but SP6 has become available, with apparently improved performance. The importance of Ki67 led us to systematically compare SP6 with MIB1.MethodsTwo sets of tissue microarrays were used. These were constructed from formalin-fixed paraffin-embedded breast cancers: (i) 177 cancers with data on response to an aromatase inhibitor for advanced disease (cohort 1); (ii) 200 mainly oestrogen-receptor-positive cancers without response data (cohort 2). Twenty-eight pairs of core-cut biopsies taken before and after aromatase inhibitor treatment were also assessed (cohort 3). Stained sections were examined either visually or by using an image analysis system (Ariol).ResultsThere was a strong correlation between the two antibodies in all cohorts of samples scored visually (cohort 1: n=161, r=0.93, p<0.0001; cohort 2: n=194, r=0.84, p<0.0001; cohort 3: n=54, r=0.89, p<0.0001). Correlation between visual and Ariol scores was markedly better with the SP6 antibody (r=0.71 and r=0.88 for MIB1 and SP6, respectively). Ki67 related similarly with time-to-treatment failure with the two antibodies (cohort 1). Changes in Ki67 values with the two antibodies after 2 weeks of aromatase inhibitor treatment also correlated strongly.ConclusionsSP6 and MIB1 provide highly comparable measures of Ki67 that predict progression of advanced disease similarly. SP6 is substantially better suited than MIB1 to image analysis.