Fully automatic X-ray image segmentation via joint estimation of image displacements.

We propose a new method for fully-automatic landmark detection and shape segmentation in X-ray images. Our algorithm works by estimating the displacements from image patches to the (unknown) landmark positions and then integrating them via voting. The fundamental contribution is that, we jointly estimate the displacements from all patches to multiple landmarks together, by considering not only the training data but also geometric constraints on the test image. The various constraints constitute a convex objective function that can be solved efficiently. Validated on three challenging datasets, our method achieves high accuracy in landmark detection, and, combined with statistical shape model, gives a better performance in shape segmentation compared to the state-of-the-art methods.

Essential spectrum of systems of singular differential equations

In this paper we develop a new method to determine the essential spectrum of coupled systems of singular differential equations. Applications to problems from magnetohydrodynamics and astrophysics are given.

Automatic X-ray landmark detection and shape segmentation via data-driven joint estimation of image displacements

In this paper, we propose a new method for fully-automatic landmark detection and shape segmentation in X-ray images. To detect landmarks, we estimate the displacements from some randomly sampled image patches to the (unknown) landmark positions, and then we integrate these predictions via a voting scheme. Our key contribution is a new algorithm for estimating these displacements. Different from other methods where each image patch independently predicts its displacement, we jointly estimate the displacements from all patches together in a data driven way, by considering not only the training data but also geometric constraints on the test image. The displacements estimation is formulated as a convex optimization problem that can be solved efficiently. Finally, we use the sparse shape composition model as the a priori information to regularize the landmark positions and thus generate the segmented shape contour. We validate our method on X-ray image datasets of three different anatomical structures: complete femur, proximal femur and pelvis. Experiments show that our method is accurate and robust in landmark detection, and, combined with the shape model, gives a better or comparable performance in shape segmentation compared to state-of-the art methods. Finally, a preliminary study using CT data shows the extensibility of our method to 3D data.

Synergistic action of image-guided radiotherapy and androgen deprivation therapy.

The combined use of androgen deprivation therapy (ADT) and image-guided radiotherapy (IGRT) can improve overall survival in aggressive, localized prostate cancer. However, owing to the adverse effects of prolonged ADT, it is imperative to identify the patients who would benefit from this combined-modality therapy relative to the use of IGRT alone. Opportunities exist for more personalized approaches in treating aggressive, locally advanced prostate cancer. Biomarkers--such as disseminated tumour cells, circulating tumour cells, genomic signatures and molecular imaging techniques--could identify the patients who are at greatest risk for systemic metastases and who would benefit from the addition of systemic ADT. By contrast, when biomarkers of systemic disease are not present, treatment could proceed using local IGRT alone. The choice of drug, treatment duration and timing of ADT relative to IGRT could be predicated on these personalized approaches to prostate cancer medicine. These novel treatment intensification and reduction strategies could result in improved prostate-cancer-specific survival and overall survival, without incurring the added expense of metabolic syndrome and other adverse effects of ADT in all patients.

Evaluation of a portable image overlay projector for the visualisation of surgical navigation data: phantom studies

Presenting visual feedback for image-guided surgery on a monitor requires the surgeon to perform time-consuming comparisons and diversion of sight and attention away from the patient. Deficiencies in previously developed augmented reality systems for image-guided surgery have, however, prevented the general acceptance of any one technique as a viable alternative to monitor displays. This work presents an evaluation of the feasibility and versatility of a novel augmented reality approach for the visualisation of surgical planning and navigation data. The approach, which utilises a portable image overlay device, was evaluated during integration into existing surgical navigation systems and during application within simulated navigated surgery scenarios.

Image registration for triggered and non-triggered DTI of the human kidney: Reduced variability of diffusion parameter estimation

BACKGROUND: To investigate if non-rigid image-registration reduces motion artifacts in triggered and non-triggered diffusion tensor imaging (DTI) of native kidneys. A secondary aim was to determine, if improvements through registration allow for omitting respiratory-triggering. METHODS: Twenty volunteers underwent coronal DTI of the kidneys with nine b-values (10-700 s/mm2 ) at 3 Tesla. Image-registration was performed using a multimodal nonrigid registration algorithm. Data processing yielded the apparent diffusion coefficient (ADC), the contribution of perfusion (FP ), and the fractional anisotropy (FA). For comparison of the data stability, the root mean square error (RMSE) of the fitting and the standard deviations within the regions of interest (SDROI ) were evaluated. RESULTS: RMSEs decreased significantly after registration for triggered and also for non-triggered scans (P < 0.05). SDROI for ADC, FA, and FP were significantly lower after registration in both medulla and cortex of triggered scans (P < 0.01). Similarly the SDROI of FA and FP decreased significantly in non-triggered scans after registration (P < 0.05). RMSEs were significantly lower in triggered than in non-triggered scans, both with and without registration (P < 0.05). CONCLUSION: Respiratory motion correction by registration of individual echo-planar images leads to clearly reduced signal variations in renal DTI for both triggered and particularly non-triggered scans. Secondarily, the results suggest that respiratory-triggering still seems advantageous.J. Magn. Reson. Imaging 2014. (c) 2014 Wiley Periodicals, Inc.

The influence of body temperature on image contrast in post mortem MRI

To assess the temperature dependency of tissue contrast on post mortem magnetic resonance (PMMR) images both objectively and subjectively; and to visually demonstrate the changes of image contrast at various temperatures.

Patient exposure and image quality of low-dose pulmonary computed tomography angiography: comparison of 100- and 80-kVp protocols

OBJECTIVE: Measures to reduce radiation exposure and injected iodine mass are becoming more important with the widespread and often repetitive use of pulmonary CT angiography (CTA) in patients with suspected pulmonary embolism. In this retrospective study, we analyzed the capability of 2 low-kilovoltage CTA-protocols to achieve these goals. MATERIALS AND METHODS: Ninety patients weighing less than 100 kg were examined by a pulmonary CTA protocol using either 100 kVp (group A) or 80 kVp (group B). Volume and flow rate of contrast medium were reduced in group B (75 mL at 3 mL/s) compared with group A (100 mL at 4 mL/s). Attenuation was measured in the central and peripheral pulmonary arteries, and the contrast-to-noise ratios (CNR) were calculated. Entrance skin dose was estimated by measuring the surface dose in an ovoid-cylindrical polymethyl methacrylate chest phantom with 2 various dimensions corresponding to the range of chest diameters in our patients. Quantitative image parameters, estimated effective dose, and skin dose in both groups were compared by the t test. Arterial enhancement, noise, and overall quality were independently assessed by 3 radiologists, and results were compared between the groups using nonparametric tests. RESULTS: Mean attenuation in the pulmonary arteries in group B (427.6 +/- 116 HU) was significantly higher than in group A (342.1 +/- 87.7 HU; P < 0.001), whereas CNR showed no difference (group A, 20.6 +/- 7.3 and group B, 22.2 +/- 7.1; P = 0.302). Effective dose was lower by more than 40% with 80 kVp (1.68 +/- 0.23 mSv) compared with 100 kVp (2.87 +/- 0.88 mSv) (P < 0.001). Surface dose was significantly lower at 80 kVp compared with 100 kVp at both phantom dimensions (2.75 vs. 3.22 mGy; P = 0.027 and 2.22 vs. 2.73 mGy; P = 0.005, respectively). Image quality did not differ significantly between the groups (P = 0.151). CONCLUSIONS: Using 80 kVp in pulmonary CTA permits reduced patient exposure by 40% and CM volume by 25% compared with 100 kVp without deterioration of image quality in patients weighing less than 100 kg.

Application and assessment of a robust elastic motion correction algorithm to dynamic MRI

The purpose of this study was to assess the performance of a new motion correction algorithm. Twenty-five dynamic MR mammography (MRM) data sets and 25 contrast-enhanced three-dimensional peripheral MR angiographic (MRA) data sets which were affected by patient motion of varying severeness were selected retrospectively from routine examinations. Anonymized data were registered by a new experimental elastic motion correction algorithm. The algorithm works by computing a similarity measure for the two volumes that takes into account expected signal changes due to the presence of a contrast agent while penalizing other signal changes caused by patient motion. A conjugate gradient method is used to find the best possible set of motion parameters that maximizes the similarity measures across the entire volume. Images before and after correction were visually evaluated and scored by experienced radiologists with respect to reduction of motion, improvement of image quality, disappearance of existing lesions or creation of artifactual lesions. It was found that the correction improves image quality (76% for MRM and 96% for MRA) and diagnosability (60% for MRM and 96% for MRA).

Estimation of tool pose based on force-density correlation during robotic drilling

The application of image-guided systems with or without support by surgical robots relies on the accuracy of the navigation process, including patient-to-image registration. The surgeon must carry out the procedure based on the information provided by the navigation system, usually without being able to verify its correctness beyond visual inspection. Misleading surrogate parameters such as the fiducial registration error are often used to describe the success of the registration process, while a lack of methods describing the effects of navigation errors, such as those caused by tracking or calibration, may prevent the application of image guidance in certain accuracy-critical interventions. During minimally invasive mastoidectomy for cochlear implantation, a direct tunnel is drilled from the outside of the mastoid to a target on the cochlea based on registration using landmarks solely on the surface of the skull. Using this methodology, it is impossible to detect if the drill is advancing in the correct direction and that injury of the facial nerve will be avoided. To overcome this problem, a tool localization method based on drilling process information is proposed. The algorithm estimates the pose of a robot-guided surgical tool during a drilling task based on the correlation of the observed axial drilling force and the heterogeneous bone density in the mastoid extracted from 3-D image data. We present here one possible implementation of this method tested on ten tunnels drilled into three human cadaver specimens where an average tool localization accuracy of 0.29 mm was observed.

Angiographic C-arm CT- versus MDCT-guided stereotactic punctures of liver lesions: nonrigid phantom study

OBJECTIVE Angiographic C-arm CT may allow performing percutaneous stereotactic tumor ablations in the interventional radiology suite. Our purpose was to evaluate the accuracy of using C-arm CT for single and multimodality image fusions and to compare the targeting accuracy of liver lesions with the reference standard of MDCT. MATERIALS AND METHODS C-arm CT and MDCT scans were obtained of a nonrigid rapid prototyping liver phantom containing five 1-mm targets that were placed under skin-simulating deformable plastic foam. Target registration errors of image fusion were evaluated for single-modality and multimodality image fusions. A navigation system and stereotactic aiming device were used to evaluate target positioning errors on postinterventional scans with the needles in place fused with the C-arm CT or MDCT planning images. RESULTS Target registration error of the image fusion showed no significant difference (p > 0.05) between both modalities. In five series with a total of 25 punctures for each modality, the lateral target positioning error (i.e., the lateral distance between the needle tip and the planned trajectory) was similar for C-arm CT (mean [± SD], 1.6 ± 0.6 mm) and MDCT (1.82 ± .97 mm) (p = 0.33). CONCLUSION In a nonrigid liver phantom, angiographic C-arm CT may provide similar image fusion accuracy for comparison of intra- and postprocedure control images with the planning images and enables stereotactic targeting accuracy similar to that of MDCT.

A comparative study of different in vitro lung cell culture systems to assess the most beneficial tool for screening the potential adverse effects of carbon nanotubes

To determine the potential inhalatory risk posed by carbon nanotubes (CNTs), a tier-based approach beginning with an in vitro assessment must be adopted. The purpose of this study therefore was to compare 4 commonly used in vitro systems of the human lung (human blood monocyte-derived macrophages [MDM] and monocyte-derived dendritic cells [MDDC], 16HBE14o- epithelial cells, and a sophisticated triple cell co-culture model [TCC-C]) via assessment of the biological impact of different CNTs (single-walled CNTs [SWCNTs] and multiwalled CNTs [MWCNTs]) over 24h. No significant cytotoxicity was observed with any of the cell types tested, although a significant (p < .05), dose-dependent increase in tumor necrosis factor (TNF)-α following SWCNT and MWCNT exposure at concentrations up to 0.02mg/ml to MDM, MDDC, and the TCC-C was found. The concentration of TNF-α released by the MDM and MDDC was significantly higher (p < .05) than the TCC-C. Significant increases (p < .05) in interleukin (IL)-8 were also found for both 16HBE14o- epithelial cells and the TCC-C after SWCNTs and MWCNTs exposure up to 0.02mg/ml. The TCC-C, however, elicited a significantly (p < .05) higher IL-8 release than the epithelial cells. The oxidative potential of both SWCNTs and MWCNTs (0.005-0.02mg/ml) measured by reduced glutathione (GSH) content showed a significant difference (p < .05) between each monoculture and the TCC-C. It was concluded that because only the co-culture system could assess each endpoint adequately, that, in comparison with monoculture systems, multicellular systems that take into consideration important cell type-to-cell type interactions could be used as predictive in vitro screening tools for determining the potential deleterious effects associated with CNTs.

Development, implementation, and evaluation of a structured reporting web tool for abdominal aortic aneurysms

BACKGROUND The majority of radiological reports are lacking a standard structure. Even within a specialized area of radiology, each report has its individual structure with regards to details and order, often containing too much of non-relevant information the referring physician is not interested in. For gathering relevant clinical key parameters in an efficient way or to support long-term therapy monitoring, structured reporting might be advantageous. OBJECTIVE Despite of new technologies in medical information systems, medical reporting is still not dynamic. To improve the quality of communication in radiology reports, a new structured reporting system was developed for abdominal aortic aneurysms (AAA), intended to enhance professional communication by providing the pertinent clinical information in a predefined standard. METHODS Actual state analysis was performed within the departments of radiology and vascular surgery by developing a Technology Acceptance Model. The SWOT (strengths, weaknesses, opportunities, and threats) analysis focused on optimization of the radiology reporting of patients with AAA. Definition of clinical parameters was achieved by interviewing experienced clinicians in radiology and vascular surgery. For evaluation, a focus group (4 radiologists) looked at the reports of 16 patients. The usability and reliability of the method was validated in a real-world test environment in the field of radiology. RESULTS A Web-based application for radiological "structured reporting" (SR) was successfully standardized for AAA. Its organization comprises three main categories: characteristics of pathology and adjacent anatomy, measurements, and additional findings. Using different graphical widgets (eg, drop-down menus) in each category facilitate predefined data entries. Measurement parameters shown in a diagram can be defined for clinical monitoring and be adducted for quick adjudications. Figures for optional use to guide and standardize the reporting are embedded. Analysis of variance shows decreased average time required with SR to obtain a radiological report compared to free-text reporting (P=.0001). Questionnaire responses confirm a high acceptance rate by the user. CONCLUSIONS The new SR system may support efficient radiological reporting for initial diagnosis and follow-up for AAA. Perceived advantages of our SR platform are ease of use, which may lead to more accurate decision support. The new system is open to communicate not only with clinical partners but also with Radiology Information and Hospital Information Systems.

The Forensic Reference Phantom-a new tool for quality assurance of attenuation measurements in forensic radiology

Introduction The purpose of this paper is to present the technical specifications of the Forensic Reference Phantom (FRP), to test its behavior relative to organic test materials, and discuss potential applications of the phantom in forensic radiology. Materials and method The FRP prototype is made of synthetic materials designed to simulate the computed tomography (CT) attenuation of water. It has six bore holes that accommodate multiuse containers. These containers were filled with test materials and scanned at 80 kVp, 120 kVp, and 140 kVp. X-ray attenuation was measured by two readers. Intra- and inter-reader reliability was assessed using the intra-class correlation coefficient (ICC). Significance levels between mean CT numbers at 80 kVp, 120 kVp, and 140 kVp were assessed with the Friedman-test. The T-test was used to assess significance levels between the FRP and water. Results Overall mean CT numbers ranged from −3.0–3.7HU for the FRP; −1000.3–−993.5HU for air; −157.7– −108.1HU for oil; 35.5–42.0HU for musle tissue; and 1301.5–2354.8HU for cortical bone. Inter-reader and intra-reader reliability were excellent (ICC>0.994; and ICC=0.999 respectively). CT numbers were significantly different at different energy levels. There was no significant difference between the attenuation of the FRP and water. Conclusions The FRP is a new tool for quality assurance and research in forensic radiology. The mean CT attenuation of the FRP is equivalent to water. The phantom can be scanned during routine post-mortem CT to assess the composition of unidentified objects. In addition, the FRP may be used to investigate new imaging algorithms and scan protocols in forensic radiology.