Three-phase 18F-fluorocholine PET/CT in the evaluation of prostate cancer recurrence.

AIM: Contribution of 3-phase 18F-fluorocholine PET/CT in suspected prostate cancer recurrence at early rise of PSA. PATIENTS, METHODS: Retrospective analysis was performed in 47 patients after initial treatment with radiotherapy (n=30) or surgery (n=17). Following CT, 10 minutes list-mode PET acquisition was done over the prostate bed after injection of 300 MBq of 18F-fluorocholine. Three timeframes of 3 minutes each were reconstructed for analysis. All patients underwent subsequent whole body PET/CT. Delayed pelvic PET/CT was obtained in 36 patients. PET/CT was interpreted visually by two observers and SUVmax determined for suspicious lesions. Biopsies were obtained from 13 patients. RESULTS: Biopsies confirmed the presence of cancer in 11 of 13 patients with positive PET for a total of 15 local recurrences in which average SUVmax increased during 14 minutes post injection and marginally decreased in delayed scanning. Conversely inguinal lymph nodes with mild to moderate metabolic activity on PET showed a clearly different pattern with decreasing SUVmax on dynamic images. Three-phase PET/CT contributed to the diagnostic assessment of 10 of 47 patients with biological evidence of recurrence of cancer. It notably allowed the discrimination of confounding blood pool or urinary activity from suspicious hyperactivities. PET/CT was positive in all patients with PSA>or=2 ng/ml (n=34) and in 4/13 patients presenting PSA values<2 ng/ml. CONCLUSION: 18F-fluorocholine 3-phase PET/CT showed a progressively increasing SUVmax in biopsy confirmed cancer lesions up to 14 minutes post injection while decreasing in inguinal lymph nodes interpreted as benign. Furthermore, it was very useful in differentiating local recurrences from confounding blood pool and urinary activity.

Decision-making in lumbar spinal stenosis: A survey on the influence of the morphology of the dural sac.

Surgical decision-making in lumbar spinal stenosis involves assessment of clinical parameters and the severity of the radiological stenosis. We suspected that surgeons based surgical decisions more on dural sac cross-sectional area (DSCA) than on the morphology of the dural sac. We carried out a survey among members of three European spine societies. The axial T2-weighted MR images from ten patients with varying degrees of DSCA and morphological grades according to the recently described morphological classification of lumbar spinal stenosis, with DSCA values disclosed in half the assessed images, were used for evaluation. We provided a clinical scenario to accompany the images, which were shown to 142 responding physicians, mainly orthopaedic surgeons but also some neurosurgeons and others directly involved in treating patients with spinal disorders. As the primary outcome we used the number of respondents who would proceed to surgery for a given DSCA or morphological grade. Substantial agreement among the respondents was observed, with severe or extreme stenosis as defined by the morphological grade leading to surgery. This decision was not dependent on the number of years in practice, medical density or specialty. Disclosing the DSCA did not alter operative decision-making. In all, 40 respondents (29%) had prior knowledge of the morphological grading system, but their responses showed no difference from those who had not. This study suggests that the participants were less influenced by DSCA than by the morphological appearance of the dural sac. Classifying lumbar spinal stenosis according to morphology rather than surface measurements appears to be consistent with current clinical practice.

Decision-Making in Social Enterprises: Exploring the Link between Employee Participation and Organizational Commitment

This article studies the influence of the procedural justice resulting from participation in decision-making on employees' affective commitment in social enterprises. It also examines whether any potential link between participation and commitment is due to social exchange, as is the case with for-profit companies. The study is based on data from employees of French work integration social enterprises. The results confirm the positive relationship between procedural justice and affective commitment and the mediating role of perceived organizational support and leader-member exchanges. Managerial recommendations are then given to best maintain or increase employees' involvement in the decision-making processes of social enterprises.

The use of contrast-enhanced MRI angiography for planning interventional catheterization

Background: Interventional catheterization is being increasingly used for relief of residual lesions in congenital heart disease. Exact anatomical imaging is crucial in the planning of an intervention. This can be provided non-invasively and without radiation by contrast-enhanced MR angiography (CEMRA). Aim: To evaluate the accuracy of the measurements of the vessels obtained by CEMRA in comparison to those obtained by conventional X-ray angiography (CXA). Methods: Retrospective blinded measurement of the diameters of aorta and pulmonary arteries on the CEMRA and CXA images, in the same locations. Comparison of the results by Pearson correlation and by calculating the limits of agreement. Results: Twenty-one children with congenital heart disease, mean age 5.6 +- 5.2 years, weight 21.1 +- 18.4 kg, underwent CEMRA and catheterization for assessment or treatment of a residual lesion. The time interval between the CEMRA and the CXA examination was 2.6 +- 2.3 months. A total of 98 measurements, 37 of the aorta and 61 of the pulmonary arteries were performed on the images obtained by each technique. The correlation between CEMRA and CXA measurements was excellent, r = 0.97, p < 0.0001. The mean difference between the two techniques was 0.018 +- 1.1mm; the limits of agreement were -2.14 and +2.18mm. Similar agreement was found for measures of the aorta (r +- 0.97, mean difference 0.20 = 1.08 mm) and of the pulmonary arteries (r +- 0.97, mean difference 0.048 = 0.89 mm). Conclusions: CEMRA provide accurate quantitative anatomical information, which highly agrees with CXA data, and can therefore be used for planning interventional catheterization.

Quality assessment of cardiovascular magnetic resonance in the setting of the European CMR registry: description and validation of standardized criteria.

BACKGROUND: Cardiovascular magnetic resonance (CMR) has become an important diagnostic imaging modality in cardiovascular medicine. However, insufficient image quality may compromise its diagnostic accuracy. We aimed to describe and validate standardized criteria to evaluate a) cine steady-state free precession (SSFP), b) late gadolinium enhancement (LGE), and c) stress first-pass perfusion images. These criteria will serve for quality assessment in the setting of the Euro-CMR registry. METHODS: Thirty-five qualitative criteria were defined (scores 0-3) with lower scores indicating better image quality. In addition, quantitative parameters were measured yielding 2 additional quality criteria, i.e. signal-to-noise ratio (SNR) of non-infarcted myocardium (as a measure of correct signal nulling of healthy myocardium) for LGE and % signal increase during contrast medium first-pass for perfusion images. These qualitative and quantitative criteria were assessed in a total of 90 patients (60 patients scanned at our own institution at 1.5T (n=30) and 3T (n=30) and in 30 patients randomly chosen from the Euro-CMR registry examined at 1.5T). Analyses were performed by 2 SCMR level-3 experts, 1 trained study nurse, and 1 trained medical student. RESULTS: The global quality score was 6.7±4.6 (n=90, mean of 4 observers, maximum possible score 64), range 6.4-6.9 (p=0.76 between observers). It ranged from 4.0-4.3 for 1.5T (p=0.96 between observers), from 5.9-6.9 for 3T (p=0.33 between observers), and from 8.6-10.3 for the Euro-CMR cases (p=0.40 between observers). The inter- (n=4) and intra-observer (n=2) agreement for the global quality score, i.e. the percentage of assignments to the same quality tertile ranged from 80% to 88% and from 90% to 98%, respectively. The agreement for the quantitative assessment for LGE images (scores 0-2 for SNR <2, 2-5, >5, respectively) ranged from 78-84% for the entire population, and 70-93% at 1.5T, 64-88% at 3T, and 72-90% for the Euro-CMR cases. The agreement for perfusion images (scores 0-2 for %SI increase >200%, 100%-200%,<100%, respectively) ranged from 81-91% for the entire population, and 76-100% at 1.5T, 67-96% at 3T, and 62-90% for the Euro-CMR registry cases. The intra-class correlation coefficient for the global quality score was 0.83. CONCLUSIONS: The described criteria for the assessment of CMR image quality are robust with a good inter- and intra-observer agreement. Further research is needed to define the impact of image quality on the diagnostic and prognostic yield of CMR studies.

Atrial septal pacing for the termination of atrial fibrillation: study in a biophysical model of human atria.

AIMS: While successful termination by pacing of organized atrial tachycardias has been observed in patients, single site rapid pacing has not yet led to conclusive results for the termination of atrial fibrillation (AF). The purpose of this study was to evaluate a novel atrial septal pacing algorithm for the termination of AF in a biophysical model of the human atria. METHODS AND RESULTS: Sustained AF was generated in a model based on human magnetic resonance images and membrane kinetics. Rapid pacing was applied from the septal area following a dual-stage scheme: (i) rapid pacing for 10-30 s at pacing intervals 62-70% of AF cycle length (AFCL), (ii) slow pacing for 1.5 s at 180% AFCL, initiated by a single stimulus at 130% AFCL. Atrial fibrillation termination success rates were computed. A mean success rate for AF termination of 10.2% was obtained for rapid septal pacing only. The addition of the slow pacing phase increased this rate to 20.2%. At an optimal pacing cycle length (64% AFCL) up to 29% of AF termination was observed. CONCLUSION: The proposed septal pacing algorithm could suppress AF reentries in a more robust way than classical single site rapid pacing. Experimental studies are now needed to determine whether similar termination mechanisms and rates can be observed in animals or humans, and in which types of AF this pacing strategy might be most effective.

Waveform inversion of crosshole georadar data: influence of source wavelet variability and the suitability of a single wavelet assumption

Waveform-based tomographic imaging of crosshole georadar data is a powerful method to investigate the shallow subsurface because of its ability to provide images of electrical properties in near-surface environments with unprecedented spatial resolution. A critical issue with waveform inversion is the a priori unknown source signal. Indeed, the estimation of the source pulse is notoriously difficult but essential for the effective application of this method. Here, we explore the viability and robustness of a recently proposed deconvolution-based procedure to estimate the source pulse during waveform inversion of crosshole georadar data, where changes in wavelet shape with location as a result of varying near-field conditions and differences in antenna coupling may be significant. Specifically, we examine whether a single, average estimated source current function can adequately represent the pulses radiated at all transmitter locations during a crosshole georadar survey, or whether a separate source wavelet estimation should be performed for each transmitter gather. Tests with synthetic and field data indicate that remarkably good tomographic reconstructions can be obtained using a single estimated source pulse when moderate to strong variability exists in the true source signal with antenna location. Only in the case of very strong variability in the true source pulse are tomographic reconstructions clearly improved by estimating a different source wavelet for each transmitter location.

Observational study on the consumption of recreational drugs and alcohol by Swiss travelers.

BACKGROUND: Studies carried out on specific travelers' groups such as students describe an increase in the consumption of alcohol and drugs during travel and vacation time. The present study investigates the risk behaviors (alcohol and drugs) in a general adult population in Switzerland travelling abroad who visited a travel clinic before departure. METHODS: This retrospective study was conducted in a travel clinic between January 2006 and December 2008. 14,496 patients came to the clinic for a pre-travel consultation. 3,537 of them answered a questionnaire about their life habits in Switzerland and during their last trip. The only exclusion criterion was an age inferior to 18 years old.The consumption habits of drugs and at-risk alcohol intake (8 standard drinks (SD) per week for women and 15 SD for men) was analyzed according to gender, sex, destination and profession. Predictors of adopting a risky behavior between habits in Switzerland and during their previous trip were also analyzed. RESULTS: 7% (229/3477) of participants declared having at-risk alcohol consumption in Switzerland and 14% (473/3275 [95% CI 13-16]) during their trip. 9% (332/3527) of the participants used drugs in Switzerland and 5% (178/3481) during their trip. Risk factors for at-risk alcohol consumption during a trip were: at-risk alcohol consumption in Switzerland (OR 31[95% CI 21-45]), smoking (1.7 [95% CI 1-2]), use of drugs in Switzerland (OR 2.2 [95% CI 2-3]), leisure travel (OR 1.6 [95% CI 1-2]) and managerial professions (OR 1.8 [95% CI 1-3]). Risk factors for the use of drugs during a trip were: alcohol consumption in Switzerland (OR 2.1 [95% CI 1-4]), smoking (OR 1.9 [95% CI 1-3]), and use of drugs in Switzerland (OR 29.7 [95% CI 19-45]). CONCLUSIONS: At-risk alcohol consumption and, to a lesser extent, use of drugs, affect a large number of travelers which expose them to health problems during a trip. Exploring the alcohol and drugs consumption patterns of people visiting a travel clinic should be part of the pre-travel routine consultation and would allow to identifying people who would benefit most from a specific prevention.

A noninvasive method for measuring the velocity of diffuse hydrothermal flow by tracking moving refractive index anomalies

Diffuse flow velocimetry (DFV) is introduced as a new, noninvasive, optical technique for measuring the velocity of diffuse hydrothermal flow. The technique uses images of a motionless, random medium (e.g.,rocks) obtained through the lens of a moving refraction index anomaly (e.g., a hot upwelling). The method works in two stages. First, the changes in apparent background deformation are calculated using particle image velocimetry (PIV). The deformation vectors are determined by a cross correlation of pixel intensities across consecutive images. Second, the 2-D velocity field is calculated by cross correlating the deformation vectors between consecutive PIV calculations. The accuracy of the method is tested with laboratory and numerical experiments of a laminar, axisymmetric plume in fluids with both constant and temperaturedependent viscosity. Results show that average RMS errors are ∼5%–7% and are most accurate in regions of pervasive apparent background deformation which is commonly encountered in regions of diffuse hydrothermal flow. The method is applied to a 25 s video sequence of diffuse flow from a small fracture captured during the Bathyluck’09 cruise to the Lucky Strike hydrothermal field (September 2009). The velocities of the ∼10°C–15°C effluent reach ∼5.5 cm/s, in strong agreement with previous measurements of diffuse flow. DFV is found to be most accurate for approximately 2‐D flows where background objects have a small spatial scale, such as sand or gravel

Exploring the connection between the stellar wind and the non-thermal emission in LS 5039

Context.LS 5039 has been observed with several X-ray instruments so far showing quite steady emission in the long term and no signatures of accretion disk. The source also presents X-ray variability at orbital timescales in flux and photon index. The system harbors an O-type main sequence star with moderate mass-loss. At present, the link between the X-rays and the stellar wind is unclear. Aims.We study the X-ray fluxes, spectra, and absorption properties of LS 5039 at apastron and periastron passages during an epoch of enhanced stellar mass-loss, and the long term evolution of the latter in connection with the X-ray fluxes. Methods.New XMM-Newton observations were performed around periastron and apastron passages in September 2005, when the stellar wind activity was apparently higher. April 2005 Chandra observations on LS 5039 were revisited. Moreover, a compilation of H EW data obtained since 1992, from which the stellar mass-loss evolution can be approximately inferred, was carried out. Results.XMM-Newton observations show higher and harder emission around apastron than around periastron. No signatures of thermal emission or a reflection iron line indicating the presence of an accretion disk are found in the spectrum, and the hydrogen column density () is compatible with being the same in both observations and consistent with the interstellar value. 2005 Chandra observations show a hard X-ray spectrum, and possibly high fluxes, although pileup effects preclude conclusive results from being obtained. The H EW shows yearly variations of 10%, and does not seem to be correlated with X-ray fluxes obtained at similar phases, unlike what is expected in the wind accretion scenario. Conclusions.2005 XMM-Newton and Chandra observations are consistent with 2003 RXTE/PCA results, namely moderate flux and spectral variability at different orbital phases. The constancy of the seems to imply that either the X-ray emitter is located at 1012 cm from the compact object, or the density in the system is 3 to 27 times smaller than that predicted by a spherical symmetric wind model. We suggest that the multiwavelength non-thermal emission of LS 5039 is related to the observed extended radio jets and is unlikely to be produced inside the binary system.

Evaluation of the potential use of trabecular bone score to complement bone mineral density in the diagnosis of osteoporosis: a preliminary spine BMD-matched, case-control study.

The trabecular bone score (TBS) is a new parameter that is determined from gray-level analysis of dual-energy X-ray absorptiometry (DXA) images. It relies on the mean thickness and volume fraction of trabecular bone microarchitecture. This was a preliminary case-control study to evaluate the potential diagnostic value of TBS as a complement to bone mineral density (BMD), by comparing postmenopausal women with and without fractures. The sample consisted of 45 women with osteoporotic fractures (5 hip fractures, 20 vertebral fractures, and 20 other types of fracture) and 155 women without a fracture. Stratification was performed, taking into account each type of fracture (except hip), and women with and without fractures were matched for age and spine BMD. BMD and TBS were measured at the total spine. TBS measured at the total spine revealed a significant difference between the fracture and age- and spine BMD-matched nonfracture group, when considering all types of fractures and vertebral fractures. In these cases, the diagnostic value of the combination of BMD and TBS likely will be higher compared with that of BMD alone. TBS, as evaluated from standard DXA scans directly, potentially complements BMD in the detection of osteoporotic fractures. Prospective studies are necessary to fully evaluate the potential role of TBS as a complementary risk factor for fracture.

Domain Adaptation in remote sensing: increasing the portability of land-cover classifiers

Among the types of remote sensing acquisitions, optical images are certainly one of the most widely relied upon data sources for Earth observation. They provide detailed measurements of the electromagnetic radiation reflected or emitted by each pixel in the scene. Through a process termed supervised land-cover classification, this allows to automatically yet accurately distinguish objects at the surface of our planet. In this respect, when producing a land-cover map of the surveyed area, the availability of training examples representative of each thematic class is crucial for the success of the classification procedure. However, in real applications, due to several constraints on the sample collection process, labeled pixels are usually scarce. When analyzing an image for which those key samples are unavailable, a viable solution consists in resorting to the ground truth data of other previously acquired images. This option is attractive but several factors such as atmospheric, ground and acquisition conditions can cause radiometric differences between the images, hindering therefore the transfer of knowledge from one image to another. The goal of this Thesis is to supply remote sensing image analysts with suitable processing techniques to ensure a robust portability of the classification models across different images. The ultimate purpose is to map the land-cover classes over large spatial and temporal extents with minimal ground information. To overcome, or simply quantify, the observed shifts in the statistical distribution of the spectra of the materials, we study four approaches issued from the field of machine learning. First, we propose a strategy to intelligently sample the image of interest to collect the labels only in correspondence of the most useful pixels. This iterative routine is based on a constant evaluation of the pertinence to the new image of the initial training data actually belonging to a different image. Second, an approach to reduce the radiometric differences among the images by projecting the respective pixels in a common new data space is presented. We analyze a kernel-based feature extraction framework suited for such problems, showing that, after this relative normalization, the cross-image generalization abilities of a classifier are highly increased. Third, we test a new data-driven measure of distance between probability distributions to assess the distortions caused by differences in the acquisition geometry affecting series of multi-angle images. Also, we gauge the portability of classification models through the sequences. In both exercises, the efficacy of classic physically- and statistically-based normalization methods is discussed. Finally, we explore a new family of approaches based on sparse representations of the samples to reciprocally convert the data space of two images. The projection function bridging the images allows a synthesis of new pixels with more similar characteristics ultimately facilitating the land-cover mapping across images.

Disentangling in vivo the effects of iron content and atrophy on the ageing human brain.

Evidence from magnetic resonance imaging (MRI) studies shows that healthy aging is associated with profound changes in cortical and subcortical brain structures. The reliable delineation of cortex and basal ganglia using automated computational anatomy methods based on T1-weighted images remains challenging, which results in controversies in the literature. In this study we use quantitative MRI (qMRI) to gain an insight into the microstructural mechanisms underlying tissue ageing and look for potential interactions between ageing and brain tissue properties to assess their impact on automated tissue classification. To this end we acquired maps of longitudinal relaxation rate R1, effective transverse relaxation rate R2* and magnetization transfer - MT, from healthy subjects (n=96, aged 21-88 years) using a well-established multi-parameter mapping qMRI protocol. Within the framework of voxel-based quantification we find higher grey matter volume in basal ganglia, cerebellar dentate and prefrontal cortex when tissue classification is based on MT maps compared with T1 maps. These discrepancies between grey matter volume estimates can be attributed to R2* - a surrogate marker of iron concentration, and further modulation by an interaction between R2* and age, both in cortical and subcortical areas. We interpret our findings as direct evidence for the impact of ageing-related brain tissue property changes on automated tissue classification of brain structures using SPM12. Computational anatomy studies of ageing and neurodegeneration should acknowledge these effects, particularly when inferring about underlying pathophysiology from regional cortex and basal ganglia volume changes.

Virtual anthropology: A comparison between the performance of conventional X-ray and MDCT in investigating the trabecular structure of long bones.

Recently, modern cross-sectional imaging techniques such as multi-detector computed tomography (MDCT) have pioneered post mortem investigations, especially in forensic medicine. Such approaches can also be used to investigate bones non-invasively for anthropological purposes. Long bones are often examined in forensic cases because they are frequently discovered and transferred to medico-legal departments for investigation. To estimate their age, the trabecular structure must be examined. This study aimed to compare the performance of MDCT with conventional X-rays to investigate the trabecular structure of long bones. Fifty-two dry bones (24 humeri and 28 femora) from anthropological collections were first examined by conventional X-ray, and then by MDCT. Trabecular structure was evaluated by seven observers (two experienced and five inexperienced in anthropology) who analyzed images obtained by radiological methods. Analyses contained the measurement of one quantitative parameter (caput diameter of humerus and femur) and staging the trabecular structure of each bone. Preciseness of each technique was indicated by describing areas of trabecular destruction and particularities of the bones, such as pathological changes. Concerning quantitative parameters, the measurements demonstrate comparable results for the MDCT and conventional X-ray techniques. In contrast, the overall inter-observer reliability of the staging was low with MDCT and conventional X-ray. Reliability increased significantly when only the results of the staging performed by the two experienced observers were compared, particularly regarding the MDCT analysis. Our results also indicate that MDCT appears to be better suited to a detailed examination of the trabecular structure. In our opinion, MDCT is an adequate tool with which to examine the trabecular structure of long bones. However, adequate methods should be developed or existing methods should be adapted to MDCT.

Influence of the morphology of the dural sac on surgical decision making in lumbar spinal stenosis

Introduction: Surgical decision making in lumbar spinal stenosis (LSS) takes into account primarily clinical symptoms as well as concordant radiological findings. We hypothesized that a wide variation of operative threshold would be found in particular as far as judgment of severity of radiological stenosis is concerned. Patients and methods: The number of surgeons who would proceed to decompression was studied relative to the perceived severity of radiological stenosis based either on measurements of dural sac cross sectional area (DSCA) or on the recently described morphological grading as seen on axial T2 MRI images. A link to an electronic survey page with a set of ten axial T2 MRI images taken from ten patients with either low back pain or LSS were sent to members of three national or international spine societies. Those 10 images were randomly presented initially and re-shuffled on a second page including this time DSCA measurements in mm2, ranging from 14 to 226 mm2, giving a total of 20 images to appraise. Morphological grades were ranging from grade A to D. Surgeons were asked if they would consider decompression given the radiological appearance of stenosis and that symptoms of neurological claudication were severe in patients who were otherwise fit for surgery. Fisher's exact test was performed following dichotomization of data when appropriate. Results: A total of 142 spine surgeons (113 orthopedic spine surgeons, 29 neurosurgeons) responded from 25 countries. A substantial agreement was observed in operating patients with severe (grade C) or extreme (grade D) stenosis as defined by the morphological grade compared to lesser stenosis (A&B) grades (p<0.0001). Decision to operate was not dependent on number of years in practice, medical density in practicing country or specialty although more neurosurgeons would operate on grade C stenosis (p<0.005). Disclosing the DSCA measurement did not alter the decision to operate. Although 20 surgeons only had prior knowledge of the description of the morphological grading, their responses showed no statistically significant difference with those of the remaining 122 physicians. Conclusions: This study showed that surgeons across borders are less influenced by DSCA in their decision making than by the morphological appearance of the dural sac. Classifying LSS according to morphology rather than surface measurements appears to be consistent with current clinical practice.