Magnetic resonance imaging-guided attenuation correction in whole-body PET/MRI using a sorted atlas approach

Quantitative whole-body PET/MR imaging is challenged by the lack of accurate and robust strategies for attenuation correction. In this work, a new pseudo-CT generation approach, referred to as sorted atlas pseudo-CT (SAP), is proposed for accurate extraction of bones and estimation of lung attenuation properties. This approach improves the Gaussian process regression (GPR) kernel proposed by Hofmann et al. which relies on the information provided by a co-registered atlas (CT and MRI) using a GPR kernel to predict the distribution of attenuation coefficients. Our approach uses two separate GPR kernels for lung and non-lung tissues. For non-lung tissues, the co-registered atlas dataset was sorted on the basis of local normalized cross-correlation similarity to the target MR image to select the most similar image in the atlas for each voxel. For lung tissue, the lung volume was incorporated in the GPR kernel taking advantage of the correlation between lung volume and corresponding attenuation properties to predict the attenuation coefficients of the lung. In the presence of pathological tissues in the lungs, the lesions are segmented on PET images corrected for attenuation using MRI-derived three-class attenuation map followed by assignment of soft-tissue attenuation coefficient. The proposed algorithm was compared to other techniques reported in the literature including Hofmann's approach and the three-class attenuation correction technique implemented on the Philips Ingenuity TF PET/MR where CT-based attenuation correction served as reference. Fourteen patients with head and neck cancer undergoing PET/CT and PET/MR examinations were used for quantitative analysis. SUV measurements were performed on 12 normal uptake regions as well as high uptake malignant regions. Moreover, a number of similarity measures were used to evaluate the accuracy of extracted bones. The Dice similarity metric revealed that the extracted bone improved from 0.58 ± 0.09 to 0.65 ± 0.07 when using the SAP technique compared to Hofmann's approach. This enabled to reduce the SUV_mean bias in bony structures for the SAP approach to -1.7 ± 4.8% as compared to -7.3 ± 6.0% and -27.4 ± 10.1% when using Hofmann's approach and the three-class attenuation map, respectively. Likewise, the three-class attenuation map produces a relative absolute error of 21.7 ± 11.8% in the lungs. This was reduced on average to 15.8 ± 8.6% and 8.0 ± 3.8% when using Hofmann's and SAP techniques, respectively. The SAP technique resulted in better overall PET quantification accuracy than both Hofmann's and the three-class approaches owing to the more accurate extraction of bones and better prediction of lung attenuation coefficients. Further improvement of the technique and reduction of the computational time are still required.     

A method of 2D/3D registration of a statistical mouse atlas with a planar X-ray projection and an optical photo

The development of sophisticated and high throughput whole body small animal imaging technologies has created a need for improved image analysis and increased automation. The registration of a digital mouse atlas to individual images is a prerequisite for automated organ segmentation and uptake quantification. This paper presents a fully-automatic method for registering a statistical mouse atlas with individual subjects based on an anterior–posterior X-ray projection and a lateral optical photo of the mouse silhouette. The mouse atlas was trained as a statistical shape model based on 83 organ-segmented micro-CT images. For registration, a hierarchical approach is applied which first registers high contrast organs, and then estimates low contrast organs based on the registered high contrast organs. To register the high contrast organs, a 2D-registration-back-projection strategy is used that deforms the 3D atlas based on the 2D registrations of the atlas projections. For validation, this method was evaluated using 55 subjects of preclinical mouse studies. The results showed that this method can compensate for moderate variations of animal postures and organ anatomy. Two different metrics, the Dice coefficient and the average surface distance, were used to assess the registration accuracy of major organs. The Dice coefficients vary from 0.31 ± 0.16 for the spleen to 0.88 ± 0.03 for the whole body, and the average surface distance varies from 0.54 ± 0.06 mm for the lungs to 0.85 ± 0.10 mm for the skin. The method was compared with a direct 3D deformation optimization (without 2D-registration-back-projection) and a single-subject atlas registration (instead of using the statistical atlas). The comparison revealed that the 2D-registration-back-projection strategy significantly improved the registration accuracy, and the use of the statistical mouse atlas led to more plausible organ shapes than the single-subject atlas. This method was also tested with shoulder xenograft tumor-bearing mice, and the results showed that the registration accuracy of most organs was not significantly affected by the presence of shoulder tumors, except for the lungs and the spleen.     

Evaluation of atlas selection strategies for atlas-based image segmentation with application to confocal microscopy images of bee brains

This paper evaluates strategies for atlas selection in atlas-based segmentation of three-dimensional biomedical images. Segmentation by intensity-based nonrigid registration to atlas images is applied to confocal microscopy images acquired from the brains of 20 bees. This paper evaluates and compares four different approaches for atlas image selection: registration to an individual atlas image (IND), registration to an average-shape atlas image (AVG), registration to the most similar image from a database of individual atlas images (SIM), and registration to all images from a database of individual atlas images with subsequent multi-classifier decision fusion (MUL). The MUL strategy is a novel application of multi-classifier techniques, which are common in pattern recognition, to atlas-based segmentation. For each atlas selection strategy, the segmentation performance of the algorithm was quantified by the similarity index (SI) between the automatic segmentation result and a manually generated gold standard. The best segmentation accuracy was achieved using the MUL paradigm, which resulted in a mean similarity index value between manual and automatic segmentation of 0.86 (AVG, 0.84; SIM, 0.82; IND, 0.81). The superiority of the MUL strategy over the other three methods is statistically significant (two-sided paired t test, P < 0.001). Both the MUL and AVG strategies performed better than the best possible SIM and IND strategies with optimal a posteriori atlas selection (mean similarity index for optimal SIM, 0.83; for optimal IND, 0.81). Our findings show that atlas selection is an important issue in atlas-based segmentation and that, in particular, multi-classifier techniques can substantially increase the segmentation accuracy.     

Fast and robust multi-atlas segmentation of brain magnetic resonance images

We introduce an optimised pipeline for multi-atlas brain MRI segmentation. Both accuracy and speed of segmentation are considered. We study different similarity measures used in non-rigid registration. We show that intensity differences for intensity normalised images can be used instead of standard normalised mutual information in registration without compromising the accuracy but leading to threefold decrease in the computation time. We study and validate also different methods for atlas selection. Finally, we propose two new approaches for combining multi-atlas segmentation and intensity modelling based on segmentation using expectation maximisation (EM) and optimisation via graph cuts. The segmentation pipeline is evaluated with two data cohorts: IBSR data (N = 18, six subcortial structures: thalamus, caudate, putamen, pallidum, hippocampus, amygdala) and ADNI data (N =   60, hippocampus). The average similarity index between automatically and manually generated volumes was 0.849 (IBSR, six subcortical structures) and 0.880 (ADNI, hippocampus). The correlation coefficient for hippocampal volumes was 0.95 with the ADNI data. The computation time using a standard multicore PC computer was about 3–4 min. Our results compare favourably with other recently published results.     

A supervised learning framework of statistical shape and probability priors for automatic prostate segmentation in ultrasound images

Prostate segmentation aids in prostate volume estimation, multi-modal image registration, and to create patient specific anatomical models for surgical planning and image guided biopsies. However, manual segmentation is time consuming and suffers from inter-and intra-observer variabilities. Low contrast images of trans rectal ultrasound and presence of imaging artifacts like speckle, micro-calcifications, and shadow regions hinder computer aided automatic or semi-automatic prostate segmentation. In this paper, we propose a prostate segmentation approach based on building multiple mean parametric models derived from principal component analysis of shape and posterior probabilities in a multi-resolution framework. The model parameters are then modified with the prior knowledge of the optimization space to achieve optimal prostate segmentation. In contrast to traditional statistical models of shape and intensity priors, we use posterior probabilities of the prostate region determined from random forest classification to build our appearance model, initialize and propagate our model. Furthermore, multiple mean models derived from spectral clustering of combined shape and appearance parameters are applied in parallel to improve segmentation accuracies. The proposed method achieves mean Dice similarity coefficient value of 0.91 ± 0.09 for 126 images containing 40 images from the apex, 40 images from the base and 46 images from central regions in a leave-one-patient-out validation framework. The mean segmentation time of the procedure is 0.67 ± 0.02 s.     

Multi-scale patch and multi-modality atlases for whole heart segmentation of MRI

A whole heart segmentation (WHS) method is presented for cardiac MRI. This segmentation method employs multi-modality atlases from MRI and CT and adopts a new label fusion algorithm which is based on the proposed multi-scale patch (MSP) strategy and a new global atlas ranking scheme. MSP, developed from the scale-space theory, uses the information of multi-scale images and provides different levels of the structural information of images for multi-level local atlas ranking. Both the local and global atlas ranking steps use the information theoretic measures to compute the similarity between the target image and the atlases from multiple modalities. The proposed segmentation scheme was evaluated on a set of data involving 20 cardiac MRI and 20 CT images. Our proposed algorithm demonstrated a promising performance, yielding a mean WHS Dice score of 0.899 ± 0.0340, Jaccard index of 0.818 ± 0.0549, and surface distance error of 1.09 ± 1.11 mm for the 20 MRI data. The average runtime for the proposed label fusion was 12.58 min.     

Comparative study of indices of activity evaluation in rheumatoid arthritis

IntroductionChoosing between the different indices of activity evaluation in RA is often difficult considering the very heterogeneous clinical expression of the disease. The objective of our study was to evaluate the level of similarity between SDAI, CDAI, DAS28-_ESR and DAS28-_CRP indices in the evaluation of RA activity.Patients and methodsIn this transversal study, a total of 100 patients with RA responding to the ACR 87 criteria were followed up for a period of 20 months. The correlations between the four indices were studied through the Pearson's correlation coefficient (r). The similarity between these tools was evaluated through Kendall's (K) “tau” similarity coefficient.ResultsThe 87 female and 13 male patients (sex ratio: 6.7F/1M) were of a mean age of 52.9 ± 11.6 years (17–77) and have been living with RA for a mean of 8.3 ± 9 years (2 months–41 years). The DAS28-_ESR mean score was 5.53 ± 1.46 [1.25–8.05]. The DAS28-_CRP mean score was 5.01 ± 1.44 [1.68–7.81]. The CDAI mean score was 30.72 ± 15.04 [2–62] and that of SDAI was 28.86 ± 15.86 [2.3–71.3]. A positive, statistically significant correlation was noted between the four indices of RA activity. The level of similarity between the different indices was good (K variation between 0.758 and 0.943). DAS28-_ESR allowed classifying the patients in the same category of disease activity than DAS28-_CRP in a proportion of 85%. This proportion was 88% when comparing DAS28-_ESR to CDAI and SDAI, respectively. Regarding DAS28-_CRP and CDAI, these two indices classified the patients in the same category in a proportion of 80%, compared to 87% regarding DAS28-_CRP and SDAI. Finally, CDAI and SDAI classified the patients in the same category in a proportion of 92% with an excellent level of similarity.ConclusionDifferent evaluation indices of RA activity are currently available. DAS28 is the most used. CDAI and especially SDAI have a good level of similarity with DAS28. Their advantage is to be simple and quick, and seem therefore well adapted to the follow-up of outpatients.     

Comparison of intranasal ketamine versus IV morphine in reducing pain in patients with renal colic

Background

Various drugs have been used to relieve abdominal pain in patients with renal colic. Ketamine is a popular choice as an analgesic.

Differences in levels of platelet-derived microparticles in platelet components prepared using the platelet rich plasma,buffy coat,and apheresis procedures

Background

There has been an increased interest in platelet-derived microparticles (PMPs) in transfusion medicine. Little is known about PMP status during the preparation of platelet concentrates for transfusion.

Relationship of age-related concentrations of serum FSH and LH with bone mineral density, prevalence of osteoporosis in native Chinese women

BackgroundFollicle-stimulating hormone (FSH) and luteinizing hormone (LH) may play an important role in bone mass regulation in postmenopausal women.MethodsA cross-sectional study of 699 healthy Chinese women, aged 20 to 82 y, was conducted. Serum FSH and LH and BMD were measured at the posteroanterior (PA) spine, lateral spine, total hip, and distal forearm.ResultsThe geometric mean values (± SD) of serum FSH and LH in premenopausal women were 3.94 ± 2.08 and 7.51 ± 2.58 IU/l, respectively, and in postmenopausal women were 28.8 ± 1.88 and 25.6 ± 1.95 IU/l, respectively. The correlation of FSH to BMD at different skeletal regions (r = ? 0.597 – ? 0.492, P = 0.000) was higher than that of LH to BMD (r = ? 0.452 – ? 0.332, P = 0.000). The prevalences of osteoporosis for the quartiles of FSH at various skeletal sites were 0.57%, 0.43%, 27.1%, and 30.9%, respectively; and of LH were 2.14%, 4.43%, 19.5%, and 26.0%, respectively. The prevalence of osteoporosis in 3rd and 4th quartile was more significantly increased than the 1st and 2nd quartile.ConclusionsThese data suggest that FSH and LH levels in circulation are associated with BMD changes and osteoporosis occurrence in Chinese women.     

Role of NF-E2-related factor 2 in neuroprotective effect of l-carnitine against high glucose-induced oxidative stress in the retinal ganglion cells

l-Carnitine (LC) has protective effects on high glucose-induced oxidative stress in the retinal ganglion cells (RGCs). The aim of this study was to investigate the role of NF-E2-related factor 2 (Nrf2), Kelch like-ECH-associated protein 1 (Keap1), haemoxygenase-1 (HO-1) and γ-glutamyl cysteine synthetase (γ-GCS) in the protective effect of LC on RGCs. RGCs were first processed with high concentrations of glucose. LC treatment at three concentrations (50 μM, 100 μM and 200 μM) was applied to high glucose stimulated RGCs. The expression of Nrf2, Keap1, haemoxygenase-1 (HO-1) and γ-glutamyl cysteine synthetase (γ-GCS) was quantified by Western blot in the treatment and control (high glucose stimulation) groups. In the three LC groups (50 μM, 100 μM and 200 μM), Nrf-2 (0.71 ± 0.04, 0.89 ± 0.05, 1.24 ± 0.05 vs 0.56 ± 0.03, p < 0.05), HO-1 (0.58 ± 0.04, 0.76 ± 0.06, 0.89 ± 0.07 vs 0.25 ± 0.03, p < 0.01), and γ-GCS protein expression (0.66 ± 0.03, 0.79 ± 0.05, 0.84 ± 0.08 vs 0.84 ± 0.08, p < 0.01) was higher than in the control group. The levels of Keap1 protein were in the LC groups were lower than in the control group (0.50 ± 0.03, 0.45 ± 0.02, 0.53 ± 0.03 vs 0.86 ± 0.05, p < 0.01). In conclusion, in high glucose stimulated RGCs, LC treatment was associated with an increased level of Nrf2, HO-1and γ-GCS. LC treatment was also associated with a reduced expression of Keap1 protein. These results suggest that the protective effect of LC treatment on RGCs may be related to Nrf2-Keap1 pathway.     

Efectividad de una intervención educativa y de ejercicio físico sobre la capacidad funcional de los pacientes en hemodiálisis

Objective

To describe the impact of a standard hospital educational intervention including active physical exercises on personal well-being, functional capacity and knowledge of the benefits of prescribed physical activity for patients undergoing haemodialysis.

Tilting for perfusion: Head-up position during cardiopulmonary resuscitation improves brain flow in a porcine model of cardiac arrest

IntroductionCerebral perfusion is compromised during cardiopulmonary resuscitation (CPR). We hypothesized that beneficial effects of gravity on the venous circulation during CPR performed in the head-up tilt (HUT) position would improve cerebral perfusion compared with supine or head-down tilt (HDT).MethodsTwenty-two pigs were sedated, intubated, anesthetized, paralyzed and placed on a tilt table. After 6 min of untreated ventricular fibrillation (VF) CPR was performed on 14 pigs for 3 min with an automated CPR device called LUCAS (L) plus an impedance threshold device (ITD), followed by 5 min of L-CPR + ITD at 0° supine, 5 min at 30° HUT, and then 5 min at 30° HDT. Microspheres were used to measure organ blood flow in 8 pigs. L-CPR + ITD was performed on 8 additional pigs at 0°, 20°, 30°, 40°, and 50° HUT.ResultsCoronary perfusion pressure was 19 ± 2 mmHg at 0° vs. 30 ± 3 at 30° HUT (p < 0.001) and 10 ± 3 at 30° HDT (p < 0.001). Cerebral perfusion pressure was 19 ± 3 at 0° vs. 35 ± 3 at 30° HUT (p < 0.001) and 4 ± 4 at 30° HDT (p < 0.001). Brain–blood flow was 0.19 ± 0.04 ml min⁻¹ g⁻¹ at 0° vs. 0.27 ± 0.04 at 30° HUT (p = 0.01) and 0.14 ± 0.06 at 30° HDT (p = 0.16). Heart blood flow was not significantly different between interventions. With 0, 10, 20, 30, 40 and 50° HUT, ICP values were 21 ± 2, 16 ± 2, 10 ± 2, 5 ± 2, 0 ± 2, −5 ± 2 respectively, (p < 0.001), CerPP increased linearly (p = 0.001), and CPP remained constant.ConclusionDuring CPR, HDT decreased brain flow whereas HUT significantly lowered ICP and improved cerebral perfusion. Further studies are warranted to explore this new resuscitation concept.     

Detection of serum β2-GPI–Lp(a) complexes in patients with systemic lupus erythematosus

BackgroundCirculating β₂-glycoprotein-I-oxidized low-density lipoprotein (β₂-GPI–ox-LDL) complexes have been found in patients with systemic lupus erythematosus (SLE) and other autoimmune diseases as a contributor to the development of autoimmune-mediated atherosclerosis. In vitro study showed that β₂-GPI also bound with high affinity to atherogenic lipoprotein (a) [Lp(a)] which shares structural similarity to LDL. We examined the existence and clinical significance of serum complexes of β₂-GPI with Lp(a) in SLE patients.MethodsA “sandwich” ELISA was developed for measuring serum concentrations of β₂-GPI–Lp(a) complexes, using rabbit anti-human β₂-GPI antibody as capturing antibody, and quantitating with antibody against apo(a). Forty-seven SLE patients and 42 healthy controls were studied.ResultsBoth Lp(a) (400 ± 213 mg/l vs. 181 ± 70 mg/l) and ox-Lp(a) (27.07 ± 22.30 mg/l vs. 8.20 ± 4.55 mg/l) concentrations were higher in SLE patients than in controls (P < 0.0001). β₂-GPI–Lp(a) complexes were detectable in both controls and SLE. The complexes levels in SLE were higher than in controls (0.96 ± 0.41 U/ml vs. 0.59 ± 0.20 U/ml, P < 0.0001) and was positively correlated with ox-Lp(a) (P < 0.001).ConclusionsWe report the existence of β₂-GPI–Lp(a) complexes in both controls and SLE patients. The complexes levels increase in SLE.     

Isolation and activation of human neutrophils in vitro. The importance of the anticoagulant used during blood collection

ObjectivesTo assess the effect of different anticoagulants (EDTA, citrate and heparin) on the isolation procedure of human neutrophils and in the subsequent alterations of calcium levels and respiratory burst induced by phorbol myristate acetate (PMA).Design and methodsIsolation of human neutrophils from whole blood was performed by the gradient density centrifugation method. PMA-induced neutrophil burst was measured by chemiluminescence. Intracellular calcium ([Ca²⁺]_i) was measured using Fluo-3 AM, a calcium-sensitive dye.ResultsEDTA provided the highest number of isolated neutrophils/mL of blood (1.7 × 10⁶ ± 1.5 × 10⁵) when compared with citrate (0.46 × 10⁶ ± 0.95 × 10⁵) and heparin (0.66 × 10⁶ ± 0.15 × 10⁵). EDTA originated less degree of PMA-induced activation (370 ± 30%) relatively to citrate (830 ± 98%) and heparin (827 ± 77%). [Ca²⁺]_i was lower with EDTA (122 ± 11 nM) when compared with citrate and heparin (150 ± 13 and 230 ± 30 nM).ConclusionThe anticoagulant used during blood collection interfered differently with the yield of isolated neutrophils as well as on their calcium levels and reactivity to PMA.     

Androgenic-anabolic steroids inhibited post-exercise hypotension: a case control study

Background

There is evidence of hypertensive effects caused by anabolic androgenic steroids (AAS). A single exercise session promotes the acute reduction of blood pressure, but the effects of AAS on this phenomenon are unknown.

Effect of leukapheresis on blood coagulation in patients with hyperleukocytic acute myeloid leukemia

Introduction

Leukapheresis has been proposed to reduce white blood cell (WBC) count in hyperleukocytic acute myeloid leukemia (AML). However, no survival benefit has been proven and leukapheresis can potentially affect coagulation and worsen bleeding and disseminated intravascular coagulation (DIC). We analyzed the effect of leukapheresis on coagulation tests in a cohort of hyperleukocytic AML patients.

The effect of trimetazidine treatment in patients with type 2 diabetes undergoing percutaneous coronary intervention for AMI

Purpose

Trimetazidine (TMZ) improves clinical outcomes in patients with chronic heart failure and stable coronary artery disease. No study has yet evaluated the efficacy of TMZ in type 2 diabetes patients with acute myocardial infarction (AMI) undergoing Percutaneous Coronary Intervention (PCI). We performed this study to evaluate the efficacy TMZ in DM patients with AMI undergoing PCI, such as the effect on reductions in myocardial enzyme, improvements in liver function, modulation of glucose levels, and improvement in cardiac function.