Three-dimensional static displacement, stimulated echo NMR elasticity imaging

This article presents a method for measuring three-dimensional mechanical displacement and strain fields using stimulated echo MRI. Additional gradient pulses encode internal displacements in response to an externally applied deformation. By limiting the mechanical transition to the stimulated echo mixing time, a more accurate static displacement measurement is obtained. A three-dimensional elasticity reconstruction within a region of interest having a uniform shear modulus along its boundary is performed by numerically solving discretized elasticity equilibrium equations. Data acquisition, strain measurements and reconstruction were performed using a silicone gel phantom containing an inclusion of known elastic properties. A comparison between two-dimensional and three-dimensional reconstructions from simulated and experimental displacement data shows higher accuracy from the three-dimensional reconstruction. The long-term objective of this work is to provide a method for remotely palpating and elastically quantitating manually inaccessible tissues.     

Lithium treatment enhances estradiol-induced proliferation and hyperplasia formation in the uterus of mice

OBJECTIVES: It is suggested that the Wnt/beta-catenin pathway plays a role in the regulation of estrogen action in the uterus. However, this suggestion has not been proved. Lithium can mimic increased activity of the Wnt/beta-catenin pathway by blocking the activity of glycogen synthase kinase-3beta. There are no data on the effects of lithium on estrogen-dependent processes in the uterus. This work was therefore aimed to examine the action of lithium on proliferative and morphogenetic reactions in the uterus under short- and long-term estrogen treatments. STUDY DESIGN: Ovariectomized mice received estradiol dipropionate (2 microg per 100g; s.c.) once a week or vehicle and drank tap water with 0.05% lithium chloride or plain tap water for 2 or 30 days. RESULTS: In animals treated with estradiol and lithium for a month, the incidence of atypical endometrial hyperplasia was significantly higher. In animals treated with estradiol and lithium for 2 days or for a month, uterine mass, the number of mitotic cells and BrdU-labelled cells in luminal epithelium, glandular epithelium, stromal and myometrial cells was markedly greater, whereas the levels of estrogen receptors-alpha, beta-catenin and glycogen synthase kinase-3beta were markedly lower in all uterine compartments, than in those in mice received estradiol with no lithium to drink. CONCLUSIONS: Lithium treatment results in an increase in estradiol-induced proliferative and morphogenetic changes in the uterus. This action of lithium is associated with decreased expression of estrogen receptors-alpha, beta-catenin and glycogen synthase kinase-3beta in the uterus.     

Theatre staff members and exposure to halogenated agents

Ninety-eight measurements were made to evaluate the level of pollution by halogenated anaesthetics, in 27 operating rooms of 12 hospitals in the Paris area. Air sampling was made during ordinary work sessions to evaluate the degree of personal pollution to which different members of the operating room staff were exposed. Samples were analysed by gas chromatography. The degree of personal pollution was particularly high in hospitals devoted to paediatric surgery. Anaesthetists were most at risk. Scavenging equipment and a large volume of air in the operating room helped in a reduction in the level of pollution. A high rate of air extraction and the use of a filter appeared to be necessary to reduce pollution.     

A clinical study of amiodarone as a single oral dose in patients with recent-onset atrial tachyarrhythmia

Forty-five patients with recent-onset sustained atrial tachyarrhythmia(mean heart rate at entry; 140.0± 3.5 beats. min^–1)associated with various cardiovascular diseases were treatedby oral amiodarone, given as a single loading dose of 25.7±0.9 mg. kg–1 body weight. Conversion to sinus rhythm wasobserved in 29 patients during the first 24 h of treatment,leading to a success rate of 64.4%. Five additional patientsconverted to sinus rhythm with continuation of oral amiodarone,(10–15 mg. kg^–1 by day) with a mean delay of 4.2days. A similar population of 27 patients (mean heart rate atentry; 140 ± 3 beats. min^–1) was treated by intravenousamiodarone, given as a bolus infusion of 3–5mg. kg^–1over 30min (mean; 41±02 mg. kg^–1), followed bya continuous infusion of 10–15mg. kg^–1 for 24 h(mean; 11.1±0.7 mg. kg^–1). Eighteen patients convertedto sinus rhythm during the first 24 h of therapy, leading toa success rate of 66.7%. Minor adverse effects of therapy wereobserved in two patients given oral amiodarone, and in sevengiven intravenous amiodarone. No major effect was observed.We suggest that amiodarone given as a single oral loading doseof 25–30mg. kg^–1 body weight is an effective, simpleand well-tolerated therapy, suitable for most patients withrecent-onset ATA.     

Standardized (simulated) patients'' accuracy in recording clinical performance check-list items

In large-scale performance-based assessment of medical professionals' clinical competence, simulated patients (standardized patients-SPs) are used not only to simulate case problems but also to record on check-list the examinees' clinical performance during their encounter with the SPs. The purposes of this study were to determine the SPs' overall accuracy in recording check-list items, and whether their accuracy was affected by the various characteristics of the check-list, and by the different times during a day and the different days within the examination when the recordings were obtained. Results showed that the SPs' accuracy in recording check-list items was good to very good and was affected by the length of the check-list, as well as by the type and the clarity of the check-list item. It was further found that the SPs' accuracy was consistent and did not vary over the course of a one-day or a 15-day examination.     

An In-vitro Evaluation of Silicone Elastomer Latex for Topical Drug Delivery

A silicone elastomer latex was evaluated as a topical drug-delivery system. With the addition of a fumed silica and the removal of water, the latex produced elastomeric solid films. The water vapour permeability of the solid film was found to be a function of the film composition. An increase in silica content and the incorporation of a water-soluble component, PEG 3350, rendered the silicone elastomer-free film even more permeable to water vapour. The release of hydrocortisone from the elastomer film can be described by a matrix-diffusion-controlled mechanism. Drug diffusion is thought to occur through the hydrophobic silicone polymer network and the hydrated hydrophilic silica region in the film matrix. Silicone elastomer film with a higher silica content exhibited a faster drug-release rate. The addition of PEG 3350 to the film further enhanced the drug-release rate.     

Triplex ultrasound: elasticity imaging to age deep venous thrombosis

Deep venous thrombosis (DVT), and its sequela, pulmonary embolism (PE), is the leading cause of preventable in-hospital mortality in the USA and other developed countries. After it is detected, acute clots must be differentiated from chronic DVT for appropriate treatment. However, there are no reliable thrombus staging methods presently available in clinical practice. In this study, we tested the hypothesis that blood clots can be detected and staged using a triplex ultrasound (US) test. Triplex US is based on a "gold standard" duplex US technique augmented by US-based reconstructive elasticity imaging. Fibrin-composed blood clots harden with development and organization. By imaging clot elasticity, it may be possible to both detect and differentiate clots and, therefore, provide an urgently needed noninvasive means of DVT staging.     

Sonographic elasticity imaging of acute and chronic deep venous thrombosis in humans.

OBJECTIVE: The purpose of this study was to assess the ability of sonographic elasticity imaging to distinguish acute from chronic deep venous thrombosis (DVT). METHODS: Fifty-four patients, 26 with acute DVT and 28 with chronic DVT, were studied, and we analyzed the data in 46 patients, 23 with acute (mean age, 5.7 days) and 23 with chronic (>8 months) DVT. Scanning was performed with a 5-MHz linear array transducer during continuous freehand external deformation of each thrombus using the ultrasound scan head. The strains in the thrombi were normalized to the average strain between the skin surface and the back wall of the vein. Relative thrombus echogenicity was measured by comparing the echogenicity of the thrombus with that of the adjacent arterial lumen. Statistical analyses were performed with the Mann-Whitney U test and receiver operating characteristic analysis. RESULTS: The median normalized strain magnitude for the acute cases was 2.75, with an interquartile range of 2.4 to 3.71, whereas the median normalized strain magnitude for the chronic cases was 0.94, with interquartile range of 0.48 to 1.36. The difference was highly significant (P < 10(-7)). The area under the receiver operating characteristic curve (A(z)) was 0.97 +/- 0.02 (SE). The echogenicity difference between the populations was highly significant (P < 10(-5)), with A(z) of 0.92 +/- 0.04. The difference between the A(z) values was not significant (P > .05). CONCLUSIONS: In this population, sonographic elasticity imaging performs at least as well as thrombus echogenicity. Thrombus aging using elasticity imaging would be particularly helpful in evaluating symptoms in patients with post-thrombotic syndrome.     

Introduction to the BIOMED 2012 Feature Issue

The guest editors introduce a feature issue containing papers based on research presented at the BIOMED 2012 conference.OCIS code: (170.0170) Medical optics and biotechnologyFor the past two decades, the Optical Society of America has been organizing biennial topical meetings under the conference name BIOMED [1]. The presentations covered in this meeting are at the heart of biomedical optics, and the diversity of meeting themes covered has continued to grow with the application areas of the field. The papers published in this issue of Biomedical Optics Express are contributions from authors who presented their work at this past meeting, in April/May 2012 held in Miami FL.The meeting covered four full days of talks and posters in the areas of (1) Biomedical Applications of Digital Holography, (2) BioNanophotonic and Molecular Probes, (3) Optical Microscopy Techniques, (4) Photoacoustic Imaging and Spectroscopy, (5) Optical Coherence Tomography, (6) Optical Imaging and Tomography, and (7) Optical Spectroscopy. The conference was chaired by Dr. Claude A. Boccara (France), Dr. Xingde Li (USA) and Dr. Lev T. Perelman (USA). The intent of the conference is to bring together people to present in all of these areas, and every two years to repeat this conference. It has run every two years in Florida since 2002 and is planned to continue again in 2014 and beyond.This issue bands together 25 papers submitted to Biomedical Optics Express from talks and posters that were presented at the BIOMED 2012 conference.     

In vivo Intravascular Ultrasound-guided Photoacoustic Imaging of Lipid in Plaques Using an Animal Model of Atherosclerosis

We present a preliminary study demonstrating the capability of ultrasound-guided intravascular photoacoustic (IVPA) imaging to visualize the depth-resolved distribution of lipid deposits in atherosclerotic plaques in vivo. Based on the characteristic optical absorption of lipid in the near infrared wavelength range, IVPA imaging at a single, 1720 nm, wavelength was used to provide a spatially-resolved, direct measurement of lipid content in atherosclerotic arteries. By overlaying an IVPA image with a spatially co-registered intravascular ultrasound (IVUS) image, the combined IVPA/IVUS image was used to visualize lipid distribution within the vessel wall. Ultrasound-guided IVPA imaging was performed in vivo in the abdominal aorta of a Watanabe heritable hyperlipidemic (WHHL) rabbit. Subsequently, the excised rabbit aorta filled with a solution of red blood cells (RBC) was then imaged ex vivo, and histology was obtained in the section adjacent to the imaged cross-section. To demonstrate the potential for future clinical application of IVPA/IVUS imaging, a sample of diseased human right coronary artery (RCA) was also imaged. Both in vivo and ex vivo IVPA images clearly showed the distribution of lipid in the atherosclerotic vessels. In vivo IVPA imaging was able to identify diffuse, lipid-rich plaques in the WHHL rabbit model of atherosclerosis. Furthermore, IVPA imaging at a single wavelength was able to identify the lipid core within the human RCA ex vivo. Our results demonstrate that ultrasound-guided IVPA imaging can identify lipid in atherosclerotic plaques in vivo. Importantly, the IVPA/IVUS images were obtained in presence of luminal blood and no saline flush or balloon occlusion was required. Overall, our studies suggest that ultrasound-guided IVPA imaging can potentially be used for depth-resolved visualization of lipid deposits within the anatomical context of the vessel wall and lumen. Therefore, IVUS/IVPA imaging may become an important tool for the detection of rupture-prone plaques.