Multispectral analysis of magnetic resonance images

Magnetic resonance (MR) imaging systems produce spatial distribution estimates of proton density, relaxation time, and flow, in a two dimensional matrix form that is analogous to that of the image data obtained from multispectral imaging satellites. Advanced NASA satellite image processing offers sophisticated multispectral analysis of MR images. Spin echo and inversion recovery pulse sequence images were entered in a digital format compatible with satellite images and accurately registered pixel by pixel. Signatures of each tissue class were automatically determined using both supervised and unsupervised classification. Overall tissue classification was obtained in the form of a theme map. In MR images of the brain, for example, the classes included CSF, gray matter, white matter, subcutaneous fat, muscle, and bone. These methods provide an efficient means of identifying subtle relationships in a multi-image MR study.     

Public opponents of vaccination: a case study

Opposition to mass childhood vaccination is a world-wide phenomenon, particularly in industrialised countries. Unfounded claims about vaccination are perpetuated by parental lobby groups and individual spokespeople, some of whom have a medical or scientific background. This article focuses on one such spokesperson who has achieved particular notoriety. Dr. Viera Scheibner is a retired micropalaeontologist, without any formal training in health-related sciences, who tours the world claiming that vaccines are ineffective and dangerous and lead to a host of ills such as cancer and asthma. Professionals in public health or the clinical arena are from time to time called upon to publicly respond to her, or similar, claims disseminated during tours of Europe, North America or Australasia and in books and articles. Health professionals have expressed at how such spokespersons misrepresent the evidence on vaccine safety, resulting in the potential to undermine public confidence in immunisation. Media coverage, or proposed coverage, particularly of her more extreme claims, often makes health professionals engaged in immunisation feel obliged to respond. This paper describes Viera Scheibner’s approach, which follows a repetitious path and is representative of that taken by other public opponents of immunisation. We conclude by suggesting how health professionals might respond in the public arena.     

Focus group composition: a comparison between natural and constructed groups

OBJECTIVE: To provide insight into the effects of focus group composition. METHOD: In an early phase of an ongoing study of parental reception to messages about childhood immunisation, we conducted four focus groups; two with participants who had never met before (constructed groups) and two with participants who were part of a pre-established first-time mothers' group (natural groups). RESULTS: Marked differences were noted in the group dynamics, depth of interaction and diversity between groups. Discussions with constructed groups were animated, enthusiastic, expressed more divergent views and articulated greater complexities of the topic. Discussions with natural groups were generally flatter and less enthusiastic, displaying a higher level of apparent conformity to conventional wisdom. The need to protect other participants from potentially disturbing information about vaccination was expressed across groups but acted to censor natural groups, where participants knew more of each others' sensitivities. IMPLICATIONS: Insight into the factors contributing to such differences may enhance understanding of the contexts in which constructed groups are more appropriate. The processes of social censorship may be of primary interest to the researcher. However, where it is paramount to elicit a range of opinions about a potentially controversial topic, we suggest that natural groups in the delicate stage of norming be avoided. The peculiarities of each individual research circumstance are best explored in pilot studies.     

Rapid method for isolation of normal human peripheral blood eosinophils on discontinuous Percoll gradients and comparison with neutrophils

Previous studies on human eosinophils often have used cells from patients with hypereosinophilia syndrome or parasitosis owing to the difficulty in isolating pure populations of eosinophils from normal individuals. In the present study, human eosinophils were isolated with a purity of 97%, with 70% recovery from normal individuals with blood eosinophil counts of less than 3%. Human eosinophils are denser than neutrophils, but the range of densities of the two cell types overlap, making purification of eosinophils by density-gradient centrifugation difficult. However, if neutrophils were exposed to the chemotactic peptide (f-Met-Leu-Phe), which did not stimulate eosinophils, the neutrophils' density decreased, shifting them away from the density of eosinophils. Whole normal blood anticoagulated with EDTA was incubated at 37 degrees C for 15 minutes with 10(-6) mol/L f-Met-Leu-Phe and then layered over a discontinuous Percoll gradient (65% and 75% in diluted phosphate-buffered saline) and centrifuged at 400 g for 25 minutes at 22 degrees C. The cell layer between the 65% and 75% Percoll was collected and washed, and hypotonic lysis was used to remove erythrocytes. This cell layer contained 97.3 +/- 0.7% eosinophils (N = 8) with a yield of 4.9 X 10(4) eosinophils per milliliter of whole blood, or 70% of the total eosinophil count. The isolated eosinophils were in a quiescent state but responded to Escherichia coli endotoxin- activated serum with shape change and chemotaxis, membrane depolarization, and reduced nitroblue tetrazolium (96.0 +/- 1.0%), when stimulated with phorbol myristate acetate. In phagocytic assays, 89.3 +/- 1.3% of the eosinophils ingested Candida albicans v 96.0% +/- 1.0% of neutrophils. In contrast, the eosinophils did not respond chemotactically, alter membrane potential, or reduce nitroblue tetrazolium when treated with f-Met-Leu-Phe, and studies with f-Met-Leu- [3H]Phe showed that normal eosinophils lacked expression of receptors for f-Met-Leu-Phe. In control studies, normal eosinophils that were not exposed to f-Met-Leu-Phe during purification also failed to respond to f-Met-Leu-Phe, indicating intrinsic differences between normal eosinophils and neutrophils. Thus, exposure of whole blood to f-Met-Leu- Phe, followed by separation on Percoll is a simple method for rapid isolation of normal human eosinophils.     

Surgical versus non-surgical endodontic re-treatment for periradicular lesions

Background : Though success rates of endodontic initial treatment have been improving over the years, persistence of periapical disease is far from being a rare condition. The most common therapeutical options for the re‐treatment of teeth with periapical pathosis are non‐surgical orthograde treatment and surgical treatment. Selection between alternative treatments should be based on assessment of respective benefits (mainly healing) and risks from studies consistent with a high level of evidence. Objectives : To test the null hypothesis of no difference in outcome between surgical and non‐surgical therapy for endodontic re‐treatment of periradicular lesions. Search strategy : The Cochrane Oral Health Group Trials Register, CENTRAL, MEDLINE and EMBASE were searched with appropriate search strategies. Handsearching included eight dental journals. The bibliographies of relevant clinical trials and relevant articles were checked for identifying studies outside the handsearched journals. Seven manufacturers of instruments in the field of endodontics or endodontic surgery or both, as well as the authors of the identified randomized controlled trials (RCTs) were contacted in order to identify unpublished or ongoing RCTs. No language restriction was placed. The last electronic search was conducted on 3rd April 2007. Selection criteria : All RCTs about re‐treatment of teeth with periapical pathosis in which both surgical and non‐surgical approaches were used and having a follow up of at least 1 year were considered for the analysis. Data collection and analysis : A quality assessment of the included RCTs was carried out and the authors were contacted for missing information. We independently extracted the data in duplicate. We followed the Cochrane Oral Health Group's statistical guidelines. Main results : Three RCTs were identified, two of them reporting different data from the same clinical study. The risk of bias was judged as moderate for one study and high for the other one. One hundred and twenty‐six cases were followed up for at least 1 year, and 82 had a follow up of 4 years. At the 1‐year follow up the success rate for surgical treatment was slightly better than non‐surgical (risk ratio (RR) 1.13; 95% confidence interval (CI) 0.98 to 1.30). When the follow up was extended to 4 years (only one RCT made it) the outcome for the two procedures became similar. Authors' conclusions : The finding that healing rates can be higher for cases treated surgically as compared to those treated non‐surgically, at least in the short term, is based on two RCTs only. A single RCT reported that in the medium to long term healing rates for the two procedures are very similar. There is currently scarce evidence for a sound decision making process among alternative treatments for the re‐treatment of a periradicular pathosis. More well‐designed RCTs should be performed with follow up of at least 4 years, and with a consistent sample size, to detect a true difference in the long term between the outcomes of the two alternative treatments, if any exist.