The optimal reference population for cardiac normality in myocardial SPET in the detection of coronary artery stenoses: patients with normal coronary angiography or subjects with low likelihood of coronary artery disease?

Both subjects with a low likelihood for coronary artery disease (CAD) and patients with normal findings on coronary angiography have been used as reference populations in non-invasive stress testing, including myocardial perfusion scintigraphy. Both of these criteria of normality--low likelihood of CAD and normal coronary angiography--have been criticised, and consensus on this issue is lacking. The aim of this study was to compare two different reference populations by testing the performance of artificial neural networks designed to interpret myocardial scintigrams. The networks were trained on myocardial perfusion scintigrams from 87 patients with angiographically documented CAD and on studies from one of two different reference groups: 48 patients with no signs of CAD based on angiography or 128 healthy volunteers with a likelihood for CAD <5%. The performance of the two different networks was then tested using scintigrams from a separate test group of 68 patients. Coronary angiography was used as the gold standard in this group. The network trained on patients with no signs of CAD based on angiography showed an area under the receiver operating characteristic (ROC) curve of 93%. The ROC area for the network trained on healthy volunteers was 72%, and this difference was statistically significant (P=0.03). The results of this study using artificial neural networks suggest that normal angiography should be preferred as the reference standard in myocardial scintigraphy when a patient is examined for CAD prior to possible angiography. Whether the same is true for other indications, e.g. in prognostic evaluation, is unknown.

The impact on outcomes in a community hospital setting of using the AANS traumatic brain injury guidelines. Americans Associations for Neurologic Surgeons

BACKGROUND

Traumatic brain injury poses a serious public health challenge. Treatment paradigms have dramatically shifted with the introduction of the American Association of Neurologic Surgeons (AANS) Guidelines for the Management of Severe Head Injury. Implementation of the AANS guidelines positively affects patient outcomes and can be successfully introduced in a community hospital setting.

METHODS

Data were collected both retrospectively and prospectively from the records of all trauma patients between 1994 and 1999. A cohort of 93 patients was selected. Thirty-seven patients were treated before the implementation of the AANS guidelines, and these were statistically compared with 56 patients treated after the implementation of the guidelines.

RESULTS

Implementation of the recommendations in the AANS guidelines in a standardized protocol resulted in a 9.13 times higher odds ratio of a good outcome relative to the odds of a poor outcome or death compared with a group managed before the practice change. A Glasgow Coma Scale (GCS) admission score > 8 was associated with a 6.58 times higher odds ratio of a good outcome compared with a GCS admission score < or = 8. Odds ratio of a good outcome decreased by a factor of 0.92 for each year increase in age of patients starting at age 9. A dedicated neurotrauma team and comprehensive treatment algorithms are critical elements to this success. Hospital charges increased by more than $97,000 per patient, but are justifiable in the face of significantly improved outcomes.

CONCLUSION

Implementation of a traumatic brain injury protocol in a community hospital setting is practical and efficacious. Appropriate invasive monitoring of systemic and cerebral parameters guides care decisions. The protocol results in an increase in resource usage, but it also results in statistically improved outcomes justifying the increase in expenditures.

The transition from scotopic to photopic vision in 3-month-old infants and adults: an evaluation of the rod dominance hypothesis

The scotopic to photopic transition was tested in adults and 12-week-old infants using a large field motion nulling technique at a series of luminances between -3.57 and 2.70 log cd m(-2). The stimuli were composed of 0.25 cyc deg(-1), 5.6 Hz blue/black and yellow/black sinusoidal grating components, superimposed and moving in opposite directions. The contrasts of the two components were traded off to determine motion nulls at each luminance level. An eye movement based response measure was used for infant subjects, whereas self-report was used in adults. In both age groups, the motion null values approached a scotopic asymptote consistent with V'(lambda) at the lowest luminance levels, and a photopic asymptote consistent with V(10)(lambda) at the highest luminance levels. The scotopic to photopic transition was gradual and occurred over about 3 log units between about -2 and 1 log cd m(-2) in both groups. The null values for infants and adults were highly similar at each luminance level, and the shapes of the transition curves were virtually identical at the two ages. These data suggest that at each different luminance level, the balance between rod-initiated and cone-initiated signals in the extrafoveal luminance channel is similar or identical in 12-week-old infants and adults.

Electrokinetic injection for stacking neutral analytes in capillary and microchip electrophoresis

An on-column mechanism for electrokinetically injecting long sample plugs with simultaneous stacking of neutral analytes in capillary electrokinetic chromatography is presented. On-column stacking methods allow for the direct injection of long sample plugs into the capillary, with narrowing of the analyte peak width to allow for an increase in the detected signal. Low-pressure injections (approximately 50 mbar) are commonly used to introduce sample plugs containing neutral analytes. We demonstrate that injection can be accomplished by applying an electric field from the sample vial directly into the capillary, with neutral analytes injected by electroosmotic flow at up to 1 order of magnitude faster than the corresponding pressure injections. Since stacking occurs simultaneously with electrokinetic injection, stacking is initiated at the capillary inlet, resulting in an increased length of capillary remaining for separation. Reproducibility obtained for peak height and peak area with electroosmotic flow injection is comparable to that obtained with the pressure injection mode, while reproducibility of analysis time is markedly improved. Electrokinetic stacking of neutral analytes utilizing electroosmotic flow is demonstrated with discontinuous (high conductivity, high mobility) as well as continuous (equal conductivity, equal mobility) sample electrolytes. Injecting neutral analytes by electroosmotic flow affords a 10-fold or greater decrease in analysis times when capillaries of 50-microm i.d. or smaller are used. This stacking method should be exportable to dynamic pH junction stacking and electrokinetic chromatography with capillary arrays. Equations describing this electrokinetic injection mode are introduced and stacking of a neutral analyte on a microchip by electrokinetic injection using a simple cross-T channel configuration is demonstrated.

The growth of Bacillus stearothermophilus on stainless steel

AIMS

To determine the potential for Bacillus stearothermophilus cells to form biofilms of significance in dairy manufacture.

METHODS AND RESULTS

The ability of isolates of B. stearothermophilus from dairy manufacturing plants to attach to stainless steel surfaces was demonstrated by exposing stainless steel samples to suspensions of spores or vegetative cells and determining the numbers attaching using impedance microbiology. Spores attached more readily than vegetative cells. The attachment of cells to stainless steel was increased 10-100-fold by the presence of milk fouling the stainless steel. The growth of B. stearothermophilus as a biofilm on stainless steel surfaces was determined using a continuously flowing experimental reactor. Vegetative cells were released in greater numbers than spores from biofilms of most strains studied. Biofilms of one strain (B11) were studied in detail. Biofilms of > 106 cells cm-2 formed in the reactor and released approximately 106 cells ml-1 into milk passing over the biofilm. A doubling time of 25 min was calculated for this organism grown as a biofilm.

CONCLUSION

The formation of biofilms of thermophilic Bacillus species within the plant appears to be a likely cause of contamination of manufactured dairy products. Methods to control the formation of biofilms in dairy manufacturing plants are required to reduce the contamination of dairy products with thermophilic bacilli.

SIGNIFICANCE AND IMPACT OF THE STUDY

Biofilms of B. stearothermophilus growing in dairy manufacturing plants can explain the contamination of dairy products with these bacteria.

Infant light adaptation shows Weber's law at photopic illuminances

In the present study we investigate the dependence of photopic contrast thresholds on retinal illuminance in infants and adults. Contrast thresholds were measured at five retinal illuminances between about 6 and about 20,000 Td in subjects in both age groups. The forced-choice preferential looking technique was used in 3-month-old infants, and standard forced-choice techniques were used in adults. The stimulus was a 0.25 cy/deg squarewave grating phase alternated at 6 Hz. Infants' contrast thresholds were more than two log units higher than those of adults at all retinal illuminances. Contrast thresholds had a similar dependence on retinal illuminance in both infants and adults. For both age groups, contrast thresholds initially decreased with increasing retinal illuminance. However, at both ages, above a critical illuminance of about 200 Td, contrast thresholds remained constant, following Weber's law. Thus a vertical shift was sufficient to bring the two data sets into correspondence. In the context of a two-site model of light adaptation, our results imply that infants' elevated contrast thresholds cannot be explained solely on the basis of photoreceptoral immaturities. Later physiological immaturities must also limit infants' photopic contrast thresholds.

Long-term cancer risk in women given diethylstilbestrol (DES) during pregnancy

From 1940 through the 1960s, diethylstilbestrol (DES), a synthetic oestrogen, was given to pregnant women to prevent pregnancy complications and losses. Subsequent studies showed increased risks of reproductive tract abnormalities, particularly vaginal adenocarcinoma, in exposed daughters. An increased risk of breast cancer in the DES-exposed mothers was also found in some studies. In this report, we present further follow-up and a combined analysis of two cohorts of women who were exposed to DES during pregnancy. The purpose of our study was to evaluate maternal DES exposure in relation to risk of cancer, particularly tumours with a hormonal aetiology. DES exposure status was determined by a review of medical records of the Mothers Study cohort or clinical trial records of the Dieckmann Study. Poisson regression analyses were used to estimate relative risks (RR) and 95% confidence intervals (CI) for the relationship between DES and cancer occurrence. The study results demonstrated a modest association between DES exposure and breast cancer risk, RR = 1.27 (95% CI = 1.07-1.52). The increased risk was not exacerbated by a family history of breast cancer, or by use of oral contraceptives or hormone replacement therapy. We found no evidence that DES was associated with risk of ovarian, endometrial or other cancer.

Distal anterior compartment myopathy: a dysferlin mutation causing a new muscular dystrophy phenotype

We report a family with a new phenotype of autosomal recessive muscle dystrophy caused by a dysferlin mutation. The onset of the illness is distal, in the muscles of the anterior compartment group. The disease is rapidly progressive, leading to severe proximal weakness. Muscle biopsy showed moderate dystrophic changes with no vacuoles. Dysferlin immunostaining was negative. Gene analysis revealed a frameshift mutation in the exon 50 (delG5966) of the DYSF gene. This phenotype further demonstrates the clinical heterogeneity of the dysferlinopathies.

[Comparative study of echocardiography and magnetic resonance imaging in the assessment of left ventricular mass]

AIM OF THE STUDY

Echocardiography is a widely applied technique for the estimation of left ventricular mass, although magnetic resonance is considered as a reference method for this purpose. Both techniques were compared in the present study and the usefulness of a simplified method of calculation by magnetic resonance was also tested.

METHODS

Left ventricular mass was determined in 42 patients by M-mode echocardiography by the application of two equations: the so-called Penn's convention and that proposed by the American Society of Echocardiography. Magnetic resonance studies were also performed, left ventricular mass being estimated from an anatomical method (summation of contiguous transverse ventricular slices) that was considered as a reference, and also by means of a geometrical method (planimetry on a single longitudinal view).

RESULTS

Echocardiographic studies were judged as technically inadequate in 3/42 (7%) patients, while magnetic resonance was performed in all cases. Comparison between each echocardiographic method and the anatomical method of magnetic resonance showed a coefficient correlation of r = 0.70 (Penn's convention formula), and r = 0.71 (American Society of Echocardiography), with an overestimation being observed, particularly with Penn's convention method. The geometrical method of magnetic resonance showed an excellent correlation with the anatomical technique (r =0.93).

CONCLUSIONS

Magnetic resonance is more applicable for the estimation of left ventricular mass than M-mode echocardiography, with the latter showing an overestimation when compared with magnetic resonance, particularly with the Penn's convention method. A simplified method of geometrical estimation of left ventricular mass by magnetic resonance is a reliable alternative to the anatomical method.

Identification of somatic mutations of the MEN1 gene in sporadic endocrine tumours

Endocrine tumours of the pancreas, anterior pituitary or parathyroids arise either sporadically in the general population, or as a part of inherited syndromes such as multiple endocrine neoplasia type 1 (MEN 1). The mechanisms responsible for the development of sporadic endocrine lesions are not well understood, although loss of heterozygosity (LOH) of the MEN1 locus on chromosome 11q13 and somatic mutation of the MEN1 gene have been frequently associated with the development of MEN 1-type sporadic endocrine lesions. To further investigate the role of the MEN1 gene in sporadic endocrine tumorigenesis, we analysed DNA from 14 primary parathyroid lesions, 8 anterior pituitary tumours and 3 pancreatic tumours for the presence of somatic MEN1 gene mutations and LOH of seven microsatellite markers flanking the MEN1 locus. In addition, we similarly analysed 8 secondary parathyroid lesions which arose in patients with chronic renal failure. None of the patients studied had a family history of MEN 1. Three primary parathyroid lesions and one pancreatic tumour (glucagonoma) were found to have lost one allele at the MEN1 locus. Somatic mutations were identified by SSCP and sequence analysis in one of these parathyroid lesions (P320L) and in the glucagonoma (E179V). These results support previous findings that inactivation of the MEN1 tumour suppressor gene contributes to the development of sporadic MEN 1-type endocrine lesions but is not associated with the development of parathyroid hyperplasia seen in some renal failure patients.

Nonseptic monoarthritis: imaging features with clinical and histopathologic correlation

Diagnosis of septic arthritis requires aspiration and analysis of joint fluid. However, nonseptic articular disorders are fairly common and represent a significant diagnostic and therapeutic challenge. Such disorders include gout, Milwaukee shoulder, rapidly destructive articular disease, amyloid arthropathy, hemophilic arthropathy, primary synovial osteochondromatosis, pigmented villonodular synovitis, neuropathic arthropathy, and foreign-body synovitis. The clinical signs of articular disease, which include pain, swelling, and limitation of motion, are often nonspecific and can overlap with those of osseous or extraarticular disorders. Many articular processes have characteristic radiologic appearances that allow definitive diagnosis. Radiography is an important part of the evaluation of patients with articular disease. However, magnetic resonance (MR) imaging is the method of choice for characterizing the various disorders and assessing the full extent of osseous, chondral, and soft-tissue involvement. MR imaging can exquisitely demonstrate joint effusions, synovial proliferation, articular cartilage abnormalities, subchondral bone, ligaments, muscles, and juxtaarticular soft tissues. Although a wide spectrum of noninfectious processes may involve the joints, careful analysis of the imaging findings and correlation of these findings with the patient's clinical history can suggest a more specific diagnosis in most cases. Awareness and understanding of the underlying histopathologic findings aids in interpretation of MR images.

Identification of MEN1 gene mutations in families with MEN 1 and related disorders

Following identification of the MEN1 gene, we analysed patients from 12 MEN 1 families, 8 sporadic cases of MEN 1, and 13 patients with MEN 1-like symptoms (e.g. cases of familial isolated hyperparathyroidism (FIHPT), familial acromegaly, or atypical MEN 1 cases) for the presence of germline MEN1 mutations. The entire coding region of the MEN1 gene was sequenced, and mutations were detected in 11 MEN 1 families; one sporadic MEN 1 patient, one case of FIHPT and one MEN 1-like case. Constitutional DNA samples from individuals without MEN1 mutations were digested with several restriction enzymes, Southern blotted and probed with MEN1 cDNA to analyse for the presence of larger deletions of the MEN1 gene unable to be detected by PCR. One MEN 1 patient was found to carry such a deletion. This patient was heterozygous for the D418D polymorphism, however sequence analysis of RT-PCR products showed that only the variant allele was transcribed, thus confirming the result obtained by Southern analysis, which indicated loss of a region containing the initiation codon of one allele.

Management of raised intracranial pressure in children

Children suffer a significant number of head injuries as a result of their high activity levels, immature developmental skills and increased head-to-body mass ratio. Primary brain injury is irreversible, but secondary insults can be limited. Central to this is the management of raised intracranial pressure (ICP). The pathophysiology of head injury can explain some of the causes of raised ICP. Monitoring of ICP is important and this is closely linked to the maintenance of an adequate cerebral perfusion pressure and the importance of normovolaemia. Other interventions that have been shown to limit rises in ICP are appropriate use of positioning, mechanical ventilation and drug therapy. Less common therapies include jugular venous bulb oxygen saturation monitoring and the use of trometamol (THAM). Most nursing interventions do not actively reduce ICP, but they are central to its management. Reducing stimuli, avoiding cluster care, manual hyperinflation and limiting routine endotracheal suction may prevent an accumulative rise in ICP. Based on this literature review, it is possible to divide these interventions into first and second tier treatments, as shown in the protocol. Much of the suggested management will occur simultaneously, but it is important to assess the child's own response to each intervention and thus tailor treatment to minimize secondary brain injury.

Intra-abdominal hypertension and abdominal compartment syndrome in burn patients

BACKGROUND

Intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS) are known to occur in patients after major abdominal surgery. The incidence of IAH and ACS in the burn population is not known.

METHODS

We prospectively recorded the intra-abdominal pressures of major burn patients admitted to our burn center from February 1999 to September 1999. A bladder pressure greater than 25 mm Hg was diagnosed as IAH. ACS was diagnosed when pulmonary compliance decreased in association with persistent IAH and was treated with abdominal decompression.

RESULTS

Ten patients were placed on the protocol; of these, seven developed IAH. Five responded to conservative treatment. Two patients with 80% body surface area burns developed ACS and required decompression.

CONCLUSIONS

IAH occurs commonly in major burn patients, and ACS is seen regularly in patients with more than 70% body surface area burns. We recommend bladder pressure measurements after infusion of more than 0.25 L/kg during the acute resuscitation phase and for peak inspiratory pressures greater than 40 cm H2O. Whereas ACS warrants surgical decompression of the abdominal cavity, IAH usually responds to conservative therapy.

The psychophysics of visual search

Most theories of visual search emphasize issues of limited versus unlimited capacity and serial versus parallel processing. In the present article, we suggest a broader framework based on two principles, one empirical and one theoretical. The empirical principle is to focus on conditions at the intersection of visual search and the simple detection and discrimination paradigms of spatial vision. Such simple search conditions avoid artifacts and phenomena specific to more complex stimuli and tasks. The theoretical principle is to focus on the distinction between high and low threshold theory. While high threshold theory is largely discredited for simple detection and discrimination, it persists in the search literature. Furthermore, a low threshold theory such as signal detection theory can account for some of the phenomena attributed to limited capacity or serial processing. In the body of this article, we compare the predictions of high threshold theory and three versions of signal detection theory to the observed effects of manipulating set size, discriminability, number of targets, response bias, external noise, and distractor heterogeneity. For almost all cases, the results are inconsistent with high threshold theory and are consistent with all three versions of signal detection theory. In the Discussion, these simple theories are generalized to a larger domain that includes search asymmetry, multidimensional judgements including conjunction search, response time, search with multiple eye fixations and more general stimulus conditions. We conclude that low threshold theories can account for simple visual search without invoking mechanisms such as limited capacity or serial processing.

Scandinavian test of artificial neural network for classification of myocardial perfusion images

Artificial neural networks are systems of elementary computing units capable of learning from examples. They have been applied to automated interpretation of myocardial perfusion images and have been shown to perform even better than experienced physicians. It has been shown that physicians interpreting myocardial perfusion images benefit from the advice of such networks. These networks have been developed and validated in the same hospital. However, widespread use of neural networks will only take place if the networks can maintain a high accuracy in other hospitals, i.e. hospitals using different gamma cameras, different acquisition techniques, different study protocols, etc. The purpose of this study was to develop a neural network in one hospital and test it in another. An artificial neural network was trained to detect coronary artery disease using myocardial perfusion scintigrams from 135 patients at a Swedish hospital. Thereafter, this network was tested using scintigrams from 68 patients at a Danish hospital and compared to six criteria based on expert physician analysis and quantitative analysis by the CEqual program. The sensitivity of the network was significantly higher than that of one of the physician criteria (0. 92 versus 0.71) and two of the CEqual-based criteria (0.94 versus 0. 63 and 0.96 versus 0.65) compared at equal specificities. It was concluded that an artificial neural network can maintain high accuracy in a hospital other than the one where it was developed.

Automated interpretation of ventilation-perfusion lung scintigrams for the diagnosis of pulmonary embolism using artificial neural networks

The purpose of this study was to develop a completely automated method for the interpretation of ventilation-perfusion (V-P) lung scintigrams used in the diagnosis of pulmonary embolism. An artificial neural network was trained for the diagnosis of pulmonary embolism using 18 automatically obtained features from each set of V-P scintigrams. The techniques used to process the images included their alignment to templates, the construction of quotient images based on the ventilation and perfusion images, and the calculation of measures describing V-P mismatches in the quotient images. The templates represented lungs of normal size and shape without any pathological changes. Images that could not be properly aligned to the templates were detected and excluded automatically. After exclusion of those V-P scintigrams not properly aligned to the templates, 478 V-P scintigrams remained in a training group of consecutive patients with suspected pulmonary embolism, and a further 87 V-P scintigrams formed a separate test group comprising patients who had undergone pulmonary angiography. The performance of the neural network, measured as the area under the receiver operating characteristic curve, was 0.87 (95% confidence limits 0.82-0.92) in the training group and 0.79 (0.69-0.88) in the test group. It is concluded that a completely automated method can be used for the interpretation of V-P scintigrams. The performance of this method is similar to others previously presented, whereby features were extracted manually.

Ketoacidosis in young adults is not related to the islet antibodies at the diagnosis of Type 1 diabetes mellitus--a nationwide study

AIMS

To test the hypothesis that there is lower prevalence of islet antibodies in subjects with newly diagnosed Type 1 diabetes mellitus in young adulthood than in children is associated with less severe diabetes at time of diagnosis.

METHODS

This investigation was based on a nationwide study (Diabetes Incidence Study in Sweden) of 15-34-year-old newly diagnosed diabetic subjects. During 1992-1993, all diabetic subjects (excluding secondary and gestational diabetes) were reported on standardized forms, with information about clinical characteristics at diagnosis. The study examined islet cell antibodies (ICA) by indirect immunofluorescence, and autoantibodies to glutamic acid decarboxylase (GADA), tyrosine phosphatase-like antigen (IA-2A) and insulin (IAA) as well as C-peptide by radioimmunoassay.

RESULTS

Blood samples were available from 78 patients with diabetic ketoacidosis (DKA) and 517 non-acidotic patients. The prevalence of ICA (63% vs. 57%), GADA (63% vs. 66%), IA-2A (35% vs. 44%) and IAA (20% vs. 15%) were very similar in patients with or without DKA. The median levels of the four autoantibodies did not differ between the two groups. High blood glucose (P < 0.001) and low C-peptide levels (P < 0.001) were the only parameters found to be related to DKA.

CONCLUSIONS

The similarities in findings of newly diagnosed diabetic patients with or without DKA regarding ICA, GADA, IA-2A and IAA suggest that there is no relationship between the expression of antigenicity and the severity of beta-cell dysfunction. The lower prevalence of the four autoantibodies in 15-34-year-old diabetic subjects compared with previous findings in children is not explained by misclassification of diabetes type.

A signal detection model predicts the effects of set size on visual search accuracy for feature, conjunction, triple conjunction, and disjunction displays

Recently, quantitative models based on signal detection theory have been successfully applied to the prediction of human accuracy in visual search for a target that differs from distractors along a single attribute (feature search). The present paper extends these models for visual search accuracy to multidimensional search displays in which the target differs from the distractors along more than one feature dimension (conjunction, disjunction, and triple conjunction displays). The model assumes that each element in the display elicits a noisy representation for each of the relevant feature dimensions. The observer combines the representations across feature dimensions to obtain a single decision variable, and the stimulus with the maximum value determines the response. The model accurately predicts human experimental data on visual search accuracy in conjunctions and disjunctions of contrast and orientation. The model accounts for performance degradation without resorting to a limited-capacity spatially localized and temporally serial mechanism by which to bind information across feature dimensions.