Masthead,Volume 65, Issue 1

At sufficiently high Larmor frequencies, traveling electromagnetic waves along a magnet bore can be used for remote magnetic resonance excitation and detection, effectively using the bore as a waveguide. So far, this approach has relied only on the lowest waveguide modes and thus has not supported multiple‐channel operation for radiofrequency shimming and parallel imaging. In this work, this limitation is addressed by establishing a larger number of propagating modes and tapping their spatial field diversity with multiple waveguide ports. The number of available modes is increased by loading with dielectric inserts; the ports are implemented by stub and loop couplers at the end of a waveguide extension. The resulting traveling‐wave array, operated at 298 MHz in a 7T whole‐body magnet, is shown to enable radiofrequency shimming as well as parallel imaging with commonly used acceleration factors. The last part of the study concerns the amount of dielectric loading that is required. For the given Larmor frequency and bore dimensions, it is found that rather few water‐filled inserts, occupying ～5% of the bore cross‐section, are sufficient for effective parallel imaging. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Analysis of heritability of hormonal responses to alcohol in twins: beta-endorphin as a potential biomarker of genetic risk for alcoholism

BACKGROUND: Hormonal responses to alcohol have been reported to differ in subjects with and without a family history of alcoholism which suggests that alcohol-induced hormonal changes might be used to identify individuals who are at elevated genetic risk for developing alcoholism. However, before a biological response can be used as a marker of genetic risk for disease, it must first be demonstrated that the response is, in fact, heritable. The present study was designed to determine whether hormonal responses to alcohol are heritable. METHODS: The adrenocorticotropic hormone (ACTH), beta-endorphin (beta-E), cortisol (CORT), and prolactin (PRL) responses to alcohol were examined in male and female identical (monozygotic or MZ) and fraternal (dizygotic or DZ) twin pairs. Male subjects consumed 0.35 g ethanol/kg body weight (BW) and females consumed 0.325 g ethanol/kg BW in each of two alcohol drinking sessions administered 1 hr apart (total dose of 0.7 g/kg BW in males and 0.65 g/kg BW in females). Plasma hormone content was analyzed in samples collected before (resting conditions) and at 15, 60, 75, 120, 180, and 240 min after onset of drinking. Hormonal responses to alcohol were examined with twin analyses using the TWINAN90 program. A separate analysis was performed for each of the four hormones. A subset of subjects from each zygosity was seen on two separate occasions to establish retest reliability. Heritability of hormonal responses to alcohol was estimated using the intraclass correlation approach before and after removing the contribution of covariates that have the potential of influencing the plasma levels of these hormones. RESULTS: Resting plasma levels of all four hormones were within the expected range, and the beta-E, ACTH, and PRL responses to the alcohol challenge evidenced good test-retest reliability. Of the four hormones examined, the only one that showed significant heritability after alcohol drinking was beta-E. Heritability estimates were not altered for any of the four hormones after removal of the variance contributed by covariates, such as gender and age. CONCLUSIONS: Taken together with other recent findings, the results suggest that the beta-E response to alcohol may represent a new biomarker that can be used to identify individuals who are at elevated genetic risk for developing alcoholism.     

18F‐fluorodeoxyglucose positron emission tomography imaging in brain tumours: The Western Australia positron emission tomography/cyclotron service experience

¹⁸F‐fluorodeoxyglucose positron emission tomography (FDG‐PET) scans in the first 49 patients referred with either possible brain tumour or brain tumour recurrence were reviewed. FDG‐PET imaging was reported with reference to anatomical imaging. Based on the report the FDG study was classified as either positive or negative for the presence of tumour. Thirty‐eight cases were included in the analysis, 21 having pathological data and 17 with diagnostic clinical follow up. Eleven were excluded, as they had inadequate follow‐up data. Of the 21 cases with pathology, 18 were shown to have tumour. In this group there were five false‐negative scans and two false‐positive PET scans. Seventeen cases were assessed by clinical follow up, nine were considered to have been tumour. There were two false negatives with one false positive. The overall sensitivity, specificity and positive and negative predictive values were 74, 73, 87 and 53% respectively. This is similar to figures previously quoted in published work. Despite relatively limited numbers, the utility of FDG PET imaging in our hands is similar to published reports. With a positive predictive value of 87%, a positive FDG study indicates a high likelihood that there is brain tumour present. A negative study does not exclude the presence of tumour.     

American College of Cardiology/American Heart Association preoperative assessment guidelines reduce resource utilization before aortic surgery

BACKGROUND: Methods used for evaluation of cardiac risk before noncardiac surgery vary widely. We evaluated the effect over time on practice and resource utilization of implementing the American College of Cardiology/American Heart Association Guidelines on Preoperative Risk Assessment. METHODS: We compared 102 historical control patients who underwent elective abdominal aortic surgery (from January 1993 to December 1994) with 94 consecutive patients after guideline implementation (from July 1995 to December 1996) and 104 patients in a late after guideline implementation (from July 1, 1997, to September 30, 1998). Resource use (testing, revascularization, and costs) and outcomes (perioperative death and myocardial infarction) were examined. Patients with and without clinical markers of risk for perioperative cardiac complications were compared. RESULTS: The use of preoperative stress testing (88% to 47%; P <.00001), cardiac catheterization (24% to 11%; P <.05), and coronary revascularization (25% to 2%; P <.00001) decreased between control and postguideline groups, respectively. These changes persisted in the late postguideline group. Mean preoperative evaluation costs also fell ($1087 versus $171; P <.0001). Outcomes of death (4% versus 3% versus 2%) and myocardial infarction (7% versus 3% versus 5%) were not significantly different between control, postguideline, and late postguideline groups, respectively. Stress test rates were similar for patients at low risk versus high risk in the historical control group (84% versus 91%; P =.29) but lower for patients at low risk after guideline implementation (31% versus 61%; P =.003). CONCLUSION: Implementation of the American College of Cardiology/American Heart Association cardiac risk assessment guidelines appropriately reduced resource use and costs in patients who underwent elective aortic surgery without affecting outcomes. This effect was sustained 2 years after guideline implementation.     

Appropriateness of colorectal cancer screening: appraisal of evidence by experts.

OBJECTIVE: . To evaluate how the level of evidence perceived by an international panel of experts was concordant with the level of evidence found in the literature, to compare experts perceived level of evidence to their appropriateness scores, and to compare appropriateness criteria for colonoscopy between experts and an evidence-based approach. DESIGN: Comparison of expert panel opinions and systematic literature review regarding the level of evidence and appropriateness of colonoscopy indications. PARTICIPANTS: European Panel on the Appropriateness of Gastrointestinal Endoscopy multidisciplinary experts from 14 European countries. MAIN OUTCOME MEASURES: Concordance and weighted kappa coefficient between level of evidence as perceived by the experts' and that found in the literature, and between panel- and literature-based appropriateness categories. RESULTS: Experts overestimated the level of published evidence of 57 indications. Concordance between the level of evidence perceived by the experts and the actual level of evidence found in the literature was 36% (weighted kappa 0.18). Indications for colonoscopy were reported to be appropriate, uncertain, and inappropriate by the experts in 54, 19, and 27% of the cases, and by the literature in 37, 46, and 17% of the cases. A 46% agreement (weighted kappa 0.29) was found between literature-based and experts' appropriateness criteria. CONCLUSIONS: Experts often overestimated the level of evidence on which they based their decisions. However, rarely did the experts' judgement completely disagree with the literature, although concordance between panel- and literature-based appropriateness was only fair. A more explicit discussion of existing evidence should be undertaken with the experts before they evaluate appropriateness criteria.     

难治性青光眼两种治疗方法的比较

临床资料 2003-02／2004—10，难治性青光眼36例36眼，(男19，女17)例；年龄37—81(平均59．6)岁；术前视力：无光感6例，光感15例，手动13例，眼前数指2例；术前眼压：在5．59—10．77(平均8．01)kPa；1例系玻切术后继发性青光眼，35例系新生血管性青光眼(其中：视网膜静脉阻塞15例，糖尿病视网膜病变18例，原因不明2例)．①眼内窥镜下睫状体光凝术18例：在角膜缘环形剪开结膜，充分止血；在     

Innervation of supporting cells in the apical turns of the guinea pig cochlea is from type II afferent fibers

The outer supporting cells in the apical turns of the guinea pig cochlea receive a dense innervation. Our previous study (Fechner et al. [1998] J. Comp. Neurol. 400:299-300) suggested that this innervation of the Deiters' and Hensen's supporting cells was not derived from efferent fibers of the olivocochlear bundle, but its origin has not been further specified. To test the hypothesis that the innervation was afferent in origin, we traced apical afferent fibers that were retrogradely labeled by extracellular injections of horseradish peroxidase. Labeled afferent fibers were of two types: type I fibers contacted inner hair cells, whereas type II fibers crossed the tunnel and contacted outer hair cells. Significantly, most of the type II fibers also formed branches to the outer supporting cells. Although a few olivocochlear efferent fibers formed such branches, counts indicated that the overwhelming majority of the branches were produced by type II afferent fibers. These branches were not produced by basal type II fibers. Apical type II fibers also differed from basal fibers by having shorter lengths, spiraling both apically and basally, and contacting all three rows of outer hair cells. These innervation differences suggest differences in the ways that information from outer hair cells is processed in the apex versus the base of the cochlea.