Clinical assessment of standard and generalized autocalibrating partially parallel acquisition diffusion imaging: effects of reduction factor and spatial resolution.

BACKGROUND AND PURPOSE: PI improves routine EPI-based DWI by enabling higher spatial resolution and reducing geometric distortion, though it remains unclear which of these is most important. We evaluated the relative contribution of these factors and assessed their ability to increase lesion conspicuity and diagnostic confidence by using a GRAPPA technique. MATERIALS AND METHODS: Four separate DWI scans were obtained at 1.5T in 48 patients with independent variation of in-plane spatial resolution (1.88 mm(2) versus 1.25 mm(2)) and/or reduction factor (R = 1 versus R = 3). A neuroradiologist with access to clinical history and additional imaging sequences provided a reference standard diagnosis for each case. Three blinded neuroradiologists assessed scans for abnormalities and also evaluated multiple imaging-quality metrics by using a 5-point ordinal scale. Logistic regression was used to determine the impact of each factor on subjective image quality and confidence. RESULTS: Reference standard diagnoses in the patient cohort were acute ischemic stroke (n = 30), ischemic stroke with hemorrhagic conversion (n = 4), intraparenchymal hemorrhage (n = 9), or no acute lesion (n = 5). While readers preferred both a higher reduction factor and a higher spatial resolution, the largest effect was due to an increased reduction factor (odds ratio, 47 ± 16). Small lesions were more confidently discriminated from artifacts on R = 3 images. The diagnosis changed in 5 of 48 scans, always toward the reference standard reading and exclusively for posterior fossa lesions. CONCLUSIONS: PI improves DWI primarily by reducing geometric distortion rather than by increasing spatial resolution. This outcome leads to a more accurate and confident diagnosis of small lesions.

A novel P300-based brain-computer interface stimulus presentation paradigm: moving beyond rows and columns.

OBJECTIVE: An electroencephalographic brain-computer interface (BCI) can provide a non-muscular means of communication for people with amyotrophic lateral sclerosis (ALS) or other neuromuscular disorders. We present a novel P300-based BCI stimulus presentation - the checkerboard paradigm (CBP). CBP performance is compared to that of the standard row/column paradigm (RCP) introduced by Farwell and Donchin (1988). METHODS: Using an 8x9 matrix of alphanumeric characters and keyboard commands, 18 participants used the CBP and RCP in counter-balanced fashion. With approximately 9-12 min of calibration data, we used a stepwise linear discriminant analysis for online classification of subsequent data. RESULTS: Mean online accuracy was significantly higher for the CBP, 92%, than for the RCP, 77%. Correcting for extra selections due to errors, mean bit rate was also significantly higher for the CBP, 23 bits/min, than for the RCP, 17 bits/min. Moreover, the two paradigms produced significantly different waveforms. Initial tests with three advanced ALS participants produced similar results. Furthermore, these individuals preferred the CBP to the RCP. CONCLUSIONS: These results suggest that the CBP is markedly superior to the RCP in performance and user acceptability. SIGNIFICANCE: The CBP has the potential to provide a substantially more effective BCI than the RCP. This is especially important for people with severe neuromuscular disabilities.

Toward a high-throughput auditory P300-based brain-computer interface.

OBJECTIVE: Brain-computer interface (BCI) technology can provide severely disabled people with non-muscular communication. For those most severely disabled, limitations in eye mobility or visual acuity may necessitate auditory BCI systems. The present study investigates the efficacy of the use of six environmental sounds to operate a 6x6 P300 Speller. METHODS: A two-group design was used to ascertain whether participants benefited from visual cues early in training. Group A (N=5) received only auditory stimuli during all 11 sessions, whereas Group AV (N=5) received simultaneous auditory and visual stimuli in initial sessions after which the visual stimuli were systematically removed. Stepwise linear discriminant analysis determined the matrix item that elicited the largest P300 response and thereby identified the desired choice. RESULTS: Online results and offline analyses showed that the two groups achieved equivalent accuracy. In the last session, eight of 10 participants achieved 50% or more, and four of these achieved 75% or more, online accuracy (2.8% accuracy expected by chance). Mean bit rates averaged about 2 bits/min, and maximum bit rates reached 5.6 bits/min. CONCLUSIONS: This study indicates that an auditory P300 BCI is feasible, that reasonable classification accuracy and rate of communication are achievable, and that the paradigm should be further evaluated with a group of severely disabled participants who have limited visual mobility. SIGNIFICANCE: With further development, this auditory P300 BCI could be of substantial value to severely disabled people who cannot use a visual BCI.

Comparison of multidetector CT angiography and MR imaging of cervical artery dissection.

BACKGROUND AND PURPOSE: Conventional angiography has been historically considered the gold standard for the diagnosis of cervical artery dissection, but MR imaging/MR angiography (MRA) and CT/CT angiography (CTA) are commonly used noninvasive alternatives. The goal of this study was to compare the ability of multidetector CT/CTA and MR imaging/MRA to detect common imaging findings of dissection. MATERIALS AND METHODS: Patients in the data base of our Stroke Center between 2003 and 2007 with dissections who had CT/CTA and MR imaging/MRA on initial work-up were reviewed retrospectively. Two neuroradiologists evaluated the images for associated findings of dissection, including acute ischemic stroke, luminal narrowing, vessel irregularity, wall thickening/hematoma, pseudoaneurysm, and intimal flap. The readers also subjectively rated each vessel on the basis of whether the imaging findings were more clearly displayed with CT/CTA or MR imaging/MRA or were equally apparent. RESULTS: Eighteen patients with 25 dissected vessels (15 internal carotid arteries [ICA] and 10 vertebral arteries [VA]) met the inclusion criteria. CT/CTA identified more intimal flaps, pseudoaneurysms, and high-grade stenoses than MR imaging/MRA. CT/CTA was preferred for diagnosis in 13 vessels (5 ICA, 8 VA), whereas MR imaging/MRA was preferred in 1 vessel (ICA). The 2 techniques were deemed equal in the remaining 11 vessels (9 ICA, 2 VA). A significant preference for CT/CTA was noted for VA dissections (P < .05), but not for ICA dissections. CONCLUSION: Multidetector CT/CTA visualized more features of cervical artery dissection than MR imaging/MRA. CT/CTA was subjectively favored for vertebral dissection, whereas there was no technique preference for ICA dissection. In many cases, MR imaging/MRA provided complementary or confirmatory information, particularly given its better depiction of ischemic complications.

Physiological activation of presynaptic metabotropic glutamate receptors increases intracellular calcium and glutamate release.

Activation of metabotropic glutamate receptors (mGluRs) has diverse effects on the functioning of vertebrate synapses. The cellular mechanisms that underlie these changes, however, are largely unknown. The role of presynaptic mGluRs in modulating Ca(2+) dynamics and regulating neurotransmitter release was investigated at the vestibulospinal-reticulospinal (VS-RS) synapse in the lamprey brain stem. Application of the specific Group I mGluRs antagonist 7-(hydroxyimino) cyclopropa[b]chromen-1a-carboxylate ethyl ester (CPCCOEt) reduced the amplitude of consecutive high-frequency evoked excitatory postsynaptic currents (EPSCs). A series of experiments using techniques of electrophysiology and calcium imaging were carried out to determine the cellular mechanisms by which this phenomenon occurs. Concentration-dependent increases in the pre- and postsynaptic [Ca(2+)](i) were seen with the application of mGluR agonists. Similarly, high-frequency stimulation of axons caused a Group I mGluR-dependent enhancement in presynaptic Ca(2+) transients. Application of mGluR agonist caused a depolarization of the presynaptic elements, while thapsigargin decreased the high-frequency stimulus- and agonist-induced rises in [Ca(2+)](i). These data suggest that both membrane depolarization and the release of Ca(2+) from intracellular stores potentially play a role in mGluR-induced Ca(2+) signaling. To determine the effect of this modulation of Ca(2+) dynamics on spontaneous glutamate release, miniature EPSCs were recorded from postsynaptic reticulospinal neurons. A potent Group I mGluR agonist, (S)-homoquisqualic acid, caused a large increase in the frequency of events. These results demonstrate the presence of presynaptic Group I mGluRs at the VS-RS synapse. Activation of these receptors leads to a rise in [Ca(2+)](i) and enhances the spontaneous and evoked release of glutamate. Taken together, these studies highlight the importance of synaptic activation of these facilitatory autoreceptors in both short-term plasticity and synaptic transmission.

Modulation of pre- and postsynaptic calcium dynamics by ionotropic glutamate receptors at a plastic synapse.

This study was conducted to assess the role of ionotropic glutamate receptors in the modulation of calcium dynamics on both sides of a vertebrate plastic synapse. Retrograde labeling of neuronal elements with high-affinity calcium-sensitive dyes was used in conjunction with confocal imaging techniques in an in vitro lamprey brain stem preparation. A prolonged calcium transient was measured both pre- and postsynaptically in response to a period of high-frequency ("tetanic") stimulation to the vestibulospinal-reticulospinal synapse. The ionotropic glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (10 microM) and D,L-2-amino-5-phosphonopentanoate (D,L-AP5; 100 microM) reduced the calcium signal in both compartments of the synapse. The presynaptic D,L-AP5-sensitive component was enhanced markedly by the removal of Mg2+ from the superfusate. Increasing the extracellular stimulus intensity progressively augmented the presynaptic calcium signal, suggesting the recruitment of excitatory axo-axonic inputs onto these fibers. Further, the presence of an excitatory amino acid-mediated presynaptic potential underlying a component of the Ca2+ signal was demonstrated by electrophysiological recordings from vestibulospinal axons. Bath application of agonist, in the presence of tetrodotoxin (1 microM), confirmed the existence of N-methyl-D-aspartate receptors at the presynaptic element capable of modulating calcium levels. The postsynaptic Ca2+ response, which is known to be necessary for long-term potentiation (LTP) induction at this synapse, was localized to areas of the dendritic tree that correlated with the location of known synaptic inputs; thus the synaptically activated rise in postsynaptic calcium may confer the synapse specificity of LTP induction previously demonstrated. In summary, we have demonstrated the existence of physiologically activated presynaptic ionotropic glutamate receptors that are capable of modulating levels of intracellular calcium and have highlighted the importance of receptor-mediated increases in postsynaptic calcium for neuronal plasticity in the lamprey.

What do consumers really think about dietary fat?

Nutrition communications in recent years have placed a priority on reducing dietary fat. Survey findings suggest this priority has fostered consumer obsession with and confusion about dietary fat and contributed to misperceptions about healthful eating. The obsession, confusion, and misperceptions about dietary fat and healthful eating, in turn, have created obstacles to achieving dietary goals. This overview of consumer knowledge, attitudes, and behaviors regarding dietary fat may allow dietetics and other professionals to tailor nutrition communication efforts toward clearing the confusion and better fostering success in reaching dietary goals. Nutrition communicators are encouraged to work together to restore reason to nutrition messages and recommendations and joy to food and eating in an effort to help consumers truly achieve nutrition and health goals.

Narrowing the gap: practical strategies for increasing whole-grain consumption.

Overcoming consumer confusion and doubt regarding nutrition recommendations is key to communicating the message to increase whole-grain foods in the diet. Nutrition communicators may do that more successfully by using four tactics to fashion messages about whole grains: (1) present a positive message; (2) keep it short and simple; (3) keep the message practical and flexible; (4) speak with a united voice. The quantitative recommendation to eat at least three servings of whole-grain foods daily also must be integrated into national nutrition documents, such as Healthy People 2000, Dietary Guidelines for Americans, the Food Guide Pyramid, Nutrition Recommendations for Canadians, and Canada's Food Guide to Healthy Eating, if we are to be truly successful in communicating the need to increase whole-grain consumption.

Survey of outpatient diet counselling services in British Columbia hospitals.

A fall 1985 mail survey of British Columbia (B.C.) hospitals offering outpatient diet counselling services documented a diversity of policies and procedures regarding both structural factors (i.e. personnel and facilities) and generic factors (i.e. referrals accepted and services provided). Results indicate a need to address many issues in outpatient dietetics in B.C. with a view to implementing changes and an ongoing program of evaluation, to ensure cost-effectiveness. Implications inferred from these results may be of value to dietitians elsewhere in Canada faced with the challenges of increasing competition for scarce health care resources.

Assessment of continuing education needs and preferences of British Columbia dietitians and nutritionists.

A survey was conducted among members of the B.C. Dietitians' and Nutritionists' Association to determine their perceived continuing education needs and preferences. Responses were received from 68.3% of the membership. The self-administered questionnaire elicited information about preferred format and timing of continuing education activities, incentives and deterrents to participation, employers' contributions to continuing education, and perceived need for further study of 78 topics categorized as nutritional care sciences, behavioural/communicative sciences and managerial sciences. Respondents indicated a preference for workshops, seminars and lectures, held outside of working hours. Topic, time and location were the major incentives/deterrents to participation in continuing education. Most respondents reported receiving paid time off work, but few reported receiving paid time off work, but few reported receiving any financial contribution towards their continuing education from their employers. Learning needs were higher for topics in the nutritional care and communication areas than for the managerial sciences topics. The questionnaire developed for this study has provided valuable information for program planners and could be readily adapted for use with other groups of dietitians/nutritionists.

A study of the clinical role of the dietitian as viewed by allied health professionals.

This study was designed to determine, among a sample of hospital administrators and directors of medicine and nursing, expectations and perceptions of the clinical role of dietitians employed in their hospitals. Data were collected by a mail questionnaire, consisting of an inventory of 40 clinical dietetics activities, developed in previous research on dietitians' role expectations and performance. Results indicated that respondents viewed the majority of inventory items as congruent with their expectations of the dietitians' ideal role. However, dietitians were perceived as not performing a role consistent with respondents' expectations. Activities related to the professional development, education, and research role of dietitians yielded higher disparity than did activities related to the provision of nutritional care. Interpretation of these findings and comparison with results of the dietitians' survey provide a basis for identifying sources of role conflict and ambiguity among the dietitians and allied professionals surveyed.

Evaluation of a nutrition innovation in secondary school home economics education.

The impact of a nutrition innovation, 'Foodstyles: perspectives on food for people' (BC Dairy Foundation, 1978), on the teaching practices of secondary school home economics educators in British Colombia, was evaluated. Teacher use of the Foodstyles program was the criterion used for evaluating its impact. Research questions were designed to determine how teachers use Foodstyles, whether those who use it accept its rationale, what factors influence teachers in their use of the program, and the value of Foodstyles in nutrition education practice. Implications from the results may be of value to nutrition educators elsewhere.

Clinical role expectations and performance of dietitians employed in British Columbia hospitals.

A mail survey was conducted among a sample of 232 dietitians employed in British Columbia hospitals to investigate their clinical role. An inventory of 40 typical clinical activities was developed, validated and administered to determine role expectations, role performance and role disparity. Questionnaires were returned by 181 (78%) of the dietitians but results are based on the responses of 140 as the others did not meet criteria for inclusion in the study. The majority of respondents were under 33 years of age and employed full time in hospitals with 200 or more beds. Nearly half were generalists and one-third were clinical specialists. Although their role expectations agree with the inventory for 92.5% of the activities, only 62.5% of the activities were actually performed. A moderate or high disparity, indicating a discrepancy between role expectation and role performance, was registered for 60% of the activities. Deterrents cited most frequently as responsible for role disparity were 'opportunity has never occurred' and 'lack of time'. Implications inferred from these results may be of value to dietetic educators and practitioners in British Columbia and elsewhere in Canada.

Physicians' opinions and counseling practices in maternal and infant nutrition.

Opinions and practices regarding maternal and infant nutrition of general practitioners, pediatricians, and obstetricians in the province of British Columbia were surveyed by mail questionnaires. Scores were significantly higher for physicians who: (a) Were female; (b) consulted with a nutritionist-dietitian; (c) had additional training; (d) attended continuing education programs; and (e) had studied nutrition in their medical school curriculum. Pediatricians' and obstetricians' practice scores were significantly higher than those of general practitioners. However, there were no significant differences among the nutrition opinion scores for the three groups of physicians.