Continuous ASL perfusion fMRI investigation of higher cognition: Quantification of tonic CBF changes during sustained attention and working memory tasks

Arterial spin labeling (ASL) perfusion fMRI is an emerging method in clinical neuroimaging. Its non-invasiveness, absence of low frequency noise, and ability to quantify the absolute level of cerebral blood flow (CBF) make the method ideal for longitudinal designs or low frequency paradigms. Despite the usefulness in the study of cognitive dysfunctions in clinical populations, perfusion activation studies to date have been conducted for simple sensorimotor paradigms or with single-slice acquisition, mainly due to technical challenges. Using our recently developed amplitude-modulated continuous ASL (CASL) perfusion fMRI protocol, we assessed the feasibility of a higher level cognitive activation study in twelve healthy subjects. Taking advantage of the ASL noise properties, we were able to study tonic CBF changes during uninterrupted 6-min continuous performance of working memory and sustained attention tasks. For the visual sustained attention task, regional CBF increases (6–12 ml/100 g/min) were detected in the right middle frontal gyrus, the bilateral occipital gyri, and the anterior cingulate/medial frontal gyri. During the 2-back working memory task, significantly increased activations (7–11 ml/100 g/min) were found in the left inferior frontal/precentral gyri, the left inferior parietal lobule, the anterior cingulate/medial frontal gyri, and the left occipital gyrus. Locations of activated and deactivated areas largely concur with previous PET and BOLD fMRI studies utilizing similar paradigms. These results demonstrate that CASL perfusion fMRI can be successfully utilized for the investigation of the tonic CBF changes associated with high level cognitive operations. Increased applications of the method to the investigation of cognitively impaired populations are expected to follow

Usability and Feasibility of a Spoken Language Outcome Monitoring Procedure in a Canadian Early Hearing Detection & Intervention Program: Results of a 1-Year Pilot

Abstract Purpose: Best practice recommendations for Early Hearing Detection and Intervention (EHDI) programs include routine spoken language outcome monitoring. The present article reports on pilot data that evaluated the usability and feasibility of a spoken language outcome monitoring procedure developed for Ontario’s Infant Hearing Program (IHP). This procedure included both Program-level monitoring using omnibus language tests from birth to 6;0 and individual vulnerability monitoring of key domains of spoken language known to be at risk in children who are deaf/hard-of-hearing. Methodology: Speech-language pathologists (SLPs) in the IHP piloted the new procedures for one year and provided feedback on the procedure through surveys at the end of the pilot. Results: Data was suggestive that the Program-level procedure might be sensitive to change over time and known predictors of spoken language outcomes. Some, but not all, Program-level test scores were predicted by the presence of additional developmental factors. None of the test scores were significantly predicted by severity of hearing loss. Depending on the tests and scores used, some aspects of the Program-level procedure to change over time. There was insufficient evidence to support individual vulnerability monitoring. SLPs reported significant concerns about the time involved in implementing both procedures. Conclusions: This article describes preliminary evidence suggesting that the Program-level procedure might be feasible to implement and useful for evaluating EHDI programs. Future evaluations are needed to determine whether the procedure can be accurately implemented to scale in the IHP, and whether the data that results from the procedure can meaningfully inform stakeholders’ decision-making

Developing a Spoken Language Outcome Monitoring Procedure for a Canadian Early Hearing Detection and Intervention Program: Process and Recommendations

Abstract Purpose: Routine spoken language outcome monitoring is one component of Early Hearing Detection and Intervention (EHDI) programs for children who are hard of hearing and learning a spoken language. However, there is no peerreviewed research that documents how spoken language outcome monitoring may be achieved, or what processes EHDI programs can use to develop these procedures. The present article describes the process used by a Canadian EHDI program and the final recommendations that were developed from this process. Methodology: Through consultation with the program’s stakeholders, consideration of the Joint Committee on Infant Hearing’s recommendations, and drawing on our own expertise in spoken language assessment, we developed an overall framework for monitoring spoken language. Based on the needs of the EHDI program, we conducted a scoping review and critical appraisal of norm-referenced tests to identify candidate tests to use within this framework. Results: We recommended a two-pronged assessment approach to measuring spoken language outcomes, including program-level assessment and individual vulnerability testing. We identified several tests that have been previously used to measure spoken language outcomes. There was little consistency in how tests were used across studies with no clear indicators as to which tests are the most appropriate to accomplish for which outcome monitoring purposes. Conclusions: This article reports on the framework and tests used by a Canadian EHDI program to accomplish spoken language outcome monitoring. We highlight different factors that need to be considered when designing spoken language outcome monitoring procedures and the complexity in doing so. Future work evaluating the effectiveness and feasibility of our recommendations is warranted. Keywords: Spoken language outcome monitoring; Program Evaluation Acronyms: CASL = Comprehensive Assessment of Spoken Language; CDI = Child Development Inventory; CELF = Comprehensive Evaluation of Language Fundamentals; COSMIN = Consensus Based Standards for the Selection of Health Status Measurement Instruments; DEAP = Diagnostic Evaluation of Articulation and Phonology; EHDI = Early Hearing Detection and Intervention; EOWPVT = Expressive One Word Vocabulary Test; EVT = Expressive Vocabulary Test; GFTA = Goldman-Fristoe Test of Articulation; IHP = Infant Hearing Program; KLPA = Khan-Lewis Phonological Analysis; MBCDI = MacArthur Bates Communicative Development Inventories; (M)CDI = (Minnesota) Child Development Inventory; MSEL = Mullen Scales of Early Learning; PLAI = Preschool Language Assessment Inventory; PLS = Preschool Language Scale; PPVT= Peabody Picture Vocabulary Test; SLP = speech language pathologist; TACL = Test of Auditory Comprehension of Language, VABS = Vineland Adaptive Behavior Scales Acknowledgements: The authors have no conflicts of interest to declare. This work was funded by the Ontario Ministry of Children, Community and Social Services. The authors would like to thank the speech-language pathologists, audiologists, and program managers who contributed to the development of these procedures and recommendations. We would also like to thank Kelsi Breton for her work in evaluating articles for inclusion and exclusion. Correspondence concerning this article should be addressed to: Olivia Daub, Graduate Program in Health and Rehabilitation Sciences, The University of Western Ontario, Elborn College, London, Ontario, Canada, N6G 1H1. Email: [email protected]

Quantification of perfusion fMRI using a numerical model of arterial spin labeling that accounts for dynamic transit time effects

A new approach to modeling the signal observed in arterial spin labeling (ASL) experiments during changing perfusion conditions is presented in this article. The new model uses numerical methods to extend first-order kinetic principles to include the changes in arrival time of the arterial tag that occur during neuronal activation. Estimation of the perfusion function from the ASL signal using this model is also demonstrated. The estimation algorithm uses a roughness penalty as well as prior information. The approach is demonstrated in numerical simulations and human experiments. The approach presented here is particularly suitable for fast ASL acquisition schemes, such as turbo continuous ASL (Turbo-CASL), which allows subtraction pairs to be acquired in less than 3 s but is sensitive to arrival time changes. This modeling approach can also be extended to other acquisition schemes. Magn Reson Med, 2005. © 2005 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48765/1/20613_ftp.pd

Improved quantification of perfusion in patients with cerebrovascular disease.

In recent years measurements of cerebral perfusion using bolus-tracking MRI have become common clinical practice in the diagnosis and management of patients with stroke and cerebrovascular disease. An active area of research is the development of methods to identify brain tissue that is at risk of irreversible damage, but amenable to salvage using reperfusion treatments, such as thrombolysis. However, the specificity and sensitivity of these methods are limited by the inaccuracies in the perfusion data. Accurate measurements of perfusion are difficult to obtain, especially in patients with cerebrovascular diseases. In particular, if the bolus of MR contrast is delayed and/or dispersed due to cerebral arterial abnormalities, perfusion is likely to be underestimated using the standard analysis techniques. The potential for such underestimation is often overlooked when using the perfusion maps to assess stroke patients. Since thrombolysis can increase the risk of haemorrhage, a misidentification of 'at-risk' tissue has potentially dangerous clinical implications. This thesis presents several methodologies which aim to improve the accuracy and interpretation of the analysed bolus-tracking data. Two novel data analysis techniques are proposed, which enable the identification of brain regions where delay and dispersion of the bolus are likely to bias the perfusion measurements. In this way true hypoperfusion can be distinguished from erroneously low perfusion estimates. The size of the perfusion measurement errors are investigated in vivo, and a parameterised characterisation of the bolus delay and dispersion is obtained. Such information is valuable for the interpretation of in vivo data, and for further investigation into the effects of abnormal vasculature on perfusion estimates. Finally, methodology is presented to minimise the perfusion measurement errors prevalent in patients with cerebrovascular diseases. The in vivo application of this method highlights the dangers of interpreting perfusion values independently of the bolus delay and dispersion