Biomedical subjects

Robert C Welsh

Publications and source records attributed to Robert C Welsh.

At least 19 recordsLinked to original sources

PubMed2006

Differentiation of recurrent brain tumor versus radiation injury using diffusion tensor imaging in patients with new contrast-enhancing lesions.

BACKGROUND AND PURPOSE: The purpose of this study was to assess the use of diffusion tensor imaging (DTI) in the evaluation of new contrast-enhancing lesions and perilesional edema in patients previously treated for brain neoplasm in the differentiation of recurrent neoplasm from treatment-related injury. METHODS: Twenty-eight patients with new contrast-enhancing lesions and perilesional edema at the site of previously treated brain neoplasms were retrospectively reviewed. Nine directional echoplanar DTIs with b=1000 s/mm(2) were obtained using a single-shot spin-echo echoplanar imaging. Standardized regions of interest were manually drawn in several regions. Mean apparent diffusion coefficient (ADC), fractional anisotropy (FA) and eigenvalue indices (lambda( parallel) and lambda( perpendicular)) and their ratios relative to the contralateral side were compared in patients with recurrent neoplasm versus patients with radiation injury, as established by histological examination or by clinical course, including long-term imaging studies and magnetic resonance spectroscopy. RESULTS: The ADC values in the contrast-enhancing lesions were significantly higher (P=.01) for the recurrence group (range=1.01 x 10(-3) to 1.66 x 10(-3) mm(2)/s; mean+/-S.D.=1.27+/-0.15) than for the nonrecurrence group (range=0.9 x 10(-3) to 1.31 x 10(-3) mm(2)/s; mean+/-S.D.=1.12+/-0.14). The ADC ratios in the white matter tracts in perilesional edema trended higher (P=.09) in treatment-related injury than in recurrent neoplasm (mean+/-S.D.=1.85+/-0.30 vs. 1.60+/-0.27, respectively). FA ratios were significantly higher in normal-appearing white matter (NAWM) tracts adjacent to the edema in the nonrecurrence group (mean+/-S.D.=0.89+/-0.15) than in those in the recurrence group (mean+/-S.D.=0.74+/-0.14; P=.03). Both eigenvalue indices lambda( parallel) and lambda( perpendicular) were significantly higher in contrast-enhancing lesions in the recurrence group than in those in the nonrecurrence group (P=.02). As well, both eigenvalue indices lambda( parallel) and lambda( perpendicular) were significantly higher in perilesional edema than in normal white matter (P<.01 and P<.001, respectively) in both groups. CONCLUSION: The assessment of diffusion properties, especially ADC values and ADC ratios, in contrast-enhancing lesions, perilesional edema and NAWM adjacent to the edema in the follow-up of new contrast-enhancing lesions at the site of previously treated brain neoplasms may add to the information obtained by other imaging techniques in the differentiation of radiation injury from tumor recurrence.

Adolescent↗

PubMed2006

Catheter thrombosis during primary percutaneous coronary intervention for acute ST elevation myocardial infarction despite subcutaneous low-molecular-weight heparin, acetylsalicylic acid, clopidogrel and abciximab pretreatment.

BACKGROUND: Subcutaneous enoxaparin is increasingly employed as the antithrombin of choice in non-ST elevation myocardial infarction and in conjunction with various fibrinolytic regimens in acute ST elevation myocardial infarction (STEMI). Few data exist describing the use of subcutaneous or intravenous enoxaparin as an anticoagulant in the highly thrombotic setting of primary percutaneous coronary intervention (PCI) for STEMI. METHODS: The Which Early ST Elevation Therapy (WEST) study compared fibrinolysis (with and without early cardiac catheterization) with primary PCI in a setting that expedited both strategies on first medical contact. Patients assigned primary PCI are administered acetylsalicylic acid 325 mg, clopidogrel 300 mg and subcutaneous enoxaparin 1 mg/kg before transport to a PCI centre. Of 36 initial patients treated with primary PCI, three patients had procedures that were complicated by extensive thrombosis within coronary catheters and on PCI equipment. RESULTS: Index cases were men aged 43 to 68 years who presented with confirmed STEMI and angiographically proven acute total or subtotal occlusion of a major epicardial coronary segment. During PCI, performed 76 min to 102 min following enoxaparin administration, a clot developed within the guide catheter or on the coronary guidewires and balloon catheter shafts, thus necessitating the replacement of all PCI equipment. In one case, there was evidence of continued intracoronary clot propagation and embolization. CONCLUSION: A single, conventional, weight-adjusted dose of subcutaneous enoxaparin before expedited primary PCI for STEMI may not provide a reliable antithrombotic effect. Supplementary intravenous enoxaparin is now strongly recommended within the WEST study, and a substudy evaluating pre- and postprocedural antifactor Xa activity has been initiated.

Abciximab↗

PubMed2006

Medial frontal cortex activity and loss-related responses to errors.

Making an error elicits activity from brain regions that monitor performance, especially the medial frontal cortex (MFC). However, uncertainty exists about whether the posterior or anterior/rostral MFC processes errors and to what degree affective responses to errors are mediated in the MFC, specifically the rostral anterior cingulate cortex (rACC). To test the hypothesis that rACC mediates a type of affective response, we conceptualized affect in response to an error as a reaction to loss and amplified this response with a monetary penalty. While subjects performed a cognitive interference task during functional magnetic resonance imaging, hemodynamic activity in the rACC was significantly greater when subjects lost money as a result of an error compared with errors that did not lead to monetary loss. A significant interaction between the incentive conditions and error events demonstrated that the effect was not merely attributable to working harder to win (or not lose) money, although an effect of motivation was noted in the mid-MFC. Activation foci also occurred in similar regions of the posterior MFC for error and interference processing, which were not modulated by the incentive conditions. However, at the level of the individual subject, substantial functional variability occurred along the MFC during error processing, including foci in the rostral/anterior extent of the MFC not appearing in the group analysis. The findings support the hypothesis that the rostral extent of the MFC (rACC) processes loss-related responses to errors, and individual differences may account for some of the reported variation of error-related foci in the MFC.

Adult↗

PubMed2006

Decreased neural specialization in old adults on a working memory task.

Compelling evidence shows that there is decreased neural specialization in the ventral visual cortex in older adults under passive viewing conditions. We assessed whether such specialization would be maintained on a working memory task and whether decreased specialization co-occurred with increased prefrontal activations. Participants encoded three faces or houses and maintained the set across an 8-s interval. Results provided evidence for less specialization of faces and houses in older adults than in younger adults, while the middle and inferior frontal cortex showed increased activation in elders compared with the young.

Adolescent↗

PubMed2006

Effect of acute increases in pulmonary vascular pressures on exercise pulmonary gas exchange.

The purpose of this study was to determine the effect of acute increases in pulmonary vascular pressures, caused by the application of lower-body positive pressure (LBPP), on exercise alveolar-to-arterial PO2 difference (A-aDO2), anatomical intrapulmonary (IP) shunt recruitment, and ventilation. Eight healthy men performed graded upright cycling to 90% maximal oxygen uptake under normal conditions and with 52 Torr (1 psi) of LBPP. Pulmonary arterial (PAP) and pulmonary artery wedge pressures (PAWP) were measured with a Swan-Ganz catheter. Arterial blood samples were obtained from a radial artery catheter, cardiac output was calculated by the direct Fick method, and anatomical IP shunt was determined by administering agitated saline during continuous two-dimensional echocardiography. LBPP increased both PAP and PAWP while upright at rest, and at all points during exercise (mean increase in PAP and PAWP 3.7 and 4.0 mmHg, respectively, P<0.05). There were no differences in exercise oxygen uptake or cardiac output between control and LBPP. Despite the increased PAP and PAWP with LBPP, A-aDO2 was not affected. In the upright resting position, there was no evidence of shunt in the control condition, whereas LBPP caused shunt in one subject. At the lowest exercise workload (75 W), shunt occurred in three subjects during control and in four subjects with LBPP. LBPP did not affect IP shunt recruitment during subsequent higher workloads. Minute ventilation and arterial PcO2 were not consistently affected by LBPP. Therefore, small acute increases in pulmonary vascular pressures do not widen exercise A-aDO2 or consistently affect IP shunt recruitment or ventilation.

Adult↗

PubMed2006

Does fitness level modulate the cardiovascular hemodynamic response to exercise?

Subjects with greater aerobic fitness demonstrate better diastolic compliance at rest, but whether fitness modulates exercise cardiac compliance and cardiac filling pressures remains to be determined. On the basis of maximal oxygen consumption (VO2max), healthy male subjects were categorized into either low (LO: VO2max=43+/-6 ml.kg-1.min-1; n=3) or high (HI: VO2max=60+/-3 ml.kg-1.min-1; n=5) aerobic power. Subjects performed incremental cycle exercise to 90% Vo(2max). Right atrial (RAP) and pulmonary artery wedge (PAWP) pressures were measured, and left ventricular (LV) transmural filling pressure (TMFP=PAWP-RAP) was calculated. Cardiac output (CO) and stroke volume (SV) were determined by direct Fick, and LV end-diastolic volume (EDV) was estimated from echocardiographic fractional area change and Fick SV. There were no between-group differences for any measure at rest. At a submaximal workload of 150 W, PAWP and TMFP were higher (P<0.05) in LO compared with HI (12 vs. 8 mmHg, and 9 vs. 4 mmHg, respectively). At peak exercise, CO, SV, and EDV were lower in LO (P<0.05). RAP was not different at peak exercise, but PAWP (23 vs. 15 mmHg) and TMFP (12 vs. 6 mmHg) were higher in LO (P<0.05). Compared with less fit subjects, subjects with greater aerobic fitness demonstrated lower LV filling pressures during exercise, whereas SV and EDV were either similar (submaximal exercise) or higher (peak exercise), suggesting superior diastolic function and compliance.

Adult↗

PubMed2006

Neural correlates of social and nonsocial emotions: An fMRI study.

Common theories of emotion emphasize valence and arousal dimensions or alternatively, specific emotions, and the search for the underlying neurocircuitry is underway. However, it is likely that other important dimensions for emotional neurocircuitry exist, and one of them is sociality. A social dimension may code whether emotions are addressing an individual's biological/visceral need versus more remote social goals involving semantic meaning or intentionality. Thus, for practical purposes, social emotions may be distinguished from nonsocial emotions based in part on the presence of human forms. In the current fMRI study, we aimed to compare regional coding of the sociality dimension of emotion (nonsocial versus social) versus the valence dimension of emotion (positive versus negative). Using a novel fMRI paradigm, film and picture stimuli were combined to induce and maintain four emotions varying along social and valence dimensions. Nonsocial emotions of positively valenced appetite and negatively valenced disgust and social emotions of positively valenced joy/amusement and negatively valenced sadness were studied. All conditions activated the thalamus. Appetite and disgust activated posterior insula and visual cortex, whereas joy/amusement and sadness activated extended amygdala, superior temporal gyrus, hippocampus, and posterior cingulate. Activations within the anterior cingulate, nucleus accumbens, orbitofrontal cortex, and amygdala were modulated by both social and valence dimensions. Overall, these findings highlight that sociality has a key role in processing emotional valence, which may have implications for patient populations with social and emotional deficits.

Adult↗

PubMed2006

Feasibility and applicability of paramedic-based prehospital fibrinolysis in a large North American center.

BACKGROUND: Although considered the highest level of evidence and critical-to-test novel therapies, clinical trials are unrepresentative of the "real world" as they lack a true patient denominator, which limits general applicability of results. Accordingly, in conjunction with the Assessment of the Safety and Efficacy of a New Thrombolytic Regimen 3+ trial, we evaluated a comprehensive contemporary cohort of patients with ST segment elevation myocardial infarction (STEMI) to investigate: feasibility, applicability, safety, and efficacy of de novo paramedic-based prehospital fibrinolysis (PHF) program. METHODS: Prospective observational comparative cohort of all patients with STEMI encountered during the Assessment of the Safety and Efficacy of a New Thrombolytic Regimen 3+ enrollment period. Time-to-treatment, systematic electrocardiographic (ECG) analysis, peak creatine kinase, inhospital clinical events, and mortality were assessed. RESULTS: During the 22-month study period, 1095 patients with STEMI were admitted to hospital; 46% (119/258) of eligible patients received PHF (< or = 6 hours of symptom onset by ambulance). Paramedics contacted the study physician 3.6 times per week: 33% (119/357) of patients enrolled, and ECG transmission failure is 6%. Time-to-treatment was reduced with PHF versus inhospital (1 hour 43 minutes vs 2 hours 38 minutes; P < .001). Despite higher baseline Thrombolysis in Myocardial Infarction Scores and greater ECG territory at risk (ST), prehospital patients achieved more favorable outcomes: peak creatine kinase (1413 vs 1549 U/L; P = .122), Q wave at discharge (56.3% vs 70.7%; P = .003), and intracranial hemorrhage (0% vs 0.8%; P < 1.0), respectively. Inhospital mortality for PHF versus inhospital patients was 3.4% versus 4.8% (P = .627), with an adjusted odds ratio of 0.60 (confidence interval, 0.19-1.87). CONCLUSION: Feasibility and applicability of PHF was demonstrated with a substantial reduction in treatment delay and favorable clinical outcomes. Extending the unrealized potential of paramedic-based PHF programs in North America is feasible and desirable.

Aged↗

PubMed2006

Cultural differences in neural function associated with object processing.

Behavioral research suggests that Westerners focus more on objects, whereas East Asians attend more to relationships and contexts. We evaluated the neural basis for these cultural differences in an event-related fMRI study. East Asian and American participants incidentally encoded pictures of (1) a target object alone, (2) a background scene with no discernable target object, and (3) a distinct target object against a meaningful background. Americans, relative to East Asians, activated more regions implicated in object processing, including bilateral middle temporal gyrus, left superior parietal/angular gyrus, and right superior temporal/supramarginal gyrus. In contrast to the cultural differences in object-processing areas, few differences emerged in background-processing regions. These results suggest that cultural experiences subtly direct neuralactivity, particularly for focal objects, at an early stage of scene encoding.

Adolescent↗

PubMed2005

Prolonged strenuous exercise alters the cardiovascular response to dobutamine stimulation in male athletes.

Prolonged strenuous exercise has been associated with transient impairment in left ventricular (LV) systolic and diastolic function that has been termed 'cardiac fatigue'. It has been postulated that cardiac beta-adrenoreceptor desensitization may play a central role; however, data are limited. Accordingly, we assessed the cardiovascular response to progressive dobutamine stimulation after prolonged strenuous exercise (2 km swim, 90 km bike, 21 km run). Nine experienced male athletes were studied: PRE (2-3 days before), POST (after) and REC (1-2 days later). The cardiovascular response to progressive continuous dobutamine stimulation (0, 5, 20, and 40 microg kg(-1) min(-1)) was assessed, including heart rate (HR), systolic blood pressure (SBP), LV cavity areas (two-dimensional echocardiography) and contractility (end-systolic elastance, SBP/end-systolic cavity area (ESCA)). POST there was limited evidence of myocardial necrosis (measured by troponin I), while catecholamines were elevated. HR was higher POST (mean +/-s.d.; PRE, 58 +/- 9; POST, 79 +/- 9; REC, 57 +/- 7 beats min(-1); P < 0.05), while SBP was lower (PRE, 127 +/- 15; POST, 116 +/- 9; REC, 121 +/- 12 mmHg; P < 0.05). A blunted HR, SBP and LV contractility (SBP/ESCA; PRE 29 +/- 6 versus POST 20 +/- 6 mmHg cm(-2); P < 0.05) response to dobutamine was demonstrated POST, with values returning towards baseline in REC. Following prolonged strenuous exercise, the chronotropic and inotropic response to dobutamine stimulation is blunted. This study supports the hypothesis that beta-receptor downregulation and/or desensitization may play a major role in prolonged-strenuous-exercise-mediated cardiac fatigue.

Adult↗

PubMed2005

Sustained activation of the hippocampus in response to fearful faces in schizophrenia.

BACKGROUND: In healthy individuals, the activity of the medial temporal lobe habituates rapidly with the repeated presentation of a stimulus. Using functional magnetic resonance imaging (fMRI), we tested the hypothesis that habituation of the medial temporal lobe is reduced in schizophrenia. METHODS: During fMRI scanning, fearful and happy faces were presented repeatedly to healthy control subjects (n =16) and patients with schizophrenia (n =18). Habituation of medial temporal lobe structures was measured by comparing the hemodynamic response occurring during the early and late portions of the presentation of each face. RESULTS: Control subjects demonstrated significant medial temporal lobe habituation to fearful but not to happy faces. In contrast, patients with schizophrenia did not demonstrate medial temporal lobe habituation in response to fearful or happy faces. In a direct, between-group comparison, right hippocampal habituation to fearful faces was significantly greater in control subjects than in the schizophrenia patients. Also, there were no significant differences between the patients and control subjects in the early medial temporal lobe response to fearful faces, suggesting that attenuated hippocampal habituation in schizophrenia is not associated with a reduction in initial activation. CONCLUSIONS: These findings suggest that there is abnormal modulation of hippocampal responses to fearful faces in schizophrenia.

Adult↗

PubMed2005

Error-related hyperactivity of the anterior cingulate cortex in obsessive-compulsive disorder.

BACKGROUND: Hyperactivity of the anterior cingulate cortex (ACC) in patients with obsessive-compulsive disorder (OCD) has been shown to increase with symptom provocation and to normalize with treatment-induced symptom reduction. Although the functional significance of anterior cingulate involvement in OCD remains unknown, electrophysiological evidence has linked this region to error-processing abnormalities in patients with OCD. In this functional magnetic resonance imaging (fMRI) study, we sought to further localize error-processing differences within the ACC of OCD patients compared with healthy subjects. METHODS: Event-related fMRI data were collected for eight OCD patients and seven healthy subjects during the performance of a simple cognitive task designed to elicit errors but not OCD symptoms. RESULTS: Both OCD patients and healthy subjects demonstrated dorsal ACC activation during error commission. The OCD patients exhibited significantly greater error-related activation of the rostral ACC than comparison subjects. Activity in this region was positively correlated with symptom severity in the patients. CONCLUSIONS: Error-processing abnormalities within the rostral anterior cingulate occur in the absence of symptom expression in patients with OCD.

Adult↗

PubMed2005

Aging and the neural correlates of successful picture encoding: frontal activations compensate for decreased medial-temporal activity.

We investigated the hypothesis that increased prefrontal activations in older adults are compensatory for decreases in medial-temporal activations that occur with age. Because scene encoding engages both hippocampal and prefrontal sites, we examined incidental encoding of scenes by 14 young and 13 older adults in a subsequent memory paradigm using functional magnetic resonance imaging (fMRI). Behavioral results indicated that there were equivalent numbers of remembered and forgotten items, which did not vary as a function of age. In an fMRI analysis subtracting forgotten items from remembered items, younger and older adults both activated inferior frontal and lateral occipital regions bilaterally; however, older adults showed less activation than young adults in the left and right parahippocampus and more activation than young adults in the middle frontal cortex. Moreover, correlations between inferior frontal and parahippocampal activity were significantly negative for old but not young, suggesting that those older adults who showed the least engagement of the parahippocampus activated inferior frontal areas the most. Because the analyses included only the unique activations associated with remembered items, these data suggest that prefrontal regions could serve a compensatory role for declines in medial-temporal activations with age.

Adult↗

PubMed2005

Coronary artery disease is common in nonuremic, asymptomatic type 1 diabetic islet transplant candidates.

OBJECTIVE: Coronary artery disease (CAD) is the most common cause of death in patients with type 1 diabetes. Asymptomatic CAD is common in uremic diabetic patients, but its prevalence in nonuremic type 1 diabetic patients is unknown. The prevalence of CAD was determined by coronary angiography and the performance of noninvasive cardiac investigation evaluated in type 1 diabetic islet transplant (ITX) candidates with preserved renal function. RESEARCH DESIGN AND METHODS: A total of 60 consecutive type 1 diabetic ITX candidates (average age 46 years [mean 24-64], 23 men, and 47% ever smokers) underwent coronary angiography, electrocardiographic stress testing (EST), and myocardial perfusion imaging (MPI) in a prospective cohort study. CAD was indicated on angiography by the presence of stenoses >50%. Models to predict CAD were examined by logistic regression. RESULTS: Most subjects (53 of 60) had no history or symptoms of CAD; 23 (43%) of these asymptomatic subjects had stenoses >50%. CAD was associated with age, duration of diabetes, hypertension, and smoking. Although specific, EST and MPI were not sensitive as predictors of CAD on angiography (specificity 0.97 and 0.93, sensitivity 0.17 and 0.04, respectively) but helped identify two of three subjects requiring revascularization. EST and MPI did not enhance logistic regression models. A clinical algorithm to identify low-risk subjects who may not require angiography was highly sensitive but was applicable only to a minority (n = 8, sensitivity 1.0, specificity 0.27, negative predictive value 1.0). CONCLUSIONS: Nonuremic type 1 diabetic patients with hypoglycemic unawareness and/or metabolic lability referred for ITX are at high risk for asymptomatic CAD despite negative noninvasive investigations. Aggressive management of cardiovascular risk factors and further investigation into optimal cardiac risk stratification in type 1 diabetes are warranted.

Adult↗

PubMed2005

Tumour on the tricuspid valve: metastatic osteosarcoma and the heart.

The antemortem diagnosis of cardiac metastases in osteogenic sarcoma has been documented in only 25 cases over the past 50 years, whereas a prevalence as high as 20% is seen at autopsy, suggesting that cardiac involvement is a late stage complication. As the survival times for primary osteosarcoma continue to improve, previously rare, late stage complications will undoubtedly become more prevalent. In addition to presenting a new case of cardiac metastasis with prolonged survival, the present case report reviews the 25 cases from the literature to illustrate the distinguishing characteristics and clinical presentation, as well as to draw conclusions regarding investigation and management. The demographic differences include female sex, advanced age at the time of diagnosis and longer interval to onset of secondary disease. The clinical characteristics involve hemodynamic compromise or precordial abnormality, with magnetic resonance imaging emerging as the gold standard for diagnosis. Cardiac involvement is a strong predictor of disease elsewhere and mandates careful surveillance, with surgical management likely providing the best outcome.

Adolescent↗

PubMed2004

Intra-pulmonary shunt and pulmonary gas exchange during exercise in humans.

In young, healthy people the alveolar-arterial P(O(2)) difference (A-aDO(2)) is small at rest, but frequently increases during exercise. Previously, investigators have focused on ventilation/perfusion mismatch and diffusion abnormalities to explain the impairment in gas exchange, as significant physiological intra-pulmonary shunt has not been found. The aim of this study was to use a non-gas exchange method to determine if anatomical intra-pulmonary (I-P) shunts develop during exercise, and, if so, whether there is a relationship between shunt and increased A-aDO(2). Healthy male participants performed graded upright cycling to 90% while pulmonary arterial (PAP) and pulmonary artery wedge pressures were measured. Blood samples were obtained from the radial artery, cardiac output was calculated by the direct Fick method and I-P shunt was determined by administering agitated saline during continuous 2-D echocardiography. A-aDO(2) progressively increased with exercise and was related to (r = 0.86) and PAP (r = 0.75). No evidence of I-P shunt was found at rest in the upright position; however, 7 of 8 subjects developed I-P shunts during exercise. In these subjects, point bi-serial correlations indicated that I-P shunts were related to the increased A-aDO(2) (r = 0.68), (r = 0.76) and PAP (r = 0.73). During exercise, intra-pulmonary shunt always occurred when A-aDO(2) exceeded 12 mmHg and was greater than 24 l min(-1). These results indicate that anatomical I-P shunts develop during exercise and we suggest that shunt recruitment may contribute to the widened A-aDO(2) during exercise.

Adult↗

PubMed2004

Effects of prolonged exercise to exhaustion on left-ventricular function and pulmonary gas exchange.

The purpose of this study was to simultaneously examine left-ventricular (LV) function and pulmonary gas exchange during prolonged constant-rate cycling in an attempt to explain the exercise-induced impairment in gas exchange. Eleven competitive cyclists rode their racing bicycles on a computerized cycle trainer at 25 W below the lactate threshold until exhaustion (exercise time = 2.51 +/- 0.86 h). LV systolic function was evaluated with two-dimensional echocardiography while arterial blood gases were used to assess pulmonary gas exchange. All variables were assessed concurrently before, during, and after exercise. LV function and cardiac output increased at the onset of exercise and were maintained until exhaustion. The alveolar-arterial P(O(2)) difference (A-a D(O(2))) increased within 15 min of the onset of exercise, was unchanged through to exhaustion, and returned to baseline 5 min post-exercise. Gas exchange was not related to cardiovascular function at the onset, or at end exercise. The results indicate that the widening A-aD(O(2)) during exercise is due to a readily reversible change in gas exchange function.

Adult↗

PubMed2004

Clinical applications of diffusion tensor imaging.

Directionally-ordered cellular structures that impede water motion, such as cell membranes and myelin, result in water mobility that is also directionally-dependent. Diffusion tensor imaging characterizes this directional nature of water motion and thereby provides structural information that cannot be obtained by standard anatomic imaging. Quantitative apparent diffusion coefficients and fractional anisotropy have emerged from being primarily research tools to methods enabling valuable clinical applications. This review describes the clinical utility of diffusion tensor imaging, including the basic principles of the technique, acquisition, data analysis, and the major clinical applications.

Anisotropy↗