23 results found
Statton BK, Smith J, Finnegan ME, et al., 2022, Temperature dependence, accuracy, and repeatability of T-1 and T-2 relaxation times for the ISMRM/NIST system phantom measured using MR fingerprinting, Magnetic Resonance in Medicine, Vol: 87, Pages: 1446-1460, ISSN: 0740-3194
PurposeBefore MR fingerprinting (MRF) can be adopted clinically, the derived quantitative values must be proven accurate and repeatable over a range of T1 and T2 values and temperatures. Correct assessment of accuracy and precision as well as comparison between measurements can only be performed when temperature is either controlled or corrected for. The purpose of this study was to investigate the temperature dependence of T1 and T2 MRF values and evaluate the accuracy and repeatability of temperature-corrected relaxation values derived from a B1-corrected MRF–fast imaging with steady-state precession implementation using 2 different dictionary sizes.MethodsThe International Society of MR in Medicine/National Institute of Standards and Technology phantom was scanned using an MRF sequence of 2 different lengths, a variable flip angle T1, and a multi-echo spin echo T2 at 14 temperatures ranging from 15°C to 28°C and investigated with a linear regression model. Temperature-corrected accuracy was evaluated by correlating T1 and T2 times from each MRF dictionary with reference values. Repeatability was assessed using the coefficient of variation, with measurements taken over 30 separate sessions.ResultsThere was a statistically significant fit of the model for MRF-derived T1 and T2 and temperature (p < 0.05) for all the spheres with a T1 > 500 ms. Both MRF methods showed a strong linear correlation with reference values for T1 (R2 = 0.996) and T2 (R2 = 0.982). MRF repeatability for T1 values was ≤1.4% and for T2 values was ≤3.4%.ConclusionMRF demonstrated relaxation times with a temperature dependence similar to that of conventional mapping methods. Temperature-corrected T1 and T2 values from both dictionaries showed adequate accuracy and excellent repeatability in this phantom study.
Henson DP, Edgar C, Ding Z, et al., 2021, Understanding lower limb muscle volume adaptations to amputation., Journal of Biomechanics, Vol: 125, Pages: 1-8, ISSN: 0021-9290
Amputation of a major limb, and the subsequent return to movement with a prosthesis, requires the development of compensatory strategies to account for the loss. Such strategies, over time, lead to regional muscle atrophy and hypertrophy through chronic under or overuse of muscles compared to uninjured individuals. The aim of this study was to quantify the lower limb muscle parameters of persons with transtibial and transfemoral amputations using high resolution MRI to ascertain muscle volume and to determine regression equations for predicting muscle volume using femur- and tibia-length, pelvic-width, height, and mass. Twelve persons with limb loss participated in this study and their data were compared to six matched control subjects. Subjects with unilateral transtibial amputation showed whole-limb muscle volume loss in the residual-limb, whereas minor volume changes in the intact limb were found, providing evidence for a compensation strategy that is dominated by the intact-limb. Subjects with bilateral-transfemoral amputations showed significant muscle volume increases in the short adductor muscles with an insertion not affected by the amputation, the hip flexors, and the gluteus medius, and significant volume decreases in the longer adductor muscles, rectus femoris, and hamstrings. This study presents a benchmark measure of muscle volume discrepancies in persons with limb-loss, and can be used to understand the compensation strategies of persons with limb-loss and the impact on muscle volume, thus enabling the development of optimised intervention protocols, conditioning therapies, surgical techniques, and prosthetic devices that promote and enhance functional capability within the population of persons with limb loss.
Favier C, Finnegan M, Quest R, et al., 2021, An open-source musculoskeletal model of the lumbar spine and lower limbs: a validation for movements of the lumbar spine, Computer Methods in Biomechanics and Biomedical Engineering, Vol: 24, Pages: 1310-1325, ISSN: 1025-5842
Musculoskeletal models of the lumbar spine have been developed with varying level of detail for a wide range of clinical applications. Providing consistency is ensured throughout the modelling approach, these models can be combined with other computational models and be used in predictive modelling studies to investigate bone health deterioration and the associated fracture risk. To provide precise physiological loading conditions for such predictive modelling studies, a new full-body musculoskeletal model including a detailed and consistent representation of the lower limbs and the lumbar spine was developed. The model was assessed against in-vivo measurements from the literature for a range of spine movements representative of daily living activities. Comparison between model estimations and electromyography recordings was also made for a range of lifting tasks. This new musculoskeletal model will provide a comprehensive physiological mechanical environment for future predictive finite element modelling studies on bone structural adaptation. It will be made freely available on https://simtk.org/projects/llsm/.
Winfield JM, Wakefield JC, Dolling D, et al., 2019, Diffusion-weighted MRI in Advanced Epithelial Ovarian Cancer: Apparent Diffusion Coefficient as a Response Marker, RADIOLOGY, Vol: 293, Pages: 374-383, ISSN: 0033-8419
Klemt C, Nolte D, Ding Z, et al., 2019, Anthropometric scaling of anatomical datasets for subject-specific musculoskeletal modelling of the shoulder, Annals of Biomedical Engineering, Vol: 47, Pages: 924-936, ISSN: 0090-6964
Linear scaling of generic shoulder models leads to substantial errors in model predictions. Customisation of shoulder modelling through magnetic resonance imaging (MRI) improves modelling outcomes, but model development is time and technology intensive. This study aims to validate 10 MRI-based shoulder models, identify the best combinations of anthropometric parameters for model scaling, and quantify the improvement in model predictions of glenohumeral loading through anthropometric scaling from this anatomical atlas. The shoulder anatomy was modelled using a validated musculoskeletal model (UKNSM). Ten subject-specific models were developed through manual digitisation of model parameters from high-resolution MRI. Kinematic data of 16 functional daily activities were collected using a 10-camera optical motion capture system. Subject-specific model predictions were validated with measured muscle activations. The MRI-based shoulder models show good agreement with measured muscle activations. A tenfold cross-validation using the validated personalised shoulder models demonstrates that linear scaling of anthropometric datasets with the most similar ratio of body height to shoulder width and from the same gender (p < 0.04) yields best modelling outcomes in glenohumeral loading. The improvement in model reliability is significant (p < 0.02) when compared to the linearly scaled-generic UKNSM. This study may facilitate the clinical application of musculoskeletal shoulder modelling to aid surgical decision-making.
Newbould R, Muraro P, Bishop C, et al., 2016, Analysis of ageing-associated grey matter volume in patients with multiple sclerosis shows excess atrophy in subcortical regions, NeuroImage-Clinical, Vol: 13, Pages: 9-15, ISSN: 2213-1582
Age of onset in multiple sclerosis (MS) exerts an influence on the course of disease. This study examined whether global and regional brain volumes differed between “younger” and “older” onset MS subjects who were matched for short disease duration, mean 1.9 years and burden as measured by the MS Severity Score and relapses.21 younger-onset MS subjects (age 30.4 ± 3.2 years) were compared with 17 older-onset (age 48.7 ± 3.3 years) as well as age-matched controls (n = 31, 31.9 ± 3.5 years and n = 21, 47.3 ± 4.0 years). All subjects underwent 3D volumetric T1 and T2-FLAIR imaging. White matter (WM) and grey matter (GM) lesions were outlined manually. Lesions were filled prior to tissue and structural segmentation to reduce classification errors.Volume loss versus control was predominantly in the subcortical GM, at > 13% loss. Younger and older-onset MS subjects had similar, strong excess loss in the putamen, thalamus, and nucleus accumbens. No excess loss was detected in the amygdala or pallidum. The hippocampus and caudate showed significant excess loss in the younger group (p < 0.001) and a strong trend in the older-onset group.These results provide a potential imaging correlate of published neuropsychological studies that reported the association of younger age at disease onset with impaired cognitive performance, including decreased working memory.
De Simoni S, Grover PJ, Jenkins PO, et al., 2016, Disconnection between the default mode network and medial temporal lobes in post-traumatic amnesia, Brain, Vol: 139, Pages: 3137-3150, ISSN: 0006-8950
Post-traumatic amnesia is very common immediately after traumatic brain injury. It is characterised by a confused, agitated state and a pronounced inability to encode new memories and sustain attention. Clinically, post-traumatic amnesia is an important predictor of functional outcome. However, despite its prevalence and functional importance, the pathophysiology of post-traumatic amnesia is not understood. Memory processing relies on limbic structures such as the hippocampus, parahippocampus and parts of the cingulate cortex. These structures are connected within an intrinsic connectivity network, the Default Mode Network. Interactions within the Default Mode Network can be assessed using resting state functional magnetic resonance imaging, which can be acquired in confused patients unable to perform tasks in the scanner. Here we used this approach to test the hypothesis that the mnemonic symptoms of post-traumatic amnesia are caused by functional disconnection within the Default Mode Network. We assessed whether the hippocampus and parahippocampus showed evidence of transient disconnection from cortical brain regions involved in memory processing. 19 traumatic brain injury patients were classified into post-traumatic amnesia and traumatic brain injury control groups, based on their performance on a paired associates learning task. Cognitive function was also assessed with a detailed neuropsychological test battery. Functional interactions between brain regions were investigated using resting-state functional magnetic resonance imaging. Together with impairments in associative memory patients in post-traumatic amnesia demonstrated impairments in information processing speed and spatial working memory. Patients in post-traumatic amnesia showed abnormal functional connectivity between the parahippocampal gyrus and posterior cingulate cortex. The strength of this functional connection correlated with both associative memory and information processing speed and normal
Winfield JM, Collins DJ, Priest AN, et al., 2016, A framework for optimization of diffusion-weighted MRI protocols for large field-of-view abdominal-pelvic imaging in multicenter studies., Medical Physics, Vol: 43, Pages: 95-110, ISSN: 0094-2405
PURPOSE: To develop methods for optimization of diffusion-weighted MRI (DW-MRI) in the abdomen and pelvis on 1.5 T MR scanners from three manufacturers and assess repeatability of apparent diffusion coefficient (ADC) estimates in a temperature-controlled phantom and abdominal and pelvic organs in healthy volunteers. METHODS: Geometric distortion, ghosting, fat suppression, and repeatability and homogeneity of ADC estimates were assessed using phantoms and volunteers. Healthy volunteers (ten per scanner) were each scanned twice on the same scanner. One volunteer traveled to all three institutions in order to provide images for qualitative comparison. The common volunteer was excluded from quantitative analysis of the data from scanners 2 and 3 in order to ensure statistical independence, giving n = 10 on scanner 1 and n = 9 on scanners 2 and 3 for quantitative analysis. Repeatability and interscanner variation of ADC estimates in kidneys, liver, spleen, and uterus were assessed using within-patient coefficient of variation (wCV) and Kruskal-Wallis tests, respectively. RESULTS: The coefficient of variation of ADC estimates in the temperature-controlled phantom was 1%-4% for all scanners. Images of healthy volunteers from all scanners showed homogeneous fat suppression and no marked ghosting or geometric distortion. The wCV of ADC estimates was 2%-4% for kidneys, 3%-7% for liver, 6%-9% for spleen, and 7%-10% for uterus. ADC estimates in kidneys, spleen, and uterus showed no significant difference between scanners but a significant difference was observed in liver (p < 0.05). CONCLUSIONS: DW-MRI protocols can be optimized using simple phantom measurements to produce good quality images in the abdomen and pelvis at 1.5 T with repeatable quantitative measurements in a multicenter study.
Newbould RD, Nicholas R, Thomas CL, et al., 2014, Age independently affects myelin integrity as detected by magnetization transfer magnetic resonance imaging in multiple sclerosis, NeuroImage: Clinical, Vol: 4, Pages: 641-648, ISSN: 2213-1582
BackgroundMultiple sclerosis (MS) is a heterogeneous disorder with a progressive course that is difficult to predict on a case-by-case basis. Natural history studies of MS have demonstrated that age influences clinical progression independent of disease duration.ObjectiveTo determine whether age would be associated with greater CNS injury as detected by magnetization transfer MRI.Materials and methodsForty MS patients were recruited from out-patient clinics into two groups stratified by age but with similar clinical disease duration as well as thirteen controls age-matched to the older MS group. Images were segmented by automated programs and blinded readers into normal appearing white matter (NAWM), normal appearing gray matter (NAGM), and white matter lesions (WMLs) and gray matter lesions (GMLs) in the MS groups. WML and GML were delineated on T2-weighted 3D fluid-attenuated inversion recovery (FLAIR) and T1 weighted MRI volumes. Mean magnetization transfer ratio (MTR), region volume, as well as MTR histogram skew and kurtosis were calculated for each region.ResultsAll MTR measures in NAGM and MTR histogram metrics in NAWM differed between MS subjects and controls, as expected and previously reported by several studies, but not between MS groups. However, MTR measures in the WML did significantly differ between the MS groups, in spite of no significant differences in lesion counts and volumes.ConclusionsDespite matching for clinical disease duration and recording no significant WML volume difference, we demonstrated strong MTR differences in WMLs between younger and older MS patients. These data suggest that aging-related processes modify the tissue response to inflammatory injury and its clinical outcome correlates in MS.
Malcolme-Lawes LC, Juli C, Karim R, et al., 2013, Automated analysis of atrial late gadolinium enhancement imaging that correlates with endocardial voltage and clinical outcomes: A 2-center study, HEART RHYTHM, Vol: 10, Pages: 1184-1191, ISSN: 1547-5271
Laurence I, Ariff B, Quest RA, et al., 2012, Is there a role for free breathing non-contrast steady-state free precession renal MRA imaging for assessing live donors? A preliminary study, BRITISH JOURNAL OF RADIOLOGY, Vol: 85, Pages: E448-E454, ISSN: 0007-1285
Malcolme-Lawes L, Juli C, Karim R, et al., 2012, AUTOMATED ANALYSIS OF ATRIAL DELAYED ENHANCEMENT CARDIAC MRI CORRELATES WITH VOLTAGE, AF RECURRENCE POST-ABLATION, AND HIGH STROKE RISK, Annual Conference of the British-Cardiovascular-Society (BCS)
Soto D, Mok AYF, McRobbie D, et al., 2011, Biasing visual selection: Functional neuroimaging of the interplay between spatial cueing and feature memory guidance, NEUROPSYCHOLOGIA, Vol: 49, Pages: 1537-1543, ISSN: 0028-3932
Morrell MJ, Jackson ML, Twigg GL, et al., 2010, Changes in brain morphology in patients with obstructive sleep apnoea, THORAX, Vol: 65, Pages: 908-914, ISSN: 0040-6376
Gatehouse PD, Rolf MP, Graves MJ, et al., 2010, Flow measurement by cardiovascular magnetic resonance: a multi-centre multi-vendor study of background phase offset errors that can compromise the accuracy of derived regurgitant or shunt flow measurements, Journal of Cardiovascular Magnetic Resonance, Vol: 12, ISSN: 1097-6647
AimsCardiovascular magnetic resonance (CMR) allows non-invasive phase contrast measurements of flow through planes transecting large vessels. However, some clinically valuable applications are highly sensitive to errors caused by small offsets of measured velocities if these are not adequately corrected, for example by the use of static tissue or static phantom correction of the offset error. We studied the severity of uncorrected velocity offset errors across sites and CMR systems.Methods and ResultsIn a multi-centre, multi-vendor study, breath-hold through-plane retrospectively ECG-gated phase contrast acquisitions, as are used clinically for aortic and pulmonary flow measurement, were applied to static gelatin phantoms in twelve 1.5 T CMR systems, using a velocity encoding range of 150 cm/s. No post-processing corrections of offsets were implemented. The greatest uncorrected velocity offset, taken as an average over a 'great vessel' region (30 mm diameter) located up to 70 mm in-plane distance from the magnet isocenter, ranged from 0.4 cm/s to 4.9 cm/s. It averaged 2.7 cm/s over all the planes and systems. By theoretical calculation, a velocity offset error of 0.6 cm/s (representing just 0.4% of a 150 cm/s velocity encoding range) is barely acceptable, potentially causing about 5% miscalculation of cardiac output and up to 10% error in shunt measurement.ConclusionIn the absence of hardware or software upgrades able to reduce phase offset errors, all the systems tested appeared to require post-acquisition correction to achieve consistently reliable breath-hold measurements of flow. The effectiveness of offset correction software will still need testing with respect to clinical flow acquisitions.
de Llano SRM, Perry R, Waldman A, et al., 2009, In- vivo diagnosis of atypical Alzheimer disease using pathology-sensitive brain imaging, 11C-PIB and short TE spectroscopy MR imaging in Posterior Cortical Atrophy, EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING, Vol: 36, Pages: S244-S244, ISSN: 1619-7070
de Llano SRM, Perry R, Waldman A, et al., 2009, In- vivo diagnosis of atypical Alzheimer disease using pathology-sensitive brain imaging, 11C-PIB and short TE spectroscopy MR imaging in Posterior Cortical Atrophy, Publisher: SPRINGER, Pages: 244-244, ISSN: 1619-7070
Morrell MJ, Jackson ML, Twigg G, et al., 2009, Changes in Brain Morphology Associated with Obstructive Sleep Apnea (OSA), Publisher: AMER THORACIC SOC, ISSN: 1073-449X
Ball T, Malik O, Roncaroli F, et al., 2007, Apparent diffusion coefficient changes and lesion evolution in Balo's type demyelination - correlation with histopathology, CLINICAL RADIOLOGY, Vol: 62, Pages: 498-503, ISSN: 0009-9260
McRobbie DW, Pritchard S, Quest RA, 2003, Studies of the human oropharyngeal airspaces using magnetic resonance imaging.: 1.: Validation of a three-dimensional MRI method for producing <i>ex vivo</i> virtual and physical casts of the oropharyngeal airways during inspiration, JOURNAL OF AEROSOL MEDICINE-DEPOSITION CLEARANCE AND EFFECTS IN THE LUNG, Vol: 16, Pages: 401-415, ISSN: 0894-2684
Morrell MJ, McRobbie DW, Quest RA, et al., 2003, Changes in brain morphology associated with obstructive sleep apnea, SLEEP MEDICINE, Vol: 4, Pages: 451-454, ISSN: 1389-9457
Mort DJ, Perry RJ, Mannan SK, et al., 2003, Differential cortical activation during voluntary and reflexive saccades in man, NEUROIMAGE, Vol: 18, Pages: 231-246, ISSN: 1053-8119
McRobbie DW, Quest RA, 2002, Effectiveness and relevance of MR acceptance testing: results of an 8 year audit, BRITISH JOURNAL OF RADIOLOGY, Vol: 75, Pages: 523-531, ISSN: 0007-1285
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