PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-11 (11)
 

Clipboard (0)
None

Select a Filter Below

Journals
Year of Publication
author:("bedder, G M")
1.  The Agfa Mayneord lecture: MRI of short and ultrashort T2 and T2* components of tissues, fluids and materials using clinical systems 
The British Journal of Radiology  2011;84(1008):1067-1082.
A variety of techniques are now available to directly or indirectly detect signal from tissues, fluids and materials that have short, ultrashort or supershort T2 or T2* components. There are also methods of developing image contrast between tissues and fluids in the short T2 or T2* range that can provide visualisation of anatomy, which has not been previously seen with MRI. Magnetisation transfer methods can now be applied to previously invisible tissues, providing indirect access to supershort T2 components. Particular methods have been developed to target susceptibility effects and quantify them after correcting for anatomical distortion. Specific methods have also been developed to image the effects of magnetic iron oxide particles with positive contrast. Major advances have been made in techniques designed to correct for loss of signal and gross image distortion near metal. These methods are likely to substantially increase the range of application for MRI.
doi:10.1259/bjr/74368403
PMCID: PMC3473831  PMID: 22101579
2.  Optimization of Iron Oxide Nanoparticle Detection Using Ultrashort TE Pulse Sequences: Comparison of T1, T2* and Synergistic T1-T2* Contrast Mechanisms 
Iron oxide nanoparticles (IONPs) are used in various MRI applications as negative contrast agents. A major challenge is to distinguish regions of signal void due to IONPs from those due to low signal tissues or susceptibility artifacts. To overcome this limitation, several positive contrast strategies have been proposed. Relying on IONP T1 shortening effects to generate positive contrast is a particularly appealing strategy since it should provide additional specificity when associated with the usual negative contrast from T2* effects. In this paper, Ultrashort TE (UTE) imaging is shown to be a powerful technique which can take full advantage of both contrast mechanisms. Methods of comparing T1 and T2* contrast efficiency are described and general rules that allow optimizing IONP detection sensitivity are derived. Contrary to conventional wisdom, optimizing T1 contrast is often a good strategy for imaging IONPs. Under certain conditions, subtraction of a later echo signal from the UTE signal not only improves IONP specificity by providing long T2* background suppression, but also increases detection sensitivity, as it enables a synergistic combination of usually antagonist T1 and T2* contrasts. In vitro experiments support our theory and a molecular imaging application is demonstrated using tumor-targeted IONPs in vivo.
doi:10.1002/mrm.22755
PMCID: PMC3097261  PMID: 21305596
UTE; iron oxide nanoparticle; sequence optimization; positive contrast
3.  Nuclear magnetic resonance imaging of the brain. 
Archives of Disease in Childhood  1983;58(6):401-403.
Images
PMCID: PMC1627993  PMID: 6859929
4.  Unsuspected organic disease in chronic schizophrenia demonstrated by computed tomography 
Unsuspected intracranial pathology was demonstrated in 12 of 136 chronic schizophrenic patients examined by computed tomography (CT). Seven cases of cerebral infarction were found, and one each of porencephalic cyst, meningioma, cystic enlargement of the pineal body, and two of subdural haematoma. Attention is drawn to the value of CT in demonstrating organic disease in schizophrenia.
PMCID: PMC490778  PMID: 7217951
5.  High resolution magnetic resonance imaging of the anal sphincter using an internal coil. 
Gut  1995;37(2):284-287.
An internal receiver coil was used to obtain high resolution transverse and oblique coronal magnetic resonance images of the anal sphincter in five normal volunteers and five patients. The internal sphincter had a high signal intensity on T1 weighted, T2 weighted, and STIR sequences whereas the conjoined longitudinal muscle and external sphincter had a low signal intensity. The internal sphincter (but not the external sphincter) showed contrast enhancement after administration of intravenous gadopentetate dimeglumine. The oblique coronal plane was particularly useful for showing the thickness and the relations of the external sphincter. Sphincteric abscesses as well as muscle defects, hypertrophy, and atrophy were clearly shown. The coil was well tolerated by most subjects. It has considerable potential for improving the diagnosis of anorectal disease.
Images
PMCID: PMC1382733  PMID: 7557583
6.  Magnetic resonance imaging in partial epilepsy: additional abnormalities shown with the fluid attenuated inversion recovery (FLAIR) pulse sequence. 
Thirty six patients with a history of partial epilepsy had MRI of the brain performed with conventional T1 and T2 weighted pulse sequences as well as the fluid attenuated inversion recovery (FLAIR) sequence. Abnormalities were found in 20 cases (56%), in whom there were 25 lesions or groups of lesions. Twenty four of these lesions were more conspicuous with the FLAIR sequence than with any of the conventional sequences. In 11 of these 20 cases, lesions thought to be of aetiological importance were only seen with the FLAIR sequence. In eight this was a solitary lesion. In the other three, an additional and apparently significant lesion (or lesions) was only seen with the FLAIR sequence when another lesion had been identified with both conventional and FLAIR sequences. The 11 additional lesions or groups of lesions were seen in the hippocampus, amygdala, cortex, or subcortical and periventricular regions. No lesion was found with any pulse sequence in 16 (44%) of the original group of 36 patients. In the eight cases where a lesion was seen only with the FLAIR sequence, localisation was concordant with the electroclinical features. Two of the eight patients with solitary lesions seen only on the FLAIR sequence underwent surgery, after which there was pathological confirmation of the abnormality identified with imaging. In one patient with a congenital cavernoma, the primary lesion was best seen with a contrast enhanced T1 weighted spin echo sequence. In this selected series, the FLAIR sequence increased the yield of MRI examinations of the brain by 30%.
Images
PMCID: PMC1073429  PMID: 7738550
7.  Nuclear magnetic resonance imaging of the brain in children 
A preliminary study of nuclear magnetic resonance imaging of the brains of four normal children (36 weeks' postmenstrual age to 5 years) showed long T1 areas in the periventricular region of the neonate as well as evidence of progressive myelinisation with increasing age. Study of 18 patients of 40 weeks' postmenstrual age to 4 years showed an apparent deficit in myelinisation in an infant with probable rubella embryopathy and another with ventricular dilatation of unknown cause. Abnormal scans were obtained in an infant with congenital muscular dystrophy, and abnormalities were visualised at the lateral ventricular margins in a case of acute hydrocephalus after shunt blockage. Periventricular regions of increased T2 were seen in a term infant aged 4 days after severe birth asphyxia and convulsions.
Nuclear magnetic resonance imaging appears to provide a unique demonstration of myelinisation in vivo and shows changes in pathological processes of importance in paediatric practice.
Images
PMCID: PMC1499499  PMID: 6810994
9.  Developmental sequence of periventricular leukomalacia. Correlation of ultrasound, clinical, and nuclear magnetic resonance functions. 
Archives of Disease in Childhood  1985;60(4):349-355.
The evolution of severe periventricular leukomalacia was followed by ultrasonography in three newborn infants, and the subsequent myelination of the brain was assessed by nuclear magnetic resonance imaging. Four stages of periventricular leukomalacia could be identified by ultrasonography; (1) initial congestion, followed by (2) relative normalisation, (3) development of cysts, and (4) resolution of cysts but development of ventricular enlargement. All infants exhibited abnormal neurological signs from 36 weeks conceptual age and had unequivocal signs of cerebral palsy by 6 to 9 months of age. One infant became cortically blind but the other two seemed to have normal vision. Nuclear magnetic resonance imaging showed some abnormality of the ventricular system and delayed myelination in all three infants. The delay was most noticeable in the opticothalamic region, which was also the site of the most extensive lesions observed on ultrasonography. Progress in myelination was observed in the infants where a repeat scan was performed.
Images
PMCID: PMC1777237  PMID: 3890765
10.  Nuclear magnetic resonance imaging of the heart. Current status and future prospects. 
British Heart Journal  1983;50(3):202-208.
The basic principles and current status of proton nuclear magnetic resonance imaging are outlined. Nuclear magnetic resonance images of the heart have improved in quality with advances in technique and better gating but clinical experience remains very limited. Myocardial infarction has been shown in animals and man, and plaques of atheroma have been seen with nuclear magnetic resonance flow studies. Further improvements in image quality, faster examination times, 23Na imaging, and the use of paramagnetic contrast agents are advances that are anticipated in the near future.
Images
PMCID: PMC481398  PMID: 6311232
11.  A magnetic resonance study of early schizophrenia. 
Patients with untreated first schizophrenic episodes and others who had made varying degrees of recovery from such episodes were blindly compared with normal volunteers in terms of the periventricular appearances on spin echo magnetic resonance scans. Significant differences were not found.
Images
PMCID: PMC1028678  PMID: 2869111

Results 1-11 (11)