PubMed Health⌕ Search

Biomedical subjects

G M Bydder

Publications and source records attributed to G M Bydder.

188 records · Page 11Linked to original sources
PubMedDate not supplied

Contrast-enhanced MR imaging of malignant brain tumors.

Magnetic resonance (MR) imaging was performed before and serially after intravenous injection of 1 mmol/kg gadolinium-DTPA (Schering) in 17 patients with clinical and histologic diagnosis of malignant cerebral tumors. There was a decrease of 1% in T1 and 10% in T2 in normal white matter and a decrease of 8% in T1 and 14% in T2 in normal gray matter. Contrast enhancement was observed in 16 of the 17 tumors. In the region of maximal enhancement a mean decrease of 16% in T1 was observed in low-grade gliomas, a mean decrease in T1 of 29% was seen in high-malignancy gliomas, and a mean decrease in T1 of 33% was observed in metastases. The decreases in T1 persisted for at least 50 min. In one case the central cystic region of the tumor displayed a decrease in T1 and T2. Measurements of signal intensity displayed maximal contrast enhancement with an IR 1500/500/44 sequence, much less with SE 1500/44, and least with SE 1500/80. Edema was observed on precontrast images in 14 cases, but satisfactory definition of the tumor-edema margin was only possible in four cases. After contrast enhancement this margin was defined in 10 cases. In four of the 17 cases areas of apparent "edema" seen before administration of Gd-DTPA displayed significant contrast enhancement and probably represented tumor infiltration. Comparison with CT showed a greater degree of contrast enhancement on MR images in eight cases, an equal degree in eight cases, and greater enhancement on CT in one case.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain Edema↗
PubMedDate not supplied

Respiratory ordered phase encoding (ROPE): a method for reducing respiratory motion artefacts in MR imaging.

A method of reducing respiratory artefact when using the spin warp technique of magnetic resonance imaging is described. A respiratory signal is used to determine the order in which the rows of the data matrix are measured. The aim is to make the respiratory signal at the time of each phase encoding gradient a slowly varying function of the time integral of the gradient and hence of the row number. Data are collected during each cycle of the imaging sequence; thus the scanning time is not increased.

Humans↗
PubMedDate not supplied

Magnetic resonance imaging of intracranial tumors in children and adolescents.

Magnetic resonance (MR) scans were reviewed of 25 children and adolescents from the age of 9 months to 18 years referred with a suspected or proven diagnosis of intracranial tumor. Twenty-one of these children had MR scans positive for tumor. Histology was available in 14. The other seven patients were managed clinically as cases of cerebral tumor, although histologic confirmation was lacking. Seventeen tumors displayed an increase in both T1 and T2. One dermoid tumor and part of another displayed a very short T1 (less than that of white matter). Two hamartomas had T1s similar to that of gray matter and a small increase in T2. Four of the children did not show MR or computed tomographic (CT) evidence of intracranial tumors. Follow-up of these cases for 1-23 months after the MR and CT studies revealed no subsequent clinical evidence of tumor. MR scans showed more extensive abnormality than did third-generation CT scans in eight of 10 cases and more extensive abnormality than EMI CT 1010 scans in 10 of 11 cases. Mass effects were better demonstrated in 14 of the 16 patients in whom they were seen. CT demonstrated calcification better than did MR in all four cases in which it was identified. The tumor-edema interface was shown better on CT in each of the three cases with contrast enhancement on CT. MR is a sensitive method of evaluating intracranial tumors in children and adolescents.

Adolescent↗
PubMedDate not supplied

The role of NMR imaging in the diagnosis and management of acoustic neuroma.

Nuclear magnetic resonance (NMR) scans of 15 patients with acoustic neuroma are compared with the results of computed tomography (CT). The absence of signal from bone has meant that the images are unaffected by artifacts and that small intracanalicular tumors can be visualized. The multiplanar facility of NMR is emphasized as this allows precise assessment of both tumor volume and its relationship to the ventricular system, brainstem, and tentorial hiatus. The different appearances produced by alternative scan sequences are illustrated and the possibility of predicting the physical constitution from scan appearances is discussed.

Cerebellar Neoplasms↗
PubMedDate not supplied

Extracerebral collections: recognition by NMR imaging.

After head injury, nuclear magnetic resonance (NMR) scanning is, like computed tomography (CT), an effective method of distinguishing between intracerebral and extracerebral lesions. The location and shape of extracerebral collections are excellently displayed using the multiplanar facility of NMR. There are good grounds for believing that the problem of the isodense subdural hematoma encountered in CT scanning can almost certainly be overcome by the use of NMR imaging.

Brain Concussion↗
PubMedDate not supplied

NMR imaging in the diagnosis and management of intracranial angiomas.

Fourteen intracranial angiomas were clearly visualized and diagnosed with certainty on fast saturation-recovery images, which highlight blood vessels without the use of contrast media, and on steady-state free-precession images, in which the moving blood leads to removal of signal. Performed as the initial investigation, nuclear magnetic resonance obviates angiography when the site and extent of the angioma would preclude operation, and in other cases provides useful anatomic information complementing the angiogram. When clinical presentation follows hemorrhage the size and position of the associated hematoma can be reliably assessed.

Brain Neoplasms↗
PubMedDate not supplied

Effect of oxygen tension on NMR spin-lattice relaxation rate of blood in vivo.

Spin-lattice relaxation rate (1/T1) was measured in the left (LV) and right (RV) ventricular cavities in four conscious normal humans and four anesthetized greyhound dogs breathing spontaneously. Inspired oxygen concentration (FIO2) was varied in five steps from 21 to 100%. In dogs, blood was sampled from indwelling catheters in the pulmonary artery and aorta for measurement of PO2. Saturation-recovery and inversion-recovery tomographic images of the ventricular cavities were obtained supine during quiet breathing using a whole-body NMR scanner operating at a static magnetic field strength of 0.15 Tesla. From FIO2 21 to 100%, 1/T1 of LV increased by 11.6% in humans and 9.6% in dogs. In dogs, 1/T1 increased by 2.8% per 100 mm Hg increase in aortic PO2 (r greater than 0.87). There was no correlation in dogs between 1/T1 in RV and pulmonary artery PO2. The LV/RV 1/T1 ratio in dogs increased by 4% per 100 mm Hg increase in the LV-RV PO2 difference, and by 8% in humans as FIO2 increased from 21 to 100%. A rise in dissolved oxygen concentration increases NMR spin-lattice relaxation rates of blood in vivo to a small but significant extent.

Adult↗