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Biomedical subjects

G M Bydder

Publications and source records attributed to G M Bydder.

At least 145 records · Page 8Linked to original sources
PubMed1982

Initial clinical evaluation of a whole body nuclear magnetic resonance (NMR) tomograph.

A nuclear magnetic resonance (NMR) imaging system is described, and preliminary results from its clinical use are presented. The properties and detection of the magnetisation due to hydrogen protons are outlined, and a rotating frame is introduced to describe the motion of the magnetisation. Radiofrequency (RF) pulses are used to rotate the magnetisation, and slice selection is achieved using a 90 degree RF pulse and a magnetic field gradient. Data acquisition and image reconstruction are explained. Three scanning sequences are described: repeated free induction decay (FID), inversion - recovery, and spin-echo. These sequences produce images whose pixel values have different dependencies on hydrogen proton density, T1 and T2. Inversion-recovery images show striking differentiation between grey and white matter in the brain. The absence of bone artifact is a significant advantage over X-ray computed tomography in the posterior fossa, where rapid repeated FID sequences can also be used to demonstrate flow effects. The considerable soft tissue contrast available with NMR is of value in demonstrating disease within the liver where T1 appears to be sensitive but relatively nonspecific diagnostic parameter. High resolution scans are of value in demonstrating the adrenal gland and spinal cord.

Brain↗
PubMed1982

Nuclear magnetic resonance imaging of the liver: initial experience.

Nuclear magnetic resonance (NMR) scans of the liver were obtained in 12 normal volunteers and 32 patients using a whole-body machine developed by Thorn-EMI Ltd., and the results were compared with x-ray computed tomography (CT). Two types of NMR scan, saturation-recovery and inversion-recovery, were performed in order to obtain values for the spin-lattice relaxation time, T1. Although the saturation-recovery scans show little soft-tissue detail, the inversion-recovery scans demonstrated the interlobar fissure, hepatic veins, portal veins, bile ducts, and gallbladder. In comparison with CT (Siemens Somatom 2), both types of NMR scan showed some blurring due to respiratory movement but much less linear artifact across the liver from the air-fluid interface in the stomach. Focal disease within the liver was demonstrated by both CT and NMR, although an area of focal atrophy and another of hepatic infarction were only recognized with NMR. In diffuse disease the pattern varied. In steatosis CT was virtually diagnostic, while NMR showed no specific features. In hemochromatosis, hepatitis, eight cases of cirrhosis, and one of Wilson disease, both techniques showed abnormalities of varying specificity. In two cases of cirrhosis and one of primary biliary cirrhosis, only the NMR scan was abnormal. Nuclear magnetic resonance images are now sufficiently anatomically detailed to permit serious comparisons with technically advanced computed tomography. The information revealed is fundamentally different and can be expected to have some diagnostic utility.

Adult↗
PubMed1982

Clinical NMR imaging of the brain: 140 cases.

Cranial nuclear magnetic resonance (NMR) scans were performed on 13 healthy volunteers and 140 patients with a broad spectrum of neurologic disease and compared with x-ray computed tomography (CT) scans. The NMR scans included a variety of sequences reflecting proton density, blood flow, T1, and T2 as well as transverse, sagittal, and coronal images. White matter, gray matter, and cerebrospinal fluid were clearly distinguished in the normal brain with inversion-recovery (IR) sequences, and normal progressive myelination was demonstrated in infants and children. Acute hemorrhages displayed short T1 values, but other pathologic processes such as infarction, infection, demyelination, edema, and malignancy were associated with long T1 values. Cysts had very long T1 values (about that of cerebrospinal fluid). Spin-echo (SE) sequences showed increased values of T2 in a variety of conditions and highlighted lesions against the relatively featureless background of the remaining brain. With inversion-recovery scans, different stages of infarction were recognized in the hemispheres. NMR was more useful than CT in demonstrating brainstem infarction. The white matter lesions in demyelinating diseases were well demonstrated with NMR scans. Many more lesions were observed in multiple sclerosis with NMR than with CT. Benign tumors were well seen and usually had shorter T1 values than malignant tumors. Mass effects from tumors were generally better demonstrated with NMR than with CT, including more subtle mass effects such as displacement of the external capsule. Abnormalities were seen in diseases of the basal ganglia, including marked atrophy of the head of the caudate nucleus in Huntington chorea. Advantages of NMR imaging include the high level of gray-white matter contrast, lack of bone artifact, variety of possible sequences, transverse, sagittal, and coronal imaging, sensitivity to pathologic change, and lack of known hazard. Disadvantages include lack of bone detail, limited spatial resolution, lack of contrast agents, and cost. Promising directions for future clinical research include developmental neurology, tissue characterization with T1 and T2, assessment of blood flow, and the development of contrast agents. Much more detailed evaluation will be required, but NMR seems to be a potentially important addition to existing techniques of neurologic diagnosis.

Adolescent↗
PubMed1981

Nuclear magnetic resonance imaging of the brain in multiple sclerosis.

Ten patients with multiple sclerosis (MS) were scanned by means of cranial X-ray computed tomography (CT) with and without intravenous contrast enhancement, and by nuclear magnetic resonance (NMR) using an inversion-recovery sequence. Altogether 19 lesions varying in size between about 7 mm X 5 mm and 13 mm X 8 mm were demonstrated by CT. They were all situated in the periventricular region. Two patients also showed moderate ventricular enlargement. In addition to these abnormalities 112 further lesions were demonstrated on the NMR scans. These lesions varied in size from 4 mm X 3 mm to 12 mm X 7 mm and were particularly well seen in the periventricular region and brainstem. Care is required in the assessment of NMR scans to exclude artefacts, background noise, and mottle as well as normally situated grey matter and partial volume effects from cerebral sulci. NMR nevertheless demonstrates abnormalities in MS on a scale not previously seen except at necropsy.

Adolescent↗
PubMed1981

Imaging of the brain by nuclear magnetic resonance.

A nuclear magnetic resonance (NMR) machine constructed by Thorn-EMI Ltd was used to produce tomographic images of the brain in eight volunteers and fourteen patients. The use of an inversion recovery technique designed to emphasise variations in the spin-lattice time constant (T1) resulted in remarkable differentiation between grey and white matter in all subjects examined. White matter was seen both centrally and peripherally to subcortical level and the basal ganglia were clearly demarcated by the surrounding white matter and ventricular system. The posterior fossa was visualised with substantially less artefact than with X-ray computed tomography (CT) and both the brainstem and middle cerebellar peduncle were clearly shown. Pathological appearances in patients with glioblastoma multiforme, cerebral infarction, and cerebral aneurysm were demonstrated and compared with those seen with CT. The technique will require thorough clinical evaluation but appears to have considerable potential in the diagnosis of neurological disease.

Brain↗
PubMed1981

Body computed tomography in the diagnosis of malignant melanoma metastases.

The results of body CT examination in 32 cases of histologically proven malignant melanoma are reviewed. In a total of 38 examinations, positive findings were obtained in 27 cases (71%). Metastases were detected in the lungs (6 cases), liver (2 cases), and lymph nodes (26 cases). Local recurrences were recognized in 2 cases. Clinical suspicion of metastases was supported in 19 cases (50%), suspected metastases were not confirmed in 5 cases (15%), and additional evidence of metastasis was obtained in 14 cases (37%). CT was of particular value in demonstrating additional metastases in the lungs and lymphadenopathy in the abdomen and pelvis.

Female↗
PubMed1981

Computed tomography attenuation values in fatty liver.

The accuracy of CT diagnosis of increased fat deposition in the liver was assessed in 11 alcoholic patients with suspected fatty liver. Single-energy CT attenuation values were compared with histological assessment of fatty liver and chemical analysis of liver triglyceride concentrations, obtained from liver biopsy specimens. Measured attenuation values showed an inverse correlation with the degree of fatty change assessed histologically (r =--0.90; p Less Than 0.0001) and with that assessed chemically (r=--0.57; p Less Than 0.05). CT scanning may provide a useful non-invasive method for detecting and following patients with fatty liver, particularly when liver biopsy is contraindicated.

Adult↗
PubMed1981

Role of computed tomography in the management of infectious disease.

All cases referred for computed tomography (CT) from a 48-bed infectious disease unit over a 3-year period were reviewed. Thirty patients were examined on 45 occasions with head and body cases approximately equal in number. Positive diagnoses were made in 38 examinations (84%), although this included 3 incidental findings. The most common indication for CT was exclusion of cerebral abscess presenting as meningitis (11 cases). The most common disease was tuberculosis (12 cases), although a wide spectrum of disease including four noninfective cases was encountered. CT made a direct contribution to the management of patients with meningitis, encephalitis, cerebral abscess, septicemia, hepatic abscess, tuberculosis, and lymphoma. Although CT was only utilized in a small proportion of patients admitted to this unit, the technique provided valuable information in the management of a number of problematic cases.

Abscess↗
PubMed1981

Enhancement of relaxation rate with paramagnetic contrast agents in NMR imaging.

Enhancement of spin-lattice relaxation using oral ferric chloride and using inhaled oxygen is illustrated. A 0.06% solution of ferric chloride reduced the spin-lattice relaxation time in the fundus of the stomach from 730 ms to 285 ms. Ferric chloride may be useful as a bowel-labeling agent. In 5 volunteers inhalation of 100% oxygen decreased the mean observed spin-lattice relaxation time of blood within the left ventricular cavity. Although the change was small, it may have important uses in monitoring metabolic processes.

Abdomen↗
PubMed1981

Pleural calcification in pancreatitis demonstrated by computed tomography.

Three cases of pleural calcification associated with pancreatitis are reported, each of which showed bilateral basal curvilinear calcification. There was no known history of asbestos exposure. Although pleural effusion due to pancreatitis is well known, pleural calcification has not been recognized previously as a complication of this disease.

Aged↗
PubMed1981

Magnetic resonance properties of hydrogen: imaging the posterior fossa.

Posterior fossa scans were performed on five healthy volunteers using a nuclear magnetic resonance (NMR) machine constructed by Thorn-EMI Ltd. Three different NMR scanning sequences were used. In the first, a type of saturation-recovery technique was used to produce images strongly dependent on the density of hydrogen nuclei, but with some dependence on the spin-lattice relaxation time (T1). In the second, an inversion-recovery technique was used to produce images with a stronger dependence on the spin-lattice relaxation time. In the third, a spin-echo technique was used to obtain images with a dependence on the spin-spin relaxation time (T2). All three types of NMR image were unaffected by bone artifact. Visualization of brain adjacent to the skull base was obtained without loss of detail due to partial-volume effect from bone. The saturation-recovery images highlighted arteries and veins that were clearly visible without the use of contrast agents. The inversion-recovery images showed remarkable gray-white matter differentiation enabling internal structure to be seen within the brainstem and cerebellum. The trigeminal nerve and ganglion were also seen outside the brain. Experience with the spin-echo technique is limited, but the images at the base of the brain show considerable soft-tissue detail. The NMR images of the posterior fossa in this study were comparable in quality to those obtained from a new rotate-rotate x-ray computed tomography machine and were superior in several respects.

Adult↗
PubMed1980

Computed tomography of fluid collections within the abdomen.

Computed tomography is ideally suited for detecting mass lesions and for distinguishing "solid" from "cystic" masses. In the majority of cases, the recognition of fluid collections is unequivocal and lead to direct management decisions. Subphrenic, intrahepatic, and subhepatic abscesses can be recognized, aspirated, and drained. Using CT control, pancreatic pseudocysts can be managed similarly. Renal cysts can be accurately diagnosed with CT, especially with contrast enhancement, and then even the occasional case in which hydronephrosis may be a problem can be distinguished. Very occasionally, solid tumors containing mucinous material or lipoid can appear as cystic lesions, especially in the suprarenal, ovary, liver, or lymph nodes, and, conversely, abscesses may have higher tissue attenuation values, suggesting a solid lesion. It is most important to ensure that bowel is adequately labeled with contrast so that is is not misdiagnosed as a mass lesion.

Abdominal Neoplasms↗
PubMed1980

Computed tomography in the diagnosis of abdominal abscess.

The CT features in 30 cases of suspected intra-abdominal abscesses are reviewed. The cases were grouped into proven (24), probable (4), and possible (2) abscess on clinical grounds, and were analyzed according to site within the abdomen. Two cases of carcinoma with fluid collections mimicking abscesses are also discussed. In the appropriate clinical context, abdominal abscess is identified on CT as a circumscribed low-density region within the abdomen. Subphrenic, hepatic, and splenic abscesses were readily recognized without contrast enhancement inthe majority of cases, although contrast enhancement consistently rendered loculation within hepatic abscesses more obvious. Aspiration and drainage under CT control were invaluable in diagnosis, permitting the identification of the causative organism in 18 cases. The precise anatomical detail provided by CT was important in achieving successful catheter placement for drainage.

Abscess↗
PubMed1980

Attenuation values of fluid collections within the abdomen.

In vivo attenuation values of 19 fluid collections in 17 patients were compared with in vitro values obtained on examination of the aspirated fluids within the calibration phantom of an EMI CT5005 body scanner. While the in vitro values showed a 5.2 Hounsfield unit (HU:1,000 scale). difference between cysts and abscesses, spectral errors of up to 28.6 HU were sufficiently large for this distinction to be lost in vivo. Good correlation was found between ascitic fluid protein concentration and in vitro attenuation values, but not with in vivo values. An experimental reconstruction program appeared to give more accurate in vivo results than the standard commercial algorithm. A water control showed errors of similar magnitude to those with the fluid collections and did not provide any simple correction for the errors in the fluid attenuation values. Similar results were found for urine examined in vitro and in vivo. The administration of intravenous contrast agents tended to elevate in vivo fluid attenuation values, but refrigeration for 6 months produced little change in in vitro values.

Abscess↗
PubMed1980

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.

Adult↗