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Biomedical subjects

I D Wilkinson

Publications and source records attributed to I D Wilkinson.

87 records · Page 5Linked to original sources
PubMed1993

The prevalence of paranasal sinus disease in HIV infection and AIDS on cranial MR imaging.

Sinusitis poses a difficult clinical challenge in the management of patients with AIDS because of high rates of relapse and the association with unusual pathogens. To determine the prevalence and severity of sinus disease in this group we prospectively analysed the condition of the paranasal sinuses shown on cranial MR scans of 156 patients referred for the investigation of suspected intracranial pathologies. These included 104 HIV seropositive patients, including 93 with an AIDS-defining diagnosis (CDC IV). Forty-two scans were performed on age-matched controls. The scans were timed to control for seasonal variations in sinus disease and were interpreted by two radiologists who were blinded to the clinical and serological status of the patients. Severe mucosal disease (more than one sinus showing > 75% obliteration) or moderate mucosal disease (only one sinus showing > 75% obliteration) was seen in 15.1% (14/93) patients with AIDS and none of the 42 controls (chi 2 = 6.73, P < 0.01). The mean maximum mucosal thickness in patients with AIDS was significantly greater than the control group (P < 0.001) and also significantly greater than in seropositive patients who had not had an AIDS-defining diagnosis (CDC II/III) (P = 0.006). Paranasal sinus mucosal abnormalities seen on MRI are greater in prevalence and severity in patients with AIDS and about one in seven would be expected to have at least one sinus largely obliterated.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Proton spectroscopy of the brain in HIV infection: correlation with clinical, immunologic, and MR imaging findings.

Abnormalities at cerebral proton spectroscopy occur in patients with the acquired immunodeficiency syndrome (AIDS). N-acetyl aspartate (NAA) is believed to be a neuronal marker, and neuronal loss is thought to underlie the human immunodeficiency virus (HIV)-associated cognitive/motor complex. The proton spectra in 103 HIV-seropositive patients and 23 control subjects were compared and correlated with clinical, immunologic, and radiologic measures of HIV infection. Significant (P < .05) reductions in the mean NAA/choline (Cho) and NAA/creatine (Cr) ratios were seen in patients with immune suppression and neurologic signs. Significant increases in the Cho/Cr ratios were seen in patients with low CD4 lymphocyte counts and abnormal magnetic resonance (MR) images. Reduced NAA ratios correlated with diffuse but not focal MR imaging abnormalities. Combined MR imaging and spectroscopy provides closer relationships to clinical and immunologic measures of disease than either modality alone. Spectroscopy is an adjunct to MR imaging and augments the value of an MR imaging study.

Adult↗
PubMed1993

MR cholangiography: clinical evaluation in 40 cases.

PURPOSE: To determine the reliability and efficacy of magnetic resonance (MR) cholangiography in demonstrating the site and extent of stricture. MATERIALS AND METHODS: In 40 patients with obstructive jaundice, three-dimensional MR cholangiography was performed with a sequence of mirrored fast imaging with steady-state precession and was compared with conventional cholangiography in 39 cases. The level of obstruction was determined by examining all imaging data available. RESULTS: Diagnostic MR cholangiograms were acquired in 39 patients; absence of obstruction was confirmed in three, and obstruction was seen in 36. The level of obstruction or absence of obstruction was accurately shown in 36 of 40 patients with MR cholangiography and in 37 of 39 patients with conventional cholangiography. The peripheral biliary tree was shown more completely with MR cholangiography than with endoscopic retrograde cholangiography in all 32 patients undergoing diagnostic studies with both modalities. CONCLUSION: Three-dimensional MR cholangiography shows particular promise for the assessment of complex strictures, in which conventional cholangiography carries a higher risk of sepsis, for planning optimal drainage before intervention.

Adult↗
PubMed1992

Viral hepatitis in the Christchurch community.

AIM: To determine the relative frequency of known causes of viral hepatitis in the Christchurch community. METHODS: Serum samples were collected at a private laboratory from patients aged 15-75 years who had an elevated transaminase of at least twice normal. RESULTS: One hundred and thirty-three subjects entered the study of whom 32 were positive for Epstein Barr virus, three for cytomegalovirus, nine for hepatitis A virus, and eight for hepatitis B virus. Paired convalescent samples were obtained from 64 of the remaining 81 subjects (17 lost or declined) and seven of these were positive for hepatitis C. Assuming a similar percentage in the lost/declined group this corrects to nine. CONCLUSION: The relative frequency of viral agents causing hepatitis was Epstein Barr virus 52%, cytomegalovirus 5%, hepatitis A virus 15%, hepatitis B virus 13% and hepatitis C virus 15%. Hepatitis C virus is a common cause of viral hepatitis in the Christchurch community.

Adolescent↗
PubMed1992

The prevalence of antibodies to hepatitis C virus in patients with chronic liver disease.

OBJECT: to determine the prevalence of antibodies to hepatitis C virus in selected groups of patients with chronic liver disease. METHODS: serum specimens were obtained from 39 patients with chronic liver function abnormalities of uncertain cause (group A), from 15 patients with autoimmune chronic active hepatitis (group B) and from 10 patients with chronic hepatitis B (group C). In an extension of the study, serum was collected from sexual partners of patients found to be HCV seropositive. A second generation ELISA assay (Abbott) was used to analyse the specimens. RESULTS: ten patients (26%) in group A were seropositive, one (7%) in group B and three (30%) in group C. Risk factors for infection included blood transfusion in three, intravenous drug use in six (including the only positive patient in group B) and both factors in another patient. Only one of the 10 sexual partners tested was positive but this subject was also an intravenous drug user. CONCLUSIONS: hepatitis C virus is a significant cause of chronic liver disease in Christchurch. Important risk factors include blood transfusion and intravenous drug use although sporadic cases occur. Transmission to sexual partners is uncommon. The second generation assay does not appear to give false positive results in autoimmune chronic active hepatitis.

Adult↗
PubMed1991

Localized in vivo proton spectroscopy of the human kidney.

In vivo 1H spectroscopy using the STEAM sequence for localization has been applied to the human kidney in normal volunteers and subjects with successful renal transplants. We show that, within the resolution of our measurements, trimethylamines are present in the spectra from some of the subjects and absent from others. The prominent peak seen at 5.8 ppm in the spectrum is identified as that from urea and not lipid, as previously suggested.

Humans↗
PubMed1991

Measurement of regional left ventricular function using labelled magnetic resonance imaging.

A technique for assessing regional left ventricular function using magnetic resonance imaging is described. Spatial modulation of magnetization (SPAMM) is effected immediately before images are obtained at various intervals during the cardiac cycle using a modified field echo even rephasing technique (FEER). By performing such modulation in two planes, a grid pattern of labelling can be produced across the image. On the resulting labelled short axis images of the left ventricle, the systolic increase in thickness (thickening) and decrease in length (shortening) of different regions of myocardium can then be measured. The findings in five normal volunteers are presented. Radial shortening was twice as great in the endocardium (mean 20.4%, standard deviation (SD) 5.7) than in the epicardium (mean 10.2%, SD 5.5) and appears to offer more promise as a marker of regional function than simple thickening (mean 9.8%, SD 13.6).

Adult↗
PubMed1983

Latex agglutination test for detection of Candida antigen in patients with disseminated disease.

A latex agglutination test has been devised which allows detection of a circulating antigen in patients with systemic infection due to Candida albicans, Candida tropicalis and Candida parapsilosis. Latex is sensitized with serum from rabbits immunized with whole heat killed Candida albicans blastoconidia. The active component of this serum is IgG. Control latex, used to differentiate non-specific agglutination, is sensitized with the same dilution of serum from a rabbit without antibody to Candida species. Sera from a number of patient groups were tested. While none of the hundred normal controls had an antigen titer of greater than or equal to 1:4, 30 of 33 patients with documented disseminated candida infection had antigen titers of 1:4 to 1:32. Two of the 33 gave false negative results, and one caused nonspecific agglutination. In all patients who recovered after antifungal therapy antigen levels returned to within the range found in normal controls.

Adult↗
PubMed1982

Plate method for detection of phospholipase activity in Candida albicans.

Intracellular phospholipase activity has previously been detected in Candida albicans. A plate method is described which allows rapid detection and measurement of the extracellular activity in a number of clinical isolates. The ratio of colony diameter to diameter of the dense white zone of precipitation around phospholipase positive colonies, (Pz value), correlates with hydrolysis of [14C]phosphatidylcholine by concentrated culture filtrates of selected test isolates. A large variation in phospholipase activity is found between different isolates of C. albicans, however the Pz value is constant for any one isolate regardless of the site from which it is recovered in the patient. Fifty five % of fresh blood isolates are positive and these are also the most potent phospholipase producers. Fifth % of wound isolates and 30% of urine isolates are also positive. A larger sample group must be studied, however, before it can be determined whether these differences are highly significant.

Blood↗
PubMedDate not supplied

The effects of dehydration on brain volume -- preliminary results.

In adults the cranium is a rigid bony vault of fixed size and therefore the intra-cranial volume is a constant which equals the sum of the volume of the brain, the intra-cranial volume of CSF and the intra-cranial volume of blood. There can be marked changes in the volumes of these three intra-cranial compartments which may influence susceptibility to brain damage after head injury. This is the first study to investigate the relationship between dehydration and changes in the volume of the brain and the cerebral ventricles. Six healthy control subjects underwent magnetic resonance imaging of the brain before and after a period of exercise in an environmental chamber. The subjects lost between 2.1 % and 2.6 % of their body mass due to water loss through sweating. We found a correlation between the degree of dehydration and the change in ventricular volume (r=0.932, p=0.007). The changes in ventricular volume caused by dehydration were much larger than those seen in day-to-day fluctuations in a normally hydrated healthy control subject.

Adolescent↗
PubMedDate not supplied

Three-dimensional imaging of the postmortem fetus by MRI: early experience.

OBJECTIVE: The feasibility and significance of three-dimensional (3D) visualization of the postmortem fetus using magnetic resonance imaging (MRI) was investigated. METHODS: 3D reconstruction of sectional MRI data sets from 8 postmortem fetuses was performed. RESULTS: Fetal configurations and internal structures, both normal and pathological, were clearly demonstrated by 3D display. CONCLUSION: This new technique provides high quality fetal 3D images for postmortem morphological diagnosis and interactive visual teaching. It may eventually have applications in prenatal diagnosis and the preoperative simulation of fetal surgery.

Anatomy, Cross-Sectional↗
PubMedDate not supplied

Brain arteriovenous malformations: assessment with dynamic MR digital subtraction angiography.

BACKGROUND AND PURPOSE: Conventional catheter angiography (CCA) is the current reference standard for the diagnosis, assessment, and management of pial brain arteriovenous malformations (AVMs). The purpose of this study was to develop an MR angiographic technique that produces dynamic images comparable to those provided by CCA and to apply the technique to the investigation of pial brain AVMs. METHODS: Twenty patients with brain AVMs referred for stereotactic radiosurgery were recruited. All patients had CCA performed on a 1.5-T superconducting system. Sixty images were obtained at a rate of one image per second. Slices were orientated to produce Towne, lateral, and anteroposterior projections. A set of mask images was taken and then a series during the passage of a bolus of contrast material. MR examinations were assessed independently by neuroradiologists blinded to the conventional catheter angiographic findings. RESULTS: The nidus of the AVMs was depicted in 19 of the 20 patients, and correlation with CCA was excellent for measurements of maximum diameter. Venous drainage was correctly assessed in 18 of 19 cases. CONCLUSION: MR digital subtraction angiography shows promise as a noninvasive, dynamic angiographic tool for planning stereotactic radiosurgery of AVMs already delineated by catheter angiography. At present, it suffers from temporal and spatial resolution, which impede the assessment of some brain AVMs.

Adolescent↗
PubMedDate not supplied

Proton MR spectroscopy of cortical tubers in adults with tuberous sclerosis complex.

BACKGROUND AND PURPOSE: Significant advances have been made in understanding the origin of brain manifestations associated with tuberous sclerosis complex (TSC), most recently the idea that cortical tubers and subependymal nodules are a disorder of neocortical formation. The present study was designed to test the hypothesis that MR proton spectra of cortical tubers are abnormal because of the developmental immaturity of the tubers' neurons and glia. METHODS: Twenty-six adults with TSC were studied. Proton spectroscopy was performed with a single-voxel point-resolved spectroscopy technique in two 8-mL regions: one over a cortical tuber and the other over a corresponding anatomic area of normal-appearing brain in the contralateral cerebral hemisphere. The results were expressed in terms of the ratio of the area under the three prominent resonances of choline (Cho), creatine + phosphocreatine (Cr), and N-acetyl groups (NA). RESULTS: Cortical tubers showed statistically significantly lower NA/Cr (1.54 +/- 0.24 vs. 1.72 +/- 0.23), NA/(Cho+Cr) (0.80 +/- 0.14 vs. 0.91 +/- 0.12), and NA/Cho (1.69 +/- 0.36 vs. 1.97 +/- 0.38) than did normal-appearing brain. No statistically significant difference was found in the Cho/Cr ratios between the tubers and the contralateral brain (0.93 +/- 0.15 vs. 0.90 +/- 0.12). No lactate was identified in any cortical tubers. CONCLUSION: Proton spectroscopy can show differences between cortical tubers and normal-appearing white matter in patients with TSC. The reduced NA/Cr ratio is probably due to reduced levels of NA, most likely caused by the presence of immature neurons and glia in tubers that do not express NA, or by the presence of gliosis, a known histologic component of tubers.

Adult↗