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Biomedical subjects

J H Gillard

Publications and source records attributed to J H Gillard.

At least 19 recordsLinked to original sources
PubMed2001

Reproducibility of quantitative CT perfusion imaging.

The ability to demonstrate regions of abnormal cerebral blood flow in the setting of acute stroke is of diagnostic and prognostic importance. It may also influence therapeutic strategies. The advantage of CT perfusion imaging is its ability to give quantifiable measurements of cerebral blood flow on any modern CT machine without the need to buy specialized equipment. The aim was to assess day-to-day variability of values of cerebral blood volume obtained with this technique. Seven patients with cerebral gliomas were studied using dynamic CT perfusion imaging on two occasions, approximately 24 h apart to reduce variability from diurnal variations. Regions of interest were produced in predominately middle cerebral artery locations in both hemispheres on the first and second CT perfusion studies. Absolute values for cerebral blood flow were produced for these regions and were correlated with flows obtained in the same regions of interest on the follow-up study. The Pearson correlation coefficient obtained was 0.884. CT perfusion imaging is easily performed on conventional modern CT equipment and demonstrates little variability in measures of absolute cerebral blood flow within individuals when studied on two occasions within 24 h.

Adult↗
PubMed2001

MR diffusion tensor imaging of white matter tract disruption in stroke at 3 T.

Recent advances in MR diffusion weighted imaging (DWI) enable the identification of anisotropic white matter tracts with diffusion tensor imaging (DTI). We aimed to use a novel DTI technique to safely study patients with recent stroke in a high field (3 T) MR machine with its intrinsically higher spatial resolution and signal-to-noise ratio. Of ten patients studied, six had disruption of white matter tracts as determined by DTI. A further patient had distortion of white matter tracts around an infarct rather than actual disruption of the tracts themselves. The lack of tract destruction may imply a beneficial prognosis, information that is not available with conventional DWI.

Adult↗
PubMed2000

Recent changes in the workload and clinical experience of pre-registration house officers: experiences over four years in south-west England.

We aimed to measure changes in the training and workload of pre-registration house officers using a postal questionnaire. Two hundred and six pre-registration house officers in the south-western region of England were surveyed and asked to report on the education, training and workload of their posts. Results were compared with a survey conducted four years earlier. Since the previous survey, the number of hours on duty had reduced from a median of 80 h week-1 in 1992/3 to 72 h week-1 in 1996/7 (P < 0.0001). There were no statistically significant changes in the number of patients admitted or clerked in an average week, but house officers' clinical experience had fallen. All but five of 26 marker conditions showed a decline, which was statistically significant in seven cases. House officers were keener to include four months of general practice in the pre-registration year and were less adverse to extending the pre-registration year to two years. The reduction in hours of work for house officers has been accompanied by a decline in their clinical exposure to common medical and surgical emergencies. The long-term effects of these changes are unknown.

Emergency Medicine↗
PubMed2000

Assessment of quantitative computed tomographic cerebral perfusion imaging with H2(15)O positron emission tomography.

Assessment of quantitative cerebral blood flow on a conventional fast CT machine without the use of specialized equipment may be valuable in the investigation of acute stroke and head injury. We aimed to compare a single slice CT perfusion sequence with H2(15)O positron emission tomography using the sagittal sinus as an input function, a method that avoids unnecessary orbital irradiation. Eight patients were studied, two patients with gliomas, and six with arteriovenous malformations. The dynamic CT perfusion sequence was performed by acquiring the same 10 mm slice 10 times over 30 sec during a 50 ml bolus of intravenous contrast medium given at a rate of 7.5 ml sec-1 using a power injector. The CT perfusion studies were completed without complication. Co-registration was sub-optimal in one patient. Overall the correlation between the two methodologies was encouraging with an average r2 value of 0.524 for individual analyses. When two patients with high flow arteriovenous malformations were excluded the average r2 value increased to 0.640. The results of this CT perfusion methodology are encouraging. Having shown its feasibility, further studies in conditions with lower rates of cerebral blood flow are warranted.

Adult↗
PubMed1999

Evaluation of carotid endarterectomy with sequential MR perfusion imaging: a preliminary 12-month follow up.

AIM: The clinical benefit of carotid endarterectomy is partially determined by peri-operative mortality and morbidity. Post-operative abnormalities in cerebral perfusion may be a risk factor for cerebral haemorrhage, and may be estimated from Bolus Arrival Time (BAT) as demonstrated by MR perfusion imaging. We aimed to use MR perfusion imaging to determine the temporal extent of these changes. MATERIALS AND METHODS: A single slice gradient recalled echo sequence was employed in five patients who underwent carotid endarterectomy. Sequential studies were undertaken pre-operatively, 3-5 days post carotid endarterectomy, and additionally at 3, 6 and 12 months. RESULTS: Asymmetric BATs were demonstrated in 3/5 patients, changes occurring as late as 6 to 12 months after carotid endarterectomy. These changes were not associated with either clinical or conventional MR morphological complications. CONCLUSIONS: MR perfusion imaging is able to demonstrate changes in BAT characteristics for up to 12 months after carotid endarterectomy. The clinical significance and underlying cause of these changes, including any association with post carotid endarterectomy hyperaemia, remains unknown.

Aged↗
PubMed1999

TCD, MRA and MRI in acute cerebral ischemia.

OBJECTIVES: The aim of this study was to determine accuracy of transcranial Doppler ultrasound (TCD) and compare efficacy of three non-invasive tests [TCD, magnetic resonance angiography (MRA), and magnetic resonance imaging (MRI)] in patients with acute cerebral ischemia. MATERIAL AND METHODS: This prospective study involved 30 patients. MRI, MRA, and TCD were performed within 24 h after onset of ictus. The 2nd MRI was repeated at 48-72 h and was used as the standard for the evaluation of sensitivity and specificity of MRA, TCD, and initial MRI. RESULTS: TCD showed a sensitivity of 96% and a specificity of 33% for recognizing abnormal cerebral blood flow velocities. MRA showed a sensitivity of 46% and a specificity of 75% for assessing intracranial vascular anatomy, while initial MRI revealed a sensitivity of 84% and a specificity of 100% for evaluation of ischemic parenchymal changes. CONCLUSION: Our results revealed that TCD is an accurate indicator of blood flow status and correlated well with MRI, MRA abnormalities in acute stroke.

Adult↗
PubMed1999

Wegener granulomatosis: MR imaging findings in brain and meninges.

PURPOSE: To determine the spectrum of intracranial magnetic resonance (MR) imaging appearances of Wegener granulomatosis. MATERIALS AND METHODS: MR imaging studies in 19 patients with Wegener granulomatosis and possible central nervous system involvement were reviewed by two neuroradiologists. Intermediate-weighted and T2-weighted fast spin-echo MR images of the brain had been acquired in all patients, and spin-echo T1-weighted nonenhanced and gadolinium-enhanced images had been acquired in 18 patients. RESULTS: MR imaging findings included diffuse linear dural thickening and enhancement (n = 6); focal dural thickening and enhancement contiguous with orbital, nasal, or paranasal disease (n = 5); infarcts (n = 4); nonspecific white matter areas of high signal intensity on intermediate-weighted and T2-weighted images (n = 10); enlarged pituitary gland with infundibular thickening and enhancement (n = 2); a discrete cerebellar lesion that was probably granulomatous in origin (n = 1); and cerebral (n = 8) and cerebellar atrophy (n = 2). CONCLUSION: MR imaging demonstrated the wide spectrum of findings of central nervous system involvement in patients with Wegener granulomatosis and was particularly useful for the evaluation of direct intracranial spread from orbital, nasal, or paranasal disease.

Adolescent↗
PubMed1998

Riedel's lobe of the liver: fact or fiction?

Riedel's lobe should be considered in all patients undergoing cross-sectional imaging. It may harbor a lesion that might not be demonstrated unless the most inferior aspect of the liver is imaged. We have tried to identify the prevalence of Riedel's lobe in a series of patients with normal abdominopelvic computed tomographic (CT) findings. We reviewed the digital CT data of 105 patients, ages 20-89 years, to define the position of the liver in relation to the costal margin and the iliac crest. There were no significant differences in the prevalence of Riedel's lobe between sexes. The proportion of individuals in whom the most caudal margin of the liver was inferior to the most caudal costal margin was age-dependent and increased to 65% in the 50-59 age group. The craniocaudal dimension of the liver decreased with age (P < 0.02). Riedel's lobe appears to be a common variant of normal anatomy, its prevalence being dependent on age-related changes in liver size and skeletal shape.

Adult↗
PubMed1998

Duplicated superficial femoral veins: a source of error in the sonographic investigation of deep vein thrombosis.

PURPOSE: To determine whether the number of false-negative ultrasound (US) findings of thrombosis is larger when a duplicated femoropopliteal venous system is present. MATERIALS AND METHODS: A retrospective review was performed of 381 venograms obtained after initial US findings were considered negative for thigh or popliteal thrombosis in patients in whom deep vein thrombosis was suspected Venograms were evaluated for the presence of thrombosis and the presence and configuration of duplicated superficial femoral veins. RESULTS: Multiple superficial femoral veins were present on 177 (46%) of the 381 venograms; 149 (84%) were duplex systems. False-negative US findings occurred in four (2%) of 204 patients with single femoral veins and in 10 (6%) of 177 patients with duplicated femoral veins (P = .056, not statistically significant). CONCLUSION: The frequency of missed proximal thrombosis at sonography appears to be increased when duplicated superficial femoral veins are present. Data from clinical and imaging studies are insufficient to support the adoption of a totally noninvasive imaging strategy.

Congenital Abnormalities↗
PubMed1998

Digital radiology in skeletal trauma: assessment of casualty officers' performance.

Radiographic images can now be produced without the requirement of film processing and development, and can be displayed rapidly on a computer monitor. We assessed junior doctors' performance in interpreting images from 25 patients being investigated for possible fracture and also compared the diagnostic abilities of casualty officers with those of radiology specialist registrars. For interpretation of images viewed at a workstation or as filmed laser images, respectively, sensitivities were 75% and 78%, and specificities were 65% and 76%. These differences were not significant. There was a tendency for radiology specialist registrars to be less specific when reviewing images at a workstation. The demonstration that there is no loss in diagnostic quality when casualty officers interpret fracture images in a purely digitally acquired and viewed format forms a robust basis for economic evaluation of the technology.

Clinical Competence↗
PubMed1998

Computed radiology.

Explore the source record for details and available documents.

Attitude of Health Personnel↗
PubMed1998

Evaluation of carotid endarterectomy with sequential MR perfusion imaging: a preliminary report.

BACKGROUND AND PURPOSE: Current indications for carotid endarterectomy are determined by balancing the relative risks of surgery with the benefits of reduced risk of subsequent stroke. Our purpose was to use MR perfusion imaging to assess patients being considered for carotid endarterectomy and to monitor sequential changes in MR perfusion characteristics after surgery. In particular, we wished to determine whether this technique could be used to detect changes that might be related to post-carotid endarterectomy hyperemia. METHODS: We used a single-section gradient-recalled echo sequence to investigate 14 patients being examined before possible surgery for carotid artery disease. In the 12 patients in whom carotid endarterectomy was performed, sequential studies were performed 3 to 5 days after surgery and at 3 months. Analysis of bolus-arrival-time (BAT) images was performed. RESULTS: Significant delays in preoperative BAT images of 0.89 seconds (range, 0.05 to 3.22 seconds) were apparent between hemispheres. Excluding the two patients with contralateral internal carotid artery (ICA) occlusion, early arrival, possibly indicating postoperative hyperemia, was seen in five patients immediately after carotid endarterectomy but resolved within 3 to 5 months after surgery. CONCLUSION: MR perfusion imaging shows differences in BAT between hemispheres in patients with ICA stenosis. Changes in perfusion characteristics after carotid endarterectomy are complex, and early BAT on the operative side can occur soon after endarterectomy in over half those patients without an occluded contralateral vessel. The significance of these findings with regard to patient outcome and risk of postoperative hyperemia requires further investigation.

Aged↗
PubMed1997

MR angiography in acute cerebral ischemia of the anterior circulation: a preliminary report.

PURPOSE: To determine the prevalence of major vessel occlusion in cases of acute cerebral ischemia of the anterior circulation by using MR angiography and to assess the frequency of spontaneous thrombolysis. METHODS: Thirty patients with an initial clinical diagnosis of possible acute stroke of the anterior circulation made within 24 hours of the event were studied with conventional T2-weighted MR imaging and with two-dimensional and three-dimensional time-of-flight MR angiography. Studies were repeated if the initial study showed partial or complete occlusion. RESULTS: Of the 30 patients studied six (20%) had a final diagnosis of a transient ischemic attack and 24 (80%) had a stroke of the anterior circulation as confirmed by T2 abnormalities and persistence of clinical symptoms. Twelve (50%) of the stroke patients had a major vessel abnormality, either partial or complete occlusion, at MR angiography. Of these 12 patients, nine subsequently had follow-up MR angiography, and only two of these had a change in the findings. One patient with diminished flow signal had progression of the occlusion and another patient had flow signal in a vessel where no flow was seen initially. CONCLUSION: MR angiography can show patients with acute cerebral ischemia and major vascular occlusive disease. Of those with partial or complete occlusion, progression of thrombus or spontaneous recanalization occurs infrequently.

Acute Disease↗
PubMed1996

Proton MR spectroscopy in acute middle cerebral artery stroke.

PURPOSE: To investigate the feasibility of performing multisection proton MR spectroscopy in patients with acute stroke, and to determine whether this imaging technique can depict ischemic or infarcted brain regions. METHODS: Multisection proton MR spectroscopy, MR imaging, and MR angiography were performed within 24 hours of stroke onset (mean, 12 hours) in 12 patients who had had a stroke of the middle cerebral artery. Spectra were analyzed from brain regions containing T2 hyperintensity abnormalities on MR images, from regions immediately adjacent to these abnormalities, and from anatomically similar contralateral regions. Areas of brain containing lactate were compared with areas of T2 hyperintensities on MR images. RESULTS: One data set was discarded because of excessive artifacts from patient motion. Regions of T2 hyperintensities on MR images were found to contain elevated lactate (all 11 cases) and reduced N-acetyl-aspartate (10 of 11 cases) relative to contralateral measurements. Lactate levels in regions adjacent to T2 hyperintensities were not significantly different from those of infarcted brain. On the other hand, N-acetyl-aspartate was significantly lower in regions of infarction compared with periinfarct tissue. Areas of brain containing elevated lactate significantly exceeded those of T2 abnormality. CONCLUSIONS: Proton MR spectroscopy is feasible for imaging patients with acute stroke. In the early stages of stroke, tissue containing elevated lactate but no other spectroscopic or MR imaging abnormality can be identified. Such regions may represent an ischemic zone at risk of infarction.

Acute Disease↗