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Biomedical subjects

T Hindmarsh

Publications and source records attributed to T Hindmarsh.

At least 37 records · Page 2Linked to original sources
PubMed1997

Global cerebral blood flow during infusion of adenosine in humans: assessment by magnetic resonance imaging and positron emission tomography.

Adenosine, an endogenous vasodilator, induces a cerebral vasodilation at hypotensive infusion rates in anaesthetized humans. At lower doses (< 100 micrograms kg-1 min-1), adenosine has shown to have an analgesic effect. This study was undertaken to investigate whether a low dose, causing tolerable symptoms of peripheral vasodilation affects the global cerebral blood flow (CBF). In nine healthy volunteers CBF measurements were made using axial magnetic resonance (MR) phase images of the internal carotid and vertebral arteries at the level of C2-3. Quantitative assessment of CBF was also obtained with positron emission tomography (PET) technique, using intravenous bolus [15O]butanol as tracer in four of the subject at another occasion. During normoventilation (5.4 +/- 0.2 kPa, mean +/- s.e.m.), the cerebral blood flow measured by magnetic resonance imaging technique, as the sum of the flows in both carotid and vertebral arteries, was 863 +/- 66 mL min-1, equivalent to about 64 +/- 5 mL 100 g-1 min-1. The cerebral blood flow measured by positron emission tomography technique, was 59 +/- 4 mL 100 g-1 min-1. All subjects had a normal CO2 reactivity. When adenosine was infused (84 +/- 7 micrograms kg-1 min-1.) the cerebral blood flow, measured by magnetic resonance imaging was 60 +/- 5 mL 100 g-1 min-1. The end tidal CO2 level was slightly lower (0.2 +/- 0.1 kPa) during adenosine infusion than during normoventilation. In the subgroup there was no difference in cerebral blood flow as measured by magnetic resonance imaging or positron emission tomography. In conclusion, adenosine infusion at tolerable doses in healthy volunteers does not affect global cerebral blood flow in unanaesthetized humans.

Adenosine↗
PubMed1997

Rectal tumours--MR imaging with endorectal and/or phased-array coils, and histopathological staging on giant sections. A comparative study.

OBJECTIVE: To investigate the accuracy of MR imaging in the preoperative staging of patients with clinically resectable rectal tumours. MATERIAL AND METHODS: Forty-eight consecutive patients with rectal tumours were examined, 29 with a pelvic phased-array coil and 19 with a multi-coil arrangement including a pelvic phased-array coil and an endorectal coil. MR images and histopathological specimens and sections were reviewed independently and tumours were staged according to the TNM classification. RESULTS: A more complete visualisation of the various layers of the rectal wall was achieved on the endorectal MR images than on the pelvic phased-array images. The sensitivity of MR in correctly staging T3 tumours compared with histopathology was 81% with a specificity of 82%. Penetration of the rectal wall was predicted with a sensitivity of 82% and a specificity of 87%. Sensitivity and specificity in predicting lymph node metastases was 83% and 74% respectively. CONCLUSION: MR imaging with both pelvic phased-array and endorectal coils allowed the preoperative staging of rectal tumours with a high degree of accuracy.

Adult↗
PubMed1997

Functional magnesium deficiency in critically ill patients identified using a magnesium-loading test.

OBJECTIVE: To determine the feasibility of the magnesium-loading test in the critically ill and to validate serum ionized magnesium assay using the magnesium-loading test as a reference in this same patient population. DESIGN: Double-blind, randomized, controlled clinical investigation. SETTING: Tertiary level intensive care unit. PATIENTS: Forty-four consecutive critically ill patients without evidence of renal insufficiency. INTERVENTION: Patients were randomly allocated to receive 30 mmol (7.5 g) of magnesium sulfate daily for 3 days, or an equivalent amount of normal saline. MEASUREMENTS AND MAIN RESULTS: We recorded baseline characteristics, and serial serum biochemical measurements included creatinine, glucose, sodium, potassium, phosphate, total calcium, ionized calcium, total magnesium, and ionized magnesium. Serum assays were accompanied by 24-hr urine collections of creatinine and magnesium over the 3-day period. Baseline characteristics were comparable in both groups. In patients receiving magnesium, serum ionized magnesium and total magnesium concentrations were increased by 43% (p = .0001) and 59% (p = .0002), respectively, on day 1 as compared with the control group. Magnesium excretion in the control group averaged 4.8 +/- 2.3 mmol/day during the 3-day study period, while the magnesium excretion in the magnesium-loaded group was significantly increased to 22.7 +/- 10.9 mmol/day (p < .0001). Following day 1 magnesium loading, patients who excreted < 70% of the total magnesium (30 mmol infused magnesium plus 4.8 mmol basal excretion) were termed as functionally magnesium-deficient retainers (n = 12), and patients who excreted > 70% of the total magnesium were termed as nonretainers (n = 7). In addition, magnesium retainers on day 2 (nine of ten patients) and day 3 (five of six patients) excreted > 70% of the total magnesium, indicating a replenishment of body magnesium stores. In contrast, nonretainers on day 2 (four of five patients), and day 3 (four of four patients) continued to excrete excess amounts of magnesium. In the retainer group, only two patients had a low serum ionized magnesium concentration, while two other patients had low total serum magnesium values. In addition, magnesium retention was associated with low ionized calcium and high phosphate values. CONCLUSIONS: The magnesium-loading test is feasible and appears to be valid based on its performance during the 3-day evaluation. Using the magnesium-loading test as a reference, serum ionized magnesium appears to be an insensitive biochemical marker of functional hypomagnesemia. Larger cohort studies using the magnesium-loading test will help establish the true prevalence of magnesium deficiency and its associated risk factors in critically ill patients.

APACHE↗
PubMed1997

Radiosurgical lesions in the normal human brain 17 years after gamma knife capsulotomy.

OBJECTIVE: To our knowledge, this is the first long-term follow-up study of high-dose single-session irradiation to the human brain and provides new data concerning late tissue reactions after irradiation to small target volumes. The long-term lesional brain changes in 14 patients subjected to bilateral gamma knife capsulotomy for otherwise intractable anxiety disorders were retrospectively analyzed by magnetic resonance imaging. METHODS: The prototype gamma unit was used for the radiosurgical procedure, and the collimators provided rectangular cross-sectional fields with an anteroposterior diameter of 3 mm and a transverse diameter of 5 or 11 mm. Maximum target doses were 120 to 180 Gy. Magnetic resonance imaging was performed 15 to 18 years (mean, 17 yr) after treatment, and dose-volume histograms were calculated for the dose distributions. RESULTS: One patient had been irradiated twice on one side. In all but one of the remaining 27 targets, lesions with a volume of less than 100 mm3 were revealed by magnetic resonance imaging. The volumes of the lesions were confined within the volume corresponding to a minimum dose of approximately 110 Gy, with one exception. In one of three targets receiving a maximum dose of 120 Gy, no lesion was detected. There were no late radiation effects such as cyst formations, telangiectasias, hemorrhagic infarctions, or neoplasms. CONCLUSION: This investigation indicates that a minimum dose of 110 Gy, with the currently used 4-mm collimator, to the edge of the target volume is required to create a lesion. The results prove that gamma knife surgery can be used in functional neurosurgery for producing small permanent lesions in the normal human brain.

Adult↗
PubMed1997

A new view on the CSF-circulation with the potential for pharmacological treatment of childhood hydrocephalus.

A new model of the cerebrospinal fluid (CSF) circulation is proposed, implying that the main absorption of CSF occurs through the brain capillaries. This model is based on recent observations of CSF dynamics using radionuclide cisternography and cardiac gated magnetic resonance imaging. Magnetic resonance imaging of communicating hydrocephalus has demonstrated a highly significant decrease of CSF flow through the foramen magnum, which is explained by decreased expansion of the intracranial arteries. This invariable finding in combination with the new view of the CSF-circulation makes a hemodynamic pathogenesis of hydrocephalus very probable. Communicating hydrocephalus may be caused by any process that restricts the arterial pulsations and is therefore termed restricted arterial pulsation hydrocephalus. In obstructive hydrocephalus, the ventricular dilatation leads to a compression of the cortical veins and consequently is termed venous congestion hydrocephalus. Based on these considerations, a new concept of pharmacological treatment of hydrocephalus is proposed by using a selective venous constrictor.

Adult↗
PubMed1996

Further scientific evidence of the non-poisonous death of Napoleon.

Napoleon's death has been historically attributed to cancer of the stomach. This has been documented in numerous writings including those of Antommarchi, Henry, and Shortt, all of whom were present at Napoleon's autopsy in 1821. These documents have been well preserved and have been accepted by historians and scholars worldwide as the probable cause of Napoleon's death. In an earlier presentation, the senior author presented a detailed historical review of Napoleon's death in a paper entitled 'The Last Days and Hours of Napoleon-What Really Happened'. This was given at the famous 'Debate of the Century' at the Napoleonic Society Meeting in Chicago, Illinois, in September of 1994. This paper will concern itself more specifically with new scientific material giving additional support to the cancerous cause of Napoleon's death, and with the lack of evidence of any substance which could cause his death to be attributed to arsenic poisoning. Hairs previously untested and even unknown to exist provide the basis for this new evidence.

Arsenic Poisoning↗
PubMed1995

MR imaging of adult colo-rectal intussusception. A case report.

MR imaging of an intussuscepted sigmoid cancer misinterpreted as a rectal carcinoma is described. High-resolution technique with pelvic-phased array coils and fast spin-echo was used. The diagnosis is discussed in relation to the MR findings.

Colonic Diseases↗
PubMed1994

Haemorrhagic pituitary tumours.

In a group of 69 patients with pituitary tumours, 12 were found to have evidence of intratumoral haemorrhage on MRI, characterized by high signal intensity on short TR/TE sequences. This was verified in all but 1 patient. The majority of the bleedings occurred in macroadenomas. Five (42%) were prolactinomas and 4 (33%) were non-functioning adenomas. There were 2 GH- and 1 ACTH-secreting tumours. All 5 patients with prolactinomas were on bromocriptine medication. Two of the patients had a clinical picture of pituitary apoplexy. The haemorrhage was not large enough to prompt surgery in any of the patients. However, surgical verification of the diagnosis was obtained in 5 cases, while 6 patients were examined with follow-up MRI.

Adenoma↗
PubMed1993

Carcinoma of the cervix: predictive value of clinical and magnetic resonance (MR) imaging assessment of prognostic factors.

PURPOSE: This retrospective study assesses the predictive value of magnetic resonance imaging (MRI) to identify high risk cervical cancer patients. METHODS AND MATERIALS: The MRI evaluation of morphologic risk factors in patients with invasive cervical carcinoma treated with definitive radiation therapy were correlated with clinical factors and with complete tumor regression (CTR) at 6 months, tumor local control (TLC), and patient outcome at 12 months after irradiation. Sixty-six patients, median age 44.5 years, with bulky Stage I or greater disease were included in the study. RESULTS: In univariate analysis, clinical International Federation of Gynecology and Obstetrics (FIGO) stage had significant correlation with patient outcome, but it correlated poorly with complete tumor regression and tumor local control. In contrast, MRI stage showed significant correlation with complete tumor regression, tumor local control, and disease-free survival at 12 months. When each stage was analyzed separately, the greatest difference was demonstrated between clinical and MRI assignment of stage Ib disease. MRI Stage Ib disease significantly correlated with all three categories analyzed, while clinical Stage Ib did not. Superiority of MRI assessment of low stage disease was also evident in the detection of lymph node metastasis. Significant risk for nodal metastasis was related to tumor size greater than 4 cm, invasion of the parametria and urinary bladder, and stage of the disease. CONCLUSION: The multivariate analysis demonstrated that the most related variables in order of significance were the presence of juxta-regional and paraaortic lymph nodes, patient age, tumor size, and MRI tumor stage. This study demonstrates the value of MR imaging as an adjunct to clinical assessment of bulky invasive cervical cancer, rendering more complete assessment of morphologic risk factors important in patient prognosis.

Adult↗
PubMed1993

PET analysis of [11C]flumazenil binding to benzodiazepine receptors in chronic alcohol-dependent men and healthy controls.

Benzodiazepine (BZ) receptor binding in the brain was determined in five chronic alcohol-dependent men and in five healthy male control subjects using [11C]flumazenil (Ro 15-1788) and positron emission tomography (PET). Magnetic resonance imaging was used to evaluate brain anatomy and pathology, and to define regions of interest in the brain. [11C]Flumazenil binding was quantified by applying a saturation procedure with two PET experiments, the first with high (400-3400 Ci/mmol) and the second with low (approximately 1 Ci/mmol) specific radioactivity. Radioactivity in the pons was taken as an estimate of free and nonspecifically bound radioligand. Equilibrium was defined to prevail when the derivative of specific binding (dCb(t)/dt) was equal to zero. The values were used in a Scatchard analysis for determination of the maximum density of binding sites (Bmax) and the equilibrium binding constant (Kd). The mean values of Bmax and Kd were about the same in the two groups, but the Bmax variance for the alcoholics was significantly greater for all regions of interest as compared with the healthy volunteers. The results may indicate that chronic alcohol consumption has multiple effects on the BZ receptor complex.

Adult↗
PubMed1993

Effects of alfentanil on the hemodynamic and catecholamine response to tracheal intubation.

A randomized, placebo-controlled study was conducted in 60 ASA Class I, II, and III patients to determine the dose response of alfentanil in moderating the cardiovascular and catecholamine response to tracheal intubation (INT). Patients were randomly allocated into one of four groups to receive either 15 micrograms/kg alfentanil (A15), 30 micrograms/kg alfentanil (A30), 45 micrograms/kg alfentanil (A45), or normal saline (control), given intravenously (i.v.) before induction of anesthesia. One minute after administration of 4.0 mg/kg thiopental and 1.5 mg/kg succinylcholine i.v., tracheal intubation was performed using direct laryngoscopy. In response to INT, increases in heart rate, systolic blood pressure, and systemic vascular resistance occurred in the control group. These changes were significantly more than corresponding changes of heart rate, systolic blood pressure, and systemic vascular resistance in all three alfentanil groups (P < 0.05). In contrast, cardiac index and ejection fraction decreased moderately in every group during the study period, but there were no differences among groups with respect to either cardiac index or ejection fraction at corresponding times following INT. In the control group, epinephrine and norepinephrine serum concentrations increased by 152 +/- 52% and 58 +/- 62%, respectively, following INT (different from A30 and A45, P < 0.05). However, up to a dose of 30 micrograms/kg (A30), a dose-dependent decrease in the maximum percent changes of both epinephrine and norepinephrine occurred in response to INT. A larger dose of alfentanil was no more efficacious as the catecholamine response to tracheal intubation was not significantly different when comparing the A45 and A30 groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Magnetic resonance imaging of the brain before and after open heart operations.

Magnetic resonance imaging of the brain was performed in 29 adult male patients before and 1 week after elective coronary artery bypass grafting to study the cerebral effect of cardiopulmonary bypass. The mean age of the patients was 60 years (range, 45 to 69 years). During cardiopulmonary bypass, either a bubble oxygenator without an arterial line filter (n = 9), a bubble oxygenator with a depth adsorption filter (n = 10), or a flat-sheet membrane oxygenator without a filter (n = 10) was used. The mean bypass time was 88 minutes (standard deviation, 31 minutes) and did not differ significantly between the three groups. Preoperative magnetic resonance imaging revealed high signal intensity foci on T2-weighted images (white matter abnormalities) in 17 (59%; 95% confidence limits, 39% to 76%) of the 29 patients, all of which were nonspecific and of the common type considered to be related to aging, and all were unchanged at the postoperative examination. Preoperative and postoperative frontal horn indices, bicaudate diameters, and third ventricle widths did not differ significantly regardless of oxygenator type or whether or not an arterial line filter was used during cardiopulmonary bypass. Two patients (7%; 95% confidence limits, 1% to 23%), both receiving bubble oxygenation (1 without a filter and 1 with an arterial line filter) sustained a cerebral infarction during cardiopulmonary bypass.

Aged↗
PubMed1990

[The value of magnetic resonance scanning in the diagnosis of small acoustic neurinomas].

This article describes three cases of acustic neurinoma in which both clinical examination and audiovestibular investigations raised strong suspicions of acustic neurinoma but no tumours could be demonstrated by CT. Magnetic resonance scanning employing gadolinium-DTPA revealed small intrameatal acustic neurinomas in all three cases. Attention is drawn to the fact that magnetic resonance scanning provides a new diagnostic possibility for acustic neurinoma and is a valuable supplement to the established diagnostic procedures in suspected acustic neurinoma even although CT reveals normal anatomical conditions in the internal auditory meatus.

Adult↗
PubMed1990

Central nervous system malformations and white matter changes in pseudo-neonatal adrenoleukodystrophy.

Clinical, biochemical and morphological findings in a 16-month-old infant girl with pseudo-neonatal adrenoleukodystrophy are reported. The parents were first cousins and the baby was born at term, small for gestational age. The neonatal period was characterized by convulsions resistant to treatment, generalized, severe muscle hypotonus, feeding difficulties and poor weight gain. Developmentally she remained at a neonatal level. A CT-scan showed low density of cerebral white matter and MR examination white matter changes, a thin corpus callosum, cerebellar malformation and dorsal displacement of the brainstem. There was an accumulation of very long chain fatty acids (VLCFA) in serum lipids and cultured skin fibroblasts but plasmalogen and phytanic acid levels were normal. A liver biopsy revealed enlarged peroxisomes staining for catalase. Three similar cases have been reported previously; in two of these there was a deficiency of acyl-CoA oxidase. MR evidence of leukodystrophy combined with gross cerebral and cerebellar morphologic changes have not been reported earlier.

Acyl-CoA Oxidase↗