Biomedical subjects
Publications and source records attributed to R L Guy.
Lipiodol is a frequently used contrast agent for lymphangiography and more recently has been used in the investigation of hepatoma. We describe the magnetic resonance characteristics of lipiodol using a Siemens 1.5 T Magnetom with reference to the appearance and behaviour of lipiodol in abdominal lymphadenopathy. The characteristics described differ from previously published reports.
A new method for measuring tibial torsion is described which can be applied to both ultrasound (US) and computed tomography (CT). The method has been validated in dry tibiae by comparison with direct measurements and with Jend's established CT method. In clinical practice a good statistical level of agreement has been demonstrated between the values obtained from US and CT scans. Both compared well with values obtained using Jend's CT technique. The use of US avoids exposure to radiation and is therefore suited to studying young subjects and controls and making repeat measurements.
A total of 16 patients with acetabular fractures were evaluated by plain radiography, axial computed tomography (CT) and three dimensional (3D) CT. It was possible to classify the fracture type in each case from the plain radiographs alone. Axial CT gave additional detail in certain areas, notably the region of the teardrop, the obturator foramen and the acetabular roof. Intra-articular and impacted roof fragments and associated soft tissue injuries were also shown. 3D CT provided the best and most easily interpreted overall assessment of the fractures. In addition to projections equivalent to the plain radiographs, two other views were of particular clinical value in demonstrating surgically inaccessible areas, namely the view of the pelvis from above and the view of the inner aspect of the fractured hemipelvis. However, fracture lines demonstrated on plain radiographs and axial CT were not always apparent on the 3D CT scans. Although 3D CT is a valuable addition to the imaging of acetabular fractures, it is not a substitute for good quality plain radiography and analysis of the axial CT images.
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Using radio-iron uptake into erythrocytes as a measure of hematopoiesis, it was demonstrated that p-benzoquinone (BQ) and muconaldehyde (MUC) are potent inhibitors of bone marrow function in female mice. These two benzene metabolites reduced iron uptake at dosages of less than 5-6 mg kg-1. The combination of MUC and hydroquinone (HQ) (100 mg kg-1) was additive, reducing iron incorporation to an extent that was the sum of the effect of each chemical given alone. The combined effect of MUC and BQ was significantly less than additive, demonstrating antagonism in the response. Multiple regression was used to study the contributions of the components of binary mixtures of the benzene metabolites (METAB). Data obtained from standard curves of METAB and their mixtures are separable in regression analysis. Thus, for zero interaction of METAB, the responses would be simply additive, while positive and negative interaction would indicate synergy and antagonism, respectively. T-testing of the data resulted in non-significant values for the mixture MUC + HQ, indicating zero interaction and an additive response. The negative t-values obtained for the mixture MUC + BQ, however, indicate negative interaction or an antagonistic response. Since mutually exclusive agents share the same binding sites and occupation of a site by one agent excludes its occupation by another, they cannot interact in producing the effect; combinations of these agents show zero interaction and are simply additive. This suggests that HQ and MUC are mutually exclusive and share the same binding site.(ABSTRACT TRUNCATED AT 250 WORDS)
We have carried out a prospective study to compare high resolution thin slice, contrast-enhanced, axial computed tomography (CT) with unenhanced magnetic resonance imaging (MRI) at 1.5T in the assessment of the pituitary and parasellar region. Forty patients with suspected pituitary disease presenting to an endocrine unit were studied. MRI was superior to CT for the identification of the posterior pituitary and pituitary stalk and was better at showing the cystic nature of tumours. Visualization of the optic chiasm and assessment of displacement of the optic chiasm and the carotid arteries were also better with MRI. CT was equally good at showing cavernous sinus displacement or invasion, sphenoid sinus invasion and erosion of the floor of the sella turcica and was the only technique able to show calcification of the gland. More focal abnormalities were seen in the pituitary gland with CT than with unenhanced MRI, but there was a higher false positive rate for microadenoma detection with CT. All the scans were interpreted separately by three observers, two radiologists and one clinician. The percentage agreement between the observers for the identification of pituitary and parasellar structures was better for MRI than for CT and the clinician in particular found interpretation of the MR images easier. MRI thus not only gives more information overall than CT but it is a more reliable technique between different observers for the assessment of the pituitary and parasellar region.
Malignant external otitis is a severe infection of the external auditory meatus occurring predominantly in diabetics and usually caused by Pseudomonas aeruginosa. The infection may spread along several routes: directly by bony erosion into the adjacent mastoid bone, anteriorly into the parotid gland and temporomandibular joint and inferiorly into the soft tissues of the infratemporal fossa. We present four cases of malignant external otitis that illustrate the typical patterns of spread of this disease and the role that radiology, and in particular computed tomography, plays in its diagnosis and management.
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Four cases of limb shortening presenting in childhood are described. All four children had been managed in a neonatal intensive care unit and had developed complications following the insertion of intravascular cannulae. In two, lower limb shortening and deformity were secondary to direct epiphyseal damage following extravasation of calcium or dextrose from a peripheral venous line. In the other two, forearm shortening followed ischaemia, secondary to either radial artery thrombosis from a radial artery cannula or spasm of the brachial artery following extravasation from a venous cannula in a neonate who also had a radial artery cannula. These cases highlight an important complication of the use of vascular cannulae in neonates and the problems this may pose to the orthopaedic surgeon.
Using radioiron uptake into erythrocytes as a measure of hematopoiesis, it was demonstrated that benzene inhibited bone marrow function in female mice. Hydroquinone was marginally effective, but the inhibition occurred only at the highest dose tested (100 mg/kg). The combination of phenol and hydroquinone was more effective in reducing erythrocyte production than either chemical given alone. Catechol given alone was not inhibitory but when phenol was added to catechol, erythropoiesis was suppressed, as observed for the phenol and hydroquinone combination. It appears that benzene toxicity may be the result of cooperative inhibitory effects produced by its metabolites.
Sixty knees presenting with chronic anterior pain were investigated. A diffusely increased uptake indicated sympathetically mediated pain provided other diagnoses such as synovitis or widespread arthrosis were excluded. Focal uptake was not specific to any one condition, but could occur in chondromalacia patellae or recent dislocations. However, the commonest appearance found in chondromalacia patellae was a normal scan. A characteristic scintigraphic appearance in symptomatic postpatellectomy knees, which has not been previously reported, was increased uptake in the femoral groove. In all the cases where no clinical or arthroscopic diagnosis was made, the bone scan was normal. The use of radioisotope scintigraphy is recommended in the problem knee presenting with anterior pain.
Transabdominal ultrasound of the female pelvis has been compared with transvaginal ultrasound, using a 7.5 MHz transducer, in 80 women. Transvaginal ultrasound required less patient time and was preferred in 56% of patients. Image quality was superior in 72% of cases, and visualisation of the pelvic organs was equivalent with each technique. Transabdominal ultrasound gives a more global view of the pelvis, and is of more value in assessing large pelvic masses. Transvaginal ultrasound is of more value in assessing early pregnancy, ectopic pregnancy, ovarian abnormalities, and for visualising the ovaries following hysterectomy.
Pressor sensitivities to infusions of arginine vasopressin (AVP), noradrenaline (NA) and angiotensin II (AII), as well as cardiovascular responses to head-up tilt, were assessed in subjects with central diabetes insipidus (CDI) and compared with those in normal control subjects. During incremental i.v. infusions of AVP at 0.2-5.0 pmol min-1 kg-1, mean arterial blood pressure (MABP) rose progressively in CDI subjects only and the rise was significantly greater than that which occurred in control subjects during their final infusion. The pressor effects of incremental i.v. infusions of NA and AII were greater, and the bradycardia associated with NA was more pronounced, in CDI subjects than in controls. Whole body tilt from supine to 45 degrees head-up was associated with increased heart rate and an insignificant rise in MABP in both groups, although a rise in plasma AVP occurred in control subjects only. These results demonstrate that subjects with CDI are more sensitive than control subjects to the pressor effects of NA and AII, and also develop sensitivity to the pressor effects of AVP. Their cardiovascular responses to head-up tilt remain intact. Presumably the increased vascular sensitivity to NA and AII in subjects with CDI is sufficient to compensate for their lack of AVP response during head-up tilt.