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Biomedical subjects

A D Murray

Publications and source records attributed to A D Murray.

At least 19 recordsLinked to original sources
PubMed1999

Accuracy of T1 measurement in dynamic contrast-enhanced breast MRI using two- and three-dimensional variable flip angle fast low-angle shot.

In vivo T1 measurements, used to monitor the uptake of contrast agent by tissues, are typically performed as a first step in implementing compartmental analysis of contrast-enhanced breast magnetic resonance imaging (MRI) data. We have extended previously described methodology for in vivo T1 measurement (using a variable flip-angle gradient-recalled echo technique) to two-dimensional (2D), fast low-angle shot (FLASH). This approach requires computational modeling of slice-selective radiofrequency (RF) excitation to correct for nonrectangular slice profiles. The accuracy with which breast tissue T1 values can be measured by this approach is examined: T1 measurements from phantom and in vivo image data acquired with 2D and 3D FLASH imaging sequences are presented. Significant sources of error due to imaging pulse sequence quality and RF transmit field nonuniformity in the breast coil device that will have detrimental consequences for compartmental analysis are identified. Rigorous quality assurance programs with calibrated phantoms are thus recommended, to verify the accuracy with which T1 measurements are obtained.

Breast↗
PubMed1999

Metformin and contrast media--a dangerous combination?

Metformin is a biguanide used to treat type II diabetes mellitus. Since the recent introduction of this drug into the United States there has been considerable interest in metformin associated lactic acidosis (MALA) following intravenous contrast media. The Royal College of Radiologists published advice in November, 1996 (Advice to Members and Fellows with regard to metformin-induced lactic acidosis and X-ray contrast medium agents, RCR Publication) supporting the manufacturers' advice that metformin should not be used in the 48 h before or after intravenous (i.v.) contrast medium. We performed a systematic review of the literature and this has shown that almost all reported cases of MALA following i.v. contrast medium occurred where there was either pre-existing poor renal function or another contraindication to metformin usage. There has been only one reported case of lactic acidosis following the use of intravenous contrast medium in a patient with normal renal function. We suggest that the Royal College of Radiologists' advice should be modified and that it is safe to give i.v. contrast medium to patients on metformin with normal renal function.

Acidosis, Lactic↗
PubMed1998

Untreated essential infantile esotropia: factors affecting the development of amblyopia.

PURPOSE: A concomitant esotropia, presenting within the first 6 months of life, associated with a high incidence of dissociated vertical deviation, manifest latent nystagmus and asymmetric optokinetic nystagmus is termed essential infantile esotropia. Most studies concern patients diagnosed in infancy and treated throughout childhood. This paper addresses the factors that may influence the development of amblyopia in patients who remain untreated until visual adulthood. METHODS: During a 3 year period 113 patients aged 8 years or more with a history of esotropia occurring within the first 6 months of life were examined for the study. All patients underwent full ocular motility assessment and cycloplegic refraction, and only those with one or more signs of essential infantile esotropia were included. RESULTS: Of the 113 patients, 16 (14.3%) had a difference of 2 or more lines in the visual acuity of the two eyes and were diagnosed as having amblyopia. Anisometropia was present in 10 of the 16 (62.5%). The correlation between anisometropia and amblyopia was statistically significant (p = 0.0001). CONCLUSIONS: Amblyopia following early surgical intervention in essential infantile exotropia is well documented, but the risk is outweighed by the chance of obtaining some form of binocular vision. However, where access to ongoing therapy is not available, patients with essential infantile esotropia, free alternation and no anisometropia have a significant chance of retaining good visual acuity in both eyes if surgery is delayed until visual adulthood.

Adolescent↗
PubMed1997

Maternal directive and facilitative interaction styles: associations with language and cognitive development of low risk and high risk toddlers.

The purpose of this study was to examine the relation of maternal interaction styles to the development of a sample of 56 toddlers (19 low risk, 37 high risk) seen at 12 and 24 months of age. At 12 months, videotapes of mother-child interaction were coded for directiveness, sensitivity, and elaborativeness. At 12 and 24 months, cognitive and language measures were collected. A directive maternal style was negatively correlated with sensitivity and elaborativeness, whereas sensitive and elaborative ratings were positively correlated, suggesting a facilitative style. Regression models significantly predicted receptive language and cognitive development at 24 months but not expressive language. Maternal directiveness at 12 months was negatively relative to later receptive language skills, whereas elaborativeness at 12 months was positively predictive of later cognitive development. Child status variables and maternal interactional styles contributed about equally to the prediction of later cognitive and language outcomes.

Child Language↗
PubMed1996

Choice of contrast enhancement index for dynamic magnetic resonance mammography.

Indices are often used in dynamic MRI of the breast to quantitate signal enhancement within suspicious lesions. Two indices are commonly used: one calculates the difference in pre- and postcontrast signal intensity, normalised to a base-line signal intensity such as that of fat (which does not enhance) whilst the other calculates the ratio of pre- to postcontrast signal intensity. The results of a computational simulation are presented which demonstrate the superiority of the normalised signal difference index, based on the criterion that the best index is that which is least influenced by initial tissue T1. This hypothesis was tested by comparing the two indices in a group of patients with clinical or mammographic suspicion of recurrent breast carcinoma. Of 37 patient examinations using Gadolinium enhanced MRI of the breast, 11 patients showed 13 lesions with some degree of enhancement, which were subsequently diagnosed histologically as either benign or malignant. The normalised signal difference index showed no overlap between the benign and malignant groups, whereas some overlap was observed with the signal ratio index. The clinical findings are therefore consistent with the results of the computational simulation.

Adult↗
PubMed1996

Clinically suspected scaphoid fracture: a comparison of magnetic resonance imaging and bone scintigraphy.

59 patients with clinical suspicion of scaphoid fracture, but negative radiographs at presentation and review, were examined by magnetic resonance imaging (MRI) and bone scintigraphy (BS). The diagnoses were compared with subsequent follow-up. There were four scaphoid fractures, 10 other fractures and three significant ligamentous injuries. All scaphoid fractures were identified by MRI and BS. MRI showed better interobserver agreement for scaphoid injury than BS and fewer false positive reports. Significant ligamentous injury and carpal instability diagnosed by MRI were not evident on scintigraphy. Using fast scanning protocols, the cost of MRI is comparable with that of BS. MRI should be considered as the appropriate second line investigation in these clinical circumstances.

Adolescent↗
PubMed1996

Measurement of spin-lattice relaxation times with FLASH for dynamic MRI of the breast.

Using a variable flip angle gradient refocused imaging technique, dynamic quantitative T1 relaxation maps acquired before and after the administration of a gadolinium contrast bolus enable the concentration-time curve of the paramagnetic agent in breast tissue to be calculated. This imaging technique has the aim of improving the diagnostic accuracy of MR mammography. Measurements with phantoms of calibrated T1 values have been carried out to investigate the accuracy of the method, with particular reference to errors caused by incomplete spoiling of residual transverse magnetization and inaccurate radio frequency (RF) flip-angle settings. A clinical example is presented. The method has potential use for any patient study which necessitates rapid quantitation of changing in vivo T1 values as a result of contrast agent injection.

Breast Neoplasms↗
PubMed1996

Dynamic magnetic resonance mammography of both breasts following local excision and radiotherapy for breast carcinoma.

The purpose of this study was to evaluate a dynamic gadolinium-diethylene-triaminepentacetate (Gd-DTPA) enhanced magnetic resonance mammography (MRM) protocol, incorporating image subtraction and using a dedicated double breast coil, in patients with treated breast cancer. 36 patients who had undergone breast conserving surgery and radiotherapy, with clinical or mammographic suspicion of locally recurrent breast carcinoma, were examined. 3D rapid volume imaging of both breasts was performed before and repeated three times, at 1, 2 and 3 min, following Gd-DTPA enhancement. Image subtraction allowed identification of enhancing lesions and quantitative analysis of these was performed. Five patients had six lesions demonstrating rapid enhancement in the first minute, all of which were histologically confirmed recurrent or second primary tumours. Slower enhancement was seen in six benign lesions and diffuse enhancement was seen in one patient within 6 months of treatment. The dynamic protocol used allowed sufficient temporal resolution for distinguishing malignant from benign lesions at the site of previous surgery and ensured that both breasts were imaged in their entirety, thus enabling the diagnosis of multifocal and second primary tumours.

Adult↗
PubMed1995

The effect of reducing the exposure time of mitomycin C in glaucoma filtering surgery.

BACKGROUND: The use of adjunctive intraoperative mitomycin C has considerably improved the success rate of glaucoma filtering surgery. However, the ideal concentration and exposure time of mitomycin C is unknown. The purpose of this study is to determine whether a satisfactory surgical outcome can be achieved with a lower incidence of adverse side effects by using a shorter exposure time of mitomycin C than has been recommended previously. METHODS: Twenty-five eyes of 25 consecutive patients who were considered to be at high risk for surgical failure because of their age (< 55 years), previous failure of trabeculectomy, previous cataract surgery, or traumatic glaucoma received a single intraoperative application of mitomycin C (0.2 mg/ml for 2 minutes). They were case-matched with a group of 48 consecutive patients who received a single intraoperative application of mitomycin C (0.2 mg/ml for 5 minutes) by using age, race, type of refractory glaucoma, and preoperative intraocular pressure (IOP) as variables. RESULTS: Eighteen months after surgery, 22 (88%) patients in the 2-minute group and 21 (84%) patients in the 5-minute group had an IOP less than 21 mmHg with or without treatment. No significant differences were found in the complication rate: in 2 (8%) of 25 eyes of the 2-minute group, chronic hypotony developed compared with 3 (12%) of 25 eyes in the 5-minute group. Hypotony-related maculopathy developed in one eye in the 5-minute group. A cystic bleb was found in 15 (60%) eyes in the 2-minute group compared with 19 (76%) eyes in the 5-minute group, although this difference was not statistically significant. Two (8%) eyes in the 2-minute group and one eye (4%) in the 5-minute group had a bleb-related infection. In one (4%) patient in each group, late severe endophthalmitis developed. CONCLUSION: These results suggest that a 2-minute intraoperative application of 0.2 mg/ml mitomycin C is as effective as a 5-minute exposure, but the complication rate remains unaltered.

Adult↗
PubMed1993

Trabeculectomy with mitomycin C for refractory glaucoma in blacks.

The use of one intraoperative application of mitomycin C at the filtration site has been effective in eyes at increased risk for failure of routine trabeculectomy. To study the efficacy and safety of this technique in patients with refractory glaucoma, we prospectively examined 30 eyes of 26 black patients in whom a 0.2-mg/ml solution of mitomycin C was applied between Tenon's capsule and the sclera for five minutes before trabeculectomy. The results were compared to those found in a matched group of 30 eyes of 28 patients who underwent trabeculectomy without mitomycin C. The mean postoperative intraocular pressures were significantly lower in the mitomycin C group than in the control group (P = .001). Of the 30 eyes in the mitomycin C group, 25 (83%) had an intraocular pressure of less than 21 mm Hg without glaucoma medication, compared to 11 of 30 (37%) in the control group (P = .00006). In the mitomycin C group, 19 eyes (63%) developed a cystic avascular thin-walled filtering bleb, four eyes (13%) a late positive Seidel test, and one eye slight scleral thinning over the area where the mitomycin C was applied. Although mitomycin C is effective when used in this manner, further study is required to determine the long-term complications.

Adult↗
PubMed1993

Surgical management of post-traumatic angle recession glaucoma.

PURPOSE: The purpose of this study is to compare the results of three different drainage procedures performed for uncontrolled post-traumatic angle recession glaucoma. METHODS: A retrospective analysis was undertaken of 87 drainage procedures performed on 65 patients over an 8-year period. The results of trabeculectomy (47 procedures), Molteno single-plate implantation (20 procedures), and trabeculectomy combined with antimetabolite (20 procedures) were compared. Of those treated with antimetabolite, 11 received postoperative subconjunctival injections of 5-fluorouracil and 9 received an intraoperative application of 0.02% mitomycin C to the trabeculectomy site. RESULTS: In the group undergoing trabeculectomy with antimetabolite therapy, the intraocular pressure (IOP) drop was significantly greater, the percentage of successful cases at 3 and 6 months postoperatively was significantly higher, and the number of postoperative glaucoma medications was significantly lower than the other two groups. No statistically significant differences were found between the groups undergoing trabeculectomy without antimetabolite therapy and Molteno implantation. Of concern were three cases of late bleb infection in the group that received postoperative antimetabolite therapy. CONCLUSION: In medically uncontrolled post-traumatic angle recession glaucoma, trabeculectomy with antimetabolite therapy is the most effective surgical procedure. However, late bleb infection is a significant risk.

Adolescent↗
PubMed1993

Post-traumatic angle recession glaucoma: a risk factor for bleb failure after trabeculectomy.

In order to determine if post-traumatic angle recession is a risk factor for failure of glaucoma filtering surgery independent of age or race, the surgical results of trabeculectomy performed in 35 consecutive patients with angle recession glaucoma were compared with those of 35 matched patients with primary open angle glaucoma. A postoperative intraocular pressure of < or = 21 mm Hg (with or without glaucoma medication) was found in 15 of the 35 (43%) patients with angle recession glaucoma compared with 26 of the 35 (74%) patients with primary open angle glaucoma. The long term success of trabeculectomy was significantly worse in angle recession glaucoma when the results were analysed using Kaplan-Meier survival curves. Bleb failure occurred a mean period of 3.1 (SD 1.2) months after trabeculectomy in angle recession glaucoma compared with 9.4 (5) months in primary open angle glaucoma (p < or = 0.001). The finding that posttraumatic angle recession is a risk factor for failure of trabeculectomy, supports the use of antimetabolite therapy to suppress fibrosis after trabeculectomy in these patients.

Adult↗
PubMed1993

Proptosis as a presenting sign of extradural haematoma.

A conscious 15-year-old boy presented with progressive proptosis and a severe headache 2 weeks after minor blunt trauma to the head. No neurological deficit was present. Computed tomography demonstrated intracranial and intraorbital cyst-like masses. At craniotomy a subacute extradural haematoma was found which communicated with an orbital subperiosteal haematoma through a shelved orbital roof fracture. The haematomas were drained and the patient made an uneventful postoperative recovery. Although rare, an extradural haemorrhage should be considered in any patient presenting to an ophthalmologist with progressive proptosis and headache following a head injury.

Adolescent↗
PubMed1993

Molteno tube implantation for neovascular glaucoma. Long-term results and factors influencing the outcome.

BACKGROUND: The Molteno implant has been shown to be useful in the treatment of neovascular glaucoma. However, a wide range of success rates has been reported. This is related to the use of differing criteria for success, varying periods of follow-up, and difficulty in quantifying the preoperative condition of the eye. METHODS: The authors studied the long-term results of the Molteno single-plate implant in 60 eyes with neovascular glaucoma using Kaplan-Meier life-table analysis. Age, visual acuity, underlying retinal diseases, and preoperative retinal ablation treatment were evaluated to establish factors influencing the surgical outcome. The criteria for success included a postoperative intraocular pressure (IOP) of less than or equal to 21 mmHg and maintenance of vision. RESULTS: The success rate was 62.1% at 1 year, 52.9% at 2 years, 43.1% at 3 years, 30.8% at 4 years, and 10.3% at 5 years. The main causes for failure were loss of light perception in 48% of eyes (29/60), progression to phthisis bulbi in 18% (11/60), and encapsulation of the filtering bleb in 10% (6/60). The long-term surgical outcome was significantly better in patients older than 55 years of age (P = 0.048) and in those with a preoperative visual acuity equal to or better than 6/60 (P = 0.019). Eyes with neovascular glaucoma secondary to diabetic retinopathy had a better prognosis than those with a central retinal vein occlusion (P = 0.003). CONCLUSION: Although the IOP can be significantly reduced after Molteno implantation, this study suggests that in severely compromised eyes with neovascular glaucoma the main advantage of Molteno implantation is pain relief and avoidance of enucleation.

Adolescent↗
PubMed1992

The association of iridoschisis and primary angle-closure glaucoma.

Twelve patients with iridoschisis in one or both eyes were studied to determine the clinical features of the condition and to examine the relationship of iridoschisis to primary angle-closure glaucoma. A spectrum of iris pathology, from subtle intrastromal atrophy to extensive splitting of the anterior layer of iris with fibrillar disintegration, was found in the affected and fellow eyes. Gonioscopy revealed partial or complete angle closure, particularly involving the superior angle, in all patients. Seven had glaucomatous disc damage and five had normal discs. The mean axial length and anterior chamber depth measurements in patients with iridoschisis were similar to those found in matched patients with primary angle-closure glaucoma but were significantly less than the measurements found in matched normals (p < 0.001). This study suggests that iridoschisis is an unusual manifestation of iris stromal atrophy and results from intermittent or acute elevation of intraocular pressure. Primary angle-closure glaucoma should be excluded in patients who present with iridoschisis.

Adult↗
PubMed1992

Intravenous sedation for ocular surgery under local anaesthesia.

Anterior segment ophthalmic surgery is commonly performed under local anaesthesia. In order to improve patient comfort, a variety of sedation techniques has been employed in the past. The object of this study was, firstly, to determine whether continuous intravenous sedation during surgery offered any advantages in patients premedicated with temazepam and metoclopramide, and, secondly, to compare midazolam to propofol for this purpose. Forty nine patients were randomly allocated to receive no intravenous sedation (n = 15), continuous propofol infusion (n = 17), or continuous intravenous midazolam infusion (n = 17) after peribulbar anaesthesia. Each technique provided cardiovascular and respiratory stability and allowed early recovery with minimal postoperative sequelae. Unexpected ocular field movement occurred more commonly in the patients receiving intravenous sedation, although statistical significance was not shown (p = 0.06). Significantly more patients in the intravenous sedation groups reported amnesia (p = 0.03). Patient acceptability was good irrespective of the technique used. This study suggests that continuous sedation using propofol or midazolam is not beneficial and should be avoided in ophthalmic patients who have received a simple premedication.

Aged↗