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Biomedical subjects

M Doyle

Publications and source records attributed to M Doyle.

At least 19 recordsLinked to original sources
PubMed1992

Slice thickness reduction by partial overlapping presaturation.

We present a new approach to slice thickness reduction that does not require strengthening the selection gradient or increasing the RF pulse duration. The basis of the approach is to employ a thick slice and suppress a portion of its width, thereby forming a thin slice. Two distinct implementations of the technique are introduced and demonstrated by imaging slice profiles in a phantom and generating images of a volunteer's knee.

Humans↗
PubMed1992

The relationship between relative's Expressed Emotion and schizophrenic relapse: an Australian replication.

We report a predictive study, carried out in Sydney Australia, investigating the association between the Expressed Emotion (EE) status of the household to which the patient is discharged and schizophrenic relapse. Expressed Emotion was not related to illness severity either at admission or discharge, but was related to variables reflecting chronicity and employment history. There was a significant association between returning to a high EE household and both re-hospitalisation and relapse. The significant association between EE and relapse held only for: patients not on medication, males, and those patients in high contact with their relatives. A discriminant function analysis found that decline in occupational status and the number of critical comments expressed by the relative were the strongest predictors of relapse. The results presented here are consistent with the majority of published reports on EE and relapse and contradict the negative findings of a recently published but smaller study also carried out in Sydney.

Adult↗
PubMed1992

The Sydney intervention trial: a controlled trial of relatives' counselling to reduce schizophrenic relapse.

The result of a psychosocial intervention which aimed to reduce schizophrenic relapse through relatives' counselling is presented. Thirty-six schizophrenic patients living in high Expressed Emotion (EE) parental households were randomly allocated to an intervention or control group. The parents of patients allocated to the intervention were offered ten weekly sessions of counselling. The patient was not included in these sessions. Patients in both groups received standard after-care of medication and support. Relapses in the intervention group, although fewer, were not significantly different from the control group. Given the impressive evidence in favour of family interventions in reducing relapse rates in schizophrenic patients possible reasons for this result are discussed. Aspects of the intervention described here, exclusion of the patient, no control over the patients' medication or involvement with their management, short duration of intervention and lack of individual assessment, could explain this finding. This negative result is important in indicating what factors should be included in an effective psychosocial intervention.

Adult↗
PubMed1992

Non-invasive optical monitoring of cerebral blood oxygenation in the foetus and newborn: preliminary investigation.

Near infra-red spectroscopy was applied as a non-invasive and continuous technique for the in vivo monitoring of blood and tissue oxygenation in human neonates. Monitoring of cerebral blood oxygenation in the wavelength range 775-904 nm was carried out on preterm infants after inducing a transient mild hypoxic change; the measurements were performed either by the transmission or reflection (backscattering) mode of monitoring. The results of these investigations were used to assess the application of the technique to foetal monitoring. A series of foetal monitoring studies was performed to investigate the influence of maternal contractions on foetal cerebral blood oxygenation. Although only changes in haemoglobin concentration can be monitored at present, the results suggest that near infra-red monitoring could provide a non-invasive, real-time monitoring method in intensive neonatal and intrapartum care.

Brain↗
PubMed1992

Outflow refreshment angiography: a bright blood, bright static tissue technique.

A new "bright blood" strategy, outflow refreshment imaging, is introduced in which a number of overlapping slices are excited in rapid succession. Flowing spins that refresh each overlapped slice portion contribute a bright signal. Additionally, static tissue in each non-overlapped slice portion also yields a bright signal. However, the flow/static contrast is comparable to that produced in inflow refreshment images, and angiograms can be generated by conventional maximum intensity projection processing. The dual ability to visualize angiograms and static tissue images is a major benefit of the strategy. Computer simulations of flow sensitivities and in vivo results are presented which compare the outflow and inflow refreshment imaging strategies.

Blood Flow Velocity↗
PubMed1992

Prevalence of human immunodeficiency virus risk factors in patients attending an accident and emergency department.

The prevalence of human immunodeficiency virus (HIV) risk factors was evaluated by questionnaire survey in 1565 consecutive patients who attended an adult A&E department in Brisbane over a 2-month period. The survey revealed that a total of 144 (9.2%) patients could be considered at risk of HIV infection (high-risk group) because of known seropositivity, admission to HIV high-risk factors or engaging in high-risk activities. The remaining 1421 patients who did not acknowledge any high-risk behaviour were classified as an 'unknown-risk' group. More than 70% of the HIV high-risk patient group were under the age of 30 years. A total of 275 (17.6%) patients presented with open wounds and/or needed hospitalization (23 [1.5%] high-risk patients). Of the 490 respondents who engaged in short term sexual relationships, 310 (63.3%) practised unprotected coitus, 32 of these including four seropositives were classified in the high-risk group. The patients were asked if they were in favour of an HIV testing service at their local A&E department; 1324 (86.6%) were in agreement 121 of whom were in the high-risk group. There was no significant difference (chi 2 = 0.093: P greater than 0.7) in opinion between the 'unknown risk' and high-risk patient groups on this matter.

Adolescent↗
PubMed1991

Immunologic correlates of spontaneous lymphocyte proliferation in human T-lymphotropic virus infection.

Previously we showed that mononuclear cells from about half of human T-lymphotropic virus (HTLV)-seropositive persons exhibit spontaneous proliferation in vitro. We sought to determine if proliferation was associated with other immunologic changes characteristic of HTLV infection. The parameters assessed were (1) percentages of lymphocytes expressing CD4 and/or CD25 (interleukin-2 receptor), (2) serum levels of soluble CD25, (3) serostatus for other viruses, (4) anti-HTLV antibody levels, and (5) HTLV type determined by polymerase chain reaction or serologic reactivity with type-specific peptides. The proliferation+ HTLV (PROL+) group, proliferation HTLV (PROL-) group, and control group showed similar percentages of CD4+, CD25+, and CD4+CD25+ lymphocytes; serum levels of soluble CD25 were also similar. Antibodies to cytomegalovirus, hepatitis B core, and hepatitis C were present in similar proportions of PROL+ and PROL+ groups. However, a significant association was found between spontaneous proliferation and anti-HTLV antibody levels; sera from 67% of PROL+ persons, but only 18% of PROL- persons, required dilution to yield absorbance values within the linear range of the anti-HTLV antibody assay. In the PROL+ group, persons whose sera required the most dilution had proliferative responses significantly higher than those whose sera required no dilution. The PROL+ and PROL groups were similar with regard to the relative distribution of HTLV-I and HTLV-II infection. These findings indicate that HTLV-related spontaneous lymphocyte proliferation is related to levels of circulating anti-HTLV antibodies, and characterizes both HTLV-I and HTLV-II infection.

Antibodies, Viral↗
PubMed1991

Visualization of altered myocardial lipids by 1H NMR chemical-shift imaging following ischemic insult.

Acute myocardial infarction is associated with an accumulation of lipids. Spectroscopic and chemical-shift imaging strategies which can depict the spatial distribution of these chemical species are evolving. The present study was undertaken to test whether the Dixon method could detect spatially lipids known to accumulate in myocardium after an ischemic insult. Seven dogs underwent a 24-h coronary artery occlusion (LAD = 4, Cx = 3). Post mortem, hearts were removed and imaged ex vivo. Myocardial samples were also evaluated by high-resolution 1H NMR spectroscopy. Lipid images revealed regions of increased signal intensity, in the regions corresponding to the myocardial infarction, particularly in the periphery of the infarction. An increase in mobile lipids was observed by 1H NMR spectroscopy of myocardial samples with moderately reduced blood flow and corresponding to regions with increased signal intensity on the lipid image. This study shows that chemical-shift imaging may be useful for detecting alterations in myocardial lipid levels following an ischemic insult.

Animals↗
PubMed1991

A new acquisition mode for 2D inflow refreshment angiography.

Time-of-flight angiography methods rely on blood/tissue contrast generated when fresh blood spins enter a partially saturated region. A series of projective angiographic views is generated by application of a maximum intensity projection algorithm to data acquired from a 3D volume. When the data are acquired as a set of 2D slices, the angiograms exhibit sensitivity to body motion, resulting in the generation of artifacts. We present a new 2D time-of-flight angiographic technique, STREAM, Suppressed Tissue with Refreshment Angiography Method. It exhibits low sensitivity to internal body motion, thus allowing acquisition of good quality, single average angiograms. To suppress the static tissue signal a unique "active" suppression strategy is employed. Additionally, to further suppress the lipid signal, the chemical-shift phenomenon is exploited in the STREAM sequence.

Algorithms↗
PubMed1991

Direct projective time-of-flight NMR angiography within 4s.

To enhance contrast between flow and static tissue, NMR projective angiographic methods usually require data subtraction, or alternatively the application of special data processing routines such as the "maximum intensity projection" algorithm. We have successfully developed a direct projection method which yields sufficient flow/static contrast in a single acquisition, producing angiograms in under 4 s. Direct projection angiograms of the cervical and abdominal vessels were obtained. The cervical vessels were uniformly depicted in a number of different projection views. The abdominal vessels exhibit intensity variations due to the pulsatile flow pattern. A series of abdominal angiograms were acquired, each triggered at a different starting cardiac phase. When displayed as a movie sequence the pulsatile flow pattern was seen to advance along the arteries. To more uniformly represent the abdominal vessels a 24-s average was adequate. This new technique should allow NMR angiograms to be obtained in a "fluoroscopic" mode.

Abdomen↗
PubMed1991

SLIP, a lipid suppression technique to improve image contrast in inflow angiography.

In rapidly acquired gradient echo images, lipid regions usually appear as areas of high signal intensity. In 2D inflow angiograms processed by the maximum intensity projection algorithm, this high lipid signal may prevent angiographic visualization of some blood vessels. We present a new approach to suppress the lipid signal, SLIP, spatially separated lipid presaturation. The SLIP technique suppresses lipid signal over a narrow region by exploiting the chemical-shift effect. SLIP requires an arrangement of a thin slice and a wide presaturation slab already available in 2D inflow refreshment angiography. Thus SLIP was incorporated to an inflow angiography sequence without increasing the acquisition time. The use of SLIP resulted in considerable improvement in angiographic contrast and increased the number of vessels detected in projection angiograms. The SLIP technique does not require high homogeneity of the main magnet field.

Algorithms↗
PubMed1991

Peripheral arterial occlusive disease: prospective comparison of MR angiography and color duplex US with conventional angiography.

Conventional angiography, two-dimensional inflow magnetic resonance (MR) angiography, and color duplex ultrasound (US) were performed on 12 patients in a blinded, prospective study. The ability to grade arterial lesions and plan revascularization interventions were compared. Arterial lesions were categorized as nonsignificant (0%-49% diameter reduction) or significant (50%-100% diameter reduction). Determination of nonsignificant and significant lesions with MR angiography was in agreement with that at conventional angiography in 100 of 140 lesions (71%). Agreement between results of conventional angiography and color duplex US occurred with 114 of 123 infrainguinal lesions (93%). Twenty-one vascular interventions were planned by using conventional angiography; there was agreement with color duplex US in 11 cases and MR angiography in five. Color duplex US performed well in the assessment of infrainguinal disease but was limited in the evaluation of iliac segments because of nonvisualization. The iliac region was visualized in more patients with MR angiography than with color duplex US, but image quality with MR angiography was inconsistent. Strategies to improve MR angiography of the peripheral vasculature merit further study.

Aged↗
PubMed1990

The Doppler probe for planning flaps: anatomical study and clinical applications.

The Doppler probe was used to identify the dominant cutaneous perforating arteries in a series of 10 patients. The results were compared with our previous total body fresh cadaver anatomical studies and a close correlation was found. The instrument was used in a series of patients to plan the base, the axis and the dimensions of skin flaps for local, distant and free transfer. A dominant perforator was located at the base of the flap, the surrounding skin was scanned to identify the next dominant perforator in each direction and the appropriate axis was chosen by drawing a line between two nominated perforators. Often the flap was based distally or its axis departed from the main course of the supplying vessel. The technique proved to be simple and reliable and in many cases flaps of unusual dimensions and directions were transferred successfully. The instrument provides a useful link between the anatomical dissecting room and the operating theatre.

Adolescent↗