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Biomedical subjects

B Kane

Publications and source records attributed to B Kane.

At least 19 recordsLinked to original sources
PubMed2001

Pulsatile flow simulation in arterial vascular segments with intravascular ultrasound images.

Previous studies have indicated a correlation between local variation in wall shear stress in arterial blood flow and atheroma development. The purpose of this study was to analyze the hemodynamics in vascular segments from morphologically realistic three-dimensional (3D) reconstruction, and to compare the computed wall shear stress in a compliant vascular segment model and the corresponding rigid walled model. Cross-sectional images of the segments of femoral and carotid arteries in five Yucatan miniswine were obtained using intravascular ultrasound (IVUS) imaging and the segment geometry was reconstructed at different times in the cardiac cycle. The actual measured wall motion from the reconstruction was employed to specify the moving boundaries for simulation of physiological distensibility. Velocity profiles and wall shear stress were computed using unsteady computational fluid dynamics analysis. The computed results revealed that the maximum wall shear stress in the compliant model was approximately 4-17 percent less than that in the rigid model if the wall motion is larger than 10 percent. Our analysis demonstrates that inaccuracies due to inflow velocity profile can be minimized by the extension of the model upstream. The phase angle between the diameter change and wall shear is affected by the local changes in geometry of the arteries. These simulations can be potentially used to analyze the effect of regional wall motion changes in the presence of atherosclerotic lesions on the local fluid dynamics and to correlate the same with subsequent growth of the lesions.

Animals↗
PubMed1998

Left ventricular functional improvement after transmyocardial laser revascularization.

BACKGROUND: Transmyocardial laser revascularization has been used to treat patients with end-stage coronary artery disease that is not amenable to standard revascularization. Although there is evidence of angina relief and quality of life enhancement, there is little information concerning improvement in myocardial contractility. The purpose of this study was to determine whether transmyocardial laser revascularization improves myocardial function in chronically ischemic myocardium. METHODS: In a model of chronic ischemia by Ameroid occlusion of the circumflex artery, domestic pigs (n = 8) were treated with transmyocardial laser revascularization. Before laser treatment, segmental contraction was assessed at rest and with dobutamine stress echocardiography. Myocardium subtended by the occlusion was compared with that remote from the occlusion. Six weeks after transmyocardial laser revascularization, the animals were restudied at rest and with stress, and then sacrificed. Sham-treated control animals (n = 4) underwent the same procedures but were not treated with transmyocardial laser revascularization. Control animals did not demonstrate significant recovery of function. RESULTS: Transmyocardial laser revascularization improved resting function in chronically ischemic myocardium by 100%. CONCLUSIONS: Transmyocardial laser revascularization significantly improves the function of chronically ischemic myocardium. These data may help explain the mechanisms by which transmyocardial laser revascularization is clinically effective.

Animals↗
PubMed1997

Use of electronic portal imaging to assess cardiac irradiation in breast radiotherapy.

An audit was performed to assess the frequency of cardiac irradiation in patients receiving radiotherapy for left-sided breast cancer. Images from an 'online' electronic portal imaging device were reviewed in patients who were treated with a tangential pair of megavoltage fields. In 169 consecutive patients treated on a Philips SL25 6 MV linear accelerator equipped with an SRI 100 imaging device, the cardiac apex was included in the radiotherapy field in 15 patients (9%). The long term sequelae of such cardiac irradiation is uncertain. The results of this audit suggest that careful treatment technique and quality control with portal imaging can minimize unnecessary cardiac irradiation in the majority of patients.

Breast Neoplasms↗
PubMed1997

In vitro targeting of antibody-conjugated echogenic liposomes for site-specific ultrasonic image enhancement.

Tissue-specific ultrasonic enhancement can be used for the detection and characterization of atherosclerosis. We have previously demonstrated the generation of inherently echogenic (acoustically reflective) liposomes solely by varying lipid composition and controlling the method of production. In this study, echogenic liposomes composed of phosphatidylcholine (PC), 4-(p-maleimidophenyl) butyryl phosphatidylethanolamine (MPB-PE), phosphatidylglycerol (PG), and cholesterol were conjugated to human gamma globulin to determine the effect of antibody conjugation on liposomal acoustic reflectivity. The liposomes remained highly echogenic following antibody conjugation. Echogenic liposomes were also conjugated to rabbit antihuman fibrinogen to study their ability to target fibrin. Antibody-conjugated liposomes were targeted to fibrin-coated filter paper and slides, thrombi made in vitro, and segments of atheroma in an animal model of atherosclerosis. Liposomes were detected by scanning electron microscopy, radiolabeling, and imaging with intravascular ultrasound. Electron microscopy revealed attachment of antibody-conjugated liposomes to fibrin on slides and to the fibrous plaques of the arterial segments, whereas unconjugated liposomes did not attach. Similarly, conjugated liposomes did not attach to normal arteries, indicating their binding to the arterial segment is directed towards a component of the fibrous plaque. Ultrasound imaging of the thrombi demonstrated surface attachment of the acoustic conjugated liposomes. 125I-Labeled liposomes conjugated to rabbit anti-human were targeted to fibrin-coated paper. Counting specifically bound radioactivity showed that > 84% of applied liposomes remained attached to the fibrin after washing with saline. These results demonstrate the potential of acoustically reflective liposomes for site-specific targeting and acoustic enhancement.

Animals↗
PubMed1997

Human immunodeficiency virus type 1 nucleocapsid protein promotes efficient strand transfer and specific viral DNA synthesis by inhibiting TAR-dependent self-priming from minus-strand strong-stop DNA.

During the first strand transfer in reverse transcription, minus-strand strong-stop DNA [(-) SSDNA] is annealed to the 3' end of the acceptor RNA in a reaction mediated by base-pairing between terminal repeat sequences in the RNA and their complement in the DNA. The large stem-loop structure in the repeat region known as TAR could interfere with this annealing reaction. We have developed an in vitro human immunodeficiency virus type 1 (HIV-1) system to investigate the effect of TAR on strand transfer. Mutational analysis demonstrates that the presence of TAR in the donor and acceptor templates inhibits strand transfer and is correlated with extensive synthesis of heterogeneous DNAs formed by self-priming from (-) SSDNA. These DNAs are not precursors to the transfer product. Interestingly, products of self-priming are not detected in HIV-1 endogenous reactions; this suggests that virions contain a component which prevents self-priming. Our results show that the viral nucleocapsid protein (NC), which can destabilize secondary structures, drastically reduces self-priming and dramatically increases the efficiency of strand transfer. In addition, the data suggest that the ability to eliminate self-priming is a general property of NC which is manifested during reverse transcriptase pausing at sites of secondary structure in the template. We conclude that this activity of NC is critical for achieving highly efficient and specific viral DNA synthesis. Our findings raise the possibility that inactivation of NC could provide a new approach for targeting reverse transcription in anti-HIV therapy.

DNA, Single-Stranded↗
PubMed1996

Computation of vascular flow dynamics from intravascular ultrasound images.

Analysis of three-dimensional velocity profiles and wall shear stress distribution in a segment of an artery reconstructed from in vivo imaging data are presented in this study. Cross-sectional images of a segment of the abdominal aorta in dogs were obtained using intravascular ultrasound (IVUS) imaging employing a constant pull back technique. Simultaneous measurement of pressures distal and proximal to the vessel segment along with gated pulsed Doppler velocity measurements were also obtained. The three-dimensional geometry of the vascular segment was reconstructed from the IVUS images during peak forward flow phase, and a computational mesh was constructed from the data. A quasi-steady analysis of incompressible Newtonian fluid was performed with a finite difference general purpose computational analysis program FLOW3D. The velocity at the inlet and pressure at the outlet measured at the corresponding time (time referenced to ECG) were used to specify the boundary conditions for the computational flow model. The computed results compared favorably with previously reported results. The purpose of the present study was to analyze the hemodynamics in vascular segments from morphologically realistic three-dimensional reconstructions. The method can be potentially employed in analyzing the hemodynamics in the region of atherosclerotic plaques at various stages of development and the reactivity of the vessel in response to pharmacological and mechanical interventions.

Animals↗
PubMed1996

Exfoliated malignant cells in glove and instrument washings following head and neck surgery.

Loco-regional recurrence following resection of squamous cell carcinoma of the upper aero-digestive tract is a major problem. Cells exfoliated from malignant tumours have been considered capable of implanting and giving rise to local recurrence or metastatic deposits. A prospective study was performed examining washings from the gloves and instruments used in major head and neck operations to determine if exfoliated cells were indeed present. Following removal of the main tumour specimen all surgeons washed their hands in a solution containing a cell fixative and all instruments were soaked in the solution. Samples were then centrifuged and stained using a modified PAP technique. On occasions nuclear fragments consistent with squamous cell carcinoma were present in both glove and instrument washings. We recommend that all surgeons change gloves and instruments following removal of the main tumour specimen and prior to irrigation of the operative field with a tumoricidal agent.

Carcinoma, Squamous Cell↗
PubMed1995

Clinical applications of composite and realtime megavoltage imaging.

The versatility of electronic portal imaging devices (EPIDs) is best demonstrated by their ability to perform novel megavoltage imaging protocols, which are still pertinent to good radiotherapy practice. This paper examines two such techniques: composite and realtime imaging. Our EPID can be programmed to acquire and manipulate images very easily, allowing images from segmented treatment protocols to be mixed and displayed, giving a composite image of the effective treatment result. Its use for verifying the efficacy of spinal shielding using a segmented, offset collimator technique is described. By acquiring images very quickly, realtime imaging sequences can be obtained and used to analyse anatomical movement within a single treatment field. The technique is employed here to investigate movement in radical lung, breast, abdomen, pelvis and thyroid treatments. Our results show that the protocol is vital for treatment sites involving the lungs; changes up to 5 mm have been observed in the maximum lung depth for breast treatments, and displacements up to 16 mm for radical lung treatments. It is also useful in other anatomical sites for ensuring that no movement occurs.

Fluoroscopy↗
PubMed1995

Technical note: the efficacy of megavoltage imaging in the radical radiotherapy of non-small cell lung cancer.

Megavoltage imaging (MVI) has been used to obtain digital images of treatment fields during therapy for non-small cell lung cancer. Tumours were seen in all 33 cases studied and in three cases MVI was used to improve the set-up. It is concluded that in the setting of radical radiotherapy for non-small cell lung cancer this is an appropriate technique for the verification and correction of field position and is an aid to quality assurance.

Aged↗