Biomedical subjects

A Hartov

Publications and source records attributed to A Hartov.

23 records · Page 2Linked to original sources

PubMed1992

Further development and clinical application of the stereotactic operating microscope.

Implementation of a Vicom-VME image processing workstation for the frameless stereotactic operating microscope system has allowed an improved interpolation algorithm for more accurate reconstruction of three-dimensional data, the integration graphically of multimodality imaging information, an additional stereotactic graphics display outside of the microscope optics and optional three-dimensional displays through communication with a Convex mini-supercomputer. A precision-milled coupling for reproducible attachment of the spark gap bracket to the microscope has eliminated the need for that transformation calculation during each case. Clinical utility has been greatest in providing navigational guidance to small subcortical or deep lesions and in defining the extent of preoperatively planned resection of larger, infiltrating tumors. Mean accuracy in the past 17 cases has been 3.5-6.5 mm. The frameless methodology has also enabled extracranial stereotactic surgical procedures in 7 patients.

Brain Neoplasms↗

PubMed1989

The stereotactic operating microscope: accuracy refinement and clinical experience.

Accuracy of a stereotactic operating microscope, by which imaging data may be superimposed on the operative field without a stereotactic frame, has been most limited by the resolution of imaging information. Using newer algorithms and pilot pole calibration of the digitizer, an error in registration of 2 mm and in contour display of 3 mm has been demonstrated. Greatest utility of the system clinically has been in providing navigational guidance to small lesions undergoing resection.

Brain Neoplasms↗

PubMedDate not supplied

Erythrocyte membrane ATP binding cassette (ABC) proteins: MRP1 and CFTR as well as CD39 (ecto-apyrase) involved in RBC ATP transport and elevated blood plasma ATP of cystic fibrosis.

In addition to the better-known roles of the erythrocyte in the transport of oxygen and carbon dioxide, the concept that the red blood cell is involved in the transport and release of ATP has been evolving (J. Luthje, Blut 59, 367, 1989; G. R. Bergfeld and T. Forrester, Cardiovasc. Res. 26, 40, 1992; M. L. Ellsworth et al., Am. J. Physiol. 269, H2155, 1995; R. S. Sprague et al., Am. J. Physiol. 275, H1726, 1998). Membrane proteins involved in the release of ATP from erythrocytes now appear to include members of the ATP binding cassette (ABC) family (C. F. Higgins, Annu. Rev. Cell Biol. 8, 67, 1992; C. F. Higgins, Cell 82, 693, 1995). In addition to defining physiologically the presence of ABC proteins in RBCs, accumulating gel electrophoretic evidence suggests that the cystic fibrosis transmembrane conductance regulator (CFTR) and the multidrug resistance-associated protein (MRP1), respectively, constitute significant proteins in the red blood cell membrane. As such, this finding makes the mature erythrocyte compartment a major mammalian repository of these important ABC proteins. Because of its relative structural simplicity and ready accessibility, the erythrocyte offers an ideal system to explore details of the physiological functions of ABC proteins. Moreover, the presence of different ABC proteins in a single membrane implies that interaction among these proteins and with other membrane proteins may be the norm and not the exception in terms of modulation of their functions.

ATP-Binding Cassette Transporters↗

PubMedDate not supplied

Analysis and testing of a concentric ring applicator for ultrasound hyperthermia with clinical results.

A planar ultrasound transducer was modified by etching concentric circles on one surface of a piezoelectric ceramic to create four rings. The 10 cm diameter transducer had four active rings and an unenergized centre. The transducer housing was designed to be completely immersed in fluid, suitable for intraoperative hyperthermia. The transducer was resonant at 1.0 MHz and was tested in a water tank and in an acoustic absorbing medium where the steady-state temperatures were measured. A comparison between a single 10 cm element and the concentric ring modification with all rings at equal power density showed the performance to be nearly identical. In vivo experiments in canine thigh verified the phantom predictions as individual rings were energized. Theoretical intensity calculations were made and compared favourably to water tank test results. Clinical hyperthermia treatments for chest wall and head and neck tumours showed that the temperature distribution could be highly modified by adjusting the power to individual rings while holding the transducer stationary. Automated temperature mapping parallel to the transducer face was used to compare a single element applicator to the concentric ring applicator in clinical treatments on the same lesion. The concentric ring applicator was radially adjustable and was found to be advantageous in lowering the central peak temperatures and flattening the temperature distribution in tumours. A comparison between the single element clinical and operating room series showed that when pain is removed as a treatment limiting factor, higher central tumour temperatures are possible and more of the tumour volume achieves therapeutic temperatures. The concentric ring design improves the temperature distribution such that the higher central temperatures will not be necessary.

Evaluation Studies as Topic↗

PubMedDate not supplied

Performance of an adaptive MIMO controller for a multiple-element ultrasound hyperthermia system.

A prototype adaptive automatic control algorithm was implemented to regulate temperatures measured at several points in a tumour by adjusting the power applied to several ultrasound transducers. The goal was to control the temperatures under the elements of a mosaic applicator individually without any priori knowledge of which probes are under which elements. The control algorithm was devised for clinical applications where the position of each probe with respect to the heat sources is difficult to determine precisely. Instead, the program 'learns' the relationship between the inputs (power levels) and the outputs (temperatures) automatically. Based on the observed transfer function relating the power at m sources to the temperatures n probes, where n and m are not necessarily the same, a new method was used to implement a feedback controller. This method simplifies the design of the controller for a multiple-input/multiple-output (MIMO) system, while taking into account the coupling that may exist between the various elements of the system. As a result of using an adaptive scheme, the regulator continuously tracks changes in the system, such as blood flow variations or patient motion, by modifying its control parameters. The algorithm performance has been tested in simulations as well as experiments in dog thigh and a perfused kidney model.

Algorithms↗