A focusing circuit for generating a focus control signal for a cathode ray tube has a modulation input for influencing the focus control signal, which focus control signal contains a measure for an envelope of excursions of horizontal scan lines across the cathode ray tube. The present invention binds a static database query to a new query execution plan that produces the same result set as an original QEP bound to the static database query. The tissue sample can be a tumor or other pathological tissue.