MEDICAL APPARATUS, NAMELY TROCARS, CANNULAS, DRAINAGE TUBES, PROBE-RECEIVING TUBES FOR ALLOWING ULTRASOUND PROBES OR OTHER SENSORS TO BE INSERTED INTO PATIENTS' BODY CAVITIES, BIOPSY NEEDLES, ULTRASONICALLY-GUIDED TROCARS, ULTRASONICALLY-GUIDED CANNULAS, ULTRASONICALLY-GUIDED BIOPSY NEEDLES, ULTRASOUND TRANSDUCERS, ULTRASOUND PROBES, AND SENSORS FOR DETERMINING THE pH LEVEL OF BLOOD, OR FOR DETERMINING THE LEVEL OF OXYGEN CONTENT, OR THE LEVELS OF POTASSIUM, GLUCOSE, HEMOGLOBIN, RED BLOOD CEL...