The present invention provides medical devices with enhanced 
ultrasound visibility.  The device uses real-time 
ultrasound monitoring of the position of the needle tip within the patient's body for 
topical drug delivery, probe positioning, fluid drainage, 
biopsy, or delivery of 
ultrasound pulses.  The device controls the 
diffusion of drugs in 
solid tissues, injects particles into 
solid tissues, and delivers drugs to specific blood vessels.  As the needle is inserted, a fluid with a different ultrasound 
visibility than the organ environment is injected into the patient.  The fluid travels a 
short distance before being slowed and stopped by the patient's tissues, and the flow can be detected ultrasonically.  During 
needle insertion, the 
needle position is monitored with ultrasound until the needle is at the ideal point of action.  Therapeutic drugs are then delivered through the needle or probes are inserted to perform treatments such as removing tumors with radiofrequency heat.  The flow rate can be adjusted during 
needle insertion to maintain a properly set image of the needle tip.  At the point of application, the 
ultrasound imaging agent can be repeated and pulsed at different flow rates until a satisfactory fluid profile is obtained, after which the 
drug can be delivered.  
Ultrasound can also be sent through the needle with a 
detector mounted in the handheld 
assembly.