so that the vicinity of a site is available for palpation and is visible for visual inspection another embodiment of the apparatus improves the sensitivity of detection by positioning an energy source and a receiver between a first layer of a high dielectric material and a second lay of a low dielectric material the apparatus may further include a third layer of a conductive material to shield the apparatus from stray capacitance in addition a system for detection of extravasation includes an array of sensors located at adjacent to and or remote from an injection site application_number US 23387402 A description referring to fig1 a prior art transducer for an electrical impedance plethysmograph 10 such as the eda u2122 patch manufactured by e z em co of westbury n y is illustrated transducer 10 can be applied to an extremity of a patient to detect extravasation during injection of a fluid into the patient at an injection site transducer 10 is positioned so that the injection site is covered by the approximate geometric center of the device transducer 10 includes four electrodes 12 a d electrodes 12 a d can be formed of a mixture of silver silver chloride or any other suitable conductive material when transducer 10 is applied to a patient to detect extravasation electrodes 12 a d can be.