the present invention is designed to simulate the human ophthalmic artery running through both the brain and orbital spaces . the purpose of the device of the present invention is to provide a suitable testing environment for multiple element ultrasound transducer and associate controlling hardware and software . as illustrated in fig1 , the device 1 consists of two chambers , a first larger chamber 2 representing the intra - cranial space , and a second smaller chamber 3 representing the orbital or extra - cranial space . in a preferred embodiment , the second chamber 3 is placed inside the first chamber 2 to more accurately simulate the orbital space located within the intra - cranial space . a tube or an artificial vessel 18 runs through both first chamber 2 and second chamber 3 , simulating the course of the ophthalmic artery as it passes through an optic canal from the intra - cranial to the orbital space . a region between the two chambers , representative of an optic canal , is filled with a plug 4 , which seals the first chamber 2 from the second chamber 3 , and which is designed to imitate a barrier between the intra - cranial space and the orbital space . the plug 4 is preferably made with latex or silicone material , although other suitable materials known in the art may be used instead . the plug 4 provides a mechanism for mechanically joining the tube 18 and the barrier between the two chambers 2 and 3 . the plug 4 is also designed to attenuate the ultrasound as little as possible . the second chamber 3 contains a cavity 5 that is preferably conical in shape and is preferably designed such that its defining shape and volume are representative of a human orbital cavity . the portion of the orbital cavity that would be the surface of the eyeball is instead an open orifice , closed only on insertion of an ultrasound transducer 10 that is tightly fitted , sealing the orbital chamber 3 . each of the chambers 2 and 3 can be independently pressurized by using at least two pressure loops . as illustrated in fig2 , a first pressure loop 6 is connected to the first chamber 2 , and a second pressure loop 7 is connected to the second chamber 3 . each of the pressure loops 6 and 7 includes a water bag 9 , a pressure sensor 8 , and tubing interconnecting all of the components of the pressure loop . tubing may comprise silicone material , or any other suitable material known in the art . the first chamber 2 and the second chamber 3 are pressurized by filling both chambers with a fluid , such as water , sealing the chambers , and then filling the water bags 9 with the fluid to independently adjust the pressure within the first chamber 2 and the second chamber 3 . the pressure sensors 8 are also electrically connected 6 a , 7 a to a processor 11 to measure and record pressure within each chamber . it should be appreciated that while the example identified in this application utilizes water bags to adjust the pressure within the chambers , it is envisioned that any other device known in the art that is suitable for adjusting pressure may be utilized instead . the lumen of the tube 18 can also be pressurized , simulating an arterial pressure . the tube 18 is made with a material designed to simulate an arterial wall , and its compliance and diameter are key in the operation of the phantom device of the present invention . preferably , the tube 18 is made with latex material . however , any other material known in the art that is responsive to pressure changes may be used without departing from the spirit of the present invention . the apparatus of the present invention further comprises a flow loop 12 for controlling a fluid flow and pressure within the tube 18 . a schematic view of the flow loop 12 is shown in fig3 . the flow loop 12 includes a flow reservoir 15 , at least one constant - flow pump 13 , at least one pulsatile - flow pump 14 , and a pressure line 16 , 17 interconnected by tubing . the flow loop 12 is connected to the tube 18 running through the first chamber 2 , the second chamber 3 , and the sealing plug 4 placed between the two chambers . in an exemplary embodiment of the present invention , the pressure line includes a water bag 17 and a pressure sensor 16 . the water bag 17 is used to adjust / change pressure within the flow loop 12 and the tube 18 . however , it should be understood that any other known device that is suitable for varying pressure within the flow loop may be used instead . the pressure sensor 16 is electrically connected 16 a to the processor 11 for measuring and recording the pressure within the flow loop 12 and the tube 14 . once the flow loop 12 is assembled , the water bag 17 is preferably filled with blood simulating fluid , and the constant - flow pump 13 and the pulsatile - flow pump 14 are used to pump fluid through the tube 18 to simulate the blood flow in the human ophthalmic artery . it is possible to use only the constant - flow pump 13 or only the pulsatile - flow pump 14 to pump the fluid through the flow loop 12 . the constant - flow pump 13 and the pulsatile - flow pump 14 are placed on a surface isolated from the rest of the device in order to prevent transfer of mechanical vibrations from the pumps . the pumps 13 and 14 are connected in parallel so that they can be run separately or simultaneously without reconnecting tubing . on the outflow side of the pumps 13 and 14 latex tubing ( not shown ) may be placed in line to help absorb mechanical vibration from the pump as well as help shape the diastolic component of the pulsatile wave . alternatively , a pulse dampener ( not shown ) may also be placed in line for the same purpose as described above . the device is operated by independently pressurizing the first chamber 2 by using the first pressure loop 6 and the second chamber 3 by using the second pressure loop 7 , and by pumping the blood simulating fluid through the tube 18 in a pulsatile manner . an ultrasound beam from the ultrasound transducer 10 that is tightly fitted into the conical cavity 5 of the second chamber 3 is then turned on , and the flow of blood simulating fluid in the intra - cranial space ( the first chamber 2 ) and the orbital space ( the second chamber 3 ) is visualized in the form of two spectrograms . the points at which the flow is interrogated are thus spacialy distinct , both in terms of depth ( distance from the transducer 10 ), and lateral location . the ultrasound transducer 10 is connected to the processor 11 , which receives and processes the signal from the ultrasound transducer 10 . in the exemplary embodiment of the present invention , water columns are used to individually pressurize the two chambers 2 and 3 of the device . the height - pressure relationship is preferably as follows : 1 . 36 cm h 20 = 1 mmhg . once the pressure loops are assembled and filled with water , pressure is changed by raising or lowering the water bags 9 in relation to the device . the water lines provided are preferably 200 cm in length , which will allow for over 140 mmhg . pressure within the first pressure loop 6 and the second pressure loop 7 , as well as in the flow loop 12 may be measured by any known type of blood pressure sensor that is placed in the pressure loop and the flow loop lines . the voltage signal from the pressure sensors 8 and 16 representative of the pressure measurement is transmitted to the processor 11 via electrical lines 6 a and 7 a . this voltage signal may then be converted to a digital signal and the digitized signal may be sent to a host computer ( not shown ) which converts the digitized signal to a pressure measurement . the above description is for the purpose of teaching the person of ordinary skill in the art how to practice the present invention , and it is not intended to detail all of those obvious modifications and variations of it which will become apparent to the skilled worker upon reading the description . it is intended however , that all such obvious modifications and variations be included within the scope of the present invention which is defined by the following claims .