referring now to the plan view in fig1 of an mri system , the scanning room 9 is disposed within shielding boundary walls 11 , with a control room 13 for operators or attendant personnel positioned outside the boundaries of the scanning room 9 . the scanning room 9 includes the image acquisition equipment including a source 15 of intense magnetic field 16 that emanates from the source in substantially homogenous array throughout the adjacent space and around a patient 17 . various components of the system for performing the image acquisition operations , including gradient 19 and sensor 21 and rf coils 23 are disposed about the patient 17 for stimulating the nuclei ‘ echos ’ to map the positions thereof within the spatially - homogenous magnetic field 16 as the patient &# 39 ; s body is scanned in conventional manner along multiple orthogonal axes . the shielding boundary walls 11 ( and ceiling and floor ) provide shielding against radio - frequency interference and , as fabricated with ferrous materials , may also establish outer limits of the magnetic field distribution around magnetic 15 . the control room 13 is disposed outside the shielding boundary walls 11 and is equipped with computer input keyboard 25 , computer display 27 , monitor 29 of patient &# 39 ; s vital life signs , controls 31 for liquid infusion apparatus , and the like . such representative equipment is housed outside the shielding boundary walls 11 to inhibit intrusion of spurious magnetic and electrostatic and rf signals into the image acquisition operations within the scanning room 9 . similarly , the gradient amplifiers 33 for amplifying signals from conventional gradient coils 1921 , along x , y , and z coordinates and rf amplifiers 35 and the image - processing computer 37 are also located outside the shielding boundary walls 11 for the same reason . the thru - wall interconnections 39 between the components within the scanning room 9 and the electronic equipment 25 , 27 , 29 , 31 , 33 , 35 , 37 disposed outside the room 9 typically also includes rf shielding to diminish the sources and the portals by which and through which rfi signals may enter the scanning room 9 . a liquid - infusion device 41 commonly resides within the scanning room 9 to administer iv injection into the patient 17 of liquid compositions , for example , that enhance image acquisition ( e . g ., contrast medium ) or that otherwise provide diagnostic or therapeutic benefits to the patient 17 being scanned . such conventional infusion device 41 should desirably be positioned close to the patient 17 to facilitate iv liquid infusion , but must be positioned remotely to avoid disrupting the homogeneous magnetic field 16 , and to minimize rfi and operational failures of the infusion device 41 resulting from operating in the intense magnetic field adjacent the patient 17 . control of such infusion device 41 may be via remote controller 31 disposed within control room 13 . in accordance with the embodiment of the invention illustrated in fig2 , an improved liquid infusion device 43 is operable within intense magnetic fields and with negligible rfi to provide positive displacement of a liquid 45 such as saline or contrast medium , or sedative , or the like , in controlled volumes per unit time . the device does not include any ferrous or magnetic materials , and is substantially shielded against irradiating any rfi during operation . specifically , the device 43 includes a pump in the lower chamber 47 , as later described herein . the pump chamber 47 receives therein the flexible , resilient tubing 49 that is pre - packaged and sterilized as a component of a conventional iv liquid infusion set that also includes a conventional drip chamber 51 as part of the infusion set . controls for the pump in chamber 47 include an operator &# 39 ; s input keypad 48 for setting infusion parameters , and a drip detector 53 that can be disposed about the drip chamber 51 to detect flow of liquid from the supply 45 . a display 53 is positioned in the upper portion of the housing 55 which may be formed of non - magnetic , rf - shielding material such as conductively - coated plastic or aluminum , or the like . the housing 55 attaches with one or more clamps 57 to a rigid support 59 formed of non - magnetic material such as fiberglass or aluminum , or the like . various visual and audible enunciators 61 may be provided to signal operational conditions either within acceptable limits , or within error or failure conditions . referring now to the pictorial block schematic diagram of fig3 , there is shown a peristaltic - type positive - displacement pump 60 disposed within the pump chamber 47 of the housing 55 to operate with the length of tubing 49 that passes therethrough between the drip chamber 51 and the patient . the peristaltic pump 60 ( linear or rotational ) is driven by an ultrasonic motor 64 via appropriate mechanical linkage 65 to actuate a squeeze roller against the tubing 49 in known peristaltic pumping manner , or to actuate a series of elements 67 through a linear tubing - squeezing sequence to produce peristaltic pumping action in known manner . a conventional ultrasonic driving motor 64 is powered in known manner by multiphasic signals applied thereto from the motor drive circuit 69 . a controller 71 for the device includes a central processing unit 73 with associated peripheral components including random access memory 75 , read - only memory 77 , digital - to - analog converter 79 , and an input / output channel 81 . this controller 71 receives input control information from the operator &# 39 ; s keypad 48 , and receives feedback information about pump speed from sensor 83 and about liquid flow from drip detector 85 disposed about the drip chamber 51 . in response to the inputs supplied thereto , the controller 71 operates on stored programs to actuate a display 53 of operating parameters ( or other data ), and to actuate the motor drive circuit 69 for energizing the ultrasonic motor 64 for rotation at a controlled speed . a power supply 63 is connected to the controller 71 and drive circuit 69 to supply electrical power thereto , and is connected to a battery 87 to receive electrical power therefrom during stand - alone operation , or to receive line voltage via plug 63 , as required . in accordance with this embodiment of the present invention , no magnetic material is used in any of the components of the infusion device 43 including the ultrasonic motor 64 , pump 60 , power supply 63 , controller 71 and associated components . additionally , none of such components is adversely affected during operation by a strong magnetic field . and , any rf energy that may be generated by electronic signals within the ultrasonic motor 64 , drive circuit 69 , controller 71 , power supply 63 or associated components is specifically shielded by conductive structures 91 , 93 disposed around such components to inhibit radiation of rfi . additionally , radio - frequency interference filters 95 are disposed about all throughshield conductors to inhibit radiation of rfi through such portals . therefore , the liquid infusion device of the present invention is configured without magnetic materials for operation within intense magnetic fields to administer i . v . fusion of liquids to a patient in an mri environment . the infusion device may be positioned close to a patient during image acquisition without significantly distorting the homogeneous magnetic field around an mri scanner , and without emitting harmful rfi in the vicinity around a patient from whom extremely low - level rf ‘ echos ’ are being detected during image acquisition .
liquid infusion apparatus includes non - magnetic materials in a pumping structure and drive motor therefor , and in a controller that supplies drive signals to the motor to facilitate convenient operation in intense magnet fields without distorting the magnetic fields and without radiating objectionable radio - frequency interference .