Control unit for a medical device

A control unit for a medical device has an actuation part and an electrical signal output that, due to an actuation of the actuation part, emits a control signal for a control computer of the medical device. The actuation device is secured to a work chair at the level of the heel of the foot of a person on the work chair.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is directed to a medical device control unit of the 
type having an actuation part and an electrical signal output that, due to 
an actuation of the actuation part, emits an electrical control signal for 
a control computer of the medical device. 
2. Description of the Prior Art 
A control unit of the above general type is known from German OS 4 125 313. 
A foot switch from which control signals are transmitted to a central 
control unit is thereby provided for controlling a dental treatment 
apparatus. The foot switch is actuated with the sole of the foot, for 
example the heel or ball region. 
A control unit of the type initially described is also disclosed in U.S. 
Pat. No. 5,365,927. This control unit has a foot switch fashioned as an 
actuation part for use in conjunction with a magnetic resonance apparatus. 
The foot switch is arranged immediately next to the magnetic resonance 
apparatus and can be actuated by a physician or an examining person during 
medical procedures being performed on a patient supported in the magnetic 
resonance apparatus. The foot switch is connected via evaluation 
electronics to a control computer of the magnetic resonance apparatus, and 
its actuation causes magnetic resonance image datasets, corresponding to 
those image regions that the physician or examining person previously 
marked with a hand-held pointer, to be displayed on a monitor. It is 
advantageous in this context that the physician or examining person can 
operate the magnetic resonance system via the foot switch without having 
to use his other hands, which are in the sterile work field. It could be 
disadvantageous in some situations, however, if the physician or examining 
person would have to turn his or her eyes away from the patient in order 
to seek the foot switch before its actuation. When the physician or 
examining person is seated during the examination, care would have to be 
exercised to be sure that the foot switch is placed in a proximity within 
reach of the foot. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a control unit for medical 
apparatus that can be easily and reliably operated by a seated physician 
or examining person. 
The above object is achieved in accordance with the principles of the 
present invention in a medical apparatus control unit having an actuation 
component, actuatable by a physician or an examination attendant at the 
medical device, which upon actuation emits an electrical signal to a 
control computer which operates the medical device, the actuation 
component being secured to a work chair at a height coinciding with the 
location of the heel of a person seated on the work chair, so that the 
actuation component can be actuated by a side region of the foot of 
physician or examination attendant. 
In an embodiment the actuation part is a closed pressure bellows, and in 
that the pressure bellows is connected via a hose conduit to a pressure 
transducer i.e., a transducer which emits an electrical signal when acted 
on by a suitable degree of pressure. The pressure transmission is in turn 
connected to evaluation electronics, the evaluation electronics emits an 
electrical control signal upon a suitable magnitude of pressure acting on 
the transducer. The control unit is thus compatible with the cleaning and 
sterilization requirements of clinical operating rooms. In particular, the 
control unit, even without further measures, meets the demands made of the 
electromagnetic compatibility of diagnostic magnetic resonance systems 
because all electrical components of the pressure-electrical transducer 
can be arranged outside the radio-frequency space. 
In another embodiment the evaluation electronics generates the control 
signal due to a change in the pressure occurring at the 
pressure-electrical transducer. A hose conduit having a smaller inside 
diameter can then be used, compared to that needed for a static pressure 
transducer. If the hose conduit is stepped on or when something rolls over 
it, because of its small inside diameter only a small pressure wave is 
generated that is recognized by the evaluation electronics as a noise 
signal and can be blanked out. 
In another embodiment for use in conjunction with a computer keyboard, the 
electrical control signal from the evaluation electronics corresponds to a 
control signal triggered by a function key of the computer keyboard. The 
control unit can thus be connected into conventional systems without 
requiring hardware or software modifications. The installation of the 
control unit is thus very simple and could even be retrofitted in existing 
systems already in use. 
In a further embodiment the electrical control signal corresponds to a 
digital word that can be emitted by a function key of the computer 
keyboard. The function triggered by the control unit can thus be 
programmed like the function keys of a standard keyboard.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As a medical apparatus to be controlled, FIG. 1 shows the schematic 
structure of a diagnostic magnetic resonance apparatus. The actual 
examination part of the magnetic resonance apparatus is composed of an 
open magnet system 2 with two pole shoes 4 arranged opposite one another 
that are connected to one another via a C-shaped magnetic return 6. The 
magnetic drive is composed of respective electromagnet windings 8 arranged 
at the pole shoes 4. In an approximately spherical region, the magnet 
system 2 generates a uniform and vertically aligned basic magnetic field 
between the pole shoes 4. A region of a patient 12 to be examined is 
positioned within the uniform basic magnetic field region on a patient 
support 10. In addition to the patient access, a lateral access symbolized 
by an arrow 14 is established for a physician or examining person. 
Gradient coils for generating gradient fields in three directions residing 
perpendicularly on one another as well as radio-frequency antennas for 
exciting or receiving magnetic resonance signals are present in a known 
manner, but are not shown. The magnet system 2, including the gradient 
coils and radio-frequency antennas, is located in a radio-frequency 
compartment 16. A control computer 18, which generates the control signals 
required for the operation, is arranged outside the radio-frequency 
compartment 16. These control signals are the control signals for gradient 
amplifiers 20, likewise arranged outside the radio-frequency compartment, 
and for a radio-frequency transmission/reception system 22. The high-power 
output signals of the gradient amplifiers 20 and of the radio-frequency 
transmission/reception system 22 are conducted into the radio-frequency 
compartment 16 via waveguide filters 24. A keyboard 26 is arranged outside 
the radio-frequency compartment 16. A monitor 28 is likewise connected to 
the control computer 18. 
In addition, a control unit 30, via which a physician located inside the 
radio-frequency compartment 16, for example during a magnetic 
resonance-guided procedure, can operate the magnetic resonance system, is 
connected to the control computer 18. The control unit 30 is ergonomically 
fashioned for a seated position, so that it can be actuated with a foot or 
a heel without a change in the operator's position. The control unit 30 
includes a pressure bellows 32 forming an actuation part that is secured 
to a post 34 of a work chair 36. A hose conduit 38 has one end connected 
to the lower part of the pressure bellows 32 and is conducted out of the 
radio-frequency compartment 16 via a radio-frequency-tight bushing 40. The 
bushing 40 is composed essentially of an elongated, conductive hollow 
cylinder. The other end of the hose conduit 38 is connected to a 
pressure-electrical transducer 42 that converts a pressure signal 
transmitted via the hose conduit into an electrical signal. 
The pressure transducer 42 can be a dynamic pressure transducer, such as 
with a spring-supported coil arranged so as to be movable in a magnetic 
field. A movement of the coil in the magnetic field due to a pressure wave 
emanating from the pressure bellows 32 induces a voltage pulse that is 
processed by evaluation electronics 44 to form an output signal of the 
control unit 30. The control unit 30 emits the output signal at an output 
46. The output signal corresponds to a digital word such as can be emitted 
by depression of a function key of the computer keyboard 26. The digital 
word can be programmed and prescribed via miniature switches 43 and/or a 
memory 45. The digital word can likewise be programmable via a flash 
memory card that is not shown in FIG. 1. 
The output 46 produced in a signal path that includes an electrical 
connecting line 48 that connects the computer keyboard 26 to the 
evaluation electronics 44, and leads to the control computer 18. A data 
word emitted by the computer keyboard 26 is intermediately stored in a 
buffer memory 50 that is organized according to the "first in first out" 
principle (FIFO). A processor 52 in the evaluation electronics 44 receives 
an interrupt signal if the pressure bellows 32 was actuated, and transmits 
the data word from the keyboard 26 to the control computer 18 only if the 
pressure bellows 32 was not actuated. The magnetic resonance apparatus can 
be operated and the function linked to the signal or word can thus be 
started by an operator upon actuation of the corresponding function key, 
but also by a physician or examining person in the radio-frequency 
compartment 16 by actuating the pressure bellows 32. 
In a front view, FIG. 2 shows a kneeler stool fashioned as work chair 
having a seat 54 and a knee support 56 that are both carried by the 
central column 34. The work chair 36 is provided with rollers 58 for 
movement. Two elongated, pneumatic pressure bellows 32 are secured 
opposite one another at both sides of the column 34 at the level of the 
heel of the foot. By pivoting the right or left heel, the physician can 
exert pressure on the corresponding pressure bellows 32. The arising 
pressure wave is then supplied to the evaluation electronics via the hose 
conduit 38 connected to the pressure bellows 32. Due to the change in 
pressure exerted by the pressure wave at the pressure transducer 42, the 
correspondingly programmed data word is emitted as an output signal at the 
output 46. 
Although modifications and changes may be suggested by those skilled in the 
art, it is the intention of the inventors to embody within the patent 
warranted hereon all changes and modifications as reasonably and properly 
come within the scope of their contribution to the art.