Lithotripter including a holding device for an ultrasound locating transducer

A lithotripter in general includes a patient's rest, a therapeutic head for the production of shockwaves, an ultrasonic transducer, and a locating arm for moveably mounting the transducer on the therapeutic head; and an additional holding arm has one end connected to the patient's rest and the other end is releasably connectible to the transducer for providing for a dual holding of the transducer once a concrement has been located. The holder includes a structure for motion retardation, i.e. braking action on of the one end relative to the other end.

BACKGROUND OF THE INVENTION 
The present invention relates to the treatment of patients by means of 
extracorporally produced shockwaves, particularly under utilization of 
contact-free lithotripsy; and more particularly the invention relates to 
lithotripters which include in each instance a focussing shockwave source, 
a patient's rest, and equipment for locating concrements in the body of 
human beings. 
Equipment of the type to which the invention pertains generally is, for 
example, disclosed in German patent application 39 15 382.7 (equivalent to 
U.S. Pat. No. 5,092,721). The lithotripter in this publication is 
associated with a locating arm at the therapeutic head. The term "locating 
arm" is used here for describing a holder for transducers or the like 
which are provided for finding a concrement using, e.g. ultrasonic 
equipment. The therapeutic head is the source for carrying out 
lithotripsy, i.e. for producing focussed shockwaves. 
The reference above disclose a geometric and physical relation in between a 
locating arm and a transducer mounted on the locating arm, and a so-called 
therapeutic focus as established by the shock-wave source. That relation 
between is variable and adjustable and can be tracked by means of 
appropriate measuring equipment. 
The requirements as far as the mechanics of this device are concerned are 
considerably smaller than in the case of a locating arm that has no fixed 
connection in relation to the therapeutic head. However, it was found that 
this advantage is considerably diminished owing to the problems that 
result from the relative motion of the arm once it is fixed in relation to 
the patient. In addition, there is a problem that a kidney stone, e.g. 
which is imaged by way of an ultrasonic image, may be "lost" and still 
furthermore there is a problem of danger to the patient through collision 
between the body of the patient and the equipment. 
Another possibility is given in German petty patent utility model 8800985 
wherein it is disclosed that there is a locating arm affixed to the 
patient rest. This particular arrangement has the advantage that once the 
kidney stone has been located the arm can be fixed in some fashion to the 
surface of the patient without changing the position of the arm relative 
to the patient once the patient rest has been moved relative to the 
therapeutic head. The therapeutic head in turn remains coupled and the 
image portion as displayed in not varied; hence there is no danger of 
collision. 
However, this arrangement has the disadvantage that the position of the 
therapeutic focus relative to the rest has to be determined and 
redetermined and adjusted, which is deemed a disadvantage. Aside from the 
inaccuracies in the acquisition of these parameters there is another 
possibility for error, namely any possible deformation of the patient rest 
under the load of the patient's weight which from that point of view 
remains unforeseeable but may introduce a locating error as regards the 
relation between the locating arm and the therapeutic head. 
Affixing the locating arm for the ultrasonic locating transducer to the 
patient's rest is definitely disadvantageous as compared with connecting 
that locating arm to the therapeutic unit. The accuracy that is needed 
will suffer; on the other hand an arm affixed or connected to the 
therapeutic unit is more difficult to control during positioning. 
Moreover, developments in the past have led to a highly accurate 
transducer positioning arm that is realizable only by means of a very 
complex and usually rather heavy and unwielding mechanism. U.S. Pat. No. 
4,669,438, corresponding to German patent 3427001 C1, discloses a 
lithotripter with a locating device that is affixed to a patient's rest; a 
second locating device is connected to the therapeutic head (FIG. 2 of 
that reference) but this duplication is relatively unwieldy in its own 
right. Moreover the range of permissible and possible motion of the second 
locating device is quite limited; there are just too many pieces of 
equipment in too limited a space. 
For further information on the kinematics see U.S. patent applications, 
Ser. Nos. 513,612 and 513,613 now U.S. Pat. No. 5,078,124. 
DESCRIPTION OF THE INVENTION 
It is an object of the present invention to provide new and improved 
equipment for the treatment of a patient with extracorporally produced 
shockwaves wherein the locating of the body part to be treated and to be 
determined in relation to a focal point of the equipment can be determined 
in relation to the therapeutic unit but the control of the position of the 
shockwave producing head is fixed vis-a-vis the patient. 
It is a specific object of the present invention to improve lithotripters 
which include a patient rest, a therapeutic head for the production of 
shockwaves and an ultrasonic transducer on a locating arm. 
In accordance with preferred features of the present invention the objects 
are attained by maintaining as features for the contact-free lithotripsy, 
a patient's rest, a therapeutic head for the production of shockwaves and 
structure for positioning that head in relation to the patient on the 
rest; also maintained as a critical feature is an ultrasonic transducer 
being connected to a locating arm which is mounted on and movable in 
relation to the therapeutic head, and there are position sensing 
transducers for appropriately determining the position of the locating 
transducer relative to the therapeutic head. 
In accordance with the preferred embodiment of the present invention, a 
holding device for the locating transducer is mounted on the patient's 
rest for holding the transducer. In other words the ultrasonic locating 
transducer is normally just adjustably mounted on the therapeutic head but 
once the locating procedure has been completed an additional holding is 
provided relative to the patient's rest by connecting the transducer to an 
articulating arm that is mounted on the patients rest and now there is a 
physical position relation established between the therapeutic head and 
the rest; a brake and motion retarding structure is interposed and 
included in the holding arm so that the transducer can at will be moved 
vis-a-vis the patient and his/her rest, but the brake retards any 
unintended motion and, for most instances, just holds the transducer 
immobile in relation to the patient on the rest. 
It is therefore central to the invention to reconcile the two requirements 
made above concerning the relationship between locating equipment and the 
therapeutic head. It is the underlying principle of the invention to 
actually physically separate these two requirements. Owing to the braking 
or brakable holding equipment the ultrasonic head can now also be fixed 
vis-a-vis the patient's rest. As stated, a braking or brakable holding 
device is understood to be an arm which is equipped with a structure for 
braking the motion of individual parts of the arm in relation to each 
other. 
It can thus be seen that the invention fulfills two contradictory tasks. 
First of all and as far as the locating procedure is concerned, the 
locating device acquires precise data on the position of the particular 
body part to be treated such as a concrement in relation to the focus of 
the treatment unit, i.e. the therapeutic device that is the lithotripter 
proper. The position and path acquisition system must accurately determine 
the position of the ultrasonic transducer on the locating arm relative to 
the therapeutic unit. Upon using a hinged arm one will preferably obtain 
this goal by fastening that locating arm directly to the therapeutic unit. 
These structure features are known per se and the above-noted problems 
encountered with this approach have been discussed. 
The entire equipment is to be positioned or connected in some fashion to 
the patient or rest. Without further steps, one needs an additional 
position and path transducing and acquisition system in order to determine 
the relative position between the patient's rest, the therapeutic unit, 
and the locating equipment. Under such a conditions, however, there is an 
accumulation of errors from position acquisition of the locating device 
relative to the therapeutic unit and another position determination of the 
therapeutic unit in relation to the patient's rest. Possible mechanical 
uncertainties and inaccuracies are accumulative, and result in measuring 
errors or at least in a significant deterioration of the locating accuracy 
vis-a-vis the patient. Moreover, the locating device with its ultrasonic 
transducer should be movable in all directions and should not limit the 
mobility of the ultrasonic transducer by the doctor. Under these 
circumstances it is very clear that a small and lightweight, easily 
movable hinge arm is of advantage. As regards treatment control, the 
ultrasonic transducer must be positioned vis-a-vis the patient's body. 
That means that the organ to be treated must be imaged during treatment. 
The imaging is of course by an ultrasonic imaging device. In accordance 
with the invention the arm that carries the ultrasonic transducer is 
positively held by the brake in order to prevent positioning motions and 
deflections relative to the patient.

Proceeding now to the detailed description of the drawings, the FIGURE 
shows a therapeutic head TK which is mounted in a manner shown for example 
in the two U.S. patent applications referred to above. A locating arm O is 
connected to the therapeutic head and carries a ultrasonic imaging 
transducer T1. The connection is made as follows. A rotatable ring R is 
part of the therapeutic head TK and carries in radially outwardly 
extending direction an arm O1. These two parts together are a first 
component of the articulating arm assembly O. A hinge H1 connects arm O1 
to a second arm O2, which in turn carries a hinge H2 for hingedly 
connecting a third arm O3 to arm O2. Arm O3 carries the transducer T1 for 
the ultrasonic locating structure. 
The mobility of the locating arm O vis-a-vis the therapeutic head TK is 
indicated by various double arrows wherein arrow A1 indicates the motion 
of ring R around the central axis of the therapeutic head TK. A2 is a 
pivot motion around and by a hinge H1 that connects the middle arm O2 of 
the connection to the arm O1 that is connected to the ring R of the 
therapeutic head TK. Arrow A3 indicates a pivot motion of the latter hinge 
around the axis of arm O1 which is perpendicular to the axis of the pivot 
motion A2. The double arrow A4 indicates length extension and shortening 
of the middle arm O2 of the locating arm assembly O. 
A curved double arrow A5 denotes the pivot motion of hinge H2 for the third 
arm O3 of the arm assembly O; as stated, arm O3 carries the transducer T1. 
The curved double arrow A6 denotes pivot motions of arm O3 around the axis 
of the middle arm O2; it can also be said that this turning motion A6 is 
carried out around the direction of motion indicated by the double arrow 
A4. The curved double arrow A7 indicates a motion of the transducer head 
T1 around its own axis which is the length axis of arm O3. The transducer 
T1 therefore is provided with many degrees of freedom of motion as regards 
treatment and positioning of the transducer relative to the patient. 
Reference character L denotes the patient's rest, i.e. a bedlike structure 
on which the patient is positioned. Reference character H is now 
indicative of the inventive holding structure to which either the 
transducer T1 or another one, namely, T2 is or can be connected. In 
accordance with the invention the locating arm O is connected to the 
therapeutic head Tk through whose locating arm assembly O the position of 
both the ultrasonic transducer T1 and concrement made visible through the 
ultrasonic transducer T1 in relation to a particular imaging and 
coordinate system, can readily be measure in terms of coordinate values. 
This arm assembly with its integrated part and angle transducing equipment 
is exclusively provided for purposes of determining and acquiring the 
coordinate values. It is important that this piece of equipment is not 
subject to any braking. 
The arm assembly O which is of very light weight; the position sensing 
transducers inside of arm and the parts and components of the arm assembly 
itself, are all very light; the transducer T1 is thus very easily movable 
in any and all directions. The task of positioning the transducer head T1 
when necessary in a positive and position arresting fashion is carried out 
by a holding device or holder H that is affixed at one end to the 
patient's rest L. This particular holder H is an articulated arm of 
multiple link construction, each link member being, if desired, is movable 
(articulated) in relation to its adjoining and connecting link members but 
that movement is impeded or retarded or braked. 
The free end of holder H is connectable to the locating arm assembly O 
particularly the transducer T1 thereof, whenever that is desired and 
needed. Alternatively another transducer T2, which is completely free from 
any other restraint, can be connected to that arm H. This is an optional 
feature. The essential part of the invention is to have a braking and 
brakable connection provided between the transducer on the locating arm 
normally only connected to the therapeutic head; after the locating 
procedure has been completed and the transducer T1 positioned on the 
patient; and after the coordinate values of the concrement (image) 
vis-a-vis the therapeutic focus has been determined, the position of 
transducer T1 is now position-arrested by the holder H and its motion 
impeding action. The braking equipment and the holding equipment for the 
brake is thus affixed to the patient's rest when problems of locating 
accuracies no longer enter into the picture! 
The invention is not limited to the embodiments described above but all 
changes and modifications thereof, not constituting departures from the 
spirit and scope of the invention, are intended to be included.