Probe translation system for use in hyperthermia treatment

An automated temperature scanning system for monitoring hyperthermia treatment has a linear drive assembly operatively connected to a non-rotational extended-length screw shaft which is linearly translated by a stepper motor. A first tube having a thermometric probe concentrically positioned therein is fixedly secured to the linear drive assembly so as to be motivated thereby. A second tube is secured at one end to an interstitial catheter and is adapted to be at least partially slidably received within the first tube so that linear movement of the first tube toward the second tube slidably moves the thermometric probe within the second tube and an interstitial catheter associated therewith. A computer is electrically connected to the stepper motor to control the movement of the thermometric probe utilizing real time data generated thereby.

TECHNICAL FIELD 
This invention relates generally to a system for controlling and optimizing 
the heating pattern used by a hyperthermia device to treat tumors, and 
more specifically to an automated system of improved design providing for 
greater accuracy and ease of use so as to enhance the effect of 
hyperthermia treatment on a patient. 
BACKGROUND ART 
Hyperthermia treatment provides for the heating of living tissue for 
therapeutic purposes, most typically the treatment of malignant tumors. 
Hyperthermia has been used as a method of treating cancer by raising the 
temperature of a malignant tumor locally since it has been proven that 
relatively high heat can contribute to the natural regression and/or 
remission of tumors Hyperthermia treatment can be used as an independent 
therapy or it may be used in conjunction with other cancer therapies such 
as radiation, surgery, chemotherapy, and immunotherapy to enhance the 
effectiveness of the other therapeutic treatments. 
Typically, in hyperthermia treatment a tumor is heated to a temperature 
slightly below that which would injure normal cells in order to thermally 
destroy it. The treatment is believed to be effective because many types 
of malignant cell masses have been found to have less heat dissipation 
capability than normal tissues do, due apparently, to reduced blood flow 
characteristics. The most common types of hyperthermia modality used 
presently are radiofrequency, microwave and ultrasound treatment. 
Radiofrequency and microwave equipment can be used for local, regional and 
whole body heating. Ultrasound can be used for local and regional heating. 
Hyperthermia is presently in an early stage of dose quantification which is 
similar to that of conventional ionizing radiotherapy of the early 
twentieth century. Development of dosimetric indices with therapeutic 
significance strongly depends on the few temperature measurements which 
are made interstitially. However, problems of scanning thermometers in 
tissues include choices of measurement dwell times and inter-measurement 
spacing. With present hyperthermia heat delivery systems, manual scanning 
of thermometric probes within tissues is awkward. Also, slippage of 
thermometry catheters and other difficulties limit the extent and accuracy 
of manual probe temperature scanning. Nevertheless, detailed and strategic 
temperature measurements are vital to hyperthermia treatment planning. 
Thus, an improved temperature scanning system for use in hyperthermia 
treatment is greatly needed at this time. 
An automated device presently utilized for thermal mapping is the BSD-1000 
manufactured by BSD Medical Corporation of Salt Lake City. This computer 
controlled apparatus is adapted to move from one to eight thermometric 
probes within stationary catheters which have been inserted into the 
tissue volume of interest. The probes are moved at fixed distance 
intervals through the catheters during conditions approximating thermal 
stability and are allowed to remain long enough at each position for 
sufficient thermal equilibration. The temperature is then recorded and the 
probe withdrawn or moved to the next position. The apparatus utilizes only 
one stepper motor and therefore the eight thermometric probes are all 
forced to move within catheters for the same scan length and all utilize 
the same measurement spacing and dwell time. Moreover, the device utilizes 
a friction drive and a probe translation mechanism which can result in 
bending of one or more of the thermometric probes with the resulting 
problems and inaccuracies which can result therefrom. Because of the 
relatively large size and rigidity of BSD thermometry tubes, it is 
difficult to position multiple probes at varying angles to each other and 
it is not possible to use these tubes for translation of widely used 
thermometers that are more fragile than BSD thermometers. 
Therefore, a need exists for an automated system which will allow for more 
efficient, accurate and versatile thermal mapping by the movement of 
thermometric probes within stationary catheters which have been inserted 
into tissue volume of interest. The new system should overcome the 
shortcomings presently existing in both manual and automated apparatus now 
available for use in thermal mapping associated with hyperthermia 
treatment. 
DISCLOSURE OF THE INVENTION 
The system of the present invention for characterizing the heating pattern 
for a hyperthermia device is an improvement over the prior art and 
overcomes the shortcomings inherent in previous thermal mapping equipment. 
The automated temperature scanning system of the present invention is 
comprised of a stepper motor and an operatively connected linear drive 
assembly which are mounted at one end of an adjustable support arm which 
has a magnetic base secured to the other end thereof. The linear drive 
assembly comprises a plug element which is secured to one end of an 
extended-length, non-rotating screw shaft extending through the stepper 
motor and linearly driven by a rotating armature within the motor. A 
thermometer linear translation assembly is connected to the linear drive 
assembly and comprises a first tube secured to the plug element of the 
linear drive assembly. The first tube includes a thermometric probe 
secured thereto and positioned substantially concentrically therein. The 
thermometer translation assembly also includes a second tube which is at 
least partially slidably received by the first tube and is secured at its 
remote end to an interstitial catheter. In this fashion, linear movement 
of the first tube toward the second tube causes the thermometric probe to 
be slidably moved within the second tube and an associated interstitial 
catheter. Finally, computer means comprising selected hardware and 
software is electrically connected to the stepper motor in order to 
control the movement of the thermometric probe within an interstitial 
catheter. 
The stepper motor and linear drive assembly of the present invention allow 
for very precise control of the linear movement imparted to a thermometric 
probe, and the telescoping guide described hereinbefore provides for 
precise support and guidance of a thermometric probe and obviates any 
tendency to kink or bend and the inaccuracies of measurement which can 
result therefrom. In this fashion, an improved computer controlled 
automated temperature scanning system is provided which may be used either 
singularly or with multiple units connected to a computer. The system 
provides for independent control and accurate real time data from each 
automated scanner. 
It is therefore the object of this invention to provide an improved 
temperature scanning system which will provide for greater accuracy and 
ease of use than temperature scanning systems used in conjunction with 
hyperthermia systems heretofore. 
It is another object of the present invention to provide a temperature 
scanning system which allows for independent and simultaneous control of 
each thermometric probe if a plurality of the units are utilized in 
thermal mapping procedures associated with hyperthermia treatment. 
It is still another object of the present invention to provide a 
temperature scanning system which will not kink or bend a thermometric 
probe being translated thereby and which can handle more fragile 
thermometric probes than has heretofore been feasible with an automated 
system.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now more specifically to the drawings, a preferred embodiment of 
a temperature scanning system for use in hyperthermia treatment according 
to the present invention is shown in FIGS. 1-5. The temperature scanning 
apparatus shown in FIGS. 1-4 comprises a base 12 which may be magnetized 
as needed by pushing button 14 so that base 12 can be fixed to the metal 
slats or the like along the side rails of a hyperthermia treatment couch. 
An adjustable, pivotable support arm 16 is secured at one end to base 12 
and at the other end to a mounting means including adjustable mount 18 
secured to stepper motor 22. Stepper motor 22 mounted to adjustable mount 
18 includes a non-rotational shaft 24 which is driven by an internally 
rotating armature (not shown) within stepper motor 22. Cylinder 20 is 
adapted to fit over the collar of stepper motor 22 and includes two 
longitudinally extending parallel slots 28A, 28B (not shown) positioned on 
opposite sides of cylinder 20 and a third longitudinally extending and 
parallel slot 30 which is coextensive with side slots 28A, 28B (not shown) 
and is located at the top of cylinder 20. 
A drive assembly for the temperature scanning apparatus of the present 
invention includes plug 32 (see FIGS. 2 and 4) fixed to the end of 
non-rotational shaft 24 and having a shaft plug extension 34 which extends 
through top slot 30. Shaft plug extension 34 defines a slotted aperture 35 
therein which can be adjustably tightened by screw 37 about a thermometer 
translation assembly to be described in detail hereafter. Plug 32 also 
includes guide screws 36A, 36B on opposing sides thereof which extend 
through longitudinally extending slots 28A, 28B, respectively, in order to 
guide the linear movement of plug 32 within cylinder 20. A magnet 38, is 
embedded in plug 32 and serves to trip reed switches 40A, 40B mounted at 
opposing ends of cylinder 20 so as to de-actuate stepper motor 22 when 
plug 32 reaches the furthermost ends of its travel in order to prevent 
non-rotational shaft 24 from being driven by stepper motor 22 beyond the 
mechanical limits of cylinder 20. Although this is matter of design 
choice, it is anticipated that the preferred embodiment of the invention 
will allow for travel of plug 32 for a linear distance of between about 2 
centimeters and 20 centimeters. 
The linear motion provided by stepper motor 22 and non-rotational shaft 24 
is translated to a thermometric probe by a thermometer translation 
assembly. The thermometer translation assembly comprises a first guide or 
tube 42 (see FIGS. 2 and 3) which is fixedly secured to shaft plug 
extension 34 and includes a thermometric probe lead 44, most suitably a 
fiber optic thermometer of the type manufactured by Luxtron Corporation, 
secured thereto and positioned concentrically therein. First tube 42 most 
suitably also includes a second tube 46 concentrically positioned therein 
and of a substantially coextensive length with first tube 42. Second tube 
46 surrounds thermometric probe lead 44 so that thermometric probe lead 
44, second tube 46 and first tube 42 are all parallel and concentric to 
each other. First tube 42 slidably extends through an aperture 47 within 
flange 48 extending around the proximal end of cylinder 20 so that first 
tube 42 may freely slide therethrough during linear movement thereof by 
plug 32. A third tube 50 is slidably received within first tube 42 and 
over second tube 46 so as to be movable in relation thereto. Third tube 50 
is connected at its free end to hub 49 connected to flexible connector 
tube 51 which is in turn connected to fixed interstitial catheter 52 which 
extends into a tissue volume of interest. Hub 49 is preferably secured to 
cylinder 20 with a suitable spacer element 55 to assist in maintaining 
tube 50 colinear with probe lead 44 and deter buckling of tube 50. In this 
fashion, third tube 50 is fixed relative to first and second tubes 42, 46, 
respectively, and movement of first tube 42 and second tube 46 by plug 32 
serves to move thermometric probe lead 44 and probe 53 within interstitial 
catheter 52 so as to obtain desired probe position. 
Preferably, tubes 42, 46, 50 and flexible connector tube 51 are constructed 
of plastic, interstitial catheter 52 is a blind-ended catheter suitable 
for thermometry, and thermometric probe 53 is a single or multiple sensor 
fiber optic probe. Miniature washers can be inserted into interstitial 
catheter 52 to change its diameter and to accommodate other size 
thermometric probes 53. 
The use of the telescoping guide tube design described herein solves a 
mechanical problem wherein the inner diameter of tube 46 must be large 
enough to allow free movement of flexible thermometer probe lead 44, but 
not so large that kinking or significant bending of the thermometer probe 
lead is possible. The wall thickness of tube 46 must also be thin, such 
that the inner diameter of tube 50 is also small enough to prevent kinking 
of thermometer probe lead 44 when tube 46 is displaced relative to tube 
50, and only tube 50 constrains the thermometer against kinking. This 
design requires tube 46 itself to have limited resistance to bending and 
kinking by virtue of its small inner diameter and wall thickness. To 
compensate for the flexibility of tube 46, tube 42, relatively rigid, has 
an inner diameter sufficiently small to constrain tube 46 relative to 
bending and kinking, while still allowing tube 50 to move relative to tube 
42. Mechanical strength and rigidity of the thermometer translation 
assembly is thus accomplished by the configuration of the telescoping 
tubes. 
Finally, the apparatus of the invention includes control means, most 
suitably computer means, electrically connected to stepper motor 22 for 
controlling the movement of thermometric probe 53 within interstitial 
catheter 52. A better understanding of the preferred computer control can 
be had with reference to FIG. 5 of the drawings. Most suitably, a personal 
computer with at least 1 Megabyte of RAM and a hard disc with at least 20 
Megabytes of memory and less than 30 milliseconds access time is used to 
control one or more of the temrature scanning apparatus through one or 
more parallel ports of the computer or one parallel port and an external 
multiplexer. The computer provides for independent control of each 
scanning apparatus since each thermometric probe 53 is being linearly 
translated by a separate stepper motor 22 and thermometer translation 
assembly. Signals derived from each thermometric probe 53 within its 
respective interstitial catheter 52 are serial ported back to the memory 
of the computer. This particular configuration forms a loop allowing for 
real time temperature feedback control and display of variables such as 
temperature (T), temperature difference between points (.DELTA.T), 
position (r), spacing (.DELTA.r), time (t) and dwell time (.DELTA.t). 
These can be displayed in graphic or tabular form, for example, T as a 
function of r or t, or .DELTA.t as a function of r. For hyperthermia 
treatments scan parameters are ideally functions of the measured 
temperatures. 
Most suitably, each temperature scanning apparatus is connected to the 
computer in a conventional fashion. Software is utilized which allows T to 
be analyzed and scan parameters to be altered by keyboard entries or 
software in an automatic mode. Software is utilized which can 
independently control up to six temperature scanning apparatus and provide 
monitor screens with data from multiple channels in real time. All of the 
software is modular in design with a choice of algorithms for generating 
scan patterns from cumulative T(r,t), and it is most suitably stored on 
the hard disk of the computer. Summarily, the hardware serves to interface 
the computer with the one or more temperature scanning apparatus utilized 
therewith, and the software serves to regulate thermometric probe 
movements and to display temperature profiles for each temperature 
scanning apparatus. 
The temperature scanning system of the present invention allows for the use 
of one or more independently controlled thermometric probes within a 
tissue volume of interest. The apparatus allows for substantial geometric 
latitude in the placement of a plurality of interstitial catheters in 
close proximity to each other as well as more precise translation of 
thermometric probes within the tissue volume. Moreover, shortcomings of 
previous systems relating to bending or buckling of probe leads within 
large diameter guides have been overcome with the telescopic tube 
thermometer translation assembly utilized in the apparatus of the 
invention. 
Although thermometric probe translation has been described hereinabove it 
should also be appreciated that the system of the invention can be used to 
translate probes other than thermometers, for example, radiation 
detectors, pressure detectors or blood flow meters. Thus the invention can 
be applied to scan physical characteristics other than temperature. 
Moreover, it should be further appreciated that the system of the 
invention can be used to scan materials other than tissues, for example, 
the containment vessel of a nuclear reactor and the like. 
It will thus be understood that various details of the invention may be 
changed without departing from the scope of the invention. Furthermore, 
the foregoing description is for the purpose of illustration only, and not 
for the purpose of limitation--the invention being defined by the claims.