GB2038150A - Improvements in or related to radiography - Google Patents

Abstract

In radiotherapy treatment and radiotherapy treatment planning, which comprises diagnostic radiography including computerised tomography (CT) and planning on a therapy simulator, it is desirable that the patient be in an exactly reproducible position each time so that tumours which are found may be exactly relocated. To this end the patient is placed on a flat platter (3) on each occasion. This invention provides devices (19, 20), an example of which can be associated with the platter in each apparatus used, which place the patient's head and arms each time such that reproducible positioning of organs in the relevant part of the body is provided. The devices may include means (29) for positioning the legs and a marker (31) which assists in finding the body centreline against suitable reference marks, (33). <IMAGE>

Description

SPECIFICATION Improvements in or related to radiography The present invention relates to patient positioning in radiotherapy treatment and radiotherapy treatment planning.

One important and well established procedure for treating patients having tumours is to irradiate the tumour so as to kill it. Care must, however, be taken not to damage to a greater extent than necessary healthy tissue surrounding the tumour. Irradiation may be by implantation of, say, radium needles. A convenient and controllable method, however, involves irradiation of the patient with beams of X-rays, electrons or other particles generated in a high power source such as a linear accelerator or perhaps an isotope source. Such treatment is generally referred to as radiotherapy and apparatus therefor may take many well known forms.

Radiotherapy procedure involves irradiating the tumour tissue many times over an extended period and from many different directions so as to ensure a significantly greater dose in the tumour than in surrounding tissue.

It will be apparent that to be successful such treatment should be carefully controlled and meticulously planned and it is the practice to draw up detailed treatment plans before irradiation is begun.

Radiotherapy treatment planning takes into account information of different kinds including diagnostic radiography. Conventional shadowgraph X-ray pictures can be used to indicate the position of a tumour, although it is not very suitable for brain tumour. Recently however there has been made available a diagnostic X-ray technique invented by G. N.

Ilounsfield (British Patent No. 1283915) and known as computerised tomography (CT). This technique provides detailed cross-sectional Xray pictures which are not obscured by shadows of adjacent features and are also obtainable for the brain. Such pictures are extremely valuable for radiotherapy planning and have been used to determine the exact position and extent of tumours prior to therapy.

It is an object of this invention to provide a patient positioning arrangement which can be used with CT scanners, therapy apparatus and other apparatus used in radiotherapy planning.

According to the invention there is provided a patient positioning device for reproducibly positioning a patient in successive stages of radiotherapy planning procedures, the device comprising, in association with respective platters on which the patient is supported for each such procedure, a support for the patient's head and at least one positioning member against which the patient's hands may be placed in substantially the same position at each said procedure.

In order that the invention may be clearly understood and readily carried into effect it will now be described by way of example with reference to the accompanying drawings of which Figure 1 is a flow chart for radiotherapy, Figures 2a and 2b show a paitent positioned by the upper thorax device in a CT scanner, Figures 3a, 3b and 3c shows the upper thorax device in more detail, Figures 4a, 4b and 4c show the patient positioned supine by the device of this invention on a scanogram apparatus, Figures 5a, 5b and 5c show the patient positioned supine by the upper thorax device in a therapy simulator, Figures 6a and 6b show the patient positioned supine by the upper thorax device in a therapy apparatus Figure 7a, 7b and 7c show the patient positioned in a prone position by the upper thorax device on a scanogram apparatus, Figures 8a, 8b and 8c show the patient positioned in a prone position by the upper thorax device in a CT apparatus, Figures 9a, 9b and 9c show the patient position in a prone position by the upper thorax device in a therapy simulator Figures 1 0a and 1 Ob show the patient positioned in a prone position by the upper thorax device in a therapy apparatus.

Figures 1 lea to Ilc, show a patient positioned for CT scanning using the lower thorax device, Figure 12 shows the patient of Fig. 11 inserted into the CT scanner, Figures 1 3a to 1 3c show the lower thorax device in more detail, Figure 14 shows another view of part of the lower thorax device, Figures 1 5a to 1 sic show the patient positioned with the lower thorax device on a scanogram table, Figures 1 6a to 1 6c show the patient positioned with the lower thorax device on a therapy simulator, Figures 1 7a to 1 7c show the patient positioned with the lower thorax device on a radiotherapy apparatus, Figures 1 8a and 1 8b show in side elevation and plan respectively a leg positioning device associated with the lower thorax device on a CT machine, Figures 1 9a, b and c show in plan, side and end elevation respectively the leg positioning device, Figures 20a, b and c show in plan, side and end elevation a detail of Figs. 19, Figures 21a and 21b show the leg positioning device associated with the upper thorax device, Figure 22 shows a variation of the lower thorax device, and Figure 23 shows a variation of the upper thorax device.

As mentioned hereinbefore, radiotherapy treatment planning and treatment is a comprehensive procedure which requires examination and treatment of the patient at several stages.

Fig. 1 is a flow chart of the entire radiotherapy procedure and the stages indicated by stars are those at which the patient is physically involved. The clinical and diagnostic examinations first mentioned include examination of the patient by CT scanning. It also, with the exception of brain tumours, includes prior production of a so-called "scanogram" shadowgraph picture which may be used to select cross sections suitable for the more detailed CT scanning.

When the positions of the tumour(s) have been established by diagnostic radiography a treatment plan is drawn up and suitable dosages devised. In this procedure the patient is measured and any casts or jigs etc. required are constructed. The patient is also placed on a simulator which represents the therapy equipment but includes picture taking X-ray equipment instead of the high energy therapy source. The simulator is used to check and refine the planned treatment to ensure that no problems arise during actual treatment.

After the planning has been completed treatment can proceed, the patient being placed on the therapy machine couch in positions determined with the simulator. The last stage starred in Fig. 1, the follow-up, involves further examination, perhaps by CT, to evaluate the success of the treatment and to decide if further treatment is required.

Since the treatment is required to irradiate the tumour with minimum damage to surrounding tissue it is important that all of these stages of examination, planning and treatment should be properly coordinated. When the patient is examined the position of the tumour is determined in relation to external or externally visible features, such as particular bone structures, skin markings etc. It is assumed that at later stages the tumour is in the same relationship to these features. It is important therefore that this should be so and the procedure required is to ensure that the patient lies in the same position as exactly as possible for each examination, planning and treatment stage. Current procedure is to place the patient prone or supine on a flat platter so that all organs relax into the same position whether the patient is in CT or therapy machine.It is now found that even this may not ensure sufficient reproducibility of position.

This invention therefore provides an arrangement which can be provided identically with the flat platters used for CT, therapy and other stages of the procedure and which will in each stage hold the patient in the same position to a greater extent than in previous procedures while allowing undisturbed operation of the individual machines.

Many therapy treatments concern organs in the thorax and abdomen, which are particularly sensitive to the positions of the arms and shoulders. This invention can be implemented in different forms, in one exam ple providing an arrangement particularly suit able for reproducible positioning of the upper thorax and in particular for allowing radiogra phic examination and therapeutic irradiation of the lymph glands which are known to be a -common site of metastases in cancer patients.

The device of the invention may also be used for examination of other parts and in another example discussed herein is particularly suit able for reproducible positioning of the lower thorax.

For examining and treating the upper thorax and in particular the lymph glands it is desir able to keep the arms and shoulders as much as possible out of the radiation so as to reduce unnecessary dosage of those parts.

This can also have advantages in allowing entry of relatively large persons into the aper tures of CT machines which in some cases are relatively narrow. For the purposes of this invention it is therefore required to provide firm and reproducible positioning for the arms while keeping them and the shoulders raised.

Figs. 2a and 2b show side elevation and plan views respectively of a patient undergo ing a CT scan and positioned using this inven tion. The CT scanner gantry is shown in outline at 1 with the X-ray plane marked X-X.

The patient 2 is lying on a platter 3 which is arranged to move laterally to move the patient into and out of the aperture 4 of the machine.

As discussed hereinbefore platter 3 has a flat surface for reproducible positioning of the patient.

In this example the patient 2 is supine and positioned by the device 5 of the invention.

The device is secured to the platter 3 by dowels so as to be readily removable. The device includes a head support 6 and two hand grips. (This position will be considered to be above the- patient's head regardless of orientation relative the ground). He then jams his elbows firmly against the two side pieces 8 and the head support, which is movable along the machine axis, is moved to provide a comfortable position for the patient. The de vice also includes a movable position indicator 9 which is placed against the top of the patient's head. The setting of this indicator is read from a scale thereon and, at the first positioning is recorded in the patient's file. At subsequent positioning of the patient, on the same or other apparatus having similar posi tioning devices, the procedure is to set the indicator 9 at the recorded setting first, then to place his head against it and to have him cross his arms and grasp the grips 7. It should be noted that it may be necessary for comfort of the patient to place a pad 10 under his knees as shown.

Figs. 3a, b and c are respectively plan, endand side-elevational views of the device with outlines of a patient shown in broken line to assist in appreciating the use of the device.

These figures show more clearly the positions of the headrest 6, which is movable on tracks 11, hand grips 7 and position indicator 9, which is shown both in extended and withdrawn positions (the latter in broken outline).

It will be appreciated that small adults or children may not be able to brace the elbows against sides 8 and still hold grips 7, the figure illustrated herein being the 97.5 percentile American male (U.S.). In that event it is more important to brace the elbows against sides 8 and the lower arms can be placed perpendicular to those sides with each hand gripping the other arm. This position can also be adopted by larger adults if more widely spaced sides 8 are desired, perhaps if the CT machine available offers a generous aperture 4.

It has been mentioned that the device of this invention is for use with several different stages of the radiotherapy procedure. It is proposed that each item of equipment used, for which patient positioning is required, should be provided with a substantially identical flat surfaced platter 3 and positioning device so that identical conditions may be set up on each occasion. Figs. 2a and 2b showed a patient supine on a CT scanner couch. Figs.

4a and 4b respectively show side elevation and plan of the patient on a scanogram apparatus used for preliminary examination prior to CT and Fig. 4c is an end elevation view from arrow A on Fig. 4a. General features of the device of the invention are indicated with the same numeral as hereinbefore. The scanogram apparatus comprises a flat table 12, on which the positioning device is fixed, and an X-ray film cassette 13. Irradiation is by an Xray source 14 moving between suitable extreme positions indicated to irradiate the patient over the region of interest. Source 14 is essentially a conventional X-ray source, differing mainly in that the radiation is collimated by a slit collimator perpendicular to the direction of motion.

Figs. 5a, b and c are end-and side-elevations and plan view respectively of the patient positioned by a substantially identical device in a therapy simulator 15 for evaluation of the future treatment. Similarly Figs. 6a and 6b show the end-and side-elevational views of the patient positioned in the therapy machine itself. In this example the machine is a linac 16.

The Figures described so far show the patient lying in a supine position but the device is also suitable for positioning a patient in the prone position which may sometimes be desired. Views of a patient in the prone position in the scanogram apparaturs, CT apparatus, simulator and therapy apparatus (i.e. in the order of actual use) are shown in Figs. 7, 8, 9 and 10 respectively. The individual views of those Figures are labelled as for the supine views. Little variation needs to be provided to the device for use in the prone position, the mode of use being essentially as described hereinbefore. It will be appreciated that proper provision should be made to allow the patient to be comfortable lying face down, for example by providing a suitable aperture for the nose. Furthermore the optional pad 10 may be placed to support the calf to avoid discomfort to the feet.

Turning now to an alternative form of the invention which is specifically adapted to reproducible positioning of the lower thorax of a patient, Figs. 1 1 a and 1 1 b show side elevation and plan views respectively of a patient prepared for a CT scan as in Fig. 2 but positioned using this example of the invention. The CT scanner gantry is shown in outline at 1 generally as in Fig. 2 with the Xray plane as marked. There is also marked the line of a light sight which is used to set up the patient with a region of interest a predetermined distance from the X-ray plane.

In Fig. 11 the patient 2 is supine and positioned by the lower thorax device 17. The device is secured to the platter 3 in the same manner as the upper thorax positioning device and may also be positioned closer to gantry 1 for short patients or children. The device includes a head support part 18 and positioning parts 19 with arm rests or elbow supports 20. Fig. 1 1 c shows an end elevation as from the direction of arrow A in Fig. 1 1 a and allows some details of positioning to be more clearly seen.

For positioning the patient is laid on platter 3 3 with the head on support 18 and the top of the head pressed against parts 19. The arms are placed behind the head with elbows on rests 20 as shown at 21 and the hands placed around parts 19 as shown at 22. The hands and head are placed by the radiographer with the head centred in relation to the platter and the arms comfortable. To allow comfortable positioning the height of the arm rests is adjustable (23) and the angle automatically adjusts to the slope of the patient's arms. The first time the device is used, usually for the scanogram, the position of the hands is noted relative to a datum and recorded in the patients file for use with the similar devices on the other equipment. The height adjustment, if any, of the arm rests is also noted. The procedure for a prone patient is similar.

IS Slmllar.

The patient is introduced into the CT scan- ner by mechanised motion of the platter 3, without the need to disturb the position set.

Fig. 12 shows the view of Fig. 2b with the patient introduced to the maximum extent allowed for this embodiment by the aperture of the scanner illustrated. Other equipment may have larger apertures.

Figs. 1 2a and 1 3b are end elevational views of the head rest part 18 and the remainder of the device respectively and Fig.

1 3c shows a plan view of the entire device, all three views being disassembled from the platter 3. In addition to the features previously described, which are identified by the same reference numerals there can be seen the rose joints 24, which allow free movement of arm rests 20, and dowels 25 by which the device is mounted on platter 3. If the device is to be used by prone patients suitable provision should be made for the patient's comfort on the head rest. Preferably a cut out should be# made for the nose as shown in broken outline at 26.

When the patient is positioned as described with elbows on rests 20 the hands are placed around parts 19 with the palms in contact at points 27 and the tips of the fingers (if the hand is sufficiently large) reaching around to the inside surface at 28. The positions of the hands may be recorded by noting the positions of the finger tips against marks on parts 19 while ensuring that the hands are firmly in contact with the support surface 29.

Fig. 14 shows a view of part of the device disassembled showing padding 30 which may be provided on head contact surfaces of part 19.

Figs. 15a-15c, 16a-16e and 17a-17c show the lower thorax device used with the pre-CT scanogram, the therapy simulator and the therapy machine (LINAC) respectively.

The arrangements described so far allow patient positioning to be firmer and more reproducible than had previously been possible. There are still, however, problems which may reduce reproducability of positioning.

One problem is that the patient has considerable freedom to move the legs and lower abdomen and this affects positioning of the upper parts. The lower abdomen may be positioned prior to examination or treatment, using markers such as light sights or projected light (laser) patterns. Nevertheless the patient may still move, after this has been done, and has no reference to regain the desired position.

A further development of this invention aids positioning by providing a firm surface, in a reproducible position, against which the legs may be braced. This may be achieved both by an attendant during setting up or actually by the patient in the case of a later involuntary movement.

The arrangement is shown in Figs. 1 8a and 1 8b, in side elevation and plan respectively, for a patient positioned on a CT machine with the lower thorax device.

The main positioning element is a centreboard 29, conveniently of plywood, removably fixed centrally of the lower part of the platter 3. This is placed between the patient's legs preferably after the positioning of the patient's head. The patient can thus be placed with both legs pressing firmly against the board 29. As before the arrangement is provided for ea#ch stage of the planning and treatment procedure and the same position of the legs can be found each time. The positioning of the lower thorax will not then be upset by varied leg and abdomen positions. Of course if the patient makes an involuntary movement he may reposition himself by pressing his legs against the centreboard.To allow fitting smaller adults or children it is proposed that the upper and lower thorax arrangements could be placed at several positions on the platter so that the patients crotch will always be in the same position relative to centreboard 29.

As a further aid to positioning, the centreboard 29 may be provided with an additional fixture 30, in this example a post, to which there is attached an elastic or otherwise tensioned cord 31. The cord 31 is also attached removably to a fixture at the patient's head. In this example the latter fixture is another post 32 behind the patient's head. The cord 31 is attached to post 32 after the patient has been situated on the platter.

Cord 31, being straight under suitable tension and as close as convenient to the patient's body, indicates the centre line of the platter from centreboard 29 to head. It thus provides a relatively inexpensive device aiding in detailed positioning of the patient against either obvious physical features or marks 33, perhaps tattoos, at, say, super sternal notch (SSN), umbilicus and pubis. This positioning is thus potentially easily reproducible. It will be appreciated however, that since the cord 31 is not in intimate contact with the patient there is still the potential for parallax error. It is recommended that light beams, perhaps lines of laser light, projected from the machine in use or the ceiling of the room, should be used in conjunction with cord 31 for minimum error. Advantageously the cord 31 is made of material which will appear on X-ray shadowgraphs or CT pictures taken, to indicate the centreline but it must also not be so dense as to cause artefacts on the picture.

Most elastic cords will be suitable.

The centreboard 29 may also be provided with movable rests 34 against which the patients feet may be placed or held.

The centreboard 29 is shown in more detail in the plan, side elevation and end elevational views of Figs. 19a, 19b, and 1 9c respectively. At the foot end the board is in this example fixed by a U-section 35 fitting over a post 36. The post fits in this example into an extension board 37 fitted at the foot of platter 3. The extension is not, however necessary.

At the other end the board is fitted by a post 38 fitting into platter 3 and is held by an aluminium block 39 to match the height in crease from extension 37.

It will be appreciated that it is the practice to make the platter internally of a light weight, radiologically tissue equivalent, material 40. The hole into which post 38 fits is firm but also tissue equivalent. Furthermore a tissue equivalent plug (not shown) is provided to fill the said hole for radiographs using that part of the platter without the centreboard 29. Conveniently several such holes, suitably plugged, may be provided to allow the centreboard 29 to be differently placed for different sizes of patient as an alternative to moving the upper or lower thorax devices. Other forms of positioning of centreboard 29 may be substituted as desired.

In this example fixture 30 is also a post fitting into a tubular hole 41. It may be slid in this hole to adjust the height of cord 31.

However, to avoid too free movement the post 30 and the end 42 of the centreboard, which includes hole 41, are made of a suitable friction material, in this example the nylon known as DELRIN. Making part 42 also of this material reduces discomfort to the patient.

The cord 31 passes through post 30 and passes along a slot 43 in the bottom of centreboard 29 to be fixed at a movable fitting 44. It will be appreciated that if the distance between posts 30 and 32 is varied for smaller or larger patients, the position of fitting 44 may be adjusted to correspondingly vary the length of cord 31 stowed beneath the centreboard and thus to maintain the correct tension (typically about 21 b is suitable).

The arrangement of post 30 is shown in more detail in the plan, side and end elevational views of Figs. 20a, b and c respectively. It can be seen from Fig. 20b, how the cord 31 passes right through the post 30.

Also shown is a hinged part 45, which generally lies flat along the centreboard, which can be used to extract post 30 if it is inserted far into hole 41.

Although the centreboard has so far been illustrated in terms of the lower thorax position, it is, of course, applicable to the upper thorax device, as shown in side elevation and plan in Figs. 21a and 21b, using the same references numerals as in the other Figures.

Other positioning aids may be combined with these devices. For example pads 46, may be included to raise the patient's knees slightly to aid gripping the centreboard. Also variable sizes of lumbar support 47 may be used.

Preferably one size is determined with a suitable measurement on the first occasion the positioning devices are used and the same size is used on all subsequent occasions to hold the spine at the same height. Such supports tend to reduce twisting of the body.

It will be apparent that other constructional and fixing arrangements of centreboard 29 may be used without departing from the principles of the invention.

It will be apparent that the device of the invention can be used with other stages of the therapy procedure, such as cast making. Furthermore it can be varied by these with the appropriate skills to suit a particular apparatus with which it is to be used or to suit the individual requirements of a particular patient.

As examples of the scope of variation possible, Fig. 22 shows a modified lower thorax device in which the patients arms are raised to a position in which they protrude to a lesser extent beyond the platter sides. This allows examination to extend towards the upper thorax if desired and in fact allows greater penetration into the narrower CT apparatus than does the embodiment illustrated hereinbefore.

Similarly Fig. 23 shows an upper thorax and shoulder alignment device with a modified hand grip arrangement which may prove to be more comfortable for some patients.

This arrangement also allows easier entry into the narrower CT apparatus. For a further provision against movement a strap 48 holds the patients arms firmly and, by passing across the forehead, assists in restraining the head.

Claims (19)

1. A patient positioning device for reproducibly positioning a patient in successive stages of radiotherepy planning procedures, the device comprising, in association with respective platters on which the patient is supported for each such procedure, a support for the patient's head and and at least one positioning member against which the patient's hands may be placed in substantially the same position at each said procedure.

2. A device according to Claim 1 in which the positioning member is placed relative to the head support in such a manner as to extend the patient's arms to reach above the head.

3. A device according to either of the preceding claims in which at least one positioning member comprises at least one hand grip adapted for the patient to hold in an identical manner at each said procedure.

4. A device according to any of the preceding claims including supports for the patient's elbows.

5. A device according to Claim 4 in which said supports are adjustable.

6. A device according to Claim 5 including means for setting said supports in reproducible positions.

7. A device according to any of the preceding claims, including means for setting the patient's head in a reproducible position.

8. A device according to any of the preceding claims in which the positioning of the head support and the at least one positioning member are arranged to reproduce the posi tion of the patient's lower thorax.

9. A device according to any of claims 1-7 in which the positioning of the head support and the at least one positioning member are arranged to reproduce the position of the patient's upper thorax.

10. A device according to Claim 9 in which the said support and positioning member are also placed so as to reduce the patient's width at the shoulders.

11. A device according to any of the preceding claims including a member arranged to reproducibly position the patient's legs.

12. A device according to Claim 11 in which said leg positioning member comprises a board member placed between the patient's legs.

13. A device according to either of Claims 11 and 12 including a centreline marker extending between the head positioning member and the leg positioning member to mark the centreline of said patient.

14. A device according to Claim 13 in which said centreline marker is a tensioned cord.

15. A device according to either of Claims 13 and 14 in which the centreline marker is radioopaque.

16. A patient positioning device for reproducible positioning of a patient in successive stages of radiotherapy planning procedures, the device being substantially as herein described with reference to the accompanying drawings.

17. A method of reproducibly positioning a patient for successive stages of radiotherapy planning procedures, the method including positioning the patient's head and hands in the same position for each said stage.

18. A method according to Claim 17 including positioning the patient's legs in the same position for each said stage.

19. A method of reproducibly positioning a patient for succesive stages of radiotherapy planning procedures, the method being substantially as herein described with reference to the accompanying drawings.