GB2452065A

GB2452065A - Apparatus And Method For Scanning A Patient and Detecting Patient Movement

Info

Publication number: GB2452065A
Application number: GB0716449A
Authority: GB
Inventors: Timor Kadir; Julian Bernard Hayball
Original assignee: Siemens Medical Solutions USA Inc
Current assignee: Siemens Medical Solutions USA Inc
Priority date: 2007-08-23
Filing date: 2007-08-23
Publication date: 2009-02-25
Also published as: GB0716449D0

Abstract

Patient scanning apparatus and a method is provided in which the patient movement is detected during a first and a second scan type. If the movement is detected as passing a threshold then remedial action may be taken which may include a re-scan. This confers the advantage of ensuring rapid patient throughput as problems with a scan are detected at an early stage. The movement of the patient relative to the patient support may be detected using a plurality of piezoelectric sensors or pneumatic sensors mounted on the patient support. The invention may be used in PET-CT imaging where the first scan is a CT scan and the second scan is a PET scan.

Description

Aiaratus And Method For Scanning A Patient This invention relates to apparatus and method for scanning a patient, in particular, using a Positron Emission Tomography (PET) and another scanning technique such as Magnetic Resonance Imagery (MRI) or Computer Tomography (CT) scans.

PET-CT is a hybrid imaging technology combining a PET and a CT scan in one machine. The CT scan provides anatomical information and the PET scan functional information. It is desirable for the scans to be accurately registered when combined to give an accurate basis for subsequent diagnosis.

The time required for producing a PET scan is considerably longer than that required for producing a CT scan. A CT scan may be carried out in a few minutes whereas a PET scan can take over thirty minutes. Movement of the patient during the scanning process can cause difficulties when the two scans are later registered. It may be difficult or even impossible to achieve accurate registration. As a result of this a rescan may be necessary causing significant disruption to the processing of patients. Furthermore, a rescan increases the patient's exposure to radiation which is undesirable. A subsequent PET rescan may be of poorer quality due to the decay in the radiopharmaceutical used.

As scans are costly, financial constraints may mean that a re-scan is not possible and the clinician may have to rely on a poor quality scan for a subsequent diagnosis.

Usually the CT is the first scan to be made in the protocol for scanning a patient. Then the PET scan is performed. PET scanners only have a limited field of view and it is therefore necessary to move the patient through a number of so called "bed positions" and for a scan to be carried out at each position. A patient will therefore have to remain in a particular position for many minutes.

The data from the scans is then processed and "reconstructed" with the PET scan and the CT scan displayed side by side to a technician. The technician then sends the data to a review workstation where the two scans are displayed and checked for quality before the patient is allowed to exit the scanning process. The images are then sent to a physician for consideration. The time elapsed from the scan to the physician viewing the output may be thirty or forty minutes. If errors or quality problems are observed at this stage and they require a rescan then the disruption to the process for the patient and other patients may be considerable. In particular, for the PET scan the radiopharmaceutical may have to be re-administered and the patient required to wait for an hour or so to allow it to be evenly absorbed. Often it is necessary to schedule the patient for another scan rather than disrupt the schedule for that particular day.

Delays in the throughput of the scanning process thus produce significant problems for the patient and the clinicians.

The present invention arose in an effort to alleviate these problems.

According to the invention there is provided patient scanning apparatus having a scanner, a patient support on which in use a patient is positioned, means to provide relative movement between the patient support and the scanner to enable scans to be performed by the scanner at a number of positions along the patient's body, patient movement monitoring means to monitor for the moment of the patient relative to the patient support, a patient movement analyser to compare the patient movement to a predetermined movement and to provide an alarm where a particular movement state is indicated by the comparison.

The patient movement analyser may compare a pattern of movement with a predetermined movement pattern but in the the preferred embodiment the movement is compared with a threshold.

By movement state it is meant whether or not the patient's movement meets the criterion for a satisfactory scan. Particular patterns of movement may be stored selectable to be applied depending upon the use for the scan. This may for example, detect movement over the patient and to accept a greater degree of movement in certain regions (not of particular interest) than in areas which are regions of interest for the subsequent diagnosis.

The scans may be of the same or of different types. For example, the scans may be PET only, SPECT only, MR or combinations of these. In the specific embodiment there is a first scan type and then a second scan type.

Preferably, the patient movement analyser includes a sensor to detect the patient movement. In the described embodiment, which is preferred, the sensors comprises pressure sensors mounted on or in the patient support to determine pressure applied by the patient at sensed points over the patient support.

The preferred type of sensor is a piezoelectric sensor which confers the advantage of durability in use and exposure to the scanner.

Other types of sensor can be air pressure sensors which are preferably provided as a matrix of points distributed over the support. Air displaced by the patient movement may then be conducted by tubing to pressure sensors outside of the scanning station. This confers the advantage that pressure sensors of a type potentially unsuitable for location within a scanner may be used.

Alternatively, the patient movement monitoring may be achieved by image capture and recognition using a camera having a field of view of the patient. In this process an image is captured and compared with a previous image to determine the amount of movement.

The movement may be analysed to determine whether a particular region exceeds a certain threshold of movement or alternatively a measure of the movement of the whole patient may be compared.

The invention also provides a method.

A specific embodiment of the invention will now be described with reference to and as illustrated by the drawing of which: Figure 1 shows a scanning arrangement including apparatus in accordance with the invention; Figure 2 shows a block diagram of part of the scanning arrangement; and Figure 3 is a block diagram showing the steps carried out by the scanning arrangment.

As is shown in figure 1 a scanning arrangement generally indicated at 1 comprises a Positron Emission Tomography scanner 2 comprising a scanning doughnut 3 having a field of view over body length 4, a data capture processor 5, an image re-constructor 6 which converts the data to an image representing a "slice" through the patient in the field of view. The reconstructed image data is output to an image combiner 7.

The scanning apparatus also includes a Computer Tomography scanner doughnut 8 having a field of view of the patient length indicated by arrow 9. The data gathered is passed to a data capture processor 10 which outputs it to a CT image re-constructor 11.

The reconstructed CT image is passed to the image combing system 7 from where it is passed to a computer VDU 12 for display to an operator 13.

Both the CT and the PET scanners operate in accordance with well known principles and will not be described further.

The scanning arrangement further includes a patient support which in this case is a rectangular bed 14. The bed 14 has buried within the padding a plurality of sensors 15 which, in this case, are evenly distributed. (In alternative embodiments they may have a distribution to favour certain areas.) The sensors 15 are piezoelectric sensors that operate on the beam deflection principle. The patient's weight bearing down on the sensors results in deflection of a beam of piezoelectric material resulting in the generation of a small electrical current. The current is representative of the beam deflection and hence the applied weight. The sensed currents are passed via a bus 16 to a patient monitoring system processor 17. This is a suitably programmed microprocessor which analyses the signals from the sensors and determines from them the amount of patient movement. The determined movement is compared with a movement threshold held in memory 18 and if the threshold is exceeded an alarm state is passed to an alarm system 19. In this case the alarm system displays an alarm state by a flashing light and audible alarm to the operator 13. Alternatively, an alarm signal may be output to the computer 12 via output 20.

The patient support is connected to a motor and rack and pinion mechansim (not shown) to provide relative movement of the support along the axis of the scanner.

The way in which the movement is analysed to determine the crossing of a threshold may be as a result of overall movement of the body using the outputs collectively or over certain parts of the body, for example, those within the field of view of the scanner or certain parts of the body that are of interest. For example, the patients head may be that part of the body that is of most interest for the diagnosis of the patient. In such a case then sensor outputs from sensors over region 21 are analysed to determine if the movement has passed a threshold.

Figure 2 shows the patient motion sensing system in greater detail. The sensor signals are captured by the processor and the movement of the patient at the location of each of the sensors 15 is determined. The determined motion is stored in a sensed motion table 18a in memory 18. The operator enters via keyboard input 22 a region of interest, for example sensors 21. The region is held in memory partition 18c. A threshold value for the movment is also set at the input 23 and held in the memory 1 8b.

The processor then performs the motion determination for the region of interest (this could be all the sensors or some). To do this it accesses the region of interest in the memory 18c and accesses the appropriate data from the sensed motion table 18a.

That data may be processed in a number of ways, for example, an average may be used but, in this case, the maximum sensed motion by any sensor in the region is compared with the threshold value held in memory 18b. In the event that the threshold is crossed then the alarm signal is sent to alarm systeml9.

In response to the alarm, the operator may halt and restart the scanning process or make a judgement as to whether or not the scan ning process may continue.

The scanning process will flow be further described with reference to figure 3.

In a first step 31, a point of interest and a movement threshold is entered by the user 13 at the computer terminal 12. The point of interest may be determined by selection of a part of the body represented on the screen using a mouse and keyboard. The movement threshold may be similarly selected. Alternatively, a number of scan type options may be displayed for selection and pre-programmed parameters then selected.

For example, scan types "Brain", "Chest", "Colon" may be displayed and select of say "Brain" will load a point of interest centred on the patient's head and a movement threshold for movement of the upper portion of the body.

In the next step 32, scan one, the CT scan, is started. Motion monitoring is implemented at the same time by the patient monitoring system processor 17 in conjunction with the sensors 15.

In step 33, consideration is given as to whether or not the motion of the patient has exceeded the threshold at the point of interest input at step 31. If the movement has crossed the threshold then an alarm is output and remedial activity is carried out at step 34. The remedial activity will include advising of the patient of the need to perform a repeat scan and a request to the patient to remain still. The process then returns to step 32 and scan I repeated.

If scan I has satisfied the movement criteria, then scan 2, the PET scan, is initiated in step 35. Again patient movement is monitored and analysed by the patient monitoring system processor 17. The scan is carried out and a decision made in step 36 as to whether or not the movement of the patient has crossed the threshold at the point of interest. If the threshold has been crossed then and alarm is given and remedial activity is carried out at step 37. This will again involve a request to the patient to remain still and the process returns to step 35 for a repeat of scan 2.

If the movement is determined to be satisfactory then in a next step, step 38 the data from both scans is passed to further systems and or a clinician.

It will be appreciated that the order of the scans and the type of scans carried out may be varied. For example, the PET scan may be carried out first and the CT scan carried out second. More than two scan types may be involved.

The patient movement may be detected by image analysis of an output of a camera viewing the patient during the scan. This may be used alone or in combination with the patient support sensors.

Claims

Claims 1. Patient scanning apparatus having a scanner, a patient support on which in use a patient is positioned, means to provide relative movement between the patient support and the scanner to enable scans to be performed by the scanner at a number of positions along the patient's body, patient movement monitoring means to monitor for the movement of the patient relative to the patient support, a patient movement analyser to compare the patient movement to a predetermined movement and to provide an alarm when the comparison indicates a particular movement state.
2. Apparatus as claimed in claim 1 wherein the patient movement is compared with a movement threshold and the alarm is provided in response to the threshold being crossed.
3. Apparatus as claimed in claim 1 or claim 2 wherein the patient movement monitoring means comprises a plurality of sensors mounted on the patient support.
4. Apparatus as claimed in claim 3 wherein the sensors are piezoelectric sensors.
5. Apparatus as claimed in claim 3 wherein the sensors are pneumatic sensors.
6. Apparatus as claimed in claim I or claim 2 wherein the patient movement monitoring means comprises a camera and an image processing system to detect from the camera output patient motion relative to the patient support.
7. Apparatus as claimed in any preceding claim when dependent on claim 2 comprising means to enable the input of the movement threshold.
8. Apparatus as claimed in any preceding claim comprising means to enable the input of a point of interest for the scan.
9. Apparatus as claimed in claim 8 wherein the patient movement monitoring means determines patient movement at the point of interest for the scan and compares that movement with the movement threshold.
10. Apparatus as claimed in any preceding claim comprising a scanner operating in accordance with one or more of PET, CT, MR, SPECT scanning techniques
11. A patient scan fling method comprising: providing scanning apparatus for carrying out a first and a second scan; providing patient movement detection means; carrying out a first scan whilst detecting patient movement; comparing the detected patient movement with a predetermined movement; in the event of detecting a non-satisfactory movement state performing remedial activity and repeating the first scan; in the event of detecting the movement being in a satisfactory movement state performing a second scan whilst detecting patient movement; comparing the detected patient movement in the second scan with a predetermined movement; in the event of detecting the movement being a non-satisfactory movement state performing remedial activity and repeating the second scan; and in the event of the detecting the movement being in a satisfactory movement state completing the scanning method.
12. A method as claimed in claim 11 wherein the scans are of the same scan type.
13. A method as claimed in claim 11 wherein the scans are of different scan types.
14. A method as claimed in claim 13 wherein the first scan is a CT scan and the second scan is a PET scan.
15. A method as claimed in any preceding claim wherein a point of interest is input and the movement detected is detected over that part of the patient that includes that point of interest.
16. A method as claimed in any preceding claim comprising a preliminary step of providing a patient support including sensors for determining patient movement.
17. A method as claimed in any preceding claim wherein the sensors are at least one of piezoelectric or pneumatic sensors.
18. A method as claimed in any preceding claim wherein patient movement is determined by image analysis.