JP2002516136A - X-ray image forming device - Google Patents

Abstract

(57) Abstract: An X-ray imaging apparatus including a movable C-arm (16) having an X-ray source (12) at one end and a linear camera array (14) at the other end is provided. The arm is driven relative to the patient and scans the patient's body with a narrow fan beam. A position encoder (150) generates a timing signal which is used to synchronize the movement of this arm with the imaging circuit to generate a relatively large object image signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus that can be used for, for example, radiology.

[0002] Conventional X-ray imaging devices have limited versatility and are generally not suitable for use in continuous whole-body imaging of a patient at a resolution sufficient for diagnostic purposes. South African Patent No. 93
No./8427 is designed to facilitate full-body imaging of a subject to detect smuggled articles such as diamonds hidden in the subject's body, while at the same time minimizing the radiation dose received by the subject. Described system.

[0003] It is an object of the present invention to provide an alternative device that can produce diagnostic-quality images over a range of image areas from small to whole body with relatively low radiation doses and most conventional procedures. .

According to the present invention, there is provided an image forming apparatus, comprising: a radiation source for generating an imaging beam; an imaging device for generating a signal representing an image of a subject on which the imaging beam is incident. A supporting member for supporting the radiation source and the imaging means in a predetermined spatial relationship; a driving means for moving the supporting member in a first direction with respect to the subject; and generating a signal representing the image. Motion sensor means for generating a signal related to the speed of motion of the support member for use by the imaging means when performing the imaging.

The movement sensor means includes a position encoder arranged to detect movement of the support member and to generate a clock signal for the imaging means having a frequency related to the speed of movement of the support member. May be. The position encoder may be a linear encoder arranged to detect relative linear movement between the support means and the frame.

The image forming apparatus includes a clock signal adjusting unit arranged to process a clock signal generated by the position encoder, and an operation of the imaging unit in response to the processed clock signal. Circuit for generating a digital timing signal for synchronizing with the movement of the robot.

The image forming apparatus includes a plurality of cameras arranged end-to-end and having respective outputs, and a front-end processor for generating a combined output signal by combining the camera outputs. , And a signal processor for generating image data from the combined output signal. The image forming apparatus may include mounting means for mounting the support member to the drive means such that the support member is rotatable about an axis coinciding with the first direction.

[0008] The radiation source is adapted to generate a relatively narrow beam in a first direction of movement of the support member, but relatively wide in a second direction perpendicular to the first direction of movement. The beam is preferably an x-ray source that scans the full width of the subject in one pass. The radiation source may include a light source arranged to generate a visible light beam consistent with the imaging beam to facilitate alignment of the imaging beam with a portion of the subject to be imaged.

An X-ray translucent mirror may be positioned in the path of the imaging beam and oriented to direct light from the light source along a path substantially coincident with the X-rays passing through the mirror. Good. A lens may be placed close to the light source to spread the light into a fan beam whose shape corresponds to the imaging beam.

The radiation source may move in a second direction of movement to adjust the width of the beam, X
An adjustable shutter comprising at least one shutter member of a line opaque material may be included. The shutter preferably includes a pair of shutter members that can move vertically within the track. Preferably, these shutter members can move independently.

The image forming apparatus may include a main body supporting means including a frame for supporting the main body, and a positioning means for maintaining the frame at a fixed position with respect to the supporting means during operation of the apparatus. Good. The frame preferably forms a trolley, and the positioning means preferably includes electromagnetic clamping means arranged to operate during operation of the device. The electromagnetic clamping means may include a pair of arms each supporting an electromagnet arranged to hold a complementary portion of the trolley.

[0012] The clamping means preferably includes a proximity switch associated with each electromagnet and arranged to activate the electromagnet only when the trolley is in close proximity to the clamping means. The clamping means detects the position of the support surface of the trolley during use, and if the support surface is improperly positioned during use, the drive means reacts and disables the drive means. Preferably, it includes a sensor for generating a signal to be generated. The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which:

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1-3 show three different views of a prototype of an X-ray imaging or scanning device of the present invention. The apparatus includes a head 10 having an X-ray source 12 that emits a narrow, fan-shaped beam of X-rays toward a detector device 14. The X-ray source 12 and detector 14 are supported on opposite ends of a generally semi-circular or C-shaped curved arm 16. A frame 18 mounted on the wall 8 or other fixed structure forms a pair of rails 20 with which a motorized drive mechanism 22 engages to linearly move the arm back and forth in a first axial direction of movement. Drive. Moreover, the drive mechanism includes a housing 24 in which the arm 16 rotates the x-ray source and detector about an axis parallel to a first direction of movement of the mechanism. It can be moved by a drive mechanism.

A typical application of the image forming apparatus of the present invention is in a radiation facility as shown in FIG. This image forming apparatus is shown, for example, as being located at a corner of a room that is a resuscitation area or a trauma room in a hospital. Alternatively, the device may be in a hospital radiology department or other location. Located near the imaging device is a local positioning console 26, which allows the operator to set the required viewing parameters (eg, angle of arm 16, start and stop position, and width of the area to be X-rayed). Can be set.
A main operator console 28 is provided behind the shield 30 and is used by the operator to set up the required radiographic procedures. The radiograph is used to operate the image forming apparatus to scan the subject 32, which is supported on a dedicated trolley 36 (see below), so that an operator can determine whether a good image has been taken. Is displayed on the screen of the console 28. A high resolution monitor 34 is provided for diagnostic observation and is located so that attended clinical staff can review the radiographs taken. In addition, there is provided a console 38 which forms part of a standard radiology information system, which allows the observation and recording of images.

The apparatus of FIG. 4 provides a rapid, large area X-ray image of an injured patient,
Designed for use in the resuscitation room of the trauma unit. Once the patient has settled, the patient can be conveniently placed in place, scanned, and the casters rolled out for further treatment, and the resulting radiograph is virtually instantaneously displayed on the diagnostic screen. appear. The low x-ray dose handled by this device reduces the risk of radiation exposure of staff and patients. Next, various functional aspects of the device will be described in detail. In order to take advantage of the rapid x-ray imaging potential of the present invention, a special trolley 36 with low table top x-ray attenuation is provided, which is adjustable in height and which allows the arm of this scanning device to operate during operation. An electromagnetic positioning device is provided for positioning with respect to 16.

FIGS. 6 and 7 show the trolley and the electromagnetic positioning device, respectively.
This trolley has a lower C-shaped frame with a main frame member 42 and end members 44 and 46. Centrally mounted on members 44 and 46 are respective upright telescoping struts 48 and 50, which support table top 52. A raising / lowering mechanism is provided to tilt or raise the table top 52 so that it can then be clamped in place and the casters 54 allow for easy movement of the trolley. As shown in FIG. 7, the positioning device includes a pair of arms 56 and 58 mounted below the main frame 18 of the device. These arms 56 and 58 are mounted so as to be rotatable about a vertical axis XX, and are provided with detents to hold the arms in the position shown in FIG. 7, i.e. at right angles to the scanning direction. Although this detent mechanism positions these arms firmly in place, collisions with the trolley during a scanning operation or obstacles between the movable C-arm and the trolley may cause these arms to pivot, potentially resulting in potential safety problems. In order to eliminate points, less force is required to pivot these arms from their extended position.

At each end of the arms 56 and 58 there is an electromagnetic clamping and positioning mechanism, which in each case has a pole piece or contact surface with trolley frame members 44 and 46
And an electromagnet 60 disposed in contact with a complementary ferromagnetic plate 122 attached to each end of the electromagnet 60. The positioning mechanism on the arm 56 includes horizontal positioning means in the form of a pair of angled surfaces 124 and 126 on opposite sides of the electromagnet 60 such that when the plate 122 engages the electromagnet 60, The ends of the trolley frame member 46 are complementarily shaped so as to be positioned axially (ie, with respect to the scanning direction) with respect to the frame, while still maintaining the correct distance away from the device. The positioning mechanism at the end of the arm 56 has only a flat positioning surface surrounding the electromagnet 60 and serves to position the other end of the trolley at the correct distance from the scanning device.

Associated with each of the clamping / positioning mechanisms is a proximity switch 130 that operates when the trolley engages the positioning mechanisms. When the trolley is correctly positioned, these proximity switches issue a "trolley complete" signal so that the control system of the device can automatically activate these electromagnets to hold the trolley in place. The force exerted by these electromagnets is sufficient to hold the trolley in place in normal use, but light to moderate forces acting on the trolley or mechanical arms 56 and 58 in the scanning direction may cause these magnetic forces. Weak enough to release clamp. Moreover, these electromagnets can be deactivated via this control system.

At the ends of the arms 56 and 58 is an upward pointing ultrasonic distance sensor 132 arranged to sense the position of the trolley tabletop 52 relative to the arms 56 and 58. The output signals of these sensors 132 are used to ensure that the table top is at its highest position, which is necessary to ensure safe rotation of the C-arm. The prototype system of the present invention requires vertical adjustment of the trolley table top to the scanner, but it may be alternatively or optionally provided with active vertical adjustment of the scanner frame. Would.

The C-arm 16 is supported and controlled by the drive and support mechanism shown in FIGS. 10 and 11, and is clamped in place during use by the electromagnetic clamp assembly shown in FIG. The interrelationship of these mechanisms is schematically illustrated in the block diagram of FIG. FIG.
As shown, the C-arm 16 has two sets of rollers 62 and 6 within the housing 24.
4 is slidably supported. The rollers 62 are non-adjustably mounted on a base plate 66 and run against the inner surfaces of respective flanges 68 formed on the inner edge of the C-arm. Rollers 64 are adjustable to ensure correct tracking of the C-arm in housing 24 and to adjust for backlash in the movement of the arm. FIG. 10 shows this C-arm drive mechanism. This drive device has a pinion gear 7
2 is included. The segment gear 74 is attached to the inner edge of the C-arm 16,
It is fixed between the respective flanges 68 so that the rotation of the pinion gear 72
Move the arm relative to this housing. Alternatively, a chain drive can be used. FIG. 11 is located in a housing 78 bolted to the housing 24 and arranged to effectively clamp the sides of the C-arm 16 when biased to hold the C-arm 16 in a desired position. 6 shows the applied electromagnetic clamp 76.

Once the trolley 36 is in place, images in the front-back and back-front directions can be taken. If you need any radial images, including side images,
Raise table top 52 to its maximum height. Once the table top is at its uppermost position, the C-arm 16 can be rotated to any angle between the front-rear position and the side position. Once positioning is complete, it is electromagnetically clamped to scan it. The shape of this arm forms a cavity large enough to surround the patient's body supported on the trolley 36. Arm 16 is clamped or held in place with respect to housing 24 of the drive, and trolley 36 is also securely positioned to operate the linear drive so that the device performs a horizontal linear scan. As the x-ray source and detector move from the start to the end of the scan, a narrow fan-shaped beam of x-rays illuminates the trolley tabletop or thin strip across the width of the patient's bed.

The normal position of the operation of the apparatus is a position where the X-ray source 12 is at the highest position so that an AP (front-back direction) whole body image can be taken. Arm 16 is used for another screen,
Can rotate to side view. As shown in FIG. 3, an upright chest image is also possible by rotating the arm by 90 °. In this prototype device, the thickness (in the scanning direction) of the X-ray beam on the detector is:
Determined by a thin slit collimator preset at less than 10 mm at the factory. Mounted before the slit is a beam width controller that determines the width of the rectangular strip to be exposed to X-rays. This width is adjustable from a minimum of 100 mm to a maximum of 680 mm of exposed area, in addition to an offset from the bed centerline.

The X-ray beam width controller 80 shown in FIGS. 12 to 15 controls not only the offset from the center of the X-ray image but also its width by adjustment of the operator. This reduces unnecessary exposure to the patient. It is also useful to limit the beam width to the X-ray camera to avoid saturation. The beam width controller comprises two elongated shutter elements 82 and 84 made of a radiopaque material. These shutter elements 82 and 84 have a T-shaped cross section and slide in a channel 86 controlled by a respective rack and pinion mechanism. Each rack and pinion mechanism includes a control wheel 88 coupled to a shaft 90 having a pinion gear 92 at an end. The gear 92 engages a toothed rack at the upper edge of the shutter element, so that rotating the handle moves the shutter element linearly from end to end. These shutters can be moved independently so that both the beam width and its offset relative to the centerline of the trolley tabletop can be controlled.

Referring to FIG. 16, the X-ray source includes an X-ray tube, an X-ray shutter, a coincidence light source, a collimator, and an X-ray beam width controller. The X-ray tube 100 generates X-rays,
It is driven by a high voltage power supply. The tube uses a rotating anode and is at a high power rating for more effective dissipation of heat from the anode. The x-ray shutter 102 controls exposure of the patient to x-rays when the tube is powered but all operating conditions are not met, for example, during start-up or when increasing the scanner arm speed. prevent. It also acts as a security device for this control system. X-ray filter 104 ensures that this spectrum is filtered to the correct "hardness" by removing "soft" or low energy x-rays that are absorbed by the patient's body and do not contribute to image quality. The light source 106 and the X-ray translucent mirror 108 provide a light beam incident thereon in the same shape as the X-ray beam. This informs the operator of the size and position of the X-ray beam. The x-ray collimator 110 blocks unwanted divergent x-rays that are detrimental to image quality, promote diffusion, and unnecessarily increase dose to the patient.

The light source / mirror device of FIG. 16 is shown in detail in FIG. The light source typically includes a laser diode that produces a single beam of coherent light. Associated with the laser diode is a lens arrangement that spreads the light into a fan beam with an arc greater than 34 °. This fan beam of visible light is directed to mirror 108, which is a fixed translucent x-ray mirror disposed in the x-ray path of x-ray source 12, so that the visible light beam coincides with the x-ray beam. The distance A from the light source 106 to the mirror 108 is
It is made equal to the distance B from the X-ray source 12 to the mirror 108. By ensuring that the focal spot sizes of the X-ray source and the light source are equal, that they are perpendicular to each other, and that the angle of mirror 108 is 45 ° in the direction of both sources.
This visible light sector is matched with the X-ray beam. This allows visual confirmation of the position of the X-ray beam during use. The mirror 108 can be made of a suitable material, such as aluminum, to replace the x-ray filter 104.

The X-ray detector 14 is schematically illustrated in FIG. 18, and includes a plurality of X-ray cameras 114,
Each of them has an associated CCD, joined end-to-end together to create an elongated linear camera
It has a headboard 116. The output of each headboard 116 is sent to a front-end processor 118, which has a fiber optic data link output 120. These multiple X-ray cameras are spliced together to obtain a composite detector about 700 mm wide. The gap between these cameras is minimized to about 50 μm to reduce the amount of missing information at the junction. The consequences of human error in the image are removed during image correction performed by the image post-processor. Each X-ray camera 114 detects X-rays transmitted through the patient and converts them to analog electronic output signals. This output signal is amplified by a respective CCD headboard 116 attached directly to the X-ray camera, and the amplified output is sent via coaxial cable to a front-end processor 118, which outputs a separate output to a further signal. Combine into a single combined output signal for processing.

The configuration of a single camera is shown schematically in FIGS. 19a and 19b. This camera is
Includes a scintillator 122, a fiber optic taper bundle 124 and an associated CCD headboard 116. Charge coupled devices (CCDs) are effective at detecting radiation in the visible wavelength range and convert it to an analog electronic output signal. They are not very effective at detecting X-rays and are destroyed by X-ray radiation. Therefore, using a scintillator, X
Converts lines to visible light. These scintillators cover the entire area that X-rays hit the camera. CCDs are limited in size and very expensive. Thus, this image area is covered by a plurality of CCDs, the total number of which is determined by a cost-resolution trade-off. An optical fiber tapered bundle is used to reduce the image size and project the image from the scintillator onto a separate CCD.

These CCDs operate in a time-delayed and integrated mode to gain maximum benefit from drift scanning operation. These CCD pixels are scanned by the scanning speed of the C-arm 16 (
(See below), and send the clock at a speed synchronized with it. The CCD comprises a plurality of rows of pixels. The pixel rows are oriented perpendicular to the scanning direction. The electrons generated by the photons are fully integrated into the pixel during the time delay between the pixel's phase clocks and are transferred to the next row by these phase clocks. In each next row, additional electrons are generated by the X-rays, thereby extending the image exposure period. Image smearing is prevented by clocking the pixels according to the mechanical action, as described above. Therefore,
The signal is integrated over the entire thickness of the x-ray fan beam, and there is virtually no costly x-ray signal.

FIG. 20 shows the electronic circuit of the detector 14. A front end processor (FEP) 118 is mounted on the C-arm 16 close to the CCD headboard. The cable from the CCD head board is this FEP
This ends in another amplification / buffering step. After this stage, a standard correlation twice extraction (C
DS) procedure is performed on this signal. The CDS is performed using digital timing signals generated locally for the FEP in a digitally programmable block 134 comprising one or more field programmable gate arrays (FPGAs) and the required memory. These timing signals are synchronized with the rest of the system by using the C-arm encoder clock 136. The physical movement of the C-arm generates this clock by the position encoder 150. The encoder used in this prototype system was a sealed linear encoder of the type that included a light source, a lens, and a scanning reticle positioned adjacent to and in relative movement with a finely graduated grating. In this prototype, an encoder from HEIDENHAIN was used.

A pair of linear gratings, each having a resolution of 20 μm and moving 90 ° with respect to each other, are scanned simultaneously by the LED light sources, resulting in an effective 5 μm resolution. The output of the encoder is an encoder clock signal 136, which is used to synchronize the rest of the system. The C-arm encoder clock 136 does not need to be adjusted depending on the format of the output from the C-arm motion encoder. This clock is TTL
Must be compatible at the level. Conditioning clock circuit 138 ensures this. The gain through this analog path is variable to provide for different intensities due to different dose levels required for different procedures. This gain is controlled by a control signal from a controller.

After the CDS procedure, the analog signal is converted by an analog-to-digital converter to a 14-bit digital bus (including image data). This operation is repeated as many times as the number of CCDs to use the CDS and A / D converter circuit. This 14-bit bus is then sent to the programmable digital block. In this block, another digital signal processing function is performed on the image data. These functions include pixel binning. The programmable nature of this block is D
An SP function is added to allow parameters to be changed at a later stage. This image data is also multiplexed onto one 14-bit bus before sending it to the fiber optic link interface. This programmable digital block also generates a CCD drive signal. These signals are level-shifted to appropriate levels for driving the CCD. This CC
The D operation voltage is generated by an external power supply. Next, these CCD drive signals and operating voltages are sent to the CCD head board via an appropriate cable.

There is also a connector 144 on this PCB that communicates with the power supply unit. This covers the entire power demand of this circuit. A controller 142 controls the different modes of operation of this FEP and performs built-in test purposes. It monitors voltage levels and basic functions on this PCB. The state is returned to the user interface via the RS232 cable 146 and reported. It also controls the different configurations of the programmable digital block 134. This is done by configuring the FPGA differently each time a different operation mode is needed. This is necessary for different scan speeds and to make alignment corrections to this data. An X-ray beam width control and a feedback signal 140 from the shutter are also sent to the controller 142. The controller 142 executes using a microprocessor.

The X-ray intensity feedback is converted into a digital signal. This signal is sent to a digital signal processing (DSP) block, where it is processed. The processed data is
It can be used by the programmable digital block 134 and the image preprocessor to correct for X-ray intensity variations. Oscillator 148 provides the oscillator frequency which is a very stable clock frequency over one scan period. Next, the clock signal 136 from the C-arm encoder is compared with this frequency. The result of this comparison indicates a variation in speed from the C-arm. The result can then be used to correct for non-uniform illumination caused by speed fluctuations. This oscillator frequency is also used to clock the electronics when the C-arm is not moving.

[Brief description of the drawings]

FIG. 1 is a pictorial diagram of an image forming apparatus according to the present invention.

FIG. 2 is an end view of the device of FIG.

FIG. 3 is a view similar to FIG. 2, showing an alternative use of the device.

FIG. 4 is a pictorial diagram of a radiation facility incorporating the device of the present invention.

FIG. 5 is a schematic block diagram showing main mechanical parts of the device.

FIG. 6 is a pictorial view of the trolley of the patient support and positioning system of the device.

FIG. 7 is a partial pictorial view of the positioning and sensing components of the patient support and positioning device.

FIG. 8 is a schematic block diagram of a mechanical device of a main support arm of the device.

FIG. 9 is a schematic sectional view of a part of a roller mechanism of the support arm.

FIG. 10 is a schematic sectional view of a part of a drive mechanism of the support arm.

FIG. 11 is a schematic sectional view of the clamp device for a support arm.

FIG. 12 is a schematic explanatory view of this X-ray source beam width adjuster.

FIG. 13 is a pictorial diagram, an end view, and a side view of the beam width adjuster mechanism, respectively.

FIG. 14 is a pictorial diagram, an end view, and a side view of the beam width adjuster mechanism, respectively.

FIG. 15 is a pictorial diagram, an end view, and a side view of the beam width adjuster mechanism, respectively.

FIG. 16 is a schematic explanatory diagram of the configuration of the X-ray source.

FIG. 17 is a schematic diagram of a light source assembly related to the X-ray source.

FIG. 18 is a schematic block diagram of an X-ray detector of the device.

19a is a schematic illustration of an individual X-ray camera of the detector of FIG.

19b is a schematic illustration of an individual X-ray camera of the detector of FIG.

FIG. 20 is a schematic block diagram of an electronic control circuit of the device.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR , BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS , JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZA, ZW (72) Inventor Boisen, André Rodeport, South Africa Janet Street, Florida 40 (72) Inventor Van Roy, Paul Randburg, Windsor Glenn, South Africa, Alend Avenue 8 (72) Inventor de Jaguar, Garhardas South Africa Cape, Newlands, Hiddiff Avenue 2 (72) Inventor Benningfield, Stephen James Barthveld Avenue, Constantia, South Africa 7 (72) Inventor Bau , Peter Coat, Pinelands, South Africa, Woodlands Close 1 (72) Inventor Bowie, Giran Pinelands, South Africa, Pinelands, Tecoma Way 8 F term (reference) 4C093 AA01 AA19 CA50 EA12 EA17 EB12 EB18 EC16 EC33 ED01 FA19 FA43 FA46 FA54

Claims (18)

[Claims] 1. An image forming apparatus, comprising: a radiation source for generating an imaging beam; an imaging means for generating a signal representing an image of a subject on which the imaging beam is incident; A support member for supporting a predetermined spatial relationship; a driving means for moving the support member in a first direction with respect to the main body; and a driving means for using the imaging means when generating a signal representing the image. Motion sensor means for generating a signal related to the speed of motion of the support member. 2. The image forming apparatus according to claim 1, wherein said movement sensor means detects movement of said support member and has a clock signal having a frequency related to a movement speed of said support member for said imaging means. An apparatus including a position encoder arranged to generate the position encoder. 3. The image forming apparatus according to claim 2, wherein said position encoder is a linear encoder arranged to detect a relative linear movement between said support means and said frame. 4. An image forming apparatus according to claim 2, wherein said clock signal adjusting means is arranged to process a clock signal generated by said position encoder, and is responsive to said processed clock signal. And an apparatus including a circuit for generating a digital timing signal for synchronizing the operation of the imaging means with the movement of the support member. 5. An image forming apparatus according to claim 1, wherein said image forming apparatus comprises a plurality of cameras arranged end-to-end and having respective outputs. An apparatus including a front-end processor for combining these camera outputs to generate a combined output signal, and a signal processor for generating image data from the combined output signal. 6. An image forming apparatus according to claim 1, wherein said support member is rotatable around an axis coinciding with said first direction. An apparatus including attachment means for attaching to the drive means. 7. An image forming apparatus according to claim 1, wherein said radiation source is relatively narrow in a first direction of said movement of said support member, but said radiation source is relatively narrow in said first direction of said movement of said support member. An apparatus which is adapted to generate a relatively wide beam in a second direction perpendicular to one direction, so that the beam is an X-ray source which scans the full width of the subject in one single pass. 8. An image forming apparatus according to claim 7, wherein said radiation source has a visible light beam coincident with said imaging beam for facilitating alignment of said imaging beam with a main part to be imaged. An apparatus comprising a light source arranged to generate a light source. 9. An image forming apparatus according to claim 8, wherein an X-ray translucent mirror is disposed in a path of said imaging beam, and light from said light source substantially coincides with X-rays passing through said mirror. A device that directs this mirror to guide it along a path. 10. An image forming apparatus according to claim 9, wherein a lens is arranged in proximity to said light source to spread the light into a fan-shaped beam whose shape corresponds to said imaging beam. 11. An X-ray opaque material according to claim 7, wherein said radiation source is movable in a second direction of movement to adjust the width of said beam. An adjustable shutter comprising at least one shutter member. 12. The image forming apparatus according to claim 11, wherein said shutter includes a pair of elongated shutter members movable vertically in a track. 13. An image forming apparatus according to claim 12, wherein said shutter members can move independently. 14. An image forming apparatus according to claim 1, wherein said frame includes a frame for supporting said main body, and said frame is supported during operation of said apparatus. An apparatus including positioning means for maintaining a fixed position relative to the means. 15. An apparatus according to claim 14, wherein said frame forms a trolley, and said positioning means includes electromagnetic clamping means arranged to operate during operation of said apparatus. 16. An image forming apparatus according to claim 15, wherein said electromagnetic clamping means includes a pair of arms each supporting an electromagnet arranged to hold a complementary portion of said trolley. 17. An image forming apparatus according to claim 16, wherein said clamping means is associated with each electromagnet and is arranged to actuate said electromagnet only when said trolley is in close proximity to said clamping means. Apparatus including a proximity switch. 18. An image forming apparatus according to claim 16, wherein said clamping means detects the position of said trolley support surface in use, and if said support surface is improperly used in use. An apparatus that includes a sensor for generating a signal that, when positioned, the drive means reacts to disable the drive means.