RU2181984C1 - Test object - Google Patents

Abstract

FIELD: medicine. SUBSTANCE: device has casing manufactured from rigid material transparent for X- ray and light radiation like polymethyl methacrylate filled with water and metric members. The casing has two chambers separated with piston having the metric members mounted on one of its end face surfaces. The chambers are connected with external pipeline passing through water pump of reverse type. Ruler is attached to the external side of the test object, its scale corresponding to piston movement direction. EFFECT: enabled examination of lacking contrast throughout the material thickness. 2 cl

Description

 The invention relates to x-ray technology, and in particular to devices for evaluating the accuracy of the topometry of internal organs from x-rays.

 Also known is a test object (phantom) made of epoxy in the form of a mammary gland. Inside the test object are metric standards of various shapes and sizes made of radiopaque material [1].

 The test object is designed to control the parameters of X-ray mammography devices and cannot be used to assess the accuracy of X-ray topometry of volume organs, such as lungs.

 Known test object for assessing the quality of x-ray images of the lungs of the company "INOVISION", having a body of x-ray material filled with a substance whose density is close to the density of lung tissue. Inside the test object there are also metric standards from radiopaque material [2].

 The closest technical solution to the proposed one is a test object (water phantom) containing a body of hard X-ray and translucent material filled with water, inside of which metric elements made of X-ray contrast material are rigidly fixed [3, p. 348].

 A well-known test object is designed to assess the quality of digital x-ray images obtained on a computer tomograph, and cannot be used as an accurate device for monitoring the quality of x-ray images obtained by the central beam, for example, when evaluating geometric blur. This is due to the fact that the geometric blur of the image is minimal in the immediate vicinity of the radiation receiver, for example, an X-ray cartridge, and increases linearly with the removal of the structural elements of the subject above the plane of the cartridge. Therefore, a test object designed to study geometric blur, should contain a mechanism for moving the metric elements of the test object relative to its base. There is no such mechanism in the prototype.

 The purpose of the invention is the ability to study geometric blurring of the image over the entire thickness of the object of radiography.

 This goal is achieved by the fact that in a test object having a body made of hard X-ray and translucent material, for example plexiglass filled with water and metric elements, the body consists of two chambers separated by a piston, metric elements are fixed on one of its end surfaces, and the chambers interconnected by an external pipe passing through a reversible type water pump. In addition, a ruler is fixed on the outside of the test object body, the scale of which runs along the direction of piston movement.

 Figure 1, 2, 3 shows the design of the test object. Figure 1 is a test object in section. Figure 2 is a side view and a top view. Figure 3 shows a metric standard for evaluating geometric blur (enlarged image).

 The housing 1 of the test object is made of hard X-ray and translucent material, such as plexiglass, in the form of a hollow cylinder. It has a cover 2, hermetically connected to the cylinder by means of a thread 3. Cover 2 is made of the same material as the cylinder. Inside the housing 1 there is a piston 4, dividing the cylinder into two chambers 5 and 6. The piston 4 is also made of plexiglass. On the upper end surface of the piston 4 there are five sockets 7 in which metric standards are fixed 8. With a central X-ray beam, metric standards 8 are projected into the center and into the corner zones of the image. The boundaries of the x-ray beam in the plane of metric standards 8 are shown by a square 9. At the base of the piston 4 there is a through hole 10 with a thread closed by a screw-shaped plug 11. And on the diametrically opposite side of the piston there is a handle 12. To orient the test object relative to the x-ray emitter, a crosshair 13 is used, applied on the outer surface of the cover 2 with X-ray transparent paint. Orientation is performed using the light centralizer of the x-ray tube. The housing 1 has two side openings 14 and 15, in which the nozzles 16 and 17 are fixed. The chambers 5 and b are filled with water 18 and are interconnected through the nozzles 16 and 17 with a flexible pipe 19 and 20 passing through the water pump 21 of the reversal type. On a cross section of the test object (figure 1), a layer of water is not shown. Using the remote control 22 connected to the pump 21, you can change the direction of movement of the fluid 18 and, accordingly, the direction of movement of the piston 4. The piston 4 can be moved between the stops 23 and 24 made of plexiglass. When the piston 4 reaches its extreme position, the electric motor of the water pump 21 is automatically turned off. The engine shutdown mechanism is not shown in the drawings. The position of the piston 4 in the cylinder can be determined using a ruler 25, mounted on the outside of the translucent body 1.

 When measuring the geometric blur of the x-ray image using a metric standard having the shape of a cross (figure 3). The standard is formed by radiopaque elements deposited on the surface of a disk 26 made of plexiglass. At the base of the disk 26 there is a protrusion 27 of a round shape, designed to fix the metric standard in the seat socket 7 of the piston 4. The x-ray contrast elements are made of lead 0.3 mm thick. The vertical elements 28 are designed to measure geometric blur in a direction parallel to the x-ray abscissa axis. Horizontal elements 29 are used to measure geometric blur in a direction parallel to the x-ray ordinate axis. The central element 30, having the shape of a ring, is designed to measure geometric blur along a line running at an angle to the axes of the x-ray image.

 In FIG. 4 shows the position of test object 1 on a horizontal table of an x-ray machine. Here: 1 - test object; 31 - deck horizontal table; 32 - x-ray cassette or full-scale digital matrix; 33 - x-ray emitter; 34 - optical centralizer.

 In FIG. Figure 5 shows the position of the test object when assessing the quality of an X-ray image on a digital pulmonary fluorograph. Here: 1 - test object; 35 - stand for the test object; 36 - patient lift; 37 - digital x-ray camera mounted on a tripod 38; 39 - x-ray emitter with an optical centralizer 40, mounted on a tripod 41.

 Consider the method of using the test object in the analysis of geometric blurring of the x-ray image.

 In the intervals between studies, the device is stored in a warehouse, while the housing 1 of the test object is not filled with water 18 and disconnected from the flexible pipelines (hoses) 19 and 20.

 In the process of preparing the test object for operation with the cover 2 removed, the handle 12 lifts the piston 4 to the upper position and unscrew the plug 11. Metric standards 8 are installed in the sockets 7, which are designed to study the geometric blur of the x-ray image. These standards have the shape of a cross (see figure 3). It is necessary to ensure that the orientation of the crosshairs of the metric standards corresponds to the image of Fig. 1 (section AA). After completing this operation, the piston 4 is lowered down to the contact of its base with the stop 23. The flexible hose 19, which goes to the water pump 21, is connected to the pipe 16, and the hose 20 is introduced into a container of water. Water should be purified from salts (distilled) and not contain solid microparticles. After that, turn on the pump 21 and monitor the water filling of the housing 1. First, the water fills the space under the bottom of the piston 4 and then through the hole 10 enters the upper chamber 6. As soon as the water level 18 rises above the piston 4 by about 30 mm, the hole 10 is closed with a stopper 11. With further operation of the pump 21 under the action of water pressure in the lower chamber 5, the piston 4 will slowly rise up. When the piston 4 reaches the upper limiter 24, the pump 21 is turned off. After that, the upper hole of the housing 1 is closed by a cover 2, and the hose 20 is connected to the pipe 15. Using the control panel 22, the operation mode of the pump 21 is reversed, as a result of which water 18 will flow from the lower chamber 5 to the upper chamber 6, as a result of which the piston 4 will fall down. When the piston 4 reaches the lower limiter 23, the water pump 21 is turned off. In this position, the test object is ready for operation.

 The test object 1 is installed on the deck 31 of the horizontal x-ray table, under which there is an x-ray cassette 32, and in the case of digital radiography, a special detector, for example a full-scale semiconductor matrix (figure 4). The x-ray emitter 33 is brought into a horizontal position and by moving it is achieved so that the light crosshair of the optical centralizer 34 coincides with the crosshair 13 applied on the cover 2 of the test object. In this case, the focal length of the x-ray tube should correspond to the operating mode of the survey.

 When examining the geometric blur of the x-ray image on a digital pulmonary fluorograph, the test object 1 is installed in front of the input window of the digital fluorography camera 37 using the stand 35, as shown in Fig.5.

 Figure 6 shows the geometry of the formation of the investigated blur.

 Here: F is the magnitude of the focal spot of the x-ray tube; r is the x-ray receiver (film or semiconductor matrix); k is the radiopaque element of the metric standard 8: f is the focal length of the image; h is the excess of the radiopaque element k over the plane of the receiver r; d is the densitogram of the image of the radiopaque element k.

 Geometric blur is expressed in edge blur (blur) q of the x-ray image. It is characterized by the following well-known equation: q = Fh / (f-h).

 In each specific x-ray examination, for example, when obtaining a survey picture of the lungs, the focal length f and the focal spot F of the x-ray tube are constant. Therefore, according to the above formula, the geometric blur of the x-ray image of the structural elements of the subject will depend on their excess of h over the plane of the receiver r. For elements of the object located near the receiver r, geometric blur will be minimal (Fig.6, a). The densitogram of image d is characterized by a sharp difference in optical density. With the removal of the structural elements of the subject from the plane of the receiver r, the geometric image blur q increases. This is clearly seen in Fig.6, b, c. On the densitogram d, geometric blur is expressed in a gentle difference in the optical densities of the x-ray image.

 In an experimental study of the geometric blurring of the x-ray image using the test object we have proposed, a series of x-ray diffraction patterns of the metric standard elements are performed 8. The first picture is taken with the control elements above the plane of the radiation receiver with a minimum when the piston 4 is in its lowest position (in contact with the limiter 23) . Further, moving the piston 4 using the water pump 21 in increments of, for example, 20 mm, other shots are taken. The movement of the piston 4 is controlled using a ruler 25. The obtained images are processed on a computer according to a special program. As a result, digital and graphic data are obtained that characterize the geometric blurring of the image for a specific x-ray examination.

 The proposed test object can be used for other experimental studies, for example, the analysis of the spatial resolution of the x-ray image. For this, only a replacement of metric standards is required. When studying the spatial resolution of an x-ray image, special radiopaque worlds are used as metric standards.

Literary references
1. Chikirdin E. G., Kochetova G. P., Kolos A. S. Checking the parameters of x-ray mammography devices in the office // Medical equipment, 1999, 5, S. 27-30.

 2. The catalog of the company "INOVISION" "Diagnostic imaging and radiation therapy catalog", 2000, S. 73-75.

 3. X-ray technology (reference book), Moscow: Engineering, 1980, Book 2, p. 348.

Claims (2)

 1. The test object, comprising a housing made of hard X-ray and translucent material, filled with water and having metric standards inside, characterized in that the housing has two chambers separated by a piston that can be moved between two stops, and metric standards are mounted on one from the end surfaces of the piston, while the chambers are interconnected by an external pipe passing through a reversible type water pump.  2. The test object according to claim 1, characterized in that a ruler is installed on the outside of the housing, the scale of which corresponds to the direction of movement of the piston.

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