RU2284148C1 - Method for producing x-ray pictures in performing x-ray examination - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: method involves arranging an organ under study on the axis between the X-ray source and picture receiver having X-ray-sensitive film with intensifying screen, forming focal spot of X-ray radiation source which determining size does not exceed 0.15 mm. The focal spot is set at some distance from the surface of the organ under X-ray examination. The distance is equal to its thickness in radiation propagation direction. X-ray radiation receiver is provided with intensifying screen possessing screen resolution not exceeding 0.25 mm and placed close to the surface of the organ under X-ray examination.

EFFECT: high quality of images produced with smaller focal distance and radiation power of the apparatus.

2 cl, 1 tbl

Description

The invention relates to the field of medical x-ray diagnostics and can be used to obtain x-ray images of the skull, limbs, spine, etc. excluding dental shots.

A known method of obtaining x-rays [Kishkovsky AN, Tyutin L.A., Esinovskaya GN, Atlas of styling during x-ray studies. - L .: Medicine, 1987, p. 8], in which the translucent organ is located on the same axis as the x-ray emitter and the image receiver, which is an x-ray film placed in an opaque cassette [ibid, p. 39, 43].

Due to the fact that the focal spot of the x-ray emitter has finite dimensions, the determining size is usually 1-2 mm, the permissible total blurring H = 0.25 mm of the x-ray image of the vast majority of the transmitted organs when shooting using this method can be ensured if the distance between the emitter and this body (focal length) is 1000-2000 mm [ibid., p. 34-35].

Closest to the claimed technical solution is a method of dental radiography (RU, 2194449 C2, 20.12.2000), which consists in translucent of the investigated organ located on the same axis between the x-ray source and the image receiver, including an x-ray film with an amplifying screen, the formation of the focal spot of the source X-ray radiation with a determining size at a distance from the organ under investigation.

As you know, the total blurriness of the x-ray image is determined by the expression (1)

where N _g is the geometric component of the blur due to the x-ray optical scheme of shooting, N _e is the screen component due to the type of amplifying screen of the image receiver.

Since the intensity of x-ray radiation in accordance with the known expression (2)

where J is the radiation intensity, k is the proportionality coefficient, i _a is the tube current, Z _M is the atomic number of the target material, U is the tube working voltage, R is the distance at which the intensity is measured; is inversely proportional to the square of the distance from the emitter to the point of radiation, shooting at such a large focal length requires the use of X-ray diagnostic devices with a current of several tens of mA and a power of several kW.

The use of powerful X-ray diagnostic devices (hereinafter referred to as the devices), respectively, with a high intensity of the generated radiation, causes a rather high radiation load on the patients, maintenance staff and the environment. This requires the use of additional radiation protection measures: the arrangement of specialized X-ray rooms, the limitation of prescribed radiological procedures and the working hours of radiologists.

It is not possible to reduce the power of the apparatus, while arbitrarily reducing the focal length and current of the x-ray tube.

Indeed, a decrease in the focal length R, for example, by a factor of two in accordance with expression (2) allows one to reduce the power of the x-ray apparatus by a factor of four by reducing the current of the x-ray tube at the same intensity of the generated radiation. However, with a constant size of the focal spot of the emitter d, this will lead to an increase in the total image blur N due to the geometric component of H _g and, accordingly, to a decrease in its quality and information content.

It is well known that power can also be reduced by increasing the sensitivity of image receivers, for example, the use of amplifying screens. However, in this case, increasing the sensitivity of the receiver will not significantly reduce the focal length, since the screen component H _e will be added to the blurriness of the image due to the geometric component of N _g .

Thus, the known method of obtaining x-ray images can provide the necessary quality only when shooting from a large focal length with powerful devices.

The technical result, the invention is aimed at, is to obtain high-quality images while reducing the focal length and power of the device, which will reduce the radiation dose to patients, staff and the environment. Therefore, the method becomes more secure.

To achieve this technical result, in the method of obtaining x-ray images during x-ray studies, in which the translucent organ is placed on the same axis between the x-ray source and the image receiver, including the x-ray film with an amplifying screen, a focal spot of the x-ray source with a determining size at a distance from the investigated organ, while determining the size of the focal spot does not exceed 0.15 mm, the distance from the focal spot to the surfaces of the translucent organ are set equal to the thickness of the organ in the translucent direction, and the radiation receiver is equipped with one or two reinforcing screens with a total blur of not more than 0.25 mm and is placed close to the surface of the translucent organ.

For best results, it is advisable to use an x-ray source with a power not exceeding 50 watts.

The drawing shows the x-ray optical scheme for obtaining x-ray images by the present method, where 1 is the focal spot, 2 is the translucent organ, 3 is the organ structure element, 4 is the x-ray film, 5 is the reinforcing screen, d _f is the diameter of the focal spot, R is the focal length , R ₁ is the distance from the structural element to the image receiver, D is the thickness of the translucent organ.

The geometric component of the blur N _g image obtained by the claimed method can be calculated in accordance with the expression (3)

where d _f is the diameter of the focal spot, R is the focal length, R ₁ is the distance from the structure element to the image receiver.

The aforementioned X-ray optical shooting parameters are interconnected and only together can solve the complex task.

As noted above, a person’s eye notices blur if it is 0.25 mm or more. When shooting according to the scheme shown in the drawing, the geometric component of the blurring N _g in accordance with expression (3) does not exceed 0.15 mm, regardless of how elements of its structure are located along the thickness of the translucent organ. If the screen component of the blur N _e does not exceed 0.2 mm, then, in accordance with expression (2), the total blur N is no more than 0.25 mm, which is quite sufficient to ensure the required image quality.

Since the thickness of any translucent organ of an adult patient does not exceed 30 cm [ibid., P. 43], the x-ray intensity in accordance with expression (1) can be reduced by almost a factor of 10 even without taking into account the effect of the amplifying screen. The use of one or two amplifying screens in the image receiver additionally reduces the radiation intensity by one and a half to two orders of magnitude. The best result is achieved when Gd ₂ O ₂ S is used as the material of the amplifying screen. In general, the power of the device when shooting by the present method can be reduced from several kilowatts to several tens of watts without any damage to the quality of the images obtained.

An example of a specific implementation of the method.

On the basis of the RNII Traumatology and Orthopedics. PP Damaged in conjunction with specialists from the Research Institute of Radiation Hygiene and the State Pediatric Medical Academy, X-ray studies of some organs of the body of patients of different ages were carried out using the prototype method and the claimed method. As a radiation source when shooting according to the claimed method, an X-ray diagnostic apparatus of the Pardus series with a focal spot size of about 100 μm was used. The image receiver, an X-ray film cassette, contained front and rear gadolinium reinforcing screens with a load of 40 and 80 mg / cm ^2, respectively. The necessary and sufficient density of the blackening of the images was provided by the choice of exposure time.

The table shows the values of the focal length, the power of the shooting mode and the effective dose to patients in one study.

The presented results allow us to conclude that the inventive method for obtaining x-rays can be applied to almost all organs of the human body except for the teeth. With sufficient image quality, firstly, the power of the device and, consequently, the dimensions, weight, power consumed from the electric network are significantly reduced, and secondly, which is especially important, the patient dose.

These properties of the claimed method guarantee the effectiveness and safety of its use, primarily when examining critically ill patients and patients of critical groups, including in the field, in emergency and emergency situations.

Table Type of study Patient age Focal length, cm Shooting mode power, W Dose, mk3v Prototype method The claimed method Prototype method The claimed method Prototype method The claimed method Skull (direct projection) Children under 5 years old one hundred fifteen 1.810 ³ twenty 2.2 0.3 Adults - - - - - Chest (direct projection) Children under 5 years old one hundred fifteen 3.8 · 10 ³ twenty 2.7 0.2 Adults twenty 35 5.5 0.4 Hip joint Children under 5 years old one hundred fifteen 3.8 · 10 ³ 25 8.8 0.7 Adults twenty 40 14.8 1.2

Claims (2)

1. The method of obtaining x-ray images during x-ray studies, in which the translucent organ is placed on the same axis between the x-ray source and the image receiver, including an x-ray film with an amplifying screen, form a focal spot of the x-ray source with a determining size, at a distance from the investigated organ, different the fact that the determining size of the focal spot does not exceed 0.15 mm, the distance from the focal spot to the surface of the translucent organ set equal to the thickness of the organ in the direction of transmission, and the radiation receiver is equipped with one or two reinforcing screens with a total blur of not more than 0.25 mm and placed close to the surface of the translucent organ. 2. The method according to claim 1, characterized in that the power of the x-ray source does not exceed 50 watts.