DE102024000863A1 - C-arm X-ray diagnostic device with a limiting device on the emitter housing to limit the skin dose rate of a patient - Google Patents

Abstract

The invention relates to a C-arm X-ray diagnostic device 1 with an X-ray-transparent limiting device 15 on the radiation source housing 8 for limiting a patient's skin dose rate. The limiting device 15 is guided captively along trajectories by means of mechanical guides when switching between an active position 16 and a parked position 17. In the active position 16 and the parked position 17, the limiting device 15 is held on the radiation source housing 8 by means of threaded or bayonet connections.

Description

X-ray procedures and X-ray machines have been used for decades to create medical images by passing X-rays through the body of a patient, whether a living person or an animal. Despite its enormous medical benefits, such ionizing radiation is not without risks to the patient's health. Therefore, the use of X-rays on living patients is strictly regulated by law. In particular, there are maximum permissible limits on the rate of X-ray dose reaching the patient's body surface. For example, the 21st Code of Federal Regulations of the U.S. Department of Health and Human Services, in DHHS 21 CFR 1020.32e, defines the so-called Maximum Input Exposure Factor for permissible doses, i.e., the dose rate at the skin entry, in mGy/s, on the side of the patient facing the radiation source.

C-arm X-ray machines are used to acquire projection images, generate 3D image data sets, and for fluoroscopy and intraoperative fluoroscopy control. Surgeons utilize the ability to adjust the C-arm to generate the desired projection images. The dose rate emitted by an X-ray source onto a given control surface decreases perpendicularly to the distance of the control surface from the X-ray source, based on the inverse square law and the specified maximum, i.e., the limit value, for example, the dose rate. The minimum distance that biological tissue must travel from the focal point of the X-ray source or X-ray source can be calculated on the control surface. The X-ray tube should not be lowered to avoid exceeding the specified dose limit, i.e., the initial irradiation power. This minimum distance depends primarily on the primary dose delivered by the X-ray source and thus on the limits of the X-ray energy and the maximum achievable beam current in the X-ray tube. In some X-ray machines, the distance between the X-ray source and the patient is always constant. The X-ray generator is then selected by designing the X-ray tube or a generator drives it or filters are placed in the beam path on the source side to ensure that no patient is exposed to unacceptably high dose rates.

It differs, for example, from the X-ray machine used in urology. In the so-called under-table X-ray station, the X-ray generator is placed under the patient table. However, the patient table is height-adjustable, meaning the distance between the patient lying on the table or tabletop and the X-ray generator or tabletop can be adjusted. Your focus is on change. Therefore, desk positions at different heights are desirable, for example, someone can sit at the table or tabletop. The urologist working with the patient can adjust the table to an ergonomically comfortable working position.

The patient table can often be so close to the X-ray machine that the patient lying on it is exposed to unacceptably high radiation doses while the X-ray machine is in operation. When the urologist is standing, the table is often raised, placing the patient outside the critical dose-ratio range. The patient can then undergo fluoroscopy without risk. For example, if the physician wishes to sit during longer X-ray endocrine procedures, the patient table must be lowered significantly, i.e., very close to the X-ray generator. This makes it impossible to maintain the minimum distance, resulting in an unacceptably high input dose ratio for the patient when the X-ray source is switched on.

If, for example, a doctor reduces the distance of the X-ray focus from the patient's surface in the direction of the central beam, the patient's skin dose rate increases while the radiation parameters remain unchanged, and this can lead to inadmissible exceedances of legal limits for the skin dose rate.

To ensure that the skin dose limit is not exceeded during certain examination procedures, the use of a skin protection tube is mandatory. This mechanically limits the minimum distance between the patient's surface and the X-ray focus. Furthermore, a robust skin protection tube protects a beam limiter or light aiming device from lateral impacts. For imaging procedures where the use of a skin protection tube is not required, it can be removed from the radiation pyramid and quickly reattached when needed. It is therefore desirable that a removable skin protection tube be stored in a secure and easily retrievable location when not in use.

To avoid exposing patients to excessive doses in all cases, many technical solutions are available. X-ray machines with a skin protection tube, especially those with a removable skin protection tube, are well known.

Furthermore, it is known that the path of the patient table is mechanically limited, so that He cannot move closer to the X-ray source than a predetermined safety distance. This limits the ergonomics of the ward, as the table cannot be lowered if the urologist wishes to work without taking an X-ray. It is also known to deactivate the X-ray source or disable its operation if a safety distance is not maintained. However, fluoroscopy cannot be performed on patients in this table position. In this case, however, the doctor could not adjust the X-ray table to a suitable position or had to raise it again to take X-rays of the patient.

Furthermore, it is known that the X-ray generator is permanently operated below its maximum power range by control, i.e., with the product of beam current and acceleration energy lower than the maximum energy the X-ray source can actually emit. This also leads to a permanent reduction in the minimum safety distance. However, just like permanently installed filters, this often impairs the image quality of the X-ray system, as the X-ray source is never at its optimal operating point. The same measure applies to actual desk positions that are above a safe distance and offer better image quality. The decrease in transmission power leads to a decrease in the number of X-ray quanta generated while simultaneously increasing quantum noise. X-rays appear thicker and less visible. Thus, all known solutions are compromises between X-ray contrast or X-ray image quality and the ergonomics of the overall system. The object of the present invention is to improve a suitable method and a suitable X-ray device for screening a patient.

From the document DE1317696U an X-ray sphere with a non-removable dental tube “n” is known, which can be used as an aiming device for the alignment of the central beam.

From the document DE4447856C2 An X-ray source is known, on the housing of which rod-shaped, non-removable spacers 56a, 56b are provided, arranged parallel to the central beam, which serve, on the one hand, to protect an X-ray collimator from impacts and, on the other hand, to ensure a minimum focus-skin distance, for example to meet FDA (US Food and Drug Administration) requirements.

From the document DE3781171T2 A mobile C-arm for military use (Philips BV 25 T) is known, which can be disassembled into several components without tools for better transportability. Operation Manual for the device, English from 2020 (http://hdl.handle.net/20.500.12091/1430, source: https://www.usa.philips.com/healthcare , accessed on April 27, 2023 ) and from the instruction manual Philips X-ray device, field, light, BV 25 T, German with year of publication 1989 of the scanned printed copy, (http://www.frankshospitalworkshop.com/equipment/documents/x-ray/usermanuals/Philips%20BV25T%20-%20Aufbau%20und%20Bedanleitung.pdf , accessed on 27.04.2023 ) is in the 22 and 23 and the accompanying description text, it is known that various tubes (for fluoroscopy and dental) are removable and replaceable along with a holding plate. It is disclosed that the X-ray device cannot be operated without the tube attached.

From the document DE29520926U1 A tube tube is known which is integrated into a tube housing half and cannot be removed from the radiation field, in which a radiation limiting part is detachably held.

From the document DE60128722T2 A mobile C-arm with a tube is provided to ensure a safety distance; the possibility of removing the tube is not disclosed.

A disadvantage of the known X-ray devices is that a skin protection tube is not secured against unwanted loss when not in use.

The object of the invention is to provide a skin protection tube in the form of a mechanical, X-ray transparent limiting device for the skin dose rate of a patient, which is arranged on the radiator housing and can be positioned as required at an effective position within the radiation pyramid or at a defined parking position outside the radiation pyramid.

The object of the invention is achieved by the features of the main claim. Further embodiments of the invention can be found in the dependent claims.

The invention is explained in more detail with reference to the figures.

In 1 A C-arm X-ray diagnostic device 1 with a C-arm 13 is schematically shown. The C-arm 13 carries an X-ray emitter with a focus 5 at one end and an X-ray flat panel detector FPD 3 at the opposite end. The radiation field between the focus 5 and the FPD 3 forms a radiation pyramid 6 with a beam path extending from the focus 5 to the center of the FPD 3 extending central beam 7. A patient 2 to be x-rayed is arranged between the focus 5 and the FPD 3, wherein the distance between focus 5 and the patient 2 can be changed by relative displacement of the C-arm 13 with respect to the patient 2.

In 2a) A radiation source housing 8 accommodating an X-ray tube 4 with a focus 5 is schematically shown, with an X-ray transparent limiting device 15 having a stop surface 19 in an active position 16. In the active position 16, the stop surface 19 lies completely within the radiation pyramid 6 and rests against the patient-side radiation source housing surface 9. In the example of the 2 the patient-side radiator housing surface 9 in the area of the central beam 7 has a focus-radiator housing distance of 12, the stop surface 15 to the focus 5 has a minimum FHA of 11 and the patient 2 to the focus 5 has a focus-skin distance of FHA of 10.

In 2b) the limiting device 15 is shown schematically with a stop surface 19 in a parking position 17.

In 2c ) the limiting device 15 is schematically shown with a stop surface 19 in a parking position 17, wherein the patient is in contact with the patient-side radiator housing surface 9 in the region of the central beam 7 and the skin dose rate in the FHA 10 is greater than the skin dose rate in the minimum FHA 11 when using the limiting device 15 with a stop surface 19 in the active position 16.

In 3 is an embodiment of a movement trajectory 20 of the limiting device 15 between an active position 16 and a park position 17 with a sliding guide 25 in the form of a rounded T-slot profile 28 integrated in the radiator housing 8. The sliding guide 25 preferably follows the contour of the patient-side radiator housing surface 9 close to the housing. Within the scope of the invention, it is provided to hold the limiting device 15 in the active position 16 and in the park position 17 by means of a detachable threaded or bayonet connection on the radiator housing 8 or on the X-ray beam exit window 18. For this purpose, it is necessary that the limiting device 15 is mounted rotatably in the active position 16 and in the park position 17 about an axis perpendicular to the longitudinal axis of the sliding guide 28.

In 4 An embodiment of a movement trajectory 20 of the limiting device 15, remote from the radiator housing, between the active position 16 and the parking position 17 is schematically shown, in which a holding arm 26 is preferably pivotally mounted at a bearing point 27 about a pivot axis 22 lying in the orbital plane 14 of the C-arm 13, wherein the holding arm 26 is preferably formed from a flexible or elastic flat or round material.

In the 3 and 4 Position monitoring sensors 30, 30' are provided in the area of the active position 16 and the parking position 17, which allow the correct positioning of the limiting device 15 to be monitored.

In 5 an embodiment of a holding arm is schematically shown, in which a plurality of movement trajectories 20 of the limiting device 15 remote from the radiator housing between the active position 16 and the parking position 17 can be realized, wherein the holding arm in the extended state has a length between the centers of the two bores 32, 33 which corresponds in each case to the length of a curved path between the bearing point 27 and the center of the limiting device 15 in the active position 16 and the parking position 17.

List of illustrations

• 1 : C-arm X-ray diagnostic facility
• 2 : Lamp housing with mechanical limiting device for limiting the skin dose rate of a patient
  1. a) Limiting device 15 in active position 16
  2. b) Limiting device 15 in parking position 17
  3. c) Radiator housing 8 without limiting device 15
• 3 : Curved guide rail for a housing-near trajectory of the limiting device 15 between an active position 17 and a parking position 17
• 4 : Limiting device arranged at a bearing point and pivotably mounted around a pivot axis lying in the orbital plane15.
• 5 : Design example of the holding arm made of flexible or elastic material

List of reference symbols

1

C-arm X-ray diagnostic facility

2

patient

3

X-ray flat panel detector FPD

4

X-ray tube

5

focus

6

Ray pyramid

7

Central ray

8

Spotlight housing

9

Patient-side radiator housing surface

10

Focus-skin distance (FHA, Source-Skin-Distance SSD)

11

Minimum FHA

12

Focus-radiator housing distance

13

C-arm

14

Orbital plane

15

Limiting device

16

Effective position

17

Parking position

18

X-ray exit window

19

Stop surface

20

Movement trajectory

22

Swivel axis

25

Sliding guide

26

Holding arm

27

storage location

28

T-slot profile

30, 30'

Position monitoring sensor

31

Retaining groove (is in 4 not yet drawn)

32

Bearing bore

33

Hole for the limiting device

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4447856C2 [0011]
• DE 3781171T2 [0012]
• DE 29520926U1 [0013]
• DE 60128722T2 [0014]

Cited non-patent literature

• Operation Manual for the device, English from 2020 (http://hdl.handle.net/20.500.12091/1430, source: https://www.usa.philips.com/healthcare , accessed on April 27, 2023 [0012]
• of the scanned printed copy, (http://www.frankshospitalworkshop.com/equipment/documents/x-ray/usermanuals/Philips%20BV25T%20-%20Aufbau%20und%20Bedanleitung.pdf , accessed on 27.04.2023 [0012]

Claims (5)

C-arm X-ray diagnostic device (1) for the examination and fluoroscopy of a patient (2), comprising an X-ray flat panel detector FPD (3), a radiator housing (8) with an X-ray tube (4) having a focus (5) and an X-ray transparent limiting device (15) for limiting the skin dose rate of the patient (2) in a radiation pyramid (6) with a central beam (7) between focus (5) and FPD (3) at a focus-skin distance (FHA, Source-Skin-Distance SSD 10) less than or equal to a predetermined minimum FHA (11), characterized in that the X-ray transparent limiting device (15) is movably held on the radiator housing (8) and can be displaced along a movement trajectory (20) between an active position (16) and a parking position (17), wherein the limiting device (15) in the active position (16) in the region of the ray pyramid (6) has a stop surface (19) oriented perpendicular to the central ray (7) which has a distance from the focus (5) which corresponds to a predetermined minimum FHA (11). C-arm X-ray diagnostic device (1) according to Claim 1 , characterized in that the X-ray transparent limiting device (15) is mechanically actuated. C-arm X-ray diagnostic device (1) according to Claim 1 , characterized in that the X-ray transparent limiting device (15) is operated partially or fully automatically. C-arm X-ray diagnostic device (1) according to Claim 1 , characterized in that the X-ray transparent limiting device (15) is motorized. C-arm X-ray diagnostic device (1) according to Claim 1 , characterized in that the X-ray source is switched off at the same time as the X-ray transparent limiting device (15) is actuated.