CBCT (cone beam computed tomography) oral cavity die body

Abstract

The invention discloses a CBCT (cone beam computed tomography) oral cavity mold body, which relates to the field of CT calibration and comprises a first carrier, a polyvinyl chloride ring and a second carrier which are stacked, the first carrier and the second carrier are used for fixing the polyvinyl chloride ring; the polyvinyl chloride ring is used for calibrating an X-ray radiation source of the medical oral and maxillofacial CBCT device to be tested; the CBCT oral cavity die body is arranged in the center of a ray irradiation field of the X-ray radiation source of the medical oral and maxillofacial CBCT device to be detected, an irradiation image is collected, and the spatial resolution, the contrast-to-noise ratio coefficient and the image uniformity index of the X-ray radiation source of the medical oral and maxillofacial CBCT device to be detected are calculated according to the irradiation image; according to the method, whether the X-ray radiation source of the CBCT device is qualified or not can be judged, and the radiation source is calibrated based on the judgment result.

Description

Technical Field

[0001] The present application relates to the field of CT calibration, and in particular to a CBCT oral phantom. Background Art

[0002] It is a general trend for Cone Beam Computed Tomography (CBCT) to replace panoramic machines and traditional CT. With the rapid development of orthodontics and implants, the core businesses of dentistry, accurate three-dimensional modeling of the interior of the oral cavity is required to clearly depict the location of blood vessels in the oral cavity and the thickness of the maxillary bones. Therefore, with the increase in the penetration rate of orthodontics and implants, dental clinics will be inseparable from CBCT application equipment in the future. In actual applications, people often only pay attention to the final modeling results, while the X-ray radiation source of the CBCT device directly affects the accuracy of the constructed three-dimensional model. The accuracy of the three-dimensional model is related to the spatial resolution, contrast-to-noise ratio coefficient and image uniformity index of the X-ray radiation source of the CBCT device. Therefore, it is very important to judge whether the X-ray radiation source of the CBCT device is qualified and calibrate it. Summary of the invention

[0003] The purpose of the present application is to provide a CBCT oral phantom to solve the problem of being unable to determine whether the X-ray radiation source of the CBCT device is qualified and to calibrate the radiation source.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] In a first aspect, the present application provides a CBCT oral cavity phantom, comprising: a stacked first carrier, a polyvinyl chloride ring, and a second carrier;

[0006] The first carrier and the second carrier are used to fix the polyvinyl chloride ring;

[0007] The polyvinyl chloride ring is used to calibrate the X-ray radiation source of the medical oral and maxillofacial CBCT device to be tested;

[0008] The CBCT oral phantom is placed at the center of the irradiation field of the X-ray radiation source of the medical oral and maxillofacial CBCT device to be tested, and an irradiation image is collected. The spatial resolution, contrast-to-noise ratio coefficient and image uniformity index of the X-ray radiation source of the medical oral and maxillofacial CBCT device to be tested are calculated based on the irradiation image; the irradiation image includes the polyvinyl chloride ring.

[0009] According to the specific embodiments provided by the present application, the present application discloses the following technical effects: the present application provides a CBCT oral phantom, comprising: a stacked first carrier, a polyvinyl chloride ring and a second carrier; an X-ray radiation source of a medical oral and maxillofacial CBCT device to be tested is allowed to irradiate the CBCT oral phantom, and an irradiated image is collected, thereby calculating the spatial resolution, contrast-to-noise ratio coefficient and image uniformity index of the X-ray radiation source of the medical oral and maxillofacial CBCT device to be tested; based on the above parameters calculated, whether the X-ray radiation source of the CBCT device is qualified is judged, and based on the judgment result, the X-ray radiation source of the CBCT device is calibrated. The CBCT oral phantom is used for the initial calibration, subsequent calibration and in-use inspection of the X-ray radiation source of the medical oral and maxillofacial CBCT device, so as to make the constructed three-dimensional model more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 This is a schematic diagram of a CBCT oral phantom structure in an embodiment of the present application;

[0012] Figure 2 A schematic diagram of a radiation source irradiating a CBCT oral phantom provided in an embodiment of the present application;

[0013] Figure 3 A schematic diagram of the location and boundaries of a region of interest provided in an embodiment of the present application;

[0014] Figure 4 for Figure 3 Schematic diagram of region of interest selection shown. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0016] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0017] like Figure 1-Figure 3As shown, a CBCT oral phantom 2-1 comprises: a stacked first carrier 1, a polyvinyl chloride ring 2 and a second carrier 3; the first carrier 1 and the second carrier 3 are used to fix the polyvinyl chloride ring 2; the polyvinyl chloride ring 2 is used to calibrate the X-ray radiation source (referred to as the radiation source) 2-2 of the medical oral and maxillofacial CBCT device to be tested; the CBCT oral phantom 2-1 is placed at the center of the radiation field of the X-ray radiation source 2-2 of the medical oral and maxillofacial CBCT device to be tested, collects the irradiation image, and calculates the spatial resolution, contrast-to-noise ratio coefficient and image uniformity index of the X-ray radiation source 2-2 of the medical oral and maxillofacial CBCT device to be tested according to the irradiation image; the irradiation image includes the polyvinyl chloride ring 2.

[0018] In an exemplary embodiment, a third carrier 4 is provided between the first carrier 1 and the polyvinyl chloride ring 2; a fourth carrier 5 is provided between the second carrier 3 and the polyvinyl chloride ring 2;

[0019] The first carrier 1, the second carrier 3, the third carrier 4 and the fourth carrier 5 together constitute a phantom having a volume comparable to that of a human head, so as to better simulate the imaging conditions during scanning of a patient.

[0020] In actual operation, the third carrier 4 and the fourth carrier 5, in addition to being used to fix the polyvinyl chloride ring, form a whole with the polyvinyl chloride ring. In some cases where it is difficult to place the entire mold, the first carrier and the second carrier can be removed and only the middle module can be used for detection.

[0021] In an exemplary embodiment, the first carrier 1, the third carrier 4, the fourth carrier 5 and the second carrier 3 are fixedly connected by positioning pins 6. The positioning pins 6 are connected to the lower end of the first carrier 1, the upper end of the second carrier 3 and the upper end of the fourth carrier 5 in an interference fit manner, and the end faces of the remaining carriers are connected in a clearance fit manner.

[0022] In an exemplary embodiment, it further includes: a level bubble 7; the level bubble 7 is arranged at the bottom of the second carrier 3 and is used to detect whether the CBCT oral phantom 2-1 is in a horizontal state.

[0023] In an exemplary embodiment, it further includes: a base 8; the base 8 is arranged at the bottom of the second carrier 3 and is used to support the CBCT oral phantom 2-1.

[0024] In an exemplary embodiment, it further includes: an adjusting leg; the adjusting leg 9 is disposed at the bottom of the base 8 and is used to adjust the base 8 so that the base 8 is in a horizontal state.

[0025] The CBCT oral phantom 2-1 is placed in the center of the radiation field of the X-ray radiation source 2-2 of the medical oral and maxillofacial CBCT device to be tested, and the CBCT oral phantom 2-1 is scanned under conventional recognition conditions. There should be no material that affects the radiation beam around it. A rectangular region of interest (ROI) 3-1 is selected in the reconstructed axial slice obtained by the detector 2-3. The four sides of the ROI 3-1 should be parallel to the pixel rows (columns) and only include the polyvinyl chloride (PVC) and air area 3-2 in the CBCT oral phantom 2-1. The transition edge between PVC and air should be parallel to the upper and lower sides. The parallelism of the edges is optimized by repositioning the CBCT oral phantom 2-1 and repeatedly acquiring images. Further, the upper and lower widths of the ROI 3-1 correspond to the width in the CBCT oral phantom 2-1, which can be 5 mm, and each segment of the vertical edges located in the PVC and air areas is at least 3 mm.

[0026] Based on the region of interest, the spatial resolution, contrast-to-noise ratio coefficient and image uniformity index of the X-ray radiation source 2-2 of the medical oral and maxillofacial CBCT device to be tested are calculated, so as to accurately calibrate whether the X-ray radiation source 2-2 of the medical oral and maxillofacial CBCT device to be tested is qualified.

[0027] Furthermore, based on the region of interest, a spatial frequency value at 10% on the measured modulation transfer function MTF curve is calculated, and the spatial frequency value is characterized as the spatial resolution.

[0028] The contrast-to-noise ratio coefficient CNI is: is the mth max The pixel average of the row; is the mth min The pixel average of the row; is the mth max The standard deviation of the pixel values ​​of the row; is the mth min The standard deviation of the pixel values ​​for the row.

[0029] in, and It is calculated as follows:

[0030] Read the pixel average value (P1, P2, P3, ..., P n ) and standard deviation (s1, s2, s3, ..., s n ), use the sliding average to make the first-order difference to get P'5, P'6, P'7, ..., P' n-4 , the calculation formula is:

[0031] m is the row number.

[0032] For the obtained P' m According to the formula P m =P' m+1 -P' m , calculate the second-order difference to obtain P"6, P"7, ..., P" n-6 .

[0033] From P"6, P"7, ..., P" n-6 Get the extreme point and The pixel row m max and m min .

[0034] The image uniformity index H is: Among them, H z is the average pixel value in the central area of ​​the region of interest, H o is the average pixel value in the upper region of the region of interest, H l is the average pixel value in the left area of ​​the region of interest, H r is the average pixel value in the right area of ​​the region of interest, H u is the average pixel value in the lower area of ​​the region of interest, H M H z , H o , H l , H r and H u The average value of Figure 4 shown.

[0035] The CBCT oral phantom 2-1 provided in the present application can determine whether the X-ray radiation source 2-2 of the CBCT device is qualified, and calibrate the radiation source 2-2 based on the judgment result. The CBCT oral phantom 2-1 can be used for the initial calibration, subsequent calibration and in-use inspection of the X-ray radiation source 2-2 of the medical oral and maxillofacial CBCT device to make the constructed three-dimensional model more accurate.

[0036] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0037] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A CBCT oral phantom, characterized in that: The CBCT oral cavity model comprises: a first carrier, a polyvinyl chloride ring and a second carrier stacked together; The first carrier and the second carrier are used to fix the polyvinyl chloride ring; The polyvinyl chloride ring is used to calibrate the X-ray radiation source of the medical oral and maxillofacial CBCT device to be tested; The CBCT oral phantom is placed at the center of the irradiation field of the X-ray radiation source of the medical oral and maxillofacial CBCT device to be tested, and an irradiation image is collected. The spatial resolution, contrast-to-noise ratio coefficient and image uniformity index of the X-ray radiation source of the medical oral and maxillofacial CBCT device to be tested are calculated based on the irradiation image; the irradiation image includes the polyvinyl chloride ring.

2. The CBCT oral phantom according to claim 1, characterized in that: A third carrier is arranged between the first carrier and the polyvinyl chloride ring; and a fourth carrier is arranged between the second carrier and the polyvinyl chloride ring.

3. The CBCT oral phantom according to claim 2, characterized in that: The first carrier, the third carrier, the fourth carrier and the second carrier are fixedly connected by positioning pins.

4. The CBCT oral cavity phantom according to claim 1, characterized in that: Also includes: Horizontal bubble; The level bubble is arranged at the bottom of the second carrier and is used to detect whether the CBCT oral phantom is in a horizontal state.

5. The CBCT oral cavity phantom according to claim 1, characterized in that: Also includes: Base; The base is arranged at the bottom of the second carrier and is used to support the CBCT oral cavity model.

6. The CBCT oral cavity phantom according to claim 5, characterized in that: Also includes: Adjustment leg; the adjustment leg is arranged at the bottom of the base and is used to adjust the base so that the base is in a horizontal state.

Images