JP2009080053A - X-ray ct apparatus, x-ray detection method using x-ray ct apparatus, x-ray sensor signal processing system, and x-ray sensor signal processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus capable of preventing quality deterioration of a CT image and enhancing quality of an image photographed by the X-ray CT apparatus by suppressing output variation of X-ray sensors while enhancing measuring sensitivity in detection of X-rays. <P>SOLUTION: The X-ray CT apparatus includes an X-ray emission means for emitting an X-ray to an object to be tested, a plurality of X-ray sensors for detecting X-rays transmitted through the object to be tested, and a signal processing device for processing output signals of the X-ray sensors. The signal processing device includes a bias current supply means for supplying a bias current of a forward direction to the X-ray sensor and supplying a bias current equal to the respective X-ray sensors. Quality degradation of the CT image is prevented and quality of the photographed image by the X-ray CT apparatus can be improved by improving the measuring sensitivity in the detection of X-rays, and suppressing the output variation of the X-ray sensors. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an X-ray CT apparatus, an X-ray detection method for an X-ray CT apparatus, an X-ray sensor signal processing system, and an X-ray sensor signal processing method.

  The industrial X-ray CT apparatus is a very useful nondestructive inspection apparatus for observing and measuring the internal shape of an object. For this reason, it has recently been used mainly by automobile companies for measuring the shape of developed products and measuring the distribution of casting nests. In order to take a tomographic image of a large cast product or the like, an X-ray CT apparatus using an accelerator that generates high-energy X-rays with high transmission power as an X-ray source has been developed. For example, Non-Patent Document 1 discloses an industrial X-ray CT apparatus using an electron beam accelerator as an X-ray source and a strip-shaped silicon semiconductor sensor as an X-ray detector. This X-ray CT apparatus is a so-called third generation X-ray CT apparatus that takes a tomographic image by rotating the object under test once around an axis perpendicular to the X-ray fan beam.

  An X-ray CT apparatus using a semiconductor sensor is described in Patent Document 1 (Japanese Patent Publication No. 10-512398). In particular, an X-ray CT apparatus that uses a CdTe (cadmium telluride) sensor, which is a compound semiconductor, to improve the measurement sensitivity of X-ray detection and prevent a sensor output decrease phenomenon that becomes a problem during long-time imaging is disclosed in Patent Document 2. (Japanese Unexamined Patent Application Publication No. 2006-010364).

Japanese National Publication No. 10-512398 JP 2006-010364 A Hiroshi Uemura, Industrial high-energy X-ray CT system and its application to digital engineering, Journal of the Institute of Electrical Engineers of Japan, Vol. 122, No. 2, pp. 100-103, 2002

  However, it has not been considered to suppress variations in output in individual semiconductor sensors that are used in many X-ray CT apparatuses while improving measurement sensitivity of X-ray detection. If the output of each semiconductor sensor varies, the captured image is adversely affected.

  Therefore, an object of the present invention is to improve the quality of a captured image by an X-ray CT apparatus by improving the measurement sensitivity of X-ray detection and suppressing the output variation of the X-ray sensor to prevent the deterioration of the quality of the CT image. There is.

  The present invention provides an X-ray emitting means for emitting X-rays to a device under test, a plurality of X-ray sensors for detecting X-rays transmitted through the device under test, and signal processing for processing an output signal of the X-ray sensor. A bias current supply means for supplying a forward bias current to the X-ray sensors and supplying a bias current having a magnitude equal to each of the X-ray sensors. It is characterized by.

  According to the present invention, it is possible to improve the quality of a captured image by an X-ray CT apparatus by improving the measurement sensitivity of the X-ray detection and suppressing the output variation of the X-ray sensor to prevent the quality deterioration of the CT image. it can.

  As a sensor used for an industrial X-ray CT apparatus, there is a silicon semiconductor sensor. A silicon semiconductor sensor has a high-energy X-ray detection efficiency of about 20%, although it varies depending on the sensor size and X-ray energy. However, in order to improve the density resolution of the tomographic image, it is desirable that the detection efficiency (sensitivity) of the X-ray sensor is high. For this reason, it is considered to use a CdTe semiconductor sensor whose density is twice as high as that of silicon and whose detection efficiency can be improved about twice.

  One of the CdTe sensors is a sensor in which one of the electrodes is a Schottky diode electrode. When this electrode is used, the leakage current is also small, so that application to an X-ray CT apparatus has been widely studied.

  However, in the CdTe sensor, an output reduction phenomenon occurs due to a long-time bias application. In order to prevent this output reduction phenomenon, Patent Document 2 discloses a method for preventing the output reduction phenomenon by applying a bias voltage opposite to the direction in which the current is cut off by the Schottky diode to the CdTe sensor. Here, the direction in which current flows in the Schottky diode is defined as the forward direction of the Schottky diode and is defined as a forward bias. The forward bias not only improves the X-ray detection sensitivity of the CdTe sensor by about twice that of the Si semiconductor sensor, but also increases the output current by about four times that of the reverse bias, improving the S / N and thus the CT tomographic image quality. Improvement is possible.

  Here, it is necessary to consider that a single X-ray CT apparatus uses a large number of sensors (500 to 100). That is, in order to improve the image quality of the captured CT image, it is desirable that the X-ray detection characteristics of the sensors are as equal as possible. However, when the output of the CdTe sensor was measured with a forward bias, it was found that there was a large variation in output current, and there was a risk of adversely affecting the image quality of the CT image.

  The reason why the output current varies when the CdTe sensor is used in the forward bias is that the leak current (bias current) generated by the forward bias of a constant voltage varies greatly depending on the sensor element. For this reason, by making the leak current constant among a plurality of X-ray sensors, it is possible to reduce variations in current output from the sensor when the CdTe sensor detects X-rays. Hereinafter, an embodiment of the present invention that reduces variations in current output from the sensor will be described.

  FIG. 2 is a diagram illustrating the configuration of the first embodiment.

  The X-ray CT apparatus 100 includes an electron beam accelerator 1 that outputs an X-ray fan beam 2 as an X-ray emission means, a scanner 3 on which a device under test 14 is installed, and an X-ray that detects X-rays transmitted through the device under test 14. In order to improve the S / N ratio of the X-ray sensors 4-1 to 4-512 and the X-ray sensor 4, the collimator 5 that suppresses the amount of scattered X-rays incident on the X-ray sensor 4 is amplified. A signal processing device 10 for converting into a digital signal, a control device 6 for collecting the digital data from the signal processing device 10 and controlling the entire device, an image reconstruction device 7 for reconstructing an image, and an image reconstruction device A display device 8 for displaying the displayed image and other information, and a controller 9 for controlling the operation of the electron beam accelerator 1, the scanner 3, and the signal processing device 10 in accordance with a control command from the control device 6. .

  The X-ray CT apparatus of FIG. 2 shows a third generation X-ray CT apparatus that rotates the device under test 14 and images one cross section. In addition to the rotation function, the scanner 3 has a function of operating in the vertical direction in order to perform cross-sectional imaging at each height of the DUT 14.

  The electron beam accelerator 1 is connected to a controller 9 by a control cable 16, and generation / stop of the X-ray fan beam 2 is controlled by the controller 9. Similarly, the scanner 3 is connected to the controller 9 by a control cable 15 to adjust the rotation and vertical position of the scanner.

  The X-ray sensors 4 are arranged in a row so as to anticipate the generation point of the X-ray fan beam 2, and 512 pieces are installed in this embodiment. The X-ray sensor 4 can improve the imaging resolution as the number of sensors increases. The X-ray sensor 4 detects X-rays in synchronism with the rotation of the scanner, and an X-ray pulse is output from the electron beam accelerator 1 at every fixed angle at which the scanner 3 rotates and passes through the device under test 14. The detected X-ray is detected. A signal corresponding to the X-ray dose output from the X-ray sensor 4 is amplified by the signal processing device 10 and converted into a digital signal. The converted digital signal is transmitted to the control device 6 through the signal cable 17. Thereafter, a digital signal is transmitted from the control device 6 to the image reconstruction device 7 and used for the reconstruction of the CT image.

  In the case of an X-ray CT apparatus using an accelerator, the X-rays emitted from the accelerator are pulsed X-rays that are periodically generated due to the characteristics of the accelerator. In general, a powerful X-ray pulse (collection of X-ray photons) having a width of 5 μs is output in a period of 5 ms. In this embodiment, X-ray pulses are emitted 1920 times during one rotation of the DUT, and data is measured. That is, the X-ray dose is measured every 0.1875 degrees. In this embodiment, since there are 512 X-ray sensors, the data for reconstructing one slice is 512 × 1920 data.

  The X-ray sensors 4-1 to 4-512 of the present embodiment are CdTe semiconductor sensors (In / CdTe / Pt sensors) using In as an anode and a Pt electrode as a cathode. The bias is applied by applying a positive voltage adjusted for each X-ray sensor to the Pt electrode, which is originally a cathode, so that a bias current having an equal magnitude is supplied to each X-ray sensor. The junction is forward biased. For this reason, the X-ray sensor of this embodiment is used in a direction (forward direction) in which the bias current increases.

  Hereinafter, the structure of the X-ray sensor will be described in detail with reference to FIG. FIG. 3 is an elevation view and a plan view showing the structure of the X-ray sensor used in this embodiment. The CdTe crystal 200 has an elongated rectangular parallelepiped shape, and the size of the CdTe crystal is 3 mm long × about 40 mm wide × 0.5 mm high. X-rays are incident in parallel with the lateral direction of the CdTe crystal. A Pt electrode 201 and an In electrode 202 are deposited on the upper and lower surfaces of the CdTe crystal 200 to form an In / CdTe / Pt sensor. The In / CdTe / Pt sensor is bonded to the insulating substrate 203. The In electrode 202 on the insulating substrate 203 side is directly bonded to the printed wiring terminal 208 with a conductive adhesive, and the Pt electrode 201 on the upper surface is bonded to the printed wiring terminal 207 with a bonding wire 206. A flexible substrate is used for the insulating substrate 203. The heavy metal substrate 204 is made of a tungsten alloy. The heavy metal substrate 204 plays a role of shielding the incident X-rays and recoil electrons scattered by the adjacent X-ray sensor as well as protecting the X-ray sensor.

  FIG. 4 is a diagram showing an example of current-voltage characteristics of the X-ray sensor in the forward bias. The vertical axis represents the leakage current value, and the horizontal axis represents the voltage value. Due to the forward bias, leakage current begins to flow at a low voltage. The current-voltage characteristic varies depending on the X-ray sensor. Also in the two X-ray sensors shown in this figure, it is understood that the leak current differs by several tens of percent when the bias voltage is constant. In the reverse bias, a leak current of about 1 nA occurs even when 100 V is applied.

  Here, the phenomenon that occurs in the CdTe sensor will be described separately for the reverse bias and the forward bias.

  The output decrease phenomenon of the CdTe sensor in the reverse bias is caused by electrons trapped in energy levels (hereinafter referred to as trap levels) caused by impurities in the CdTe crystal, and electrons / holes generated inside the sensor by X-rays. Occurs due to insufficient pair collection. Since the trap level has a negative charge, the electric field inside the sensor becomes weaker as the number of trap levels increases. Therefore, it is considered that electron / hole pairs generated by X-rays are not easily collected by both electrodes of the sensor, and the output current of the sensor is reduced.

  The time variation dN / dt of the number N of trap levels can be expressed by a generation term and an annihilation term as shown in equation (1).

dN / dt = C1 · (N0−N) −C2 · N (1)
Here, N0 is the number of existing energy levels, N is the number of trap levels, C1 is the probability of occurrence, and C2 is the probability of disappearance. In the reverse bias, since the generation term> the extinction term, it is considered that N gradually increases and the output decreases.

  Next, since the leakage current flows more in the forward bias than in the reverse bias, the generation term is very large. Therefore, as soon as a bias is applied, electrons are trapped at the energy level, and N becomes saturated (since N0 is finite). For this reason, as can be seen from FIG. 4, the electric field in CdTe is reduced. However, unlike the reverse bias, there is no energy barrier, so electrons and holes can freely enter and exit the CdTe crystal from the electrodes. Accordingly, the electron-hole pairs generated by X-rays have a low recombination rate, and most of them are output outside the sensor. This is considered to be the reason why the output current becomes larger than the reverse bias when the CdTe sensor is used with the forward bias.

Here, if dN / dt = 0 in equation (1), N is
N = (1-C2 / (C1 + C2)) N0≈ (1-C2 / C1)) N0 (2)
(Since C1 >> C2), the difference in the value of N by the X-ray sensor depends on C2. In order to eliminate the trap level, it is necessary that many holes exist in the crystal. For this reason, if the leak current is large, C2 is increased, whereby the trap level number N is decreased, and the output of the X-ray sensor is increased. Therefore, variations in the X-ray sensor output in the forward bias can be reduced by supplying a bias current (leakage current) having the same magnitude to each X-ray sensor.

  However, if the leak current is too large, it appears as noise in the measurement result, and ultimately the quality of the CT image is deteriorated. In order to avoid this, it is necessary to suppress the leakage current to about 1 μA or less. For example, in order to control the leakage current to 1 μA with the X-ray sensor shown in FIG. 4, it is necessary to apply a forward bias voltage of about 0.6 V for sensor 1 and about 0.75 V for sensor 2. Therefore, in this embodiment, bias current supply means for supplying a constant current is provided for each X-ray sensor.

  FIG. 1 shows an internal configuration of the signal processing apparatus 10. The preamplifiers 21-1 to 21-512 convert the output current of the X-ray sensor 4 into a voltage and amplify it. Sample and hold amplifiers (S / H amplifiers) 22-1 to 22-512 hold the outputs of the preamplifiers 21 connected thereto. Then, the AD converters 23-1 to 23-512 convert the output of the sample / hold amplifier 22 into a digital value. The control circuit 24 controls these timings by a signal 19 from the controller 9.

  The bias current supply means 27 is provided corresponding to each X-ray sensor 4. The bias current instruction means 28 supplies the corresponding bias voltage with a corresponding instruction voltage so that each of the bias current supply means 27-1 to 27-512 supplies a bias current of the same magnitude to each X-ray sensor 4. The bias current supply means 27-1 to 27-512 supply a constant bias current to the X-ray sensors 4-1 to 4-512, respectively, according to the instruction voltage. The measured values of the respective X-ray sensors (output values of the AD converters 23-1 to 23-512) are output as a signal 17 to the control device 6 via the bus 25 and the interface 26.

  FIG. 5 is a detailed circuit diagram of the preamplifier 21 and the bias current supply means 27. The preamplifier 21 has a two-stage configuration of current integration and waveform shaping. Since the bias current (leakage current) supplied to the X-ray sensor 4 is a DC component current, the bias current is removed by the capacitor 31. On the other hand, the pulse current of the X-ray sensor 4 generated by the X-ray pulse is accumulated in the capacitor 33 after passing through the capacitor 31. The resistor 32 is a resistor for protecting the input circuit of the OP amplifier 36, and the resistor 34 is a resistor for gradually discharging the output voltage obtained by integrating the current. The time constant is determined by multiplying the values of the capacitor 31 and the resistor 34. The next stage is a differentiating circuit for shaping the output waveform of the first stage. The time constant is determined by the product of the capacitor 37 and the resistance 38.

  In order for the pulse current to flow into the capacitor 33 and the resistor 34, it is necessary that the output impedance of the bias current supply means 27 >> the value of the resistor 32. However, there is no problem because the output impedance of the bias current supply means 27 is several MΩ or more and 100 to 0Ω is used for the resistor 32. The capacitor 31 uses 0.1 μF, the capacitor 33 uses about 10 to 200 pF, and the resistor 34 uses about 1 to 10 MΩ. And the capacitor | condenser 37 and the resistance 38 are adjusted so that the differentiation time constant may be set to about 200 microseconds. When such a constant is used, when an X-ray pulse having a width of 5 μs enters the X-ray sensor 4, the pulse current flows into the capacitor 33 and is integrated, and an output voltage proportional to the incident X-ray dose (photon number) is 21 output terminals.

  The bias current supply means 27 can be realized by combining a commercially available instrumentation amplifier IC and an OP amplifier. The instrumentation amplifier 43 normally has +, − inputs, a reference input (REF in FIG. 6), and an output terminal. The instrumentation amplifier 43 also has an input terminal for controlling the voltage gain, but is omitted because it is used with a gain of 1 in this embodiment. The instruction voltage Vc from the bias current instruction means 28 is input to the + input of the instrumentation amplifier 43. The output of the instrumentation amplifier 43 is connected to the resistor 41, and the other end of the resistor 41 is connected to the CdTe sensor 4.

The OP amplifier 42 constitutes a buffer amplifier with a gain of 1. The + input is connected to the CdTe sensor side terminal of the resistor 41, and the output is connected to the REF terminal of the instrumentation amplifier 43. When the bias current supply means 27 is configured in this way, the leakage current (bias current) I supplied to the X-ray sensor 4 is
I = Vc / R (3)
Is controlled to a constant value. Here, R is a resistance value of the resistor 41, and Vc is an instruction voltage from the bias current instruction means 28. In order to supply a bias current of 1 μA to the X-ray sensor, it is sufficient to set R of the resistor 41 to 100 kΩ and set the instruction voltage Vc from the bias current instruction means 28 to 0.1V.

  The bias current I supplied to each X-ray sensor is held constant by the action of the bias current supply means 27 regardless of the difference in characteristics of the CdTe sensor. For this reason, it is possible to suppress variations in output currents output from a plurality of X-ray sensors, and to improve the quality of images taken by the X-ray CT apparatus. In order to change the bias current I, it is only necessary to change the instruction voltage Vc from the bias current instruction means 28.

  FIG. 6 is a diagram showing a time change of the X-ray pulse incident on the X-ray sensor, the output current of the sensor, the preamplifier output voltage, and the S / H amplifier output voltage of the next stage. The vertical axis shows parameters such as X-ray pulse and output current, and the horizontal axis shows time.

  As described above, the X-ray pulse width Tp (= t1-t0) is 5 μS. Further, the generation interval (t3-t0) of the X-ray pulse is controlled by the controller 9 and is constant, and is 5 ms in this embodiment. Regardless of the presence or absence of X-ray pulses, the X-ray sensor 4 has an equal leakage current flowing through each X-ray sensor, and is caused by X-rays only while X-rays are incident on the X-ray sensor 4. Pulse current to increase. In the preamplifier 21, only the pulse current due to X-rays is integrated into the capacitor 33, and becomes a preamplifier output voltage.

  Therefore, when the In / CdTe / Pt sensor is used with a forward bias voltage and the bias current supply means 27 that supplies a constant bias current regardless of the difference in the characteristics of the CdTe sensor, the high sensitivity of the CdTe sensor is used. Not only can the output of the preamplifier be increased, but also the disadvantages that there is no decrease in sensitivity due to the polarization effect and the output variation between sensors is large can be eliminated.

  The preamplifier output voltage is 0 V before the generation of the X-ray pulse, and increases (in the negative direction because it is an inverting circuit) while the X-ray pulse is incident on the X-ray sensor (from time t0 to t1) to integrate the current. When the generation of the line disappears, it attenuates with a constant time constant by the current integration stage and the waveform shaping stage of the preamplifier and returns to zero. Since the S / H amplifier holds the output at time t1 under the control of the timing controller, it can be converted into a digital value by the AD converter during the hold period (from time t1 to t2).

  Of course, the values of the capacitors and resistors in the above-described embodiments are not limited to these values. In this embodiment, the In electrode side is grounded, and the bias supply means and the preamplifier are connected to the Pt electrode side. However, contrary to the present embodiment, the Pt electrode side can be grounded, and the bias supply means and the preamplifier can be connected to the In electrode side.

  Furthermore, it goes without saying that the X-ray emitting means is not limited to an accelerator as long as it is an X-ray source that generates pulsed X-rays. Furthermore, in the above-described embodiment, the pulse current is converted into a voltage and integrated by a preamplifier that is AC-coupled with the X-ray sensor. However, the preamplifier may perform only current-voltage conversion, and the post-stage circuit may have an integration function. Furthermore, in order to improve the signal-to-noise ratio of the measurement signal, it is possible to shape the waveform with a bandpass filter after the integrating circuit.

  As described above, according to this embodiment, a CdTe compound semiconductor sensor using an In electrode and a Pt electrode is used as the X-ray sensor of the X-ray CT apparatus, and the diode junction of the In electrode portion of the X-ray sensor is used. A means for supplying a constant bias current is provided so as to be a forward bias, and an AC coupling current integration circuit is provided to detect the output current from the X-ray sensor, thereby removing the bias current (leakage current). Thus, not only an increase in preamplifier output by a highly sensitive CdTe sensor can be obtained, but also an output change due to a polarization effect can be avoided. Furthermore, it is possible to provide an industrial X-ray CT apparatus that can reduce variations in the magnitude of the output between sensors and improve the quality of CT reconstructed images.

  Further, the semiconductor material of the X-ray sensor is not limited to CdTe described in this embodiment, and is a semiconductor having a polarization effect, which is a II-VI group described in Patent Document 1 (CdTe: Cl, Even if a bias voltage is applied so that the diode junction is forward biased using CdI-XZnXTe, CdTeI-XSeX, CdI-XZnXTe: Cl, GaAs, HgIn) or TlBr (thallium bromide). Can be expected.

  The sensitivity of the X-ray sensor used in the X-ray CT apparatus can be improved and the output variation can be reduced. As a result, the CT image quality can be improved.

2 is a diagram illustrating an internal configuration of a signal processing device 10. It is a figure which shows the structure of one Example of this invention. It is the elevation which shows the structure of the X-ray sensor currently used for the Example, and a top view. It is a figure which shows an example of the current-voltage characteristic in the forward bias of the X-ray sensor in a present Example. 3 is a detailed circuit diagram of a preamplifier 21 and a bias current supply means 27. FIG. It is the figure which showed the time change of the X-ray pulse which injects into an X-ray sensor, the output current of a sensor, the preamplifier output voltage, and the output voltage of the S / H amplifier of the next stage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electron beam accelerator 3 Scanner 4 X-ray sensor 5 Collimator 6 Control apparatus 7 Image reconstruction apparatus 8 Display apparatus 9 Controller 10 Signal processing apparatus 21 Preamplifier 22 S / H amplifier 23 AD converter 24 Control circuit 25 Bus 26 Interface 27 Bias current Supply means 28 Bias current indicating means 200 CdTe crystal 201 Pt electrode 202 In electrode 203 Insulating substrate 204 Heavy metal substrate

Claims (8)

X-ray emitting means for emitting X-rays to a device under test, a plurality of X-ray sensors for detecting X-rays transmitted through the device under test, and a signal processing device for processing an output signal of the X-ray sensor ,
The signal processing device includes a bias current supply unit that supplies a forward bias current to the X-ray sensors and supplies a bias current having a magnitude equal to each X-ray sensor. Line CT device.   X-ray emitting means for emitting X-rays to the device under test, a plurality of X-ray sensors for detecting X-rays transmitted through the device under test, and a signal processing device for processing output signals of the plurality of X-ray sensors The X-ray sensor is a semiconductor sensor, a bias voltage is applied to the X-ray sensor in the forward direction in which a large amount of bias current flows, and a plurality of bias currents of the same magnitude are supplied to the X-ray sensors. An X-ray CT apparatus comprising: a bias current supply means; and means for removing a direct current component from an output signal from the X-ray sensor.   X-ray emitting means for emitting X-rays to the device under test, a plurality of X-ray sensors for detecting X-rays transmitted through the device under test, and a signal processing device for processing output signals of the plurality of X-ray sensors The X-ray sensor is a semiconductor sensor, a bias voltage is applied in the forward direction in which a large amount of bias current flows to the X-ray sensor, and a plurality of bias current supplies for supplying a bias current to each X-ray sensor are provided. Means, bias current indicating means for controlling the bias current supply means to supply a bias current of the same magnitude to each of the X-ray sensors, and DC component current and bias current output from the X-ray sensors. And an X-ray CT apparatus.   The X-ray CT apparatus according to claim 1, wherein the semiconductor sensor is a CdTe sensor having a diode junction. X-ray emitting means for emitting X-rays to a device under test, a plurality of X-ray sensors for detecting X-rays transmitted through the device under test, and a signal processing device for processing an output signal of the X-ray sensor An X-ray detection method for an X-ray CT apparatus,
An X-ray detection method for an X-ray CT apparatus, wherein a forward bias current is supplied to the X-ray sensors, and a bias current having an equal magnitude is supplied to each X-ray sensor. The X-ray detection method of the X-ray CT apparatus according to claim 5,
Causing the X-ray sensor to generate the bias current together with a pulse current caused by X-rays transmitted through the device under test;
An X-ray detection method using an X-ray CT apparatus, wherein the bias current is removed and the pulse current is detected. X-ray emitting means for emitting X-rays to a device under test, a plurality of X-ray sensors for detecting X-rays transmitted through the device under test, and a signal processing device for processing an output signal of the X-ray sensor ,
The signal processing device includes a bias current supply unit that supplies a forward bias current to the X-ray sensors and supplies a bias current having a magnitude equal to each X-ray sensor. Line sensor signal processing system. X-ray emitting means for emitting X-rays to a device under test, a plurality of X-ray sensors for detecting X-rays transmitted through the device under test, and a signal processing device for processing an output signal of the X-ray sensor An X-ray sensor signal processing method for an X-ray CT apparatus,
A forward current to the X-ray sensor, and a bias current of the same magnitude supplied to each X-ray sensor and a pulse current due to the X-ray transmitted through the device under test,
An X-ray sensor signal processing method, wherein the bias current is removed and the pulse current is detected.

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