# US 2019/0170880 A1 · Processing of a corrected x-ray detector signal

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- Number: US 2019/0170880 A1
- Document ID: US20190170880A1
- Status: Published application
- Kind: A1
- Application number: 15/756,620
- Filed: 2016-09-15
- Published: 2019-06-06
- Earliest claimed: 2015-09-18
- Assignees: Koninklijke Philips N.V.
- Applicants: Koninklijke Philips N.V.
- Inventors: Roger STEADMAN BOOKER; Christoph HERRMANN; Amir LIVNE
- Web page: https://patentgrep.com/patent/US20190170880A1

## CPC

- G01T 1/17: Circuit arrangements not adapted to a particular type of detector {(pulse-selection circuits H03K, G01R)}
- G01T 1/247: {Detector read-out circuitry (for processing gain or off-set correction H04N)}
- G01T: MEASUREMENT OF NUCLEAR OR X-RADIATION (radiation analysis of materials, mass spectrometry G01N23/00; tubes for determining the presence, intensity, density or energy of radiation or particles H01J47/00)

## Abstract

The present invention relates to the correction of a detector signal d by superposing the detector signal with a correction signal. For providing a valid correction signal, a sampling pulse Ps is periodically or randomly provided. This sampling pulse serves as the initiator for sampling a process signal p of a process unit (14), which is configured to process the corrected detector signal. During the sampling of the process signal, the process signal is observed. In case a pulse at the process signal is detected, the sampling is assumed as not being suitable to correct the detector signal, since the pulse affects the process signal. Otherwise, namely in case such a process signal pulse does not occur during the sampling period, the process signal is further observed during a validation period, which is subsequently arranged to the sampling period. This validation period is used to validate, whether the sampled process value of the process signal has already been influenced by an upcoming pulse at the process signal. In case the sampling is assumed as valid, the sampled process value is used as a basis for providing, in particular setting or updating, the correction signal. An updated or a new set correction signal in turn changes the baseline of the corrected detector signal. As an effect of the invention, the baseline of the corrected detector signal may be corrected independent of the direct knowledge of a timing, at which an X-ray source provides X-ray radiation to the object-receiving space and/or at least a part thereof to an X-ray detector (42). Therefore, the invention may be applied to any X-ray imaging system, independently of the knowledge, when X-ray quanta and/or X-ray photons impinge on the X-ray detector.

## Claims

### Claim 1

An apparatus for correcting an X-ray detector signal d, comprising:
an input interface;
a signal processing unit; and
a signal correction unit;
wherein the input interface is configured to receive a detector signal d representing X-ray radiation detected by an X-ray detector, wherein the detector is configured such that the detector signal comprises one or more pulses that relate to a detected X-ray quanta and/or X-ray photons;
wherein the apparatus is configured to determine a basis signal b on the basis of a difference between the detector signal and a correction signal c and to periodically or randomly provide a sampling pulse Ps, wherein the basis signal can be regarded as a corrected detector signal when no pulse is detected at the detector and as such the basis signal forms a baseline for the detector signal;
wherein the signal processing unit is configured to provide a process signal p on the basis of the basis signal, wherein the signal processing unit is configured to process the corrected detector signal to provide the process signal;
wherein the signal correction unit is configured to (i) sample a first process value V1 of the process signal at a first sampling period Ts1 subsequent to the sampling pulse,
(ii) observe the process signal during the first sampling period and a first validation period Tv1 subsequent to the first sampling period,
(iii) detect a first process signal pulse U1 at the process signal, in case the first process signal pulse occurs during the first sampling period and/or the first validation period; and
(iv) provide the correction signal on the basis of the first process value subsequent to the first validation period, if the first process signal pulse has not been detected.

### Claim 2 (depends on 1)

The apparatus according to claim 1, wherein
for (iii) detecting the first process signal pulse, the signal correction unit is further configured to compare the value of the process signal with an upper threshold value pth,max and/or a lower threshold value pth,min, wherein the upper threshold value is larger than a baseline value pbase and the lower threshold value is smaller than the baseline value, and to determine an occurrence of the first process signal pulse, if the value of the process signal exceeds the upper threshold value or the lower threshold value.

### Claim 3 (depends on 1)

The apparatus according to claim 1, wherein the signal correction unit is further configured to detect, if the first process signal pulse has been detected, an end time Te of the first process signal pulse, to sample a second process value V2 of the process signal at a second sampling period Ts2 subsequent to the end time of the first process signal pulse, to observe the process signal during the second sampling period and a second validation period Tv2 subsequent to the second sampling period, to detect a second process signal pulse U2 at the process signal, in case the second process signal pulse occurs during the second sampling period and/or the second validation period, and provide the correction signal on the basis of the second process value subsequent to the second validation period, if the second process signal pulse has not been detected.

### Claim 4 (depends on 1)

The apparatus according to claim 1, wherein the signal correction unit is further configured to determine a provided signal pulse as a forced signal pulse psf, if the first process signal pulse has been detected during the previous first sampling period and/or during the previous first validation period and/or if the second process signal pulse has been detected during the previous second sampling period and/or during the previous second validation period; to sample a third process value V3 of the process signal at a third sampling period Ts3 subsequent to the forced sampling pulse; and to provide the correction signal on the basis of the third process value subsequent to the third sampling period.

### Claim 5 (depends on 1)

The apparatus according to claim 1, wherein the signal correction unit is further configured to determine a first auxiliary signal a1 by high-pass-filtering the process signal, to determine a second auxiliary signal a2 by comparing the first auxiliary signal with a first auxiliary threshold value, wherein the value of second auxiliary signal is a high second value, if the value of the first auxiliary signal exceeds the first auxiliary threshold value, and a low second value otherwise, wherein the high second value is larger than the low second value, to determine a third auxiliary signal a3 by low-pass-filtering the second auxiliary signal, to determine a fourth auxiliary signal a4 by comparing the third auxiliary signal with a fourth auxiliary threshold value, wherein the value of fourth auxiliary signal is a high fourth value, if the value of the third auxiliary signal exceeds the second auxiliary threshold value, and a low fourth value otherwise, wherein the high fourth value is larger than the low fourth value, and to interrupt an update of the correction signal and/or determination of the forced signal pulse, while the value of the fourth auxiliary signal is equal to the high fourth value.

### Claim 6 (depends on 1)

The apparatus according to claim 1, wherein the signal correction unit is configured to interrupt, subsequently after the detection of the second process signal pulse, the observation of the process signal during the second sampling period and the second validation period and/or to interrupt, subsequently after the detection of the second process signal pulse, the detection of the second process signal pulse; and/or wherein the signal correction unit is configured to interrupt, subsequent after the detection of the first process signal pulse, the observation of the process signal during the first sampling period and the first validation period and/or to interrupt, subsequently after the detection of the first process signal pulse, the detection of the first process signal pulse.

### Claim 7 (depends on 1)

An X-ray imaging system, comprising:
an apparatus according to claim 1;
a detector unit configured to detect X-ray radiation; and
an evaluation unit configured to resolve the value of the process signal into different value levels and to provide an evaluation signal e on the basis the resolving results.

### Claim 8

A method for correcting an X-ray detector signal d, comprising the following steps:
a) Receiving the detector signal representing X-ray radiation detected by an X-ray detector, wherein the detector is configured such that the detector signal comprises one or more pulses that relate to a detected X-ray quanta and/or X-ray photons;
b) Determining a basis signal b on the basis of a difference between the detector signal and a correction signal c, wherein the basis signal can be regarded as a corrected detector signal when no pulse is detected at the detector and as such the basis signal forms a baseline for the detector signal;
c) Providing a process signal p by signal processing the basis signal, wherein the signal processing unit is configured to process the corrected detector signal to provide the process signal;
d) Periodically or randomly providing a sampling pulse Ps;
e) Sampling a first process value V1 of the process signal at a first sampling period Ts1 subsequent to the sampling pulse;
f) Observing the process signal during the first sampling period and a first validation period Tv1 subsequent to the first sampling period; wherein step f) comprises the sub-step f1): Detecting a first process signal pulse U1 at the process signal, in case the first process signal pulse occurs during the first sampling period and/or the first validation period; and
g) Providing the correction signal on the basis of the first process value subsequent to the first validation period, if the first process signal pulse has not been detected.

### Claim 9 (depends on 8)

The method according to claim 8, wherein the step f) comprises the sub-step f2): Interrupting step f), if and subsequently after the first process signal pulse has been detected.

### Claim 10 (depends on 8)

The method according to claim 8, wherein step f1) comprises the sub-steps:
f1.1) Comparing the value of the process signal with an upper threshold value pth,max and/or a lower threshold value pth,min, wherein the upper threshold value is larger than a baseline value pbase and the lower threshold value is smaller than the baseline value; and
f1.2) Determining an occurrence of the first process signal pulse, if the value of the process signal exceeds the upper threshold value or the lower threshold value.

### Claim 11 (depends on 8)

The method according to claim 8, further comprising the following steps:
h) Detecting an end time Te of the first process signal pulse, if the first process signal pulse has been detected;
i) Sampling a second process value V2 of the process signal at a second sampling period Ts2 subsequent to the end time of the first process signal pulse;
j) Observing the process signal during the second sampling period and a second validation period Tv2 subsequent to the second sampling period; wherein step j) comprises the sub-steps j1): Detecting of a second process signal pulse at the process signal, in case the second process signal pulse occurs during the second sampling period and/or the second validation period;
k) Providing the correction signal on the basis of the second process value subsequent to the second validation period, if the second process signal pulse has not been detected.

### Claim 12 (depends on 8)

The method according to claim 8, further comprising the steps:
l) determining a provided signal pulse ps as a forced signal pulse psf, if a first process signal pulse has been detected during the previous first sampling period and/or during the previous first validation period and/or if a second process signal pulse has been detected during the previous second sampling period and/or during the previous second validation period;
m) sampling a third process value V3 of the process signal at a third sampling period Ts3 subsequent to the forced sampling pulse; and
n) providing the correction signal on the basis of the third process value subsequent to the third sampling period.

### Claim 13 (depends on 8)

The method according to claim 8, further comprising the following steps:
o) Determining a first auxiliary signal a1 by high-pass-filtering the process signal;
p) Determining a second auxiliary signal a2 by comparing the first auxiliary signal with a first auxiliary threshold value, wherein the value of second auxiliary is set to a high second value, if the first auxiliary value exceeds the first auxiliary threshold value, and to a low second value otherwise, wherein the high second value is larger than the low second value;
q) Determining a third auxiliary signal a3 by low-pass-filtering the second auxiliary signal;
r) Determining a fourth auxiliary signal a4 by comparing the third auxiliary signal with a second auxiliary threshold value, wherein the value of fourth auxiliary is set to a high fourth value, if the third auxiliary value exceeds the second auxiliary threshold value, and to a low fourth value otherwise, wherein the high fourth value is larger than the low fourth value; and
s) Interrupting step g) or step l), while the value of the fourth signal is equal to the high fourth value.

### Claim 14 (depends on 8)

A computer program element for controlling a device, which, when being executed by a processing unit, is adapted to perform the method steps of claim 8.

### Claim 15 (depends on 14)

A computer readable medium having stored the program element of claim 14.