Method and device for slit radiography

Claim 2

Method for slit radiography in which use is made of an X-ray source and a slit diaphragm placed in front of the X-ray source to form a fan-shaped X-ray beam with which a body to be investigated is at least partially scanned to form an X-ray shadow image on an X-ray detector placed behind the body, which fan-shaped X-ray beam is formed by a number of sectors situated next to each other, and in which the transmitted X-ray radiation is controlled instantaneously for each sector during the scanning movement by means of controllable beam sector modulators acting in conjunction with the slit diaphragm, characterized in that the X-ray radiation is cyclically modulated in a predetermined manner for all the sectors taken together and in that the controllable beam sector modulators are individually controlled in order to select cyclically a part of the X-ray radiation for each sector, which cyclic selection is synchronized with the predetermined cyclic modulation of the X-ray radiation.

Claim 3

Method according to claim 1, characterized in that the cyclic selection takes place by varying the position of the beam sector modulators with a fixed cycle between a first position essentially transmitting the X-ray beam and a second variable position.

Claim 4

Method according to claim 1, characterized in that the cyclic selection takes place by varying the position of the beam sector modulators between a first position essentially transmitt­ing the X-ray beam and a second position controlling the X-ray beam in a minimum manner, at least the phase of the occurrence of the second position being varied with respect to the common pre­determined cyclic modulation.

Claim 5

Method according to claim 3, characterized in that the starting point of time of the first position is varied.

Claim 6

Method according to claim 3, characterized in that the end point of time of the first position is varied.

Claim 7

Method according to claim 3, characterized in that the duration of the first position is varied.

Claim 8

Method according to claim 1, characterized in that the cyclic selection is carried out with beam sector modulators made to vibrate, the phase of the vibration being varied.

Claim 9

Method according to claim 1, characterized in that the cyclic selection is carried out with beam sector modulators made to vibrate, the amplitude of the vibration being varied.

Claim 10

Method according to claim 1, characterized in that the cyclic selection is carried out with beam sector modulators made to vibrate, the phaseand the amplitude of the vibration being varied

Claim 11

Method according to one of the claims 7 to 9 incl., characterized in that a faster second vibration is superimposed on the vibration.

Claim 12

Method according to one of the preceding claims, characterized in that for each sector signals are generated which are representative of the transmission of the body to be investigated and in that each controllable beam sector modulator is controlled in accordance with the associated signal.

Claim 13

Method for slit radiography, in which use is made of an X-ray source and a slit-type diaphragm placed in front of the X-ray source to form a fan-shaped X-ray beam with which a body to be investigated is at least partially scanned to form an X-ray shadow image on an X-ray detector placed behind the body, and in which the quantity of X-ray radiation transmitted by the slit diaphragm is controlled instantaneously for each sector of the X-ray beam during the scanning movement by means of controllable beam sector modulators acting in conjunction with the slit diaphragm as a function of the quantity of X-ray radiaion trans­mitted in the sector by the body, characterized in that the X-ray beam is cyclically modulated during operation in a predetermined manner, in that the quantity of radiation transmitted by the body in each sector is measured in synchronism with the cyclic modulat­ion during measurement intervals, in that the beam sector modulators are each brought, in a manner synchronized with the cyclic modulation during at least a part of first time intervals, which are alternated with second time intervals to the open position in which the X-ray radiation is transmitted in the sector corresponding to the beam sector modulator concerned, in that the measurement intervals at least partially coincide with at least the first time intervals, and in that each beam sector modulator is brought during at least a part of the second time intervals, to a position which is dependent on the quantity of radiation transmitted by the body measured in at least one preceding measurement interval in the associated sector.

Claim 14

Method for slit radiography, in which use is made of an X-ray source and a slit-type diaphragm placed in front of the X-ray source to form a fan-shaped X-ray beam with which a body to be investigated is at least partially scanned to form an X-ray shadow image on an X-ray detector placed behind the body, and in which the quantity of X-ray radiation transmitted by the slit diaphragm is controlled instantaneously for each sector of the X-ray beam during the scanning movement by means of controllable beam sector modulators acting in conjunction with the slit diaphragm as a function of the quantity of X-ray radiaion trans­mitted in the sector by the body, characterized in that the X-ray beam is cyclically modulated during operation in a predetermined manner, in that the quantity of radiation transmitted by the body in each sector is measured in synchronism with the cyclic modulat­ion during measurement intervals, in that the beam sector modulators are each brought, in a manner synchronized with the cyclic modulation during at least a part of first time intervals, which are alternated with second time intervals to the open position in which the X-ray radiation is transmitted in the sector corresponding to the beam sector modulator concerned, in that the measurement intervals at least partially coincide with at least the first time intervals, and in that each beam sector modulator is brought during at least a part of the second time intervals, to a position which is dependent on the quantity of radiation transmitted by the body measured in at least one preceding measurement interval in the associated sector.

Claim 15

Method according to claim 12, characterized in that the beam sector modulators are each brought to one of a number of possible discrete positions during at least a part of the second time intervals.

Claim 16

Method according to claim 13, characterized in that the possible discrete positions of the bem sector modulators during the second time intervals include the open position and the closed position in which a beam sector modulator controls the X-ray beam in the sector concerned in a maximum manner, and in that, if the quantity of radiation in a sector measured during a measurement interval exceeds a predetermined value, the associated beam selector modulator is brought to the closed position in a subsequent second time interval, while the beam sector modulator is maintained in the open position if the measured quantity of radiation in the sector does not exceed the predetermined value.

Claim 17

Method according to claim 14, characterized in that each beam sector modulator can take up at least one further discrete position to which a beam sector modulator is brought during a second time interval if the quantity of radiation measured in the associated sector during the preceding measurement interval is between two predetermined values.

Claim 18

Method for slit radiography in which use is made of an X-ray source and a slit diaphragm placed in front of the X-ray source to form a fan-shaped X-ray beam with which a body to be investigated is at least partially scanned to form an X-ray shadow image on an X-ray detector placed behind the body, and in which the quantity of X-ray radiation transmitted by the slit diaphragm for each sector of the X-ray beam is controlled instantaneously for each sector during the scanning movement by means of controllable beam sector modulators acting in conjunct­ion with the slit diaphragm as a function of the quantity of X-ray radiation transmitted in the sector by the body, character­ized in that, during operation, the X-ray beam is modulated cyclically in a predetermined manner, in that the quantity of radiation transmitted by the body in each sector is measured in synchronism with the cyclic modulation during the measurement intervals, in that each beam sector modulator is brought in each case during consecutive time intervals synchronized with the cyclic modulation alternately to the open position, in which the X-ray radiation in the sector corresponding to the beam sector modulator concerned is transmitted, and the closed position in which the X-ray radiation in the sector concerned is controlled in a maximum manner, in that the measurement of the quantity of radiation transmitted by the body in a sector takes place during the open position of the associated beam sector modulator, and in that, depending on the amount of radiation measured, the phase of a subsequent time interval in which the beam sector modulator is in the open position is controlled with respect to the cyclic modulation.

Claim 19

Method for slit radiography in which use is made of an X-ray source and a slit diaphragm placed in front of the X-ray source to form a fan-shaped X-ray beam with which a body to be investigated is at least partially scanned to form an X-ray shadow image on an X-ray detector placed behind the body, and in which the quantity of X-ray radiation transmitted by the slit diaphragm for each sector of the X-ray beam is controlled instantaneously for each sector during the scanning movement by means of controllable beam sector modulators acting in conjunct­ion with the slit diaphragm as a function of the quantity of X-ray radiation transmitted in the sector by the body, character­ized in that, during operation, the X-ray beam is modulated cyclically in a predetermined manner, in that the quantity of radiation transmitted by the body in each sector is measured in synchronism with the cyclic modulation during the measurement intervals, in that each beam sector modulator is brought in each case during consecutive time intervals synchronized with the cyclic modulation alternately to the open position, in which the X-ray radiation in the sector corresponding to the beam sector modulator concerned is transmitted, and the closed position in which the X-ray radiation in the sector concerned is controlled in a maximum manner, in that the measurement of the quantity of radiation transmitted by the body in a sector takes place during the open position of the associated beam sector modulator, and in that, depending on the amount of radiation measured, the phase of a subsequent time interval in which the beam sector modulator is in the open position is controlled with respect to the cyclic modulation.

Claim 20

Method according to claim 16, characterized in that the length of the "open position" time interval is also controlled.

Claim 21

Method according to one of the preceeding claims characterized in that the cyclic modulation is brought about by amplitude modulation of the supply high voltage of the X-ray source.

Claim 22

Method according to one of the claims 1 to 17 incl., characterized in that the cyclic modulation is brought about by modulation of the current flowing through the X-ray tube of the X-ray source.

Claim 23

Method according to one of the claims 1 to 17 incl., characterized in that the cyclic modulation is brought about by covering the slit of the slit diaphragm cyclically with at least one element which attenuates X-ray radiation.

Claim 24

Method according to claim 20, characterized in that the cyclic modulation is obtained by cyclically and consecutively covering the slit of the slit diaphragm with first or second elements which attenuate X-ray radiation, the first and second elements influencing the X-ray radiation in different manners.

Claim 25

Method according to claim 18 or 19, characterized in that, during predetermined cyclic phase trajectories of the cyclic modulation, during which phase trajectories the X-ray source delivers both relatively hard and relatively soft X-ray radiation, the slit of the slit diaphragm is covered synchronously by an element absoring soft X-ray radiation.

Claim 28

A device according to claim 23, characterized in that the control means control the beam sector modulators in a manner such that the beam sector modulators are each brought to the open position, in which the X-ray radiation is able to pass the beam sector modulators, during at least a part of the first time inter­vals in a rhythm synchronized with the modulation of the X-ray beam, and can be brought to the closed position, in which the beam sector modulators control the X-ray beam in a maximum manner, during at least a part of the second time intervals which are each situated between two first time intervals, and in that the control means are constructed to receive input signals from the radiation detector, which input signals represent the quantity of radiation transmitted by the body during at least one measurement interval coinciding at least partially in each case with a first time interval, and if the quantity of radiation in a sector measured during a measurement interval is less than a pre­determined value, the control means deliver a control signal which has the effect that the beam sector modulator associated with said sector is not brought to the closed position during a second time interval following the measurement interval.

Claim 29

A device according to claim 24, characterized in that the control means are constructed so as to deliver, if the quantity of radiation transmitted by the body during a measurement interval in a sector is less than the predetermined value, a signal which keeps the beam sector modulator associated with said sector in the open position during the subsequent second time interval.

Claim 30

A device according to claim 25, characterized in that the control means are constructed so as to deliver, if the quantity of radiation measured during a measurement interval in a sector is between two predetermined values, a control signal which brings the beam sector modulator associated with said sector to a predetermined intermediate position situated between the open and the closed position.

Claim 31

According to claim 23, characterized in that the control means control the beam sector modulators in a manner such that the beam sector modulators are each brought to the open position, in which the X-ray beam is able to pass the beam sector modulators, in a rythm synchronized with the modulation of the X-ray beam during at least a part of the first time intervals, and are brought to the closed position in which the beam sector modulators control the X-ray beam in a maximum manner during at least a part of the second time intervals which are each situated between two first time intervals, and in that the control means are constructed so as to receive input signals from the radiation detector, which input signals represent the quantity of radiation transmitted by the body during a measurement interval coinciding in each case at least partially with a first time interval, the control means delivering control signals which correspond to the input signals and which control the phase of a subsequent "open position" interval with respect to the cyclic modulation.

Claim 32

28,. A device according to claim 27, characterized in that the control signals control the length of a subsequent "open position" interval.

Claim 33

A device according to claim 23, characterized in that the means of modulation comprise means which modulate the supply voltage of the X-ray tube of the X-ray source in amplitude.

Claim 34

A device according to claim 23, characterized in that the modulation means comprise means which modulate the current flowing through the X-ray tube of the X-ray source in amplitude.

Claim 35

A device according to claim 23, characterized in that the modulation means are means which comprise at least one element which attenuates X-ray radiation and which cyclically covers or exposes the slit of the slit diaphragm.

Claim 36

A device according to claim 31, characterized in that the modulation means comprise a plate-type element which extends essentially parallel to the longitudinal direction of the slit of the slit-type diaphragm over the full length of the slit and which can be brought at least partially cyclically into a position covering the slit.

Claim 37

A device according to claim 32, characterized in that the plate-type element is mounted in a pivotable manner with respect to a spindle situated outside the X-ray beam and extending essentially parallel to the longitudinal direction of the slit.

Claim 38

A device according to claim 32, characterized in that the plate-type element is manufactured from piezoelectric material and can swivel into the X-ray beam under the influence of electrical signals with respect to a longitudinal edge, mounted in a fixed manner, of the plate-type element by means of the other longitudinal edge.

Claim 39

A device according to claim 31, characterized in that the modulation means comprise a roller which can be rotated about a spindle extending essentially parallel to the longitudinal direction of the slit, which roller is provided with a number of radial blades of material which attenuates X-ray radiation extending over the full length of the slit.

Claim 40

According to claim 35, characterized in that the blades are manufactured in turn of different materials which influence X-ray radiation in different manners.

Claim 41

A device according to claim 31, characterized in that the modulation means comprise a segment wheel which can totate about a spindle which extends transversely with respect to the plane containing the slit of the slit diaphragm and which is located laterally next to the slit and which has a radius which is at least as large as the length of the slit, the segment wheel having at least one segment which is manufactured from material which attenuates X-ray radiation.

Claim 42

A device according to claim 37, characterized in that the segment wheel consists of a hub provided with a number of radial arms of material which attenuates X-ray radiation.

Claim 43

A device according to claim 37, characterized in that the segment wheel comprises first and second segments which alternate with each other and which are manufactured from a first or second material, which materials influence X-ray radiation in different manners.

Claim 44

40 A device according to claim 39, characterized in that the first material transmits at least soft X-ray radiation and in that the second materials transmits only essentially hard X-ray radiation.

Claim 45

A device according to claim 39, characterized in that the segments are manufactured alternately from lead and copper.

Claim 46

A device according to claim 39, characterized in that the segments are manufactured alternately from aluminum and copper.

Claim 47

A device according to claim 39, characterized in that the segments are manufactured alternately from lead and aluminum.

Claim 48

A device according to claim 23, characterized in that the controllable beam sector modulators each comprise a blade disc, each disc comprising at least one blade of material which attenuates X-ray radiation, and in that the blade discs are mounted next to each other on a rotatable spindle which extends essentially parallel to the longitudinal direction of the slit of the slit diaphragm, it being possible to vary the position of the blade discs with respect to the spindle in operation.

Claim 49

A device according to claim 44, characterized in that each blade disc is mounted in a slipping manner on the spindle.

Claim 50

A device according to claim 44, characterized in that each blade disc is mounted in a sprung manner on the spindle.

Claim 51

A device according to claim 44, characterized in that there is provided for each blade disc a brake element which can be energized by the control means and by means of which the position of the associated blade disc can be changed with respect to the spindle.

Claim 52

A device according to claim 47, characterized in that the blade discs have a circumferential face with which a small brake block can be bought into contact.

Claim 53

A device according to claim 47, characterized in that the brake element is an eddy-current brake.