Method for the automatic determination of the exposure time of a radiographic film and system of implementation thereof

Claim 1

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tube, the supply voltage V of which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, an image receiver for detecting the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen and a film sensitive to the light emitted by said screen, a cell for the detection of the X-rays that have crossed the object to be examined, placed behind the image receiver, for converting a physical variable, characterizing the X-ray beam into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure to produce a signal M, and a device to compute the yield D given by the ratio of M to the product I×S (mA·s) of the anode current I of the tube by the duration S of the exposure, wherein said method includes the following operations: (a) a first calibration of the radiology system by means of objects with a thickness E p by using a receiver without the intensifier screen or screens so as to determine the yield D se from the function: D.sub.se =f'(V.sub.m, E.sub.p) (4) and the thickness E p from the inverse function: E.sub.p =g' (V.sub.m, D.sub.se) (5) (b) a second calibration of the radiology system by means of the objects with a thickness E p by using a receiver with an intensifier screen so as to determine the yield D c from the function: D.sub.c =f" (V.sub.m, E.sub.p) (6) the thickness E p from the inverse function: E.sub.p =g" (V.sub.m D.sub.c) (7) and compute the yield on the film D f function: D.sub.f =f' (V.sub.m, E.sub.p)-f" (V.sub.m, E.sub.p) (8) (c) a third calibration to determine the reference lumination L ref that must be received by the film, under fixed reference conditions, to achieve the blackening (or optical density) chosen as a reference value comprising the following steps of: (e1) positioning the object to be radiographed; (e2) triggering the start of the exposure; (e3) measuring the yield D c1 at a certain time t' after the start of the exposure; (e4) measuring the equivalent thickness E 1 by the equation g" (V m , D c ); (e5) calculating the yield D f1 at the level of the film for the thickness E 1 by f'(V m , E p )-f" (V m , E p ); (e6) calculating the lumination L f received by the film from the illumination received by the film before step (e3) L am and the number of mA·s delivered by the tube during t',δmA·s according to the equation: L.sub.f =L.sub.am +D.sub.f1 ×δmA·s (9) (e7) calculating the lumination L ra remaining to be acquired to obtain the blackening (or optical density) determined by the equation: L.sub.ra =L.sub.ref -L.sub.f ( 10) (e8) calculating the estimated mA·s remaining to be delivered MaS r to obtain the blackening (or optical density) determined by the equationL mAs.sub.r =L.sub.ra /D.sub.f1 ( 11) (e9) measuring the mA·s delivered mAs mes from the start of the operation (e3); (e10) stopping the exposure when the mA·s measured mAs mes are equal to or greater than mAs r , or a return to the step (e3) when the mA·s measured are smaller than mAs r .

Claim 2

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tube, the supply voltage V of which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, an image receiver for detecting the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen and a film sensitive to the light emitted by said screen, a cell for the detection of the X-rays that have crossed the object to be examined, placed behind the image receiver, for converting a physical variable, characterizing the X-ray beam into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure to produce a signal M, and a device to compute the yield D given by the ratio of M to the product I×S (mA·s) of the anode current I of the tube by the duration S of the exposure, wherein said method includes the following operations: (a) a first calibration of the radiology system by means of objects with a thickness E p by using a receiver without the intensifier screen or screens so as to determine the yield D se from the function: D.sub.se =f'(V.sub.m, E.sub.p) (4) and the thickness E p from the inverse function: E.sub.p =g' (V.sub.m, D.sub.se) (5) (b) a second calibration of the radiology system by means of the objects with a thickness E p by using a receiver with an intensifier screen so as to determine the yield D c from the function: D.sub.c =f" (V.sub.m, E.sub.p) (6) the thickness E p from the inverse function: E.sub.p =g" (V.sub.m D.sub.c) (7) and compute the yield on the film D f function: D.sub.f =f' (V.sub.m, E.sub.p)-f" (V.sub.m, E.sub.p) (8) (c) a third calibration to determine the reference lumination L ref that must be received by the film, under fixed reference conditions, to achieve the blackening (or optical density) chosen as a reference value comprising the following steps of: (e1) positioning the object to be radiographed; (e2) triggering the start of the exposure; (e3) measuring the yield D c1 at a certain time t' after the start of the exposure; (e4) measuring the equivalent thickness E 1 by the equation g" (V m , D c ); (e5) calculating the yield D f1 at the level of the film for the thickness E 1 by f'(V m , E p )-f" (V m , E p ); (e6) calculating the lumination L f received by the film from the illumination received by the film before step (e3) L am and the number of mA·s delivered by the tube during t',δmA·s according to the equation: L.sub.f =L.sub.am +D.sub.f1 ×δmA·s (9) (e7) calculating the lumination L ra remaining to be acquired to obtain the blackening (or optical density) determined by the equation: L.sub.ra =L.sub.ref -L.sub.f ( 10) (e8) calculating the estimated mA·s remaining to be delivered MaS r to obtain the blackening (or optical density) determined by the equationL mAs.sub.r =L.sub.ra /D.sub.f1 ( 11) (e9) measuring the mA·s delivered mAs mes from the start of the operation (e3); (e10) stopping the exposure when the mA·s measured mAs mes are equal to or greater than mAs r , or a return to the step (e3) when the mA·s measured are smaller than mAs r .

Claim 18

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tube, the supply voltage V which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, a receiver of the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen, a film sensitive to the light emitted by said screen and a cell for the detection of the light emitted by said screen, that enables the conversion of a physical variable, characterizing the X-ray beam, into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure and gives a signal M, and a device to compute the yield D given by the ratio of M to the product I×S (mA·s) of the anode current I of the tube by the duration S of the exposure, wherein said method includes the following steps of: (a) determining by calibration the reference lumination L ref that must be received by the film, under fixed reference conditions, to achieve the blackening chosen as a reference value; (b1) positioning the object to be radiographed; (b2) triggering the start of the exposure by the practitioner; (b3) measuring the yield D f1 at a certain time t' after the start of the exposure; (b4) calculating the lumination L f received by the film from the illumination received from the film before step (b3) and from the number of mA·s delivered by the tube during t',δmA·s, according to the equation: L.sub.f =L.sub.am +D.sub.f1 ×δmA·s (9) (b5) calculating the lumination L ra remaining to be acquired to obtain the determined blackening (or optical density) by the equation: L.sub.ra =L.sub.ref =L.sub.f ( 10) (b6) calculating the estimated mA·s remaining to be delivered mAs r to obtain the determined blackening (or optical density) by the equation: mAs.sub.r =L.sub.ra /D.sub.f1 ( 11) (b7) measuring the mA·s delivered mAs mes from the start of the operation (b3); (b8) stopping the exposure when the mA·s measured mAs mes (in step (b7) are equal to or greater than mAs r , or returning to the step (b3) when the mA·s measured in step (b7) are smaller than mAs r .

Claim 19

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tube, the supply voltage V which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, a receiver of the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen, a film sensitive to the light emitted by said screen and a cell for the detection of the light emitted by said screen, that enables the conversion of a physical variable, characterizing the X-ray beam, into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure and gives a signal M, and a device to compute the yield D given by the ratio of M to the product I×S (mA·s) of the anode current I of the tube by the duration S of the exposure, wherein said method includes the following steps of: (a) determining by calibration the reference lumination L ref that must be received by the film, under fixed reference conditions, to achieve the blackening chosen as a reference value; (b1) positioning the object to be radiographed; (b2) triggering the start of the exposure by the practitioner; (b3) measuring the yield D f1 at a certain time t' after the start of the exposure; (b4) calculating the lumination L f received by the film from the illumination received from the film before step (b3) and from the number of mA·s delivered by the tube during t',δmA·s, according to the equation: L.sub.f =L.sub.am +D.sub.f1 ×δmA·s (9) (b5) calculating the lumination L ra remaining to be acquired to obtain the determined blackening (or optical density) by the equation: L.sub.ra =L.sub.ref =L.sub.f ( 10) (b6) calculating the estimated mA·s remaining to be delivered mAs r to obtain the determined blackening (or optical density) by the equation: mAs.sub.r =L.sub.ra /D.sub.f1 ( 11) (b7) measuring the mA·s delivered mAs mes from the start of the operation (b3); (b8) stopping the exposure when the mA·s measured mAs mes (in step (b7) are equal to or greater than mAs r , or returning to the step (b3) when the mA·s measured in step (b7) are smaller than mAs r .

Claim 29

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tue, the supply voltage V which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, an image receiver of the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen, a film sensitive to the light emitted by said screen and a cell for the detection of the light emitted by said screen, that enables the conversion of a physical variable, characterizing the X-ray beam, into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure and gives a signal M, and a device to compute the yield D given by the ratio of M to the product I×S (mA·s) of the anode current I of the tube by the duration S of the exposure, wherein said method includes the following steps of: (a) determining by calibration the reference lumination L ref that must be received by the film, under fixed reference conditions, to achieve the blackening (or optical density) chosen as a reference value: b1) positioning the object to be radiographed; b2) triggering the start of the exposure; b3) measuring the yield D f1 at a certain time t' after the start of the exposure; b4) calculating the lumination L f received by the film from the illumination received from the film before step B3 and from the number of mA·s delivered by the tue during t', δmA·s according to the equation: L.sub.f =L.sub.am +D.sub.f1 ×δmA·s (9) (b5) calculating the lumination L ra remaining to be acquired to obtain the blackening (or optical density) determined by the equation: L.sub.ra =L.sub.ref -L.sub.f ( 10) (b6) calculating the estimated mA·s remaining to be delivered mAs r to obtain the blackening (or optical density) determined by the equation: mAs.sub.r =L.sub.ra /D.sub.f1 ( 11) (b7) measuring the mA·s delivered mAs mes from the start of the operation (b3); (b8) calculating the remaining exposure time t r such that ##EQU29## so as to end the exposure in an open loop so that the exposure will be stopped when the time t r has elapsed.

Claim 30

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tue, the supply voltage V which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, an image receiver of the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen, a film sensitive to the light emitted by said screen and a cell for the detection of the light emitted by said screen, that enables the conversion of a physical variable, characterizing the X-ray beam, into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure and gives a signal M, and a device to compute the yield D given by the ratio of M to the product I×S (mA·s) of the anode current I of the tube by the duration S of the exposure, wherein said method includes the following steps of: (a) determining by calibration the reference lumination L ref that must be received by the film, under fixed reference conditions, to achieve the blackening (or optical density) chosen as a reference value: b1) positioning the object to be radiographed; b2) triggering the start of the exposure; b3) measuring the yield D f1 at a certain time t' after the start of the exposure; b4) calculating the lumination L f received by the film from the illumination received from the film before step B3 and from the number of mA·s delivered by the tue during t', δmA·s according to the equation: L.sub.f =L.sub.am +D.sub.f1 ×δmA·s (9) (b5) calculating the lumination L ra remaining to be acquired to obtain the blackening (or optical density) determined by the equation: L.sub.ra =L.sub.ref -L.sub.f ( 10) (b6) calculating the estimated mA·s remaining to be delivered mAs r to obtain the blackening (or optical density) determined by the equation: mAs.sub.r =L.sub.ra /D.sub.f1 ( 11) (b7) measuring the mA·s delivered mAs mes from the start of the operation (b3); (b8) calculating the remaining exposure time t r such that ##EQU29## so as to end the exposure in an open loop so that the exposure will be stopped when the time t r has elapsed.

Claim 31

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tue, the supply voltage V which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, an image receiver of the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen, a film sensitive to the light emitted by said screen and a cell for the detection of the light emitted by said screen, that enables the conversion of a physical variable, characterizing the X-ray beam, into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure and gives a signal M, and a device to compute the yield D given by the ratio of M to the product I×S (mA·s) of the anode current I of the tube by the duration S of the exposure, wherein said method includes the following steps of: (a) determining by calibration of the reference lumination L ref that must be received by the film, under fixed reference conditions, to achieve the blackening (or optical density) chosen as a reference value: (b1) positioning the object to be radiographed; (b2) triggering the start of the exposure; determining an estimation (T.E.) of the mA·s remaining to be delivered, and converting the mA·s into a signal in the units of the cell such that: CE.sub.target =mAs.sub.ra ×D.sub.c ( 16) interrupting (T.C.) the exposure which consists in decrementing the target value CE target by the signals received by the cell and in terminating the exposure when the decremented value becomes smaller than or equal to a reference value Val o .

Claim 32

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tue, the supply voltage V which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, an image receiver of the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen, a film sensitive to the light emitted by said screen and a cell for the detection of the light emitted by said screen, that enables the conversion of a physical variable, characterizing the X-ray beam, into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure and gives a signal M, and a device to compute the yield D given by the ratio of M to the product I×S (mA·s) of the anode current I of the tube by the duration S of the exposure, wherein said method includes the following steps of: (a) determining by calibration of the reference lumination L ref that must be received by the film, under fixed reference conditions, to achieve the blackening (or optical density) chosen as a reference value: (b1) positioning the object to be radiographed; (b2) triggering the start of the exposure; determining an estimation (T.E.) of the mA·s remaining to be delivered, and converting the mA·s into a signal in the units of the cell such that: CE.sub.target =mAs.sub.ra ×D.sub.c ( 16) interrupting (T.C.) the exposure which consists in decrementing the target value CE target by the signals received by the cell and in terminating the exposure when the decremented value becomes smaller than or equal to a reference value Val o .

Claim 34

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tue, the supply voltage V which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, an image receiver of the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen, a film sensitive to the light emitted by said screen, a cell for the detection of the X-rays that have crossed the object to be examined, placed being the image receiver, for converting a physical variable, characterizing the X-ray beam into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure to produce a signal M, and a device to compute the yield D given by the ratio of M to the product of the anode current I of the tube by the duration S of the exposure, wherein said method includes the following operations: (a) a first calibration of the radiology system by means of objects with a thickness E p by using a receiver without the intensifier screen or screens so as to determine the yield D se from the function: D.sub.se =f'(V.sub.m, D.sub.se) (5) (b) a second calibration of the radiology system by means of the objects with a thickness E p by using a receiver with an intensifier screen so as to determine the yield D c from the function: D.sub.c =f" (V.sub.m, E.sub.p) (6) the thickness E p from the inverse function: E.sub.p =g"(V.sub.m, D.sub.c) (7) and compute the yield on the film D f function: D.sub.d =f'(V.sub.m, E.sub.p)-f" (V.sub.m, E.sub.p) (8) (c) a third calibration to determine the reference lumination L ref that must be received by the film, under fixed reference conditions to achieve a blackening chosen as a reference value composing the following steps: (e1) positioning the object to be radiographed; (e2) triggering the start of the exposure; (e3) estimating the mA·s remaining to be delivered and converting the mA·s into a signal in the united of the cell such that: CE.sub.target =mAs.sub.ra ×D.sub.c; and, (e4) interrupting the exposure which consists in decrementing the target value CE target by the signals received by the cell and in terminating the exposure when the decremented value becomes smaller than or equal to a value Val o .

Claim 35

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tue, the supply voltage V which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, an image receiver of the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen, a film sensitive to the light emitted by said screen, a cell for the detection of the X-rays that have crossed the object to be examined, placed being the image receiver, for converting a physical variable, characterizing the X-ray beam into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure to produce a signal M, and a device to compute the yield D given by the ratio of M to the product of the anode current I of the tube by the duration S of the exposure, wherein said method includes the following operations: (a) a first calibration of the radiology system by means of objects with a thickness E p by using a receiver without the intensifier screen or screens so as to determine the yield D se from the function: D.sub.se =f'(V.sub.m, D.sub.se) (5) (b) a second calibration of the radiology system by means of the objects with a thickness E p by using a receiver with an intensifier screen so as to determine the yield D c from the function: D.sub.c =f" (V.sub.m, E.sub.p) (6) the thickness E p from the inverse function: E.sub.p =g"(V.sub.m, D.sub.c) (7) and compute the yield on the film D f function: D.sub.d =f'(V.sub.m, E.sub.p)-f" (V.sub.m, E.sub.p) (8) (c) a third calibration to determine the reference lumination L ref that must be received by the film, under fixed reference conditions to achieve a blackening chosen as a reference value composing the following steps: (e1) positioning the object to be radiographed; (e2) triggering the start of the exposure; (e3) estimating the mA·s remaining to be delivered and converting the mA·s into a signal in the united of the cell such that: CE.sub.target =mAs.sub.ra ×D.sub.c; and, (e4) interrupting the exposure which consists in decrementing the target value CE target by the signals received by the cell and in terminating the exposure when the decremented value becomes smaller than or equal to a value Val o .

Claim 37

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tue, the supply voltage V which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, an image receiver of the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen, a film sensitive to the light emitted by this screen, a cell for the detection of the X-rays that have crossed the object to be examined, placed behind the image receiver for conducting a physical variable, characterizing the X-ray beam, into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure to produce a signal M, and a device to compute the yield D given by the ratio of M to the product of the anode current I for the tube and the duration S of the exposure I×S(mA·s), wherein said method includes the following operations: (a) calibration of the radiological system so as to determine the analytical model D'.sub.f =f'"(V.sub.m, E.sub.p) with the film as the image receiver; (b) a second calibration to determine the reference lumination L ref that must be received by the film, under fixed reference conditions, to achieve the blackening (or optical density) chosen as a reference value by the practitioner; and then the following steps of: (e1) positioning the object to be radiographed; (e2) triggering the start of the exposure by the practitioner; (e3) measuring the yield D' f1 at a certain time t' after the start of the exposure; (e4) calculating the lumination L' f received by the film by the equation: L'.sub.f =L.sub.am +D'.sub.f1 ×δmA·s/CNRD (film dose rate); (e5) calculating the lumination L' ra remaining to be acquired to obtain the chosen blackening (or optical density) by the equation: L'.sub.ra =L.sub.ref -L'.sub.f; and (e6) calculating the estimated mA·s remaining to be delivered mAs' ra to obtain the blackening (or optical density) by the equation:

Claim 38

A method for automatically determining the exposure time of a radiographic film in a system of radiology designed to examine an object that includes an X-ray tue, the supply voltage V which may assume various values V m , with continuous or discrete variation, said X-ray tube emitting an X-ray beam in the form of pulses of variable duration S towards the object to be examined, an image receiver of the X-radiation that has crossed the object to form an image of said object, said receiver being constituted by at least one intensifier screen, a film sensitive to the light emitted by this screen, a cell for the detection of the X-rays that have crossed the object to be examined, placed behind the image receiver for conducting a physical variable, characterizing the X-ray beam, into a measurement signal L, an integrator circuit that integrates the measurement signal L for the duration S of the exposure to produce a signal M, and a device to compute the yield D given by the ratio of M to the product of the anode current I for the tube and the duration S of the exposure I×S(mA·s), wherein said method includes the following operations: (a) calibration of the radiological system so as to determine the analytical model D'.sub.f =f'"(V.sub.m, E.sub.p) with the film as the image receiver; (b) a second calibration to determine the reference lumination L ref that must be received by the film, under fixed reference conditions, to achieve the blackening (or optical density) chosen as a reference value by the practitioner; and then the following steps of: (e1) positioning the object to be radiographed; (e2) triggering the start of the exposure by the practitioner; (e3) measuring the yield D' f1 at a certain time t' after the start of the exposure; (e4) calculating the lumination L' f received by the film by the equation: L'.sub.f =L.sub.am +D'.sub.f1 ×δmA·s/CNRD (film dose rate); (e5) calculating the lumination L' ra remaining to be acquired to obtain the chosen blackening (or optical density) by the equation: L'.sub.ra =L.sub.ref -L'.sub.f; and (e6) calculating the estimated mA·s remaining to be delivered mAs' ra to obtain the blackening (or optical density) by the equation: