CA1055163A - Method and circuit for determining voltage and current values associated with given switch-on durations of an x-ray source - Google Patents
Method and circuit for determining voltage and current values associated with given switch-on durations of an x-ray sourceInfo
- Publication number
- CA1055163A CA1055163A CA211,098A CA211098A CA1055163A CA 1055163 A CA1055163 A CA 1055163A CA 211098 A CA211098 A CA 211098A CA 1055163 A CA1055163 A CA 1055163A
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- current
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- input
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05G—X-RAY TECHNIQUE
- H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
- H05G1/08—Electrical details
- H05G1/26—Measuring, controlling or protecting
- H05G1/30—Controlling
- H05G1/46—Combined control of different quantities, e.g. exposure time as well as voltage or current
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- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Toxicology (AREA)
- X-Ray Techniques (AREA)
- Measurement Of Radiation (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
Determination of the voltage and current values for an X-ray source by choosing a point of intersection with the lowest voltage value of an operating range limitation function of the X-ray source with a current-voltage function passed through the current-voltage coordinates of a desired current value determined by an exposure measurement.
Determination of the voltage and current values for an X-ray source by choosing a point of intersection with the lowest voltage value of an operating range limitation function of the X-ray source with a current-voltage function passed through the current-voltage coordinates of a desired current value determined by an exposure measurement.
Description
J~1r~ 71 /
~3 ~ 0 / ~ , J, 1G 9-1~7!~
lOS5163 "~lethocl o~ detcrnining ~-oltage and current valuec: associ~ed ~ith a given s~itch-on duration of an X-ray source, and circui-t arrangemcnt for performing said method".
The invelltion relates to a method of determinin~
voltage and current values associated -ith a given switch-on d~lration of an X-ray source having a given operating range limitation nomogram and to be applied to said X-ray source in which a desired culrent time product is determined with the aid of an X-ray exposure meter for a desired radiation qu~nti-ty.
Such a method is usually based on experience and is performed by those skilled in the art of operating X-ray equipment.
The invention has for its object to simplify this method so that also those less experienced and skilled in the art of operating X-ray equipment can perform this method with a very favourable result.
To this end a method of the kind described in the preamble according to the inv ntion is characterized in that the current time product is determined at a given voltage applied to the radiation source while with the aid of a voltage-cur~ent function applying to the desired radiation quantity, which function is pussed through the current inten~
sity associated with the desired current time product, and with tho aid of the operating range limitation nomogram with the same current scale as the voltage-currellt function the point of intersection of the voltage-current function
~3 ~ 0 / ~ , J, 1G 9-1~7!~
lOS5163 "~lethocl o~ detcrnining ~-oltage and current valuec: associ~ed ~ith a given s~itch-on duration of an X-ray source, and circui-t arrangemcnt for performing said method".
The invelltion relates to a method of determinin~
voltage and current values associated -ith a given switch-on d~lration of an X-ray source having a given operating range limitation nomogram and to be applied to said X-ray source in which a desired culrent time product is determined with the aid of an X-ray exposure meter for a desired radiation qu~nti-ty.
Such a method is usually based on experience and is performed by those skilled in the art of operating X-ray equipment.
The invention has for its object to simplify this method so that also those less experienced and skilled in the art of operating X-ray equipment can perform this method with a very favourable result.
To this end a method of the kind described in the preamble according to the inv ntion is characterized in that the current time product is determined at a given voltage applied to the radiation source while with the aid of a voltage-cur~ent function applying to the desired radiation quantity, which function is pussed through the current inten~
sity associated with the desired current time product, and with tho aid of the operating range limitation nomogram with the same current scale as the voltage-currellt function the point of intersection of the voltage-current function
2~ and the operating range limitation nomG~ram with the lowest :" .' ' , , ', ' , " ' ' ' ' ", ', ' .
PT~ 717~;
16-9~ 7 voltage ~ralue is determined and that said lowest voltage value is taken as a target value for the determination of the current with the aid of the load nomogram.
Furthermore the invention rclates to a circuit arrangement for performing such a method and is character-ized in that~he X-ray e~posure meter includes a circuit for determining the logarithm of the desired current value associated with the applied voltage and a chosen period and for supplying a voltage proportional to this logarithm to 10 its output which is coupled to a first input of an adder and subtractor circuit a second input of which i5 coupled to an nutput o~ a clamping circuit an input of which is coupled to an output of a voltage-current function genera-tor which supplies an output voltage proportional to the 15 logarithm o~ a current value associated with an input voltage, while a third input of the adder and subtractor circuit is ` coupled to an output of an operating range limitation nomogram function generator supplying ~n output voltage proportional to the logarithm of a current value associated with an input ` 20 voltage~ W~ILE AN INPUT OF said ~unction generators is coupled to an output of the adder and subtractor circuit, said output ¦ being furthermore coupled to a control signal input of a ~` voltage control circuit of the radiation source.
The invention will be described in greater t 25 detail with reference to the drawing.
~ Fig. 1 shows a method according to the invention ~. ' !~ by way of a voltage-current characteristic, J , Fig. 2 illustrates by way of a block-schematic ,~
~ 3~
.
,, " , , ,, , , , ,, ~ "
,, , "," ''~, ' ,' ,'''' ', :, ''':' ' ",','' ' ' , P~ 717~
diagraDI a circuit arrangement for performing a method according ~o the invention.
Fig. 3 illustrat0s by way of a block-schematic diagralll an X-ray exposure mcter for a circuit arrangement according to Fig. 2 and Fig. 4 sho~Ys by wa~ of a block-schematic dia-graltl a clamping circuit and an adder and subtractor circuit ~or a circuit arran~ement accordin~ to Fig. 2.
Fig. 1 shows a voltage-current range for voltage and currents of an X-ray source with a logarithmic current scale denoted b~ log I on th0 vertical axis and a voltage scale which, if desired, may also be logarith~ic, but is de-noted by V on the horizontal axis.
Furthermore the reference numeral 1 denotes an operating range limitation nomogram of an X-ray source ; and 2 and 3 denote some curves corresponding to some radiat-ion quantities suitable for photo or film for observation purpose obtained by irradiation of an object.
The operating range limitation nomogram 1 of the X-ray source under pick-up conditions gives the relation-,; ship for a given switch-on duration of the radiation source of the maximum suitable current value for a chosen voltage for energizing this source.
~ ~ The method is as follows. At a given voltage s 25 Vte9t applied to an X-ray source an exposure measurement at tho area of an observation device to be expos0d is per-~ormed with a giv0n switch-on duration of the radiation source. With this measurement a desired current value I
a,5,sociated with thi8 voltage Vt t is found which will -4~
, . .
. .
' 71/'~
1G-9 1~7 .
yiel~ a certain density for photo or fil~. In case of films and photos the switch on duration ~or an exposure mea~urement is equal to that for pic~-up while ~ith the use of a film exchanger a certaill ratio bet~Yeen these switcll-on durations can be taken. Through the point in rlg~ 1 corresponding to the desired current value I and tho given voltage value Vtest the curve 2 is provided which connects points with voltage and current values which would causq tlle same density. l~en the point of intersection with the lowest voltage value of one of the two points of intersec~tion of this curve 2 with the nomogram 1 is de-termined by V i and a current value Il, this is the most suitable adjustment for the radiation source because in case of a maximum con-,trol of the source according to a nomogram ~alue `,the ~ radiation is obtained at the lowest possible voltage which yields the optinum contrast for photo or film.'' In case of a large deviation between Vt t and V min1 it may occur that the-desity at the values found for V i and I1 will exhibit a slight deviation relative to the desired density. A subsequent exposure measurement is then performed at the found voltage value Vmin yielding a desired current value Iw which may slightly deviate from the current value I1 found. The curve ~ 3 for a density associated with these new voltage and cur-A 25 Vmin1, Iw is provided throu~h the point with the last determined values and the point of intersection Vmin with the nomogram yields an associated value I2 for the current which will the~ produce a more accurate approximation ,- .
.,, . . : , ,", , , : , , . . . . . . .
; 7 ~ 7 1 j7 of thc correct value. Although generally one or two e~posure measure~lents are sufficient this procedure may bc repeated, if dosired t ~ultil tl~e values fouIld ~or I and I sub-~n~1 n stantially coincide wllich will generally be the case after three e~posure measurements.
By using a logari*hmic currcnt scale the curve ~ may be obtained by shifting the curve 2 in the vertical direction so that, for example, ~ith the aid of a jig moved along a ruler this curve can be drawn in a simple manner through an arbitrary point in the graph so that the voltage and current values to be adjùsted can be determined very quickly and simply even by persons that are not very skilled in the art or have little experience in the use of X-ray equipment~
In ~ig. 2 an X-ray source 5 is connected to a voltage control circuit 7 and a current control circuit 9 each-having control signal inputs 11 and 13, respectively.
The control signal input 11 is connected to an output 15 of a control loop 17 and the control signal input 13 is connected to an output 19 of a change-over switch 23 which can be operated by means of an operating device 21 and has a first input 25 connected to an output 27 of the control loop 17 and a second input 29 applying a signal obtained from an output 31 of an operating range limitation function generator 32 to the control signal input 13. Consequently, when per-for~ning exposure measurements, in which the change-over switch 23 assumes the posit-ion, shown the current through the - ra~iation source 5 is maintained at a given value I with test thc aid of thc curr~nt control oircult 9. ~liS circuit 9 is ,` ' ~'' ' PHN. 7178.
active in the f;lament circuit of the radiation source 5 cannot sufficiently quickly be controlled to a deviating value so as to make a quick succession of experimental exposures at different current values possible. The current control circuit 9 may be formed as described in our Canadian Patent Application 211,234 which wàs filed in October 1974.
The voltage originating from the output 3 of the operating range limitation function generator 32 is also applied to an input 33 of an X-ray exposure meter 35 a further input 37 of which is connected to an output 39 of a radiation-sensitive element 41. The exposure meter 35 has an input 43 which is connected to an output 45 of a pulse signal source 47.
A further output 46 of the pulse signal source 47 is connected to an input 49 of the voltage control circuit 7. The pulse signal source 47 thus ensures that a given switch-on duration of the radiation source 5, which duration is adjustable with the aid of the operating device 21, can be obtained while also the exposure meter 35 is activated at the correct instant. The exposure meter 35 may receive information from the operating device, for example, about a film sensitivity to be used.
After performing an exposure measurement at a voltage Vtest the exposure meter 35 applies a signal to an output 51 which signal is proportional to the logarithm of the current value Iw desired for a given density and associated with the voltage Vtest or Vmjn. T g hereinafter be referred to as log Iw ~
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lOS5163 'Nle signal log I~, is applied toa first input 53 of an adder and subtractor circuit 55. A second input 57 of this adder and subtractor circuit 55 is con-nected to an output 59 of a clamping ci.rcuit 61 which : 5 recci~-e.s a pulse sig~al at an input 63 at the instant Or tlle exposure measuretnent so that its output voltage is clamped at zero.
The clamping circuit 61 is controlled at an input 65 b~ a signal originating from an output 67 of a current voltage ~unction generator 69 receiv*ng at an input 71 a voltage from the output 15 of the control loop 17 and thus being a measure of the voltage applied to the radiation source 5. A voltage proportional to the logarithm of a current value for a given density associated with a given voltage at ~he radiation source 5 is produced at its output 67. This signal is hereinafter referred to as log I .
This signal appears at the output 59 of the ~ clamping circuit 61 and is shifted due to the clamping cir-cuit 61 in such a manner that the generated function passes through the point which a~ter the nth exposure measurement is associated with a desired current value Iw found for a certain voltage value. This signal is then proportional to ~; log Iz _ log Iw .
The adde~ and subtractor circuit 55 has a third ; 25 input 73 which is connected to an output 73 of the operating range limitation nomogram function generator 32 an input . 79 of which i.s connected to the output 15 of the control ;~ loop 17 and thus also receives a voltage which is a msasure ,, ` ' ' ~ ,; , - ' ' ~ , ~ ', , , , ,f",,.",.,,. ",, , . ~ . . . . .
,, , , , , . ~
l'Tf',; '; ,', 7 i of the voltage applied by the ~tolta~e con~rol circuit 7 to the radiation source 5. The si~nal at the output 75 is then proportional to the logarit~ of the nomogram current value associated with that voltage. Th;s signal is herein-after refQrred to as log I
An output 81 of the adder and subtractor cir-cuit 55 is connected through a switch 83 which can be operated by means of the operating devico to a storage circuit 85 represented in this case by a capacitor. The output 15 of ; 10 the control loop 17 is connected to this capacitor 85. Im-mediately after an exposure measurement the switch 83 is temporarily closed and the control loop 17 is active. This control loop will attempt to render the total input vo]tage of the adder and subtractor circuit 55 zero.
When the first input 53 and the second input 57 is an adder input and the third input 73 is a subtractor - input, the total input signal of the adder and subtractor circuit will become.
g Wn + (Log Iz - Log I~" ) - Log I
This will be zero for log Iz = log I ,i.e.
for a point of intersection in the load nomogram and the curve for the desired density. By the choice sf the phase ~f the feedbackin the control loop this point of intersec-tion is chosen at the lowest voltage value. The control loop then automatically applies to its output 15 the control voltage for obtaining V i applied to the voltage control circui~ 7.
The above described circuit arrangement per-. .
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forms on a ~'irst co~and of t}l~ operating dev:ice 21 a first exposu~e measurement ~ith the aid of a voltage Vt t which is deterlr.ined by a voltage applied bcfore a series of measurements to the capacitor S5 and is obtained frorn an output ~7 of the operating device 21 whicll voltage produces ihe voltage Vt st at the radiation source 5. After the first exposure measurement the pOillt corresponding to the current value I1 is found by the radiation source 5 with the asso-ciated voltage value V in~ After the second exposure measure-ment we find I and V . and so forth. After termination 2 mln2 of a series of exposure measurements the control loop 17 i9 interrupted ~ith the aid of the switch 83 and the last value found for V . is stored in the capacitor 85 and mln~l passes through the operating range limitation function generator 3~ the control voltage for the current value I to be adjusted to the change-over switch 23 which is then set to ' the position not sho-rn and controls the current control cir-cuit 9 at the desired current intensity.
The function generators 69 and 32 may be realized in kno~n manner with the aid Or resistance, ampli-fication and diode net~orks.
2 Fig. 3 uses the same reference numerals for corresponding components as Fig. 2.
The input 37 of the exposure meter 35 receives a current upon an exposure measurement of the radiation--sonsitive element 41~ which current is a measure of the I radiation quantity passed by an object to be examined. This -~ current i~ applied through a switch 89, which is closed , - 1 O-., `,, .', ; ,, ' -\ p ~
1 G ~
during the exposure measurcment, to an input 91 of a dif-ference amplifier 93 the other input of which is connected to ground and an output 95 through a capacitor 97 is fed back to the input 91. This amplifier constitutes, with the capacitor 97, an integrator circuit passing on the integrated input current to nn input 101 of a logarithm-forming circuit 103. The capacitor 97 is --hunted by a switch 99 which dis-charges the capacitor 97 every time a~ter an e~pocure measurement.
An output 105 of the circ~lit 103 provides a voltage which is proportional to the logarithm of the passed radiation quantity at a voltage Vtest and a current IteSt ` to the radiation source 5.
,~ This voltage is referred to as log Et t. This voltage i9 passed on through a switch 106 to a storage capacitor 107 and also remains available after the exposure ~, measurement. An input 109 of a substractor circuit 111 is `~ connected ~o this capacitor 107 and receives continuously ~ the voltage Log Etest. The voltage Log It t is applied to i~ 20 another input 113, which voltage is a measure of the current ; intensity used for the radiation source. An output of the subtractor circuit 111 applies to the output 51 of the exposure meter 35 a voltage ~hich is equal to Log It t ~
~ Log Etest. This has been rendered equal to Log Iw in a i~ 25 simple manner by the choice of a parameter for the - exposure meter.
In case of an exposure measurement there ~ applies for the voltage Et t obtained at the output 95 of Y~
k , "
,.~',j ,, , ," ", ;, -,,, " ;,, : -, ."' ,: , .
.. . . . . . . . .
:PI,~ 71,~
l G~ 10 1~55163 the integrator 93, 97 that Et t = k It t where I~ t~ as alrcady mentionod abo~re, is the current through the radiation source during an expnsure measur0ment. For a desired density of t~le film tlle ~oltage at the output 95 would have to be equal t.o E = k I~ wllere I~r is the current through the radi.ation source 5 required for the desired density. The rad.io I ~ is equal to the ratio ~---- from whi.ch it test test follows that I - Etest w w~test When for the desired density the uutput voltage of the integrator is chosen to be 1 V, then Ew = 1 and w = ~ and log I~r = log Itest ~ log Etest , which is the voltage at the output 51.
i 15 In Fig. 4 the input 65 of the clamping circuit 61 is connected to an input 115 of an adder circuit 117 - an output 119 of which is connected to the output 59 and through a switch 121 closed during the exposure measurement ~, to an integration circuit which is constituted by a capacitor t 20 123 incorporated between an output and an input of a differential ampli~ier 125, while the output of the laitter amplifier 125 is connected to a second input 127 of the ~ .
adder circuit 117.
When the switch 121 is closed the voltage at the input 127 of the adder circuit 117 will be adjusted in such a manner that the input voltage of the difference '~ . amplifier 125 becomes substantially æero so that the sum ''', .
'i -12-~ .
,, , .
,, . , , ., , , , : , - . ~ , . . ~ , PT~ 7 16~ 7 1(955163 of the volta~ e at the input 127 and the voltclge at the input 115 will thus become zero. This actuallymeans a shift to zero of a voltage valu~ applied to the illpUt 11 ) or a zero cl~mping oL` the voltage at the output 119 during an exposure measuremellt.
The aci~l~ and fiubtractor circuit 55 includes an adder circuit 129 to which the illpUtS S3 and 57 are connected and an output 131 oE` which is connected through a resistor 133 to an ~I;nput 135 of a difference amp]ifier 137- ~Il output 139 o~ the difference amplifier 137 is connected to the output 81 and through a resistor 141 to the input 135. A further input 1~3 is connected through a potential divider 145, 1~7 to the input 73.
A voltage may be derived, if desired, from the output 131 of the adder circuit 129, which voltage is also a measure of the desired current adjustment of the radiation source 5. For this voltage, however, the store 85 is no longer active because the clamping circuit is present in this circuit. The voltage at the output 139 ma~ be used for example to detect whether,~luring an exposure measurement a controlled state of the control loop 17 occurs. When this is not the case the voltage at the output 131 will exceed a given value and may be used for a variation of one or more parameters or for blocking a pick-up pos~ibility of the device.
`' The described arrangement is very suitable for angiography.
The voltage scale used in the method and the ., .
, , ..... .
,, . ",, " ~ , p j r lG-9-1 lOS5163 cievice for tlle cl~aracteristic ma~r be arbitrari.ly chosen.
~ logarit~uilic scale value, also for the ~oltage coordinate, may be ad~antageous due to obtain.ing tlle same pereentual accurac~-.
It ~-ill be evident that the described method ca.n llot only be ~ormed ~rith mechanical and analog elec~ical means. but ~or e~ample also ~rith cligital electronic circuits.
l~en using, ~or e~ample, su.f~`icient stores of a eomputer program or of a multiplier c:ircui.t for obtaining the eurrent volta~e funetions, even the use o~ a logarithmie eurrent seale may be umleeessary.
, '''' . ' ' ' , .
, , 1~ .
. .
PT~ 717~;
16-9~ 7 voltage ~ralue is determined and that said lowest voltage value is taken as a target value for the determination of the current with the aid of the load nomogram.
Furthermore the invention rclates to a circuit arrangement for performing such a method and is character-ized in that~he X-ray e~posure meter includes a circuit for determining the logarithm of the desired current value associated with the applied voltage and a chosen period and for supplying a voltage proportional to this logarithm to 10 its output which is coupled to a first input of an adder and subtractor circuit a second input of which i5 coupled to an nutput o~ a clamping circuit an input of which is coupled to an output of a voltage-current function genera-tor which supplies an output voltage proportional to the 15 logarithm o~ a current value associated with an input voltage, while a third input of the adder and subtractor circuit is ` coupled to an output of an operating range limitation nomogram function generator supplying ~n output voltage proportional to the logarithm of a current value associated with an input ` 20 voltage~ W~ILE AN INPUT OF said ~unction generators is coupled to an output of the adder and subtractor circuit, said output ¦ being furthermore coupled to a control signal input of a ~` voltage control circuit of the radiation source.
The invention will be described in greater t 25 detail with reference to the drawing.
~ Fig. 1 shows a method according to the invention ~. ' !~ by way of a voltage-current characteristic, J , Fig. 2 illustrates by way of a block-schematic ,~
~ 3~
.
,, " , , ,, , , , ,, ~ "
,, , "," ''~, ' ,' ,'''' ', :, ''':' ' ",','' ' ' , P~ 717~
diagraDI a circuit arrangement for performing a method according ~o the invention.
Fig. 3 illustrat0s by way of a block-schematic diagralll an X-ray exposure mcter for a circuit arrangement according to Fig. 2 and Fig. 4 sho~Ys by wa~ of a block-schematic dia-graltl a clamping circuit and an adder and subtractor circuit ~or a circuit arran~ement accordin~ to Fig. 2.
Fig. 1 shows a voltage-current range for voltage and currents of an X-ray source with a logarithmic current scale denoted b~ log I on th0 vertical axis and a voltage scale which, if desired, may also be logarith~ic, but is de-noted by V on the horizontal axis.
Furthermore the reference numeral 1 denotes an operating range limitation nomogram of an X-ray source ; and 2 and 3 denote some curves corresponding to some radiat-ion quantities suitable for photo or film for observation purpose obtained by irradiation of an object.
The operating range limitation nomogram 1 of the X-ray source under pick-up conditions gives the relation-,; ship for a given switch-on duration of the radiation source of the maximum suitable current value for a chosen voltage for energizing this source.
~ ~ The method is as follows. At a given voltage s 25 Vte9t applied to an X-ray source an exposure measurement at tho area of an observation device to be expos0d is per-~ormed with a giv0n switch-on duration of the radiation source. With this measurement a desired current value I
a,5,sociated with thi8 voltage Vt t is found which will -4~
, . .
. .
' 71/'~
1G-9 1~7 .
yiel~ a certain density for photo or fil~. In case of films and photos the switch on duration ~or an exposure mea~urement is equal to that for pic~-up while ~ith the use of a film exchanger a certaill ratio bet~Yeen these switcll-on durations can be taken. Through the point in rlg~ 1 corresponding to the desired current value I and tho given voltage value Vtest the curve 2 is provided which connects points with voltage and current values which would causq tlle same density. l~en the point of intersection with the lowest voltage value of one of the two points of intersec~tion of this curve 2 with the nomogram 1 is de-termined by V i and a current value Il, this is the most suitable adjustment for the radiation source because in case of a maximum con-,trol of the source according to a nomogram ~alue `,the ~ radiation is obtained at the lowest possible voltage which yields the optinum contrast for photo or film.'' In case of a large deviation between Vt t and V min1 it may occur that the-desity at the values found for V i and I1 will exhibit a slight deviation relative to the desired density. A subsequent exposure measurement is then performed at the found voltage value Vmin yielding a desired current value Iw which may slightly deviate from the current value I1 found. The curve ~ 3 for a density associated with these new voltage and cur-A 25 Vmin1, Iw is provided throu~h the point with the last determined values and the point of intersection Vmin with the nomogram yields an associated value I2 for the current which will the~ produce a more accurate approximation ,- .
.,, . . : , ,", , , : , , . . . . . . .
; 7 ~ 7 1 j7 of thc correct value. Although generally one or two e~posure measure~lents are sufficient this procedure may bc repeated, if dosired t ~ultil tl~e values fouIld ~or I and I sub-~n~1 n stantially coincide wllich will generally be the case after three e~posure measurements.
By using a logari*hmic currcnt scale the curve ~ may be obtained by shifting the curve 2 in the vertical direction so that, for example, ~ith the aid of a jig moved along a ruler this curve can be drawn in a simple manner through an arbitrary point in the graph so that the voltage and current values to be adjùsted can be determined very quickly and simply even by persons that are not very skilled in the art or have little experience in the use of X-ray equipment~
In ~ig. 2 an X-ray source 5 is connected to a voltage control circuit 7 and a current control circuit 9 each-having control signal inputs 11 and 13, respectively.
The control signal input 11 is connected to an output 15 of a control loop 17 and the control signal input 13 is connected to an output 19 of a change-over switch 23 which can be operated by means of an operating device 21 and has a first input 25 connected to an output 27 of the control loop 17 and a second input 29 applying a signal obtained from an output 31 of an operating range limitation function generator 32 to the control signal input 13. Consequently, when per-for~ning exposure measurements, in which the change-over switch 23 assumes the posit-ion, shown the current through the - ra~iation source 5 is maintained at a given value I with test thc aid of thc curr~nt control oircult 9. ~liS circuit 9 is ,` ' ~'' ' PHN. 7178.
active in the f;lament circuit of the radiation source 5 cannot sufficiently quickly be controlled to a deviating value so as to make a quick succession of experimental exposures at different current values possible. The current control circuit 9 may be formed as described in our Canadian Patent Application 211,234 which wàs filed in October 1974.
The voltage originating from the output 3 of the operating range limitation function generator 32 is also applied to an input 33 of an X-ray exposure meter 35 a further input 37 of which is connected to an output 39 of a radiation-sensitive element 41. The exposure meter 35 has an input 43 which is connected to an output 45 of a pulse signal source 47.
A further output 46 of the pulse signal source 47 is connected to an input 49 of the voltage control circuit 7. The pulse signal source 47 thus ensures that a given switch-on duration of the radiation source 5, which duration is adjustable with the aid of the operating device 21, can be obtained while also the exposure meter 35 is activated at the correct instant. The exposure meter 35 may receive information from the operating device, for example, about a film sensitivity to be used.
After performing an exposure measurement at a voltage Vtest the exposure meter 35 applies a signal to an output 51 which signal is proportional to the logarithm of the current value Iw desired for a given density and associated with the voltage Vtest or Vmjn. T g hereinafter be referred to as log Iw ~
~l,.; 7~
1 6--9--1 ~) 7 !~
lOS5163 'Nle signal log I~, is applied toa first input 53 of an adder and subtractor circuit 55. A second input 57 of this adder and subtractor circuit 55 is con-nected to an output 59 of a clamping ci.rcuit 61 which : 5 recci~-e.s a pulse sig~al at an input 63 at the instant Or tlle exposure measuretnent so that its output voltage is clamped at zero.
The clamping circuit 61 is controlled at an input 65 b~ a signal originating from an output 67 of a current voltage ~unction generator 69 receiv*ng at an input 71 a voltage from the output 15 of the control loop 17 and thus being a measure of the voltage applied to the radiation source 5. A voltage proportional to the logarithm of a current value for a given density associated with a given voltage at ~he radiation source 5 is produced at its output 67. This signal is hereinafter referred to as log I .
This signal appears at the output 59 of the ~ clamping circuit 61 and is shifted due to the clamping cir-cuit 61 in such a manner that the generated function passes through the point which a~ter the nth exposure measurement is associated with a desired current value Iw found for a certain voltage value. This signal is then proportional to ~; log Iz _ log Iw .
The adde~ and subtractor circuit 55 has a third ; 25 input 73 which is connected to an output 73 of the operating range limitation nomogram function generator 32 an input . 79 of which i.s connected to the output 15 of the control ;~ loop 17 and thus also receives a voltage which is a msasure ,, ` ' ' ~ ,; , - ' ' ~ , ~ ', , , , ,f",,.",.,,. ",, , . ~ . . . . .
,, , , , , . ~
l'Tf',; '; ,', 7 i of the voltage applied by the ~tolta~e con~rol circuit 7 to the radiation source 5. The si~nal at the output 75 is then proportional to the logarit~ of the nomogram current value associated with that voltage. Th;s signal is herein-after refQrred to as log I
An output 81 of the adder and subtractor cir-cuit 55 is connected through a switch 83 which can be operated by means of the operating devico to a storage circuit 85 represented in this case by a capacitor. The output 15 of ; 10 the control loop 17 is connected to this capacitor 85. Im-mediately after an exposure measurement the switch 83 is temporarily closed and the control loop 17 is active. This control loop will attempt to render the total input vo]tage of the adder and subtractor circuit 55 zero.
When the first input 53 and the second input 57 is an adder input and the third input 73 is a subtractor - input, the total input signal of the adder and subtractor circuit will become.
g Wn + (Log Iz - Log I~" ) - Log I
This will be zero for log Iz = log I ,i.e.
for a point of intersection in the load nomogram and the curve for the desired density. By the choice sf the phase ~f the feedbackin the control loop this point of intersec-tion is chosen at the lowest voltage value. The control loop then automatically applies to its output 15 the control voltage for obtaining V i applied to the voltage control circui~ 7.
The above described circuit arrangement per-. .
,? /,, 1~~9-1'j/ '~
forms on a ~'irst co~and of t}l~ operating dev:ice 21 a first exposu~e measurement ~ith the aid of a voltage Vt t which is deterlr.ined by a voltage applied bcfore a series of measurements to the capacitor S5 and is obtained frorn an output ~7 of the operating device 21 whicll voltage produces ihe voltage Vt st at the radiation source 5. After the first exposure measurement the pOillt corresponding to the current value I1 is found by the radiation source 5 with the asso-ciated voltage value V in~ After the second exposure measure-ment we find I and V . and so forth. After termination 2 mln2 of a series of exposure measurements the control loop 17 i9 interrupted ~ith the aid of the switch 83 and the last value found for V . is stored in the capacitor 85 and mln~l passes through the operating range limitation function generator 3~ the control voltage for the current value I to be adjusted to the change-over switch 23 which is then set to ' the position not sho-rn and controls the current control cir-cuit 9 at the desired current intensity.
The function generators 69 and 32 may be realized in kno~n manner with the aid Or resistance, ampli-fication and diode net~orks.
2 Fig. 3 uses the same reference numerals for corresponding components as Fig. 2.
The input 37 of the exposure meter 35 receives a current upon an exposure measurement of the radiation--sonsitive element 41~ which current is a measure of the I radiation quantity passed by an object to be examined. This -~ current i~ applied through a switch 89, which is closed , - 1 O-., `,, .', ; ,, ' -\ p ~
1 G ~
during the exposure measurcment, to an input 91 of a dif-ference amplifier 93 the other input of which is connected to ground and an output 95 through a capacitor 97 is fed back to the input 91. This amplifier constitutes, with the capacitor 97, an integrator circuit passing on the integrated input current to nn input 101 of a logarithm-forming circuit 103. The capacitor 97 is --hunted by a switch 99 which dis-charges the capacitor 97 every time a~ter an e~pocure measurement.
An output 105 of the circ~lit 103 provides a voltage which is proportional to the logarithm of the passed radiation quantity at a voltage Vtest and a current IteSt ` to the radiation source 5.
,~ This voltage is referred to as log Et t. This voltage i9 passed on through a switch 106 to a storage capacitor 107 and also remains available after the exposure ~, measurement. An input 109 of a substractor circuit 111 is `~ connected ~o this capacitor 107 and receives continuously ~ the voltage Log Etest. The voltage Log It t is applied to i~ 20 another input 113, which voltage is a measure of the current ; intensity used for the radiation source. An output of the subtractor circuit 111 applies to the output 51 of the exposure meter 35 a voltage ~hich is equal to Log It t ~
~ Log Etest. This has been rendered equal to Log Iw in a i~ 25 simple manner by the choice of a parameter for the - exposure meter.
In case of an exposure measurement there ~ applies for the voltage Et t obtained at the output 95 of Y~
k , "
,.~',j ,, , ," ", ;, -,,, " ;,, : -, ."' ,: , .
.. . . . . . . . .
:PI,~ 71,~
l G~ 10 1~55163 the integrator 93, 97 that Et t = k It t where I~ t~ as alrcady mentionod abo~re, is the current through the radiation source during an expnsure measur0ment. For a desired density of t~le film tlle ~oltage at the output 95 would have to be equal t.o E = k I~ wllere I~r is the current through the radi.ation source 5 required for the desired density. The rad.io I ~ is equal to the ratio ~---- from whi.ch it test test follows that I - Etest w w~test When for the desired density the uutput voltage of the integrator is chosen to be 1 V, then Ew = 1 and w = ~ and log I~r = log Itest ~ log Etest , which is the voltage at the output 51.
i 15 In Fig. 4 the input 65 of the clamping circuit 61 is connected to an input 115 of an adder circuit 117 - an output 119 of which is connected to the output 59 and through a switch 121 closed during the exposure measurement ~, to an integration circuit which is constituted by a capacitor t 20 123 incorporated between an output and an input of a differential ampli~ier 125, while the output of the laitter amplifier 125 is connected to a second input 127 of the ~ .
adder circuit 117.
When the switch 121 is closed the voltage at the input 127 of the adder circuit 117 will be adjusted in such a manner that the input voltage of the difference '~ . amplifier 125 becomes substantially æero so that the sum ''', .
'i -12-~ .
,, , .
,, . , , ., , , , : , - . ~ , . . ~ , PT~ 7 16~ 7 1(955163 of the volta~ e at the input 127 and the voltclge at the input 115 will thus become zero. This actuallymeans a shift to zero of a voltage valu~ applied to the illpUt 11 ) or a zero cl~mping oL` the voltage at the output 119 during an exposure measuremellt.
The aci~l~ and fiubtractor circuit 55 includes an adder circuit 129 to which the illpUtS S3 and 57 are connected and an output 131 oE` which is connected through a resistor 133 to an ~I;nput 135 of a difference amp]ifier 137- ~Il output 139 o~ the difference amplifier 137 is connected to the output 81 and through a resistor 141 to the input 135. A further input 1~3 is connected through a potential divider 145, 1~7 to the input 73.
A voltage may be derived, if desired, from the output 131 of the adder circuit 129, which voltage is also a measure of the desired current adjustment of the radiation source 5. For this voltage, however, the store 85 is no longer active because the clamping circuit is present in this circuit. The voltage at the output 139 ma~ be used for example to detect whether,~luring an exposure measurement a controlled state of the control loop 17 occurs. When this is not the case the voltage at the output 131 will exceed a given value and may be used for a variation of one or more parameters or for blocking a pick-up pos~ibility of the device.
`' The described arrangement is very suitable for angiography.
The voltage scale used in the method and the ., .
, , ..... .
,, . ",, " ~ , p j r lG-9-1 lOS5163 cievice for tlle cl~aracteristic ma~r be arbitrari.ly chosen.
~ logarit~uilic scale value, also for the ~oltage coordinate, may be ad~antageous due to obtain.ing tlle same pereentual accurac~-.
It ~-ill be evident that the described method ca.n llot only be ~ormed ~rith mechanical and analog elec~ical means. but ~or e~ample also ~rith cligital electronic circuits.
l~en using, ~or e~ample, su.f~`icient stores of a eomputer program or of a multiplier c:ircui.t for obtaining the eurrent volta~e funetions, even the use o~ a logarithmie eurrent seale may be umleeessary.
, '''' . ' ' ' , .
, , 1~ .
. .
Claims (6)
1. A machine method of determining voltage and current values associated with a given switch-on duration of an X-ray source with a given operating range limitation nomo-gram and to be applied to said X-ray source in which a desired current time product is determined with the aid of an X-ray exposure meter for a desired radiation quantity, charac-terized in that the current time product is determined at a given voltage applied to the radiation source while with the aid of a voltage-current function for the desired radiation quantity, which function is passed through coordinates corres-ponding to the current intensity associated with the desired current time product, and with the aid of the operating range limitation nomogram with the same current scale as the voltage-current function the point of intersection of the voltage-current function and the operating range limitation nomogram having the lowest voltage value is determined, said lowest voltage value being taken as a target value for the current determination with the aid of the load nomogram.
2. A method as claimed in Claim 1, characterized in that the current scale is a logarithmic current scale and that the voltage-current function is passed through the current intensity associated with the desired current time product by shifting parallel to the current coordinate.
3. A method as claimed in Claim 1 or 2, charac-terized in that with the aid of a subsequent X-ray exposure measurement at the determined lowest voltage value a subsequent lowest voltage value is obtained by repetition of the method as claimed in Claim 1.
4. A circuit arrangement for performing the method as claimed in Claim 1, characterized in that the X-ray exposure meter includes a circuit for determining the logarithm of the desired current value associated with the applied voltage and a chosen time and for supplying a voltage to its output which voltage is proportional to this logarithm, said output being coupled to a first input of an adder and subtractor stage a second input of which is coupled to an output of a clamping circuit an input of which is coupled to an output of a voltage-current function generator, said voltage-current function generator supply-ing an output voltage which is proportional to the logarithm of a current value associated with an input voltage while a third input of the adder and subtractor circuit is coupled to an output of an operating range limitation nomogram func-tion generator supplying an output voltage which is propor-tional to the lograithm of a current value associated with an input voltage, while an input of the said function generators is coupled to an output of the adder and subtrac-tor circuit, said output being furthermore coupled to a control signal input of a voltage control circuit of the radiation source.
5. A circuit as claimed in Claim 4, characterized in that a storage circuit is coupled to an output of the adder and subtractor circuit, while the output of the operat-ing range limitation nomogram function generator is coupled through a change-over switch, which can be operated by an operating device, to a control signal input of a current control circuit for the radiation source.
6. A circuit arrangement as claimed in Claim 5, characterized in that the storage circuit is coupled to an output of the operating device for obtaining a control voltage desired for a first exposure measurement.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NLAANVRAGE7314037,A NL168392C (en) | 1973-10-12 | 1973-10-12 | DEVICE FOR ADJUSTING A ROTATING X-RAY TUBE. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1055163A true CA1055163A (en) | 1979-05-22 |
Family
ID=19819807
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA211,098A Expired CA1055163A (en) | 1973-10-12 | 1974-10-09 | Method and circuit for determining voltage and current values associated with given switch-on durations of an x-ray source |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS5721118B2 (en) |
| BE (1) | BE820939A (en) |
| CA (1) | CA1055163A (en) |
| DE (1) | DE2448309C2 (en) |
| ES (1) | ES430876A1 (en) |
| FR (1) | FR2247872B1 (en) |
| GB (1) | GB1489377A (en) |
| IT (1) | IT1032542B (en) |
| NL (1) | NL168392C (en) |
| SE (1) | SE411826B (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4638500A (en) * | 1974-10-07 | 1987-01-20 | U.S. Philips Corporation | Method of determining voltage and current for a given operating period of an X-ray source |
| DE2613997A1 (en) * | 1976-04-01 | 1977-10-13 | Philips Patentverwaltung | REGULATING DEVICE, IN PARTICULAR FOR REGULATING THE EMISSION FLOW OF AN ROENTGEN PIPE |
| US4521808A (en) * | 1979-03-22 | 1985-06-04 | University Of Texas System | Electrostatic imaging apparatus |
| JPS6046714U (en) * | 1983-09-09 | 1985-04-02 | 株式会社 住建産業 | flooring |
| JPS61250258A (en) * | 1985-04-25 | 1986-11-07 | ミサワホ−ム株式会社 | Vibration-proof floor panel |
| GB2174492A (en) * | 1985-04-29 | 1986-11-05 | Philips Nv | X-ray examination system and method of controlling an exposure therein |
| JPS6376142U (en) * | 1986-05-16 | 1988-05-20 | ||
| JPH0542417U (en) * | 1991-11-11 | 1993-06-08 | イビデン株式会社 | Insulation waterproof panel |
| JP4393090B2 (en) * | 2002-07-19 | 2010-01-06 | 東芝医用システムエンジニアリング株式会社 | X-ray computed tomography system |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1076836B (en) * | 1957-09-28 | 1960-03-03 | Siemens Reiniger Werke Ag | X-ray diagnostic apparatus with an automatic exposure device |
| DE1614150B1 (en) * | 1966-04-07 | 1971-07-15 | Medicor Muevek | X-RAY LIGHTING DEVICE / WITH PHOTOELECTRIC CONVERTER TO SCAN THE ILLUMINATED AREA FOR THE PURPOSE OF DETERMINING THE OPTIMAL VALUES OF X-RAY TUBE VOLTAGE AND CURRENT |
| DE2204453B2 (en) * | 1972-01-31 | 1977-09-01 | Siemens AG, 1000 Berlin und 8000 München | X-RAY DIAGNOSTIC APPARATUS WITH AN IMAGE AMPLIFIER TELEVISION CHAIN AND A CONTROL CIRCUIT ADJUSTING THE DOSE PERFORMANCE ACCORDING TO THE PATIENT |
| NL7314036A (en) * | 1973-10-12 | 1975-04-15 | Philips Nv | GLOW CURRENT SUPPLY FOR A HIGH VOLTAGE ELECTRON TUBE. |
-
1973
- 1973-10-12 NL NLAANVRAGE7314037,A patent/NL168392C/en not_active IP Right Cessation
-
1974
- 1974-10-09 GB GB43725/74A patent/GB1489377A/en not_active Expired
- 1974-10-09 IT IT70017/74A patent/IT1032542B/en active
- 1974-10-09 CA CA211,098A patent/CA1055163A/en not_active Expired
- 1974-10-09 SE SE7412654A patent/SE411826B/en unknown
- 1974-10-10 DE DE2448309A patent/DE2448309C2/en not_active Expired
- 1974-10-10 ES ES430876A patent/ES430876A1/en not_active Expired
- 1974-10-10 BE BE149421A patent/BE820939A/en unknown
- 1974-10-12 JP JP11763174A patent/JPS5721118B2/ja not_active Expired
- 1974-10-14 FR FR7434443A patent/FR2247872B1/fr not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5068089A (en) | 1975-06-07 |
| SE7412654L (en) | 1975-04-14 |
| NL7314037A (en) | 1975-04-15 |
| DE2448309A1 (en) | 1975-04-17 |
| ES430876A1 (en) | 1976-10-01 |
| FR2247872B1 (en) | 1981-05-29 |
| NL168392B (en) | 1981-10-16 |
| NL168392C (en) | 1982-03-16 |
| IT1032542B (en) | 1979-06-20 |
| FR2247872A1 (en) | 1975-05-09 |
| SE411826B (en) | 1980-02-04 |
| GB1489377A (en) | 1977-10-19 |
| BE820939A (en) | 1975-04-10 |
| DE2448309C2 (en) | 1986-12-04 |
| AU7398174A (en) | 1976-04-08 |
| JPS5721118B2 (en) | 1982-05-04 |
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