Method of adjusting the emission rate of radiation from a source of radiation

1. A method for adjusting the emission rate of radiation of a source of X-ray radiation comprising:

calibrating the radiation emission rate of the source as a function of a voltage applied between first and second emitting elements of the source and as a function of the heating current of the source in response to the source being active;

supplying the second element with high voltage relative to the first element;

adjusting a heating current of the second element for an expected rate of radiation emission as a function of the calibration; and

carrying out the calibration by an expression chosen to express the emission rate of radiation in which the logarithm of the value of the emission rate is a second-order polynomial function of the heating current and a first-order polynomial function of the voltage.

2. The method according to claim 1 wherein:

the source of radiation is an X-ray tube;

the first element is an anode of the tube; and

the second element is a cathode of the tube.

3. The method according to claim 2 wherein the calibrating is a function of six coefficients a, b, c, d, e, and f that, for a given tube, satisfy the equation:

ln( I tube )= aI ch 2 ln( V )+ bI ch 2 +cI ch ln( V )+ dI ch +e ln( V )+ f,

where ln is a Neperian logarithm; I tube is tube current; I ch is tube heating current; and V is tube voltage.

4. The method according to claim 3 wherein;

the tube has a wide focus, a narrow focus, or both; and

the coefficients a, b, c, d, e and f have values given by one of the columns of the following table, or values given by both columns of the following table for a dual-focus tube:

coefficients\cathode

wide focus

narrow focus

a

2.948793

4.517432

b

−7.42477

−11.1148

c

−8.01109

−10.6986

d

29.87146

37.45432

e

5.616099

6.544223

f

−23.3185

−25.8013.

5. The method according to claim 2 further comprising:

correcting the calibration of the tube as a function of the nature of the tube by

carrying out a regression type analysis to determine coefficients α and β with which a heating current I ch real to be applied to the tube is expressed in the form: I ch real=αI ch calib+β, where I ch calib is the value of the heating current that results from the calibration.

6. The method according to claim 5 further comprising:

correcting the calibration of the tube as a function of the aging of the tube by

making readings for the tube, during subsequent uses, of measurements of the tube current I tube , the heating current I ch , and the applied high voltage V; and

carrying out a mathematical regression to determine coefficients α and β with which the heating current I ch real to be applied to the tube is expressed in the form: I ch real=αI ch calib+β, where I ch calib is the value of the heating current that results from the calibration.

7. The method according to claim 2 further comprising:

correcting the calibration of the tube as a function of the aging of the tube by

making readings for the tube, during subsequent uses, of measurements of the tube current I tube , the heating current I ch , and the applied high voltage V; and

carrying out a mathematical regression to determine coefficients α and β with which the heating current I ch real to be applied to the tube is expressed in the form: I ch real=αI ch calib+β, where I ch calib is the value of the heating current that results from the calibration.

8. The method according to claim 3 further comprising:

correcting the calibration of the tube as a function of the nature of the tube by

carrying out a regression type analysis to determine coefficients α and β with which a heating current I ch real to be applied to the tube is expressed in the form: I ch real=αI ch calib+β, where I ch calib is the value of the heating current that results from the calibration.

9. The method according to claim 3 further comprising:

correcting the calibration of the tube as a function of the aging of the tube by

making readings for the tube, during subsequent uses, of measurements of the tube current I tube , the heating current I ch , and the applied high voltage V; and

carrying out a mathematical regression to determine coefficients α and β with which the heating current I ch real to be applied to the tube is expressed in the form: I ch real=αI ch calib+β, where I ch calib is the value of the heating current that results from the calibration.

10. The method according to claim 4 further comprising:

correcting the calibration of the tube as a function of the nature of the tube by

carrying out a regression type analysis to determine coefficients α and β with which a heating current I ch real to be applied to the tube is expressed in the form: I ch real=αI ch calib+β, where I ch calib is the value of the heating current that results from the calibration.

11. The method according to claim 4 further comprising:

correcting the calibration of the tube as a function of the aging of the tube by

making readings for the tube, during subsequent uses, of measurements of the tube current I tube , the heating current I ch , and the applied high voltage V; and

carrying out a mathematical regression to determine coefficients α and β with which the heating current I ch real to be applied to the tube is expressed in to form: I ch real=αI ch calib+β, where I ch calib is the value of the heating current that results from the calibration.

12. A computer program product having therein a program code comprising means for:

calibrating a radiation emission rate of an X-ray source as a function of a voltage applied between first and second emitting elements of the source and as a function of a heating current of the source in response to the source being active;

supplying the second element with high voltage relative to the first element;

adjusting a heating current of the second element for an expected rate of radiation emission as a function of the calibration; and

carrying out the calibration by an expression chosen to express the emission rate of radiation in which the logarithm of the value of the emission rate is a second-order polynomial function of the heating current and a first-order polynomial function of the voltage.

13. A data carrie comprising a medium having embedded therein a computer program code comprising means for:

calibrating a radiation emission rate of an X-ray source as a function of a voltage applied between first and second emitting elements of the source and as a function of a heating current of the source in response to the source being active;

supplying the second element with high voltage relative to the first element;

adjusting a heating current of the second element for an expected rate of radiation emission as a function of the calibration; and

carrying out the calibration by an expression chosen to express the emission rate of radiation in which the logarithm of the value of the emission rate is a second-order polynomial function of the heating current and a first-order polynomial function of the voltage.