Patent Number: 
Section: claims

1. A medical imaging method, comprising:generating an electron beam at one of a first energy level and a second energy level by an electron source, the second energy level being different from the first energy level;emitting radiation from a target through a patient and towards a detector upon receiving the electron beam at the target; andblocking or diverting the electron beam prior to reaching the target during at least one intermediate phase during which the electron source switches in a transient way from one of the first energy level and the second energy level to the other of the first energy level and the second energy level,wherein:the electron source comprises a deflection system and an electron collector positioned between the electron source and the target,the electron collector defines an aperture through which the electron beam passes, and comprises an inner surface, wherein at least a portion of the inner surface is tilted so that the cross section of the aperture changes along a path of the electron beam, andthe step of blocking or diverting the electron beam comprises deflecting the electron beam toward the inner surface of the electron collector. 2. The method according to claim 1, further comprising:modulating the duration of the at least one intermediate phase during which the electron beam is blocked or diverted depending on a dose level per image to which a patient may be subjected. 3. The method according to claim 1, wherein the electron source comprises:a source of electrons configured to emit a flux of electrons; andthe target comprising a first focal area, through which the radiation is emitted when the first focal area is exposed to the flux of electrons, the flux of electrons being diverted relative to the first focal area during the at least one intermediate phase. 4. The method according to claim 3, wherein the flux of electrons is blocked or diverted by magnetic deflection or electrostatic deflection. 5. A medical imaging device, comprising:an electron source;an X-ray detector;the electron source being controlled by a control module to generate an electron beam at one of a first energy level, and a second energy level different from the first energy level, and to emit the electron beam towards the X-ray detector, the electron source generating an electron beam of variable energy over time during an intermediate phase during which the electron source switches in a transient way from the first energy level to the second energy level or vice versa; a target comprising a focal area adapted to emit X-rays towards the detector through a patient upon receiving the electron beam;the electron source further comprising:a deflection system positioned between the electron source and the target, adapted so as to modify the trajectory of the electron beam during the intermediate phasean electron collector positioned between the deflection system and the target, the electron collector defining an aperture through which the electron beam passes, and comprising an inner surface, wherein at least a portion of the inner surface is tilted so that the cross section of the aperture changes along a path of the electron beam, andthe deflection system configured to divert the electron beam towards the inner surface of the electron collector during the intermediate phase. 6. The medical imaging device according to claim 5, wherein said electron collector is adapted for absorbing the electron beam. 7. The medical imaging device according to claim 5, wherein the target further comprises at least one second focal area through which X-rays are not emitted when the at least one second focal area is exposed to a flux of electrons, and wherein the flux of electrons is diverted by the deflection system towards the at least one second focal area during the at least one intermediate phase. 8. The medical imaging device according to claim 7, wherein the at least one second focal area is configured to absorb the flux of electrons. 9. The medical imaging device according to claim 5, wherein the target further comprises at least one second focal area through which radiations are emitted towards a direction distinct from a direction of emission of the first focal area, the medical imaging device further comprising a collimator positioned between the target and the detector, wherein the collimator is configured to block the radiations emitted from the at least one second focal area. 10. The medical imaging device according to claim 8, wherein the target is an axisymmetrical solid centered on an axis, wherein the target rotates around the axis, and wherein the first focal area and the at least one second focal area are concentric rings distinct from each other. 11. The medical imaging device according to claim 10, wherein the at least one second focal area is a groove in the target, wherein the electron beam emitted towards the at least one second focal area is blocked by a wall of the groove. 12. The medical imaging device according to claim 5, further comprising a processing unit configured to process images obtained by the detector. 13. The medical imaging device according to claim 7, wherein the at least one second focal area is on the inner surface. 14. The medical imaging device according to claim 8, wherein the at least one second focal area is on the inner surface.