METHOD FOR ACTIVATION OF AN EMITTER OF A COMPUTED TOMOGRAPHY SCANNER

• US 20080232543A1
• Filed: 03/19/2008
• Published: 09/25/2008
• Est. Priority Date: 03/20/2007
• Status: Active Grant

• Current Assignee: Cefla Societa' Cooperativa
• Original Assignee: Cefla Societa' Cooperativa
• Inventors: Nanni, Eros, Pasini, Alessandro
• Granted Patent: US 7,856,084 B2
• Time in Patent Office: Days
• US Class Current: 378/16
• CPC Class Codes: A61B 6/032 Transmission computed tomography [CT]
• CPC Class Codes: A61B 6/4441 the rigid structure being a C-arm or U-arm
• CPC Class Codes: A61B 6/488 involving pre-scan acquisition
• CPC Class Codes: A61B 6/51 for dentistry
• CPC Class Codes: A61B 6/542 involving control of exposure
• CPC Class Codes: A61B 6/544 dependent on patient size

Abstract

In a computed tomography scanner having an emitter for emitting a beam of given radiation through an object to be analysed, a detector for receiving said beam after the beam itself has traversed the object, and a rotating arm, which supports the emitter and the detector and rotates the emitter and the detector about the object along a series of angular positions, there is generated a succession of first pulses, each of which activates the detector in one respective angular position, and a succession of second pulses for activating the emitter so that it will emit a dose of radiation in each angular position, associated to which is a respective dose of radiation in such a way as to pre-define a distribution of doses of radiation along the series of angular positions.

Claims

1. A method for activation of an emitter of a computed tomography scanner comprising a detector (11) designed to receive a beam (10) of a given radiation emitted by the emitter (9) through an object to be analysed, and rotating supporting means (7), which are designed to support and rotate the emitter (9) and the detector (11) about said object;

the method comprising;

rotating the supporting means (7) along a series of angular positions (α

i);

generating a succession of first pulses (17), each of which activates the detector (11) in a respective angular position (α

i) for acquiring a respective radiography of the object; and

generating a succession of second pulses (19, 20;

21) for activating the emitter (9) in order to emit a radiation dose in each angular position (α

i);

and being characterized in that associated to each angular position (α

i) is a respective radiation dose in such a way as to pre-define a distribution of radiation doses along the series of angular positions (α

i).

2. The method according to claim 1, in which said object to be analysed is a portion of a body traversed by said beam (10) of radiation;

said distribution of radiation doses is calculated as a function of the dimensions of the body, of the type of object, and of the position of the object in the body.

3. The method according to claim 2, in which each said radiation dose is defined by at least one parameter (Ti;

Ai) associated to the respective angular position (α

i);

there corresponding to said distribution of radiation doses a distribution of parameters (Ti;

Ai).

4. The method according to claim 3, comprising:

pre-calculating, for said type of object in said position in the body, a distribution of coefficients (β

i;

δ

i) that expresses said distribution of parameters (Ti;

Ai) normalized to a first value (Tmin, Tmax;

Amin, Amax) of said parameter (Ti;

Ai) corresponding to which is a maximum and/or minimum radiation dose for said type of object in said position in the body;

said distribution of parameters (Ti;

Ai) being calculated as a function of the distribution of coefficients (β

i;

δ

i).

5. The method according to claim 4, comprising:

acquiring at least one scout-view of said body for estimating the dimensions of the body itself; and

calculating a second value (Tmin, Tmax;

Amin, Amax) of said parameter (Ti;

Ai) as a function of the dimensions estimated, there corresponding to said second value (Tmin, Tmax;

Amin, Amax) a minimum and/or maximum radiation dose for those dimensions;

said distribution of parameters (Ti;

Ai) being calculated by combining said distribution of parameters (Ti;

Ai) with the second value (Tmin, Tmax;

Amin, Amax).

6. The method according to claim 3, in which each said parameter (Ti, Ai) is constituted by a duration of emission (Ti) of said beam (10) associated to the respective angular position (α

i).

7. The method according to claim 6, in which each of said first pulses (17) has one and the same duration of exposure (TEX);

generating a succession of second pulses (19, 20) comprising;

in the case of a duration of emission (Ti) shorter than or equal to the duration of exposure (TEX), generating respective second pulses (19) in the angular positions (α

i), associated to which are said durations of emission (Ti), each second pulse (19) presenting a duration equal to the respective duration of emission (Ti).

8. The method according to claim 6, in which each of said first pulses (17) has one and the same duration of exposure (TEX);

generating a succession of second pulses (19, 20) comprising;

in the case of consecutive durations of emission (Ti) that are longer than the duration of exposure (TEX), generating just one second pulse (20) in the angular positions (α

i) associated to which are said durations of emission (Ti), said second pulse (20) having a duration substantially equal to the sums of said consecutive durations of emission (Ti).

9. The method according to claim 3, in which each second pulse (21) of said succession of second pulses (21) is associated to a respective angular position (α

i);

each said parameter (Ti, Ai) being constituted by the amplitude of the respective second pulse (19).

10. The method according to claim 1, in which said succession of first pulses (17) is generated by said detector (11).

11. The method according to claim 10, in which said succession of second pulses (19, 20;

21) is generated in such a way that each second pulse (19, 20;

21) is synchronised on the rising edge of a corresponding said first pulse (17).

12. A computed tomography scanner comprising:

an emitter for emitting a beam (10) of given radiation through an object to be analysed;

a detector (11) designed to receive said beam (10) after the beam (10) has traversed the object;

rotating supporting means (7), which are designed to support and rotate the emitter (9) and the detector (11) about said object; and

control and processing means (12, 7a, 13), which are designed to generate command pulses (17, 19, 20;

17, 21) for the detector (11) and the emitter (9) such as to synchronise emission and reception of the beam (10) with rotation of the supporting means (7) for acquiring radiographies of the object and are designed to process said radiographies for reconstructing images of the object;

the computed tomography scanner being characterized in that said control and processing means (12, 7a, 13) are configured for implementing the method for activation of an emitter of a computed tomography scanner according to claim 1.

13. A computed tomography scanner for use in dentistry characterized in that it is built according to claim 12.