Computed-tomography apparatus and control method thereof

A computed-tomography apparatus for acquiring a cross-sectional image of an object on the basis of projection data of said object obtained by scanning said object with radiation while rotating a scanner around said object, comprising:

• image processing means for assigning individual weights to projection data in a predetermined rotation angle range including the vicinity of a scan start rotation position of said scanner and the vicinity of a scan end rotation position thereof and projection data in a rotation angle range opposite to said predetermined rotation angle range, respectively, determining corrected data for the entire circumference of said object by use of the projection data assigned with said weights and projection data assigned with no weight, and generating said cross-sectional image on the basis of said corrected data;
• determining means for determining one of rotation positions of said scanner which has a smaller attenuation of radiation;
• position detecting means for detecting a scan start rotation position of said scanner;
• and
• correction range adjusting means for narrowing said predetermined rotation angle range in the case where the scan start rotation position is not the rotation position having the smaller attenuation.

A computed-tomography apparatus for acquiring a cross-sectional image of an object on the basis of projection data of said object obtained by scanning said object with radiation while rotating a scanner around said object, comprising:

• image processing means for generating said cross-sectional image on the basis of projection data obtained from the start of scan by said scanner until the end thereof;
• a plurality of scan start rotation positions set on the locus of scan rotation of said scanner;
• position detecting means for detecting said plurality of scan start rotation positions during the rotation of said scanner;
• and
• scanner controlling means for starting the actual scan from the scan start rotation position which said position detecting means first detects after the point of time when a scan start signal is given.

A control method in a computed-tomography apparatus for acquiring a cross-sectional image of an object on the basis of projection data of said object obtained by scanning said object with radiation while rotating a scanner around said object, comprising the steps of:

• determining one of rotation positions of said scanner which has a smaller attenuation of radiation;
• controlling the operation of said scanner so that the scan is started from said rotation position having the smaller attenuation;
• and
• assigning individual weights to projection data in a predetermined rotation angle range including the vicinity of a scan start rotation position of said scanner and the vicinity of a scan end rotation position thereof and projection data in a rotation angle range opposite to said predetermined rotation angle range, respectively, determining corrected data for the entire circumference of said object by use of the projection data assigned with said weights and projection data assigned with no weight, and generating said cross-sectional image on the basis of said corrected data.

A control method in a computed-tomography apparatus for acquiring a cross-sectional image of an object on the basis of projection data of said object obtained by scanning said object with radiation while rotating a scanner around said object, comprising the steps of:

• determining one of rotation positions of said scanner which has a smaller attenuation of radiation;
• detecting a scan start rotation position of said scanner;
• assigning individual weights to projection data in a predetermined rotation angle range including the vicinity of a scan start rotation position of said scanner and the vicinity of a scan end rotation position thereof and projection data in a rotation angle range opposite to said predetermined rotation angle range, respectively, determining corrected data for the entire circumference of said object by use of the projection data assigned with said weights and projection data assigned with no weight, and generating said cross-sectional image on the basis of said corrected data;
• and
• narrowing said predetermined rotation angle range in the case where the detected scan start rotation position is not the rotation position having the smaller attenuation.

A control method in a computed-tomography apparatus for acquiring a cross-sectional image of an object on the basis of projection data of said object obtained by scanning said object with radiation while rotating a scanner around said object, comprising the steps of:

• setting a plurality of scan start rotation positions on the locus of scan rotation of said scanner;
• detecting said plurality of scan start rotation positions during the rotation of said scanner;
• starting the actual scan from the scan start rotation position which is first detected after the point of time when a scan start signal is given;
• and
• generating said cross-sectional image on the basis of projection data obtained from the start of scan by said scanner until the end thereof.

A computed-tomography apparatus for acquiring a cross-sectional image of an object on the basis of projection data of said object obtained by scanning said object with radiation while rotating a scanner around said object, comprising:

• image processing means for assigning individual weights to projection data in a predetermined rotation angle range including the vicinity of a scan start rotation position of said scanner and the vicinity of a scan end rotation position thereof and projection data in a rotation angle range opposite to said predetermined rotation angle range, respectively, determining corrected data for the entire circumference of said object by use of the projection data assigned with said weights and projection data assigned with no weight, and generating said cross-sectional image on the basis of said corrected data;
• determining means for determining one of rotation positions of said scanner which has a smaller attenuation of radiation;
• position detecting means for detecting a scan start rotation position of said scanner;
• and
• correction range adjusting means for changing said predetermined rotation angle range in accordance with the scan start rotation position.

A computed-tomography apparatus for acquiring a cross-sectional image of an object on the basis of projection data of said object obtained by scanning said object with radiation while rotating a scanner around said object, comprising:

• image processing means for generating said cross-sectional image on the basis of projection data obtained from the start of scan by said scanner until the end thereof;
• position information provided on a rotating portion of said scanner;
• position detecting means for detecting a plurality of scan start rotation positions of said scanner during the rotation of said scanner on the basis of said position information;
• and
• scanner controlling means for starting the actual scan from the scan start rotation position which said position detecting means first detects after the point of time when a scan start signal is given.

A control method in a computed-tomography apparatus for acquiring a cross-sectional image of an object on the basis of projection data of said object obtained by scanning said object with radiation while rotating a scanner around said object, comprising the steps of:

• providing position information on a rotating portion of said scanner;
• detecting a plurality of scan start rotation positions of said scanner during the rotation of said scanner on the basis of said position information;
• starting the actual scan from the scan start rotation position which is first detected after the point of time when a scan start signal is given;
• and
• generating said cross-sectional image on the basis of projection data obtained from the start of scan by said scanner until the end thereof.