US6504894B2 — Phase-driven multisector reconstruction for multi…

Claim 1

Independent Claim 126 words

A method for multisector computed tomographic (CT) imaging of a cyclically moving object comprising the steps of: helically scanning a cyclically moving object with a CT imaging system having multiple detector rows and a rotating gantry, at a gantry rotation speed selected either to lead or to lag a cycle of the cyclically moving object; retrospectively gating the projection data of the object with a gating signal related to the motion of the cyclically moving object so that a geometric phase difference is created between a cycle of the rotating gantry and the motion of the cyclically moving object; and reconstructing an image of the cyclically moving object using gated sector data from image data representing a plurality of consecutive cycles of the cyclically moving object.

Claim 2

Independent Claim 126 words

A method for multisector computed tomographic (CT) imaging of a cyclically moving object comprising the steps of: helically scanning a cyclically moving object with a CT imaging system having multiple detector rows and a rotating gantry, at a gantry rotation speed selected either to lead or to lag a cycle of the cyclically moving object; retrospectively gating the projection data of the object with a gating signal related to the motion of the cyclically moving object so that a geometric phase difference is created between a cycle of the rotating gantry and the motion of the cyclically moving object; and reconstructing an image of the cyclically moving object using gated sector data from image data representing a plurality of consecutive cycles of the cyclically moving object.

Claim 3

Dependent Claim 56 words

A method in accordance with claim 1 wherein the cyclically moving object is a patient's heart, the cycles of the cyclically moving object are cardiac cycles, and said step of retrospectively gating the projection data of the object with a gating signal comprises the step of recording an EKG signal representative of the patient's cardiac cycle.

Claim 4

Dependent Claim 101 words

A method in accordance with claim 2 wherein said step of helically scanning a cyclically moving object with a CT imaging system comprises the step of selecting a gantry rotation speed from the group consisting of G′ s and G s † , where G s ′ = 360 7  B , and   G s † = 360 5  B ,  and   B   is   the   patient '  s   heart   rate   in   beats   per   minute .

Claim 5

Dependent Claim 41 words

A method in accordance with claim 3 wherein said step of reconstructing an image of the cyclically moving object comprises the step of reconstructing an image of the cyclically moving object using projection data representative of n s =4 cardiac cycles.

Claim 6

Dependent Claim 22 words

A method in accordance with claim 3 wherein said selection of gantry rotation speed depends upon a heart rate of the patient.

Claim 7

Dependent Claim 45 words

A method in accordance with claim 2 wherein said step of helically scanning a cyclically moving object with a CT imaging system comprises the step of selecting a gantry rotation speed from the group consisting of 0.8 seconds per rotation and 1.0 seconds per rotation.

Claim 8

Dependent Claim 108 words

A method in accordance with claim 2 wherein the CT imaging system has a z-axis; said step of helically scanning the cyclically moving object comprises the steps of moving the cyclically moving object parallel to the z-axis; and acquiring a plurality of sectors of projection data of the cyclically moving object; said step of reconstructing an image of the cyclically moving object comprises using said plurality of sectors of projection data to reconstruct the image; and further comprising the step of selecting a helical pitch for said helical scanning step so that sectors used for said step of reconstructing an image are aligned at the same z-axis location.

Claim 9

Dependent Claim 83 words

A method in accordance with claim 7 wherein said helical pitch p is selected as: p = N - 1 + ⌊ n s ⌋ ( 60 / b ) × ( n s / G s ) , where: └n s ┘ is the fractional portion of n s ; n s is a number of cardiac cycles used for reconstruction; B is the heart rate in beats per minute; and G s is the gantry rotation speed in seconds per revolution.

Claim 10

Dependent Claim 44 words

A method in accordance with claim 7 wherein the sectors used for reconstruction have overlapping boundaries, and further comprising the step of applying a smoothing function at a junction of boundaries between sectors to provide a smooth transition from one sector to the next.

Claim 11

Dependent Claim 31 words

A method in accordance with claim 7 further comprising the step of weighting data by interpolation between two detector rows of the multirow detector closest to a z-location of image reconstruction.

Claim 12

Dependent Claim 126 words

A computed tomographic (CT) imaging system for imaging a cyclically moving object, said imaging system having a multirow detector and a rotating gantry, and said imaging system being configured to: helically scan a cyclically moving object at a gantry rotation speed selected either to lead or to lag a cycle of the cyclically moving object; retrospectively gate the projection data of the object with a gating signal related to the motion of the cyclically moving object so that a geometric phase difference is created between a cycle of the rotating gantry and the motion of the cyclically moving object; and reconstruct an image of the cyclically moving object using gated sector data from image data representing a plurality of consecutive cycles of the cyclically moving object.

Claim 13

Dependent Claim 126 words

A computed tomographic (CT) imaging system for imaging a cyclically moving object, said imaging system having a multirow detector and a rotating gantry, and said imaging system being configured to: helically scan a cyclically moving object at a gantry rotation speed selected either to lead or to lag a cycle of the cyclically moving object; retrospectively gate the projection data of the object with a gating signal related to the motion of the cyclically moving object so that a geometric phase difference is created between a cycle of the rotating gantry and the motion of the cyclically moving object; and reconstruct an image of the cyclically moving object using gated sector data from image data representing a plurality of consecutive cycles of the cyclically moving object.

Claim 14

Dependent Claim 37 words

An imaging system in accordance with claim 11 wherein to retrospectively gate the projection data of the object with a gating signal, said system is configured to use an EKG signal representative of a patient's cardiac cycle.

Claim 15

Dependent Claim 54 words

An imaging system in accordance with claim 12 configured to helically scanning the cyclically moving object at a gantry rotation speed selected from the group consisting of G′ s and G s † , where G′ s , and G s † , and B is the patient's heart rate in beats per minute.

Claim 16

Dependent Claim 34 words

An imaging system in accordance with claim 13 wherein to reconstruct an image of the cyclically moving object, said imaging system is configured to use projection data representative of n s =4 cardiac cycles.

Claim 17

Dependent Claim 24 words

An imaging system in accordance with claim 13 configured to scan at a gantry rotation speed dependent upon a heart rate of the patient.

Claim 18

Dependent Claim 46 words

An imaging system in accordance with claim 12 wherein to helically scan a cyclically moving object, said imaging system is configured to scan the cyclically moving object at gantry rotation speed selected from the group consisting of 0.8 seconds per rotation and 1.0 seconds per rotation.

Claim 19

Dependent Claim 98 words

An imaging system in accordance with claim 12 having a z-axis, said imaging system configured to: helically scan the cyclically moving object, said imaging system is configured to move the cyclically moving object parallel to the z-axis; and acquire a plurality of sectors of projection data of the cyclically moving object; reconstruct an image of the cyclically moving object, said imaging system is configured to use said plurality of sectors of projection data for reconstructing the image; and scan at a helical pitch such that sectors used for reconstructing said image are aligned at the same z-axis location.

Claim 20

Dependent Claim 84 words

An imaging system in accordance with claim 17 wherein said helical pitch p is written as: p = N - 1 + ⌊ n s ⌋ ( 60 / b ) × ( n s / G s ) , where: └n s ┘ is the fractional portion of n s ; n s is a number of cardiac cycles used for reconstruction; B is the heart rate in beats per minute; and G s is the gantry rotation speed in seconds per revolution.

Claim 21

Dependent Claim 47 words

An imaging system in accordance with claim 17 wherein the sectors used for reconstruction have overlapping boundaries, and said imaging system is further configured to apply a smoothing function at a junction of boundaries between sectors to provide a smooth transition from one sector to the next.

Claim 22

Dependent Claim 30 words

An imaging system in accordance with claim 17 further configured to weight data by interpolation between two detector rows of the multirow detector closest to a z-location of image reconstruction.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	2006-01-06	2006-07-08	2007-01-07	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2010-01-06	2010-07-08	2011-01-07	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2014-01-06	2014-07-08	2015-01-07	$7700.00	Window Closed / Lapsed

Phase-driven multisector reconstruction for multislice helical CT imaging

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