Coil sensitivity map generating method, parallel imaging method, and MRI apparatus
AssigneeGE Yokogawa Medical Systems, Limited
InventorYoshikazu Ikezaki
Life of this patent
Estimating the term…
Abstract
For a purpose of improving homogeneity of an image obtained in a self-calibration by a parallel imaging method generally referred to as SENSE (SENSitivity Encoding), sensitivity factors Sn(p) are calculated using an additive image Ab=Σ|Cn| of complex images Cn obtained by conducting a calibration scan of an entire FOV for phased array coils Coil_n (n=1−N, N≧2) (Steps V2, V3). Moreover, sensitivity maps Sn are generated by conducting curve fitting by the method of least squares weighted by the square of a pixel value Ab(P) of the absolute value additive image Ab (Step V4).
Claims15
A coil sensitivity map generating method comprising:
- when a pixel value of a pixel p in a complex image Cn obtained by conducting a calibration scan of an entire FOV for each of phased array coils Coil_n (n=1−N, N≧2) is represented as Cn(p), and a pixel value of a pixel p in an additive image Ab=Σ|Cn| obtained by adding absolute value images |Cn| produced from said complex images Cn is represented as Ab(p), calculating a sensitivity factor Sn(p) at a pixel p in a phased array coil Coil_n by:
- Sn(p)=Cn(p)/Ab(p);
- and generating respective sensitivity maps Sn of the phased array coils Coil_n based on said sensitivity factors Sn(p).
A parallel imaging method comprising:
- obtaining respective complex images Cn by conducting a calibration scan of an entire FOV for phased array coils Coil_n (n=1−N, N≧2);
- producing an absolute value image |Cn| from each said complex image Cn;
- producing an additive image Ab=Σ|Cn| by adding said absolute value images |Cn|;
- calculating a sensitivity factor Sn (p) at a pixel p in a phased array coil Coil_n by:
- Sn(p)=Cn(p)/Ab(p),
- where a pixel value of a pixel p in said complex image Cn is represented as Cn(p), and a pixel value of a pixel p in said additive image Ab is represented as Ab(p);
- generating respective sensitivity maps Sn of the phased array coils Coil_n based on said sensitivity factors Sn(p);
- obtaining respective complex images An by conducting a scan with a smaller FOV for the phased array coils Coil_n;
- and producing a complex image of the entire FOV from said sensitivity maps Sn and said complex images An.
An MRI apparatus comprising:
- a transmitting coil for transmitting an RF pulse;
- a gradient coil for applying a gradient magnetic field;
- phased array coils Coil_n (n=1−N, N≧2) for receiving an MR signal;
- calibration scan means for driving said transmitting coil, gradient coil, and phased array coils Coil_n to conduct a calibration scan of an entire FOV and obtain respective complex images Cn for the phased array coils Coil_n;
- absolute value additive image producing means for producing an absolute value image |Cn| from each said complex image Cn and producing an additive image Ab=Σ|Cn| by adding said absolute value images |Cn|;
- sensitivity factor calculating means for calculating a sensitivity factor Sn(p) at a pixel p in a phased array coil Coil_n by:
- Sn(p)=Cn(p)/Ab(p),
- where a pixel value of a pixel p in said complex image Cn is represented as Cn(p), and a pixel value of a pixel p in said additive image Ab is represented as Ab(p);
- sensitivity map generating means for generating respective sensitivity maps Sn of the phased array coils Coil_n based on said sensitivity factors Sn(p);
- parallel scan means for driving said transmitting coil, gradient coil, and phased array coils Coil_n to conduct a scan with a smaller FOV and obtain respective complex images An;
- and entire FOV image producing means for producing a complex image of the entire FOV from said sensitivity maps Sn and said complex images An.
Dependencies are inferred from the claim text.