The present invention relates to a magnetic resonance imaging (MRI) apparatus and a magnetic resonance imaging method. The present invention relates particularly to a magnetic resonance imaging apparatus and a magnetic resonance imaging method which carry out a fast spin echo (FSE) method.
An image diagnostic apparatus such as a magnetic resonance imaging system or apparatus has been known as an apparatus for imaging or photographing a slice image about each tomographic plane of a subject. The image diagnostic apparatus has been used in various fields such as a medical application, an industrial application, etc.
When, for example, a slice image is photographed using the magnetic resonance imaging apparatus, a subject is held or accommodated in a space formed with a static magnetic field and the directions of spins of proton in the subject corresponding to a living body are aligned in the direction of the static magnetic field, thereby bringing about a state in which magnetization vectors have been obtained.
Thereafter, an electromagnetic wave having a resonance frequency is applied to the subject through an RF coil to generate a nuclear magnetic resonance phenomenon, thereby changing the magnetization vector of proton of the subject. The magnetic resonance imaging apparatus receives a magnetic resonance signal from the proton of the subject returned to the original magnetization vector at a probe coil (reception coil unit) and generates a slice image, based on the received magnetic resonance signal (refer to, for example, a patent document 1).
Meanwhile, a flow such as a bloodstream exists in the subject, and there is a case in which the intensity of a magnetic resonance signal corresponding to a bloodstream or bloodflow signal is suppressed to draw the flow at low luminance at the magnetic resonance imaging apparatus. To this end, there is provided one in which as known as a Double IR (Inversion Recovery) method, signals other than at a target slice section are inverted using slice selection IR pulses at the target slice section after the inversion of signals in coil sensitivity using slice non-selection IR pulses, and magnetic resonance signals are acquired and the signals other than at the target slice section are brought into null-signal form.
As known as a Flow-spoiled FBI method, there is provided one in which in the FBI method (Fresh Blood Imaging) (refer to, for example, a patent document 2), spoiling pulses in a read-out direction are used to enable separation of blood-vessel arteries and veins.
[Patent Document 1] Japanese Unexamined Patent Publication No. 2005-270304
[Patent Document 2] Japanese Unexamined Patent Publication No. 2000-5144
In the Double IR method, the slice selection IR pulses are transmitted to a target slice section having a predetermined thickness. Therefore, when, for example, three-dimensional imaging is performed, it is difficult to make out or draw a bloodstream about a wide region of a predetermined thickness or more at low luminance.
Since the quantitativity of each spoiling pulse cannot be adjusted in the Flow-spoiled FBI method, a preparation scan is required before an actual scan when a delay time from the generation of a trigger pulse to the start of actual imaging or photography is optimized and the gradient of the spoiling pulse is adjusted.
The spoiling pulses are transmitted to a subject even upon acquisition of magnetic resonance signals at an actual scan. Therefore, the fast spin echo method involves a problem that when it is adopted, the interval (echo space) between pulses applied to obtain respective echoes is spread, thus resulting in an obstacle to fast imaging. Further, the FSE method was inadequate to deal with spoiling of magnetic resonance signals about the bloodstream by the spoiling pulses.