Magnetic resonance imaging apparatus and imaging-time shortening method

A magnetic resonance imaging apparatus, comprising:

• sequence control circuitry configured to perform a first sequence and a second sequence under different saturation pulse conditions in a chemical exchange saturation transfer “CEST” imaging in which a plurality of saturation pulses is applied to acquire a plurality of magnetic resonance “MR” signals responsive to the plurality of saturation pulses, the first sequence being configured to acquire first MR signals corresponding to a first frequency region of a k-space and second MR signals corresponding to a second frequency region of the k-space, the second sequence being configured to acquire third MR signals corresponding to at least the first frequency region, the first frequency region being lower in frequency the second frequency region;
• and
• processing circuitry configured to assign the third MR signals and the second MR signals to a single k-space generated for the second sequence, wherein
• the sequence control circuitry is further configured to perform the first sequence while shifting a frequency of the saturation pulses from a free-water resonance frequency based on a predetermined static field strength, until an MR image generated from the first MR signals and the second MR signals exhibits signal intensity of a minimum value,
• the processing circuitry is further configured to:
• set, as a saturation pulse condition for the first sequence, frequencies offset from a frequency corresponding to the minimum value at a predetermined frequency interval and frequencies included in a predetermined range centered around the frequency corresponding to the minimum value, and
• set frequencies located among the set frequencies as a saturation pulse condition for the second sequence,
• the sequence control circuitry is further configured to perform the first sequence and the second sequence until completion of applying the plurality of saturation pulses at the frequencies in the respective saturation pulse conditions, and
• the processing circuitry is further configured to:
• generate multiple MR images, corresponding to the saturation pulse frequencies of the second sequence from the second MR signals and the third MR signals assigned to the single k-space, and
• control a display to display the multiple MR images.

An imaging-time shortening method comprising:

• setting, as a saturation pulse condition for a first sequence in a chemical exchange saturation transfer “CEST” imaging in which a plurality of saturation pulses is applied to acquire a plurality of magnetic resonance “MR” signals responsive to the plurality of saturation pulses, a free-water resonance frequency based on a predetermined static field strength and frequencies offset from the free-water resonance frequency at a predetermined frequency interval;
• setting frequencies located between the offset frequencies as a saturation pulse condition for a second sequence in the CEST imaging;
• performing the first sequence and the second sequence under the different saturation pulse conditions in the CEST imaging configured to acquire first MR signals corresponding to a first frequency region of a k-space and second MR signals corresponding to a second frequency region of the k-space, the second sequence configured to acquire third MR signals corresponding to at least the first frequency region, and the first frequency region being lower in frequency than the second frequency region;
• and
• assigning the third MR signals and the second MR signals to a single k-space generated for the second sequence such that the low frequency region of the k-space related to the second sequence is filled with the third MR signals while the high frequency region of the k-space related to the second sequence is filled with the second MR signals;
• generating multiple MR images, each MR image of the multiple MR images corresponding to the saturation pulse frequencies of the second sequence from the second MR signals and the third MR signals assigned to the single k-space;
• and
• controlling a display to display the multiple MR images.