Magnetic Resonance Imaging
301
15.6 APPLICATIONS OF MRI AND fMRI
Pathological conditions and injuries can be revealed with great detail based on T 1 and
T 2 weighing. Some examples of the diagnostic use are the localization of tumors and
identification of internal hemorrhaging. Knowing that MRI is rather harmless, this
technology can be used for practically all applications described for x-ray CT and
many applications in which ultrasound imaging is used for. However, the cost of performing MRI and the fact that during the acquisition of MRI, the patient is expected
to stay still are limiting the actual usage of this technology.
Another factor that limits the use of MRI for certain applications such as intraoperational imaging is the fact that ferromagnetic tools cannot be used in the MRI
room. In other words, while it is desirable to conduct MRI while the surgery is performed, the typical tools used in surgery cannot be used in the same room MRI is
taken. Surgery tools made of titanium can be used in the MRI room, but due to the
high cost of such tools, they are not used in typical surgeries.
Due to the substantial similarities between the applications of x-ray CT and
MRI, the specific applications of MRI in acquiring anatomical information are not
described in detail, and, rather, we focus on the main applications of f MRI.
Typical examples of the clinical applications of f MRI predominantly revolve
around the detection of focal neuron depolarization in the brain. Specific conditions involved with focal neuronal activity are in visual, auditory, sensory motor, and
language activities. For most of these functions, the typical locations of the cortical
activity are known. f MRI is used to aid the diagnosis of certain diseases such as
epilepsy, schizophrenia, Alzheimer’s, Parkinson’s, intracranial lesions, depression,
and hearing impairment. Location and identification of brain tumors is also a clinical issue that can be resolved with f MRI. Some of the activities are further described
in the following.
A representative NMR image of the neurovascular activity is presented in
Figure 15.15.
15.6.1 fMRI FOR MONITORING AUDIO ACTIVITIES OF BRAIN
Specific auditory tasks are presented while a subject is inside the MRI machine, and
the changes in blood supply to the areas of the brain that apparently are active in data
processing will become evident.
Auditory stimuli can be voice or language recognition or purely sound perception. Examples of auditory tasks are the delivery of sound burst with a particular
frequency pattern (tonotopic), sound burst with amplitude variations (amplitopic),
evoked response type of stimuli using short sentences with or without rhyme, and
additional audio–speech combination assignments. Images will need to be obtained
in a relatively fast algorithm in the order of five images per second to be able to recognize significant differences in the cortical activity. A period of rest with no input
is required between each assignment for calibration purposes, while the data acquisition is maintained at the same rate.
The auditory region of the cortex is predominantly located in the frontal section
of the brain and in the temporal section in a lesser degree. The studies of the auditory
301
15.6 APPLICATIONS OF MRI AND fMRI
Pathological conditions and injuries can be revealed with great detail based on T 1 and
T 2 weighing. Some examples of the diagnostic use are the localization of tumors and
identification of internal hemorrhaging. Knowing that MRI is rather harmless, this
technology can be used for practically all applications described for x-ray CT and
many applications in which ultrasound imaging is used for. However, the cost of performing MRI and the fact that during the acquisition of MRI, the patient is expected
to stay still are limiting the actual usage of this technology.
Another factor that limits the use of MRI for certain applications such as intraoperational imaging is the fact that ferromagnetic tools cannot be used in the MRI
room. In other words, while it is desirable to conduct MRI while the surgery is performed, the typical tools used in surgery cannot be used in the same room MRI is
taken. Surgery tools made of titanium can be used in the MRI room, but due to the
high cost of such tools, they are not used in typical surgeries.
Due to the substantial similarities between the applications of x-ray CT and
MRI, the specific applications of MRI in acquiring anatomical information are not
described in detail, and, rather, we focus on the main applications of f MRI.
Typical examples of the clinical applications of f MRI predominantly revolve
around the detection of focal neuron depolarization in the brain. Specific conditions involved with focal neuronal activity are in visual, auditory, sensory motor, and
language activities. For most of these functions, the typical locations of the cortical
activity are known. f MRI is used to aid the diagnosis of certain diseases such as
epilepsy, schizophrenia, Alzheimer’s, Parkinson’s, intracranial lesions, depression,
and hearing impairment. Location and identification of brain tumors is also a clinical issue that can be resolved with f MRI. Some of the activities are further described
in the following.
A representative NMR image of the neurovascular activity is presented in
Figure 15.15.
15.6.1 fMRI FOR MONITORING AUDIO ACTIVITIES OF BRAIN
Specific auditory tasks are presented while a subject is inside the MRI machine, and
the changes in blood supply to the areas of the brain that apparently are active in data
processing will become evident.
Auditory stimuli can be voice or language recognition or purely sound perception. Examples of auditory tasks are the delivery of sound burst with a particular
frequency pattern (tonotopic), sound burst with amplitude variations (amplitopic),
evoked response type of stimuli using short sentences with or without rhyme, and
additional audio–speech combination assignments. Images will need to be obtained
in a relatively fast algorithm in the order of five images per second to be able to recognize significant differences in the cortical activity. A period of rest with no input
is required between each assignment for calibration purposes, while the data acquisition is maintained at the same rate.
The auditory region of the cortex is predominantly located in the frontal section
of the brain and in the temporal section in a lesser degree. The studies of the auditory