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To: JDN who wrote (106679)	3/30/2005 7:17:26 AM
From: unclewest	Respond to of 793622

Here is a nearly comprehensible version of what the fMRI can do. Introduction to Functional MRI The physiology of neuronal activity involves many complex processes. It has been established, as long ago as 1890 [11], that physiological functions in the brain respond regionally to brain activity. Magnetic resonance has the capability to measure parameters related to several of these physiological functions, including changes in phosphorus metabolism and metabolic byproducts, blood flow, blood volume, and blood oxygenation. The most common technique uses blood oxygen level dependent (BOLD) contrast [1-4]. This technique is based on the magnetic susceptibility of hemoglobin (Hb). Deoxygenated Hb is paramagnetic, while fully oxygenated Hb is diamagnetic. The presence of the paramagnetic deoxy-Hb distorts the static magnetic field. Spins in this non-uniform magnetic field now precess at different frequencies causing more rapid phase dispersal and decay of the NMR signal. Therefore, changes in blood oxygenation can cause changes in the MR decay parameter, T 2 , leading to changes in image intensity in T 2 -weighted images. Table 1, below summarizes the changes in physiology and MR parameters that enable MRI to detect signal changes based on blood oxygenation. functionalmri.org

To: JDN who wrote (106679)	3/30/2005 7:27:34 AM
From: unclewest	Read Replies (1) \| Respond to of 793622

Scroll down to find a link to a site that explains how to lie with an fMRI and a PET scan. "How to Lie with fMRI Statistics" functionalmri.org

To: JDN who wrote (106679)	3/30/2005 7:38:31 AM
From: unclewest	Respond to of 793622

perhaps he mentioned a PET scan?? From Columbia University Medical Center: "The main advantages to fMRI as a technique to image brain activity related to a specific task or sensory process include 1) the signal does not require injections of radioactive isotopes, 2) the total scan time required can be very short, i.e., on the order of 1.5 to 2.0 min per run (depending on the paradigm), and 3) the in-plane resolution of the functional image is generally about 1.5 x 1.5 mm although resolutions less than 1 mm are possible. To put these advantages in perspective, functional images obtained by the earlier method of positron emission tomography, PET, require injections of radioactive isotopes, multiple acquisitions, and, therefore, extended imaging times. Further, the expected resolution of PET images is much larger than the usual fMRI pixel size. Additionally, PET usually requires that multiple individual brain images are combined in order to obtain a reliable signal. Consequently, information on a single patient is compromised and limited to a finite number of imaging sessions. Although these limitations may serve many neuroscience applications, they are not optimally suitable to assist in a neurosurgical or treatment plan for a specific individual." Scroll down and click on...About functional MRI: Columbia University functionalmri.org