Functional MRI of Skeletal Muscle Before and After Exercise
Functional MRI (fMRI) has been applied to the study of brain function with relatively rapid success. The basis for fMRI is believed to be the paramagnetic nature of deoxy-hemoglobin and it’s effect on the magnetic susceptibility of the local tissue, i.e the Blood Oxygenation Level Dependent (BOLD) e...
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| Format: | Dissertation |
| Language: | English |
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ProQuest Dissertations & Theses
01-01-1997
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| Online Access: | Get full text |
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| Summary: | Functional MRI (fMRI) has been applied to the study of brain function with relatively rapid success. The basis for fMRI is believed to be the paramagnetic nature of deoxy-hemoglobin and it’s effect on the magnetic susceptibility of the local tissue, i.e the Blood Oxygenation Level Dependent (BOLD) effect. This experiment is intended to validate the premise of the BOLD theory and determine the applicability of fMRI to the study of skeletal muscle function and disease. Ten normal human volunteers performed a forced elbow flexion (“curl”) to fatigue. An oblique axial scan of the biceps brachii muscle was performed before and after exercise (“pre-exercise relaxed” and “post-exercise relaxed”), as well as during a sustained isometric contraction (“post-exercise flexed”). T2 measurements were obtained using a spin echo sequence (TR/TE = 2000/20,40,60,80). T2* measurements were obtained using a spoiled gradient echo sequence (TR/TE=150/7, 11.5, 16, 20.5). Mean pixel values from 4 ROIs in the muscle were fitted to a monoexponential curve using a least squares algorithm. The mean T2 increased from 24.8 ms to 29.5 ms (+19%) from pre-exercise relaxed to post-exercise relaxed. This change is consistent with known changes in water content after exercise. The mean T2* increased from 24.9 ms to 30.1 ms (+21%) from pre-exercise relaxed to post-exercise relaxed. No significant difference was detected in the T2 or T2* times between the post-exercise flexed and postexercise relaxed states. The averaged data does not show a significant difference between the change in T2 and the change in T2* , implying that the BOLD effect was not detected. However, individual results showed significant differences between the change in T2 and the change in T2* that ranged from -12% to +30%. The fact that some differences were positive and some were negative caused the averaged difference to be near zero. The BOLD theory could account for these differences by correlating the positive and negative values to the conditions of oxygen-rich and oxygen-deficient muscle tissues, respectively. Further research using echo-planer imaging to reduce motion-related noise is recommended, along with a more structured exercise protocol. |
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| ISBN: | 9798380409193 |