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Titolo:
Pixel T2 distribution in functional magnetic resonance images of muscle
Autore:
Prior, BM; Foley, JM; Jayaraman, RC; Meyer, RA;
Indirizzi:
Michigan State Univ, Dept Physiol, E Lansing, MI 48824 USA Michigan State Univ E Lansing MI USA 48824 ysiol, E Lansing, MI 48824 USA Michigan State Univ, Dept Kinesiol, E Lansing, MI 48824 USA Michigan StateUniv E Lansing MI USA 48824 esiol, E Lansing, MI 48824 USA Michigan State Univ, Dept Radiol, E Lansing, MI 48824 USA Michigan State Univ E Lansing MI USA 48824 adiol, E Lansing, MI 48824 USA
Titolo Testata:
JOURNAL OF APPLIED PHYSIOLOGY
fascicolo: 6, volume: 87, anno: 1999,
pagine: 2107 - 2114
SICI:
8750-7587(199912)87:6<2107:PTDIFM>2.0.ZU;2-#
Fonte:
ISI
Lingua:
ENG
Soggetto:
SKELETAL-MUSCLE; EXERCISE INTENSITY; PROTON T2; RECRUITMENT; RELAXATION; MRI; PERFUSION; WORK;
Keywords:
skeletal muscle; magnetic resonance imaging; recruitment; motor units; spin-spin relaxation; muscle denervation;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
26
Recensione:
Indirizzi per estratti:
Indirizzo: Meyer, RA Michigan State Univ, Dept Physiol, E Lansing, MI 48824 USA Michigan State Univ E Lansing MI USA 48824 ansing, MI 48824 USA
Citazione:
B.M. Prior et al., "Pixel T2 distribution in functional magnetic resonance images of muscle", J APP PHYSL, 87(6), 1999, pp. 2107-2114

Abstract

Increases in skeletal muscle H-1-NMR transverse relaxation time (T2) observed by magnetic resonance imaging have been used to map whole muscle activity during exercise. Some studies further suggest that intramuscular variations in T2 after exercise can be used to map activity on a pixel-by-pixel basis by defining an active T2 threshold and counting pixels that exceed the threshold as "active muscle. " This implies that motor units are nonrandomlydistributed across the muscle and, therefore, that the distribution of pixel T2 values ought to be substantially broader after moderate exercise thanat rest or after more intense exercise, since moderate-intensity exercise should recruit some motor units, and hence some pixels, but not others. This study examined the distribution of pixel T2 values in three muscles (quadriceps, anterior tibialis, and biceps/brachialis) of healthy subjects (5 men and 2 women, 18-46 yr old) at rest, after exercise to fatigue (50% 1 repetition maximum at 20/min to failure = Max), and at 1/2 Max (25% 1 repetition maximum, same number of repetitions as Max). Although for each muscle there was a linear relationship between exercise intensity and mean pixel T2, there was no significant difference in the variance of pixel T2 between 1/2Max and Max exercise. There was a modest (10-43%) increase in variance of pixel T2 after both exercises compared with rest, but this was consistent with a Monte Carlo simulation of muscle activity that assumed a random distribution of motor unit territories across the muscle and a random distribution of muscle cells within each motor unit's territory. In addition, 40% of the pixel-to-pixel muscle T2 variations were shown to be due to imaging noise. The results indicate that magnetic resonance imaging T2 cannot reliablymap active muscle on a pixel-by-pixel basis in normal subjects.

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Documento generato il 03/12/20 alle ore 12:36:08