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5. Leg muscle volume during 30-day 6-degree head-down bed rest with isotonic and isokinetic exercise training

Author

Greenleaf, J. E, Lee, P. L, Ellis, S, Selzer, R. H, and Ortendahl, D. A

Subjects
Life Sciences (General)
Abstract

Magnetic resonance imaging (MRI) was used to compare the effect of two modes of lower-extremity exercise training on the mass (volume) of posterior leg group (PLG) muscles (soleus, flexor hallucis longus, tibialis posterior, lateral and medial gastrocnemius, and flexor digitorum longus) on 19 men (ages 32-42 years) subjected to intense dynamic-isotonic (ITE, cycle ergometer, number of subjects (N) = 7), isokinetic (IKE, torque egrometer, N = 7), and no exercise (NOE, N = 5) training for 60 min/day during head-down bed rest (HDBR). Total volume of the PLG muscles decreased (p less than 0.05) similarly: ITE = 4.3 +/- SE 1.6%, IKE = 7.7 +/- 1.6%, and NOE = 6.3 +/- 0.8%; combined volume (N = 19) loss was 6.1 +/- 0.9%. Ranges of volume changes were 2.6% to -9.0% (ITE), -2.1% to -14.9% (IKE), and -3.4% to -8/1% (NOE). Correlation coefficients (r) of muscle volume versus thickness measured with ultrasonography were: ITE r + 0.79 (p less than 0.05), IKE r = 0.27 (not significant (NS)), and NOE r = 0.63 (NS). Leg-muscle volume and thickness were highly correlated (r = 0.79) when plasma volume was maintained during HDBR with ITE. Thus, neither intensive lower extremity ITE nor IKE training influence the normal non-exercised posterior leg muscle atrophy during HDBR. The relationship of muscle volume and thickness may depend on the mode of exercise training associated with the maintenance of plasma volume.

Published
1994

14. Cephalometrically Oriented Digital Tomosynthesis of the TMJ Using a Personal Computer

Author

Kircos, L T, Ortendahl, D A, and Hagen, G T

Abstract

Digital longitudinal tomosynthesis (DLT) of the temporomandibular joint (TMJ) was performed using a modified GE Ordograph II Wehmer cephalometer tomographic imaging system and an IBM PC-AT computer. Thirteen radiographs were obtained by displacing the x-ray source over a 48° arc with respect to the long axis of the TMJ condyle. The radiographs were digitized into a 512 × 512 (8 bits deep) matrix, oriented, shifted and added to obtain tomograms at any desired fulcrum. DLT images of a 3M head phantom were of similar quality to those made by analog longitudinal tomography. The digital format of the DLT tomograms enabled the use of digital image processing techniques, including high-pass filtering, smoothing and blur subtraction. Image processing significantly increased the diagnostic quality of DLT tomograms.

Published
1988
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35. Multiple spin-echo magnetic resonance imaging.

Author

Feinberg, D A, primary, Mills, C M, additional, Posin, J P, additional, Ortendahl, D A, additional, Hylton, N M, additional, Crooks, L E, additional, Watts, J C, additional, Kaufman, L, additional, Arakawa, M, additional, and Hoenninger, J C, additional

Published
1985
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36. Partial flip angle MR imaging.

Author

Mills, T C, primary, Ortendahl, D A, additional, Hylton, N M, additional, Crooks, L E, additional, Carlson, J W, additional, and Kaufman, L, additional

Published
1987
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47. Analysis of hybrid imaging techniques.

Author

Ortendahl DA, Kaufman L, and Kramer DM

Subjects
Brain Neoplasms diagnosis, Fourier Analysis, Humans, Image Processing, Computer-Assisted, Models, Structural, Oligodendroglioma diagnosis, Time Factors, Magnetic Resonance Imaging methods
Abstract

Hybrid imaging techniques have been proposed as a means of decreasing imaging time without the cost and technical constraints of echo planar imaging. With this technique phase encoding measurements acquired at different echo times in more than one multiecho experiment are used to form a single image. This study analyzes the trade-offs which occur in the selection of this technique over more conventional imaging in terms of signal/noise, contrast, resolution, imaging time, and efficiency. Hybrid imaging is shown to be advantageous when raw speed is essential such as in abdominal or pediatric imaging. When coverage rather than time becomes the important factor, hybrid imaging does not offer a significant advantage over conventional methods. T2 decay will also serve as a roll-off filter which will reduce the spatial resolution, but not the noise, for short TE hybrid imaging.

Published
1992
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48. Fluoroscopic MR imaging at 0.064 Tesla.

Author

Kramer DM, Hawryszko C, Ortendahl DA, and Minaise M

Abstract

The authors developed a system for ultrafast magnetic resonance imaging (MRI) protocols at low field. The system design permits the acquisition of the raw data in the background while the reconstruction and display steps repeat as fast as they can in the foreground. The performance speeds depends partly on the desired use. By collecting raw data at a rate of 20 ms per echo with an echo delay of 9 ms, a complete data cycle for a 128x64 image takes 1.28 s. However, once half of that data is incorporated into the reconstruction, the image appears complete. Using this set of parameters the authors were able to get the rate of the recon/display loop to paint about two times per completed raw data cycle, showing an entirely new image at least once per second with an apparent frame rate of two per second. Interleaving of two or three orthogonal scans reduces the speed of update but provides better information. The authors discuss the system design for rapid scan/recon/display and demonstrate the image quality available at low field strength with scan times below one second.

Published
1991
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49. NMR in experimental cerebral edema: value of T1 and T2 calculations.

Author

Brant-Zawadzki M, Bartkowski HM, Ortendahl DA, Pitts LH, Hylton NM, Nishimura MC, and Crooks LE

Subjects
Animals, Brain Edema metabolism, Dogs, Time Factors, Tomography, Brain Edema diagnosis, Magnetic Resonance Spectroscopy
Abstract

In an experimental investigation, the efficacy of nuclear magnetic resonance (NMR) relaxation times in measuring brain water was studied. Cerebral edema was induced in four dogs with a freeze lesion, which was produced by contact with a steel cylinder cooled in liquid nitrogen and placed on the exposed dural surface of the brain. NMR proton imaging was performed 2, 3, 6, or 24 hr after production of the lesion, at a field strength of 0.35 T, using multiparametric spin-echo (SE) technique. The animals were sacrificed immediately after imaging, and brain samples were analyzed for water content (wet-to-dry, microgravimetry). Correlation between water content, NMR imaging, and resulting T1, T2 relaxation times and mobile proton density values calculated with SE technique was performed. Brain sample analysis showed elevation of water content in the white matter subjacent to the lesion in all four dogs, rising at least 15% in each of the animals. NMR imaging detected the freeze lesion and subjacent vasogenic edema of the white matter in all animals. The 2 sec pulse interval SE technique was most sensitive in the detection of the abnormality, and provided optimal differentiation of gray and white matter. The second echo sampling (56 msec) was most sensitive to the detection of edema. The T1 and T2 relaxation values, as well as the mobile proton density values, were elevated in the normal gray matter and in the abnormal white matter when compared with normal white matter in any given animal.(ABSTRACT TRUNCATED AT 250 WORDS)

Published
1984

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