scholarly journals High-Resolution CMRO2 Mapping in Rat Cortex: A Multiparametric Approach to Calibration of BOLD Image Contrast at 7 Tesla

2000 ◽  
Vol 20 (5) ◽  
pp. 847-860 ◽  
Author(s):  
Ikuhiro Kida ◽  
Richard P. Kennan ◽  
Douglas L. Rothman ◽  
Kevin L. Behar ◽  
Fahmeed Hyder
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Spin Echo ◽  
7 Tesla ◽  
Relaxation Rates ◽  
Resonance Imaging ◽  
Gradient Echo ◽  
Transverse Relaxation ◽  
Physiologic Parameters ◽  
Spin Echo Sequences

The blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) method, which is sensitive to vascular paramagnetic deoxyhemoglobin, is dependent on regional values of cerebral metabolic rate of oxygen utilization (CMRO2), blood flow (CBF), and volume (CBV). Induced changes in deoxyhemoglobin function as an endogenous contrast agent, which in turn affects the transverse relaxation rates of tissue water that can be measured by gradient-echo and spin-echo sequences in BOLD fMRI. The purpose here was to define the quantitative relation between BOLD signal change and underlying physiologic parameters. To this end, magnetic resonance imaging and spectroscopy methods were used to measure CBF, CMRO2, CBV, and relaxation rates (with gradient-echo and spin-echo sequences) at 7 Tesla in rat sensorimotor cortex, where cerebral activity was altered pharmacologically within the autoregulatory range. The changes in tissue transverse relaxation rates were negatively and linearly correlated with changes in CBF, CMRO2, and CBV. The multiparametric measurements revealed that CBF and CMRO2 are the dominant physiologic parameters that modulate the BOLD fMRI signal, where the ratios of (ΔCMRO2/CMRO2)/(ΔCBF/CBF) and (ΔCBV/CBV)/(ΔCBF/CBF) were 0.86 ± 0.02 and 0.03 ± 0.02, respectively. The calibrated BOLD signals (spatial resolution of 48 μL) from gradient-echo and spin-echo sequences were used to predict changes in CMRO2 using measured changes in CBF, CBV, and transverse relaxation rates. The excellent agreement between measured and predicted values for changes in CMRO2 provides experimental support of the current theory of the BOLD phenomenon. In gradient-echo sequences, BOLD contrast is affected by reversible processes such as static inhomogeneities and slow diffusion, whereas in spin-echo sequences these effects are refocused and are mainly altered by extravascular spin diffusion. This study provides steps by which multiparametric MRI measurements can be used to obtain high-spatial resolution CMRO2 maps.

scholarly journals High isotropic resolution magnetic resonance imaging of the mandibular canal at 1.5 T: a comparison of gradient and spin echo sequences

2017 ◽  
Vol 46 (2) ◽  
pp. 20160268 ◽  
Author(s):  
Jakob Kreutner ◽  
Andreas Hopfgartner ◽  
Daniel Weber ◽  
Julian Boldt ◽  
Kurt Rottner ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Spin Echo ◽  
Mandibular Canal ◽  
Resonance Imaging ◽  
Isotropic Resolution ◽  
Spin Echo Sequences

Noninvasive measurement and imaging of liver iron concentrations using proton magnetic resonance

Blood ◽  
2005 ◽  
Vol 105 (2) ◽  
pp. 855-861 ◽  
Author(s):  
Timothy G. St. Pierre ◽  
Paul R. Clark ◽  
Wanida Chua-anusorn ◽  
Adam J. Fleming ◽  
Gary P. Jeffrey ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Needle Biopsy ◽  
Hereditary Hemochromatosis ◽  
Iron Concentration ◽  
Relaxation Rates ◽  
Resonance Imaging ◽  
Liver Iron ◽  
Transverse Relaxation

AbstractMeasurement of liver iron concentration (LIC) is necessary for a range of iron-loading disorders such as hereditary hemochromatosis, thalassemia, sickle cell disease, aplastic anemia, and myelodysplasia. Currently, chemical analysis of needle biopsy specimens is the most common accepted method of measurement. This study presents a readily available noninvasive method of measuring and imaging LICs in vivo using clinical 1.5-T magnetic resonance imaging units. Mean liver proton transverse relaxation rates (R2) were measured for 105 humans. A value for the LIC for each subject was obtained by chemical assay of a needle biopsy specimen. High degrees of sensitivity and specificity of R2 to biopsy LICs were found at the clinically significant LIC thresholds of 1.8, 3.2, 7.0, and 15.0 mg Fe/g dry tissue. A calibration curve relating liver R2 to LIC has been deduced from the data covering the range of LICs from 0.3 to 42.7 mg Fe/g dry tissue. Proton transverse relaxation rates in aqueous paramagnetic solutions were also measured on each magnetic resonance imaging unit to ensure instrument-independent results. Measurements of proton transverse relaxivity of aqueous MnCl2 phantoms on 13 different magnetic resonance imaging units using the method yielded a coefficient of variation of 2.1%.

COMPARISON OF SPIN ECHO, GRADIENT ECHO AND FAT SATURATION MAGNETIC RESONANCE IMAGING SEQUENCES FOR IMAGING THE CANINE ELBOW

1998 ◽  
Vol 39 (6) ◽  
pp. 518-523 ◽  
Author(s):  
Frederic R. Snaps ◽  
Jimmy H. Saunders ◽  
Richard D. Park ◽  
Benedicte Daenen ◽  
Marc H. Balligand ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Spin Echo ◽  
Resonance Imaging ◽  
Gradient Echo ◽  
Fat Saturation

scholarly journals Low-field magnetic resonance imaging of changes after femoral osteosynthesis failure: a case report

2017 ◽  
Vol 62 (No. 11) ◽  
pp. 625-630
Author(s):  
J. Glodek ◽  
Z. Adamiak ◽  
M. Mieszkowska ◽  
A. Przeworski
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Hip Joint ◽  
Spin Echo ◽  
Fracture Site ◽  
Resonance Imaging ◽  
Gradient Echo ◽  
Quadriceps Femoris Muscle ◽  
Low Field ◽  
Femoris Muscle

We describe here a case study of a 16-month-old female European shorthair cat examined about 6 months after the osteosynthesis of a femoral fracture. Clinical examination revealed a non-weightbearing left limb, pain upon manipulation of the hip joint, complete immobilisation of the stifle joint and muscle atrophy in the left thigh. Low-field magnetic resonance images were acquired in sagittal, transverse and dorsal planes with T1-weighted spin echo, T2-weighted fast spin echo, T1-weighted gradient echo, gradient echo short tau inversion recovery and T1-weighted XBone sequences. Total examination time was 59 min 20 s. The obtained images revealed the presence of osteophytes on the surface of the femoral head, subluxation of the hip joint, atrophy and fatty infiltration of the quadriceps femoris muscle. The symmetry and size of callus in the fracture site were also evaluated. Based on the results of the magnetic resonance imaging exam, the patient was diagnosed with hip osteoarthritis, atrophy and fatty degeneration of the quadriceps femoris muscle with homogeneous and symmetrical distribution of callus in the fracture site. The results of this study confirm the high diagnostic value of low-field magnetic resonance imaging in diagnostics of musculoskeletal injuries in cats.

Sign in / Sign up

Export Citation Format

Share Document