Artifacts in functional magnetic resonance imaging from gaseous oxygen

Bates, Sandra R.; Yetkin, Z.; Jeśmanowicz, A; Hyde, James S.; Bandettini, Peter A.; Estkowski, Lloyd; Haughton, Victor M.

doi:10.1002/jmri.1880050413

Cited by 19 publications

(13 citation statements)

References 4 publications

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“…A transient decrease in image intensity over the whole tumour was consistently observed in all RIF-1 tumours (8% to 27%) and three out of four HT29 xenografts (6% to 15%) upon switching the gas supply from air to carbogen, with a subsequent recovery back to baseline image intensity levels within 10 min, even though the animal continued to breathe carbogen. Leakage of paramagnetic oxygen into the magnet bore would change the magnetic susceptibility around the coil (Bates et al, 1995) and produce a small Bo shift around the tumour. To minimize this effect (which could produce spurious image intensity changes), a scavenger was used routinely around the nose-piece that administered the gases.…”

Section: Methodsmentioning

confidence: 99%

The response to carbogen breathing in experimental tumour models monitored by gradient-recalled echo magnetic resonance imaging

Robinson

Rodrigues²,

Ojugo³

et al. 1997

Br J Cancer

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Summary Gradient-recalled echo magnetic resonance imaging (GRE MRI), which gives information on blood flow and oxygenation changes (Robinson SP, Howe FA, Griffiths JR 1995, Int J Radiat Oncol Biol Phys 33: 855), was used to observe the responses of six rodent tumour models to carbogen breathing. In one transplanted rat tumour, the Morris hepatoma 961 8a, and a chemically induced rat tumour, the MNUinduced mammary adenocarcinoma, there were marked image intensity increases, similar to those previously observed in the rat GH3 prolactinoma. In contrast, the rat Walker carcinosarcoma showed no response. In two mouse tumours, the RIF-1 fibrosarcoma and the human xenograft HT29, carbogen breathing induced a transient fall in signal intensity that reversed spontaneously within a few minutes. The rat GH3 prolactinoma was xenografted into nude mice, and an increase in image intensity was found in response to carbogen, suggesting that any effects that carbogen may have had on the host were not significant determinants of the tumour response. The increases in GRE image intensity of the MNU, H9618a and GH3 tumours during carbogen breathing are consistent with increases in tumour oxygenation and blood flow, whereas the responses of the RIF-1 and HT29 tumours may be the result of a transient steal effect followed by homeostatic correction.

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Section: Methodsmentioning

confidence: 99%

The response to carbogen breathing in experimental tumour models monitored by gradient-recalled echo magnetic resonance imaging

Robinson

Rodrigues²,

Ojugo³

et al. 1997

Br J Cancer

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“…This result would imply that, at higher field strengths, similar experimental conditions would not necessarily produce the expected gains in contrast to noise. A second major source of noise is non‐BOLD physiological noise, arising mainly from cardiac (66) and respiratory processes (67–69). These may impact on the time‐course of the data by either causing pulsational motion of the brain, as is the case for cardiac motion, or by modulating the B 0 field in the brain from changes in the susceptibility of gases in the lungs.…”

Section: Activation Studiesmentioning

confidence: 99%

High field human imaging

Norris¹

2003

Magnetic Resonance Imaging

164

106

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This review article examines the state of knowledge regarding human imaging using MRI at high main magnetic field strengths. The article starts with a summary of the technical issues associated with magnetic field strengths in the range of 3-8 T, including magnet characteristics and the properties of radiofrequency magnetic fields, with special reference to sensitivity, power deposition, and homogeneity. The published data on tissue-water relaxation times in the brain is tabulated and the implications for contrast and pulse sequence implementation is elucidated. The behavior of the major fast imaging sequences, fast low angle shot (FLASH), rapid acquisition with relaxation enhancement (RARE), and echo planar imaging (EPI), is examined in this context. A number of anatomical images from 3 T systems are presented as examples. Particular attention is given to various forms of vascular imaging, namely, time of flight angiography, venography, and arterial spin labeling. The most complex changes in contrast with main magnetic field strength are in activation studies utilizing the blood oxygen level dependent mechanism, which are examined in detail. Improvements in spatial specificity are emphasized, particularly in conjunction with spin-echo imaging. The article concludes with a discussion of the current status and the potential impact of technical developments such as parallel imaging. THE MAIN MAGNETIC FIELD STRENGTH of an MRI system is not changed after installation. The choice of main magnetic field strength (B 0 ) is, therefore, one of the most fundamental faced by those intending to use and purchase MRI equipment. In the early days of MRI, it was argued that radio frequency (RF) penetration would determine an upper limit for the main magnetic field strength (1,2). Since these fears were subsequently dispelled, the discussion moved on to a consideration of sensitivity and contrast (3). As the breadth of MRI applications has increased, and our understanding of the corresponding contrast mechanisms has improved, it has become increasingly clear that any ideal field strength is dependent upon the application being considered. Given the recent introduction of routine wholebody imaging at 3 T and the advent of experimental systems of 7 T and higher, it is timely to review the experience obtained with these systems and to examine how contrast and sensitivity for various imaging applications vary with main magnetic field strength. This review begins with a summary of the technical issues associated with high field imaging and then moves on to examine the characteristics of anatomical imaging, the imaging of blood and blood flow, and finally, activation studies. The article concludes with a discussion that summarizes our current knowledge, examines potential technological developments, and assesses potential future applications. Examples are drawn from main magnetic field strengths over the whole range of current application, i.e., 3-8 T. Experience obtained at 1.5 T is taken as a reference point for comparison. Where pe...

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“…Air or carbogen was delivered through a nose cone to the animal. In the NMR study, breathing gases were scavenged from the magnet, since oxygen levels could influence the GE scans due to altered susceptibility (31). EPR and NMR were undertaken in parallel, in different groups of animals.…”

Section: Protocolmentioning

confidence: 99%

Changes in oxygenation of intracranial tumors with carbogen: A BOLD MRI and EPR oximetry study

Dunn

O’Hara

Wadghiri

et al. 2002

Magnetic Resonance Imaging

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Purpose: To examine, using blood oxygen level dependent (BOLD) MRI and EPR oximetry, the changes in oxygenation of intracranial tumors induced by carbogen breathing. Materials and Methods:The 9L and CNS-1 intracranial rat tumor models were imaged at 7T, before and during carbogen breathing, using a multi-echo gradient-echo (GE) sequence to map R 2 *. On a different group of 9L tumors, tissue pO 2 was measured using EPR oximetry with lithium phthalocyanine as the oxygen-sensitive material. Results:The average decline in R 2 * with carbogen breathing was 13 Ϯ 1 s -1 in the CNS-1 tumors and 29 Ϯ 4 s -1 in the 9L tumor. The SI vs. TE decay curves indicate the presence of multiple components in the tumor. Tissue pO 2 in the two 9L tumors measured was 8.6 Ϯ 0.5 and 3.6 Ϯ 0.6 mmHg during air breathing, and rose to 20 Ϯ 7 and 16 Ϯ 4 mmHg (mean Ϯ SE) with carbogen breathing. Significant changes were observed by 10 minutes, but changes in pO 2 and R 2 * continued in some subjects over the entire 40 minutes. Conclusion:EPR results indicate that glial sarcomas may be radiobiologically hypoxic. Both EPR and BOLD data indicate that carbogen breathing increases brain tumor oxygenation. These data support the use of BOLD imaging to monitor changes in oxygenation in brain tumors.

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Artifacts in functional magnetic resonance imaging from gaseous oxygen

Cited by 19 publications

References 4 publications

The response to carbogen breathing in experimental tumour models monitored by gradient-recalled echo magnetic resonance imaging

The response to carbogen breathing in experimental tumour models monitored by gradient-recalled echo magnetic resonance imaging

High field human imaging

Changes in oxygenation of intracranial tumors with carbogen: A BOLD MRI and EPR oximetry study

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