Evaluation of the susceptibility effect on the phase images of a simple gradient echo.

Yamada, Naoaki; Imakita, Satoshi; Sakuma, Toshiharu; Nishimura, Y; Yamada, Yukinori; Naito, Hiroyuki; Nishimura, T; Takamiya, Makoto

doi:10.1148/radiology.175.2.2326482

Cited by 32 publications

(14 citation statements)

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“…The screening constant uis of the molecules in interaction with its neighbors relates the local field with the macroscopic field. An approximated relation between these fields is given by (15) where T(r) is the temperature at position r inside the object. Hydrogen bonds distort the electronic configuration of the molecules (16) resulting in a less effective electronic screening.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Noninvasive MRI Thermometry with the Proton Resonance Frequency (PRF) Method: In Vivo Results in Human Muscle

Poorter

Wagter

Deene

et al. 1995

Magnetic Resonance in Med

530

425

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The noninvasive thermometry method is based on the temperature dependence of the proton resonance frequency (PRF). High-quality temperature images can be obtained from phase information of standard gradient-echo sequences with an accuracy of 0.2 degrees C in phantoms. This work was focused on the in vivo capabilities of this method. An experimental setup was designed that allows a qualitative in vivo verification. The lower-leg muscles of a volunteer were cooled and afterwards reheated with an external water bolus. The temperature of the bolus water varied between 17 degrees C and 37 degrees C. The in vivo temperature images can be used to extract the temperature in muscle tissue. The data in the fat tissue are difficult to interpret because of the predominance of susceptibility effects. The results confirm the method's potential for hyperthermia control.

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Section: Theoretical Considerationsmentioning

confidence: 99%

Noninvasive MRI Thermometry with the Proton Resonance Frequency (PRF) Method: In Vivo Results in Human Muscle

Poorter

Wagter

Deene

et al. 1995

Magnetic Resonance in Med

530

425

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“…Moreover, up to an order of magnitude phase gap change was measured between one PKAN patient and an age-matched healthy volunteer (see Table 3). Assuming that phase gap differences scale linearly with iron concentration (33) and taking into account published data for iron concentration in the GP of healthy volunteers (3), we estimate that up to 2 mg Fe/g ww accumulates in the GP of these patients. Our pilot study has certain limitations, and to prove that phase could indeed be a useful index of PKAN progression a number of necessary developmental steps are needed.…”

Section: Discussionmentioning

confidence: 99%

“…5. We used phase gap measurements corresponding to a minimum and maximum phase (defined as a phase gap) as a metrics that, we believe, reflects the level of iron concentration in GP (23,33). The results of these measurements averaged for left and right GP in PKAN patients and results of phase profile measurements in a healthy volunteer are summarized in Table 3.…”

Section: Phase Measurementsmentioning

confidence: 99%

Measurement of brain iron distribution in Hallevorden‐Spatz syndrome

Szumowski

Bas

Gaarder

et al. 2010

Magnetic Resonance Imaging

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Purpose: To investigate spatial distribution of iron accumulation in the globus pallidus (GP) in patients with Hallevorden-Spatz syndrome (HSS) using phase imaging. We compared sensitivity of a phase imaging technique to relaxation rate measurement methods (R1,R2,R2*) for iron quantification.Materials and Methods: R1, R2, and R2* were measured in GP structure of the brain of eight pantothenate kinaseassociated neurodegeneration (PKAN) patients and a healthy volunteer using a 3T magnetic resonance imaging (MRI) scanner. The phase of gradient-echo images was preprocessed to eliminate phase 2p wrapping and filtered to remove phase background variations. Phase gap across GP structure was used as a metric for iron effects quantification.Results: Among the relaxation rates the most sensitive to iron accumulation was the R2* rate. The R1 and R2 rates demonstrated only small variations in this group of subjects. Up to an order of magnitude phase gap changes were measured between one PKAN patient and an agematched healthy volunteer. Assuming that phase gap differences scale linearly with iron concentration we estimate that up to 2 mg Fe/g ww accumulates in GP of these patients.Conclusion: Our results demonstrate significantly higher sensitivity of the phase measurements for quantitative assessment of iron concentration compared to the relaxation rate measurements. Phase measurements could potentially be used for monitoring a progression and a response to therapy in PKAN.

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“…The distortion is proportional to the eld error and inversely proportional to the strengths of the applied gradients L udeke et al 1985; Ericsson et al 1988;Chang and Fitzpatrick 1992;Bakker et al 1992;O'Donnell and Edelstein 1985. In gradient e c ho imaging, local disturbances of B 0 cause, apart from the geometric e ects mentioned above, severe intensity losses due to uncompensated intravoxel phase dispersion, the so called T 2 -e ect Young et al 1989. In the past few years several studies have been undertaken to establish the experimental conditions which determine susceptibility artifacts in spin echo and gradient echo imaging and to provide a theoretical basis for the observed phenomena Young et al 1988;Haacke et al 1989;Yamada et al 1990;Cho and Ro 1992;Summers et al 1986. In previous work Bakker et al 1993 we proposed a method for simulation of susceptibility artifacts, which follows the actual sequence of events in an imaging experiment and deals with the e ects of error elds in the time domain k-space.…”

Section: Discussionmentioning

confidence: 99%

“…The presence of a patient in a MRI scanner leads to static magnetic eld inhomogeneity, since the magnetic eld is perturbed as the consequence of the di erence in susceptibility b e t ween the patient and the surrounding air. The severity of the eld perturbations outside the body depends on the susceptibility di erence with air, the shape of the body and the orientation of the body with respect to the applied magnetic eld Cox et al 1986;Young et al 1987;Yamada et al 1990;Yamada et al 1992;Mosher and Smith 1991;Bhagwandien et al 1994. For better understanding of the objectinduced image distortions we developed a numerical technique for calculating the magnetic eld for arbitrary magnetic susceptibility distributions.…”

Section: Introductionmentioning

confidence: 99%

Magnetic resonance imaging in radiotherapy treatment planning

Moerland¹

1997

Medical Physics

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The aim of this study is to investigate the capabilities of magnetic resonance imaging (MRI) in radiotherapy treatment planning (RTP) and to explore the MR image distortions and how these distortions can be reduced or, if necessary, corrected in order to integrate MRI into RTP in a reliable manner. Image distortions and the efficacy of correction methods were evaluated in phantom, volunteer, and patient studies. From the measurement, analysis, and correction of machine‐related geometric distortions in MRI, it was concluded that MR image corrections are necessary in applications which require mm accuracy and that correction methods, based on 3D maps of static field inhomogeneity and gradient nonlinearity, are feasible in clinical practice. From the measurement and numerical analysis of object‐related geometric distortions, it was concluded that these distortions can be reduced to the order of the pixel size by imaging at 0.5 T and using gradients on the order of 3 mT normalm−1. Furthermore, in a study on volunteers, fast MRI scan techniques were used to measure the respiration induced kidney movement and in a study on patients with prostate cancer, the value of MRI for the evaluation of brachytherapy was demonstrated. The MR image artifacts induced by the I‐125 seeds were used to evaluate the dose distributions and dose volume histograms of permanent prostate implants.

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Evaluation of the susceptibility effect on the phase images of a simple gradient echo.

Cited by 32 publications

References 0 publications

Noninvasive MRI Thermometry with the Proton Resonance Frequency (PRF) Method: In Vivo Results in Human Muscle

Noninvasive MRI Thermometry with the Proton Resonance Frequency (PRF) Method: In Vivo Results in Human Muscle

Measurement of brain iron distribution in Hallevorden‐Spatz syndrome

Magnetic resonance imaging in radiotherapy treatment planning

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