Gradient moment nulling techniques require the introduction of an additional gradient on each axis for each order of motion correction to be applied. The additional gradients introduce new constraints on the sequence design and increase the demands on the gradient system. The purpose of this paper is to demonstrate techniques for optimization of gradient echo gradient moment nulling sequences within the constraints of the gradient hardware. Flow compensated pulse sequences were designed and implemented on a clinical magnetic resonance imaging system. The design of the gradient moment nulling sequences requires the solution of a linear system of equations. A Mathematica package was developed that interactively solves the gradient moment nulling problem. The package allows the physicist to specify the desired order of motion compensation and the duration of the gradients in the sequence with different gradient envelopes. The gradient echo sequences with first, second, and third order motion compensation were implemented with minimum echo time. The sequences were optimized to take full advantage of the capabilities of the gradient hardware. The sequences were used to generate images of phantoms and human brains. The optimized sequences were found to have better motion compensation than comparable standard sequences.
Axis, Cervical Vertebra ; Brain* ; Compensation and Redress* ; Humans ; Magnetic Resonance Imaging

In this work practical considerations of a pulsed arterial spin labeling MRI are presented to reliable multi-slice perfusion measurements in the human brain. Three parameters were considered in this study. First, in order to improve slice profile and inversion efficiency of a labeling pulse a high power inversion pulse of adiabatic hyperbolic secant was designed. A 900o rotation of the flip angle was provided to make a good slice profile and excellent inversion efficiency. Second, to minimize contributions of a residual magnetization between interleaved scans of control and labeling we tested three different conditions which were applied 1) only saturation pulses, 2) only spoiler gradients, and 3) combinations of saturation pulses and spoiler gradients. Applications of both saturation pulses and spoiler gradients minimized the residual magnetization. Finally, to find a minimum gap between a tagged plane and an imaging plane we tested signal changes of the subtracted image between control and labeled images with varying the gap. The optimum gap was about 20 mm. In conclusion, in order to obtain high quality of perfusion images in human brain it is important to use optimum parameters. Before routinely using in clinical studies, we recommend to make optimizations of sequence parameters.
Brain* ; Humans* ; Magnetic Resonance Imaging* ; Perfusion*

PURPOSE: To evaluate the relationship between the speed of enhancement of hepatic hemangiomas on gadolinium-enhanced MRI and ADC values by using various parameters, including the D, f, D* and ADC(fit) on intravoxel incoherent motion (IVIM) MR Imaging. MATERIALS AND METHODS: The institutional review board approved this retrospective study. A total of 47 hepatic hemangiomas from 39 patients were included (20 men and 19 women). The hemangiomas were classified into three types according to the enhancement speed of the hepatic hemangiomas on gadolinium-enhanced dynamic T1-weighted images: rapid (Type A), intermediate (Type B), and slow (Type C) enhancement. The D, f, D* and ADC(fit) values were calculated using IVIM MR imaging. The diffusion/perfusion parameters and ADC values were compared among the three types of hemangiomas. RESULTS: Both the ADC(fit) and D values of type C were significantly lower than those of type A (P = 0.0022, P = 0.0085). However, for the f and D*, there were no significant differences among the three types. On DWI with all b values (50, 200, 500 and 800 sec/mm2), the ADC values of type C were significantly lower than those of the type A (P < 0.012). For b values with 800 sec/mm2, the ADC800 values of the type C hemangiomas were significantly lower than those of type B (P = 0.0021). We found a negative correlation between hepatic hemangioma enhancement type and ADC50 (rho= -0.357, P = 0.014), ADC200 (rho= -0.537, P = 0.0001), ADC500 (rho= -0.614, P = 0.0001), and ADC800(rho= -0.607, P = 0.0001). Therefore, four ADC values of ADC50, ADC200, ADC500, and ADC800 were decreased with decreasing enhancement speed. CONCLUSION: Hepatic hemangiomas had variable ADCs according to the type of enhancement, and the reduced ADCs in slowly enhancing hemangiomas may be related to the reduced pure molecular diffusion (D).
Diffusion ; Ethics Committees, Research ; Hemangioma* ; Humans ; Magnetic Resonance Imaging* ; Male ; Retrospective Studies

Spin echo gradient moment nulling pulse sequences were designed and implemented on a clinical magnetic resonance imaging system. A new technique was introduced for flow compensation that minimized echo time and effectively suppresses unwanted echoes on the slice selection gradient axis in spin echo sequences. A unified gradient shape was used in all orders of flow compensation up to the third order. A dual-purpose gradient was applied for flow compensation and to reduce unwanted artifacts. The sequences were used to generate images of phantoms and/or human brains. This technique was especially good at reducing eddy currents and artifacts related to imperfection of the refocusing pulse. The developed sequences were found to have shorter echo times and better flow compensation in through-plane flow than those of the previous models that were used by other investigators.
Artifacts ; Axis, Cervical Vertebra* ; Brain ; Compensation and Redress* ; Humans ; Magnetic Resonance Imaging ; Research Personnel

An echo planar imaging (EPI)-based spin-echo sequence is often used to obtain diffusion tensor imaging (DTI) data on most of the clinical MRI systems. However, this sequence is confounded with the susceptibility artifacts, especially on the temporal lobe in the human brain. Therefore, the objective of this study was to design a pulse sequence that relatively immunizes the susceptibility artifacts, but can map diffusion tensor components in a single-shot mode. A multi-slice multi-echo pulsed-gradient spin-echo (MePGSE) sequence with eight echoes wasdeveloped with selective refocusing pulses for all slices to map the full tensor. The first seven echoes in the train were diffusion-weighted allowing for the observation of diffusion in several different directions in a single experiment and the last echo was for crusher of the residual magnetization. All components of diffusion tensor were measured by a single shot experiment. The sequence was applied in diffusive phantoms. The preliminary experimental verification of the sequence was illustrated by measuring the apparent diffusion coefficient (ADC) for tap water and by measuring diffusion tensor components for watermelon. The ADC values in the series of the water phantom were reliable. The MePGSE sequence, therefore, may be useful in human brain studies.
Artifacts ; Brain ; Citrullus ; Diffusion Tensor Imaging* ; Diffusion* ; Echo-Planar Imaging ; Humans ; Magnetic Resonance Imaging* ; Temporal Lobe ; Water

Recently, functional MRI has been used to investigate the neurobiological mechanisms of acupuncture and the specificity of acupoint. The group data tend to be regarded as more important than the individual data in the most of previous studies. This study was designed to investigate the effect of the variability of individual data on the group results. A functional MRI (fMRI) of the whole brain was performed in fifteen healthy subjects during placebo and acupuncture stimulations at the ST36 acupoint. After remaining at rest for 30 seconds, the acupuncture was inserted and twisted at the rate of 2 Hz for 45 seconds and then the acupuncture was removed immediately. This process was repeated three times. Individual and group analyses were performed by voxel-based analyses using SPM2 software. Visual inspections of the activation and deactivation maps from individual sessions have shown the large variability across fifteen subjects. This means that the group data reflected the brain activation responses of only a few subjects. We suggest that the individual data should be presented to demonstrate the effect of acupuncture.
Acupuncture ; Acupuncture Points ; Brain ; Magnetic Resonance Imaging ; Sensitivity and Specificity

To develop an advanced non-linear curve fitting (NLCF) algorithm for performing dynamic susceptibility contrast study of the brain. The first pass effects give rise to spuriously high estimates of Ktrans for the voxels that represent the large vascular components. An explicit threshold value was used to reject voxels. The blood perfusion and volume estimation were accurately evaluated in the T2*-weighted dynamic contrast enhanced (DCE)-MR images. From each of the recalculated parameters, a perfusion weighted image was outlined by using the modified non-linear curve fitting algorithm. The present study demonstrated an improvement of an estimation of the kinetic parameters from the DCE T2*-weighted magnetic resonance imaging data with using contrast agents.
Brain* ; Contrast Media ; Gadolinium DTPA* ; Humans* ; Magnetic Resonance Imaging ; Perfusion

PURPOSE: To evaluate the correlation of lesion-to-normal ratio (LNR) of signal intensity from double inversion recovery MR imaging and total choline-containing compound (tCho) resonance from single voxel MR spectroscopy in breast cancers. MATERIALS AND METHODS: Between August 2008 and December 2009, 28 patients who were diagnosed as breast cancer and had undergone both double inversion recovery (DIR) MR imaging and MR spectroscopy (MRS) were included in this study. The signal intensities of the lesion (L) and ipsilateral normal breast tissue (N) were measured in region of interest of each breast cancer in DIR and contrast enhance MR image (CE-T1WI) to calculate the LNR value for each technique. MRS was performed using single-voxel MR spectroscopy. The height, width and area of tCho resonance were compared with each LNR of DIR and CE-T1WI. We used Pearson's correlation coefficient (r) for correlation analysis and the significance level was p=0.05. RESULTS: There was no statistically significant correlation between LNR of CE-T1WI and height (r=-0.322, p=0.094), width (r=-0.233, p=0.232) and area (r=-0.309, p=0.109) of MRS tCho. There was no statistically significant correlation between LNR of DIR and height (r=0.067, p=0.735), width (r=-0.287, p=0.139) and area (r=0.012, p=0.953) of MRS tCho, either. The Pearson's correlation coefficient was 0.186 between LNRs of CE-T1WI and DIR (p=0.344). CONCLUSION: There was no statistically significant correlation between LNR of DIR and relative amount of tCho resonance of MRS.
Breast Neoplasms ; Breast* ; Humans ; Magnetic Resonance Imaging* ; Magnetic Resonance Spectroscopy*

OBJECTIVE: There is a rich literature confirming the default mode network found compatible with task-induced deactivation regions in normal subjects, but few investigations of alterations of the motor deactivation in patients with intracranial lesions. Therefore, we hypothesized that an intracranial lesion results in abnormal changes in a task-induced deactivation region compared with default mode network, and these changes are associated with specific attributes of allocated regions. METHODS: Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) during a motor task were obtained from 27 intracranial lesion patients (mean age, 57.3 years; range 15-78 years) who had various kinds of brain tumors. The BOLD fMRI data for each patient were evaluated to obtain activation or deactivation regions. The distinctive deactivation regions from intracranial lesion patients were evaluated by comparing to the literature reports. RESULTS: There were additive deactivated regions according to intracranial lesions: fusiform gyrus in cavernous hemangioma; lateral occipital gyrus in meningioma; crus cerebri in hemangiopericytoma; globus pallidus, lateral occipital gyrus, caudate nucleus, fusiform gyrus, lingual gyrus, claustrum, substantia nigra, subthalamic nucleus in GBM; fusiform gyrus in metastatic brain tumors. CONCLUSION: There is increasing interest in human brain function using fMRI. The authors report the brain function migrations and changes that occur in patients with intracranial lesions.
Basal Ganglia ; Brain ; Brain Neoplasms ; Caudate Nucleus ; Globus Pallidus ; Hemangioma, Cavernous ; Hemangiopericytoma ; Humans ; Magnetic Resonance Imaging ; Meningioma ; Oxygen ; Substantia Nigra ; Subthalamic Nucleus

Perfusion is a fundamental biological function that refers to the delivery of oxygen and nutrients to tissue by means of blood flow. Perfusion MRI is sensitive to microvasculature and has been applied in a wide variety of clinical applications, including the classification of tumors, identification of stroke regions, and characterization of other diseases. Perfusion MRI techniques are classified with or without using an exogenous contrast agent. Bolus methods, with injections of a contrast agent, provide better sensitivity with higher spatial resolution, and are therefore more widely used in clinical applications. However, arterial spin-labeling methods provide a unique opportunity to measure cerebral blood flow without requiring an exogenous contrast agent and have better accuracy for quantification. Importantly, MRI-based perfusion measurements are minimally invasive overall, and do not use any radiation and radioisotopes. In this review, we describe the principles and techniques of perfusion MRI. This review summarizes comprehensive updated knowledge on the physical principles and techniques of perfusion MRI.
Arteries/chemistry ; Brain Neoplasms/radiography ; Contrast Media/diagnostic use ; Humans ; Magnetic Resonance Imaging/standards/*trends ; Spin Labels ; Stroke/radiography