Jae-Yong Han

Direct visualization of deep brain stimulation targets in Parkinson disease with the use of 7-tesla magnetic resonance imaging

OBJECT A challenge associated with deep brain stimulation (DBS) in treating advanced Parkinson disease (PD) is the direct visualization of brain nuclei, which often involves indirect approximations of stereotactic targets. In the present study, the authors compared T2*-weighted images obtained using 7-T MR imaging with those obtained using 1.5- and 3-T MR imaging to ascertain whether 7-T imaging enables better visualization of targets for DBS in PD. METHODS The authors compared 1.5-, 3-, and 7-T MR images obtained in 11 healthy volunteers and 1 patient with PD. RESULTS With 7-T imaging, distinct images of the brain were obtained, including the subthalamic nucleus (STN) and internal globus pallidus (GPi). Compared with the 1.5- and 3-T MR images of the STN and GPi, the 7-T MR images showed marked improvements in spatial resolution, tissue contrast, and signal-to-noise ratio. CONCLUSIONS Data in this study reveal the superiority of 7-T MR imaging for visualizing structures targeted for DBS in the management of PD. This finding suggests that by enabling the direct visualization of neural structures of interest, 7-T MR imaging could be a valuable aid in neurosurgical procedures.

Observation of the Lenticulostriate Arteries in the Human Brain In Vivo Using 7.0T MR Angiography

Background and Purpose— We sought to examine the feasibility of observing the lenticulostriate arteries (LSAs) noninvasively by ultrahigh-field MRI with 7.0T. Methods— We used 3-dimensional time-of-flight MR angiography with a radiofrequency coil optimized for 7.0T MRI. We examined the LSAs of 6 healthy subjects and compared 7.0T MR angiography images with 1.5T ones to examine the potentials of ultrahigh-field MRI for angiography. Results— The results show clear details of LSAs and their distribution in the normal healthy subjects with large variations in the shapes, the number of branches and the sites of origin. We also observed substantial differences between the left and right sides within each subject. Although we studied only 6 subjects, we found no age- or gender-related differences in the LSAs. Conclusions— The visualization of microvasculature of the brain, such as LSAs, using 7.0T MR angiography, is possible in in vivo human studies noninvasively. We, therefore, believe that it could play a major role in the study of small vascular abnormalities, such as the early stages of cerebral strokes.

Imaging and analysis of lenticulostriate arteries using 7.0-Tesla magnetic resonance angiography

The purpose of this study was to analyze human lenticulostriate arteries (LSAs) obtained non‐invasively by 7.0‐T MRI. A three‐dimensional time‐of‐flight (3D TOF) magnetic resonance angiography (MRA) technique was used with an investigational 7.0‐T MRI scanner with a radio‐frequency coil that was optimized and designed for angiographic purposes. We obtained images from 16 healthy volunteers (8 males and 8 females, mean age 21 ± 2.7 years). For direct comparison of LSA images with digital subtraction angiography (DSA), we also obtained 7.0‐T MRA and DSA images from one patient, a 27‐year‐old woman with a posterior fossa arteriovenous malformation (AVM). We then analyzed the characteristics of LSAs using a custom data analysis method with MatLab for quantitative analysis. Analysis of LSA images included shape and number of branches and origins, findings that are essential and useful for quantification of LSA abnormalities in both healthy controls and patients. Ultra–high‐field MRA provided clear anatomic delineation of the LSAs, thereby suggesting that 7.0‐T MRA may be a promising technique for microvascular imaging of the LSAs. Magn Reson Med 61:136–144, 2009.

A fusion PET-MRI system with a high-resolution research tomograph-PET and ultra-high field 7.0 T-MRI for the molecular-genetic imaging of the brain.

We have developed a positron emission tomography (PET) and magnetic resonance imaging (MRI) fusion system for the molecular‐genetic imaging (MGI) of the in vivo human brain using two high‐end imaging devices: the HRRT‐PET, a high‐resolution research tomograph dedicated to brain imaging on the molecular level, and the 7.0 T‐MRI, an ultra‐high field version used for morphological imaging. HRRT‐PET delivers high‐resolution molecular imaging with a resolution down to 2.5 mm full width at half maximum (FWHM), which allows us to observe the brains molecular changes using the specific reporter genes and probes. On the other front, the 7.0 T‐MRI, with submillimeter resolution images of the cortical areas down to 250 μm, allows us to visualize the fine details of the brainstem areas as well as the many cortical and subcortical areas. The new PET–MRI fusion imaging system will provide many answers to the questions on neurological diseases as well as cognitive neurosciences. Some examples of the answers are the quantitative visualization of neuronal functions by clear molecular and genetic bases, as well as diagnoses of many neurological diseases such as Parkinsons and Alzheimers. The salient point of molecular‐genetic imaging and diagnosis is the fact that they precede the morphological manifestations, and hence, the early and specific diagnosis of certain diseases, such as cancers.

Quantitative analysis of the hippocampus using images obtained from 7.0 T MRI

In-vivo volumetric measurements of hippocampus have proven to be highly informative for studying various neurological diseases such as Alzheimers disease. The usefulness of volumetric imaging, however, has been limited due to the poor image resolutions obtained by currently available MRI images. In this study, a new result of volumetric image measurement of the hippocampus using 7.0 T MRI images of high contrast and resolution is described. To verify the usefulness of the proposed method, its reliability and sensitivity were examined and compared with existing imaging techniques such as 1.5 T or 3.0 T MRI imaging. The results of our study with 7.0 T MRI clearly demonstrated superior boundary detection for the hippocampal head, body, and tail compared with low field MRIs. In conclusion, robust and reproducible volumetric measurements as well as 3D images of clear contrast obtained with 7.0 T suggest the usefulness of high field MR imaging and its eventual use for the accurate diagnosis of hippocampal diseases and related research.

Sectioned Images of the Cadaver Head Including the Brain and Correspondences With Ultrahigh Field 7.0 T MRIs

Unlike computed tomographic images and magnetic resonance images (MRIs), sectioned images of the human body with real color and high resolution have certain advantages in learning and teaching anatomy. Comparisons between sectioned images of the brain and MRIs are useful in many ways. Therefore, we prepared 312 MRIs at ultrahigh field 7.0 T (axial direction 0.4 times 0.4 times 0.4 mm3 voxel size) of a cadaver brain, 2343 sectioned images (axial direction, 0.1 mm intervals, 0.1 times 0.1 mm2 pixel size, and 48 bits color) by serial-sectioning the cadaver head, 234 segmented images in which brain regions were separately delineated (1 mm intervals and 0.1 times 0.1 mm2 pixel size) by outlining 64 head structures in sectioned images. Three-dimensional images of 64 head structures were made by volume reconstruction from sectioned images. In this research, advanced techniques and equipment enabled us to prepare quality 7.0-T MRIs, sectioned images, and segmented images of the head. These images are expected to contribute to our understanding of the topographic neuroanatomy of the head and to aid interpretations of MRIs and CTs of the human brain.

Functional MR angiography with 7.0 T: Is direct observation of arterial response during neural activity possible?

We propose a new type of functional imaging in magnetic resonance imaging (MRI), a functional MR angiography (fMRA). As it is known, arterial responses during neural activities have been studied in animals, but little is known about the human brain in-vivo. Proposed fMRA at ultra-high field strength, 7.0 Tesla (T), has a potential for a direct visualization of vascular responses of those blood vessels related to the neural activity during the tasks, such as the hand movement or checker board stimulation, that is, fMRA. The results of this paper clearly indicate that there is the possibility that one can directly observe the vascular changes in individual blood vessels related to the tasks in human brain in-vivo, similar to fMRI.

A Proposal of New Reference System for the Standard Axial, Sagittal, Coronal Planes of Brain Based on the Serially-Sectioned Images

Sectional anatomy of human brain is useful to examine the diseased brain as well as normal brain. However, intracerebral reference points for the axial, sagittal, and coronal planes of brain have not been standardized in anatomical sections or radiological images. We made 2,343 serially-sectioned images of a cadaver head with 0.1 mm intervals, 0.1 mm pixel size, and 48 bit color and obtained axial, sagittal, and coronal images based on the proposed reference system. This reference system consists of one principal reference point and two ancillary reference points. The two ancillary reference points are the anterior commissure and the posterior commissure. And the principal reference point is the midpoint of two ancillary reference points. It resides in the center of whole brain. From the principal reference point, Cartesian coordinate of x, y, z could be made to be the standard axial, sagittal, and coronal planes.

Evaluation of MR angiography at 7.0 Tesla MRI using birdcage radio frequency coils with end caps.

The purpose of this study was to evaluate the feasibility of MR angiography (MRA) at 7.0 Tesla (T) using optimized birdcage (BC) coils with simple end cap configurations. Shielded 16‐rung high‐pass BC coils were built with identical geometry and compared with different sizes and locations of end caps. To determine whether the end cap configuration was effective, the signal intensity profiles along the superior–inferior (S–I) direction were analyzed in phantom and in vivo human experiments. The effects were also investigated in two‐dimensional (2D) and three‐dimensional (3D) time‐of‐flight (TOF) MRA experiments. The signal intensity profiles showed that B1 homogeneity at the service end, that is, the end cap side, was improved as the diameter of the end caps increased and the end cap became closer to the coil end ring. The results of 2D and 3D TOF experiments showed the best improvement of vessel visibility at the BC coil with an 80% end cap, when compared with BC coils with other end cap sizes or without an end cap. In conclusion, the BC coil with an end cap was effective for improving S–I directional homogeneity and suitable for MRA applications, especially at ultrahigh field MRI, such as 7.0T. Magn Reson Med 60:330–338, 2008.