Chang-Ki Kang

Neural substrates, experimental evidences and functional hypothesis of acupuncture mechanisms.

Objectives –  Athough acupuncture therapy has demonstrated itself to be effective in several clinical areas, the underlying mechanisms of acupuncture in general and the analgesic effect in particular are, however, still not clearly delineated. We, therefore, have studied acupuncture analgesic effect through fMRI and proposed a hypothesis, based on the obtained result, which will enlighten the central role of the brain in acupuncture therapy.

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.

Hypertension Correlates With Lenticulostriate Arteries Visualized by 7T Magnetic Resonance Angiography

Hypertension, a major risk factor for stroke, is associated with altered arterial anatomy and function; however, the limited resolution of current imaging techniques has restricted the in vivo study of microvascular changes in the brain. In this report, we quantitatively examined the lenticulostriate arteries in hypertensive patients using ultrahigh-field 7T MRI. We compared the number of stems and branches, curvature, and tortuosity of the lenticulostriate arteries by 3D time-of-flight magnetic resonance angiography among 20 hypertensive patients (mean age: 46.6±9.1 years) and 20 age-matched healthy subjects (mean age: 47.7±8.1 years). The average numbers of stems and branches in hypertensive patients were significantly less than those of healthy subjects (P<0.002). However, this difference was abolished in older volunteers (>45 years old), whereas the difference between young hypertensive patients (≤45 years old) and age-matched healthy controls was augmented by 55% for stems and 91% for branches (P=0.001). In comparison, there were no differences in the average curvature and tortuosity of the lenticulostriate arteries and no significant difference when corrected for smoking (P=0.064). In conclusion, our results showed that there was a substantial difference in the lenticulostriate arteries of hypertensive patients compared with healthy individuals when observed in vivo by ultrahigh-resolution 7T magnetic resonance angiography, and the difference was considerable in young subjects.

Lenticulostriate arteries in chronic stroke patients visualised by 7 T magnetic resonance angiography.

Background Noninvasive magnetic resonance angiography using ultra-high-field magnetic resonance imaging has recently provided us with the potential to image cerebral microvascular structures such as the lenticulostriate arteries. However, most studies using ultra-high-field magnetic resonance angiography have been limited to the visualisation of microvessels in healthy subjects, and the direct comparison of patients with microvascular disease has not been reported. Aim The aim of this study was to investigate the lenticulostriate arteries of patients with lacunar strokes of the basal ganglia and surrounding areas using 7 T magnetic resonance angiography. Methods Ten stroke patients who had infarctions in the basal ganglia and adjacent areas detected using T2*-weighted images obtained from a conventional 1.5 T magnetic resonance imaging and 10 age-matched healthy subjects were recruited for this study. The large main vessels in the patient group were inspected to identify abnormalities such as stenosis. The characteristics of the lenticulostriate arteries visualised by 7 T magnetic resonance angiography, such as the number of branches and stems, curvature and tortuosity were analysed and compared between the patient and the control groups. Results All patients had infarctions in the basal ganglia and adjacent regions, which were clearly determined by T2*-weighted images. However, there was no evidence of large-vessel abnormalities in the patient group. Analysis of 7 T magnetic resonance angiography data revealed that the overall number of lenticulostriate arteries branches in the patient group was significantly less than the control group (P = 0.003). However, no statistical difference in the number of stems, curvature and tortuosity between the two groups was found (P = 0.396, 0.258 and 0.888, respectively). Conclusions This study demonstrates that noninvasive magnetic resonance angiography using 7 T magnetic resonance imaging can visualise abnormalities in the cerebral microvasculature of stroke patients, and that the number of lenticulostriate arteries supplying the region of the basal ganglia is less in these patients compared with age-matched controls.

Non-invasive visualization of basilar artery perforators with 7T MR angiography.

To visualize the perforating arteries originating from basilar artery (BA) by using ultra‐high resolution 7T MR angiography (MRA) and optimizing MR parameters as well as radio frequency (RF) coils, which may provide important information for neurosurgery and understanding diseases of the pons, but was unable to clearly visualize with conventional MRA techniques.

Effect of Stellate Ganglion Block on the Cerebrovascular System Magnetic Resonance Angiography Study

Background:Several studies have shown that stellate ganglion block (SGB) is an effective treatment for certain cerebrovascular related diseases; however, the direct effect of SGB on the cerebral vasculature is still unknown. The present study investigated the effect of SGB on the cerebral vascular system using magnetic resonance angiography. Methods:Time-of-flight magnetic resonance angiography images of 19 healthy female volunteers (mean ages of 46.4 ± 8.9 yr) were obtained before and after SGB with 1.5-T magnetic resonance imaging. The authors determined successful interruption of sympathetic innervation to the head with the appearance of Horner syndrome and conjunctival injection. We measured changes in the average signal intensity and diameter of the major intracranial and extracranial arteries and their branches, which were presented with mean (±SE). Results:The signal intensity changes were observed mainly in the ipsilateral extracranial vessels; the external carotid artery (11.2%, P < 0.001) and its downstream branches, such as the occipital artery (9.5%, P < 0.001) and superficial temporal artery (14.1%, P < 0.001). In contrast, the intensities of the intracranial arteries did not change with the exception of the ipsilateral ophthalmic artery, which increased significantly (10.0%, P = 0.008). After SGB, only the diameter of the ipsilateral external carotid artery was significantly increased (26.5%, P < 0.001). Conclusions:We were able to observe significant changes in the extracranial vessels, whereas the intracranial vessels were relatively unaffected (except for the ophthalmic artery), demonstrating that both perivascular nerve control and sympathetic nerve control mechanisms may contribute to the control of intracranial and extracranial blood vessels, respectively, after SGB.

Measurements of lenticulostriate arteries using 7T MRI: new imaging markers for subcortical vascular dementia

Recent studies have demonstrated that ultra-high resolution MRA imaging using 7 Tessla (T) MRI can be employed to noninvasively visualize the lenticulostriate arteries (LSA) that supply the basal ganglia and internal capsule. Subcortical vascular dementia (SVaD) is believed to involve these regions from an early stage. We investigated whether LSA abnormalities measured by 7T MRA correlate with MRI ischemia markers and neuropsychological/motor deficits. A total of 24 subjects (12 with SVaD, 12 normal controls (NC)) were imaged with 3T and 7T MRIs. We assessed the severity of white matter hyperintensities (WMH) and the number of lacunes and microbleeds (MB) by visually inspecting images obtained from conventional 3T MRI. We also analyzed three-dimensional models of the measured LSAs obtained from 7T MRI. Compared to the NC, the SVaD subjects had fewer branches of LSAs and greater radii of LSAs. The number of branches was correlated with the number of lacunes. The number of branches was correlated with the delayed recall scores on Reys Complex Figure Test (RCFT). While not quite reaching statistical significance, the immediate recall, recognition scores on the RCFT, recognition scores on the Seoul Verbal Learning Test, and the word and color readings of Stroop trended in the direction of correlation with the number of branches, as well as with the extrapyramidal scores. Our findings suggest that LSA imaging using 7T MRI might be a potent candidate for the detection of SVaD.

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.

The effects of caffeine ingestion on cortical areas: Functional imaging study☆ , ☆☆

The effect of caffeine as a cognitive enhancer is well known; however, caffeine-induced changes in the cortical regions are still not very clear. Therefore, in this study, we conducted an investigation of the activation and deactivation with blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) and of metabolic activity change with positron emission tomography (PET) in the human brain. Fourteen healthy subjects performed a visuomotor task inducing attention with 3T MRI, and PET imaging was also carried out in seven subjects to determine the cerebral glucose metabolic changes of caffeine at rest. The result by fMRI showed increased BOLD activation in the left cerebellum, putamen, insula, thalamus and the right primary motor cortex, and decreased BOLD deactivation in the posterior medial and the left posterior lateral cortex. Also, the resting state PET data showed reduced metabolic activity in the putamen, caudate nucleus, insula, pallidum and posterior medial cortex. The common cortical regions between fMRI and PET, such as putamen, insula and posterior medial cortex, where significant changes occurred after caffeine ingestion, are well known to play an important role in cognitive function like attention. This result suggests that the effect of caffeine as a cognitive enhancer is derived by modulating the attentional areas.

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.