Characteristics of basilar artery atherosclerotic plaques in pontine infarctions: A high-resolution magnetic resonance imaging study.

Objective: This study used a 3.0T high-resolution magnetic resonance imaging approach to explore basilar artery plaque characteristics in patients suffering from acute isolated pontine infarction. Materials and methods: 30 consecutive patients suffering from acute isolated pontine infarction were enrolled in this study and underwent examinations including high-resolution MRI assessment of the basilar artery within 7 days following infarction. Results: The basilar artery plaque burden of 16 patients with paramedian pontine infarction was 0.26±0.085, while the reconstruction index and enhancement rate index values in these patients were 1.097±0.133 and 1.750±0.447, respectively. In the 14 patients suffering from deep pontine infarction, these three values were 0.21±0.055, 0.896±0.223, and 1.285±0.611, respectively.These values differed significantly when comparing patients suffering from paramedian pontine infarction to those suffering from deep pontine infarction. Conclusion: This study suggests that the characteristics of basilar artery plaques differ between the two subtypes of pontine infarctions, which may account for the differences in prognosis associated with these two infarct subtypes.

[Ultrasmall superparamagnetic iron oxide-enhanced magnetic resonance angiography combined with inflammatory factors for detecting atherosclerotic plaques in rabbits].

OBJECTIVE: To investigate the feasibility of Ultrasmall superparamagnetic iron oxide-enhanced magnetic resonance angiography (USPIO-MRA) combined with interleukin-6 (IL-6) and IL-10 detection for detecting atherosclerotic plaques in rabbits. METHODS: Twenty-four normal male rabbits were randomly assigned (n=8) into group A with atherosclerosis induced by damaging the aortic tunica intima with Foley's tube in combination with a high fat diet, group B with a high fat diet, and group C without any intervention. At week 12, plain and USPIO-MRA was performed in all the 24 rabbits and the results were compared with pathological examinations; blood samples were collected from the ear vein to examine blood lipids and levels of IL-6 and IL-10. RESULTS: The rabbits in groups A and B showed significantly different IL-6 levels (167 ± 21.3 vs 116 ± 14.3 pg/ml, P<0.05) but comparable blood lipids and IL-10 levels (P>0.05). The levels of IL-6, IL-10, TC, TG, and LDL, but not HDL, differed significantly between groups A and C and between groups B and C (P<0.01). Continuous MRA scan showed significantly different signal-to-noise ratios (SNR) between the 3 groups. CONCLUSION: USPIO-MRA combined with IL-6 and IL-10 detection is feasible in detecting atherosclerotic plaques in rabbits.

The clinical value of dynamic contrast-enhanced magnetic resonance imaging at 3.0T to detect prostate cancer.

OBJECTIVE: To compare dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) and T2-weighted imaging (T2WI) at 3.0 T for detection of prostate cancer. METHODS: Patients with elevated prostate-specific antigen underwent T2WI and DCE-MRI prior to prostate needle biopsy. The sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) of T2WI and DCE-MRI to diagnose prostate cancer were evaluated. The relationship between Gleason score and prostate cancer detection by DCE-MRI was evaluated. RESULTS: Prostate adenocarcinoma was histopathologically confirmed in 44/75 patients. DCE-MRI had significantly higher sensitivity, accuracy and NPV than T2WI. The detection rate of prostate cancer by DCE-MRI was significantly better for tumours with Gleason score 7-9 than for those Gleason score 4-6. CONCLUSION: DCE-MRI at 3.0 T can significantly improve prostate cancer detection using simple visual diagnostic criteria, compared with T2WI.

Determination of the detectable concentration of manganese used in neuronal MEMRI and its effect on cortical neurons in vitro.

OBJECTIVE: Manganese (Mn(2+))-enhanced magnetic resonance imaging (MEMRI) has received increasing attention because of its functional and anatomic value in brain studies. However, the contrast agent, Mn(2+), will lead to neurotoxicity at high concentrations, which limits its use in biomedical research. This study was designed to determine whether Mn(2+) can significantly enhance the signal intensity (SI) of primary cultured cortical neurons at non-toxic levels. METHOD: Neurons were incubated with different concentrations of Mn(2+) (control and 0.01, 0.05, 0.10, and 0.20 mM), then a cellular MRI was performed in vitro and the intracellular Mn(2+) concentrations were analyzed by ICP-MS. At the same time, the cell viability, LDH release assay, intracellular ROS level, and apoptosis were measured 24 h after treatment. RESULTS: (1) After the neurons were treated with Mn(2+) at a low concentration (0.01 mM), there was no impact on cell viability and cytotoxicity, and no significant signal was enhanced on MEMRI. (2) When the neurons were exposed to higher concentrations of Mn(2+) (0.05, 0.1, and 0.2 mM), a significant increase in signal quality was achieved, but cell viability was significantly reduced and the intracellular ROS formation and percentage of TUNEL-positive cells were increased significantly. CONCLUSION: At Mn(2+) concentrations > 0.05 mM, significant enhancement of MEMRI SI occurred, but with overt cytotoxicity.

Three-dimensional turbo-spin-echo amide proton transfer MR imaging at 3-Tesla and its application to high-grade human brain tumors.

PURPOSE: Amide proton transfer (APT) imaging is able to extend the achievable magnetic resonance imaging (MRI) contrast to the protein level. In this study, we demonstrate the feasibility of applying a turbo-spin-echo (TSE)-based, three-dimensional (3D) APT sequence into routine clinical practice for patients with brain tumors. PROCEDURES: Experiments were performed on a Philips 3-Tesla (3-T) MRI scanner using an eight-channel phased-array coil for reception. A fast 3D APT sequence with a TSE acquisition was proposed (saturation power, 2 µT; saturation time, 500 ms; 8 slices). The gradient echo (GRE)-based field-mapping technique or water-saturation-shift-referencing (WASSR) technique was used to acquire B(0) maps to correct for B(0)-induced artifacts in APT images. The test was performed on a box of homogenous protein solution, four healthy volunteers, and eight patients with high-grade gliomas. RESULTS: The experimental data from a homogenous, protein-containing phantom and healthy volunteers show that the sequence produced a uniform contrast across all slices. The average MTR(asym)(3.5 ppm) values with GRE B(0)-corrected 3D APT imaging and WASSR-corrected 3D APT imaging were both comparable to the values obtained using the undemanding single-slice acquisition. The average APT image intensity was consistently higher in the tumor core than in the peripheral edema and in the contralateral normal-appearing white matter (both P < 0.001). CONCLUSION: 3D APT imaging of brain tumors can be performed in about 5 min at 3-T using a routine, commercial eight-channel SENSE coil.

Functional mapping of rat brain activation following rTMS using activity-induced manganese-dependent contrast.

OBJECTIVE: Functional neuroimaging techniques act as the navigator to assess changes in brain activity induced by repetitive transcranial magnetic stimulation (rTMS) in rTMS studies. The aim of this study was to investigate the feasibility of using manganese-enhanced magnetic resonance imaging (MEMRI) to measure the brain activity in rTMS studies. METHODS: Eighteen Wistar rats were randomized into three groups (n = 6) including a high rTMS group, a low rTMS group and a sham stimulation group (controls). They were given rTMS of 10 Hz, 1 Hz or sham stimulation for 5 hours separately. MEMRI was used to assess the changes of brain activity. RESULTS: Compared with the controls, image intensity was enhanced differently in various brain regions on T1-weighted images after rTMS with different frequencies, higher intensity and wider enhancement occurred in the high frequency rTMS group as compared with that in the low frequency rTMS group. CONCLUSION: MEMRI can be used to reveal the changes of brain activity in live rats following rTMS. SIGNIFICANCE: The current experiment might provide a new functional neuroimaging technique for the study of rTMS.

Effects of temporarily disrupting BBB on activity-induced manganese-dependent functional MRI.

This study further investigates the influence of temporarily disrupting the blood-brain barrier (BBB) on the level of manganese used in AIM fMRI other than the recognized function of allowing that substance to enter into the activated brain regions more effectively during the BBB opening. We injected manganese into Wistar rats through ICA following the disruption of BBB with mannitol in a functional MRI test of the visual cortex. Through comparing MRI signal intensity and manganese contents in the visual cortex of rats received visual stimuli of unequal degree after the restoration of BBB, we found that the signal in the visual cortex could be further enhanced on T1WI given visual stimulation after the restoration of BBB. Temporary BBB disruption has an additional advantage in allowing Mn(2+) to enter the CSF or brain for later transference to the activated brain area. So the dosage of manganese in AIM fMRI could be minimized by extending the stimulus.

Saturation power dependence of amide proton transfer image contrasts in human brain tumors and strokes at 3 T.

Amide proton transfer (APT) imaging is capable of detecting mobile cellular proteins and peptides in tumor and monitoring pH effects in stroke, through the saturation transfer between irradiated amide protons and water protons. In this work, four healthy subjects, eight brain tumor patients (four with high-grade glioma, one with lung cancer metastasis, and three with meningioma), and four stroke patients (average 4.3 ± 2.5 days after the onset of the stroke) were scanned at 3 T, using different radiofrequency saturation powers. The APT effect was quantified using the magnetization transfer ratio (MTR) asymmetry at 3.5 ppm with respect to the water resonance. At a saturation power of 2 µT, the measured APT-MRI signal of the normal brain tissue was almost zero, due to the contamination of the negative conventional magnetization transfer ratio asymmetry. This irradiation power caused an optimal hyperintense APT-MRI signal in the tumor and an optimal hypointense signal in the stroke, compared to the normal brain tissue. The results suggest that the saturation power of 2 µT is ideal for APT imaging of these two pathologies at 3 T with the existing clinical hardware.

Activity-induced manganese-dependent functional MRI of the rat visual cortex following intranasal manganese chloride administration.

Manganese-enhanced MRI (MEMRI) of the brain requires delivery of manganese into the target brain regions. It was previously shown that, following intranasal application, ongoing olfactory stimulation facilitates manganese transport along the olfactory nerve into the olfactory bulb, so bypassing the blood-brain barrier (BBB). We report on experiments to evaluate whether visual stimulation can permit manganese transport onwards from the olfactory bulb to the visual cortex. Rats in intact olfactory bulb group were reserved intact olfactory bulb, while those in olfactory bulbectomy group received bilateral bulbectomy. After intranasal MnCl(2) administration, olfactory and visual stimulations were performed on all the animals for a consecutive 20 h. The visual cortex was then examined using MEMRI. Enhanced imaging on T1WI was noted in the visual cortex of the intact olfactory bulb group. Image subtraction revealed that the signal intensity in the visual cortex of the intact olfactory bulb group was significantly higher than that of olfactory bulbectomy group. Volume of interest (VOI) analysis also showed that normalized intensities in the visual cortex of the intact olfactory bulb group were significantly higher as compared with those of the olfactory bulbectomy group. Inductively coupled plasma mass spectrometry (ICP-MS) confirmed that the manganese content in the visual cortex of the intact olfactory bulb group was increased in comparison with that of the olfactory bulbectomy group. These findings indicate that activity-induced manganese-dependent functional MRI (AIM fMRI) of the rat visual cortex can be performed following intranasal administration of manganese and demonstrate that manganese can migrate from the olfactory bulb to the visual cortex.

MR imaging of high-grade brain tumors using endogenous protein and peptide-based contrast.

Amide proton transfer (APT) imaging is a novel MRI technique, in which the amide protons of endogenous proteins and peptides are irradiated to accomplish indirect detection using the bulk water signal. In this paper, the APT approach was added to a standard brain MRI protocol at 3T, and twelve patients with high-grade gliomas confirmed by histopathology were scanned. It is shown that all tumors, including one with minor gadolinium enhancement, showed heterogeneous hyperintensity on the APT images. The average APT signal intensities of the viable tumor cores were significantly higher than those of peritumoral edema and normal-appearing white matter (P<0.001). The average APT signal intensities were significantly lower in the necrotic regions than in the viable tumor cores (P=0.004). The APT signal intensities of the cystic cavities were similar to those of the viable tumor cores (P>0.2). The initial results show that APT imaging at the protein and peptide level may enhance non-invasive identification of tissue heterogeneity in high-grade brain tumors.

Adenoviral-mediated interleukin-18 expression in mesenchymal stem cells effectively suppresses the growth of glioma in rats.

Glioma is the most common primary intracranial malignant tumor. Despite advances in surgical techniques and adjuvant radio- and chemotherapies, the prognosis for patients with glioma remains poor. We have explored the effects of using genetically modified mesenchymal stem cells (MSCs) to treat malignant glioma in rats. Mesenchymal stem cells isolated from Sprague-Dawley rats can directly suppress the growth of C6 cells in vitro. MSCs transplanted intratumorally can also significantly inhibit the growth of glioma and prolong survival in C6 glioma-bearing models. MSCs producing Interleukin-18 infected by adenoviral vector inhibited glioma growth and prolonged the survival of glioma-bearing rats. Transplantation of IL-18 secreting MSCs was associated with enhanced T cell infiltration and long-term anti-tumor immunity. Thus, IL-18 may be an effective adoptive immunotherapy for malignant glioma. When used in conjunction with MSCs as targeting vehicles in vivo, IL-18 may offer a promising new treatment option for malignant glioma.

Quantitative evaluation of diffusion-weighted magnetic resonance imaging of focal hepatic lesions.

AIM: To explore the quantitative analysis of diffusion-weighted magnetic resonance imaging (DWMRI) in differential diagnosis of focal hepatic lesions. METHODS: DWMRI was performed in 149 hepatic lesions, including hepatocellular carcinoma (34 cases), hepatic metastases (37 cases), cavernous hemangioma (42 cases), hepatic cyst (36 cases). Apparent diffusion coefficient (ADC) values were evaluated using four different b values in different sequences. The ratio of ADC values of lesion/liver in hepatocellular carcinoma and hepatic metastases was also calculated. RESULTS: The mean ADC values of hepatic lesions were as follows: hepatocellular carcinoma (0.95+/-0.11)x10(-3) mm2/s, hepatic metastasis (1.13+/-0.21)x10(-3)mm2/s, cavernous hemangioma (1.86+/-0.36)x10(-3) mm2/s, hepatic cyst (3.14+/-0.31)x10(-3) mm2/s. The ratio of ADC values in lesion/liver in hepatocellular carcinoma was 0.91+/-0.11, being significantly different from that in hepatic metastasis (1.21+/-0.18, P<0.05). CONCLUSION: ADC values and quantitative analysis of focal hepatic lesions are of significant values in differential diagnosis of focal hepatic lesions.

[A simple method for evaluation of the stability of magnetic resonance scanner during brain function imaging].

OBJECTIVE: To develop a simple method for evaluating the stability of magnetic resonance (MR) scanner during brain function imaging. METHOD: A symmetrical water phantom was scanned using the same sequence and parameters as for brain function imaging. The stability of MR scanner was evaluated in view of the signal levels of phantom images. RESULT: The quality control chart of the mean value, standard deviation and the range of the signal level in the region of interest (ROI) within the same region on 128 phantom images were obtained, demonstrating the state of stability of the MR scanner. CONCLUSION: The quality control chart of ROI can be used to evaluate the stability of the MR scanner.

[Quantitative study of diffusion weighted imaging on magnetic resonance imaging in focal hepatic lesions less than 3 cm].

OBJECTIVE: To evaluate the characteristics of MR imaging of hepatic lesions using measurement of apparent diffusion coefficient (ADC) value of hepatic lesions on diffusion weighted imaging. METHODS: MR diffusion weighted images were obtained in patients with 97 hepatic lesions (22 hepatocellular carcinomas, 21 metastatic tumors, 28 hemangiomas, 26 cysts). ADC values were evaluated with different sequences. The ADC ratio of lesion/liver was estimated. RESULTS: Average ADC values of hepatic lesions were as follows: carcinomas (0.91 +/- 0.07) x 10(-3) mm(2)/s, metastatic tumors (1.13 +/- 0.27) x 10(-3) mm(2)/s, cavernous hemangiomas (1.94 +/- 0.37) x 10(-3) mm(2)/s, cysts (3.26 +/- 0.30) x 10(-3) mm(2)/s. The ADC ratio of lesion/liver was significantly different between primary carcinomas and metastatic tumors (P < 0.05). CONCLUSION: Quantitative study in hepatic lesions using ADC values and the ADC ratio of lesion/liver, would improve the accuracy in diagnosing hepatic lesions.

[Role of the marginal division of human neostriatum in working memory capacity for numbers received through hearing: a functional magnetic resonance imaging study].

OBJECTIVE: With the help with functional magnetic resonance imaging (fMRI) technique, we aim to clarify whether the marginal division of the striatum (MrD) is involved in the working memory function of human brain for remembering numbers received through hearing. METHODS: Thirteen healthy volunteers were instructed to undertake both a working memory task, in which the subjects were asked to remember as many numbers read to them as possible, and a non-working memory control task, in which the subjects were not asked to remember the numbers. FMRI of the brain was performed in the 2 groups while the tests were being carried out separately, and the activity of the brain regions was compared between these 2 tasks. RESULTS: Eleven volunteers passed the working memory task for digit remembering. Highly active areas were observed in the prefrontal cortex and the MrD with predominance by the left side during performance of the working memory task, while other regions of the neostriatum were not excited. The prefrontal cortex and the MrD were not obviously activated during the performance in the control test. CONCLUSION: The results suggest that the MrD, along with the prefrontal cortex in the human brain, is involved in working memory function in remembering numbers assigned through hearing. The MrD is probably a subcortical memory center, which is linked to other memory-related brain areas.

[Preoperative cochlear implantation imaging].

OBJECTIVE: To investigate the value of CT and MRI as preoperative imaging technique for cochlear implant candidates. METHOD: Axial high-resolution temporal bone CT and T2-weighted FSE-MRI were performed in 26 patients with sensorineural hearing loss. Three-dimensional reconstruction of inner ear was compared between CT and MRI. RESULT: There were 1 case (2 ears) with Mondini malformation type I , 1 case (2 ears)with Mondini malformation type II , 1 case (2 ears) with inner fibrosis in 18 patients with congenital sensorineural hearing loss. There were 1 case (2 ears) with chronic suppurative otitis meadia, 1 case (2 ears) with inner ossification in 5 patients with postlingually deafness. CONCLUSION: CT plays an indispensable role in evaluation of cochlear implantation. T2-weighted FSE-MRI is necessarily complementary to CT. MRI three-dimensional reconstruction of inner ear is better than CT.