High-Resolution Numerical Simulation of Respiration-Induced Dynamic B₀ Shift in the Head in High-Field MRI

PURPOSE: To demonstrate the high-resolution numerical simulation of the respiration-induced dynamic B0 shift in the head using generalized susceptibility voxel convolution (gSVC). MATERIALS AND METHODS: Previous dynamic B0 simulation research has been limited to low-resolution numerical models due to the large computational demands of conventional Fourier-based B0 calculation methods. Here, we show that a recently-proposed gSVC method can simulate dynamic B0 maps from a realistic breathing human body model with high spatiotemporal resolution in a time-efficient manner. For a human body model, we used the Extended Cardiac And Torso (XCAT) phantom originally developed for computed tomography. The spatial resolution (voxel size) was kept isotropic and varied from 1 to 10 mm. We calculated B0 maps in the brain of the model at 10 equally spaced points in a respiration cycle and analyzed the spatial gradients of each of them. The results were compared with experimental measurements in the literature. RESULTS: The simulation predicted a maximum temporal variation of the B0 shift in the brain of about 7 Hz at 7T. The magnitudes of the respiration-induced B0 gradient in the x (right/left), y (anterior/posterior), and z (head/feet) directions determined by volumetric linear fitting, were < 0.01 Hz/cm, 0.18 Hz/cm, and 0.26 Hz/cm, respectively. These compared favorably with previous reports. We found that simulation voxel sizes greater than 5 mm can produce unreliable results. CONCLUSION: We have presented an efficient simulation framework for respiration-induced B0 variation in the head. The method can be used to predict B0 shifts with high spatiotemporal resolution under different breathing conditions and aid in the design of dynamic B0 compensation strategies.

Self-Gated Late Gadolinium Enhancement at 7T to Image Rats with Reperfused Acute Myocardial Infarction

OBJECTIVE: A failed electrocardiography (ECG)-trigger often leads to a long acquisition time (TA) and deterioration in image quality. The purpose of this study was to evaluate and optimize the technique of self-gated (SG) cardiovascular magnetic resonance (CMR) for cardiac late gadolinium enhancement (LGE) imaging of rats with myocardial infarction/reperfusion. MATERIALS AND METHODS: Cardiovascular magnetic resonance images of 10 rats were obtained using SG-LGE or ECG with respiration double-gating (ECG-RESP-gating) method at 7T to compare differences in image interference and TA between the two methods. A variety of flip angles (FA: 10°–80°) and the number of repetitions (NR: 40, 80, 150, and 300) were investigated to determine optimal scan parameters of SG-LGE technique based on image quality score and contrast-to-noise ratio (CNR). RESULTS: Self-gated late gadolinium enhancement allowed successful scan in 10 (100%) rats. However, only 4 (40%) rats were successfully scanned with the ECG-RESP-gating method. TAs with SG-LGE varied depending on NR used (TA: 41, 82, 154, and 307 seconds, corresponding to NR of 40, 80, 150, and 300, respectively). For the ECG-RESP-gating method, the average TA was 220 seconds. For SG-LGE images, CNR (42.5 ± 5.5, 43.5 ± 7.5, 54 ± 9, 59.5 ± 8.5, 56 ± 13, 54 ± 8, and 41 ± 9) and image quality score (1.85 ± 0.75, 2.20 ± 0.83, 2.85 ± 0.37, 3.85 ± 0.52, 2.8 ± 0.51, 2.45 ± 0.76, and 1.95 ± 0.60) were achieved with different FAs (10°, 15°, 20°, 25°, 30°, 35°, and 40°, respectively). Optimal FAs of 20°–30° and NR of 80 were recommended. CONCLUSION: Self-gated technique can improve image quality of LGE without irregular ECG or respiration gating. Therefore, SG-LGE can be used an alternative method of ECG-RESP-gating.

T1-Based MR Temperature Monitoring with RF Field Change Correction at 7.0T

PURPOSE: The objective of this study is to determine the effect of physical changes on MR temperature imaging at 7.0T and to examine proton-resonance-frequency related changes of MR phase images and T1 related changes of MR magnitude images, which are obtained for MR thermometry at various magnetic field strengths. MATERIALS AND METHODS: An MR-compatible capacitive-coupled radio-frequency hyperthermia system was implemented for heating a phantom and swine muscle tissue, which can be used for both 7.0T and 3.0T MRI. To determine the effect of flip angle correction on T1-based MR thermometry, proton resonance frequency, apparent T1, actual flip angle, and T1 images were obtained. For this purpose, three types of imaging sequences are used, namely, T1-weighted fast field echo with variable flip angle method, dual repetition time method, and variable flip angle method with radio-frequency field nonuniformity correction. RESULTS: Signal-to-noise ratio of the proton resonance frequency shift-based temperature images obtained at 7.0T was five-fold higher than that at 3.0T. The T1 value increases with increasing temperature at both 3.0T and 7.0T. However, temperature measurement using apparent T1-based MR thermometry results in bias and error because B1 varies with temperature. After correcting for the effect of B1 changes, our experimental results confirmed that the calculated T1 increases with increasing temperature both at 3.0T and 7.0T. CONCLUSION: This study suggests that the temperature-induced flip angle variations need to be considered for accurate temperature measurements in T1-based MR thermometry.

MRI detection method for human gastric cancer orthotopic transplantation model in nude mice / 中国药科大学学报

@#The study aims to establish a human gastric cancer orthotopic transplantation model in nude mice and to use 7T MRI for detection. After poorly differentiated human gastric adenocarcinoma SGC-7901 cells were injected subcutaneosly into the right flanks of nude mice, the model of in nude mice was established with orthotopic transplanted cancer of gastric tumor by the Compont® gel pasted method. 7T MRI scan was conducted on the mice after operating model about 20 days later. Histopathological examinations were carried out on the stomach. Two of three mice on which 7T MRI scan were performed showed visible suspected stomach tumor and their presence was verified again by histopathological examinations; tumor formation rate in the nude mice gastric orthotopic transplantation model was 66. 7%. This study suggested that 7T MRI could be used in the live detection of in situ tumor and that MRI could be used for pre-clinical gastric cancer drug development and clinical gastric carcinoma diagnosis.

Contrast-enhanced Magnetic Resonance Imaging of Brain Metastases at 7.0T versus 1.5T: A Preliminary Result

PURPOSE: To compare the depiction of brain metastases on contrast-enhanced images with 7.0 tesla (T) and at 1.5T MRI. MATERIALS AND METHODS: Four consecutive patients with brain metastases were scanned on 7.0T whole-body scanner and 1.5T MRI. A 3D T1-weighted gradient echo sequence (3D T1-GRE) at 1.5T (voxel size = 0.9 x 0.9 x 1.5 mm3 after double-dose, gadoterate meglumine, Gd-DOTA) was compared to a 7.0T 3D T1-GRE sequence (voxel size = 0.4 x 0.4 x 0.8 mm3, single-dose Gd-DOTA) in four patients after a 5 minute delay. The number of contrast-enhancing metastases in MPRAGE images was compared in each patient by two radiologists in consensus. We measured contrast ratio of enhancing brain metastases and white matter in 1.5T and 7.0T. RESULTS: In all four patients 7.0T 3D T1-GRE images after single-dose Gd-DOTA and 1.5T after double-dose Gd-DOTA depicted 11 brain metastases equally. In the quantitative analysis of contrast ratios of enhancing brain metastases and white matter, the 1.5T 3D T1-GRE after double-dose showed an increased contrast ratio compared to 7.0T 3D T1-GRE after single-dose (0.961 +/- 0.571 versus 0.885 +/- 0.494; n = 11 metastases). But this difference was not statistically significant (P = 0.711). CONCLUSION: Our preliminary results indicate that 7.0T single-dose Gd-enhanced images were not different to 1.5T double-dose Gd-enhanced images for the detection of brain metastases.

CD127 and T Lymphocytes / 中国生物工程杂志

CD127 is the interleukin7 receptor ?(IL7R?),it regulates the specific respond of T lymphocytes to IL7.CD127 plays an indispensable role in the development of thymocytes into T lymphocytes,the survival and homeostatic proliferation of memory T cells.There are only two phases of the life period of T cells that do not express CD127:immature CD4+8+double positive(DP)thymocytes and activated T cells.Recently,it was found that CD127 play an important role as the specific marker of memory T cells and regulator T cells.The role and mechanism of CD127 in the life period of T cells were discussed herein.

Immunohistochemical Study of T lymphocytes Infiltrated in Mycosis Fungoides: Comparison with Psoriasis and Eczema / 대한피부과학회지

BACKGROUND: Sometimes, the clinical distinction between early-stage mycosis fungoides and benign inflammatory deimatoses such as psoriasis and dermatitis can be difficult, and it is not uncommon for the histological changes to be non-diagnostic in early-stage mycosis fungoides. Aberrant immunophenotypic expression of T cells occurs frequently in mycosis fungoides, but is uncommon in benign dermatosis. OBJECTIVE: We investigated the distribution and relative numbers of T lyinphocytes and epidermal cells labelled with various monoclonal antibodies in mycosis fungoides, psoriatic, and eczematous lesions by the immunoperoxidase technique. METHODS: Lesional skin tissues were obtained from 7 mycosis fungoides(10 tissues), 9 psoriasis, and 9 eczema patients. Immunohistochemical staining was done on the frozen sections using a labelled streptavidin-biotin-peroxidase complex method with primary antibodies against CD3, CD4, CD5, CD7, CD8, Leu-8, and HLA-DR. RESULTS: The infiltrating cells in mycosis fungoides, psoriatic, and eczematous lesions were uniformly stained with anti-CD3 and most of CD3+ T cells were also stained with anti-CD4. CD 7 expression of T cells was decreased predominantly in mycosis fungoides but loss of CD7 expression was not prominent in psoriatic and eczematous lesions. In the epidermis, HLA-DR was stained extensively in keratinocytes of mycosis fungoides, but only focal staining of HLA-DR was seen in psoriatic and eczematous lesions. CONCLUSION: These findings suggest that CD4+, CD7- T cells and HLA-DR expression of keratinocytes participate in the development of mycosis fungoides, and are helpful in differentiating mycosis fungoides from psoriasis and eczema.