Application of CFD mesh generation technology in finite element modeling of skeleton / 医用生物力学

Objective To study high-quality and high efficient meshing methods for skeleton.Methods Based on characteristics of bone structure,the mesh generation technology of computational fluid dynamics (CFD) was applied in mesh generation for bone biomechanics.Hexahedron elements and tetrahedron elements were used to simulate cortical bone and cancellous bone,respectively.Results By using CFD mesh generation technology,high-quality hexahedral elements could be obtained,the structure characteristics of skeleton could be preferably simulated,and computer automatic meshing could be implemented.The amount of time for meshing bones by the new method was only about 1/5 of that by the traditional method,and the calculation results obtained from the finite element model were basically consistent with the results from the cadaver experiment.Conclusions The CFD mesh generation technology can be applied in the field of bone biomechanics,which provides an effective approach to reconstruct complex human skeleton.

Application of CFD mesh generation technology in finite element modeling of skeleton / 医用生物力学

Objective To study high-quality and high efficient meshing methods for skeleton. Methods Based on characteristics of bone structure, the mesh generation technology of computational fluid dynamics (CFD) was applied in mesh generation for bone biomechanics. Hexahedron elements and tetrahedron elements were used to simulate cortical bone and cancellous bone, respectively. Results By using CFD mesh generation technology, high-quality hexahedral elements could be obtained, the structure characteristics of skeleton could be preferably simulated, and computer automatic meshing could be implemented. The amount of time for meshing bones by the new method was only about 1/5 of that by the traditional method, and the calculation results obtained from the finite element model were basically consistent with the results from the cadaver experiment. Conclusions The CFD mesh generation technology can be applied in the field of bone biomechanics, which provides an effective approach to reconstruct complex human skeleton.

Diffusion weighted imaging combined with magnetic resonance conventional sequences for the diagnosis of rectal cancer / 中国医学科学院学报

<p><b>OBJECTIVE</b>To evaluate the clinical value of diffusion weighted imaging (DWI) combined with conventional sequences of magnetic resonance imaging (T1 and T2-weighted imaging) for the diagnosis of rectal cancer.</p><p><b>METHODS</b>DWI and conventional sequences were performed in 29 patients with endoscopically diagnosed rectal cancer and 15 patients without rectal cancer. Two doctors who were blind to the history of the patients interpreted the imaging findings. The sensitivity and specificity of conventional sequences with and without DWI were analyzed using receiver operating characteristic curve (ROC).</p><p><b>RESULTS</b>The areas under ROC were 0.915 and 0.930 for conventional sequences alone, and 0.990 and 0.994 for conventional sequences with DWI, respectively, indicating that although both of them were optimal methods for the diagnosis of rectal cancer, the accuracy of conventional sequences with DWI was significantly superior to that of conventional sequence alone (P < 0.05). The Kappa value was 0.850 for conventional sequences alone and 0.858 for DWI with conventional sequences.</p><p><b>CONCLUSION</b>DWI was necessary for the diagnosis of rectal cancer when performing conventional sequences.</p>

Differences in interictal perfusion patterns between refractory and non-refractory temporal lobe epilepsies evaluated with fair at 3. 0T / 中国医学科学杂志(英文版)

<p><b>OBJECTIVE</b>To investigate the difference in interictal perfusion patterns between refractory and non-refractory temporal lobe epilepsies evaluated with flow-sensitive alternating inversion recovery (FAIR) magnetic resonance (MR) sequence.</p><p><b>METHODS</b>Nine patients with refractory temporal lobe epilepsy, 21 patients with non-refractory temporal lobe epilepsy, and 13 normal volunteers underwent FAIR MR scanning. The relative cerebral blood flow (rCBF) in bilateral hemispheres and mesial temporal lobes were measured. And we also calculated the asymmetry index (AI) values.</p><p><b>RESULTS</b>The AI values of bilateral hemispheres in refractory and non-refractory epilepsy patients were both significantly different from those of volunteers (P = 0.012 and 0.029, respectively). There was significant difference in AI values of bilateral mesial temporal lobes between non-refractory epilepsy patients and volunteers (P = 0.049), while no significant difference between refractory epilepsy patients and volunteers.</p><p><b>CONCLUSIONS</b>The hypoperfusion pattern of interictal refractory temporal lobe epilepsy patients is different from that of non-refractory patients. Although the hypoperfusion tends to extend out of temporal lobes in all patients, the refractory epilepsy patients have a preference of bilateral mesial temporal hypoperfusion, which may be valuable for evaluating prognosis.</p>

Evaluation of mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes with magnetic resonance imaging and proton magnetic resonance spectroscopy / 中国医学科学杂志(英文版)

<p><b>OBJECTIVE</b>To study the characteristics of spectra on proton magnetic resonance spectroscopy (1H-MRS) and its value in patients with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS).</p><p><b>METHODS</b>Seven clinically diagnosed patients with MELAS underwent magnetic resonance imaging (MRI) and 1H-MRS examinations. The 1H-MRS techniques, characteristics of the spectra, and its correlation with the laboratory tests were analyzed.</p><p><b>RESULTS</b>Cerebral abnormalities were revealed in all 7 patients on conventional MR images, and most abnormal signals were observed in bilateral occipital, parietal, and temporal lobes. We found 4 cases with basal ganglia involvement, 2 cases with mild frontal lobe lesions, and 1 case with involvement of lateral cerebral peduncles and thalami. Additionally, 1 patient was involved with left insular lobe. Spectra from prominent lesions in brain parenchyma showed lactate doublet peak in 6 patients, 3 of whom were also noted lactate peak in ventricular cerebrospinal fluid (CSF).</p><p><b>CONCLUSION</b>1H-MRS may provide more direct information about the metabolism changes, which aids to affirm the diagnosis, and may replace the conventional invasive method of quantifying lactate in CSF.</p>

Comparison of radiographs and magnetic resonance imaging in the detection of carpal lesions in patients with rheumatoid arthritis / 中国医学科学院学报

<p><b>OBJECTIVE</b>To compare MR imaging with radiographs in detection of the erosions of the wrists in patients with rheumatoid arthritis (RA).</p><p><b>METHODS</b>In 50 wrists of 25 patients with RA, radiographs of AP projection and MR imaging examination were performed within 1 week. The MRI sequences were SE T1-weighted image, FSE T2-weighted image, and GE T2* weighted image in coronal plane. Gd-DTPA enhanced SE T1-weighted image with same parameters of pre-contrast administration SE T1WI was performed in 25 wrists, which showed prominent lesions in each 25 patients.</p><p><b>RESULTS</b>In 50 wrists of 25 patients with RA, bone erosions were found by MR images compared to radiographs in 46 versus 14 wrists, respectively. There were 170 sites of carpal erosions found by MR images, while radiographs found only 23 sites of carpal erosions. Among them triquetrum and lunate were the most frequently involved sites. Significant difference (P < 0.001) was statistically found between conventional radiography and MR imaging in detection of erosions of the wrists of RA. MR imaging also permitted demonstrating synovitis and joint effusion in the wrists. Gd-DTPA-enhanced images allowed distinguishing pannus changes from joint effusion.</p><p><b>CONCLUSION</b>MRI is superior to conventional radiography with respect to detection of bone erosion in wrists. For those whose conventional radiographs show suspected RA, MRI examination should be advised for the early diagnosis.</p>

Fat at sacroiliac joints: MR imaging findings (comparison and analysis of 18 volunteers and 52 patients with ankylosing spondylitis) / 中国医学科学院学报

<p><b>OBJECTIVE</b>In aid of MR imaging diagnosis of ankylosing spondylitis (AS), MRI findings of sacroiliac (SI) joints in volunteers were compared with those in patients with AS, with special reference to the fat findings.</p><p><b>METHODS</b>18 normal volunteers and 52 AS patients underwent the MRI examinations with the same protocols, i.e., SE T1WI, FSE T2WI, GE T2*WI sequences were taken using a 0.3T imager. All the images were observed and analyzed by two radiologists.</p><p><b>RESULTS</b>Symmetric or patchy distribution fat component either in sacrum and/or ilium was detected in 52.8% of SI joints of volunteers. Thin zone distribution of fat was seen in 35.6% of SI joints of AS patients, which was adjacent to the erosion and sclerosis. In another 25.0% of SI joints of AS patients, the distribution of fat component was found similar to that of the normal volunteers. Cartilage changes were detected in 85.6% of the SI joints of AS patients. In addition, bone erosion, sclerosis and subchondral bone marrow edema were also detected.</p><p><b>CONCLUSION</b>Subchondral fat infiltration associated with erosion and sclerosis should be considered as sacroiliitis. The knowledge of the characteristics of fat component could be helpful for evaluating sacroiliac joints.</p>