Advanced Methods in Dynamic Contrast Enhanced Arterial Phase Imaging of the Liver

Dynamic contrast enhanced (DCE) magnetic resonance (MR) imaging plays an important role in non-invasive detection and characterization of primary and metastatic lesions in the liver. Recently, efforts have been made to improve spatial and temporal resolution of DCE liver MRI for arterial phase imaging. Review of recent publications related to arterial phase imaging of the liver indicates that there exist primarily two approaches: breath-hold and free-breathing. For breath-hold imaging, acquiring multiple arterial phase images in a breath-hold is the preferred approach over conventional single-phase imaging. For free-breathing imaging, a combination of three-dimensional (3D) stack-of-stars golden-angle sampling and compressed sensing parallel imaging reconstruction is one of emerging techniques. Self-gating can be used to decrease respiratory motion artifact. This article introduces recent MRI technologies relevant to hepatic arterial phase imaging, including differential subsampling with Cartesian ordering (DISCO), golden-angle radial sparse parallel (GRASP), and X-D GRASP. This article also describes techniques related to dynamic 3D image reconstruction of the liver from golden-angle stack-of-stars data.

Value of in-flow inversion recovery sequence in diagnosis of Budd-Chiari syndrome / 实用放射学杂志

Objective To explore the feasibility of in-flow inversion recovery (IFIR)sequence of magnetic resonance imaging (MRI)at 1.5T in diagnosis of Budd-Chiari syndrome (BCS).Methods A total of 45 patients with Budd-Chiari syndrome diagnosed by surgery or interventional surgery in our institution were enrolled.The prerequisite of the study was that all medical imaging data including MRI and digital subtraction angiography (DSA)should be integrated.Then,the diagnostic accuracy rates between IFIR sequence and DSA were analyzed and compared.Results Of all 45 patients with BCS,40 (88.9%)were diagnosed accurately by IF-IR sequence,including typeⅠa in 10,typeⅠb in 14,typeⅡ in 10 and type Ⅲ in 6.Meanwhile,41 (91.1%)were diagnosed accu-rately by DSA,including typeⅠa in 8,typeⅠb in 14,typeⅡ in 13 and type Ⅲ in 6.No significant difference was showed in diag-nostic accuracy between two imaging methods (P >0.05).Spearman rank correlation analysis revealed that the diagnostic accuracy of IFIR sequence was highly consistent with that of DSA(r =0.853,P <0.001 ).However,there existed significant difference be-tween two methods in accurate diagnosis of typeⅠa and typeⅡ BCS (P <0.05).Conclusion MRI IFIR sequence at 1.5T is highly consistent with DSA in diagnosis and classification of BCS,which can be used as a reliable method of preoperative screening for BCS diagnosis.

Application of Two-dimensional 1H-31P Inverse NMR Pulse Sequence in Detection of Organophosphorus Chemical Warfare Agents and Related Compounds / 分析化学

Combined pulsed-field gradient, shaped pulses, and product operator calculations (algorithm), two-dimensional 1 H-31 P hetero-nuclear multiple quantum coherence ( HMQC) pulse sequence was established with the aid of C language. The result showed that coherent transfer path selection could be achieved by adjusting the ratio of two gradient strength ( g1 , g2 ) . The best ratio of g1 and g2 was -5:4 . The HMQC method based on the above sequence can be used for identifying the alkyl groups coupling with phosphorous nucleus. For the different alkyl groups, the sensitivity of this method decreased in the order methyl>isopropyl>ethyl>propyl. The limit of detection was about 10 mg/L. This method can be directly used for the screening and identification of phosphorus chemical warfare agents and related compounds.

The Development of RAGE Pulse Sequence with Clinical MRI Scanner / 中国医学物理学杂志

Objective:To implement rapid acquisition gradient echo(RAGE)pulse sequence in clinical MRI scaner.Methods:Pascal language is engaged to edit source code.Number of slice excited,order of phase encoded,phase recycle of RF pulse,NEX,on/off of the gradients,and so on are all controlled by sequence parameters.SI×N_(phase)×N_(slice) data of 32 bctys were allocated to restore the k space.Source code of sequence was compiled with executable file and is loaded to RINMR software.Image of human brain are acquired.The experiment has been conducted on 0.36T permanent MRI system.Resuits:In the case of 256×256 matrix acquisition,time of single slice is 4 seconds.The resolution and SNR of the image are all adquately satisfy the clinical application.

Relationship between contrast pulsed sequencing parameters and changes of placental vascular bed in different stage of pregnant rats / 中国医学影像技术

Objective To quantitatively measure the perfusion parameters of placenta in different stage of pregnant rats using contrast-enhanced ultrasonography (CEUS) with contrast pulsed sequencing (CPS), and to analyze the relationship between perfusion parameters and changes of placental vascular bed. Methods Sixty healthy pregnant rats in according to the requirements of the experiment was divided into three groups: 15 days, 17 days and 20 days of gestation with 20 animals in each group. One blous injection of SonoVue (Sonovue 1.0 ml/kg) via a tail vein was administered to each rat, and the time-intensity curves (TIC) of placenta and uterine muscle wall were drawn with ACQ using CPS technique with MI 0.20, and the perfusion parameters were calculated. Then 4 μm vertical placenta sections were cut and stained with hematoxylin and eosin. Surface area densities of placental maternal blood space was measured with image analysis software. Results The peak intensity (PI) of 17 days and 20 days was higher than that of 15 days pregnant rats (P＜0.05). There was no difference in PI between 17 days and 20 days (P＞0.05), and nor of arrivel time (AT) and time-to-peak (TTP) (P＞0.05) among the three groups. There was significant difference of surface area densities of placental maternal blood space among the three groups (P＜0.05). PI was positively correlated to the surface area densites of placenta (P＜0.05). Conclusion There is close relationship between peak intensity and area densities of placental maternal blood space. CPS technique can sensitivly detect changes of the placenta vascular bed in different stage of pregnant rats.

Usefulness of Post-enhanced Delayed FLAIR Imaging for Making the Diagnosis of Leptomeningitis

PURPOSE: To evaluate the usefulness of post-enhanced delayed FLAIR (fluid-attenuated inversion-recovery) images in the diagnosis of leptomeningitis. MATERIALS AND METHODS: We obtained the pre- and post-enhanced FLAIR images of 7 rabbits every hour after infusing triple doses of contrast, and we measured the signal intensities of the CSF (cerebrospinal fluid) and the brain parenchyma. Five leptomeningitis patients and 5 volunteers were enrolled to obtain the pre-enhanced FLAIR images, the early post-enhanced FLAIR images and the delayed post-enhanced FLAIR images, with using a standard dose of contrast, and to measure the signal intensities of the CSF and brain parenchyma. The statistical significances were determined by a mixed procedure and the Wilcoxon rank-sum test (p<0.05). RESULTS: In the rabbits, the signal intensities of the CSF began to increase after an hour of contrast infusion, but those of the parenchyma did not increase. The time of maximum CSF enhancement was 2 hours after contrast infusion (p<0.001; standard estimate=750.43) and we obtained the post-enhanced delayed FLAIR images for clinical studies according to this result. The signal intensities of the CSF in the subarachnoid space were higher in the patient group compared with those of the normal control group on both the early post-enhanced FLAIR images and the delayed post-enhanced FLAIR images (p=0.0096) (p=0.0391). In the patient group, changes of signal intensities of the CSF in the subarachnoid space were more conspicuous on the delayed post-enhanced FLAIR images than on the early post-enhanced FLAIR images (p=0.0042). However, those of the parenchyma were not different in either group. CONCLUSION: The post-enhanced delayed FLAIR images obtained at 2 hours after contrast infusion are more useful for making the the diagnosis of leptomeningitis than are the post-enhanced early FLAIR images.

Design and optimization of pulse sequence for quantitative measurement of ?-aminobutyric acid concentration using MR spectroscopy / 国际生物医学工程杂志

Objective To design and optimize the MRS pulse sequence which used to measure gamma-aminobutyric acid(GABA) in vivo. Methods In-depth research for the MRS sequence was carried out and a theoretical analysis and simulation by software using product-operator algebra for the design and optimization of pulse sequence was discussed. Results Through the simulation of MRUI software, Cr signal at ?3.0 was seen to be suppressed and the weak GABA signal was displayed clearly. Conclusion The sequence was designed and optimized. Method to increase the efficiency and the stability of the measurement was studied. Our research gives theoretical preparation for the coming programming work.

Histogram Analysis of Noise Performance on Fractional Anisotropy Brain MR Image with Different Diffusion Gradient Numbers

PURPOSE: We wished to analyze, qualitatively and quantitatively, the noise performance of fractional anisotropy brain images along with the different diffusion gradient numbers by using the histogram method. MATERIALS AND METHODS: Diffusion tensor images were acquired using a 3.0 T MR scanner from ten normal volunteers who had no neurological symptoms. The single-shot spin-echo EPI with a Stejskal-Tanner type diffusion gradient scheme was employed for the diffusion tensor measurement. With a b-valuee of 1000 s/mm2, the diffusion tensor images were obtained for 6, 11, 23, 35 and 47 diffusion gradient directions. FA images were generated for each DTI scheme. The histograms were then obtained at selected ROIs for the anatomical structures on the FA image. At the same ROI location, the mean FA value and the standard deviation of the mean FA value were calculated. RESULTS: The quality of the FA image was improved as the number of diffusion gradient directions increased by showing better contrast between the WM and GM. The histogram showed that the variance of FA values was reduced as the number of diffusion gradient directions increased. This histogram analysis was in good agreement with the result obtained using quantitative analysis. CONCLUSION: The image quality of the FA map was significantly improved as the number of diffusion gradient directions increased. The histogram analysis well demonstrated that the improvement in the FA images resulted from the reduction in the variance of the FA values included in the ROI.

The Evaluation of ROC Curve in Qualitative and Quantitative Analysis of Pancreatic Diseases on Fat Saturation FSPGR Sequence / 实用放射学杂志

Objective To evaluate the accuracy of fatsuppressed fast spoiled gradient echo(FSPGR) T_1WI in detection of pancreaticdisease using the receiver operating characteristic curve(ROC).Methods The pancreas were evaluated in 92 subject investigated(57normal and 35 with pancreatic disease) with fat saturation FSPGR T_1WI.The signal intensity(SI) ratio of pancreas relative to liver and spleen was quantitatively measured using regions of interest(ROIs),then qualitatively assessed by one independent observers.Results The mean values of pancreas-liver ratios and pancreas-spleen ratios between a normal and an abnormal pancreas were significantlydifferent.Thearea under ROC curve of the pancreas-liver SI ratio and the pancreas-spleen SI ratio was 0.92?0.03 and 0.91?0.04,respectively.There was no statistically significant difference between quantitative and qualitative analysis for the diagnosis of pancreatic disease when using liver as comparable standard.The sensitivity of qualitative pancreas in comparison with liver was 86.7%,while specificity was 91.2%.Conclusion When the SI ratio of pancreas-liver is used to distinguish normal from abnormal pancreas,qualitative analysis by observers is as accuracy as quantitative measurement.

MRI Study the Acute Disseminated Encephalomyelitis(ADE) Using FastFluid-attenuated Inversion Recovery Pulse Sequence / 实用放射学杂志

Objective To evaluate the clinical application of fast fluid-attenuated inversion recovery(FLAIR) pulse sequence in MRI study of ADE.Methods Thirty cases with ADE were studied with fast FLAIR sequence and T 2 weighted spinecho sequence.The results were compared in terms of image quality.Results We found the fast-FLAIR could suppress CSF signal effectively,and more lesions were displayed on FLAIR images than on turbo SE T 2-weighted images.The extent of the lesions and the contrast between lesions and normal brain tissue were demonstrated better with fast-FLAIR sequence.Conclusion The lesions in ADE are demonstrated on fast-FLAIR sequence better than on turbo SE T 2 weighted sequence and FAST-flair could be a complementing modality to display lesions in ADE.