Multimodality magnetic resonance imaging in hepatic encephalopathy: An update

Hepatic encephalopathy(HE) is a neuropsychiatric complication of cirrhosis or acute liver failure. Currently, HE is regarded as a continuous cognitive impairment ranging from the mildest stage, minimal HE to overt HE. Hyperammonaemia and neuroinflammation are two main underlying factors which contribute to the neurological alterations in HE. Both structural and functional impairments are found in the white mater and grey mater involved in HE. Although the investigations into HE pathophysiological mechanism are enormous, the exact pathophysiological causes underlying HE remain controversial. Multimodality magnetic resonance imaging(MRI) plays an important role in helping to understand the pathological process of HE. This paper reviews the up-to-date multimodality MRI methods and predominant findings in HE patients with a highlight ofthe increasingly important role of blood oxygen level dependent functional MRI.

128-slice Dual-source Computed Tomography Coronary Angiography in Patients with Atrial Fibrillation: Image Quality and Radiation Dose of Prospectively Electrocardiogram-triggered Sequential Scan Compared with Retrospectively Electrocardiogram-gated Spiral

Objective To evaluate the image quality (IQ) and radiation dose of 128-slice dual-source computed tomography (DSCT) coronary angiography using prospectively electrocardiogram (ECG)-triggered sequential scan mode compared with ECG-gated spiral scan mode in a population with atrial fibrillation. Methods Thirty-two patients with suspected coronary artery disease and permanent atrial fibrillation referred for a second-generation 128-slice DSCT coronary angiography were included in the prospective study. Of them, 17 patients (sequential group) were randomly selected to use a prospectively ECG-triggered sequential scan, while the other 15 patients (spiral group) used a retrospectively ECG-gated spiral scan. The IQ was assessed by two readers independently, using a four-point grading scale from excellent (grade 1) to non-assessable (grade 4), based on the American Heart Association 15-segment model. IQ of each segment and effective dose of each patient were compared between the two groups. Results The mean heart rate (HR) of the sequential group was 96±27 beats per minute (bpm) with a variation range of 73±25 bpm, while the mean HR of the spiral group was 86±22 bpm with a variationrange of 65±24 bpm. Both of the mean HR (t=1.91, P=0.243) and HR variation range (t=0.950, P=0.350) had no significant difference between the two groups. In per-segment analysis, IQ of the sequential group vs. spiral group was rated as excellent (grade 1) in 190/244 (78%) vs. 177/217 (82%) by reader1 and 197/245 (80%) vs. 174/214 (81%) by reader2, as non-assessable (grade 4) in 4/244 (2%) vs. 2/217 (1%) by reader1 and 6/245 (2%) vs. 4/214 (2%) by reader2. Overall averaged IQ per-patient in the sequential and spiral group showed equally good (1.27±0.19 vs. 1.25±0.22, Z=-0.834, P=0.404). The effective radiation dose of the sequential group reduced significantly compared with the spiral group (4.88±1.77 mSv vs. 10.20±3.64 mSv; t=-5.372, P=0.000). Conclusion Compared with retrospectively ECG-gated spiral scan, prospectively ECG-triggered sequential DSCT coronary angiography provides similarly diagnostically valuable images in patients with atrial fibrillation and significantly reduces radiation dose.

Features of Computed Tomography Perfusion of Mediastinal Lymphadenopathies:a Pathology-based Retrospective Study

Objective To explore the features of various mediastinal lymphadenopathies using computed tomography perfusion(CTP).Methods CTP parameters(CTPs) of the selected mediastinal nodes from 59 patients with pathology-proven malignant lymph nodes and of those from 29 patients with clinically diagnosed or pathology-proven inflammatory lymphadenopathies were collected.Patients were divided into subgroups by etiology and phase of primary disease,including different pathological malignant nodes and diverse inflammatory nodes.CTPs were defined as blood flow(BF),blood volume(BV),mean transit time(MTT),permeability(PMB),and time to peak(TTP).Differences of CTPs were compared between malignant and benign nodes,and among subgroups,respectively.Results In the mediastinum,no significant differences of CTPs were found between malignant and benign groups(all P>0.05),the same for subgroups of malignant nodes(all P>0.05).Acute lymphadenitis had higher BF and BV than chronic inflammatory,lymphoid tuberculosis,sarcoidosis and malignant nodes.The BF of malignant nodes was markedly slower than that of acute lymphadenitis(P=0.01),but faster than chronic inflammatory nodes(P=0.04) and sarcoidosis(P=0.03),with no significant difference compared with lymphoid tuberculosis.Pneumonia-complicated lymphoid tuberculosis showed the longest MTT while sarcoidosis displayed the shortest MTT,and inflammatory nodes,lymphoid tuberculosis without complicated pneumonia and malignant nodes had moderate MTT.Conclusion CTPs show promising potential in distinguishing various lymphadenopathies in the mediastinum,but more studies are needed to improve their specificity.

Comparison of Positron Emission Tomography Using 2-[^18F]-fluoro-2-deoxy-D-glucose and 3-deoxy-3-[^18F]-fluorothymidine in Lung Cancer Imaging

Background： The detection of solitary pulmonary nodules （SPNs） that may potentially develop into a malignant lesion is essential for early clinical interventions. However, grading classification based on computed tomography （CT） imaging results remains a significant challenge. The 2-[^18F]-fluoro-2-deoxy-D-glucose （^18F-FDG） positron emission tomography （PET）/CT imaging produces both false-positive and false-negative findings for the diagnosis of SPNs. In this study, we compared 18F-FDG and 3-deoxy-3-[^18F]-fluorothymidine （^18F-FLT） in lung cancer PET/CT imaging. Methods： The binding ratios of the two tracers to A549 lung cancer cells were calculated. The mouse lung cancer model was established （n = 12）, and micro-PET/CT analysis using the two tracers was performed. Images using the two tracers were collected from 55 lung cancer patients with SPNs. The correlation among the cell-tracer binding ratios, standardized uptake values （SUVs）, and Ki-67 proliferation marker expression were investigated. Results： The cell-tracer binding ratio for the A549 cells using the ^18F-FDG was greater than the ratio using 18F-FLT （P 〈 0.05）. The Ki-67 expression showed a significant positive correlation with the ^18F-FLT binding ratio （r = 0.824, P〈 0.01）. The tumor-to-nontumor uptake ratio of ^18F-FDG imaging in xenografts was higher than that of ^18F-FLT imaging. The diagnostic sensitivity, specificity, and the accuracy of ^18F-FDG for lung cancer were 89%, 67%, and 73%, respectively. Moreover, the diagnostic sensitivity, specificity, and the accuracy of ^18F-FLT for lung cancer were 71%, 79%, and 76%, respectively. There was an obvious positive correlation between the lung cancer Ki-67 expression and the mean maximum SUV of ^18F-FDG and ^18F-FLT （r = 0.658, P〈 0.05 and r = 0.724, P〈 0.01, respectively）. Conclusions： The ^18F-FDG uptake ratio is higher than that of ^18F-FLT in A549 cells at the cellular level.^18F-FLT imaging might be superior for the quantitative diagnosis of lung tumor tissue and could distinguish lung cancer nodules from other SPNs.

Magnetic Resonance Gd？RGD Imaging Study of Hepatocellular Carcinoma with High and Low Metastatic Potential before and after Human Bone Marrow？derived Mesenchymal Stem Cell Intervention

Background： Biotherapy based on human bone marrow-derived mesenchymal stem cells （BMSCs） is currently the focus of research, especially in the field of autologous stem cell transplantation. A novel type of metastasis-associated magnetic resonance （MR） molecular imaging probe was constructed, and the changes in metastasis and proliferation of hepatocellular carcinoma （HCC） before and after BMSC intervention were observed through MR imaging （MRI）. Methods：Metastasis-associatedMRmolecularimagingprobe,integrin αvβ3 ligandcRGD-PEG-DGL-DTPA-Gd （Gd-RGD）,wereconstructed. After human BMSC intervention was performed for 6weeks, tumor weight inhibition rates were calculated, and the RGD molecular probe was imaged through MRI with molecular imaging agent Gd-DTPAas control.The signal-to-noise ratio （SNR） and contrast-to-noise ratio （CNR） in the MRI experiment were used as semi-quantitative indicators. Polymerase chain reaction method was performed to detect proliferation- and metastasis-associated indicators, transforming growth factor β-1 （TGFβ1）, osteopontin （OPN）, and integrin subunit αv and β3. Results： The highest tumor weight inhibition rates were observed 3 weeks after the BMSC transplantation. The MR Gd-RGD in the HCC tissues after the BMSC intervention showed less enhancement than Gd-DTPA. The Gd-DTPAMRI of control group had higher SNR and CNR than Gd-RGD MRI in the experimental groups （P 〈 0.05）. For high metastatic potential hepatocellular carcinoma （MHCC97-H）, significant differenceswereobservedintheSNRsandCNRsofGd-RGDMRIbeforeandaftertheBMSCintervention（P〈0.05）.Forlowmetastaticpotential hepatocellular carcinoma （MHCC97-L）, the CNRs of Gd-RGD MRI were statistically different before and after BMSC intervention （P 〈 0.05）. With regard to MHCC97-H, OPN, β3, and TGFβ1 expression significantly decreased after BMSC intervention （P 〈 0.05）. In MHCC97-L and OPN, β3, TGFβ1, and αv expression after BMSC intervention decreased, and the difference was statistically significant （P 〈 0.05）. Conclusions： The CNR index of MRI is a good indicator for distinguishing high- and low-metastatic potential HCC tissues.After BMSC transplantation of MRI through the two kinds of tracer, the SNR and CNR indexes can distinguish two kinds of high and low metastatic potential HCC tissues, and Gd-RGD imaging is more suitable in distinguishing the metastatic potential changes through BMSC intervention.