Xiao Hua Huang

Abdominal MRI at 3.0 T: LAVA-Flex compared with conventional fat suppression T1-weighted images.

To study liver imaging with volume acceleration‐flexible (LAVA‐Flex) for abdominal magnetic resonance imaging (MRI) at 3.0 T and compare the image quality of abdominal organs between LAVA‐Flex and fast spoiled gradient‐recalled (FSPGR) T1‐weighted imaging.

GRE T2-Weighted MRI: Principles and Clinical Applications

The sequence of a multiecho gradient recalled echo (GRE) T2*-weighted imaging (T2*WI) is a relatively new magnetic resonance imaging (MRI) technique. In contrast to T2 relaxation, which acquires a spin echo signal, T2* relaxation acquires a gradient echo signal. The sequence of a GRE T2*WI requires high uniformity of the magnetic field. GRE T2*WI can detect the smallest changes in uniformity in the magnetic field and can improve the rate of small lesion detection. In addition, the T2* value can indirectly reflect changes in tissue biochemical components. Moreover, it can be used for the early diagnosis and quantitative diagnosis of some diseases. This paper reviews the principles and clinical applications as well as the advantages and disadvantages of GRE T2*WI.

Renal and perirenal space involvement in acute pancreatitis: An MRI study

OBJECTIVES To study the prevalence and characteristics of renal and perirenal space involvement and its relation to the severity of acute pancreatitis (AP) using MRI. METHODS 115 patients with AP who underwent MRI with the clinical kidney function test were retrospectively analyzed in this study. MRI sequences included conventional and diffusion weighted imaging (DWI) sequences. The renal and perirenal space involvement in AP was noted on MRI. The renal apparent diffusion coefficient (ADC) on DWI was measured for each kidney. The severity of AP on MRI was graded using MR severity index (MRSI). The relationships among the renal and perirenal space involvement on MRI, the renal ADC, MRSI and the results of the kidney function test were analyzed. RESULTS In the 115 patients with AP, the renal and perirenal space abnormalities detected included renal parenchymal abnormalities (0.8%), abnormalities of the renal collecting system (2.6%), renal vascular abnormalities (1.7%), thickened renal fascia (99%), perirenal stranding (62%) and perirenal fluid collection (40%). The prevalence of perirenal space abnormalities was correlated with the severity of AP based on MRSI (P<0.05). The renal ADC values were lower in patients with abnormal kidney function than in those without kidney injury (P<0.05). The prevalence of kidney function abnormalities was 9.4%, 32% and 100% in mild, moderate, and severe AP cases, respectively (P=0.00). CONCLUSION Perirenal space involvement is much more than renal parenchymal involvement in AP. The prevalence of perirenal space involvement in AP on MRI has a positive correlation with the severity of AP according to MRSI.

Common bile duct diameter in an asymptomatic population: A magnetic resonance imaging study

AIM To measure the common bile duct (CBD) diameter by magnetic resonance cholangiopancreatography (MRCP) in a large asymptomatic population and analyze its some affecting factors. METHODS This study included 862 asymptomatic subjects who underwent MRCP. The CBD diameter was measured at its widest visible portion on regular end-expiration MRCP for all subjects. Among these 862 subjects, 221 volunteers also underwent end-inspiration MRCP to study the effect of respiration on the CBD diameter. The age, sex, respiration, body length, body weight, body mass index (BMI), portal vein diameter (PVD), length of the extrahepatic duct and CBD, cystic junction radial orientation and location were recorded. The subjects were divided into 7 groups according to age. All of the above factors were compared with the CBD diameter on end-expiration MRCP. RESULTS Among the 862 subjects, the CBD diameter was 4.13 ± 1.11 mm (range, 1.76-9.45 mm) and was correlated with age (r = 0.484; P < 0.05), with a dilation of 0.033 mm per year. The upper limit of the 95% reference range was 5.95 mm, resulting in a reasonable upper limit of 6 mm for the asymptomatic population. Respiration and other factors, including sex, body length, body weight, BMI, PVD, length of the extrahepatic duct and CBD, cystic junction radial orientation and location, were not related to the CBD diameter. CONCLUSION We established a reference range for the CBD diameter on MRCP for an asymptomatic population. The CBD diameter is correlated with age. Respiration did not affect the non-dilated CBD diameter.

Pancreatic Duct Patterns in Acute Pancreatitis: A MRI Study

Objectives To study the MRI findings of the pancreatic duct in patients with acute pancreatitis. Materials and Methods A total of 239 patients with acute pancreatitis and 125 controls were analyzed in this study. The severity of acute pancreatitis was graded using the MR severity index (MRSI) and the Acute Physiology And Chronic Healthy Evaluation II(APACHE II) scoring systems. The number of main pancreatic duct (MPD) segments visualized, and both MPD diameter and pancreatic duct disruption were noted and compared with the severity of acute pancreatitis. Results The frequency of MPD segment visualization in the control group was higher than that in the acute pancreatitis group (p<0.05). The number of MPD segments visualized was negatively correlated with the MRSI score (p<0.05) and the APACHE II score (p<0.05). There was no difference in the MPD diameter between the acute pancreatitis and control groups or among the patients with different severities of acute pancreatitis (p>0.05). The prevalence of pancreatic duct disruption was 7.9% in the acute pancreatitis group. The prevalences of pancreatic duct disruption were 4.8% and 15.3% in the mild and severe acute pancreatitis groups based on the APACHE II score, respectively, and were 0%, 5.7% and 43.5% in the mild, moderate and severe acute pancreatitis groups according the MRSI score, respectively. The prevalence of pancreatic duct disruption was correlated with the severity of acute pancreatitis based on the APACHE II score (p<0.05) and MRSI score (p<0.05). Conclusion The pancreatic duct in acute pancreatitis patients was of normal diameter. The number of MPD segments visualized and visible pancreatic duct disruption on MRI may be supplementary indicators for determining the severity of acute pancreatitis.

Various diffusion magnetic resonance imaging techniques for pancreatic cancer.

Pancreatic cancer is one of the most common malignant tumors and remains a treatment-refractory cancer with a poor prognosis. Currently, the diagnosis of pancreatic neoplasm depends mainly on imaging and which methods are conducive to detecting small lesions. Compared to the other techniques, magnetic resonance imaging (MRI) has irreplaceable advantages and can provide valuable information unattainable with other noninvasive or minimally invasive imaging techniques. Advances in MR hardware and pulse sequence design have particularly improved the quality and robustness of MRI of the pancreas. Diffusion MR imaging serves as one of the common functional MRI techniques and is the only technique that can be used to reflect the diffusion movement of water molecules in vivo. It is generally known that diffusion properties depend on the characterization of intrinsic features of tissue microdynamics and microstructure. With the improvement of the diffusion models, diffusion MR imaging techniques are increasingly varied, from the simplest and most commonly used technique to the more complex. In this review, the various diffusion MRI techniques for pancreatic cancer are discussed, including conventional diffusion weighted imaging (DWI), multi-b DWI based on intra-voxel incoherent motion theory, diffusion tensor imaging and diffusion kurtosis imaging. The principles, main parameters, advantages and limitations of these techniques, as well as future directions for pancreatic diffusion imaging are also discussed.

Gallbladder Patterns in Acute Pancreatitis: An MRI Study

RATIONALE AND OBJECTIVES The aim of this study was to assess the gallbladder patterns on magnetic resonance imaging (MRI) associated with acute pancreatitis (AP). MATERIALS AND METHODS There were 197 patients with AP, all of whom had undergone abdominal MRI. AP was categorized as either edematous or necrotizing according to its findings on MRI and graded as mild (0-3 points), moderate (4-6 points), or severe (7-10 points) according to the magnetic resonance severity index. The changes to the walls and dimensions of the gallbladder and common bile duct, in addition to the presence of biliary stones and pericholecystic fluid, were noted and compared with the severity of AP on the basis of the magnetic resonance severity index. RESULTS Of the 197 patients with AP, 81% were classified as edematous and 19% as necrotizing on MRI. There were 35%, 59%, and 6% of patients with mild, moderate, and severe AP according to the magnetic resonance severity index, respectively. Seventy-six percent of patients had at least one gallbladder abnormality on MRI, including a thickened gallbladder wall (42%), pericholecystic fluid (38%), gallbladder stones (35%), an enlarged gallbladder (24%), dilatation of the common bile duct (16%), and subserosal edema (15%). Eighty-nine percent of patients (34 of 38) with necrotizing AP had gallbladder abnormalities, which was significantly higher than the 72% of patients (115 of 159) with edematous AP (P < .05). The prevalence of gallbladder abnormalities was 64% in patients with mild AP, 81% in those with moderate AP, and 91% in those with severe AP (P < .05 among the three groups). CONCLUSIONS Most patients with AP have gallbladder abnormalities on MRI, including a thickened gallbladder wall and pericholecystic fluid. The prevalence of gallbladder abnormalities has a positive correlation with the severity of AP on MRI.

The Features of Extrahepatic Collateral Arteries Related to Hepatic Artery Occlusion and Benefits in the Transarterial Management of Liver Tumors

Purpose. To investigate the extrahepatic collateral arteries related to hepatic artery occlusion (HAO) and to determine its benefits in the transarterial management of liver tumors. Methods and Findings. Eleven patients (7 hepatocellular carcinomas, 3 liver metastases, and 1 with hemangioma) with HAO confirmed with digital subtraction angiography (DSA) were admitted to our hospital. Of the 11 patients, 7 were men and 4 were women, with an average age of 41.5 ± 15.5 years (range: 29 to 70 years). DSA was performed to evaluate the collateral routes to the liver. In the 11 patients with HAO, DSA showed complete occlusion of the common hepatic artery in 9 patients and the proper hepatic artery (PHA) in 2 patients. Extrahepatic collateral arteries supplying the liver were readily evident. The collateral arteries originated from the superior mesenteric artery (SMA) in 8 patients, from the gastroduodenal artery in 2 patients, and from the left gastric artery (LGA) in 1 patient. Transcatheter treatment was successfully performed via the collateral artery in all patients except the one who had hemangioma. Conclusions. DSA is an effective method for detecting collateral circulation related to HAO and may provide information to guide transcatheter management decisions.

MR imaging of acute pancreatitis: Correlation of abdominal wall edema with severity scores

OBJECTIVE To study MRI findings of abdominal wall edema (AWE) in acute pancreatitis as well as correlations between AWE and the severity of acute pancreatitis according to the MR severity index (MRSI) and the Acute Physiology And Chronic Healthy Evaluation III (APACHE III) scoring system. MATERIALS AND METHODS A total of 160 patients with AP admitted to our institution between December 2009 and March 2011 were included in this study. MRI was performed within 48 h after admission. MRI findings of acute pancreatitis were noted, including AWE on the MRI. The abdominal wall area was divided into quarters, and each area involved was recorded as 1 point to score the severity of AWE. The severity of acute pancreatitis was studied using both the MRSI and the APACHE III scoring system. Spearman correlation of AWE with the MRSI and the APACHE III scoring system was analyzed. RESULTS In 160 patients with acute pancreatitis, 53.8% had AWE on MRI. The average AWE score was 1.2±1.4 points. The prevalence of AWE was 30.5%, 64.5% and 100% in mild, moderate and severe AP, respectively, according to MRSI. AWE on MRI was correlated with MRSI scores (r=0.441, p=0.000). According to APACHE III scores, the averages were 2.0±1.1 and 2.6±1.1 points in mild AP and severe AP, respectively (P=0.016). AWE was slightly correlated with the APACHE III scores (r=0.222, p=0.005). CONCLUSION AWE on MRI in acute pancreatitis is common, which may be a supplementary indicator in determining the severity of AP.

Acute pancreatitis with gradient echo T2*-weighted magnetic resonance imaging.

BACKGROUND To study gradient recalled echo (GRE) T2*-weighted imaging (T2*WI) for normal pancreas and acute pancreatitis (AP). METHODS Fifty-one patients without any pancreatic disorders (control group) and 117 patients with AP were recruited. T2* values derived from T2*WI of the pancreas were measured for the two groups. The severity of AP was graded by the magnetic resonance severity index (MRSI) and the Acute Physiology and Chronic Healthy Evaluation II (APACHE II) scoring system. Logistic regression was used to analyze the relationship between the T2* values and AP severity. The usefulness of the T2* value for diagnosing AP and the relationship between the T2* values and the severity of AP were analyzed. RESULTS On GRE-T2*WI, the normal pancreas showed a well-marinated and consistently homogeneous isointensity. Edematous AP, as well as the non-necrotic area in necrotizing AP, showed ill-defined but homogeneous signal intensity. AP with pancreatic hemorrhage showed a decreased T2* value and a signal loss on the signal decay curve. The T2* value of pancreas in the AP group was higher than that of the control group (t=-8.20, P<0.05). The T2* value tended to increase along with the increase in MRSI scores but not with the APACHE II scores (P>0.05). AP was associated with a one standard deviation increment in the T2* value (OR =1.37; 95% CI: 1.216-1.532). CONCLUSIONS T2*WI demonstrates a few characteristics of the normal pancreas and AP, which could potentially be helpful for detecting hemorrhage, and contributes to diagnosing AP and its severity.