Evaluation of intraportal venous flow distribution by unenhanced MR angiography using three‐dimensional fast spin‐echo with a selective tagging pulse: Efficacy of subtraction of tag‐on and tag‐off images acquired during a single breath‐hold

Purpose

To evaluate the efficacy of subtracted MR images from two sets of unenhanced three‐dimensional (3D) MR angiography data (tag‐on and tag‐off images) acquired simultaneously during a single breath‐hold in assessing the intraportal venous flow distribution to the distal branches from the superior mesenteric vein (SMV) and the splenic vein (SpV).

Materials and Methods

Tag‐on and tag‐off MR images during a single breath‐hold were obtained in 25 normal subjects. Tagging pulse was placed on the SMV or SpV separately to study inflow correlation of tagged blood into the portal vein.

Results

On the MR images tagged on the SMV, the mean ratings of visibility of tagged blood flow on the subtracted images were significantly higher (P = 0.016–0.0001) than those on the source images in almost all branches except second‐ordered left portal vein (P = 0.096). On the subtracted MR images tagged on SMV, the tramline (16 of the 25 subjects) was the most common distribution pattern of the tagged blood inflow in the main portal vein.

Conclusion

Subtracted MR images from two sets of unenhanced 3D MR angiography data (tag‐on and tag‐off images) acquired simultaneously would be effective to show the blood flow distribution of tagged blood into the portal vein and distal branches from SMV and SpV under the physiological condition without contrast injections. J. Magn. Reson. Imaging 2009;29:1224–1229. © 2009 Wiley‐Liss, Inc.     

Evaluation of MR/fluoroscopy-guided portosystemic shunt creation in a swine model

PURPOSE: To evaluate three different percutaneous portosystemic shunts created with magnetic resonance (MR) imaging and fluoroscopy guidance in a swine model. MATERIALS AND METHODS: In stage 1 of the experiment, an active MR intravascular needle system was created for needle tracking and extracaval punctures. Twenty inferior vena cava (IVC)/superior mesenteric vein (SMV)/portal vein (PV) punctures were performed in 10 swine (weight, 40-45 kg) in a 1.5-T short-bore interventional MR imager. With use of a real-time MR imaging sequence, the needle was guided through the IVC and into the SMV or PV (N = 20 punctures). After confirmation, a wire was advanced into the portal venous system under MR imaging guidance (N = 20). In stage 2, animals were transferred to the radiographic fluoroscopy suite for deployment of shunts. Three different shunts were evaluated in this study: (i) a commercial stent-graft, (ii) a prototype bridging stent, and (iii) a prototype nitinol vascular anastomotic device. Postprocedural necropsy was performed in all animals. RESULTS: Successful MR-guided IVC/SMV punctures were performed in all 20 procedures (100%). All three shunts were deployed. Stent-grafts had the poorest mechanism for securing a shunt. The vascular anastomotic device and the bridging stent had more secure anchoring mechanisms but also had higher technical failure rates (50% and 40%, respectively). When deployed successfully, the vascular anastomotic device resulted in no bleeding at the sites of punctures at necropsy. CONCLUSION: Percutaneous shunts and vascular anastomoses between the portal mesenteric venous system and IVC were successfully created with use of a combination of MR imaging and conventional fluoroscopy for guidance.     

MR venography of the inferior mesentery vein

OBJECTIVE: To evaluate on three-dimensional (3D) dynamic contrast-enhanced (DCE) MR venography (MRV), the visibility of the inferior mesenteric vein (IMV), its insertion pattern into the portal system, and the difference of IMV diameters between healthy subjects and patients with cirrhosis. MATERIALS AND METHODS: Two hundred and seventeen consecutive patients who had abdominal 3D DCE MRI was included in this study. The original image data of 3D DCE MRI was used to generate multiple planar volume reconstruction (MPVR) images, which were evaluated for visualization of the IMV and its pattern of insertion into the portal system. The diameter of IMV was measured and compared in 24 patients with cirrhosis (Cirrhosis Group) and in 30 patients without hepatic lesions or liver disease (Healthy Group). RESULTS: In the 217 patients, the frequencies of visualization of IMV, grade 1 order branches and grade 2 order branches were, respectively, 88%, 24% and 9%. The IMV inserted into the splenic vein (SV), the portal confluence and the superior mesenteric vein (SMV) in 45%, 18% and 37%, respectively. Among patients with cirrhosis, 12.5% had IMV diameter larger than 5.1mm, although there was no significant difference between cirrhosis and healthy groups (P>0.05). However, the diameters of the main portal vein (MPV), SV and SMV were significantly larger in the Cirrhosis Group (P<0.05). CONCLUSION: The IMV and its branches can be depicted well by 3D DCE MRV. The most common insertion of the IMV is into the splenic vein. A minority of patients with cirrhosis had dilatation of the IMV.     

Pre- and postprandial alterations of portal venous flow: evaluation with single breath-hold three-dimensional half-Fourier fast spin-echo MR imaging and a selective inversion recovery tagging pulse

PURPOSE: To evaluate the influence of food intake on portal flow using unenhanced magnetic resonance imaging (MRI). MATERIALS AND METHODS: The study population included 29 healthy subjects. A selective inversion recovery tagging pulse was used on the superior mesenteric vein (SMV) and splenic vein (SpV) to study the correlation of tagged blood in the portal vein (PV). MRI was performed before and 60-90 min after a meal. RESULTS: The flow signal from the SMV increased in 97% of the subjects after the meal. Before the meal the portal flow was dominated by flow from the SpV in 59% of the subjects, while it was dominated by flow from the SMV in 76% of the subjects after the meal. The most common distribution pattern of the flow signal from the SpV before the meal was in the central part of the main PV (55%), while it was in the left side (45%) after the meal. The most common distribution pattern of the flow signal from the SMV was in the bilateral sides of the main PV both before and after the meal (62%). CONCLUSION: This technique shows potential for evaluating pre- and postprandial alterations of flow from the SpV and SMV in the PV under physiological conditions.     

Percutaneous CT-guided superior mesenteric vein access for portal vein recanalization-transjugular intrahepatic portosystemic shunt

Portal vein recanalization-transjugular intrahepatic portosystemic shunt (PVR-TIPS) is a valuable technique in the treatment cirrhosis and portal vein (PV) thrombosis. Only a few studies have reported cases of utilizing the transmesenteric approach in the procedure''s initial portal access. Here, we report the successful utilization of a CT-guided percutaneous puncture of the superior mesenteric vein (SMV) for PVR-TIPS in a patient with splenic vein thrombosis. A 54-year-old male with a history of morbid obesity (BMI: 44.67), hepatitis C, NASH cirrhosis, esophageal varices, and complete PV thrombosis presented for PVR-TIPS. An initial percutaneous transplenic approach was attempted, but was aborted due to the discovery of a splenic vein thrombosis. Subsequently, the patient was brought back into the hybrid-angio CT suite, and the SMV was accessed percutaneously with a 21-gauge needle under 4D CT-guidance. A 5-Fr micropuncture sheath was then placed. Additional portal venogram confirmed PV thrombosis. Right internal jugular vein (IJV) access was then obtained, and the right hepatic vein was catheterized. A loop snare was advanced from the SMV access into the right PV. A Colapinto needle was later positioned in the right hepatic vein, and the right PV was accessed using the loop snare as a target. A wire was then advanced and captured by the snare, and brought down through the PV. The tract was dilated with a 10 mm balloon, and a Viatorr stent was deployed. Balloon embolectomy of the SMV, splenomesenteric vein, and TIPS were then performed with a CODA balloon with improvement in flow through the TIPS on final portal venogram. Portosystemic gradient was 11 mmHg initially and 10 mmHg post-TIPS. Follow-up TIPS venogram in 3 weeks showed a widely patent TIPS. CT-guided percutaneous SMV access may serve as valuable technique in PVR-TIPS when traditional modes of initial portal access for recanalization are unobtainable.     

In vivo flow-independent T2 measurements of superior mesenteric vein blood in diagnosis of chronic mesenteric ischemia: a preliminary evaluation

RATIONALE AND OBJECTIVES: The authors attempted to determine whether the T2 relaxation time of superior mesenteric vein (SMV) blood would decrease in patients with chronic mesenteric ischemia after a meal. MATERIALS AND METHODS: Thirty-two patients without chronic mesenteric ischemia and eight patients with symptomatic chronic mesenteric ischemia underwent magnetic resonance (MR) imaging. All examinations were performed with a 1.5-T unit, a modified Carr-Purcell-Meiboom-Gill sequence, final section-selective pulse of 180 degrees, and spiral readout gradients. Measurements of SMV blood T2 were obtained after at least 6 hours of fasting and 15 and 35 minutes after ingestion of 240 mL of a liquid nutritional supplement. Maximal change of the SMV blood T2 was expressed as a percentage of the fasting T2 in all patients. RESULTS: In control patients, SMV blood T2 increased postprandially by 9.4% +/- 1.3 (95% confidence level; range, 6.8%-11.9%) (data range, -7.3% to 25.6%) compared with fasting T2. In symptomatic patients, SMV blood T2 decreased postprandially by 15.8% +/- 2.2 (95% confidence level; range, -20.1% to -10.7%) (data range, -7.9% to -25.3%). The difference between the two groups was statistically significant (P < .0001 by Student unpaired t test). CONCLUSION: Measurement of SMV blood T2 is a promising test for chronic mesenteric ischemia diagnosis. Therefore, conversion of T2 measurements to estimate oxygen saturation may not be necessary for all cases of this clinical indication.     

Portal and hepatic vein thrombosis in liver abscess: CT findings

OBJECTIVE: Our aim is to describe imaging findings of portal and hepatic vein thrombosis in pyogenic liver abscess on contrast-enhanced MDCT and to determine the incidence and evolving patterns on follow-up imaging. METHODS: Over a 5-year period, 67 patients with liver abscess underwent single-phase (n=30) or triphasic (n=37) contrast-enhanced CT. Images were reviewed for the presence of portal vein (PV) or hepatic vein (HV) thrombosis, regional parenchymal attenuation, and changes on follow-up CT. RESULTS: Venous thrombosis was seen in 28/67 patients (42%), involving PV in 16/67 (24%) and HV vein in 15/67 (22%); 3/67 (4%) had both PV and HV thrombosis. Thrombosis was seen as non-enhancing linear structures without expanding the lumen in all cases. Regional parenchymal attenuation during the portal-phase was hyperattenuating (10/16, 63%) or isoattenuating (6/16, 38%) in PV thrombosis, and mostly hypoattenuating (13/15, 87%) in HV thrombosis (P<.001). Of 27 patients with follow-up contrast-enhanced CT, venous thrombosis resolved in 10/27 (37%) within 6 months and persisted in 17/27 (63%) for 3-38 months, including 13 PV thrombosis and 4 HV thrombosis. Interval parenchymal atrophy was seen only in four all with persistent PV thrombosis. CONCLUSIONS: Both PV and HV thrombosis frequently occurs in liver abscess and is seen as non-enhancing linear structures without expanding the lumen on contrast-enhanced CT. Regional attenuation changes in hepatic vein thrombosis were often hypoattenuating whereas none with portal vein thrombosis showed hypoattenuation.     

门静脉高压CT征象与肝纤维化、肝硬化病理分期关系的探讨

目的 探讨肝纤维化、肝硬化门静脉高压的CT征象与病理分期的关系.方法 对经肝穿刺病理活检确诊的肝纤维化S1期12例、S2期14例、S3期9例、S4期13例、典型肝硬化16例以及20例对照组行16层螺旋CT上腹部3期增强容积扫描,于门静脉期最大密度投影(MIP)图像上分别测量门静脉左支、门静脉右支、门静脉主干(MPV)、脾静脉(SV)和肠系膜上静脉(SMV)的管径,并观察各组门静脉侧支循环开放情况及有无腹水和脾脏肿大,将上述指标与病理分期作对照研究.门静脉系统各血管管径的比较采用单因素方差分析,组间两两比较用SNK法;多组腹水及侧支循环发生率的比较采用R×C表x2检验,组间行x2分割计算;运用Logistic回归分析探讨门静脉系统中对肝纤维化病理分期影响最大的血管.结果 对照组门静脉左支、门静脉右支、MPV、SV和SMV的管径分别为(0.98 ±0.11)、(1.00±0.12)、(1.33±0.11)、(0.75±0.10)和(1.07±0.12)cm,脾脏体积为(128.55±30.56)cm<'3>,无侧支循环开放和腹水.S1、S2、S3期组、S4期组或早期肝硬化组、典型肝硬化组SV管径逐渐增大,分别为(0.86±0.12)、(0.96±0.11)、(1.07±0.08)、(1.09±0.10)和(1.18±0.19)cm,各组与对照组间比较,差异均有统计学意义(P<0.05),重度肝纤维化(S3期组和S4期组)、典型肝硬化以及轻度肝纤维化(S1期组和S2期组)间差异均有统计学意义(P<0.05).Logistic回归分析显示,在门静脉各血管测量指标中,SV的标准化回归系数最大(2.719),且差异有统计学意义(P<0.01).典型肝硬化的侧支循环开放及腹水发生率明显高于正常肝脏和肝纤维化各期,S4期的侧支循环出现率明显高于对照组、S1期组及S2期组.结论 当慢性肝病发展至重度肝纤维化或早期肝硬化时,CT检查有助于早期诊断.     

CT criteria for venous invasion in patients with pancreatic head carcinoma

The purpose of the study was to evaluate CT criteria for venous invasion in patients with potentially resectable carcinoma of the pancreatic head, with surgical and histopathological correlation. In 113 patients evaluated with spiral CT for suspected pancreatic head carcinoma, several CT criteria for venous invasion were scored prospectively for the portal vein (PV) and the superior mesenteric vein (SMV): length of tumour contact with PV/SMV (0 mm, < 5 mm, > 5 mm); circumferential involvement of the vein (0 degree, 0-90 degrees, 90-180 degrees, > 180 degrees); degree of stenosis; irregularity of the vessel margin; and tumour convexity towards vessel. 65 patients underwent surgery. Pancreatic head carcinoma was proven and pathology of the vascular margin was obtained in 50 of these patients. CT findings for single and combined criteria were correlated with pathology in these 50 patients, 30 of whom showed venous ingrowth. Invasion was found in all cases with SMV narrowing (n = 7), PV contour involvement > 90 degrees (n = 6), PV narrowing (n = 5) and PV wall irregularity (n = 3). The vascular ingrowth rate was 88% (15/17) for tumour concavity towards the PV or SMV. Poor predictors of ingrowth were length of tumour contact with PV > 5 mm (78% ingrowth, 14/18) and contour involvement of the SMV > 90 degrees (83% ingrowth, 10/12). Absence of vascular ingrowth could not be predicted in 100%. In conclusion, CT criteria can predict a high risk of invasion in potentially resectable tumours. Narrowing of the SMV and the PV seems the most reliable criterion, as well as circumferential involvement of the PV > 90 degrees. The best combination of criteria was tumour concavity with circumferential involvement > 90 degrees (sensitivity 60% and positive predictive value 90%).     

MR angiography and dynamic flow evaluation of the portal venous system

We studied the value of MR angiographic techniques in imaging the portal venous system. Projection angiograms were created by postprocessing a series of two-dimensional, flow-compensated gradient-echo images. Flow velocity was determined by a bolus-tracking method with radiofrequency tagging and multiple data readout periods. Each image was acquired during a breath-hold. MR angiography was applied to six normal subjects and four patients with abnormal hemodynamics in the portal venous system. Flow velocity determined by MR was correlated with the results of duplex sonography. The main portal vein and intrahepatic branches were shown in all cases. Portosystemic collaterals were identified in all patients with portal hypertension. In normal subjects, peak flow velocities (17.9 +/- 2.8 cm/sec) on MR correlated well with values determined by duplex sonography (17.5 +/- 2.2 cm/sec) (r = .846, p less than .04). Reversed portal blood flow was shown in two patients. One patient with portal vein thrombosis had no evidence of flow by MR angiography. Our results indicate that MR angiography can provide a three-dimensional display of normal and abnormal vascular anatomy as well as functional information in the portal venous system.     

磁共振THRIVE序列三维血管成像肝门静脉变异研究

目的 应用肝"一站式"检查的THRIVE序列采集并重建肝门静脉图像,分析肝门静脉变异.方法 收集648例应用THRIVE序列采集并重建的肝门静脉三维图像,分析肝门静脉解剖变异,并分别测量肝门静脉主干(MPV)、脾静脉(SV)、肠系膜上静脉(SMV)及肠系膜下静脉(IMV)的管径.结果 (1)肝门静脉的肝内变异:正常型79.2%(514/648)、Ⅰ型变异8.3%(54/648)、Ⅱ型变异9.0%(58/648)、Ⅲ型变异3.4%(22/648);(2)肝门静脉的肝外变异:Ⅰ型37.4%(167/447)、Ⅱ型20.4%(91/447)、Ⅲ型36.2%(162/447)、其他6.0%(27/447);(3)管径测量:MPV(14.03±2.44) mm、SV(9.51±2.40) mm、SMV(11.14±1.99) mm、IMV(6.01±0.78) mm.结论 肝"一站式"检查中,应用THRIVE序列采集、重建的血管图像,分析肝门静脉变异是可行的.     

Observation of portal circulation through superior mesenteric vein by enteric coated capsule of thallium-201

A new method of oral administration of an enteric coated capsule of 201Tl (201Tl-capsule) was developed to evaluate the portal circulation through the superior mesenteric vein (SMV). The 201Tl-capsule was not collapsed in the artificial gastric juice, whereas it melted soon after soaking in the artificial intestinal juice. In a clinical trial of 42 cases, 201Tl was satisfactory released in the duodenum in 36 cases where clear liver images were observed except in 1 patient. Heart to liver ratio (H/L) at 60 or 90 min after duodenal release of 201Tl was 0.32 +/- 0.07 (mean +/- 1 s.d.) in normal controls, 0.34 +/- 0.12 in chronic hepatitis, 0.31 +/- 0.12 in acute hepatitis, 0.45 +/- 0.13 in liver cirrhosis and 0.48 +/- 0.32 in cirrhosis with hepatocellular carcinoma. In 11 patients who had both oral and rectal studies with 201Tl, 7 showed a high H/L ratio of more than 0.8 in the rectal study but only 1 showed a similarly high ratio of 1.07 in the oral study. In the group of varied liver disorders we have studied so far, it was found that most of the SMV blood flowed into the liver and the degree of portal systemic shunting (PSS) from the SMV was much smaller compared to that from the inferior mesenteric vein. The present study with oral administration of the 201Tl-capsule was of value in understanding portal circulation through the SMV, however, this technique seemed of limited usefulness for evaluating overall pathologic PSS.     

Right hemidiaphragmatic mobility: assessment with US measurement of craniocaudal displacement of left branches of portal vein

PURPOSE: To evaluate the correlation and agreement between ultrasonographic (US) measurement of craniocaudal displacement of the left intrahepatic branches of the portal vein and radiographic measurement of right hemidiaphragmatic mobility. MATERIALS AND METHODS: Fifty-one patients with indications for abdominal angiography or percutaneous cholangiography prospectively underwent radiographic evaluation of right hemidiaphragmatic mobility and B-mode US measurement of craniocaudal displacement of the left intrahepatic branches of the portal vein. US was performed by using a 3.5-MHz convex transducer in a right subcostal position with a longitudinal orientation. Statistical analyses were performed by using linear regression, paired Student t test, and Bland-Altman analyses. RESULTS: The correlation between the US and radiographic measurements was found to be linear: hemidiaphragmatic mobility = (-1.562 + 1.032) x portal vein branch displacement (r = 0.651, P <.001). The mean craniocaudal displacement of the intrahepatic branches of the portal vein measured at US was 35.2 mm +/- 10.7 (SD). The mean right hemidiaphragmatic mobility measured at radiography was 34.8 mm +/- 17.0. The mean difference between the two measurements was not statistically significant (0.4 mm +/- 12.9, P =.807). CONCLUSION: US measurement of craniocaudal displacement of the left intrahepatic branches of the portal vein can be used for indirect assessment of right hemidiaphragmatic mobility.     

经颈静脉肝穿刺门静脉途径门静脉及肠系膜上静脉血栓溶栓治疗6例报告

目的 评价经颈静脉经肝穿刺门静脉(TIPSS)途径门静脉及肠系膜上静脉血栓溶栓治疗的安全性和治疗效果。方法 对6例诊断为门静脉(PV)和肠系膜静脉(SMV)广泛血栓形成的患者进行了经TIPSS途径介入溶栓治疗。患者主要症状有腹痛、腹胀、厌食等。腹部体检有压痛,均无明确腹肌紧张和反跳痛。经B超、增强CT检查和直接PV-SIV造影确诊为本病。溶栓方法：穿刺PV分支成功后插入导管做PV-SMV造影,确定诊断及了解栓塞范围,抽吸及捣碎血栓,间断将尿激酶经多侧孔导管注入PV和SMV清除大部分血栓后,保留多侧孔导管于SMV内持续溶栓3～13天。术后药物抗凝治疗6个月左右。此间,密切监测出凝血时间及影像学变化。结果 介入治疗后,大部分血栓被清除,PV和SMV有血流通过,腹痛、腹胀和腹泻症状逐步缓解。经留置于SMV的导管造影显示,PV和SMV主干及主要分支血流通畅,3例门静脉的肝内少数分支有残留血栓,但无明显症状。随访4个月至3年,除1例死于外科手术并发症外,其余5例患者健在,无血栓复发证据及上消化道出血发生。结论 经TIPSS途径介入溶栓治疗急性PV和SMV血栓形成是安全有效的,近期及中远期疗效均好。     

Doppler ultrasonography evaluation of paraumbilical vein and portal hypertension

Portal hypertension is associated to the development of portosystemic collateral veins, particularly the paraumbilical vein. PURPOSE: To evaluate the biometric and hemodynamic characteristics of the portal vessels related to the presence of a patent paraumbilical vein, in the setting of portal hypertension secondary to hepatosplenic schistosomiasis. METHODS: 75 patients with portal hypertension secondary to hepatosplenic schistosomiasis were evaluated by Doppler US. The patients were studied based on the presence (group B) or not (Group A) of a patent paraumbilical vein. The diameter and blood flow velocity of the portal vessels and of the paraumbilical vein were recorded. RESULTS: The paraumbilical vein was detected in 17.33% of patients. The results showed an increase of the diameter of the main and left portal vessels whenever a patent paraumbilical vein was present (portal vein: A = 1.14 +/- 0.29 cm/B = 1.33 +/- 0.16 cm; left branch: A = 0.95 +/- 0.25 cm/B = 1.30 +/- 0.24 cm). The mean blood flow velocity was also increased in the portal trunk (A = 15.96 +/- 6.17 cm/sec/B = 19.82 +/- 6.26 cm/sec) and in the left portal branch (A = 14.77 +/- 4.29 cm/sec/B = 19.92 +/- 6.88 cm/sec). CONCLUSION: The presence of a patent paraumbilical vein is related to significant biometric and hemodynamic variations in the portal venous system, in the setting of portal hypertension secondary to hepatosplenic schistosomiasis.     

经颈静脉肝内门体内支架分流术中经下腔静脉直接穿刺门静脉分支的可行性研究

目的：通过观察肝门部门静脉、肝实质与肝后段下腔静脉之间的解剖关系，探讨经颈静脉肝内门体内支架分流术（ＴＩＰＳＳ）中经下腔静脉直接穿刺门静脉分支的可行性。材料与方法：观察１０例新鲜人体尸检正常肝脏标本的肝后段下腔静脉与肝脏以及门静脉分歧部、门静脉左右主支与肝脏和肝后段下腔静脉间的解剖关系，并对１０％福尔马林固定后的标本做光镜下观察。结果：１０例标本中，肝后段下腔静脉的一部分通过肝尾状叶与门静脉分歧部相连。门静脉分歧部及左右主支均位于肝外。门脉分歧部与门脉左右主支的上壁、后上壁与肝实质连接紧密。光镜下见门静脉分歧部、门静脉左右主支与肝实质间存在致密结缔组织。结论：肝外门静脉分歧部、门静脉左右主支均可作为ＴＩＰＳＳ术中的安全穿刺点；经下腔静脉直接穿刺门静脉分支，在一些情况下，可以作为一种新的ＴＩＰＳＳ入路。     

Liver transplantation: MR angiography with surgical validation

Thirty patients (mean age, 45 years) were evaluated with magnetic resonance (MR) angiography before liver transplantation to assess the accuracy of MR angiography. A series of breath-hold, two-dimensional images were acquired and subsequently processed to form three-dimensional projection angiograms. Graphic information on blood flow in the portal vein was acquired by using presaturation bolus tracking. Correlative duplex ultrasound (US) was performed in 28 patients, and surgical or autopsy correlation was available in all cases. MR angiography demonstrated patency of the portal vein in 26 (96%) of 27 patients, made possible the diagnosis of portal venous occlusion in three of three patients, depicted reversed portal flow in one patient, and provided clear delineation of the extent of varices and specific portosystemic collateral vessels. When duplex US was successful, there was full agreement with MR angiographic results in assessing portal vein patency and flow direction. All of the MR findings were corroborated at surgical exploration or autopsy. The authors conclude that MR angiography is very accurate in the portal system and is valuable in preoperative assessment for liver transplantation.     

Portal venous system: evaluation with unenhanced MR angiography with a single-breath-hold ECG-synchronized 3D half-Fourier fast spin-echo sequence

OBJECTIVE: Eighteen healthy persons underwent unenhanced MR angiography with a breath-hold ECG-synchronized 3D half-Fourier fast spin-echo technique to evaluate the visibility of the portal vein and its branches. CONCLUSION: Our results indicated that unenhanced MR angiography with a singlebreath-hold ECG-synchronized 3D half-Fourier fast spin-echo sequence facilitates precise visualization of the anatomic features of the portal vein and its branches without the use of contrast agents.     

A comprehensive approach using MR imaging to diagnose acute segmental mesenteric ischemia in a porcine model.

OBJECTIVE: Acute mesenteric ischemia is a lethal disease that lacks a noninvasive diagnostic test. We evaluated the abilities of contrast-enhanced MR angiography, MR oximetry, and real-time interactive MR imaging to diagnose segmental mesenteric ischemia in a porcine model. MATERIALS AND METHODS: Segmental mesenteric ischemia was created by subselective Gelfoam embolization of the mesenteric circulation in eight pigs. Conventional digital subtraction angiography (DSA), MR oximetry, and real-time interactive MR imaging of the small bowel were performed before and after embolization. Changes in the perfusion pattern seen on DSA established the regions of true ischemia. Postembolization DSA and MR angiography were compared with this gold standard. RESULTS: Both MR angiography and DSA had high sensitivity (91% and 100%, respectively) for detecting ischemic regions. The difference was not statistically significant (p > .2). MR angiography yielded lower specificity than DSA (80% and 90%, respectively; p < .01). After embolization, the oxygen saturation in the superior mesenteric vein (SMV) dropped significantly (p < .005). After embolization, the SMV also showed oxygen saturation significantly lower than that in the inferior vena cava (p < .005). In two of the animals, segmental hypomotility of the small bowel was observed. CONCLUSION: MR oximetry is capable of detecting oxygen desaturation caused by segmental ischemia. A loss of oxygen saturation in the SMV relative to that in the inferior vena cava provides a convenient marker of mesenteric ischemia. Contrast-enhanced MR angiography has sensitivity and specificity approaching those of DSA. Both MR techniques hold promise for the detection of acute mesenteric ischemia.     

部分性脾动脉栓塞术前后脾动静脉及门静脉血液动力学变化定量研究

目的:定量研究脾脏动脉、静脉及门静脉在部分性脾动脉栓塞(PSE)术前后的血液动力学变化情况。方法:术前、术后即刻、术后1周分别测定脾脏动脉、静脉及门静脉血液动力学各项指标。结果:20例患者的脾动脉PSV、EDV、MV,脾静脉MV在PSE术后均显著降低(P<0.01);脾动、静脉血管截面积S术后显著减小(P<0.01);脾动静脉及门静脉血流量Q术后均显著降低(P<0.01)。术后1周PSV、EDV和MV、脾静脉S、血流量Q较术后即刻又有明显恢复(P<0.01);S/D、PI、RI术后显著增加;术后脾静脉血流量减少程度与脾脏栓塞程度成正相关,r=0.545(P<0.05);结论:PSE术能有效减少门静脉血流量,缓解门脉高压,从而降低上消化道大出血的风险。但门静脉的血流量减少程度与脾脏栓塞程度无相关性。