Udo P. Schmiedl

Dynamic sequential MR imaging of focal liver lesions : initial experience in 22 patients at 1.5 T

The feasibility of dynamic sequential magnetic resonance (MR) imaging of focal hepatic lesions using Gd-diethylenetriamine pentaacetic acid (DTPA) was evaluated in this study. Three patients with hepatocellular carcinoma, 12 patients with metastases, and 7 patients with hemangiomas were studied with pre- and postcontrast multislice spin echo (SE) images using a repetition time of 500 ms and an echo time of 15 ms. The dynamic distribution phase of Gd-DTPA (0.1 mmol/kg) was investigated by using a sequential, transverse partial flip imaging sequence [fast low angle shot (FLASH)] before and after intravenous administration of Gd-DTPA. The lesion-liver contrast-to-noise ratio showed a great variability in patients with metastases and was significantly improved following administration of Gd-DTPA in patients with hemangiomas, two patients with hepatocellular carcinoma, and eight patients with metastases both on FLASH and SE images. Hemangiomas appeared darker than liver parenchyma on precontrast SE and FLASH images, increasingly enhanced over 5 min postinjection (pi) on FLASH images, and were still greatly enhanced at 10 min pi on SE images. During the dynamic sequential image acquisition the contrast enhancement of hemangiomas was significantly different from the enhancement observed in malignant lesions. The results of this study indicate the clinical potential of dynamic sequential imaging for the MR assessment of focal hepatic lesions.

CT blood pool enhancement in primates with lopromide-carrying liposomes containing soy phosphatidyl glycerol*

RATIONALE AND OBJECTIVES The purpose of this study was to determine the feasibility of using iodinated liposomes as blood pool agents for computed tomography (CT) in nonhuman primates. MATERIALS AND METHODS Five normal adult baboons (15-21 kg) were anesthetized and intravenously injected with iopromide containing soy phosphatidyl glycerol liposomes with a diameter of 195 nm. Each animal received a dose of 300 mg total iodine per kilogram (46% encapsulation). RESULTS The animals tolerated the injections well, experiencing no measurable electrocardiographic changes, and recovered uneventfully from anesthesia. Sequential helical CT scans of the baboons from the base of the skull to the symphysis pubis acquired up to 40 minutes after injection showed persistent blood pool enhancement. Maximum mean enhancement of major vascular structures was 106 HU at 1 minute after contrast medium injection. Mean blood pool enhancement was 76, 72, and 67 HU at 10, 20, and 40 minutes after injection, respectively. Liver and spleen were enhanced by 40 and 41 HU, respectively, 40 minutes after injection. No significant enhancement was measured in the brain and pancreas. CONCLUSION Soy phosphatidyl glycerol with iopromide liposomes produces prolonged vascular enhancement and has potential as a blood pool CT contrast agent in primates.

Preoperative evaluation of patients awaiting liver transplantation: Comparison of multiphasic contrast-enhanced 3D magnetic resonance to helical computed tomography examinations†

To determine the feasibility of using a multiphasic magnetic resonance (MR) examination to evaluate the hepatic arterial anatomy and parenchyma in patients awaiting orthotopic liver transplantation (OLT).

Assessment of fetal and placental blood flow in primates using contrast enhanced ultrasonography.

Ultrasonographic contrast agents that stay within the vascular space and do not cross the placenta may permit differentiation between the maternal and fetal portions of the placenta and may be clinically useful for diagnosis of placental abnormalities. This study was performed to assess the effects of Levovist (Schering AG, Berlin) on the placental circulation and to determine whether hemodynamic effects on the fetus occur. Ten studies were performed in five pregnant macaques (median weight, 9.15 kg; range, 6.15 to 11 kg; median gestational age, 121 days; range, 34 days to term) under anesthesia. Gray scale, color, and duplex Doppler sonographic scans of the fetus and placenta were acquired using a 5 MHz curved array transducer. Fetal heart rate, resistive index, and systolic‐diastolic ratios were measured in the fetal middle cerebral artery, aorta, umbilical artery, and uterine artery before and after administration of contrast agent. The following dose regimen was tested: 5 ml of physiologic saline solution followed by 0.1 ml/kg of 300 mg/ml Levovist (diagnostic dose), 0.5 ml/kg of 400 mg/ml Levovist (maximum dose), and 5 ml physiologic saline solution. The order of diagnostic dose and maximal dose was randomized among animals. Color enhancement of the basal portions of the placenta was documented after administration of contrast agent. Heart rate and middle cerebral artery systolic‐diastolic ratio did not change between baseline and injections. A 7% decrease of the resistive index from baseline to maximum dose was measured in the uterine artery (not significant). A 7.7% decrease in the systolic‐diastolic ratio from baseline to maximum dose was recorded in the umbilical artery. However, an identical change was measured after saline solution was injected. The resistive index in the aorta increased by 2.6% from baseline to maximum dose, a change that was not significant (P > 0.5). Ultrasonographic contrast enhancement of the maternal circulation in placenta is demonstrated to be without significant effects on the fetal circulation as measured in this limited population.

HEPATIC CONTRAST-ENHANCING PROPERTIES OF MANGANESE-MESOPORPHYRIN AND MANGANESE-TPPS4 : A COMPARATIVE MAGNETIC RESONANCE IMAGING STUDY IN RATS

OBJECTIVES.Manganese (III) mesoporphyrin (Mn–mesoporphyrin), a synthetic and stable complex, was investigated for its hepatic magnetic resonance imaging (MRI) properties and compared with manganese tetrakis–(4 sulfonatophenyl) porphyrin (Mn–TPPS4). METHODS.Liver abscesses (n = 10) and tumors (n = 14) were induced in rats. These rats then underwent MRI at 2.0 T. Animals received one of the two contrast agents, and measurement of lesion enhancement was performed. RESULTS.At an intravenous dose of 0.035 mmol/kg, Mn–mesoporphyrin caused significant enhancement of normal liver parenchyma and increased the lesion–to–liver contrast in both the models of heptic liver abscess and metastatic liver disease. Mn–TTPS4 at an intravenous dose of 0.04 mmol/kg typically enhanced both lesion and normal liver parenchyma and therefore did not improve the lesion–to–liver contrast. CONCLUSIONS.The hepatotrophic properties of Mnmesoporphyrin indicate its potential as an intravenous contrast agent for liver imaging

Computed tomography-guided neurolytic celiac plexus block with alcohol complicated by superior mesenteric venous thrombosis.

Neurolytic celiac plexus block (CPB) under radiological guidance is often performed to manage pain associated with pancreatic cancer. Serious complications related to the block are rare. Computed Tomography (CT)-guided neurolytic CPB is advocated to improve the efficacy of the block and to reduce the incidence of associated complications. We describe a case of superior mesenteric vein thrombosis associated with neurolytic CPB performed under CT guidance.

Primary Placement of Palmaz Long Medium Stents in Transjugular Intrahepatic Portosystemic Shunts

PURPOSE To describe our results with primary placement of the long-medium Palmaz stent for transjugular intrahepatic portosystemic shunts (TIPS). MATERIALS AND METHODS Between December 1997 and December 1998 primary placement of long-medium Palmaz stents was performed for TIPS procedures in 17 patients. Patency was determined with ultrasound, angiography, or pathologic examination in the event of transplant. RESULTS Primary patency was achieved in 13 of 17 patients (76.5%) (follow up, 1-399 days; mean, 99 days). Secondary patency was achieved in 17 of 17 patients (100%) (follow-up, 1-399 days; mean, 110 days). Among the four patients who required revision, the mean time to revision from initial shunt creation was 81 days (range, 13-125 days). Two of these four patients had symptoms of worsening ascites as well as abnormal ultrasound findings prior to their revision; the other two patients were asymptomatic and had abnormal ultrasound findings only. Revisions were performed for intimal hyperplasia within the stent in three of the patients and acute thrombus within the stent in the remaining patient. Kaplan-Meier survival analysis for primary patency yielded mean survival time of 265 days (standard error, 52 days). CONCLUSION The long-medium Palmaz stent is a viable stent for creation of TIPS shunts.

CT angiography of the visceral vessels

CT angiography (CTA) is a promising new technique for vascular imaging. This review focuses first on the technique necessary for successful scanning of the visceral vessels. As in many new modalities, there are different protocols for scanning and rendering of images. The relative strengths and weaknesses of these different approaches are discussed. A discussion of the applications of CTA to depict normal and abnormal anatomy of the visceral vessels follows. These applications include celiac stenosis, splenic artery aneurysms, evaluation for hepatic arterial anatomy before liver transplantation, visceral arterial anatomy in pancreaticoduodenal surgery, the superior mesenteric artery in intestinal ischemia, vascular encasement in patients with pancreatic neoplasms, and, finally, the hepatic vessels before hepatic tumor resection.

Methods and compositions for the enteral administration of hepatobiliary MRI contrast agents

Hepatobiliary magnetic resonance imaging of a human or animal subject is enhanced by enterally administering to the subject an effective amount of a lipophilic contrast enhancing agent. Representative contrast enhancing agents include manganese mesoporphyrin, manganese deuteroporphyrin, manganese pheophorbide and manganese pyrophenophoribide, and, when administered orally, an enteric delivery agent.

Time-of-flight MR angiography with Gd-DTPA hexamethylene diamine co-polymer blood pool contrast agent: comparison of enhanced MRA and conventional angiography for arterial stenosis induced in rabbits.

Vascular stenoses were induced in the external iliac arteries of New Zealand white rabbits by a combination of hypercholesterolemic diet and repeat balloon injury. Two‐dimensional (2D) and three‐dimensional (3D) time‐of‐flight (TOF) magnetic resonance angiography (MRA) was performed with a specifically designed phased array coil in a 1.5 T system. Enhancement with gadolinium‐diethylene triamine pentaacetic acid (Gd‐DTPA) hexamethylene diamine co‐polymer (Nycomed: NC 22181), a blood pool MR contrast agent, was measured after contrast administration and compared with pre‐contrast images at the same levels. Vessel diameter measurements were obtained at multiple levels and compared with comparable levels on conventional angiograms of the same animals. Stable enhancement, averaging 227% above baseline, was observed with the 3D TOF MRA over the 40 minutes of this study. Enhancement was not observed with the 2D TOF technique. Measurement of the smallest vessels in this study with 3D TOF MRA was slightly improved following contrast enhancement, although both pre‐ and post‐contrast diameter measurements tended to underestimate the assumed true vessel diameter. Thus, Gd‐DTPA hexamethylene diamine co‐polymer (Nycomed: NC 22181), a blood pool MR contrast agent, produces significant, stable enhancement with the 3D TOF technique and may improve MRA measurement of small vessels. J. Magn. Reson. Imaging 2000;11:638–646.