Contrast-enhanced MR imaging of the liver

Ultrasmall Mn-doped iron oxide nanoparticles with dual hepatobiliary and renal clearances for T1 MR liver imaging

Although magnetic nanoparticles demonstrate significant potential as magnetic resonance imaging (MRI) contrast agents, their negative contrasts, liver accumulation, and limited excretion hinder their application. Herein, we developed ultrasmall Mn-doped iron oxide nanoparticles (UMIOs) with distinct advantages as T1 MRI contrast agents. Exceptionally small particle sizes (ca. 2 nm) and magnetization values (5 emu gMn+Fe-1) of UMIOs provided optimal T1 contrast effects with an ideally low r2/r1 value of ∼1. Furthermore, the use of Mn as a dopant facilitated hepatocyte uptake of the particles, allowing liver imaging. In animal studies, UMIOs exhibited significantly enhanced contrasts for sequential T1 imaging of blood vessels and the liver, distinguishing them from conventional magnetic nanoparticles. UMIOs were systematically cleared via dual hepatobiliary and renal excretion pathways, highlighting their safety profile. These characteristics imply substantial potential of UMIOs as T1 contrast agents for the accurate diagnosis of liver diseases.

Study on the Anticancer Drug 5-Fluorouracil-Conjugated Polyaspartamide Containing Hepatocyte-Targeting Group

Anticancer conjugates of 5-fluorouracil (5-Fu) and polyaspartamide, containing pyridoxamine as the hepatocyte-targeting group, were synthesized and characterized. Their sustained release properties and biodistribution were evaluated. The 5-Fu was targeted to specific organs, such as the liver, and had a sustained in vitro release rate in PBS. In vitro cytotoxicity assay showed that the polymeric drugs exhibited low cytotoxicity to the human liver cells (L-02). These polymeric drugs possess high anticancer efficiencies and induced apoptosis in the human hepatic tumor cells (Bel-7204).

Evaluation of Dendritic Gadolinium Complexes as MRI Contrast Agents

A series of dendritic gadolinium complexes based on dendrimers with 1,4,7,10-tetraazacyclododecane as the core were synthesized. Both diethylenetriaminepentaacetic acid and pyridoxamine were incorporated to the amine groups on the surface to give the dendritic ligands. These dendritic ligands were then reacted with gadolinium chloride to yield the corresponding dendritic gadolinium complexes. The dendritic ligands and their gadolinium complexes were characterized by 1HNMR, IR, UV and elemental analysis. Relaxivity studies showed that the dendritic gadolinium complexes have higher relaxation effectiveness than that of the clinically used small molecular gadolinium complexes. Magnetic resonance imaging of the liver in rats indicated that the dendritic gadolinium complex containing pyridoxamine enhances the image contrast of the liver, provides prolonged intravascular duration and produces highly contrasted visualization of blood vessels in the liver.

Electron paramagnetic resonance: a powerful tool to support magnetic resonance imaging research

The purpose of this paper is to describe some of the areas where electron paramagnetic resonance (EPR) has provided unique information to MRI developments. The field of application mainly encompasses the EPR characterization of MRI paramagnetic contrast agents (gadolinium and manganese chelates, nitroxides) and superparamagnetic agents (iron oxide particles). The combined use of MRI and EPR has also been used to qualify or disqualify sources of contrast in MRI. Illustrative examples are presented with attempts to qualify oxygen sensitive contrast (i.e. T1 - and T2 *-based methods), redox status or melanin content in tissues. Other areas are likely to benefit from the combined EPR/MRI approach, namely cell tracking studies. Finally, the combination of EPR and MRI studies on the same models provides invaluable data regarding tissue oxygenation, hemodynamics and energetics. Our description will be illustrative rather than exhaustive to give to the readers a flavour of 'what EPR can do for MRI'.

Diagnostics of Biliary Dilatation By Means of Magnetic Resonance Cholangiopancreatography

Background

Material/Methods

Results

Conclusions

Primovist, Eovist: what to expect?

Gadolinium ethoxybenzyl dimeglumine (Gd-EOB-DTPA, Primovist in Europe and Eovist in the USA) is a liver-specific magnetic resonance imaging contrast agent that has up to 50% hepatobiliary excretion in the normal liver. After intravenous injection, Gd-EOB-DTPA distributes into the vascular and extravascular spaces during the arterial, portal venous and late dynamic phases, and progressively into the hepatocytes and bile ducts during the hepatobiliary phase. The hepatocyte uptake of Gd-EOB-DTPA mainly occurs via the organic anion transporter polypeptides OATP1B1 and B3 located at the sinusoidal membrane and biliary excretion via the multidrug resistance-associated proteins MRP2 at the canalicular membrane. Because of these characteristics, Gd-EOB-DTPA behaves similarly to non-specific gadolinium chelates during the dynamic phases, and adds substantial information during the hepatobiliary phase, improving the detection and characterization of focal liver lesions and diffuse liver disease. This information is particularly relevant for the detection of metastases, and for the detection and characterization of nodular lesions in liver cirrhosis, including early hepatocellular carcinomas. Finally, GD-EOB-DTPA-enhanced magnetic resonance imaging may provide quantitative assessment regarding liver perfusion and hepatocyte function in diffuse liver diseases. The full potential of GD-EOB-DTPA-enhanced magnetic resonance imaging has to be established further. It is already clear that GD-EOB-DTPA-enhanced magnetic resonance imaging provides anatomic and functional information in the setting of focal and diffuse liver disease that is unattainable with magnetic resonance imaging enhanced with non-specific contrast agents.

Liver transplantation to treat suspected hepatocellular carcinoma in iron-free foci in congenital hemochromatosis: case report

Hepatocellular carcinoma (HCC) commonly develops in cirrhotic or noncirrhotic livers affected by congenital hemochromatosis. In patients with congenital hemochromatosis and HCC, liver transplantation is a therapeutic option with a 5-year posttransplantation survival rate as high as 80%. Herein is reported congenital hemochromatosis in a 37-year-old man. During a routine checkup, 2 liver nodules were detected. Signal characteristics at magnetic resonance imaging indicated the presence of iron-free foci (IFF). The serum α-fetoprotein concentration was within the range of normal, and repeated liver biopsy did not show histomorphologic signs of malignancy but confirmed the presence of IFF in surrounding siderosis. The patient was listed for liver transplantation with match MELD (Model of End-Stage Liver Disease including exceptions) because of suspected HCC. After 173 days on the waiting list, liver transplantation was performed successfully. Histologic examination of the explanted liver confirmed 2 HCC lesions with a diameter of 0.9 cm in the exact projection as the IFF detected at magnetic resonance imaging. At 20 months of rapamycin-based immunosuppression therapy, there were no signs of HCC recurrence. This is, to our knowledge, the first report of liver transplantation performed to treat suspected HCC based on the finding of IFF in congenital hemochromatosis, with histopathologic confirmation of the diagnosis of HCC after transplantation. According to this case and the current literature, IFF in patients with congenital hemochromatosis should be considered preneoplastic lesions vulnerable to possible development of HCC.

Synthesis and evaluation of gadolinium complexes based on PAMAM as MRI contrast agents

Diethylenetriaminepentaacetic acid (DTPA) and pyridoxamine (PM) were incorporated into the amine groups on the surface of ammonia-core poly(amidoamine) dendrimers (PAMAM, Generation 2.0–5.0) to obtain dendritic ligands. These dendritic ligands were reacted with gadolinium chloride to yield the corresponding dendritic gadolinium (Gd) complexes. The dendritic ligands and their gadolinium complexes were characterized by 1HNMR, IR, UV and elemental analysis. Relaxivity studies showed that the dendritic gadolinium complexes possessed higher relaxation effectiveness compared with the clinically used Gd-DTPA. After administration of the dendritic gadolinium complexes (0.09 mmol kg−1) to rats, magnetic resonance imaging of the liver indicated that the dendritic gadolinium complexes containing pyridoxamine groups enhanced the contrast of the MR images of the liver, provided prolonged intravascular duration and produced highly contrasted visualization of blood vessels.

Detection of hepatocellular carcinoma by ferucarbotran-enhanced magnetic resonance imaging: the efficacy of accumulation phase fat-suppressed T1-weighted imaging

AIM

To evaluate the effectiveness of accumulation phase, fat-suppressed, T1-weighted imaging (FS-T1WI) when detecting hepatocellular carcinoma (HCC) by ferucarbotran-enhanced magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Thirty patients who underwent ferucarbotran-enhanced MRI, which resulted in 35 confirmed HCCs, were included in this prospective study. Two image sets were prepared and two radiologists independently reviewed these in two reading sessions; set A was without contrast-enhanced accumulation phase FS-T1WI and set B included contrast-enhanced accumulation phase FS-T1WI. All HCCs had been confirmed by operation (n=4), by biopsy (n=28), and by follow-up study for at least 1 year (n=3).

RESULTS

The contrast-to-noise ratio significantly increased from -1.2+/-7.5 to 12.7+/-7.3 with contrast-enhanced accumulation phase FS-T1WI, but was only slightly increased from 12.2+/-10.3 to 15.5+/-12.2 with contrast-enhanced T2WI (p<0.001). The signal-to-noise ratio (SNR) was decreased with T1WI and T2WI for liver parenchyma. With T2WI, the SNR for HCCs was decreased; however, it was slightly increased with T1WI (p<0.001). Overall, 29 HCCs were detected using set A, and 35 nodules were identified using set B, which included the contrast-enhanced accumulation phase FS-T1WI. Thus, the detection rate significantly increased using post-contrast medium accumulation phase FS-T1WI (p<0.05).

CONCLUSION

Due to the improved CNR with the post-contrast medium accumulation phase FS-T1WI, which helped to increase HCC detection, accumulation phase FS-T1WI is recommended as one of the routine protocols for inclusion in HCC detection.

High-resolution computed tomography accurately predicts resectability in hilar cholangiocarcinoma

INTRODUCTION

Despite the use of radiologic, endoscopic, and laparoscopic staging techniques, the rate of nontherapeutic laparotomies in patients with hilar cholangiocarcinoma remains high. This study evaluated the accuracy of preoperative high-resolution computed tomography (HRCT) to determine resectability in this setting.

PATIENTS AND METHODS

Preoperative helical HRCT (2 contrast phases, rapid intravenous contrast bolus, 2.5-mm section thickness) for 32 consecutive patients who underwent laparotomy for the diagnosis of hilar cholangiocarcinoma from 2000 to 2005 were reviewed by a hepatobiliary radiologist. The accuracy of HRCT was determined by comparison of the imaging interpretation to intraoperative and pathologic findings. The chi-square test was used to identify imaging findings that best predicted unresectability.

RESULTS

Fourteen of the 32 (44%) study patients were unresectable (extension along bile duct, 4; peritoneal metastases, 4; vascular encasement, 3; noncontiguous liver metastases, 2; N2 lymphadenopathy, 1). HRCT correctly predicted resectability in 17 of 18 patients who underwent therapeutic laparotomy (sensitivity = 94%). HRCT correctly predicted the inability to resect in 11 of the remaining 14 cases (specificity = 79%). In the 3 cases in which HRCT predicted resectability and the patient was unresectable, subcentimeter peritoneal disease, a subcentimeter liver metastasis, and distal bile duct involvement were responsible factors. The negative and positive predictive values of HRCT were 92% and 85%, respectively. Individual radiographic findings that best predicted unresectability were peritoneal spread (P = .015) and hepatic artery (P = .006) or portal vein (P = .002) involvement.

CONCLUSIONS

Preoperative HRCT accurately predicts resectability in patients with hilar cholangiocarcinoma. Identification of specific radiographic features, in particular major vascular involvement and peritoneal abnormalities, is now used by our group to avoid unnecessary laparotomy.

Laparoscopic approach to colonic cancer: critical appraisal of the literature

BACKGROUND/AIMS

As laparoscopic colectomy finds its place in the surgical armamentarium, the literature concerning the safety, efficacy, and oncological rational for treatment of colonic cancer is also enriched. A review and critical appraisal of the literature on this subject was the aim of this paper.

METHODS

A systematic research and a hand search were conducted to gain access to all controlled studies involving laparoscopic colectomy using the Medline, Embase, HealthSTAR, Cumulative Index for Nursing and Allied Health Literature, CancerLit data bases and the Cochrane Central Register of Controlled Trials for the years 1991-2006.

RESULTS

Over 40 controlled randomized trials and ten systematic reviews and/or meta-analyses were found. Several of the completed controlled randomized trials have published either short- or long-term results; only partial and short-term results are available in rectal cancer. The principal conclusions are that the laparoscopic approach affords better short-term outcomes including surgical site morbidity, but with increased operative times and direct costs. Among the proven long-term outcomes, cancer recurrence and survival do not seem to be worse. Whether conversion, a source of increased operative time and costs, is responsible for poorer outcomes or whether specific settings associated with poorer outcomes are among the causes of conversion remains to be shown. However, there are still concerns as regards specific laparoscopic-related complications.

CONCLUSION

There seems to no real safety problems in performing laparoscopic colectomy for cancer; improvement in operative times, conversion rates, and complications should make laparoscopy the best cost-effective approach to colectomy.

Preoperative application of selective angiographic embolization in the treatment of focal nodular hyperplasia

A focal nodular hyperplasia (FNH) rarely requires surgical intervention unless complications or clinical symptoms come into play. In 2 female patients, ages 35 and 44, with symptomatic tumors of that entity (10 and 14 cm, respectively, in size) we performed a laparoscopic liver resection. Directly before undergoing this operation they underwent a selective angiographic embolization of the arterial inflow for control of hemorrhage by application of polyvinyl alcohol particles to the afferent arteries. This procedure led to a complete interruption in arterial inflow and the subsequent laparoscopic resection itself could be carried out as planned with minimal blood loss as well an uncomplicated postoperative course. The patients demonstrated a high degree of subjective satisfaction with the procedure. A reduction in arterial inflow through selective embolization is a useful tool in the preparation for laparoscopic resection of large, well-vascularized liver tumors.

Detection of hepatocellular carcinoma by ferumoxides-enhanced MR imaging in cirrhosis: Incremental value of dynamic gadolinium-enhancement

PURPOSE

To investigate the incremental value of dynamic gadolinium-enhancement performed immediately after ferumoxides-enhanced magnetic resonance (MR) imaging on the detection of hepatocellular carcinoma in patients with cirrhosis.

MATERIALS AND METHODS

We retrospectively reviewed MR scans of 62 cirrhotic patients over a two-year period. Sequences included ferumoxides-enhanced T2-weighted fast spin echo followed by dynamic gadolinium-enhanced T1-weighted spoiled gradient echo. Two readers independently documented the presence of hepatocellular carcinoma on a three-point confidence scale, without and with gadolinium-enhanced images. The presence or absence of hepatocellular carcinoma was established by histopathology (58 patients) or follow-up imaging (four patients) over a mean period of nine months.

RESULTS

A total of 71 hepatocellular carcinomas were found in 42 patients. There was no statistically significant difference in sensitivity for the diagnosis of hepatocellular carcinoma without vs. with gadolinium-enhanced images (68% vs. 74% for reader 1 and 62% vs. 73% for reader 2, respectively, P > 1.3). However, both readers showed a lower mean confidence for tumor detection without vs. with gadolinium-enhanced images (2.3 vs. 2.7 for reader 1, 2.3 vs. 2.9 for reader 2, P < 0.01).

CONCLUSION

In our study, the addition of dynamic gadolinium-enhancement to ferumoxides-enhanced MR imaging did not improve hepatocellular carcinoma detection, but the addition of gadolinium-enhancement is recommended if ferumoxides-enhanced imaging is used because it increased reader confidence.

Contrast-enhanced dynamic magnetic resonance imaging findings of hepatocellular carcinoma and their correlation with histopathologic findings

PURPOSE

To investigate the correlations of contrast-enhanced magnetic resonance (MR) imaging findings of large (> 5 cm) hepatocellular carcinomas with tumor size and histopathologic findings.

MATERIALS AND METHODS

MR imaging was performed in 30 patients with a histopathologic diagnosis of hepatocellular carcinoma. The imaging protocol included non-contrast, hepatic arterial, portal venous and late phases. The signal intensities relative to the liver, enhancement patterns and the morphologic features of the lesions were evaluated in relation to size and degree of differentiation.

RESULTS

On histopathologic examination, 12 of 30 (40%) tumors were well-differentiated (grade 1), 6 of 30 (20%) were moderately differentiated (grades 2 and 3) and 12 of 30 (40%) were poorly differentiated (grade 4). Tumor size, tumor boundry, serum alpha-fetoprotein level and portal vein invasion were found to have statistically significant correlations with the degree of differentiation (p < 0.05). Portal vein invasion, capsule formation and tumor surface characteristics showed statistically significant correlations with tumor size (p < 0.05).

CONCLUSION

MR imaging findings of hepatocellular carcinomas larger than 5 cm are partially dependent on tumor size and degree of differentiation.

Targeting of lanthanide(III) chelates of DOTA-type glycoconjugates to the hepatic asyaloglycoprotein receptor: cell internalization and animal imaging studies

The characterization of a new class of hydrophilic liver-targeted agents for gamma-scintigraphy and MRI, consisting, respectively, of [(153)Sm](3+) or Gd(3+) complexes of DOTA monoamide or bisamide linked glycoconjugates (DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), is reported. In vitro studies show high uptake of radiolabeled [(153)Sm]-DOTAGal(2) by the human hepatocyte carcinoma cell line Hep G2 containing the asialoglycoprotein receptor (ASGP-R), which is decreased to less than 50% by the presence of its high-affinity ligand asialofetuin (ASF). In vivo biodistribution, gamma-imaging and pharmacokinetic studies on Wistar rats using the [(153)Sm](3+)-labeled glycoconjugates show a high uptake in the receptor-rich organ liver of the radiolabeled compounds containing terminal galactosyl groups, but very little uptake for those compounds with terminal glycosyl groups. Blocking the receptor in vivo reduced liver uptake by 90%, strongly suggesting that the liver uptake of these compounds is mediated by their binding to the asyaloglycoprotein receptor (ASGP-R). This study also demonstrated that the valency increase improves the targeting capability of the glycoconjugates, which is also affected by their topology. However despite the specific liver uptake of the radiolabeled galactose-bearing multivalent compounds, the animal MRI assessment of the corresponding Gd(3+) chelates shows liver-to-kidney contrast effects which are not significantly better than those shown by GdDTPA. This probably results from the quick wash-out from the liver of these highly hydrophilic complexes, before they can be sufficiently concentrated within the hepatocytes via receptor-mediated endocytosis.

Angiography-proven liver metastases explain low efficacy of lymph node dissections in medullary thyroid cancer patients

AIM

To report the role of liver angiography in the staging of medullary thyroid cancer (MTC) patients.

MATERIAL AND METHODS

Sixty MTC patients with persistent or recurrent hypercalcitonemia (n=49), a characteristic general symptom (diarrhea, n=4) or a normal basal calcitonin level without general symptoms (n=7) were investigated by dynamic liver CT, MRI and angiography between 06/1998 and 06/2002.

RESULTS

Dual-phase CT and MRI investigations identified hepatic metastases with relatively low frequency (8/58 on MRI, and 7/60 on CT). Angiography indicated liver involvement in 54/60 cases. The hepatic metastases were typically multiple, hypervascular, small foci (only 13 foci measured >/=10 mm). With one exception significant disease progression was not observed over 5 years of follow-up.

CONCLUSIONS

Liver angiography is a powerful tool to reveal hepatic metastases in MTC patients. Frequent, inoperable liver metastases in hypercalcitoninemic MTC patients demonstrate that secondary lymph node dissection is an inefficient technique for restoration of a normal calcitonin level.

Current status of laparoscopic resection for colorectal cancer

GOALS

To define the current role of laparoscopic resection for colorectal cancer.

BACKGROUND

Perhaps in no other field has so much controversy been generated by laparoscopy as in its application to curative resection of cancer of the colon and rectum. The main controversy centers around the oncologic outcomes of laparoscopic resections. The 3 major issues are: the adequacy of oncologic resection, recurrence rates and patterns, and the long-term survival.

STUDY

A review of published data by search of Medline database with focus on clinical studies.

RESULTS

Laparoscopic colectomy is feasible and safe. Modest benefits in the quality of life are observed. Same oncologic resection can be performed laparoscopically with no adverse influence on the recurrence rates. In particular, wound recurrences are not a specific complication of laparoscopic technique. At least equivalent survival is obtained by laparoscopic colectomy.

CONCLUSIONS

Laparoscopy does not seem to adversely affect chance of cure of colorectal cancer.

Impact of positron emission tomography on strategy in liver resection for primary and secondary liver tumors

PURPOSE

Outcome of patients with metastatic disease mainly depends on accurate preoperative tumor staging. 18[F]fluorodeoxyglucose positron emission tomography (18F-PET) has been proven to be a valuable diagnostic tool in a number of different tumors but its direct influence on liver surgery has not been thoroughly investigated.

MATERIALS AND METHODS

Between July 1999 and March 2000, 50 consecutive patients with 174 suspected liver lesions were admitted to the University Hospital Jena. All 50 patients underwent abdominal ultrasound, CT-scan, and 18-FDG positron emission tomography scanning. In 23 patients the diagnostic work-up was completed by MRI scan.

RESULTS

Altogether there were a total of 174 histologically proven intrahepatic lesions, nine of which were benign. The sensitivity, specificity, and positive predictive value of PET for all hepatic lesions was 82%, 25%, and 96% compared with 63%, 50%, and 96% for abdominal ultrasound, 71%, 50%, and 97% for CT-scan, and 83%, 57%, and 97% for MRI-scan. In 23 of 50 patients 24 extrahepatic lesions were identified. In these patients the sensitivity and specificity of PET-compared to abdominal ultrasound, CT-scan, and MRI-scan for all extrahepatic lesions-was 63% and 60%, 29% and 25%, 47% and 50% and 40% and 50%, respectively. The findings on PET scan had a direct impact on operative management in nine patients (18%).

CONCLUSIONS

Our series demonstrates good sensitivity and specificity for the detection of primary and secondary liver lesions which is superior to ultrasound and CT scan but not to MRI scan. The main value of PET scan consists in the detection of extrahepatic tumor (64%). Due to better detection of extrahepatic tumor, FDG-PET is a very useful addition to the currently used anatomically-based images in all cases of advanced tumor spread with high risk of extrahepatic tumor.

Evaluation of [Gd(Bz-TTDA)]2- as a potential contrast agent in MR imaging of the hepatobiliary system: An animal study

PURPOSE

To evaluate the potential of a new lipophilic paramagnetic complex [Gd(Bz-TTDA)]2- [(4s)-4-benzyl-3,6,10-tri(carboxymethyl)-3,6,10-triazadodecandioic acid]2- designed for use as a hepatobiliary MR contrast agent.

MATERIALS AND METHODS

MR imaging studies for normal and hepatocellular carcinoma (HCC) rat models were performed using a 1.5-T scanner. Sequential multislice T1-weighted turbo field echo (TFE) (TR/TE/flip angle: 15 msec/6.1 msec/25 degrees) coronal images of normal rats were obtained before and after intravenous injections of 0.1 mmol/kg [Gd(Bz-TTDA)]2- in study groups (N = 12) or 0.1 mmol/kg gadopentate dimeglumine (Gd-DTPA)2- in control groups (N = 12). Similar protocols of MR imaging with additional T2-weighted images were used for the rats with implanted HCC in both study and control groups (N = 12, in each group). MR images were analyzed to evaluate the time-enhancement change (% increase of signal-to-noise ratio [SI/N]) in normal liver, renal cortex, renal medulla, and tumors. The liver-lesion contrast-to-noise ratios (CNR) were also evaluated in study and control groups. The rats were killed immediately after the last MR scan to undergo autopsy and histopathologic observation. The acute toxicity test (medial lethal dose, LD50) in mice was also done.

RESULTS

The liver enhancement in normal rats reached a plateau 5-50 minutes after injection of [Gd(Bz-TTDA)]2-, maintained for three hours, then gradually declined. Intensity of enhancement in liver, renal cortex, and medulla after injection of [Gd(Bz-TTDA)]2- was significantly higher than with Gd-DTPA. The efficacy of tumor characterization with injection of [Gd(Bz-TTDA)]2- was similar to that of Gd-DTPA at the early dynamic phase of the contrast study. However, the liver-lesion CNRs were significantly higher in the study group in the later phase, when tumor enhancement decreased and liver enhancement persisted. The dose of LD50 in acute toxicity test of [Gd(Bz-TTDA)]2- in mice was 7.5 mmol/kg.

CONCLUSION

The preliminary results in this animal study indicated that [Gd(Bz-TTDA)]2- has the potential of becoming a reliable liver MR contrast agent.

Currently used non-specific extracellular MR contrast media

Magnetic resonance contrast agents have demonstrated their clinical usefulness in a variety of organs for improved detection of various neoplastic, inflammatory and functional abnormalities. Gadolinium chelates are the most widely used. They are extracellular, non-specific contrast agents. Their use in many clinical indications is justified because, in conjunction with improved imaging techniques, these safe and image-enhancing contrast agents add morphologic and functional information compared with unenhanced MR images. This article describes the commercially available compounds, and summarizes their approval status on the international market regarding indications and doses. Their mechanisms of action, biodistributions, toxicities and tolerance profiles in normal and high-risk patient populations are described. Additionally, this article reviews the specific recommendations by the manufacturers for patients at risk. Finally, their main clinical applications are reviewed.

Detection of colorectal liver metastases: a prospective multicenter trial comparing unenhanced MRI, MnDPDP-enhanced MRI, and spiral CT

The aim of this study was to compare unenhanced MRI, MnDPDP-enhanced MRI, and spiral CT in the detection of hepatic colorectal metastases. Forty-four patients with hepatic colorectal metastases were examined with unenhanced and MnDPDP-enhanced MRI and with unenhanced and contrast-enhanced spiral CT. The MR examination protocol included baseline T1-weighted spin-echo (SE), T1-weighted gradient-recalled-echo (GRE), and T2-weighted fast-SE sequences; and T1-weighted SE and T1-weighted GRE sequences obtained 30-60 min after administration of 0.5 micromol/kg (0.5 ml/kg) mangafodipir trisodium (MnDPDP). Images were interpreted by three blinded readers. Findings at CT and MRI were compared with those at intraoperative US, which were used as term of reference. Intraoperative US detected 128 metastases. In a lesion-by-lesion analysis, the overall detection rate was 71% (91 of 128) for spiral CT, 72% (92 of 128) for unenhanced MRI, and 90% (115 of 128) for MnDPDP-enhanced MRI. MnDPDP-enhanced MRI was more sensitive than either unenhanced MRI ( p<0.0001) or spiral CT ( p=0.0007). In a patient-by-patient analysis, agreement with gold standard was higher for MnDPDP-enhanced MRI (33 of 44 cases) than for spiral CT (22 of 44 cases, p=0.0023) and unenhanced MRI (21 of 44 cases, p=0.0013). MnDPDP-enhanced MRI is superior to unenhanced MRI and spiral CT in the detection of hepatic colorectal metastases.

The role of staging laparoscopy in hepatobiliary malignancy: prospective analysis of 401 cases

BACKGROUND

Patients with potentially resectable hepatobiliary malignancy are frequently found to have unresectable tumors at laparotomy. We prospectively evaluated staging laparoscopy in patients with resectable disease on preoperative imaging.

METHODS

Staging laparoscopy was performed on 410 patients with potentially resectable hepatobiliary malignancy. The preoperative likelihood of resectability was recorded. Data on preoperative imaging, operative findings, and hospital course were analyzed.

RESULTS

Laparoscopic inspection was complete in 291 (73%) patients. In total, 153 patients (38%) had unresectable disease, 84 of whom were identified laparoscopically, increasing resectability from 62% to 78%. On multivariate analysis, a complete examination, preoperative likelihood of resection, and primary diagnosis were significant predictors of identifying unresectable disease at laparoscopy. The highest yield was for biliary cancers, and the lowest was for metastatic colorectal cancer. In patients with unresectable disease identified at laparoscopy, the mean hospital stay was 3 days, and postoperative morbidity was 9%, compared with 8 days and 27%, respectively, in patients found to have unresectable disease at laparotomy.

CONCLUSIONS

Laparoscopy spared one in five patients a laparotomy while reducing hospital stay and morbidity. Targeting laparoscopy to patients at high risk for unresectable disease requires consideration of disease-specific factors; however, the surgeons' preoperative impression of resectability is also important.

Characterization of focal liver lesions with superparamagnetic iron oxide-enhanced MR imaging: value of distributional phase T1-weighted imaging

OBJECTIVE

To determine the potential value of distributional-phase T1-weighted ferumoxides-enhanced magnetic resonance (MR) imaging for tissue characterization of focal liver lesions.

MATERIALS AND METHODS

Ferumoxides-enhanced MR imaging was performed using a 1.5-T system in 46 patients referred for evaluation of known or suspected hepatic malignancies. Seventy-three focal liver lesions (30 hepatocellular carcinomas (HCC), 12 metastases, 15 cysts, 13 hemangiomas, and three cholangiocarcinomas) were evaluated. MR imaging included T1-weighted double-echo gradient-echo (TR/TE: 150/4.2 and 2.1 msec), T2*-weighted gradient-echo (TR/TE: 180/12 msec), and T2-weighted turbo spin-echo MR imaging at 1.5 T before and after intravenous administration of ferumoxides (15 mmol/kg body weight). Postcontrast T1-weighted imaging was performed within eight minutes of infusion of the contrast medium (distributional phase). Both qualitative and quantitative analysis was performed.

RESULTS

During the distributional phase after infusion of ferumoxides, unique enhancement patterns of focal liver lesions were observed for hemangiomas, metastases, and hepatocellular carcinomas. On T1-weighted GRE images obtained during the distributional phase, hemangiomas showed a typical positive enhancement pattern of increased signal; metastases showed ring enhancement; and hepatocellar carcinomas showed slight enhancement. Quantitatively, the signal-to-noise ratio of hemangiomas was much higher than that of other tumors (p <.05) and was similar to that of intrahepatic vessels. This finding permitted more effective differentiation between hemangiomas and other malignant tumors.

CONCLUSION

T1-weighted double-echo FLASH images obtained soon after the infusion of ferumoxides, show characteristic enhancement patterns and improved the differentiation of focal liver lesions.

Contrast-enhanced MRI of the liver with mangafodipir trisodium: imaging technique and results

Magnetic resonance (MR) contrast agents are now routinely used for detecting and characterizing focal liver lesions. Liver specific, hepatobiliary, MRI contrast agent mangafodipir trisodium (Mn-DPDP) is taken up by the functioning hepatocytes and excreted by the biliary system. Contrast uptake leads to persistent elevation of T1-weighted signal of normal liver parenchyma within 10 minutes of injection. Most tumors of non-hepatocellular origin typically are hypointense relative to enhanced liver parenchyma on T1 weighted images and are more conspicuous than on unenhanced images. Whereas, tumors of hepatocellular origin such as focal nodular hyperplasia (FNH), adenoma, and well-differentiated hepatocellular carcinomas (HCC) have been shown to accumulate Mn-DPDP, providing characterization information to discriminate hepatocellular from non-hepatocellular tumors. The purpose of this pictorial essay is to illustrate the appearance of various liver tumors on mangafodipir enhanced liver MR imaging.

MRI contrast agents for evaluating focal hepatic lesions

Contrast-enhanced magnetic resonance imaging (MRI) has become an important tool in the detection and characterization of focal hepatic lesions especially when other investigations such as ultrasound (US) and computed tomography (CT) are inconclusive. The purpose of this pictorial review is to briefly summarize the properties of various MRI contrast agents used in hepatic imaging and to highlight their role in evaluation of focal hepatic lesions.

Superior diagnostic strength of combined contrast enhanced MR-angiography and MR-imaging compared to intra-arterial DSA in liver transplantation candidates

To evaluate the diagnostic value of combined contrast enhanced MRA (ce-MRA) and MRI compared to that of intra-arterial DSA (i.a.DSA) in liver transplantation, transjugular porto-systemic (TIPSS) and spleno-renal shunt candidates. 50 patients in the workup for liver transplantation underwent ce-MRA/MRI and i.a.DSA within a three days interval. Both examinations were assessed with respect to vessel anatomy and patency of the arterial, portal venous, porto-systemic collateral and systemic venous system. The results were compared with the intra-operative findings when available. Malignancy detection in ce-MRA/MRI and i.a.DSA were compared. There are no significant differences for the arterial part of the vascular supply to the liver that is important for transplantation. Although the differences for the portal system are not significant, the difference between the two techniques is of clinical importance because i.a.DSA failed to detect portal vein occlusion in 4 patients. Ce-MRA is significantly better for the detection of collaterals (p < 0.001) and the assessment of the inferior vena cava, the hepatic and the renal veins (p < 0.001). Although the detection of liver malignancy is poor in both techniques, ce-MRA/MRI is superior to i.a.DSA. This study shows that a one step diagnostic approach with a combination of ce-MRA and MRI is a valuable radiological tool with a superior diagnostic strength compared to i.a.DSA in the liver transplantation and shunt candidate. Therefore, ce-MRA/MRI should replace i.a.DSA in these patients groups.

Dual contrast enhanced magnetic resonance imaging of the liver with superparamagnetic iron oxide followed by gadolinium for lesion detection and characterization

AIM

Iron oxide contrast agents are useful for lesion detection, and extracellular gadolinium chelates are advocated for lesion characterization. We undertook a study to determine if dual contrast enhanced liver imaging with sequential use of ferumoxides particles and gadolinium (Gd)-DTPA can be performed in the same imaging protocol.

MATERIALS AND METHODS

Sixteen patients underwent dual contrast magnetic resonance imaging (MRI) of the liver for evaluation of known/suspected focal lesions which included, metastases (n = 5), hepatocellular carcinoma (HCC;n = 3), cholangiocharcinoma(n = 1) and focal nodular hyperplasia (FNH;n = 3). Pre- and post-iron oxide T1-weighted gradient recalled echo (GRE) and T2-weighted fast spin echo (FSE) sequences were obtained, followed by post-Gd-DTPA (0.1 mmol/kg) multi-phase dynamic T1-weighted out-of-phase GRE imaging. Images were analysed in a blinded fashion by three experts using a three-point scoring system for lesion conspicuity on pre- and post-iron oxide T1 images as well as for reader's confidence in characterizing liver lesions on post Gd-DTPA T1 images.

RESULTS

No statistically significant difference in lesion conspicuity was observed on pre- and post-iron oxide T1-GRE images in this small study cohort. The presence of iron oxide did not appreciably diminish image quality of post-gadolinium sequences and did not prevent characterization of liver lesions.

CONCLUSION

Our results suggest that characterization of focal liver lesion with Gd-enhanced liver MRI is still possible following iron oxide enhanced imaging.Kubaska, S.et al. (2001). Clinical Radiology, 56, 410-415

Biodistribution of ultrasmall iron oxide particles in the rat liver

Ferumoxtran, an ultrasmall superparamagnetic iron oxide particle, can be located in several tissue compartments in the liver, namely the extracellular space (blood and interstitium), reticuloendothelial cells, and possibly hepatocytes. To better understand the compartmental distribution of ferumoxtran in the liver, we performed a longitudinal study in the rat using microscopy and magnetic resonance imaging. At light microscopy, no substantial cellular uptake of ferumoxtran was observed before one hour after injection. With a dose of 15 micromol Fe/kg, the number of ferumoxtran particles in the reticuloendothelial cells peaked between one and four hours and with a 150 micromol Fe/kg dose, it peaked between eight and 24 hours. Within hepatocytes, only sparse particles were observed with electron microscopy, at a dose of 150 micromol Fe/kg. Imaging performed up until one hour after ferumoxtran injection showed a significant increase in liver signal intensity on T1-weighted images. These results suggest that ferumoxtran mainly acts as an extracellular agent for at least one hour in the rat and that reticuloendothelial accumulation peaks at later time points. Substantial uptake within hepatocytes did not occur.

Radiologic diagnosis of hepatocellular carcinoma

Substantial recent technologic improvements in CT scanning, US scanning, and MR imaging, together with advances in the understanding of the optimal application of contrast administration techniques, have facilitated advances in radiologic imaging detection for HCC diagnosis. Despite a large number of earlier publications reporting a high sensitivity for imaging detection of HCC, more recent screening studies of large cirrhotic populations confirm that only 37% to 45% of HCC tumor nodules are detected by CT scanning, US scanning, or MR imaging. Future investigation will include efforts to improve the detection of small tumors and to characterize with greater specificity the spectrum of nodular changes that occur with cirrhosis. Although several small series have attempted to characterize cirrhotic nodules by evaluating the relative arterial or portal blood supply, these preliminary results require substantiation with larger series. Continued technologic advances such as multidetector helical CT scanning and new US and MR contrast agents under investigation may improve the imaging characterization of cirrhotic nodules.

Multicentre dose-ranging study on the efficacy of USPIO ferumoxtran-10 for liver MR imaging

AIM

A dose ranging multicentre phase-II clinical trial was conducted to evaluate the efficacy of ultrasmall superparamagnetic iron oxide (USPIO) ferumoxtran-10 for magnetic resonance (MR) imaging of focal hepatic lesions.

MATERIAL AND METHODS

Ninety-nine patients with focal liver lesions received USPIO at a dose of 0.8 (n = 35), 1.1 (n = 32), or 1.7 (n = 32) mg Fe/kg. Liver MR imaging was performed before and after USPIO with T1-weighted and T2-weighted pulse sequences. Images were analysed by two independent readers for additional information (lesion detection, exclusion, characterization and patient management). Signal intensity (SI) based quantitative measurements were also taken.

RESULTS

Post-contrast medium MR imaging showed additional information in 71/97 patients (73%) for reader one and 83/96 patients (86%) for reader two. The results with all three doses were statistically significant (P < 0.05). Signal intensity analysis revealed that all three doses increased liver SI on T1-weighted images and decreased liver SI on T2-weighted images. On T2-weighted images metastases increased in contrast relative to normal hepatic parenchyma whereas haemangiomas decreased in contrast. On T2-weighted images there was statistically improved efficacy at the intermediate dose, which did not improve at the highest dose.

CONCLUSION

Ultrasmall superparamagnetic iron oxide was an effective contrast agent for liver MR imaging at all doses and a dose of 1.1 mg Fe/kg was recommended for future clinical trials.

Phase II double-blind, dose-ranging clinical evaluation of gadobenate dimeglumine in focal liver lesions: with analysis of liver and kidney signal change on early and delayed imaging

To evaluate the effect of contrast dose using gadobenate dimeglumine, 30 patients with focal liver lesions documented by computed tomography or ultrasound were studied by magnetic resonance imaging at 1.5 T. Patients received one of four doses of gadobenate dimeglumine (0.025, 0.05, 0.1, or 0.2 mmol/kg) or saline. The order of dosage was randomized, with both the physician and patient blinded to the administered dose. Scans were obtained before, immediately following injection, and after 80 minutes of delay. Enhancement effects were quantified by region of interest measurements. Films were also reviewed in a randomized prospective fashion by an abdominal radiologist blinded to contrast dose and diagnosis. Higher doses led to a statistically significant improvement in enhancement of normal liver, both on immediate (P = 0.01 for the comparison of 0.1 and 0.2 mmol/kg immediately post-contrast) and delayed scans (P = 0.003 for the same comparison). Liver-lesion contrast-to-noise ratio also increased with dose, although results for most comparisons by dose were not statistically significant. Scans following gadobenate dimeglumine injection were judged to provide additional diagnostic confidence sufficient to affect patient management in 10 of 24 cases. In seven cases this information was provided by dynamic scans, in one case by delayed scans, and in two cases by both dynamic and delayed scans. In 2 of the 10 cases the dose was 0.025 mmol/kg, in 2 cases 0.05 mmol/kg, in 3 cases 0.1 mmol/kg, and in 3 cases 0.2 mmol/kg. Gadobenate dimeglumine is effective for imaging of focal liver lesions at a range of doses, with trends toward improved diagnostic information at higher doses.

Improved tissue characterization of focal liver lesions with ferumoxide-enhanced T1 and T2-weighted MR imaging

The purpose of our study was to evaluate the potential value of ferumoxide-enhanced T1-weighted magnetic resonance (MR) imaging for tissue characterization of focal liver lesions when combined with T2-weighted sequences. Images were acquired within 30 minutes after the end of ferumoxide administration, when ferrite particles were not totally cleared from the intravascular compartment. Thirty-eight patients with 47 focal liver lesions underwent T1-weighted gradient-echo (TR/TE 150/4.1 msec) and T2-weighted fast spin-echo (3180-8638/90 msec) MR imaging at 1.5 T before and after intravenous administration of ferumoxides (10 micromol/kg body weight). A qualitative and quantitative analysis was performed. During the early phase after infusion of ferumoxide, blood vessels showed hypersignal intensity on T1-weighted fast low-angle shot (FLASH) images, while liver signal decreased. Hemangiomas showed both homogeneous and inhomogeneous enhancement patterns, and liver metastasis most typically showed ring enhancement. Hypervascular tumors (hepatocellular carcinomas and focal nodular hyperplasias) showed a slight degree of homogeneous enhancement. Quantitatively, the degree of enhancement and lesion-to-liver contrast on ferumoxide-enhanced images were significantly different among these tumors. Our results demonstrate that distinct enhancement patterns obtained on ferumoxide-enhanced T1-weighted MR imaging improve tissue characterization of focal liver lesions when combined with T2-weighted images.

The changing role of radiology in imaging liver tumors: an overview

The surgical and the radiological advances in liver tumors in last two decades have made some malignant tumors operable which were considered inoperable and have completely changed the expectations from radiology. However, accurate staging, that is performed by imaging modalities, has critical importance in the selection of patients who can benefit from resection. Radiologists and referring physicians, therefore, should be aware of the current concepts in imaging liver tumors. This report updates both the changing role of radiology in hepatic neoplasms and the appropriate use of radiological modalities in liver tumors.