Using superparamagnetic iron oxide-enhanced MRI to differentiate metastatic hepatic tumors and nonsolid benign lesions

The Application of Nanoparticles in Diagnosis and Treatment of Kidney Diseases

Nanomedicine is currently showing great promise for new methods of diagnosing and treating many diseases, particularly in kidney disease and transplantation. The unique properties of nanoparticles arise from the diversity of size effects, used to design targeted nanoparticles for specific cells or tissues, taking renal clearance and tubular secretion mechanisms into account. The design of surface particles on nanoparticles offers a wide range of possibilities, among which antibodies play an important role. Nanoparticles find applications in encapsulated drug delivery systems containing immunosuppressants and other drugs, in imaging, gene therapies and many other branches of medicine. They have the potential to revolutionize kidney transplantation by reducing and preventing ischemia-reperfusion injury, more efficiently delivering drugs to the graft site while avoiding systemic effects, accurately localizing and visualising the diseased site and enabling continuous monitoring of graft function. So far, there are known nanoparticles with no toxic effects on human tissue, although further studies are still needed to confirm their safety.

T2-Weighted Magnetic Resonance Imaging of Hepatic Tumor Guided by SPIO-Loaded Nanostructured Lipid Carriers and Ferritin Reporter Genes

Nowadays, there is a high demand for supersensitive contrast agents for the early diagnostics of hepatocarcinoma. It has been recognized that accurate imaging information is able to be achieved by constructing hepatic tumor specific targeting probes, though it still faces challenges. Here, a AGKGTPSLETTP peptide (A54)-functionalized superparamagnetic iron oxide (SPIO)-loaded nanostructured lipid carrier (A54-SNLC), which can be specifically uptaken by hepatoma carcinoma cell (Bel-7402) and exhibited ultralow imaging signal intensity with varied Fe concentration on T2-weighted imaging (T2WI), was first prepared as an effective gene carrier. Then, an endogenous ferritin reporter gene for magnetic resonance imaging (MRI) with tumor-specific promoter (AFP-promoter) was designed, which can also exhibit a decrease in signal intensity on T2WI. At last, using protamine as a cationic mediator, novel ternary nanoparticle of A54-SNLC/protamine/DNA (A54-SNPD) as an active dual-target T2-weighted MRI contrast agent for imaging hepatic tumor was achieved. Owing to the synergistic effect of A54-SNLC and AFP-promoted DNA targeting with Bel-7402 cells, T2 imaging intensity values of hepatic tumors were successfully decreased via the T2 contrast enhancement of ternary nanoparticles. It is emphasized that the novel A54-SNPD ternary nanoparticle as active dual-target T2-weighted MRI contrast agent were able to greatly increase the diagnostic sensitivity and specificity of hepatic cancer.

Active-target T1-weighted MR Imaging of Tiny Hepatic Tumor via RGD Modified Ultra-small Fe3O4 Nanoprobes

Developing ultrasensitive contrast agents for the early detection of malignant tumors in liver is highly demanded. Constructing hepatic tumors specific targeting probes could provide more sensitive imaging information but still faces great challenges. Here we report a novel approach for the synthesis of ultra-small Fe3O4 nanoparticles conjugated with c(RGDyK) and their applications as active-target T1-weighted magnetic resonance imaging (MRI) contrast agent (T1-Fe3O4) for imaging tiny hepatic tumors in vivo. RGD-modified T1-Fe3O4 nanoprobes exhibited high r1 of 7.74 mM(-1)s(-1) and ultralow r2/r1 of 2.8 at 3 T, reflecting their excellent T1 contrast effect at clinically relevant magnetic field. High targeting specificity together with favorable biocompatibility and strong ability to resist against non-specific uptake were evaluated through in vitro studies. Owing to the outstanding properties of tumor angiogenesis targeting with little phagocytosis in liver parenchyma, hepatic tumor as small as 2.2 mm was successfully detected via the T1 contrast enhancement of RGD-modified T1-Fe3O4. It is emphasized that this is the first report on active-target T1 imaging of hepatic tumors, which could not only significantly improve diagnostic sensitivity, but also provide post therapeutic assessments for patients with liver cancer.

Magnetite/dextran-functionalized graphene oxide nanosheets for in vivo positive contrast magnetic resonance imaging

In vivo positive contrast MRI by magnetite/dextran-functionalized graphene oxide (SPIO-Dex-FGO) as compared to Magnevist® (the right rat).

Magnetite Nanoparticles for Medical MR Imaging

Nanotechnology has given scientists new tools for the development of advanced materials for the detection and diagnosis of disease. Iron oxide nanoparticles (SPIONs) in particular have been extensively investigated as novel magnetic resonance imaging (MRI) contrast agents due to a combination of favorable superparamagnetic properties, biodegradability, and surface properties of easy modification for improved in vivo kinetics and multifunctionality. This review discusses the basics of MR imaging, the origin of SPION's unique magnetic properties, recent developments in MRI acquisition methods for detection of SPIONs, synthesis and post-synthesis processes that improve SPION's imaging characteristics, and an outlook on the translational potential of SPIONs.

Transparent magnetic photoresists for bioanalytical applications

Microfabricated devices possessing magnetic properties are of great utility in bioanalytical microdevices due to their controlled manipulation with external magnets. Current methods for creating magnetic microdevices yield a low-transparency material preventing light microscopy-based inspection of biological specimens on the structures. Uniformly transparent magnetic photoresists were developed for microdevices that require high transparency as well as consistent magnetism across the structure. Colloidal formation of 10 nm maghemite particles was minimized during addition to the negative photoresists SU-8 and 1002F through organic capping of the nanoparticles and utilization of solvent-based dispersion techniques. Photoresists with maghemite concentrations of 0.01-1% had a high transparency due to the even dispersal of maghemite nanoparticles within the polymer as observed with transmission electron microscopy (TEM). These magnetic photoresists were used to fabricate microstructures with aspect ratios up to 4:1 and a resolution of 3 μm. Various cell lines showed excellent adhesion and viability on the magnetic photoresists. An inspection of cells cultured on the magnetic photoresists with TEM showed cellular uptake of magnetic nanoparticles leeched from the photoresists. Cellular contamination by magnetic nanoparticles was eliminated by capping the magnetic photoresist surface with native 1002F photoresist or by removing the top layer of the magnetic photoresist through surface roughening. The utility of these magnetic photoresists was demonstrated by sorting single cells (HeLa, RBL and 3T3 cells) cultured on arrays of releasable magnetic micropallets. 100% of magnetic micropallets with attached cells were collected following release from the array. 85-92% of the collected cells expanded into colonies. The polymeric magnetic materials should find wide use in the fabrication of microstructures for bioanalytical technologies.

Comparison of ferucarbotran-enhanced fluid-attenuated inversion-recovery echo-planar, T2-weighted turbo spin-echo, T2*-weighted gradient-echo, and diffusion-weighted echo-planar imaging for detection of malignant liver lesions

PURPOSE

To compare the diagnostic accuracy of superparamagnetic iron oxide (SPIO)-enhanced fluid-attenuated inversion-recovery echo-planar imaging (FLAIR EPI) for malignant liver tumors with that of T2-weighted turbo spin-echo (TSE), T2*-weighted gradient-echo (GRE), and diffusion-weighted echo-planar imaging (DW EPI).

MATERIALS AND METHODS

SPIO-enhanced magnetic resonance imaging (MRI) that included FLAIR EPI, T2-weighted TSE, T2*-weighted GRE, and DW EPI sequences was performed using a 3 T system in 54 consecutive patients who underwent surgical exploration with intraoperative ultrasonography. A total of 88 malignant liver tumors were evaluated. Images were reviewed independently by two blinded observers who used a 5-point confidence scale to identify lesions. Results were correlated with results of histopathologic findings and surgical exploration with intraoperative ultrasonography. The accuracy of each MRI sequence was measured with jackknife alternative free-response receiver operating characteristic analysis. The sensitivity of each observer with each MRI sequence was compared with McNemar's test.

RESULTS

Accuracy values were significantly higher with FLAIR EPI sequence (0.93) than with T2*-weighted GRE (0.80) or DW EPI sequences (0.80) (P < 0.05). Sensitivity was significantly higher with the FLAIR EPI sequence than with any of the other sequences.

CONCLUSION

SPIO-enhanced FLAIR EPI sequence was more accurate in the diagnosis of malignant liver tumors than T2*-weighted GRE and DW EPI sequences. SPIO-enhanced FLAIR EPI sequence is helpful for the detection of malignant liver tumors.

Detection of hepatic metastases by superparamagnetic iron oxide-enhanced MR imaging: prospective comparison between 1.5-T and 3.0-T images in the same patients

OBJECTIVE

To prospectively compare the diagnostic performance of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging at 3.0 T and 1.5 T for detection of hepatic metastases.

METHODS

A total of 28 patients (18 men, 10 women; mean age, 61 years) with 80 hepatic metastases were prospectively examined by SPIO-enhanced MR imaging at 3.0 T and 1.5 T. T1-weighted gradient-recalled-echo (GRE) images, T2*-weighted GRE images and T2-weighted fast spin-echo (SE) images were acquired. The tumour-to-liver contrast-to-noise ratio (CNR) of the lesions was calculated. Three observers independently reviewed each image. Image artefacts and overall image quality were analysed, sensitivity and positive predictive value for the detection of hepatic metastases were calculated, and diagnostic accuracy using the receiver-operating characteristics (ROC) method was evaluated.

RESULTS

The tumour-to-liver CNRs were significantly higher at 3.0 T. Chemical shift and motion artefact were more severe, and overall image quality was worse on T2-weighted fast SE images at 3.0 T. Overall image quality of the two systems was similar on T1-weighted GRE images and T2*-weighted GRE images. Sensitivity and area under the ROC curve for the 3.0-T image sets were significantly higher.

CONCLUSION

SPIO-enhanced MR imaging at 3.0 T provided better diagnostic performance for detection of hepatic metastases than 1.5 T.

Approach to a liver mass

Incidentally discovered liver masses are becoming more common with the increasing application and power of imaging techniques for the evaluation of abdominal conditions. Although such masses are often benign, conclusive diagnoses must be established in order to provide appropriate patient care. Various imaging modalities can be utilized to accurately diagnose such masses without resort to more invasive diagnostic measures.

Imaging of small hepatic metastases of colorectal carcinoma: how to use superparamagnetic iron oxide-enhanced magnetic resonance imaging in the multidetector-row computed tomography age?

PURPOSE

To compare the accuracy of dynamic contrast-enhanced multidetector-row computed tomography (CT) and superparamagnetic iron oxide-enhanced magnetic resonance imaging (MRI) in the evaluation of small hepatic metastases of colorectal carcinoma.

MATERIALS AND METHODS

Of 94 patients with colorectal carcinoma analyzed, 76 hepatic metastases (<2 cm) were diagnosed in 17 patients. Superparamagnetic iron oxide (SPIO)-magnetic resonance (precontrast and postcontrast MRI) and dynamic contrast-enhanced multidetector-row CT (dynamic CT [precontrast, arterial, portal-venous, and delayed phase]) were evaluated. The alternative free-response receiver operating characteristic analysis was performed, and the sensitivities and positive predictive values were analyzed.

RESULTS

The Az values and sensitivities of portal-venous phase CT, dynamic CT, and SPIO-MRI (0.62/59%, 0.69/61%, and 0.67/61%) were identical. The mean positive predictive value of dynamic CT (82%) was inferior to that of SPIO-MRI (91%).

CONCLUSIONS

The diagnostic ability of dynamic CT is identical to that of SPIO-MRI in Az value and sensitivity. Superparamagnetic iron oxide-MRI should be recommended only if an equivocal lesion is detected by dynamic CT.

Resovist-enhanced MRI for preoperative assessment of colorectal hepatic metastases: a case of multiple bile duct hamartomas associated with colon cancer

Extensive preoperative assessment of hepatic metastases is required in colon cancer patients. We report a case in whom the preoperative investigation by ultrasound scan and contrast-enhanced computed tomography revealed numerous cystic lesions of the liver, suspicious of von Meyenburg complex. Magnetic resonance and magnetic resonance cholangiographic images demonstrated typical features of von Meyenburg complex. Further Resovist-enhanced magnetic resonance imaging detected two hemangiomas in addition to the multiple cystic lesions. So-called Kupffer cell imaging strongly helped the detection of these hemangiomas, and a combination of various magnetic resonance pulse sequences was of great value for the differential diagnosis of cystic lesions and hemangiomas. In cases in whom conventional imaging studies fail to give a definite diagnosis, such as in the present case, superparamagnetic iron oxide-enhanced magnetic resonance imaging is meaningful for adequate preoperative staging.

Ferucarbotran-enhanced T2-weighted magnetic resonance imaging: differentiation of hepatic cavernous hemangiomas from malignant solid lesions

BACKGROUND

To demonstrate the characteristic feature of hepatic cavernous hemangiomas on ferucarbotran-enhanced T2-weighted MR imaging as a new diagnostic finding.

METHODS

In 201 hepatic lesions (61 hemangiomas, 61 cysts, 41 hepatocellular carcinomas, 31 metastatic carcinomas, and 7 cholangiocarcinomas), lesion-to-liver contrast on ferucarbotran-enhanced T2-weighted images was qualitatively compared with pre-contrast images by three independent readers using a four-grade scale (group 1, marked increase; group 2, mild increase; group 3, no change; group 4, decrease). The change in the contrast-to-noise ratio (CNR) for each lesion was quantitatively measured.

RESULTS

Only hemangiomas showed a significant decrease in CNR; 10% and 90% of the hemangiomas were categorized as group 3 and 4 lesions, respectively. Besides the hemangiomas, there was no other lesion categorized into group 4 except for one cyst. When group 4 lesions were considered hemangiomas, the accuracy of identification was 96.4%.

CONCLUSION

Hemangiomas show a significant decrease in lesion-to-liver contrast on T2-weighted images after ferucarbotran injection, which might be another typical diagnostic imaging finding of hemangiomas distinguished from solid malignant lesions.

Mechanism of hepatic parenchyma-specific contrast of microbubble-based contrast agent for ultrasonography: microscopic studies in rat liver

OBJECTIVE

The objective of this study was to elucidate the mechanism of hepatic parenchyma-specific contrast of Sonazoid (microbubble contrast agent) using microscopic techniques.

MATERIALS AND METHODS

Sonazoid was intravenously injected into rats to investigate the microbubble dynamics and distribution within hepatic microcirculation in exteriorized liver using intravital microscopy and to observe dose dependency of ultrasound hepatic contrast effect. In vitro and in vivo uptake of microbubbles by Kupffer cells was examined using confocal laser scanning microscopy.

RESULTS

Intravital observation demonstrated freely flowing microbubbles in the sinusoid and some microbubbles co-localized with Kupffer cells. The microbubbles internalized in Kupffer cells were identified with reflected light by confocal laser scanning microscopy. The percentage of Kupffer cells taking up microbubbles was about 1% at clinical dose at which the homogeneous hepatic contrast was observed.

CONCLUSIONS

The hepatic parenchyma-specific contrast by Sonazoid is due to distribution of the microbubbles in Kupffer cells.

Hepatobiliary MRI: current concepts and controversies

Evaluation of the liver and biliary system is a frequent indication for abdominal MRI. Hepatobiliary MRI comprises a set of noninvasive techniques that are usually very effective in answering most clinical questions. There are significant limitations, however, as well as considerable variation and disagreement regarding the optimal protocols for standard hepatic MRI and magnetic resonance cholangiopancreaticography (MRCP). This review discusses pulse sequences most often used in hepatic MRI and MRCP, examines a few sources of controversy in the current literature, and summarizes some recent and future developments in the field.

USPIO-enhanced MR imaging of macrophage infiltration in native and transplanted kidneys: initial results in humans

The purpose of this study was to evaluate the detection and characterization of macrophage infiltration in native and transplanted kidneys using ultrasmall superparamagnetic iron oxide particles (USPIO). Among 21 patients initially enrolled, 12 scheduled for renal biopsy for acute or rapidly progressive renal failure (n = 7) or renal graft rejection (n = 5) completed the study. Three magnetic resonance (MR) sessions were performed with a 1.5-T system, before, immediately after and 72 h after i.v. injection of USPIO at doses of 1.7-2.6 mg of iron/kg. Signal intensity change was evaluated visually and calculated based on a region of interest (ROI) positioned on the kidney compartments. Histological examination showed cortical macrophage infiltration in four patients (>5 macrophages/mm(2)), two in native kidneys (proliferative extracapillary glomerulonephritis) and two in transplants (acute rejection). These patients showed a 33 +/- 18% mean cortical signal loss on T2*-weighted images. In the remaining eight patients, with <5 macrophages/mm(2), there was no cortical signal loss. However, in three of these, presenting with ischemic acute tubular necrosis, a strong (42 +/- 18%) signal drop was found in the medulla exclusively. USPIO-enhanced MR imaging can demonstrate infiltration of the kidneys by macrophages both in native and transplanted kidneys and may help to differentiate between kidney diseases.

Evaluation of the changes in signals from the spleen using ferucarbotran

PURPOSE

Because superparamagnetic iron oxide is actively taken into the reticuloendothelial system, the signal intensity observed on T2-weighted images is reduced not only in the liver but also in the spleen. There is no difference in the reduction in signal intensity in the liver after contrast between the ferumoxides and ferucarbotran, but the reduction in signal intensity in the spleen is considerable. In the present study, we examined the efficacy of T2*-weighted imaging to compensate for the reduction in signal intensity in the spleen by administering ferucarbotran.

MATERIALS AND METHODS

We examined the images obtained from 35 patients who underwent MRI with ferucarbotran. T2-weighted images and T2*-weighted images were obtained before and after administration of ferucarbotran, and the changes in signal intensity in the liver and spleen were then analyzed.

RESULTS

A reduction in signal intensity was observed in the liver by both T2- and T2*-weighted imaging. In the spleen, the signal intensity was reduced on T2-weighted images but was not reduced on T2*-weighted images.

CONCLUSION

The reduction in signal intensity due to administration of ferucarbotran is low in the spleen. Thus, it was considered necessary to approach the problem of diagnosing ectopic splenic tissue using ferucarbotran with caution.

Changes in signal-to-noise ratios and contrast-to-noise ratios of hypervascular hepatocellular carcinomas on ferucarbotran-enhanced dynamic MR imaging

PURPOSE

To verify changes in the signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) of hypervascular hepatocellular carcinomas (HCCs) on ferucarbotran-enhanced dynamic T1-weighted MR imaging.

MATERIALS AND METHODS

Fifty-two patients with 61 hypervascular HCCs underwent ferucarbotran-enhanced dynamic MR imaging, and then hepatic resection. Hypervascular HCCs were identified when definite enhancement was noted during the arterial dominant phase of three-phase MDCT. Dynamic MR Images with T1-weighted fast multiplanar spoiled gradient-recalled echo sequence (TR200/TE4.2) were obtained before and 20 s, and 1, 3, 5, and 10 min, after bolus injection of ferucarbotran. We estimated the signal intensities of tumors and livers, and calculated the SNRs and CNRs of the tumors.

RESULTS

On ferucarbotran-enhanced dynamic MR imaging, SNR measurements showed a fluctuating pattern, namely, an increase in SNR followed by a decrease and a subsequent increase (or a decrease in SNR followed by a increase and a subsequent decrease) in 50 (82.0%) of 61 tumors, a single-peak SNR pattern (highest SNR on 20 s, 1, 3, or 5 min delayed images followed by a decrease) in seven (11.5%), and a decrease in SNR followed by an increase in four (6.6%). Maximum absolute CNRs with positive value were noted on 10 min delayed images in 41 (67.2%) tumors, and maximum absolute CNRs with negative value were observed on 20 s delayed images in 12 (19.7%) and on 1 min delayed images in eight (13.1%).

CONCLUSION

Despite showing various SNR and CNR changes, the majority of hypervascular HCCs demonstrated a fluctuating SNR pattern on ferucarbotran-enhanced dynamic MR imaging and a highest CNR on 10 min delayed image, which differed from the classic enhancement pattern on multiphasic CT.

Relaxometry model of strong dipolar perturbers for balanced-SSFP: application to quantification of SPIO loaded cells

Magnetic resonance microscopy using magnetically labeled cells is an emerging discipline offering the potential for non-destructive studies targeting numerous cellular events in medical research. The present work develops a technique to quantify superparamagnetic iron-oxide (SPIO) loaded cells using fully balanced steady state free precession (b-SSFP) imaging. An analytic model based on phase cancellation was derived for a single particle and extended to predict mono-exponential decay versus echo time in the presence of multiple randomly distributed particles. Numerical models verified phase incoherence as the dominant contrast mechanism and evaluated the model using a full range of tissue decay rates, repetition times, and flip angles. Numerical simulations indicated a relaxation rate enhancement (DeltaR(2b)=0.412 gamma . LMD) proportional to LMD, the local magnetic dose (the additional sample magnetization due to the SPIO particles), a quantity related to the concentration of contrast agent. A phantom model of SPIO loaded cells showed excellent agreement with simulations, demonstrated comparable sensitivity to gradient echo DeltaR(*) (2) enhancements, and 14 times the sensitivity of spin echo DeltaR(2) measurements. We believe this model can be used to facilitate the generation of quantitative maps of targeted cell populations.

Diffusion-weighted imaging of the liver: technical challenges and prospects for the future

Diffusion-weighted imaging (DWI) has recently been attempted in the abdominal region. We review diffusion-weighted images of the liver, especially from the technical point of view. We discuss selection of pulse sequence parameters, effects of anti-breathing motion technique, tips for measuring apparent diffusion coefficient (ADC), and utility of superparamagnetic iron oxide (SPIO), showing clinical cases, including those at 3T. Our current trial of new pulse sequencing, such as SPIO-mediated breath-holding black-blood fluid-attenuated inversion recovery (BH-BB-FLAIR), imaging is shown. Some prospects for the future in DWI of the liver are also stated.

Gradient- and spin-echo T2-weighted imaging for SPIO-enhanced detection and characterization of focal liver lesions

PURPOSE

To evaluate superparamagnetic iron oxide (SPIO)-enhanced breathhold T2-weighted GRASE imaging in detection and characterization of focal liver lesions.

MATERIALS AND METHODS

In 30 patients (including 20 with cirrhosis) with 39 malignant and 25 benign lesions, gradient- and spin-echo (GRASE) images with two echo times (75 and 90 msec; GRASE75 and GRASE90) were obtained prior to and following administration of SPIO, and compared with respiratory-triggered and breathhold fast spin-echo (RT-FSE and BH-FSE) images. Two readers evaluated image quality and reviewed 240 liver segments for sensitivity and specificity. Signal-to-noise ratio (SNR), and its reduction in liver and spleen after administration of SPIO, and lesion-to-liver contrast-to-noise ratio (CNR) were measured.

RESULTS

Compared with RT-FSE and BH-FSE, GRASE reduced scan time by 77% to 82% and 21% to 27%, respectively. The image qualities with BH-FSE and GRASE75 were higher than with BH-FSE and GRASE90. BH-FSE showed higher specificity than RT-FSE and GRASE90, but otherwise there were no significant differences between pulse sequences for sensitivity or specificity. The mean SNR and CNR of the lesions with RT-FSE were significantly higher than with the other methods. SPIO-induced signal reduction of liver SNR was smallest with BH-FSE.

CONCLUSION

GRASE is faster and more sensitive to SPIO than FSE, but its sensitivity and specificity were slightly inferior to those of BH-FSE. Image quality is a current limitation.

Detection of Portal Perfusion Abnormalities

OBJECTIVE

To estimate the accuracy, sensitivity, and specificity of 3 ferucarbotran-enhanced magnetic resonance (MR) imaging sequences prospectively for the detection of nontumoral portal perfusion abnormalities.

METHODS

Thirty-nine noncirrhotic patients with liver metastases underwent computed tomography during arterial portography (CTAP) and MR imaging comprising T1-weighted gradient recalled echo (GRE), T2-weighted fast spin echo (FSE), and T2*-weighted GRE sequences with and without ferucarbotran. Magnetic resonance images were reviewed by 4 blinded observers for rating based on the confidence scale. The accuracy, sensitivity, and specificity for each sequence were measured by receiver operating characteristic analysis. Contrast-to-noise ratio (CNR) and relative signal-to-noise ratio changes were statistically compared.

RESULTS

Thirty-nine nontumoral perfusion defects were observed in 22 patients by CTAP. Receiver operating characteristic analysis showed the accuracy was higher for T2*-weighted GRE (0.884) than for T1-weighted GRE (0.572) and T2-weighted FSE (0.597). T2*-weighted imaging achieved the highest sensitivity (81.4%) and the lowest specificity (86.6%). Postenhanced T2*-weighted imaging achieved the highest CNR (19.3 +/- 9.2).

CONCLUSIONS

T2*-weighted imaging was the most accurate and sensitive method for detecting portal perfusion abnormalities compared with T1- or T2-weighted imaging, whereas T1- or T2-weighted imaging is superior in specificity to T2*-weighted imaging during ferucarbotran-enhanced MR imaging.

Hepatic metastases: detection with multi-detector row CT, SPIO-enhanced MR imaging, and both techniques combined

PURPOSE

To retrospectively compare the accuracy in detection of hepatic metastases among contrast material-enhanced multi-detector row computed tomography (CT) alone, superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging alone, and a combination of contrast-enhanced CT and SPIO-enhanced MR imaging.

MATERIALS AND METHODS

The ethics committee did not require its approval or informed consent for this retrospective study, which was compliant with Declaration of Helsinki principles. Data in 38 patients (22 men, 16 women; mean age, 64.5 years; range, 35-78 years) suspected of having hepatic metastases who underwent both contrast-enhanced CT and SPIO-enhanced MR imaging were retrospectively analyzed. Twenty-one of the 38 patients had 61 metastases. Seventeen of the 61 metastases were confirmed histologically; the remaining 44 metastases were defined with imaging follow-up. At MR imaging, SPIO-enhanced heavily T1-weighted images, T2*-weighted gradient echo images, and T2-weighted fast spin-echo images were evaluated. Contrast-enhanced multi-detector row CT images obtained in the portal phase were evaluated. Four blinded observers independently reviewed CT images, MR images, and the combination of CT and MR images. Diagnostic accuracy was evaluated by using the alternative free-response receiver operating characteristic (AFROC) method. Sensitivities and positive predictive values were also analyzed with the Fisher protected least significant difference test and generalized estimating equations.

RESULTS

The mean area under the AFROC curve for the combined approach (0.70) was significantly higher than that for SPIO-enhanced MR imaging alone (0.58, P < .05, Fisher protected least significant difference test), and there was no significant difference between each of them and that for contrast-enhanced CT alone (0.66). For all lesions, the mean sensitivity of combined imaging (0.59) was significantly higher than that of CT (0.48) or MR imaging (0.43) alone (P < .05, Fisher protected least significant difference test and generalized estimating equations). For all lesions, the mean positive predictive values were 0.82, 0.89, and 0.81, for combined MR and CT, CT alone, and MR alone, respectively.

CONCLUSION

The addition of SPIO-enhanced MR imaging to contrast-enhanced multi-detector row CT (ie, combined analysis of SPIO-enhanced MR images and contrast-enhanced CT images) can improve sensitivity in the detection of hepatic metastases, although this improvement in sensitivity was not significant at AFROC analysis.

Hemodynamic characterization of focal hepatic lesions: Role of ferucarbotran-enhanced dynamic MR imaging using T2-weighted multishot spin-echo echo-planar sequence

PURPOSE

To investigate the role of ferucarbotran-enhanced dynamic MR imaging using multishot spin-echo echo-planar sequence in the evaluation of hemodynamics of focal hepatic lesions.

MATERIALS AND METHODS

Sixty-three focal hepatic lesions (24 benign and 39 malignant) from 53 consecutive patients who underwent both ferucarbotran-enhanced MR imaging and dynamic computed tomography (CT) were included in this study. MR imaging was performed with a 1.5-T scanner with a phased-array coil. T2-weighted multishot spin-echo echo-planar sequences (TR/TE = 1714-2813/80 msec) were obtained during a single breathhold before and 15, 60, 120, 180, and 600 seconds after intravenous injection of ferucarbotran. The enhancement patterns of lesions were classified into three categories by a study coordinator on the basis of dynamic CT images as hypervascular, hypovascular, and hemangioma type. The study coordinator created mean contrast-to-noise ratio of lesions vs. time curves for each enhancement pattern for quantitative analyses. Moreover, three radiologists separately and blindly reviewed MR images, and then assigned three confidence scores for the three enhancement patterns to each lesion. Sensitivity, specificity, and receiver operating characteristic analyses were performed.

RESULTS

Quantitative analyses showed characteristic enhancement curves for each enhancement pattern. Mean sensitivities/specificities were 0.816/0.882, 0.897/0.863, and 0.800/0.989 for hypervascular, hypovascular, and hemangioma types, respectively. Mean areas under the receiver operating characteristic curve were 0.886 for hypervascular type and 0.913 for hypovascular type.

CONCLUSION

Ferucarbotran-enhanced dynamic MR imaging can be used to successfully characterize the hemodynamics of focal hepatic lesions.

Focal liver lesions: Breathhold gradient- and spin-echo T2-weighted imaging for detection and characterization

PURPOSE

To evaluate breathhold gradient- and spin-echo (GRASE) T2-weighted imaging for the detection and characterization of focal liver lesions.

MATERIALS AND METHODS

Two GRASE sequences with different echo times (75 and 90 msec, GRASE75 and GRASE90) were compared with respiratory-triggered fast spin-echo (SE) and breathhold fast SE in 64 patients with 103 malignant and 51 benign lesions. Compared with respiratory-triggered and breathhold fast SE, GRASE reduced scan time by 77% to 82% and 21% to 27%, respectively. Two independent readers evaluated image quality and reviewed 504 liver segments on a segment-by-segment basis. Observer performance was evaluated with receiver operating characteristic (ROC) curve analysis. The signal-to-noise ratio (SNR) of liver and spleen, and lesion-to-liver contrast-to-noise ratio (CNR) were also measured.

RESULTS

The overall quality of the GRASE images was higher than that of the respiratory-triggered and breathhold fast SE images, although signal inhomogeneities were more frequently observed with GRASE. No significant difference in the values of the area under the ROC curve (Az) for malignant lesion detection was found. The mean SNR and CNR were highest for respiratory-triggered fast SE.

CONCLUSION

T2-weighted breathhold GRASE has the potential to provide faster liver imaging.

Hepatocellular carcinoma in cirrhosis: enhancement patterns at dynamic gadolinium- and superparamagnetic iron oxide-enhanced T1-weighted MR imaging

PURPOSE

To prospectively compare intraindividual differences in enhancement patterns between gadolinium- and superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging in patients with histologically proved hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Twenty-two patients (18 men, four women; mean age, 58.9 years) with 36 pathologically proved HCC lesions underwent contrast material-enhanced dynamic T1-weighted gradient-echo MR imaging twice. Gadopentetate dimeglumine was used at the first session. After a mean interval of 5 days, a second session was performed with a bolus-injectable SPIO agent, ferucarbotran. Qualitative analysis of contrast enhancement patterns with each agent during hepatic arterial, portal venous, and equilibrium phases was performed by two readers who classified lesions as isointense, hypointense, or hyperintense compared with surrounding liver parenchyma and searched for presence of hyperintense peritumoral ring enhancement. Results of signal intensity analysis during different vascular phases at both sessions were compared by using the McNemar test, and kappa statistic was used to evaluate agreement between signal intensity and enhancement pattern of lesions during different vascular phases.

RESULTS

On gadolinium-enhanced hepatic arterial phase images, HCC lesions (n = 36) were hyperintense in 21 (58%) cases, hypointense in 10 (28%), and isointense in five (14%). On ferucarbotran-enhanced hepatic arterial phase images, HCC lesions were isointense in 18 (50%) cases, hypointense in 11 (31%), and hyperintense in seven (19%). On gadolinium-enhanced portal venous and equilibrium phase images, respectively, HCC lesions were hypointense in 17 (47%) and 21 (58%) cases, hyperintense in 10 (28%) cases and one (3%) case, and isointense in nine (25%) and 14 (39%) cases. On ferucarbotran-enhanced portal venous and equilibrium phase images, respectively, HCC lesions were hypointense in 15 (42%) and 11 (31%) cases, hyperintense in three (8%) and three (8%) cases, and isointense in 18 (50%) and 22 (61%) cases.

CONCLUSION

For HCC, contrast enhancement pattern on T1-weighted gradient-echo MR images shows marked variability with gadolinium or SPIO contrast agents.

Utilidad de la gammagrafía selectiva con hematíes desnaturalizados Tc-99m en un caso de esplenosis hepática

The term splenosis, first used in the medical literature in 1939, refers to the autotransplantation of splenic tissue in a heterotopic location. We report the case of a known hepatitis C carrier in whom computed tomography scanning revealed a hepatic lesion suggestive of hepatocarcinoma. Magnetic Resonance imaging was performed for suspected hepatic splenosis, which was confirmed by Tc-99m labeled heat-denatured red blood cell scintigraphy. In addition to confirming the suspected diagnosis, this technique showed several pathological foci in distinct abdominal locations compatible with splenosis that had not previously been identified.

[Current status of MRI diagnostics with liver-specific contrast agents. Gd-EOB-DTPA and Gd-BOPTA]

The contrast agents Gd-EOB-DTPA and Gd-BOPTA can be administered by bolus injection and are appropriate for use in MRI both as vascularization markers and markers of hepatobiliary excretion. This contribution presents an overview of the specific characteristics of contrast media and the status of clinical development. In comparison to CT and to MRI with unspecific extracellular Gd-chelates, liver-specific contrast agents offer advantages in differentiating unclear liver lesions, increasing the detection rate, and examining the bile duct system.

MRI after magnetic drug targeting in patients with advanced solid malignant tumors

The purpose of this study was to evaluate the ability of MRI to detect magnetic particle uptake into advanced solid malignant tumors and to document the extension of these tumors, carried out in the context of magnetic drug targeting. In a prospective phase I trial, 11 patients were examined with MRI before and after magnetic drug targeting. The sequence protocol included T1-WI and T2-WI in several planes, followed by quantitative and qualitative evaluation of the signal intensities and tumor extensions. In nine patients, a signal decrease was observed in the early follow-up (2-7 days after therapy) on the T2-weighted images; two patients did not show a signal change. The signal changes in T1-WI were less distinct. In late follow-up (4-6 weeks after therapy), signal within nine tumors reached their initially normal level on both T1-WI and T2-WI; two tumors showed a slight signal decrease on T2-WI and a slight signal increase on T1-WI. Within the surveillance period, tumor remission in 3 out of 11 patients was observed, and in 5 patients tumor growth had stopped. The remaining three patients showed significant tumor growth. There was no statistically significant correlation between signal change and response. MRI is a suitable method to detect magnetite particles, deposited at the tumor site via magnetic drug targeting. MRI is therefore eligible to control the success of MDT and to assess the tumor size after the end of therapy.

Comparison of dynamic gadolinium-enhanced and ferumoxides-enhanced MRI of the liver on high- and low-field scanners

PURPOSE

To compare the performance of dynamic gadolinium-enhanced and ferumoxides-enhanced MRI in the detection and characterization of hepatic lesions, on 1.5-T and 0.2-T magnets

MATERIALS AND METHODS

In 41 patients (23 men, 18 women), 52 hepatic MR examinations were performed and retrospectively analyzed; 39 and 13 examinations were performed on 1.5-T and 0.2-T magnets, respectively. A total of 33 of 41 patients had known malignancies, and 31 of 33 patients had biopsy of at least one lesion. First, a combination of unenhanced T2-weighted sequences and gradient-echo T1-weighted sequences were performed. Then, dynamic gadolinium-enhanced (0.1 mmol/kg) T1 GRE sequences were obtained, followed by intravenous drip infusion of ferumoxides (10 micromol/kg). The T2-weighted sequences were then repeated. The unenhanced and gadolinium-enhanced images (the Gd set) were reviewed separately from the unenhanced and ferumoxides-enhanced images (the ferumoxides set) by two abdominal imagers. The reviewers were blinded to clinical history and reviewed the individual studies in each set randomly. Each detected lesion was scored on a five-point scale for characterization scores: nonsolid (1 or 2), indeterminate (3), or solid (4 or 5). A consensus review was then performed correlating all available pathology, imaging, clinical findings, and follow-up to act as a gold standard. Receiver-operating-characteristic (ROC) curves were generated and both area-under-the-curve (Az values) and sensitivity values were calculated. Significance of Az and sensitivity differences was assessed using standard Z-test and chi-square.

RESULTS

Of 270 lesions detected by consensus, 211 were on 1.5-T and 59 were on 0.2-T scanners. The accuracy (Az values) of lesion detection overall, of both readers, was greater for the ferumoxides set than for the Gd set (reader 1: 0.95 vs. 0.89 (P < 0.05); reader 2: 0.91 vs. 0.78 (P < 0.05)). Az values for both readers were greater on the ferumoxides set for both the 1.5-T scans and the 0.2-T scans. Out of 270 lesions detected, 231 were characterized by consensus review as solid (185) or nonsolid (46). There was a significant improvement in lesion characterization for both readers on the GD set compared with the ferumoxides set on both high and low field scanners (Az reader 1: 0.99 vs. 0.96 (P < 0.05); Az reader 2: 0.99 vs. 0.95 (P < 0.05)), respectively.

CONCLUSION

At both 1.5-T and 0.2-T, ferumoxides-enhanced sequences were better for lesion detection, while gadolinium-enhanced sequences were better for lesion characterization, respectively.