Superparamagnetic Iron Oxide-enhanced Magnetic Resonance Imaging Research Articles

Efficacy of SPIO-MR Imaging in the Diagnosis of Liver Metastases from Colorectal Carcinomas

Aim: To determine whether superparamagnetic iron oxide-enhanced magnetic resonance imaging (SPIO-MRI) could replace intravenous contrast-enhanced spiral CT (iv-CT) and spiral CT during arterial portography (CTAP) combined with spiral CT hepatic angiography (CTHA) in the diagnosis of liver metastases from colorectal carcinomas. Methods: Twenty-six adult patients with liver metastases were studied preoperatively by means of iv-CT, CTAP/CTHA, and SPIO-MRI. Preoperative diagnoses using iv-CT, CTAP/CTHA, and SPIO-MRI were compared with intraoperative and pathological findings in resected specimens. The gold standard for the lesions that were resected was histological examination. Intraoperative findings represented the gold standard for lesions that were not resected. Results: Twenty-six patients were found to have a total number of 43 liver metastases. The sensitivities of iv-CT, CTAP/CTHA, and SPIO-MRI were 74.4, 100, and 90.7%, respectively. SPIO-MRI was significantly superior to iv-CT (p < 0.05). The positive predictive values of iv-CT, CTAP/CTHA, and SPIO-MRI were 97.0, 91.5, and 100%, respectively. CTAP/CTHA yielded four false-positive lesions. In contrast, we detected no false-positive findings using SPIO-MRI. Conclusions: These results suggest that SPIO-MRI might not completely replace CTAP/CTHA, but could replace iv-CT in the diagnosis of liver metastases from colorectal carcinomas. It is thought that SPIO-MRI is a promising imaging modality for diagnosing liver metastases in patients with colorectal carcinoma because of its relatively high sensitivity and extremely high specificity.

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

ObjectiveTo determine the potential value of distributional-phase T1-weighted ferumoxides-enhanced magnetic resonance (MR) imaging for tissue characterization of focal liver lesions.Materials and MethodsFerumoxides-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.ResultsDuring 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.ConclusionT1-weighted double-echo FLASH images obtained soon after the infusion of ferumoxides, show characteristic enhancement patterns and improved the differentiation of focal liver lesions.

Detection of small hypervascular hepatocellular carcinomas in cirrhotic patients: comparison of superparamagnetic iron oxide-enhanced MR imaging with dual-phase spiral CT.

ObjectiveTo compare the performance of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging at 1.5T and dual-phase spiral computed tomography (CT) for the depiction of small hypervascular hepatocellular carcinomas (HCCs).Materials and MethodsForty-three patients with 70 small nodular HCCs (5-20 mm; mean, 13.7 mm) were examined. Diagnosis was based on the results of surgical biopsy in 22 patients and by the combined assessment of MR imaging, lipiodol CT, alpha feto-protein levels, and angiographic findings in 21. MR imaging consisted of respiratory-triggered turbo spin-echo T2-weighted imaging, T1-weighted fast low-angle shot, and T2*-weighted fast imaging with steady-state precession imaging before and after SPIO enhancement. CT imaging was performed with 5-mm collimation and 1:1.4 pitch, and began 30 and 65 secs after the injection of 150 mL of contrast medium at a rate of 3 mL/sec. Two blinded observers reviewed all images independently on a segment-by-segment basis. Diagnostic accuracy was evaluated using receiver operating characteristics (ROC) analysis.ResultsThe mean areas (Az) under the ROC curves were 0.85 for SPIO-enhanced MR imaging and 0.79 for dual-phase spiral CT (p < .05). The mean sensitivity of SPIO-enhanced MR imaging was significantly higher than that of CT (p < .05), i.e. 70.6% for MR imaging and 58.1% for CT. MR imaging had higher false-positive rates than dual-phase spiral CT, but the difference was not statistically significant (3.7% vs 3.3%) (p > .05).ConclusionSPIO-enhanced MR imaging is more sensitive than dual-phase spiral CT for the depiction of small hypervascular hepatocellular carcinomas.

Effect of superparamagnetic iron oxide-enhanced MRI of the liver with hepatocellular carcinoma and hyperplastic nodule.

To evaluate the possibility of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging (MRI) of the liver in predicting the histologic grade of hepatocellular carcinoma (HCC) and differentiating HCC from benign hyperplastic nodule (HPN). Thirty patients with 31 histologically proved HCC and HPN underwent MRI (1.5 Tesla). HCCs were graded into well-differentiated HCC (HCCw; n = 10) and moderately to poorly differentiated HCC (HCCmp; n = 15). HPN was categorized into dysplastic nodule (DN; n = 1) and focal nodular hyperplasia (FNH; n = 6). T2-weighted fast spin echo images were obtained before and after administration of SPIO. Signal-to-noise ratios (SNR) of the lesion and surrounding liver parenchyma and contrast-to-noise ratios (CNR) were calculated pre- and postcontrast study. Relative enhancement ratios (RER), also known as signal intensity reduction ratios of the lesions, were also calculated. HCCw, HCCmp, DN, and FNH decreased in SNR after injection of SPIO. RER of HCCw was 19.5 +/- 13.3%, that of HCCmp was 6.8 +/- 5.8%, DN was 44.0%, and FNH was 42.9 +/- 4.8%. Significant statistical differences were seen between HCCw and HCCmp and HCC and HPN in RER. HCCw, HCCmp, and DN increased in CNR, and FNH decreased in CNR, but no lesion showed a statistically significant difference in CNR. SPIO-enhanced MR images may help to predict the histologic grade of HCC and distinguish HCC from HPN.

Superparamagnetic iron oxide–enhanced magnetic resonance images of hepatocellular carcinoma: Correlation with histological grading

Superparamagnetic iron oxide (SPIO)–enhanced magnetic resonance (MR) imaging has been used for the detection of hepatic tumors. However, little is known about this technique in relation to hepatocellular carcinoma (HCC). The aim of this study was to investigate whether SPIO–enhanced MR imaging can be useful in assessing histological grades of HCC. The authors studied histologically proven tumors including 31 HCCs and 6 dysplastic nodules. The ratio of the Kupffer-cell count in the tumorous tissue relative to that in the nontumorous tissue (Kupffer-cell–count ratio) decreased as HCCs became less well differentiated. The ratio of the intensity of the tumorous lesion to that of the nontumorous area on SPIO–enhanced MR images (SPIO intensity ratio) correlated inversely with Kupffer-cell–count ratio in HCCs and dysplastic nodules (r = −.826, P < .001) and increased as the degree of differentiation of HCCs decreased, indicating that the uptake of SPIO in HCCs decreased as the degree of differentiation of HCCs declined. All of the dysplastic nodules and some well-differentiated HCCs showed hypointense or isointense enhancement, relative to the surrounding liver parenchyma, indicating greater or similar uptake of SPIO in the tumor when compared with nontumorous areas. These results suggest that SPIO–enhanced MR imaging reflects Kupffer-cell numbers in HCCs and dysplastic nodules, and is useful for estimation of histological grading in HCCs, although uncertainties persist in differentiating dysplastic nodules from well-differentiated HCCs. (Hepatology 2000;32:205-212.)

Early detection of radiation-induced liver injury in rat by superparamagnetic iron oxide-enhanced MR imaging.

The detectability of early liver injury induced by irradiation was studied using magnetic resonance (MR) imaging enhanced with superparamagnetic iron oxide (SPIO), a tissue-specific contrast agent against the reticuloendothelial system (RES). In rat, 3 days after focal irradiation (0-10 Gy), MR imaging was performed and specimens were obtained to observe the phagocytic function of RES. The irradiated portion of the liver was visualized with a clear demarcation from the nonirradiated part by SPIO-enhanced MR images as a decrease in negative enhancement reflecting the function of RES (P < 0.05), whereas this was impossible with nonenhanced MR images. Significant regression was observed as a dose-related change of the signal intensity in the irradiated portion on SPIO-enhanced MR images (R = 0.867, P < 0.0001). SPIO-enhanced MR imaging was reliable for detecting the range and extent of liver injury a few days after low-dose irradiation, and it may be a useful procedure for verifying the target area in clinical cases of radiation therapy.

Detection of liver metastases: comparison of superparamagnetic iron oxide-enhanced and unenhanced MR imaging at 1.5 T with dynamic CT, intraoperative US, and percutaneous US.

To compare the sensitivities of superparamagnetic iron oxide-enhanced and unenhanced magnetic resonance (MR) imaging at 1.5 T with those of percutaneous ultrasound (US), intraoperative US (IOUS), and dynamic computed tomography (CT) in the preoperative assessment of metastatic liver disease. Eighteen patients with liver metastases who were candidates for curative surgery underwent presurgical imaging. Thirteen patients underwent surgery and IOUS after undergoing preoperative US, CT, and MR imaging. In the preoperative imaging group, the standard of reference was the total number of lesions detected with any of the modalities. Superparamagnetic iron oxide-enhanced MR imaging was the most sensitive modality (99%). In the surgical group, the standard of reference was the total number of metastases identified at IOUS and pathologic examination. IOUS had the highest sensitivity (80%), followed by superparamagnetic iron oxide-enhanced MR imaging (56%). Superparamagnetic iron oxide-enhanced high-field-strength MR imaging facilitates the preoperative evaluation of potentially curable metastatic liver disease; however, it is inferior to IOUS.

Superparamagnetic iron oxide-enhanced MR imaging: pulse sequence optimization for detection of liver cancer.

The effects of magnetic resonance (MR) pulse sequences and timing parameters on tumor-liver contrast were studied in an animal model of metastatic liver cancer. Six spin-echo (SE), three inversion-recovery (IR), and four gradient-echo (GRE) sequences were evaluated at 0.6 T before and after injection of super-paramagnetic iron oxide. GRE techniques, irrespective of echo time and flip angle, showed the greatest change in signal intensity (enhancement) of the liver after administration of iron oxide. Single-acquisition GRE sequences (16 seconds) matched the contrast-to-noise ratio (C/N) performance of the most effective 6.4-minute SE sequences. Multiexcitation GRE sequences showed tumor-liver C/Ns per unit time that were significantly (P less than .05) higher than those achieved with SE and IR sequences. GRE sequences, which recruit intravoxel dephasing as an additional source of transverse relaxation enhancement (T2*), show a higher C/N per unit time and in this respect seem superior to SE and IR sequences for MR imaging with superparamagnetic iron oxide.