Info

Fatty Liver Remedy

Fatty Liver Diet Plan

Get Instant Access

50 (69%)*

64 (89%)

62 (86%)

studies should be carefully weighed since imaging equipment and parameters were not uniform among institutions (Table 4.2).

4.3.2.1. SPIO-MRI vs Non-enhanced MRI

In the early years of SPIO-enhanced MR imaging, Stark et al. reported that SPIO-enhanced images of the liver obtained with standard pulse sequence techniques significantly increased the number of hepatic lesions detected and reduced the threshold size for detection to 3 mm (Stark et al., 1988). SPIO-enhanced MR imaging is more accurate than non-enhanced MR imaging for the detection of focal hepatic lesions (Figure 4.2), and combined analysis of non-enhanced and SPIO-enhanced images is more accurate in the characterization of focal hepatic lesions on SPIO-enhanced images alone (Reimer et al., 2000; Stark et al., 1988).

4.3.2.2. SPIO-MRI vs Dynamic CT

SPIO-enhanced MRI is particularly advantageous for detecting hepatic metastases, because the surrounding liver sustains normal phagocytic activity, and metastatic liver tumors have no Kupffer cells. Therefore, the diagnosis is more straightforward than HCC derived from liver cirrhosis. Ward et al. compared SPIO-enhanced MR imaging with dual phase dynamic CT for 51 hepatic resection candidates with known colorectal metastases (Ward et al., 1999). The mean sensitivity of MR was significantly higher than that of CT (p < 0.02): 79.8% for MR and 75.3% for CT for all lesions, and 80.6% for MR and 73.5% for CT for malignant lesions. SPIO-enhanced MR imaging was more sensitive than dual-phase CT in the depiction of colorectal metastases (Ward et al., 1999). The development of multi-detector row helical CT (MDCT) allows multiple images to be obtained simultaneously during spiral acquisition. This technological advance has allowed effective scanning of the liver at collimations less than 5 mm in a single breath hold. Haider et al. (2002) investigated the value of collimations less than 5 mm in detecting hepatic metastases 1.5 cm or smaller by using MDCT. They found that no significant difference was noted in the pooled sensitivity for metastatic lesions (80% [20 of 25 lesions]) and in the conspicuity of lesions at different collimations (5.00, 3.75, and 2.50 mm) (Haider et al., 2002).

Recently, Onishi et al. (2006) compared SPIO-enhanced MR imaging with MDCT. There was no significant difference in the sensitivity of detection of hepatic metastases between contrast-enhanced MDCT alone and SPIO-enhanced

Picture Liver Metastases
Figure 4.2. Liver metastasis from gastric cancer in a 52-year-old male: Unenhanced vs SPIO-enhanced MR imaging. No lesion is found on unenhanced T2-weighted FSE (a). SPIO-enhanced MR imaging reveals a small mass exhibiting decreased phagocytic activity in the lateral segment (b; arrow).

MR images alone. However, the addition of SPIO-enhanced MR imaging to contrast-enhanced MDCT can improve sensitivity in the detection of hepatic metastases. Another study using MDCT, Gd-enhanced MR imaging and SPIO-enhanced MR imaging showed that accuracy for gadolinium-enhanced MR imaging and SPIO-enhanced MR imaging was similar, but both techniques were significantly more accurate than CT (Ward et al., 2005). Because they used a four-detector row CT scanner, further studies will be needed to assess diagnostic capability of recent 64-detector row CT scanner.

It has been documented that SPIO-enhanced MR imaging is more sensitive than dual-phase spiral CT in depicting hypervascular HCC (Reimer et al., 2000). Lee et al. (2003) showed that the mean sensitivity of SPIO-enhanced MR imaging was significantly higher (70.6%, P < 0.05) than that of dual-phase spiral CT (58.1%). Kim et al. (2005) compared SPIO (ferucarbotran)-enhanced MR imaging with triple-phase MDCT for pre-operative detection of HCC. In their study, the mean sensitivities of MR imaging and triple-phase MDCT were 90.2% and 91.3%, respectively, their mean specificities were 97.0% and 95.3%, respectively. SPIO-enhanced MR imaging was as accurate as triple-phase MDCT in pre-operative detection of HCC (Kim et al., 2005). SPIO-enhanced MR imaging provides information supplementary to that obtained with dynamic CT, particularly by excluding pseudolesions. SPIO-enhanced MR imaging may be preferable because it features no exposure to irradiation.

4.3.2.3. SPIO-MRI vs Dynamic MRI

Vogl et al. (1996) assessed the efficacy of static and dynamic MR imaging using SPIO versus Gd-DTPA in patients with focal liver lesions. Detection rate was improved for metastatic lesions revealing 36 lesions unenhanced versus 53 focal lesions using SPIO-enhanced MR imaging, whereas Gd-DTPA-enhanced scans showed no additional lesion versus unenhanced and Resovist-enhanced MR imaging (Vogl et al., 1996). Also, SPIO decreased the signal intensity of benign tumors and helped differentiate benign from malignant tumors (specificity: SPIO-MRI 93%, gadolinium-MRI 81.5%) (Vogl et al., 1996). In view of sensitivity and specificity for hepatic metastases, SPIO-enhanced MR imaging has priority to dynamic CT and Gd-enhanced MR imaging.

Several studies have shown that Gd-based dynamic MR imaging is slightly better than SPIO-enhanced MR imaging in the detection of small HCCs (Tang et al., 1999, Pauleit et al., 2002). In lesion conspicuity, Gd-enhanced MR imaging is superior to SPIO-enhanced MR imaging (Tang et al., 1999). Paulait et al., (2002) reported similar findings, but they used only respiratory-triggered T2-weighted turbo spin echo as a pulse sequence for SPIO enhancement. However, SPIO yields additional information when imaging findings on dynamic MR imaging are questionable because of intrahepatic arterioportal shunt (AP shunt) and/or post-therapeutic liver damage (Oudkerk et al., 1997) (Figure 4.3). Pseudolesions caused by AP shunt can be circumvented by the use of SPIO, since Kupffer cell function is usually maintained in liver parenchyma exhibiting AP shunt (Oudkerk et al., 1997). Ward et al. (2000) reported the usefulness of double-contrast MR imaging, i.e. combined SPIO- and Gd-dynamic MR imaging on the same day, for diagnosis of HCC. SPIO-enhanced MR imaging (mean accuracy = 0.76) was more accurate than unenhanced MR imaging (mean accuracy = 0.64, P < 0.04), and double-contrast MR imaging (mean accuracy = 0.86) was more accurate than SPIO-enhanced imaging (P < 0.05). Both HCCs and dysplastic nodules were correctly characterized with all three techniques, although observer confidence in lesion characterization was greatest

Figure 4.3. HCC in a 71-year-old male: dynamic MR imaging vs SPIO-enhanced MR imaging. On dynamic MR imaging (a), multiple enhancing lesions are noted in the liver (arrows). SPIO-MR imaging demonstrated only one lesion in S8 (b; arrow). At surgery, the lesion in S8 was proven to be HCC, and the other lesions were not detected and were considered pseudolesions due to AP-shunt.

Figure 4.3. HCC in a 71-year-old male: dynamic MR imaging vs SPIO-enhanced MR imaging. On dynamic MR imaging (a), multiple enhancing lesions are noted in the liver (arrows). SPIO-MR imaging demonstrated only one lesion in S8 (b; arrow). At surgery, the lesion in S8 was proven to be HCC, and the other lesions were not detected and were considered pseudolesions due to AP-shunt.

with double-contrast MR imaging (Figure 4.4). Double-contrast MR imaging significantly improves the diagnosis of HCC compared with SPIO-enhanced and SPIO-non-enhanced imaging (P < 0.01).

4.3.2.4. SPIO-MRI vs Paramagnetic Hepatobiliary Agents-Enhanced MRI

Paramagnetic hepatobiliary compounds are referred to as "value-added versions" of extracellular Gd compounds because they increase tumor-liver contrast in

Figure 4.4. Comparison between dynamic MR imaging and SPIO-enhanced MR imaging in differentiating borderline lesions. Dysplastic nodule in a 75-year-old male (a-d) and, well-differentiated HCC in a 65-year-old male (e-h). On pre-contrast T1W-GRE, both lesions (a and e, arrows) exhibit high intensity and are hypovascular on dynamic MR imaging (b, c, f, and g; arrows), and they cannot be distinguished from each other. On SPIO-enhanced MR imaging, DN takes up SPIO (d, arrow) but HCC exhibits decreased phagocytic activity (h, arrow).

Figure 4.4. Comparison between dynamic MR imaging and SPIO-enhanced MR imaging in differentiating borderline lesions. Dysplastic nodule in a 75-year-old male (a-d) and, well-differentiated HCC in a 65-year-old male (e-h). On pre-contrast T1W-GRE, both lesions (a and e, arrows) exhibit high intensity and are hypovascular on dynamic MR imaging (b, c, f, and g; arrows), and they cannot be distinguished from each other. On SPIO-enhanced MR imaging, DN takes up SPIO (d, arrow) but HCC exhibits decreased phagocytic activity (h, arrow).

both perfusion phase and hepatobiliary phase. These agents are partially taken up by hepatocytes, yielding positive and sustained enhancement of the liver parenchyma on T1 -weighted images. There are few reports regarding comparison of efficacy between SPIO and paramagnetic hepatobiliary agents in the diagnosis of focal hepatic lesions. Kim et al. (2004, 2005) have recently reported comparative studies between SPIO and gadobenate dimeglumine (Gd-BOPTA) for the detection of hepatic metastases or HCC. In the detection of liver metastases, the mean accuracy (Az values) and sensitivity of Gd-BOPTA-enhanced delayed phase imaging (0.982, 95.5%) were comparable to those of SPIO-enhanced imaging (0.984, 97.2%) (Kim et al., 2005). They concluded that Gd-BOPTA-enhanced delayed phase imaging showed comparable diagnostic performance to SPIO-enhanced imaging for the detection of liver metastases. In another study, the authors concluded that Gd-BOPTA-enhanced 3D dynamic imaging exhibited better diagnostic performance than SPIO-enhanced imaging in the detection of HCC (Kim et al., 2004). The mean sensitivity and positive predictive value of SPIO-enhanced imaging were 81.0% and 85.0%, respectively, while those of Gd-BOPTA-enhanced MRI were 91.4% and 88.1%, respectively (Kim et al., 2004). For gadoxetic acid (Gd-EOB-DTPA), one animal study showed that the detectability of tumors with SPIO-enhanced MR imaging was comparable to that of Gd-EOB-enhanced "static" MR imaging (Tanimoto et al., 1997). Gadoxetic acid might have been better than SPIO for use with dynamic MR imaging.

4.3.2.5. SPIO-MRI vs CTAP/CTHA

CT during arterial portography (CTAP) plus CT hepatic arteriography (CTHA) is a relatively invasive combination of modalities, but has been considered the most sensitive method for detection of focal hepatic lesions (Li et al., 1999). SPIO-enhanced MR imaging has been found at least as accurate as CT during arterial portography (CTAP) in the detection of liver metastases (Figure 4.5) (Seneterre et al., 1996). Additional merit has also been documented for SPIOs in the differentiation between true lesions and pseudo-lesions (perfusion defect on CTAP caused by localized AP shunt) (Oudkerk et al., 1997). Therefore, SPIO-enhanced MR imaging is a good alternative to CTAP, which is both invasive and expensive. The combination of CTAP and CTHA is superior to CTAP alone

Figure 4.5. Liver metastasis from colonic cancer in a 74-year-old male. On CTAP, a small perfusion defect is noted in S4 (a, arrow). On SPIO-enhanced T2*-weighted GRE, a small mass exhibiting decreased phagocytic activity is noted in the same region (b, arrow).

for the detection of hypervascular HCCs (Murakami et al., 1997; Makita et al., 2000). However, the use of CTAP plus CTHA is limited by pseudolesions due to intrahepatic AP shunts particularly in the setting of chronic liver damage, and its specificity is relatively low (Makita et al., 2000). Some authors do not recommend CTAP plus CTHA for pre-operative evaluation of HCC, because of its invasiveness, cost, and its unacceptably high false-positive rate without substantially increasing sensitivity compared with triple-phase helical CT (Jang et al., 2000).

Kwak et al. (2004) compared Gd-enhanced dynamic MR imaging, SPIO-enhanced MR imaging, and combined Gd-enhanced dynamic and SPIO-enhanced MR imaging with combined CTAP and CTHA in the detection of HCC using receiver operating characteristic (ROC) analysis for 24 patients with 38 HCCs. The diagnostic accuracies of combined CTAP/CTHA and combined Gd-enhanced dynamic/SPIO-enhanced MR imaging were significantly higher than those of Gd-enhanced dynamic MR imaging or SPIO-enhanced MR imaging by themselves (p < 0.005). The mean specificities of combined CTAP and CTHA (93%) and combined Gd-enhanced dynamic and SPIO-enhanced MR imaging (95%) were significantly higher than those of Gd-enhanced dynamic MR imaging (87%) and SPIO-enhanced MR imaging (88%; p < 0.05). Combined Gd-enhanced dynamic and SPIO-enhanced MR imaging may obviate the need for more invasive combined CTAP and CTHA for pre-operative evaluation of patients with HCC. In our study, SPIO-enhanced MR imaging exhibited a diagnostic efficacy equivalent to that of CTAP plus CTHA as a pre-operative test for HCCs (Tanimoto et al., 2005). SPIO-enhanced MR imaging has the potential to replace CTAP plus CTHA in certain clinical settings, and is recommended for the pre-operative work-up of candidates for surgical resection of malignant hepatic tumors. Because CTAP plus CTHA is approximately three times more expensive than SPIO-enhanced MR imaging, the use of SPIOs is also economically favorable. However, it should be noted that inhomogeneity of SPIO uptake can occur because of reduction in Kupffer cell density caused by inflammation, scarring, and regeneration in cirrhosis (Elizondo et al., 1990).

Was this article helpful?

0 0

Post a comment