The Significance of Vascular MR Contrast Enhancement in Carotid Stenosis

PURPOSE: To determine the significance of vascular MR contrast enhancement in carotid stenosis. MATERIALS AND METHODS: Forty patients that had angiographically proved carotid stenosis were selected for the study. A blind interpretation of vascular enhancement on an enhanced T1 weighted image, the lesion pattern on a DWI (diffusion weighted image), a perfusion defect on a MR perfusion image, the degree of stenosis, and collateral flow on cerebral DSA (digital subtraction angiography) was made by two observers, retrospectively. DWI lesion patterns were classified as having no high signal intensity, small PAI (perforating artery infarcts), large PAI, pial infarcts, territorial infarcts, and border zone infarcts. We evaluated the statistical correlation between vascular enhancement and the degree of stenosis, collateral flow, the DWI lesion pattern and the presence of a perfusion defect, respectively. RESULTS: The degree of carotid stenosis and the frequency of vascular enhancement correlated statistically (p=0.000). The presence of retrograde collateral flow on cerebral DSA and the border zone infarcts pattern on DWI were related with the occurrence of vascular enhancement (p=0.002, p=0.004). In 23 patients that underwent a MR perfusion study, the presence of a perfusion defect was also related to the occurrence of vascular enhancement (p=0.002). CONCLUSION: Vascular MR contrast enhancement may indicate a cerebral hypoperfusion in carotid stenosis.

Contrast Enhanced MR Findings of Lesions Associated with Radial Scar: Correlation with Histopathology

PURPOSE: To evaluate the contrast-enhanced MR findings of lesions associated with a radial scar and to compare the MR findings with the histopathology results. MATERIALS AND METHODS: From Mar. 2001 to Sep. 2005, 8 patients with a surgically proven radial scar who had undergone MRI, mammography, and ultrasonography were enrolled in this study. The morphological findings and dynamic enhancement pattern of the time-intensity curve were retrospectively reviewed using non-contrast and contrast-enhanced MRI. Mammography and ultrasonography were also analyzed according to the BI-RADS category and correlated with the histopathological diagnosis. RESULTS: The age of the patients ranged from 42 to 53 years (mean, 47 years). Five patients presented with a left breast lesion and the others presented with a right breast lesion. The histopathological diagnosis associated with the radial scar were fibrocystic changes (n=1), adenosis (n=2), atypical ductal hyperplasia (n=2), lobular carcinoma in situ (n=1), ductal carcinoma in situ (n=1), and invasive ductal carcinoma (n=1). In all patients, architectural distortion without microcalcification was observed with mammography. Irregular shaped hypoechoic lesions with an indistinct, spiculated, or angular margin was observed in all patients with ultrasonography. Posterior shadowing was observed in 4cases. MR enhancement revealed two cases with foci enhancement (adenosis and fibrocystic change), five cases with non-mass-like focal enhancement (fibrocystic change, atypical ductal hyperplasia, lobular carcinoma in situ, ductal carcinoma in situ, invasive ductal carcinoma), and one irregular homogeneous mass enhancement (atypical ducal hyperplasia). The time-signal intensity curves are as follows: persistent type (n=2), adenosis, and fibrocystic changes, respectively; plateu type (n=4), one adenosis, two atypical ductal hyperplasia, and one ductal carcinoma in situ; and washout type (n=2), lobular carcinoma in situ, and invasive ductal carcinoma, respectively. CONCLUSION: Although a combined benign or malignant pathology with a radial scar was not predicted on the preexisting image modality, contrast-enhanced MRI can help to predict a combined benign or malignant pathology with a radial scar using the morphological findings and the dynamic enhancement type of the time-intensity curve.

Contrast Enhanced MR Findings of Lesions Associated with Radial Scar: Correlation with Histopathology

PURPOSE: To evaluate the contrast-enhanced MR findings of lesions associated with a radial scar and to compare the MR findings with the histopathology results. MATERIALS AND METHODS: From Mar. 2001 to Sep. 2005, 8 patients with a surgically proven radial scar who had undergone MRI, mammography, and ultrasonography were enrolled in this study. The morphological findings and dynamic enhancement pattern of the time-intensity curve were retrospectively reviewed using non-contrast and contrast-enhanced MRI. Mammography and ultrasonography were also analyzed according to the BI-RADS category and correlated with the histopathological diagnosis. RESULTS: The age of the patients ranged from 42 to 53 years (mean, 47 years). Five patients presented with a left breast lesion and the others presented with a right breast lesion. The histopathological diagnosis associated with the radial scar were fibrocystic changes (n=1), adenosis (n=2), atypical ductal hyperplasia (n=2), lobular carcinoma in situ (n=1), ductal carcinoma in situ (n=1), and invasive ductal carcinoma (n=1). In all patients, architectural distortion without microcalcification was observed with mammography. Irregular shaped hypoechoic lesions with an indistinct, spiculated, or angular margin was observed in all patients with ultrasonography. Posterior shadowing was observed in 4cases. MR enhancement revealed two cases with foci enhancement (adenosis and fibrocystic change), five cases with non-mass-like focal enhancement (fibrocystic change, atypical ductal hyperplasia, lobular carcinoma in situ, ductal carcinoma in situ, invasive ductal carcinoma), and one irregular homogeneous mass enhancement (atypical ducal hyperplasia). The time-signal intensity curves are as follows: persistent type (n=2), adenosis, and fibrocystic changes, respectively; plateu type (n=4), one adenosis, two atypical ductal hyperplasia, and one ductal carcinoma in situ; and washout type (n=2), lobular carcinoma in situ, and invasive ductal carcinoma, respectively. CONCLUSION: Although a combined benign or malignant pathology with a radial scar was not predicted on the preexisting image modality, contrast-enhanced MRI can help to predict a combined benign or malignant pathology with a radial scar using the morphological findings and the dynamic enhancement type of the time-intensity curve.

Relationship between the Number of SPIO-labeled Macrophage and MR Signal Intensity

PURPOSE: For the in vivo imaging of macrophages using MRI, the feasibility of labeling macrophages with iron oxide and the number of SPIO-labeled macrophage detected in 1.5 T MR, were assessed. MATERIALS AND METHODS: The MR signal intensity was measured with variable concentrations of iron oxide, ranging from 112 to 2.384x10-7 μgFe/mL. The macrophages were incubated in SPIO solution (112 μgFe/mL) for 24 hours. The MR signal intensity was measured in variable numbers of SPIO-labeled macrophages. RESULTS: The MR image signal intensity gradually increased with decreasing SPIO concentration, and reached a plateau at a concentration of 0.219 μgFe/mL. After incubation with iron oxide, the compact uptake of SPIO was detected in the cytoplasm of the macrophages using Prussian blue staining. No susceptibility effect was detected in the tubes of more than 122 macrophages. CONCLUSION: The MR signal intensity was dependent on the number of macrophages. No susceptibility effect due to a cluster of SPIO-labeled macrophages was detected in more than 488 cells.

Usefulness of Post-enhanced Delayed FLAIR Imaging for Making the Diagnosis of Leptomeningitis

PURPOSE: To evaluate the usefulness of post-enhanced delayed FLAIR (fluid-attenuated inversion-recovery) images in the diagnosis of leptomeningitis. MATERIALS AND METHODS: We obtained the pre- and post-enhanced FLAIR images of 7 rabbits every hour after infusing triple doses of contrast, and we measured the signal intensities of the CSF (cerebrospinal fluid) and the brain parenchyma. Five leptomeningitis patients and 5 volunteers were enrolled to obtain the pre-enhanced FLAIR images, the early post-enhanced FLAIR images and the delayed post-enhanced FLAIR images, with using a standard dose of contrast, and to measure the signal intensities of the CSF and brain parenchyma. The statistical significances were determined by a mixed procedure and the Wilcoxon rank-sum test (p<0.05). RESULTS: In the rabbits, the signal intensities of the CSF began to increase after an hour of contrast infusion, but those of the parenchyma did not increase. The time of maximum CSF enhancement was 2 hours after contrast infusion (p<0.001; standard estimate=750.43) and we obtained the post-enhanced delayed FLAIR images for clinical studies according to this result. The signal intensities of the CSF in the subarachnoid space were higher in the patient group compared with those of the normal control group on both the early post-enhanced FLAIR images and the delayed post-enhanced FLAIR images (p=0.0096) (p=0.0391). In the patient group, changes of signal intensities of the CSF in the subarachnoid space were more conspicuous on the delayed post-enhanced FLAIR images than on the early post-enhanced FLAIR images (p=0.0042). However, those of the parenchyma were not different in either group. CONCLUSION: The post-enhanced delayed FLAIR images obtained at 2 hours after contrast infusion are more useful for making the the diagnosis of leptomeningitis than are the post-enhanced early FLAIR images.

Differentiation of Recently Infarcted Myocardium from Chronic Myocardial Scar: The Value of Contrast-Enhanced SSFP-Based Cine MR Imaging

The purpose of this study is to demonstrate whether the signal intensity (SI) of myocardial infarction (MI) on contrast enhanced (CE)-cine MRI is useful for differentiating recently infarcted myocardium from chronic scar. This study included 24 patients with acute MI (36-84 years, mean age: 57) and 19 patients with chronic MI (44-80 years, mean age: 64). The diagnosis of acute MI was based on the presence of typical symptoms, i.e. elevation of the cardiac enzymes and the absence of any remote infarction history. The diagnosis of chronic MI was based on a history of MI or coronary artery disease of more than one month duration and on the absence of any recent MI within the previous six months. Retrospectively, the ECG-gated breath-hold cine imaging was performed in the short axis plane using a segmented, balanced, turbo-field, echo-pulse sequence two minutes after the administration of Gd-DTPA at a dose of 0.2 mmol/kg body weight. Delayed contrast-enhanced MRI (DCE MRI) in the same plane was performed 10 to 15 minutes after contrast administration, and this was served as the gold standard of reference. The SI of the infarcted myocardium on the CE-cine MRI was compared with that of the normal myocardium on the same image. The area of abnormal SI on the CE-cine MRI was compared with the area of hyperenhancement on the DCE MRI. The area of high SI on the CE-cine MRI was detected in 23 of 24 patients with acute MI (10 with homogenous high SI, 13 high SI with subendocardial low SI, and one with iso SI). The area of high SI on the CE-cine MRI was larger than that seen on the DCE MRI (p < 0.05). In contrast, the areas of chronic MI were seen as iso-SI with thin subendocardial low SI on the CE-cine MR in all the chronic MI patients. The presence of high SI on both the CE-cine MRI and the DCE MRI is more sensitive (95.8%) for determining the age of a MI than the presence of myocardial thinning (66.7%). This study showed the different SI patterns between recently infarcted myocardium and chronic scar on the CE-cine MRI. CE-cine MRI is thought to be quite useful for determining the age of myocardial infarction, in addition to its utility for assessing myocardial contractility.

MR Imaging with Gd-DTPA Enhancement in the Testicular Ischemia in Rat Model: Evaluation of Testicular Viability

PURPOSE: To find the magnetic resonance (MR) imaging patterns and to determine the viability in normal, infracted and reversible ischemic testis of the rat. MATERIALS AND METHODS: Fifteen Sprague-Dawley rats were examined and they were divided into four groups. Group 1 was the control group, group 2 had a complete testicular artery ligation, group 3 had a complete ligation with reperfusion after 1 hour and group 4 had a complete ligation with reperfusion after 12 hours. All four groups were imaged every 5 minutes for 30 minutes. Delayed MR imaging was obtained every 30 minutes for 90 minutes. Two follow-up MR images were performed in all groups at a one-week interval. The signal intensity was measured in the normal testis, ischemic testis, and in muscle, water and fat in every rat at each time, with the phantom attached near the scrotum during the scanning. The signal intensities were analyzed statistically. RESULTS: On initial and 2-week follow-up examinations, the pattern of change differed among four groups (p<0.001). Group 1 and Group 3 did not show any marked change over time at each examination. Group 3 showed strong enhancement at the first week follow-up. Group 2 showed steadily delayed enhancement at each examination. Group 4 had same pattern with the Group 2 with higher enhancement intensity in parallel. CONCLUSION: MR images with Gd-DTPA could be useful for the diagnosis of damaged testicular tissue and for the determination of testicular viability.

Are the Delay Images Necessary to Evaluate the Liver Metastatic Lesions on Mangafodipir Trisodium Enhanced Liver MRI?: Comparison with Hepatocellular Carcinomas

PURPOSE: To assess whether ring enhancements of liver metastases on Mn-DPDP enhanced, early MR images were well visualized on delayed images, as compared with those of hepatocellular carcinomas (HCC), and to investigate the detection accuracy and conspicuity of each tumor. MATERIALS AND METHODS: Twenty patients with liver metastases and 15 with HCC were studied by Mn-DPDP enhanced, T1-weighted MR images. Peripheral ring enhancement and conspicuity were investigated. Differences in detection accuracy and frequency of ring enhancement in liver metastases and HCC were assessed. RESULTS: In liver metastases (n=69), 44 cases (63.8%) without ring enhancement and 25 (36.2%) with were noted on early images. Sixteen cases (23.2%) without ring enhancement, 38 (55.1%) with ring enhancement similar to the early images, and 15 (21.7%) with prominent ring enhancement were noted on delayed images. In HCC (n=37), 36 cases (97.3%) without ring enhancement and 1 case (2.7%) with were noted on early images. There was no difference of detection accuracy in liver metastases or HCC between the 2 readings. Ring enhancement and conspicuity of each tumor were superior on delayed images. Ring enhancement in liver metastases was better seen on delayed images. CONCLUSION: Ring enhancement in liver metastases was well presented on Mn-DPDP enhanced, delayed MR images, which was useful to differentiate liver metastases from HCC.

The Usefulness of Dynamic MR Imaging for the Evaluation of Cervical Cancer

PURPOSE: We wished to evaluate the diagnostic usefulness of dynamic MRI in assessing tumor visualization and the parametrial invasion of cervical cancer, and we also wished to determine the most adequate enhancing time by comparing the T2-weighted image (T2WI) and enhanced T1-weighted image (Gd-T1WI). MATERIALS AND METHODS: Fifty-three women with histopathologically proven cervical cancer underwent a preoperative MRI. Using a 1.5 T magnet, the fast spin echo axial T2WI without fat saturation was taken; after contrast administration, 20, 40, 60, 90, 120 sec-dynamic MRIs were taken using fast SPGR and spin echo axial Gd-T1WI. Tumor conspicuity and parametrial invasion in each pulse sequence and the most adequate enhancing time for the evaluation of the tumor on dynamic MRI were evaluated prospectively by three radiologists working at three separate sessions. The results were then correlated with the histopathologic findings. RESULTS: The conspicuity of tumor on dynamic MRI (99.4%) and T2WI (95.6%) were better than on Gd-T1WI (89.3%). In the assessment of parametrial invasion of the tumor, the diagnostic accuracy of dynamic MRI, Gd-T1WI and T2WI was 79.9%, 78% and 76.1%, respectively; the highest values were for the dynamic MRI, but there was no statistically significant difference among three pulse sequences. The most adequate enhancing time on dynamic MRI was between 90 seconds and 120 seconds. CONCLUSION: Dynamic MRI is useful for the assessment of tumor visualization of cervical cancer, and the most appropriate scan time on dynamic MRI is between 90 seconds and 120 seconds. For the determination of parametrial invasion, the dynamic MRI revealed a higher diagnostic accuracy than that of T2WI or Gd-T1WI, but the differences were statistically insignificant.

Hepatic Enhancement on Gd-BOPTA-enhanced MR Imaging: Comparison between Cirrhotic and Normal Livers

PURPOSE: To compare the enhancement features of hepatic parenchyma between cirrhotic and normal liver, using Gd-BOPTA-enhanced delayed MR imaging. MATERIALS AND METHODS: The 60 patients (35 with cirrhotic and 25 with normal liver) included in our study underwent Gd-BOPTA-enhanced MR imaging using a 1.5T system with a phase-array multicoil. In all cases, T1-weighted in-phase and opposed-phase gradient-echo MR imaging was performed before and 60 minutes after intravenous administration of a bolus of Gd-BOPTA. All images were quantitatively analysed by comparing the signal-to-noise ratio (SNR) and signal enhancement (SE) of cirrhotic and normal liver before and after contrast enhancement, and in cirrhotic patients, SNR and SE were also compared in terms of the Child-Pugh classification. For qualitative analysis, the hepatic enhancement patterns of cirrhotic and normal liver were classified as homogeneous or heterogeneous according to the consensual findings of two radiologists. RESULTS: At contrast-enhanced imaging, both cirrhotic (p<0.001) and normal liver (p<0.001) showed substantially increased SNR relative to unenhanced images, and the SNR of cirrhotic liver was significantly lower than that of normal livers at both in-phase (p<0.001) and opposed-phase (p<0.001) imaging. The SE of cirrhotic liver was significantly lower than that of normal liver (in-phase: p=0.002; opposed phase: p=0.011). Both Child-Pugh class A (p<0.001) and B (p<0.001) cirrhotic liver showed a substantial increase in SNR at contrast-enhanced imaging relative to unenhanced imaging and the SNR of Child-Pugh class A was significantly higher than that of Child-Pugh class B at both in-phase (p<0.001) and opposed-phase (p=0.022) imaging. In addition, the SE of class A was significantly higher than that of class B at in-phase imaging (p=0.004). Cirrhotic liver showed heterogeneous enhancement in 20 of 35 patients (57%), whereas normal liver showed homogeneous enhancement in all patients. CONCLUSION: At Gd-BOPTA-enhanced delayed MR imaging, cirrhotic liver showed less enhancement than normal liver. In cirrhotic patients, hepatic enhancement and hepatic function decreased in tandem. Gd-BOPTAenhanced delayed MR imaging may be useful for evaluating the functional reserve of the liver.

Enhancement Pattern of Focal Hepatic Tumors with Gadobenate Dimeglumine-Enhanced Delayed MR Imaging

PURPOSE: To investigate the enhancement pattern occurring at delayed gadobenate dimeglumine (Gd-BOPTA) MR imaging, as used to characterize focal hepatic tumors. MATERIALS AND METHODS: Forty patients with 64 focal hepatic tumors (32 hepatocellular carcinomas [HCC], 15 hemangiomas, 14 metastasis and 3 cholangiocarcinomas) underwent MR imaging before and 60 minutes after the intravenous administration of 0.1 ml/kg Gd-BOPTA. For all MR studies, a 1.5-T MR system was used, and T1-weighted in-phase gradient echo (GRE) imaging was porformed. The quantitative assessment of early and delayed images included determination of the signal-to-noise ratio (SNR), tumor-to-liver contrast-to-noise ratio (CNR), and degree of enhancement (DE). Two experienced radiologists evaluated lesion conspicuity and the pattern of contrast enhancement (CE), reaching their conclusions by consensus. RESULTS: At delayed imaging, SNR and CNR showed significant increases (p>0.05), and the DE of all lesions had also increased. Lesion conspicuity, however, was not significantly different between (p>0.05). The most common enhancement patterns seen at delayed imaging were inhomogeneous hypointense in HCCs, homogeneous iso- or hyperintense in hemangiomas, and target-like in metastases. CONCLUSION: At delayed imaging with Gd-BOPTA, tumors of both hepatocytic and non-hepatocytic origin showed enhancement, and in the characterization of focal hepatic lesions, observed differences in enhancement are thus of limited usefulness. However, the observed homogeneous iso- or hyperinteuse enhancement of hemangiomas, and the target-like enhancement of metastases, may help differentiate then from other tumors.

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.

Optimal Pulse Sequence for Ferumoxides-Enhanced MR Imaging Used in the Detection of Hepatocellular Carcinoma: A Comparative Study Using Seven Pulse Sequences

OBJECTIVE: To identify the optimal pulse sequence for ferumoxides-enhanced magnetic resonance (MR) imaging in the detection of hepatocelluar carcinomas (HCCs). MATERIALS AND METHODS: Sixteen patients with 25 HCCs underwent MR imaging following intravenous infusion of ferumoxides. All MR studies were performed on a 1.5-T MR system, using a phased-array coil. Ferumoxides (Feridex IV) at a dose of 15 micro mol/Kg was slowly infused intravenously, and axial images of seven sequences were obtained 30 minutes after the end of infusion. The MR protocol included fast spin-echo (FSE) with two echo times (TR3333-8571/TE18 and 90-117), singleshot FSE (SSFSE) with two echo times (TR infinity/TE39 and 98), T2*-weighted gradient-recalled acquisition in the steady state (GRASS) (TR216/TE20), T2*-weighted fast multiplanar GRASS (FMPGR) (TR130/TE8.4-9.5), and T2*-weighted fast multiplanar spoiled GRASS (FMPSPGR) (TR130/TE8.4-9.5). Contrast-to-noise ratios (CNRs) of HCCs determined during the imaging sequences formed the basis of quantitative analysis, and images were qualitatively assessed in terms of lesion conspicuity and image artifacts. The diagnostic accuracy of all sequences was assessed using receiver operating characteristic (ROC) analysis. RESULTS: Quantitative analysis revealed that the CNRs of T2*-weighted FMPGR and T2*-weighted FMPSPGR were significantly higher than those of the other sequences, while qualitative analysis showed that image artifacts were prominent at T2*-weighted GRASS imaging. Lesion conspicuity was statistically significantly less clear at SSFSE imaging. In term of lesion detection, T2*-weighted FMPGR, T2*- weighted FMPSPGR, and proton density FSE imaging were statistically superior to the others. CONCLUSION: T2*-weighted FMPGR, T2*- weighted FMPSPGR, and proton density FSE appear to be the optimal pulse sequences for ferumoxidesenhanced MR imaging in the detection of HCCs.

The Usefulness of MR Imaging of the Temporal Bone in the Evaluation of Patients with Facial and Audiovestibular Dysfunction

OBJECTIVE: To evaluate the clinical utility of MR imaging of the temporal bone in patients with facial and audiovestibular dysfunction with particular emphasis on the importance of contrast enhancement. MATERIALS AND METHODS: We retrospectively reviewed the MR images of 179 patients [72 men, 107 women; average age, 44 (range, 1-77) years] who presented with peripheral facial palsy (n=15), audiometrically proven sensorineural hearing loss (n=104), vertigo (n=109), or tinnitus (n=92). Positive MR imaging findings possibly responsible for the patients' clinical manifestations were categorized according to the anatomic sites and presumed etiologies of the lesions. We also assessed the utility of contrast-enhanced MR imaging by analyzing its contribution to the demonstration of lesions which would otherwise not have been apparent. All MR images were interpreted by two neuroradiologists, who reached their conclusions by consensus. RESULTS: MR images demonstrated positive findings, thought to account for the presenting symptoms, in 78 (44%) of 179 patients, including 15 (100%) of 15 with peripheral facial palsy, 43 (41%) of 104 with sensorineural hearing loss, 40 (37%) of 109 with vertigo, and 39 (42%) of 92 with tinnitus. Thirty (38%) of those 78 patients had lesions that could be confidently recognized only at contrastenhanced MR imaging. CONCLUSION: Even though its use led to positive findings in less than half of these patients, MR imaging of the temporal bone is a useful diagnostic procedure in the evaluation of those with facial and audiovestibular dysfunction. Because it was only at contrast-enhanced MR imaging that a significant number of patients showed positive imaging findings which explained their clinical manifestations, the use of contrast material is highly recommended.

Evaluation of the Pedal Artery: Comparison of Three-dimensional Gadolinium-Enhanced MR Angiography with Digital Subtraction Angiography

PURPOSE: To compare the three-dimensional gadolinium-enhanced MR angiography with digital subtraction angiography (DSA) for evaluation of the pedal artery. MATERIALS AND METHODS: In 12 extremities of 11 patients, both digital subtraction angiography (DSA) and contrast-enhanced MR angiography (CE-MR angiography) were performed during the same week. Among ten of the 11 patients, the following conditions were present: atherosclerosis (n=4), diabetic foot (n=3), Buerger's disease (n=1), calciphylactic arteriopathy (n=1) and arteriovenous malformation of the foot (n=1). The remaining patient underwent angiography prior to flap surgery. For MR angiography, a 1.5T system using an extremity or head coil was used. A three-dimensional FISP (fast imaging with steady state precession) sequence was obtained before enhancement, followed by four sequential acquisitions (scan time, 20 secs; scan interval time, 10 secs) 10 seconds after intravenous bolus injection of normal saline (total 10 cc), following intravenous adminstration of gadolinium (0.02 mmol/kg, 3 ml/sec). Arterial segments of the ankle and foot were classified as the anterior or posterior tibial artery, the distal peroneal artery, the medial or lateral plantar artery, the pedal arch, and the dorsalis pedis artery. Two radiologists independently analysed visualization of each arteraial segment and the mean of visible arterial segments in one extreminty using CE-MR angiography and DSA. RESULTS: Among 84 arterial segments, 16 were invisible at both CE-MR angiography and DSA, while 39 were demonstrated by both modalities. Twenty-six segments were visible only at CE-MR angiography and three only at DSA. CE-MR angiography displayed a higher number of arterial segments than DSA (mean, 5.42 vs. mean 3.50, respectively), a difference which was statistically significant (p<0.000). The difference between each arterial segment was not statistically significant, except for the dorsalis pedis artery (t test, p<0.000). CONCLUSION: In that it provides additional information for the planning of treatment of lower-extremity arterial disease, three-dimensional CE-MR angiography is superior to DSA for evaluation of the pedal artery.

Usefulness of Three-dimensional Contrast-Enhanced MR Angiography in the Evaluation of Pelvic and Lower Extremity Arteries

PURPOSE: To evaluate the feasibility and clinical usefulness of three-dimensional contrast-enhanced MR angiography (3D-CE-MRA) as a screening test in the evaluation of pelvic and lower extremity arterial diseases. MATERIALS AND METHODS: Forty-four patients who underwent 3D-CE-MRA were included in this study. Coronal 3-dimensional gradient-echo, pre-and post contrast image were acquired with a dedicated peripheral vascular coil and moving-bed technique on a 1.5T MR system. Timing of start of data acquisition was determined by MR fluoroscopy technique, and 0.2mmol/kg Gd-DTPA was injected into an antecubital vein, at a rate of 1cc/sec with an autoinjector. For quantitative analysis, signal to noise ratio (SNR) and artery to soft tissue contrast to noise ratio (CNR) of lower extremities arterial system including lower abdominal aorta were calculated. For qualitative analysis, arterial systems were divided into six segments, and were evaluated in terms of conspicuity of arterial systems and the degree of venous enhancement by three- and four-point scale respectively. In eight patients who underwent both MR angiography and conventional angiography, the degree of the stenosis of MR angiography was compared with conventional angiography as standard reference. Imaging analysis was done by means of consensus between two experienced radiologists. RESULTS: The mean time for the examination was about 15min (+/-5 min). The mean SNR of arterial system was 26.5+/-11.6, and mean artery to soft tissue contrast to noise ratio (CNR) was 24.6+/-11.2. Among the total 525 arterial segments, 498 arterial segments (94.9%) could be demonstrated with good delineation of entire arterial tree. Good arterial imaging without or with minimal venous enhancement were demonstrated in 98.5% (260/264) in above knee and 89% (211/261) in below knee (p<0.01). Ten of 525 segments (1.9%) demonstrated severe venous overlapping and it mostly occurred in the calf region. In comparison with DSA, the sensitivity and the specificity for MR angiography for the detection of occlusions were 96% and 98,8%, respectively, and for the detection of more than 50% stenosis, 82.2% and 92.9%, respectively. CONCLUSION: 3D-CE-MRA provided adequate image for the evaluation of the lower extremity artery, and could be used as a screening test for arterial occlusive diseases.

Mangafodipir Trisodium (Mn-DPDP)-Enhanced MR Imaging of Hepatocellular Carcinoma: Correlation with Histopathological Findings

PURPOSE: To correlate the contrast enhancement pattern of hepatocellular carcinoma (HCC) seen at mangafodipir trisodium (Mn-DPDP)-enhanced MR imaging with the histopathologic findings. MATERIALS AND METHODS: In 28 patients with 36 HCCs larger than 1 cm, Mn-DPDP-enhanced T1-weighted fast multiplanar spoiled gradient-recalled echo (GRE) MR images were obtained before and 15 mins after Mn-DPDP administration. Qualitative analysis focused on signal intensity (hyper-, iso-, or hypo-) relative to surrounding liver parenchyma, while the signal enhancement ratio [ER (%)] and lesion-to-liver contrast-noise ratio (CNR) were determined quantitatively. Signal intensity relative to surrounding liver parenchyma, lesion-to-liver CNR and signal ER of the lesions were correlated with their size and histopathologic grade. RESULTS: The imaging procedure showed that relative to surrounding liver parenchyma, 74% (14/19) of HCCs 1-3 cm in size but 47% (8/17) of those larger than 3 cm were hyperintense. There was, however, no significant difference between the two groups (p>0.05). In addition, 35% (6/17) of HCCs larger than 3 cm but none of the 19 smaller lesions were hypointense, with a significant difference between the two groups (p0.05). CONCLUSION: At Mn-DPDP-enhanced MR imaging, HCCs 1-3 cm in size showed greater signal intensity and signal ER than HCCs larger than 3 cm. Well or moderately differentiated HCCs showed greater signal ER than those that were poorly differentiated. Lesion-to-liver CNR did not differ according to lesion size and histopathologic grade.

MRI after Sequential Use of Gadolinium Chelate and Mangafodipir Trisodium for the Evaluation of Focal Liver Lesions: Study of Image Findings and Safety

PURPOSE: To assess the feasibility of sequentially administering Gd-DTPA and Mn-DPDP for the MR imaging of focal hepatic lesions, and to investigate whether the procedures involved led to any adverse effects. MATERIALS AND METHODS: Forty-two patients (M:F=25:17) with suspected hepatic lesions underwent T1-weighted MR imaging procedures before and after Gd-DTPA enhancement, and after sequential Mn-DPDP administration. Two investigators reviewed the findings in terms of the size, number, morphology, and enhancement patterns of the lesions. Any adverse actions resulting from the procedures were noted. RESULTS: Fifteen patients had hepatocellular carcinoma (HCC, n=35), 13 showed liver metastases (n=40), nine had hemangioma (n=13), two had cholangiocarcinoma (CC, n=2), two had a liver abscess (n=2), and one had focal nodular hyperplasia (FNH, n=2). All focal hepatic lesions were clearly visible, with no difference in conspicuity between T1-weighted images obtained after Gd-DTPA administration and those obtained after Gd- DTPA plus Mn-DPDP administration. After the latter procedure, 12 HCCs showed high or iso- signal intensity to liver parenchyma and 23 showed no contrast enhancement. Thirty-eight liver metastases showed no contrast enhancement, but in two cases ring enhancement was observeed. In both cases of FNH, homogeneous enhancement was noted. No hemangiomas, CCs or abscesses demonstrated contrast enhancement. The only adverse reaction was five instances of facial flushing. CONCLUSION: Hepatic MR imaging after sequential Gd-DTPA plus Mn-DPDP administration may be selectively useful in differentiating between hepatocellular and non-hepatocellular tumor. No technical difficulties or severe adverse reactions were encountered.

Influence of Mn-DPDP on MRI and Proton MR Spectroscopy of the Liver

PURPOSE: To determine the influence of manganese dipyridoxyl diphosphate (Mn-DPDP) on MRI and proton MRS. MATERIALS AND METHODS: In an in-vitro study designed to determine changes in the lipid peak at 1.3 ppm, 4.7T MR equipment was used to obtain proton MR spectrographic images of a lipid solution of varying concentration, with and without Mn-DPDP. Before; at 10, 20, and 30 minutes; and at 1, 2, 4, and 24 hours after the IV injection of Mn-DPDP (10umol, 1ml/kg), the concentration of Mn in liver tissue was measured by atomic absorption spectrometry. At the same intervals, T1-weighted MR images were obtained, the signal intensity ofthe liver was thus determined, and the relative enhancement ratio was calculated. MRS of rabbit liver was performed serially at the same intervals, and the peak areas of metabolites, as well as their peak areas relative to lipids, were calculated. The findings were correlated with tissue Mn concentration. RESULTS: At 1.3 ppm with Mn-DPDP, MRS showed that the peak area of the lipid had decreased. Tissue Mn concentration increased just after Mn-DPDP injection and peaked after 20 minutes, decreasing to a level within the normal range after 24 hours. Serial changes in the signal intensity of the liver, as seen at MRI, showed a similar pattern to that of Mn concentration. There was reverse correlation between serial change in the peak area of lipids at 1.3 ppm and Mn concentration after Mn-DPDP injection. CONCLUSION: At T1-weighted MR imaging, the injection of Mn-DPDP led to the enhancement of liver tissue, and at MRS, the lipid peak at 1.3 ppm decreased. There was close correlation between these effects and tissue Mn concentration.

Mn-DPDP-enhanced MR Imaging: the Optimal Pulse Sequence for Detection of Focal Hepatic Tumor

PURPOSE: To assess the diagnostic value of Mn-DPDP for the detection of focal hepatic tumors on MR images and to determine the optimal pulse sequence to maximize its effect. MATERIALS AND METHODS: Twenty-three patients with 32 focal hepatic tumors were examined by means of 1.5-T MRI. Before and after the intravenous administration of Mn-DPDP, five pulse sequences were used to obtain T1-weighted images: two-dimensional fast low-angle shot (2D FLASH) with/without fat saturation (FS), spinecho (SE), and three-dimensional fast low angle shot reconstruction (3D FLASH) with/without FS. Quantitative assessment involved determination of the signal-to-noise ratio (SNR) of the liver and the tumor, the percentage signal enhancement ratio (PSER) of the liver, and tumor-to-liver contrast to noise ratio (CNR). Pulse sequences were also evaluated subjectively for tumor conspicuity, delineation, and image artifact. In addition, two experienced radiologists compared tumor detection rates between precontrast and postcontrast images. RESULTS: Mn-DPDP had a marked effect on liver SNR and absolute CNR at all pulse sequences (p<0.05). On postcontrast images, PSER and absolute CNR of the liver were highest at 3D FLASH and 2D FLASH FS, respectively, and significantly higher at GRE than at SE (p<0.05). On postcontrast images, the CNR of focal nodular hyperplasia and hepatocellular carcinoma was positive, while that of hemangioma, metastasis and cholangiocarcinoma was negative. The postcontrast CNR of all tumors except hepatocellular carcinoma increased more than 100%. Qualitative studies showed that tumor conspicuity increased significantly at all sequences except SE, and delineation increased significantly except at SE and postcontrast 2D GRE FS. After Mn-DPDP, GRE more effectively demonstrated tumor conspicuity and image artifact than did SE, and GRE other than 2D FLASH FS was also better than SE for tumor dilineation (p<0.05). The sensitivity of all postcontrast images increased and the tumor detection rate at GRE was significantly higher than at SE. CONCLUSION: Mn-DPDP favorably affects tumor-to-liver contrast, and may be useful in the imaging of focal hepatic tumors, more so with 2D or 3D FLASH pulse sequences than with SE.