Diffusion-Weighted Imaging with Sensitivity Encoding (SENSE) for Detecting Cranial Bone Marrow Metastases: Comparison with T1-Weighted Images

OBJECTIVE: This study was designed to determine whether diffusion-weighted imaging (DWI) with sensitivity encoding (SENSE) could detect bone marrow involvement in patients with cranial bone marrow (CBM) metastases. DWI results obtained were compared with T1-weighted imaging (T1WI) findings. MATERIALS AND METHODS: DWI with sensitivity encoding (SENSE; b value = 1,000) was performed consecutively in 13 patients with CBM metastases diagnosed pathologically and radiologically. CBM lesions were dichotomized according to the involved site, i.e., skull base or calvarium. Two radiologists qualitatively evaluated the relative conspicuousness of CBM lesions and image qualities in B0 and in isotropic DWI and in T1WI. According to region of interest analysis of normal and pathologic marrow for these three sequences, absolute signal difference percentages (SD%) were calculated to quantitatively analyze lesion contrast. RESULTS: All 20 lesions in 13 patients with CBM metastases revealed abnormal DWI signals in areas corresponding to T1WI abnormalities. Both skull base and calvarial lesions provided better lesion conspicuousness than T1WI and B0 images. Although the image quality of DWI was less satisfactory than that of T1WI, relatively good image qualities were obtained. Quantitatively, B0 images (SD%, 82.1+/-7.9%) showed better lesion contrast than isotropic DWI (SD%, 71.4+/-13.7%) and T1WI (SD%, 65.7+/-9.3%) images. CONCLUSION: For scan times of less than 30 seconds, DWI with SENSE was able to detect bone marrow involvement, and was superior to T1WI in terms of lesion conspicuity. DWI with SENSE may be helpful for the detection of cranial bone/bone marrow metastases when used in conjunction with conventional MR sequences.

Anterior Cruciate Ligament Tear: Reliability of MR Imaging to Predict Stability after Conservative Treatment

OBJECTIVE: The aim of this study is to evaluate the reliability of MR imaging to predict the stability of the torn anterior cruciate ligament (ACL) after complete recovery of the ligament's continuity. MATERIALS AND METHODS: Twenty patients with 20 knee injuries (13 males and 7 females; age range, 20-54) were enrolled in the study. The inclusion criteria were a positive history of acute trauma, diagnosis of the ACL tear by both the physical examination and the MR imaging at the initial presentation, conservative treatment, complete recovery of the continuity of the ligament on the follow up (FU) MR images and availability of the KT-2000 measurements. Two radiologists, who worked in consensus, graded the MR findings with using a 3-point system for the signal intensity, sharpness, straightness and the thickness of the healed ligament. The insufficiency of ACL was categorized into three groups according to the KT-2000 measurements. The statistic correlations between the grades of the MR findings and the degrees of ACL insufficiency were analyzed using the Cochran-Mantel-Haenszel test (p < 0.05). RESULTS: The p-values for each category of the MR findings according to the different groups of the KT-2000 measurements were 0.9180 for the MR signal intensity, 1.0000 for sharpness, 0.5038 for straightness and 0.2950 for thickness of the ACL. The MR findings were not significantly different between the different KT-2000 groups. CONCLUSION: MR imaging itself is not a reliable examination to predict stability of the ACL rupture outcome, even when the MR images show an intact appearance of the ACL.

Tuberculous Spondylitis vs Pyogenic Spondylitis: Focusing on the Discriminative MR Findings for Differentiation

PURPOSE: The purpose of this study is to analyze the most discriminative MR findings for making the differential diagnosis of tuberculous and pyogenic spondylitis. MATERIALS AND METHODS: Sixty MR scans of 18 pyogenic spondylitis patients and 42 tuberculous spondylitis patients were retrospectively reviewed. The statistical analysis was performed using stepwise discriminant analysis and Student's T-test. RESULTS: The patients with tuberculous spondylitis had a significantly higher incidence of MRI findings as follows (p <0.05): smooth margin of a paraspinal mass/abscess in 67% [28/42] of the tuberculous spondylitis patients vs 6% [1/18] in the pyogenic spondylitis patients, mild endplate erosion in 52% [22/42] vs 38% [7/18], respectively, the presence of paraspinal mass/abscess in 100% [42/42] vs 6% [1/18], respectively, central dark signal intensity of the abscess in 86% [36/42] vs 39% [7/18]), respectively, subligamentous spread in 81% [34/42] vs 50% [9/18]), respectively, severe vertebral collapse in 20% [8/42] vs 11% [2/18]), respectively, and posterior extension in 62% [26/42] vs 33% [6/18]), respectively. Among of them, the significant discriminative MR findings were the margin of a paraspinal mass, the grade of endplate erosion and the presence or absence of a paraspinal mass in that order. CONCLUSION: In the differentiation of tuberculous and pyogenic spondylitis, the margin of the paraspinal mass, the grade of endplate erosion and the presence or absence of a paraspinal mass are the most three discriminating MR findings in that order.

MRI of the Breast for the Detection and Assessment of the Size of Ductal Carcinoma in Situ

OBJECTIVE: The aim of the study was to compare the accuracy of magnetic resonance imaging (MRI) and mammography for the detection and assessment of the size of ductal carcinoma in situ (DCIS). MATERIALS AND METHODS: The preoperative contrast-enhanced MRI and mammography were analyzed in respect of the detection and assessment of the size of DCIS in 72 patients (age range: 30-67 years, mean age: 47 years). The MRI and mammographic measurements were compared with the histopathologic size with using the Pearson's correlation coefficients and the Mann-Whitney u test. We evaluated whether the breast density, the tumor nuclear grade, the presence of comedo necrosis and microinvasion influenced the MRI and mammographic size estimates by using the chi-square test. RESULTS: Of the 72 DCIS lesions, 68 (94%) were detected by MRI and 62 (86%) were detected by mammography. Overall, the Pearson's correlation of the size between MRI and histopathology was 0.786 versus 0.633 between mammography and histopathology (p < 0.001). MRI underestimated the size by more than 1 cm (including false negative examination) in 12 patients (17%), was accurate in 52 patients (72%) and overestimated the size by more than 1 cm in eight patients (11%) whereas mammography underestimated the size in 25 patients (35%), was accurate in 31 patients (43%) and overestimated the size in 16 patients (22%). The MRI, but not the mammography, showed significant correlation for the assessment of the size of tumor in noncomedo DCIS (p < 0.001 vs p = 0.060). The assessment of tumor size by MRI was affected by the nuclear grade (p = 0.008) and the presence of comedo necrosis (p = 0.029), but not by the breast density (p = 0.747) or microinvasion (p = 0.093). CONCLUSION: MRI was more accurate for the detection and assessment of the size of DCIS than mammography.

Value of Preoperative Cervical Discography

PURPOSE: The aim of this study was to describe the method and the value of cervical discography as correlated with the MR findings. MATERIALS AND METHODS: Twenty-one discs in 11 consecutive patients who underwent cervical discography were analyzed. MR and CT discography (CTD) were performed in all patients. Discography was performed after swallowing barium for visualizing the pharynx and the esophagus to prevent penetration. We also analyzed the preceding causes of the subjects' cervical pain. The results of the pain provocation test were classified into concordant pain, discordant pain and a negative test. MRI was analyzed according to the T2-signal intensity (SI) of the disc, disc height, annular bulging and disc herniation. The CTD was analyzed for degeneration or radial tear of the disc, epidural leakage of the contrast agent and pooling of the contrast agent at the periphery of the disc. The pain provocation tests were correlated with the MR and CTD findings. We used the chi-square test to analyze the results. RESULTS: Concordant pain was observed in 14 cases, discordant pain in 3 cases and there were negative tests in 4 cases. There were no complications related to the procedure. Four patients had undergone anterior cervical fusion and four patients had pain that developed after traffic injuries. The decreased T2-SI and annular bulging on MRI, disc degeneration and peripheral pooling of the contrast agent on CT were significantly correlated with pain provocation. CONCLUSION: When the diagnosis of disc disease is difficult with performing MRI, cervical discography with using swallowed barium solution to reduce the penetration of the esophagus or hypopharynx may play be helpful. The decreased T2-SI and annular bulging on MRI correlated significantly with a positive result on the pain provocation test.

Usefulness of preoperative breast MRI in breast cancer: Comparison with breast US

PURPOSE: The purpose of this study was to evaluate the usefulness of preoperative breast MRI compared with breast US and pathologic finding in breast cancer patients MATERIALS AND METHODS: A total of 50 patients with breast cancer underwent surgery at our institute between October 2004 and August 2005. They were examined preoperatively with MRI and US. The maximum diameter and the number of the lesions on MRI and US were measured. These measurements were subsequently compared with the pathologic results. The results were divided into the equal, overestimated and underestimated groups. Changes of the therapeutic approach, based on MRI, were also evaluated. RESULTS: Breast cancer was correctly evaluated in 38 of 50 (76%) patients with MRI and in 28 of 50 (56%) patients with US; the cancer was overestimated in 7 of 50 (14%) patients with MRI and in 8 of 50 (16%) patients with US; the cancer was underestimated in 5 of 50 (10%) patients with MRI and in 14 of 50 (28%) patients with US. The therapeutic approach was changed in 11 of 50 (22%) patients, and all the cases underwent modified radical mastectomy. The therapeutic approach was correctly changed in 9 (18%) patients. Unnecessary wider excision was performed in 2 (4%) patients. CONCLUSION: In conclusion, preoperative breast MRI may be a useful modality for preoperative evaluation, especially for the local staging of tumor and the treatment planning of patients with breast cancer.

Internal Disc Derangement in Patients with Low Back Pain: Correlation of MR Imaging and Provocative Discography and CT Discography

PURPOSE: The aim of this study was to correlate the MR imaging abnormalities of the lumbar intervertebral discs, with emphasis being placed on the high intensity zone (HIZ) with the use of discography for pain provocation and disc morphologic evaluation of the disc. MATERIALS AND METHODS: Consecutive patients with low back pain unresponsive to conservative treatment, and who were being considered for spinal fusion had MRI performed, and this was followed by lumbar discography. The MR imaging, discography and CT discography (CTD) were evaluated for all of the 19 patients. Forty-three lumbar discs in 19 patients were included in this study. The findings of MR and CTD images were evaluated retrospectively with the professional opinion and agreement of two radiologists. MR images were assessed for the presence or absence of decreased T2-wighted signal intensity, decreased disc height, annular bulging, HIZ on T2-weighted images and disc herniation. The results of pain provocation were graded as 0, nonconcordant pain; 1, definite pain, but only as part of the symptom complex; 2, concordant pain. The morphology of CTD was analyzed for presence or absence of disc degeneration, radial tearing and extravasation of the contrast agent. The presence of radial tearing was defined as contrast extension to the outer third of the annulus. The prevalence of all MR abnormalities was calculated, and the data were compared with disc morphologic characteristics and the pain response on provocative discography. We used the chi-square test to analyze the results. RESULTS:Grade 1 and 2 discogenic pain was observed in 8 (19%) and 12 disc levels (28%), respectively. All of the seven non-degenerated discs on MR had no pain response. The decreased SI on T2-weighted image, annular bulging and HIZ were significantly correlated with discogenic pain. Extravasation of contrast media had good correlation with annular bulging and disc herniation on MRI. Radial tearing on CT discography correlated significantly with HIZ. The HIZ was detected in 14 levels (32.6%). The HIZ on MRI correlated significantly with the pain provocation and radial tearing noted on the discograms. CONCLUSION: Several MR imaging findings correlated significantly with the severity of pain provocation to discography. For patients with symptomatic low back pain, the HIZ observed on MR may represent a painful outer annular disruption.

The Usefulness of STIR Image in Breast MRI

PURPOSE: To assess the usefulness of STIR (short tau inversion recovery) imaging in breast MRI (magnetic resonance imaging). MATERIALS AND METHODS: We retrospectively reviewed T1- and T2-weighted (T1WI, T2WI), STIR, and dynamically enhanced images of 44 pathologically confirmed breast lesions (benign, 13; malignant, 31) in 36 patients. We selected the dynamically image which best depicted a particular lesion, and then made hard copy of the corresponding T1WI, T2WI, and STIR images. Using the dynamically enhanced image as a standard, we analysed these in terms of parenchymal pattern, lesion detectability, differentiation between benign and malignant lesions, extent, multifocality, and the ductal system. The results were statistically analyzed. RESULTS: In 33 of 44 cases (75%), detectability was greater at STIR imaging than at T1- and T2WI, especially in fibrofatty or fatty breast (14/14 cases, p<0.05). STIR images did not always differentiate between benign and malignant lesions, and extent (50%) and multifocality (46%) were commonly exaggerated compared with T1- and T2WI. In 18 of 44 cases (41%), STIR images suggested the presence of ductal structures. CONCLUSION: For the detection of lesions, STIR imaging was more useful than T1- and T2WI, though STIR did not differentiate between benign and malignant lesions. The extent and multifocality of a lesion were exaggerated on STIR images, compared with T1- and T2WI.

The Significance of Perfusion Defect at Myocardial Perfusion MR Imaging in a Cat Model of Acute Reperfused Myocardial Infarction

OBJECTIVE: To determine whether the size of a perfusion defect seen at myocardial perfusion MR imaging represents the extent of irreversibly damaged myocardium in acute reperfused myocardial infarction. MATERIALS AND METHODS: In nine cats, reperfused myocardial infarction was induced by occlusion of the left anterior descending coronary artery for 90 minutes and subsequent reperfusion for 90 minutes. At single-slice myocardial perfusion MR imaging at the midventricular level using a turbo-FLASH sequence, 60 short-axis images were sequentially obtained with every heart beat after bolus injection of gadomer-17. The size of the perfusion defect was measured and compared with both the corresponding unstained area seen at triphenyl tetrazolium chloride (TTC) staining and the hyperenhanced area seen at gadophrin-2-enhanced MR imaging performed in the same cat six hours after myocardial perfusion MR imaging. RESULTS: The sizes of perfusion defects seen at gadomer-17-enhanced perfusion MR imaging, unstained areas at TTC staining, and hyperenhanced areas at gadophrin-2-enhanced MR imaging were 20.4+/-4.3%, 29.0+/-9.7%, and 30.7+/-10.6% of the left ventricular myocardium, respectively. The perfusion defects seen at myocardial perfusion MR imaging were significantly smaller than the unstained areas at TTC staining and hyperenhanced areas at gadophrin-2-enhanced MR imaging (p < .01). The sizes of both the perfusion defect at myocardial perfusion MR imaging and the hyperenhanced area at gadophrin-2- enhanced MR imaging correlated well with the sizes of unstained areas at TTC staining (r = .64, p = .062 and r = .70, p = .035, respectively). CONCLUSION: In this cat model, the perfusion defect revealed by myocardial perfusion MR imaging underestimated the true size of acute reperfused myocardial infarction. The defect may represent a more severely damaged area of infarction and probably has prognostic significance.

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.

Clinical Utility and Role of Magnetic Resonance Cholangiography in the Evaluation of Choledocholithiasis Prior to Laparoscopic Cholecystectomy

PURPOSE: To compare the findings of MR cholangiography with those of ultrasound and biochemistry in patients with suspected choledocholithiasis, and to evaluate the clinical utility and role of MR cholangiography prior to laparoscopic cholecystectomy. MATERIALS AND METHODS: We retrospectively reviewed the radiologic findings and clinical records of 103 consecutive patients in whom choledocholithiasis was suspected and who underwent both ultrasound and MR cholangiography. For MR imaging, a 1.5T unit was used, and axial T1-FLASH, True FISP, and oblique coronal HASTE and RARE images were obtained. Initial biochemical values (AST, ALT, total bilirubin) were correlated with the findings of MR cholangiography. RESULTS: Choledocholithiasis was present in 36 of 103 patients: overall, there were 34 true-positive, 63 truenegative, four false-positive, and two false-negative results. In the detection of choledocholithiasis, MR cholangiography showed the following characteristics: sensitivity, 94%; specificity, 94%; positive predictive value, 89%; negative predictive value, 96%; accuracy, 95%. Calculi in the common bile duct were detected in 3 of 33 patients (9%) in whom ultrasound showed that the caliber of the common bile duct was normal and whose laboratory findings were normal, and in 12 of 43 (28%) of those whose common bile duct was dilatated or whose laboratory values were abnormal. Calculi were present in the common bile duct of 21 of 27 patients (78%) with abnormal laboratory values and abnormal ultrasound findings. CONCLUSION: Choledocholithiasis was detected in 25% of patients without clinical suspicion and was not present in 25% of patients with strong clinical suspicion. In patients with this condition, MR cholangiography is noninvasive and accurate, and we suggest that in patients with suspected choledocholithiasis, it should be a routine diagnostic procedure prior to laparoscopic cholecystectomy.

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.

Functional MR Imaging of the Motor Cortex in Active and Passive Movement: Qualitative and Quantitative Changes

PURPOSE: To compare functional MR imaging of the motor cortex during active and passive movement. MATERIALS AND METHODS: Seven healthy, right-handed volunteers (M:F=6:1; age:25-30 years) were included in this study. A 1.5-T whole body scanner and the multislice EPI BOLD method were used. The motor paradigm was flexion-extension of a thumb against rest. In the active motion task, the thumb was flexed voluntarily once a second, while in the passive task, it was tied with a thread and pulled to flex and extend passively at the same interval and with the same intensity as in the active task. For image postprocessing, an SPM 96 program was used. The sites, numbers, and signal intensity of the activated pixels were determined, and the threshold for significance was set at p<0.001 to p<0.01. RESULTS: In the active motion task, strong activation at the contralateral side of the primary sensorimotor cortex and supplementary motor cortex occurred in all 14 examples in all seven volunteers. Additionally, the ipsilateral primary sensorimotor cortex and supplementary motor area were activated in 12/14 and 11/14 such tasks, respectively. During passive motion tasks, on the other hand, weak activation occurred at the contralateral side of the primary sensorimotor cortex in all cases, but in the contralateral supplementary motor cortex in only three. In the ipsilateral primary sensorimotor cortex and supplementary motor area, there was no activation. CONCLUSION: Compared with the active motion task, activation occurring in the contralateral primary sensorimotor cortex and supplementary cortex was weaker and less frequent during the passive task, and during this latter, the ipsilateral motor cortex remained inactive. These results may be useful for the clinical application of functional MR imaging in unconscious patients or in animal studies.

Effectiveness of MR Urography in the Evaluation of Kidney which Failed to Opacify during Excretory Urography: Comparison with Ultrasonography

OBJECTIVE: The purpose of this study was to compare the effectiveness of MR urography (MRU) with that of ultrasonography (US) in the evaluation of urinary tract when this failed to opacify during excretory urography (EXU). MATERIALS AND METHODS: Twelve urinary tracts in 11 patients were studied. In each case, during EXU, the urinary system failed to opacify within one hour of the injection of contrast media, and US revealed dilatation of the pelvocalyceal syytem. Patients underwent MRU, using a HASTE sequence with the breath-hold technique; multi-slice acquisition was then performed, and the images were reconstructed using maximal intensity projection. Each set of images was evaluated by three radiologists to determine the presence, level, and cause of urinary tract obstruction. RESULTS: Obstruction was present in all twelve cases, and in all of these, MRU accurately demonstrated its level. In this respect, however, US was successful in only ten. The cause of obstruction was determined by MRU in eight cases, but by US in only six. In all of these six, MRU also successfully demonstrated the cause. CONCLUSION: MRU is an effective modality for evaluation of the urinary tract when this fails to opacify during EXU, and appears to be superior to US in demon-strating the level and cause of obstruction.

Usefulness of MR Imaging for Diseases of the Small Intestine: Comparison with CT

OBJECTIVE: To evaluate the usefulness of MR imaging for diseases of the small intestine, emphasizing a comparison with CT. MATERIALS AND METHODS: Thirty-four patients who underwent both CT and MR imaging using FLASH 2D and HASTE sequences were analyzed. All patients had various small bowel diseases with variable association of peritoneal lesions. We compared the detectabilities of CT and MR imaging using different MR pulse sequences. The capability for analyzing the characteristics of small intestinal disease was also compared. RESULTS: MR imaging was nearly equal to CT for detecting intraluminal or peritoneal masses, lesions in the bowel and mesentery, and small bowel obstruction, but was definitely inferior for detecting omental lesions. The most successful MR imaging sequence was HASTE for demonstrating bowel wall thickening, coronal FLASH 2D for mesenteric lesions, and axial FLASH 2D for omental lesions. MR imaging yielded greater information than CT in six of 12 inflammatory bowel diseases, while it was equal to CT in six of seven neoplasms and inferior in five of seven mesenteric ischemia. In determining the primary causes of 15 intestinal obstructions, MR imaging was correct in 11 (73%) and CT in nine (60%) patients. CONCLUSION: MR imaging can serve as an alternative diagnostic tool for patients with suspected inflammatory bowel disease, small intestinal neoplasm or obstruction. is a high-speed, heavily T2-weighted sequence with a great sensitivity for fluid (11). This advance may make it possible to use breath-hold turbo spin-echo MR.

Gadolinium-Enhanced MR Angiogra p hy of Arterial Occlusive in Lower Extremity: Comparison with Conventional Digital Substraction Angiography

PURPOSE: To compare the diagnostic value of gadolinium-enhanced MR angiography with that of conventional digital substraction angiography for the evaluation of lower extremity arterial occlusive diseases. MATERIALS AND METHODS: In 26 patients with symptomatic lower extremity arterial occlusive disease, both conventional digital substraction angiography(DSA) and gadolinium-enhanced MR angiography (CE-MRA) were performed during the same week. MR angiography was performed using three-dimensional gradient-echo ac-quisition before, and two sequential acquisitions after, the administration of gadolinium(0.2 mmol/kg). In 23 patients, two separate, contiguous areas were scanned using additional doses. In three patients, only one field with a suspicious lesion was scanned. Three radiologists independantly analysed the CE-MRA and DSA find-ings of each vascular segment(20 segments per arterial tree) for the presence of obstructive lesions; the grade assigned was either mild or none (>50 %), stenotic(50 %-99 %),or occlusion(100 %). RESULTS: From among a total of 462 segments, DSA detected 99 which were significantly narrowed (stenosis, 33; occlusion, 66). Using MR angiography, 102 segments(stenosis 39; occlusion, 63)were identified, and 94 lesions (stenosis, 32; occlusion 62) were graded correctly. Seven lesions were overestimated and four were un-derestimated. For the detection of hemodynamically significant stenosis or occlusions using MR angiography, sensitivity, specificity, and diagnostic accuracy were 95%, 98%, and 98% (G=0.995, P<0.001), respectively. To prove the absence of lesions, we repeated DSA in two patients with arterial spasm due to puncture. Three occluded segments seen on DSA, which revealed intact segments on MR angiography, suggested slow distal flow after reconstitution. CONCLUSION: For the evaluation of lower extremity arterial occlusive disease, the diagnostic value of gadolini-um-enhanced MR angiography is comparable with that of digital substraction angiography. The advantages of the former are the absence of puncture-related spasm and visualization of slow distal flow.

Detectability of Hepatocellular Carcinoma: Comparison of Gd-DT PA-Enhanced and SPIO-Enhanced MR Imaging

PURPOSE: To compare the detectability of hepatocellular carcinoma (HCC) using superparamagnetic iron oxide (SPIO)-enhanced T2-weighted turbo spin echo (TSE), SPIO-enhanced T2*-weighted FISP, and dynamic Gd-DTPA-enhanced fast low-angle shot (FLASH) MR images. MATERIALS AND METHODS: In order to assess their hepatic lesions, 25 patients (20 men and 5 women) with HCC were enrolled in an MR study in which both gadolinium and SPIO were used. Since the lesions were most conspicuous during the phase of dynamic arterial dominant phase of dynamic gadolinium-enhanced imaging, this was the phase used for analysis. Images were analyzed qualitatively and quantitatively, and to compare the diagnostic value of gadolinium-enhanced imaging with that of SPIO-enhanced imaging for the detection of HCCs, a receiver-operated characteristic curve was obtained. RESULTS: Qualitative analysis revealed a significantly higher percentage of signal loss and a higher liver-lesion contrast-to-noise ratio on SPIO-enhanced FISP imaging than on SPIO-enhanced T2-weighted TSE imaging (p<0.05). It also showed that the lesions were most clearly visible on SPIO-enhanced FISP imaging(and signifi-cantlyso), followed by SPIO-enhanced T2-weighted TSE imaging, and dynamic gadolinium-enhanced imag-ing. Imaging artifacts were more prominent on SPIO-enhanced T2-weighted TSE than on SPIO-enhanced PISF imaging or dynamic gadolinium-enhanced imaging(p<0.05). According to ROC analysis, SPIO-enhanced T2-weighted turbo spin echo(TSE) or SPIO-enhanced FISP imaging achieved higher accuracy than did dynamic gadolinium-enhanced FLASH imaging(p<0.05). CONCLUSION: For the detection of hepatocellular carcinomas, SPIO-enhanced MR imaging is better than gadolinium-enhanced FLASH imaging.

The Diagnostic Concordance of Endoanal Ultrasonography and Endoanal MRI in Cases of Anorectal Fistula

PURPOSE: To evaluate the preoperative diagnostic concordance of morphologic classification of anorectal fistula by endoanal ultrasonography (EUSG) and endoanal magnetic resonance imaging (EMRI). MATERIALS AND METHODS: Between January 1998 and March 1999, 17 patients with anorectal fistula underwent endoanal ultrasonography and magnetic resonance imaging for preoperative assessment. The types of fistula and abscess formation were evaluated, and the findings compared with those obtained during surgery. RESULT: The overall accordance of anorectal fistula was 76% (13 of 17 cases) on ultrasonography and 94% (16 of 17 cases) on magnetic resonance imaging. According to the findings of EUSG, the accordance of each type of anorectal fistula was as follows: transphineteric, 92% (11 of 12 cases); suprasphinteric, 33% (1 of 3); and extrasphincteric, 50% (1 of 2), while for EMRI, the respective figures were 100% (12 of 12 cases), 67% (2 of 3), and 100% (2 of 2). An analysis of reproducibility using kappa value showed that overall concordance between endoanal ultrasonography and surgery(K=0.820) as well as between endoanal MRI and surgery (K=0.866), was very close. CONCLUSION: For the evaluation of anorectal fistula, preoperative endoanal magnetic resonance imaging was more accurate and informative than endoanal ultrasonography.

Excretory MR Urography Using Breathhold Three-dimensional FISP: Comparison with MR Urography Using HASTE Technique

PURPOSE: To compare the usefulness of gadolinium-enhanced excretory MR urography using breath-hold three-dimensional fast imaging with steady state precession (3-D FISP) with conventional MR urography using the half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence in the evaluation of obstructive uropathy. MATERIALS AND METHODS: Twenty-three patients in whom ultrasonography (US) and/or intravenous urography(IVU) revealed signs of urinary obstruction were enrolled in this study. Fifteen were men and eight were women, and their mean age was 54 (range, 21 -80) years. All MR images were obtained using a 1.5-T MR unit. MR urography using the HASTE technique (MRU) and gadolinium-enhanced excretory MR urography using the 3D-FISP technique were performed, and in all cases, reconstructions involved maximum intensity projection. For contrast-enhanced MR urography (CEMRU), images were obtained 3, 5, 20, and 30 minutes after the administration of intravenous contrast media, and for selected cases, additional images were obtained until 24 hours after contrast media injection. For qualitative analysis, two experienced radiologists compared CEMRU and MRU in terms of their diagnostic value as regards the level and cause of urinary obstruction, and morphologic accuracy. In addition, signal to noise ratio (SNR) and contrast to noise ratio (CNR) of the urinary tract at each anatomic level were quantitatively analysed. RESULTS: Quantitative analysis showed that in terms of SNR and CNR of the urinary tract at the level of the mid and distal ureter, CEMRU using 3-D FISP was better than MRU using HASTE (p<0.05). Qualitative analysis indicated that for the depiction of the whole length of normal ureter, and detection of the level of obstruction, anatomic anomalies and intrinsic tumors, 3-D FISP was superior to HASTE. There was, however, no difference between these two modalities in the diagnosis of ureteral stone and the degree of hydronephrosis. In addition, 3-D FISP was better than HASTE for the assessment of filling defect, but the difference was not statistically significant. CONCLUSION: Breath hold 3-D FISP is a very valuable tool in the evaluation of obstructive uropathy. It not only depicts very clearly the anatomy of the urinary tract system, but also provides qualitative information on renal function. We believe that CEMRU using 3-D FISP is a valuable diagnostic approach which can be added to those already available for the workup of obstructive uropathy.

Diffusion-weighted MR Imaging of Bone Marrow in the Spine: Differentiations of Metastatic Compression Fracture,Benign Compression Fracture, & Spondylitis

PURPOSE: To determine the findings of diffusion-weighted magnetic resonance (MR) imaging of acute and chronic benign compression fracture, metastatic compression fracture, and spondylitis, and to differentiate between them. MATERIALS AND METHODS: Forty-nine cases with vertebral compression fractures (17 metastatic, 16 acute osteo-porotic, 11 old osteoporotic, 5 acute traumatic) and seven with spondylitis (4 tuberculous, 3 pyogenic) underwent MR imaging. All cases were classified as belonging to one of four groups: A: acute osteoporotic and traumatic, B: metastatic, C: old osteoporotic, or D: spondylitic. For MR imaging, a 1.5-T scanner (Magnetom Vision, Siemens, Erlangen, Germany) was used, and the diffusion-weighted imaging sequence was based on reversed fast imaging with steady-state precession (PSIF) and a relatively low b value of about 150 sec/mm 2. Signal intensity characteristics were evaluated in terms of the contrast ratio (CR) and signal-to-noise ratio (SNR) of bone marrow. RESULTS: Diffusion-weighted MR imaging showed that signal intensity in group A was hypointense to adjacent normal vertebral bodies, but in group B, hyperintensity was noted. In group C, signal intensity was variable, while in group D, hyperintensity was again noted. Diffusion-weighted imaging revealed that in group A, bone marrow CR had a negative value, while in groups B and D, this value was positive (p .01). CONCLUSION: Diffusion-weighted MR imaging revealed that the signal intensity of metastatic compression fracture and spondylitis was hyperintense to adjacent normal vertebral bodies, that of acute benign compression fracture was hypointense, and that of chronic benign compression fracture was variable. This modality is therefore useful for differentiating between metastatic compression fracture, spondylitis and acute benign compression fracture.