Abdominal MR imaging with a volumetric interpolated breath-hold examination.

PURPOSE: To compare a T1-weighted, three-dimensional (3D), gradient-echo (GRE) sequence for magnetic resonance (MR) imaging of the body (volumetric interpolated breath-hold examination, or VIBE) with a two-dimensional (2D) GRE breath-hold equivalent. MATERIALS AND METHODS: Twenty consecutive patients underwent 1.5-T MR imaging. The examinations included pre- and postcontrast (20 mL gadopentetate dimeglumine) fat-saturated 2D GRE breath-hold imaging and fat-saturated volumetric interpolated breath-hold imaging before, during (arterial phase), and after injection, with thin (2-mm source images) and thick (8-mm reconstruction images) sections. The three images were compared qualitatively and quantitatively (signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]). RESULTS: Qualitatively, the 2-mm source images had poorer pancreatic edge definition on precontrast images compared with the other two data sets (P < .05). On gadolinium-enhanced images, scores for clarity of pancreatic edge, number of vessels visualized, and arterial ghosting were significantly lower for the postcontrast 2D GRE images. Quantitatively, SNR measurements in the liver, aorta, and renal cortex on pre- and postcontrast images were significantly higher for the 8-mm reconstruction images than for the 2D GRE or 2-mm source images (P < .05). Aorta-to-fat CNR was significantly higher on the 8-mm reconstruction images. CONCLUSION: Fat-saturated volumetric interpolated breath-hold images have quality comparable to that of conventional fat-saturated 2D GRE images.     

Comparison between gadolinium-enhanced 2D T1-weighted gradient-echo and spin-echo sequences in the detection of active multiple sclerosis lesions on 3.0T MRI

Objectives

To compare the sensitivity of enhancing multiple sclerosis (MS) lesions in gadolinium-enhanced 2D T1-weighted gradient-echo (GRE) and spin-echo (SE) sequences, and to assess the influence of visual conspicuity and laterality on detection of these lesions.

Methods

One hundred MS patients underwent 3.0T brain MRI including gadolinium-enhanced 2D T1-weighted GRE and SE sequences. The two sets of contrast-enhanced scans were evaluated in random fashion by three experienced readers. Lesion conspicuity was assessed by the image contrast ratio (CR) and contrast-to-noise ratio (CNR). The intracranial region was divided into four quadrants and the impact of lesion location on detection was assessed in each slice.

Results

Six hundred and seven gadolinium-enhancing MS lesions were identified. GRE images were more sensitive for lesion detection (0.828) than SE images (0.767). Lesions showed a higher CR in SE than in GRE images, whereas the CNR was higher in GRE than SE. Most misclassifications occurred in the right posterior quadrant.

Conclusions

The gadolinium-enhanced 2D T1-weighted GRE sequence at 3.0T MRI enables detection of enhancing MS lesions with higher sensitivity and better lesion conspicuity than 2D T1-weighted SE. Hence, we propose the use of gadolinium-enhanced GRE sequences rather than SE sequences for routine scanning of MS patients at 3.0T.

Key Points

? 2D SE and GRE sequences are useful for detecting active MS lesions. ? Which of these sequences is more sensitive at high field remains uncertain. ? GRE sequence showed better sensitivity for detecting active MS lesions than SE. ? We propose GRE sequence for detecting active MS lesions at 3.0T.

     

MR imaging of pancreatic lesions. Comparison of manganese-DPDP and gadolinium chelate.

RATIONALE AND OBJECTIVES: To compare manganese-DPDP-enhanced and gadolinium-DTPA-enhanced MR imaging in patients suspected of having pancreatic cancer. METHODS: Fifteen patients who underwent MR imaging for suspected pancreatic cancer and received gadolinium-DTPA took part in a clinical phase III trial in which the efficacy of manganese-DPDP for detection of pancreatic cancer was evaluated. T1-weighted gradient-echo (GRE) images with and without fat suppression were used. Signal-to-noise ratio and contrast-to-noise ratio were calculated before and after the administration of each contrast agent. Image quality was assessed using a four-step score; delineation of the normal pancreas was assessed by two readers in consensus. RESULTS: In terms of pancreatic signal-to-noise ratio, only gadolinium-DTPA-enhanced fat-suppressed and non-fat-suppressed GRE imaging showed a significant (P < 0.001) increase (72% and 61%, respectively). In the patients with a focal pancreatic lesion (n = 14), a significant increase in contrast-to-noise ratio was found only in manganese-DPDP-enhanced GRE imaging without (106%) and with (82%) fat saturation. Qualitative image analysis demonstrated a significant improvement of manganese-DPDP-enhanced fat-suppressed MR images in delineating the pancreatic parenchyma (P < 0.01) as well as pancreatic tumors (P < 0.01). CONCLUSIONS: T1-weighted manganese-DPDP-enhanced GRE imaging with fat saturation should be regarded as the most suitable combination for detecting a pancreatic lesion.     

MR imaging appearance of fetal cerebral ventricular morphology

PURPOSE: To compare T2-weighted breath-hold single-shot fast spin-echo (SE) and gadolinium-enhanced spoiled gradient-echo (GRE) MR imaging with contrast material administered orally and rectally for evaluating patients with Crohn disease. MATERIALS AND METHODS: Twenty-eight patients with Crohn disease received 2% barium sulfate and water enema. The abdomen and pelvis were imaged with transverse and coronal single-shot fast SE and gadolinium-enhanced spoiled GRE MR imaging. Two radiologists reviewed the two types of images for bowel disease. The extent, severity, and conspicuity of the disease were determined. Proof of bowel disease at MR imaging was compared with that at endoscopy, barium study, and surgery. Statistical analysis was performed with the McNemar test. RESULTS: Twenty-five of 28 patients had proven abnormal bowel segments. The per-patient sensitivity of gadolinium-enhanced spoiled GRE MR imaging for the two radiologists was 100% and 96% versus 60% and 60% (P <.05) with single-shot fast SE MR imaging. Gadolinium-enhanced spoiled GRE MR images depicted more segments (54 and 52 of 61 segments; sensitivity, 89% and 85%, respectively) of the diseased bowel than did single-shot fast SE MR images (31 and 32 of 61 segments; sensitivity, 51% and 52%, respectively; P <.001). Severity of Crohn disease was correctly depicted at gadolinium-enhanced spoiled GRE imaging in 93% of patients versus in 43% of patients at single-shot fast SE imaging. CONCLUSION: In patients with Crohn disease, gadolinium-enhanced fat-suppressed spoiled GRE MR imaging better depicted the extent and severity of intestinal disease compared with single-shot fast SE imaging.     

Diuretic-enhanced gadolinium excretory MR urography: comparison of conventional gradient-echo sequences and echo-planar imaging

The aim of this study was to investigate the utility of different gadolinium-enhanced T1-weighted gradient-echo techniques in excretory MR urography. In 74 urologic patients, excretory MR urography was performed using various T1-weighted gradient-echo (GRE) sequences after injection of gadolinium-DTPA and low-dose furosemide. The examinations included conventional GRE sequences and echo-planar imaging (GRE EPI), both obtained with 3D data sets and 2D projection images. Breath-hold acquisition was used primarily. In 20 of 74 examinations, we compared breath-hold imaging with respiratory gating. Breath-hold imaging was significantly superior to respiratory gating for the visualization of pelvicaliceal systems, but not for the ureters. Complete MR urograms were obtained within 14–20 s using 3D GRE EPI sequences and in 20–30 s with conventional 3D GRE sequences. Ghost artefacts caused by ureteral peristalsis often occurred with conventional 3D GRE imaging and were almost completely suppressed in EPI sequences (p < 0.0001). Susceptibility effects were more pronounced on GRE EPI MR urograms and calculi measured 0.8–21.7 % greater in diameter compared with conventional GRE sequences. Increased spatial resolution degraded the image quality only in GRE-EPI urograms. In projection MR urography, the entire pelvicaliceal system was imaged by acquisition of a fast single-slice sequence and the conventional 2D GRE technique provided superior morphological accuracy than 2D GRE EPI projection images (p < 0.0003). Fast 3D GRE EPI sequences improve the clinical practicability of excretory MR urography especially in old or critically ill patients unable to suspend breathing for more than 20 s. Conventional GRE sequences are superior to EPI in high-resolution detail MR urograms and in projection imaging. Received: 12 May 2000 Revised: 14 July 2000 Accepted: 17 July 2000     

Detection of hepatocellular carcinoma using double-echo FLASH sequence during the hepatic arterial phase.

PURPOSE: The purpose of this study was to compare the performance of in-phase and opposed-phase gradient-recalled echo (GRE) pulse sequences in paramagnetic contrast-enhanced magnetic resonance (MR) imaging of hepatocellular carcinomas (HCCs) during the hepatic arterial phase. MATERIAL AND METHODS: Thirty-four patients with 84 lesions with known or suspected HCCs, nine of whom had a fatty liver, were examined with double-echo GRE techniques under 1.5T before and 30 s after injection of gadopentenate dimeglumine at a dose of 0.1 mmol/kg. Echo times were 2.4 ms (opposed phase) and 5.0 ms (in phase). Contrast enhancement of the HCC detected in both in-phase and opposed-phase images was evaluated. The liver signal-to-noise ratio (SNR), lesion-liver contrast-to-noise ratio (CNR), and enhancement ratio (ER) were calculated for the largest lesion of each patient. RESULTS: In dynamic gadolinium-enhanced images of the 84 HCCs, 81 (96.4%) were detected in both in-phase and opposed-phase images, two (2.4%) were detected in only in-phase images, and one (1.2%) was detected only in opposed-phase images. The liver SNR, CNR, and ER were 46.7+/-16.1, 15.2+/-10.3, and 0.637+/-0.268 for in-phase images, and 48.9+/-16.9, 16.3+/-11.8, and 0.647+/-0.309 for opposed-phase images, respectively. In patients with a fatty liver, the SNR, CNR, and ER were 46.0+/-18.1, 21.7+/-17.9, and 0.525+/-0.231 for in-phase images, and 44.3+/-18.7, 26.0+/-21.3, and 0.793+/-0.124 for opposed-phase images, respectively. No significant statistical differences were found between the in-phase and opposed-phase images. CONCLUSION: Opposed-phase GRE imaging is equivalent to in-phase GRE sequences in patients with or without fatty liver for detection of HCC in dynamic gadolinium-enhanced images.     

Screening for skeletal metastases of the spine and pelvis: gradient echo opposed-phase MRIcompared with bone scintigraphy

Opposed-phase gradient eho (GRE) MRI at 0.5 T was compared with T1-weighted GRE MRI and bone scintigraphy regarding the detection of malignant bone marrow infiltrates of the spine and pelvis. Seventeen control patients and 41 patients with suspected skeletal metastases were studied with plain and gadolinium-enhanced MRI. In the control group only a vertebral haemangiona showed contrast enhancement, while all metastases (confirmed histologically or by follw-up) were enhancing. Opposed-phase surface coil MRI showed a significantly higher contrast-to-noise ratio of 56 metastases than T1-weighted images. In 28 patients body coil opposed-phased MRI detectedmore metastatic foci of the spine and pelvis than did bone scintigraphy (84 vs 56). No scintigraphically visualised lesion was missed by MRI. In conclusion,body coil gadolinium-enhanced opposed-phase GRE MRI may be applied as a screning method for skeletal metastases of the spine and pelvis at intermediate field strengths. Correspondence to: K. Neumann     

Magnetic resonance imaging of the brain with gadopentetate dimeglumine-DTPA: Comparison of T1-weighted spin-echo and 3D gradient-echo sequences

Short TR, short TE, high resolution, 3D gradient-recalled echo (GRE) imaging was evaluated for lesion detection in the brain. High resolution 3D GRE data acquisition was used to reduce partial volume effects and flow artifacts, to better visualize smaller structures, to minimize signal losses caused by field inhomogeneities, and to allow better image reformatting. Spin-echo (SE) and 3D GRE approaches were compared for lesion detection after the administration of an MR contrast agent, gadopentetate dimeglumine. Preliminary clinical studies demonstrated that the signal-to-noise ratio (SNR) in each slice of the GRE scan was worse than that of the SE scan because of the much thicker slices acquired with the SE technique. However, by averaging two adjacent 3D slices, the SNR of the two methods was essentially equivalent. In the averaged GRE slices, large lesions were seen just as well as in the SE images. More importantly, small lesions were better visualized in the thin 3D GRE images than in the thick SE images for the lesions studied in this work and the protocols used. These observations were confirmed by theoretical simulations.     

Detection of small, functional islet cell tumors in the pancreas: selection of MR imaging sequences for optimal sensitivity

PURPOSE: To determine the sensitivity and specificity of magnetic resonance (MR) imaging for depicting pancreatic small, functional islet cell tumors and the minimum number of sequences for expedient diagnosis. MATERIALS AND METHODS: Twenty-eight patients clinically suspected to have functional islet cell tumors underwent T1- and T2-weighted spin-echo (SE) MR imaging with and without fat suppression, T2-weighted fast SE imaging, and spoiled gradient-echo (GRE) imaging before and after injection of gadopentetate dimeglumine. Sensitivity, specificity, and the best and minimum number of sequences for definitive diagnosis were determined. RESULTS: MR images depicted proved islet cell tumors in 17 of 20 patients (sensitivity, 85%). Images were true-negative in eight patients with negative follow-up examination results for more than 1 year. Specificity was 100%; positive predictive value, 100%; and negative predictive value, 73%. Among 20 patients with tumor, T1-weighted SE images with fat suppression and nonenhanced spoiled GRE images each showed lesions in 15 (75%); T2-weighted conventional SE with fat suppression, in 13 (65%); gadolinium-enhanced spoiled GRE, in 12 (60%); and T2-weighted fast SE, in seven of 10 patients (70%). CONCLUSION: MR imaging accurately depicts small islet cell tumors. T2-weighted fast SE and spoiled GRE sequences usually suffice. Gadolinium-enhanced sequences are needed only if MR imaging results are equivocal or negative.     

Hepatic and hepatocarcinoma magnetic resonance: comparison of the results obtained with paramagnetic (gadolinium) and superparamagnetic (iron oxide particles) contrast media

PURPOSE: To compare prospectively dynamic gadolinium (Gd)-enhanced with superparamagnetic iron oxide (SPIO)-enhanced MRI for the detection of hepatocellular carcinoma (HCC). MATERIAL AND METHODS: Twenty-five patients with histologically proven HCC and liver cirrhosis (28% of them in B or C Child class) underwent dynamic Gd-enhanced MRI and, a few days later, (mean interval: three days) SPIO-enhanced MRI. Only patients with availability of clinical and imaging follow-up for at least seven months were enrolled in this prospective study. Axial dynamic Gd-enhanced imaging was performed with T1 gradient-recalled echo (GRE) sequences. Both axial and sagittal SPIO-enhanced imaging were performed with respiratory triggered T2-weighted turbo spin-echo (TSE) and T1-T2*-weighted GRE sequences. MR images were reviewed by two independent radiologists. The readers scored each lesion for the presence of HCC and assigned confidence levels based on a five-grade scale: 1, definitely or almost definitely absent; 2, possibly present; 3, probably present; 4, definitely present; 5, definitely present with optimal liver/lesion contrast or good liver/lesion contrast and morphological signs (intact capsule, intranodular septa, extra-capsular infiltration), useful for locoregional treatment planning. A positive diagnostic value was assessed for scores of 3 or higher. RESULTS: Gd-enhanced and SPIO-enhanced MRI found 44 lesions. The combined use of TSE and GRE SPIO-enhanced sequences detected 11 more lesions (25% improvement in sensitivity) than Gd-enhanced MRI. One lesion (2.27%) was detected only with Gd-enhanced MRI. Eight of twelve lesions visible with a single contrast agent measured less than 1 cm in diameter. HCC detectability was 75% with Gd-enhanced MRI and 97.7% with SPIO-enhanced MRI. SPIO-enhanced T2-weighted TSE images showed significantly higher diagnostic value than SPIO-enhanced T1-T2*GRE images only in three cases, while nodule morphological characteristics (capsule, septa, different cell differentiation components) were better depicted by TSE images. DISCUSSION AND CONCLUSIONS: In our study the combined use of SPIO-enhanced T2-weighted TSE and T1-T2*-weighted GRE sequences showed higher sensitivity than gadolinium-enhanced GRE dynamic imaging (97.7% versus 75%). These results are at least partly related to our study conditions, that is: 1) MRI was performed with a 1T system, 2) both axial and sagittal SPIO-enhanced imaging were performed with respiratory triggered T2-weighted TSE and T1-T2*-weighted GRE, 3) there was a low freaquency of severe cirrhosis.     

MR imaging of the chest using a contrast-enhanced breath-hold modified three-dimensional gradient-echo technique: comparison with two-dimensional gradient-echo technique and multidetector CT

OBJECTIVE: The purpose of this study was to assess the feasibility of performing MR imaging of the chest using a fat-suppressed gadolinium-enhanced modified three-dimensional (3D) gradient-echo technique with a volumetric interpolated breath-hold (VIB) sequence compared with using a standard two-dimensional (2D) breath-hold gradient-echo technique. MR images obtained using both techniques were compared with multidetector CT (MDCT) scans. SUBJECTS AND METHODS: Paired gadolinium-enhanced 2D gradient-echo and 3D gradient-echo VIB images were acquired in 15 consecutive patients with suspected intrathoracic abnormalities. MDCT scans were available for comparison in 12 patients. Two reviewers independently analyzed the MR images obtained using the two techniques for overall quality, the degree of artifacts, and visibility of mediastinal or parenchymal abnormalities. The detectability of lesions on the 3D gradient-echo VIB images and 2D gradient-echo images was compared with the detectability of lesions on CT scans obtained in nine patients. RESULTS: In all cases, the MR images obtained using the 3D gradient-echo technique with the VIB sequence were rated superior to those obtained using the 2D gradient-echo technique for quality, depiction of mediastinal structures, and clarity of pulmonary vessels and central airways. On the 3D gradient-echo VIB images, the degree of phase artifacts was lower (p < 0.001), but the degree of pixel graininess was higher (p < 0.05). Detectability, confidence and conspicuity levels, and marginal delineation of the pulmonary lesions were rated higher statistically on the 3D gradient-echo VIB images than on the 2D gradient-echo images. Of the 31 solid pulmonary abnormalities depicted on MDCT, 27 (87.1%) were detected on the 3D gradient-echo VIB images, and 21 (67.7%) were seen on the 2D gradient-echo images (p < 0.05). The 3D gradient-echo VIB images showed all 14 mediastinal lesions (100%) seen on MDCT, whereas the 2D gradient-echo images showed 12 (85.7%) of the 14 lesions (p > or = 0.05). CONCLUSION: The gadolinium-enhanced modified 3D gradient-echo technique with the VIB sequence provides MR images that are superior in quality, have significantly fewer artifacts, and have a higher sensitivity for the detection of intrathoracic lesions compared with images obtained using the standard 2D gradient-echo technique.     

Simulated pulmonary nodules implanted in a dedicated porcine chest phantom: sensitivity of MR imaging for detection

PURPOSE: To evaluate the diagnostic accuracy of common magnetic resonance (MR) imaging sequences for detection of small pulmonary nodules by using a chest phantom and porcine lungs containing simulated lesions. MATERIALS AND METHODS: Fourteen porcine lungs containing 366 porcine myocardial tissue implants were inflated inside a phantom. Two-dimensional (2D) and three-dimensional (3D) gradient-echo (GRE), T2-weighted turbo spin-echo (SE), and T2-weighted single-shot SE train MR sequences were performed. Spiral computed tomography (CT) was performed for comparison. Blinded observers read the images and recorded the sizes and locations of visible nodules by consensus. The sensitivity of each imaging method for depicting single nodules of given sizes was calculated. Specificities, positive predictive values (PPVs), and negative predictive values (NPVs) for detection of one or more nodules of various sizes were calculated. RESULTS: Sensitivities of 3D GRE, 2D GRE, T2-weighted turbo SE, and T2-weighted single-shot SE train MR imaging and of CT were 0.50, 0.40, 0.12, 0.00, and 0.55, respectively, for detection of 1.4-mm nodules and 0.88, 0.84, 0.69, 0.06, and 0.96, respectively, for detection of 4.2-mm nodules. The 95% CIs for CT and GRE MR imaging overlapped, but those for turbo SE and single-shot SE train MR imaging differed significantly (P <.05). For detection of nodules larger than 5 mm, all examinations except single-shot SE train MR imaging yielded a specificity, PPV, and NPV of 1.00 each. For detection of nodules smaller than 5 mm, diagnostic accuracy of 3D GRE MR imaging was high: Specificity, PPV, and NPV all were approximately 0.90. Two-dimensional GRE MR imaging results were influenced by false-positive findings: Specificity was 0.64; PPV, 0.74; and NPV, 1.00. CONCLUSION: Common MR imaging sequences such as 3D GRE have high diagnostic accuracy in depicting small pulmonary nodules when artifacts from cardiac and respiratory motion are absent.     

Enhancement effects of hepatic dynamic MR imaging at 3.0 T and 1.5 T using gadoxetic acid in a phantom study: comparison with gadopentetate dimeglumine

To identify the optimum sequence at gadoxetic acid enhanced hepatic dynamic magnetic resonance imaging in the arterial phase, we studied phantoms that contained gadoxetic acid or gadopentetate dimeglumine diluted in human blood. We obtained magnetic resonance images at 3.0 T and 1.5 T with one vendor (Siemens) using 3D‐gradient echo (GRE)‐, 2D‐fast low angle shot (FLASH)‐, and turbo spin echo sequences. Contrast ratio was highest for 3D‐GRE; at both 3.0 T and 1.5 T it was superior when the contrast agent was gadoxetic acid. With both gadoxetic acid and gadopentetate dimeglumine, contrast ratio peaked at around 5‐and 2 mmol/L on 3D‐GRE‐ and 2D‐FLASH images, respectively. Compared with gadopentetate dimeglumine, at 3.0 T, the peak contrast ratio of gadoxetic acid was 14.1% better on 3D‐GRE images and 14.0% better on 2D‐FLASH images; at 1.5 T it was 16.4% better on 3D‐GRE‐ and 5.7% better on 2D‐FLASH images. With respect to the magnetic field strength, at 3.0 T the peak contrast ratio of gadoxetic acid was 6.0% better than at 1.5 T on 3D‐GRE images and 49.5% better on 2D‐FLASH images; it was 8.5% better on 3D‐GRE‐ and 44.6% better on 2D‐FLASH images than when the contrast agent was gadopentetate dimeglumine. Thus, gadoxetic acid yielded better enhancement on 3D‐GRE images acquired at 3.0 T than at 1.5 T and enhancement was better than that obtained with gadopentetate dimeglumine at the same concentration. Magn Reson Med 66:213–218, 2011. © 2011 Wiley‐Liss, Inc.     

Pancreatic tumors: diagnostic patterns by 3D gradient-echo post contrast magnetic resonance imaging with pathologic correlation

Magnetic resonance (MR) imaging has considerable potential in characterizing pancreatic masses. Certain features can be used by the radiologist to establish a definitive diagnosis for most pancreatic tumors including ductal adenocarcinoma, islet cell tumors, solid and papillary epithelial neoplasms, micro- and macrocystic adenoma, and metastases. Recognition of these tumors on imaging is important since it often changes the treatment approach and may obviate the need for surgery. Recent introduction of 3D gradient recalled echo (GRE) sequence such as volumetric interpolated breath hold examination (VIBE) has dramatically improved MR imaging by providing dynamic enhanced thin-slice images with fat saturation and high signal-to-noise ratio. In this article, special emphasis will be placed on the impact of 3D GRE sequence in the diagnosis of pancreatic neoplasms with pathologic correlation.     

Expression of vascular endothelial growth factor in hepatocellular carcinoma and the surrounding liver and correlation with MRI findings

OBJECTIVE: The purpose of our study was to assess the correlation between the quantitative and qualitative imaging findings on unenhanced and gadolinium-enhanced MR images and the intensity of vascular endothelial growth factor (VEGF) expression in hepatocellular carcinomas and in the surrounding nontumorous liver. MATERIALS AND METHODS: The intensities of VEGF expression in hepatocellular carcinoma and in the surrounding liver by Western blot analysis were converted to VEGF expression indexes (VEGF(IND)) in 22 surgical specimens ranging in size from 14 to 126 mm (mean, 47.6 +/- 29.5 mm) that were resected in 22 patients (17 men and five women; age range, 41-85 years [mean, 64 years]) between April 2000 and October 2002. MR images were retrospectively evaluated to determine contrast-to-noise ratios (CNRs), signal intensity SD ratios, and phase-shift indexes. Signal intensity characteristics of hepatocellular carcinomas were reviewed independently by two experienced radiologists who were unaware of the pathologic diagnosis or the results of immunoblotting. CNRs, SD ratios, and phase-shift indexes were correlated with VEGF(IND) using a simple regression test, and signal intensity characteristics were correlated with VEGF(IND) using the Spearman's rank correlation test. RESULTS: On opposed-phase T1-weighted spoiled gradient-recalled echo (GRE) images, CNRs correlated inversely with the VEGF(IND) of hepatocellular carcinomas (r = -0.46, p = 0.038). CNRs on T2-weighted fast spin-echo images correlated directly with the VEGF(IND) of hepatocellular carcinomas (r = 0.49, p = 0.025), and on gadolinium-enhanced hepatic arterial phase GRE images marginally and inversely correlated with VEGF(IND) (r = -0.39, p = 0.081). On T2-weighted fast spin-echo images, SD ratios correlated directly with the VEGF(IND) of hepatocellular carcinomas (r = 0.44, p = 0.044). No correlation was found between phase-shift indexes and VEGF expression. The qualitatively assessed signal intensity heterogeneities of hepatocellular carcinomas correlated directly with the VEGF(IND) of hepatocellular carcinomas on opposed-phase T1-weighted GRE, T2-weighted fast spin-echo, hepatic arterial phase GRE, and equilibrium phase GRE images. CONCLUSION: Our results indicate that the signal intensity and heterogeneity of hepatocellular carcinomas on MR images correlate with the degree of VEGF expression in hepatocellular carcinomas.     

Cerebral microbleeds: accelerated 3D T2*-weighted GRE MR imaging versus conventional 2D T2*-weighted GRE MR imaging for detection

The purpose of this study was to prospectively compare high-spatial-resolution accelerated three-dimensional (3D) T2*-weighted gradient-recalled-echo (GRE) magnetic resonance (MR) images with conventional two-dimensional (2D) T2*-weighted GRE MR images for the depiction of cerebral microbleeds. After obtaining institutional review board approval and informed consent, 200 elderly participants (age range, 69.7-96.7 years; 108 [54%] women) were imaged at 1.5 T by using both sequences. Presence, number, and location of microbleeds were recorded for both sequences, and differences were tested by using McNemar and signed rank tests. Cerebral microbleeds were detected in significantly more participants on 3D T2*-weighted GRE images (35.5%) than on 2D T2*-weighted GRE images (21.0%; P < .001). Furthermore, in persons with microbleeds visualized on both image sets, significantly more microbleeds (P < .001) were seen on 3D images than on 2D images. For both sequences, the proportion of participants with a microbleed in a lobar (cortical gray and subcortical white matter), deep, or infratentorial location was similar. In conclusion, accelerated 3D T2*-weighted GRE images depict more microbleeds than do conventional 2D T2*-weighted GRE images.     

Sulcal hyperintensity on fluid-attenuated inversion recovery imaging in acute ischemic stroke patients treated with intra-arterial thrombolysis: iodinated contrast media as its possible cause and the association with hemorrhagic transformation

OBJECTIVE: To investigate the effect of iodinated contrast medium on sulcal hyperintensity on fluid-attenuated inversion recovery (FLAIR) imaging immediately after intra-arterial thrombolysis in patients with acute ischemic stroke and to determine whether it may be associated with subsequent hemorrhagic transformation (HT). METHODS: Fourteen consecutive patients with acute ischemic stroke who were treated with intra-arterial thrombolysis were enrolled. All patients underwent noncontrast computed tomography (NCT) and diffusion-weighted (DWI), perfusion-weighted, gradient-recalled echo (GRE), and gadolinium-enhanced T1-weighted magnetic resonance imaging (MRI). Immediate follow-up NCT and MRI (T2-weighted, FLAIR, GRE, DWI, perfusion-weighted, T1-weighted, and gadolinium-enhanced T1-weighted) were obtained and evaluated to determine the presence of sulcal hyperintensity or subarachnoid hemorrhage (SAH). The same follow-up images were obtained on days 1, 3, and 7 and evaluated to determine HT. RESULTS: Sulcal hyperintensity was found in 8 (57.1%) of 14 patients and was seen as hyperattenuation on immediate follow-up NCT and as hyperintensity on T1-weighted images in 4 (50%) of 8 patients. It may be suggested that the sulcal hyperattenuation was responsible for the sulcal hyperintensity, considering signal intensity and follow-up imaging. All patients with sulcal hyperintensity showed enhancement in the corresponding gyri on gadolinium-enhanced T1-weighted imaging. Hemorrhagic transformation developed in 5 of 8 patients with sulcal hyperintensity and in 1 of 4 patients without (P = 0.031). CONCLUSIONS: In acute ischemic patients treated with intra-arterial thrombolysis, sulcal hyperintensity on FLAIR imaging may be caused by iodinated contrast medium, which should not be considered SAH. Sulcal hyperintensity is significantly associated with subsequent HT.     

Three-dimensional contrast-enhanced hepatic MR imaging: comparison between a centric technique and a linear approach with partial Fourier along both slice and phase directions

Purpose

To compare the image quality of two variants of a three‐dimensional (3D) gradient echo sequence (GRE) for hepatic MRI.

Materials and Methods

Thirty‐nine patients underwent hepatic MRI on a 3.0 Tesla (T) magnet (Intera Achieva; Philips Medical Systems). The clinical protocol included two variants of a 3D GRE with fat suppression: (i) a “centric” approach, with elliptical centric k‐space ordering and (ii) an “enhanced” approach using linear sampling and partial Fourier in both the slice and phase encoding direction. “Centric” and “Enhanced” 3D GRE images were obtained both precontrast (n = 32) and after gadoxetic acid injection (n = 39). Two reviewers jointly reviewed MR images for anatomic sharpness, overall contrast, homogeneity, and absence of artifacts. The liver‐to‐lesion signal difference ratio (SDR) was measured. Paired sample Wilcoxon test and paired t‐tests were used.

Results

Enhanced 3D GRE images performed better than centric 3D GRE images with respect to anatomic sharpness (P = 0.0156), overall contrast (P = 0.0195), homogeneity (P < 0.0001), and absence of artifacts (P = 0.0003) on precontrast images. For postcontrast MRI, enhanced 3D GRE images showed better quality in terms of overall contrast (P = 0.0195), homogeneity (P < 0.0001), and absence of artifacts (P = 0.009). Liver‐to‐lesion SDR on enhanced 3D GRE images (0.48 ± 0.13) was significantly higher than that of conventional 3D GRE images (0.40 ± 0.19, P = 0.0004) on postcontrast images, but not on precontrast images.

Conclusion

The enhanced 3D GRE sequence available on our scanner provided better hepatic image quality than the centric variant, without compromising lesion contrast. J. Magn. Reson. Imaging 2011;33:160–166. © 2010 Wiley‐Liss, Inc.     

Feasibility of free-breathing dynamic contrast-enhanced MRI of gastric cancer using a golden-angle radial stack-of-stars VIBE sequence: comparison with the conventional contrast-enhanced breath-hold 3D VIBE sequence

Objectives

To investigate the feasibility and diagnostic value of free-breathing, radial, stack-of-stars three-dimensional (3D) gradient echo (GRE) sequence (“golden angle”) on dynamic contrast-enhanced (DCE) MRI of gastric cancer.

Methods

Forty-three gastric cancer patients were divided into cooperative and uncooperative groups. Respiratory fluctuation was observed using an abdominal respiratory gating sensor. Those who breath-held for more than 15 s were placed in the cooperative group and the remainder in the uncooperative group. The 3-T MRI scanning protocol included 3D GRE and conventional breath-hold VIBE (volume-interpolated breath-hold examination) sequences, comparing images quantitatively and qualitatively. DCE-MRI parameters from VIBE images of normal gastric wall and malignant lesions were compared.

Results

For uncooperative patients, 3D GRE scored higher qualitatively, and had higher SNRs (signal-to-noise ratios) and CNRs (contrast-to-noise ratios) than conventional VIBE quantitatively. Though 3D GRE images scored lower in qualitative parameters compared with conventional VIBE for cooperative patients, it provided images with fewer artefacts. DCE parameters differed significantly between normal gastric wall and lesions, with higher Ve (extracellular volume) and lower Kep (reflux constant) in gastric cancer.

Conclusions

The free-breathing, golden-angle, radial stack-of-stars 3D GRE technique is feasible for DCE-MRI of gastric cancer. Dynamic enhanced images can be used for quantitative analysis of this malignancy.

Key Points

? Golden-angle radial stack-of-stars VIBE aids gastric cancer MRI diagnosis. ? The 3D GRE technique is suitable for patients unable to suspend respiration. ? Method scored higher in the qualitative evaluation for uncooperative patients. ? The technique produced images with fewer artefacts than conventional VIBE sequence. ? Dynamic enhanced images can be used for quantitative analysis of gastric cancer.

     

Pancreatic carcinoma versus chronic pancreatitis: dynamic MR imaging.

PURPOSE: To determine if dynamic gadolinium-enhanced magnetic resonance (MR) imaging can distinguish chronic pancreatitis from pancreatic carcinoma. MATERIALS AND METHODS: A retrospective review of MR and pathology examination findings was performed for 24 patients with pancreatic ductal adenocarcinoma and seven with chronic pancreatitis who underwent dynamic gadolinium-enhanced breath-hold spoiled gradient-echo imaging. Arterial, portal, and delayed phase images were obtained after injection of gadopentatate dimeglumine. The MR images of 14 patients without clinical evidence of pancreatic disease were also reviewed as controls. Signal intensity (SI) was measured on the precontrast (pre) and gadolinium-enhanced (post) images of the area of the pancreas sampled at biopsy and of the nontumorous pancreas. Percentage enhancement was defined as SIpre/SIpost x 100. RESULTS: Normal pancreas showed rapid enhancement that peaked in the arterial or portal phase. For both diseases, T1-weighted images showed hypointense masses with progressive enhancement (differences were significant [P < .05] on only delayed fat-saturated images). Differences in enhancement between either disease state and normal pancreas were significant for at least one phase. Nontumorous pancreas in patients with carcinoma showed gradual enhancement that was significantly different from that of normal pancreas. CONCLUSION: Chronic pancreatitis and pancreatic carcinoma show abnormal pancreatic enhancement, but the two were not distinguished on the basis of degree and time of enhancement.