MRI of normal and abnormal duodenum using Half-Fourier Single-Shot RARE and gadolinium-enhanced spoiled gradient echo sequences.

The objective of this research was two-fold: First, to describe the normal and abnormal MR appearances of the duodenum using combined Half-Fourier Acquisition Single Shot RARE (HASTE) and gadolinium-enhanced standard and fat suppressed spoiled gradient echo (SGE) sequences. The second objective was to assess the ability of these combined sequences to detect and characterize duodenal diseases. MR examinations were performed on fifty consecutive patients with no clinical history of duodenal diseases, who were 1) imaged with HASTE and gadolinium-enhanced standard and fat suppressed SGE sequences and 2) referred to MR examination for reasons other than duodenal diseases, and were reviewed retrospectively to determine the normal MR appearances of the duodenum. A second population of patients with abnormal duodenum who were imaged with the same MR sequences were included in the second part of this study. This population was composed of 20 consecutive patients with subsequently proven duodenal abnormalities, including: malrotation (2), diverticula (4), intussusception (1), sprue (1), polyps (2), neurofibroma (1), lymphoma (1), Zollinger Ellison syndrome (1), metastatic disease (1), Crohn's disease (1), and wall thickening and duodenitis (5). Normal measurements of the duodenum are described. Abnormalities of wall thickness and duodenal masses required combined HASTE and gadolinium-enhanced SGE images to evaluate well. Abnormalities of the bowel lumen (e.g., diverticula and intussusception), and developmental variants (e.g., malrotation), were sufficiently visualized on HASTE images alone. Bowel inflammation was best shown on gadolinium-enhanced fat suppressed SGE images. HASTE and gadolinium-enhanced fat suppressed SGE sequences are complementary techniques for the demonstration of normal and abnormal duodenum. The combined use of both sequences allows evaluation of different aspects of bowel diseases; abnormalities of position, lumen, and contents are well shown on HASTE, while inflammation is best shown on gadolinium enhanced fat suppressed SGE, and wall thickening and masses are best evaluated with the combined use of both techniques.     

Evaluation of Crohn's disease using half-fourier RARE and gadolinium-enhanced SGE sequences: initial results

To assess the bowel changes in Crohn's disease, 11 consecutive patients underwent magnetic resonance imaging (MRI) study using T(2)-weighted half-Fourier rapid acquisition with relaxation enhancement (RARE) and gadolinium-enhanced standard and fat suppressed spoiled gradient echo (SGE) sequences. Comparison was made between MR findings of disease extent, severity, and complications and clinical data, endoscopic findings and/or surgical specimens in all patients. We found that the half-Fourier RARE images showed bowel wall thickening, dilatation of bowel and bowel obstruction well in all patients, however severity of bowel disease could not be determined as the signal intensity of diseased bowel was comparable to normal bowel in 10/11 patients. Gadolinium-enhanced fat suppressed SGE demonstrated variations of mural enhancement that correlated well with extent of disease severity in 10/11 patients. Complications such as intraperitoneal (i. p.) abscess (2 patients), gastric outlet obstruction (1 patient), bowel obstruction (2 patients), and fistula formation (3 patient), were accurately shown. We conclude that T(2)-weighted half-Fourier RARE and gadolinium-enhanced fat suppressed SGE sequences are complementary techniques that possess different imaging features that are of value for assessing bowel changes in Crohn's disease.     

MR imaging findings of infectious cholangitis

The purpose of this study was to evaluate the appearance of infectious cholangitis on MRI. The MR images of 13 patients (9 women, 4 men; age range, 14-79 years) with clinically confirmed infectious cholangitis, who represent our complete 9.5 year experience with this entity, were retrospectively evaluated. All MR studies were performed at 1.5 T and included: in-phase and out-of-phase T(1)-weighted spoiled gradient echo (SGE), T(2)-weighted fat-suppressed echo train spin echo, single shot T(2)-weighted sequences, and serial postgadolinium T(1)-weighted SGE sequences without and with fat-suppression. The biliary ductal system was evaluated regarding presence of dilatation, stenosis, wall irregularities, wall thickening, and gadolinium enhancement of duct walls. The liver parenchyma was evaluated regarding focal signal abnormalities on precontrast and serial postgadolinium images. Biliary ductal dilatation was observed in 100% of patients. Mild to moderate thickening of bile duct walls combined with increased enhancement on postgadolinium images was observed in 92% of patients. The liver parenchyma showed periportal or wedge-shaped areas of hyperintense signal on T(2)-weighted images in 69% of patients. On T(1)-weighted images, 54% of patients showed areas of hypointense signal and 15% of patients showed wedge-shaped hyperintense areas. Areas with increased enhancement on immediate postgadolinium SGE were observed in 58% of patients, and in 42% of patients increased enhancement persisted on 2 min postgadolinium fat-suppressed images. Distinctive MRI findings on pre- and postgadolinium images are appreciated for infectious cholangitis.     

MR imaging of coarctation of the aorta and its postoperative complications in adults: assessment with spin-echo and cine-MR imaging

To evaluate the ability of ECG-gated spin-echo (SE)-MR imaging vs. cine-MR imaging to assess coarctation of the aorta, 11 patients aged 15–45 years, with known or suspected coarctation of the aorta, and five patients suspected of re-stenosis or postoperative false-aneurysms after coarctation repair were examined by multisection SE-MR imaging and single-section multiphase cine-MR imaging on a 1.0 Tesla device. Aortography was performed in 15, and surgery in 14 of these 16 patients. Qualitatively, the location, severity, and length of the coarctation were shown in all cases with MR imaging, as well as the relationship with the arteries arising from the aortic arch. The respective sensitivities and specificities in the assessment of severity of stenoses were 86% and 100% for SE MR images, and 100% and 100% for cine-MR images. Cine-MR imaging was superior to SE imaging in stenosis diameter assessment with contrast angiography as reference, as well as to identify the site of leakage in cases of postoperative pseudoaneurysm. Pre-stenotic dilation or post-stenotic aneurysm, collateral channels, and associated malformations were better identified on SE images. Quantitatively, a better stenosis diameter correlation was found between cine-MR images and angiography than between SE-MR images and angiography (r = 0.99 vs. r = 0.78; p = 0.001 vs. p = 0.004), related to overestimation of stenoses with SE-MR imaging. The use of a combination of spin-echo and cine-MR imaging correlates well with conventional angiographic findings in this small series of patients with coarctation of aorta or postoperative pseudoaneurysmal complications. Cine-MRI can provide anatomic information that is equivalent to angiography for surgical planning.     

Cardiac-synchronized gadolinium-enhanced MR angiography: preliminary experience for the evaluation of the thoracic aorta

Gadolinium (Gd)-enhanced three-dimensional breath-hold magnetic resonance cardiac-synchronized angiography was performed in 13 patients suspected or known to have thoracic aortic disease. High-quality angiograms of the ascending/descending thoracic aorta and coronary arteries were obtained with this method. MR angiograms were compared with Gd-enhanced angiograms obtained without cardiac synchronization. Synchronized imaging showed significantly better aortic valve leaflet and proximal coronary artery depiction. Synchronization reduced motion artifacts, allowing better visualization of the aortic root and proximal coronary arteries.     

Comparison of gadolinium chelates with manganese-DPDP for liver lesion detection and characterization: Preliminary results

Nonspecific extracellular gadolinium chelate (NEGd) was prospectively compared with manganese (Mn)-DPDP (Mn) for the detection and characterization of focal liver lesions of various histology. Seventeen patients with known or suspected focal liver lesions underwent NEGd and Mn-enhanced studies at 1.5 T. Study findings were correlated with histology (five patients), computed tomography (CT) examinations (17 patients), and 4- to 13-month imaging follow-up by CT and/or MR (five patients). NEGd studies were performed as serial postcontrast spoiled gradient echo (SGE) sequences, and Mn studies were performed as SGE sequences 15 and 30 min postcontrast and T₁-weighted, fat-suppressed spin echo at 16 min. NEGd and Mn images were prospectively interpreted in a separate blinded fashion. Lesion detection and characterization were determined. NEGd and Mn-enhanced images demonstrated 61 and 49 lesions, respectively (p = .1, NS). A total of 60 and 33 lesions were characterized on NEGd and Mn images, respectively, which was significantly different (p = .008). No differences were observed for the detection and characterization of liver metastases; whereas there was a trend for superior detection and characterization for hepatocellular carcinoma with NEGA.     

Bowel-related abscesses: MR demonstration preliminary results

The purpose of this study is to describe the appearance of bowel-related abscesses on magnetic resonance (MR) images. Sixteen consecutive patients who had bowel-related abscesses underwent MR examination at 1.5T. MR sequences included T₁-weighted fat-suppressed imaging pre- and post-intravenous gadolinium chelate administration (all patients) and breathing-independent single-shot T₂-weighted half Fourier turbo (fast) spin echo (6 patients). Patients with pelvic abscesses also underwent sagittal imaging with post-gadolinium T₁-weighted images (9 patients) and T₂-weighted turbo (fast) spin echo (8 patients). Abscesses were confirmed by open surgery or surgical drainage (6 patients), percutaneous drainage (8 patients), or combined physical examination, fluoroscopic fistulogram, and clinical follow-up (2 patients). Oval-shaped fluid collections were identified in all of the patients, which ranged in diameter from 2 cm to 18 cm, mean: 8 cm. Abscesses were low to intermediate in signal on T₁-weighted images, heterogenous and moderately high signal on T₂-weighted images, and low signal on post-gadolinium images. A layering effect of lower signal material in the dependent portion of the abscess was noted in abscesses in 6 of 14 patients on T₂-weighted images. Post-gadolinium images demonstrated a definable 3- to 7-mm thick abscess wall, which enhanced substantially with contrast. Definition of the wall was best shown on fat-suppressed images post-gadolinium. Substantial enhancement of surrounding periabscess tissues was demonstrated in all cases and was most clearly defined on fat-suppressed images. Image acquisition in two orthogonal planes was of value to demonstrate that fluid collections were oval, and separate from bowel. Image acquisition in the sagittal plane was useful in the evaluation of pelvic abscesses. The results from this preliminary study show that bowel-related abscesses are demonstrable on MR images using gadolinium-enhanced fat-suppressed T₁-weighted and turbo (fast) spin-echo T₂-weighted sequences. The presence of a thickened, enhancing lesion wall and enhancement of perilesional tissues on T₁-weighted fat-suppressed images were observed in all abscesses. A layering effect of low signal intensity material in the dependent portion of the abscess was an important ancillary feature.     

Exophytic benign tumors of the liver: appearance on MRI.

The purpose of our study was to determine the MR imaging appearance of exophytic benign liver tumors on precontrast and postgadolinium images. We reviewed our 9.5 year experience with MRI of the liver with dynamic gadolinium enhanced imaging to identify four patients with five histologically proven exophytic benign liver tumors. The histological diagnoses were cavernous hemangioma (2), focal nodular hyperplasia (FNH) (1), and hepatocellular adenoma (HCA) (2 exophytic adenomas in a patient with adenomatosis of the liver). All MRI studies were performed at 1.5 T and included: in-phase and out-of-phase T1-weighted spoiled gradient echo (SGE), T2-weighted fat-suppressed echo train spin echo, single shot T2-weighted sequences, and serial postgadolinium T1-weighted SGE sequences without and with fat-suppression. Prospective interpretations were reviewed and retrospective consensus readings of all MR images were performed assessing location, size, origin, morphology, visibility of the connection to the liver, signal characteristics on precontrast T1-weighted and T2-weighted images, and enhancement patterns on serial postgadolinium images. Three of the five tumors were pedunculated and connected to the liver by a thin stalk, which was prospectively identified in one patient. On precontrast and serial postgadolinium images, all exophytic tumors showed signal characteristics comparable to imaging features of standard intraparenchymal benign liver tumors. Our findings illustrate that the characteristic T1, T2, and postgadolinium imaging findings of these tumors permit correct identification of their liver origin despite their exophytic location, even if their connection with liver is not visualized.     

Abdominal aortic aneurysm evaluation: comparison of US, CT, MRI, and angiography

We studied 26 cases of abdominal aortic aneurysm with magnetic resonance imaging (MRI), computed tomography (CT), ultrasonography (US), and angiography. Data acquired were compared to those obtained at surgery. Diameter of the aneurysm was correctly defined in all cases by CT and MRI, while angiography underestimated the diameter of lesions without peripheral calcifications. Involvement of renal arteries was present in four cases and correctly diagnosed with MRI and angiography in all of them. CT did provide this information in three cases and US were not useful. Also, iliac arteries involvement was depicted by CT, MRI, and angiography in 10 out of 10 patients. Coronal sections of MRI provided comparable images to those of angiography. By comparing these different techniques we verified the good reliability of MRI as investigation tool for an accurate evaluation of aneurysms; its only limit lying in the poor capability of detecting calcifications.     

Acoustic properties of aortic aneurysm obtained with scanning acoustic microscopy

In aortic aneurysm tissues, macrophages and their secretion of matrix metalloproteinases (MMPs) are playing important role for tissue degeneration. Some studies have shown that weakening of the mechanical properties of the degenerated tissues may progress the expansion of the aneurysm. However, actual measurement of the mechanical properties has not been investigated at microscopic level. The objective of the present study is to assess the mechanical properties of aortic aneurysm tissues by measuring acoustic properties by scanning acoustic microscopy (SAM). Twenty-one cases of aortic aneurysm including renal and common iliac aneurysm tissues were surgically excised. Each tissue was fixed by 4% formaldehyde and the specimens were treated as (1) picrosirius red staining for normal and polarized light microscopy, (2) CD68 staining for macrophage detection, and (3) no staining for acoustic microscopy. A specially developed SAM system operating in the frequency range of 100-200 MHz, was employed in the measurement. Images of amplitude and phase are obtained in a field of 2x2 mm. The intima was mainly consisted of degenerated collagen without polarization of picrosirius red staining. Macrophages stained by CD68 were observed near the degenerated collagen fibers. The sound speed was 1567 m/s in the intima, 1576 m/s in the media, 1640 m/s in the adventitia, respectively. Infiltration of macrophages showed higher values of attenuation and sound speed than the surrounding tissues. The sound speed of the intima was significantly lower than our previous measurement of atherosclerotic aorta without aneurismal change. As the tissue elasticity is closely correlated with the sound speed, the elasticity of the intima was considered to be lower in aneurysm tissues. This mechanical weakness may contribute to the expansion of the diameter of the aneurysm. Acoustic microscopy provided important data for assessing tissue mechanical properties of abdominal aneurysm.     

Detection and grading for esophageal varices in patients with chronic liver damage: comparison of gadolinium-enhanced and unenhanced steady-state coherent MR images

The purpose of this study was to compare observer interpreted steady-state coherent coronal images and gadolinium-enhanced axial images in terms of the detection and grading of esophageal varices. Magnetic resonance imaging (MRI) and gastrointestinal endoscopy were performed within 2 weeks in 90 patients with chronic liver damage, including 55 with untreated esophageal varices, for periodic screening purposes. Two blinded readers retrospectively reviewed T1- and T2-weighted images with gadolinium-enhanced (gadolinium image set) and steady-state coherent (coherent image set) images. Sensitivity for the detection of esophageal varices was higher (P<.001) in the gadolinium image set (76%) than in the coherent image set (35%); on the other hand, specificity was higher (P<.001) in the coherent image set (91%) than in the gadolinium image set (66%). Furthermore, area under the ROC curve was higher for the gadolinium image set (Az=0.823) than the coherent image set (Az=0.761) (P=.48). Moderate and weak positive correlations with endoscopic grades were found for the gadolinium image (r=0.48, P<.01) and coherent image sets (r=0.34, P=.018). The addition of steady-state coherent imaging to the current routine liver imaging protocol did not improve the detection or grading of esophageal varices, whereas gadolinium-enhanced imaging was found to be potentially valuable. Nevertheless, endoscopy was confirmed to be mandatory in patients with esophageal varices suspected by MRI of the liver.     

Single breath-hold multi-slab and cine cardiac-synchronized gadolinium-enhanced three-dimensional angiography

The rest period of the coronary arteries has been shown to be on the order of 120–160 msec. Restriction of the acquisition window in breath-hold cardiac-synchronized gadolinium-enhanced imaging to this duration limits the amount of sampled k-space data and hence the information when compared with conventional gadolinium-enhanced imaging. Two techniques for gadolinium-enhanced cardiac-synchronized angiography were implemented that acquire additional data during the unused portions of the cardiac cycle. Data acquisition is synchronized with the heart cycle and is restricted to a short period of each heart cycle. In a single breath-hold, a multi-slab acquisition (n = 5) allowed ECG-synchronized imaging of the entire heart or a CINE acquisition (n = 5) provided multiple stacks of images at different phases in the cardiac cycle over a smaller area. Preliminary results acquired in healthy volunteers and patients with aortic disease indicate that additional information can be acquired without an increase in breath-hold duration or a reduction in image quality.     

MRI of acute cholecystitis: Comparison with the normal gallbladder and other entities

Our purpose was to prospectively compare MRI findings with histopathologic findings in the evaluation of suspected acute cholecystitis. Fourteen patients with clinically suspected acute cholecystitis were entered into the study. MR sequences included T₁-weighted fat-suppression and breath-hold spoiled gradient echo (SGE) before and after intravenous gadolinium chelate administration. Percent contrast enhancement (%CE) of the gallbladder wall and gallbladder wall thickness (WT) were measured and liver enhancement patterns determined prospectively on MR images. Correlation was obtained with pathological findings at cholecytectomy in all patients. In a second phase of the study MR images on 10 additional subjects who underwent MR examination for reasons other than hepatobiliary disease were analyzed to determine normal values for %CE and gallbladder wall thickness. Mean %CE was 124.0% in patients with acute cholecystitis (10 patients), 58.0% in patients with chronic cholecystitis (2 patients), and 73.0% in patients with gallbladder malignancy (2 patients). Mean gallbladder WT was 6.1 mm in acute cholecystitis, 4.5 mm in chronic cholecystitis, and 6.0 mm in malignant disease. There was a significant difference in %CE between acute and chronic cholecystitis (p = 0.03); no other significant differences in %CE or WT were observed among the patients with gallbladder disease. Patients without biliary disease had %CE of 37.3% and WT of 2.9 mm, which were both significantly less (p < 0.001) than in patients with acute cholecystitis. Transient enhancement of pericholecystic hepatic parenchyma on immediate postgadolinium SGE images was seen in 7 of 10 patients with acute cholecystitis, and not observed in other patients. Patients with acute cholecystitis had increased %CE and WT on MR images that were significantly greater than normal and %CE that was significantly greater than in patients with chronic cholecystitis. Transient increased pericholecystic hepatic enhancement was observed in 70% of acute cholecystitis patients and in no other patient groups.     

Usefulness of MRI for the pre-operative evaluation of the pulmonary arteries in Tetralogy of Fallot

Adequate pre-operative evaluation of patients with Tetralogy of Fallot (TF) includes cine-angiography to delineate the pulmonary vasculature and the coronary artery anatomy and to demonstrate the presence of multiple ventricular septal defects (VSDs). All other information is obtained from color-Doppler-echocardiography. Magnetic resonance imaging (MRI), using the spin-echo sequence and cine-angiography was employed on 18 patients with TF, four of whom had aorto-pulmonary shunts. Mean age at MRI was 12.9 m (SD 2.3 m) and 14.3 m (SD 2.8 m) at cine-angiography. To compare MRI and cine-angiography we measured the ascending aorta, the main, the left and right pulmonary arteries and each structure at three levels. Diagnostic agreement between the two imaging methods was found if, for each modality, one of the three measurements in one structure differed by more than 40% from the other two measured in case of a local stenosis, and the diameter of the main pulmonary artery was less than 60% of the aorta to diagnose hypoplasia of the main pulmonary artery. There was close agreement between cine-angiography and MRI. With regard to the intracardiac anatomy, MRI was superior to color-Doppler-echocardiography in the depiction of aortic override and of right ventricular hypertrophy. In three cases local stenoses in the pulmonary arteries were detected by MRI and cine-angiography. Hypoplasia of the main pulmonary artery was detected by MRI in six patients and by cine-angiography in five patients. Cine-angiography missed one case of hypoplasia. In the remaining 11 patients normal findings were found by MRI and cine-angiography. For the demonstration of shunts, gradient-recalled-echo MRI is expected to give better results than the spin-echo sequence which depicted two out of four shunts in this series. Cine-angiography can be substituted by MRI in delineating the pulmonary arteries. New developments in MRI indicate the feasibility of delineating the coronary arteries.     

Evaluation of intracranial stenoses and aneurysms with accelerated 4D flow

The aim of this study was to evaluate intracranial arterial stenoses and aneurysms with accelerated time-resolved three-dimensional (3D) phase-contrast MRI or 4D flow. The 4D flow technique was utilized to image four normal volunteers, two patients with intracranial stenoses and two patients with intracranial aneurysms. In order to reduce scan time, parallel imaging was combined with an acquisition strategy that eliminates the corners of k-space. In the two patients with intracranial stenoses, 4D flow velocity measurements showed that one patient had normal velocity profiles in agreement with a previous magnetic resonance angiogram (MRA), while the second showed increased velocities that indicated a less significant narrowing than suspected on a previous MRA, as confirmed by catheter angiography. This result may have prevented an invasive angiogram. In the two patients with 4-mm intracranial aneurysm, one had a stable helical flow pattern with a large jet, while the other had a temporally unstable flow pattern with a more focal jet possibly indicating that the second aneurysm may have a higher likelihood of rupture. Accelerated 4D flow provides time-resolved 3D velocity data in an 8- to 10-min scan. In the stenosis patients, the addition of 4D flow to a traditional MRA adds the velocity data provided from transcranial Doppler ultrasound (TCD) possibly allowing for more accurate grading of stenoses. In the aneurysm patients, visualization of flow patterns may help to provide prognostic information about future risk of rupture.     

Electrocardiograph-triggered two-dimensional time-of-flight versus optimized contrast-enhanced three-dimensional MR angiography of the peripheral arteries

We determined whether the accuracy of magnetic resonance angiography (MRA) in the peripheral run-off vessels can be improved by using contrast-enhanced (CE) three-dimensional (3D) technique in comparison to electrocardiograph (ECG)-triggered two-dimensional (2D) time-of-flight (TOF) technique. In a prospective study 20 patients with occlusions of the pelvic and/or femoral arteries underwent a CE 3D MRA (repetition time (TR): 5 ms, (TE) echo time: 2 ms, flip angle (FA): 30°) and an ECG-triggered 2D time-of-flight (TOF) technique (TR: 408 resp. 608 ms, TE: 7 ms, FA: 70°) of the run-off vessels on a 1.5 T MR system. Each patient received a contrast material volume of 0.15 mmol/kg of body weight of gadolinium (Gd)/DTPA using an automatic injector. The tube system to the patient was flushed by 50 mL of a saline solution applied with the same injection rate as the contrast material administration. The start of the 3D MR sequence was tailored individually to the applied contrast material after determination of circulation times by a prior bolus. All patients underwent each conventional or digital arteriography for comparison, as well. The visualization of the run-off vessels was ranked on a scale of 0–3 (0 = poor, 1 = fair, 2 = good, 3 = excellent) by three blinded reviewers. They also graded the vascular segments as either occluded or significantly altered (>50% reduction in diameter) or free of significant stenosis. CE 3D MRA was significantly faster in imaging the run-off vessels in comparison to the ECG-triggered 2D TOF technique. All 160 vascular segments were visualized with the 3D method, whereas only 142/160 segments were seen with 2D technique. The resulting image quality ranking of all vascular segments was significantly higher (p < 0.05) using CE 3D MRA (2.8) than with the 2D TOF technique (2.4). The detection of the stenoses was possible with both techniques. The grading of seven of seven stenoses was correct with 3D method and in five of seven cases with the 2D TOF technique. All vessel occlusions were detected by using both techniques. Small collaterals were visualized in more detail with the CE 3D MR angiography. These data demonstrate an improvement in image quality and accuracy of MRA of the peripheral arteries using a CE 3D technique in comparison to an ECG-triggered 2D TOF sequence.     

Objective Stenosis Quantification From Post-Stenotic Signal Loss in Phase-Contrast Magnetic Resonance Angiographic Datasets of Flow Phantoms and Renal Arteries

In this study a semi-automated and observer-independent algorithm for quantifying post-stenotic signal loss (PSL) in three-dimensional phase-contrast (PC) magnetic resonance angiography (MRA) of patients with renal artery stenosis is presented. This algorithm was developed on MRA datasets of stenotic phantoms, included in a flow circuit with stationary flows. The length and the severity of the PSL (incorporating both the length and the degree of PSL) in the MRA datasets were proposed for quantifying the stenoses. The algorithm was tested in renal arteries; ten patients with renal artery stenosis and seven healthy volunteers were investigated. Digital subtraction angiography was performed in the patients and served as the gold standard. Stenosis severity showed better correlation with the severity of the PSL than with the length, both for in vitro and in vivo measurements. Spearman correlation coefficients (r_s) showed statistically significant correlations between the severity of the PSL and parameters determined by digital subtraction angiography, i.e., percent diameter stenosis (r_s = 0.90). The length of the PSL showed no correlation with the diameter stenosis (r_s = 0.37). In conclusion, this study presents a semi-automated and observer-independent way of quantifying signal loss, and the severity of the PSL is proposed for quantifying stenoses, rather than the length of PSL.     

Long-term follow-up of 82 patients with chronic disease of the thoracic aorta using spin-echo and cine gradient magnetic resonance imaging

The objective of this study to examine the clinical impact of magnetic resonance imaging in long-term follow-up of patients (pts) with chronic disease of the thoracic aorta such as coarctation of the aorta, chronic aortic dissection and true aortic aneurysm. A total of 322 magnetic resonance examinations obtained in 82 pts with chronic disease of the thoracic aorta (31 pts with coarctation of the aorta (CoA), 29 pts with chronic aortic dissection and 22 pts with true aneurysm) over a period of 0.25 to 13.5 (mean +/- SD: 6.5 +/- 3.4) years were retrospectively reviewed. Diameters of the thoracic aorta were measured at predefined levels and morphological and functional parameters of special interest were analysed in each patient group. Pts were classified as having constant or progressive disease and clinical end-points were defined as (re-)operation or death. 43 pts (52%) (CoA 15 pts, chronic dissection 16 pts, true aneurysm 12 pts) had constant findings. None of them underwent (re-)operation and seven patients (16%) died, three of them from their aortic disease more than five years later after their last magnetic resonance examination, one from an arrhythmogenic event, and in the remaining 3 pts the cause of death could not be definitely established. 39 pts (48%) (CoA 16 pts, chronic dissection 13 pts, true aneurysm 10 pts) had progressive disease as demonstrated by repetitive magnetic resonance imaging. Of these 39 pts 24 pts underwent (re-)operation, in 15 pts operation was postponed. Four pts died from their aortic disease. Repetitive magnetic resonance imaging is a clinically feasible technique for long-term follow-up of pts with chronic disease of the thoracic aorta because it can detect progressive disease in a large subset of pts requiring elective surgery. The results of magnetic resonance imaging provided the rationale for either (re-)operation or conservative management, thus guiding patient management.     

Separation of arteries and veins using flow-induced phase effects in contrast-enhanced MRA of the lower extremities

In 3-D contrast-enhanced magnetic resonance (MR) angiography of the lower extremities the goal is most often to enhance arterial structures while keeping veins and surrounding tissue unenhanced. Imaging during steady-state concentration of a blood pool agent or during poor timing of an extra-cellular contrast medium may result in simultaneous venous enhancement, making interpretation of the angiogram difficult. The aim of this study was to develop a post-processing method to separate the arteries from the veins in standard contrast-enhanced MR angiograms. The method was based on the different accumulation of flow-induced phase in the arteries and veins of the lower extremities. The method was tested in both phantom experiments and volunteers undergoing 3-D contrast-enhanced MR angiography using both an extra-cellular contrast medium and a blood pool agent. In the phantom studies, opposite directional flow was successfully separated at mean flow velocities as low as 9 cm/s. In the volunteer studies, the larger veins were successfully extinguished while the larger arteries were left unaffected. In smaller vessels with low flow velocities the separation was less successful. This was most apparent in vessels not oriented superior-inferior. The method developed here is promising for separating arteries from veins in contrast-enhanced MR angiography although the results could be further improved by either a different pulse sequence design or combining this method with other segmentation methods.     

The use of T2*-weighted multi-echo GRE imaging as a novel method to diagnose hepatocellular carcinoma compared with gadolinium-enhanced MRI: a feasibility study

Background

The goal of the study was to assess a T2*-weighted MRI sequence for the ability to identify hepatocellular carcinoma (HCC).

Methods

Hepatic iron deposition, which is common in chronic liver disease (CLD), may increase the conspicuity of HCC on GRE imaging due to increased T2* signal decay in liver parenchyma. In this study, a breath-hold T2*-weighted MRI sequence was evaluated by a blinded observer for HCC and the results compared to a reference standard of gadolinium-enhanced MRI in these same patients. Forty-one patients (mean age 56.2 years; 17 females) were included in this approved, retrospective study.

Results

By the reference standard, 14 of 41 patients had a total of 25 HCCs. The sensitivity of the T2*-weighted MR sequence for identifying HCC, per lesion, was 60%, while the specificity was 100%. There was a significantly lower T2* value of liver parenchyma in patients with HCC identified by the T2*-weighted sequence than in those with HCCs which were not identified by the T2*-weighted sequence (27.8±2.2 vs. 21.9±2.1 ms; P=.02).

Conclusions

A T2*-weighted MRI sequence can identify HCC in patients with CLD. This technique may be beneficial for imaging of patients contraindicated for gadolinium.