3D Fast Low-angle Shot Research Articles

MR-Koronarangiographie mit MS-325, einem Blood-Pool-Kontrastmittel: Vergleich einer Inversion Recovery Steady-State Free Precession und einer Inversion Recovery Fast Low Angle Shot Sequenz in Probanden

To compare the signal-to-noise and contrast-to-noise ratio as well as the image quality of 3D inversion recovery steady-state free precession (IR-SSFP) and 3D inversion recovery fast low angle shot (IR-FLASH) sequences for contrast-enhanced breath-hold MRCA. 24 healthy volunteers (10 female, 14 male, mean age 29.8 +/- 6.1 years) were involved in this study. All examinations were performed on a 1.5 T MR scanner (Magnetom Sonata, Siemens, Germany) after injection of 0.05 mmol/kg body weight MS-325 (EPIX Pharmaceuticals, Cambridge, MA and Schering AG, Berlin, Germany). MRCA was performed using IR-SSFP (TR 3.8 ms, TE 1.6 ms, FA 65 degrees , 35 phase encoded steps, bandwidth 540 Hz/pixel, slice thickness 1.5 mm, in-plane resolution 1.2 x 0.9 - 1.4 x 1.0 mm) and IR-FLASH (TR 3.8 ms, TE 1.6 ms, FA 25 degrees , bandwidth 490 Hz/pixel, slice thickness 1.5 mm, in-plane resolution 1.2 x 0.9 - 1.4 x 1.0 mm) sequences. For all scans the inversion time was set to null the signal intensity of the myocardium. Signal-to-noise ratio (SNR) as well as contrast-to-noise ratio (CNR) measurements (blood versus myocardium) were performed. The image quality was assessed based on a 5-point scale ranging from 1 (excellent) to 5 (non-diagnostic) by two radiologists in consensus. The mean signal-to-noise ratio of blood (27.7 +/- 4.7 vs. 22.6 +/- 4.9, P < 0.0001) and the contrast-to-noise ratio (21.0 +/- 4.3 vs. 15.8 +/- 4.3, P < 0.0001) showed significantly higher values for IR-SSFP sequences. The mean image quality scores were significantly higher for SSFP (3.6 +/- 0.7) than FLASH (2.8 +/- 0.9) sequences (P < 0.05). IR-SSFP sequences show a considerable overall improvement in image quality compared to IR-FLASH sequences for MRCA after injection of a gadolinium-based blood pool contrast agent.

In Vitro Evaluation of Current Thoracic Aortic Stent-Grafts for Real-time MR-Guided Placement

To systematically evaluate the magnetic resonance imaging (MRI) characteristics of current thoracic aortic stent-graft devices before, during, and after in vitro deployment as a step toward real-time MRI-guided stent placement. Six stent-graft devices used for thoracic aortic repair were examined in a dedicated phantom model using a 1.5-T MRI scanner. First, the delivery systems with the mounted stent-graft were examined using real-time fast imaging with steady-state precession (TrueFISP) with Cartesian and radial k-space filling. TrueFISP imaging was subsequently used for real-time monitoring of stent-graft expansion. The deployed stent-grafts were then examined in a water bath containing gadolinium (1:40) with high-resolution T1-weighted 3D fast low-angle shot (FLASH) sequences. The images were analyzed for artifacts, radiofrequency caging effects, and device visualization quality. Three delivery systems with mounted stent-grafts did not contain ferromagnetic elements and were well visualized. Imaging with radial k-space filling showed fewer artifacts than Cartesian imaging. Movement of the delivery system and stent-graft expansion of these devices were successfully demonstrated at a rate of up to 6 frames per second. Evaluation of the expanded stent-grafts revealed only minor susceptibility artifacts without relevant signal attenuation in the stent-graft lumen for 5 nitinol-based stent-grafts. Only a stainless steel-based stent-graft was associated with severe artifacts, thwarting visualization of its lumen or surroundings. The present study shows that 3 nitinol-based thoracic stent-graft devices are potentially suited for real-time MRI-guided placement with respect to both the delivery system and the stent-graft itself. These observations provide the basis for the evaluation of MRI-guided stent-graft placement in vivo.

Thrombus Detection in the Left Atrial Appendage Using Contrast-Enhanced MRI: A Pilot Study

Left atrial thrombi are an important cause for embolism-related morbidity and mortality. Transesophageal echocardiography (TEE), the clinical reference, is semiinvasive; thus, we aimed to assess the value of contrast-enhanced cardiovascular MRI for the detection of thrombus in the left atrial appendage. The image quality was good for both 2D perfusion (grade 4 +/- 1) and 3D turbo fast low-angle shot (FLASH) (grade 4 +/- 1, n.s.). Compared with TEE, 2D perfusion, 3D turboFLASH, and the combination of both techniques yielded sensitivities of 47/35/44%, specificities of 50/67/67%, positive predictive values of 73/75/80%, and negative predictive values of 25/27/29%, respectively. The size of the thrombus was overestimated by 2D perfusion (66%) and by 3D turboFLASH (25%) and agreement for location and shape of thrombus was 50% and 75% for 2D perfusion and 75% and 50% for 3D turboFLASH, respectively. The TEE thrombus size was significantly larger in patients with true-positive diagnoses by 2D perfusion (148%) and by 3D turboFLASH (151%) when compared with patients with false-negative diagnoses (p < 0.05 for both). No such difference was found for image quality, time delay between TEE and MRI examination, and location and shape of thrombi. Contrast-enhanced MRI lacks diagnostic accuracy for the detection of thrombi in the left atrial appendage. Future technical improvements are essential to establish this technique as a noninvasive alternative to TEE.

Three-dimensional magnetic resonance imaging after ultrasonography for assessment of fetal gastroschisis

A 24-year-old woman (Gravida I, Para I) at estimated 32 weeks of pregnancy was referred to our department for evaluation of a suspected fetal gastroschisis. Ultrasound scan revealed multiple loops of dilated bowel outside the fetal abdomen and absence of membrane surrounding the herniated loops of the intestines. Three-dimensional (3D) magnetic resonance imaging was performed to obtain more information on the bowel both outside and inside the abdomen. Images were constructed with T1-weighted fat-suppressed 3D fast low-angle shot sequences using a maximum intensity projection algorithm. The 3D images made possible the realization of fetal bowel conditions with greater definition and accuracy.

Magnetic resonance urography for the assessment of potential renal donors: comparison of the RARE technique with a low-dose gadolinium-enhanced magnetic resonance urography technique in the absence of pharmacological and mechanical intervention

The aim of this study was to determine whether magnetic resonance urography without pharmacological (diuretic) stimulation and mechanical compression allows conclusive evaluation of the urinary system in potential renal donors. In 28 consecutive patients magnetic resonance urography (MRU) was performed on a 1.5-T system. Two techniques, rapid acquisition with relaxation enhancement (RARE) and a gadolinium (Gd)-enhanced 3D fast low angle shot (FLASH) sequence were compared in the absence of adjunctive measures. Two reviewers assessed image quality, presence of artifacts and completeness of visualization of the collecting systems and ureters. Among the 53 MR urograms, there was no difference in image quality and presence of artifacts between RARE and Gd-MRU. Despite high image quality, visualization of the urinary collecting system was insufficient. Continuous visualization from the collecting system to the distal ureter was demonstrated bilaterally in only 14% of the RARE and 26% of Gd-enhanced MR urograms, respectively. Overall, Gd-enhanced MRU was superior to the RARE technique in displaying the segments of the urinary collecting system, but this difference was not found to be statistically significant. Neither the RARE technique nor the gadolinium-enhanced MRU technique is accurate enough to allow the evaluation of the collecting system and ureters in potential renal donors in the absence of pharmacological intervention and compression.

Autologous Chondrocyte Implantation in Knee Joint: MR Imaging and Histologic Features at 1-year Follow-up

To evaluate magnetic resonance (MR) imaging features of autologous chondrocyte implantation (ACI) grafts and compare these with graft histologic features 1 year after ACI for treatment of femoral condylar defects. This study was approved by the regional ethics committee, and all patients gave informed consent. Forty-one patients (mean age, 35 years; 30 men, 11 women) underwent ACI for treatment of femoral condylar defects. One year later, knee joint MR imaging and graft biopsy were performed. Graft biopsy results were categorized into those showing hyaline, mixed fibrohyaline cartilage, fibrocartilage, and fibrous tissue. Standard T1-, T2-, T2*-, and intermediate-weighted sequences were performed, as well as three-dimensional (3D) fast low-angle shot (FLASH) and double-echo steady-state sequences for cartilage assessment. ACI grafts were assessed for signal intensity (with FLASH sequence), thickness, overgrowth, surface smoothness, integration to adjacent cartilage and underlying bone, bone marrow edema underneath graft, and contour of bone underneath graft. MR images were assessed by two observers, first independently and then in consensus. MR imaging findings were correlated with histologic findings. All 41 grafts were present at 1-year follow-up. The graft consisted of hyaline cartilage in four, mixed fibrohyaline cartilage in 10, fibrocartilage in 25, and fibrous tissue in two cases. Graft signal intensity was virtually always lower than adjacent normal cartilage signal intensity, and there was no relationship between graft signal intensity and histologic appearance (P = .34). Graft thickness (P = .83), overgrowth (P = .69), surface smoothness (P = .28), and integration with adjacent cartilage and underlying bone (P = .90); edema in bone marrow underneath graft (P = .63); and bone contour underneath graft (P = .94) at MR imaging had no correlation with graft histologic appearance. Graft overgrowth (n = 16; 39%) and edema-like signal in bone marrow underneath graft (n = 23; 56%) were common. The origin of graft overgrowth remains unclear. With the methods presented here, MR imaging findings cannot predict ACI graft histologic features, and graft histologic appearance determined at biopsy was not related to graft signal intensity, graft thickness, overgrowth, surface smoothness, integration with adjacent cartilage or underlying bone, signal intensity change in underlying bone marrow, or underlying bone contour. Overgrowth and bone marrow changes underneath the graft were common.

Single-acquisition sequence for the measurement of oxygen partial pressure by hyperpolarized gas MRI.

Magnetic resonance imaging (MRI) with hyperpolarized 3-helium gas (HP 3He) offers the possibility of studying functional lung parameters such as the alveolar oxygen concentration and oxygen depletion rate. Until now, a double-acquisition technique has been utilized to extract these parameters. A complicated single-acquisition technique was previously developed to avoid the necessity of performing two identical breathing maneuvers. The results obtained with this technique were significantly less accurate than the results obtained with the double-acquisition method. In this work, a novel, easily implemented single-acquisition sequence is presented that provides results comparable to those obtained with the established double-acquisition method. This method is demonstrated in a phantom and a pig model on a 1.5 T scanner using a 2D fast low-angle shot (FLASH) gradient-echo sequence. Numerical simulations of the time evolution of the oxygen concentration were performed. Simulation results are presented to support the experimental data. Various parameter regimes were experimentally and numerically investigated.

In vitro rat colonic wall imaging with MR endoluminal coil: Feasibility study and histologic correlations 1

Rationale and objectives Despite improvements, spatial resolution and image quality with routine surface coils are too limited when detailed information about the gastrointestinal layers is requested. The objective of our feasibility study was to evaluate the potential of a dedicated endoluminal coil to depict different layers of the colonic wall in an in vitro small animal model. Materials and methods A single-loop coil (40 mm length, 5 mm width) was built using IC (printed circuit) technology. The coil was tuned to a frequency of 63.7 MHz and matched at 50 Ω for this frequency. The coil was housed in a biocompatible tube with an outer diameter of 18 F (6 mm). Ten segments of rat colon, surgically excised 5 hours earlier, were completely immersed in an isotonic solution. The coil was introduced through the lumen of colonic specimens. MRI experiments were performed on a 1.5 T MR Symphony system (Siemens, Erlangen, Germany) using imaging protocol combining high-resolution 2D Flash, fast imaging employing steady-state acquisition (TrueFISP), turbo spin echo (TSE), and 3D FastLow-Angle Shot (FLASH) sequences. After a 24-hour period of fixation in 10% formalin, colonic specimens were excised along the longitudinal axis for histologic analysis. Results The endoluminal coil provided high SNR allowing for the visualization of different layers of rat colonic walls. All the performed sequences made it possible to identify at least two different layers. On T1-weighted gradient-echo sequences, the mucosa was of high signal intensity, whereas the muscle layers had an intermediate to low signal intensity. The signal intensity of different wall layers was similar in different sequences. Histologic analysis identified three main layers. Conclusion These results are well correlated with histologic findings and suggest that endoluminal MR imaging may have potential for accurate staging of colonic tumor or inflammatory process.

Dynamic magnetic resonance imaging in determining histopathological prognostic factors of invasive breast cancers

Objective: To evaluate the relation between morphological features and enhancement parameters in dynamic contrast-enhanced magnetic resonance (DCE-MR) imaging with histopathological prognostic factors. Materials and methods: Fifty-five patients with surgicopathological diagnosis of breast carcinoma were evaluated with 1.0 T MR scanner as a part of their preoperative diagnostic work-up. Dynamic studies were performed in axial plane using 3D fast low angle shot (FLASH) sequence. Time intensity curves (TICs) were obtained from the regions showing maximal enhancement in subtraction images. The correlations between enhancement parameters and histopathological findings were analyzed using stepwise multiple regression analysis, Student’s t-test, χ 2-tests and Pearson’s moment correlation coefficient. Results: Significant correlations were found between the presence of lymph node metastasis and tumor size ( P<0.05) and edge characteristics ( P<0.05). A highly significant correlation was found between histopathological grades and qualitative enhancement patterns ( r=0.403, P<0.01). Statistically significant differences were found between the groups with and without lymph node metastasis regarding enhancement in the first minute ( P<0.01) and TIC slope ( P<0.05). A significant difference was found between the histopathological grades I and III regarding all quantitative enhancement parameters, whereas no difference was found between the grades I–II, and II–III. Conclusion: DCE-MR imaging helps to predict prognostic factors of breast cancer by revealing morphological features and enhancement parameters of the primary tumor. Additional morphological factors further improve our ability to predict lymphatic metastasis.

Invasive breast cancer: correlation of dynamic MR features with prognostic factors.

The purpose of this exploratory study was to correlate kinetic and morphologic MR features with histologic prognostic factors in invasive breast cancer. Sixty-one women with invasive breast cancer underwent dynamic contrast-enhanced MR imaging at 1.5 T, using T1-weighted 3D fast low-angle shot technique. The MR characteristics were correlated with classical pathologic prognostic factors (tumor size, histologic type, grade and lymph node status) and immunohistochemically detected biomarkers [c-erbB-2, p53, Ki-67, and estrogen receptor (ER)]. Univariate and multivariate statistical analyses were performed. Presence of rim enhancement pattern, early maximal enhancement and washout phenomenon were independently associated with established predictors of poor prognosis (higher histologic grade, positive Ki-67, and negative ER status). Our results suggest that these MR signs are not only important in differentiating benign from malignant lesions, but may also be useful to noninvasively identify highly aggressive breast carcinomas.

Comparison of whole-body MRI with automatic moving table technique and bone scintigraphy for screening for bone metastases in patients with breast cancer

The aim of this study was presentation of a whole-body MRI technique with a moving table as a screening tool for bone metastases in patients with breast cancer. Twenty-two patients with breast carcinoma underwent both a planar whole-body bone scintigraphy and whole-body MRI at 1.5 T. The MRI images were acquired with a moving table at six different anatomical positions within a measurement time of 20 min. Coronal images were acquired using a short-tau inversion recovery sequence, accomplished by an axial T2-weighted turbo-spin-echo sequence through the head, and a T1-weighted opposed-phase sagittal 2D fast low-angle shot sequence covering the whole spine. The MRI findings indicating bone metastases were compared with findings from bone scintigraphy. Metastatic lesions were confirmed by follow-up examinations over 1 year. Twelve patients showed bone metastases. Whole-body MRI was superior to bone scintigraphy in predicting lesion origin with a sensitivity of 92% (bone scintigraphy 83%), a specificity of 90% (scintigraphy 80%) and an accuracy of 91% (scintigraphy 82%). The MRI showed additional findings such as metastases of the lung and liver. Whole-body MRI with moving table technique may be an effective method of total body screening for bone in selected patients with breast carcinoma and a high risk of distant metastases, although with the higher costs of MRI bone scintigraphy must still be considered as the first method for screening patients with breast cancer.

A vascular stent as an active component for locally enhanced magnetic resonance imaging: initial in vivo imaging results after catheter-guided placement in rabbits.

A vascular stent constructed as a high frequency resonator improves the local signal-to-noise ratio at magnetic resonance (MR) imaging. After catheter placement and intravascular expansion, the stent can be used as an inductively coupled coil for MRI. The imaging properties of this balloon-expandable active MRI stent (AMRIS) were evaluated after x-ray fluoroscopy guided placement in the abdominal aorta of five rabbits using MR angiography (MRA) and flow measurements. The AMRIS was implanted in the abdominal aorta of five rabbits using a balloon catheter inserted through the common carotid artery. The rabbits were examined by MRA (3D fast low-angle shot) at 1.5 tesla before and after intravenous injection of an iron-oxide-based blood pool contrast medium (dose 50 micro mol Fe/kg) and flow measurements (ECG-triggered phase contrast cine gradient-echo sequence). Signal-to-noise ratios (SNR) were calculated and flow volume curves were generated. The in-stent increase in temperature was measured in vitro using a fiberoptic thermometry system. The SNR was 5.0 +/- 0.6 outside the stent and 23.2 +/- 14.1 within the stent ( < 0.0 5) in plain MRA, 19.5 +/- 5.0 outside and 30.7 +/- 8.2 within the stent ( < 0.05) in contrast enhanced MRA, and 5.8 +/- 1.6 and 13.9 +/- 5.9, respectively ( < 0.05) in the magnitude images of the flow measurements. Flow volume curves within and distal to the stent were comparable. The expandable active MRI stent produces local signal enhancement in MRA and MR flow measurements after catheter placement and thus may improve assessment of the stented vessel segment by MR imaging.

Selective water excitation for faster MR imaging of articular cartilage defects: initial clinical results.

Our objective was to compare a water-excitation (WE) 3D fast low-angle shot (FLASH) MR sequence for faster imaging of articular cartilage defects of the knee to a conventional fat-saturated (FS) 3D FLASH MR sequence. This prospective study included 16 knees of 16 patients with suspected cartilage lesions. The MR imaging in transverse and sagittal planes included (a) FS 3D FLASH (TR/TE: 45 ms/11 ms, scan time 8 min, flip angle 50 degrees), and (b) WE 3D FLASH (TR/TE: 28 ms/11 ms, scan time 4 min 58 s, flip angle 40 degrees). For each sequence signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were quantified. The detected cartilage lesions were evaluated using a semi-quantitative four-scale scoring system (grades 0-III). The data were compared between the sequences using the paired Student's t-test. No statistically significant differences between the sequences were found for SNR, CNR, and cartilage defect grading (p=0.14-0.8). The WE 3D FLASH MR imaging seems to be promising for fast imaging of articular cartilage lesions of the knee.

MR enteroclysis: technical considerations and clinical applications

Magnetic resonance enteroclysis (MRE) is an emerging technique for the evaluation of small bowel abnormalities. Adequate luminal distention, achieved by the administration of iso-osmotic water solution through a nasojejunal catheter, in combination with ultrafast sequences, such as single-shot turbo spin echo, true fast imaging with steady precession, half-Fourier acquired single-shot turbo spin echo, and 3D fast low-angle shot, results in excellent anatomic demonstration of the small bowel. Magnetic resonance fluoroscopy can be performed during MRE examination and might be useful in studying low-grade stenosis or motility-related disorders. Magnetic resonance enteroclysis is very promising in detecting the number and extent of involved small bowel segments in patients with Crohn's disease, and in disclosing lumen narrowing and extramural manifestations and complications of the disease. Initial experience shows that MRE is very efficient in the diagnosis of small bowel tumors and can be used in the evaluation of small bowel obstruction.

Respiration‐induced B0 fluctuations and their spatial distribution in the human brain at 7 Tesla

In functional magnetic resonance imaging (fMRI), it is known that physiological influences such as cardiac pulsation, respiration, and brain motion can induce fluctuations in signal intensity and phase. Some of the mechanisms potentially involved in those phenomena are expected to be amplified at higher magnetic fields. This study addresses the issue of B(0) fluctuations induced by susceptibility changes during respiration attributed to movements of chest and diaphragm, and variations in the oxygen concentration. It is demonstrated that respiration-induced resonance offsets (RIROs) are significant at 7T. Data were acquired with an RF pulse (no gradients), multislice echo-planar imaging (EPI), and dynamic 3D fast low-angle shot (3D- FLASH) imaging. Three main observations summarize the experimental findings. First, in FIDs measured after a single RF pulse, a RIRO with a large amplitude was consistently detected, although the average amplitude varied between subjects from 1.45 Hz to 4 Hz. Second, in transverse EPI images obtained in the occipital lobe, the RIRO amplitude showed a monotonic increase along the z axis toward the lungs. Third, a more detailed spatial analysis with 3D-FLASH phase maps revealed that a previously published analytical model can accurately describe the spatial distribution of RIRO. Consequential apparent motions in the EPI series, as well as the implications of slice orientation for correction strategies are discussed.

Right-lobe living related liver transplantation: evaluation of a comprehensive magnetic resonance imaging protocol for assessing potential donors.

The purpose of this study was to determine the practicability and diagnostic accuracy of a magnetic resonance (MR) protocol capable of replacing computed tomography, catheter angiography, and endoscopic retrograde cholangiopancreatography for the presurgical evaluation of potential liver donors before right hepatectomy. MR imaging (MRI) was performed on a 1.5 T scanner using a phased-array torso surface coil for signal reception. The following image sets were collected: axial two-dimensional (2D) T1-weighted fast low angle shot (FLASH), axial 2D T2-weighted half-Fourier acquisition single-shot turbo-spin-echo (HASTE) with fat saturation, coronal MR cholangio-pancreatography (MRCP) based on 2D multisection HASTE and single-section single-shot rapid acquisition with relaxation enhancement (RARE) imaging, dynamic contrast-enhanced three-dimensional (3D) FLASH, and contrast-enhanced T1-weighted FLASH. 3D FLASH data sets were collected before and after an intravenous administration of Multihance (gadobenate dimeglumine, Gd-BOPTA; Bracco, Milano, Italy), 0.2 mmol/kg of body weight. Thirty-eight potential liver donors were assessed by means of MRI. Twenty patients also underwent digital subtraction angiography (DSA). Of these, 16 patients underwent liver harvesting. MR angiography (MRA) data sets correlated with DSA results, and MRCP results correlated with intraoperative findings. Patients were excluded as potential donors based on insufficient liver mass of the left hepatic lobe (n = 5) or presence of hepatic pathological states (n = 9) seen at MRI, such as hemangiomas, focal nodular hyperplasias, or hepatic steatosis. MRCP showed the biliary system to the level of the first hepatic side branch. Dilated ducts were present in 4 patients. MRA depiction of hepatic arterial morphological characteristics correlated with catheter angiography results in all 20 patients: Three left hepatic arteries originating from the left gastric artery, three aberrant right hepatic arteries originating from the superior mesenteric artery, and two aberrant origins of both hepatic arteries and one common hepatic artery originating from the superior mesenteric artery were correctly identified on MRA. Similarly, the portal venous system was fully assessed on MRA. A comprehensive assessment of the hepatic parenchyma, biliary and pancreatic ductal system, and hepatic arterial, portal, and venous systems can be accomplished using the outlined protocol.

Contrast-Enhanced Three-Dimensional MR Imaging Using a Volumetric Interpolated Breath-hold Examination (VIBE): Clinical Utility in the Evaluation of Renal Tumors

Purpose: To compare, in terms of technical feasibility, image quality and clinical efficacy, contrast-enhanced three-dimensional (3D) MR imaging using volumetric interpolated breath-hold examination (VIBE) with twodimensional gradient-echo MR imaging for the evaluation of renal masses. Materials and Methods: Twenty-three patients with 25 renal masses underwent dynamic MR imaging using a 1.5-T MR system and the 3D VIBE, 2D fast low angle shot (FLASH), and combined fat saturation techniques after the injection of 20 ml of Gd-DTPA. We compared postcontrast 2D FLASH and 3D VIBE images with precontrast 2D FLASH images. For quantitative analysis, the signal-to-noise and lesion to kidney contrast-to-noise ratio of the images were calculated using the three different techniques. For qualitative analysis, two experienced radiologists analyzed the images in terms of artifacts, lesion conspicuity and delineation, and general image quality. Delineation of the anatomy of renal vasculature and pelvocalyceal systems on reconstructed 3D VIBE MIP images was also assessed. Results: Quantitative analysis showed that the SNR of a renal mass was slightly higher at postcontrast 2D FLASH than at 3D VIBE imaging, and the SNR of renal cortex was higher at 3D VIBE than at postcontrast 2D FLASH imaging. The differences were, though, statistically insignificant (p>0.05). The CNR of a renal mass was, however, significantly higher at 3D VIBE than at 2D FLASH imaging (p

MR enteroclysis protocol optimization: comparison between 3D FLASH with fat saturation after intravenous gadolinium injection and true FISP sequences.

The aim of this study was to introduce the true fast imaging with steady-state precession (FISP) sequence for MR enteroclysis and compare it with the already used T1-weighted fast low-angle shot (FLASH) sequence. Twenty-one patients underwent both MR and conventional enteroclysis. The MR enteroclysis examination was performed after administration of an iso-osmotic water solution through a nasojejunal catheter and the following sequences were included: (a) true FISP; and (b) 3D FLASH with fat saturation after intravenous injection of 20 mg Buscopan or 1 mg glucagon and 0.1 mmol/kg gadolinium chelates. The true FISP sequence provided images with significantly fewer motion artifacts, whereas 3D FLASH was less sensitive to susceptibility and chemical shift artifacts. The homogeneity of endoluminal opacification, wall conspicuity, and distention of the small bowel were very good to excellent and the two sequences presented no statistically significant differences here. True FISP provided significantly better overall image quality than did 3D FLASH. The true FISP sequence can provide good anatomic demonstration of the small bowel on T2-like images and could be combined with T1-weighted FLASH images for an integrated protocol of MR enteroclysis.

Comparison of two-dimensional gradient echo, turbo spin echo and two-dimensional turbo gradient spin echo sequences in MRI of the cervical spinal cord anatomy

The aim of this study was to assess the detectability and distinguishability of the cervical spinal cord, the anterior and posterior spinal roots and of the internal anatomy of the cord (distinction of grey and white matter). For this purpose 20 healthy volunteers were examined using a 1.5 T MR unit with 20 mT/m gradient strength and a dedicated circular polarized neck array coil. Three T2* weighted (w). 2D gradient echo sequences, two T2 w. 2D turbo spin echo (TSE) sequences and one T2 w. 2D turbo gradient spin echo (TGSE) sequence were compared. The multiecho 2D fast low angle shot (FLASH) sequence with magnetization transfer saturation pulse (me FLASH+MTS) yielded the best results for liquor/compact bone, liquor/spinal cord and grey/white matter contrast, as found with regions of interest (ROI) analysis. The single echo 2D FLASH sequence was significantly poorer than the two me FLASH+/−MTS sequences. Two-dimensional TGSE as well as 2D TSE with a 256 matrix and with a 512 matrix yielded the poorest results. In the visual analysis the contrast between liquor and compact bone, liquor and cord as well as liquor and roots was best with me FLASH+MTS, whereas grey/white matter distinction was best using me FLASH−MTS. In conclusion, we would therefore recommend the inclusion of an axial T2* w. multiecho 2D spoiled gradient echo sequence with magnetization transfer saturation pulse and gradient motion rephasing in a MR imaging protocol of the cervical spine.

International investigation of breast MRI: results of a multicentre study (11 sites) concerning diagnostic parameters for contrast-enhanced MRI based on 519 histopathologically correlated lesions.

A multicentre study was undertaken to provide fundamentals for improved standardization and optimized interpretation guidelines of dynamic contrast-enhanced MRI. Only patients scheduled for biopsy of a clinical or imaging abnormality were included. They underwent standardized dynamic MRI on Siemens 1.0 (163 valid lesions > or = 5 mm) or 1.5 T (395 valid lesions > or = 5 mm) using 3D fast low-angle shot (FLASH; 87 s) before and five times after standardized bolus of 0.2 mmol Gd-DTPA/kg. One-Tesla and 1.5 T data were analysed separately using a discriminant analysis. Only histologically correlated lesions entered the statistical evaluation. Histopathology and imaging were correlated in retrospect and in open. The best results were achieved by combining up to five wash-in or wash-out parameters. Different weighting of false-negative vs false-positive calls allowed formulation of a statistically based interpretation scheme yielding optimized rules for the highest possible sensitivity (specificity 30%), for moderate (50%) or high (64-71%) specificity. The sensitivities obtained at the above specificity levels were better at 1.0 T (98, 97, or 96%) than at 1.5 T (96, 93, 86%). Using a widely available standardized MR technique definition of statistically founded interpretation rules is possible. Choice of an optimum interpretation rule may vary with the clinical question. Prospective testing remains necessary. Differences of 1.0 and 1.5 T are not statistically significant but may be due to pulse sequences.