Pulmonary time-of-flight MR angiography at 1.0 T: comparison between 2D and 3D tone acquisitions.

The purpose of this study was to compare the performance of 2D vs. 3D time-of-flight (TOF) methods in imaging the normal pulmonary arteries with commercially available 1.0 T equipment. The study was conducted in 20 volunteers and 7 patients with suspected pulmonary embolism (PE). To reduce artifacts caused by cardiac and respiratory motion, MR images were acquired in volunteers using two-dimensional (2D), gradient-recalled echo (GRE), breath-hold techniques, and three-dimensional (3D) acquisitions. Sagittal thin (6-MM) segmented k-space 2D sections obtained with cardiac gating during systole (turboFLASH, TR/TE9/6 ms, 14 segments of 9 lines) and incremented flip-angles (TONE), and 50-mm 3D volume TONE acquisitions with 32 partitions (FISP, TR/TE34/10ms) were successively performed. In the second phase of the study, patients were examined only with the 3D technique. Images of volunteers were qualitatively and quantitatively analyzed. S/N ratios were statistically compared by means of the paired-sample Wilcoxon ranked-signed test, a value of p < .05 being significant. In volunteers, 3D acquisitions displayed significantly more segment-order pulmonary arteries on average than did 2d acquisitions displayed significantly more segment-order pulmonary arteries on average than did 2D acquisitions (2.95 +/- 0.64 vs. 2.2 +/- 0.85, respectively; p < .01). Moreover, the signal intensity of arteries within the lungs was less homogeneous in the 2D than in the 3D technique, with a signal intensity ratio between peripheral and proximal arteries of 63% +/- 7% and 73% +/- 2%, respectively (p < .05). In patients, no erroneous diagnoses were obtained using the 3D technique. 3D images of normal lungs provide MR angiograms of better quality than do 2D images, and require less contribution from subjects because they are performed in free breathing. Ongoing improvements in MR sequences and further studies are now necessary to assess the value of 3D TONE MRA in the diagnosis of PE.

Pulmonary MR angiography at 1.0 T: early results with k-space segmented and post-contrast TurboFLASH two-dimensional time-of-flight sequences.

PURPOSE: To evaluate the combined performance of two time-of-flight methods in imaging the pulmonary arteries. MATERIALS AND METHODS: This study was prospectively conducted in 28 patients suspected for pulmonary embolism (PE). Sixteen patients were free of pulmonary vascular disease, and 12 had pulmonary vascular disease as demonstrated by pulmonary angiography. To reduce artifacts caused by cardiac and respiratory motion, MR images were acquired in all subjects using bi-dimensional (2D), gradient-recalled echo (GRE), breath-hold techniques. Sagittal thin (6-mm) sections obtained with ECG gating, k-space segmentation and incremented flip-angles (TONE), and coronal thick (15-mm) sections obtained after a unique injection of Gadolinium chelate were used. RESULTS: High quality images were obtained in all 16 (100%) subjects free of pulmonary disease with both techniques, and in 10 and 12 (87% and 100%) patients suspected for pulmonary artery disease with sagittal and coronal Gd-enhanced MRA, respectively. In patients free of pulmonary disease, TONE images exhibited distal pulmonary arteries with 2.1 subsegmental divisions on average, whereas Gd-enhanced TurboFLASH images were the most accurate to identify proximal pulmonary arteries within the mediastinum, even if only 0.8 subsegmental divisions were seen on average. A correct diagnosis of pulmonary embolism was obtained in all cases but one, with use of both MRA techniques, with an overall accuracy of 86%. CONCLUSION: The association of segmented sagittal GRE images and coronal first-pass Gd-enhanced GRE images can provide information upon normal and diseased pulmonary arteries within the mediastinum until subsegmental pulmonary branches, even in patients with short-breathing. Further studies of patients with various pulmonary artery diseases will confirm whether this technique makes pulmonary MRA feasible in clinical routine situations.

Unusual complication of liver irradiation: acute thrombosis of a main hepatic vein: CT and MR imaging features.

The pathologic changes resulting from liver irradiation include congestion, fibrosis, and veno-occlusive disease. We report an unusual complication of radiation induced injury: acute thrombosis of a main hepatic vein within the radiation port. CT and MR features are described and the etiology of this unusual complication is discussed.

[Gradient echo sequences in the diagnosis of inferior vena cava thrombosis]. / Les séquences d'écho de gradient dans le diagnostic de thrombose de la veine cave inférieure.

The capability for studying noninvasively vessels has been dramatically improved with the use of gradient echo sequences. Twenty-one patients presenting a suspected inferior vena cava obstruction on cavography underwent MR examination with axial, sagittal and coronal gradient echo images. Eighteen patients were also imaged with ultrasound and/or CT. Gradient echo sequences visualized a thrombus in 19 cases and a normal vein in the remaining 2 cases. The potential MR pitfalls are illustrated and the two cases of false positive on cavography are discussed. Gradient echo sequences allow a fast and performant examination of the vessels.

Imaging of fat thrombus in the inferior vena cava originating from an angiomyolipoma.

A rare case of fat thrombus in the inferior vena cava originating from an angiomyolipoma is reported. Diagnostic imaging including ultrasonography, CT, MRI, and cavography was performed preoperatively. MRI allowed the most complete preoperative staging because of specific fatty signal intensity and good assessment of renal vein involvement.

Magnetic resonance angiography of intravascular endoprostheses: investigation of three devices.

PURPOSE: To assess the value of magnetic resonance angiography (MRA) in the evaluation of vascular patency after intravascular endoprosthesis placement. METHODS: Three different metallic stents (Wallstent, Strecker, Palmaz) were studied in vitro, and in vivo in six patients with spin-echo (SE) and gradient-echo (GRE) MR imaging. Time-of-flight, two-dimensional (2D) gadolinium-enhanced MRA was performed with GRE and flow-compensation technique, and reconstructed with a maximum-intensity projection (MIP) algorithm. MRA was compared to digital angiograms. RESULTS: In vitro studies demonstrated that the signal intensity (SI) within the stent differed according to the device employed, the lowest SI being observed within the Palmaz stent (p = .001). There was no difference in SI or apparent diameter of the stent according to the sequence (SE vs GRE) or length of echo time (TE). In patients, the endoprostheses recorded as a well-defined area of signal void or drop-out (p = 0.004), whereas vessels above and below the stent displayed high signal intensities. CONCLUSION: MRA does not seem as yet to be well suited for evaluating vascular patency after endoprosthesis placement, even if the Strecker and Wallstent endoprostheses provide fewer artifacts than the Palmaz stent.

Fast magnetic resonance imaging in the evaluation of tumoral obstructions of the inferior vena cava.

A prospective study was conducted on 9 patients with suspected obstruction of the inferior vena cava on ultrasonography, dynamic computerized tomography and/or inferior venacavography during the course of a retroperitonal tumor to assess the value of magnetic resonance imaging with gradient echo sequences. The findings on gradient echo magnetic resonance imaging were compared with the other imaging modalities and surgical or necropsy results. Our results suggest that gradient echo magnetic resonance imaging is the most appropriate imaging modality to diagnose and delineate the extent of inferior vena caval obstruction.

Regression of inflammatory pseudotumor of the liver under conservative therapy.

Inflammatory pseudotumors (IPT) of the liver are rare benign tumors of unknown origin. Most previously reported cases were initially misdiagnosed and treated surgically; thus, their course under medical treatment remains unclear. We report an additional case of hepatic IPT with a favorable outcome under medical treatment without surgical resection. New imaging and pathologic features of this disease are presented that may facilitate preoperative recognition and appropriate treatment.

Differentiation between multiple liver hemangiomas and liver metastases of gastrinomas: value of enhanced MRI.

PURPOSE: Hepatic metastases of neuroendocrine tumors are known to mimic hemangiomas on nonenhanced SE MR sequences. The usefulness of MR examination with gadolinium injection to identify lesions was prospectively evaluated. METHOD: Nine patients with multiple liver metastases of gastrinomas were compared with six patients showing multiple liver hemangiomas. Patients underwent unenhanced T2-weighted SE, T1-weighted SE, and FLASH sequences, followed by enhanced sequential FLASH sequences and a 5 min delayed T1-weighted SE sequence. RESULTS: On T2-weighted SE sequence, all hemangiomas displayed the same typical morphology as a sharply defined, homogeneous, high signal intensity lesion, but this pattern was also observed for some or all of the lesions in seven of nine patients with gastrinoma metastases. Dynamic FLASH sequences were accurate for lesions larger than 2 cm, hemangiomas displaying a nodular peripheral enhancement with centripetal filling in, and metastases displaying either an initial homogeneous or a regular peripheral enhancement. Precise assessment of lesions smaller than 2 cm remained equivocal. Delayed T1-weighted. SE sequence (performed at least 5 min after Gd-chelate injection) was the most accurate technique to identify metastases by showing hypo- or isointensity signal, whereas all hemangiomas were hyperintense. CONCLUSION: Postcontrast delayed T1-weighted sequence is the primary technique to differentiate equivocal cases of hemangiomas from metastases of gastrinoma.