Magnetic resonance tomography (MRT) in bronchial cancer

Comparative studies were made of 47 patients suffering from histologically and cytologically confirmed bronchial carcinoma, using CT and MRT respectively. CT examinations were performed before and after intravenous administration of contrast medium, whereas the MR examinations were conducted via EEG-triggered T1 and T2 marked SE sequences in the axial and coronary planes. Both methods were assessed in respect of tumour visualisation and documentation of tumour spread. Staging of tumour and lymph nodes yielded largely concurring results for CT and MRT. Exceptions were seen in 7 of 10 patients with malignant involvement of the pericardium and in 3 of 27 patients with lymph node metastases located mediastinally and subcarinally where only MRT showed a positive involvement of the pericardium or lymph nodes (with possible consequences for the staging of the tumour or lymph nodes). Decisive advantages of MRT compared with CT were seen in the identification of infiltration of the aortic-wall, in the differentiation of the poststenotic syndrome, in the visualisation of the thoracic wall infiltration and functional information on blood flow rate in upper venolus obstruction caused by a carcinoma.     

Magnetic resonance tomography (1.5 T) of traumatic extracerebral hematomas

The advantages of magnetic resonance imaging (MRI) in the diagnosis of subacute and chronic traumatic extracerebral hematomas are described. The characteristic changes in signal intensity for hematomas depend on the magnetic properties of hemoglobin and its derivatives, which shorten the relaxation times and decrease the homogeneity of the local magnetic field. MRI is superior in detecting and depicting the extent of small hematomas adjacent to the skull. Changes in signal intensity with time allow rough estimation of the age of a hematoma. Small hemorrhages were often found (missed by CT) that were contralateral to chronic subdural hematomas.     

Magnetic resonance angiography with sliding interleaved projection reconstruction (SLIPR) acquisition.

In this paper, we report on the development of a novel multiple thin-slab projection-reconstruction acquisition technique. To eliminate the slab boundary artifact, the slabs are highly overlapped and only a small fraction of the projection view angles are sampled at each slab position. After Fourier transformation in the slice direction, there are sufficient numbers of projection measurements at each slice position to obtain very high resolution MR angiograms. The technique presented has all of the advantages of multiple overlapping thin slab acquisition (MOTSA) with no evidence of slab boundary artifact. J. Magn. Reson. Imaging 1999;10:569-575.     

Magnetic resonance separation imaging using a divided inversion recovery technique (DIRT)

The divided inversion recovery technique is an MRI separation method based on tissue T₁ relaxation differences. When tissue T₁ relaxation times are longer than the time between inversion pulses in a segmented inversion recovery pulse sequence, longitudinal magnetization does not pass through the null point. Prior to additional inversion pulses, longitudinal magnetization may have an opposite polarity. Spatial displacement of tissues in inversion recovery balanced steady‐state free‐precession imaging has been shown to be due to this magnetization phase change resulting from incomplete magnetization recovery. In this paper, it is shown how this phase change can be used to provide image separation. A pulse sequence parameter, the time between inversion pulses (T180), can be adjusted to provide water‐fat or fluid separation. Example water‐fat and fluid separation images of the head, heart, and abdomen are presented. The water‐fat separation performance was investigated by comparing image intensities in short‐axis divided inversion recovery technique images of the heart. Fat, blood, and fluid signal was suppressed to the background noise level. Additionally, the separation performance was not affected by main magnetic field inhomogeneities. Magn Reson Med 63:1007–1014, 2010. © 2010 Wiley‐Liss, Inc.     

Magnetic resonance imaging appearance of anterior cruciate ligament reconstruction using Calaxo screws

Bioabsorbable interference screws are commonly used to secure the graft during anterior cruciate ligament (ACL) reconstruction, in part because they result in less image degradation on subsequent magnetic resonance imaging (MRI). However, some bioabsorbable screws are associated with abnormalities on MRI examination not reported with metallic interference screws. We describe a finding on knee MRI examination after ACL reconstruction using a polylactide carbonate (PLC) bioabsorbable screw that we believe to be previously unreported with any other bioabsorbable screws. The finding raised suspicion of hemorrhage or infection, neither of which were present clinically. Analysis of tissue from the tibial tunnel suggested an explanation for the MRI finding: calcite crystals. An additional five patients with knee MRI examinations after ACL reconstruction using a PLC screw were reviewed and correlated with clinical findings with four having similar imaging abnormalities present. The PLC (Calaxo screw, Smith and Nephew, Andover, MA) screw used in these patients has been recalled in the United States and Europe by the manufacturer after a greater than expected incidence of adverse reactions, and legal action may be pending.     

Magnetic resonance imaging of acute myocardial infarction using a nitroxyl spin label (PCA)

The effects of an intravenously administered nitroxyl spin label (PCA) on the magnetic resonance imaging (MRI) appearance and relaxation times of acute canine myocardial infarctions were studied. Twenty-four hours after ligation of the left anterior descending coronary artery (LAD), animals were either sacrificed immediately (three dogs) or injected with 3.0 mmol/kg of PCA prior to sacrifice (six dogs). The PCA group dogs were sacrificed at either 5 minutes postinjection (three dogs) or 15 minutes postinjection (three dogs). Magnetic resonance imaging (0.35 T) using spin-echo techniques demonstrated high signal intensity in the infarct relative to normal myocardium in all three groups. In the control group, the T1 and T2 relaxation times were longer in infarcted compared with normal myocardium, but only the measure in T2 reached statistical significance (P less than .05). PCA produced infarct-avid T1 shortening in the six dogs that received it. Contrast in the group sacrificed at 15 minutes postcontrast administration was greater than that in the control group due to T1 shortening in the infarct. Thus, PCA produces differential effects on normal and infarcted myocardium. Between 5 and 15 minutes after IV administration, it causes greater changes in the infarct due to prolonged retention in this region.     

Magnetic resonance imaging and computed tomography of respiratory mechanics

Radiotherapy for organs with respiratory motion has motivated the development of dynamic volume lung imaging with computed tomography (4D-CT) or magnetic resonance imaging (4D-MRI). 4D-CT can be realized in helical (continuous couch translation during image acquisition) or cine mode (translation step-by-step), either acquired prospectively or reconstructed retrospectively with temporal resolutions of up to 250 msec. Long exposure times result in high radiation dose and restrict 4D-CT to specific indications (ie, radiotherapy planning). Dynamic MRI accelerated by parallel imaging and echo sharing reaches temporal resolutions of up to 10 images/sec (2D+t) or 1 volume/s (3D+t) that allow analyzing respiratory motion of the lung and its tumors. Near isotropic 4D-MRI can be used to assess tumor displacement, chest wall invasion, and segmental respiratory mechanics. Limited temporal resolution of dynamic volume acquisitions (in their current implementation) may lead to an overestimation of tumor size, as the mass is volume averaged into many voxels during motion. Nevertheless, 4D-MRI allows for repeated and prolonged measurements without radiation exposure and therefore appears to be appropriate for patient selection in motion-adapted radiotherapy as well as for a broad spectrum of scientific applications.     

Magnetic resonance hysterography and hysterosalpingography using hyperpolarized (3)He: demonstration of feasibility in an animal model

Assessment of the uterine cavity and patency of the fallopian tubes remains a difficult goal with magnetic resonance imaging (MRI). The purpose of this paper is to describe the development of a new magnetic resonance hysterography (MR-HG) and hysterosalpingography (MR-HSG) technique employing hyperpolarized (3)He. Two-dimensional (2D) and 3D gradient-echo imaging sequences were developed and optimized using a phantom. An optimized sequence was then applied in swine cadavers. J. Magn. Reson. Imaging 2000;12:1009-1013.     

多层螺旋CT多平面重建及三维重建在复杂髋臼骨折中的临床价值

目的：探讨多层螺旋CT三维重建及多平面重建在复杂髋臼骨折中的临床价值。方法：回顾性分析36例复杂髋臼骨折的MPR、SSD、VR表现。结果：MPR、SSD、VR均显示了36例复杂髋臼骨折及16例股骨头脱位,MPR、SSD、VR还分别显示了骨盆其他骨骨折51、43、46处,MPR及VR显示了SSD没显示的髋关节内碎骨片1例。MPR在显示髋臼骨折线的方向、数量上较SSD、VR理想,SSD、VR图像立体感强,空间位置明确,对复杂髋臼骨折的分类及判断股骨头脱位的方向和距离较MPR好。结论：多层螺旋CT3D图像结合MPR及横断面图像,能立体直观地显示复杂髋臼骨折及关节脱位的空间位置,协助临床诊断和治疗。     

Magnetic resonance imaging of entheses using ultrashort TE (UTE) pulse sequences

The attachment of tendons, ligaments, and joint capsule to bone (entheses) is reviewed and new options for visualizing key components of entheses provided by ultrashort TE (UTE) pulse sequences are described. Many features of entheses are adapted to the dispersion of stress at the boundary between tendons/ligaments and bone. Of particular interest is fibrocartilage, which has mechanical properties different from those of both "pure" tendon/ligament and bone. Features typical of entheses can also be seen at sites where tendons or ligaments are in contact with (but not attached to) bone, and the concept of a "functional enthesis" has been developed to emphasize the similarities. The enthesis concept has also been broadened to include the idea of an "enthesis organ" in which many tissues play a role in dissipating stress concentration. UTE pulse sequences can specifically identify the calcified and uncalcified fibrocartilage tissue components of entheses and differentiate these from fibrous connective tissue and bone. These tissues cannot be separately visualized at entheses with conventional pulse sequences. Entheses are involved in overuse syndromes and seronegative spondyloarthropathies (SpA) and there are important issues related to tissue repair and healing following surgery.     

Magnetic resonance imaging and computed tomography of cerebral vascular disease

Magnetic resonance imaging has emerged as the primary modality in detection and characterization of cerebrovascular lesions. New applications of existing spin-echo and gradient-recalled echo techniques are described. Functional imaging techniques ranging from the characterization of macroscopic proton motion (diffusion-weighted MR imaging), rapid imaging of intravascular contrast transit times (perfusion MR imaging), fast-flow mapping (MR angiography), and in vivo metabolic assessment (MR spectroscopy) are discussed. CT scanning remains important as an initial screening examination, in identifying acute hemorrhage, and in demonstrating blood flow.     

Magnetic resonance imaging and computed tomography findings in a patient with lymphomatoid granulomatosis

A patient with lymphomatoid granulomatosis was examined with both computed tomography (CT) and magnetic resonance imaging (MRI). The CT and MRI character of the pulmonary lesions are described as well as the patient's course and progression to lymphoma.     

Magnetic resonance imaging (MRI) of diastematomyelia

Summary The MRI-features of diastematomyelia in a patient with unusually late onset of symptoms are reported. Direct visualization of the split cord and low conus on frontal MR-images was facilitated by three-dimensional Fourier transform (3-DFT) image acquisition.