Magnetic resonance imaging of the lung tissue is thought to be hardly possible due to physical limitations especially the low proton density, susceptibility, and motion artifacts. The objective of our study was to evaluate and refine a very fast MR technique at a low field strength which overcomes the limitations in MR lung imaging. Thirty-five investigations were performed in 30 pediatric patients with suspected pneumonia. The MR investigations were performed in coronal slice orientation without cardiac or respiratory triggering in a low-field MR system. An optimized true fast imaging with steady precession sequence was applied. The MR images and the corresponding conventional chest radiographs were evaluated. The examination time per slice was 1.6 s. No motion artifacts could be observed. The signal-to-noise ratio for pulmonary parenchyma ranged from 4.9 to 7.1. All pathological findings of the chest X-ray images were correctly identified by the MRI (κ=0.82-0.85). Effusions as well as small pneumonic infiltrates were more precisely detected by the MRI investigation (κ=0.82) as compared with X-ray. Low-field projection MRI is a promising alternative to pediatric chest X-ray. Due to its short examination time, it overcomes the physical limits of usual MRI methods and provides comparable diagnostic information.
A serially transplantable human prostatic carcinoma line, PC EW, has been developed through heterotransplantation of tumor tissue from a lymph node metastasis. PC EW is androgen dependent and is similar to the original tumor in terms of histological pattern, amounts of prostatic acid phosphatase secreted, and absence of a hormonally independent subline. This line is thus similar to PC 82, and we herein report the first results of comparative treatment trials conducted on PC EW.
During the past few years magnetic resonance imaging (MRI) has gained increasing importance in the noninvasive examination of congenital heart defects. Practically all existing examinations have been carried out with a magnetic field strength exceeding 1 (T high-field MRI). Flow quantification is considered to be an advanced MRI application and, in the past, has been available for high-field systems only. Therefore until recently, functional examinations such as MRI tomographic flow quantification were reported exclusively for high-field MRI units. From December 1998 to December 1999, nine patients (five girls and four boys, mean age 130 plus minus 3.6 months, range 62-185 months) were investigated by means of MRI after a previous surgical repair or interventional balloon dilatation of a coarctation of the aorta (mean postinterventional time period 23 plus minus 0.4 months). The examination was carried out without sedation in an open low-field unit (Siemens Magnetom Open 0.2 T). Cardiac-triggered spin-echo sequences were used with a 3-mm to 7-mm slice thickness in an axial and a double oblique plane. The measurement of the immediate poststenotic flow velocity was done by flow-sensitive sequences developed for the study (phase-sensitive flow measurement sequences: TE, 6-12 msec; TR, 50 msec; flip angle, 60 degrees; Vmax, 200-1200 cm/sec; two acquisitions). All patients were examined on the same day with comparative echocardiographic procedures. In all cases, an excellent anatomical evaluation of the aortic arch was possible. The diameters of the residual stenosis were measured by MRI and correlated well r = 0.95; p ? 0.001; mean difference 0.44 +/- 2.47 mm) with echocardiographic results. No wall damage was observed in any of the cases studied. The pressure gradient of the stenosis calculated from the flow sequence was between 17 and 50 mmHg and corresponded well (r = 0.93; p = 0.001; mean difference 0.67 +/- 11 mmHg) with the results obtained from echocardiography. The study demonstrates that examination of the aortic arch is possible in a low-field MRI system, with its significant advantages (lower patient discomfort and more cost-effective examination). In addition, a quantitative flow measurement in low-field MRI was realized for the first time. Low-field MRI therefore seems to be a good, noninvasive method for examining patients with a poor echocardiographic representation of the aortic arch.
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