Assessment of left ventricular function parameters with a new three-dimensional shape model.

PURPOSE: To evaluate a 3D model of the left ventricle (LV) which allows calculation of LV function parameters on the basis of both short axis (SA) and long axis (LA) cine acquisitions. Comparison with the conventional Simpson's rule method in a volunteer and patient collective. MATERIALS AND METHODS: Cine imaging was performed with a prospectively triggered SSFP sequence: trueFISP: TR 3.6 msec, TE 1.8 msec, bFFE: TR 3.0 msec, TE 1.4 msec, flip angle 60 degrees , resolution 1.37 x 1.37 mm, slice thickness 8 mm, gap 2 mm in SA orientation from apex to basis and in radial LA orientation (spacing 15 degrees) in 11 volunteers and 27 patients with mitral valve insufficiency. Five different volume computations were compared: Simpson's rule based on all SA slices (M0), 3D shape model based on all SA slices (M1a), 3D shape model based on 3 SA slices (M1b), 3D shape model based on all SA and LA slices (M2a), and 3D shape model based on 3 SA slices and 1 LA slice (M2b). RESULTS: M 0 and M 1a give similar results (r: 0.99, b: 0.98). M 2a produces larger volumes than M 0 (b: 0.85) due to the inclusion of the LA contours. M 1b effectively reproduces the volumes computed with M 0 (r: 0.99, b: 1.02). M 2b effectively reproduces the volumes computed with M 2a (r: 0.99, b: 0.94). M 2b and M 0 give similar results in the patient collective (r: 0.99, b: 0.97). CONCLUSION: The proposed 3D shape model allows merging of information acquired in different orientations and thus the combination of SA and LA contours with better coverage of the left ventricle. It provides a suitable fit with a reduced number of segmented contours.

Orthodontic springs and auxiliary appliances: assessment of magnetic field interactions associated with 1.5 T and 3 T magnetic resonance systems.

The objective of this paper is to evaluate magnetic field interactions at 1.5 and 3 T for 20 orthodontic devices used for fixed orthodontic therapy. Twenty springs and auxiliary parts made from varying ferromagnetic alloys were tested for magnetic field interactions in the static magnetic field at 1.5 and 3 T. Magnetic translational force F(z) (in millinewtons) was evaluated by determining the deflection angle beta [American Society for Testing and Materials (ASTM standard test method)]. Magnetic-field-induced rotational force F(rot) was qualitatively determined using a five-point scale. beta was found to be >45 degrees in 13(15) devices at 1.5(3) T and translational force F(z) exceeded gravitational force F(g) on the particular object [F(z) 10.17-261.4 mN (10.72-566.4 mN) at 1.5(3) T]. F(z) was found to be up to 24.1(47.5)-fold higher than F(g) at 1.5(3) T. Corresponding to this, F(rot) on the objects was shown to be high at both field strengths (> or = +3). Three objects (at 1.5 T) and one object (at 3 T) showed deflection angles <45 degrees , but F(rot) was found to be > or = +3 at both field strengths. For the remaining objects, beta was below 45 degrees and torque measurements ranged from 0 to +2. Of 20 objects investigated for magnetic field interactions at 1.5(3) T, 13(15) were unsafe in magnetic resonance (MR), based on the ASTM criteria of F(z). The implications of these results for orthodontic patients undergoing MRI are discussed.

[Modern diagnostic assessment of the upper urinary tract using multislice CT urography]. / Moderne Diagnostik des oberen Harntraktes mittels Mehrschicht-CT-Urographie.

The advent of Multislice Computed Tomography (MSCT) has made evaluation of the entire urinary tract with high-resolution sections during a single breath-hold a reality. Acquisition of multiple thin overlapping slices provides excellent two-dimensional (2D) and three-dimensional (3D) reformations of the urinary tract. The concept of "Multislice CT Urography (MSCTU)" has emerged from this technical improvement. As a result, a wide range of pathologies inside and outside the urinary tract can be identified. During the last several years, MSCTU has challenged intravenous urography (IVU) in the evaluation of urinary tract abnormalities. Compared with IVU, MSCT(U) is more sensitive and specific in the detection and characterization of a variety of urinary tract disorders, including renal masses and urolithiasis. The main advantage of IVU has been its ability to offer excellent delineation of pelvicalyceal and ureteral anatomy and to depict subtle uroepithelial abnormalities. MSCTU has already shown promising results for overcoming this challenge. Optimal opacification and distension appear to be an essential requirement for a thorough evaluation of the collecting system. Dedicated preparation strategies have been developed to meet these technical difficulties. The biggest disadvantage of MSCTU is the significant radiation exposure. For broad routine clinical application, there is still a need for dose reduction protocols despite the ongoing technical developments in MSCTU. In this article, we outline the different concepts of technical processing for MSCTU and summarize the current role of MSCTU in the evaluation of the upper urinary tract.