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Biomedical subjects

Salome Ryf

Publications and source records attributed to Salome Ryf.

6 recordsLinked to original sources
PubMed2006

Potential interference of small neodymium magnets with cardiac pacemakers and implantable cardioverter-defibrillators.

BACKGROUND: Magnetic fields may interfere with the function of cardiac pacemakers and implantable cardioverter-defibrillators (ICDs). Neodymium-iron-boron (NdFeB) magnets, which are small in size but produce strong magnetic fields, have become widely available in recent years. Therefore, NdFeB magnets may be associated with an emerging risk of device interference. OBJECTIVE: We conducted a clinical study to evaluate the potential of small NdFeB magnets to interfere with cardiac pacemakers and ICDs. METHODS: The effect of four NdFeB magnets (two spherical magnets 8 and 10 mm in diameter, a necklace made of 45 spherical magnets, and a magnetic name tag) was tested in forty-one ambulatory patients with a pacemaker and 29 patients with an ICD. The maximum distance at which the magnetic switch of a device was influenced was observed. RESULTS: Magnetic interference was observed in all patients. The maximum distance resulting in device interference was 3 cm. No significant differences were found with respect to device manufacturer and device types. CONCLUSION: Small NdFeB magnets may cause interference with cardiac pacemakers and ICDs. Patients should be cautioned about the interference risk associated with NdFeB magnets during daily life.

Aged↗
PubMed2006

Is post-systolic shortening a reliable indicator of myocardial viability? An MR tagging and late-enhancement study.

PURPOSE: In ischemic myocardium systolic strain is reduced and followed by a deformation after systole, the so-called post-systolic shortening. The presence of post systolic shortening is therefore considered a marker of viability even though its mechanism remains unclear. The hypothesis was tested whether post-systolic shortening might be a passive recoil phenomenon and therefore not uniquely associated with viability. METHODS: Five patients with a history of myocardial infarctions and fully transmural scars in late enhancement imaging and five age-matched healthy volunteers underwent a tagging study to analyze systolic and post-systolic deformation in transmurally infarcted and contra-lateral non-infarcted myocardium. From CSPAMM myocardial tagging data, mid-wall circumferential fiber shortening, radial displacement, and rotation parameters were semi-automatically extracted by harmonic phase (HARP). RESULTS: In transmurally infarcted myocardium, a post systolic shortening of 6.2 +/- 1.8% was present occurring in early diastole (time to maximum circumferential fiber shortening increased versus both, contralateral myocardium and corresponding sectors in healthy volunteers, p < 0.01). Maximum radial displacement was decreased in scar tissue (p < 0.001 versus contra-lateral), but time to maximum radial displacement did not differ. Rotation did not discriminate between infarcted and non-infarcted myocardium. CONCLUSIONS: The pure finding of post-systolic shortening is not sufficient for the diagnosis of residual myocardial viability. Post-systolic shortening may be explained in part by passive recoil, which releases energy stored in the scar tissue during systolic intra-ventricular unloading. Circumferential fiber shortening appears best suited for characterization of regional deformation, whereas radial displacement and rotation are more dependent on tethering effects, and thus, are more likely to reflect global chamber mechanics.

Analysis of Variance↗
PubMed2004

Peak-combination HARP: a method to correct for phase errors in HARP.

PURPOSE: To introduce a method to correct phase errors (e.g., from B0 inhomogeneity) in tagging images, which may affect harmonic phase (HARP) evaluation. MATERIALS AND METHODS: The phase images corresponding to the negative and positive harmonic peaks in k-space are combined before HARP evaluation to eliminate any spurious phase. To validate in vivo, two complementary spatial modulation of magnetization (CSPAMM) data sets were collected for each volunteer and evaluated with conventional HARP, using either the positive or the negative harmonic peak, and with peak-combination HARP. RESULTS: Elimination of phase distortion by peak combination was observed in vitro and in vivo. Improved reproducibility of motion parameters was found with peak-combination HARP. CONCLUSION: With peak-combination HARP, reproducibility of contractile parameters is improved, and consequently, the number of subjects needed to detect statistically significant changes in contractile function can be reduced to one third compared to conventional HARP evaluation.

Adult↗
PubMed2004

Spiral MR myocardial tagging.

In the present study, complementary spatial modulation of magnetization (CSPAMM) myocardial tagging was extended with an interleaved spiral imaging sequence. The use of a spiral sequence enables the acquisition of grid-tagged images with a tagline distance as low as 4 mm in a single breath-hold. Alternatively, a high temporal resolution of 77 frames per second was obtained with 8-mm grid spacing. Ten healthy adult subjects were studied. With this new approach, high-quality images can be obtained and the tags persist throughout the entire cardiac cycle.

Adult↗
PubMed2002

Myocardial tagging with 3D-CSPAMM.

PURPOSE: To introduce a true three-dimensional (3D) tagging technique for the assessment of myocardial tissue motion. MATERIALS AND METHODS: To generate a 3D tagging grid, a complementary spatial modulation of magnetization (CSPAMM) was applied in three spatial directions. Imaging was performed using a conventional fast 3D gradient-echo sequence. For automatic analysis of the 3D-CSPAMM data set, evaluation software, based on a 3D extension of the HARP technique, was used. RESULTS: Successful application of the 3D-CSPAMM technique in healthy subjects allowed the accurate determination of quantitative 3D motion patterns in the human heart. CONCLUSION: 3D-CSPAMM may contribute to the quantification of the local 3D myocardial motion pattern throughout the cardiac cycle.

Heart↗