Method for measuring the nuclear magnetic resonance for NMR tomography

US4535290A · kind A · utility

Assignee

• Bruker Medizintechnik GmbH · DE

Inventors

• Hans Post · Schriesheim, DE
• Dieter Ratzel · Rheinstetten, DE

Key dates

• Filing date: Mar 11, 1983
• Grant date: Aug 13, 1985
• Expiry date: Mar 11, 2003

Classification

• Technology area (CPC G): Physics
• CPC primary: G01R33/4838
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

In NMR tomography, the nuclear spins of a selected type present in a selected area of a body are selectively excited by applying first a selection gradient field and exciting thereafter the nuclear spins by a HF signal which initially effects a rotation of the nuclear spins situated in a selected plane by an angle .alpha. of less than 90.degree., then a rotation of all selected nuclear spins by 90.degree. and finally again a rotation of the nuclear spins contained in the selected plane by an angle of 90.degree.-.alpha.. As a result thereof, the nuclear spins contained in the selected area have resumed at the end of this excitation their original orientation determined by a homogeneous magnetic field, while nuclear spins located outside this area lie within a plane extending almost vertically thereto. Thereafter, a measuring gradient field may be switched on without disturbing the orientation of the nuclear spins contained in the selected area. With the measuring gradient field switched on, the nuclear spins are now excited by a 90.degree. pulse or usual pulse sequences to produce an induction signal. The measuring processes are carried out in pairs, with the selection gradient fiel…