Method for avoiding image occlusions in nuclear magnetic resonance tomography apparatus that are operated with multi-echo sequences

US5623207A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Volker Weissenberger · Baiersdorf, DE
• Peter Heubes · Baiersdorf, DE

Key dates

• Filing date: May 20, 1996
• Grant date: Apr 22, 1997
• Expiry date: May 20, 2016

Classification

• Technology area (CPC G): Physics
• CPC primary: G01R33/5617
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

In a method for avoiding image occlusions in nuclear magnetic resonance tomography apparatus that are operated with multi-echo sequences, at a time t.sub.0, a cross-magnetization in spins is generated in an examination subject with an excitation radio-frequency pulse. At times t.sub.1, t.sub.3, t.sub.5 . . . , at least two refocusing radio-frequency pulses that re-phase the cross-magnetization follow and read-out intervals follow at times t.sub.2, t.sub.4, t.sub.6 . . . The following condition is satisfied in at least one direction for the gradients G activated during the pulse sequence: ##EQU1## Even given quadratic gradient terms, thus, no phase difference occurs between a primary and a stimulated echo path. The presence of such a phase difference causes an image occlusion, and thus such occlusions are avoided by eliminating such a phase difference.