HIGH FREQUENCY RECEIVING UNIT FOR MAGNETIC RESONANCE

• Main Authors: FRIEDRICH AXEL, GREIM HELMUT, IANMIN WANG, LUDWIG KREISCHER
• Format: Patent
• Language: English
• Published: 09.02.1999
• Edition: 6
• Subjects: DIAGNOSIS; HUMAN NECESSITIES; HYGIENE; IDENTIFICATION; MEASURING; MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES; MEDICAL OR VETERINARY SCIENCE; PHYSICS; SURGERY; TESTING

PROBLEM TO BE SOLVED: To suppress amplifier noise when a receiving antenna is detuned in a high frequency receiving unit by connecting the receiving antenna to a detuning means and arranging a noise suppressing means which can be actuated when the receiving antenna is detuned. SOLUTION: When a receiving antenna 2 is detuned (with a patient), the receiving antenna 2 is provided with a comparatively low impedance of 5-10 Ωorder which is converted into an impedance of 50 Ω, for example, via a matching circuit network 6. To the matching circuit network 6, an initial end 8 of a signal line 10 constructed as a coaxial line is connected, and the coaxial line 10 is provided with a surge resistance of 50 Ω, for example. A terminal end 12 of the signal line 10 is connected to an input end 14 of a preamplifier 16 in which a low input impedance is provided and noise matching is carried out. As a first amplifier step 18, a low noise electric field effect transistor modeled of an input capacitance 20, an electricity source 22 whose voltage is controlled, and an output resistance 24 is used in the preamplifier 16.