Magnetic resonance (MR) active invasive devices for the generation of selective MR angiograms

• US 5,447,156 A
• Filed: 04/04/1994
• Issued: 09/05/1995
• Est. Priority Date: 04/04/1994
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Bottomley, Paul A., Dumoulin, Charles L., Souza, Steven P.
• Primary Examiner(s): ZELE, KRISTA MICHELLE
• Application Number:
  US08/222,053
• Time in Patent Office: 519 Days
• Field of Search: 128/653.2, 128/653.3, 128/653.5, 128/899
• US Class Current: 600/419
• CPC Class Codes: G01R 33/34084 implantable coils or coils being geometrically adaptable to the sample, e.g. flexible coils or coils comprising mutually movable parts
• CPC Class Codes: G01R 33/563 of moving material, e.g. flow contrast angiography

Abstract

A magnetic resonance (MR) active invasive device system employs a radio-frequency (RF) coil embedded in an invasive device for the purpose of generating MR angiograms of a selected blood vessels. A subject is first placed in a polarizing magnetic field. The invasive device is then placed into a selected blood vessel of the subject such that the RF coil of the invasive device is located at or near the root of a vessel tree desired to be imaged. The RF coil is then used to alter the nuclear spin magnetization of blood flowing within the vessel. This is done by employing an RF excitation signal to the coil at the Larmor frequency of the blood. The nutation of spin magnetization can change the amount of longitudinal spin magnetization or the Amount of magnetization in the transverse plane. Because the size of the radio-frequency coil in the invasive device is small, the change in spin magnetization is limited to blood flowing by the invasive device. An MR imaging pulse sequence is then applied to the subject to obtain image information from the region containing the desired vessel tree. The MR imaging pulse sequence is designed to selectively detect the blood whose spin magnetization has been changed by the MR-active invasive device. Since only blood which the magnetization has modified is detected with the imaging sequence, the vessel tree is imaged.

Claims

1. A magnetic resonance (MR) imaging system for obtaining vessel-selective MR angiographic images from a subject comprising:

a) magnet means for applying a homogeneous magnetic field having substantially uniform amplitude over said subject;

b) a first RF transmitter means located external to said subject for transmitting RF energy into said subject of a selected duration, amplitude and frequency to cause nutation of a first selected ensemble of spins within said subject;

c) a gradient means for varying the amplitude of the magnetic field in at least one spatial dimension over time;

d) an MR-active invasive device means intended to be inserted within said subject comprised of at least one RF coil attached to the invasive device, each RF coil respectively nutating nuclear spin magnetization in its vicinity;

e) a second RF transmitter means attached to said at least one RF coil within the MR-active invasive device for transmitting RF energy into said subject of a selected duration, amplitude and frequency to cause nutation of a second selected ensemble of spins;

f) an external RF receive coil for detecting a set of MR response signals from the first and second selected ensembles of nutated spins with said subject;

g) a receiver means coupled to the external RF receive coil for receiving the detected MR response signals from the selected ensemble of spins;

h) a calculation means for calculating an angiographic image from the detected MR response signals;

i) a controller means connected to the first RF transmitter means, the receiver means, the calculation means and the gradient means, for activating the first and second RF transmitter means, the receiver means, the calculation means and the gradient means each according to a predetermined MR pulse sequence; and

j) a display means connected to the calculation means for displaying the calculated angiographic image to an operator.

2. A method for obtaining a vessel-selective magnetic resonance (MR) angiographic image from a subject comprising the steps of:

a) applying a homogeneous magnetic field having substantially uniform amplitude over said subject;

b) inserting an MR-active invasive device having an RF coil, into a selected vessel of said subject;

c) transmitting RF energy from the MR-active invasive device into said subject of a selected duration, amplitude and frequency to cause nutation of a first selected ensemble of spins;

d) transmitting RF energy from an RF coil external to said subject into said subject to cause nutation of a second selected ensemble of spins;

e) varying the amplitude of the magnetic field in at least one spatial dimension over time;

f) detecting a plurality of MR response signals from the first and second selected selected ensembles of spins;

g) processing the detected MR response signals;

h) calculating an MR angiographic image of the selected vessel from the processed MR response signals; and

i) displaying the MR angiographic image to an operator.

3. The method for obtaining a vessel-selective MR angiographic image from a subject of claim 2 wherein the step of calculating an MR angiographic image comprising the steps of:

a) repeating steps `c` through `f` of claim 2 with a first predetermined value of RF energy transmitted from the MR-active invasive device to result in a first set of MR response signals;

b) repeating steps `c` through `f` of claim 2 with a second predetermined value of RF energy transmitted from the MR-active invasive device to result in a second set of MR response signals; and

c) subtracting the first set of MR response signals from the second set of MR response signals to result in the MR angiographic image.

4. The method for obtaining a vessel-selective MR angiographic image as recited in claim 2, wherein the stop of sensing the MR response signals occurs simultaneously with the stop of varying the amplitude of the magnetic field.