Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-12-13
2003-01-07
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C382S131000, C600S443000, C600S408000, C128S922000
Reexamination Certificate
active
06505063
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a diagnostic imaging system, in particular a magnetic resonance imaging system which is provided with an ultrasound probe.
Such a magnetic resonance imaging system is known from the U.S. Pat. No. 5,146,924.
The known magnetic resonance imaging system comprises a receiver antenna for receiving magnetic resonance signals which is mounted in an ultrasound transducer. The ultrasound transducer includes an ultrasound source for generating ultrasound waves in the object to be examined, such as a patient who is to be examined. The ultrasound transducer also includes the ultrasound probe. The ultrasound probe detects ultrasound echoes, i.e. ultrasound waves which are reflected in an object to be examined. The central processor of the known magnetic resonance imaging system derives from the detected ultrasound waves an ultrasound image of a part of the object to be examined. From this ultrasound image the user determines the position of the part of the anatomy to be examined, notably the organ of interest. Subsequently, on the basis of the position of the part to be examined as detected from the ultrasound image, there are excited (nuclear) spins in the object to be examined of the part to be examined upon which excitation magnetic resonance signals are generated and a magnetic resonance image of the part to be examined is reconstructed from the magnetic resonance signals. The known magnetic resonance system employs the ‘Overhauser’-effect to generate the magnetic resonance image. The known magnetic resonance imaging system employs the ultrasound image only for the determination of the position of the part of the object of which a magnetic resonance image is made.
SUMMARY OF THE INVENTION
An object of the invention is to provide a diagnostic system which is suitable to supply diagnostic image with a higher diagnostic quality, notably having a higher diagnostic information content.
This object is achieved by the diagnostic imaging system which, according to the invention comprises a reconstruction unit for reconstructing a diagnostic image from the magnetic resonance signals and the ultrasound echoes.
The magnetic resonance signals are generated by RF-excitation of (unclear) spins in the object which is placed in a stationary magnetic field. Temporary magnetic gradient fields are applied so that the Larmor frequency of the excited spins is made spatial position dependent. Thus, spatial encoding of the magnetic resonance signals by the frequencies and phases of the magnetic resonance signals is achieved.
The diagnostic image combines image information both from the magnetic resonance signals and from the ultrasound echoes. For example the diagnostic image includes a portion of pixels that are derived from the magnetic resonance signals and another portion of pixels that are derived from the ultrasound echoes. The information included in the magnetic resonance signals has a high spatial resolution but a low temporal resolution. On the other hand, the information included in the ultrasound echoes has a lower spatial resolution but a much higher temporal resolution. In particular the information in the magnetic resonance signals is time-averaged over a range of about 50 ms to about 0.5 s and the information in the ultrasound echoes pertains to short periods of time of about 5-20 ms. The information in the magnetic resonance signals may have a high spatial resolution in that details as small as 0.5 mm are faithfully represented in the magnetic resonance image. The diagnostic image thus combines image information with a high spatial resolution with image information with a high temporal resolution. Thus, the diagnostic image shows in particular image information of high temporal resolution of rapidly moving parts in the patient to be examined while the anatomical surroundings of the rapidly moving portions are accurately displayed with a high spatial resolution. For example, moving portions of the patient's heart are displayed against the correctly spatially highly resolved anatomical background.
In another example, the diagnostic image combines functional information from the ultrasound echoes of the reconstruction which is displayed in the anatomical information from the magnetic resonance signals. For example, in the diagnostic image colour-Doppler values derived from the ultrasound echoes may replace grey-values derived from the magnetic resonance signals.
These and other aspects of the invention will be elaborated with respect to the preferred embodiments as defined in the dependent Claims.
In a preferred embodiment the reconstruction unit is arranged to derive a magnetic resonance image and a preliminary ultrasound image from the magnetic resonance signals and the ultrasound echoes, respectively. The diagnostic image may be derived from the magnetic resonance image and the preliminary ultrasound image. The term ‘preliminary ultrasound image’ in this application indicates any ultrasound image to which correction on the basis of the magnetic resonance image or registration relative to the magnetic resonance image is still to be performed. For example, respective portions of the preliminary ultrasound image and of the magnetic resonance image are included into the diagnostic image. In an other example, the diagnostic image is formed in that at least respective portions of the magnetic resonance image and the preliminary ultrasound image are displayed alternatingly.
In a further preferred embodiment, the magnetic resonance image and the preliminary ultrasound image are registered in a common co-ordinate system. That is, between respective positions in the magnetic resonance image and in the preliminary ultrasound image the geometric relation is established. On the basis of this geometric relation positions in the magnetic resonance image and in the ultrasound image are registered in correspondence with the geometric relation between the imaged positions in the object. This may be achieved by relating positions in the preliminary ultrasound image an in the magnetic resonance image to a common reference frame. Such a common reference system is for example defined in the examination room in which the diagnostic imaging system is set up. Notably, a position detection system is provided in the examination room. The position detection system measures the positions of the ultrasound probe relative to the patient to be examined. The position detection system also determines the geometric relation between positions in the patient to corresponding positions in the magnetic resonance image. The position detection system may include an optical or acoustical position detection system which measures the positions of the patient and the ultrasound probe. The position of the ultrasound probe determines a region, in particular a slice, of the patient from which the ultrasound echoes are received. Thus, from the measurement of the position of the ultrasound probe, the part imaged in the preliminary ultrasound image is established. Notably, when an optical position detection system is employed, the ultrasound probe and the patient are fitted with light-emitting diodes (LEDs) or infrared-emitting diodes (IREDs). The radiation, notably light or infrared radiation, from the LEDs or IREDs is detected from two or more directions by means of a camera-unit. The camera-unit picks up images from the sets of LEDs or IREDs. The diagnostic imaging system comprises a computer which is also programmed to derive the position of the ultrasound probe relative to the patient from the image picked-up by the camera-unit of the LEDs or IREDs. The gantry of the magnetic resonance imaging system is preferably also fitted with LEDs or IREDs and the camera-unit further picks-up images of the MR-gantry, notably these images also feature images of the LEDs or IREDs on the MR-gantry. The computer is also arranged to calculate the position of the gantry relative to the patient to be examined. Further, the computer is arranged to compute the geometric relation between positions in
Kuhn Michael Harald
Van Den Brink Johan Samuel
Visser Frederik
Lateef Marvin M.
Mantis Mercader Eleni
Vodopia John
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