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Evangelos Trifon Laskaris

Bio: Evangelos Trifon Laskaris is an academic researcher from General Electric. The author has contributed to research in topics: Electromagnetic coil & Magnet. The author has an hindex of 34, co-authored 335 publications receiving 4552 citations.


Papers
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Patent
05 Jul 1988
TL;DR: In this article, a superconductive magnet for magnetic resonance imaging not requiring consumable cryogens or requiring cryogen liquid or vapor cooling of superconducting coils is provided having a resin impregnated coil of superconductor wire.
Abstract: A superconductive magnet for magnetic resonance imaging not requiring consumable cryogens or requiring cryogen liquid or vapor cooling of superconducting coils is provided having a resin impregnated coil of superconductor wire Heat conductive means having a thermal conductivity greater than the resin, contact the impregnated coil along the length of at least one of the impregnated coil surfaces A thermal radiation shield is spaced away from and surrounds the resin impregnated coil and heat conductive means An evacuable housing is spaced away from and surrounds the shield The housing supports the shield, heat conductive means and the impregnated coil A multiple stage cryocooler is mounted in the housing with one stage of the cryocooler thermally coupled to the radiation shield and with another stage capable of achieving lower temperatures than the stage coupled to the shield, thermally coupled to the heat conductive means, so that superconductive operation in a vacuum can occur without the coil being immersed in cryogen liquid or vapor

103 citations

Patent
29 May 1992
TL;DR: An open magnetic resonance imaging (MRI) magnet has first (12) and second (20) spaced-apart superconductive coil assemblies each including a toroidal-shaped coil housing (14,22) containing a superconductively main coil (40,46) and a super-conductive bucking coil (44,50) as discussed by the authors.
Abstract: An open magnetic resonance imaging (MRI) magnet having first (12) and second (20) spaced-apart superconductive coil assemblies each including a toroidal-shaped coil housing (14,22) containing a superconductive main coil (40,46) and a superconductive bucking coil (44,50). The bucking coil is spaced radially inward and radially apart from the main coil. The bucking coil carries an electric current equal in amperage, and opposite in direction, to the main coil. The bucking coils overcome the gross magnetic field distortions in the imaging volume of the main coils (created by the open space between the magnet's superconductive coil assemblies) to produce a magnetic field of high uniformity within the imaging volume.

103 citations

Journal ArticleDOI
TL;DR: The development of the generator is described and some key test results used to validate the design are presented, which indicate that the generator has a significant margin over the test points and that its performance is consistent with program specifications.
Abstract: General Electric, under contract with the Air Force Research Labs (AFRL), has successfully developed and tested a high speed, multimegawatt superconducting generator. The generator was built to demonstrate high temperature superconducting (HTS) generator technology for application in a high power density Multimegawatt Electric Power System (MEPS) for the Air Force. The demonstration tested the generator under load conditions up to 1.3 MW at over 10,000 rpm. The new MEPS generator achieved 97% efficiency including cryocooler losses. All test results indicate that the generator has a significant margin over the test points and that its performance is consistent with program specifications. This demonstration is the first successful full-load test of a superconducting generator for the Air Force. In this paper we describe the development of the generator and present some key test results used to validate the design. Extrapolation to a higher power density generator is also discussed.

85 citations

Patent
23 Dec 2002
TL;DR: In this article, a magnetic resonance imaging (MRI) device for imaging a volume is provided with at least one main magnet for generating a magnetic field, and a gradient coil for manipulating the magnetic field generated by the at least main magnet to image the volume.
Abstract: A magnetic resonance imaging (MRI) device for imaging a volume is provided with at least one main magnet for generating a magnetic field, and at least one gradient coil for manipulating the magnetic field generated by the at least one main magnet to image the volume. The magnetic fields generated by the at least one gradient coil are substantially unshielded.

72 citations

Patent
11 Jul 1994
TL;DR: In this paper, an open magnet having two magnet assemblies arranged in a spaced-apart parallel relationship to define a working space there between is provided for magnetic resonance imaging. And the specific shape of the field enhancers is determined with a nonlinear optimization design method.
Abstract: An open magnet having two magnet assemblies arranged in a spaced-apart, parallel relationship to define a working space therebetween is provided for magnetic resonance imaging. Each assembly has an annular superconductive coil and a ferromagnetic field enhancer encircled by the superconductive coil. The field enhancers are substantially cylindrical ferromagnetic pole pieces which are encircled by a respective one of the superconductive coils. The magnet assemblies are attached to a C-shaped support frame which is rotatively mounted to a pedestal member. The frame can thus be rotated between vertical and horizontal imaging positions. The field enhancers are shaped so as to maximize homogeneity in the imaging volume while keeping their weight and volume to a minimum. The specific shape of the field enhancers is determined with a nonlinear optimization design method.

69 citations


Cited by
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Patent
14 Jul 2011
TL;DR: By using a multiple receiving coil composed of receiving coils, an imaging portion of a subject is subjected to a first pulse sequence to create n sensitivity images (701 to 703) fewer than the examination images as discussed by the authors.
Abstract: By using a multiple receiving coil composed of receiving coils, an imaging portion of a subject is subjected to a first pulse sequence to create n sensitivity images (701 to 703) fewer than the examination images. When these sensitivity images are created, an NMR signal is measured for only the low-frequency region of the k space. A second pulse sequence from which a phase encode step is removed is conducted to create m (m>n) examination images (704, 705) of the subject by using the receiving coils. When sensitivity distributions (707, 708) of the receiving coils are determined for the sensitivity images (701 to 703), and if there are no sensitivity distributions corresponding to the slice positions of the examination images (704, 705), they are determined by slice interpolation using the sensitivity distributions (701 to 703), and the aliasing artifacts of the examination images (704, 705) are removed by matrix operation by using the sensitivity distributions (707, 708).

1,792 citations

Patent
04 Jun 2008
TL;DR: In this paper, a surgical instrument including a switching mechanism which allows a surgeon to selectively advance or retract a staple driver and/or cutting member within a staple cartridge is presented, where the trigger can be configured to slide between a first position in which the first pawl is engaged with the first ratchet assembly and a second position when the second pawl was engaged with second ratchet assemblies.
Abstract: A surgical instrument including a switching mechanism which allows a surgeon to selectively advance or retract a staple driver and/or cutting member within a staple cartridge. In various embodiments, the surgical instrument can include a handle, a trigger operatively coupled to the handle, a firing drive, and an end effector. The firing drive can include a first ratchet assembly configured to advance a cutting member in the end effector and a second ratchet assembly configured to retract the cutting member. The trigger can include first and second pawls pivotably mounted thereon which are configured to be selectively engaged with the first and second ratchet assemblies, respectively. In at least one embodiment, the trigger can be configured to slide between a first position in which the first pawl is engaged with the first ratchet assembly and a second position in which the second pawl is engaged with the second ratchet assembly.

1,037 citations

Patent
TL;DR: In this paper, a magnetic resonance imaging (MRI) system is presented for highly precisely detecting and compensating body motions within a short processing time during radial scanning, which includes a control unit that applies radiofrequency magnetic fields and magnetic field gradients to a subject lying down in a static magnetic field and detects magnetic resonance signals generated from the subject.

913 citations

Journal ArticleDOI
TL;DR: In this article, a superconducting magnetic resonance (MR) imager that provides direct access to the patient and permits interactive MR-guided interventional procedures was designed and constructed, and images were obtained in several anatomic regions with use of routine pulse sequences.
Abstract: PURPOSE: To develop a superconducting magnetic resonance (MR) imager that provides direct access to the patient and permits interactive MR-guided interventional procedures. MATERIALS AND METHODS: A 0.5-T superconducting magnet that allows a region of vertical access to the patient was designed and constructed. This magnet was integrated with newly designed shielded gradient coils, flexible surface coils, and nonmagnetic displays and with position-monitoring probes and device-tracking instrumentation. RESULTS: The magnet homogeneity was 12.3 ppm, and the gradient field was linear to within 1% over an imaging region 30 cm in diameter. The signal-to-noise ratio was 10% higher than in a comparable 0.5-T superconducting imager. Images were obtained in several anatomic regions with use of routine pulse sequences. Interactive image plane selection and near real-time imaging, with use of fast gradient-recalled echo sequences, were demonstrated at a rate of one image every 1.5 seconds. CONCLUSION: MR-guided interv...

423 citations

Patent
22 May 1998
TL;DR: In this paper, the authors used a movable magnetic resonance instrument to monitor hyperthermia treatments such as tissue ablation, which can be conducted under automatic control after the operator marks a treatment volume on an image of the subject, such as a magnetic resonance image acquired using the movable magnetometer.
Abstract: Magnetic resonance information acquired by a movable magnetic resonance instrument is used to monitor hyperthermia treatments such as tissue ablation. The instrument may include both the magnetic resonance equipment and an energy applicator such as a high intensity focused ultrasound unit. The treatment can be conducted under automatic control after the operator marks a treatment volume on an image of the subject, such as a magnetic resonance image acquired using the movable magnetic resonance instrument. The automatic treatment can be based on interpolation of tissue response curves at plural test points near the treatment volume. The system can also provide automatic supervisory control during manual operation, to prevent application of heat to sensitive anatomical structures.

423 citations