Diagnostic system using nuclear magnetic resonance phenomenon

Abstract: A diagnostic system a nuclear magnetic resonance phenomenon comprises an external magnetic field generator (1), provided externally, for generating a magnetic field in a living body, a thin diameter member (5) capable of inserting to a body cavity and having flexibility, a high frequency coil (6), provided at a top end of the thin diameter member (5), for transmitting and receiving a high frequency, a nuclear magnetic resonance signal measuring device (2) for receiving a nuclear magnetic resonance signal from the living body, and a transformer (12), provided between the high frequency coil (6) and the nuclear magnetic resonance signal measuring device (2), for electrically insulating and separating both high frequency coil (6) and nuclear magnetic resonance signal measuring device (2) in a manner that the nuclear magnetic resonance signal is transmittable between the high frequency coil (6) and the nuclear magnetic resonance signal measuring device (2).

Description: The present invention relates to a diagnostic system making use of a nuclear magnetic resonance phenomenon wherein a nuclear magnetic resonance signal receiving coil is inserted to a human body and a nuclear magnetic resonance image is formed. Conventionally, in the detection and diagnosis of a surface of a digestive organ of a human body, particularly to epidermal cancer generated in stomach walls or an upper layer of the intestinal canal, the general method was that the generated portion was detected by an endoscope or an X-ray diagnosis, and tissues of a living body of the generated portion was picked up, and was determined whether it is malignant or not. However, in such a conventional method, since the sampling portion became a relatively wide range, there were problems in that the result of the diagnosis was not able to be determined, and it took much time to pick up the tissues of the living body, and the human body was damaged. On the other hand, there has recently been widely used a non-attacking diagnosing method for a human body which utilizes a nuclear-magnetic resonance phenomenon (the nuclear-magnetic resonance being hereinafter referred to as the "MR"). With a magnetic resonance imaging device (the magnetic resonance imaging being hereinafter referred to as the "MRI"), a human body is placed in a static magnetic field, and a predetermined high frequency magnetic field is applied to the human body to excite nuclei having spins of the tissues in the body cavity of the human body. MR signals having a predetermined frequency produced until the excited nuclei return to the original positions are detected and processed by a computer to obtain vertical cross-sectional images of the body cavity of the human body. The cross-sectional image obtained by the MRI device are extremely effective for diagnosis such as distinction of abnormal cells such as cells suffered from cancer from normal cells. It is known that MR signals from cancer tissues and normal tissues are generated at different relaxation time. Therefore, it is possible to diagnose whether the living tissues to be examined are suffered from cancer or not by imaging a difference between the MR signals in density based on the relaxation time. Fine and accurate images must be obtained to diagnose diseases of the digestive system such as a tubular viscus and particularly to find the depths of its affected portions. However, since the MR signal receiving body coil is provided externally of a patient body with the conventional apparatus, it is difficult to obtain fine and accurate cross sectional images of depth portions of the tubular viscus of the patient. For example, with a conventional system, a surface coil for receiving MR signals is placed on the abdomen of a patient and receives MR signals to diagnose the stomach walls. However, the signal-to-noise ratio (hereinafter referred to as the "SN ratio") is too low to obtain images sufficient for required diagnosis. In order to overcome this problem, there has been proposed an insertion apparatus such as an endoscope or a probe, which is provided, on the distal end of an insertion section inserted in the body of a patient, with an MR signal receiving high frequency coil, for detecting MR signals, as disclosed in Published Examined Japanese Patent Application No. 3-5174 and Published Unexamined Patent Application No. 2-277440. With them, a coil inserted in the patient's body receives MR signals and provides fine and accurate images having a good SN ratio. Thus, fine and accurate images can be obtained for diagnosing the depths of affected portions of tubular viscus. However, the conventional nuclear magnetic resonance diagnostic apparatus is structured as shown in Fig. 1. More specifically, reference numeral 1 is an MRI apparatus, which comprises an MR signal measuring device 2. On the other hand, in the inside of a top end portion of an insertion section 5 of an endoscope 4 inserted to the body cavity of a patient 3, there is a high frequency coil, which is an MR antenna for receiving an MR signal. The high frequency coil is connected to a cable 8 through a matching circuit arranged in the top end portion 5 of the endoscope 4. The matching circuit matches impedance between the high frequency coil and the cable 8, and the cable 8 transmits the MR signal received by the high frequency coil. The cable 8 is connected to the MR signal measuring device 2 through a front amplifier 9, and a universal cord 10 of the endoscope is connected to a light power source device 11. In such a conventional nuclear magnetic resonance diagnostic apparatus, the high frequency coil provided in the insertion section 5 of the endoscope 4 is not electrically isolated from the nuclear magnetic resonance signal measuring device 2. In other words, in the endoscope with the built-in high frequency coil or the probe, the portion including the matching circuit and the cable 8 is in an electrically conductive live state. In the conventional endoscope 4 or the probe, if the outer sheath of the insertion portion 5 is broken and the high frequency coil 6 and the mucous membrane of the living body is in a conductive state, there is fear that leakage current will flow to the patient 3. It is known from US-A 5 050 607 to have an antenna coil, of a system of the general kind of interest here, installed outside the body of a patient connected to a transmitter channel and an antenna coil being insertable into a body cavity and being provided with an electrical insulation sheat, connected to a receiver channel, whereby the transmitter channel and the receiver channel are not strictly separated from each other electrically. Furthermore, US-A-4 737 712 discloses a patent monitoring system wherein power for driving such monitoring system is transmitted to a system area kept on a floating potential and comprising the patient under investigation, via an insulation medium and wherein, furthermore, measuring data are transmitted to an uninsulated area of the system via coupling means providing an electrical insulation between the non-insulated area and the insulated area of the system. The monitoring system, in its insulated area, comprises a nuclear magnetic resonance measuring system having high frequency antenna coils coming into contact with the patient. Means for interrupting short circuit loops in the monitoring and measuring area of the known system in case of a failure of the insulation of antenna coils or probes are not provided for in the just considered known device. The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a nuclear magnetic resonance diagnostic system wherein safety, in view of a patient leakage current within the system, can be ensured with high reliability even if a high frequency coil is provided in an insertion section inserted to a human cavity. According to the present invention, there is provided a diagnostic system making use of a nuclear magnetic resonance phenomenon comprising an external magnetic field generator, provided externally, for generating a magnetic field in a living body, a thin diameter member capable of being inserted into a body cavity and having flexibility, a high frequency coil, provided at a top end of the thin diameter member, for transmitting and receiving a high frequency, a nuclear magnetic resonance signal measuring device for receiving a nuclear magnetic resonance signal from the living body, and isolating means, provided between the high frequency coil and the nuclear magnetic resonance signal measuring device, for electrically isolating both high frequency coil and nuclear magnetic resonance signal measuring device in a manner that the nuclear magnetic resonance signal is transmittable between the high frequency coil and the nuclear magnetic resonance signal measuring device. An external magnetic field generator receives a nuclear magnetic resonance signal from, e.g., an excited hydrogen atom by the high frequency coil provided in the top end portion of the insertion section inserted to the body cavity of the patient. The nuclear magnetic resonance signal received by the high frequency coil is transmitted to the nuclear magnetic resonance signal measuring means of the external magnetic field generator isolated by the isolating means, and such received, transmitted nuclear magnetic resonance signal is processed by the external magnetic field generator, and a nuclear magnetic resonance signal image can be formed. According to the diagnostic system of the present invention, safety of the patient in view of electrical leakage can be ensured without deteriorating the quality of the MRI image, and extremely fine and accurate MR image-diagnosis can be performed in a safe state of MR diagnosis. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is a schematic structural view of a conventional MRI apparatus; Fig. 2 is a schematic view of an MRI apparatus for diagnostic system according to the present invention; Fig. 3 is a schematic perspective view of a portion where an endoscope using the MRI apparatus of Fig. 1 is inserted; Fig. 4 is a view of an MRI apparatus according to the other embodiment of the present invention similar to Fig. 2; and Fig. 5 is a view of an MRI apparatus according to a modification of the present invention similar to Fig. 2. Embodiments of the present invention will be explained with reference to the drawings. It is noted that the same reference numerals are added the same portions through all figures. Figs. 2 and 3 show a first embodiment of a diagnostic system using a nuclear magnetic resonance phenomenon. An MR signal receiver of an MRI apparatus or an MR signal measuring device 2 is connected to a front-stage amplifier 9 through an isolating means 12. A high frequency coil 6, which is a MR antenna for receiving an MR signal, is provided in a top end portion of an insertion portion 5 of an endoscope 4, which is inserted to a cavity of a living body 3 of a patient to be examined. The high frequency coil 6 and the front-stage amplifier 9 are connected to each other via a cable 8. The high frequency coil 6 is connected to the cable 8 through matching means or circuit 7. The matching circuit 7 matches impedance of the high frequency coil 6 and cable 8. The cable 8 transmits the MR signal received by the high frequency coil 6. The cable 8 is connected to the MR signal measuring device 2 through the front amplifier 9, and a universal cord 10 of the endoscope 4 is connected to a light source device 11. Isolating means 12 is formed of, e.g., transformer. If a side, which is connected to the MR signal measuring device 2, is a primary side and a side, which is connected to the high frequency coil 6, is a secondary side, a stabilizing d.c. voltage source 13 for supplying a bias voltage to the front-stage amplifier 9, e.g., a battery to which a voltage stabilizing circuit is attached is connected to the secondary side. According to the above-structured nuclear magnetic resonance diagnostic apparatus, the MRI apparatus 1 receives an MR signal sent from, e.g., a hydrogen atom by use of the high frequency coil 6 provided at the top end portion of the insertion portion 5 of the endoscope inserted to the cavity of the living body 3 of a patient. The MR signal received by the high frequency coil 6 is transmitted to the cable 8, whose impedance is matched by the matching circuit 7, and the received MR signal is amplified by the front-stage amplifier 9 using the stabilizing d.c. voltage source 13 as a power source. The MR signal measuring device 2 of the MRI apparatus 1 is electrically isolated/separated from the high frequency coil 6, which is connected to the cable 8, by isolating means 12 such as transformer, and the MR signal is transmitted to the MR signal measuring device 2 of the MRI apparatus 1. The MR signal, which is received by the MR signal measuring device 2, and transmitted, and isolated, is processed by the MRI apparatus 1, and an MR signal image is formed. According to the above embodiment, a patient circuit forms the high frequency coil 6, the matching circuit 7, and the cable 8 for transmitting the signal, which are isolated/separated from the MRI apparatus 1. Due to this, it is possible to control a patient leakage current, which flows to an earth from the MRI apparatus 1 via the high frequency coil 6 and the patient 3. Therefore, the leakage current to a patient mounting portion can be controlled to be lower than an allowable value, which is defined by IEC 601-1. Moreover, in the case that the high frequency coil 6 is inserted to the living body of the patient and the MR image diagnosis is performed, it is possible to ensure safety in view of the patient leakage current. Fig. 4 is a second embodiment of the present invention. Similar to the first embodiment, the front-stage amplifier 9 is connected to the cable 8, which is connected to the high frequency coil 6. The front-stage amplifier 9 is connected to the MR signal measuring device 2 of the MRI apparatus 1 through an isolation amplifier 14 serving as isolating/separating means for isolating/separating the signal and amplifying the signal. In a case that the isolation amplifier 14 is an amplifier, which does not pass the direct current, the stabilizing d.c. voltage source 13, which supplies the voltage to the front-stage amplifier 9 and the isolation amplifier 14, is connected to the front-stage amplifier 9 and the isolation amplifier 14 as shown in Fig. 4. If a case that the isolation amplifier 14 is an amplifier which passes the direct current, the direct current, which is isolated from the surrounding earth, is supplied to the front-stage amplifier 9 and the isolation amplifier 14 from the MRI apparatus 1, so that no connection of the stabilizing d.c. voltage source 13 is needed as shown in a modification of Fig. 5. According to the above-structured nuclear magnetic resonance diagnosis apparatus, the MR signal is received by the high frequency coil 6 formed at the top end portion of the insertion portion 5 of the endoscope 4. The received signal is amplified by the front stage amplifier 9, and isolated and separated by the isolation amplifier 14. Thereafter, the signal is inputted to the MR signal measuring device 2 of the MRI apparatus 1. Therefore, similar to the first embodiment, the patient circuit, which is inserted to the body of the patient 3, can be electrically isolated, and the safety of the patient 3 can be ensured in view of the leakage current. Moreover, since the signal can be amplified in the isolation and separation, an SN ratio of the diagnostic image can be improved.

Claims: A diagnostic system making use of a nuclear magnetic resonance phenomenon comprising: a external magnetic field generator (1), provided externally, for generating a magnetic field in a living body; a thin diameter member (5) being adapted to be inserted into a body cavity and having flexibility; a high frequency coil (6), provided at an end of said thin diameter member (5), for transmitting and receiving a high frequency; and a nuclear magnetic resonance signal measuring device (2) for receiving a nuclear magnetic resonance signal from the living body; characterized in that isolating means (12) is provided between said high frequency coil (6) and said nuclear magnetic resonance signal measuring device (2), for electrically isolating both said high frequency coil (6) and said nuclear magnetic resonance signal measuring device (2) in a manner that the nuclear magnetic resonance signal is transmittable between said high frequency coil (6) and said nuclear magnetic resonance signal measuring device (2). The system according to claim 1, characterized in that an amplifying means (9) is provided for amplifying the signal received by said high frequency coil (6). The system according to claim 2, characterized in that said isolating means comprises a high frequency transducer (12) having a first winding connected to said nuclear magnetic resonance signal measuring device (2), and a second winding connected to an output side of said amplifying means (9) and electrically isolated from said first winding. The system according to claim 3, characterized in that a stabilizing d.c. power source (13) is provided for supplying a bias voltage to said amplifying means (9). The system according to claim 2, characterized in that said amplifying means (9) has a pre-amplifier (9), and said isolating means has an isolation amplifier (14) provided between said pre-amplifier (9) and said nuclear magnetic resonance measuring device (2). The system according to claim 5, characterized in that a stabilizing d.c. power source (13) is provided for supplying a bias voltage to said pre-amplifier (9) and said isolation amplifier (14). The system according to claim 5, characterized in that said thin diameter member is an endoscope (5).

Inventors: FUJIO KOJI, GOTANDA MASAKAZU, HAGIWARA TOSHIHIKO, HAYASHI MASAAKI, HIBINO HIROKI, HIYAMA KEIICHI, MATSUI KOICHI, SHIMIZU KOICHI, TAKAYAMA SHUICHI, TSUKAYA TAKASHI, YAMAGUCHI TATSUYA, YOSHINO KENJI, FUJIO, KOJI, GOTANDA, MASAKAZU, HAGIWARA, TOSHIHIKO, HAYASHI, MASAAKI, HIBINO, HIROKI, HIYAMA, KEIICHI, MATSUI, KOICHI, SHIMIZU, KOICHI, TAKAYAMA, SHUICHI, TSUKAYA, TAKASHI, YAMAGUCHI, TATSUYA, YOSHINO, KENJI, Fujio, Koji, c/o Int. Prop. &amp; Legal Dept., Gotanda, Masakazu, c/o Int. Prop. &amp; Legal Dept., Hagiwara, Toshihiko, c/o Int. Prop. &amp; Legal Dept., Hayashi, Masaaki, c/o Int. Prop. &amp; Legal Dept., Hibino, Hiroki, c/o Int. Prop. &amp; Legal Dept., Hiyama, Keiichi, c/o Int. Prop. &amp; Legal Dept., Matsui, Koichi, c/o Int. Prop. &amp; Legal Dept., Shimizu, Koichi, c/o Int. Prop. &amp; Legal Dept., Takayama, Shuichi, c/o Int. Prop. &amp; Legal Dept., Tsukaya, Takashi, c/o Int. Prop. &amp; Legal Dept., Yamaguchi, Tatsuya, c/o Int. Prop. &amp; Legal Dept., Yoshino, Kenji, c/o Int. Prop. &amp; Legal Dept.
Applicants: OLYMPUS OPTICAL CO, OLYMPUS OPTICAL CO., LTD.
Application year: 1993
Main classification: G01R33
IPC codes: G01R33, A61B5, A61M25