Resonance inductance value adjustable detuning circuit for MRI radio frequency coil

Abstract

The utility model relates to the technical field of MRI (Magnetic Resonance Imaging) radio frequency coils, in particular to a detuning circuit capable of adjusting resonant inductance for an MRI radio frequency coil. A detuning circuit used for an MRI radio frequency coil and capable of adjusting the resonant inductance value is characterized in that a detuning inductor is arranged on a double-face PCB, one end of the detuning inductor is connected with one end of a capacitor, and a plurality of diodes are connected between the other end of the capacitor and the other end of the detuning inductor in parallel; an upper row of pad through holes and a lower row of pad through holes are uniformly distributed in the double-sided PCB; a copper film wire is printed between every two upper and lower bonding pad through holes in the back surface of the double-sided PCB; every two upper and lower bonding pad through holes are connected through a U-shaped jumper wire, and the two ends of the U-shaped jumper wire penetrate through the bonding pad through holes and are connected with the copper film wires. Compared with the prior art, the inductance value required by resonance of the LC circuit can be accurately adjusted by adjusting the cross sectional area and the height of the U-shaped jumper wire, and meanwhile, the quality factor of the inductor is remarkably improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to MRI radio frequency coil technical field, concretely is a kind of detuning circuit for the adjustable resonant inductance of MRI radio frequency coil. BACKGROUND

[0002] In modern magnetic resonance apparatuses, the magnetic resonance signals are received by means of local coils arranged close to the patient. The local coils comprise, in addition to the actual receiving antennas, which are preferably embodied as loop antennas, further low-noise preamplifiers in order to be able to amplify the received magnetic resonance signals. Furthermore, the local coils comprise an active detuning circuit arranged separately for each loop antenna, with which the receiving antennas can be detuned during the transmission phase.

[0003] Generally, the order of magnitude of the transmitted RF signals is greater than the order of magnitude of the magnetic resonance signals generated by the excited nuclei and detected by the RF receiving coils. In order to maintain the safety of the patient and to protect sensitive receiving devices comprising the coils, the receiving coils are generally decoupled and detuned during the transmission phase in the imaging process.

[0004] Generally, flexible circuit boards are used for the transmit RF coils, because flexible circuit boards (FPC) have high flexibility and bendability, which makes them very suitable for complex wiring in limited space while being able to adapt to various shape and size requirements. While the detuning circuit (Decouple Circuit) is a rigid circuit board, fixed on the flexible circuit board, so the smaller the overall height and physical size of the detuning circuit board, the easier it is for the radio frequency coil to adapt to various shape and size requirements.

[0005] In the detuning circuit PCB board, the resonant inductor occupies the largest space, if the resonant inductor is wound by common enameled wire, although a very high quality factor can be obtained, but the overall height of the detuning circuit board is too high, deviating from our design goal of light and thin radio frequency coil. If a simple PCB coil is used, the coil quality factor is too low to cause serious heating, and it is difficult to accurately fine-tune the inductance to make the detuning circuit resonate. Therefore, using the combination of PCB copper film wire and jumper, not only can the inductance be accurately fine-tuned under the premise of ensuring high quality factor of the coil, but also the overall height of the detuning circuit board can be significantly reduced. SUMMARY

[0006] The utility model discloses a overcome the deficiency of prior art, provide a kind of for the detuning circuit of adjustable resonant inductance of MRI radio frequency coil, provide a kind of for the detuning circuit of adjustable resonant inductance of MRI radio frequency coil, can be accurately adjusted by adjusting the cross-sectional area and height of U-shaped jumper wire, the inductance required for the resonance of LC circuit is adjusted, while the quality factor of inductor is significantly improved.

[0007] To achieve the above object, a kind of for the detuning circuit of adjustable resonant inductance of MRI radio frequency coil, including double-sided PCB board, characterized by: detuning inductance is provided on double-sided PCB board, one end of detuning inductance is connected with one end of capacitor, and a plurality of diodes are connected in parallel between the other end of capacitor and the other end of detuning inductance;The detuning inductance includes copper film wire, pad through-hole, U-shaped jumper wire, and the upper and lower two rows of pad through-holes are evenly arranged on double-sided PCB board;It is located on the back of double-sided PCB board, and copper film wire is printed between the upper and lower two pad through-holes;It is located on the front of double-sided PCB board, and the upper and lower two pad through-holes are connected by U-shaped jumper wire, and the two ends of U-shaped jumper wire are connected with copper film wire by penetrating pad through-hole.

[0008] The copper film wire is at least provided with 7, and the adjacent two copper film wires are equal in length, equidistant and parallel to each other.

[0009] The U-shaped jumper wire is at least provided with 6, and the adjacent two U-shaped jumper wires are equal in length, equidistant and parallel to each other.

[0010] The height distance between the U-shaped jumper wire and the front of double-sided PCB board is 1.8-2.5mm.

[0011] The diode is at least provided with 4.

[0012] The detuning circuit is connected in series with the receiving antenna, and the receiving antenna is connected in series by three capacitors.

[0013] Compared with prior art, the utility model discloses a kind of for the detuning circuit of adjustable resonant inductance of MRI radio frequency coil, can be accurately adjusted by adjusting the cross-sectional area and height of U-shaped jumper wire, the inductance required for the resonance of LC circuit is adjusted, while the quality factor of inductor is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is the front view of double-sided PCB board.

[0015] Figure 2 It is the back view of double-sided PCB board.

[0016] Figure 3 It is the side view of double-sided PCB board.

[0017] Figure 4It is a U-shaped jumper structure schematic diagram.

[0018] Figure 5 It is a U-shaped jumper distance double-sided PCB different height corresponding inductance value data table.

[0019] Figure 6 It is a receiving antenna detuning circuit schematic diagram in the local coil in the embodiment. DETAILED DESCRIPTION

[0020] The utility model will be further described in the following according to the drawings.

[0021] As Figures 1 to 4 Indicated, a kind of adjustable resonance inductance detuning circuit for MRI radio frequency coil, including double-sided PCB, detuning inductance is equipped on double-sided PCB 7, one end of detuning inductance is connected with one end of capacitor 6, and a plurality of diodes 1 are connected in parallel between the other end of capacitor 6 and the other end of detuning inductance;The detuning inductance includes copper film wire 5, pad via 2, U-shaped jumper 3, double-sided PCB 7 is uniformly distributed with upper and lower two rows of pad vias 2;Located at the back of double-sided PCB 7, printing copper film wire 5 between upper and lower two pad vias 2;Located at the front of double-sided PCB 7, it is connected by U-shaped jumper 3 between upper and lower two pad vias 2, and both ends of U-shaped jumper 3 are connected with copper film wire 5 by penetrating pad via 2.

[0022] Copper film wire 5 is equipped with at least 7, and adjacent two copper film wires are equal in length, equidistant, and mutually parallel.

[0023] U-shaped jumper 3 is equipped with at least 6, and adjacent two U-shaped jumpers are equal in length, equidistant, and mutually parallel.

[0024] The height distance between U-shaped jumper 3 and the front of double-sided PCB 7 is 1.8-2.5mm.

[0025] Diode 1 is equipped with at least 4.

[0026] Detuning circuit is connected in series with receiving antenna, and receiving antenna is connected in series by three capacitors in turn.

[0027] Embodiment:

[0028] Please refer to Figure 6 Each channel receiving coil includes receiving antenna LA and detuning circuit DEC. Receiving antenna LA presents four capacitors C1 to C4, which are configured to simplify receiving antenna;Detuning circuit DEC is composed of capacitor C1, detuning inductance L1, diode D1, diode D2, diode D3 and diode D4.

[0029] In the transmitting stage, not only the transmitting signal is transmitted, but also an auxiliary signal HFS as a control signal is additionally transmitted. The auxiliary signal HFS is received by the receiving antenna LA. The diode D1, the diode D2 or the diode D3, the diode D4 are turned on by the auxiliary signal HFS, so that the detuned inductor L1 resonates with the capacitor C1 to form a high resistance, thereby preventing the high-frequency signal from being received by the receiving antenna LA. Since the capacitor C1 is a finished product purchased from the market, the capacitance cannot be adjusted, and the capacitor value has a certain tolerance. In order to make the detuned inductor L1 resonate with the capacitor C1 at a specific frequency, a detuned inductor L1 with continuously adjustable inductance must be designed.

[0030] The resonant frequency f of the detuned circuit is 123MHz, and by selecting the following values of the elements, the detuned circuit will be tuned at the frequency of 123MHz.

[0031] The transformation formula of the resonant circuit is: Wherein, f is the resonant frequency (Hz) of the detuned circuit; L is the inductance (H) of the detuned inductor; C is the capacitance value (F).

[0032] The nominal capacitance value of the capacitor C1 is 15pF, and the tolerance is 5%, so the actual range of the capacitance value of the capacitor C1 is 14.25-15.75pF.

[0033] According to the above transformation formula of the resonant circuit, the inductance variation range of the detuned inductor L1 is 106.3-117.5nH.

[0034] In the embodiment of the utility model, the PCB resonant inductor is composed of 7 copper film conductors on the bottom layer of double-sided PCB, PCB pad through holes and 6 U-shaped jumpers.

[0035] The double-sided PCB is a common 1.6mm thick PCB, and the copper film conductors on the bottom layer of the double-sided PCB are not only parallel to each other, but also equal in length and distance.

[0036] The 7 copper film conductors and the 6 U-shaped jumpers constituting the PCB resonant inductor are respectively located on the front and back sides of the single-sided rigid double-sided PCB.

[0037] To ensure that the height of the entire inductor is the lowest, the height of each U-shaped jumper from the single-sided rigid double-sided PCB is equal and H (mm).

[0038] The jumper shape for adjusting the inductance is U-shaped, and by adjusting the height H (1.8mm-2.5mm) of the U-shaped jumper to the double-sided PCB, the PCB resonant inductor can obtain any inductance in the range of 106.3-117.5nH, please refer to Figure 5 .

Claims

1. A detuning circuit for an MRI radio frequency coil with adjustable resonant inductance comprising a double-sided PCB board, characterized in that: The double-sided PCB (7) is provided with a detuned inductor, one end of the detuned inductor is connected with one end of a capacitor (6), and a plurality of diodes (1) are connected in parallel between the other end of the capacitor (6) and the other end of the detuned inductor; the detuned inductor comprises a copper film lead (5), a pad through hole (2) and a U-shaped jumper wire (3), the double-sided PCB (7) is provided with two rows of pad through holes (2) in a uniform distribution; the copper film lead (5) is printed between the two pad through holes (2) on the back of the double-sided PCB (7); the U-shaped jumper wire (3) is connected between the two pad through holes (2) on the front of the double-sided PCB (7), and the two ends of the U-shaped jumper wire (3) penetrate through the pad through holes (2) and are connected with the copper film lead (5).

2. A detuning circuit for an MRI radio frequency coil having an adjustable resonant inductance according to claim 1, characterized in that: The copper film lead (5) is provided with at least 7 copper film leads, and the adjacent two copper film leads are equal in length, equidistant and parallel to each other.

3. A detuning circuit for an MRI radio frequency coil having an adjustable resonant inductance as claimed in claim 1, characterized in that: The U-shaped jumper wire (3) is provided with at least 6 U-shaped jumper wires, and the adjacent two U-shaped jumper wires are equal in length, equidistant and parallel to each other.

4. A detuning circuit for an MRI radio frequency coil having an adjustable resonant inductance according to claim 1 or 3, characterized in that: The height distance between the U-shaped jumper wire (3) and the front of the double-sided PCB (7) is 1.8-2.5 mm.

5. A detuning circuit for an MRI radio frequency coil having an adjustable resonant inductance as recited in claim 1, wherein: The diode (1) is provided with at least 4 diodes.

6. A detuning circuit for an MRI radio frequency coil having an adjustable resonant inductance as recited in claim 1, wherein: The detuned circuit is connected in series with a receiving antenna, and the receiving antenna is formed by connecting three capacitors in series.

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