Active noise cancellation apparatus in MRI apparatus

In an MRI apparatus including a table for allowing a patient to lie down thereon inside a bobbin and a magnetism generator for applying a magnetic field to said patient, disposed at an outer peripheral portion of said bobbin, wherein the improvement comprises an active noise cancellation apparatus for said MRI apparatus including:

• (a) error signal detection means for detecting signals used for calculating noise near ears of said patient lying down on said table;
• (b) noise source signal detection means for detecting a noise source signal produced from an operation of said magnetism generator;
• (c) means for generating a noise cancellation signal by processing said noise source signal detected by said noise source signal detection means so that an amplitude of a signal from said error signal detection means is minimized;
• and
• (d) sound generation means for generating sound in response to said noise cancellation signal;
• wherein said error signal detection means is disposed outside said bobbin, and said means for generating said noise cancellation signal includes means for generating said noise cancellation signal utilizing transmission characteristics of a sound wave transmission path of a space from positions near the ears of said patient to said error signal detection means.

In an MRI apparatus including a table for allowing a patient to lie down thereon inside a bobbin and a magnetism generator for applying a magnetic field to said patient, disposed at an outer peripheral portion of said bobbin, wherein the improvement comprises an active noise cancellation apparatus for said MRI apparatus including:

• (a) error signal detection means for detecting noise near ears of said patient lying down on said table;
• (b) noise source signal detection means for detecting a noise source signal produced from an operation of said magnetism generator;
• (c) means for generating a noise cancellation signal by processing said noise source signal detected by said noise source signal detection means so that an amplitude of a signal from said error signal detection means is minimized;
• and
• (d) sound generation means for generating sound in response to said noise cancellation signal;
• wherein said error signal detection means includes:
• first tubes made of a non-magnetic and non-metallic material, and extended outside said bobbin from near the ears of said patient on said table;
• and
• detection means disposed at the tips of said first tubes outside said bobbin;
• and
• wherein said means for generating said noise cancellation signal includes:
• means for generating said noise cancellation signal utilizing transmission characteristics of a sound wave transmission path of said first tubes ranging from positions near the ears of said patient to said error signal detection means.

In an MRI apparatus including a table for allowing a patient to lie down thereon inside a bobbin and a magnetism generator for applying a magnetic field to said patient, disposed at an outer peripheral portion of said bobbin, wherein the improvement comprises an active noise cancellation apparatus for said MRI apparatus including:

• (a) error signal detection means for detecting noise near ears of said patient lying down on said table;
• (b) noise source signal detection means for detecting a noise source signal produced from an operation of said magnetism generator;
• (c) means for generating a noise cancellation signal by processing said noise source signal detected by said noise source signal detection means so that an amplitude of a signal from said error signal detection means is minimized;
• and
• (d) sound generation means for generating sound in response to said noise cancellation signal;
• wherein said noise source signal detection means includes means for detecting a driving signal of said magnetism generator and further including means for delaying said driving signal inputted to said magnetism generator such that a noise due to driving of said magnetism generator by said inputted driving signal occurs later than said noise cancellation sound wave.

In an MRI apparatus including a table for allowing a patient to lie down thereon inside a bobbin and a magnetism generator for applying a magnetic field to said patient, disposed at an outer peripheral portion of said bobbin, wherein the improvement comprises an active noise cancellation apparatus for said MRI apparatus including:

• (a) error signal detection means for detecting a vibration of said bobbin to calculate noise near ears of said patient lying down on said table;
• (b) noise source signal detection means for detecting a driving signal of said MRI apparatus;
• (c) means for generating a noise cancellation signal having a phase opposite to a phase of said noise source signal from said noise source signal detection means, and having an amplitude proportional to a magnitude of a signal from said error signal detection means;
• and
• (d) sound generation means for vibrating said bobbin in response to said noise cancellation signal.