摘要:
Systems and methods for the delivery of linear accelerator radiotherapy in conjunction with magnetic resonance imaging in which components of a linear accelerator may be placed in shielding containers around a gantry, may be connected with RF waveguides, and may employ various systems and methods for magnetic and radio frequency shielding.
摘要:
Ein Verfahren der Kernspinresonanz(=NMR)-Tomographie zur Untersuchung eines Zielobjekts, bei dem Hochfrequenz(=HF)-Impulse in ein Zielvolumen einstrahlt und/oder HF-Impulse aus dem Zielvolumen detektiert werden, wobei das Zielvolumen durch die Frequenz der HF-Impulse und/oder durch Magnetfeldgradienten bestimmt ist, und wobei das Zielobjekt während der NMR-Datenaufnahme relativ zum NMR-Tomographen bewegt wird, ist dadurch gekennzeichnet, dass die Frequenz der HF-Impulse und/oder die Magnetfeldgradienten während der NMR-Datenaufnahme so verändert werden, dass das von den HF-Impulsen erfasste Zielvolumen während der NMR-Datenaufnahme mit der gleichen Geschwindigkeit und Bewegungsrichtung wie das Zielobjekt relativ zum NMR-Tomographen bewegt wird. Damit wird ein Verfahren zur Untersuchung eines bezüglich des NMR-Tomographen während der NMR-Datenaufnahme bewegten Zielobjekts vorgestellt, das schnell und einfach durchführbar ist.
摘要:
An MR imaging apparatus using NMR phenomenon includes a main magnet, a first, a second and a third gradient field coils, a RF coil, a gradient field controller connected to the first, second and third gradient field coils, a RF controller connected to the RF coil, a waveform generator, a carrier wave generator, an amplitude modulator, a RF controller connected to the RF coil, and a data processor. The waveform generator generates a modulating signal expressed by F(t) = A {cos (ωt) - cos (εωt)} / t , where A is an amplitude coefficient, ε is a non-excitation band coefficient, and ω is a frequency of the modulating signal. The RF controller causes the RF coil, in each pulse sequence, to transmit a RF signal and to apply, to the RF signal, a modulated wave outputted from the amplitude modulator as an MTC pulse having a frequency component slightly offset from a resonance frequency of free water protons, and a resonance frequency component of free water protons. The data processor collects data from the NMR signal detected by the RF coil, and reconstructs a sectional image from the data.
摘要:
Variable voxel shifts required for shifting a 3D structure into a common oblique or contoured slice volume based on an existing 3D image are achieved by effecting variable f(x,y) phase shifts in corresponding frequency domain data parallel to a selected axis dimension and then reconstructing a new three-dimensional image having the 3D structure all located within a common oblique or otherwise contoured slice volume such that it may viewed in a single planar image display without loss of volume resolution. Equivalent convolution processes within the spatial domain may also be employed. Oblique or curved reconstructions can thus be made using either originally acquired frequency domain data (used to construct the original image) or frequency domain data obtained by inverse Fourier transforming the available spatial domain data of the images themselves.
摘要:
A magnetic resonance imaging system includes one or more digital transmitters (B), one or more digital receivers (C), and digital data processing circuitry (D) which are all clocked and controlled by a single clock (F). Each digital transmitter includes a numerically controlled modulated oscillator (20) which processes digital phase and frequency signals to produce an output which addresses a wave-form map stored in a PROM (22). Each wave-form output of the PROM is multiplied (24) by a digital amplitude profile signal to generate phase, frequency, and amplitude modulated digital RF signals. A clock gate (30) controls clocking of the digital modulation to create RF pulses. A digital-to-analog converter (28) converts the digital information to an analog RF pulse which is applied to a subject in an image region. The receivers each include an analog-to-digital converter (60) which digitizes the magnetic resonance signal emanating from the subject in the image region with four fold oversampling. A pair of FIR filters (62a, 62b) multiply the digital resonance signal by digital sine and cosine filter coefficients to create in-phase and out-of-phase digital magnetic resonance signal components. After additional digital filtering (64a, 64b), the digital in-phase and quadrature components are Fourier transformed (70) and accumulated in an image memory (72) to form an image representation.
摘要:
Variable voxel shifts required for shifting a 3D structure into a common oblique or contoured slice volume based on an existing 3D image are achieved by effecting variable f(x,y) phase shifts in corresponding frequency domain data parallel to a selected axis dimension and then reconstructing a new three-dimensional image having the 3D structure all located within a common oblique or otherwise contoured slice volume such that it may viewed in a single planar image display without loss of volume resolution. Equivalent convolution processes within the spatial domain may also be employed. Oblique or curved reconstructions can thus be made using either originally acquired frequency domain data (used to construct the original image) or frequency domain data obtained by inverse Fourier transforming the available spatial domain data of the images themselves.