Abstract: This disclosure provides several methods in LC-MS/MS analysis: (1) a method of LC-MS/MS analysis technique to determine the analyte concentration of a sample wherein an In-Sample Calibration Curve (ISCC) is used instead of an external calibration curve through monitoring of multiple isotopologue transitions of an added stable isotopically labeled (SIL) analyte in each sample via MS/MS in multiple isotopologue reaction monitoring (MIRM) mode; (2) a method of LC-MS/MS analysis to determine the analyte concentration of a sample wherein a One-Sample Multipoint External Calibration Curve (OSMECC) is used instead of a multisample external calibration curve; and (3) a method of LC-MS/MS analysis to determine the analyte concentration of a sample with an analyte concentration beyond the assay's ULOQ wherein isotope sample dilution is used instead of diluting sample physically during sample preparation based on calculating the isotopic abundance of the MIRM channel monitored.

Abstract: A method for determining a position of an RF coil in a magnetic resonance imaging (MRI) system is disclosed. As an example, a center of a field of view (FOV) to be scanned may be adjusted to a magnetic field center of an MRI system, and coordinate values in a coordinate system for shape-characteristic points of the FOV may be determined, where an origin of the coordinate system is located at the magnetic field center of the MRI system. A preset gradient magnetic field may be applied to the FOV, and coil units respectively covering the shape-characteristic points may be determined. An effective region may be obtained by connecting the determined coil units according to the shape of the FOV, and a coil unit located in the effective region may be determined as an effective coil unit for imaging the FOV by the MRI system.

Abstract: Impedance matching circuits and methods for radio frequency (RF) transmission coil are disclosed. An example impedance matching circuit includes a coil matching circuit, a RF power detection circuit, and a spectrometer. The spectrometer outputs an output voltage reversely applied on a varactor diode of the coil matching circuit. An impedance of the coil matching circuit is changed based on the output voltage. The spectrometer outputs a RF transmission signal to the RF power detection circuit, receives a power of a RF reflected signal corresponded to the output voltages. The spectrometer receives powers of different RF reflected signals corresponded to different output voltages, and assigns an output voltage corresponded to a minimum power of the RF reflected signals as an impedance matching voltage, where an equivalent impedance of the coil matching circuit and the RF transmission coil matches with an impedance of RF transmission lines.

Abstract: A method for determining a position of an RF coil in a magnetic resonance imaging (MRI) system is disclosed. As an example, a center of a field of view (FOV) to be scanned may be adjusted to a magnetic field center of an MRI system, and coordinate values in a coordinate system for shape-characteristic points of the FOV may be determined, where an origin of the coordinate system is located at the magnetic field center of the MRI system. A preset gradient magnetic field may be applied to the FOV, and coil units respectively covering the shape-characteristic points may be determined. An effective region may be obtained by connecting the determined coil units according to the shape of the FOV, and a coil unit located in the effective region may be determined as an effective coil unit for imaging the FOV by the MRI system.

Abstract: A method for positioning a radio frequency (RF) receiver coil in a Magnetic Resonance Imaging (MRI) system is provided. In one example method, a distance from a center of the RF receiver coil to one end of a support bed for carrying a subject and a distance from one end of the support bed to an imaging center of the MRI system may be obtained after locations of the RF receiver coil, the subject, and the support bed may be fixed. A distance from the center of the RF receiver coil to the imaging center of the MRI system may be obtained based on the obtained two distances. Moving the support bed a displacement equal to the distance from the center of the RF receiver coil to the imaging center of the MRI system may enable centering of the RF receiver coil on the imaging center of the MRI system.

Abstract: Impedance matching circuits and methods for radio frequency (RF) transmission coil are disclosed. An example impedance matching circuit includes a coil matching circuit, a RF power detection circuit, and a spectrometer. The spectrometer outputs an output voltage reversely applied on a varactor diode of the coil matching circuit. An impedance of the coil matching circuit is changed based on the output voltage. The spectrometer outputs a RF transmission signal to the RF power detection circuit, receives a power of a RF reflected signal corresponded to the output voltages. The spectrometer receives powers of different RF reflected signals corresponded to different output voltages, and assigns an output voltage corresponded to a minimum power of the RF reflected signals as an impedance matching voltage, where an equivalent impedance of the coil matching circuit and the RF transmission coil matches with an impedance of RF transmission lines.