Abstract:
A list mode image reconstruction method includes a step of dividing list mode data into a plurality of subsets and a step of acquiring a subset balance coefficient based on the number of events in the plurality of subsets.
Abstract:
An analysis method for analyzing a sample includes a first step of acquiring measurement data including a first signal based on the sample and a second signal based on noise added to the first signal as a result of analysis of the sample, a second step of assuming a shape representing the first signal and a shape representing the second signal and modeling the measurement data using Bayesian inference, and a third step of estimating a probability distribution of characteristics of the sample based on the modeled measurement data.
Abstract:
MS1 and MS2 measurements of fractionated samples are performed. Based on the identification results and the S/N ratios of the MS1 peaks, an identification probability estimation model showing a relationship between the cumulative number of MS1 peaks and the number of MS1 peaks successfully identified through the MS2 measurements and identifications performed in ascending order of S/N ratio is created. S/N ratios of the MS1 peaks obtained by MS1 measurements are determined, and probabilities of substances in a target sample are estimated from S/N ratios using the aforementioned model. Optimization of precursor-ion selection and data-accumulation number is defined as the problem of maximizing the sum of identification probabilities of MS1 peaks selected for MS2 measurement, and formulated as an objective function using 0-1 variables. This function is solved as a 0-1 integer programming problem under preset conditions. Optimal precursor ions and data-accumulation numbers are determined from variables of the solution.
Abstract:
An identification probability estimation model, which shows the relationship between the S/N ratios of MS1 peaks and the cumulative number of the peaks in the case where MS2 measurements and identifications is performed in descending order of S/N ratio, is created beforehand from the S/N ratios of MS1 peaks as well as the results of MS1 or MS2 measurements and identifications (success or failure) performed for a number of fractionated samples obtained from a predetermined sample. Based on an evaluated value of the identification probability and that of the identification probability increment, an order of priority of MS2 measurements for a plurality of MS1 peaks is determined, and an MS2 measurement sequence which gives the maximal expectation value of the number of substances to be identified under a limitation on the number of MS2 measurements or other factors is determined.
Abstract:
Provided is a method for quantitatively estimating the probability of substance identification based on the result of an MS2 analysis using a certain MS1 peak as the precursor ion, before performing the MS2 analysis. Based on the result of MS1 and MS2 analyses and substance identification performed for each of a number of fractionated samples obtained from a known preparatory sample, an identification probability estimation model creator grasps m/z and S/N ratios of MS1 peaks having high probabilities of successful identification, calculates a parameter which determines the order of MS1 peaks and a parameter representing an identification probability estimation model, and stores the parameters in a memory. When identifying a substance, an approximate order is calculated for an MS1 peak obtained by the analysis. The identification probability for that peak is estimated from the approximate order with reference to the identification probability estimation model.
Abstract:
To enable a correct and easy discrimination of microorganisms, a microorganism discrimination method includes: acquiring mass spectra related to known microorganisms which belong to the same species and whose subspecies, strains or types are known (S11); retrieving a list describing m/z values of marker-candidate proteins which are supposed to vary in mass among different subspecies, strains or types (S12); creating a mask which gives non-zero values only within a predetermined range including each of the listed m/z values (S14); masking each of the mass spectra (S15); creating wavelet images by performing continuous wavelet transform on the mass spectra (S16); creating a discriminant model by machine learning using, as training data, the wavelet images and information of the subspecies, strains or types of the known microorganisms; and discriminating the subspecies, strain or type of an unknown microorganism by applying a mass spectrum of this microorganism to the discriminant model.