For the reconstruction of time-domain fluorescence molecular lifetime tomography, conventional methods based on the Laplace or Fourier transform utilize only part of the information from the measurement data, and rely on the selection of transformation factors. To make the best of all the measurement data, a direct reconstruction algorithm is proposed. The fluorescence yield map is first reconstructed with a full-time gate, and then an objective function for the inverse lifetime tomography (instead of the lifetime) is developed so as to avoid dealing with the singularity of the zero points in the lifetime image. Through simulations and physical phantom experiments, the proposed algorithm is demonstrated to have high localization accuracy for fluorescent targets, high quantification accuracy for fluorescence lifetime, and good contrast between different fluorescence targets.
BackgroundMR imaging has been applied to determine therapeutic response to glucocorticoid (GC) before treatment in thyroid‐associated ophthalmopathy (TAO), while the performance was still poor.PurposeTo investigate the value of T2‐weighted imaging (T2WI)‐derived radiomics for pretreatment determination of therapeutic response to GC in TAO patients, and compare its diagnostic performance with that of semiquantitative parameters.Study TypeRetrospective.PopulationA total of 110 patients (49 ± 12 years; male/female, n = 48/62; responsive/unresponsive, n = 62/48), divided into training (n = 78) and validation (n = 32) cohorts.Field Strength/Sequence3.0 T, T2‐weighted fast spin echo.AssessmentW.C. and H.H. (6 and 10 years of experience, respectively) performed the measurements. Maximum, mean, and minimum signal intensity ratios (SIRs) of extraocular muscle (EOM) bellies were collected to construct a semiquantitative imaging model. Radiomics features from volumes of interest covering EOM bellies were extracted and three machine learning‐based (logistic regression [LR]; decision tree [DT]; support vector machine [SVM]) models were built.Statistical TestsThe diagnostic performances of models were evaluated using receiver operating characteristic curve analyses, and compared using DeLong test. Two‐sided P < 0.05 was considered statistically significant.ResultsThe responsive group showed higher minimum signal intensity ratio (SIRmin) of EOMs than the unresponsive group (training: 1.46 ± 0.34 vs. 1.18 ± 0.39; validation: 1.44 ± 0.33 vs. 1.19 ± 0.20). In both cohorts, LR‐based radiomics model demonstrated good diagnostic performance (area under the curve [AUC] = 0.968, 0.916), followed by DT‐based (AUC = 0.933, 0.857) and SVM‐based models (AUC = 0.919, 0.855). All three radiomics models outperformed semiquantitative imaging model (SIRmin: AUC = 0.805) in training cohort. In validation cohort, only LR‐based radiomics model outperformed that of SIRmin (AUC = 0.745). The nomogram integrating LR‐based radiomics signature and disease duration further elevated the diagnostic performance in validation cohort (AUC: 0.952 vs. 0.916, P = 0.063).Data ConclusionT2WI‐derived radiomics of EOMs, together with disease duration, provides a promising noninvasive approach for determining therapeutic response before GC administration in TAO patients.Level of Evidence3Technical EfficacyStage 4
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