Molecular Subtype Classification in Lower-Grade Glioma with Accelerated DTI.

BACKGROUND AND PURPOSE: Image-based classification of lower-grade glioma molecular subtypes has substantial prognostic value. Diffusion tensor imaging has shown promise in lower-grade glioma subtyping but currently requires lengthy, nonstandard acquisitions. Our goal was to investigate lower-grade glioma classification using a machine learning technique that estimates fractional anisotropy from accelerated diffusion MR imaging scans containing only 3 diffusion-encoding directions. MATERIALS AND METHODS: Patients with lower-grade gliomas (n = 41) (World Health Organization grades II and III) with known isocitrate dehydrogenase (IDH) mutation and 1p/19q codeletion status were imaged preoperatively with DTI. Whole-tumor volumes were autodelineated using conventional anatomic MR imaging sequences. In addition to conventional ADC and fractional anisotropy reconstructions, fractional anisotropy estimates were computed from 3-direction DTI subsets using DiffNet, a neural network that directly computes fractional anisotropy from raw DTI data. Differences in whole-tumor ADC, fractional anisotropy, and estimated fractional anisotropy were assessed between IDH-wild-type and IDH-mutant lower-grade gliomas with and without 1p/19q codeletion. Multivariate classification models were developed using whole-tumor histogram and texture features from ADC, ADC + fractional anisotropy, and ADC + estimated fractional anisotropy to identify the added value provided by fractional anisotropy and estimated fractional anisotropy. RESULTS: ADC (P = .008), fractional anisotropy (P < .001), and estimated fractional anisotropy (P < .001) significantly differed between IDH-wild-type and IDH-mutant lower-grade gliomas. ADC (P < .001) significantly differed between IDH-mutant gliomas with and without codeletion. ADC-only multivariate classification predicted IDH mutation status with an area under the curve of 0.81 and codeletion status with an area under the curve of 0.83. Performance improved to area under the curve = 0.90/0.94 for the ADC + fractional anisotropy classification and to area under the curve = 0.89/0.89 for the ADC + estimated fractional anisotropy classification. CONCLUSIONS: Fractional anisotropy estimates made from accelerated 3-direction DTI scans add value in classifying lower-grade glioma molecular status.

Effect of intra-myocardial Algisyl-LVR™ injectates on fibre structure in porcine heart failure.

Recent preclinical trials have shown that alginate injections are a promising treatment for ischemic heart disease. Although improvements in heart function and global structure have been reported following alginate implants, the underlying structure is poorly understood. Using high resolution ex vivo MRI and DT-MRI of the hearts of normal control swine (n = 8), swine with induced heart failure (n = 5), and swine with heart failure and alginate injection treatment (n = 6), we visualized and quantified the fibre distribution and implant material geometry. Our findings show that the alginate injectates form solid ellipsoids with a retention rate of 68.7% ±â€¯21.3% (mean ±â€¯SD) and a sphericity index of 0.37 ±â€¯0.03. These ellipsoidal shapes solidified predominantly at the mid-wall position with an inclination of -4.9°â€¯±â€¯31.4° relative to the local circumferential direction. Overall, the change to left ventricular wall thickness and myofiber orientation was minor and was associated with heart failure and not the presence of injectates. These results show that alginate injectates conform to the pre-existing tissue structure, likely expanding along directions of least resistance as mass is added to the injection sites. The alginate displaces the myocardial tissue predominantly in the longitudinal direction, causing minimal disruption to the surrounding myofiber orientations.