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Whole brain neuroanatomy using tera‐voxel light‐microscopic data sets is of much current interest. A fundamental problem in this field is the mapping of individual brain data sets to a reference space. Previous work has not rigorously quantified in‐vivo to ex‐vivo distortions in brain geometry from tissue processing. Further, existing approaches focus on registering unimodal volumetric data; however, given the increasing interest in the marmoset model for neuroscience research and the importance of addressing individual brain architecture variations, new algorithms are necessary to cross‐register multimodal data sets including MRIs and multiple histological series. Here we present a computational approach for same‐subject multimodal MRI‐guided reconstruction of a series of consecutive histological sections, jointly with diffeomorphic mapping to a reference atlas. We quantify the scale change during different stages of brain histological processing using the Jacobian determinant of the diffeomorphic transformations involved. By mapping the final image stacks to the ex‐vivo post‐fixation MRI, we show that (a) tape‐transfer assisted histological sections can be reassembled accurately into 3D volumes with a local scale change of 2.0 ± 0.4% per axis dimension; in contrast, (b) tissue perfusion/fixation as assessed by mapping the in‐vivo MRIs to the ex‐vivo post fixation MRIs shows a larger median absolute scale change of 6.9 ± 2.1% per axis dimension. This is the first systematic quantification of local metric distortions associated with whole‐brain histological processing, and we expect that the results will generalize to other species. These local scale changes will be important for computing local properties to create reference brain maps. [ABSTRACT FROM AUTHOR]

Background Diffusion tensor imaging (DTI) is a magnetic resonance imaging (MRI) technique that reflects the Brownian motion of water molecules constrained within brain tissue. Fractional anisotropy (FA) is one of the most commonly measured DTI parameters, and can be applied to quantitative analysis of white matter as tract-based spatial statistics (TBSS) and voxel-wise analysis. Purpose To show an association between metallic implants and the results of statistical analysis (voxel-wise group comparison and TBSS) for fractional anisotropy (FA) mapping, in DTI of healthy adults. Material and Methods Sixteen healthy volunteers were scanned with 3-Tesla MRI. A magnetic keeper type of dental implant was used as the metallic implant. DTI was acquired three times in each participant: (i) without a magnetic keeper (FAnon1); (ii) with a magnetic keeper (FAimp); and (iii) without a magnetic keeper (FAnon2) as reproducibility of FAnon1. Group comparisons with paired t-test were performed as FAnon1 vs. FAnon2, and as FAnon1 vs. FAimp. Results Regions of significantly reduced and increased local FA values were revealed by voxel-wise group comparison analysis (a P value of less than 0.05, corrected with family-wise error), but not by TBSS. Conclusion Metallic implants existing outside the field of view produce artifacts that affect the statistical analysis (voxel-wise group comparisons) for FA mapping. When statistical analysis for FA mapping is conducted by researchers, it is important to pay attention to any dental implants present in the mouths of the participants. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the use of non-Gaussian diffusion-weighted imaging (q-space imaging [QSI]) to estimate diurnal changes in intervertebral disc (IVD) microstructure. Materials and Methods: IVDs of 15 male subjects (mean age, 27.3 years; mean body mass index, 22.50 kg/ m2) were investigated once in the morning, less than 30 min after rising, and a second time in the evening after at least 10 h of normal physical activity, using 3 Tesla (T) MR imaging. T2 mapping and QSI data values (apparent diffusion coefficient [ADC], root mean square displacement [RMSD], and apparent kurtosis coefficient [AKC]) were calculated and compared between the morning and evening imaging sessions. Results: The T2, ADC, and RMSD values showed a significant decrease in the evening (175.8 ±49.5 ms, 1.56±0.32 10-3mm2/s and 40.0 ± 3.0 μm, respectively; P<0.05 for all values; paired t-test), when compared with the morning values (226.5± 83.8 ms, 1.69 ± 0.29 10-3mm2/s and 45.2±2.9 μm, respectively). The AKC value showed a significant increase in the evening (0.67±0.08), when compared with the morning value (0.58± 0.04; P<0.05). Conclusion: The RMSD and AKC values obtained from QSI analysis may be biomarkers for IVD diurnal microstructural changes. [ABSTRACT FROM AUTHOR]

• We employed a sufficient sample size to overcome inter-individual variability and noise. • We showed the structural and functional brain connectivity within the marmoset species. • We demonstrated a significantly high similarity in structural neural connections. • We identified 7 networks under the commonly used isoflurane inhalation anesthesia. • We were able to delineate the features of isoflurane anesthesia in common marmosets. The common marmoset is an essential model for understanding social cognition and neurodegenerative diseases. This study explored the structural and functional brain connectivity in a marmoset under isoflurane anesthesia, aiming to statistically overcome the effects of high inter-individual variability and noise-related confounds such as physiological noise, ensuring robust and reliable data. Similarities and differences in individual subject data, including assessments of functional and structural brain connectivities derived from resting-state functional MRI and diffusion tensor imaging were meticulously captured. The findings highlighted the high consistency of structural neural connections within the species, indicating a stable neural architecture, while functional connectivity under anesthesia displayed considerable variability. Through independent component and dual regression analyses, several distinct brain connectivities were identified, elucidating their characteristics under anesthesia. Insights into the structural and functional features of the marmoset brain from this study affirm its value as a neuroscience research model, promising advancements in the field through fundamental and translational studies. [ABSTRACT FROM AUTHOR]

The olfactory nerve map describes the topographical neural connections between the olfactory epithelium in the nasal cavity and the olfactory bulb. Previous studies have constructed the olfactory nerve maps of rodents using histological analyses or transgenic animal models to investigate olfactory nerve pathways. However, the human olfactory nerve map remains unknown. Here, we demonstrate that high-field magnetic resonance imaging and diffusion tensor tractography can be used to visualize olfactory sensory neurons while maintaining their three-dimensional structures. This technique allowed us to evaluate the olfactory sensory neuron projections from the nasal cavities to the olfactory bulbs and visualize the olfactory nerve maps of humans, marmosets and mice. The olfactory nerve maps revealed that the dorsal-ventral and medial-lateral axes were preserved between the olfactory epithelium and olfactory bulb in all three species. Further development of this technique might allow it to be used clinically to facilitate the diagnosis of olfactory dysfunction. Combined high-field MRI and DTI analyses in post-mortem mouse, marmoset, and human samples provide insight into the neural connections between nasal cavities and olfactory bulbs. [ABSTRACT FROM AUTHOR]

• T1 relaxation time of the drowning lung was linearly dependent on water temperature. • In the lung areas of the same individuals, T2 value decreased after drowning. • Basic data of drowning lung in postmortem MRI were provided. Japanese individuals have a unique culture of soaking in a bathtub, and forensic pathologists have experienced fatal cases due to drowning. However, T1 and T2 relaxation times of a drowning lung are poorly documented. In the present study, we investigated the relationship between drowning water temperature and T1 and T2 relaxation times of drowning lung tissues at 9.4 T MRI (Bruker, BioSpec94/20USR). The mice used as animal drowning models were directly submerged in freshwater. Water temperature was set to 8 °C–10 °C (cold), 20 °C–22 °C (normal), 30 °C, and 45 °C. The regions of interest (ROIs) on the axial section of the third slice were set at the central and peripheral areas of each—the left and the right—lung. T1 relaxation times measured immediately after death differed by the presence or absence of soaking water, except in case of cold water temperature. In the drowning groups, T1 relaxation time showed a linear dependency on water temperature. By contrast, T2 relaxation time was almost constant regardless of the presence of drowning under the same temperature condition; when compared in the lung areas of the same individuals, the times were uniformly reduced in drowning models. To minimize the effects of hypostasis and decomposition, we performed measurements immediately after death and were able to determine the noticeable difference in drowning water temperature. These results may be useful for qualitative assessments of a drowning lung and may serve as a basis when imaging the human body during forensic autopsy cases. [ABSTRACT FROM AUTHOR]