utilizing-3d-printing-technology-to-merge-mri-with-histology-protocol

Utilizing 3D Printing Technology to Merge MRI with Histology: A Protocol for Brain Sectioning

Magnetic resonance imaging (MRI) allows for the delineation between normal and abnormal tissue on a macroscopic scale, sampling an entire tissue volume ...

National Institute of Neurological Disorders and Stroke

Evidence from neuroimaging and neurobiological studies suggests that abnormalities in cortical-cortical connectivity involving both local and long-distance scales may be related to autism. The present study analyzed the microstructural integrity of the long-range connectivity related to social cognition and language processing with diffusion tractography among adolescents with autism compared with neurotypical adolescents. Tract-specific analyses were used to study the long-range connectivity responsible for integrating social cognition and language processing. Specifically, three pairs of association fibers and three portions of callosal fiber tracts were analyzed. Generalized fractional anisotropy (GFA) values were measured along individual targeted fiber tracts to investigate alterations in microstructure integrity. The asymmetry patterns were also assessed in three pairs of association fibers. In neurotypical participants, we found a consistent leftward asymmetry in three pairs of association fibers. However, adolescents with autism did not demonstrate such asymmetry. Moreover, adolescents with autism had significantly lower mean GFA in three callosal fiber tracts than neurotypical participants. The loss of leftward asymmetry and reduction of interhemispheric connection in adolescents with autism suggest alterations of the long-range connectivity involved in social cognition and language processing. Our results warrant further investigation by combining developmental and neurocognitive data.

The loss of asymmetry and reduced interhemispheric connectivity in adolescents with autism: a study using diffusion spectrum imaging tractography.

Previous studies have reported white matter abnormalities in patients with obsessive-compulsive disorder (OCD). This study aimed to further explore white matter abnormalities in OCD patients through diffusion spectrum imaging (DSI) and tractography of the two white matter tracts which most probably play an important role in OCD neuropathology: the anterior segment of cingulum bundles (ACB) and the anterior thalamic radiations (ATR). Twelve right-handed, medicated adult patients with OCD and 12 matched controls underwent DSI on a 3 tesla magnetic resonance imaging (MRI) system. Tractography based on DSI data was reconstructed to define the ACB and ATR. Mean generalized fractional anisotropy (GFA) was calculated for each targeted tract and was used to analyze local changes in microstructural integrity along individual tracts. There was a significantly lower mean GFA in both the right ATR and left ACB in OCD subjects compared to controls. OCD subjects also demonstrated decreased left-lateralized asymmetry of the ACB when compared to controls. Furthermore, the mean GFA of the left ACB positively correlated with OCD subjects' obsessive subscores on the Yale-Brown Obsessive-Compulsive scale. This study supports the white matter abnormalities in the ACB and ATR of OCD subjects, which corroborates neurobiological models that posit a defect in fronto-striato-thalamic circuitry in OCD.

White matter abnormalities of fronto-striato-thalamic circuitry in obsessive-compulsive disorder: A study using diffusion spectrum imaging tractography.

The optimum sequence parameters of diffusion spectrum MRI (DSI) on clinical scanners were investigated previously. However, the scan time of approximately 30 min is still too long for patient studies. Additionally, relatively large sampling interval in the diffusion-encoding space may cause aliasing artifact in the probability density function when Fourier transform is undertaken, leading to estimation error in fiber orientations. Therefore, this study proposed a non-Cartesian sampling scheme, body-centered-cubic (BCC), to avoid the aliasing artifact as compared to the conventional Cartesian grid sampling scheme (GRID). Furthermore, the accuracy of DSI with the use of half-sphere sampling schemes, i.e. GRID102 and BCC91, was investigated by comparing to their full-sphere sampling schemes, GRID203 and BCC181, respectively. In results, smaller deviation angle and lower angular dispersion were obtained by using the BCC sampling scheme. The half-sphere sampling schemes yielded angular precision and accuracy comparable to the full-sphere sampling schemes. The optimum b(max) was approximately 4750 s/mm(2) for GRID and 4500 s/mm(2) for BCC. In conclusion, the BCC sampling scheme could be implemented as a useful alternative to the GRID sampling scheme. Combination of BCC and half-sphere sampling schemes, that is BCC91, may potentially reduce the scan time of DSI from 30 min to approximately 14 min while maintaining its precision and accuracy.

Diffusion spectrum MRI using body-centered-cubic and half-sphere sampling schemes.

An element design for receive array coils that decouples from the transmit coil without external active detuning is presented for magnetic resonance imaging (MRI) of mice. The array element uses a crisscrossed geometry on the return paths to reduce the current induced by the transmit coil. Without the need for an external active detune network, the proposed method simplifies the construction of MRI coil systems and also mitigates problems in space-limited MRI applications. In addition, an adaptable scissor-jack-like fixture is presented that allows the receive array to move parallel to the transmit coil to maintain the decoupling condition while maintaining close contact with varying sizes of mice.

Wen-Yang Chiang

Cerebral Microcirculation Section

National Institute of Neurological Disorders and Stroke

Utilizing 3D Printing Technology to Merge MRI with Histology: A Protocol for Brain Sectioning