Enhanced separation of brain tumors and edema via diffusion tensor distribution imaging: Illustration with lymphoma cases

Enhanced Separation Of Brain Tumors And Edema Via Diffusion Tensor Distribution Imaging: Illustration With Lymphoma Cases

PURPOSE OR LEARNING OBJECTIVE:

To investigate the clinical potential of diffusion tensor distribution imaging (DTD) for visually differentiating brain tumors and edema from healthy tissue non-invasively.

METHODS:

Multidimensional diffusion (MDD) MRI images were acquired in 2 lymphoma patients on a 3T Discovery 750w system (GE Healthcare) with a 32-channel head coil. Prototype spin-echo EPI sequences were performed using the following parameters: TR/TE=3298/121 ms, in-plane resolution = 3×3 mm2. MDD consisted of 43 linear and 37 spherical b-tensors at b = 100, 700, 1400, 2000 s/mm2. Total scan time was ~5 min. Post-processing of the data was done using dVIEWR powered by MICE Toolkit (www.dviewr.com). The main features related to average cell density (mean diffusivity, MD) and cell elongation (microscopic anisotropy) can be computed within “bins” corresponding to specific tissue types, i.e., “thin” for elongated cells (e.g., white matter), “thick” for densely packed round cells (e.g., grey matter), “sparse” for low cell-density diffusion environments (e.g., edema) and “big” for free water (e.g., ventricles).

RESULTS:

Bin-resolved segmentation maps (SegM) facilitate the identification of edematous regions, captured by the sparse bin (red areas in SegM). These regions surround the investigated lymphomas, themselves mostly captured by the thin bin (green in SegM), indicating that they consist of elongated cells. These cells are randomly oriented, as they appear white (red+green+blue) in the thin-bin mean-orientation maps (see Figure 1). The bin-resolved MD maps’ colors highlight the inverse relationship between MD and average cell density across different tissue types. In particular, the sparse bin exhibits an intermediate MD characteristic of edema.


Figure 1. Diffusion Tensor Distribution (DTD) parameter maps of lymphoma cases.


CONCLUSION:

DTD could provide enhanced visualization tools for radiologists aiming to better separate/characterize healthy and pathological tissues non-invasively.

LIMITATIONS:

This pilot study had limitation in terms of small sample size.

Implementation Of Fast Echo-planar Imaging (EPImix) MRI Sequence For Scan Time Reduction In Critical And Unco-operative Patients

Implementation Of Fast Echo-Planar Imaging (EPImix) MRI Sequence For Scan Time Reduction In Critical And Unco-Operative Patients​

PURPOSE OR LEARNING OBJECTIVE:

To detail how a fast multi-contrast Echo planar Image mix (EPIMix) MRI sequence can lead to a successful reduction in scan time in critical and uncooperative patients compared to the routine clinical brain imaging without compromising the adequate image quality and diagnosis.

METHODS:

A prospective pilot study was conducted on 29 patients requiring emergent brain imaging for concerns of stroke(3), tremors(2), slurring of speech(3), headache(6), memory loss(4), imbalance(2), limb weakness(6), aphasia(1), dementia(1) and Parkinson\’s disease(1) using EPIMix brain imaging sequence on the Discovery 750w 3T, GE Healthcare MR system. EPIMix brain MRI consisting of six contrasts (T2*, T1/T2-FLAIR, T2, DWI, ADC) was acquired in 72-75 seconds. Routine T1w/T2w axial, coronal FLAIR and T2w sagittal images were also concurrently acquired and were correlated with EPIMix images for all the patients. Qualitative analysis of the EPIMix scans was performed by two experienced radiologists for assessment of diagnostic accuracy, artifacts, and image quality.

RESULTS:

The image quality was diagnostic in all of these cases (100%) and the diagnostic performance was comparable between EPIMix and routine clinical MRI without much significant difference, indicating the preservation of adequate image quality on fast EPIMix scans (see Fig.1).



Fig 1. (i) 74-year-old male presented with a history of slurred speech. There is a chronic infarct with gliosis in the right parietal region. The internal content shows hyperintensity on T2WI (A) and T2-FLAIR (B), and hypointensity on T1-FLAIR (D)(arrows); no diffusion restriction on DWI (F) is seen (arrows). (ii) 71-year old male presented with a history of upper limb tremors. Hyperintensity in the right frontal periventricular white matter is seen on T2WI (G) and T2-FLAIR (H) and hypointensity on T1-FLAIR (J)(arrows) with reduced size of the frontal horn, possibly due to ependymitis granularis; no diffusion restriction on DWI is seen to suggest acute ischaemia (L) (arrows). (iii) 82-year-old male presented with a clinical profile of stroke. Cortical & subcortical gliosis is seen in the left middle frontal gyrus. The internal content shows hyperintensity on T2WI (M) and T2-FLAIR (N), and hypointensity on T1-FLAIR (P)(arrows); no diffusion restriction on DWI (R) is seen(arrows).

CONCLUSION:

The pilot study reveals that the EPIMix sequence with rapid scanning can minimize motion artifacts and can be used in unstable patients to evaluate a wide range of brain pathologies without compromising diagnostic image quality.

LIMITATIONS:

EPIMix produces six weighted MRI contrasts in a short time, albeit some image artifacts such as geometric distortion at the skull base and susceptibility artifacts, which were noticed in almost all EPIMix scans. Image degradation with the above-mentioned artifacts is the result of an inherent trade-off between scan time reduction and image quality.

Clinical Experience Using Novel Multidimensional Diffusion Magnetic Resonance Imaging For Characterization Of Tissue Microstructure In Various Brain Pathologies

Clinical Experience Using Novel Multidimensional Diffusion Magnetic Resonance Imaging For Characterization Of Tissue Microstructure In Various Brain Pathologies

TEACHING POINTS:

Multidimensional diffusion (MDD) MRI is a novel imaging technique that provides information enabling
better discrimination of the average rate, microscopic anisotropy, and orientation of diffusion within microscopic tissue environments. We share our experience in the evaluation of MDD’s clinical feasibility in various brain pathologies, where we employed Diffusion Tensor Distribution (DTD) imaging to retrieve nonparametric intravoxel DTDs. DTD allows separation of tissue-specific diffusion profiles of the main brain components, e.g., white matter, grey matter, cerebrospinal fluid and pathological tissue environments such as edema through so-called ‘bins’, namely the ‘thin’, ‘thick’, ‘big’, and the new fourth bin, ‘sparse’. Microscopic anisotropy is not confounded by cell alignment over the voxel scale, unlike conventional fractional anisotropy. Long processing times (a few hours) are needed to generate DTD maps. Current MDD sequences, albeit optimized, feature longer TE compared to conventional diffusion sequences. This imposes a lower image resolution (3×3 mm2) in order to maintain reasonable signal-to-noise ratio. Distortion artefacts could be corrected upon acquisition of a reverse phase-encoding b0 image (for ‘topup’ processing).



TABLE OF CONTENTS/OUTLINE:


1. Basic physics underlying MDD MRI
2. Pros and cons of the sequence
3. Highlight key differential diagnostic points in different brain indications: infections – tuberculomas and cysticercosis, sudden onset of loss of balance, fits, radiation damage and seizures.



The poster can be viewed here: MDD_EE_poster

Initial Clinical Experiences with EPIMIX Sequence in Multiple Brain Pathologies

Initial Clinical Experiences With EPIMIX Sequence In Multiple Brain Pathologies

TEACHING POINTS:

A new multi-contrast echo planar imaging sequence called EPIMIX has been described with a 72-75 second long
sequence providing a range of contrasts from T1 FLAIR, T2-weighted, T2-FLAIR, GRE T2*, Diffusion and ADC
images. We share our experience in a variety of brain conditions, where we employed EPIMIX in addition to
standard of care imaging. The best indications to use EPIMIX are sick or un co-operative patients needing faster
scan acquisition. This sequence runs out of the box, without any modifications necessary, with the capability to
increase the numbers of slices. Inbuilt MOCO (motion correction) aids in improving the image quality in uncooperative patients. Longer processing times are needed, ranging from 6-10 minutes after the scan. Lower
signal to noise ratio leads to increased image grain and poorer visualization of interfaces between lesions and
normal brain parenchyma



TABLE OF CONTENTS/OUTLINE:


1. Basic physics behind the sequence
2. Contrasts generated from the sequence
3. Pros and Cons of the sequence
4. Clinical experience in different indications: Infarcts, Neoplasms, Headache with normal scans, White matter lesions Infections such as tuberculomas or cysticercosis.



The presentation can be viewed here: Initial Clinical Experiences with EPIMIX

Assessment of Brain Tissue Microstructure by Diffusion Tensor Distribution MRI: An Initial Survey of Various Pathologies

Assessment Of Brain Tissue Microstructure By Diffusion Tensor Distribution MRI: An Initial Survey Of Various Pathologies

PURPOSE:

To explore the potential of the novel diffusion tensor distribution (DTD) MRI method for assessment of brain tissue microstructure in terms of nonparametric DTDs and derived parameter maps reporting on cell densities, shapes, orientations, and heterogeneity through a pilot study with single cases of neurocysticercosis, hydrocephalus, stroke, and radiation damage.

METHOD AND MATERIALS:

Four patients were scanned with a <5 min prototype diffusion-weighted (DW) sequence in conjunction to their regular MRI protocol on a GE MR750w 3T. DW images were acquired with spin echo-prepared EPI using TE=121ms, TR=3298ms, and in-plane resolution=3mm. DW was applied with four b-values up to 2000 s/mm2 for 37 isotropic and 43 directional encodings. Raw images were converted to per-voxel DTDs and metrics including means and (co)variances of tensor \”size\” (inversely related to cell density), shape, and orientation, as well as signal fractions from elongated cells (bin1, including WM), nearly isotropic cells (bin2, including GM), and free water (bin3, including CSF).

RESULTS:

Inspection of the parameter maps revealed the following conspicuous features. 1) neurocysticercosis: site of parasite (high bin3_fraction) enclosed by cyst (high bin2_fraction) and edema (high bin2_fraction and bin2_size); 2) radiation: damaged area (high bin1_fraction and bin1_size) surrounded by edema (high bin2_fraction and bin2_size); recurrent tumor: site of removed tumor filled by fluid (high bin3_fraction) lined with a rim of tumor (high bin2_fraction and elevated bin2_size); hydrocephalus: enlarged ventricles rimmed by thin intact WM (high bin1_fraction with bin1_orientation consistent with WM tracts); acute stroke: ischemic tissue (high bin1_fraction, low bin1_size) surrounded by penumbra (high cov_size_shape) (see Figure 1).


Figure 1. Diffusion Tensor Distribution (DTD) parameter maps for a case of acute stroke (arrows).


CONCLUSION:

The custom sequence for DTD can be applied as a minor addition to a clinical MRI protocol and provides novel
microstructural parameter maps with conspicuous features for a range of brain pathologies, thereby encouraging studies with larger patient groups and comparison with current gold standards.

CLINICAL RELEVANCE/APPLICATION:

The DTD method may enable detailed characterization of tissue microstructure in a wide range of brain pathologies.

Acceleration of cerebrospinal fluid flow quantification using Compressed-SENSE: A quantitative comparison with standard acceleration techniques

Acceleration Of Cerebrospinal Fluid Flow Quantification Using Compressed-SENSE: A Quantitative Comparison With Standard Acceleration Techniques

PURPOSE:


CSF quantification study is typically useful in pediatric and elderly population for normal pressure hydrocephalus (NPH). In these population, scan time reduction is particularly useful for patient cooperation and comfort. The potential for CS to accelerate MRI acquisition without hampering image quality will increase patient comfort and compliance in CSF quantification. The purpose of this study is to quantitatively evaluate the impact of Compressed-SENSE (CS), the latest image acceleration technique that combines compressed sensing with parallel imaging (or SENSE), on acquisition time and image quality in MR imaging of the Cerebrospinal fluid quantification study.



METHODS AND MATERIALS:


Standard in-practice CSF quantification study includes a 2D-gradient echo sequence for flow visualization and 2D-gradient echo T1 weighted phase-contrast sequence for flow quantification. Both these sequences were pulse gated using PPU triggering, planned perpendicular to the mid-aqueduct. Both these sequences were modified to obtain higher acceleration with CS (Table 1). Ten volunteers were scanned both, with and without CS, on a 3.0 T wide-bore MRI (Ingenia, Philips Health Systems). The study was approved by the IRB. The flow quantification was done using IntelliSpace Portal, version 9, Q-Flow analysis package (Philips Health Systems). Absolute stroke volume, mean velocity and regurgitant fraction were calculated for flow-quantification sequence with and without CS. Correlation between these three parameters for CS protocol and non-CS protocol were statistically evaluated using Spearman’s rank correlation test.



CONCLUSION:


There is no significant difference in image quality between the current standard of care and CS-based accelerated CSF quantification MRI scans. Compressed-SENSE in this segment can reliably replace the existing scan protocol of higher acquisition time without loss in image quality, quantifications and at the same time with a significant reduction in scan time. The compressed-SENSE technique was originally designed for scan time acceleration of qualitative MRI . In this work, CS proves to have the potential of being extended to quantitative MRI without any significant information loss and 44% scan time reduction.



The EPOS can be viewed here: http://dx.doi.org/10.26044/ecr2020/C-05874

Better insights with ISC when using a multi-sensory fMRI paradigm

SfN, Nov 6, 2018

*D. SINGLA1, J. KAUR2, A. DHAWAN3, V. MAHAJAN4, R. GARG2;
1Electrical Engin., 2Computer Sci. & Engin., Indian Inst. of Technology, Delhi, New Delhi, India; 3All India Inst. of Med. Sci., Delhi, India; 4Mahajan Imaging Pvt. Ltd., Delhi, India

Cue reactivity tasks have been widely employed in fMRI studies. Due to ease of use and compatibility with General Linear Model (GLM), visual cues are predominantly adopted despite their limitation in terms of replicating real life scenario. We propose using Intersubject Correlation Analysis (ISC) to analyse multi sensory paradigms over GLM based analysis and demonstrate advantages of ISC in a multi sensory paradigm using a case study of craving for alcohol in subjects with heavy alcohol use.

Four male young adults (mean age of 24) with heavy alcohol use whose score on Alcohol Use Disorder Identification Test (AUDIT) was greater than 8, were scanned using a 3T GE MRI Scanner while undergoing a multi sensory craving paradigm. The paradigm included 20 blocks with short videos with fixation cross after every block. Ten videos contained alcohol which were matched with neutral videos based on colour, background, presence of faces, emotions, etc. The order of blocks was randomized once and then kept same across all subjects.

Preprocessing of fMRI data included BET extraction, slice timing correction (ascending interleaved), spatial smoothing (FWHM of 5mm) and temporal filtering of 0.01Hz using FSL. Contrast between alcohol cues and fixation was computed using GLM analysis and compared with statistical maps obtained using ISC analysis. Both the statistical maps were corrected for multiple comparisons using False Discovery Rate (FDR) of 0.05.

With GLM analysis, both visual and auditory regions were observed to be activated along with thalamus. With ISC analysis, regions previously known to be involved in craving such as insula, amygdala, hippocampus, caudate, putamen, anterior cingulate cortex (ACC), posterior cingulate cortex (PCC), orbitofrontal cortex (OFC) were also activated. Refer to the attached figure for the two statistical maps and the activated areas.

We hypothesize that craving is nonlinear in nature. Linear Time Invariant (LTI) assumption of GLM makes it harder to capture craving regions when applied to multi-sensory cues. ISC analysis is a better option in this case.

Read more here

Neuroimaging Evidence of Structural and Functional Brain Plasticity After Sight Onset Late in Childhood

(RSNA 2018, Mon Nov 26 2018 3:00PM – 3:10PM ROOM Z21)

PURPOSE

Direct data from human subjects on the validity of the “critical period” of brain development and the permanent detrimental impact of sensory deprivation during this period is lacking. We present evidence for neural plasticity in congenitally blind children following sight restoration.

METHOD AND MATERIALS

Pre- and post-treatment scans of 15 participants (8 to 24 years) who had been treated for bilateral congenital blindness were done on a 3.0T MRI (750w, GE Healthcare) using a 32 channel brain coil. A high-resolution T1-weighted fast spoiled gradient echo anatomical scan was acquired for each participant. To measure blood oxygen level dependent (BOLD) contrast, 35 slices parallel to the AC/PC were acquired using standard T2 weighted gradient-echo echoplanar imaging. A diffusion-weighted scan (40 direction + 5 b0; 74.4 ms TE; 13.7s TR; 2×0.86×0.86 mm3; FOV: 256 x 256 x 72; b = 1000 nm/s2) was performed for diffusion tensor tractography.

RESULTS

Using functional connectivity analyses, we find marked changes in the functional organization of the visual cortex. There is a significant enhancement of cortical decorrelation as a function of time following sight onset. The fusiform facial area (FFA) and occipital facial area (OFA) develop rapidly. Structural imaging demonstrates increase in both volume and thickness of grey matter compared to controls, especially in the fusiform. Analysis of the optic tract in the same participants revealed no change in mean diffusivity (MD) and fractional anisotropy (FA) during the post-treatment period, while the FA of the optic radiation decreased steeply over 2 years.

CONCLUSION

Contrary to our expectation of limited neural plasticity late in the developmental timeline, we find strong evidence of brain malleability using both functional and structural imaging. Our findings help explain the behaviourally observed gains in visual proficiency congenitally blind individuals exhibit as a function of time after sight restoring surgery.

CLINICAL RELEVANCE/APPLICATION

Our study presents evidence for brain plasticity and hence opens up treatment avenues for conditions such as late-diagnosed congenital blindness.