Development and validation of an open source quantification tool for DSC-MRI studies

DSC MR Perfusion at 7T MRI: An Initial Single-Center Study for Validity and Practicability

BACKGROUND AND PURPOSE

DSC perfusion is an advanced imaging technique routinely used at 1.5T and 3T MRI. However, its utility is not well known in 7T MRI systems. We aim to evaluate if DSC perfusion is a valid and practicable tool at 7T MRI.

MATERIALS AND METHODS

A successful DSC perfusion was performed in 9 patients with an FDA-approved 7T MRI system (Siemens Terra with 1tx/32rx Nova head coil) in 2023. Half-dose contrast was administered by hand, followed by saline flush. Acquisition was initiated 45 seconds before contrast injection. Voxel size was 1.5 × 1.5 × 1.6 mm3. Perfusion maps were generated by using either SyngoVia or DynaSuite software. Parameters including relative CBV (rCBV), relative CBF (rCBF), relative MTT (rMTT), and relative TTP (rTTP) were measured in 5 anatomic locations bilaterally (precentral gyrus, middle frontal gyrus, corona radiata, thalamus, occipital cortex) and enhancing lesions if present. Normalized ratios of rCBV (nrCBV), rCBF (nrCBF), rMTT (nrMTT), and rTTP (nrTTP) were calculated and compared on boxplots. Two neuroradiologists reviewed each scan visually by using a 5-point Likert scale regarding imaging quality and artifacts. Qualitative and quantitative assessments were made on DSC perfusion in cases with enhanced target lesions.

RESULTS

Uploading the source images to imaging software took approximately 30 minutes to a few hours. In a few circumstances, large data caused software crashes. Map generation took approximately 10-15 minutes. Susceptibility artifacts varied from mild to moderate in cerebellum, temporal lobes, brainstem, and basal ganglia and none to minimal in the frontal, occipital, and parietal gyri. Map quality was excellent to reasonably good for all cases. The nrCBV, nrCBF, nrMTT, and nrTTP resulted in similar measurements for each anatomic area. Six target lesions were assessed in 2 different patients with well to excellent visualization on fused maps. Three lesions were characterized as tumor progression (1 biopsy-confirmed, 2 unconfirmed), 1 lesion as indeterminant (regressed in follow-up), and 2 lesions as radiation necrosis (1 stable, 1 regressed on follow-up).

CONCLUSIONS

Despite limitations with postprocessing issues, it is possible to reliably measure nrCBV, nrCBF, nrMTT, and nrTTP values with DSC perfusion by using a clinical 7T MRI system, and qualitatively, excellent or reasonably good fusion maps can be generated with high resolution.

Perfusion-weighted software written in Python for DSC-MRI analysis

Introduction

Dynamic susceptibility-weighted contrast-enhanced (DSC) perfusion studies in magnetic resonance imaging (MRI) provide valuable data for studying vascular cerebral pathophysiology in different rodent models of brain diseases (stroke, tumor grading, and neurodegenerative models). The extraction of these hemodynamic parameters via DSC-MRI is based on tracer kinetic modeling, which can be solved using deconvolution-based methods, among others. Most of the post-processing software used in preclinical studies is home-built and custom-designed. Its use being, in most cases, limited to the institution responsible for the development. In this study, we designed a tool that performs the hemodynamic quantification process quickly and in a reliable way for research purposes.

Methods

The DSC-MRI quantification tool, developed as a Python project, performs the basic mathematical steps to generate the parametric maps: cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), signal recovery (SR), and percentage signal recovery (PSR). For the validation process, a data set composed of MRI rat brain scans was evaluated: i) healthy animals, ii) temporal blood-brain barrier (BBB) dysfunction, iii) cerebral chronic hypoperfusion (CCH), iv) ischemic stroke, and v) glioblastoma multiforme (GBM) models. The resulting perfusion parameters were then compared with data retrieved from the literature.

Results

A total of 30 animals were evaluated with our DSC-MRI quantification tool. In all the models, the hemodynamic parameters reported from the literature are reproduced and they are in the same range as our results. The Bland-Altman plot used to describe the agreement between our perfusion quantitative analyses and literature data regarding healthy rats, stroke, and GBM models, determined that the agreement for CBV and MTT is higher than for CBF.

Conclusion

An open-source, Python-based DSC post-processing software package that performs key quantitative perfusion parameters has been developed. Regarding the different animal models used, the results obtained are consistent and in good agreement with the physiological patterns and values reported in the literature. Our development has been built in a modular framework to allow code customization or the addition of alternative algorithms not yet implemented.

Use of some cost-effective technologies for a routine clinical pathology laboratory

Classically, the need for highly sophisticated instruments with important economic costs has been a major limiting factor for clinical pathology laboratories, especially in developing countries. With the aim of making clinical pathology more accessible, a wide variety of free or economical technologies have been developed worldwide in the last few years. 3D printing and Arduino approaches can provide up to 94% economical savings in hardware and instrumentation in comparison to commercial alternatives. The vast selection of point-of-care-tests (POCT) currently available also limits the need for specific instruments or personnel, as they can be used almost anywhere and by anyone. Lastly, there are dozens of free and libre digital tools available in health informatics. This review provides an overview of the state-of-the-art on cost-effective alternatives with applications in routine clinical pathology laboratories. In this context, a variety of technologies including 3D printing and Arduino, lateral flow assays, plasmonic biosensors, and microfluidics, as well as laboratory information systems, are discussed. This review aims to serve as an introduction to different technologies that can make clinical pathology more accessible and, therefore, contribute to achieve universal health coverage.

The Disconnection Hypothesis in Alzheimer's Disease Studied Through Multimodal Magnetic Resonance Imaging: Structural, Perfusion, and Diffusion Tensor Imaging

According to the so-called disconnection hypothesis, the loss of synaptic inputs from the medial temporal lobes (MTL) in Alzheimer's disease (AD) may lead to reduced activity of target neurons in cortical areas and, consequently, to decreased cerebral blood flow (CBF) in those areas. The aim of this study was to assess whether hypoperfusion in parietotemporal and frontal cortices of patients with mild cognitive impairment who converted to AD (MCI-c) and patients with mild AD is associated with atrophy in the MTL and/or microstructural changes in the white matter (WM) tracts connecting these areas. We assessed these relationships by investigating correlations between CBF in hypoperfused areas, mean cortical thickness in atrophied regions of the MTL, and fractional anisotropy (FA) in WM tracts. In the MCI-c group, a strong correlation was observed between CBF of the superior parietal gyri and FA in the parahippocampal tracts (left: r = 0.90, p <  0.0001; right: r = 0.597, p = 0.024), and between FA in the right parahippocampal tract and the right precuneus (r = 0.551, p = 0.041). No significant correlations between CBF in hypoperfused regions and FA in the WM tract were observed in the AD group. These results suggest an association between perfusion deficits and altered WM tracts in prodromal AD, while microvasculature impairments may have a greater influence in more advanced stages. We did not find correlations between cortical thinning in the medial temporal lobes and decreased FA in the WM tracts of the limbic system in either group.