MR Tractography Using PGSE-OGSE ADC Maps for Tumor-Edema Distinction
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Solution Overview
Problem
Standard diffusion MR tractography methods fail to accurately distinguish between tumors and vasogenic edema in the brain, leading to inaccurate nerve fiber mapping and potential damage during surgical procedures.
Innovation Solution
An MR imaging system and method that employs PGSE and OGSE acquisitions to generate ADC maps, followed by an ADC ratio map, which visually distinguishes tumors and vasogenic edema, enabling precise nerve fiber tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard diffusion MR tractography is used, then nerve fiber visualization is provided, but accurate distinction between tumor and vasogenic edema cannot be achieved
Solution Approach 1:
The patent segments the diffusion imaging process into two distinct components: PGSE acquisition for structural tractography and OGSE acquisition for tumor/edema differentiation. By separating these functions into independent acquisition sequences and processing pathways, the system achieves both accurate nerve fiber mapping and reliable tumor/edema distinction without the conflicts present in standard unified approaches
Solution Approach 2:
The patent introduces ADC ratio maps as an intermediary processing step that mediates between the PGSE and OGSE acquisitions. This intermediary product combines information from both acquisition types to provide enhanced contrast between tumor and vasogenic edema, enabling accurate distinction while maintaining nerve fiber visualization capability
2Ease of operation
If FA values are used to identify nerve fibers, then tractography can be generated, but FA values cannot distinguish tumor from vasogenic edema
Solution Approach 1:
The patent adds a new dimensional parameter to the analysis by computing the ratio of ADC values from PGSE and OGSE acquisitions. This ratio creates an additional differentiation dimension that separates tumor from vasogenic edema, while the traditional FA values continue to provide nerve fiber tractography information without interference
3Measurement precision
If single acquisition sequence is used, then imaging time is reduced, but accurate distinction between tumor and edema cannot be achieved
Solution Approach 1:
The patent performs preliminary actions by acquiring OGSE data specifically for tumor/edema differentiation before the main PGSE tractography acquisition. This preliminary OGSE acquisition enables subsequent ratio map computation that provides tumor/edema distinction, allowing the system to achieve accurate differentiation without requiring additional time-consuming post-processing
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate visualization of nerve fibers extending through vasogenic edema, improving surgical planning by distinguishing between tumors and edema, thereby reducing the risk of damaging healthy nerve fibers.
Implementation Method 1
the subject or object is positioned in an examination region within a magnetic field BO that is generated by a main magnet and that extends in a longitudinal or z-direction, where magnetic moments of nuclei, such as protons, align with the magnetic field and precess about the magnetic field in a random order at the nuclei's Larmor frequency
Implementation Method 2
An excitation radiofrequency (RF) field B1, which is in a transverse or x-y plane and near the Larmor frequency, is generated by a coil and 'flips' the net magnetic moment of the nuclei from the z-direction to the x-y plane
Implementation Method 3
Magnetic field gradients (Gx, Gy, and Gz) are employed to encode the MR signals and scan through a k-space
Implementation Method 4
An MR signal is emitted by the nuclei as the magnetic moment returns to the z-direction
Data Source
AI summary
A magnetic resonance (MR) imaging system includes a main magnet configured to generate a magnetic field, gradients coils configured to generate time varying gradient magnetic fields, a radiofrequency (RF) transmit coil configured to generate RF signals, a controller configured to control the gradient and RF transmit coil based on a first sequence that includes a pulse gradient spin echo (PGSE) acquisition and an oscillating gradient spin echo (OGSE) acquisition, an RF receive coil configured to receive first MR signals generated in response to the PGSE and OGSE acquisitions, an image reconstructor configured to process the first MR signals and generate a first apparent diffusion coefficient (ADC) map for the PGSE acquisition and a second ADC map for the OGSE acquisition, and a processor configured to generate a seed point map based on the first and second ADC maps, wherein the seed point map visually distinguishes tumor and vasogenic edema.