Abstract

Background: In the last decade, sodium mag-netic resonance imaging was investigated for its potential as a functional cardiac imaging tool for ischemia. Later interest was developed in contrast enhancement for intracellular sodium. Little success was reported to suppress extracellular sodium resulting in the intracellular sodium MRI image acquisition using quantum filters or sodium transition states as contrast properties. Now its clinical application is ex-panding as a new challenge in brain and other cancer tumors. Contrast enhancement: We highlight the physical principles of sodium MRI in three different pulse sequences using filters (single quantum, multiple quantum, and triple quantum) meant for sodium contrast enhancement. The optimization of scan parameters, i.e. times of echo delay (TE), inversion recovery (TI) periods, and utility of Dysprosium (DyPPP) shift contrast agents, enhances contrast in sodium MRI images. Inversion recovery pulse sequence without any shift reagent measures the intracellular sodium concentration to evaluate ischemia, apoptosis and membrane integrity. Membrane integrity loss, apoptosis and malignancy are results of growth factor loss and poor epithelial capability related with MRI visible intracellular sodium concentration. Applications and limitations: The sodium MR imaging technical advances reduced scan time to distinguish intracellular and extracellular sodium signals in malignant tumors by use of quantum filter techniques to generate 3D sodium images without shift regents. We observed the association of malignancy with increased TSC, and reduced apoptosis and epithelial growth factor in breast cancer cells. The validity is still in question. Conclusion: Different modified sodium MRI pulse sequences are research tools of sodium contrast enhancement in brain, cardiac and tumor imaging. The optimized MRI scan pa-rameters in quantum filter techniques generate contrast in intracellular sodium MR images without using invasive contrast shift agents. Still, validity and clinical utility are in questi

Highlights

  • BACKGROUNDSodium-23 (Na-23) nuclei are in abundance in the body but exhibit poor magnetic resonance sensitivity and serve as sodium MRI clinical imaging modalities

  • In the last decade, sodium magnetic resonance imaging was investigated for its potential as a functional cardiac imaging tool for ischemia

  • This paper describes the phases and roles of quantum filters in pulse sequence design to generate intracellular/extracellular sodium contrast, high signal-to-noise ratio, and high resolution in magnetic resonance sodium images by triple-quantum filter and double inversion recovery pulse sequence without using paramagnetic shift reagents

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Summary

BACKGROUND

Sodium-23 (Na-23) nuclei are in abundance in the body but exhibit poor magnetic resonance sensitivity and serve as sodium MRI clinical imaging modalities. The low sodium concentration results in low signal-to-noise ratio of 23Na MR imaging in long imaging times and/or poor spatial resolution It needs the use of shift reagents or pulse sequences with. Later developments were made at high magnetic field MRI scanners using ultrashort echo time sequences and hardware improvements that permitted better spatial resolution with shorter imaging times and better quantitative measurements of tissue sodium concentration without use of shift reagents [6]. This paper describes the phases and roles of quantum filters in pulse sequence design to generate intracellular/extracellular sodium contrast, high signal-to-noise ratio, and high resolution in magnetic resonance sodium images by triple-quantum filter and double inversion recovery pulse sequence without using paramagnetic shift reagents. Single-, and double quantum filter tomographic magnetic resonance pulse sequences generate intracellular sodium images with high signal-to-noise ratio but need paramagnetic shift reagents as contrast agents

Nature of Sodium MR Signal
Quadruple Interactions and Sodium MR Signal
Nature of Sodium Nuclei and MRI Properties
Sodium Relaxation Times
Quantum Filters
Multiple Quantum Pulse Sequence for Origin of Double- and Triple Quantum
MRI PHYSICS OF CONTRAST ENHANCEMENT BY INVERSION RECOVERY AND TWO NULL POINTS
Projection Reconstruction Methods
Three-Dimensional Fourier Techniques
Hybrid Spin Echo Techniques
Surface Coil Techniques and Coil Sensitivity
Rotating Frame Techniques
Spectrally Weighted Twisted Projection Imaging
Biexponential Relaxation Effect and Sodium Concentration Mapping
Simultaneous Quadruple and Double Quantum Na-23 MR Imaging
Double Spin-Echo Imaging and Transverse Relaxation Time
Double-Quantum-Filtered Na-23 MR Spectroscopy
Double Quantum Filtering and Spin-Quantum Coherence
2.10. Chemical Shift Selective Acquisition of Multiple Quantum-Filtered Na-23
2.11. Double Quantum Filtering and Elimination of Intersequence Stimulated Echo
2.12. Multiple Quantum Filters of Arbitrary Phases of Na-23 Nuclei
2.13. Spiral Cardiac Respiratory Gate Multi-Shot Functional MRI as Possibility
CLINICAL SODIUM MRI TRIALS
Chemosensitivity Rapid Assays Using Sodium MRI
Correlation between Intracellular Sodium Signal and Malignancy
Limitations of Sodium Contrast and Sensitivity
Findings
CONCLUSIONS
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