Contrast enhancement methods in sodium MR imaging: a new emerging technique by ProQuest


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									Vol.2, No.6, 445-457 (2009)                                                                                            JBiSE

Contrast enhancement methods in sodium MR imaging: a
new emerging technique
Rakesh Sharma1, Avdhesh Sharma2, Soonjo Kwon3, Ross Booth3
 Department of Medicine, Columbia University, New York, USA; 2Image Processing Lab, Department of Electrical Engineering,
Maharana Pratap A&T University, Udaipur Rajasthan, India; 3Biological Engineering, Utah State University, Logan, USA.

Received 23 August 2008; revised 20 July 2009; accepted 25 July 2009.

ABSTRACT                                                           pulse sequences are research tools of sodium
                                                                   contrast enhancement in brain, cardiac and
Background: In the last decade, sodium mag-                        tumor imaging. The optimized MRI scan pa-
netic resonance imaging was investigated for its                   rameters in quantum filter techniques generate
potential as a functional cardiac imaging tool for                 contrast in intracellular sodium MR images
ischemia. Later interest was developed in con-                     without using invasive contrast shift agents.
trast enhancement for intracellular sodium. Lit-                   Still, validity and clinical utility are in question.
tle success was reported to suppress extracel-
lular sodium resulting in the intracellular so-                    Keywords: Sodium MRI; Double Quantum; Inver-
dium MRI image acquisition using quantum fil-                      sion Recovery; Contrast Enhancement; Cancer
ters or sodium transition states as contrast
properties. Now its clinical application is ex-                    1. BACKGROUND
panding as a new challenge in brain and other
                                                                   Sodium-23 (Na-23) nuclei are in abundance in the body
cancer tumors. Contrast enhancement: We
                                                                   but exhibit poor magnetic resonance sensitivity and
highlight the physical principles of sodium MRI
                                                                   serve as sodium MRI clinical imaging modalities. The
in three different pulse sequences using filters
(single quantum, multiple quantum, and triple                      sodium Na-23 nucleus is detectable by MRI due to its
quantum) meant for sodium contrast enhance-                        3/2 spin existing as -3/2, -1/2, 0, ½, 3/2 (5 states).
ment. The optimization of scan parameters, i.e.                    Physical nature of sodium-23 with spin = 3/2 is suitable
times of echo delay (TE), inversion recovery (TI)                  to have a nonvanishing magnetic moment and Larmor
periods, and utility of Dysprosium (DyPPP) shift                   frequency = 11.26 MHz and exhibits four transition
contrast agents, enhances contrast in sodium                       states with five different energy levels in the static mag-
MRI images. Inversion recovery pulse sequence                      netic field. MR detection sensitivity is very low (9.3 %)
without any shift reagent measures the intra-                      at in vivo concentration (approximately 0.05 %).
cellular sodium concentration to evaluate ische-                      Sodium is abundant (100 %) in living body tissue in
mia, apoptosis and membrane integrity. Mem-                        3/2 spin state. The sodium ion is the predominent cation
brane integrity loss, apoptosis and malignancy                     in the extracellular fluid (139 mmol/L), while its intra-
are results of growth factor loss and poor                         cellular concentration is very low (in the order of 8-10
epithelial capability related with MRI visible in-                 mmol/L), mainly bound with glycosides and proteins.
tracellular sodium concentration. Applications                     The role of increased intracellular sodium due to con-
and limitations: The sodium MR imaging tech-                       certed efflux through Na+/K+ ATP-ase intrinsic action,
nical advances reduced scan time to distinguish                    angiogenesis, and cell proliferation was described in
intracellular and extracellular sodium signals in                  ischemia, hypoxia, arrhythmia, myocardial edema, and
malignant tumors by use of quantum filter tech-                    tumors [1]. The sodium concentration is sensitive to
niques to generate 3D sodium images without                        disease as an indicator of cellular and metabolic integrity.
shift regents. We observed the association of                      Na-23 concentration in tissues is present in the order of
malignancy with increased TSC, and reduced                         tens of millimoles. The low sodium concentration results
apoptosis and epithelial growth factor in breast                   in low signal-to-noise ratio of 23Na MR imaging in long
cancer cells. The validity is still in question.                   imaging times and/or poor spatial resolution. Therefore,
Conclusion: Different modified sodium MRI                          it needs the use of shift reagents or pulse sequences with

SciRes Copyright © 2009                                                 Openly accessible at
446                    R. Sharma et al. / J. Biomedical Science and Engineering 2 (2009) 445-457

filters such as single-, double-, triple-, and multiple       data acquisition techniques with contrast enhancement
quantum (SQ, DQ, TQ and MQ) filters to enha
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