1
|
Viswanathan M, Kurmi Y, Zu Z. Nuclear Overhauser enhancement imaging at -1.6 ppm in rat brain at 4.7T. Magn Reson Med 2024; 91:615-629. [PMID: 37867419 DOI: 10.1002/mrm.29896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2023] [Revised: 09/21/2023] [Accepted: 10/04/2023] [Indexed: 10/24/2023]
Abstract
PURPOSE A new nuclear Overhauser enhancement (NOE)-mediated saturation transfer signal at around -1.6 ppm, termed NOE(-1.6), has been reported at high fields of 7T and 9.4T previously. This study aims to validate the presence of this signal at a relatively low field of 4.7T and evaluate its variations in different brain regions and tumors. METHODS Rats were injected with monocrystalline iron oxide nanoparticles to reduce the NOE(-1.6) signal. CEST signals were measured using different saturation powers before and after injection to assess the presence of this signal. Multiple-pool Lorentzian fits, with/without inclusion of the NOE(-1.6) pool, were performed on CEST Z-spectra obtained from healthy rat brains and rats with 9L tumors. These fits aimed to further validate the presence of the NOE(-1.6) signal and quantify its amplitude. RESULTS The NOE(-1.6) signal exhibited a dramatic change following the injection of monocrystalline iron oxide nanoparticles, confirming its presence at 4.7T. The NOE(-1.6) signal reached its peak at a saturation power of ∼0.75 μT, indicating an optimized power level. The multiple-pool Lorentzian fit without the NOE(-1.6) pool showed higher residuals around -1.6 ppm compared to the fit with this pool, further supporting the presence of this signal. The NOE(-1.6) signal did not exhibit significant variation in the corpus callosum and caudate putamen regions, but it showed a significant decrease in tumors, which aligns with previous findings at 9.4T. CONCLUSION This study successfully demonstrated the presence of the NOE(-1.6) signal at 4.7T, which provides valuable insights into its potential applications at lower field strengths.
Collapse
Affiliation(s)
- Malvika Viswanathan
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Yashwant Kurmi
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| |
Collapse
|
2
|
Cui J, Zhao Y, Wang F, Gochberg DF, Zu Z. Contribution of blood to nuclear Overhauser effect at -1.6 ppm. Magn Reson Med 2022; 87:409-416. [PMID: 34480767 PMCID: PMC8616842 DOI: 10.1002/mrm.28973] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Revised: 07/19/2021] [Accepted: 07/26/2021] [Indexed: 01/04/2023]
Abstract
PURPOSE A relayed nuclear Overhauser enhancement (rNOE) saturation transfer effect at around -1.6 ppm from water, termed NOE(-1.6), was previously reported in rat and human brain, and some publications suggest that it may be related to blood. Here, we studied whether the NOE(-1.6) arises from blood through in vivo and ex vivo experiments. METHODS To evaluate the contribution from in vivo blood to NOE(-1.6), intravascular signals in rat brain were suppressed by two approaches: (1) signal acquisition with a diffusion-weighting of b = 400 s/mm2 ; (2) intravascular injection of 5 mg/kg monocrystalline iron oxide nanoparticle (MION). Ex vivo blood sample was also prepared. The signals were acquired using a chemical exchange saturation transfer (CEST) pulse sequence. Multiple-pool Lorentzian fitting of CEST Z-spectra was performed to quantify the NOE(-1.6) signal. RESULTS There are no significant variations in the fitted in vivo NOE(-1.6) signals when measured with or without diffusion-weighting, but significant signal decease does occur after injection of MION. The NOE(-1.6) signal from ex vivo blood is weaker than that from in vivo tissues. CONCLUSION Considering the relatively small volume of blood in brain, the in vivo experiments with diffusion weighting and the ex vivo experiments both suggest that the NOE(-1.6) is not mainly from blood. The mechanism for the in vivo experiments with MION are less clear. MION not only suppresses MR signals from intravascular space, but changes the susceptibility in the perivascular space. This result suggests that although the NOE(-1.6) is not mainly from blood, it may be vasculature dependent.
Collapse
Affiliation(s)
- Jing Cui
- Vanderbilt University Institute of Imaging Science,
Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
| | - Yu Zhao
- Vanderbilt University Institute of Imaging Science,
Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
| | - Feng Wang
- Vanderbilt University Institute of Imaging Science,
Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
| | - Daniel F. Gochberg
- Vanderbilt University Institute of Imaging Science,
Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
- Deparment of Physics and Astronomy, Vanderbilt University,
Nashville, US
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science,
Nashville, US
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, US
| |
Collapse
|
3
|
Krikken E, van der Kemp WJ, Khlebnikov V, van Dalen T, Los M, van Laarhoven HW, Luijten PR, van den Bosch MA, Klomp DW, Wijnen JP. Contradiction between amide-CEST signal and pH in breast cancer explained with metabolic MRI. NMR IN BIOMEDICINE 2019; 32:e4110. [PMID: 31136039 PMCID: PMC6772111 DOI: 10.1002/nbm.4110] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 04/08/2019] [Accepted: 04/09/2019] [Indexed: 06/09/2023]
Abstract
PURPOSE Metabolic MRI is a noninvasive technique that can give new insights into understanding cancer metabolism and finding biomarkers to evaluate or monitor treatment plans. Using this technique, a previous study has shown an increase in pH during neoadjuvant chemotherapy (NAC) treatment, while recent observation in a different study showed a reduced amide proton transfer (APT) signal during NAC treatment (negative relation). These findings are counterintuitive, given the known intrinsic positive relation of APT signal to pH. METHODS In this study we combined APT MRI and 31 P-MRSI measurements to unravel the relation between the APT signal and pH in breast cancer. Twenty-two breast cancer patients were scanned with a 7 T MRI before and after the first cycle of NAC treatment. pH was determined by the chemical shift of inorganic phosphate (Pi). RESULTS While APT signals have a positive relation to pH and amide content, we observed a direct negative linear correlation between APT signals and pH in breast tumors in vivo. CONCLUSIONS As differentiation of cancer stages was confirmed by observation of a linear correlation between cell proliferation marker PE/Pi (phosphoethanolamine over inorganic phosphate) and pH in the tumor, our data demonstrates that the concentration of mobile proteins likely supersedes the contribution of the exchange rate to the APT signal.
Collapse
Affiliation(s)
- Erwin Krikken
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| | | | - Vitaliy Khlebnikov
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| | | | - Maartje Los
- Department of Medical OncologySt. Antonius ZiekenhuisNieuwegein/UtrechtThe Netherlands
| | - Hanneke W.M. van Laarhoven
- Department of Medical Oncology, Academic Medical Centre AmsterdamCancer Center AmsterdamAmsterdamThe Netherlands
| | - Peter R. Luijten
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| | | | - Dennis W.J. Klomp
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Jannie P. Wijnen
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| |
Collapse
|
4
|
Zöllner HJ, Butz M, Jördens M, Füllenbach ND, Häussinger D, Schmitt B, Wittsack HJ, Schnitzler A. Chemical exchange saturation transfer imaging in hepatic encephalopathy. NEUROIMAGE-CLINICAL 2019; 22:101743. [PMID: 30856541 PMCID: PMC6411782 DOI: 10.1016/j.nicl.2019.101743] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 02/04/2019] [Accepted: 03/02/2019] [Indexed: 01/08/2023]
Abstract
Hepatic encephalopathy (HE) is a common complication in liver cirrhosis and associated with an invasion of ammonia into the brain through the blood-brain barrier. Resulting higher ammonia concentrations in the brain are suggested to lead to a dose-dependent gradual increase of HE severity and an associated impairment of brain function. Amide proton transfer-weighted (APTw) chemical exchange saturation transfer (CEST) imaging has been found to be sensitive to ammonia concentration. The aim of this work was to study APTw CEST imaging in patients with HE and to investigate the relationship between disease severity, critical flicker frequency (CFF), psychometric test scores, blood ammonia, and APTw signals in different brain regions. Whole-brain APTw CEST images were acquired in 34 participants (14 controls, 20 patients (10 minimal HE, 10 manifest HE)) on a 3 T clinical MRI system accompanied by T1 mapping and structural images. T1 normalized magnetization transfer ratio asymmetry analysis was performed around 3 ppm after B0 and B1 correction to create APTw images. All APTw images were spatially normalized into a cohort space to allow direct comparison. APTw images in 6 brain regions (cerebellum, occipital cortex, putamen, thalamus, caudate, white matter) were tested for group differences as well as the link to CFF, psychometric test scores, and blood ammonia. A decrease in APTw intensities was found in the cerebellum and the occipital cortex of manifest HE patients. In addition, APTw intensities in the cerebellum correlated positively with several psychometric scores, such as the fine motor performance scores MLS1 for hand steadiness / tremor (r = 0.466; p = .044) and WRT2 for motor reaction time (r = 0.523; p = .022). Moreover, a negative correlation between APTw intensities and blood ammonia was found for the cerebellum (r = −0.615; p = .007) and the occipital cortex (r = −0.478; p = .045). An increase of APTw intensities was observed in the putamen of patients with minimal HE and correlated negatively with the CFF (r = −0.423; p = .013). Our findings demonstrate that HE is associated with regional differential alterations in APTw signals. These variations are most likely a consequence of hyperammonemia or hepatocerebral degeneration processes, and develop in parallel with disease severity. Ammonia is suggested to play a key role in the emergence of HE. Increase of ammonia in HE patients might be studied with APTw CEST. HE leads to regionally decreasing APTw CEST signal. APTw CEST correlates with blood ammonia levels and psychometric test scores. APTw CEST is possibly linked to hyperammonemia or hepatocerebral degeneration.
Collapse
Affiliation(s)
- Helge Jörn Zöllner
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University Düsseldorf, Germany; Department of Diagnostic and Interventional Radiology, Medical Faculty, Heinrich Heine University Düsseldorf, Germany.
| | - Markus Butz
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University Düsseldorf, Germany
| | - Markus Jördens
- Department of Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich Heine University Düsseldorf, Germany
| | - Nur-Deniz Füllenbach
- Department of Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich Heine University Düsseldorf, Germany
| | - Dieter Häussinger
- Department of Gastroenterology, Hepatology and Infectiology, Medical Faculty, Heinrich Heine University Düsseldorf, Germany
| | - Benjamin Schmitt
- Siemens Ltd. Australia, Healthcare Sector, 160 Herring Road, Macquarie Park, NSW 2113,Australia
| | - Hans-Jörg Wittsack
- Department of Diagnostic and Interventional Radiology, Medical Faculty, Heinrich Heine University Düsseldorf, Germany
| | - Alfons Schnitzler
- Institute of Clinical Neuroscience and Medical Psychology, Medical Faculty, Heinrich Heine University Düsseldorf, Germany
| |
Collapse
|
5
|
Khlebnikov V, van der Kemp WJM, Hoogduin H, Klomp DWJ, Prompers JJ. Analysis of chemical exchange saturation transfer contributions from brain metabolites to the Z-spectra at various field strengths and pH. Sci Rep 2019; 9:1089. [PMID: 30705355 PMCID: PMC6355971 DOI: 10.1038/s41598-018-37295-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 11/19/2018] [Indexed: 11/18/2022] Open
Abstract
Chemical exchange saturation transfer (CEST) exploits the chemical exchange of labile protons of an endogenous or exogenous compound with water to image the former indirectly through the water signal. Z-spectra of the brain have traditionally been analyzed for two most common saturation phenomena: downfield amide proton transfer (APT) and upfield nuclear Overhauser enhancement (NOE). However, a great body of brain metabolites, many of interest in neurology and oncology, contributes to the downfield saturation in Z-spectra. The extraction of these “hidden” metabolites from Z-spectra requires careful design of CEST sequences and data processing models, which is only possible by first obtaining CEST signatures of the brain metabolites possessing labile protons. In this work, we measured exchange rates of all major-for-CEST brain metabolites in the physiological pH range at 37 °C. Analysis of their contributions to Z-spectra revealed that regardless of the main magnetic field strength and pH, five main contributors, i.e. myo-inositol, creatine, phosphocreatine, glutamate, and mobile (poly)peptides, account for ca. 90% of downfield CEST effect. The fundamental CEST parameters presented in this study can be exploited in the design of novel CEST sequences and Z-spectra processing models, which will enable simultaneous and quantitative CEST imaging of multiple metabolites: multicolor CEST.
Collapse
Affiliation(s)
- Vitaliy Khlebnikov
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
| | - Wybe J M van der Kemp
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Hans Hoogduin
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Dennis W J Klomp
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Jeanine J Prompers
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands
| |
Collapse
|
6
|
Lin EC, Li H, Zu Z, Louie EA, Lankford CL, Dortch RD, Does MD, Gore JC, Gochberg DF. Chemical exchange rotation transfer (CERT) on human brain at 3 Tesla. Magn Reson Med 2018; 80:2609-2617. [PMID: 29802641 PMCID: PMC6252284 DOI: 10.1002/mrm.27365] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 03/23/2018] [Accepted: 04/24/2018] [Indexed: 12/14/2022]
Abstract
PURPOSE To test the ability of a novel pulse sequence applied in vivo at 3 Tesla to separate the contributions to the water signal from amide proton transfer (APT) and relayed nuclear Overhauser enhancement (rNOE) from background direct water saturation and semisolid magnetization transfer (MT). The lack of such signal source isolation has confounded conventional chemical exchange saturation transfer (CEST) imaging. METHODS We quantified APT and rNOE signals using a chemical exchange rotation transfer (CERT) metric, MTRdouble . A range of duty cycles and average irradiation powers were applied, and results were compared with conventional CEST analyses using asymmetry (MTRasym ) and extrapolated magnetization transfer (EMR). RESULTS Our results indicate that MTRdouble is more specific than MTRasym and, because it requires as few as 3 data points, is more rapid than methods requiring a complete Z-spectrum, such as EMR. In white matter, APT (1.5 ± 0.5%) and rNOE (2.1 ± 0.7%) were quantified by using MTRdouble with a 30% duty cycle and a 0.5-µT average power. In addition, our results suggest that MTRdouble is insensitive to B0 inhomogeneity, further magnifying its speed advantage over CEST metrics that require a separate B0 measurement. However, MTRdouble still has nontrivial sensitivity to B1 inhomogeneities. CONCLUSION We demonstrated that MTRdouble is an alternative metric to evaluate APT and rNOE, which is fast, robust to B0 inhomogeneity, and easy to process.
Collapse
Affiliation(s)
- Eugene C. Lin
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Hua Li
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Elizabeth A. Louie
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Chris L. Lankford
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
| | - Richard D. Dortch
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
| | - Mark D. Does
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
| | - John C. Gore
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, TN
- Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
| | - Daniel F. Gochberg
- Vanderbilt University Institute of Imaging Science, Nashville, TN
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, TN
| |
Collapse
|
7
|
Krikken E, Khlebnikov V, Zaiss M, Jibodh RA, van Diest PJ, Luijten PR, Klomp DWJ, van Laarhoven HWM, Wijnen JP. Amide chemical exchange saturation transfer at 7 T: a possible biomarker for detecting early response to neoadjuvant chemotherapy in breast cancer patients. Breast Cancer Res 2018; 20:51. [PMID: 29898745 PMCID: PMC6001024 DOI: 10.1186/s13058-018-0982-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 05/10/2018] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The purpose of this work was to investigate noninvasive early detection of treatment response of breast cancer patients to neoadjuvant chemotherapy (NAC) using chemical exchange saturation transfer (CEST) measurements sensitive to amide proton transfer (APT) at 7 T. METHODS CEST images were acquired in 10 tumors of nine breast cancer patients treated with NAC. APT signals in the tumor, before and after the first cycle of NAC, were quantified using a three-pool Lorentzian fit of the z-spectra in the region of interest. The changes in APT were subsequently related to pathological response after surgery defined by the Miller-Payne system. RESULTS Significant differences (P < 0.05, unpaired Mann-Whitney test) were found in the APT signal before and after the first cycle of NAC in six out of 10 lesions, of which two showed a pathological complete response. Of the remaining four lesions, one showed a pathological complete response. No significant difference in changes of APT signal were found between the different pathological responses to NAC treatment (P > 0.05, Kruskal-Wallis test). CONCLUSIONS This preliminary study shows the feasibility of using APT CEST magnetic resonance imaging as a noninvasive biomarker to assess the effect of NAC in an early stage of NAC treatment of breast cancer patients. TRIAL REGISTRATION Registration number, NL49333.041.14/ NTR4980 . Registered on 16 October 2014.
Collapse
Affiliation(s)
- Erwin Krikken
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Vitaliy Khlebnikov
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Moritz Zaiss
- Max Planck Institute for Biological Cybernetics, Tübingen, Germany
| | - Rajni A. Jibodh
- Department of Medical Oncology, Academic Medical Centre Amsterdam, Amsterdam, The Netherlands
| | - Paul J. van Diest
- Department of Pathology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Peter R. Luijten
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Dennis W. J. Klomp
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | | | - Jannie P. Wijnen
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| |
Collapse
|
8
|
Khlebnikov V, Siero JCW, Bhogal AA, Luijten PR, Klomp DWJ, Hoogduin H. Establishing upper limits on neuronal activity-evoked pH changes with APT-CEST MRI at 7 T. Magn Reson Med 2017; 80:126-136. [PMID: 29154463 PMCID: PMC5900917 DOI: 10.1002/mrm.27013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 10/15/2017] [Accepted: 10/25/2017] [Indexed: 11/12/2022]
Abstract
Purpose To detect neuronal activity–evoked pH changes by amide proton transfer–chemical exchange saturation transfer (APT‐CEST) MRI at 7 T. Methods Three healthy subjects participated in the study. A low‐power 3‐dimensional APT‐CEST sequence was optimized through the Bloch‐McConnell equations. pH sensitivity of the sequence was estimated both in phantoms and in vivo. The feasibility of pH–functional MRI was tested in Bloch‐McConnell‐simulated data using the optimized sequence. In healthy subjects, the visual stimuli were used to evoke transient pH changes in the visual cortex, and a 3‐dimensional APT‐CEST volume was acquired at the pH‐sensitive frequency offset of 3.5 ppm every 12.6 s. Results In theory, a three‐component general linear model was capable of separating the effects of blood oxygenation level–dependent contrast and pH. The Bloch‐McConnell equations indicated that a change in pH of 0.03 should be measurable at the experimentally determined temporal signal‐to‐noise ratio of 108. However, only a blood oxygenation level–dependent effect in the visual cortex could be discerned during the visual stimuli experiments performed in the healthy subjects. Conclusions The results of this study suggest that if indeed there are any transient brain pH changes in response to visual stimuli, those are under 0.03 units pH change, which is extremely difficult to detect using the existent techniques. Magn Reson Med 80:126–136, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Collapse
Affiliation(s)
- Vitaliy Khlebnikov
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands
| | - Jeroen C W Siero
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands.,Spinoza Centre for Neuroimaging, Amsterdam, Netherlands
| | - Alex A Bhogal
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands
| | - Peter R Luijten
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands
| | - Dennis W J Klomp
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands
| | - Hans Hoogduin
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands
| |
Collapse
|
9
|
Khlebnikov V, Windschuh J, Siero JC, Zaiss M, Luijten PR, Klomp DW, Hoogduin H. On the transmit field inhomogeneity correction of relaxation-compensated amide and NOE CEST effects at 7 T. NMR IN BIOMEDICINE 2017; 30:e3687. [PMID: 28111824 PMCID: PMC5412922 DOI: 10.1002/nbm.3687] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 11/22/2016] [Accepted: 11/22/2016] [Indexed: 05/08/2023]
Abstract
High field MRI is beneficial for chemical exchange saturation transfer (CEST) in terms of high SNR, CNR, and chemical shift dispersion. These advantages may, however, be counter-balanced by the increased transmit field inhomogeneity normally associated with high field MRI. The relatively high sensitivity of the CEST contrast to B1 inhomogeneity necessitates the development of correction methods, which is essential for the clinical translation of CEST. In this work, two B1 correction algorithms for the most studied CEST effects, amide-CEST and nuclear Overhauser enhancement (NOE), were analyzed. Both methods rely on fitting the multi-pool Bloch-McConnell equations to the densely sampled CEST spectra. In the first method, the correction is achieved by using a linear B1 correction of the calculated amide and NOE CEST effects. The second method uses the Bloch-McConnell fit parameters and the desired B1 amplitude to recalculate the CEST spectra, followed by the calculation of B1 -corrected amide and NOE CEST effects. Both algorithms were systematically studied in Bloch-McConnell equations and in human data, and compared with the earlier proposed ideal interpolation-based B1 correction method. In the low B1 regime of 0.15-0.50 μT (average power), a simple linear model was sufficient to mitigate B1 inhomogeneity effects on a par with the interpolation B1 correction, as demonstrated by a reduced correlation of the CEST contrast with B1 in both the simulations and the experiments.
Collapse
Affiliation(s)
- Vitaliy Khlebnikov
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Johannes Windschuh
- Division of Medical Physics in RadiologyDeutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center]HeidelbergGermany
| | - Jeroen C.W. Siero
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
- Spinoza Centre for NeuroimagingAmsterdamThe Netherlands
| | - Moritz Zaiss
- Division of Medical Physics in RadiologyDeutsches Krebsforschungszentrum (DKFZ) [German Cancer Research Center]HeidelbergGermany
| | - Peter R. Luijten
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Dennis W.J. Klomp
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Hans Hoogduin
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| |
Collapse
|