In vivo phosphorus magnetic resonance spectroscopic imaging of the whole human liver at 7 T using a phosphorus whole‐body transmit coil and 16‐channel receive array: Repeatability and effects of principal component analysis‐based denoising
Abstract:Quantitative three‐dimensional (3D) imaging of phosphorus (31P) metabolites is potentially a promising technique with which to assess the progression of liver disease and monitor therapy response. However, 31P magnetic resonance spectroscopy has a low sensitivity and commonly used 31P surface coils do not provide full coverage of the liver. This study aimed to overcome these limitations by using a 31P whole‐body transmit coil in combination with a 16‐channel 31P receive array at 7 T. Using this setup, we deter… Show more
“…3). 51 Future development of motion correction techniques is expected to improve spectral quality in the presence of (respiratory) motion, such as for pancreatic tumors, and to reduce signal ghosting from tissues outside the regions of interest.…”
Background: The incidence of liver and pancreatic cancer is rising. Patients benefit from current treatments, but there are limitations in the evaluation of (early) response to treatment. Tumor metabolic alterations can be measured noninvasively with phosphorus ( 31 P) magnetic resonance spectroscopy (MRS). Purpose: To conduct a quantitative analysis of the available literature on 31 P MRS performed in hepatopancreatobiliary cancer and to provide insight into its current and potential for therapy (non-) response assessment. Population: Patients with hepatopancreatobiliary cancer. Field Strength/Sequence: 31 P MRS. Assessment: The PubMed, EMBASE, and Cochrane library databases were systematically searched for studies published to 17 March 17, 2022. All 31 P MRS studies in hepatopancreatobiliary cancer reporting 31 P metabolite levels were included. Statistical Tests: Relative differences in 31 P metabolite levels/ratios between patients before therapy and healthy controls, and the relative changes in 31 P metabolite levels/ratios in patients before and after therapy were determined. Results: The search yielded 10 studies, comprising 301 subjects, of whom 132 (44%) healthy volunteers and 169 (56%) patients with liver cancer of various etiology. To date, 31 P MRS has not been applied in pancreatic cancer. In liver cancer, alterations in levels of 31 P metabolites involved in cell proliferation (phosphomonoesters [PMEs] and phosphodiesters [PDEs]) and energy metabolism (ATP and inorganic phosphate [Pi]) were observed. In particular, liver tumors were associated with elevations of PME/PDE and PME/Pi compared to healthy liver tissue, although there was a broad variety among studies (elevations of 2%-267% and 21%-233%, respectively). Changes in PME/PDE in liver tumors upon therapy were substantial, yet very heterogeneous and both decreases and increases were observed, whereas PME/Pi was consistently decreased after therapy in all studies (À13% to À76%). Data Conclusion: 31 P MRS has great potential for treatment monitoring in oncology. Future studies are needed to correlate the changes in 31 P metabolite levels in hepatopancreatobiliary tumors with treatment response.
“…3). 51 Future development of motion correction techniques is expected to improve spectral quality in the presence of (respiratory) motion, such as for pancreatic tumors, and to reduce signal ghosting from tissues outside the regions of interest.…”
Background: The incidence of liver and pancreatic cancer is rising. Patients benefit from current treatments, but there are limitations in the evaluation of (early) response to treatment. Tumor metabolic alterations can be measured noninvasively with phosphorus ( 31 P) magnetic resonance spectroscopy (MRS). Purpose: To conduct a quantitative analysis of the available literature on 31 P MRS performed in hepatopancreatobiliary cancer and to provide insight into its current and potential for therapy (non-) response assessment. Population: Patients with hepatopancreatobiliary cancer. Field Strength/Sequence: 31 P MRS. Assessment: The PubMed, EMBASE, and Cochrane library databases were systematically searched for studies published to 17 March 17, 2022. All 31 P MRS studies in hepatopancreatobiliary cancer reporting 31 P metabolite levels were included. Statistical Tests: Relative differences in 31 P metabolite levels/ratios between patients before therapy and healthy controls, and the relative changes in 31 P metabolite levels/ratios in patients before and after therapy were determined. Results: The search yielded 10 studies, comprising 301 subjects, of whom 132 (44%) healthy volunteers and 169 (56%) patients with liver cancer of various etiology. To date, 31 P MRS has not been applied in pancreatic cancer. In liver cancer, alterations in levels of 31 P metabolites involved in cell proliferation (phosphomonoesters [PMEs] and phosphodiesters [PDEs]) and energy metabolism (ATP and inorganic phosphate [Pi]) were observed. In particular, liver tumors were associated with elevations of PME/PDE and PME/Pi compared to healthy liver tissue, although there was a broad variety among studies (elevations of 2%-267% and 21%-233%, respectively). Changes in PME/PDE in liver tumors upon therapy were substantial, yet very heterogeneous and both decreases and increases were observed, whereas PME/Pi was consistently decreased after therapy in all studies (À13% to À76%). Data Conclusion: 31 P MRS has great potential for treatment monitoring in oncology. Future studies are needed to correlate the changes in 31 P metabolite levels in hepatopancreatobiliary tumors with treatment response.
“…26 31 P MRS of liver tumors has been performed at magnetic field strengths of 1.5 and 3 T and, because of the low intrinsic sensitivity of 31 P MRS, rather large voxel sizes have been used (up to 560 mL). Moreover, most studies made use of 31 P radiofrequency (RF) transmit-receive surface coils, which have a limited penetration depth and with which therefore metastases may be missed. In a recent study, we have shown that using a 31 P whole-body transmit coil [27][28][29] in combination with a 16-channel receive array 30 at 7 T, it was feasible to acquire 31 P MRSI data with a nominal voxel size of 8 mL and full liver coverage, yielding insight into spatial variations of 31 P metabolites within the healthy liver.…”
Section: Introductionmentioning
confidence: 99%
“…Moreover, most studies made use of 31 P radiofrequency (RF) transmit-receive surface coils, which have a limited penetration depth and with which therefore metastases may be missed. In a recent study, we have shown that using a 31 P whole-body transmit coil [27][28][29] in combination with a 16-channel receive array 30 at 7 T, it was feasible to acquire 31 P MRSI data with a nominal voxel size of 8 mL and full liver coverage, yielding insight into spatial variations of 31 P metabolites within the healthy liver. 31 In addition to the sensitivity gain at 7 T, 32,33 the spectral resolution is also enhanced in comparison with lower field strengths, allowing separate detection of the individual PMEs (phosphocholine [PC] and phosphoethanolamine [PE]) and PDEs (glycerophosphocholine [GPC] and glycerophosphoethanolamine [GPE]), 34,35 which may provide even more sensitive and/or specific markers of tumor treatment response.…”
Section: Introductionmentioning
confidence: 99%
“…16-channel body receive array at 7 T, with a field of view covering the full abdomen and a nominal voxel size of 20-mm isotropic. From the 31 P MRSI data, 12 31 P metabolite signals were quantified. Prior to chemotherapy initiation, both PMEs, that is, phosphocholine (PC) and phosphoethanolamine (PE), were significantly higher in all metastases compared with the levels previously determined in the liver of healthy volunteers.…”
Methods for early treatment response evaluation to systemic therapy of liver metastases are lacking. Tumor tissue often exhibits an increased ratio of phosphomonoesters to phosphodiesters (PME/PDE), which can be noninvasively measured by phosphorus magnetic resonance spectroscopy (31P MRS), and may be a marker for early therapy response assessment in liver metastases. However, with commonly used 31P surface coils for liver 31P MRS, the liver is not fully covered, and metastases may be missed. The objective of this study was to demonstrate the feasibility of 31P MRS imaging (31P MRSI) with full liver coverage to assess 31P metabolite levels and chemotherapy‐induced changes in liver metastases of gastro‐esophageal cancer, using a 31P whole‐body birdcage transmit coil in combination with a 31P body receive array at 7 T. 3D 31P MRSI data were acquired in two patients with hepatic metastases of esophageal cancer, before the start of chemotherapy and after 2 (and 9 in patient 2) weeks of chemotherapy. 3D 31P MRSI acquisitions were performed using an integrated 31P whole‐body transmit coil in combination with a 16‐channel body receive array at 7 T, with a field of view covering the full abdomen and a nominal voxel size of 20‐mm isotropic. From the 31P MRSI data, 12 31P metabolite signals were quantified. Prior to chemotherapy initiation, both PMEs, that is, phosphocholine (PC) and phosphoethanolamine (PE), were significantly higher in all metastases compared with the levels previously determined in the liver of healthy volunteers. After 2 weeks of chemotherapy, PC and PE levels remained high or even increased further, resulting in increased PME/PDE ratios compared with healthy liver tissue, in correspondence with the clinical assessment of progressive disease after 2 months of chemotherapy. The suggested approach may present a viable tool for early therapy (non)response assessment of tumor metabolism in patients with liver metastases.
BackgroundNon‐invasive evaluation of phosphomonoesters (PMEs) and phosphodiesters (PDEs) by 31‐phosphorus MR spectroscopy (31P MRS) may have potential for early therapy (non‐)response assessment in cancer. However, 31P MRS has not yet been applied to investigate the human pancreas in vivo.PurposeTo assess the technical feasibility and repeatability of 31P MR spectroscopic imaging (MRSI) of the pancreas, compare 31P metabolite levels between pancreas and liver, and determine the feasibility of 31P MRSI in pancreatic cancer.Study TypeProspective cohort study.Population10 healthy subjects (age 34 ± 12 years, four females) and one patient (73‐year‐old female) with pancreatic ductal adenocarcinoma.Field Strength/Sequence7‐T, 31P FID‐MRSI, 1H gradient‐echo MRI.Assessment31P FID‐MRSI of the abdomen (including the pancreas and liver) was performed with a nominal voxel size of 20 mm (isotropic). For repeatability measurements, healthy subjects were scanned twice on the same day. The patient was only scanned once. Test–retest 31P MRSI data of pancreas and liver voxels (segmented on 1H MRI) of healthy subjects were quantified by fitting in the time domain and signal amplitudes were normalized to γ‐adenosine triphosphate. In addition, the PME/PDE ratio was calculated. Metabolite levels were averaged over all voxels within the pancreas, right liver lobe and left liver lobe, respectively.Statistical TestsRepeatability of test–retest data from healthy pancreas was assessed by paired t‐tests, Bland–Altman analyses, and calculation of the intrasubject coefficients of variation (CoVs). Significant differences between healthy pancreas and right and left liver lobes were assessed with a two‐way analysis of variance (ANOVA) for repeated measures. A P‐value <0.05 was considered statistically significant.ResultsThe intrasubject CoVs for PME, PDE, and PME/PDE in healthy pancreas were below 20%. Furthermore, PME and PME/PDE were significantly higher in pancreas compared to liver. In the patient with pancreatic cancer, qualitatively, elevated relative PME signals were observed in comparison with healthy pancreas.Data ConclusionIn vivo 31P MRSI of the human healthy pancreas and in pancreatic cancer may be feasible at 7 T.Evidence Level3Technical EfficacyStage 2
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