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Supplemental Figure 2. IR triggers a temporary, reversible perturbation in cellular reducing potential.

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Ionizing radiation is the primary nonsurgical treatment modality for solid tumors. Its effectiveness is impacted by temporal constraints such as fractionation, hypoxia, and development of radioresistant clones. Biomarkers of acute radiation response are essential to developing more effective clinical algorithms. We hypothesized that acute perturbations in tumor lactate levels act as a surrogate marker of radiation response. In vitro experiments were carried out using validated human-derived cell lines from three histologies: anaplastic thyroid carcinoma (ATC), head and neck squamous cell carcinoma (HNSCC), and papillary thyroid carcinoma (PTC). Cellular metabolic activity was measured using standard biochemical assays. In vivo validation was performed using both an orthotopic and a flank derivative of a previously established ATC xenograft murine model. Irradiation of cells and tumors triggered a rapid, dose-dependent, transient decrease in lactate levels that was reversed by free radical scavengers. Acute lactate perturbations following irradiation could identify hypoxic conditions and correlated with hypoxia-induced radioresistance. Mutant TP53 cells and cells in which p53 activity was abrogated (shRNA) demonstrated a blunted lactate response to irradiation, consistent with a radioresistant phenotype. Lactate measurements therefore rapidly detected both induced (i.e., hypoxia) and intrinsic (i.e., mutTP53-driven) radioresistance. We conclude that lactate is a quantitative biomarker of acute genotoxic stress, with a temporal resolution that can inform clinical decision making. Combined with the spatial resolution of newly developed metabolic imaging platforms, this biomarker could lead to the development of truly individualized treatment strategies. Mol Cancer Ther; 14(12); 2901–8. ©2015 AACR.

Supplemental Figure 6. Loss of p53 function results in decreased radiosensitivity in HNSCC cell lines.

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Anaplastic thyroid carcinoma (ATC) accounts for more than 50% of thyroid cancer mortality and is generally refractory to conventional treatment. On the basis of recent studies, we hypothesized that ATC metabolism can be targeted to improve response to chemoradiotherapy. Eight established and authenticated ATC cell lines were sequenced at 140 sites contained within 26 commonly mutated genes to identify novel potential therapeutic targets. Cellular proliferation, energy, and reducing potential stores were measured under conditions of specific nutrient deprivation. Tumor metabolism was evaluated using hyperpolarized 13C MRI in a murine orthotopic xenograft model of ATC. Sensitivity to chemotherapeutic agents and radiation (XRT) was assayed using cytotoxicity assays. We identified mutations in BRAF, NRAS, and KIT but failed to identify generalized novel targets for therapeutic intervention. ATC cell lines exhibited a mesenchymal phenotype and generalized dependence on glucose for energy, reducing potential and survival. Glycolytic inhibition using 2-deoxyglucose (2-DG) sensitized ATC cells to conventional chemotherapy and external beam radiation. In vivo, 2-DG induced a transient, but significant reduction in ATC metabolic activity. Generalized dependence of ATC cells on glucose catabolism makes them susceptible to the sensitizing effects of 2-DG for radiation therapy and chemotherapy. Under in vivo conditions, 2-DG can inhibit ATC metabolism. However, the modest magnitude and transient nature of this effect suggest the need for antimetabolic agents with more favorable pharmacodynamics to achieve therapeutic effects. Mol Cancer Ther; 11(6); 1373–80. ©2012 AACR.

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Supplemental Figure 1. Metabolic inhibition and exogenous ROS perturb cellular reducing potential.

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Supplemental Figure 5. Acute IR effects on reducing potential and lactate can be used to detect intrinsic radioresistance driven by loss of p53 activity.

Supplemental Figure 4. Lactate accumulates in extra-cellular media as a function of cellular metabolism over time.

Supplemental Figure 3. IR effects on cellular lactate and clonogenic survival are driven by ROS.

Purpose: Anaplastic thyroid carcinoma (ATC) is one of the most lethal human cancers with a median survival of 6 months. The inhibition of epidermal growth factor receptor (EGFR) alone, or with VEGF receptor 2 (VEGFR2), represents an attractive approach for treatment of ATC. Several reports have examined agents that target these receptors. However, with the misidentification of as many as 60% of all commonly used ATC cell lines, the significance of these past findings is unclear.Experimental Design: Cell lines authenticated by short tandem repeat profiling were selected to establish xenograft tumors in an orthotopic murine model of ATC. These mice were then treated with vandetanib to evaluate its effects on ATC tumor growth. Dynamic contrast-enhanced (DCE) MRI was utilized to measure the impact of vandetanib on tumor vasculature.Results: Vandetanib inhibited tumor growth of the ATC cell lines Hth83 and 8505C in vivo by 69.3% (P < 0.001) and 66.6% (P < 0.05), respectively, when compared with control. Significant decreases in vascular permeability (P < 0.01) and vascular volume fraction (P < 0.05) were detected by DCE-MRI in the orthotopic xenograft tumors after 1 week of treatment with vandetanib as compared with control.Conclusion: The inhibition of EGFR and VEGFR2 by vandetanib and its tremendous in vivo antitumor activity against ATC make it an attractive candidate for further preclinical and clinical development for the treatment of this particularly virulent cancer, which remains effectively untreatable. Vandetanib disrupts angiogenesis and DCE-MRI is an effective method to quantify changes in vascular function in vivo. Clin Cancer Res; 17(8); 2281–91. ©2011 AACR.

Supplementary Figure S1. TH-302 has potent antitumor activity in a 3D in vitro co-culture system of leukemia cells and bone marrow-derived mesenchymal stromal cells that recapitulates the multidimensional BM niche Supplementary Figure S2. Hypoxia is present in spheroids as indicated by PIMO positive staining in spheroids incubated with PIMO for 3hr before harvesting Supplementary figure S3. In vitro synergistic activity of TH-302 in combination with chemotherapy and demethylating agents Supplementary Figure S4. TH-302 has anti-leukemia activity in an in vivo primary AML xenograft murine model. Supplementary figure S5. In vitro synergistic activity of TH-302 in combination with sorafenib Supplementary figure S6 A, B. Assessment of BM hypoxia in AML/ETO bearing mice treated with TH-302 or chemotherapy

Hyperpolarized [1-13C]-pyruvate has shown tremendous promise as an agent for imaging tumor metabolism with unprecedented sensitivity and specificity. Imaging hyperpolarized substrates by magnetic resonance is unlike traditional MRI because signals are highly transient and their spatial distribution varies continuously over their observable lifetime. Therefore, new imaging approaches are needed to ensure optimal measurement under these circumstances. Constrained reconstruction algorithms can integrate prior information, including biophysical models of the substrate/target interaction, to reduce the amount of data that is required for image analysis and reconstruction. In this study, we show that metabolic MRI with hyperpolarized pyruvate is biased by tumor perfusion and present a new pharmacokinetic model for hyperpolarized substrates that accounts for these effects. The suitability of this model is confirmed by statistical comparison with alternates using data from 55 dynamic spectroscopic measurements in normal animals and murine models of anaplastic thyroid cancer, glioblastoma, and triple-negative breast cancer. The kinetic model was then integrated into a constrained reconstruction algorithm and feasibility was tested using significantly undersampled imaging data from tumor-bearing animals. Compared with naïve image reconstruction, this approach requires far fewer signal-depleting excitations and focuses analysis and reconstruction on new information that is uniquely available from hyperpolarized pyruvate and its metabolites, thus improving the reproducibility and accuracy of metabolic imaging measurements. Cancer Res; 75(22); 4708–17. ©2015 AACR.

Supplemental Methods and Tables 1) mRNA Hybridization and Gene-expression Profiling. 2) Gene expression analysis by Nanostring technology. 3) Hyperpolarized Magnetic Resonance Spectroscopy. 4) In Vitro 1-13C Pyruvic Acid Feeding Studies and High Resolution Nuclear Magnetic Resonance (NMR) Experiments 5) Three-dimensional spheroids 6) Murine tumor models 7) Immunohistochemistry Supplementary Table S1. Cell line characteristics Supplementary Table S2. Patient characteristics Supplemental Table S3. List of upregulated DEPs in hypoxia. Supplemental Table S4. 1-13C pyruvate uptake and 1-13C lactate production in cell culture. Supplemental Table S5. TH-302 cytotoxic activity against leukemia cell lines

Purpose: To characterize the prevalence of hypoxia in the leukemic bone marrow, its association with metabolic and transcriptional changes in the leukemic blasts and the utility of hypoxia-activated prodrug TH-302 in leukemia models.Experimental Design: Hyperpolarized magnetic resonance spectroscopy was utilized to interrogate the pyruvate metabolism of the bone marrow in the murine acute myeloid leukemia (AML) model. Nanostring technology was used to evaluate a gene set defining a hypoxia signature in leukemic blasts and normal donors. The efficacy of the hypoxia-activated prodrug TH-302 was examined in the in vitro and in vivo leukemia models.Results: Metabolic imaging has demonstrated increased glycolysis in the femur of leukemic mice compared with healthy control mice, suggesting metabolic reprogramming of hypoxic bone marrow niches. Primary leukemic blasts in samples from AML patients overexpressed genes defining a “hypoxia index” compared with samples from normal donors. TH-302 depleted hypoxic cells, prolonged survival of xenograft leukemia models, and reduced the leukemia stem cell pool in vivo. In the aggressive FLT3/ITD MOLM-13 model, combination of TH-302 with tyrosine kinase inhibitor sorafenib had greater antileukemia effects than either drug alone. Importantly, residual leukemic bone marrow cells in a syngeneic AML model remain hypoxic after chemotherapy. In turn, administration of TH-302 following chemotherapy treatment to mice with residual disease prolonged survival, suggesting that this approach may be suitable for eliminating chemotherapy-resistant leukemia cells.Conclusions: These findings implicate a pathogenic role of hypoxia in leukemia maintenance and chemoresistance and demonstrate the feasibility of targeting hypoxic cells by hypoxia cytotoxins. Clin Cancer Res; 22(7); 1687–98. ©2015 AACR.

Summary statistics for kpl, the apparent rate of conversion for HP Pyruvate to lactate, under various measurement conditions and parameter constraints due to differing prior information.

Animation of the dynamic conversion of hyperpolarized pyruvate into lactate in a murine model of anaplastic thyroid cancer. Heat maps for (left) HP pyruvate and (right) HP lactate overlay T2-weighted MRI. This animation can be estimated with arbitrary temporal resolution following model-based reconstruction from highly undersampled data.

A promising clinical trial utilizing gold-silica core-shell nanostructures coated with polyethylene glycol (PEG) has been reported for near-infrared (NIR) photothermal therapy (PTT) of prostate cancer. The next critical step for PTT is the visualization of therapeutically relevant nanoshell (NS) concentrations at the tumor site. Here we report the synthesis of PEGylated Gd

Model-constrained reconstruction with Fourier-based undersampling (MoReFUn) is introduced to accelerate the acquisition of dynamic MRI using hyperpolarized [1-The MoReFUn method resolves spatial aliasing using constraints introduced by a pharmacokinetic model that describes the signal evolution of both pyruvate and lactate. Acceleration was evaluated on three single-channel data sets: a numerical digital phantom that is used to validate the accuracy of reconstruction and model parameter restoration under various SNR and undersampling ratios, prospectively and retrospectively sampled data of an in vitro dynamic multispectral phantom, and retrospectively undersampled imaging data from a prostate cancer patient to test the fidelity of reconstructed metabolite time series.All three data sets showed successful reconstruction using MoReFUn. In simulation and retrospective phantom data, the restored time series of pyruvate and lactate maintained the image details, and the mean square residual error of the accelerated reconstruction increased only slightly ( 10%) at a reduction factor up to 8. In prostate data, the quantitative estimation of the conversion-rate constant of pyruvate to lactate was achieved with high accuracy of less than 10% error at a reduction factor of 2 compared with the conversion rate derived from unaccelerated data.The MoReFUn technique can be used as an effective and reliable imaging acceleration method for metabolic imaging using hyperpolarized [1

Purpose A specialized Helmholtz-style 13 C volume transmit "clamshell" coil is currently being utilized for 13 C excitation in pre-clinical and clinical hyperpolarized 13 C MRI studies aimed at probing the metabolic activity of tumors in various target anatomy. Due to the widespread use of this 13 C clamshell coil design, it is important that the effects of the 13 C clamshell coil B1 + profile on HP signal evolution and quantification are well understood. The goal of this study was to characterize the B1 + field of the 13 C clamshell coil and assess the impact of inhomogeneities on semi-quantitative and quantitative hyperpolarized MR imaging biomarkers of metabolism. Methods The B1 + field of the 13 C clamshell coil was mapped by hand using a network analyzer equipped with an S-parameter test set. Pharmacokinetic models were used to simulate signal evolution as a function of position-dependent local excitation angles, for various nominal excitation angles, which were assumed to be accurately calibrated at the isocenter. These signals were then quantified according to the normalized lactate ratio (nLac) and the apparent rate constant for the conversion of pyruvate to lactate (kPL ). The percent difference between these metabolic imaging biomarker maps and the reference value observed at the isocenter of the clamshell coil was calculated to estimate the potential for error due to position within the clamshell coil. Finally, regions were identified within the clamshell coil where deviations in B1 + field inhomogeneity or imaging biomarker errors imparted by the B1 + field were within ±10% of the value at the isocenter. Results The B1 + field maps show that a limited volume encompassed by a region measuring approximately 12.9 × 11.5 × 13.4 cm (X-direction, Y-direction, Z-direction) centered in the 13 C clamshell coil will produce deviations in the B1 + field within ±10% of that at the isocenter. For the metabolic imaging biomarkers that we evaluated, the case when the pyruvate excitation angle (θP ) and lactate excitation angle (θL ) were equal to 10° produced the largest volumetric region with deviations within ±10% of the value at the isocenter. Higher excitation angles yielded higher signal and SNR, but the size of the region in which uniform measurements could be collected near the isocenter of the coil was reduced at higher excitation angles. The tradeoff between the size of the homogenous region at the isocenter and signal intensity must be weighed carefully depending on the particular imaging application. Conclusion This work identifies regions and optimal excitation angles (θP and θL ) within the 13 C clamshell coil where deviations in B1 + field inhomogeneity or imaging biomarker errors imparted by the B1 + field were within ±10% of the respective value at the isocenter, and thus where excitation angles are reproducible and well-calibrated. Semi-quantitative and quantitative metabolic imaging biomarkers can vary with position in the clamshell coil as a result of B1 + field inhomogeneity, necessitating care in patient positioning and the selection of an excitation angle set that balances reproducibility and SNR performance over the target imaging volume.

A promising clinical trial utilizing gold-silica core-shell nanostructures coated with polyethylene glycol (PEG) has been reported for near-infrared (NIR) photothermal therapy (PTT) of prostate cancer. The next critical step for PTT is the visualization of therapeutically relevant nanoshell (NS) concentrations at the tumor site. Here we report the synthesis of PEGylated Gd 2 O 3 -mesoporous silica/gold core/shell NSs (Gd 2 O 3 -MS NSs) with NIR photothermal properties that also supply sufficient MRI contrast to be visualized at therapeutic doses (≥10 8 NSs per milliliter). The nanoparticles have r 1 relaxivities more than three times larger than those of conventional T 1 contrast agents, requiring less concentration of Gd 3+ to observe an equivalent signal enhancement in T 1 -weighted MR images. Furthermore, Gd 2 O 3 -MS NS nanoparticles have r 2 relaxivities comparable to those of existing T 2 contrast agents, observed in agarose phantoms. This highly unusual combination of simultaneous T 1 and T 2 contrast allows for MRI enhancement through different approaches. As a rudimentary example, we demonstrate T 1 / T 2 ratio MR images with sixfold contrast signal enhancement relative to its T 1 MRI and induced temperature increases of 20 to 55 °C under clinical illumination conditions. These nanoparticles facilitate MRI-guided PTT while providing real-time temperature feedback through thermal MRI mapping.

BACKGROUND: Lactate dehydrogenase (LDH) is a critical metabolic enzyme. LDH A (LDHA) overexpression is a hallmark of aggressive malignancies and has been linked to tumour initiation, reprogramming and progression in multiple tumour types. However, successful LDHA inhibition strategies have not materialised in the translational and clinical space. We sought to develop a rational strategy for LDHA suppression in the context of solid tumour treatment. METHODS: We utilised a doxycycline-inducible short hairpin RNA (shRNA) system to generate LDHA suppression. Lactate and LDH activity levels were measured biochemically and kinetically using hyperpolarised (13)C-pyruvate nuclear magnetic resonance spectroscopy. We evaluated effects of LDHA suppression on cellular proliferation and clonogenic survival, as well as on tumour growth, in orthotopic models of anaplastic thyroid carcinoma (ATC) and head and neck squamous cell carcinoma (HNSCC), alone or in combination with radiation. RESULTS: shRNA suppression of LDHA generated a time-dependent decrease in LDH activity with transient shifts in intracellular lactate levels, a decrease in carbon flux from pyruvate into lactate and compensatory shifts in metabolic flux in glycolysis and the Krebs cycle. LDHA suppression decreased cellular proliferation and temporarily stunted tumour growth in ATC and HNSCC xenografts but did not by itself result in tumour cure, owing to the maintenance of residual viable cells. Only when chronic LDHA suppression was combined with radiation was a functional cure achieved. CONCLUSIONS: Successful targeting of LDHA requires exquisite dose and temporal control without significant concomitant off-target toxicity. Combinatorial strategies with conventional radiation are feasible as long as the suppression is targeted, prolonged and non-toxic.

Background Type II diabetes mellitus (DM2) is a significant risk factor for cancers, including breast cancer. However, a proper diabetic breast cancer mouse model is not well‐established for treatment strategy design. Additionally, the precise diabetic signaling pathways that regulate cancer growth remain unresolved. In the present study, we established a suitable mouse model and demonstrated the pathogenic role of diabetes on breast cancer progression. Methods We successfully generated a transgenic mouse model of human epidermal growth factor receptor 2 positive (Her2+ or ERBB2) breast cancer with DM2 by crossing leptin receptor mutant (Leprdb/+) mice with MMTV‐ErbB2/neu) mice. The mouse models were administrated with antidiabetic drugs to assess the impacts of controlling DM2 in affecting tumor growth. Magnetic resonance spectroscopic imaging was employed to analyze the tumor metabolism. Results Treatment with metformin/rosiglitazone in MMTV‐ErbB2/Leprdb/db mouse model reduced serum insulin levels, prolonged overall survival, decreased cumulative tumor incidence, and inhibited tumor progression. Anti‐insulin resistance medications also inhibited glycolytic metabolism in tumors in vivo as indicated by the reduced metabolic flux of hyperpolarized 13C pyruvate‐to‐lactate reaction. The tumor cells from MMTV‐ErbB2/Leprdb/db transgenic mice treated with metformin had reprogrammed metabolism by reducing levels of both oxygen consumption and lactate production. Metformin decreased the expression of Myc and pyruvate kinase isozyme 2 (PKM2), leading to metabolism reprogramming. Moreover, metformin attenuated the mTOR/AKT signaling pathway and altered adipokine profiles. Conclusions MMTV‐ErbB2/Leprdb/db mouse model was able to recapitulate diabetic HER2+ human breast cancer. Additionally, our results defined the signaling pathways deregulated in HER2+ breast cancer under diabetic condition, which can be intervened by anti‐insulin resistance therapy., Our results define the signaling pathways deregulated in HER2+ breast cancer under diabetic condition, which can be intervened by anti‐insulin resistance therapy.

PURPOSE: We aim to characterize the quantitative dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) parameters associated with advanced mandibular osteoradionecrosis (ORN) compared with the contralateral normal mandible. METHODS AND MATERIALS: Patients with a diagnosis of advanced ORN after curative-intent radiation treatment of head and neck cancer were prospectively enrolled after institutional review board approval and study-specific informed consent were obtained. Quantitative maps generated with the Tofts and extended Tofts pharmacokinetic models were used for analysis. Manual segmentation of advanced ORN 3-dimensional volume was done using anatomic sequences to create ORN volumes of interest (VOIs). Subsequently, normal mandibular VOIs were segmented on the contralateral healthy mandible of similar volume and anatomic location to create control VOIs. Finally, anatomic sequences were coregistered to DCE sequences, and contours were propagated to the respective parameter maps. RESULTS: Thirty patients were included. The median time to ORN diagnosis after completion of IMRT was 38 months (range, 6–184 months), whereas median time to ORN progression to advanced grade after initial diagnosis was 5.6 months (range, 0–128 months). There were statistically significant higher K(trans) and V(e) in ORN-VOIs compared with controls (0.23 vs 0.07 min(−)(1), and 0.34 vs 0.15; P

Methods for imaging orthotopic prostate tumors within the prostate or small tumors with extension outside the prostate are needed to more closely model human prostate tumors, which are most commonly located within the gland or may extend just through the gland. By comparing MR sequences, we found that the T2-based Dixon ‘water only’ sequence best visualized tumors within the prostate of mouse models in both young and old mice and that tumor weight derived from this sequence correlated highly with ex vivo tumor weight (r2 = 0.98, p

PURPOSE Metabolic magnetic resonance imaging (MRI) using hyperpolarized [1-13 C]-pyruvate offers unprecedented new insight into disease and response to therapy. 13 C-enriched reference standards are required to enable fast and accurate calibration for 13 C studies, but care must be taken to ensure that the reference is compatible with both 13 C and 1 H acquisitions. The goal of this study was to optimize the composition of a 13 C-urea reference for a dual-tuned 13 C/1 H endorectal coil and minimize imaging artifacts in metabolic and multiparametric MRI studies involving hyperpolarized [1-13 C]-pyruvate. METHODS Due to a high amount of Gd doping for the purpose of reducing the spin-lattice relaxation time (T1 ) of urea, the 1 H signal produced by a reference of 13 C-urea in normal water was rapidly relaxed, resulting in severe artifacts in heavily T1 -weighted images. Hyperintense ringing artifacts in 1 H images were mitigated by reducing the 1 H concentration in a 13 C-urea reference via deuteration and lyophilization. Several references were fabricated and their SNR was compared using 1 H and 13 C imaging sequences on a 3T MRI scanner. Finally, 1 H prostate phantom imaging was conducted to compare image quality and 1 H signal intensity of normal and deuterated urea references. RESULTS The deuterated 13 C-urea reference provides strong 13 C signal for calibration and an attenuated 1 H signal that does not interfere with heavily T1 -weighted scans. Deuteration and lyophilization were fundamental to the reduction in 1 H signal and hyperintense ringing artifacts. There was a 25-fold reduction in signal intensity when comparing the nondeuterated reference to the deuterated reference, while the 13 C signal was unaffected. CONCLUSION A deuterated reference reduced hyperintense ringing artifacts in 1 H images by reducing the 1 H signal produced from the 13 C-urea in the reference. The deuterated reference can be used to improve anatomical image quality in future clinical 1 H and hyperpolarized [1-13 C]-pyruvate MRI prostate imaging studies.

PURPOSE: A specialized Helmholtz-style (13)C volume transmit “clamshell” coil is currently being utilized for (13)C excitation in pre-clinical and clinical hyperpolarized (13)C MRI studies aimed at probing metabolic activity of tumors in various target anatomy. Due to widespread use of this (13)C clamshell coil design, it is important that the effects of the (13)C clamshell coil B(1)(+) profile on HP signal evolution and quantification are well understood. The goal of this study was to characterize the B(1)(+) field of the (13)C clamshell coil and assess the impact of inhomogeneities on semi-quantitative and quantitative hyperpolarized MR imaging biomarkers of metabolism. METHODS: The B(1)(+) field of the (13)C clamshell coil was mapped by hand using a network analyzer equipped with a S-parameter test set. Pharmacokinetic models were used to simulate signal evolution as a function of position dependent local excitation angles, for various nominal excitation angles, which were assumed to be accurately calibrated at isocenter. These signals were then quantified according to the normalized lactate ratio (nLac) and the apparent rate constant for the conversion of pyruvate to lactate (k(PL)). The percent difference between these metabolic imaging biomarker maps and the reference value observed at isocenter of the clamshell coil was calculated to estimate the potential for error due to position within the clamshell coil. Finally, regions were identified within the clamshell coil where deviations in B(1)(+) field inhomogeneity or imaging biomarker errors imparted by the B(1)(+) field were within ±10% of the value at isocenter. RESULTS: The B(1)(+) field maps show that a limited volume encompassed by a region measuring approximately 12.9 × 11.5 × 13.4 cm (X-direction, Y-direction, Z-direction) centered in the (13)C clamshell coil will produce deviations in the B(1)(+) field within ±10% of that at isocenter. For the metabolic imaging biomarkers that we evaluated, the case when the pyruvate excitation angle (θ(P)) and lactate excitation angle (θ(L)) were equal to 10° produced the largest volumetric region with deviations within ±10% of the value at isocenter. Higher excitation angles yielded higher signal and SNR, but the size of the region in which uniform measurements could be collected near the isocenter of the coil was reduced at higher excitation angles. The tradeoff between the size of the homogenous region at isocenter and signal intensity must be weighed carefully depending on the particular imaging application. CONCLUSION: This work identifies regions and optimal excitation angles (θ(P) and θ(L)) within the (13)C clamshell coil where deviations in B(1)(+) field inhomogeneity or imaging biomarker errors imparted by the B(1)(+) field were within ±10% of the respective value at isocenter, and thus where excitation angles are reproducible and well calibrated. Semi-quantitative and quantitative metabolic imaging biomarkers can vary with position in the clamshell coil as a result of B(1)(+) field inhomogeneity, necessitating care in patient positioning and the selection of an excitation angle set that balances reproducibility and SNR performance over the target imaging volume.

BACKGROUND: A generation of therapies targeting tumor metabolism is becoming available for treating glioma. Hyperpolarized MRI is uniquely suited to directly measure the metabolic effects of these emerging treatments. PURPOSE: To explore the feasibility of the use of hyperpolarized [1–carbon 13 {(13)C}]-pyruvate for real-time measurement of metabolism and response to treatment with a glycolytic inhibitor in an orthotopic mouse model of glioma. MATERIALS AND METHODS: In this animal study, anatomic MRI and dynamic (13)C MR spectroscopy were performed at 7 T during intravenous injection of hyperpolarized [1-(13)C]-pyruvate on mice with orthotopic U87MG glioma and healthy control mice. Anatomic MRI and dynamic (13)C MR spectroscopy were repeated after administration of the glycolytic inhibitor WP1122, a prodrug of 2-deoxy-d-glucose. All experiments were conducted in athymic nude mice between October 2016 and March 2017. Hyperpolarized lactate production was quantified as an apparent reaction rate, or k(PL), and normalized lactate ratio (nLac). The Wilcoxon signed-rank test was used to assess changes in paired measures of lactate production before and after treatment. RESULTS: Thirteen 12–16-week-old female mice and five healthy female mice underwent anatomic MRI and hyperpolarized [1-(13)C]-pyruvate spectroscopy. Large contrast agent–enhanced tumors were shown in mice with glioma at T2-weighted and T1-weighted postcontrast MRI by postimplantation day 40. After treatment with WP1122, a decrease in lactate was observed in mice with glioma (baseline and treatment mean k(PL), 0.027 and 0.018 sec(−1), respectively, P = .01; baseline and posttreatment mean nLac, 0.28 and 0.22, respectively, P = .01) whereas no significant decrease was observed in healthy control mice (baseline and posttreatment mean k(PL), 0.011 and 0.017 sec(−1), respectively, P = .91; baseline and posttreatment mean nLac, 0.16 and 0.21, respectively, P = .84). CONCLUSION: Hyperpolarized carbon 13 measurements of pyruvate metabolism can provide rapid feedback for monitoring treatment response in glioma. © RSNA, 2019

Hyperpolarized carbon-13 magnetic resonance (HP-MR) is a new metabolic imaging method the does not use ionizing radiation. Due to the inherent chemical specificity of MR, not only tracer uptake but also downstream metabolism of the agent is detected in a straightforward manner. HP [2-(13)C] dihydroxyacetone (DHA) is a promising new agent that directly interrogates hepatic glucose metabolism. DHA has three metabolic fates in the liver: glucose production, glycerol production and potential inclusion into triglycerides, and oxidation in the tricarboxylic acid cycle. Each pathway is regulated by flux through multiple enzymes. Using Duhamel’s formula, the kinetics of DHA metabolism is modeled, resulting in estimates of specific reaction rate constants. The multiple enzymatic steps that control DHA metabolism make more simplified methods for extracting kinetic data less than satisfactory. The described modeling paradigm effectively identifies changes in metabolism between gluconeogenic and glycogenolytic models of hepatic function.

This white paper discusses prospects for advancing hyperpolarization technology to better understand cancer metabolism, identify current obstacles to HP (hyperpolarized) 13C magnetic resonance imaging’s (MRI’s) widespread clinical use, and provide recommendations for overcoming them. Since the publication of the first NIH white paper on hyperpolarized 13C MRI in 2011, preclinical studies involving [1-13C]pyruvate as well a number of other 13C labeled metabolic substrates have demonstrated this technology's capacity to provide unique metabolic information. A dose-ranging study of HP [1-13C]pyruvate in patients with prostate cancer established safety and feasibility of this technique. Additional studies are ongoing in prostate, brain, breast, liver, cervical, and ovarian cancer. Technology for generating and delivering hyperpolarized agents has evolved, and new MR data acquisition sequences and improved MRI hardware have been developed. It will be important to continue investigation and development of existing and new probes in animal models. Improved polarization technology, efficient radiofrequency coils, and reliable pulse sequences are all important objectives to enable exploration of the technology in healthy control subjects and patient populations. It will be critical to determine how HP 13C MRI might fill existing needs in current clinical research and practice, and complement existing metabolic imaging modalities. Financial sponsorship and integration of academia, industry, and government efforts will be important factors in translating the technology for clinical research in oncology. This white paper is intended to provide recommendations with this goal in mind.

Background Glioblastoma remains incurable despite treatment with surgery, radiation therapy, and cytotoxic chemotherapy, prompting the search for a metabolic pathway unique to glioblastoma cells.13C MR spectroscopic imaging with hyperpolarized pyruvate can demonstrate alterations in pyruvate metabolism in these tumors. Methods Three patients with diagnostic MRI suggestive of a glioblastoma were scanned at 3 T 1–2 days prior to tumor resection using a 13C/1H dual-frequency RF coil and a 13C/1H-integrated MR protocol, which consists of a series of 1H MR sequences (T2 FLAIR, arterial spin labeling and contrast-enhanced [CE] T1) and 13C spectroscopic imaging with hyperpolarized [1-13C]pyruvate. Dynamic spiral chemical shift imaging was used for 13C data acquisition. Surgical navigation was used to correlate the locations of tissue samples submitted for histology with the changes seen on the diagnostic MR scans and the 13C spectroscopic images. Results Each tumor was histologically confirmed to be a WHO grade IV glioblastoma with isocitrate dehydrogenase wild type. Total hyperpolarized 13C signals detected near the tumor mass reflected altered tissue perfusion near the tumor. For each tumor, a hyperintense [1-13C]lactate signal was detected both within CE and T2-FLAIR regions on the 1H diagnostic images (P = .008). [13C]bicarbonate signal was maintained or decreased in the lesion but the observation was not significant (P = .3). Conclusions Prior to surgical resection, 13C MR spectroscopic imaging with hyperpolarized pyruvate reveals increased lactate production in regions of histologically confirmed glioblastoma.

Acquisition parameter selection is currently performed empirically for many quantitative MRI (qMRI) acquisitions. Tuning parameters for different scan times, tissues, and resolutions requires some amount of trial and error. There is an opportunity to quantitatively optimize these acquisition parameters in order to minimize variability of quantitative maps and post-processing techniques such as synthetic image generation. The objective of this work is to introduce and evaluate a quantitative method for selecting parameters that minimize image variability. An information theory framework was developed for this purpose and applied to a 3D-quantification using an interleaved Look-Locker acquisition sequence with T2 preparation pulse (3D-QALAS) signal model for qMRI. In this framework, mutual information is used to measure the information gained by a measurement as a function of acquisition parameters, quantifying the information content of potential acquisitions and allowing informed parameter selection. The information theory framework was tested on artificial data generated from a representative mathematical phantom, measurements acquired on a qMRI multiparametric imaging standard phantom, and in vivo measurements in a human brain. The phantom measurements showed that higher mutual information calculated by the model correlated with smaller coefficient of variation in the reconstructed parametric maps, and in vivo measurements demonstrated that information-based calibration of acquisition parameters resulted in a decrease in parametric map variability consistent with model predictions.

Imaging methods for hyperpolarized (HP) (13)C agents must sample the evolution of signal from multiple agents with distinct chemical shifts within a very brief timeframe (typically