1
|
Sharkey AR, Witney TH, Cook GJR. Is System x c- a Suitable Target for Tumour Detection and Response Assessment with Imaging? Cancers (Basel) 2023; 15:5573. [PMID: 38067277 PMCID: PMC10705217 DOI: 10.3390/cancers15235573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 11/21/2023] [Accepted: 11/22/2023] [Indexed: 02/12/2024] Open
Abstract
System xc- is upregulated in cancer cells and can be imaged using novel radiotracers, most commonly with (4S)-4-(3-[18F]fluoropropyl)-L-glutamic acid (18F-FSPG). The aim of this review was to summarise the use of 18F-FSPG in humans, explore the benefits and limitations of 18F-FSPG, and assess the potential for further use of 18F-FSPG in cancer patients. To date, ten papers have described the use of 18F-FSPG in human cancers. These studies involved small numbers of patients (range 1-26) and assessed the use of 18F-FSPG as a general oncological diagnostic agent across different cancer types. These clinical trials were contrasting in their findings, limiting the scope of 18F-FSPG PET/CT as a purely diagnostic agent, primarily due to heterogeneity of 18F-FSPG retention both between cancer types and patients. Despite these limitations, a potential further application for 18F-FSPG is in the assessment of early treatment response and prediction of treatment resistance. Animal models of cancer have shown that changes in 18F-FSPG retention following effective therapy precede glycolytic changes, as indicated by 18F-FDG, and changes in tumour volume, as measured by CT. If these results could be replicated in human clinical trials, imaging with 18F-FSPG PET/CT would offer an exciting route towards addressing the currently unmet clinical needs of treatment resistance prediction and early imaging assessment of therapy response.
Collapse
Affiliation(s)
- Amy R. Sharkey
- School of Biomedical Engineering and Imaging Sciences, King’s College London, St. Thomas’ Hospital, London SE1 7EH, UK
| | - Timothy H. Witney
- School of Biomedical Engineering and Imaging Sciences, King’s College London, St. Thomas’ Hospital, London SE1 7EH, UK
| | - Gary J. R. Cook
- School of Biomedical Engineering and Imaging Sciences, King’s College London, St. Thomas’ Hospital, London SE1 7EH, UK
- King’s College London and Guy’s and St. Thomas’ PET Centre, St. Thomas’ Hospital, London SE1 7EH, UK
| |
Collapse
|
2
|
Colovic M, Yang H, Southcott L, Merkens H, Colpo N, Bénard F, Schaffer P. Comparative Evaluation of [ 18F]5-Fluoroaminosuberic Acid and (4 S)-4-3-[ 18F]fluoropropyl)-l-Glutamate as System xC--Targeting Radiopharmaceuticals. J Nucl Med 2023:jnumed.122.265254. [PMID: 37116917 DOI: 10.2967/jnumed.122.265254] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 03/21/2023] [Indexed: 04/30/2023] Open
Abstract
System [Formula: see text] is an appealing biomarker for targeting oxidative stress with oncologic PET imaging and can serve as an alternative PET biomarker to other metabolic indicators. In this paper, we report a direct comparison of 2 18F-labeled amino acid radiopharmaceuticals targeting system [Formula: see text], [18F]5-fluoroaminosuberic acid ([18F]FASu) and (4S)-4-(3-[18F]fluoropropyl)-l-glutamate ([18F]FSPG), in terms of their uptake specificity and ability to image glioma and lung cancer xenografts in vivo. Methods: Both tracers were synthesized according to previously published procedures. In vitro uptake specificity assays were conducted using prostate (PC-3), glioblastoma (U-87), colorectal (HT-29), ovarian (SKOV3), breast (MDA-MB-231), and lung cancer (A549) cell lines. PET/CT imaging and biodistribution studies were conducted in immunocompromised mice bearing U-87 or A549 xenografts. Results: In vitro cell uptake assays showed that the tracers accumulated in cancer cells in a time-dependent manner and that the uptake of [18F]FASu was blocked by the system [Formula: see text] inhibitor sulfasalazine and rose bengal, but not by system L inhibitor 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid, system [Formula: see text] inhibitor L-trans-pyrrolidine-2,4-dicarboxylic acid, or l-serine, which is a substrate for transporter systems A, ACS, B0, and B0,+ Conversely, [18F]FSPG uptake decreased significantly in the presence of an excess of L-trans-pyrrolidine-2,4-dicarboxylic acid in 2 of 3 tested cell lines, indicating some reliance on system [Formula: see text] in these cells. In an in vivo setting, [18F]FASu and [18F]FSPG generated good-contrast PET images in U-87 and A549 tumor-bearing mice. Tracer accumulation in A549 tumors was 5.0 ± 0.8 percentage injected dose (%ID)/g ([18F]FASu, n ≥ 5) and 6.3 ± 1.3 %ID/g ([18F]FSPG, n ≥ 6, P = 0.7786), whereas U-87 xenografts demonstrated uptake of 6.1 ± 2.4 %ID/g ([18F]FASu, n ≥ 4) and 11.2 ± 4.1 %ID/g ([18F]FSPG, n ≥ 4, P = 0.0321) at 1 h after injection. Conclusion: [18F]FSPG had greater in vitro uptake than [18F]FASu in all cell lines tested; however, our results indicate that residual uptake differences exist between [18F]FSPG and [18F]FASu, suggesting alternative transporter activity in the cell lines tested. In vivo studies demonstrated the ability of both [18F]FASu and [18F]FSPG to image glioblastoma (U-87) and non-small cell lung cancer (A549) xenografts.
Collapse
Affiliation(s)
- Milena Colovic
- Life Sciences Division, TRIUMF, Vancouver, British Columbia, Canada
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, British Columbia, Canada
| | - Hua Yang
- Life Sciences Division, TRIUMF, Vancouver, British Columbia, Canada
| | - Lily Southcott
- Life Sciences Division, TRIUMF, Vancouver, British Columbia, Canada
| | - Helen Merkens
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, British Columbia, Canada
| | - Nadine Colpo
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, British Columbia, Canada
| | - Francois Bénard
- Department of Molecular Oncology, BC Cancer Research Institute, Vancouver, British Columbia, Canada
- Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada; and
| | - Paul Schaffer
- Life Sciences Division, TRIUMF, Vancouver, British Columbia, Canada;
- Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada; and
- Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| |
Collapse
|
3
|
STING-driven interferon signaling triggers metabolic alterations in pancreas cancer cells visualized by [ 18F]FLT PET imaging. Proc Natl Acad Sci U S A 2021; 118:2105390118. [PMID: 34480004 PMCID: PMC8433573 DOI: 10.1073/pnas.2105390118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 07/26/2021] [Indexed: 01/19/2023] Open
Abstract
Type I interferons (IFNs) are critical effectors of emerging cancer immunotherapies designed to activate pattern recognition receptors (PRRs). A challenge in the clinical translation of these agents is the lack of noninvasive pharmacodynamic biomarkers that indicate increased intratumoral IFN signaling following PRR activation. Positron emission tomography (PET) imaging enables the visualization of tissue metabolic activity, but whether IFN signaling-induced alterations in tumor cell metabolism can be detected using PET has not been investigated. We found that IFN signaling augments pancreatic ductal adenocarcinoma (PDAC) cell nucleotide metabolism via transcriptional induction of metabolism-associated genes including thymidine phosphorylase (TYMP). TYMP catalyzes the first step in the catabolism of thymidine, which competitively inhibits intratumoral accumulation of the nucleoside analog PET probe 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT). Accordingly, IFN treatment up-regulates cancer cell [18F]FLT uptake in the presence of thymidine, and this effect is dependent upon TYMP expression. In vivo, genetic activation of stimulator of interferon genes (STING), a PRR highly expressed in PDAC, enhances the [18F]FLT avidity of xenograft tumors. Additionally, small molecule STING agonists trigger IFN signaling-dependent TYMP expression in PDAC cells and increase tumor [18F]FLT uptake in vivo following systemic treatment. These findings indicate that [18F]FLT accumulation in tumors is sensitive to IFN signaling and that [18F]FLT PET may serve as a pharmacodynamic biomarker for STING agonist-based therapies in PDAC and possibly other malignancies characterized by elevated STING expression.
Collapse
|
4
|
Greenwood HE, Witney TH. Latest advances in imaging oxidative stress in cancer. J Nucl Med 2021; 62:1506-1510. [PMID: 34353871 PMCID: PMC7611938 DOI: 10.2967/jnumed.120.256974] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 07/15/2021] [Indexed: 11/16/2022] Open
Abstract
Oxidative stress is the imbalance of harmful reactive oxygen species (ROS) and the action of neutralizing antioxidant mechanisms. If left unchecked, the deleterious effects of oxidative stress results in damage to DNA, proteins, and membranes, ultimately resulting in cell death. Tumors are highly proliferative and consequently generate high levels of mitochondrial ROS. To compensate and maintain redox homeostasis, cancer cells upregulate protective antioxidant pathways, which are further amplified in drug-resistant tumors. This review provides an overview of the latest molecular imaging techniques designed to image oxidative stress in cancer. New probes are now able to assess heterogeneous ROS and antioxidant production within tumors and across lesions. Together, the non-invasive imaging of these dynamic processes holds great promise for treatment response monitoring, prediction of drug resistance, and may provide insight into the metastatic potential of tumors.
Collapse
|
5
|
Edwards R, Greenwood HE, McRobbie G, Khan I, Witney TH. Robust and Facile Automated Radiosynthesis of [ 18F]FSPG on the GE FASTlab. Mol Imaging Biol 2021; 23:854-864. [PMID: 34013395 PMCID: PMC8578107 DOI: 10.1007/s11307-021-01609-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 03/19/2021] [Accepted: 04/18/2021] [Indexed: 01/18/2023]
Abstract
Purpose (S)-4-(3-18F-Fluoropropyl)-ʟ-Glutamic Acid ([18F]FSPG) is a radiolabeled non-natural amino acid that is used for positron emission tomography (PET) imaging of the glutamate/cystine antiporter, system xC-, whose expression is upregulated in many cancer types. To increase the clinical adoption of this radiotracer, reliable and facile automated procedures for [18F]FSPG production are required. Here, we report a cassette-based method to produce [18F]FSPG at high radioactivity concentrations from low amounts of starting activity. Procedures An automated synthesis and purification of [18F]FSPG was developed using the GE FASTlab. Optimization of the reaction conditions and automated manipulations were performed by measuring the isolated radiochemical yield of [18F]FSPG and by assessing radiochemical purity using radio-HPLC. Purification of [18F]FSPG was conducted by trapping and washing of the radiotracer on Oasis MCX SPE cartridges, followed by a reverse elution of [18F]FSPG in phosphate-buffered saline. Subsequently, the [18F]FSPG obtained from the optimized process was used to image an animal model of non-small cell lung cancer. Results The optimized protocol produced [18F]FSPG in 38.4 ± 2.6 % radiochemical yield and >96 % radiochemical purity with a molar activity of 11.1 ± 7.7 GBq/μmol. Small alterations, including the implementation of a reverse elution and an altered Hypercarb cartridge, led to significant improvements in radiotracer concentration from <10 MBq/ml to >100 MBq/ml. The improved radiotracer concentration allowed for the imaging of up to 20 mice, starting with just 1.5 GBq of [18F]Fluoride. Conclusions We have developed a robust and facile method for [18F]FSPG radiosynthesis in high radiotracer concentration, radiochemical yield, and radiochemical purity. This cassette-based method enabled the production of [18F]FSPG at radioactive concentrations sufficient to facilitate large-scale preclinical experiments with a single prep of starting activity. The use of a cassette-based radiosynthesis on an automated synthesis module routinely used for clinical production makes the method amenable to rapid and widespread clinical translation. Supplementary Information The online version contains supplementary material available at 10.1007/s11307-021-01609-w.
Collapse
Affiliation(s)
- Richard Edwards
- School of Biomedical Engineering & Imaging Sciences, King's College London, St. Thomas' Hospital, London, SE1 7EH, UK
| | - Hannah E Greenwood
- School of Biomedical Engineering & Imaging Sciences, King's College London, St. Thomas' Hospital, London, SE1 7EH, UK
| | - Graeme McRobbie
- Pharmaceutical Diagnostics, Life Sciences, GE Healthcare, Pollards Wood, Nightingales Lane, Chalfont St. Giles, Buckinghamshire, HP8 4SP, UK
| | - Imtiaz Khan
- Pharmaceutical Diagnostics, Life Sciences, GE Healthcare, Pollards Wood, Nightingales Lane, Chalfont St. Giles, Buckinghamshire, HP8 4SP, UK
| | - Timothy H Witney
- School of Biomedical Engineering & Imaging Sciences, King's College London, St. Thomas' Hospital, London, SE1 7EH, UK.
| |
Collapse
|
6
|
Park SY, Mosci C, Kumar M, Wardak M, Koglin N, Bullich S, Mueller A, Berndt M, Stephens AW, Chin FT, Gambhir SS, Mittra ES. Initial evaluation of (4S)-4-(3-[ 18F]fluoropropyl)-L-glutamate (FSPG) PET/CT imaging in patients with head and neck cancer, colorectal cancer, or non-Hodgkin lymphoma. EJNMMI Res 2020; 10:100. [PMID: 32857284 PMCID: PMC7455665 DOI: 10.1186/s13550-020-00678-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 07/28/2020] [Indexed: 01/17/2023] Open
Abstract
Purpose (4S)-4-(3-[18F]Fluoropropyl)-l-glutamic acid ([18F]FSPG) measures system xC− transporter activity and shows promise for oncologic imaging. We present data on tumor uptake of this radiopharmaceutical in human subjects with head and neck cancer (HNC), colorectal cancer (CRC), and non-Hodgkin lymphoma (NHL). Methods A total of 15 subjects with HNC (n = 5), CRC (n = 5), or NHL (n = 5) were recruited (mean age 66.2 years, range 44–87 years). 301.4 ± 28.1 MBq (8.1 ± 0.8 mCi) of [18F]FSPG was given intravenously to each subject, and 3 PET/CT scans were obtained 0–2 h post-injection. All subjects also had a positive [18F]FDG PET/CT scan within 1 month prior to the [18F]FSPG PET scan. Semi-quantitative and visual comparisons of the [18F]FSPG and [18F]FDG scans were performed. Results [18F]FSPG showed strong uptake in all but one HNC subject. The lack of surrounding brain uptake facilitated tumor delineation in the HNC patients. [18F]FSPG also showed tumor uptake in all CRC subjects, but variable uptake in the NHL subjects. While the absolute [18F]FDG SUV values were comparable or higher than [18F]FSPG, the tumor-to-background SUV ratios were greater with [18F]FSPG than [18F]FDG. Conclusions [18F]FSPG PET/CT showed promising results across 15 subjects with 3 different cancer types. Concordant visualization was mostly observed between [18F]FSPG and [18F]FDG PET/CT images, with some inter- and intra-individual uptake variability potentially reflecting differences in tumor biology. The tumor-to-background ratios were greater with [18F]FSPG than [18F]FDG in the cancer types evaluated. Future studies based on larger numbers of subjects and those with a wider array of primary and recurrent or metastatic tumors are planned to further evaluate the utility of this novel tracer.
Collapse
Affiliation(s)
- Sonya Y Park
- Department of Radiology, Division of Nuclear Medicine, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.,Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Camila Mosci
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Meena Kumar
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Mirwais Wardak
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Norman Koglin
- Bayer Pharma AG, Berlin, Germany.,Life Molecular Imaging GmbH, Berlin, Germany
| | | | - Andre Mueller
- Bayer Pharma AG, Berlin, Germany.,Life Molecular Imaging GmbH, Berlin, Germany
| | - Mathias Berndt
- Bayer Pharma AG, Berlin, Germany.,Life Molecular Imaging GmbH, Berlin, Germany
| | - Andrew W Stephens
- Bayer Pharma AG, Berlin, Germany.,Life Molecular Imaging GmbH, Berlin, Germany
| | - Frederick T Chin
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Sanjiv S Gambhir
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA.,Department of Bioengineering, Stanford University, Stanford, CA, USA.,Department of Materials Science & Engineering, Stanford University, Stanford, CA, USA.,Bio-X Program, Stanford University, Stanford, CA, USA
| | - Erik S Mittra
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University School of Medicine, Stanford, CA, USA. .,Department of Diagnostic Radiology, Division of Nuclear Medicine & Molecular Imaging, Oregon Health & Science University, 3181 SW Sam Jackson Park Rd., Mail Code L340, Portland, OR, 97239, USA.
| |
Collapse
|
7
|
PET Imaging of l-Type Amino Acid Transporter (LAT1) and Cystine-Glutamate Antiporter (xc−) with [18F]FDOPA and [18F]FSPG in Breast Cancer Models. Mol Imaging Biol 2020; 22:1562-1571. [DOI: 10.1007/s11307-020-01529-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 08/05/2020] [Accepted: 08/06/2020] [Indexed: 02/07/2023]
|
8
|
Park SY, Na SJ, Kumar M, Mosci C, Wardak M, Koglin N, Bullich S, Mueller A, Berndt M, Stephens AW, Cho YM, Ahn H, Chae SY, Kim HO, Moon DH, Gambhir SS, Mittra ES. Clinical Evaluation of (4S)-4-(3-[ 18F]Fluoropropyl)-L-glutamate ( 18F-FSPG) for PET/CT Imaging in Patients with Newly Diagnosed and Recurrent Prostate Cancer. Clin Cancer Res 2020; 26:5380-5387. [PMID: 32694158 DOI: 10.1158/1078-0432.ccr-20-0644] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 05/25/2020] [Accepted: 07/14/2020] [Indexed: 12/24/2022]
Abstract
PURPOSE (4S)-4-(3-[18F]Fluoropropyl)-L-glutamic acid (18F-FSPG) is a radiopharmaceutical for PET imaging of system xC - activity, which can be upregulated in prostate cancer. We present data on the first evaluation of patients with newly diagnosed or recurrent prostate cancer with this radiopharmaceutical. EXPERIMENTAL DESIGN Ten patients with primary and 10 patients with recurrent prostate cancer were enrolled in this prospective multicenter study. After injection of 300 MBq of 18F-FSPG, three whole-body PET/CT scans were obtained. Visual analysis was compared with step-section histopathology when available as well as other imaging studies and clinical outcomes. Metabolic parameters were measured semiquantitatively. Expression levels of xCT and CD44 were evaluated by IHC for patients with available tissue samples. RESULTS 18F-FSPG PET showed high tumor-to-background ratios with a relatively high tumor detection rate on a per-patient (89%) and per-lobe (87%) basis. The sensitivity was slightly higher with imaging at 105 minutes in comparison with 60 minutes. The maximum standardized uptake values (SUVmax) for cancer was significantly higher than both normal (P < 0.005) and benign pathology (P = 0.011), while there was no significant difference between normal and benign pathology (P = 0.120). In the setting of recurrence, agreement with standard imaging was demonstrated in 7 of 9 patients (78%) and 13 of 18 lesions (72%), and revealed true local recurrence in a discordant case. 18F-FSPG accumulation showed moderate correlation with CD44 expression. CONCLUSIONS 18F-FSPG is a promising tumor imaging agent for PET that seems to have favorable biodistribution and high cancer detection rate in patients with prostate cancer. Further studies are warranted to determine the diagnostic value for both initial staging and recurrence, and how it compares with other investigational radiotracers and conventional imaging modalities.
Collapse
Affiliation(s)
- Sonya Youngju Park
- Department of Radiology, College of Medicine, The Catholic University of Korea, Seocho-gu, Seoul, Republic of Korea (South).,Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University, Stanford, California
| | - Sae Jung Na
- Department of Radiology, College of Medicine, The Catholic University of Korea, Seocho-gu, Seoul, Republic of Korea (South).,Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Songpa-gu, Seoul, Republic of Korea (South)
| | - Meena Kumar
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University, Stanford, California
| | - Camila Mosci
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University, Stanford, California
| | - Mirwais Wardak
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University, Stanford, California
| | | | | | | | | | | | - Yong Mee Cho
- Department of Pathology, Asan Medical Center, University of Ulsan College of Medicine, Songpa-gu, Seoul, Republic of Korea (South)
| | - Hanjong Ahn
- Department of Urology, Asan Medical Center, University of Ulsan College of Medicine, Songpa-gu, Seoul, Republic of Korea (South)
| | - Sun Young Chae
- Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Songpa-gu, Seoul, Republic of Korea (South)
| | - Hye Ok Kim
- Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Songpa-gu, Seoul, Republic of Korea (South).,Department of Nuclear Medicine, Ewha Woman's University College of Medicine, Seodaemun-gu, Seoul, Republic of Korea (South)
| | - Dae Hyuk Moon
- Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Songpa-gu, Seoul, Republic of Korea (South)
| | - Sanjiv S Gambhir
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University, Stanford, California.,Department of Bioengineering, Department of Materials Science & Engineering, Stanford Bio-X Program, Stanford University, Stanford, California
| | - Erik S Mittra
- Molecular Imaging Program at Stanford (MIPS), Department of Radiology, Stanford University, Stanford, California. .,Department of Diagnostic Radiology, Oregon Health & Science University, Portland, Oregon
| |
Collapse
|