A clickable alkyne-modified arylborimidine is rapidly converted in 15 minutes to a highly polar 18F-aryltrifluoroborate anion (18F-ArBF3
-) at high specific activity. Following labeling, the alkyne-18F-ArBF3
- was conjugated to the peptide bombesin (BBN) within 25 minutes in a second step without need for prior work-up making this one-pot-two-step method easy, user-friendly, and generally applicable. Bombesin was chosen to provide functional PET images of prostate cancer xenografts in mice of which there are few. Whereas BBN is labeled to provide some of the first in vivo tumor images based on this technique, click-labeling is recognized for its generality and broad substrate scope. Hence these results are likely to be useful for click labeling most peptides and other biomolecules.
18F-labeling; PET imaging; click chemistry; bombesin imaging
The radioiodinated thymidine analogue, FIAU, is a tracer that has been developed for reporter gene, for cells that were transfected with herpes simplex virus thymidine kinase, HSV-TK. FIAU is also a specific substrate of bacterial TK due to the homology between viral and bacterial TK. In this issue of AJNMMI (http://www.ajnmmi.us), Pullamb-hatla et al. reported that the accumulation of 125I-FIAU in pulmonary infectious foci correlated with the bacterial burden in the lungs. 125I-FIAU could be used to monitor the efficacy of anti-microbial therapy in mice. Potentially 124I-FIAU PET could be used to discriminate microbial from sterile inflammation in patients with prosthetic implants.
Infection; inflammation; reporter gene imaging; positron emission tomography (PET)
6-Deoxy-6-[18F]fluoro-D-fructose (6-[18F]FDF) is a promising PET radiotracer for imaging GLUT5 in breast cancer. The present work describes GMP synthesis of 6-[18F]FDF in an automated synthesis unit (ASU) and dosimetry calculations to determine radiation doses in humans. GMP synthesis and dosimetry calculations are important prerequisites for first-in-human clinical studies of 6-[18F]FDF. The radiochemical synthesis of 6-[18F]FDF was optimized and adapted to an automated synthesis process using a Tracerlab FXFN ASU (GE Healthcare). Starting from 30 GBq of cyclotron-produced n.c.a. [18F]fluoride, 2.9 ± 0.1 GBq of 6-[18F]FDF could be prepared within 50 min including HPLC purification resulting in an overall decay-corrected radiochemical yield of 14 ± 3% (n = 11). Radiochemical purity exceeded 95%, and the specific activity was greater than 5.1 GBq/μmol. Sprague-Dawley rats were used for biodistribution experiments, and dynamic and static small animal PET experiments. Biodistribution studies served as basis for allometric extrapolation to the standard man anatomic model and normal organ-absorbed dose calculations using OLINDA/EXM software. The calculated human effective dose for 6-[18F]FDF was 0.0089 mSv/MBq. Highest organ doses with a dose equivalent of 0.0315 mSv/MBq in a humans were found in bone. Injection of 370 MBq (10 mCi) of 6-[18F]FDF results in an effective whole body radiation dose of 3.3 mSv in humans, a value comparable to that of other 18F-labeled PET radiopharmaceuticals. The optimized automated synthesis under GMP conditions, the good radiochemical yield and the favorable human radiation dosimetry estimates support application of 6-[18F]FDF in clinical trials for molecular imaging of GLUT5 in breast cancer patients.
Positron emission tomography; automated synthesis; dosimetry; 6-[18F]FDF; GLUT5
Utilizing novel imaging modalities for defining response and predicting long-term outcome after treatment may have a significant impact on cancer patient management. 18F-FDG PET/CT has great potential for use in early assessment of response to cancer therapy. However, the lack of a general consensus on a specific set of response criteria makes adoption of PET difficult for the oncology community. The optimal time after initiating therapy for assessing response to treatment also has yet to be clearly determined.
18F-FDG; PET/CT; Therapeutic response; Cancer
111In-capromab pendetide is an imaging probe for noninvasive detection of prostate cancer dissemination, and can be difficult to interpret because of low photon statistics resulting in noisy images with limited anatomical precision. We examined if a 16-slice multidetector computed tomography (MDCT) combined with single photon emission computed tomography (SPECT) could increase the impact on the clinical management and improve confidence in SPECT image interpretations in comparison to a relatively low-mA (limited resolution) CT. 17 scans were reviewed from a SPECT combined with low-mA CT scanner; 21 scans were reviewed from a SPECT combined with 16-slice MDCT scanner. Reports of the clinical interpretations from the imaging studies, additional examinations performed by referring physicians as a follow-up to the imaging results, and long-term clinical and laboratory follow-ups were used to define confidence of the SPECT/CT readings and impact of the readings on the patient management. The impact was defined as: the occurrence of the 111In-capromab pendetide interpretation resulted in additional imaging studies or biopsies. MDCT improved the quality and confidence in the characterization of small lymph nodes with or without uptake of 111In-capromab pendetide. The increased confidence with MDCT in SPECT/CT readings was evident in all cases reviewed in this study, and the impact on the clinical management was higher (8 out of 21) using SPECT/MDCT than the impact using SPECT combined with low-mA CT (2 out of 17). The dual-modality SPECT/CT provides a quantifiable benefit when MDCT is used instead of low-mA CT, particularly for prostate cancer evaluations using 111In-capromab pendetide.
Prostate cancer; capromab pendetide; SPECT/CT; MDCT; prostate specific membrane antigen (PSMA)
We aimed to explore the effects of 90Y-DOTATOC and 90Y-DOTATOC plus 177Lu-DOTATOC on survival of patients with metastasized gastrinoma. Patients with progressive metastasized gastrinoma were treated with repeated cycles of 90Y-DOTATOC or with cycles alternating between 90Y-DOTATOC and 177Lu-DOTATOC until tumor progression or permanent toxicity. Multivariable Cox regression analyses were used to study predictors of survival. A total of 36 patients were enrolled; 30 patients received 90Y-DOTATOC (median activity per patient 11.8GBq; range: 6.1-62.2GBq) and 6 patients received 90Y-DOTATOC plus 177Lu-DOTATOC (median activity per patient: 14.8GBq; range: 7.4-14.8GBq). Response was found in 26 patients (72.2%), including morphological (n=12, 33.3%), biochemical (n=14, 38.9%) and/or clinical response (n=6, 16.2%). A total of 21 patients (58.3%) experienced hematotoxicity grade 1/2, while 1 patient (2.8%) experienced hematotoxicity grade 3; no grade 4 hematotoxicity occurred. Furthermore, 2 patients (5.6%) developed grade 4 renal toxicity; no grade 5 renal toxicity occurred. Responders had a significantly longer median survival from time of enrollment than non-responders (45.1 months, range: 37.1-53.1 months vs. 12.6 months, range: 11.0-14.2, hazard ratio: 0.12 (0.027-0.52), p=0.005). Additionally, there was a trend towards longer median survival with 90Y-DOTATOC plus 177Lu-DOTATOC as compared to 90Y-DOTATOC alone (60.2 months, range: 19.8-100.6 months vs. 27.0 months, range: 4.0-50.0, hazard ratio: 0.21 (0.01-3.98), p=0.16). Response to 90Y-DOTATOC and 90Y-DOTATOC plus 177Lu-DOTATOC therapy is associated with a longer survival in patients with metastasized gastrinoma. Both treatment regimens are promising tools for management of progressive gastrinoma.
Yttrium; lutetium; somatostatin; survival; gastrinoma
To evaluate 18F-labeled-fluorodeoxyglucose (18F-FDG-) and 18F-labeled-sodium fluoride (18F-NaF-) positron emission tomography/computed tomography (PET/CT) as biomarkers in metastatic castrate-resistant prostate cancer (mCRPC). Nine men (53-75 years) in a phase 1 trial of abiraterone and cabozantinib had 18F-FDG-PET/CT, 18F-NaF-PET/CT and standard imaging (99mTc-labeled-methylene-diphosphonate (99mTc-MDP) bone scan and abdominal/pelvic CT) at baseline and after 8 weeks of therapy. Baseline disease was classified as widespread 18F-FDG-avid, oligometastatic 18F-FDG-avid (1 site), or non-18F-FDG-avid. Metabolic response was classified using European Organisation for Research and Treatment of Cancer (EORTC) criteria. Treatment response using Response Evaluation Criteria in Solid Tumors (RECIST) 1.1, Prostate Cancer Working Group 2 (PCWG2) guidelines and days on trial (DOT) were recorded. All men were followed for 1 year or until progression. Four men had 18F-FDG-avid disease: two with widespread (DOT 53 and 76) and two with oligometastatic disease (DOT 231 and still on trial after 742+ days). Five men had non-18F-FDG-avid disease; three remained stable or improved (2 still on trial while one discontinued for non-oncologic reasons; DOT 225-563+), and 2 progressed (DOT 285 and 532). Despite the small sample size, Kaplan-Meier analysis showed a significant difference in progression free survival (PFS) between men with widespread 18F-FDG-avid, oligometastatic 18F-FDG-avid and non-18F-FDG-avid disease (p < 0.01). All men had 18F-NaF-avid disease. Neither 18F-NaF-avid disease extent nor intensity was predictive of treatment response. 18F-FDG-PET/CT may be superior to 18F-NaF-PET/CT and standard imaging in men with mCRPC on abiraterone and cabozantinib. 18F-FDG-PET/CT may have potential to stratify men into 3 groups (widespread vs. oligometastatic 18F-FDG-avid vs. non-18F-FDG-avid mCRPC) to tailor therapy. Further evaluation is warranted.
PET/CT; FDG; NaF; prostate cancer; bone scan
A rare subpopulation of cancer cells known as cancer stem cells (CSCs) have distinct characteristics resembling stem cells, including cell renewal capability, differentiation into multiple lineages, and endless proliferation potential. Cumulating evidence has revealed that CSCs are responsible for tumorigenicity, invasion, metastasis, and therapeutic resistance. Despite continued investigation of CSCs, in vivo behavior of CSCs is not yet fully understood. The in vivo imaging modalities of optical, nuclear, and magnetic resonance are currently being employed to investigate the complexity behind the CSCs behavior. Valuable information that were previously obscured by the limitations of in vitro techniques now are currently being revealed. These studies give us a more comprehensive insight about what happen to CSCs in vivo. This review will briefly discuss the recent findings on CSCs behavior as informed by in vivo imaging studies.
Cancer stem cell; MRI; PET; fluorescence imaging; in vivo imaging; molecular imaging; cell tracking
Multi-modal imaging approaches of tumor metabolism that provide improved specificity, physiological relevance and spatial resolution would improve diagnosing of tumors and evaluation of tumor progression. Currently, the molecular probe FDG, glucose fluorinated with 18F at the 2-carbon, is the primary metabolic approach for clinical diagnostics with PET imaging. However, PET lacks the resolution necessary to yield intratumoral distributions of deoxyglucose, on the cellular level. Multi-modal imaging could elucidate this problem, but requires the development of new glucose analogs that are better suited for other imaging modalities. Several such analogs have been created and are reviewed here. Also reviewed are several multi-modal imaging studies that have been performed that attempt to shed light on the cellular distribution of glucose analogs within tumors. Some of these studies are performed in vitro, while others are performed in vivo, in an animal model. The results from these studies introduce a visualization gap between the in vitro and in vivo studies that, if solved, could enable the early detection of tumors, the high resolution monitoring of tumors during treatment, and the greater accuracy in assessment of different imaging agents.
Glucose; glucose uptake; FDG; deoxyglucose; FDG-PET; multi-modal imaging
Activated macrophages which express somatostatin receptor-2 (SSTR-2) play a vital role in rupture of the vulnerable atherosclerotic plaques, which result in death. 68Ga-DOTATATE binds to somatostatin receptors 2, and therefore, can serve as potential radiotracer to detect atherosclerotic plaques. The purpose of this study was to generate preliminary data with this agent in vulnerable or fibrotic atherosclerotic plaques in the coronary arteries. We evaluated a total of 44 patients with neuroendocrine tumors (NET) who underwent 68Ga-DOTATATE PET/CT. In each subject, 7 segments in the coronary arteries were assessed, maximum SUV values and target-to-background ratios (TBRs) were calculated. The lesions detected by CT (a total of 308) were divided into 3 groups based on the Hounsfield unites (HU), and of which, 131 with HU less than 70 were classified as being normal (Control Group), 129 with HU 71-188 as fibrotic plaques (Group 2), and. 48 lesions with HU more than 188 as atherosclerotic plaques (Group 3). The mean TBR value in the normal group was 1.345 ± 0.58 while the mean TBR value in the fibrotic plaque group was 1.752 ± 1.50 (p 0.0043) and in atherosclerotic plaques group was (2.043 ± 1.76, p<0.0001). There was a significant correlation (p=0.0026) between 68Ga-DOTATATE uptake and the progression to formation of atherosclerotic plaques, based on HU. In patients with neuroendocrine tumors, 68Ga-DOTATATE PET/CT showed significantly increased uptake in the fibrotic and vulnerable atherosclerotic plaques compared to normal coronary arteries suggesting a potential role of this tracer for molecular assessment of coronary artery disease in this population.
Atherosclerotic plaques; 68Ga-DOTATATE; somatostatin receptor; cardiovascular risk factors; macrophage
New developments in PET/CT technology have enabled the commercial availability of continuous bed motion (CBM) acquisition methods. This technology has some potential performance benefits compared to standard step and shoot (SS) imaging, however, this technology has not been assessed with regard to quantitative and image quality parameters compared to traditional SS techniques. This study seeks to compare clinically relevant quantitative and image quality parameters using CBM and SS data collection methods with the intent of providing assistance in making educated decisions regarding imaging protocol development when using CBM technology versus SS imaging.
PET; CT; continuous bed motion; CBM
In this paper we demonstrate, for the first time, the feasibility of a new imaging concept - combined hyperpolarized 13C-pyruvate magnetic resonance spectroscopic imaging (MRSI) and 18F-FDG-PET imaging. This procedure was performed in a clinical PET/MRI scanner with a canine cancer patient. We have named this concept hyper PET. Intravenous injection of the hyperpolarized 13C-pyruvate results in an increase of 13C-lactate, 13C-alanine and 13C-CO2 (13C-HCO3) resonance peaks relative to the tissue, disease and the metabolic state probed. Accordingly, with dynamic nuclear polarization (DNP) and use of 13C-pyruvate it is now possible to directly study the Warburg Effect through the rate of conversion of 13C-pyruvate to 13C-lactate. In this study, we combined it with 18F-FDG-PET that studies uptake of glucose in the cells. A canine cancer patient with a histology verified local recurrence of a liposarcoma on the right forepaw was imaged using a combined PET/MR clinical scanner. PET was performed as a single-bed, 10 min acquisition, 107 min post injection of 310 MBq 18F-FDG. 13C-chemical shift imaging (CSI) was performed just after FDG-PET and 30 s post injection of 23 mL hyperpolarized 13C-pyruvate. Peak heights of 13C-pyruvate and 13C-lactate were quantified using a general linear model. Anatomic 1H-MRI included axial and coronal T1 vibe, coronal T2-tse and axial T1-tse with fat saturation following gadolinium injection. In the tumor we found clearly increased 13C-lactate production, which also corresponded to high 18F-FDG uptake on PET. This is in agreement with the fact that glycolysis and production of lactate are increased in tumor cells compared to normal cells. Yet, most interestingly, also in the muscle of the forepaw of the dog high 18F-FDG uptake was observed. This was due to activity in these muscles prior to anesthesia, which was not accompanied by a similarly high 13C-lactate production. Accordingly, this clearly demonstrates how the Warburg Effect directly can be demonstrated by hyperpolarized 13C-pyruvate MRSI. This was not possible with 18F-FDG-PET imaging due to inability to discriminate between causes of increased glucose uptake. We propose that this new concept of simultaneous hyperpolarized 13C-pyruvate MRSI and PET may be highly valuable for image-based non-invasive phenotyping of tumors. This methods may be useful for treatment planning and therapy monitoring.
Cancer; DNP; hyperpolarized; 13C-pyruvate; MR; response monitoring; 18F-FDG-PET; PET/MR; molecular imaging
Monitoring response to chemo- or radiotherapy is of great importance in clinical practice. Apoptosis imaging serves as a very useful tool for the early evaluation of tumor response. The goal of this study was PET imaging of apoptosis with 18F-labeled recombinant human annexin V linked with 10 histidine tag (18F-rh-His10-annexin V) in nude mice bearing an A549 tumor and rabbits bearing a VX2 lung cancer after paclitaxel therapy. 18F-rh-His10-annexin V was prepared by conjugation of rh-His10-annexin V with N-succinimidyl 4-[18F]fluorobenzoate. Biodistribution was determined in mice by the dissection method and small-animal PET. Single-dose paclitaxel (175 mg/m2) was used to induce apoptosis in A549 and VX2 tumor models. 18F-rh-His10-annexin V was injected into A549 mice and VX rabbits to acquire dynamic and static PET images 72 h after paclitaxel treatment. The uptake of 18F-rh-His10-annexin V in apoptotic cells 4 h after induction was 6.45±0.52 fold higher than that in non-induced cells. High focal uptake of 18F-rh-His10-annexin V was visualized in A549 (SUVmax: 0.35±0.13) and VX2 (0.41±0.23) tumor models after paclitaxel treatment, whereas lower uptake was found in the corresponding tumors before treatment (A549 SUVmax: 0.04±0.02; VX2: 0.009±0.002). The apoptotic index was 75.61±11.56% in the treated VX2 cancer, much higher than that in the untreated VX2 (8.03±2.81%). This study demonstrated the feasibility of 18F-rh-His10-annexin V for the detection of apoptosis after chemotherapy in A549 and VX2 tumor models.
Apoptosis; molecular imaging; recombinant human His10-annexin V; tumor response
Co-infection of human immunodeficiency virus (HIV) and neurosyphilis (NS) has become a rising trend, but the extent of brain damage associated with the concomitant infections remains unknown. Proton magnetic resonance spectroscopy (1H-MRS) can evaluate metabolic changes underlying early brain infections. 25 syphilitic patients (7 HIV-positive with NS; 6 HIV-positive without NS; 5 HIV-negative with NS; 7 non-HIV, non-NS) and 17 healthy controls (HC) underwent single-voxel 1H-MRS in the bilateral hippocampi. Absolute concentrations of major metabolites were measured using a 3T MRI scanner. No significant structural abnormality was detected in all patients. However, metabolic changes were found in the left hippocampus of both the HIV-positive and NS subgroups, showing significantly higher choline (Cho), creatine (Cr) and myo-inositol (mI) compared to HC. In the right hippocampus, HIV-positive subgroup showed significantly higher Cr and reduced NAA, while NS subgroup only showed significantly reduced NAA compared to HC. The non-HIV, non-NS syphilitic subgroup showed no significant difference compared to HC. Substantial metabolic changes occurred in bilateral hippocampi in HIV and NS co-infections. NAA reduction might represent early neuronal damage, while mI/Cho elevation reflects gliosis/inflammatory changes. 1H-MRS could serve as a non-invasive tool to triage patients suspected of NS for lumbar puncture in non-HIV syphilitic patients.
HIV; neurosyphilis; co-infection; magnetic resonance spectroscopy; hippocampus
Tumor hypoxia is associated with increased therapeutic resistance leading to poor treatment outcome. Therefore the ability to detect and quantify intratumoral oxygenation could play an important role in future individual personalized treatment strategies. Positron Emission Tomography (PET) can be used for non-invasive mapping of tissue oxygenation in vivo and several hypoxia specific PET tracers have been developed. Evaluation of PET data in the clinic is commonly based on visual assessment together with semiquantitative measurements e.g. standard uptake value (SUV). However, dynamic PET contains additional valuable information on the temporal changes in tracer distribution. Kinetic modeling can be used to extract relevant pharmacokinetic parameters of tracer behavior in vivo that reflects relevant physiological processes. In this paper, we review the potential contribution of kinetic analysis for PET imaging of hypoxia.
Cu-ATSM; 18F-FMISO; 18F-FETNIM; 18F-FAZA; oxygenation
Pyropheophorbide a (Pyro) is a near-infrared (NIR) fluorescent dye and photosensitizer with high quantum yield that makes the dye suitable for tumor treatment both as an imaging and therapy agent. We have designed and synthesized a series of a Pyro-based NIR probes, based on the conjugation of Pyro with lipids. The nature of our probes requires the use of a lipophilic carrier to deliver the probes to cancer cell membranes. To address this, we have utilized lipid-based nanoparticles (LNPs) consisting of PEGylated lipids, which form the nanoparticle shell, and a lipid core. To endow the LNPs with targeting properties, nitrilotriacetic acid (NTA) lipids were included in the composition that enables the non-covalent attachment of His-tag targeting proteins preserving their functional activity. We found that the nature of the core molecules influence the nanoparticle size, shelf-life and stability at physiological temperature. Two different Pyro-lipid conjugates were loaded either into the core or shell of the LNPs. The conjugates revealed differential ability to be accumulated in the cell membrane of the target cells with time. Thus, the modular organization of the core-shell LNPs allows facile adjustment of their composition with goal to fine tuning the nanoparticle properties for in vivo application.
Lipid-based nanoparticles; near-infrared fluorescent probes; lipid-based fluorescent imaging agent; pyropheophorbide a
Identification by molecular imaging of key processes in handling of transition state metals, such as copper (Cu), will be of considerable clinical value. For instance, the ability to diagnose Wilson’s disease with molecular imaging by identifying copper excretion in an ATP7B-dependent manner will be very significant. To develop highly effective diagnostic approaches, we hypothesized that targeting of radiocopper via the asialoglycoprotein receptor will be appropriate for positron emission tomography, and examined this approach in a rat model of Wilson’s disease. After complexing 64Cu to asialofetuin we studied handling of this complex compared with 64Cu in healthy LEA rats and diseased homozygous LEC rats lacking ATP7B and exhibiting hepatic copper toxicosis. We analyzed radiotracer clearance from blood, organ uptake, and biliary excretion, including sixty minute dynamic positron emission tomography recordings. In LEA rats, 64Cu-asialofetuin was better cleared from blood followed by liver uptake and greater biliary excretion than 64Cu. In LEC rats, 64Cu-asialofetuin activity cleared even more rapidly from blood followed by greater uptake in liver, but neither 64Cu-asialofetuin nor 64Cu appeared in bile. Image analysis demonstrated rapid visualization of liver after 64Cu-asialofetuin administration followed by decreased liver activity in LEA rats while liver activity progressively increased in LEC rats. Image analysis resolved this difference in hepatic activity within one hour. We concluded that 64Cu-asialofetuin complex was successfully targeted to the liver and radiocopper was then excreted into bile in an ATP7B-dependent manner. Therefore, hepatic targeting of radiocopper will be appropriate for improving molecular diagnosis and for developing drug/cell/gene therapies in Wilson’s disease.
ATP7B; diagnosis; metal complex; positron emission tomography; radiocopper; therapy; Wilson’s disease
Towards the development of iron oxide nanoparticles with intrinsically incorporated radionuclides for dual Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) and more recently of Single Photon Emission Computed Tomography/Magnetic Resonance Imaging (SPECT/MRI), we have developed intrinsically radiolabeled [59Fe]-superparamagnetic iron oxide nanoparticles ([59Fe]-SPIONs) as a proof of concept for an intrinsic dual probe strategy. 59Fe was incorporated into Fe3O4 nanoparticle crystal lattice with 92±3% efficiency in thermal decomposition synthesis. Multidentate poly(acrylic acid)-dopamine-poly(ethylene-glycol-2000) (PAA-DOP-PEG) ligands were designed and synthesized based on facile EDC chemistry and utilized to functionalize the [59Fe]-SPIONs. The transverse relaxivity of [59Fe]-SPIONs (97±3 s-1mM-1) was characterized and found to be similar to non-radioactive SPIONs (72±10 s-1mM-1), indicating that 59Fe incorporation does not alter the SPIONs’ MRI contrast properties. [59Fe]-SPIONs were used to evaluate the nanoparticle biodistribution by ex vivo gamma counting and MRI. Nude mice (n=15) were injected with [59Fe]-SPIONs and imaged at various time points with 7T small animal MRI scanner. Ex vivo biodistribution was evaluated by tissue-based gamma counting. MRI signal contrast qualitatively correlates with the %ID/g of [59Fe]-SPIONs, with high contrast in liver (45±6%), medium contrast in kidneys (21±5%), and low contrast in brain (4±6%) at 24 hours. This work demonstrates the synthesis and in vivo application of intrinsically radiolabeled [59Fe]-SPIONs for bimodal detection and provides a proof of concept for incorporation of both gamma- and positron-emitting inorganic radionuclides into the core of metal based MRI contrast agent nanoparticles.
Superparamagnetic iron oxide nanoparticles; intrinsic radiolabeling; biodistribution; PET/MRI; SPECT/MRI; molecular imaging; bimodal detection
The often fatal outcome of ovarian cancer (OC) is related to inadequate detection methods, which may be overcome by development of nuclear imaging agents. Cancer targeting peptides have been identified using in vivo bacteriophage (phage) display technology; however, the majority of these ligands target tumor vasculature. To overcome this problem, a two-tier phage display method was employed to select an ovarian cancer targeting peptide with good pharmacokinetic and imaging properties. A fUSE5 15-amino acid peptide library was screened against xenografted human OC SKOV-3 tumors in mice, which was followed by selection against enriched SKOV-3 cells. The selected peptide RSLWSDFYASASRGP (J18) was synthesized with a GSG-spacer and a 1,4,7,10-tetraazacyclodecane-1,4,7,10-tetraacetic acid (DOTA) chelator and radiolabeled with 111In. SKOV-3 xenografted mice were used to evaluate the biodistribution and single photon emission computed tomography (SPECT) imaging capabilities of the radiolabeled peptide. Competitive binding experiments using 111In-DOTA-GSG-J18 indicated that the peptide displayed a half maximal inhibitory concentration (IC50) value of 10.5 ± 1.1 μM. Biodistribution studies revealed that tumor uptake was 1.63 ± 0.68, 0.60 ± 0.32, 0.31 ± 0.12 and 0.10 ± 0.02% injected dose/g at 30 min, 1 h, 2 h and 4 h post-injection of 111In-DOTA-GSG-J18, respectively. SPECT/CT imaging demonstrated good tumor uptake and minimal background binding. This study demonstrated successful utilization of a two-tier phage display selection process to identify an ovarian cancer avid peptide with excellent SPECT/CT imaging capabilities.
Ovarian cancer; peptide; phage display; SPECT imaging
Increased blood flow and vascular permeability are key events in inflammation. Based on the fact that Gadolinium-1,4,7,10-tetraazacyclododecane-N,N‘,N‘‘,N‘‘‘-tetraacetic acid (Gd-DOTA) is commonly used in magnetic resonance (MR) imaging of blood flow (perfusion), we evaluated the feasibility of its Gallium-68 labeled DOTA analog (68Ga-DOTA) for positron emission tomography (PET) imaging of blood flow in experimental inflammation. Adult, male Sprague-Dawley rats with turpentine oil induced sterile skin/muscle inflammation were anesthetized with isoflurane, and imaged under rest and adenosine-induced hyperemia by means of dynamic 2-min Oxygen-15 labeled water (H2
15O) and 30-min 68Ga-DOTA PET. For the quantification of PET data, regions of interest (ROIs) were defined in the focus of inflammation, healthy muscle, myocardium and heart left ventricle. Radioactivity concentration in the ROIs versus time after injection was determined for both tracers and blood flow was calculated using image-derived input. According to the H2
15O PET, blood flow was 0.69 ± 0.15 ml/min/g for inflammation and 0.15 ± 0.03 ml/min/g for muscle during rest. The blood flow remained unchanged during adenosine-induced hyperemia 0.67 ± 0.11 and 0.12 ± 0.03 ml/min/g for inflammation and muscle, respectively, indicating that adenosine has little effect on blood flow in peripheral tissues in rats. High focal uptake of 68Ga-DOTA was seen at the site of inflammation throughout the 30-min PET imaging. According to the 68Ga-DOTA PET, blood flow measured as the blood-to-tissue transport rate (K1) was 0.60 ± 0.07 ml/min/g for inflammation and 0.14 ± 0.06 ml/min/g for muscle during rest and 0.63 ± 0.08 ml/min/g for inflammation and 0.09 ± 0.04 ml/min/g for muscle during adenosine-induced hyperemia. The H2
15O-based blood flow and 68Ga-DOTA-based K1 values correlated well (r = 0.94, P < 0.0001). These results show that 68Ga-DOTA PET imaging is useful for the quantification of increased blood flow induced by inflammation.
Blood flow; DOTA; Gallium-68; inflammation; Oxygen-15 water; PET; rat
Positron emission tomography (PET) with a number of tracers targeted to particular biological features of cancer has been explored for the imaging evaluation of patients with biochemical recurrence of prostate cancer after curative primary treatment. However, these reports are often heterogeneous in study design, patient cohorts, standards of reference for the imaging findings, data analysis, and data reporting. The aim of our study was to address these limitations by extracting and re-analyzing the PET detection data only from studies that satisfied pre-defined sets of patient selection criteria and verification standards. Our investigation analyzed the effects of 5 tracers (18F-fluorodeoxyglucose (FDG), 11C-acetate (ACET), 11C- or 18F-choline (CHOL), anti-1-amino-3-18F-fluorocyclobutane-1-carboxylic acid (FACBC), and radiolabeled ligand targeted to prostate-specific membrane antigen (PSMA)), 2 treatment types (radical prostatectomy and radiation therapy), and whether the detected disease was local or metastatic, including lesion type (bone, lymph node, soft tissue). FDG exhibited the lowest detection rate for any suspected disease. ACET tended to be advantageous over CHOL in detecting local recurrence and lymph node lesions, even though the difference was not statistically significant. FACBC had greater likelihood of detecting local recurrence, when compared to CHOL, though this difference was not statistically significant. PSMA tended to show a higher proportion of patients with suspected disease compared to the other four tracers. Patients treated with radiation therapy had greater odds of displaying local recurrence on PET than those treated with radical prostatectomy. We also provide suggestions for future investigations that facilitate communication and the impact of the findings.
PET; prostate; cancer; biochemical; recurrence
A retrospective study was conducted from a review of the medical records of patients with early-stage, invasive breast cancer who underwent surgical treatment and sentinel node biopsy with a radiotracer from January 2008 to August 2012 at a single institution (221 patients included). The patients were grouped according to the time of 99mTc Dextran-500 injection, which was preoperatively (with lymphoscintigraphy) (81 patients) or intraoperatively (140 patients). The purpose of the report is to compare the results of sentinel node biopsy of early-stage breast cancer patients who were subjected to intraoperative 99mTc Dextran-500 injections with the patients who received preoperative injections. The following parameters were analyzed: clinical tumor staging, histological and pathological results, size and number of tumor foci, peritumoral vascular invasion, number of lymph nodes removed, size of lymph node metastasis and hormone receptor expression.There were no differences in sentinel lymph node localization whether 99mTc Dextran-500 was injected preoperatively or intraoperatively.
Sentinel lymph node; breast cancer; 99mTc Dextran-500; intraoperative injection; preoperative injection; lymphoscintigraphy
Malignant gliomas, especially glioblastoma multiforme, are the most widely distributed and deadliest brain tumors because of their resistance to surgical and medical treatment. Research of glioma-specific bioconjugates for diagnosis and therapy developed rapidly during the past several years. Many studies have demonstrated that chlorotoxin (CTX) and Buthus martensii Karsch chlorotoxin (BmK CT) specifically inhibited glioma cells growth and metastasis, and accelerated tumor apoptosis. The bioconjugates of CTX or BmK CT with other molecules have played an increasing role in diagnostic imaging and treatment of gliomas. To date, CTX-based bioconjugates have achieved great success in phase I/II clinical trials about safety profiles. Here, we will provide a review on the important role of ion channels in the underlying mechanisms of gliomas invasive growth and how CTX suppresses gliomas proliferation and migration. We will summarize the recent advances in the applications of CTX bioconjugates for gliomas diagnosis and treatment. In addition, we will review recent studies on BmK CT bioconjugates and compare their efficacies with CTX derivatives. Finally, we will address advantages and challenges in the use of CTX or BmK CT bioconjugates as specific agents for theranostic applications in gliomas.
Chlorotoxin (CTX); Buthus martensii Karsch chlorotoxin (BmK CT); glioma; imaging; therapy
Venous thromboembolism (VTE) mostly presenting as deep venous thrombosis (DVT) and pulmonary embolism (PE) affects up to 600,000 individuals in United States each year. Clinical symptoms of VTE are nonspecific and sometimes misleading. Additionally, side effects of available treatment plans for DVT are significant. Therefore, medical imaging plays a crucial role in proper diagnosis and avoidance from over/under diagnosis, which exposes the patient to risk. In addition to conventional structural imaging modalities, such as ultrasonography and computed tomography, molecular imaging with different tracers have been studied for diagnosis of DVT. In this review we will discuss currently available and newly evolving targets and tracers for detection of DVT using molecular imaging methods.
FDG-PET/CT; venous thromboembolism; deep vein thrombosis; SPECT; molecular imaging
Neuroendocrine tumors (NETs) are rare group of neoplasms arising from nervous and endocrine systems. Somatostatin analogue imaging is a functional imaging modality of choice for evaluating the NETs. Recent availability of positron emitting radioisotope labeled somatostatin analogues to image neuroendocrine cancers, has raised the interests to use this new imaging modality in management of patients with NETs. 68Ga-DOTATATE PET/CT has demonstrated superiority in lesion detection compared to Octreoscan, MIBG scintigraphy and MRI. In this article, we reviewed the published studies evaluating the role of 68Ga-DOTATATE PET in diagnosis and management of patients with neuroendocrine tumors and comparing it to current FDA approved imaging modalities including Octreoscan, MIBG scintigraphy, 18F FDG PET/CT, CT and MRI.
Gallium 68; neuroendocrine tumors; DOTATATE; positron emission tomography; hybrid imaging