PET Imaging Protocol Research Articles

Assessing amyloid plaque burden in aging marmosets and genetically engineered PSEN1 mutation carriers using 11C‐PiB PET

AbstractBackgroundThere is an urgent need to develop novel animal models to investigate the underlying cellular and molecular root causes of the pathogenesis and progression of AD. Our group has worked to establish the common marmoset as the first primate‐specific model of AD to reveal the earliest cellular and molecular events of AD processes and allow charting of AD progression from its inception. For this, we established a colony of outbred marmosets and used genetic engineering techniques to generate marmosets carrying the PSEN1‐C410Y and PSEN1‐A426P mutations that cause early‐onset, familial AD. The present study aims to use PET imaging to access and track the progression of Ab plaque burden non‐invasively and longitudinally in our marmoset models of AD.MethodMarmosets anesthetized with isoflurane delivered via a facemask were placed in a preclinical PET/CT scanner customized with marmoset‐specific beds. Respiratory rate, heart rate, arterial O2 saturation, and rectal temperature were monitored and maintained at normal physiological values. Our PET imaging protocol follows the Alzheimer’s Disease Neuroimaging Initiative (ADNI). The amyloid‐binding 11C‐Pittsburgh Compound B (11C‐PiB) was delivered intravenously in doses varying from 18.5 – 185 MBq (0.5 – 5 mCi). A 90‐min dynamic acquisition was performed immediately following the radiotracer injection, followed by a 3D CT scan acquired at 200 µm isotropic resolution. After the PET/CT neuroimaging scan, the marmosets were recovered from anesthesia and returned to their home cages.ResultWe observed positive 11C‐PiB binding and retention in the brains of aging outbred marmosets and in marmosets harboring PSEN1 mutations. Significant 11C‐PiB retention was observed in the cortex and white matter tracts. The areas with the highest 11C‐PiB retention were the lateral frontal cortex, anterior cingulate cortex, and temporal lobe regions.ConclusionThis study demonstrates using 11C‐PiB to track Ab plaque burden in the brains of aging marmosets and marmosets harboring PSEN1 mutations. As observed in human patients of AD, the amount of 11C‐PiB bound (measured in SUV and SUVR units) varied from animal to animal, and we are currently performing group analysis to investigate the dependence of 11C‐PiB retention on age and sex. This research was funded by NIH/NIA grants R24AG073190 and U19AG074866.

Assessing amyloid plaque burden in aging marmosets and genetically engineered PSEN1 mutation carriers using 11C‐PiB PET

AbstractBackgroundThere is an urgent need to develop novel animal models to investigate the underlying cellular and molecular root causes of the pathogenesis and progression of AD. Our group has worked to establish the common marmoset as the first primate‐specific model of AD to reveal the earliest cellular and molecular events of AD processes and allow charting of AD progression from its inception. For this, we established a colony of outbred marmosets and used genetic engineering techniques to generate marmosets carrying the PSEN1‐C410Y and PSEN1‐A426P mutations that cause early‐onset, familial AD. The present study aims to use PET imaging to access and track the progression of Ab plaque burden non‐invasively and longitudinally in our marmoset models of AD.MethodMarmosets anesthetized with isoflurane delivered via a facemask were placed in a preclinical PET/CT scanner customized with marmoset‐specific beds. Respiratory rate, heart rate, arterial O2 saturation, and rectal temperature were monitored and maintained at normal physiological values. Our PET imaging protocol follows the Alzheimer’s Disease Neuroimaging Initiative (ADNI). The amyloid‐binding 11C‐Pittsburgh Compound B (11C‐PiB) was delivered intravenously in doses varying from 18.5 – 185 MBq (0.5 – 5 mCi). A 90‐min dynamic acquisition was performed immediately following the radiotracer injection, followed by a 3D CT scan acquired at 200 µm isotropic resolution. After the PET/CT neuroimaging scan, the marmosets were recovered from anesthesia and returned to their home cages.ResultWe observed positive 11C‐PiB binding and retention in the brains of aging outbred marmosets and in marmosets harboring PSEN1 mutations. Significant 11C‐PiB retention was observed in the cortex and white matter tracts. The areas with the highest 11C‐PiB retention were the lateral frontal cortex, anterior cingulate cortex, and temporal lobe regions.ConclusionThis study demonstrates using 11C‐PiB to track Ab plaque burden in the brains of aging marmosets and marmosets harboring PSEN1 mutations. As observed in human patients of AD, the amount of 11C‐PiB bound (measured in SUV and SUVR units) varied from animal to animal, and we are currently performing group analysis to investigate the dependence of 11C‐PiB retention on age and sex.This research was funded by NIH/NIA grants R24AG073190 and U19AG074866.

A Microdose PET Study of the Safety, Immunogenicity, Biodistribution, and Radiation Dosimetry of 18F-FB-A20FMDV2 for Imaging the Integrin αvβ6.

The αvβ6 integrin is involved in the pathogenesis of cancer and fibrosis. A radiolabeled 20-amino-acid αvβ6-binding peptide, derived from the foot and mouth virus (NAVPNLRGDLQVLAQKVART [A20FMDV2]), has been developed to image αvβ6 levels preclinically. This study was designed to translate these findings into a clinical PET imaging protocol to measure the expression of αvβ6 in humans. Methods: Preclinical toxicology was undertaken, and a direct immunoassay was developed for 4-fluorobenzamide (FB)-A20FMDV2. Four healthy human subjects (2 male and 2 female) received a single microdose of 18F-FB-A20FMDV2 followed by a multibed PET scan of the whole body over more than 3 h. Results: There were no findings in the preclinical toxicology assessments, and no anti-A20FMDV2 antibodies were detected before or after dosing with the PET ligand. The mean and SD of the administered mass of 18F-FB-A20FMDV2 was 8.7 ± 4.4 μg (range, 2.7-13.0 μg). The mean administered activity was 124 ± 20 MBq (range, 98-145 MBq). There were no adverse or clinically detectable pharmacologic effects in any of the subjects. No significant changes in vital signs, laboratory study results, or electrocardiography results were observed. Uptake of radioactivity was observed in the thyroid, salivary glands, liver, stomach wall, spleen, kidneys, ureters, and bladder. Time-activity curves indicated that the highest activity was in the bladder content, followed by the kidneys, small intestine, stomach, liver, spleen, thyroid, and gallbladder. The largest component of the residence times was the voided urine, followed by muscle, bladder, and liver. Using the mean residence time over all subjects as input to OLINDA/EXM, the effective dose was determined to be 0.0217 mSv/MBq; using residence times from single subjects gave an SD of 0.0020 mSv/MBq from the mean. The critical organ was the urinary bladder, with an absorbed dose of 0.18 mGy/MBq. Conclusion:18F-FB-A20FMDV2 successfully passed toxicology criteria, showed no adverse effects in this first-in-humans study, and has an effective dose that enables multiple scans in a single subject.

In vivo [64Cu]CuCl2 PET imaging reveals activity of Dextran-Catechin on tumor copper homeostasis.

Given the strong clinical evidence that copper levels are significantly elevated in a wide spectrum of tumors, copper homeostasis is considered as an emerging target for anticancer drug design. Monitoring copper levels in vivo is therefore of paramount importance when assessing the efficacy of copper-targeting drugs. Herein, we investigated the activity of the copper-targeting compound Dextran-Catechin by developing a [64Cu]CuCl2 PET imaging protocol to monitor its effect on copper homeostasis in tumors.Methods: Protein expression of copper transporter 1 (CTR1) in tissue microarrays representing 90 neuroblastoma patient tumors was assessed by immunohistochemistry. Western blotting analysis was used to study the effect of Dextran-Catechin on the expression of CTR1 in neuroblastoma cell lines and in tumors. A preclinical human neuroblastoma xenograft model was used to study anticancer activity of Dextran-Catechin in vivo and its effect on tumor copper homeostasis. PET imaging with [64Cu]CuCl2 was performed in such preclinical neuroblastoma model to monitor alteration of copper levels in tumors during treatment.Results: CTR1 protein was found to be highly expressed in patient neuroblastoma tumors by immunohistochemistry. Treatment of neuroblastoma cell lines with Dextran-Catechin resulted in decreased levels of glutathione and in downregulation of CTR1 expression, which caused a significant decrease of intracellular copper. No changes in CTR1 expression was observed in normal human astrocytes after Dextran-Catechin treatment. In vivo studies and PET imaging analysis using the neuroblastoma preclinical model revealed elevated [64Cu]CuCl2 retention in the tumor mass. Following treatment with Dextran-Catechin, there was a significant reduction in radioactive uptake, as well as reduced tumor growth. Ex vivo analysis of tumors collected from Dextran-Catechin treated mice confirmed the reduced levels of CTR1. Interestingly, copper levels in blood were not affected by treatment, demonstrating potential tumor specificity of Dextran-Catechin activity.Conclusion: Dextran-Catechin mediates its activity by lowering CTR1 and intracellular copper levels in tumors. This finding further reveals a potential therapeutic strategy for targeting copper-dependent cancers and presents a novel PET imaging method to assess patient response to copper-targeting anticancer treatments.

A cross-sectional comparison of brain glucose and ketone metabolism in cognitively healthy older adults, mild cognitive impairment and early Alzheimer's disease

IntroductionDeteriorating brain glucose metabolism precedes the clinical onset of Alzheimer's disease (AD) and appears to contribute to its etiology. Ketone bodies, mainly β-hydroxybutyrate and acetoacetate, are the primary alternative brain fuel to glucose. Some reports suggest that brain ketone metabolism is unchanged in AD but, to our knowledge, no such data are available for MCI. ObjectiveTo compare brain energy metabolism (glucose and acetoacetate) and some brain morphological characteristics in cognitively healthy older adult controls (CTL), mild cognitive impairment (MCI) and early AD. Methods24 CTL, 20 MCI and 19AD of similar age and metabolic phenotype underwent a dual-tracer PET and MRI protocol. The uptake rate constants and cerebral metabolic rate of glucose (KGlu, CMRGlu) and acetoacetate (KAcAc, CMRAcAc) were evaluated with PET using [18F]-fluorodeoxyglucose ([18F]-FDG), a glucose analogue, and [11C]-acetoacetate ([11C]-AcAc), a ketone PET tracer. Regional brain volume and cortical thickness were evaluated by T1-weighted MRI. ResultsIn AD compared to CTL, CMRGlu was ~11% lower in the frontal, parietal, temporal lobes and in the cingulate gyrus (p<0.05). KGlu was ~15% lower in these same regions and also in subcortical regions. In MCI compared to CTL, ~7% glucose hypometabolism was present in the cingulate gyrus. Neither regional nor whole brain CMRAcAc or KAcAc were significantly different between CTL and MCI or AD. Reduced gray matter volume and cortical thinning were widespread in AD compared to CTL, whereas, in MCI compared to CTL, volumes were reduced only in the temporal cortex and cortical thinning was most apparent in temporal and cingulate regions. DiscussionThis quantitative kinetic PET and MRI imaging protocol for brain glucose and acetoacetate metabolism confirms that the brain undergoes structural atrophy and lower brain energy metabolism in MCI and AD and demonstrates that the deterioration in brain energy metabolism is specific to glucose. These results suggest that a ketogenic intervention to increase energy availability for the brain is warranted in an attempt to delay further cognitive decline by compensating for the brain glucose deficit in MCI and AD.

DEEP AND FREQUENT PHENOTYPING STUDY: PET AND MR IMAGING PROTOCOL

DEEP AND FREQUENT PHENOTYPING STUDY: PET AND MR IMAGING PROTOCOL

DEEP AND FREQUENT PHENOTYPING STUDY: PET AND MR IMAGING PROTOCOL

DEEP AND FREQUENT PHENOTYPING STUDY: PET AND MR IMAGING PROTOCOL

Abstract 1485: Pilot study of VPAC1 targeted PET imaging of prostate cancer

Abstract Introduction: Vasoactive Intestinal Peptide and Pituitary Adenylate Cyclase Activating Peptide Receptor 1 (VPAC1) is over-expressed in prostate cancer (PC), representing a highly suitable target for imaging and treatment. VPAC1 expression occurs at the onset of the malignancy, before alterations of cell morphology, which may be prior to elevation of serum PSA. We have successfully used VPAC1 receptor-specific peptide constructs to image breast cancer in experimental animal models, and in humans. We hypothesized that VPAC1 expressed in high density on PC can be targeted for detection of intraprostatic tumor foci, as correlated with whole mount radical prostatectomy specimens, using TP3805, a VPAC1 specific biomolecule labeled with Cu-64 a PET imaging radionuclide. Methods: Twenty five men with prostate cancer undergoing radical prostatectomy were imaged preoperatively as part of a PET imaging protocol targeting VPAC1. The PET images were compared to whole mount radical prostatectomy pathologic analysis. De-paraffinized whole mount pathology slides from two patients who participated in VPAC1 PET imaging protocol, as well as slides from 3 BPH patients, one malignant lymph node and one benign lymph node were incubated with Cu-64-TP3805, washed thoroughly with PBS, dried and subjected to 15 second digital autoradiography. Slides were then H&amp;E stained and autoradiography images were compared with prostate H&amp;E staining in which tumor foci were delineated. Results: Prostate cancer foci (n = 30/31) were identified by autoradiography imaging. Autoradiography missed one malignant lesion due to technical artifact. Additionally 6 small cancerous lesions were identified by autoradiography that were not previously noted by histologic examinations. A total of 7 additional lesions seen by autoradiography in areas without prostate cancer foci corresponded to areas of high grade prostatic intraepithelial neoplasia (HGPIN). The positive lymph node and the benign lymph node were correctly identified by autoradiography. For the three BPH patients without any cancer, no lesions were noted by autoradiography. Conclusion: VPAC1 peptide analog constructs accurately identified foci of prostate cancer on whole mount radical prostatectomy specimens. Several additional lesions were also identified. Detection of HGPIN is consistent with the early expression of VPAC1 prior to the modulations in cell morphology. The PPV (97%) and NPV(100%) were excellent, validating VPAC1 as a potential theranostic target for prostate cancer imaging and treatment. Support: NIH R01 CA157372-01 and by NuView, Inc. (MLT). Citation Format: Edouard J. Trabulsi, Pradeep Kumar, Sushil Tripathi, Ruth Birbe, Peter McCue, Eric Wickstrom, Charles Intenzo, Sung Kim, Robert Den, Leonard Gomella, Mathew L. Thakur. Pilot study of VPAC1 targeted PET imaging of prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1485. doi:10.1158/1538-7445.AM2015-1485

PD4-09 VASOACTIVE INTESTINAL PEPTIDE AND PITUITARY ADENYLATE CYCLASE ACTIVATING PEPTIDE RECEPTOR 1 (VPAC1) TARGETED IMAGING OF PROSTATE CANCER: A PILOT STUDY

INTRODUCTION AND OBJECTIVES: Prostate cancer (CaP) overexpresses VPAC1, representing a highly suitable target for imaging and treatment. VPAC1 is over-expressed at the onset of the malignancy, which may be prior to elevation of PSA, and before cell morphology is altered. We have successfully used VPAC1 receptor-specific peptide constructs to image breast cancer in experimental animal models, and in humans. We hypothesized that VPAC1 expressed in high density on PC can be targeted for detection of intraprostatic tumor foci on whole mount radical prostatectomy specimens, using TP3805, a VPAC1 specific biomolecule labeled with Cu-64 a PET imaging radionuclide. METHODS: As part of a PET imaging protocol targeting VPAC1, men (N1⁄425) with prostate cancer undergoing radical prostatectomy were imaged preoperatively, and compared to whole mount radical prostatectomy pathologic analysis. De-paraffinized slides from whole mount pathology from two patients who participated the protocol, as well as one malignant lymph node and one benign lymph node specimens and 3 BPH negative controls underwent digital autoradiography with Cu-64, and then were H&E stained. Autoradiography images were compared with prostate H&E staining in which tumor foci were delineated. RESULTS: Prostate cancer foci (n1⁄430/31) were identified by autoradiography imaging (Figure 1). Autoradiography missed one malignant lesion due to technical artifact. Additionally, 6 small cancerous lesions were identified by autoradiography that were not previously noted by histologic examinations. A total of 7 additional lesions seen by autoradiography corresponded with HGPIN. The positive lymph node and the benign lymph node were correctly identified by auto radiography (Fig.2). For the 3 BPH patients, no cancer foci were noted by autoradiography. CONCLUSIONS: VPAC1 peptide analog constructs accurately identified foci of prostate cancer on whole mount radical prostatectomy specimens. Several additional lesions were also identified. Detection of HGPIN is consistent with the early expression of VPAC1 prior to the modulations in cell morphology. The PPV (97%) and NPV(100%) were excellent, validating VPAC1 as a potential theragnostic target for prostate cancer imaging and treatment.

Correlation of perfusion MRI and 18F-FDG PET imaging biomarkers for monitoring regorafenib therapy in experimental colon carcinomas with immunohistochemical validation.

ObjectivesTo investigate a multimodal, multiparametric perfusion MRI / 18F-fluoro-deoxyglucose-(18F-FDG)-PET imaging protocol for monitoring regorafenib therapy effects on experimental colorectal adenocarcinomas in rats with immunohistochemical validation.Materials and MethodsHuman colorectal adenocarcinoma xenografts (HT-29) were implanted subcutaneously in n = 17 (n = 10 therapy group; n = 7 control group) female athymic nude rats (Hsd:RH-Foxn1rnu). Animals were imaged at baseline and after a one-week daily treatment protocol with regorafenib (10 mg/kg bodyweight) using a multimodal, multiparametric perfusion MRI/18F-FDG-PET imaging protocol. In perfusion MRI, quantitative parameters of plasma flow (PF, mL/100 mL/min), plasma volume (PV, %) and endothelial permeability-surface area product (PS, mL/100 mL/min) were calculated. In 18F-FDG-PET, tumor-to-background-ratio (TTB) was calculated. Perfusion MRI parameters were correlated with TTB and immunohistochemical assessments of tumor microvascular density (CD-31) and cell proliferation (Ki-67).ResultsRegorafenib significantly (p<0.01) suppressed PF (81.1±7.5 to 50.6±16.0 mL/100mL/min), PV (12.1±3.6 to 7.5±1.6%) and PS (13.6±3.2 to 7.9±2.3 mL/100mL/min) as well as TTB (3.4±0.6 to 1.9±1.1) between baseline and day 7. Immunohistochemistry revealed significantly (p<0.03) lower tumor microvascular density (CD-31, 7.0±2.4 vs. 16.1±5.9) and tumor cell proliferation (Ki-67, 434.0 ± 62.9 vs. 663.0 ± 98.3) in the therapy group. Perfusion MRI parameters ΔPF, ΔPV and ΔPS showed strong and significant (r = 0.67-0.78; p<0.01) correlations to the PET parameter ΔTTB and significant correlations (r = 0.57-0.67; p<0.03) to immunohistochemical Ki-67 as well as to CD-31-stainings (r = 0.49-0.55; p<0.05).ConclusionsA multimodal, multiparametric perfusion MRI/PET imaging protocol allowed for non-invasive monitoring of regorafenib therapy effects on experimental colorectal adenocarcinomas in vivo with significant correlations between perfusion MRI parameters and 18F-FDG-PET validated by immunohistochemistry.

Heterogeneity in stabilization phenomena in FLT PET images of canines

3ʹ-(18F)fluoro-3ʹ-deoxy-L-thymidine (FLT) is a PET marker of cellular proliferation. Its tissue uptake rate is often quantified with a Standardized Uptake Value (SUV), although kinetic analysis provides a more accurate quantification. The purpose of this study is to investigate the heterogeneity in FLT stabilization phenomena.The study was done on 15 canines with spontaneously occurring sinonasal tumours. They were imaged dynamically for 90 min with FLT PET/CT twice; before and during the radiotherapy. Images were analyzed for kinetics on a voxel basis through compartmental analysis. Stabilization curves were calculated as a time-dependant correlation between the time-dependant SUV and the kinetic parameters (voxel values within the tumour were correlated). Stabilization curves were analyzed for stabilization speed, maximal correlation and correlation decrease following the maximal correlation. These stabilization parameters were correlated with the region-averaged kinetic parameters.The FLT SUV was highly correlated with vasculature fraction immediately post-injection, followed by maximum in correlation with the perfusion/permeability. At later times post-injection the FLT SUV was highly correlated (Pearson correlation coefficient above 0.95) with the FLT influx parameter for cases with tumour-averaged SUV30–50 min above 2, while others were indeterminate (correlation coefficients from 0.1 to 0.97). All cases with highly correlated SUV and FLT influx parameter had correlation coefficient within 0.5% of its maximum in the period of 30–50 min post-injection. Stabilization time was inversely proportional to the FLT influx rate. Correlation between the FLT SUV and FLT influx parameter dropped at later times post-injection with drop being proportional to the dephosphorylation rate. The FLT was found to be metabolically stable in canines.FLT PET imaging protocol should define minimal and maximal FLT uptake period, which would be 30–50 min for our patients. Additionally, kinetic analysis should be used when low FLT avidity is expected. Low SUVs should be treated with great caution.

Dopaminergic Mechanisms of Individual Differences in Human Effort-Based Decision-Making

Preferences for different combinations of costs and benefits are a key source of variability in economic decision-making. However, the neurochemical basis of individual differences in these preferences is poorly understood. Studies in both animals and humans have demonstrated that direct manipulation of the neurotransmitter dopamine (DA) significantly impacts cost/benefit decision-making, but less is known about how naturally occurring variation in DA systems may relate to individual differences in economic behavior. In the present study, 25 healthy volunteers completed a dual-scan PET imaging protocol with [(18)F]fallypride and d-amphetamine to measure DA responsivity and separately completed the effort expenditure for rewards task, a behavioral measure of cost/benefit decision-making in humans. We found that individual differences in DA function in the left striatum and ventromedial prefrontal cortex were correlated with a willingness to expend greater effort for larger rewards, particularly when probability of reward receipt was low. Additionally, variability in DA responses in the bilateral insula was negatively correlated with willingness to expend effort for rewards, consistent with evidence implicating this region in the processing of response costs. These findings highlight the role of DA signaling in striatal, prefrontal, and insular regions as key neurochemical mechanisms underlying individual differences in cost/benefit decision-making.