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PURPOSE: Current checkpoint inhibitor immunotherapy strategies in glioblastoma are challenged by mechanisms of resistance including an immunosuppressive tumor microenvironment. T cell immunoglobulin domain and mucin domain 3 (TIM3) is a late phase checkpoint receptor traditionally associated with T cell exhaustion. We apply fluorescent imaging techniques to explore feasibility of in vivo visualization of the immune state in a glioblastoma mouse model. PROCEDURES: TIM3 monoclonal antibody was conjugated to a near-infrared fluorescent dye, IRDye-800CW (800CW). The TIM3 experimental conjugate and isotype control were assessed for specificity with immunofluorescent staining and flow cytometry in murine cell lines (GL261 glioma and RAW264.7 macrophages). C57BL/6 mice with orthotopically implanted GL261 cells were imaged in vivo over four days after intravenous TIM3-800CW injection to assess tumor specific uptake. Cell specific uptake was then assessed on histologic sections. RESULTS: The experimental TIM3-800CW, but not its isotype control, bound to RAW264.7 macrophages in vitro. Specificity to RAW264.7 macrophages and not GL261 tumor cells was quantitatively confirmed with the corresponding clone of TIM3 on flow cytometry. In vivo fluorescence imaging of the 800CW signal was localized to the intracranial tumor and significantly higher for the TIM3-800CW cohort, relative to non-targeting isotype control, immediately after tail vein injection and for up to 48 hours after injection. Resected organs of tumor bearing mice showed significantly higher uptake in the liver and spleen. TIM3-800CW was seen to co-stain with CD3 (13%), CD11b (29%), and CD206 (26%). CONCLUSIONS: We propose fluorescent imaging of immune cell imaging as a potential strategy for monitoring and localizing immunologically relevant foci in the setting of brain tumors. Alternative markers and target validation will further clarify the temporal relationship of immunosuppressive effector cells throughout glioma resistance.

The purpose of this study is to prospectively evaluate the performance of sodium 18F]fluoride (Na[18F]F)/2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) simultaneous time-of-flight enabled positron emission tomography (PET)/magnetic resonance imaging (MRI) for the detection of skeletal metastases in selected patients with advanced breast and prostate cancers. The institutional review board approved this HIPAA-compliant protocol. Written informed consent was obtained from each patient. A total of 74 patients (23 women and 51 men with breast and prostate cancer, respectively) referred for standard-of-care whole-body bone scintigraphy (WBBS) were enrolled in this prospective study. All patients underwent a [99mTc]methyldiphosphonate ([99mTc]MDP) WBBS followed by Na[18F]F/[18F]FDG PET/MRI. Lesions detected by each imaging modality were tabulated and a lesion-based and patient-based analysis was conducted. On a patient-based analysis, [99mTc]MDP WBBS identified skeletal lesions in 37 patients and PET/MRI in 45 patients. On a lesion-based analysis, WBBS identified a total of 81 skeletal lesions, whereas PET/MRI identified 140 lesions. Additionally, PET/MRI showed extra-skeletal lesions in 19 patients, including lymph nodes (16), prostate (4) lung (3), and liver (2) lesions. The ability of Na[18F]F/[18F]FDG PET/MRI to identify more skeletal lesions than 99mTc-MDP WBBS and to additionally identify extra-skeletal disease may be beneficial for patient care and represent an alternative to the single modalities performed separately. Na[18F]F/[18F]FDG PET/MRI is a promising approach for evaluation of skeletal and extra-skeletal lesions in a selected population of breast and prostate cancer patients.

There is a strong, unmet need for superior positron emission tomography (PET) imaging agents that are able to measure biochemical processes specific to prostate cancer. Pyruvate kinase M2 (PKM2) catalyzes the concluding step in glycolysis and is a key regulator of tumor growth and metabolism. Elevation of PKM2 expression was detected in Gleason 8–10 tumors compared to Gleason 6–7 carcinomas, indicating that PKM2 may potentially be a marker of aggressive prostate cancer. We have recently reported the development of a PKM2-specific radiopharmaceutical [18F]DASA-23 and herein describe its evaluation in cell culture and preclinical models of prostate cancer. The cellular uptake of [18F]DASA-23 was evaluated in a panel of prostate cancer cell lines and compared to that of [18F]FDG. The specificity of [18F]DASA-23 to measure PKM2 levels in cell culture was additionally confirmed through the use of PKM2-specific siRNA. PET imaging studies were then completed utilizing subcutaneous prostate cancer xenografts using either PC3 or DU145 cells in mice. [18F]DASA-23 uptake values over 60-min incubation period in PC3, LnCAP, and DU145 respectively were 23.4 ± 4.5, 18.0 ± 2.1, and 53.1 ± 4.6 % tracer/mg protein. Transient reduction in PKM2 protein expression with siRNA resulted in a 50.1 % reduction in radiotracer uptake in DU145 cells. Small animal PET imaging revealed 0.86 ± 0.13 and 1.6 ± 0.2 % ID/g at 30 min post injection of radioactivity in DU145 and PC3 subcutaneous tumor bearing mice respectively. Herein, we evaluated a F-18-labeled PKM2-specific radiotracer, [18F]DASA-23, for the molecular imaging of prostate cancer with PET. [18F]DASA-23 revealed rapid and extensive uptake levels in cellular uptake studies of prostate cancer cells; however, there was only modest tumor uptake when evaluated in mouse subcutaneous tumor models.

Sigma-1 receptors (S1Rs) play an important role in many neurological disorders. Simultaneous positron emission tomography (PET)/magnetic resonance imaging (MRI) with S1R radioligands may provide valuable information for diagnosing and guiding treatment for these diseases. Our previously reported S1R radioligand, [18F]FTC-146, demonstrated high affinity for the S1R (K i = 0.0025 nM) and excellent selectivity for the S1R over the sigma-2 receptor (S2Rs; K i = 364 nM) across several species (from mouse to non-human primate). Herein, we report the clinical-grade radiochemistry filed with exploratory Investigational New Drug (eIND) and first-in-human PET/MRI evaluation of [18F]FTC-146. [18F]FTC-146 is prepared via a direct [18F] fluoride nucleophilic radiolabeling reaction and formulated in 0.9 % NaCl containing no more than 10 % ethanol through sterile filtration. Quality control (QC) was performed based on USP 823 before doses were released for clinical use. The safety and whole body biodistribution of [18F]FTC-146 were evaluated using a simultaneous PET/MR scanner in two representative healthy human subjects. [18F]FTC-146 was synthesized with a radiochemical yield of 3.3 ± 0.7 % and specific radioactivity of 8.3 ± 3.3 Ci/μmol (n = 10, decay corrected to EOB). Both radiochemical and chemical purities were >95 %; the prepared doses were stable for 4 h at ambient temperature. All QC test results met specified clinical criteria. The in vivo PET/MRI investigations showed that [18F]FTC-146 rapidly crossed the blood brain barrier and accumulated in S1R-rich regions of the brain. There were also radioactivity distributed in the peripheral organs, i.e., the lungs, spleen, pancreas, and thyroid. Furthermore, insignificant uptake of [18F]FTC-146 was observed in cortical bone and muscle. A reliable and automated radiosynthesis for providing routine clinical-grade [18F]FTC-146 for human studies was established in a modified GE TRACERlab FXFN. PET/MRI demonstrated the initial tracer biodistribution in humans, and clinical studies investigating different S1R-related diseases are in progress.

It is well known that cancers exploit immune checkpoints (programmed death 1 receptor (PD-1) and its ligand (PD-L1)) to evade anti-tumor immune responses. Although immune checkpoint (IC) blockade is a promising approach, not all patients respond. Hence, imaging of tumor-infiltrating lymphocytes (TILs) is of high specific interest, as they are known to express PD-1 during activation and subsequent exhaustion in the tumor microenvironment and are thought to be potentially predictive of therapeutic responses to IC blockade. We developed immune-tracers for positron emission tomography (PET) to image hPD-1 status of human peripheral blood mononuclear cells (hPBMCs) adoptively transferred to NOD-scid IL-2Rγnull (NSG) mice (hNSG) bearing A375 human skin melanoma tumors. The anti-PD-1 human antibody (IgG; keytruda) was labeled with either Zr-89 or Cu-64 radiometals to image PD-1-expressing human TILs in vivo. [89Zr] Keytruda (groups = 2; NSG-ctl (control) and hNSG-nblk (non-blocking), n = 3–5, 3.2 ± 0.4 MBq/15–16 μg/200 μl) and [64Cu] Keytruda (groups = 3; NSG-ctl, NSG-blk (blocking), and hNSG-nblk; n = 4, 7.4 ± 0.4 MBq /20-25 μg/200 μl) were administered in mice. PET-CT scans were performed over 1–144 h ([89Zr] Keytruda) and 1–48 h ([64Cu] Keytruda) on mice. hNSG mice exhibited a high tracer uptake in the spleen, lymphoid organs and tumors. At 24 h, human TILs homing into melanoma of hNSG-nblk mice exhibited high signal (mean %ID/g ± SD) of 3.8 ± 0.4 ([89Zr] Keytruda), and 6.4 ± 0.7 ([64Cu] Keytruda), which was 1.5- and 3-fold higher uptake compared to NSG-ctl mice (p = 0.01), respectively. Biodistribution measurements of hNSG-nblk mice performed at 144 h ([89Zr] Keytruda) and 48 h ([64Cu] Keytruda) p.i. revealed tumor to muscle ratios as high as 45- and 12-fold, respectively. Our immunoPET study clearly demonstrates specific imaging of human PD-1-expressing TILs within the tumor and lymphoid tissues. This suggests these anti-human-PD-1 tracers could be clinically translatable to monitor cancer treatment response to IC blockade therapy.

A hallmark of cancer is metabolic reprogramming, which is exploited by cancer cells to ensure rapid growth and survival. Pyruvate kinase M2 (PKM2) catalyzes the final step in glycolysis, a key step in tumor metabolism and growth. Recently, we reported the radiosynthesis of the first positron emission tomography tracer for visualizing PKM2 in vivo—i.e., [11C]DASA-23. Due to the highly promising imaging results obtained with [11C]DASA-23 in rodent model glioblastoma, we set out to generate an F-18-labeled version of this tracer, with the end goal of clinical translation in mind. Herein, we report the radiosynthesis of 1-((2-fluoro-6-[18F]fluorophenyl)sulfonyl)-4-((4-methoxyphenyl)sulfonyl)piperazine ([18F]DASA-23) and our initial investigation of its binding properties in cancer cells. We synthesized [18F]DASA-23 via fluorination of 1-((2-fluoro-6-nitrophenyl)sulfonyl)-4-((4-methoxyphenyl)sulfonyl)piperazine (10) with K[18F]F/K2.2.2 in N,N-dimethylformamide at 110 °C for 20 min. Subsequently, we evaluated uptake of [18F]DASA-23 in HeLa cervical adenocarcinoma cells and in vitro stability in human and mouse serum. We successfully prepared [18F]DASA-23 in 2.61 ± 1.54 % radiochemical yield (n = 10, non-decay corrected at end of synthesis) with a specific activity of 2.59 ± 0.44 Ci/μmol. Preliminary cell uptake experiments revealed high uptake in HeLa cells, which was effectively blocked by pretreating cells with the structurally distinct PKM2 activator, TEPP-46. [18F]DASA-23 remained intact in human and mouse serum up to 120 min. Herein, we have identified a F-18-labeled PKM2 specific radiotracer which shows potential for in vivo imaging. The promising cell uptake results reported herein warrant the further evaluation of [18F]DASA-23 for its ability to detect and monitor cancer noninvasively.

We evaluated the dosimetry of [(89)Zr]rituximab, an anti-CD20 immunoPET tracer to image B cell non-Hodgkin's lymphoma (NHL) using a humanized transgenic mouse model that expresses human CD20 transgenic mice (huCD20TM).Rituximab was conjugated to desferrioxamine (Df) for radiolabeling of Zirconium-89. [(89)Zr]rituximab (2.8 ± 0.2 MBq) was tail vein-injected into huCD20T mice. Positron emission tomography (PET)/CT imaging was performed on the two groups of mice (blocking = 2 mg/kg pre-dose of rituximab and non-blocking; n = 5) at eight time points (1, 4, 24, 48, 72, 96, 120, and 168 h) post injection.The novel [(89)Zr]rituximab PET tracer had good immunoreactivity, was stable in human serum, and was able to specifically target human CD20 in mice. The human equivalents of highest dose (mean ± SD) organs with and without pre-dose are liver (345 ± 284 μSv/MBq) and spleen (1165 ± 149 μSv/MBq), respectively.Dosimetry of the human patient whole-body dose was found to be 145 MBq per annum, and the patient dose-limiting organ will be the liver (with rituximab pre-dose blocking) and spleen for non-blocking. The [(89)Zr]rituximab (t½ = 78.4 h) imaging of B cell NHL patients could permit the observation of targeting lesions in NHL patients over an extended period due to longer half-life as compared to the [(64)Cu] rituximab (t½ = 12.7 h).

Sigma-1 receptors (S1Rs) play an important role in many neurological disorders. Simultaneous positron emission tomography (PET)/magnetic resonance imaging (MRI) with S1R radioligands may provide valuable information for diagnosing and guiding treatment for these diseases. Our previously reported S1R radioligand, [[[A reliable and automated radiosynthesis for providing routine clinical-grade [

To develop novel positron emission tomography (PET) agents for visualization and therapy monitoring of bacterial infections.It is known that maltose and maltodextrins are energy sources for bacteria. Hence, (18)F-labelled maltose derivatives could be a valuable tool for imaging bacterial infections. We have developed methods to synthesize 4-O-(α-D-glucopyranosyl)-6-deoxy-6-[(18)F]fluoro-D-glucopyranoside (6-[(18)F]fluoromaltose) and 4-O-(α-D-glucopyranosyl)-1-deoxy-1-[(18)F]fluoro-D-glucopyranoside (1-[(18)F]fluoromaltose) as bacterial infection PET imaging agents. 6-[(18)F]fluoromaltose was prepared from precursor 1,2,3-tri-O-acetyl-4-O-(2',3',-di-O-acetyl-4',6'-benzylidene-α-D-glucopyranosyl)-6-deoxy-6-nosyl-D-glucopranoside (5). The synthesis involved the radio-fluorination of 5 followed by acidic and basic hydrolysis to give 6-[(18)F]fluoromaltose. In an analogous procedure, 1-[(18)F]fluoromaltose was synthesized from 2,3, 6-tri-O-acetyl-4-O-(2',3',4',6-tetra-O-acetyl-α-D-glucopyranosyl)-1-deoxy-1-O-triflyl-D-glucopranoside (9). Stability of 6-[(18)F]fluoromaltose in phosphate-buffered saline (PBS) and human and mouse serum at 37 °C was determined. Escherichia coli uptake of 6-[(18)F]fluoromaltose was examined.A reliable synthesis of 1- and 6-[(18)F]fluoromaltose has been accomplished with 4-6 and 5-8% radiochemical yields, respectively (decay-corrected with 95 % radiochemical purity). 6-[(18)F]fluoromaltose was sufficiently stable over the time span needed for PET studies (∼96% intact compound after 1-h and ∼65% after 2-h incubation in serum). Bacterial uptake experiments indicated that E. coli transports 6-[(18)F]fluoromaltose. Competition assays showed that the uptake of 6-[(18)F]fluoromaltose was completely blocked by co-incubation with 1 mM of the natural substrate maltose.We have successfully synthesized 1- and 6-[(18)F]fluoromaltose via direct fluorination of appropriate protected maltose precursors. Bacterial uptake experiments in E. coli and stability studies suggest a possible application of 6-[(18)F]fluoromaltose as a new PET imaging agent for visualization and monitoring of bacterial infections.

The efficacy and safety of cardiac gene therapy depend critically on the level and the distribution of therapeutic gene expression following vector administration. We aimed to develop a titratable two-step transcriptional amplification (tTSTA) vector strategy, which allows modulation of transcriptionally targeted gene expression in the myocardium.We constructed a tTSTA plasmid vector (pcTnT-tTSTA-fluc), which uses the cardiac troponin T (cTnT) promoter to drive the expression of the recombinant transcriptional activator GAL4-mER(LBD)-VP2, whose ability to transactivate the downstream firefly luciferase reporter gene (fluc) depends on the binding of its mutant estrogen receptor (ER(G521T)) ligand binding domain (LBD) to an ER ligand such as raloxifene. Mice underwent either intramyocardial or hydrodynamic tail vein (HTV) injection of pcTnT-tTSTA-fluc, followed by differential modulation of fluc expression with varying doses of intraperitoneal raloxifene prior to bioluminescence imaging to assess the kinetics of myocardial or hepatic fluc expression.Intramyocardial injection of pcTnT-tTSTA-fluc followed by titration with intraperitoneal raloxifene led to up to tenfold induction of myocardial fluc expression. HTV injection of pcTnT-tTSTA-fluc led to negligible long-term hepatic fluc expression, regardless of the raloxifene dose given.The tTSTA vector strategy can effectively modulate transgene expression in a tissue-specific manner. Further refinement of this strategy should help maximize the benefit-to-risk ratio of cardiac gene therapy.

This study aims to evaluate 64Cu-DOTA-rituximab (PETRIT) in a preclinical transgenic mouse model expressing human CD20 for potential clinical translation. 64Cu was chelated to DOTA-rituximab. Multiple radiolabeling, quality assurance, and imaging experiments were performed. The human CD20 antigen was expressed in B cells of transgenic mice (CD20TM). The mice groups studied were: (a) control (nude mice, n = 3) that received 7.4 MBq/dose, (b) with pre-dose (CD20TM, n = 6) received 2 mg/kg pre-dose of cold rituximab prior to PETRIT of 7.4 MBq/dose, and (c) without pre-dose (CD20TM, n = 6) PETRIT alone received 7.4 MBq/dose. Small animal PET was used to image mice at various time points (0, 1, 2, 4, 24, 48, and 72 h). The OLINDA/EXM software was used to determine the human equivalent dose for individual organs. PETRIT was obtained with a specific activity of 545 ± 38.91 MBq/nmole, radiochemical purity >95%, and immunoreactivity >75%. At 24 h, spleenic uptake of PETRIT%ID/g (mean ± STD) with and without pre-dose was 1.76 ± 0.43% and 16.5 ± 0.45%, respectively (P value = 0.01). Liver uptake with and without pre-dose was 0.41 ± 0.51% and 0.52 ± 0.17% (P value = 0.86), respectively. The human equivalents of highest dose organs with and without pre-dose are osteogenic cells at 30.8 ± 0.4 μSv/MBq and the spleen at 99 ± 4 μSv/MBq, respectively. PET imaging with PETRIT in huCD20 transgenic mice provided human dosimetry data for eventual applications in non-Hodgkins lymphoma patients.

Technetium (Tc) methylene diphosphonate (MDP) has been the standard method for bone scintigraphy for three decades. (18)F sodium fluoride ((18)F NaF) positron emission tomography (PET)/computed tomography (CT) has better resolution and is considered superior. The role of 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)F FDG) PET/CT is proven in a variety of cancers, for which it has changed the practice of oncology. There are few prospective studies comparing these three methods of detection of skeletal metastases. Thus, we were prompted to initiate this prospective pilot trial.This is a prospective study (Sep 2007-Dec 2010) of 52 patients with proven malignancy referred for evaluation of skeletal metastases. There were 37 men and 15 women, 19-84 years old (average, 55.6 ± 15.9). Technetium-99m ((99m)Tc) MDP bone scintigraphy, (18)F NaF PET/CT, and (18)F FDG PET/CT were subsequently performed within 1 month.Skeletal lesions were detected by (99m)Tc MDP bone scintigraphy in 22 of 52 patients, by (18)F NaF PET/CT in 24 of 52 patients, and by (18)F FDG PET/CT in 16 of 52 patients. The image quality and evaluation of extent of disease were superior by (18)F NaF PET/CT over (99m)Tc MDP scintigraphy in all 22 patients with skeletal lesions on both scans and over (18)F FDG PET/CT in 11 of 16 patients with skeletal metastases on (18)F FDG PET/CT. In two patients, (18)F NaF PET/CT showed skeletal metastases not seen on either of the other two scans. Extraskeletal lesions were identified by (18)F FDG PET/CT in 28 of 52 subjects.Our prospective pilot-phase trial demonstrates superior image quality and evaluation of skeletal disease extent with (18)F NaF PET/CT over (99m)Tc MDP scintigraphy and (18)F FDG PET/CT. At the same time, (18)F FDG PET detects extraskeletal disease that can significantly change disease management. As such, a combination of (18)F FDG PET/CT and (18)F NaF PET/CT may be necessary for cancer detection. Additional evaluation with larger cohorts is required to confirm these preliminary findings.

A reliable and routine process to introduce a new ¹⁸F-labeled dimeric RGD-peptide tracer ([¹⁸F]FPP(RGD₂) for noninvasive imaging of α(v)β₃ expression in tumors needed to be developed so the tracer could be evaluated for the first time in man. Clinical-grade [¹⁸F]FPP(RGD)₂ was screened in mouse prior to our first pilot study in human.[¹⁸F]FPP(RGD)₂ was synthesized by coupling 4-nitrophenyl-2-[¹⁸F]fluoropropionate ([¹⁸F]NPE) with the dimeric RGD-peptide (PEG₃-c(RGDyK)₂). Imaging studies with [¹⁸F]FPP(RGD)₂ in normal mice and a healthy human volunteer were carried out using small animal and clinical PET scanners, respectively.Through optimization of each radiosynthetic step, [¹⁸F]FPP(RGD)₂ was obtained with RCYs of 16.9 ± 2.7% (n = 8, EOB) and specific radioactivity of 114 ± 72 GBq/μmol (3.08 ± 1.95 Ci/μmol; n = 8, EOB) after 170 min of radiosynthesis. In our mouse studies, high radioactivity uptake was only observed in the kidneys and bladder with the clinical-grade tracer. Favorable [¹⁸F]FPP(RGD)₂ biodistribution in human studies, with low background signal in the head, neck, and thorax, showed the potential applications of this RGD-peptide tracer for detecting and monitoring tumor growth and metastasis.A reliable, routine, and automated radiosynthesis of clinical-grade [¹⁸F]FPP(RGD)₂ was established. PET imaging in a healthy human volunteer illustrates that [¹⁸F]FPP(RGD)₂ possesses desirable pharmacokinetic properties for clinical noninvasive imaging of α(v)β₃ expression. Further imaging studies using [¹⁸F]FPP(RGD)₂ in patient volunteers are now under active investigation.

We tested a novel imaging strategy, in which both the survival of transplanted myoblasts and their therapeutic transgene expression, a recombinant hypoxia-inducible factor-1α (HIF-1α-VP2), can be monitored using firefly luciferase (fluc) and Renilla luciferase (hrl) bioluminescence reporter genes, respectively.The plasmid pUbi-hrl-pUbi-HIF-1α-VP2, which expresses both hrl and HIF-1α-VP2 using two ubiquitin promoters, was characterized in vitro. C2c12 myoblasts stably expressing fluc and transiently transfected with pUbi-hrl-pUbi-HIF-1α-VP2 were injected into the mouse hindlimb. Both hrl and fluc expression were monitored using bioluminescence imaging (BLI).Strong correlations existed between the expression of hRL and each of HIF-1α-VP2, VEGF, and PlGF (r(2)0.83, r(2)0.82, and r(2)0.97, respectively). In vivo, both transplanted cells and HIF-1α-VP2 transgene expression were successfully imaged using BLI.An objective evaluation of myoblast-mediated gene transfer in living mice can be performed by monitoring both the survival and the transgene expression of transplanted myoblasts using the techniques developed herein.

We tested the hypothesis that modulation of the microenvironment (using antioxidants) will increase stem cell survival in hypoxia and after transplantation to the myocardium.Rat cardiomyoblasts were stably transfected with a reporter gene (firefly luciferase) for bioluminescence imaging (BLI). First, we examined the role of oxidative stress in cells under hypoxic conditions. Subsequently, stem cells were transplanted to the myocardium of rats using high-resolution ultrasound, and their survival was monitored daily using BLI.Under hypoxia, oxidative stress was increased together with decreased cell survival compared to control cells, both of which were preserved by antioxidants. In living subjects, oxidative stress blockade increased early cell survival after transplantation to the myocardium, compared to untreated cells/animals.Modulation of the local microenvironment (with antioxidants) improves stem cell survival. Increased understanding of the interaction between stem cells and their microenvironment will be critical to advance the field of regenerative medicine.

Purpose: We quantified the performance of time-domain imaging (TDI) and spectral imaging (SI) for fluorescence imaging of quantum dots (QDs) in three distinct imaging instruments: eXplore Optix (TDI, Advanced Research Technologies Inc.), Maestro (SI, CRi Inc.), and IVIS-Spectrum (SI, Caliper Life Sciences Inc.). Procedure: The instruments were compared for their sensitivity in phantoms and living mice, multiplexing capabilities (ability to resolve the signal of one QD type in the presence of another), and the dependence of contrast and spatial resolution as a function of depth. Results: In phantoms, eXplore Optix had an order of magnitude better sensitivity compared to the SI systems, detecting QD concentrations of ~40 pM in vitro. Maestro was the best instrument for multiplexing QDs. Reduction of contrast and resolution as a function of depth was smallest with eXplore Optix for depth of 2–6 mm, while other depths gave comparable results in all systems. Sensitivity experiments in living mice showed that the eXplore Optix and Maestro systems outperformed the IVIS-Spectrum. Conclusion: TDI was found to be an order of magnitude more sensitive than SI at the expense of speed and very limited multiplexing capabilities. For deep tissue QD imaging, TDI is most applicable for depths between 2 and 6 mm, as its contrast and resolution degrade the least at these depths.

The development of molecular probes based on novel engineered protein constructs is under active investigation due to the great potential of this generalizable strategy for imaging a variety of tumor targets.In this report, human epidermal growth factor receptor type 2 (HER2)-binding Affibody molecules were radiolabeled with (64)Cu and their imaging ability was further evaluated in tumor mice models to understand the promise and limitations of such probes. The anti-HER2 Affibody molecules in monomeric (Z(HER2:477)) and dimeric [(Z(HER2:477))(2)] forms were site specifically modified with the maleimide-functionalized chelator, 1,4,7,10-tetraazacyclododecane-1,4,7-tris(acetic acid)-10-acetate mono (N-ethylmaleimide amide) (Mal-DOTA). The resulting DOTA-Affibody conjugates were radiolabeled with (64)Cu and evaluated in nude mice bearing subcutaneous SKOV3 tumors. Biodistribution experiments showed that tumor uptake values of (64)Cu-DOTA-Z(HER2:477) and (64)Cu-DOTA-(Z(HER2:477))(2) were 6.12 +/- 1.44% and 1.46 +/- 0.50% ID/g, respectively, in nude mice (n = 3 each) at 4 h postinjection. Moreover, (64)Cu-labeled monomer exhibited significantly higher tumor/blood ratio than that of radiolabeled dimeric counterpart at all time points examined in this study. MicroPET imaging of (64)Cu-DOTA-Z(HER2:477) in SKOV3 tumor mice clearly showed good and specific tumor localization. This study demonstrates that (64)Cu-labeled Z(HER2:477) is a promising targeted molecular probe for imaging HER2 receptor expression in living mice. Further work is needed to improve the excretion properties, hence dosimetry and imaging efficacy, of the radiometal-based probe.

We present a systematic approach for studying positron emission tomography-computed tomography (PET/CT) 3-D virtual fly-through endoscopy and for assessing the accuracy of this technology for visualizing and detecting endobronchial lesions as a function of focal lesion morphology and activity.Capsules designed to simulate endobronchial lesions were filled with activity and introduced into a porcine lung-heart phantom. PET/CT images were acquired, reconstructed, and volume rendered as 3-D fly-through and fly-around visualizations. Anatomical positioning of lesions seen on the 3-D-volume-rendered PET/CT images was compared to the actual position of the capsules.Lesion size was observed to be highly sensitive to PET threshold parameter settings and careful opacity and color transfer function parameter assignment.We have demonstrated a phantom model for studies of PET/CT 3-D virtual fly-through bronchoscopy and have applied this model for understanding the effect of PET thresholding on the visualization and detection of lesions.

In this study, we introduce a methodology for preparing 18F-labeled Affibody protein, specifically 18F-Anti-HER2 dimeric Affibody (14 kDa), for in vivo imaging of HER2neu with positron emission tomography (PET).We have used 4-[18F]fluorobenzaldehyde as a synthon to prepare 18F-Anti-HER2 Affibody. Aminooxy-functionalized Affibody (Anti-HER2-ONH2) was incubated with 4-[18F]fluorobenzaldehyde in ammonium acetate buffer at pH 4 in the presence of methanol at 70 degrees C for 15 min. The resulting 18F-labeled Affibody molecule was evaluated as a PET probe in xenograft models expressing HER2.We have successfully prepared 18F-Anti-HER2 dimeric Affibody (14 kDa), N-(4-[18F]fluorobenzylidine)oxime-Anti-HER2 Affibody, [18F]FBO-Anti-HER2, in 26-30% radiochemical yields (decay corrected). High-contrast small-animal PET images with relatively moderate tumor uptake (1.79 +/- 0.40% ID/g) were observed for the 18F-Anti-HER2 Affibody.Site-specific 18F-labeled Affibody against HER2 has been synthesized via chemoselective oxime formation between an aminooxy-functionalized Affibody and 18F-fluorobenzaldehyde. The results have implications for radiolabeling of other affibodies and macromolecules and should also be important for advancing Affibody imaging with PET.

2'-deoxy-2'-[(18)F]fluoro-5-ethyl-1-beta-D-arabinofuranosyluracil ([(18)F]FEAU) is a promising radiolabeled nucleoside designed to monitor Herpes Simplex Virus Type 1 thymidine kinase (HSV1-tk) reporter gene expression with positron emission tomography (PET). However, the challenging radiosynthesis creates problems for being able to provide [(18)F]FEAU routinely. We have developed a routine method using a commercial GE TRACERlab FX-FN radiosynthesis module with customized equipment to provide [(18)F]FEAU. All radiochemical yields are decay corrected to end-of-bombardment and reported as means +/- SD. Radiofluorination (33 +/- 8%; n = 4), bromination (85 +/- 8%; n = 4), coupling reaction (83 +/- 6%; n = 4), base hydrolysis steps, and subsequent high-performance liquid chromatography purification afforded purified [(18)F]FEAU beta-anomer in 5 +/- 1% overall yield (n = 3 runs) after approximately 5.5 h and a beta/alpha-anomer ratio of 7.4. Radiochemical/chemical purities and specific activity exceeded 99% and 1.3 Ci/micromol (48 GBq/micromol), respectively. In cell culture, [(18)F]FEAU showed significantly (P0.05) higher accumulation in C6 cells expressing HSV1-tk/sr39tk as compared to wild-type C6 cells. Furthermore, [(18)F]FEAU showed slightly higher accumulation than 9-[4-[(18)F]fluoro-3-(hydroxymethyl)butylguanine ([(18)F]FHBG) in cells expressing HSV1-tk (P0.05), whereas [(18)F]FHBG showed significantly higher (P0.05) accumulation than [(18)F]FEAU in HSV1-sr39tk-expressing cells. micro-PET imaging of mice carrying tumor xenografts of C6 cells stably expressing HSV1-tk or HSV1-sr39tk are consistent with the cell uptake results. The [(18)F]FEAU mouse images also showed very low gastrointestinal signal with predominant renal clearance as compared to [(18)F]FHBG. The routine radiosynthesis of [(18)F]FEAU was successfully semiautomated using a commercial module along with customized equipment to provide the beta-anomer in modest yields. Although further studies are needed, early results also suggest [(18)F]FEAU is a promising PET radiotracer for monitoring HSV1-tk reporter gene expression.

The goal of this study is to demonstrate the feasibility of chemically modified human adenovirus (Ad) vectors for tumor retargeting.E1- and E3-deleted Ad vectors carrying firefly luciferase reporter gene under cytomegalovirus promoter (AdLuc) was surface-modified with cyclic arginine-glycine-aspartic acid (RGD) peptides through a bifunctional poly(ethyleneglycol) linker (RGD-PEG-AdLuc) for integrin alpha(v)beta(3) specific delivery. The Coxsackie and adenovirus viral receptor (CAR) and integrin alpha(v)beta(3) expression in various tumor cell lines was determined by reverse transcriptase PCR and fluorescence-activated cell sorting. Bioluminescence imaging was performed in vitro and in vivo to evaluate RGD-modified AdLuc infectivity.RGD-PEG-AdLuc abrogated the native CAR tropism and exhibited significantly enhanced transduction efficiency of integrin-positive tumors than AdLuc through intravenous administration.This approach provides a robust platform for site-specific gene delivery and noninvasive monitoring of the transgene delivery efficacy and homing.

Evaluation of selective killing of Herpes Simplex Virus 1 thymidine kinase (HSV1-tk) expressing tumors by radiolabeled (131)I-fialuridine (FIAU), and of synergy between (131)I-FIAU and Ganciclovir (GCV).HSV1-tk-expressing cell lines and parental cell lines were exposed to (131)I-FIAU alone, GCV alone, or combinations. Activity and concentration were varied widely, concurrent and sequential administrations tested, and dose rate effects were studied.HSV1-tk-expressing cells accumulated up to 15.7-fold more (131)I-FIAU, were growth inhibited by 2 muCi/ml, or 5 muCi/ml (131)I-FIAU, and were inhibited by two log orders lower concentrations of GCV than parental cells. However, no synergy or additive effect was observed. Dose rate variations, or sequential treatment, did not alter outcome.Radioisotope therapy of HSV1-tk-expressing tumor cells with (131)I-FIAU is reported for the first time. Lack of synergy between (131)I-FIAU and GCV does not warrant further investigation of combination treatment with the two agents.

The purpose of this study was to map the distribution of 2-deoxy-2-[18F]fluoro-d-glucose (FDG) uptake in organs of patients with no known abnormalities in those tissues. We measured maximum and mean standardized uptake values (SUV) from FDG-positron emission tomography (PET)/computed tomography (CT) obtained from 98 patients (48 males and 50 females). Significant uptake (mean SUVmean > 2.5) was visualized in the cerebellum (8.0 ± 2.2), soft palate (2.92 ± 0.86), palatine tonsils (3.45 ± 1.4), lingual tonsils (3.08 ± 1.05), sublingual glands (3.3 ± 1.5), and testes (2.57 ± 0.56). Negative correlation for FDG uptake versus age was observed for the palatine tonsils, sublingual glands, and lungs (P

To assess the optimal reporter probe/reporter gene combination for monitoring herpes simplex virus type 1 thymidine kinase (HSV1-tk) gene expression, we compared the cellular uptake of 1-(2'-fluoro-2'-deoxy-D-arabinofuranosyl)-5-methyluracil (FMAU), 2'-fluoro-2'-deoxyarabinofuranosyl-5-ethyluracil (FEAU), 2'-fluoro-2'-deoxy-beta-D-arabinofuranosyl-5-iodouracil (FIAU) and penciclovir (PCV) in both HSV1-tk and HSV1-sr39tk expressing cells.For stably transfected cell studies, C6 rat glioma cells, C6 HSV1-tk transfectant, C6 mutant HSV1-sr39tk transfectant, rat Morris hepatoma cells (MH3924A), and MH3924A HSV1-tk transfectant cells were used. For adenoviral infection studies, C6 rat glioma cells were exposed to serial titers of AdCMV-HSV1-tk, AdCMV-HSV1-sr39tk, or AdCMV-fluc for 24 hours. These cells were incubated with [(14)C]FMAU, [(3)H]FEAU, [(14)C]FIAU, and [(3)H]PCV, and cellular uptake of radioactivity was measured.[(3)H]FEAU exhibited the highest or second highest accumulation and the most selectivity regardless of the mode of gene transfer for both HSV1-tk and mutant HSV1-sr39tk reporter genes.This combination of high accumulation and high selectivity for both HSV1-tk and HSV1-sr39tk makes suitably radiolabeled FEAU a promising candidate as a radiotracer for imaging HSV1-tk/HSV1-sr39tk gene expression in living subjects.

Human pluripotency gene networks (PGNs), controlled in part by Oct4, are central to understanding pluripotent stem cells, but current fluorescent reporter genes (RGs) preclude noninvasive assessment of Oct4 dynamics in living subjects. To assess Oc4 activity noninvasively, we engineered a mouse embryonic stem cell line which encoded both a pOct4-hrluc (humanized renilla luciferase) reporter and a pUbi-hfluc2-gfp (humanized firefly luciferase 2 fused to green fluorescent protein) reporter. In cell culture, pOct4-hRLUC activity demonstrated a peak at 48 h (day 2) and significant downregulation by 72 h (day 3) (p=0.0001). Studies in living subjects demonstrated significant downregulation in pOct4-hRLUC activity between 12 and 144 h (p = 0.001) and between 12 and 168 h (p = 0.0003). pOct4-hRLUC signal dynamics after implantation was complex, characterized by transient upregulation after initial downregulation in all experiments (n = 10, p = 0.01). As expected, cell culture differentiation of the engineered mouse embryonic stem cell line demonstrated activation of mesendodermal, mesodermal, endodermal, and ectodermal master regulators of differentiation, indicating potency to form all three germ layers. We conclude that the Oct4-hrluc RG system enables noninvasive Oct4 imaging in cell culture and in living subjects.

This research aimed to study the use of Cerenkov luminescence imaging (CLI) for non-Hodgkin's lymphoma (NHL) using 89Zr-rituximab positron emission tomography (PET) tracer with a humanized transgenic mouse model that expresses human CD20 and the correlation of CLI with PET.Zr-rituximab (2.6 MBq) was tail vein-injected into transgenic mice that express the human CD20 on their B cells (huCD20TM). One group (n=3) received 2 mg/kg pre-dose (blocking) of cold rituximab 2 h prior to tracer; a second group (n=3) had no pre-dose (non-blocking). CLI was performed using a cooled charge-coupled device optical imager. We also performed PET imaging and ex vivo studies in order to confirm the in vivo CLI results. At each time point (4, 24, 48, 72, and 96 h), two groups of mice were imaged in vivo and ex vivo with CLI and PET, and at 96 h, organs were measured by gamma counter.huCD20 transgenic mice injected with 89Zr-rituximab demonstrated a high-contrast CLI image compared to mice blocked with a cold dose. At various time points of 4-96 h post-radiotracer injection, the in vivo CLI signal intensity showed specific uptake in the spleen where B cells reside and, hence, the huCD20 biomarker is present at very high levels. The time-activity curve of dose decay-corrected CLI intensity and percent injected dose per gram of tissue of PET uptake in the spleen were increased over the time period (4-96 h). At 96 h, the 89Zr-rituximab uptake ratio (non-blocking vs blocking) counted (mean±standard deviation) for the spleen was 1.5±0.6 for CLI and 1.9±0.3 for PET. Furthermore, spleen uptake measurements (non-blocking and blocking of all time points) of CLI vs PET showed good correlation (R2=0.85 and slope=0.576), which also confirmed the corresponding correlations parameter value (R2=0.834 and slope=0.47) obtained for ex vivo measurements.CLI and PET of huCD20 transgenic mice injected with 89Zr-rituximab demonstrated that the tracer was able to target huCD20-expressing B cells. The in vivo and ex vivo tracer uptake corresponding to the CLI radiance intensity from the spleen is in good agreement with PET. In this report, we have validated the use of CLI with PET for NHL imaging in huCD20TM.

The role of 2-deoxy-2-[F-18]fluoro-D-glucose-positron emission tomography (FDG-PET) was studied in a variety of cancers, including head and neck squamous cell carcinomas (HNSCC) and nasopharyngeal carcinomas (NPC), with several presentations indicating that for these clinical entities a “whole-body” (i.e., eyes to thighs) may yield little additional information. Therefore, we were prompted to review our experience with PET/computed tomography (CT) in the management of patients with HNSCC and NPC. This is a retrospective study of 133 patients with HNSCC, 23-90 years old (average: 58.2 ± 12.7) and 26 patients with NPC, ages 16-75 (average: 47.3 ± 17.1), who had whole body PET/CT at our institution from Jan 2003 to Nov 2006. Reinterpretation of the imaging studies for accuracy and data analysis from medical records was performed. Lesions identified on PET/CT below the level of the adrenal glands were recorded and tabulated. Lesions were identified below the adrenal glands in seven patients (5.2%) with HNSCC. These included hepatic and osseous metastases from HNSCC in two patients (1.5%), a new renal cancer (0.75%), a new pancreatic cancer (0.75%), a new colon cancer (0.75%) and findings proven benign on follow-up (focal colon uptake in one patient and an inflammatory inguinal lymph node in another patient; 1.5%). Lesions were identified below the adrenal glands in three patients (11.5%) with NPC. These included osseous metastases from NPC in two patients (7.7%) and findings proven benign on follow-up (focal colon uptake in one patient; 3.84%). This study suggests that whole body PET/CT imaging in HNSCC has a relatively low yield (3%, 95% CI: 1.33-8.42) of significant findings below the level of the adrenal glands. Therefore, implementing a more limited protocol (through the level of adrenal glands), especially in low-risk cases of HNSCC, may be considered. However, whole body PET/CT imaging in NPC may have a significant yield (7.7%, 95% CI: 1.02-25.26) of medically relevant findings below the level of the adrenal glands. Thus, the whole body (i.e., vertex to thighs) PET/CT scan of NPC patients appears to be the appropriate imaging protocol for this population. This recommendation requires further evaluation and validation in larger prospective studies.

Protein phosphorylation mediated by protein kinases controls numerous cellular processes. A genetically encoded, generalizable split firefly luciferase (FL)-assisted complementation system was developed for noninvasive monitoring phosphorylation events and efficacies of kinase inhibitors in cell culture and in small living subjects by optical bioluminescence imaging. An Akt sensor (AST) was constructed to monitor Akt phosphorylation and the effect of different PI-3K and Akt inhibitors. Specificity of AST was determined using a non-phosphorylable mutant sensor containing an alanine substitution (ASA). The PI-3K inhibitor LY294002 and Akt kinase inhibitor perifosine led to temporal- and dose-dependent increases in complemented FL activities in 293T human kidney cancer cells stably expressing AST (293T/AST) but not in 293T/ASA cells. Inhibition of endogenous Akt phosphorylation and kinase activities by perifosine also correlated with increase in complemented FL activities in 293T/AST cells but not in 293T/ASA cells. Treatment of nude mice bearing 293T/AST xenografts with perifosine led to a 2-fold increase in complemented FL activities compared to that of 293T/ASA xenografts. Our system was used to screen a small chemical library for novel modulators of Akt kinase activity. This generalizable approach for noninvasive monitoring of phosphorylation events will accelerate the discovery and validation of novel kinase inhibitors and modulators of phosphorylation events.

Intraoperative gamma probe guidance has become widely utilized for sentinel lymph node dissection in patients with breast cancer and melanoma, using (99m)Tc sulfur colloid. However, new indications are possible and need to continue to be investigated. We report the use during a wedge liver biopsy of a new hand-held gamma probe designed for (123)I intraoperative guidance. The patient studied is a 5-year-old boy with history of stage 4 high-risk neuroblastoma. Anatomic imaging (CT, MRI), (99m)Tc bone scintigraphy and 2-deoxy-2-[F-18]fluoro-d-glucose-positron emission tomography/computed tomography (FDG-PET/CT) were negative, but the (123)I MIBG scintigraphy suggested recurrent liver disease. A decision was made to biopsy these lesions to obtain histopathological confirmation. Intraoperative gamma probe mapping of the liver identified areas with signal above the background, but these were prove to be hemosiderin deposits on histo-pathology examination.

This work investigated whether fLuc-catalyzed oxidation of d-luciferin generates sufficient light to induce photodynamic toxicity in cancer cells. Light emission was assessed via cooled CCD (charge-coupled device) camera. Parental and fLuc expressing cancer cells were exposed to subtoxic concentrations of photosensitizers (Rose Bengal or hypericin) and d-luciferin, sunlight, or lamplight. Toxicity was assessed by MTT assay. fLuc expressing cells emitted up to 500-fold higher levels of photons than parental cell lines. Although exposure to photosensitizer and sunlight reduced survival of various cell lines, survival of fLuc expressing cells incubated with photosensitizer and d-luciferin, or photosensitizer and lamplight, did not differ significantly from parental or untreated cells. Contesting recent reports, fLuc bioluminescence does not generate sufficient photons to induce Rose Bengal or hypericin photodynamic toxicity in a range of malignant and nonmalignant cell lines, and is not suitable as a generalizable approach to antineoplastic therapy.

2-Deoxy-2-[F-18]fluoro-D-glucose (FDG)-positron emission tomography (PET)/computed tomography (CT) is becoming widely available as a powerful imaging modality, combining the ability to detect active metabolic processes and their morphologic features in a single study. The role of FDG-PET/CT is proven in lymphoma, melanoma, colorectal carcinoma, and other cancers. However, there are rare malignancies such as Merkel cell carcinoma that can potentially be evaluated with PET/CT. We were therefore prompted to review our experience with FDG-PET/CT in the management of patients with Merkel cell carcinoma.This is a retrospective case series of six patients with Merkel cell carcinoma, 58-81 years old (average 69 +/- 8.3), who had whole-body PET/CT at our institution from January 1st, 2003 to August 31st, 2005. Two patients were women and four were men. Reinterpretation of the imaging studies for accuracy and data analysis from medical records were performed.Twelve examinations were acquired for the six patients (one patient had six PET/CT, one patient had two PET/CT, and four patients had one PET/CT). The injected FDG doses ranged 381.1-669.7 MBq (average 573.5 +/- 70.3). Four patients had the PET/CT as part of initial staging, and two patients had the exam for restaging (after surgery and XRT). A total of six Merkel lesions (pancreas, adrenal, lip, submandibular lymph nodes, cervical lymph nodes, and parapharyngeal soft tissue) were identified in three patients and confirmed on histopathological examination. The FDG uptake in these areas was intense, with maximum standardized uptake value (SUVmax) values of 5-14 (average 10.4 +/- 3.8). In one patient, the PET/CT scan identified abnormal focal distal sigmoid uptake that was biopsied and diagnosed as adenocarcinoma. Two patients had negative scans and had no clinical evidence of disease on follow-up office visits (up to one year after PET/CT).This case series suggests that FDG-PET/CT may have a promising role in the management of patients with Merkel cell carcinoma.

The therapeutic benefits of cell transplantation may depend on the survival of sufficient numbers of grafted cells. We evaluate four potent immunosuppressive medications aimed at preventing acute donor cell death.Embryonic rat H9c2 myoblasts were stably transduced to express firefly luciferase reporter gene (H9c2-Fluc). H9c2-Fluc cells (3x10(6)) were injected into thigh muscles of Sprague-Dawley rats (N=30) treated with cyclosporine, dexamethasone, mycophenolate mofetil, tacrolimus, or saline from day -3 to day +14. Longitudinal optical bioluminescence imaging was performed over two weeks. Fluc activity was 40.0+/-12.1% (dexamethasone), 30.5+/-12.5% (tacrolimus), and 21.5+/-3.5% (mycophenolate) vs. 12.0+/-5.0% (control) and 8.3+/-5.0% (cyclosporine) at day 4 (P0.05). However, by day 14, cell signals had decreased drastically to10% for all groups despite drug therapy.This study demonstrates the ability of optical molecular imaging for tracking cell survival noninvasively and raises important questions with regard to the overall efficacy of immunosuppressives for prolonging transplanted cell survival.

Purpose Previous work showed quantitative imaging of T-cell migration into a tumor site by positron emission tomography (PET), using retroviral transduction of mutated thymidine kinase (sr39TK) reporter genes into immunized T-lymphocytes. Procedures and results In order to improve the sensitivity and flexibility of the imaging analysis, lentivirus, that expressed sr39TK, was used to transduce the lymphocytes that migrated to an immunogenic sarcoma site. In comparison to retrovirally transduced lymphocytes, the lentivirally transduced lymphocytes showed enhanced PET signal when equal numbers of transduced lymphocytes were transferred. Furthermore, in order to utilize multimodality in vivo imaging capability, a tri-fusion reporter gene containing sr39TK, synthetic Renilla luciferase (hRluc), and enhanced green florescent protein (eGFP) was inserted into a lentiviral transfer vector. Using the adoptive transfer model, tumor-specific lymphocytic migration was detected by both microPET scan and bioluminescence imaging. Conclusion The multimodal imaging strategy coupled with lentiviral reporter construct delivery demonstrated here can facilitate future molecular imaging studies.

Growing evidence indicates that appropriate incorporation of positron emission tomography (PET) into the evaluation of patients with early symptoms of cognitive decline can improve diagnostic and prognostic accuracy. In the present work, an explicitly defined role for PET and its associated impact on expected clinical outcomes were systematically examined.We compared the relative value of two strategies for assessing whether Alzheimer's disease (AD) was responsible for cognitive decline in geriatric patients, and in subsequently managing those patients according to the recommended standards of the American Academy of Neurology (AAN). The first strategy was based on an approach already endorsed by the AAN, following evidence-based reviews carried out by its quality standards subcommittee. The second approach was based on many of the same AAN recommendations-with respect to initial general medical and neurologic examination, structural imaging and laboratory tests, as well as ultimate management-but additionally incorporated PET in appropriate cases, to determine the presence or absence of a pattern of regional cerebral metabolism characteristic of AD. Clinical outcomes accruing to each strategy were calculated using formalized tools of decision analysis.The strategy making use of PET increased diagnostic accuracy, yielding decreased rates of both false negative (from 8.3 to 3.1%) and false positive (from 23.0 to 11.9%) diagnoses for AD, compared with the conventional strategy. When coupled with AAN treatment recommendations for patients having (or not having) non-severe AD, these differences in diagnostic accuracy corresponded to approximately a 62% decrease in avoidable months of nursing home care, and a 48% decrease in months of unnecessary drug therapy resulting from inaccurate diagnoses. The benefit in clinical outcome of the proposed strategy was maintained over a wide range of values for sensitivity, specificity, and projected impact on need for nursing home care.Use of PET for evaluating early cognitive decline in geriatric patients can add valuable information to the clinical assessment, resulting in a greater number of patients being accurately diagnosed and properly treated. PET can be used to diminish disease-related and treatment-related morbidity of dementia, through earlier institution of appropriate management.

Repetitive imaging with microPET of endogenous albumin gene expression by using transgenic mice in which the Herpes Simplex Virus Type 1 thymidine kinase (HSV1-tk) reporter gene is driven by the albumin promoter (AL-HSV1-tk).Transgenic mice were imaged repeatedly on a microPET scanner with approximately 200 microCi of 9-[4-[18F]fluoro-3-(hydroxymethyl)butyl]guanine (FHBG) (a substrate for HSV1-TK enzyme). Four transgenic mice were monitored for body weight, serum albumin, and imaged at the end of each of three dietary phases (17%, 0%, and 25% protein diet). Each phase last 14-21 days. The 0% protein diet has been reported previously to reduce albumin gene expression in rats. Twenty non-transgenic mice of the same strain followed a similar feeding schedule and were monitored for serum albumin, body weight, and sacrificed at various time points for determination of their GAPDH normalized albumin mRNA levels.Transgenic mice showed a relatively high FHBG signal from the liver region as expected. Variation of the mean FHBG signal in two mice with a fixed 17% protein diet over a four-month period was19% s.d. The mean +/- s.e. FHBG liver standardized uptake value (SUV) in four transgenics went from 4.49 +/- 0.32 to 2.17 +/- 0.52 to 6.21 +/- 0.72 as the mice went through the three diets of 17%, 0%, and 25% sequentially. Non-transgenic mice showed GAPDH normalized albumin mRNA that went from 37.68 +/- 6.04 to 26.41 +/- 4.29 to 52.42 +/- 4.09. The FHBG SUV from transgenics was well correlated with GAPDH normalized albumin mRNA from non-transgenics (r(2) = 0.97) supporting that endogenous gene expression of albumin can be indirectly imaged with FHBG.Measuring correlated changes in albumin expression in wild type mice and HSV1-TK expression by microPET in transgenic mice in which the reporter gene is driven by the albumin promoter demonstrates that the HSV1-tk gene can be used to monitor, in living animals, modulated expression of transgenes.