Gamma Camera Imaging Research Articles

Antibody inhibition of contact factor XII reduces platelet deposition in a model of extracorporeal membrane oxygenator perfusion in nonhuman primates

BackgroundThe contact factor XII (FXII) activates upon contact with a variety of charged surfaces. Activated FXII (FXIIa) activates factor XI, which activates factor IX, resulting in thrombin generation, platelet activation, and fibrin formation. In both in vitro and in vivo rabbit models, components of medical devices, including extracorporeal oxygenators, are known to incite fibrin formation in a FXII‐dependent manner. Since FXII has no known role in hemostasis and its inhibition is therefore likely a safe antithrombotic approach, we investigated whether FXII inhibition also reduces accumulation of platelets in extracorporeal oxygenators. ObjectivesWe aimed to determine the effect of FXII inhibition on platelet deposition in perfused extracorporeal membrane oxygenators in nonhuman primates. MethodsA potent FXII neutralizing monoclonal antibody, 5C12, was administered intravenously to block contact activation in baboons. Extracorporeal membrane oxygenators were temporarily deployed into chronic arteriovenous access shunts. Radiolabeled platelet deposition in oxygenators was quantified in real time using gamma camera imaging. Biochemical assays were performed to characterize the method of action of 5C12. ResultsThe anti‐FXII monoclonal antibody 5C12 recognized both the alpha and beta forms of human and baboon FXII by binding to the protease‐containing domain, and inhibited FXIIa activity. Administration of 5C12 to baboons reduced platelet deposition and fibrin formation in the extracorporeal membrane oxygenators, in both the presence and absence of systemic low‐dose unfractionated heparin. The antiplatelet dose of 5C12 did not cause measurable increases in template bleeding times in baboons. ConclusionsFXII represents a possible therapeutic and safe target for reducing platelet deposition and fibrin formation during medical interventions including extracorporeal membrane oxygenation.

Designing and Fabrication of Switching High Voltage Power Supply for Nuclear Medicine Imaging Systems

This paper describes design considerations of the High voltage (HV) module with low ripple and good stability in order to improve the efficiency of nuclear imaging systems consist of Single Photon Emission Computed Tomography (SPECT). In the design of the current HV module, push-pull topology is preferred, due to the fact; it has a better efficiency in comparison with other technologies. The module receives a positive continuous voltage about 5-8 V as input, and provides a programmable positive or negative continuous voltage from 800-2500 V as output for a total load of 200-KΩ. The ripple of the output voltage is 10 mV that it is measured by laboratory equipment’s and safe high voltage (SHV) probe. The measured output power in the designed module is 25 W. Experiment results show that minimum efficiency at full load is around 65%. The proposed HV module shows a good stability, low ripple (noise), fast rise time. So, it can be used in SPECT or gamma camera imaging system to provide the constant voltage for PMTS.

Liver homing of clinical grade Tregs after therapeutic infusion in patients with autoimmune hepatitis

Background & AimsAutoimmune hepatitis (AIH) is an immune-mediated disease with no curative treatment. Regulatory T cell (Treg) therapy is potentially curative in AIH given the critical role of Tregs in preventing autoimmunity. To work effectively, adoptively transferred Tregs must migrate to and survive within the inflamed liver. We conducted a proof-of-concept study aiming to assess the safety and liver-homing properties of good manufacturing practice (GMP)-grade autologous Tregs in patients with AIH.MethodsAutologous polyclonal GMP-grade Tregs were isolated using leukapheresis and CliniMACS, labelled with indium tropolonate and re-infused intravenously to 4 patients with AIH. GMP-Treg homing to the liver was investigated with longitudinal gamma camera and SPECT-CT scanning. GMP-Treg immunophenotype, function and immunometabolic state were assessed during the study.ResultsWe observed that the isolated Tregs were suppressive and expressed CXCR3, a chemokine receptor involved in recruitment into the inflamed liver, as well as Treg functional markers CD39, CTLA-4 and the transcription factor Foxp3. Serial gamma camera and SPECT-CT imaging demonstrated that 22–44% of infused Tregs homed to and were retained in the livers of patients with autoimmune hepatitis for up to 72 h. The infused cells did not localise to any off-target organs other than the spleen and bone marrow. GMP-Tregs were metabolically competent and there were no infusion reactions or high-grade adverse effects after Treg infusion.ConclusionOur novel findings suggest that the liver is a good target organ for Treg cellular therapy, supporting the development of clinical trials to test efficacy in autoimmune hepatitis and other autoimmune liver diseases.Lay summaryAutoimmune liver diseases occur when the body’s immune cells target their own liver cells. Regulatory T cells (Tregs) prevent autoimmunity, thus they are a potential therapy for autoimmune liver diseases. In patients with autoimmune hepatitis, Treg infusion is safe, with nearly a quarter of infused Tregs homing to the liver and suppressing tissue-damaging effector T cells. Thus, Tregs are a potentially curative immune cell therapy for early autoimmune liver diseases.

Gamma probe-guided confirmation of balloon placement in endovascular procedures.

Gamma probes can provide real-time information on lesion location and allow radioguided surgery in many diseases. The purpose of this study was to determine whether a gamma probe could be used to confirm balloon location in resuscitative endovascular balloon occlusion of the aorta and to determine the ease-of-use of the gamma probe localization method using human vasculature phantom and large animal. This investigation comprised a proof-of-concept study using human vasculature phantom and feasibility study using large animal. An assistant and two general surgeons with no prior experience in handling a gamma probe participated in both studies. A gamma probe was used by each surgeon to explore the location of a catheter balloon filled with 8 mL of normal saline containing 37 MBq of Technetium. The differences between predicted and actual balloon locations and the times taken to perform the trials were recorded. Balloon locations were confirmed by planar gamma camera images. The results were analyzed and compared according to the operators and experiments. Overall sensitivity and specificity for the localization of the catheter balloon were 100% and 91% in phantom study, respectively, and 100% and 100% in animal study, respectively. The performance of the two operators for exploring the balloon location was similar in both the phantom and the animal studies. The mean time taken to explore the balloon locations with the aid of the gamma probe was only 2.36 minutes in phantom study and 2.65 minutes in the animal study. The gamma probe method was accurate and rapid for confirming balloon location. We suggest that the gamma probe has potential for confirming balloon placement in endovascular procedures without the need for fluoroscopy.

A novel dual-modality imaging agent targeting folate receptor of tumor for molecular imaging and fluorescence-guided surgery.

Folate receptor (FR) is an ideal target for cancer imaging because it is frequently overexpressed in major types of human tumor, whereas its expression in normal organs is highly limited. Combining nuclear and fluorescence-imaging techniques provides a novel approach for cancer imaging and monitoring the surgery. The objective of this study was to report the synthesis and characteristics of a dual-modality imaging agent, Tc-99m Folate-Gly-His-Glu-Gly-Glu-Cys-Gly-Lys(-5-carboxy-X-rhodamine)-NH2 (Folate-ECG-ROX), and verify its feasibility as both molecular imaging agent and intra-operative guidance. Folate-ECG-ROX was synthesized using Fmoc solid-phase peptide synthesis. Radiolabeling of Folate-ECG-ROX with Tc-99m was done using ligand exchange via tartrate. Binding affinity and in vitro cellular uptake studies were performed. Gamma camera imaging, biodistribution and ex vivo imaging studies were performed using KB and HT-1080 tumor-bearing murine models. Tumor tissue slides were prepared and analyzed with immunohistochemistry staining and confocal microscopy. Surgical removal of tumor nodules in murine models with peritoneal carcinomatosis was performed under the fluorescence-imaging system. After radiolabeling procedures with Tc-99m, Tc-99m Folate-ECG-ROX complexes were prepared in high yield (> 97%). The binding affinity value (Kd) of Tc-99m Folate-ECG-ROX for KB cells was estimated to be 6.9 ± 0.9nM. In gamma camera imaging, tumor to normal muscle uptake ratio of Tc-99m Folate-ECG-ROX increased with time (3.4 ± 0.4, 4.4 ± 0.7, and 6.6 ± 0.8 at 1, 2, and 3h, respectively). In biodistribution study, %IA/g for KB tumor was 2.50 ± 0.80 and 4.08 ± 1.16 at 1 and 3h, respectively. Confocal microscopy with immunohistochemistry staining detected strong Tc-99m Folate-ECG-ROX fluorescence within KB tumor tissue which is correlating with the fluorescent activity of anti-FR antibody. Under real-time optical imaging, the removal of visible nodules was successfully performed. In vivo and in vitro studies revealed substantial and specific uptake of Tc-99m Folate-ECG-ROX in FR-positive tumors. Thus, Tc-99m Folate-ECG-ROX could provide both pre-operative molecular imaging and fluorescence image-guidance for tumor.

Mucociliary Clearance in Former Tobacco Smokers with Both Chronic Obstructive Pulmonary Disease and Chronic Bronchitis and the Effect of Roflumilast.

Background: Little is known of the repeatability and reliability of mucociliary clearance (MCC) in former tobacco smokers who have both chronic obstructive pulmonary disease (COPD) and chronic bronchitis (CB). Less is known of the effect of roflumilast, a selective inhibitor of PDE4, on MCC in these patients. Methods: Former tobacco smokers with COPD and CB were treated for 4 weeks with either roflumilast, or placebo, in a randomized, crossover trial. The following were measured on two baseline and two posttreatment visits: MCC values through 90 minutes, following inhalation of 99mtechnetium sulfur colloid and gamma camera imaging; outer:inner (O:I) deposition ratio; forced expiratory volume in 1 second (FEV1); and symptom scores. Comparisons included: MCC measures through 30 minutes (MCC30), 60 minutes (MCC60), and 90 minutes (MCC90) on the two baseline visits (n = 9) and mean change [(roflumilast - baseline)-(placebo - baseline)] for MCC30, MCC60, MCC90, and FEV1 (n = 8). Associations between MCC measurements, FEV1 and O:I ratio with symptom scores were also examined. Results: Pearson correlation tests indicated good repeatability for baseline measures of MCC30, MCC60, and MCC90 and intraclass correlation coefficients indicated good reliability. Only FEV1 (percent predicted) improved significantly following roflumilast treatment. There were no statistically significant correlations between MCC measures and symptom scores. Lower FEV1 values were significantly associated with increased shortness of breath (dyspnea), and lower O:I ratios (more inner region deposition) were significantly associated with increased cough and sputum. Conclusions: Measurements of MCC30, MCC60, and MCC90 are repeatable and reliable in former tobacco smokers with both COPD and CB. One month of treatment with roflumilast did not improve MCC in this limited study. Airway narrowing in the larger, central airways of these subjects could lead to decreased FEV1, increased inner region deposition of the radiolabeled particles, and the associated increase in symptoms of dyspnea, cough, and sputum.

Deposition studies of aerosol delivery by nasal cannula to infants.

Nasal cannulas are used to provide oxygen support for infants and have been considered as a means for delivering aerosols to the lungs. To measure mucociliary clearance in the lungs of infants with congenital heart defects, we delivered radiopharmaceutical aerosols via a nasal cannula. Here we report on the pulmonary and nasal deposition of these aerosols. A total of 18 infants (median age = 26 days; quartiles = 11-74 days) performed clearance measurements soon before or after corrective cardiac surgery. The regional aerosol deposition was assessed using gamma camera imaging. Cannula flow rate significantly affected pulmonary dosing. Flow rates useful for oxygen support were associated with low pulmonary deposition (2 L/min; mean, 4.5% of deposited dose; range, 2%-9%; n = 7) and high nasal deposition. Much lower cannula flow rates increased the pulmonary deposition (0.2 L/min; mean, 33.5% of deposited dose; range, 15%-51%; n = 5; P = 0.005 vs 2 L/min). The ratio of nose/lung dosing was approximately 26:1 at 2 L/min and 2:1 at 0.2 L/min. Bench studies demonstrated cannula output rates of 10.2 ± 1.7% (2 L/min) and 3.3 ± 0.4% (0.2 L/min) of the loaded nebulizer dose during a 2-minute delivery. Combining in vitro and in vivo results, we estimate that 0.46% of the loaded nebulizer dose reaches the lungs at 2 L/min vs 1.10% at 0.2 L/minduring a 2-minute delivery. With the delivery system used here, pulmonary aerosol delivery via nasal cannula was very inefficient at the flow rates required to provide oxygen support. Even at low flows, nasal deposition was substantial and local toxicity must be considered.

Development of techniques based on Monte Carlo simulations for clearance of Co-57 and Ge-68/Ga-68 sealed radioactive sources

Sealed radioactive sources of Co-57 and Ge-68/Ga-68 are used for the calibration of various nuclear medicine systems like Gamma camera and PET imaging. After their useful life, these sealed sources need to be kept in control for decay until meeting the general clearance criterion. The aim of this work is to determine the activity of spent sealed radioactive sources of Ge-68 / Ga-68 and Co-57. For this purpose, techniques based on Monte Carlo simulation by the use of the MCNPX code was developed for evaluation of the 3”x3” NaI(Tl) scintillator efficiency for specific source–detector geometries. These techniques proved to be accurate.

Clinical Applications of Technetium-99m Quantitative Single-Photon Emission Computed Tomography/Computed Tomography.

Single-photon emission computed tomography/computed tomography (SPECT/CT) is an already established nuclear imaging modality. Co-registration of functional information (SPECT) with anatomical images (CT) paved the way to the wider application of SPECT. Recent advancements in quantitative SPECT/CT have made it possible to incorporate quantitative parameters, such as standardized uptake value (SUV) or %injected dose (%ID), in gamma camera imaging. This is indeed a paradigm shift in gamma camera imaging from qualitative to quantitative evaluation. In fact, such quantitative approaches of nuclear imaging have only been accomplished for positron emission tomography (PET) technology. Attenuation correction, scatter correction, and resolution recovery are the three main features that enabled quantitative SPECT/CT. Further technical improvements are being achieved for partial-volume correction, motion correction, and dead-time correction. The reported clinical applications for quantitative SPECT/CT are mainly related to Tc-99m-labeled radiopharmaceuticals: Tc-99m diphosphonate for bone/joint diseases, Tc-99m pertechnetate for thyroid function, and Tc-99m diethylenetriaminepentaacetic acid for measurement of glomerular filtration rate. Dosimetry before trans-arterial radio-embolization is also a promising application for Tc-99m macro-aggregated albumin. In this review, clinical applications of Tc-99m quantitative SPECT/CT will be discussed.

Quantitative Assessment of Mucociliary Clearance in Smokers with Mild-to-Moderate Chronic Obstructive Pulmonary Disease and Chronic Bronchitis from Planar Radionuclide Imaging Using the Change in Penetration Index.

Background: Mucociliary clearance (MCC) rate from the lung has been shown to be reduced in chronic obstructive pulmonary disease (COPD). This study compared the use of change in penetration index (PI) with conventional whole lung clearance in assessing MCC in mild-to-moderate disease. Methods: Measurement of lung MCC using planar gamma camera imaging was performed in three groups: (1) healthy nonsmoking controls (n = 9), (2) smoking controls who were current smokers with normal lung function (n = 10), and (3) current smokers with mild-to-moderate COPD and bronchitis (n = 15). The mean (±standard deviation) forced expiratory volume at 1 second (FEV1) for the three groups was 109 (±18), 94 (±5), and 78 (±12), respectively. Following inhalation of a technetium-99m labeled aerosol, planar imaging was performed over 4 hours and then at 24 hours. Total lung clearance and tracheobronchial clearance (TBC; normalized to 24-hour clearance) were calculated. A novel parameter, the normalized change in PI (NOCHIP), was also evaluated. PI is the ratio of counts between outer and inner lung zones normalized to lung volume. Results: More aerosol was deposited in central airways in COPD compared to nonsmoking controls, using 24-hour clearance measurements (p < 0.001). Smoking controls had intermediate values. The optimal endpoint for MCC assessment was chosen to be 3 hours, when intersubject variability was minimal, while preserving a measure of early clearance. There was no statistical difference between the three groups in mean total lung clearance, or TBC, at 3 hours. NOCHIP at 3 hours was reduced significantly, compared to nonsmoking controls, in both smoking controls (p = 0.007) and COPD (p < 0.0001). It also correlated with FEV1 (p = 0.003). A higher proportion of smoking control subjects had NOCHIP values in the nonsmoking control range than in the COPD group. Conclusions: NOCHIP was a more sensitive measure of MCC than whole lung clearance and TBC in mild-to-moderate COPD.

Quantitative Imaging of Alpha-Emitting Therapeutic Radiopharmaceuticals.

Targeted alpha therapy (TAT) is an active area of drug development as a highly specific and highly potent therapeutic modality that can be applied to many types of late-stage cancers. In order to properly evaluate its safety and efficacy, understanding biokinetics of alpha-emitting radiopharmaceuticals is essential. Quantitative imaging of alpha-emitting radiopharmaceuticals is often possible via imaging of gammas and positrons produced during complex decay chains of these radionuclides. Analysis of the complex decay chains for alpha-emitting radionuclides (Tb-149, At-211, Bi-212 (decayed from Pb-212), Bi-213, Ra-223, Ac-225, and Th-227) with relevance to imageable signals is attempted in this mini-review article. Gamma camera imaging, single-photon emission computed tomography, positron emission tomography, bremsstrahlung radiation imaging, Cerenkov luminescence imaging, and Compton cameras are briefly discussed as modalities for imaging alpha-emitting radiopharmaceuticals.

Gastrointestinal motility in patients with end-stage renal disease on chronic hemodialysis.

Previous studies indicated delayed gastric emptying in patients with end-stage renal disease (ESRD) using indirect methods. The objective of the current study was to examine gastrointestinal motility using a direct method as well as the role of the incretin hormones and glucagon. Patients on chronic hemodialysis and with either normal glucose tolerance, impaired glucose tolerance or type 2 diabetes, and healthy control subjects (N=8, respectively) were studied. Gastric emptying time was measured by repeated gamma camera imaging for 6 hours after intake of a radioactive labeled standardized mixed solid and liquid meal. Glucagon, glucagon-like peptide-1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) levels were measured. Patients were age, gender and BMI matched with controls. We found significantly higher gastric retention at 15 minutes, prolonged gastric mean emptying time, and gastric half-emptying time of the solid marker in all three groups of ESRD patients compared to controls. Significant differences in mean total area under the concentration curve (AUC) values across the four groups for GIP (P=0.001), but not for GLP-1 and glucagon. The ESRD group had significant higher total AUC of GIP and glucagon compared to controls (P<0.001 and P<0.04) but not for GLP-1 (P=0.4). No difference in incremental AUC was found. We found altered gastrointestinal motility in dialysis patients, with higher gastric retention and prolonged gastric emptying, and higher total AUC of GIP and glucagon independent of the presence of diabetes or prediabetes.

Prevention of Burn Wound Progression by Mesenchymal Stem Cell Transplantation: Deeper Insights Into Underlying Mechanisms.

Burns are dynamic wounds that may present a progressive expansion of necrosis into the initially viable zone of stasis. Therefore, salvage of this zone is a major subject of focus in burn research. The beneficial effects of mesenchymal stem cells (MSCs) on the survival of the zone of stasis have been previously documented. However, many gaps still exist in our knowledge regarding the underlying protective mechanisms. Hence, this study was designed to evaluate the pathophysiological basis of MSCs in the prevention of burn wound progression. Wistar rats received thermal trauma on the back according to the "comb burn" model. Animals were randomly divided into sham, control, and stem cell groups with sacrifice and analysis at 72 hours after the burn. The stasis zones were evaluated using histochemistry, immunohistochemistry, biochemistry, real-time polymerase chain reaction assay, and scintigraphy to evaluate the underlying mechanisms. Gross evaluation of burn wounds revealed that vital tissue percentage of the zone of stasis was significantly higher in the stem cell group. Semiquantitative grading of the histopathologic findings showed that MSCs alleviated burn-induced histomorphological alterations in the zone of stasis. According to CC3a staining and expression analysis of Bax (B-cell leukemia 2-associated X) and Bcl-2 (B-cell leukemia 2) genes, MSCs attenuated increases in apoptosis postburn. In addition, these transplants showed an immunomodulatory effect that involves reduced neutrophilic infiltration, down-regulation of proinflammatory cytokines (tumor necrosis factor α, interleukin 1β [IL-1β], and IL-6), and up-regulation of the anti-inflammatory cytokine IL-10 in the zone of stasis. Burn-induced oxidative stress was significantly relieved with MSCs, as shown by increased levels of malondialdehyde, whereas the expression and activity of the antioxidant enzyme superoxide dismutase were increased. Finally, MSC-treated interspaces had enhanced vascular density with higher expression levels for vascular endothelial growth factor A, platelet-derived growth factor, fibroblast growth factor, and transforming growth factor β. Gamma camera images documented better tissue perfusion in animals treated with MSCs. The protective effects of MSCs are mediated by the inhibition of apoptosis through immunomodulatory, antioxidative, and angiogenic actions.

Safety and Efficacy of Yttrium-90-Labeled Anti-CD45 Antibody (90Y-DOTA-BC8) Followed By a Standard Reduced-Intensity Hematopoietic Stem Cell Transplant (HCT) Regimen for Patients with Refractory/Relapsed Leukemia or High-Risk Myelodysplastic Syndrome (MDS)

▪Although HCT offers the best potential for cure for patients with high risk leukemia and MDS, the procedure may not be an option for all patients due to the toxicity of the conditioning regimen. Reduced-intensity conditioning (RIC) allo-HCT regimens are associated with lower non-relapse mortality (NRM), but patients receiving these regimens have a higher risk of relapse. Radioimmunotherapy (RIT) can potentially deliver high doses of targeted radiation while minimizing toxicity to normal tissue. When combined with RIC allo-HCT, RIT may improve responses without increasing toxicity associated with myeloablative conditioning.We evaluated the safety and efficacy of yttrium 90 (90Y)-anti-CD45 antibody (MAb; BC8) followed by a standard RIC regimen with fludarabine (Flu) and 2 Gy total body irradiation (TBI) as a means of developing an improved HCT strategy for high-risk acute leukemia or MDS patients. We used CD45 as a target due to its ubiquitous expression on hematopoietic stem cells including the leukemic blasts. We used the high-energy (2.2 MeVmax) beta-emitter 90Y, which has a relatively short half-life (2.7 days) to eliminate targeted malignant cells.This phase I dose-escalation trial (NCT01300572) was designed to estimate the safety, feasibility and maximum tolerated dose (MTD) of 90Y-BC8-DOTA MAb when combined with Flu and 2 Gy TBI followed by HLA‐matched, related or unrelated allo-HCT for patients with high-risk leukemia or MDS. The MTD was defined as the radiation absorbed dose delivered by 90Y-BC8-DOTA MAb associated with a true dose-limiting toxicity (DLT) rate of 25%, where a DLT is defined as Bearman grade III/IV regimen-related toxicity. Doses of 90Y were escalated in increments of 2 Gy depending on the occurrence of DLT. Inclusion required patients to have advanced leukemia or high-risk MDS (defined as primary refractory or relapsed AML/ALL, secondary AML, MDS expressed as RAEB or CMML). To determine the dose of 90Y-BC8-DOTA, patients first underwent a biodistribution step using a trace-labeled infusion of 111Indium (111In)-BC8-DOTA followed by gamma-camera imaging. On pre-HCT day -12, patients received 90Y-BC8-DOTA at a prescribed radiation dose calculated from the trace-labeled 111In-BC8-DOTA biodistribution, followed by Flu (30 mg/m2/day) on days -4 to -2. TBI (2 Gy) was administered on day 0, prior to G-CSF mobilized donor PBSC infusion. GVHD prophylaxis consisted of mycophenolate mofetil and cyclosporine.Fifteen patients, median age of 62 (range 37-76), were treated (10 with advanced AML, 5 with high-risk MDS). At time of HCT, 9 patients had refractory active disease while 6 were in remission with minimal residual disease (Table 1). The patients received 22.8 to 151.2 mCi of 90Y, delivering an average of 10.5 Gy to marrow, 70 Gy to spleen, and 17 Gy to liver. Although a maximum dose of 28 Gy was delivered to the liver, no DLT was observed. Therefore, the MTD could not be estimated.Treatment led to complete remission in 13 patients (87%), 2 patients had persistent disease after HCT. All patients engrafted with a median donor-derived CD3 and CD33 chimerism both 100% by day 28 after HCT. Ten patients (67%) developed grade II-IV acute GVHD (grade II: n=7; III: n=2; IV: n=1). Five patients (33%) developed chronic GVHD. Six patients relapsed, 5 of whom subsequently died due to progression of disease. The median time to relapse among these 6 patients was 59 days (range, 6- 351 days). One patient died from stage IV steroid-refractory GVHD. One patient died in remission from acute renal failure at 7 months after HCT. Eight patients (53%) are surviving with a median follow-up of 1.8 (range, 0.9-5.9) years. Estimated overall survival at one and two years were 66% and 46%, respectively, with progression-free survival estimated to be 46% at each of these time points. The 1-year estimate of relapse was 41% (Fig. 1).The inclusion of 90Y-BC8-DOTA into a RIC allo-HCT regimen is feasible, tolerable and no DLTs were observed. The efficacy of this approach is promising considering the high-risk leukemia/MDS patients with active disease enrolled. Current studies are evaluating the use of an alpha emitter, astatine-211, which is short-lived (t ½ = 7.2 hours) and provides high-energy radiation, conjugated to anti-CD45 MAb BC8 as part of an HCT conditioning regimen for patients with advanced AML, ALL, or high-risk MDS, in place of 90Y with the goal of continuing to improve outcomes using RIT for allo-HCT (NCT03128034). [Display omitted] DisclosuresOrozco:Actinium Pharmaceuticals: Research Funding. Green:Juno Therapeutics: Patents & Royalties, Research Funding. Gopal:Incyte: Consultancy; Pfizer: Research Funding; Gilead: Consultancy, Research Funding; Teva: Research Funding; Aptevo: Consultancy; Merck: Research Funding; Janssen: Consultancy, Research Funding; Spectrum: Research Funding; Takeda: Research Funding; BMS: Research Funding; Seattle Genetics: Consultancy, Research Funding; Brim: Consultancy; Asana: Consultancy. Pagel:Pharmacyclics, an AbbVie Company: Consultancy; Gilead: Consultancy.

In vivo Non-invasive Imaging of Radio-Labeled Exosome-Mimetics Derived From Red Blood Cells in Mice.

Exosomes are natural nano-sized membrane vesicles that have garnered recent interest owing to their potential as drug delivery vehicles. Though exosomes are effective drug carriers, their production and in vivo biodistribution are still not completely elucidated. We analyzed the production of exosome mimetics (EMs) from red blood cells (RBCs) and the radio-labeling of the RBC-EMs for in vivo imaging. Engineered EMs from RBCs were produced in large-scale by a one-step extrusion method, and further purified by density-gradient centrifugation. RBC-EMs were labeled with technetium-99m (99mTc). For non-invasive imaging, 99mTc (free) or 99mTc-RBC-EMs were injected in mice, and their biodistribution was analyzed by gamma camera imaging. Animals were sacrificed, and organs were collected for further biodistribution analysis. RBC-EMs have similar characteristics as the RBC exosomes but have a 130-fold higher production yield in terms of particle numbers. Radiochemical purity of 99mTc-RBC-EMs was almost 100% till 2 h reduced to 97% at 3 h. Radio-labeling did not affect the size and morphology of RBC-EMs. In contrast to free 99mTc, in vivo imaging of 99mTc-RBC-EMs in mice showed higher uptake in the liver and spleen, and no uptake in the thyroid. Ex vivo imaging confirmed the in vivo findings. Furthermore, fluorescent imaging confirmed the nuclear imaging findings. Immunofluorescent imaging revealed that the hepatic uptake of RBC-EMs was significantly mediated by kupffer cells (resident hepatic macrophages). Our results demonstrate a simple yet large-scale production method for a novel type of RBC-EMs, which can be effectively labeled with 99mTc, and feasibly monitored in vivo by nuclear imaging. The RBC-EMs may be used as in vivo drug delivery vehicles.

Tc-99m and Fluorescence-Labeled Anti-Flt1 Peptide as a Multimodal Tumor Imaging Agent Targeting Vascular Endothelial Growth Factor-Receptor 1.

We developed a Tc-99m and fluorescence-labeled peptide, Tc-99m TAMRA-GHEG-ECG-GNQWFI, to target tumor cells, and evaluated the diagnostic performance as a dual-modality imaging agent for tumor in a murine model. TAMRA-GHEG-ECG-GNQWFI was synthesized using Fmoc solid-phase peptide synthesis. Radiolabeling of TAMRA-GHEG-ECG-GNQWFI with Tc-99m was done using ligand exchange via tartrate. Binding affinity and in vitro cellular uptake studies were performed. Gamma camera imaging, biodistribution, and ex vivo imaging studies were performed in murine models with U87MG tumors. Tumor tissue slides were prepared and analyzed with immunohistochemistry using confocal microscopy. After radiolabeling procedures with Tc-99m, Tc-99m TAMRA-GHEG-ECG-GNQWFI complexes were prepared in high yield (> 95%). The K d of Tc-99m TAMRA-GHEG-ECG-GNQWFI determined by saturation binding was 29.5 ± 4.5nM. Confocal microscopy images of U87MG cells incubated with TAMRA-GHEG-ECG-GNQWFI showed strong fluorescence in the cytoplasm. Gamma camera imaging revealed substantial uptake of Tc-99m TAMRA-GHEG-ECG-GNQWFI in tumors. Tumor uptake was effectively blocked by the co-injection of an excess concentration of GNQWFI. Specific uptake of Tc-99m TAMRA-GHEG-ECG-GNQWFI was assessed by biodistribution, ex vivo imaging, and immunohistochemistry stain studies. In vivo and in vitro studies revealed substantial and specific uptake of Tc-99m TAMRA-GHEG-ECG-GNQWFI in tumor cells. Tc-99m TAMRA-GHEG-ECG-GNQWFI could be a good candidate dual-modality imaging agent for tumors.

Radiolabelled leucocytes in human pulmonary disease.

Radionuclides for leucocyte kinetic studies have progressed from non-gamma emitting cell-labelling radionuclides through gamma emitting nuclides that allow imaging of leucocyte kinetics, to the next goal of positron emission tomography (PET). Mostly the authors' own studies, following on from studies of the early pioneers. From early imaging studies, it appeared that the majority of the marginated granulocyte pool was located in the lungs. However, later work disputed this by demonstrating the exquisite sensitivity of granulocytes to ex vivo isolation and labelling, and that excessive lung activity is artefactual. Following refinement of labelling techniques, it was shown that the majority of marginated granulocytes are located in the spleen and bone marrow. The majority of leucocytes have a pulmonary vascular transit time only a few seconds longer than erythrocytes. The minority showing slow transit, ~5% in healthy persons, is increased in systemic inflammatory disorders that cause neutrophil priming and loss of deformability. Using a range of imaging techniques, including gamma camera imaging, whole-body counting and single photon-emission computerized tomography, labelled granulocytes were subsequently used to image pulmonary trafficking in lobar pneumonia, bronchiectasis, chronic obstructive pulmonary disease and adult respiratory distress syndrome. More recently, eosinophils have been separated in pure form using magnetic bead technology for the study of eosinophil trafficking in asthma. These include advancement of eosinophil imaging, development of monocyte labelling, development of cell labelling with PET tracers and the tracking of lymphocytes.

In vivo tracking of intravenously injected mesenchymal stem cells in an Alzheimer’s animal model

Purpose: The purpose of this study was to investigate how intravenously injected bone marrow-derived mesenchymal stem cells (BMSCs) are distributed in the body of an Alzheimer’s disease (AD) animal model. Methods: Stem cells were collected from bone marrow of mice and labeled with Indium-111 (111In). The 111In-labeled BMSCs were infused intravenously into 3×Tg-AD mice in the AD group and non-transgenic mice (B6129SF2/J) as controls. Biodistribution was evaluated with a gamma counter and gamma camera 24 and 48 h after injecting the stem cells. Results: A gamma count of the brain showed a higher distribution of labeled cells in the AD model than in the control group at 24 (p = .0004) and 48 h (p = .0016) after injection of the BMSCs. Similar results were observed by gamma camera imaging (i.e., brain uptake in the AD model was significantly higher than that in the control group). Among the other organs, uptake by the spleen was the highest in both groups. More BMSCs were found in the lungs of the control group than in those of the AD group. Conclusions: These results suggest that more intravenously infused BMSCs reached the brain in the AD model than in the control group, but the numbers of stem cells reaching the brain was very small.

Quantification of radioactivity by planar gamma-camera images, a promoted method of absorbed dose in the thyroid after iodine-131 treatment

Iodine-131 (131I) is an essential and widely used radioisotope in thyroid diseases and animal experiments. Planar imaging has been considered the most popular method for 131I thyroid uptake radioactive activity quantification. The ROI defining section is essential and can affect the accuracy of quantitative results. However, a consistent method has not been proposed. In this study, a UC-ROI defining method based on ULWL setting and colour display grade was applied. Three steps were performed: image acquisition of five standard activity models and obtaining the exact value that the counts per radioactive activity contributes to the ROI; image acquisition of 20 rat thyroids and obtaining the counts of the ROI (thyroid); and calculating the rat thyroid radioactive activity and comparing these values with the true values. The accuracy of quantification activity of 131I in rat thyroid reached 2.62% ± 0.41%. The mean quantification within 5% could be achieved in 19 of 20 rat thyroids. No significant difference existed between calculated thyroid 131I activity and true values with a paired matched-test (t = −0.384, P = 0.706 > 0.05). The results indicated that with the UC-ROI defining method, more accurate thyroid uptake 131I radioactive activity quantification by SPECT planar imaging can be achieved in vivo rat study.

Evaluation of the dosimetry approaches in ablation treatment of thyroid cancer

In this study, we aimed to evaluate dosimetric approaches in ablation treatment of Differentiated Thyroid Carcinoma (DTC) without interrupting the clinical routine. Prior to therapy, 10.7 MBq 131I in average was orally given to 24 patients suffering from DTC. MIRD formalism was used for dosimetric calculations. For blood and bone marrow dosimetry, blood samples and whole‐body counts were collected at 2, 24, 72, and 120 h after I‐131 administration. For remnant tissue dosimetry, uptake measurements were performed at the same time intervals. To estimate the remnant volume, anterior and lateral planar gamma camera images were acquired with a reference source within the field of view at 24 h after I‐131 administration. Ultrasound imaging was also performed. Treatment activities determined with the fixed activity method were administered to the patients. Secondary cancer risk relative to applied therapy was evaluated for dosimetric approaches. The average dose to blood and bone marrow were determined as 0.15 ± 0.04 and 0.11 ± 0.04 Gy/GBq, respectively. The average remnant tissue dose was 0.58 ± 0.52 Gy/MBq and the corresponding required activity to ablate the remnant was approximately 1.3 GBq of 131I. A strong correlation between 24th‐hour uptake and time‐integrated activity coefficient values was obtained. Compared to fixed activity method, approximately five times higher secondary cancer risk was determined in bone marrow dosimetry, while the risk was about three times lower in lesion‐based dosimetry.