Scintigraphic Tracking of Allogeneic Mesenchymal Stem Cells in the Distal Limb After Intra-Arterial Injection in Standing Horses.

OBJECTIVE: To assess the feasibility of intra-arterial administration of allogeneic mesenchymal stem cells (MSC) in the median artery of standing horses and evaluate the distribution and retention of radiolabeled cells. STUDY DESIGN: In vivo experimental study. ANIMALS: Six research horses. METHODS: Technetium(99m) -HexaMethyl-Propylene-Amine Oxime-labeled MSC were injected under ultrasound guidance in the median artery of 6 front limbs of 3 horses, standing under sedation. Scintigraphic images were obtained at the time of injection, and at 1, 6, and 24 hours postinjection. Six additional limbs from 3 horses were similarly injected with unlabeled MSC. Ultrasound was performed the following day for assessment of vascular changes. RESULTS: Intra-arterial injection was performed successfully in 11 of 12 limbs. In 1 limb, partial periarterial injection compromised the success of the procedure. Homogeneous distribution of radiolabeled MSC was observed through the entire distal limb, including within the hoof. Partial venous thrombosis was found in both groups of horses, but was subjectively less severe in horses injected with unlabeled MSC. No lameness was observed. Transient swelling of the distal limb occurred in only 1 limb. CONCLUSION: Intra-arterial injection of MSC can be performed in standing horses under sedation and successfully distribute MSC to the distal limb. A risk of periarterial injection was identified but can be reduced with proper sedation, local anesthesia, and increased experience. Partial venous thrombosis was observed as a complication, but did not cause changes of clinical importance, other than rare transient swelling.

Functional Brain Imaging in Cornelia de Lange Syndrome: Case Report and Literature review.

Functional brain imaging with brain single photon emission computer tomography (Brain SPECT) has been used for many years in the evaluation of multiple neuro-degenerative and neuro-developmental disorders. Brain SPECT is a nuclear medicine tomographic study performed with a lipophilic radiopharmaceutical labeled with 99mTc-pertechnetate. It is a cerebral perfusion agent that depicts the global and regional perfusion patterns in the cortical gray matter and subcortical structures. Cornelia de Lange syndrome (CdLS) is a rare neuro-developmental and genetic condition, associated to several malformations. There are a limited number of cases reported in the medical literature and few of them report neuro-radiological and/or neuro-pathologic abnormalities. We report a case of a 15 year old patient, clinically diagnosed at birth with CdLS, who presents limited anatomical findings on Computed Tomography and Magnetic Resonance Imaging. To the best of our knowledge, this is the first report of the Brain SPECT findings in this syndrome.

Vascular physiology and protein disposition in a preclinical model of neurodegeneration.

The development of clinically relevant preclinical models that mimic the hallmarks of neurodegenerative disease is an ongoing pursuit in early drug development. In particular, robust physiological characterization of central nervous system (CNS) disease models is necessary to predict drug delivery to target tissues and to correctly interpret pharmacodynamic responses to disease-modifying therapeutic candidates. Efficient drug delivery across the blood-CNS barrier is a particularly daunting task, prompting our strategy to evaluate the biodistribution of five distinct molecular probes in a well-characterized mouse model of neurodegeneration. A transgenic mouse model of amyotrophic lateral sclerosis was selected based on a phenotype resembling clinical symptoms, including loss of motor neurons from the spinal cord and paralysis in one or more limbs, due to expression of a G93A mutant form of human superoxide dismutase (SOD1). The tissue distributions of two proteins, albumin and a representative immunoglobulin G antibody, as well as two blood flow markers, the lipophilic blood flow marker Ceretec (i.e., (99m)Tc-HMPAO) and the polar ionic tracer, rubidium-86 chloride ((86)RbCl), were measured following intravenous injection in SOD1(G93A) and age-matched control mice. The radiopharmaceutical TechneScan PYP was also used to measure the distribution of (99m)Tc-labeled red blood cells as a blood pool marker. Both the antibody and (86)Rb were able to cross the blood-spinal cord barrier in SOD1(G93A) mice to a greater extent than in control mice. Although the biodistribution patterns of antibody, albumin, and RBCs were largely similar, notable differences were detected in muscle and skin. Moreover, vastly different biodistribution patterns were observed for a lipophilic and polar perfusion agent, with SOD1(G93A) mutation resulting in reduced renal filtration rates for the former but not the latter. Overall, the multiprobe strategy provided an opportunity to efficiently collect an abundance of physiological information, including the degree and regional extent of blood-CNS barrier permeability, in a preclinical model of neurodegeneration.

Brain perfusion SPECT in the mouse: normal pattern according to gender and age.

Regional cerebral blood flow (rCBF) is a useful surrogate marker of neuronal activity and a parameter of primary interest in the diagnosis of many diseases. The increasing use of mouse models spawns the demand for in vivo measurement of rCBF in the mouse. Small animal SPECT provides excellent spatial resolution at adequate sensitivity and is therefore a promising tool for imaging the mouse brain. This study evaluates the feasibility of mouse brain perfusion SPECT and assesses the regional pattern of normal Tc-99m-HMPAO uptake and the impact of age and gender. Whole-brain kinetics was compared between Tc-99m-HMPAO and Tc-99m-ECD using rapid dynamic planar scans in 10 mice. Assessment of the regional uptake pattern was restricted to the more suitable tracer, HMPAO. Two HMPAO SPECTs were performed in 18 juvenile mice aged 7.5 ± 1.5weeks, and in the same animals at young adulthood, 19.1 ± 4.0 weeks (nanoSPECT/CTplus, general purpose mouse apertures: 1.2kcps/MBq, 0.7mm FWHM). The 3-D MRI Digital Atlas Database of an adult C57BL/6J mouse brain was used for region-of-interest (ROI) analysis. SPECT images were stereotactically normalized using SPM8 and a custom made, left-right symmetric HMPAO template in atlas space. For testing lateral asymmetry, each SPECT was left-right flipped prior to stereotactical normalization. Flipped and unflipped SPECTs were compared by paired testing. Peak brain uptake was similar for ECD and HMPAO: 1.8 ± 0.2 and 2.1 ± 0.6 %ID (p=0.357). Washout after the peak was much faster for ECD than for HMPAO: 24 ± 7min vs. 4.6 ± 1.7h (p=0.001). The general linear model for repeated measures with gender as an intersubject factor revealed an increase in relative HMPAO uptake with age in the neocortex (p=0.018) and the hippocampus (p=0.012). A decrease was detected in the midbrain (p=0.025). Lateral asymmetry, with HMPAO uptake larger in the left hemisphere, was detected primarily in the neocortex, both at juvenile age (asymmetry index AI=2.7 ± 1.7%, p=0.000) and at young adult age (AI=2.4 ± 1.7%, p=0.000). Gender had no effect on asymmetry. Voxel-wise testing confirmed the ROI-based findings. In conclusion, high-resolution HMPAO SPECT is a promising technique for measuring rCBF in preclinical research. It indicates lateral asymmetry of rCBF in the mouse brain as well as age-related changes during late maturation. ECD is not suitable as tracer for brain SPECT in the mouse because of its fast clearance from tissue indicating an interspecies difference in esterase activity between mice and humans.

Guidelines for the labelling of leucocytes with (99m)Tc-HMPAO. Inflammation/Infection Taskgroup of the European Association of Nuclear Medicine.

We describe here a protocol for labelling autologous white blood cells with (99m)Tc-HMPAO based on previously published consensus papers and guidelines. This protocol includes quality control and safety procedures and is in accordance with current European Union regulations and International Atomic Energy Agency recommendations.

Pharmacokinetics of 99mTc-HMPAO in isolated perfused rat lungs.

Lung uptake of technetium-labeled hexamethylpropyleneamine oxime (HMPAO) increases in rat models of human acute lung injury, consistent with increases in lung tissue glutathione (GSH). Since 99mTc-HMPAO uptake is the net result of multiple cellular and vascular processes, the objective was to develop an approach to investigate the pharmacokinetics of 99mTc-HMPAO uptake in isolated perfused rat lungs. Lungs of anesthetized rats were excised and connected to a ventilation-perfusion system. 99mTc-HMPAO (56 MBq) was injected into the pulmonary arterial cannula, a time sequence of images was acquired, and lung time-activity curves were constructed. Imaging was repeated with a range of pump flows and perfusate albumin concentrations and before and after depletion of GSH with diethyl maleate (DEM). A pharmacokinetic model of 99mTc-HMPAO pulmonary disposition was developed and used for quantitative interpretation of the time-activity curves. Experimental results reveal that 99mTc-HMPAO lung uptake, defined as the steady-state value of the 99mTc-HMPAO lung time-activity curve, was inversely related to pump flow. Also, 99mTc-HMPAO lung uptake decreased by ~65% after addition of DEM to the perfusate. Increased perfusate albumin concentration also resulted in decreased 99mTc-HMPAO lung uptake. Model simulations under in vivo flow conditions indicate that lung tissue GSH is the dominant factor in 99mTc-HMPAO retention in lung tissue. The approach allows for evaluation of the dominant factors that determine imaging biomarker uptake, separation of the contributions of pulmonary versus systemic processes, and application of this knowledge to in vivo studies.NEW & NOTEWORTHY We developed an approach for studying the pharmacokinetics of technetium-labeled hexamethylpropyleneamine oxime (99mTc-HMPAO) in isolated perfused lungs. A distributed-in-space-and-time computational model was fit to data and used to investigate questions that cannot readily be addressed in vivo. Experimental and modeling results indicate that tissue GSH is the dominant factor in 99mTc-HMPAO retention in lung tissue. This modeling approach can be readily extended to investigate the lung pharmacokinetics of other biomarkers and models of lung injury and treatment thereof.

Biodistribution and radiation dosimetry of 99mTc-HMPAO-labeled monocytes in patients with rheumatoid arthritis.

UNLABELLED: Rheumatoid arthritis (RA) involves the accumulation of monocyte-derived macrophages in the affected synovial tissue. This process of cell migration could be portrayed scintigraphically to monitor noninvasively the effects of therapy on the progress of the disease. For this purpose, labeling of purified autologous monocytes with 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) at very high specific radioactivity has recently been developed. The aim of this study was to assess the biodistribution and radiation dosimetry of 99mTc-HMPAO-labeled monocytes in adult patients with RA. METHODS: In 8 patients with RA, monocytes were isolated from 100 mL of blood and labeled with 99mTc-HMPAO to a yield of 10 Bq/cell. Multiple whole-body scans were performed up to 20 h after reinjection of an average of 200 MBq of 99mTc-HMPAO-labeled monocytes. Urine and blood samples were collected. The fraction of administered activity in 7 source organs was quantified from the attenuation-corrected geometric mean counts in conjugate views. Radiation-absorbed doses were estimated with OLINDA/EXM software. RESULTS: Autologous monocytes labeled with 99mTc-HMPAO at high intracellular yields showed in vivo kinetics comparable with labeled leukocytes, with initial trapping in the lungs followed by distribution into the liver, spleen, and bone marrow. The radiation-absorbed estimates for 99mTc-HMPAO-labeled monocytes were comparable with those for 99mTc-HMPAO-labeled mixed white blood cells, with an effective dose of 0.011 mSv/MBq. CONCLUSION: 99mTc-HMPAO-labeled monocytes have biodistribution and radiation dosimetry similar to those of 99mTc-HMPAO-labeled mixed white blood cells and might therefore be used for in vivo monitoring of immunomodulating therapy in patients with RA.

Mitochondrial function is related to alterations at brain SPECT in depressed patients.

INTRODUCTION: 99mTc-d,l-hexamethylpropylene amine oxime (99mTc-HMPAO) retention in brain is proportional to cerebral blood flow and related to both the local hemodynamic state and to the cellular content of reduced glutathione. Alterations of the regional distribution of 99mTc-HMPAO retention, with discrepant results, have been reported at functional brain imaging of unipolar depression. Since mitochondrial involvement has been reported in depressed patients, the aim of the study was to explore whether the 99mTc-HMPAO retention at single-photon emission computed tomography in depressed patients may relate to different levels of mitochondrial function. METHODS: All patients had audiological and muscular symptoms, somatic symptoms that are common in depression. Citrate synthase (CS) activity assessed in muscle mitochondria correlated strongly with the activities of three mitochondrial respiratory chain enzymes and was used as a marker of mitochondrial function. K-means clustering performed on CS grouped eight patients with low and 11 patients with normal CS. Voxel-based analysis was performed on the two groups by statistical parametric mapping. RESULTS: Voxel-based analysis showed significantly higher 99mTc-HMPAO retention in the patients with low CS compared with the patients with normal CS in the posterior and inferior frontal cortex, the superior and posterior temporal cortex, the somato-sensory cortex, and the associative parietal cortex. CONCLUSION: Low muscle CS in depressed patients is related to higher regional 99mTc-HMPAO retention that may reflect cerebrovascular adaptation to impaired intracellular metabolism and/or intracellular enzymatic changes, as previously reported in mitochondrial disorder. Mitochondrial dysfunction in varying proportions of the subjects may explain some of the discrepant results for 99mTc-HMPAO retention in depression.

PLA-PEG nanocapsules radiolabeled with 99mTechnetium-HMPAO: release properties and physicochemical characterization by atomic force microscopy and photon correlation spectroscopy.

The present work describes the preparation, characterization and labelling of conventional and surface-modified nanocapsules (NC) with 99m Tc-HMPAO. The size, size distribution and homogeneity were determined by photon correlation spectroscopy (PCS) and zeta potential by laser doppler anemometry. The morphology and the structural organization were evaluated by atomic force microscopy (AFM). The stability and release profile of the NC were determined in vitro in plasma. The results showed that the use of methylene blue induces significant increase in the encapsulation efficiency of 99m Tc-HMPAO, from 24.4 to 49.8% in PLA NC and 22.37 to 52.93% in the case of PLA-PEG NC (P<0.05) by improving the complex stabilization. The average diameter of NC calculated by PCS varied from 216 to 323 nm, while the average diameter determined by AFM varied from 238 to 426 nm. The AFM analysis of diameter/height ratios suggested a greater homogeneity of the surface-modified PLA-PEG nanocapsules compared to PLA NC concerning their flattening properties. The in vitro release of the 99m Tc-HMPAO in plasma medium was faster for the conventional PLA NC than for the surface-modified NC. For the latter, 60% of the radioactivity remained associated with NC, even after 12h of incubation. The results suggest that the surface-modified 99m Tc-HMPAO-PLA-PEG NC was more stable against label leakage in the presence of proteins and could present better performance as radiotracer in vivo.

Biodistribution study and identification of inflammation sites using 99mTc-labelled stealth pH-sensitive liposomes.

PURPOSE: To investigate the biodistribution and the ability of stealth pH-sensitive liposomes radiolabelled with 99mTc to identify inflammatory regions in a rat focal inflammation model. METHODS: Preformed glutathione-containing stealth pH-sensitive liposomes were labelled with 99mTc-hexamethylpropylene amine oxime (99mTc-HMPAO). The 99mTc-HMPAO radiolabelled stealth pH-sensitive liposomes (99mTc-SpHL) were administered intravenously in Wistar male rats with inflammation induced by injection subplantar of carrageenan in the right foot. At pre-established time intervals the animals were anaesthetized and tissues were removed and analysed for 99mTc content using an automatic scintillation apparatus. Scintigraphic imaging was also performed after 2, 4 and 8 h of intravenous injection of 99mTc-SpHL. RESULTS: The 99mTc-SpHL was significantly taken up by the spleen (19.21+/-2.98%ID/g at 30 min post-injection). Low radioactivity levels were found in the liver, lungs, and kidney. Moreover, the 99mTc-SpHL uptake was significantly higher in the inflamed foot when compared to the respective control (0.386+/-0.059 and 0.215+/-0.018%ID/g at 2 h post-injection, respectively). As early as 30 min after administration of 99mTc-SpHL, the focus of inflammation could be visualized scintigraphically. The value of the inflammatory and non-inflammatory site radioactivity counting ratio was greater than 5. CONCLUSION: This result indicates that the 99mTc-SpHL presents a high tropism for inflammatory regions and may be useful as a radiopharmaceutical to identify these foci.

Usefulness of rCBF analysis in diagnosing Parkinson's disease: supplemental role with MIBG myocardial scintigraphy.

UNLABELLED: (123)I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy is a useful tool for differentiating idiopathic Parkinson's disease (PD) from parkinsonism (PS) caused by other disorders. However, cardiac MIBG uptake is affected by various causes. Alternatively, hypoperfusion in the occipital lobe of PD is reported recently. OBJECTIVE: The objective is to clarify the correlation between regional cerebral blood flow (rCBF) alteration and cardiac MIBG uptake in PD. In addition, we examined whether additional brain perfusion analysis improved the differential diagnostic ability for PD from PS when compared with MIBG scintigraphy alone. METHODS: Forty-nine patients with PD (27 mild groups: Hoehn and Yahr stages I, II; 22 severe groups: Hoehn and Yahr stages III, IV) and 28 patients with PS participated. We compared absolute rCBF values between PD and PS. In addition, we determined correlation between MIBG parameters and each rCBF value. Finally, we compared the diagnostic ability for the differentiation of PD from PS between two diagnostic criteria, each MIBG index abnormality alone [heart-to-mediastinum ratio, H/M (E) < 1.9, H/E (D) < 1.7, washout rate > 40%] and each MIBG index abnormality or occipital lobe hypoperfusion (<36 ml/100 g per min). RESULTS: Absolute rCBF value of occipital lobe was significantly lower in severe PD as compared with PS or mild PD. In the correlation analysis, rCBF of occipital lobe correlated positively with MIBG parameters (H/M). Regarding the diagnostic ability, sensitivity improved by accounting for occipital hypoperfusion as compared with MIBG indices alone. In contrast, neither specificity nor accuracy improved by adding occipital lobe analysis. CONCLUSIONS: MIBG parameters (H/M) correlated positively with occipital hypoperfusion in PD. In the differential diagnosis between PD and PS, although its usefulness might be limited, analysis of rCBF in the occipital lobe added to (123)I-MIBG myocardial imaging can be recommended.

Study of Binding Kinetics and Specificity of 99mTc-SSS-Complex and 99mTc-HMPAO to Blood Cells.

Nuclear medicine offers several techniques and procedures to image infection, but radiolabelled autologous white blood cells (WBCs) are still the gold standard. These cells are usually labelled with 111In or 99mTc bound to a hydrophobic chelating agent that allows these isotopes to pass through the plasma membrane and enter in the cytoplasm. The most common compound in Europe is HMPAO that efficiently chelates 99mTc. However, up to 20-40% of the complex is released from the cells in the first few hours. The aim of this study was to radiolabel a new compound, (S3CPh)2 (S2CPh)-complex (SSS-complex) with 99mTc and compare its binding kinetics and specificity for WBC with HMPAO. The SSS-complex was labelled with 99mTc and analysed by iTLC and RP-HPLC. In vitro quality controls included a stability assay in serum and saline. Results showed a labelling efficiency of 95 ± 1.2% and 98 ± 1.4% for 99mTc-SSS-complex and 99mTc-HMPAO, respectively (p=ns). 99mTc-SSS-complex was stable in serum and in saline up to 24 h (94 ± 0.1%). Cell labelling experiments showed a higher incorporation of 99mTc-SSS-complex than 99mTc-HMPAO by granulocytes (62.6 ± 17.8% vs 40.5 ± 15%, p=0.05), lymphocytes (59.9 ± 22.2% vs 29.4 ± 13.5%; p=0.03), and platelets (44.4 ± 24% vs 20.5 ± 10.7%; p=ns), but the release of radiopharmaceutical from granulocytes at 1 h was lower for HMPAO than for SSS-complex (10.3 ± 1.9% vs 21.3 ± 1.8%; p=0.001). In conclusion, 99mTc-SSS-complex, although showing high labelling efficiency, radiochemical purity, and stability, is not a valid alternative to 99mTc-HMPAO, for example, in vivo white blood cells labelling because of high lymphocyte and platelet uptake and rapid washout from granulocytes.

Comparing brain activity patterns during spontaneous exploratory and cue-instructed learning using single photon-emission computed tomography (SPECT) imaging of regional cerebral blood flow in freely behaving rats.

Learning can be categorized into cue-instructed and spontaneous learning types; however, so far, there is no detailed comparative analysis of specific brain pathways involved in these learning types. The aim of this study was to compare brain activity patterns during these learning tasks using the in vivo imaging technique of single photon-emission computed tomography (SPECT) of regional cerebral blood flow (rCBF). During spontaneous exploratory learning, higher levels of rCBF compared to cue-instructed learning were observed in motor control regions, including specific subregions of the motor cortex and the striatum, as well as in regions of sensory pathways including olfactory, somatosensory, and visual modalities. In addition, elevated activity was found in limbic areas, including specific subregions of the hippocampal formation, the amygdala, and the insula. The main difference between the two learning paradigms analyzed in this study was the higher rCBF observed in prefrontal cortical regions during cue-instructed learning when compared to spontaneous learning. Higher rCBF during cue-instructed learning was also observed in the anterior insular cortex and in limbic areas, including the ectorhinal and entorhinal cortexes, subregions of the hippocampus, subnuclei of the amygdala, and the septum. Many of the rCBF changes showed hemispheric lateralization. Taken together, our study is the first to compare partly lateralized brain activity patterns during two different types of learning.

Radiotoxicity of alpha particles versus high and low energy electrons in hypoxic cancer cells.

PURPOSE: Hypoxic regions of tumors are less sensitive to radio- and chemotherapy, leading to poor prognosis of patients. One option to overcome the radioresistance is the irradiation of hypoxic tumors with high linear energy transfer (LET) α- or Auger electronemitters assuming their radiotoxicity would be less dependent on the cellular oxygenation status. Therefore, the aim of the present study was to determine whether irradiation with the intracellularly distributed Auger electron/γ-emitter 99mTc using the tracer [99mTc]TcHMPAO is a promising therapeutic option for the treatment of hypoxic tumor cells. Thus, the high LET α-particleemitter 223Ra ([223Ra]RaCl2) and the low LET ß-emitter 188Re ([188Re]NaReO4) were studied in comparison to [99mTc]Tc-HMPAO. MATERIALS AND METHODS: A431 tumor cells were incubated with [99mTc]Tc-HMPAO (1-20 MBq/2 mL), [223Ra]RaCl2 (1.4-16.3 kBq/2 mL) or [188Re]NaReO4 (0.3-13.7 MBq/2 mL) under normoxic or hypoxic conditions. The degree of radiotoxicity was analyzed using the colony forming assay (CFA), and the intracellular radionuclide uptake of the radiotracers was quantified. RESULTS: Hypoxic A431 cells are less radiosensitive to irradiation with [99mTc]Tc-HMPAO or [188Re]NaReO4 than normoxic ones. In contrast, the radiosensitivity of A431 cells is almost independent of the oxygen status when treated with the [223Ra]RaCl2. CONCLUSIONS: We demonstrate that the Auger electron/γ-emitter 99mTc ([99mTc]Tc-HMPAO), which does not bound directly to the DNA, is not a promising therapeutic option for hypoxic tumor cells. But the high LET α-particle-emitter 223Ra is more suitable for the treatment of hypoxic tumor cells than irradiation with [99mTc]Tc-HMPAO or the low LET bemitter 188Re. ZIELSETZUNG: Hypoxische Tumorregionen sind bei Radio- und Chemotherapie weniger sensitiv als Tumorregionen mit ausreichender Sauerstoffversorgung. Dies verursacht eine schlechte Prognose für Tumorpatienten. Eine Option die Radioresistenz zu überwinden, stellt die Bestrahlung mit α-Partikel-Emittern oder Auger-Elektronen-Emittern mit einem hohen linearen Energietransfer (LET) dar. In dieser Studie soll untersucht werden, ob die Bestrahlung von hypoxischen Tumorzellen mit dem intrazellulär aufgenommenen γ- sowie Auger-Elektronen-Emitter 99mTc unter Verwendung des Radiotracers [99mTc]Tc-HMPAO eine vielversprechende Therapieoption darstellen könnte. Vergleichend wurde der Hoch-LET α-Partikel-Emitter 223Ra ([223Ra]RaCl2) und der Niedrig-LET ß-Emitter 188Re ([188Re]NaReO4) eingesetzt. METHODEN: A431 Tumorzellen wurden unter normoxischen oder hypoxischen Kulturbedingungen mit [99mTc]Tc-HMPAO (1-20 MBq/2 ml), [223Ra]RaCl2 (1,4-16,3 kBq/2 ml) und [188Re]NaReO4 (0,3-13,7 MBq/2 ml) inkubiert. Zur Detektion der resultierenden strahlenbiologischen Wirkung wurde der Koloniebildungsassay angewendet. Zusätzlich wurde die intrazelluläre Aufnahme der Radiotracer quantifiziert. ERGEBNISSE: Nach Inkubation von [99mTc]Tc-HMPAO sind hypoxische A431-Zellen weniger strahlensensitiv als normoxische Zellen. Im Gegensatz zur Behandlung mit [99mTc]Tc-HMPAO oder [188Re]NaReO4 wurde bei Behandlung mit [223Ra]RaCl2 ein geringerer Einfluss des Sauerstoffstatus auf die Radiosensitivität von A431-Zellen gefunden. SCHLUSSFOLGERUNG: Damit konnte gezeigt werden, dass der nicht direkt an die DNA gebundene Auger-Elektronen-/ γ-Emitter 99mTc ([99mTc]Tc-HMPAO) die Radioresistenz von hypoxischen Tumorzellen nicht überwinden kann. Jedoch stellt der Hoch-LET α-Partikel-Emitter 223Ra ([223Ra]RaCl2) eine bessere Behandlungsoption dar.

Early sensory experience influences the development of multisensory thalamocortical and intracortical connections of primary sensory cortices.

The nervous system integrates information from multiple senses. This multisensory integration already occurs in primary sensory cortices via direct thalamocortical and corticocortical connections across modalities. In humans, sensory loss from birth results in functional recruitment of the deprived cortical territory by the spared senses but the underlying circuit changes are not well known. Using tracer injections into primary auditory, somatosensory, and visual cortex within the first postnatal month of life in a rodent model (Mongolian gerbil) we show that multisensory thalamocortical connections emerge before corticocortical connections but mostly disappear during development. Early auditory, somatosensory, or visual deprivation increases multisensory connections via axonal reorganization processes mediated by non-lemniscal thalamic nuclei and the primary areas themselves. Functional single-photon emission computed tomography of regional cerebral blood flow reveals altered stimulus-induced activity and higher functional connectivity specifically between primary areas in deprived animals. Together, we show that intracortical multisensory connections are formed as a consequence of sensory-driven multisensory thalamocortical activity and that spared senses functionally recruit deprived cortical areas by an altered development of sensory thalamocortical and corticocortical connections. The functional-anatomical changes after early sensory deprivation have translational implications for the therapy of developmental hearing loss, blindness, and sensory paralysis and might also underlie developmental synesthesia.

Evaluation of Brain Nuclear Medicine Imaging Tracers in a Murine Model of Sepsis-Associated Encephalopathy.

PURPOSE: The purpose of this study was to evaluate a set of widely used nuclear medicine imaging agents as possible methods to study the early effects of systemic inflammation on the living brain in a mouse model of sepsis-associated encephalopathy (SAE). The lipopolysaccharide (LPS)-induced murine systemic inflammation model was selected as a model of SAE. PROCEDURES: C57BL/6 mice were used. A multimodal imaging protocol was carried out on each animal 4 h following the intravenous administration of LPS using the following tracers: [99mTc][2,2-dimethyl-3-[(3E)-3-oxidoiminobutan-2-yl]azanidylpropyl]-[(3E)-3-hydroxyiminobutan-2-yl]azanide ([99mTc]HMPAO) and ethyl-7-[125I]iodo-5-methyl-6-oxo-4H-imidazo[1,5-a][1,4]benzodiazepine-3-carboxylate ([125I]iomazenil) to measure brain perfusion and neuronal damage, respectively; 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) to measure cerebral glucose uptake. We assessed microglia activity on another group of mice using 2-[6-chloro-2-(4-[125I]iodophenyl)-imidazo[1,2-a]pyridin-3-yl]-N-ethyl-N-methyl-acetamide ([125I]CLINME). Radiotracer uptakes were measured in different brain regions and correlated. Microglia activity was also assessed using immunohistochemistry. Brain glutathione levels were measured to investigate oxidative stress. RESULTS: Significantly reduced perfusion values and significantly enhanced [18F]FDG and [125I]CLINME uptake was measured in the LPS-treated group. Following perfusion compensation, enhanced [125I]iomazenil uptake was measured in the LPS-treated group's hippocampus and cerebellum. In this group, both [18F]FDG and [125I]iomazenil uptake showed highly negative correlation to perfusion measured with ([99mTc]HMPAO uptake in all brain regions. No significant differences were detected in brain glutathione levels between the groups. The CD45 and P2Y12 double-labeling immunohistochemistry showed widespread microglia activation in the LPS-treated group. CONCLUSIONS: Our results suggest that [125I]CLINME and [99mTc]HMPAO SPECT can be used to detect microglia activation and brain hypoperfusion, respectively, in the early phase (4 h post injection) of systemic inflammation. We suspect that the enhancement of [18F]FDG and [125I]iomazenil uptake in the LPS-treated group does not necessarily reflect neural hypermetabolism and the lack of neuronal damage. They are most likely caused by processes emerging during neuroinflammation, e.g., microglia activation and/or immune cell infiltration.

99mTc-HMPAO brain SPECT in the monitoring of cerebral vasculitis therapy. / 99mTc-HMPAO SPECT cerebral en la monitorización de la terapia de vasculitis.

OBJECTIVE: The central nervous system (CNS) may be involved in a variety of inflammatory diseases of the blood vessels, generally known as vasculitis. The clinical diagnosis of such involvement in early stages is difficult, since a mild cognitive impairment can be the only symptom. It was hypothesized that brain-perfusion SPECT would be able to reveal CNS involvement and to monitor the course of the disease. The purpose of this study was assess if and when an improvement of cerebral perfusion can be registered by SPECT during the follow-up of these diseases. MATERIAL AND METHODS: Eighteen patients affected by Systemic Lupus Erythematosus (SLE), 22 by undifferentiated vasculitis (UV), 5 by Behcet's disease (BD) and 5 by primary Sjogren's Syndrome (pSS) were enrolled in this prospective study. A 99mTc-HMPAO brain perfusion SPECT was performed before the treatment and was repeated during the follow-up at different time intervals. Image analysis was performed on 10 cerebral areas using a specific software. RESULTS: In the SLE patients, no significant improvement of brain perfusion was found. On the contrary, in the UV the cerebral uptake of the tracer significantly improved from the twenty-fourth month (18/22 patients). Patients with BD showed an improvement of scintigraphic findings (5/5 patients), while a similar result was obtained only in 2 of the patients with pSS. CONCLUSIONS: In conclusion, brain SPECT seems to be able to monitor the disease in UV, indicating the moment when an improvement of the cerebral perfusion is achieved. In SLE patients this scintigraphic technique did not show a significant improvement in CNS perfusion.

Effects of EMDR psychotherapy on 99mTc-HMPAO distribution in occupation-related post-traumatic stress disorder.

BACKGROUND: Post-traumatic stress disorder (PTSD) is a derangement of mood control with involuntary, emotionally fraught recollections that may follow deep psychological trauma in susceptible individuals. This condition is treated with pharmacological and/or cognitive therapies as well as psychotherapy with eye movement desensitization and reprocessing (EMDR). However, only a very limited number of studies have been published dealing with work-related PTSD, and investigations on the effect of treatment on cerebral blood flow represent an even smaller number. AIM: To investigate the short-term outcome of occupation-related PTSD after EMDR therapy by 99mTc-HMPAO SPECT. METHOD: Fifteen patients, either train drivers suffering from PTSD after having been unintentionally responsible for a person-under-train accident or employees assaulted in the course of duty, were recruited for the study. 99mTc-HMPAO SPECT was performed on these patients both before and after EMDR therapy while they listened to a script portraying the traumatic event. Tracer distribution analysis was then carried out at volume of interest (VOI) level using a three-dimensional standardized brain atlas, and at voxel level by SPM. The CBF data of the 15 patients were compared before and after treatment as well as with those of a group of 27 controls who had been exposed to the same psychological traumas without developing PTSD. RESULTS: At VOI analysis significant CBF distribution differences were found between controls and patients before and after treatment (P=0.023 and P=0.0039, respectively). Eleven of the 15 patients responded to treatment, i.e., following EMDR they no longer fulfilled the DSM-IV criteria for PTSD. When comparing only the eleven responders with the controls, the significant group difference found before EMDR (P=0.019) disappeared after treatment. Responders and non-responders showed after therapy significant regional differences in frontal, parieto-occipital and visual cortex and in hippocampus. SPM analysis showed significant uptake differences between patients and controls in the orbitofrontal cortex (Brodmann 11) and the temporal pole (Brodmann 38) both before and after treatment. A significant tracer distribution difference present before treatment in the uncus (Brodmann 36) disappeared after treatment, while a significant difference appeared in the lateral temporal lobe (Brodmann 21). CONCLUSION: Significant 99mTc-HMPAO uptake regional differences were found, mainly in the peri-limbic cortex, between PTSD patients and controls exposed to trauma but not developing PTSD. Tracer uptake differences between responders and patients not responding to EMDR were found after treatment suggesting a trend towards normalization of tracer distribution after successful therapy. These findings in occupational related PTSD are consistent with previously described effects of psychotherapy on anxiety disorders.

The value of quantitative uptake of (99m)Tc-MDP and (99m)Tc-HMPAO white blood cells in detecting osteomyelitis in violated peripheral bones.

UNLABELLED: Our objective in this study was to evaluate whether measurement of quantitative uptake of (99m)Tc-methylene diphosphate (MDP) and (99m)Tc-hexamethylpropyleneamine oxime (HMPAO) white blood cells (WBCs) is useful in detecting osteomyelitis in peripheral bony lesions. METHODS: Twenty-four patients (12 men and 12 women; age range, 25-72 y) were referred for imaging because of clinically suspected osteomyelitis. They had a traumatic fracture (n = 10), knee prosthesis (n = 5), hip prosthesis (n = 2), diabetic foot (n = 4), or chronic osteomyelitis (n = 3). Three-phase bone scanning and (99m)Tc-HMPAO WBC studies were performed on all patients within the same week. Regions of interest were drawn over the abnormal bony sites and the contralateral normal sites, and the abnormal-to-normal uptake ratios (A/N ratios) were obtained for both studies. RESULTS: All patients had abnormal findings on 3-phase bone scanning, whereas 17 (71%) had abnormal findings on (99m)Tc-HMPAO WBC studies, of which 15 were confirmed to be true-positive. In those 15 patients, the mean A/N ratios for (99m)Tc-MDP and (99m)Tc-HMPAO WBC were 3.0 +/- 1.6 (range, 1.3-6.2) and 1.8 +/- 0.3 (range, 1.4-2.2), respectively. In the other 9 patients, whose scan results were clinically confirmed to be true-negative, the mean A/N ratios for (99m)Tc-MDP and (99m)Tc-HMPAO WBC were 2.1 +/- 1.2 and 1.2 +/- 0.2, respectively. In the group with a (99m)Tc-MDP A/N ratio greater than 2 (n = 15), 87% (13/15) had a high (99m)Tc-HMPAO WBC A/N ratio (>1.5), including 2 that were false-positive. In the remaining 2 patients, one with chronic osteomyelitis and the other with a recent hip prosthesis, (99m)Tc-HMPAO WBC ratios were normal. In the group with a bone A/N ratio of less than 2 (n = 9), only 4 patients (44%) were true-positive for acute osteomyelitis. CONCLUSION: (99m)Tc-MDP bone scanning alone, with an A/N ratio of more than 2, is useful in detecting osteomyelitis in violated bone except in the case of a recent hip prosthesis or chronic osteomyelitis.

Intraarticular and intravenous administration of 99MTc-HMPAO-labeled human mesenchymal stem cells (99MTC-AH-MSCS): In vivo imaging and biodistribution.

INTRODUCTION: Therapeutic application of intravenous administered (IV) human bone marrow-derived mesenchymal stem cells (ahMSCs) appears to have as main drawback the massive retention of cells in the lung parenchyma, questioning the suitability of this via of administration. Intraarticular administration (IAR) could be considered as an alternative route for therapy in degenerative and traumatic joint lesions. Our work is outlined as a comparative study of biodistribution of 99mTc-ahMSCs after IV and IAR administration, via scintigraphic study in an animal model. METHODS: Isolated primary culture of adult human mesenchymal stem cells was labeled with 99mTc-HMPAO for scintigraphic study of in vivo distribution after intravenous and intra-articular (knee) administration in rabbits. RESULTS: IV administration of radiolabeled ahMSCs showed the bulk of radioactivity in the lung parenchyma while IAR images showed activity mainly in the injected cavity and complete absence of uptake in pulmonary bed. CONCLUSIONS: Our study shows that IAR administration overcomes the limitations of IV injection, in particular, those related to cells destruction in the lung parenchyma. After IAR administration, cells remain within the joint cavity, as expected given its size and adhesion properties. ADVANCES IN KNOWLEDGE: Intra-articular administration of adult human mesenchymal stem cells could be a suitable route for therapeutic effect in joint lesions. IMPLICATIONS FOR PATIENT CARE: Local administration of adult human mesenchymal stem cells could improve their therapeutic effects, minimizing side effects in patients.