Impact of Fat Distribution and Metabolic Diseases on Cerebral Microcirculation: A Multimodal Study on Type 2 Diabetic and Obese Patients.

Background: Since metabolic diseases and atherosclerotic vascular events are firmly associated, herein we investigate changes in central microcirculation and atherosclerosis-related body fat distribution in patients with type 2 diabetes mellitus and obesity. Methods: Resting brain perfusion single-photon emission computed tomography (SPECT) imaging with Technetium-99m hexamethylpropylene amine oxime ([99mTc]Tc-HMPAO SPECT) was performed, and the breath-holding index (BHI) and carotid intima-media thickness (cIMT) were measured to characterise central microcirculation. Besides CT-based abdominal fat tissue segmentation, C-peptide level, glycaemic and anthropometric parameters were registered to search for correlations with cerebral blood flow and vasoreactivity. Results: Although no significant difference was found between the resting cerebral perfusion of the two patient cohorts, a greater blood flow increase was experienced in the obese after the breath-holding test than in the diabetics (p < 0.05). A significant positive correlation was encountered between resting and provocation-triggered brain perfusion and C-peptide levels (p < 0.005). BMI and cIMT were negatively correlated (rho = -0.27 and -0.23 for maximum and mean cIMT, respectively), while BMI and BHI showed a positive association (rho = 0.31 and rho = 0.29 for maximum and mean BHI, respectively), which could be explained by BMI-dependent changes in fat tissue distribution. cIMT demonstrated a disproportional relationship with increasing age, and higher cIMT values were observed for the men. Conclusions: Overall, C-peptide levels and circulatory parameters seem to be strong applicants to predict brain microvascular alterations and related cognitive decline in such patient populations.

Diagnosis of Melanoma with 61Cu-Labeled PET Tracer.

Until the recent years, substances containing radioactive 61Cu were strongly considered as potential positron-emitting radiopharmaceuticals for use in positron emission tomography (PET) applications; however, due to their suitably long half-life, and generator-independent and cost-effective production, they seem to be economically viable for human imaging. Since malignant melanoma (MM) is a major public health problem, its early diagnosis is a crucial contributor to long-term survival, which can be achieved using radiolabeled α-melanocyte-stimulating hormone analog NAPamide derivatives. Here, we report on the physicochemical features of a new CB-15aneN5-based Cu(II) complex ([Cu(KFTGdiac)]-) and the ex vivo and in vivo characterization of its NAPamide conjugate. The rigid chelate possesses prompt complex formation and suitable inertness (t1/2 = 18.4 min in 5.0 M HCl at 50 °C), as well as excellent features in the diagnosis of B16-F10 melanoma tumors (T/M(SUVs) (in vivo): 12.7, %ID/g: 6.6 ± 0.3, T/M (ex vivo): 22).

Acute Myelomonoblastic Leukemia (My1/De): A Preclinical Rat Model.

BACKGROUND/AIM: Since acute myeloid leukemias still represent the most aggressive type of adult acute leukemias, the profound understanding of disease pathology is of paramount importance for diagnostic and therapeutic purposes. Hence, this study aimed to explore the real-time disease fate with the establishment of an experimental myelomonoblastic leukemia (My1/De) rat model using preclinical positron emission tomography (PET) and whole-body autoradiography. MATERIALS AND METHODS: In vitro [18F]F-FDG uptake studies were performed to compare the tracer accumulation in the newly cultured My1/De tumor cell line (blasts) with that in healthy control and My1/De bone marrow suspensions. Post transplantation of My1/De cells under the left renal capsule of Long-Evans rats, primary My1/De tumorigenesis, and metastatic propagation were investigated using [18F]F-FDG PET imaging, whole-body autoradiography and phosphorimage analyses. To assess the organ uptake profile of the tumor-carrying animals we accomplished ex vivo biodistribution studies. RESULTS: The tracer accumulation in the My1/De culture cells exceeded that of both the tumorous and the healthy bone marrow suspensions (p<0.01). Based on in vivo imaging, the subrenally transplanted My1/De cells resulted in the development of leukemia in the abdominal organs, and metastasized to the mesenterial and thoracic parathymic lymph nodes (PTLNs). The lymphatic spread of metastasis was further confirmed by the significantly higher %ID/g values of the metastatic PTLNs (4.25±0.28) compared to the control (0.94±0.34). Cytochemical staining of the peripheral blood, autopsy findings, and wright-Giemsa-stained post-mortem histological sections proved the leukemic involvement of the assessed tissues/organs. CONCLUSION: The currently established My1/De model appears to be well-suited for further leukemia-related therapeutic and diagnostic investigations.

In Vivo Imaging of Acute Hindlimb Ischaemia in Rat Model: A Pre-Clinical PET Study.

BACKGROUND: To better understand ischaemia-related molecular alterations, temporal changes in angiogenic Aminopeptidase N (APN/CD13) expression and glucose metabolism were assessed with PET using a rat model of peripheral arterial disease (PAD). METHODS: The mechanical occlusion of the base of the left hindlimb triggered using a tourniquet was applied to establish the ischaemia/reperfusion injury model in Fischer-344 rats. 2-[18F]FDG and [68Ga]Ga-NOTA-c(NGR) PET imaging performed 1, 3, 5, 7, and 10 days post-ischaemia induction was followed by Western blotting and immunohistochemical staining for APN/CD13 in ischaemic and control muscle tissue extracts. RESULTS: Due to a cellular adaptation to hypoxia, a gradual increase in [68Ga]Ga-NOTA-c(NGR) and 2-[18F]FDG uptake was observed from post-intervention day 1 to 7 in the ischaemic hindlimbs, which was followed by a drop on day 10. Conforming pronounced angiogenic recovery, the NGR accretion of the ischaemic extremities differed significantly from the controls 5, 7, and 10 days after ischaemia induction (p ≤ 0.05), which correlated with the Western blot and immunohistochemical results. No remarkable radioactivity was depicted between the normally perfused hindlimbs of either the ischaemic or the control groups. CONCLUSIONS: The PET-based longitudinal assessment of angiogenesis-associated APN/CD13 expression and glucose metabolism during ischaemia may continue to broaden our knowledge on the pathophysiology of PAD.

Concomitant [18F]F-FAZA and [18F]F-FDG Imaging of Gynecological Cancer Xenografts: Insight into Tumor Hypoxia.

BACKGROUND/AIM: Herein we assessed the feasibility of imaging protocols using both hypoxia-specific [18F]F-FAZA and [18F]F-FDG in bypassing the limitations derived from the non-specific findings of [18F]F-FDG PET imaging of tumor-related hypoxia. MATERIALS AND METHODS: CoCl2-generated hypoxia was induced in multidrug resistant (Pgp+) or sensitive (Pgp-) human ovarian (Pgp- A2780, Pgp+ A2780AD), and cervix carcinoma (Pgp- KB-3-1, Pgp+ KB-V-1) cell lines to establish corresponding tumor-bearing mouse models. Prior to [18F]F-FDG/[18F]F-FAZA-based MiniPET imaging, in vitro [18F]F-FDG uptake measurements and western blotting were used to verify the presence of hypoxia. RESULTS: Elevated GLUT-1, and hexokinase enzyme-II expression driven by CoCl2-induced activation of hypoxia-inducible factor-1α explains enhanced cellular [18F]F-FDG accumulation. No difference was observed in the [18F]F-FAZA accretion of Pgp+ and Pgp- tumors. Tumor-to-muscle ratios for [18F]F-FAZA measured at 110-120 min postinjection (6.2±0.1) provided the best contrasted images for the delineation of PET-oxic and PET-hypoxic intratumor regions. Although all tumors exhibited heterogenous uptake of both radiopharmaceuticals, greater differences for [18F]F-FAZA between the tracer avid and non-accumulating regions indicate its superiority over [18F]F-FDG. Spatial correlation between [18F]F-FGD and [18F]F-FAZA scans confirms that hypoxia mostly occurs in regions with highly active glucose metabolism. CONCLUSION: The addition of [18F]F-FAZA PET to [18F]F-FGD imaging may add clinical value in determining hypoxic sub-regions.

In Vivo Evaluation of Brain [18F]F-FDG Uptake Pattern Under Different Anaesthesia Protocols.

BACKGROUND/AIM: Since the use of anaesthetics has the drawback of altering radiotracer distribution, preclinical positron emission tomography (PET) imaging findings of anaesthetised animals must be carefully handled. This study aimed at assessing the cerebral [18F]F-FDG uptake pattern in healthy Wistar rats under four different anaesthesia protocols using microPET/magnetic resonance imaging (MRI) examinations. MATERIALS AND METHODS: Post-injection of 15±1.2 MBq of [18F]F-FDG, either while awake or during the isoflurane-induced incubation phase was applied. Prior to microPET/MRI imaging, one group of the rats was subjected to forane-only anaesthesia while the other group was anaesthetised with the co-administration of forane and dexmedetomidine/Dexdor® Results: While as for the whole brain it was the addition of dexmedetomidine/Dexdor® to the anaesthesia protocol that generated the differences between the radiotracer concentrations of the investigated groups, regarding the cortex, the [18F]F-FDG accumulation was rather affected by the way of incubation. To ensure the most consistent and highest uptake, forane-induced anaesthesia coupled with an awake uptake condition seemed to be most suitable method of anaesthetisation for cerebral metabolic assessment. Diminished whole brain and cortical tracer accumulation detected upon dexmedetomidine/Dexdor® administration highlights the significance of the mechanism of action of different anaesthetics on radiotracer pharmacokinetics. CONCLUSION: Overall, the standardization of PET protocols is of utmost importance to avoid the confounding factors derived from anaesthesia.

Targeted Radium Alpha Therapy in the Era of Nanomedicine: In Vivo Results.

Targeted alpha-particle therapy using radionuclides with alpha emission is a rapidly developing area in modern cancer treatment. To selectively deliver alpha-emitting isotopes to tumors, targeting vectors, including monoclonal antibodies, peptides, small molecule inhibitors, or other biomolecules, are attached to them, which ensures specific binding to tumor-related antigens and cell surface receptors. Although earlier studies have already demonstrated the anti-tumor potential of alpha-emitting radium (Ra) isotopes-Radium-223 and Radium-224 (223/224Ra)-in the treatment of skeletal metastases, their inability to complex with target-specific moieties hindered application beyond bone targeting. To exploit the therapeutic gains of Ra across a wider spectrum of cancers, nanoparticles have recently been embraced as carriers to ensure the linkage of 223/224Ra to target-affine vectors. Exemplified by prior findings, Ra was successfully bound to several nano/microparticles, including lanthanum phosphate, nanozeolites, barium sulfate, hydroxyapatite, calcium carbonate, gypsum, celestine, or liposomes. Despite the lengthened tumor retention and the related improvement in the radiotherapeutic effect of 223/224Ra coupled to nanoparticles, the in vivo assessment of the radiolabeled nanoprobes is a prerequisite prior to clinical usage. For this purpose, experimental xenotransplant models of different cancers provide a well-suited scenario. Herein, we summarize the latest achievements with 223/224Ra-doped nanoparticles and related advances in targeted alpha radiotherapy.

Radiolabeled NGR-Based Heterodimers for Angiogenesis Imaging: A Review of Preclinical Studies.

Since angiogenesis/neoangiogenesis has a major role in tumor development, progression and metastatic spread, the establishment of angiogenesis-targeting imaging and therapeutic vectors is of utmost significance. Aminopeptidase N (APN/CD13) is a pivotal biomarker of angiogenic processes abundantly expressed on the cell surface of active vascular endothelial and various neoplastic cells, constituting a valuable target for cancer diagnostics and therapy. Since the asparagine-glycine-arginine (NGR) sequence has been shown to colocalize with APN/CD13, the research interest in NGR-peptide-mediated vascular targeting is steadily growing. Earlier preclinical experiments have already demonstrated the imaging and therapeutic feasibility of NGR-based probes labeled with different positron emission tomography (PET) and single-photon emission computed tomography (SPECT) radionuclides, including Gallium-68 (68Ga), Copper-64 (64Cu), Technetium-99m (99mTc), Lutetium-177 (177Lu), Rhenium-188 (188Re) or Bismuth-213 (213Bi). To improve the tumor binding affinity and the retention time of single-receptor targeting peptides, NGR motifs containing heterodimers have been introduced to identify multi-receptor overexpressing malignancies. Preclinical studies with various tumor-bearing experimental animals provide useful tools for the investigation of the in vivo imaging behavior of NGR-based heterobivalent ligands. Herein, we review the reported preclinical achievements on NGR heterodimers that could be highly relevant for the development of further target-specific multivalent compounds in diagnostic and therapeutic settings.

Investigation of the Effect on the Albumin Binding Moiety for the Pharmacokinetic Properties of 68Ga-, 205/206Bi-, and 177Lu-Labeled NAPamide-Based Radiopharmaceuticals.

Although radiolabeled alpha-melanocyte stimulating hormone-analogue NAPamide derivatives are valuable melanoma-specific diagnostic probes, their rapid elimination kinetics and high renal uptake may preclude them from being used in clinical settings. We aimed at improving the pharmacokinetics of radiolabeled DOTA-NAPamide compounds by incorporating a 4-(p-iodo-phenyl)-butanoic acid (IPB) into the molecules. Followed by 68Ga-, 205/206Bi-, and 177Lu-labelling, the radiopharmaceuticals ([68Ga]Ga-DOTA-IPB-NAPamide, [205/206Bi]Bi-DOTA-IPB-NAPamide, [177Lu]Lu-DOTA-IPB-NAPamide) were characterized in vitro. To test the imaging behavior of the IPB-containing probes, B16F10 tumor-bearing C57BL/6 mice were subjected to in vivo microPET/microSPECT/CT imaging and ex vivo biodistribution studies. All tracers were stable in vitro, with radiochemical purity exceeding 98%. The use of albumin-binding moiety lengthened the in vivo biological half-life of the IPB-carrying radiopharmaceuticals, resulting in elevated tumor accumulation. Both [68Ga]Ga-DOTA-IPB-NAPamide (5.06 ± 1.08 %ID/g) and [205/206Bi]Bi-DOTA-IPB-NAPamide (4.50 ± 0.98 %ID/g) exhibited higher B16F10 tumor concentrations than their matches without the albumin-binding residue ([68Ga]Ga-DOTA-NAPamide and [205/206Bi]Bi-DOTA-NAPamide: 1.18 ± 0.27 %ID/g and 3.14 ± 0.32; respectively), however; the large amounts of off-target radioactivity do not confirm the benefits of half-life extension for short-lived isotopes. Enhanced [177Lu]Lu-DOTA-IPB-NAPamide tumor uptake even 24 h post-injection proved the advantage of IPB-based prolonged circulation time regarding long-lived radionuclides, although the significant background noise must be addressed in this case as well.

NGR-Based Radiopharmaceuticals for Angiogenesis Imaging: A Preclinical Review.

Angiogenesis plays a crucial role in tumour progression and metastatic spread; therefore, the development of specific vectors targeting angiogenesis has attracted the attention of several researchers. Since angiogenesis-associated aminopeptidase N (APN/CD13) is highly expressed on the surface of activated endothelial cells of new blood vessels and a wide range of tumour cells, it holds great promise for imaging and therapy in the field of cancer medicine. The selective binding capability of asparagine-glycine-arginine (NGR) motif containing molecules to APN/CD13 makes radiolabelled NGR peptides promising radiopharmaceuticals for the non-invasive, real-time imaging of APN/CD13 overexpressing malignancies at the molecular level. Preclinical small animal model systems are major keystones for the evaluation of the in vivo imaging behaviour of radiolabelled NGR derivatives. Based on existing literature data, several positron emission tomography (PET) and single-photon emission computed tomography (SPECT) radioisotopes have been applied so far for the labelling of tumour vasculature homing NGR sequences such as Gallium-68 (68Ga), Copper-64 (64Cu), Technetium-99m (99mTc), Lutetium-177 (177Lu), Rhenium-188 (188Re), or Bismuth-213 (213Bi). Herein, a comprehensive overview is provided of the recent preclinical experiences with radiolabelled imaging probes targeting angiogenesis.

Evaluation of the therapeutic efficacy of 213Bi-labelled DOTA-conjugated alpha-melanocyte stimulating hormone peptide analogues in melanocortin-1 receptor positive preclinical melanoma model.

Melanocortin-1 receptor (MC1-R) targeting alpha-melanocyte stimulating hormone-analogue (α-MSH) biomolecules labelled with α-emitting radiometal seem to be valuable in the targeted radionuclide therapy of MC1-R positive melanoma malignum (MM). Herein is reported the anti-tumor in vivo therapeutic evaluation of MC1-R-affine [213Bi]Bi-DOTA-NAPamide and HOLDamide treatment in MC1-R positive B16-F10 melanoma tumor-bearing C57BL/6J mice. On the 6th, 8th and 10th days post tumor cell inoculation; the treated groups of mice were intravenously injected with approximately 5 MBq of both amide derivatives. Beyond body weight and tumor volume assessment, [68Ga]Ga-DOTA-HOLDamide and NAPamide-based PET/MRI scans, and ex vivo biodistribution studies were executed 30,- and 90 min postinjection. In the PET/MRI imaging studies the B16-F10 tumors were clearly visualized with both 68Ga-labelled tracers, however, significantly lower tumor-to-muscle (T/M) ratios were observed by using [68Ga]Ga-DOTA-HOLDamide. After alpha-radiotherapy treatment the tumor size of the control group was larger relative to both treated cohorts, while the smallest tumor volumes were observed in the NAPamide-treated subclass on the 10th day. Relatively higher [213Bi]Bi-DOTA-NAPamide accumulation in the B16-F10 tumors (%ID/g: 2.71 ± 0.15) with discrete background activity led to excellent T/M ratios, particularly 90 min postinjection. Overall, the therapeutic application of receptor selective [213Bi]Bi-DOTA-NAPamide seems to be feasible in MC1-R positive MM management.

Implant Imaging: Perspectives of Nuclear Imaging in Implant, Biomaterial, and Stem Cell Research.

Until now, very few efforts have been made to specifically trace, monitor, and visualize implantations, artificial organs, and bioengineered scaffolds for tissue engineering in vivo. While mainly X-Ray, CT, and MRI methods have been used for this purpose, the applications of more sensitive, quantitative, specific, radiotracer-based nuclear imaging techniques remain a challenge. As the need for biomaterials increases, so does the need for research tools to evaluate host responses. PET (positron emission tomography) and SPECT (single photon emission computer tomography) techniques are promising tools for the clinical translation of such regenerative medicine and tissue engineering efforts. These tracer-based methods offer unique and inevitable support, providing specific, quantitative, visual, non-invasive feedback on implanted biomaterials, devices, or transplanted cells. PET and SPECT can improve and accelerate these studies through biocompatibility, inertivity, and immune-response evaluations over long investigational periods at high sensitivities with low limits of detection. The wide range of radiopharmaceuticals, the newly developed specific bacteria, and the inflammation of specific or fibrosis-specific tracers as well as labeled individual nanomaterials can represent new, valuable tools for implant research. This review aims to summarize the opportunities of nuclear-imaging-supported implant research, including bone, fibrosis, bacteria, nanoparticle, and cell imaging, as well as the latest cutting-edge pretargeting methods.

Scandium-44: Diagnostic Feasibility in Tumor-Related Angiogenesis.

Angiogenesis-related cell-surface molecules, including integrins, aminopeptidase N, vascular endothelial growth factor, and gastrin-releasing peptide receptor (GRPR), play a crucial role in tumour formation. Radiolabelled imaging probes targeting angiogenic biomarkers serve as valuable vectors in tumour identification. Nowadays, there is a growing interest in novel radionuclides other than gallium-68 (68Ga) or copper-64 (64Cu) to establish selective radiotracers for the imaging of tumour-associated neo-angiogenesis. Given its ideal decay characteristics (Eß+average: 632 KeV) and a half-life (T1/2 = 3.97 h) that is well matched to the pharmacokinetic profile of small molecules targeting angiogenesis, scandium-44 (44Sc) has gained meaningful attention as a promising radiometal for positron emission tomography (PET) imaging. More recently, intensive research has been centered around the investigation of 44Sc-labelled angiogenesis-directed radiopharmaceuticals. Previous studies dealt with the evaluation of 44Sc-appended avb3 integrin-affine Arg-Gly-Asp (RGD) tripeptides, GRPR-selective aminobenzoyl-bombesin analogue (AMBA), and hypoxia-associated nitroimidazole derivatives in the identification of various cancers using experimental tumour models. Given the tumour-related hypoxia- and angiogenesis-targeting capability of these PET probes, 44Sc seems to be a strong competitor of the currently used positron emitters in radiotracer development. In this review, we summarize the preliminary preclinical achievements with 44Sc-labelled angiogenesis-specific molecular probes.

Overview of Prostaglandin E2 (PGE2)-Targeting Radiolabelled Imaging Probes from Preclinical Perspective: Lessons Learned and Road Ahead.

As malignancies still represent one of the major health concerns worldwide, early tumor identification is among the priorities of today's science. Given the strong association between cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2), PGE2 receptors (EPs), and carcinogenesis, target-specific molecules directed towards the components of the COX2/PGE2/EP axis seem to be promising imaging probes in the diagnostics of PGE2pos. neoplasms and in the design of anti-cancer drugs. Featured with outstanding inclusion forming capability, ß-cyclodextrins (CDs) including randomly methylated ß-CD (RAMEB) were reported to complex with PGE2. Therefore, radiolabelled ß-CDs could be valuable vectors in the molecular imaging of PGE2-related tumorigenesis. In vivo preclinical small animal model systems applying positron emission tomography (PET) ensure a well-suited scenario for the assessment of PGE2-affine labelled CD derivatives. Previous translational studies dealt with the evaluation of the tumor-homing capability of Gallium-68 (68Ga) and Bismuth-205/206 (205/206Bi)-appended ß-CD compounds conjugated with chelator NODAGA or DOTAGA: [68Ga]Ga-NODAGA-2-hydroxypropyl-ß-cyclodextrin/HPBCD, [68Ga]Ga-NODAGA-RAMEB, [68Ga]Ga-DOTAGA-RAMEB, and [205/206Bi]Bi-DOTAGA-RAMEB in experimental tumors with different PGE2 expression. These imaging probes project the establishment of tailor-made PET diagnostics of PGE2pos. malignancies. In the present review, we provide a detailed overview of the in vivo investigations of radiolabelled PGE2-directed CDs, highlighting the importance of the integration of translational discoveries into routine clinical usage.

Insights into recent preclinical studies on labelled cyclodextrin-based imaging probes: Towards a novel oncological era.

As malignancies remain one of the major health concerns worldwide, increasing focus has been centered around the application of cyclodextrins (CDs) in cancer imaging and therapy due to their outstanding inclusion forming capability. Albeit the physicochemical properties of CDs were intensively elucidated, the spread of their clinical application is limited by the relative paucity of knowledge about their pharmacokinetic profile, especially biodistribution. Studies applying fluorescently- CDs, or CD-based MRI contrast agents revealed much about pharmacokinetics and diagnostic applications; however, derivatives labelled with positron emitters seem superior molecular probes in the investigation of the route of CDs in biological niche. In vivo imaging based on preclinical tumor-bearing model systems are well-suited to evaluate the whole-body distribution of the two most frequently assessed CDs: randomly methylated ß-cyclodextrin (RAMEB), and hydroxypropyl-ß-cyclodextrin (HPBCD). Exploiting the firm signaling interaction between cancer-related cyclooxygenase-2, prostaglandin E2 (PGE2) and RAS oncoprotein, radioconjugated, PGE2-affine CDs project the establishment of novel imaging probes and therapeutic agents. Currently, we provide an overview of the preclinical studies on CD pharmacokinetics highlighting the significance of the integration of translational discoveries into human patient care.

In Vivo evaluation of newly synthesized 213Bi-conjugated alpha-melanocyte stimulating hormone (α-MSH) peptide analogues in melanocortin-1 receptor (MC1-R) positive experimental melanoma model.

Given the rising pervasiveness of melanocortin-1 receptor (MC1-R) positive melanoma malignum (MM) and pertinent metastases, radiolabelled receptor-affine alpha-melanocyte stimulating hormone-analogue (α-MSH analogue) imaging probes would be of crucial importance in timely tumor diagnostic assessment. Herein we aimed at investigating the biodistribution and the MM targeting potential of newly synthesized 213Bi-conjugated MC1-R specific peptide-based radioligands with the establishment of MC1-R overexpressing MM preclinical model. DOTA-conjugated NAP, -HOLD, -FOLD, -and MARSamide were labelled with 213Bi. Ex vivo biodistribution studies were conducted post-administration of 3.81 ± 0.32 MBq [213Bi]Bi-DOTA conjugated deriva-tives into twenty B16-F10 tumor-bearing C57BL/6 J and healthy mice. Organ Level Internal Dose Assessment (OLINDA) and IDAC-Dose were used to calculate translational data-based absorbed radiation dose in human organs. Moderate or low %ID/g uptake of [213Bi]Bi-DOTA conjugated NAP, -HOLD, -and MARSamide and significantly increased [213Bi]Bi-DOTA-FOLDamide accumulation was observed in the thoracic and abdominal organs (p ≤ 0.01). High [213Bi]Bi-DOTA-NAP (%ID/g:3.76 ± 0.96), -and FOLDamide (%ID/g:3.28 ± 0.95) tumor tracer activity confirmed their MC1-R-affinity. The bladder wall received the highest radiation absorbed dose followed by the kidneys (bladder wall: 1.95·10-2 and 8.97·10-2 mSv/MBq; kidneys: 7.47·10-3 vs. 5.88·10-2 mSv/MBq measured by IDAC and OLINDA; respectively) indicating the suitability of the NAPamide derivative for clinical use. These novel [213Bi]Bi-DOTA-linked peptide probes displaying meaningful MC1-R affinity could be promising molecular probes in MM imaging.

Therapeutic Performance Evaluation of 213Bi-Labelled Aminopeptidase N (APN/CD13)-Affine NGR-Motif ([213Bi]Bi-DOTAGA-cKNGRE) in Experimental Tumour Model: A Treasured Tailor for Oncology.

Since NGR-tripeptides (asparagine-glycine-arginine) selectively target neoangiogenesis-associated Aminopeptidase N (APN/CD13) on cancer cells, we aimed to evaluate the in vivo tumour targeting capability of radiolabelled, NGR-containing, ANP/CD13-selective [213Bi]Bi-DOTAGA-cKNGRE in CD13pos. HT1080 fibrosarcoma-bearing severe combined immunodeficient CB17 mice. 10 ± 1 days after cancer cell inoculation, positron emission tomography (PET) was performed applying [68Ga]Ga-DOTAGA-cKNGRE for tumour verification. On the 7th, 8th, 10th and 12th days the treated group of tumourous mice were intraperitoneally administered with 4.68 ± 0.10 MBq [213Bi]Bi-DOTAGA-cKNGRE, while the untreated tumour-bearing animals received 150 µL saline solution. In addition to body weight (BW) and tumour volume measurements, ex vivo biodistribution studies were conducted 30 and 90 min postinjection (pi.). The following quantitative standardised uptake values (SUV) confirmed the detectability of the HT1080 tumours: SUVmean and SUVmax: 0.37 ± 0.09 and 0.86 ± 0.14, respectively. Although no significant difference (p ≤ 0.05) was encountered between the BW of the treated and untreated mice, their tumour volumes measured on the 9th, 10th and 12th days differed significantly (p ≤ 0.01). Relatively higher [213Bi]Bi-DOTAGA-cKNGRE accumulation of the HT1080 neoplasms (%ID/g: 0.80 ± 0.16) compared with the other organs at 90 min time point yields better tumour-to-background ratios. Therefore, the therapeutic application of APN/CD13-affine [213Bi]Bi-DOTAGA- cKNGRE seems to be promising in receptor-positive fibrosarcoma treatment.

Subrenal Capsule Assay - SRCA: The Promising Re-Emergence of a Long-Forgotten Method in Preclinical Nuclear Medical Cancer Diagnostics.

Since metastases are responsible for the majority of cancer-related death, in-depth understanding of metastatisation may provide an opportunity for the introduction of new therapeutic as well as diagnostic approaches in cancer management. Previously, preclinical research into the development and progression of malignancies has been hampered by the relative paucity of in vivo tumor models. Subrenal capsule assay (SRCA)-induced tumor-bearing experimental animal models, however, serve as potential preclinical model systems for the assessment of primary tumors and the route of metastatic spread. Several studies implementing either Hepatocarcinoma (He/De), Mesoblastic Nephroma (Ne/De), chemically induced Myeloid Leukemia (My1/De), or spontaneous Myeloid Myelomonocytic Leukemia (My2/De) cells under the left renal capsule of rats applying SRCA method were underway to study secondary tumor formation. Based on the results of this research, subrenally transplanted neoplastic cells led to the appearance of metastasis in the parathymic lymph nodes. Therefore, renal capsule/parathymic lymph node complex seems to be valuable in the in vivo evaluation of the process of metastatisation and the occurrence of secondary neoplasms. The re-emergence of this highly promising SRCA-based renal capsule/parathymic lymph node complex in preclinical nuclear medicine and experimental oncology may open a novel field towards drug trials and radiopharmaceutical development. In the present review, we provide a detailed overview of the history of SRCA as well as the series of research on the establishment of renal capsule/parathymic lymph node complex.

Imaging with [99mTc]HMPAO - a novel perspective: investigation of [99mTc]HMPAO leg muscle uptake in metabolic diseases.

BACKGROUND: Sensitive imaging modalities in the diagnosis of microcircular complications of the lower extremities induced by metabolic diseases are becoming a focus of interest. PURPOSE: To investigate the [99mTc]HMPAO uptake of the legs in type 2 diabetes mellitus (T2DM) and obesity, and to search for associations with clinical parameters and nerve conducting studies. MATERIAL AND METHODS: A total of 57 patients with controlled T2DM and 46 obese participants without DM were enrolled in the study. [99mTc]HMPAO SPECT/CT examinations were performed to evaluate the radiopharmaceutical accumulation of the legs. For the quantitative assessment of tracer uptake, standardized uptake value (SUVpeak) was measured in fixed spheric volumes of interest placed on both sural muscles on the attenuation-corrected images. Measurement of current perception threshold applying Neurometer (NM-01/CPT) was used to evaluate peripheral nerve dysfunction. Laboratory parameters assessing the glucose homeostasis of the study participants were also measured. RESULTS: In the diabetic group, significantly lower leg SUV values were detected compared to the non-DM obese group (median: 0.517 vs. 0.607; P < 0.001). Body mass index (BMI) (P < 0.0001), age (P = 0.0283), HbA1c (P = 0.0068), and glucose level (P = 0.0044) proved to be significant predictors of muscle tracer uptake. Neurometer studies showed positive correlation with HbA1c levels in the T2DM group (P = 0.0002). CONCLUSION: We assume that [99mTc]HMPAO uptake of leg muscles is associated with microcirculation, so quantitative [99mTc]HMPAO SPECT/CT might be a sensitive method for evaluating lower limb microvascular alterations. BMI, age, HbA1c, and glucose level may be significant predictors of peripheral vascular abnormalities triggered by metabolic disturbances.

In vivo assessment of tumor targeting potential of 68Ga-labelled randomly methylated beta-cyclodextrin (RAMEB) and 2-hydroxypropyl-ß-cyclodextrin (HPßCD) using positron emission tomography.

Cyclodextrin derivates (CyDs) can form complexes with cyclooxygenase-2 induced tumor promoting prostaglandin E2 (PGE2). Based on our previous observations, 68Ga-labelled CyDs may represent promising radiopharmaceuticals in the positron emission tomography (PET) diagnostics of PGE2 positive tumors. We aimed at evaluating the tumor-targeting potential of 68Ga-NODAGA conjugated randomly methylated beta-cyclodextrin (68Ga-NODAGA-RAMEB) and 2-hydroxypropyl-ß-cyclodextrin (68Ga-NODAGA-HPßCD) using in vivo PET imaging with experimental tumor models. Tumor radiopharmaceutical uptake was assessed applying PET and gamma counter in vivo and ex vivo respectively, following the administration of 18FDG, 68Ga-NODAGA-RAMEB or 68Ga-NODAGA-HPßCD via the lateral tail vein to the subsequent tumor-bearing animals: HT1080, A20, PancTu-1, BxPC3, B16-F10, Ne/De and He/De. All investigated tumors were identifiable with both 68Ga-labelled CyDs; however, in vivo results, in correlation with the ex vivo data, revealed that the PGE2 positive BxPC3, A20, Ne/De and He/De tumors presented the highest accumulation. In case of HT1080, A20, B16-F10 tumors significant differences were encountered between the accumulations of both 68Ga-labelled radiopharmaceuticals of the same tumor. Subcutaneously and the orthotopically transplanted Ne/De tumors differed significantly (p ≤ 0.01) regarding tracer uptake. 68Ga-labelled CyDs may open a novel field in the PET diagnostics of PGE2 positive primary tumors and metastases.