SPECT/CT imaging of inflammation and calcification in human carotid atherosclerosis to identify the plaque at risk of rupture

BACKGROUND

Calcification and inflammation are atherosclerotic plaque compositional biomarkers that have both been linked to stroke risk. The aim of this study was to evaluate their co-existing prevalence in human carotid plaques with respect to plaque phenotype to determine the value of hybrid imaging for the detection of these biomarkers.

METHODS

Human carotid plaque segments, obtained from endarterectomy, were incubated in [111In]In-DOTA-butylamino-NorBIRT ([111In]In-Danbirt), targeting Leukocyte Function-associated Antigen-1 (LFA-1) on leukocytes. By performing SPECT/CT, both inflammation from DANBIRT uptake and calcification from CT imaging were assessed. Plaque phenotype was classified using histology.

RESULTS

On a total plaque level, comparable levels of calcification volume existed with different degrees of inflammation and vice versa. On a segment level, an inverse relationship between calcification volume and inflammation was evident in highly calcified segments, which classify as fibrocalcific, stable plaque segments. In contrast, segments with little or no calcification presented with a moderate to high degree of inflammation, often coinciding with the more dangerous fibrous cap atheroma phenotype.

CONCLUSION

Calcification imaging alone can only accurately identify highly calcified, stable, fibrocalcific plaques. To identify high-risk plaques, with little or no calcification, hybrid imaging of calcification and inflammation could provide diagnostic benefit.

Favorable tumor uptake and nuclear transport of Auger electrons by nuclear targeting with 111In-trastuzumab in an intraperitoneal tumor mouse model

OBJECTIVES

The 111In-labeled anti-HER2 antibody trastuzumab modified with a nuclear-localizing sequence (NLS) peptide (111In-trastuzumab-NLS) is a radiopharmaceutical candidate for Auger electron radioimmunotherapy (AE-RIT). However, in-vivo action of 111In-trastuzumab-NLS is poorly understood in intraperitoneal tumors. We aimed to elucidate the nuclear targeting activity of 111In-trastuzumab-NLS in a mouse model of intraperitoneal tumors.

METHODS

Trastuzumab, trastuzumab-NLS-S with shorter NLS peptides, and trastuzumab-NLS-L with longer NLS peptides were tested in an intraperitoneal tumor xenograft. The AE-emitting radionuclide 111In was labeled with these antibodies. The cell-binding activity, nuclear importation, and cytotoxicity of those radiolabeled antibodies were examined in human cancer cell lines. Analyses of the biodistribution and in-vivo nuclear importation of 111In were conducted in a mouse model.

RESULTS

The two111In-trastuzumab-NLS variants delivered the radionuclide into the nucleus more efficiently and had a comparable cytotoxicity to 111In-trastuzumab against human gastric cancer cells, although had a lower cell binding affinity. 111In-trastuzumab-NLS-L exhibited both a superior tumor uptake and in vivo nuclear transportation of the radionuclide than 111In-trastuzumab.

CONCLUSION

Nuclear targeting using 111In-trastuzumab-NLS promotes a more efficient tumor cell uptake and subsequent nuclear translocation of the 111In AE-emitting radionuclide in vivo. This radio-immunoconjugate will likely be an effective agent for HER2-targeting by AE-RIT.

Imaging inflammation in atherosclerotic plaques, targeting SST2 with [111In]In-DOTA-JR11

BACKGROUND

Imaging Somatostatin Subtype Receptor 2 (SST2) expressing macrophages by [DOTA,Tyr3]-octreotate (DOTATATE) has proven successful for plaque detection. DOTA-JR11 is a SST2 targeting ligand with a five times higher tumor uptake than DOTATATE, and holds promise to improve plaque imaging. The aim of this study was to evaluate the potential of DOTA-JR11 for plaque detection.

METHODS AND RESULTS

Atherosclerotic ApoE-/- mice (n = 22) fed an atherogenic diet were imaged by SPECT/CT two hours post injection of [111In]In-DOTA-JR11 (~ 200 pmol, ~ 50 MBq). In vivo plaque uptake of [111In]In-DOTA-JR11 was visible in all mice, with a target-to-background-ratio (TBR) of 2.23 ± 0.35. Post-mortem scans after thymectomy and ex vivo scans of the arteries after excision of the arteries confirmed plaque uptake of the radioligand with TBRs of 2.46 ± 0.52 and 3.43 ± 1.45 respectively. Oil red O lipid-staining and ex vivo autoradiography of excised arteries showed [111In]In-DOTA-JR11 uptake at plaque locations. Histological processing showed CD68 (macrophages) and SST2 expressing cells in plaques. SPECT/CT, in vitro autoradiography and immunohistochemistry performed on slices of a human carotid endarterectomy sample showed [111In]In-DOTA-JR11 uptake at plaque locations containing CD68 and SST2 expressing cells.

CONCLUSIONS

The results of this study indicate DOTA-JR11 as a promising ligand for visualization of atherosclerotic plaque inflammation.

IMPROVEMENTS OF 111IN SPECT IMAGES RECONSTRUCTED WITH SPARSELY ACQUIRED PROJECTIONS BY DEEP LEARNING GENERATED SYNTHETIC PROJECTIONS

The aim was to improve single-photon emission computed tomography (SPECT) quality for sparsely acquired 111In projections by adding deep learning generated synthetic intermediate projections (SIPs). Method: The recently constructed deep convolutional network for generating synthetic intermediate projections (CUSIP) was used for improving 20 sparsely acquired 111In-octreotide SPECTs. Reconstruction was performed with 120 (120P) or 30 (30P) projections, or 120 projections with 90 SIPs generated from 30 projections (30-120SIP). The SPECT reconstructions were performed with attenuation, scatter and collimator response corrections. Postfiltered 30P reconstructed SPECT was also analyzed. Image quality were quantitatively evaluated with root-mean-square error, peak signal-to-noise ratio and structural similarity index metrics. Result: The 30-120SIP reconstructed SPECT had statistically significant improved image quality parameters compared to 30P reconstructed SPECT with and without post filtering. The images visual appearance was similar to slightly filtered 120P SPECTs. Thereby, substantial acquisition time reduction with SIPs seems possible without image quality degradation.

EVALUATION OF THE SPATIAL RESOLUTION IN MONTE CARLO-BASED SPECT/CT RECONSTRUCTION OF 111IN-OCTREOTIDE IMAGES

The purpose was to evaluate the spatial resolution in 111In-octreotide single-photom emission computed tomography (SPECT)/computed tomography (CT) imaging following reconstructions with three different ordered subset expectation maximizations (OSEM) reconstruction algorithms; attenuation corrected (AC) OSEM, AC OSEM with resolution recovery (ACRR OSEM) and Monte Carlo-based OSEM reconstruction (MC OSEM). SPECT/CT imaging of a triple line phantom containing 111In in air and water was performed. The spatial resolution, represented by the full width at half maximum (FWHM) of a line profile, was determined for each line, for X and Y direction and for all reconstructions. The mean FWHM was 12.2 mm (±standard deviation [SD] 3.7 mm) for AC OSEM, 9.3 mm (±SD 2.5 mm) for ACRR OSEM and 8.2 mm (±SD 2.0 mm) for MC OSEM. MC-based SPECT/CT reconstruction clearly improves the spatial resolution in 111In-octreotide imaging and since MC simulations can be performed for all photon energies MC OSEM has the potential to improve SPECT/CT imaging overall.

A Radiolabeled Self-assembled Nanoparticle Probe for Diagnosis of Lung-Metastatic Melanoma

Melanoma is a highly malignant skin cancer that frequently metastasizes to the lung, bone, and brain at an early phase. Therefore, noninvasive detection of metastasized melanoma could be beneficial to determine suitable therapeutic strategies. We previously reported a biocompatible ternary anionic complex composed of plasmid DNA (pDNA), polyethyleneimine (PEI), and γ-polyglutamic acid (γ-PGA) based on an electrostatic interaction, which was highly taken up by melanoma cells (B16-F10), even if it was negatively charged. Here, we developed a radiolabeled γ-PGA complex by using indium-111 (111In)-labeled polyamidoamine dendrimer (4th generation; G4) instead of pDNA and iodine-125 (125I)-labeled PEI instead of native PEI, and evaluated its effectiveness as a melanoma-targeted imaging probe. This ternary complex was synthesized at a theoretical charge ratio; carboxyl groups of 111In-diethylenetriaminepentaacetic acid (DTPA)-G4 : amino groups of 125I-PEI : carboxyl groups of γ-PGA was 1 : 8 : 16, and the size and zeta potential were approximately 29 nm and -33 mV, respectively. This complex was taken up by B16-F10 cells with time. Furthermore, a biodistribution study, using normal mice, demonstrated its accumulation in the liver, spleen, and lung, where macrophage cells are abundant. Almost the same level of radioactivity derived from both 111In and 125I was observed in these organs at an early phase after probe injection. Compared with the normal mice, significantly higher lung-to-blood ratios of radioactivity were observed in the B16-F10-lung metastatic cancer model. In conclusion, the radiolabeled γ-PGA complex would hold potentialities for nuclear medical imaging of lung metastatic melanoma.

F18-FDG PET/CT Diagnoses Vasculitis after a Negative Indium-111 Leukocyte Scan

We present a case of a 38-year-old man with a prior episode of fever of unknown origin (FUO) four years ago who presented with acute severe dull nonradiating abdominal pain centered in the epigastric region associated with nausea and vomiting. Bloodwork showed a normal leukocyte count but elevated erythrocyte sedimentation rate of 26 and elevated C-reactive protein of 40; syphilis titers and anti-neutrophil cytoplasmic antibodies (pANCA and cANCA) were negative. CT angiogram (CTA) of the abdomen and pelvis showed diffuse medium vessel vascular inflammation. Indium-111 labeled leukocyte scan did not show evidence of infection and, specifically, no evidence of infectious vasculitis. Subsequent F18-FDG PET/CT scan showed diffuse uptake in the mesenteric vasculature in the area of abnormality seen on prior contrast-enhanced CT and confirmed the diagnosis of vasculitis, subsequently deemed by rheumatology to be most consistent with segmental arterial mediolysis.

Synthesis and evaluation of indium-111-labeled imidazothiadiazole sulfonamide derivative for single photon emission computed tomography imaging targeting carbonic anhydrase-IX

Carbonic anhydrase-IX (CA-IX) is a zinc enzyme overexpressed in the hypoxic regions of many types of solid tumors; therefore, in vivo imaging of CA-IX may contribute to cancer diagnosis. In this study, we newly designed and synthesized an ¹¹¹In-labeled CA-IX imaging agent based on an imidazothiadiazole sulfonamide (IS) scaffold conjugated with a chelating moiety, DO3A ([¹¹¹In]DO3A-IS1), and evaluated its utility for imaging of CA-IX high-expressing tumors. [¹¹¹In]DO3A-IS1 was successfully synthesized at a 76% radiochemical yield by reacting its precursor with ¹¹¹InCl₃ in acetate buffer. In in vitro assays, [¹¹¹In]DO3A-IS1 showed marked stability in murine plasma and greater binding to CA-IX high-expressing (HT-29) cells (118 ± 21% initial dose/mg protein) than CA-IX low-expressing (MDA-MB-231) cells (1.4 ± 0.3% initial dose/mg protein). Moreover, in an in vivo biodistribution assay, [¹¹¹In]DO3A-IS1 showed marked accumulation in the HT-29 tumor (8.71 ± 1.41% injected dose/g at 24 h postinjection). In addition, in a single photon emission computed tomography (SPECT) study, [¹¹¹In]DO3A-IS1 clearly and selectively visualized the HT-29 tumor as compared with the MDA-MB-231 tumor. These results indicate that [¹¹¹In]DO3A-IS1 may serve as a useful SPECT imaging agent with the novel scaffold targeting CA-IX.

Imaging DNA Damage Repair In Vivo After 177Lu-DOTATATE Therapy

Molecular radiotherapy using 177Lu-DOTATATE is a most effective treatment for somatostatin receptor-expressing neuroendocrine tumors. Despite its frequent and successful use in the clinic, little or no radiobiologic considerations are made at the time of treatment planning or delivery. On positive uptake on octreotide-based PET/SPECT imaging, treatment is usually administered as a standard dose and number of cycles without adjustment for peptide uptake, dosimetry, or radiobiologic and DNA damage effects in the tumor. Here, we visualized and quantified the extent of DNA damage response after 177Lu-DOTATATE therapy using SPECT imaging with 111In-anti-γH2AX-TAT. This work was a proof-of-principle study of this in vivo noninvasive biodosimeter with β-emitting therapeutic radiopharmaceuticals. Methods: Six cell lines were exposed to external-beam radiotherapy (EBRT) or 177Lu-DOTATATE, after which the number of γH2AX foci and the clonogenic survival were measured. Mice bearing CA20948 somatostatin receptor-positive tumor xenografts were treated with 177Lu-DOTATATE or sham-treated and coinjected with 111In-anti-γH2AX-TAT, 111In-IgG-TAT control, or vehicle. Results: Clonogenic survival after external-beam radiotherapy was cell-line-specific, indicating varying levels of intrinsic radiosensitivity. Regarding in vitro cell lines treated with 177Lu-DOTATATE, clonogenic survival decreased and γH2AX foci increased for cells expressing high levels of somatostatin receptor subtype 2. Ex vivo measurements revealed a partial correlation between 177Lu-DOTATATE uptake and γH2AX focus induction between different regions of CA20948 xenograft tumors, suggesting that different parts of the tumor may react differentially to 177Lu-DOTATATE irradiation. Conclusion:111In-anti-γH2AX-TAT allows monitoring of DNA damage after 177Lu-DOTATATE therapy and reveals heterogeneous damage responses.

Immuno-imaging of ICAM-1 in tumours by SPECT

PURPOSE

Molecular imaging of cancer cells' reaction to radiation damage can provide a non-invasive measure of tumour response to treatment. The cell surface glycoprotein ICAM-1 (CD54) was identified as a potential radiation response marker. SPECT imaging using an 111In-radiolabelled anti-ICAM-1 antibody was explored.

METHODS

PSN-1 cells were irradiated (10 Gy), and protein expression changes were investigated using an antibody array on cell lysates 24 h later. Results were confirmed by western blot, flow cytometry and immunofluorescence. We confirmed the affinity of an 111In-labelled anti-ICAM-1 antibody in vitro, and in vivo, in PSN-1-xenograft bearing mice. The xenografts were irradiated (0 or 10 Gy), and [111In]In-anti-ICAM-1 SPECT/CT images were acquired 24, 48 and 72 h after intravenous administration.

RESULTS

ICAM-1 was identified as a potential marker of radiation treatment using an antibody array in PSN-1 cell lysates following irradiation, showing a significant increase in ICAM-1 signal compared to non-irradiated cells. Western blot and immunohistochemistry confirmed this upregulation, with an up to 20-fold increase in ICAM-1 signal. Radiolabelled anti-ICAM-1 bound to ICAM-1 expressing cells with good affinity (Kd = 24.0 ± 4.0 nM). [111In]In-anti-ICAM-1 uptake in tumours at 72 h post injection was approximately 3-fold higher than non-specific isotype-matched [111In]In-mIgG2a control (19.3 ± 2.5%ID/g versus 6.3 ± 2.2%ID/g, P = 0.0002). However, ICAM1 levels, and [111In]In-anti-ICAM-1 uptake in tumours was no different after irradiation (uptake 9.2%ID/g versus 14.8%ID/g). Western blots of the xenograft lysates showed no significant differences, confirming these results.

CONCLUSION

Imaging of ICAM-1 is feasible in mouse models of pancreatic cancer. Although ICAM-1 is upregulated post-irradiation in in vitro models of pancreatic cancer, it shows little change in expression in an in vivo mouse xenograft model.

Indium-111 labelling of liposomal HEGF for radionuclide delivery via ultrasound-induced cavitation

The purpose of this exploratory study was to investigate the combination of a radiopharmaceutical, nanoparticles and ultrasound (US) enhanced delivery to develop a clinically viable therapeutic strategy for tumours overexpressing the epidermal growth factor receptor (EGFR). Molecularly targeted radionuclides have great potential for cancer therapy but are sometimes associated with insufficient delivery resulting in sub-cytotoxic amounts of radioactivity being delivered to the tumour. Liposome formulations are currently used in the clinic to reduce the side effects and improve the pharmacokinetic profile of chemotherapeutic drugs. However, in contrast to non-radioactive agents, loading and release of radiotherapeutics from liposomes can be challenging in the clinical setting. US-activated cavitation agents such as microbubbles (MBs) have been used to release therapeutics from liposomes to enhance the distribution/delivery in a target area. In an effort to harness the benefits of these techniques, the development of a liposome loaded radiopharmaceutical construct for enhanced delivery via acoustic cavitation was studied. The liposomal formulation was loaded with peptide, human epidermal growth factor (HEGF), coupled to a chelator for subsequent radiolabelling with ¹¹¹Indium ([¹¹¹In]In³⁺), in a manner designed to be compatible with preparation in a radiopharmacy. Liposomes were efficiently radiolabelled (57%) within 1 h, with release of ~12% of the radiopeptide following a 20 s exposure to US-mediated cavitation in vitro. In clonogenic studies this level of release resulted in cytotoxicity specifically in cells over-expressing the epidermal growth factor receptor (EGFR), with over 99% reduction in colony survival compared to controls. The formulation extended the circulation time and changed the biodistribution compared to the non-liposomal radiopeptide in vivo, although interestingly the biodistribution did not resemble that of liposome constructs currently used in the clinic. Cavitation of MBs co-injected with liposomes into tumours expressing high levels of EGFR resulted in a 2-fold enhancement in tumour uptake within 20 min. However, owing to the poor vascularisation of the tumour model used the same level of uptake was achieved without US after 24 h. By combining acoustic-cavitation-sensitive liposomes with radiopharmaceuticals this research represents a new concept in achieving targeted delivery of radiopharmaceuticals.

Noninvasive Evaluation of GPR119 Agonist Effects on β-Cell Mass in Diabetic Male Mice Using 111In-Exendin-4 SPECT/CT

Longitudinal observation of pancreatic β-cell mass (BCM) remains challenging because noninvasive techniques for determining BCM in vivo have not been established. Such observations would be useful for the monitoring of type 2 diabetes mellitus, a progressive disease involving loss of pancreatic BCM and function. An indium 111 (111In)-labeled exendin-4 derivative ([Lys12(111In-BnDTPA-Ahx)]exendin-4) targeting the glucagon-like peptide-1 receptor has been developed recently as a promising probe for quantifying the BCM noninvasively. In the present study, we used the 111In-exendin-4 single-photon emission CT/CT (SPECT/CT) technique to investigate the efficacy of DS-8500a, a novel G protein-coupled receptor-119 agonist currently under investigation for type 2 diabetes mellitus treatment in prediabetic db/db mice under dietary restriction. During the 8-week study, the treatment of mice with DS-8500a delayed and attenuated the progression of glucose intolerance compared with mice under dietary restriction alone. 111In-exendin-4 SPECT/CT of db/db mice revealed continuously decreasing radioactive isotope (RI) intensity in the pancreas during the 8-week intervention. DS-8500a attenuated this decrease and preserved pancreatic RI accumulation compared with dietary restriction alone at the end of the observation period. This result was corroborated not only by ex vivo pancreatic analysis using the [Lys12(111In-BnDTPA-Ahx)]exendin-4 probe but also by conventional histological BCM analysis. These results indicate that DS-8500a attenuates the progression of BCM loss beyond that of dietary restriction alone in prediabetic db/db mice. These results have shown that 111In-exendin-4 SPECT/CT will be useful for noninvasive longitudinal investigation of BCM in vivo.

Imaging inflammation in atherosclerotic plaques: Just make it easy!

The presence of inflammatory cells is a hallmark of unstable atherosclerotic plaques. Several imaging approaches have been developed for the noninvasive detection of inflammatory activities in atherosclerotic plaques. Positron emission tomography (PET) imaging with the injection of 18F-fluorodeoxyglucose (FDG) is currently the most widely used imaging technique to evaluate the density of activated macrophages in atherosclerotic plaques. Nevertheless, FDG-PET imaging has logistical and technical constraints that represent an important obstacle to the wider use of this approach for the evaluation of patients with atherosclerosis. In a similar way as in the oncological field, the balance between the benefits and costs of new drugs need to be improved in patients with cardiovascular diseases. PET imaging of plaque inflammation might represent a very useful tool to identify patients who could benefit the most from anti-inflammatory treatments and to exclude patients with other causes of inflammation who are the most likely to develop severe side effects under these drugs. The availability of radiotracers targeting more specifically inflammation in atherosclerotic plaques would greatly facilitate the logistic organization of this imaging and help to expand the use of PET for the evaluation of atherosclerotic patients.

Intraoperative Gamma Probe Detection of Head and Neck Paragangliomas with 111In-Pentetreotide: A Pilot Study

Aims and background

The aim of this study was to assess whether intraoperative radiolocalization of head and neck paragangliomas with 111In-pentetreotide may increase surgical effectiveness, reducing the risk of recurrence.

Methods

Our study included eight patients with untreated, recently diagnosed paragangliomas (four unilateral and four bilateral tumors of the carotid body). After iv injection of −150 MBq 111In-pentetreotide, preoperative somatostatin receptor scintigraphy (SRS) was performed. SPECT of the neck was performed at four hours and planar Images of the head and neck were also obtained at four and 24 hours post injection. Scintigraphy was always compared with the results of conventional imaging methods (MRI, angiography and sonography). Intraoperative detection was performed on 11 lesions 24 hours after radiopharmaceutical administration using a handheld gamma probe.

Results

Preoperative SRS showed high radiotracer uptake in all patients. All the intraoperatively detected lesions were radically resected and histologically confirmed to be involved by tumor. No false positive results were recorded. Gamma probe detection revealed a small intracranial extension not detected by other imaging methods in a patient with a paraganglioma of the right carotid, and partial involvement of the carotid artery in another patient. During follow-up (median 3.5 years; range, 4 months-7 years) all patients remained disease free according to all parameters.

Conclusions

To our knowledge, this is the first experience of radioguided surgery in paraganglioma. Although our study included a relatively small number of patients, we suggest that intraoperative gamma probe detection may be a powerful tool to improve surgical effectiveness.

The pharmacological properties of 3-arm or 4-arm DOTA constructs for conjugation to α-melanocyte-stimulating hormone analogues for melanoma imaging

Background

Although a 3-arm DOTA construct, which has three carboxylic acids, h has been applied for conjugation to many peptides, we investigated if a 4-arm DOTA construct conjugated to peptides improves chemical properties for melanoma imaging of the melanocortin 1 receptor compared to 3-arm DOTA-conjugated peptides.

Methods

Specific activities, radiolabeling efficiencies, and partition coefficients were evaluated using ¹¹¹In-labeled 3-arm and 4-arm DOTA-α-melanocyte-stimulating hormone (MSH). For assessment of MC1-R affinity and accumulation in tumor cells in vitro, B16-F1 melanoma and/or 4T1 breast cancer cells were incubated with ¹¹¹In-labeled 3-arm and 4-arm DOTA-α-MSH with and without α-MSH as a substrate. The stability was evaluated using mouse liver homogenates and plasma. Biological distribution and whole-body single photon emission computed tomography imaging of ¹¹¹In-labeled 3-arm and 4-arm DOTA-α-MSH were obtained using B16-F1 melanoma-bearing mice.

Results

Specific activities and radiolabeling efficiencies of both radiotracers were about 1.2 MBq/nM and 90–95%, respectively. The partition coefficients were −0.28 ± 0.03 for ¹¹¹In-labeled 3-arm DOTA-α-MSH and −0.13 ± 0.04 for ¹¹¹In-labeled 4-arm DOTA-α-MSH. Although accumulation was significantly inhibited by α-MSH in B16-F1 cells, the inhibition rate of ¹¹¹In-labeled 4-arm DOTA-α-MSH was lower than that of ¹¹¹In-labeled 3-arm DOTA-α-MSH. ¹¹¹In-labeled 4-arm DOTA-α-MSH was taken up early into B16-F1 cells and showed higher accumulation than ¹¹¹In-labeled 3-arm DOTA-α-MSH after 10 min of incubation. Although these stabilities were relatively high, the stability of ¹¹¹In-labeled 4-arm DOTA-α-MSH was higher than that of ¹¹¹In-labeled 3-arm DOTA-α-MSH. Regarding biological distribution, ¹¹¹In-labeled 4-arm DOTA-α-MSH showed significantly lower average renal accumulation (1.38-fold) and significantly higher average melanoma accumulation (1.32-fold) than ¹¹¹In-labeled 3-arm DOTA-α-MSH at all acquisition times. ¹¹¹In-labeled 4-arm DOTA-α-MSH showed significantly higher melanoma-to-kidney, melanoma-to-blood, and melanoma-to-muscle ratios than ¹¹¹In-labeled 3-arm DOTA-α-MSH.

Conclusions

The 4-arm DOTA construct has better chemical properties for peptide radiotracers than the 3-arm DOTA construct.

Dual-isotope imaging allows in vivo immunohistochemistry using radiolabelled antibodies in tumours

While radiolabelled antibodies have found great utility as PET and SPECT imaging agents in oncological investigations, a notable shortcoming of these agents is their propensity to accumulate non-specifically within tumour tissue. The degree of this non-specific contribution to overall tumour uptake is highly variable and can ultimately lead to false conclusions. Therefore, in an effort to obtain a reliable measure of inter-individual differences in non-specific tumour uptake of radiolabelled antibodies, we demonstrate that the use of dual-isotope imaging overcomes this issue, enables true quantification of epitope expression levels, and allows non-invasive in vivo immunohistochemistry. The approach involves co-administration of (i) an antigen-targeting antibody labelled with zirconium-89 (89Zr), and (ii) an isotype-matched non-specific control IgG antibody labelled with indium-111 (111In). As an example, the anti-HER2 antibody trastuzumab was radiolabelled with 89Zr, and co-administered intravenously together with its 111In-labelled non-specific counterpart to mice bearing human breast cancer xenografts with differing HER2 expression levels (MDA-MB-468 [HER2-negative], MDA-MB-231 [low-HER2], MDA-MB-231/H2N [medium-HER2], and SKBR3 [high-HER2]). Simultaneous PET/SPECT imaging using a MILabs Vector4 small animal scanner revealed stark differences in the intratumoural distribution of [89Zr]Zr-trastuzumab and [111In]In-IgG, highlighting regions of HER2-mediated uptake and non-specific uptake, respectively. Normalisation of the tumour uptake values and tumour-to-blood ratios obtained with [89Zr]Zr-trastuzumab against those obtained with [111In]In-IgG yielded values which were most strongly correlated (R = 0.94; P = 0.02) with HER2 expression levels for each breast cancer type determined by Western blot and in vitro saturation binding assays, but not non-normalised uptake values. Normalised intratumoural distribution of [89Zr]Zr-trastuzumab correlated well with intratumoural heterogeneity HER2 expression.

Optimization of HER3 expression imaging using affibody molecules: Influence of chelator for labeling with indium-111

Radionuclide molecular imaging of human epidermal growth factor receptor 3 (HER3) expression using affibody molecules could be used for patient stratification for HER3-targeted cancer therapeutics. We hypothesized that the properties of HER3-targeting affibody molecules might be improved through modification of the radiometal-chelator complex. Macrocyclic chelators NOTA (1,4,7-triazacyclononane-N,N',N''-triacetic acid), NODAGA (1-(1,3-carboxypropyl)-4,7-carboxymethyl-1,4,7-triazacyclononane), DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), and DOTAGA (1,4,7,10-tetraazacyclododececane,1-(glutaric acid)-4,7,10-triacetic acid) were conjugated to the C-terminus of anti-HER3 affibody molecule Z08698 and conjugates were labeled with indium-111. All conjugates bound specifically and with picomolar affinity to HER3 in vitro. In mice bearing HER3-expressing xenografts, no significant difference in tumor uptake between the conjugates was observed. Presence of the negatively charged 111In-DOTAGA-complex resulted in the lowest hepatic uptake and the highest tumor-to-liver ratio. In conclusion, the choice of chelator influences the biodistribution of indium-111 labeled anti-HER3 affibody molecules. Hepatic uptake of anti-HER3 affibody molecules could be reduced by the increase of negative charge of the radiometal-chelator complex on the C-terminus without significantly influencing the tumor uptake.

Establishment of a method for in-vivo SPECT/CT imaging analysis of 111In-labeled exendin-4 pancreatic uptake in mice without the need for nephrectomy or a secondary probe

INTRODUCTION

Radiolabeled exendin derivatives have been developed to visualize and quantify pancreatic beta cells. However, there are currently no established methods for analyzing in-vivo SPECT/CT images to quantify probe accumulation in the pancreas in rodent models. In this study, we aimed to establish an analytical method for murine in-vivo SPECT/CT imaging.

METHODS

First, we investigated the correlation between radioactivity measured by curiemeter and uptake calculated from SPECT/CT images of pancreata harvested after probe injection. Second, ROI volume necessary for reliable estimation of pancreatic uptake value was also examined. Third, the influence of high renal uptake on analysis was investigated with SPECT/CT imaging of harvested kidneys. Fourth, we compared pancreatic uptake values and ROI volumes estimated from in-vivo SPECT/CT images of pre- and post-nephrectomy mice. Finally, we assessed the correlation between the pancreatic uptake values from in-vivo SPECT/CT image analysis and radioactivity of harvested pancreata determined with a curiemeter.

RESULTS

Radioactivity of harvested pancreata measured by curiemeter and uptake values derived from SPECT/CT imaging of harvested pancreas showed an almost perfect correlation (r = 0.99, p < 0.001). Analysis using ROIs with >40% of the volume of the whole pancreas enabled reliable estimates of uptake (%CV < 10%). Exclusion of the perirenal space 2.7 mm from the kidney surface removed the influence of high renal uptake. Setting the uptake value of post-nephrectomy pancreatic ROIs as 100%, the uptake estimated from pre-nephrectomy images was comparable (102.9 ± 2.2%). A strong correlation was observed between pancreatic radioactivity measured by curiemeter and the uptake value derived from in-vivo SPECT/CT imaging (r = 0.90, p < 0.001).

CONCLUSION

Our analytical method without nephrectomy or additional probes enables reliable quantification of the pancreatic uptake of ¹¹¹In-labeled exendin-4 using in-vivo SPECT/CT imaging. The quantification of rodent BCM with our method would be helpful to drug development.

111In-labelled polymeric nanoparticles incorporating a ruthenium-based radiosensitizer for EGFR-targeted combination therapy in oesophageal cancer cells

Radiolabelled, drug-loaded nanoparticles may combine the theranostic properties of radionuclides, the controlled release of chemotherapy and cancer cell targeting. Here, we report the preparation of poly(lactic-co-glycolic acid) (PLGA) nanoparticles surface conjugated to DTPA-hEGF (DTPA = diethylenetriaminepentaacetic acid, hEGF = human epidermal growth factor) and encapsulating the ruthenium-based DNA replication inhibitor and radiosensitizer Ru(phen)2(tpphz)2+ (phen = 1,10-phenanthroline, tpphz = tetrapyridophenazine) Ru1. The functionalized PLGA surface incorporates the metal ion chelator DTPA for radiolabelling and the targeting ligand for EGF receptor (EGFR). Nanoparticles radiolabelled with 111In are taken up preferentially by EGFR-overexpressing oesophageal cancer cells, where they exhibit radiotoxicity through the generation of cellular DNA damage. Moreover, nanoparticle co-delivery of Ru1 alongside 111In results in decreased cell survival compared to single-agent formulations; an effect that occurs through DNA damage enhancement and an additive relationship between 111In and Ru1. Substantially decreased uptake and radiotoxicity of nanoparticles towards normal human fibroblasts and oesophageal cancer cells with normal EGFR levels is observed. This work demonstrates nanoparticle co-delivery of a therapeutic radionuclide plus a ruthenium-based radiosensitizer can achieve combinational and targeted therapeutic effects in cancer cells that overexpress EGFR.

Cancer radiotheranostics targeting carbonic anhydrase-IX with 111In- and 90Y-labeled ureidosulfonamide scaffold for SPECT imaging and radionuclide-based therapy

Hypoxic cells dynamically translocate during tumor growth and after radiotherapy. The most desirable direction for therapy targeting hypoxic cells is combining imaging and therapy (theranostics), which may help realize personalized medicine. Here, we conducted cancer radiotheranostics targeting carbonic anhydrase-IX (CA-IX), which is overexpressed in many kinds of hypoxic cancer cells, using low-molecular-weight 111In and 90Y complexes with a bivalent ureidosulfonamide scaffold as the CA-IX-binding moiety ([111In/90Y]US2). Methods: The targeting ability of [111In]US2 was evaluated by in vivo biodistribution study in CA-IX high-expressing (HT-29) tumor-bearing mice. In vivo imaging of HT-29 tumors was carried out using single photon emission computed tomography (SPECT). [90Y]US2 was administered to HT-29 tumor-bearing mice to evaluate cancer therapeutic effects. Results: [111In]US2 highly and selectively accumulated within HT-29 tumors (4.57% injected dose/g tumor at 1 h postinjection), was rapidly cleared from the blood pool and muscle after 4 h based on a biodistribution study, and visualized HT-29 tumor xenografts in mice at 4 h postinjection with SPECT. Radionuclide-based therapy with [90Y]US2 significantly delayed HT-29 tumor growth compared with that of untreated mice (P = 0.02 on day 28, Student's t-test), without any critical hematological toxicity due to its rapid pharmacokinetics. Conclusion: These results indicate that cancer radiotheranostics with [111In/90Y]US2 provides a novel strategy of theranostics for cancer hypoxia.

Indium-111-DTPA-octreotide Scintigraphy Modulation by Treatment with Unlabelled Somatostatin Analogue in Smali-Cell Lung Cancer

Aims and background

Small-cell lung cancer (SCLC) tissue expresses somatostatin receptors and can be visualized by means of the indium-111-labelled somatostatin analogue DTPA-D-Pheoctreotide. The aim of the study was to investigate whether treatment with a cold somatostatin analogue can affect the imaging of somatostatin receptor scintigraphy.

Methods

Three patients with SCLC were treated with 200 μg of cold octreotide three times a day subcutaneously for 7 days. Whole body and planar scintigraphy was performed before and after the treatment.

Results

111In-DTPA-octreotide uptake was increased in cancer lesions, whereas fixation in normal tissues (liver, spleen, kidneys) decreased.

Conclusions

This is the first demonstration of an enhancement of SCLC imaging following unlabelled somatostatin analogue administration. Similar results have been described by other authors in a limited number of carcinoid tumors.

Bone Lesion in a Patient with Transplanted Liver for a Metastatic Carcinoid. The Role of Somatostatin Receptor Scintigraphy

A patient who had previously undergone ileal resection and liver transplantation for a gastroenteropancreatic (GEP) tumor was evaluated with somatostatin receptor scintigraphy (SRS) using 111In-DTPA-D-Phe1-pentetreotide. Eighteen months after surgery, during follow-up procedures, conventional imaging techniques (ultrasound, computed tomography, magnetic resonance imaging) only showed a relapse in the gastropancre-atic lymph nodes, while SRS demonstrated skeletal spread. This case report emphasizes the clinical impact of SRS on the management of patients affected by neuroendocrine gastroenteropancreatic tumors.

Radiolabelled Stripped Mucin, SM3, Monoclonal Antibody for Immunoscintigraphy of Ovarian Tumours

A new monoclonal antibody, SM3, against stripped mucin core protein has been evaluated for the radioimmunoscintigraphy of ovarian cancer. It was radiolabelled with In-111, I-123 and Tc-99m and results showed a sensitivity of 95%, 100% and 100% and an accuracy of 73%, 86% and 100% for malignancy; respectively.

Immunoscintigraphy with 131I or 111In Labelled OC 125 F(ab')2 Fragments in Patients with Ovarian Carcinoma

To evaluate the clinical usefulness of immunoscintigraphy with OC 125 in ovarian carcinoma, we studied 25 patients suspected of having ovarian carcinoma or in follow-up after surgery. Fourteen patients were studied with 131I-OC 125 F(ab')2 and 11 with 111In-OC 125 F(ab')2. No differences were observed with the use of either radionuclide.

Global diagnostic indexes obtained were S = 100%, Sp = 44,5% and A = 81%. The low specificity obtained was remarkable: 5 false positive results in two uterine myomas, one abscess, one follicular cyst and one granulation tissue scar. On the other hand, all lesions of ovarian carcinoma were detected. Analysis of the evolution of tumor/background (T/B) uptake ratios from the first to the second day of exploration revealed a tendency for the ratio to diminish significantly (> 15%) in false positive cases with the exception of the abscess while this did not happen in true positive cases, with the exception of a regional recurrence. Analysis of T/B ratio variations could contribute towards elevating the test's specificity.

Pretargeting of Carcinomas with the Avidin-Biotin System

Diagnosis and experimental therapy of cancer have been performed with encouraging results using radiolabelled monoclonal antibodies. However, the high background due to non-specific uptake by normal tissue and blood is a major drawback in antibody-guided tumor detection. Various strategies have been proposed to overcome this problem, such as computed background subtraction, use of a second antibody, and local delivery. An antibody is a slow “bullet” for tumor targeting, since in many lesions it requires two or three days to accumulate. The use of fragments such as F(ab’)2 or Fab, which display a faster blood clearance than whole antibody, improves tumor localization to a sufficient extent (hours) to allow the use of the most suitable radionuclides, e.g. 99m-Tc. In therapeutic applications we are still far away from the optimal condition in terms of the absolute amount of radioactivity delivered to the tumor. The high specificity of antibodies could be exploited at its best by delaying the delivery of the label to a time when the ratio tumor-bound to non-tumor-bound antibody has reached its maximum value. To obtain this goal, the label should display a fast clearance and should be captured by the antibody already targeted onto tumor cells. These considerations have led to strategies of tumor pretargeting where antibody and label are administered separately. One of these strategies, based on the avidin-biotin system, has already been used extensively for several years in immunohistochemistry and in ELISA. Due to the flexibility of this system, several alternative protocols are possible.

We describe a three-step and a two-step pretargeting protocol based on the avidin-biotin system.

Clinical Diagnostic Application of111In-DTPA-Octreotide Scintigraphy in Small Cell Lung Cancer

Some years ago it was proved that a good percentage of small cell lung cancers, classified among cancers of the APUD system, produces somatostatin receptors that can be detected in vivo by scintigraphy with 111In-DTPA-octreotide. With the method in the whole body it is possible to identify the principal neoformation and the probable metastases. The authors present a study of 21 patients afflicted with small cell lung cancer diagnosed histologically. The study, carried out between January 1995 and December 1997, compared the radiologic iconography of the CT scan with the scintigraphic map obtained by a planar scintigraphy and in SPECT 1, 4 and 24-hr after iv injection of 110 MBq of 111In-DTPA-octreotide. The comparison was made with reference to the principal neoplasm and probable metastases. A scintigraphic study, a CT of restaging and a follow-up, done after 3 and 6 months of chemotherapy, on 15 patients with cancer that produces somatostatin receptors proved that the neoplasm sometimes regresses and sometimes progresses. In the latter case, it is possible to identify cerebral, mediastinal and hepatic metastases with the administration of 200 microg of octreotide 3 times a day for 7 days before the scintigraphy. In fact, the administration lowers background activity. The authors concluded that scintigraphy with 111In-DTPA-octreotide plays an important part in the study of patients afflicted with small cell lung cancer. Scintigraphy identifies the subgroups of patients who can be cured with somatostatin analogues together with chemotherapy. Scintigraphy presents a good sensibility in the re-staging and in the follow-up of patients who are treated, even though it is difficult to identify subdiaphragmatic metastases where liver, spleen and kidney show an increase in 111In-DTPA-octreotide.

Correlating Labeling Chemistry and in-vitro Test Results with the Biological Behavior of Radiolabeled Proteins

A study of the effect of various rediochemical labeling parameters on the in-vivo behavior of proteins, in particular of monoclonal antibodies, was carried out. Both radioiodination, and radiometal labeling (using protein-chelating agent conjugates), of antimelanoma, antiplatelet, and anticolon carcinoma monoclonal antibodies (222.28s, 7E3, and GA-733 respectively), as well as the direct labeling of human serum albumin with 99m Tc, were investigated. Different aspects of the biological behavior are affected in relation to the labeling chemistry involved. These include the immunoreactivity, blood clearance and tissue uptake kinetics, and rates and routes of excretion. Individual radionuclide effects have often to be addressed separately. Some antibodies are more susceptable to alteration from labeling conditions than others. Careful optimization of labeling and purification procedures is thus necessary for particular radionuclide/antibody combinations in order to obtain predictable and reproducible in-vivo results for both immunoscintigraphy and immunotherapy applications.

Cardioprotection by minocycline in a rabbit model of ischemia/reperfusion injury: Detection of cell death by in vivo 111In-GSAO SPECT

BACKGROUND

Preclinical studies indicate that minocycline protects against myocardial ischemia/reperfusion injury. In these studies, minocycline was administered before ischemia, which can rarely occur in clinical practice. The current study aimed to evaluate cardioprotection by minocycline treatment upon reperfusion.

METHODS

Rabbits were subjected to myocardial ischemia/reperfusion injury and received either intravenous minocycline (n = 8) or saline (n = 8) upon reperfusion. Cardiac cell death was assessed by in vivo micro-SPECT/CT after injection of Indium-111-labeled 4-(N-(S-glutathionylacetyl)amino) phenylarsonous acid (111In-GSAO). Thereafter, hearts were explanted for ex vivo imaging, γ-counting, and histopathological characterization.

RESULTS

Myocardial damage was visualized by micro-SPECT/CT imaging. Quantitative GSAO uptake (expressed as percent injected dose per gram, %ID/g) in the area at risk was lower in minocycline-treated animals than that in saline-treated control animals (0.32 ± 0.13% vs 0.48 ± 0.15%, P = 0.04). TUNEL staining confirmed the reduction of cell death in minocycline-treated animals.

CONCLUSIONS

This study demonstrates cardioprotection by minocycline in a clinically translatable protocol.

Factor VIII efficient and specific non-covalent binding to PEGylated liposomes enables prolongation of its circulation time and haemostatic efficacy

Haemophilia A is a bleeding disorder caused by the lack of factor VIII (FVIII). We report the prolongation of exogenous FVIII circulation time and haemostatic efficacy by its formulation with PEGylated liposomes (PEGLip). FVIII binds non-covalently but with high affinity in a specific mode with the external surface of PEGLip neither losing its activity nor its binding to von Willebrand Factor. Experiments in haemophilic and non-haemophilic mice indicate that the circulation time and clotting efficacy of PEGLip-formulated exogenous FVIII (PEGLip-FVIII) are significantly enhanced over those of free FVIII. The data support the feasibility of using PEGLip-FVIII to extend the duration of haemostatic efficacy in the treatment of haemophilia A.

SPECT imaging evaluation of 111indium-chelated cetuximab for diagnosing EGFR-positive tumor in an HCT-15-induced colorectal xenograft

BACKGROUND

Epidermal growth factor receptor (EGFR) overexpressed in colorectal cancer (CRC) is a tumor target for developing the anti-tumor theranostic agents. Cetuximab, an anti-EGFR monoclonal antibody against EGFR-positive tumors, inhibits cell proliferation and growth was labeled with radioactive ¹¹¹indium (¹¹¹In) in this study for diagnosing EGFR-positive CRC. The aim of this study was to evaluate the efficacy of noninvasive nuclear imaging agent ¹¹¹In-cetuximab and investigate the biological distribution of ¹¹¹In-cetuximab in the HCT-15-induced EGFR-positive CRC tumor xenografts.

METHODS

We conjugated cetuximab with an isotope chelator, diethylene triamine penta acetic acid (DTPA), and consequently labeled cetuximab-DTPA with ¹¹¹In and measured the labeling efficacy by an instant thin layer chromatography (iTLC). Furthermore, the ¹¹¹In-cetuximab was investigated and compared for imaging small (50 mm³) and large (250 mm³) tumor of CRC xenografts, respectively.

RESULTS

The conjugated ratio between cetuximab and DTPA was 1:6 measured by MALDI-TOF-MS. The better labeling concentration of cetuximab with 10 mCi of ¹¹¹In was calculated and experimented as 48 μg, resulting in labeling efficacy >80% detected by iTLC. The results revealed that the ¹¹¹In-cetuximab accumulated in the both sizes of tumors as a reliable noninvasive diagnostic agent, whereas the ratio of tumor to muscle in the large tumor was 7.5-fold. The biodistribution data indicated that the ¹¹¹In-cetuximab bound to tumor specifically that was higher than that in other organs.

CONCLUSION

We suggested that the ¹¹¹In-cetuximab was potential for early diagnosis and prognostic monitor of EGFR-positive CRC in further clinical practice.

Antithrombotic effects of saratin on human atherosclerotic plaques

Platelets play a primary role in thrombus formation after plaque rupture. Platelets recognize the exposed collagen via Von Willebrand factor (VWF) and become activated. Saratin, an inhibitor of the VWF-dependent binding of platelets to collagen, may reduce the thrombotic risk associated to atherosclerosis. Our objective was to evaluate the antithrombotic effects of local treatment with saratin on human atherosclerotic lesions. Thrombus formation was assessed by the deposition of 111Inplatelets on different human atherosclerotic lesions under three local shear conditions (800,1700 and 3400/s) with blood derived from catheterized pigs. Human atherosclerotic lesions were locally treated with saratin (30 µg/ml) at 37ºC for 5 min and placed in the chamber. Under stenotic shear conditions of 800/s, saratin significantly (p<0.05) reduced platelet deposition triggered by human denuded vessel wall (44%), fatty streaks (47%), severely damaged vessel (50%) and atherosclerotic plaque (57%). Thrombus characterization by immunohistochemistry showed also a reduction in fibrin deposition in treated vessels. These results suggest that the local site-specific treatment with saratin inhibits atherosclerotic plaque thrombogenicity at haemodynamic conditions typical of moderately stenotic coronary arteries.

Radiology of the adrenal incidentalomas. Review of the literature

The term "adrenal incidentaloma" is a radiological term. Adrenal incidentalomas are adrenal tumors discovered in an imaging study that has been obtained for indications exclusive to adrenal conditions (Udelsman 2001; Linos 2003; Bulow et al. 2006; Anagnostis et al. 2009). This definition excludes patients undergoing imaging testing as part of staging and work-up for cancer (Grumbach et al. 2003; Anagnostis et al. 2009). Papierska et al. (2013) have added the prerequisite that the size of a tumor must be "greater than 1cm in diameter", in order to be called incidentaloma. Although in the most cases these masses are non-hypersecreting and benign, they still represent an important clinical concern because of the risk of malignancy or hormone hyperfunction (Barzon et al. 2003). Th e adrenal tumors belong to the commonest incidental findings having been discovered (Kanagarajah et al. 2012).

Synthesis and biological evaluation of an 111In-labeled exendin-4 derivative as a single-photon emission computed tomography probe for imaging pancreatic β-cells

A non-invasive method of pancreatic β-cell mass measurement is needed to enhance our understanding of the pathogenesis of diabetes, facilitate the early diagnosis of this disease, and promote the development of novel therapeutics. Here, we described the synthesis of a novel indium-111 (¹¹¹In) exendin-4 derivative, [Lys¹²(In-BnDTPA-Ahx)]exendin-4, through a process involving isothiocyanate-benzyl-DTPA (BnDTPA) and 6-aminohexanoic acid (Ahx) attached to an ɛ-amino group at the lysine-12 residue. We further evaluated the potential use of this derivative as a SPECT probe for pancreatic β-cell imaging. An in vitro binding assay revealed that [Lys¹²(^natIn-BnDTPA-Ahx)]exendin-4 has a high affinity for GLP-1 receptors (IC₅₀=0.43nM). In biodistribution experiments involving normal mice, high [Lys¹²(¹¹¹In-BnDTPA-Ahx)]exendin-4 uptake was observed in the pancreas (21.8 ± 4.0%ID/g) and was maintained for 2h after injection. Pre-injection of excess exendin(9-39) markedly reduced the pancreatic uptake of [Lys¹²(¹¹¹In-BnDTPA-Ahx)]exendin-4 (95.2%), indicating that the uptake of this tracer is specific and mediated by GLP-1 receptors. Ex vivo autoradiography experiments involving pancreatic sections from MIP-GFP mice confirmed the accumulation of [Lys¹²(¹¹¹In-BnDTPA-Ahx)]exendin-4 in pancreatic β-cells. Finally, in mice, [Lys¹²(¹¹¹In-BnDTPA-Ahx)]exendin-4 SPECT/CT yielded clear images of the pancreas at 30min post-injection. In conclusion, SPECT with [Lys¹²(¹¹¹In-BnDTPA-Ahx)]exendin-4 enables to visualize β-cells in vivo non-invasively.

Non-invasive in vivo determination of viable islet graft volume by 111In-exendin-3

Pancreatic islet transplantation is a promising therapy for patients with type 1 diabetes. However, the duration of long-term graft survival is limited due to inflammatory as well as non-inflammatory processes and routine clinical tests are not suitable to monitor islet survival. 111In-exendin-SPECT (single photon emission computed tomography) is a promising method to non-invasively image islets after transplantation and has the potential to help improve the clinical outcome. Whether 111In-exendin-SPECT allows detecting small differences in beta-cell mass (BCM) and measuring the actual volume of islets that were successfully engrafted has yet to be demonstrated. Here, we evaluated the performance of 111In-exendin-SPECT using an intramuscular islet transplantation model in C3H mice. In vivo imaging of animals transplanted with 50, 100, 200, 400 and 800 islets revealed an excellent linear correlation between SPECT quantification of 111In-exendin uptake and insulin-positive area of islet transplants, demonstrating that 111In-exendin-SPECT specifically and accurately measures BCM. The high sensitivity of the method allowed measuring small differences in graft volumes, including grafts that contained less than 50 islets. The presented method is reliable, convenient and holds great potential for non-invasive monitoring of BCM after islet transplantation in humans.

A Multifunctional Radiotheranostic Agent for Dual Targeting of Breast Cancer Cells

A straightforward synthetic route for a new multifunctional 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) derivative is described. To demonstrate the versatility of this pro-chelator for the preparation of radiolabeled hybrid compounds containing two different biological targeting moieties, an antitumor agent (e.g., a DNA-intercalating agent) and an estrogen receptor (ER) ligand (e.g., LXXLL-based peptide) were regiospecifically conjugated to the DOTA derivative. The bifunctional probe was radiolabeled with the auger electron emitter indium-111, and the resulting radioconjugate was demonstrated to induce DNA damage in vitro, which, along with the nuclear internalization exhibited in breast cancer cells, might enhance its therapeutic activity. This favorable in vitro performance suggests that these hybrid compounds could be attractive probes for theranostic applications.

Limitations of In-Vitro Labeling of Endothelial Cells with Indium-111 Oxine

Indium-111 oxine labeling is widely used as a marker of endothelial cell attachment to vascular prostheses. The long term effect of labeling human adult endothelial cells (HAECs) with this isotope has not been determined. In this study the viability of labeled HAECs, leakage of isotope from labeled cells and adherence of circulating isotope to fibronectin coated prostheses were investigated over 24 h. The effect of incubation time on labeling efficiency was also assessed. There were significant differences in cell viability between the labeled and unlabeled groups beyond 4 h (p < 0.005, 2-tailed, unpaired t-test). In the control group cell numbers increased by 42% while in the labeled group this had decreased by 20% at 24 h. Spontaneous leakage increased with time but was maximal in the first 2 h. Adherence of circulating isotope to fibronectin coated expanded polytetrafluoroethylene (ePTFE) grafts was minimal but was significantly greater to gelatin impregnated Dacron (GEL-SEAL) beyond 1 hour (p < 0.05). Incubation times greater than 5 minutes during labeling do not significantly improve labeling efficiency, and may contribute to toxicity by prolonging exposure to oxine. Indium-111 oxine labeling of HAECs is a suitable technique for acute studies of endothelial cell kinetics up to 4 h, but its use in chronic studies may lead to significant underestimations of cell retention.

[Effects of Different Containers on Radioactivity Measurements using a Dose Calibrator with Special Reference to 111In and 123I]

Low-energy characteristic x-rays emitted by ¹¹¹In and ¹²³I sources are easily absorbed by the containers of the sources, affecting radioactivity measurements using a dose calibrator. We examined the effects of different containers on the estimated activities. The radioactivities of ¹¹¹In, ¹²³I, ²⁰¹Tl, and ^99mTc were measured in containers frequently employed in clinical practice in Japan. The ¹¹¹In measurements were performed in the vials A and B of the ¹¹¹In-pentetreotide preparation kit and in the plastic syringe. The activities of ¹²³I-metaiodobenzylguanidine and ²⁰¹Tl chloride were measured in the prefilled glass syringes and plastic syringes. The milking vial, vial A, vial B, and plastic syringe were used to assay ^99mTc. For ¹¹¹In and ¹²³I, measurements were performed with and without a copper filter. The filter was inserted into the well of the dose calibrator to absorb low-energy x-rays. The relative estimate was defined as the ratio of the activity estimated with the dose calibrator to the standard activity. The estimated activities varied greatly depending on the container when ¹¹¹In and ¹²³I sources were assayed without the copper filter. The relative estimates of ¹¹¹In were 0.908, 1.072, and 1.373 in the vial A, vial B, and plastic syringe, respectively. The relative estimates of ¹²³I were 1.052 and 1.352 in the glass syringe and plastic syringe, respectively. Use of the copper filter eliminated the container-dependence in ¹¹¹In and ¹²³I measurements. Container-dependence was demonstrated in neither ²⁰¹Tl nor ^99mTc measurements. The activities of ¹¹¹In and ¹²³I estimated with a dose calibrator differ greatly among the containers. Accurate estimation may be attained using the container-specific correction factor or using the copper filter.

Synthesis and evaluation of an 18 F-labeled derivative of F3 for targeting surface-expressed nucleolin in cancer and tumor endothelial cells

The surface overexpression of nucleolin provides an anchor for the specific attachment of biomolecules to cancer and angiogenic endothelial cells. The peptide F3 is a high-affinity ligand of the nucleolin receptor (NR) that has been investigated as a carrier to deliver biologically active molecules to tumors for both therapeutic and imaging applications. A site-specific PEGylated F3 derivative was radiolabeled with [18 F]Al-F. The binding affinity and cellular distribution of the compound was assessed in tumor (H2N) and tumor endothelial (2H-11) cells. Specific uptake via the NR was demonstrated by the siRNA knockdown of nucleolin in both cell lines. The partition and the plasma stability of the compound were assessed at 37°C. The enzyme-mediated site-specific modification of F3 to give NODA-PEG-F3 (NP-F3) was achieved. Radiolabeling with [18 F]Al-F gave 18 F-NP-F3. 18 F-NP-F3 demonstrated high affinity for cancer and tumor endothelial cells. The siRNA knockdown of nucleolin resulted in a binding affinity reduction of 50% to 60%, confirming cell surface binding via the NR. NP-F3 was stable in serum for 2 h. 18 F-NP-F3 is reported as the first 18 F-labeled F3 derivative. It was obtained in a site-specific, high-yield, and efficient manner and binds to surface NR in the low nanomolar range, suggesting it has potential as a tumor and angiogenesis tracer.

Production of transient ischaemic events by platelet emboli in baboons

To investigate the pathophysiological process of transient ischaemic events in a clinically relevant model, we produced transient focal cerebral ischaemia in five baboons using endogenously generated platelet microemboli. Thrombogenic segments of Dacron vascular graft were incorporated as unilateral carotid arterio-arterial shunts to produce endogenous platelet microemboli. The embolized microparticles were quantified by isotopic imaging using 111In-platelets and by transcranial Doppler ultrasonography. Platelet microemboli accumulated rapidly in the shunted carotid territory and reached a maximum value of 3.2 +/- 0.8 x 10(9) in the embolized hemisphere 20 min after initiating blood flow through the graft segment. Sixty min after removing the grafts 111In-platelets were largely cleared from hemispheric vasculature. Recovered animals exhibited mild contralateral hemiparesis which disappeared completely within 24 h. We conclude that endogenously generated platelet microemboli accumulate transiently in the dependent cerebral circulation and produce corresponding transient focal neurological dysfunction. This model may be useful in the evaluation of new therapeutic strategies in acute stroke.

Polymeric Surface Modifications of Tantalum Stents

Purpose:

To compare two kinds of polymer-coated tantalum stents with bare tantalum stents (control) to determine if the coatings can improve thromboresistance.

Methods:

Twenty-seven Fontaine-Dake stents were balloon expanded in three 8-mm × 80-cm.polytetrafluoroethylene (PTFE) grafts; 9 stents were bare tantalum (T); 9 were coated with polyetherurethane (PL); and 9 were coated with parylene (PA). There were 9 stents placed in each graft as follows: 3 tantalum, 3 polyetherurethane, and 3 parylene. In swine whose platelets had been radiolabeled with indium 111, the ends of each stented graft were connected to 14F femoral and venous sheaths to create an ex vivo fistula. Each graft was exposed to blood for 30, 60, and 120 minutes. At the end of each test period, the stented grafts were disconnected from the sheaths, flushed with saline until clear, and then flushed with formalin. The stents were removed from the grafts, and a radionuclide well counter recorded radionuclide counts from each stent type at each period of blood contact. These values were converted to platelet density per 1000 mUm2. Stents were then photographed and scanned with electron microscopy (EM) for qualitative analysis. Possible significant differences in platelet adhesion with the three types of stents (both between stent groups and within stent groups) were examined using a two-tailed Student's f-test.

Results:

There were significantly fewer platelets adsorbed on PA versus T at all time periods (p < 0.005); on PL versus T at 60 and 120 minutes (p < 0.005); and on PA versus PL at 30 and 120 minutes (p < 0.0005). There was no significant difference in platelet density within each stent group (p = 0.1). Mean platelet density (number of platelets per 1000 mUm2 ± SD) was as follows: at 30 minutes: T = 1891 ± 965; PL = 373 ± 193; and PA = 27 ± 3; at 60 minutes: T = 6226 ± 1621; PL = 1573 ± 793; and PA = 1185 ± 710; at 120 minutes: T = 5307 ± 591; PL = 3164 ± 318; and PA = 180 ± 100. Gross inspection of the 120-minute groups demonstrated focal areas of thrombus on T, less on PL, and none on PA. Scanning EM demonstrated extensive platelet accumulation covering T at all time periods, less on PL, and even less on PA.

Conclusions:

Polymeric surface modification of tantalum stents with parylene and/or polyetherurethane can improve the acute thromboresistance of these devices; parylene appears to be the more thromboresistant of the two coatings.

A new approach for simple radioisotope cisternography examination in cerebrospinal fluid leakage detection

OBJECTIVE

We developed a new quantitative interpretation technique of radioisotope cisternography (RIC) for the diagnosis of spontaneous cerebrospinal fluid hypovolemia (SCH).

METHODS

RIC studies performed for suspected SCH were evaluated. (111)In-DTPA RIC images were taken at 0, 1, 3, 6, and 24-h after radioisotope injection following the current protocol. Regions of interest (ROI) were selected on 3-h images to include brain, spine, bladder or the whole body. The accumulative radioactivity counts were calculated for quantitative analysis. Final diagnoses of SCH were established based on the diagnostic criteria recently proposed by Schievink and colleagues.

RESULTS

Thirty-five patients were focused on. Twenty-one (60.0%) patients were diagnosed as having SCH according to the Schievink criteria. On the 3-h images, direct cerebrospinal fluid leakage sign was detected in nine of 21 SCH patients (42.9%), as well as three patients with suspected iatrogenic leakage. Compared to non-SCH patients, SCH patients showed higher bladder accumulation at 3-h images (P = 0.0002), and higher brain clearance between the 6- and 24-h images (P < 0.0001). In particular, the 24-h brain clearance was more conclusive for the diagnosis than 24-h whole cistern clearance. The combination of direct sign and 24-h brain accumulation resulted in 100% of accuracy in the 32 patients in whom iatrogenic leakage was not observed. 1- and 6-h images did not provide any additional information in any patients.

CONCLUSIONS

A new simple ROI setting method, in which only the 3-h whole body and 24-h brain images were necessary, was sufficient to diagnose SCH.

Somatostatin and dopamine receptor expression in neuroendocrine neoplasms: correlation of immunohistochemical findings with somatostatin receptor scintigraphy visual scores

CONTEXT

The expression of somatostatin (sstr1-5) and dopamine (DR) receptors in neuroendocrine neoplasms (NENs) facilitates diagnosis by tumour visualization with somatostatin receptor scintigraphy (SRS) and directs towards specific treatment with peptide receptor radionuclide therapy (PRRT) with radiolabelled somatostatin analogues.

OBJECTIVE

To investigate the co-expression of sstrs, D2R in relation to pre-operative SRSs in NENs.

DESIGN

Prospective two-centre study.

PATIENTS AND MEASUREMENTS

We analysed pre-operative SRS of 60 patients [44 with gastrointestinal (GI) NENs and 16 with lung NENs] and compared SRS results with immunohistochemical (IHC) reactivity for sstr2, sstr3, sstr5 in sample tissues from primary (n = 54) and metastatic (n = 27) lesions and IHC reactivity for D2R in 23 samples from primary GI-NENs lesions.

RESULTS

Sstr2 was the commonest sstr expressed (65·4%) and was co-expressed with sstr3 and sstr5 in 32·1% and 24·7% of the specimens, respectively. In 67 of 81 specimens (82·7%), there was concordance of sstr2 immunohistochemistry with SRS findings (P < 0·001). D2R was expressed in only 8 of 23 (34·8%) GI-NENs while was co-expressed with sstr2 in all cases. SRS grade, as per Krenning scale, was higher in metastatic foci, large-size (>2 cm) tumours and GI-NENs, whereas sstr2 intensity was greater in GI compared to lung NENs. SRS grade showed higher correlation with sstr2 (r = 0·6, P < 0·001) and D2R (r = 0·5, P < 0·001) IHC intensity scores than tumour size (r = 0·4, P < 0·001) and sstr3 (r = 0·4, P < 0·001) intensity score.

CONCLUSIONS

Sstr2 IHC expression and SRS are useful tools for the diagnosis and management of NENs because they display a high concordance. IHC expression of DR2 seems to be of potential clinical significance in GI-NENs tumours.

111In-Pentetreotide SPECT/CT in Pulmonary Carcinoid

AIM

We evaluated somatostatin receptor scintigraphy (SRS) with (111)In-pentetreotide incremental value in pulmonary carcinoid (PC) diagnosis compared to contrast enhanced Computed Tomography (ceCT).

PATIENTS AND METHODS

We enrolled 81 patients with ascertained PC, 39 at initial staging and 42 in follow-up; the primary tumor had already been excised in 68 cases. Single Photon emission Computed Tomography (SPECT) images were reconstructed with the iterative method and fused with non-enhanced Computed tomography (CT) images.

RESULTS

Primary PC or metastatic lesions were ascertained in 55/81 patients and SPECT/CT was positive in 50/55 cases, while ceCT was positive in 44/55. Comparing SPECT/CT with ceCT results, we found a sensitivity of 96 vs. 87.5%, and specificity of 92% vs. 97% for the detection of primary lesion or recurrent disease. A total of 198 lesions were ascertained at SPECT/CT, while 161 at ceCT, with values of sensitivity and specificity of 85.5% and 84.6% for SRS and 75.2% and 90.5% respectively.

CONCLUSION

(111)In-Pentetreotide SPECT/CT proved to be more sensitive and accurate than ceCT, thus enhancing its role in evaluating patients with PC.

Claudin-4 SPECT Imaging Allows Detection of Aplastic Lesions in a Mouse Model of Breast Cancer

The expression of claudin-4, a protein involved in tight junction complexes, is widely dysregulated in epithelial malignancies. Claudin-4 is overexpressed in several premalignant precursor lesions, including those of cancers of the breast, pancreas, and prostate, and is associated with poor survival. A noncytotoxic C-terminal fragment of Clostridium perfringens enterotoxin (cCPE) is a natural ligand for claudin-4. Here, we demonstrate whole-body quantitative SPECT imaging of preneoplastic breast cancer tissue using (111)In-labeled cCPE.

METHODS

cCPE.GST or GST (GST is glutathione S-transferase) was conjugated to the metal ion chelator benzyl-diethylenetriaminepentaacetic acid to allow (111)In radiolabeling. The affinity of radiolabeled cCPE.GST for claudin-4 was confirmed using claudin-4-expressing MDA-MB-468 and SQ20b cells, compared with claudin-4-negative HT1080 cells. In vivo SPECT imaging was performed using athymic mice bearing MDA-MB-468 or HT1080 xenografts and using genetically modified BALB/neuT mice, which spontaneously develop claudin-4-expressing breast cancer lesions.

RESULTS

The uptake of (111)In-cCPE.GST in claudin-4-positive MDA-MB-468 xenograft tumors in athymic mice was significantly higher than in (111)In-GST or claudin-4-negative HT1080 tumors (6.72 ± 0.18 vs. 3.88 ± 1.00 vs. 2.36 ± 1.25 percentage injected dose per gram [%ID/g]; P < 0.0001). No other significant differences were observed in any of the examined organs. BALB/neuT mice, expressing rat neuT under mmtv promotor control, spontaneously developed tumorous lesions within their mammary fat pads over the course of 130 d. Overt mammary tumors were claudin-4-positive, and (111)In-cCPE.GST uptake was 3.2 ± 0.70 %ID/g, significantly higher than (111)In-GST (1.00 ± 0.60 %ID/g; P < 0.05). Mammary fat pads in mice aged 80 d bore claudin-4-positive aplastic lesions and accumulated (111)In-cCPE.GST (3.17 ± 0.51 %ID/g) but not (111)In-GST (0.99 ± 0.39 %ID/g; P < 0.001).

CONCLUSION

Taken together, (111)In-cCPE.GST targets claudin-4 expression in frank tumors and preneoplastic tissue, and cCPE imaging may be used as an early detection tool for breast, prostate, and pancreatic cancer.