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Nanomedicines allow active targeting of cancer for diagnostic and therapeutic applications through incorporation of multiple functional components. Frequently, however, clinical translation is hindered by poor intratumoural delivery and distribution. The application of physical stimuli to promote tumour uptake is a viable route to overcome this limitation. In this study, ultrasound-mediated cavitation of microbubbles was investigated as a mean of enhancing the delivery of a liposome designed for chemo-radionuclide therapy targeted to EGFR overexpressing cancer. Method: Liposomes (111In-EGF-LP-Dox) were prepared by encapsulation of doxorubicin (Dox) and surface functionalisation with Indium-111 tagged epidermal growth factor. Human breast cancer cell lines with high and low EGFR expression (MDA-MB-468 and MCF7 respectively) were used to study selectivity of liposomal uptake, subcellular localisation of drug payload, cytotoxicity and DNA damage. Liposome extravasation following ultrasound-induced cavitation of microbubbles (SonoVue®) was studied using a tissue-mimicking phantom. In vivo stability, pharmacokinetic profile and biodistribution were evaluated following intravenous administration of 111In-labelled, EGF-functionalised liposomes to mice bearing subcutaneous MDA-MB-468 xenografts. Finally, the influence of ultrasound-mediated cavitation on the delivery of liposomes into tumours was studied. Results: Liposomes were loaded efficiently with Dox, surface decorated with 111In-EGF and showed selective uptake in MDA-MB-468 cells compared to MCF7. Following binding to EGFR, Dox was released into the intracellular space and 111In-EGF shuttled to the cell nucleus. DNA damage and cell kill were higher in MDA-MB-468 than MCF7 cells. Moreover, Dox and 111In were shown to have an additive cytotoxic effect in MDA-MB-468 cells. US-mediated cavitation increased the extravasation of liposomes in an in vitro gel phantom model. In vivo, the application of ultrasound with microbubbles increased tumour uptake by 66% (p

Molecular radiotherapy using177Lu-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 after177Lu-DOTATATE therapy using SPECT imaging with111In-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) or177Lu-DOTATATE, after which the number of γH2AX foci and the clonogenic survival were measured. Mice bearing CA20948 somatostatin receptor–positive tumor xenografts were treated with177Lu-DOTATATE or sham-treated and coinjected with111In-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 with177Lu-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 between177Lu-DOTATATE uptake and γH2AX focus induction between different regions of CA20948 xenograft tumors, suggesting that different parts of the tumor may react differentially to177Lu-DOTATATE irradiation.Conclusion:111In-anti-γH2AX-TAT allows monitoring of DNA damage after177Lu-DOTATATE therapy and reveals heterogeneous damage responses.

Commercial mouse chow is designed to provide a complete, nutrient-rich diet, and it can contain upwards of 100 mg/kg manganese, an essential mineral. Manganese acts as a relaxation time shortening contrast agent for both T1 and T2, and where standard chow is hydrated in the gastrointestinal tract, bright signals are produced when using T1-weighted imaging (T1WI). As a result of peristalsis, gastrointestinal hyperintensities result in temporally unstable signals, leading to imageghosting and decreased resolution from that prescribed. To avoid the problem, various methods of gastrointestinal tract modulation including the use of intestinal cleansing with laxatives and dietary modulation have been reported. Here, dietary modulation has extended to use of a biologically innocuous, long-term change of diet. In this study, we report on the use of a commercially available manganese-free chow to improve image quality of the gastrointestinal tract. This manganese-free chow, apart from the omitted manganese which is available in tap water, is a complete diet and readily available. We investigated the time-dependent, diet-related gastrointestinal intensities on short TR, T1WI MRI; monitored body mass, food and water consumption and standard blood biochemistry analysis following diet change; and determined manganese concentration in blood plasma following a 5-day change to manganese-free chow. We show that the manganese-free chow presents a refinement to other gastrointestinal tract modulation as it avoids the need for invasive procedures for gut voiding and can be provided ad libitum so animals can be maintained with no need for prescribed diet change before imaging

Purpose: Multi-slice scanning in the abdomen and thorax of small animals is compromised by the effects of respiration unless imaging and respiration are synchronised. To avoid the signal modulations that result from respiration motion and a variable TR, blocks of fully relaxed slices are typically acquired during inter-breath periods, at the cost of scan efficiency. This paper reports a conceptually simple yet effective prospective gating acquisition mode for multi-slice scanning in free breathing small animals at any fixed TR of choice with reduced sensitivity to respiratory motion. Methods: Multi-slice scan modes have been implemented in which each slice has its own specific projection or phase encode loop index counter. When a breath is registered RF pulses continue to be applied but data are not acquired, and the corresponding counters remain fixed so that the data are acquired one TR later, providing it coincides with an inter-breath period. The approach is refined to reacquire the slice data that are acquired immediately before each breath is detected. Only the data with reduced motion artefact are used in image reconstruction. The efficacy of the method is demonstrated in the RARE scan mode which is well known to be particularly useful for tumour visualization. Results: Validation in mice with RARE demonstrates improved stability with respect to ungated scanning where signal averaging is often used to reduce artefacts. SNR enhancement maps demonstrate the improved efficiency of the proposed method that is equivalent to at least a 2.5 fold reduction in scan time with respect to ungated signal averaging. A steady-state magnetisation transfer contrast prepared gradient echo implementation is observed to highlight tumour structure. Supplementary simulations demonstrate that only small variations in respiration rate are required to enable efficient sampling with the proposed method. Conclusions The proposed prospective gating acquisition scheme enables efficient multi-slice scanning in small animals at the optimum TR with reduced sensitivity to respiratory motion. The method is compatible with a wide range of complementary methods including non-Cartesian scan modes, partially parallel imaging, and compressed sensing. In particular, the proposed scheme reduces the need for continual close monitoring to effect operator intervention in response to respiratory rate changes, which is both difficult to maintain and precludes high throughput.

Purpose:Increased activity of matrix metalloproteinases (MMPs) is associated with worse prognosis in different cancer types. The protective antigen (PA-WT) of the binary anthrax lethal toxin was modified to form a pore in cell membranes only when cleaved by MMPs (PA-L1). Anthrax lethal factor (LF) is then able to translocate through these pores. Here, we used an111In-radiolabelled form of LF with the PA/LF system for non-invasive in vivo imaging of MMP activity in tumour tissue by single photon emission computed tomography (SPECT). Methods:MMP-mediated activation of PA-L1 was correlated to anthrax receptor expression and MMP activity in a panel of cancer cells (HT1080, MDA-MB-231, B8484 and MCF7). Uptake of111In-radiolabelled PA-L1,111In-PA-WTK563Cor111In-LFE687A(a catalytically inactive LF mutant) in tumour and normal tissues was measured using SPECT/CT imaging in vivo. Results:Activation of PA-L1 in vitro correlated with anthrax receptor expression and MMP activity (HT1080>MDA-MB-231>B8484>MCF7). PA-L1-mediated delivery of111In-LFE687Awas demonstrated, and corroborated using confocal microscopy with fluorescently labelled LFE687A. Uptake was blocked by the broad-spectrum MMP inhibitor GM6001. In vivo imaging showed selective accumulation of111In-PA-L1 in MDA-MB-231 tumour xenografts (5.7±0.9%ID/g) at 3 h post intravenous administration.111In-LFE687A was selectively delivered to MMP-positive MDA-MB-231 tumour tissue by MMP-activatable PA-L1 (5.98±0.62%ID/g), but not by furin cleavable PA-WT (1.05±0.21%ID/g), or a non-cleavable PA variant control, PA-U7 (2.74 ± 0.24%ID/g). Conclusion:Taken together, our results indicate that radiolabelled forms of mutated anthrax lethal toxin hold promise for non-invasive imaging of MMP activity in tumour tissue.

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.

Neuroblastoma is the most frequent extra-cranial tumour in younger childhood. The current treatment of high-risk (stage 4) inoperable neuroblastoma includes a combination of chemotherapy and/or total irradiation with either autologous bone marrow transplantation or peripheral blood stem cell reinfusion. Despite these treatments the 4-year overall survival for high-stage neuroblastoma is still low (69%). Targeted/molecular radiotherapy (MRT) where the overexpressed noradrenaline transporter is targeted with 131I-MIBG (Meta-iodobenzylguanidine) an analogue of noradrenaline is an effective treatment for relapsed or refractory neuroblastoma. The aim of this study is to investigate whether in vivo imaging could be used to inform scheduling of MRT with 131I-MIBG in a human neuroblastoma xenograft model (SK-N-SH) to optimize and enhance the efficacy of external beam irradiation (EBRT).

Poly(ADP-ribose) polymerase (PARP) inhibitors are increasingly being studied as cancer drugs, as single agents, or as a part of combination therapies. Imaging of PARP using a radiolabeled inhibitor has been proposed for patient selection, outcome prediction, dose optimization, genotoxic therapy evaluation, and target engagement imaging of novel PARP-targeting agents. Methods: Here, via the copper-mediated 18F-radiofluorination of aryl boronic esters, we accessed, for the first time (to our knowledge), the 18F-radiolabeled isotopolog of the Food and Drug Administration-approved PARP inhibitor olaparib. The use of the 18F-labeled equivalent of olaparib allows direct prediction of the distribution of olaparib, given its exact structural likeness to the native, nonradiolabeled drug. Results: 18F-olaparib was taken up selectively in vitro in PARP-1-expressing cells. Irradiation increased PARP-1 expression and 18F-olaparib uptake in a radiation-dose-dependent fashion. PET imaging in mice showed specific uptake of 18F-olaparib in tumors expressing PARP-1 (3.2% ± 0.36% of the injected dose per gram of tissue in PSN-1 xenografts), correlating linearly with PARP-1 expression. Two hours after irradiation of the tumor (10 Gy), uptake of 18F-olaparib increased by 70% (P = 0.025). Conclusion: Taken together, we show that 18F-olaparib has great potential for noninvasive tumor imaging and monitoring of radiation damage.

The book first presents introductory material on small animal imaging, therapy, and research ethics. It next covers ionizing radiation and nonionizing radiation methods in small animal imaging, hybrid imaging, and imaging agents.

Purpose: Cardiac and respiratory motion derived image artefacts are reduced when data are acquired with cardiac and respiratory synchronisation. Where steady state imaging techniques are required in small animals, synchronisation is most commonly performed using retrospective gating techniques but these invoke an inherent time penalty. This paper reports the development of prospective gating techniques for cardiac and respiratory motion desensitised MRI with significantly reduced minimum scan time compared to retrospective gating. Methods: Prospective gating incorporating the automatic reacquisition of data corrupted by motion at the entry to each breath was implemented in short TR 3D spoiled gradient echo imaging. Motion sensitivity was examined over the whole mouse body for scans performed without gating, with respiratory gating, and with cardio-respiratory gating. The gating methods were performed with and without automatic reacquisition of motion corrupted data immediately after completion of the same breath. Prospective cardio-respiratory gating, with acquisition of 64 k-space lines per cardiac R-wave, was used to enable whole body DCE-MRI in the mouse. Results: Prospective cardio-respiratory gating enabled high fidelity steady state imaging of physiologically mobile organs such as the heart and lung. The automatic reacquisition of data corrupted by motion at the entry to each breath minimised respiratory motion artefact and enabled a highly efficient data capture that was adaptive to changes in the inter-breath interval. Prospective cardio-respiratory gating control enabled DCE-MRI to be performed over the whole mouse body with the acquisition of successive image volumes every 12-15 s at 422 μm isotropic resolution. Conclusions: Highly efficient cardio-respiratory motion desensitised steady state MRI can be performed in small animals with prospective synchronisation, centre-out phase-encode ordering, and the automatic reacquisition of data corrupted by motion at the entry to each breath. The method presented is robust against spontaneous changes in the breathing rate. Steady state imaging with prospective cardio-respiratory gating is much more efficient than with retrospective gating, and enables the examination of rapidly changing systems such as those found when using DCE-MRI.

Purpose: Tumor vessels influence the growth and response of tumors to therapy. Imaging vascular changes in vivo using dynamic contrast-enhanced MRI (DCE-MRI) has shown potential to guide clinical decision making for treatment. However, quantitative MR imaging biomarkers of vascular function have not been widely adopted, partly because their relationship to structural changes in vessels remains unclear. We aimed to elucidate the relationships between vessel function and morphology in vivo. Experimental Design: Untreated preclinical tumors with different levels of vascularization were imaged sequentially using DCE-MRI and CT. Relationships between functional parameters from MR (iAUC, Ktrans, and BATfrac) and structural parameters from CT (vessel volume, radius, and tortuosity) were assessed using linear models. Tumors treated with anti-VEGFR2 antibody were then imaged to determine whether antiangiogenic therapy altered these relationships. Finally, functional–structural relationships were measured in 10 patients with liver metastases from colorectal cancer. Results: Functional parameters iAUC and Ktrans primarily reflected vessel volume in untreated preclinical tumors. The relationships varied spatially and with tumor vascularity, and were altered by antiangiogenic treatment. In human liver metastases, all three structural parameters were linearly correlated with iAUC and Ktrans. For iAUC, structural parameters also modified each other's effect. Conclusions: Our findings suggest that MR imaging biomarkers of vascular function are linked to structural changes in tumor vessels and that antiangiogenic therapy can affect this link. Our work also demonstrates the feasibility of three-dimensional functional–structural validation of MR biomarkers in vivo to improve their biological interpretation and clinical utility.

Purpose: To assess the efficacy of different schedules for combining external beam radiotherapy (EBRT) with molecular radiotherapy (MRT) using 131I-mIBG in the management of neuroblastoma. Materials and Methods: Balb/c nu/nu mice bearing SK-N-SH neuroblastoma xenografts were assigned to five treatment groups: 131I-mIBG 24h after EBRT, EBRT 6 days after 131I-mIBG, EBRT alone, 131I-mIBG alone and control (untreated). A total of 56 mice were assigned to 3 studies. Study 1: Vessel permeability was evaluated using dynamic contrast-enhanced (DCE)-MRI (n=3). Study 2: Tumour volume and overall survival were assessed by longitudinal MR imaging (n=25). Study 3: Tumour uptake of 131I-mIBG in excised lesions was evaluated by -counting and autoradiography (n=28). Tumour dosimetry was performed using Monte Carlo simulations of absorbed fractions with the radiation transport code PENELOPE. Results: Given alone, both 131I-mIBG and EBRT resulted in a seven-day delay in tumour regrowth. Following EBRT, vessel permeability was evaluated by DCE-MRI and showed an increase at 24h post irradiation that correlated with an increase in 131I-mIBG tumour uptake, absorbed dose and overall survival in the case of combined treatment. Similarly, EBRT administered seven days after MRT to coincide with tumour regrowth, significantly decreased the tumour volume and increased overall survival. Conclusions: This study demonstrates that combining EBRT and MRT has an enhanced therapeutic effect and emphasizes the importance of treatment scheduling according to pathophysiological criteria such as tumour vessel permeability and tumour growth kinetics.

Radiolabelled antibodies and peptides hold promise for molecular radiotherapy but are often limited by low payload resulting in delivery of inadequate amounts of radioactivity to tumour tissue and, therefore, modest therapeutic effect. We have developed PEGylated epidermal growth factor (EGF)-gold nanoparticles (NP) with a high indium-111 (111In) payload (111In-EGF-Au-PEG NPs) as a prototypic NP-based theranostic radiopharmaceutical.

Hypoxia in solid tumours is associated with the promotion of various metabolic mechanisms and induces resistance to radio- and chemotherapy. Non-invasive positron emission tomography (PET) or single photon emission computed tomography by use of selective biomarkers has emerged as valuable tools for the detection of hypoxic areas within tumours so treatment can be modified accordingly. The aim of this investigation was to evaluate [(18)F]3-NTR, a 3-nitro-1,2,4-triazole analogue (N(1) substituted) of [(18)F]FMISO as a potential hypoxia selective tracer. 3-NTR and its (18)F-radiolabelled isotopic isomer were synthesised and compared with FMISO in vitro and in vivo. Their physicochemical properties were measured, the enzymatic reduction was evaluated, and the reactivity of their metabolites was investigated. Biodistribution and PET scans were performed on CBA mice bearing hypoxic CaNT tumour cells, using (18)F-labelled versions of the tracers. [(18)F]3-NTR uptake within hypoxic cells was lower than [(18)F]FMISO and [(18)F]3-NTR did not exhibit any better selectivity than FMISO as a PET tracer in vivo. Both (18)F-radiolabelled compounds are relatively evenly distributed within the whole body and the radioactive uptake within hypoxic tumours reaches a maximum at 30 min post injection and decreases thereafter. Xanthine oxidase exhibited a nitroreductase activity toward 3-NTR under anaerobic conditions, but reduced metabolites did not bind covalently. It is confirmed that 3-NTR is an electron acceptor. It is postulated that radiolabelled metabolites and fragments of [(18)F]3-NTR are freely diffusing due to their poor binding capacities. Thus [(18)F]3-NTR cannot be used as a hypoxia selective tracer for PET. The investigation provides insights into the importance of the propensity to form covalent adducts for such biomarkers.

In this paper, the use of 123 I-Annexin V for the detection of farnesyltransferase inhibitor (FTI)-induced apoptosis in tumour-bearing athymic mice is described. In vitro binding assays on LoVo cells show time- and dosage-dependent 125 I-Annexin V binding upon treatment with Tipifarnib (Zarnestra, R115777), a selective and potent FTI. In vivo experiments using planar gamma scintigraphy on LoVo inoculated mice show a 40% increased 123 I-Annexin V uptake 8 h after a single oral administration of 100 mg/kg Tipifarnib in 20% β-cyclodextrin in 0.1 M HCl, as well as after 3 days of twice daily treatments with the same dose. Ex vivo TUNEL assays, detecting end-stage apoptotic cells, correlate significantly with both in vitro and in vivo results. The percentage of necrosis is also increased by Tipifarnib treatment, but is too low to interfere with the 123 I-Annexin V uptake. It can be concluded that 123 I-Annexin V can be used to monitor Tipifarnib-induced apoptosis in LoVo xenograft tumours in athymic mice. Future applications might include the early prediction of FTI response and the selection of FTI-sensitive patients very shortly after treatment initiation. Subsequently, such patients would greatly benefit from a noninvasive and fast therapy evaluation.

The 21st annual symposium of the International Isotope Society's United Kingdom Group took place at the Møller Centre, Churchill College, Cambridge, UK, on Friday 12th October 2012. The meeting was attended by around 60 delegates from academia and industry, the life sciences, chemical, radiochemical and scientific instrument suppliers. Delegates were welcomed by Dr Ken Lawrie (GlaxoSmithKline, UK, chair of the IIS UK group). The subsequent scientific programme consisted of oral and poster presentations on isotopic chemistry and applications of labelled compounds or of chemistry with potential implications for isotopic synthesis. Both short-lived and long-lived isotopes were represented, as were stable isotopes. The symposium programme was divided into a morning session chaired by Professor Chris Willis (University of Bristol, UK) and afternoon sessions chaired by Mr Mike Chappelle (Quotient Biosciences, UK) and by Dr Sofia Pascu (University of Bath, UK). The UK meeting concluded with remarks from Dr Ken Lawrie (GlaxoSmithKline, Stevenage, UK).

Introduction: DNA damage repair (DDR) signalling is upregulated during tumorigenesis and acts as a p53-mediated block on proliferation. Expression of the DNA double strand break (DSB) repair protein, γH2AX, is induced by the activated kinases pATM or pATR during oncogenesis. Previously, we showed that γH2AX presents an abundant epitope for non-invasive in vivo imaging of DSBs. We used 111In-labelled anti-γH2AX antibodies, conjugated to the cell penetrating peptide, TAT, to non-invasively image DDR during oncogenesis in a genetically engineered mouse model of HER2/neu-overexpression driven breast cancer. Methods: Balb/neuT mice, genetically modified to express mutated rat neuT under MMTV promotor control, form multiple palpable carcinomas in mammary fat pads when animals are 130 days old. SPECT images were acquired weekly from balb/neuT mice (age 40-140 days; n=23) 24 h after i.v. injection of 111In-labelled anti-γH2AX-Tat or the non-selective agent, 111In-rIgG-Tat using a small animal SPECT/CT scanner. 111In uptake in fat pads was determined using volume of interest analysis. 111In uptake of >5%ID/g was deemed positive. Anatomical and histological changes were assessed at different ages using DCE-MRI imaging and immunohistochemistry. Results: Balb/neuT mice that were 80 days old developed multiple hyperplastic and dysplastic lesions in mammary fat pads. γH2AX foci were observed in these regions in balb/neuT mice that were 80-100 days old (10-15 foci/cell), but were less numerous in overt tumor tissue in 130-day-old mice (4-5 foci/cell). γH2AX foci were not observed in normal tissues in older mice (0 foci/cell), in mammary fat pads in younger mice (0 foci/cell), or in wild type mice (0 foci/cell). Serial SPECT imaging revealed a 7-fold increase in 111In-anti-γH2AX-Tat accumulation in mammary fat pads in mice 80-110 days old (up to 8.5 %ID/g), compared to non-specific control (P=0.0007), but not in younger or older mice (P>0.05). Repeated SPECT imaging itself did not influence tumor occurrence (P>0.05). The median time to detection of positive tissue was 96 days, much sooner than detection of lesions >150 μm by DCE-MRI (117 days), or palpation (130 days) (P Conclusion: Using a γH2AX-targeted radiopharmaceutical, we were able to image the DNA damage response during neuT-mediated oncogenesis in balb/neuT mice. DDR imaging identified neoplastic tissue significantly earlier than anatomical imaging. These results suggest that γH2AX imaging has potential as a screening tool for cancer-prone individuals.

UNLABELLED: Earlier reports described the preferential uptake of d-amino acids in tumor-bearing mice. Moreover, it was shown that in tumor cells in vitro the L-amino acid transporter system seemed to lack stereospecificity. Because of the successful results with 123/125I-2-iodo-L-phenylalanine, 123/125I-2-iodo-D-phenylalanine was developed, and its tumor-detecting characteristics were evaluated in vivo. METHODS: 123I labeling of 2-iodo-D-phenylalanine was performed with a kit formulation by use of Cu1+-assisted nucleophilic exchange. 123I-2-Iodo-D-phenylalanine was evaluated in R1M tumor-bearing athymic mice by dynamic planar imaging (DPI) and dissection. The in vivo stability of the tracer was tested by high-performance liquid chromatography. Tumor tracer retention and tracer contrast were evaluated as a function of time. Two-compartment blood modeling from DPI results and dosimetric calculations from biodistribution results were carried out. Moreover, 125I-2-iodo-D-phenylalanine and 18F-FDG uptake in acute inflammation was investigated. RESULTS: 123I-2-Iodo-D-phenylalanine was metabolically stable. Fast, high, and specific tumor retention was observed. Two-compartment modeling confirmed the fast clearance of the tracer through the kidneys to the bladder, as observed by DPI and dissection. Moreover, compared with the L-isomer, 123I-2-iodo-D-phenylalanine demonstrated faster clearance and faster uptake in the peripheral compartment. No accumulation in the abdomen or in the brain was noted. Dosimetry revealed that 123I-2-iodo-D-phenylalanine demonstrated a low radiation burden comparable to those of 123I-2-iodo-L-phenylalanine and 123I-2-iodo-L-tyrosine. Although 123I-2-iodo-D-phenylalanine showed a tumor retention of only 4%, the tumor contrast was increased up to 350% at 19 h after injection. CONCLUSION: 123I-2-Iodo-D-phenylalanine is a promising tracer for diagnostic oncologic imaging because of its high, fast, and specific tumor uptake and fast clearance from blood.

Cancer is a leading cause of death worldwide with an estimated 14 million new cases occurring yearly and approximately 8 million deaths. Although much progress has been made in the understanding and treatment of cancer, there are still many mechanisms that remain poorly understood. The development of vasculature is known to be a key element in facilitating the growth of a tumour. Modern imaging modalities such as multi-photon fluorescence microscopy allow unprecedented opportunities to examine and quantify this vasculature in vivo. However, the appearance of vascular networks, imaged at these scales, can be extremely complex and the automatic delineation of such large, tortuous and chaotic vascular networks is a non-trivial task. In this thesis we develop a number of methods for the automatic delineation of tumour vasculature, imaged using in vivo microscopy. Recent developments in machine learning have provided a powerful set of techniques for the automated analysis of complex structures in images. Leveraging these, it is possible to develop algorithms, capable of learning from human annotations, which are able to analyse extremely large images quickly and with a high degree of accuracy. The key contributions of this thesis are as follows: we present a novel supervoxel algorithm for use in a lightweight machine learning framework for segmentation. We adapt the current state-of-the-art in segmentation using 2D deep fully convolutional neural networks for use in 3D vascular segmentation. We further demonstrate the use of hybrid convolutional-recurrent networks for extracting 3D vessel centrelines. We propose the use of Conditional Adversarial Networks for refining the extraction of vessel centrelines directly. Finally, we demonstrate the ability of the developed methods to make quantitative observations on longitudinal changes to in vivo tumour vasculature development.