PURPOSE:Most effective antitumor therapies induce tumor cell death. Non-invasive, rapid and accurate quantitative imaging of cell death is essential for monitoring early response to antitumor... Show morePURPOSE:Most effective antitumor therapies induce tumor cell death. Non-invasive, rapid and accurate quantitative imaging of cell death is essential for monitoring early response to antitumor therapies. To facilitate this, we previously developed a biocompatible necrosis-avid near-infrared fluorescence (NIRF) imaging probe, HQ4, which was radiolabeled with 111Indium-chloride (111In-Cl3) via the chelate diethylene triamine pentaacetic acid (DTPA), to enable clinical translation. The aim of the present study was to evaluate the application of HQ4-DTPA for monitoring tumor cell death induced by radiation therapy. Apart from its NIRF and radioactive properties, HQ4-DTPA was also tested as a photoacoustic imaging probe to evaluate its performance as a multimodal contrast agent for superficial and deep tissue imaging.MATERIALS AND METHODS:Radiation-induced tumor cell death was examined in a xenograft mouse model of human breast cancer (MCF-7). Tumors were irradiated with three fractions of 9 Gy each. HQ4-DTPA was injected intravenously after the last irradiation, NIRF and photoacoustic imaging of the tumors were performed at 12, 20, and 40 h after injection. Changes in probe accumulation in the tumors were measured in vivo, and ex vivo histological analysis of excised tumors was performed at experimental endpoints. In addition, biodistribution of radiolabeled [111In]DTPA-HQ4 was assessed using hybrid single-photon emission computed tomography-computed tomography (SPECT-CT) at the same time points.RESULTS:In vivo NIRF imaging demonstrated a significant difference in probe accumulation between control and irradiated tumors at all time points after injection. A similar trend was observed using in vivo photoacoustic imaging, which was validated by ex vivo tissue fluorescence and photoacoustic imaging. Serial quantitative radioactivity measurements of probe biodistribution further demonstrated increased probe accumulation in irradiated tumors.CONCLUSION:HQ4-DTPA has high specificity for dead cells in vivo, potentiating its use as a contrast agent for determining the relative level of tumor cell death following radiation therapy using NIRF, photoacoustic imaging and SPECT in vivo. Initial preclinical results are promising and indicate the need for further evaluation in larger cohorts. If successful, such studies may help develop a new multimodal method for non-invasive and dynamic deep tissue imaging of treatment-induced cell death to quantitatively assess therapeutic response in patients. Show less
Bioluminescence imaging (BLI) has shown its appeal as a sensitive technique for in vivo whole body optical imaging. However, the development of injectable tumor-specific near-infrared fluorescent ... Show moreBioluminescence imaging (BLI) has shown its appeal as a sensitive technique for in vivo whole body optical imaging. However, the development of injectable tumor-specific near-infrared fluorescent (NIRF) probes makes fluorescence imaging (FLI) a promising alternative to BLI in situations where BLI cannot be used or is unwanted (e.g., spontaneous transgenic tumor models, or syngeneic mice to study immune effects).In this study, we addressed the questions whether it is possible to detect tumor progression using FLI with appropriate sensitivity and how FLI correlates with BLI measurements. In addition, we explored the possibility to simultaneously detect multiple tumor characteristics by dual-wavelength FLI (∼700 and ∼800 nm) in combination with spectral unmixing. Using a luciferase-expressing 4T1-luc2 mouse breast cancer model and combinations of activatable and targeting NIRF probes, we showed that the activatable NIRF probes (ProSense680 and MMPSense680) and the targeting NIRF probes (IRDye 800CW 2-DG and IRDye 800CW EGF) were either activated by or bound to 4T1-luc2 cells. In vivo, we implanted 4T1-luc2 cells orthotopically in nude mice and were able to follow tumor progression longitudinally both by BLI and dual-wavelength FLI. We were able to reveal different probe signals within the tumor, which co-localized with immuno-staining. Moreover, we observed a linear correlation between the internal BLI signals and the FLI signals obtained from the NIRF probes. Finally, we could detect pulmonary metastases both by BLI and FLI and confirmed their presence histologically.Taken together, these data suggest that dual-wavelength FLI is a feasible approach to simultaneously detect different features of one tumor and to follow tumor progression with appropriate specificity and sensitivity. This study may open up new perspectives for the detection of tumors and metastases in various experimental models and could also have clinical applications, such as image-guided surgery. Show less
Baiker, M.; Snoeks, T.J.A.; Kaijzel, E.L.; Que, I.; Dijkstra, J.; Lelieveldt, B.P.F.; Lowik, C.W.G.M. 2012
The aim of this work was to develop methods to measure structural changes in the skeleton using MicroCT. In addition, these new methods should be able to quantify biologically relevant changes. In... Show moreThe aim of this work was to develop methods to measure structural changes in the skeleton using MicroCT. In addition, these new methods should be able to quantify biologically relevant changes. In order to do this, normalized methods to analyse MicroCT scans and perform quantitative measurements within these datasets are described in this thesis. These techniques were combined with a biological angiogenesis assay and used as research tools in a study comparing various different combination treatments of bone metastases. Show less
PURPOSE: Quantification of osteolysis is crucial for monitoring treatment effects in preclinical research and should be based on MicroCT data rather than conventional 2D radiographs to obtain... Show morePURPOSE: Quantification of osteolysis is crucial for monitoring treatment effects in preclinical research and should be based on MicroCT data rather than conventional 2D radiographs to obtain optimal accuracy. However, data assessment is greatly complicated in the case of 3D data. This paper presents an automated method to follow osteolytic lesions quantitatively and visually over time in whole-body MicroCT data of mice. PROCEDURES: This novel approach is based on a previously published approach to coarsely locate user-defined structures of interest in the data and present them in a standardized manner (Baiker et al., Med Image Anal 14:723-737, 2010; Kok et al., IEEE Trand Vis Comput Graph 16:1396-1404, 2010). Here, we extend this framework by presenting a highly accurate way to automatically measure the volumes of individual bones and demonstrate the technique by following the effect of osteolysis in the tibia of a mouse over time. Besides presenting quantitative results, we also give a visualization of the measured volume to be able to investigate the performance of the method qualitatively. In addition, we describe an approach to measure and visualize cortical bone thickness, which allows assessing local effects of osteolysis and bone remodeling. The presented techniques are fully automated and therefore allow obtaining objective results, which are independent of human observer performance variations. In addition, the time typically required to analyze whole-body data is greatly reduced. RESULTS: Evaluation of the approaches was performed using MicroCT follow-up datasets of 15 mice (n = 15), with induced bone metastases in the right tibia. All animals were scanned three times: at baseline, after 3 and 7 weeks. For each dataset, our method was used to locate the tibia and measure the bone volume. To assess the performance of the automated method, bone volume measurements were also done by two human experts. A quantitative comparison of the results of the automated method with the human observers showed that there is a high correlation between the observers (r = 0.9996), between the first observer and the presented method (r = 0.9939), and also between the second observer and the presented method (r = 0.9937). In addition, Bland-Altman plots revealed excellent agreement between the observers and the automated method (interobserver bone volume variability, 0.59 ± 0.64%; Obs1 vs. Auto, 0.26 ± 2.53% and Obs2 vs. Auto, -0.33 ± 2.61%). Statistical analysis yielded no significant difference (p = .10) between the manual and the automated bone measurements and thus the method yields optimum results. This could also be confirmed visually, based on the graphical representations of the bone volumes. The performance of the bone thickness measurements was assessed qualitatively. CONCLUSIONS: We come to the conclusion that the presented method allows to measure and visualize local bone volume and thickness in longitudinal data in an accurate and robust manner, proving that the automated tool is a fast and user friendly alternative to manual analysis. Show less
