Musiré: multimodal simulation and reconstruction framework for the radiological imaging sciences.

A software-based workflow is proposed for managing the execution of simulation and image reconstruction for SPECT, PET, CBCT, MRI, BLI and FMI packages in single and multimodal biomedical imaging applications. The workflow is composed of a Bash script, the purpose of which is to provide an interface to the user, and to organize data flow between dedicated programs for simulation and reconstruction. The currently incorporated simulation programs comprise GATE for Monte Carlo simulation of SPECT, PET and CBCT, SpinScenario for simulating MRI, and Lipros for Monte Carlo simulation of BLI and FMI. Currently incorporated image reconstruction programs include CASToR for SPECT and PET as well as RTK for CBCT. MetaImage (mhd) standard is used for voxelized phantom and image data format. Meshlab project (mlp) containers incorporating polygon meshes and point clouds defined by the Stanford triangle format (ply) are employed to represent anatomical structures for optical simulation, and to represent tumour cell inserts. A number of auxiliary programs have been developed for data transformation and adaptive parameter assignment. The software workflow uses fully automatic distribution to, and consolidation from, any number of Linux workstations and CPU cores. Example data are presented for clinical SPECT, PET and MRI systems using the Mida head phantom and for preclinical X-ray, PET and BLI systems employing the Digimouse phantom. The presented method unifies and simplifies multimodal simulation setup and image reconstruction management and might be of value for synergistic image research. This article is part of the theme issue 'Synergistic tomographic image reconstruction: part 2'.

High Doses of Photons and Carbon Ions Comparably Increase Vascular Permeability in R3327-HI Prostate Tumors: A Dynamic Contrast-Enhanced MRI Study.

Carbon- (12C-) ion radiotherapy exhibits enhanced biological effectiveness compared to photon radiotherapy, however, the contribution of its interaction with the vasculature remains debatable. The effect of high-dose 12C-ion and photon irradiation on vascular permeability in moderately differentiated rat prostate tumors was compared using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Syngeneic R3327-HI rat prostate tumors were irradiated with a single dose of either 18 or 37 Gy 12C ions, or 37 or 75 Gy 6-MV photons (sub-curative and curative dose levels, respectively). DCE-MRI was performed one day prior to and 3, 7, 14 and 21 days postirradiation. Voxel-based tumor concentration-time curves were clustered based on their curve shape and treatment response was assessed as the longitudinal changes in the relative abundance per cluster. Radiation-induced vascular damage and increased permeability occurred at day 7 postirradiation for all treatment groups except for the 75 Gy photon-irradiated group, where the onset of vascular damage was delayed until day 14. No differences between irradiation modalities were found. Therefore, early vascular damage cannot explain the higher effectiveness of 12C ions relative to photons in terms of local tumor control for this moderately differentiated prostate tumor and the applied single high doses.

Impact of Single Dose Photons and Carbon Ions on Perfusion and Vascular Permeability: A Dynamic Contrast-Enhanced MRI Pilot Study in the Anaplastic Rat Prostate Tumor R3327-AT1.

We collected initial quantitative information on the effects of high-dose carbon (12C) ions compared to photons on vascular damage in anaplastic rat prostate tumors, with the goal of elucidating differences in response to high-LET radiation, using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). Syngeneic R3327-AT1 rat prostate tumors received a single dose of either 16 or 37 Gy 12C ions or 37 or 85 Gy 6 MV photons (iso-absorbed and iso-effective doses, respectively). The animals underwent DCE-MRI prior to, and on days 3, 7, 14 and 21 postirradiation. The extended Tofts model was used for pharmacokinetic analysis. At day 21, tumors were dissected and histologically examined. The results of this work showed the following: 1. 12C ions led to stronger vascular changes compared to photons, independent of dose; 2. Tumor growth was comparable for all radiation doses and modalities until day 21; 3. Nonirradiated, rapidly growing control tumors showed a decrease in all pharmacokinetic parameters (area under the curve, Ktrans, ve, vp) over time; 4. 12C-ion-irradiated tumors showed an earlier increase in area under the curve and Ktrans than photon-irradiated tumors; 5. 12C-ion irradiation resulted in more homogeneous parameter maps and histology compared to photons; and 6. 12C-ion irradiation led to an increased microvascular density and decreased proliferation activity in a largely dose-independent manner compared to photons. Postirradiation changes related to 12C ions and photons were detected using DCE-MRI, and correlated with histological parameters in an anaplastic experimental prostate tumor. In summary, this pilot study demonstrated that exposure to 12C ions increased the perfusion and/or permeability faster and led to larger changes in DCE-MRI parameters resulting in increased vessel density and presumably less hypoxia at the end of the observation period when compared to photons. Within this study no differences were found between curative and sub-curative doses in either modality.

Bolus arrival time estimation in dynamic contrast-enhanced magnetic resonance imaging of small animals based on spline models.

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is used to quantify perfusion and vascular permeability. In most cases a bolus arrival time (BAT) delay exists between the arterial input function (AIF) and the contrast agent arrival in the tissue of interest which needs to be estimated. Existing methods for BAT estimation are tailored to tissue concentration curves, which have a fast upslope to the peak as frequently observed in patient data. However, they may give poor results for curves that do not have this characteristic shape such as tissue concentration curves of small animals. In this paper, we propose a method for BAT estimation of signals that do not have a fast upslope to their peak. The model is based on splines which are able to adapt to a large variety of concentration curves. Furthermore, the method estimates BATs on a continuous time scale. All relevant model parameters are automatically determined by generalized cross validation. We use simulated concentration curves of small animal and patient settings to assess the accuracy and robustness of our approach. The proposed method outperforms a state-of-the-art method for small animal data and it gives competitive results for patient data. Finally, it is tested on in vivo acquired rat data where accuracy of BAT estimation was also improved upon the state-of-the-art method. The results indicate that the proposed method is suitable for accurate BAT estimation of DCE-MRI data, especially for small animals.

Automated closed-loop management of body temperature using forced-air blankets: preliminary feasibility study in a porcine model.

BACKGROUND: Management of a patient's body temperature is an important aspect of care that should be addressed by targeted temperature management (TTM). Often, non-invasive methods like forced-air blankets are used. Especially in the operating room this management may be a subsidiary and repetitive task requiring constant observation of the patient's body temperature and adaption using the limited set of available settings. Thus, automation of TTM is a feasible target to improve patient outcome and reduce caregiver workload. METHODS: A Philips IntelliVue MP 50 patient monitor with an arterial PiCCO catheter system was used to measure patient blood temperature. Thermal management was performed with a 3M Bair Hugger 755 warming unit with forced air blankets. The warming unit was extended by a computer interface to allow for remote and automated control. A proposed closed-loop algorithm reads the measured temperature and performs automated control of the 3M Bair Hugger. Evaluation was performed in an experimental intensive care setting for animal studies. Two fully automated trials are compared with two manual and two uncontrolled trials in the same study setting using six female pigs for prolonged observation times of up to 90 hours in each trial. RESULTS: The developed system and proposed algorithm allow more precise temperature management by keeping a set target temperature within a range of ± 0.5 °C in 88% of the observation time and within a range of ± 1.0 °C at all times. The proposed algorithm yielded better performance than did manual control or uncontrolled trials. It was able to adapt to individual patient needs as it is more dynamic than look-up table approaches with fixed settings for various temperatures. CONCLUSIONS: Closed-loop TTM using non-invasive forced-air warming blankets was successfully tested in a porcine study with the proposed hardware interface and control algorithm. This automation can be beneficial for patient outcome and can reduce caregiver workload and patient risk in clinical settings. As temperature readings are most often available, existing devices like the 3M Bair Hugger can easily be expanded. However, even if clinical application is feasible, open questions regarding approval and certification of such automated systems within the current legal situation still need to be answered.

Photoacoustic imaging to assess pixel-based sO2 distributions in experimental prostate tumors.

A protocol for photoacoustic imaging (PAI) has been developed to assess pixel-based oxygen saturation (sO2) distributions of experimental tumor models. The protocol was applied to evaluate the dependence of PAI results on measurement settings, reproducibility of PAI, and for the characterization of the oxygenation status of experimental prostate tumor sublines (Dunning R3327-H, -HI, -AT1) implanted subcutaneously in male Copenhagen rats. The three-dimensional (3-D) PA data employing two wavelengths were used to estimate sO2 distributions. If the PA signal was sufficiently strong, the distributions were independent from signal gain, threshold, and positioning of animals. Reproducibility of sO2 distributions with respect to shape and median values was demonstrated over several days. The three tumor sublines were characterized by the shapes of their sO2 distributions and their temporal response after external changes of the oxygen supply (100% O2 or air breathing and clamping of tumor-supplying artery). The established protocol showed to be suitable for detecting temporal changes in tumor oxygenation as well as differences in oxygenation between tumor sublines. PA results were in accordance with histology for hypoxia, perfusion, and vasculature. The presented protocol for the assessment of pixel-based sO2 distributions provides more detailed information as compared to conventional region-of-interest-based analysis of PAI, especially with respect to the detection of temporal changes and tumor heterogeneity.

Fully automated life support: an implementation and feasibility pilot study in healthy pigs.

BACKGROUND: Automated systems are available in various application areas all over the world for the purpose of reducing workload and increasing safety. However, such support systems that would aid caregivers are still lacking in the medical sector. With respect to workload and safety, especially, the intensive care unit appears to be an important and challenging application field. Whereas many closed-loop subsystems for single applications already exist, no comprehensive system covering multiple therapeutic aspects and interactions is available yet. This paper describes a fully closed-loop intensive care therapy and presents a feasibility analysis performed in three healthy pigs over a period of 72 h each to demonstrate the technical and practical implementation of automated intensive care therapy. METHODS: The study was performed in three healthy, female German Landrace pigs under general anesthesia with endotracheal intubation. An arterial and a central venous line were implemented, and a suprapubic urinary catheter was inserted. Electrolytes, glucose levels, acid-base balance, and respiratory management were completely controlled by an automated fuzzy logic system based on individual targets. Fluid management by adaption of the respective infusion rates for the individual parameters was included. RESULTS: During the study, no manual modification of the device settings was allowed or required. Homoeostasis in all animals was kept stable during the entire observation period. All remote-controlled parameters were maintained within physiological ranges for most of the time (free arterial calcium 73%, glucose 98%, arterial base excess 89%, and etCO2 98%). Subsystem interaction was analyzed. CONCLUSIONS: In the presented study, we demonstrate the feasibility of a fully closed-loop system, for which we collected high-resolution data on the interaction and response of the different subsystems. Further studies should use big data approaches to analyze and investigate the interactions between the subsystems in more detail.

Review on Sustained Relief of Osteoarthritis Symptoms with a Proprietary Extract from Pine Bark, Pycnogenol.

This review summarizes the effects of the standardized proprietary bark extract of the French maritime pine (Pycnogenol®) in mild osteoarthritis (OA), stage 1 and 2. The extract exerts antioxidative, anti-inflammatory, and chondroprotective effects in vitro and in vivo. Its phenolic acids as well as catechin and taxifolin are quickly absorbed. Active metabolites, produced by gut microbiota in the intestinal tract from oligomeric procyanidins, appear in blood 6 h following ingestion and remain for at least 14 h, providing a long-lasting flow of anti-inflammatory substances for relief of OA symptoms. These constituents of Pycnogenol could be detected in serum, blood cells, and synovial fluid of OA patients. The resulting inhibition of cartilage-destructing proteases and pain-producing cyclo-oxygenases provides the basis for relief from pain, improvement of stiffness, enhanced mobility, and well-being in three clinical studies with the pine bark extract as an adjunct supplement. Sparing the use of nonsteroidal anti-inflammatory drugs, supplementation with the pine bark extract reduced gastric complications and hospital admissions of OA patients. Because of its favorable safety profile and sustained anti-inflammatory action, Pycnogenol represents an option as an add-on supplement for OA patients.

Algorithm-based arterial blood sampling recognition increasing safety in point-of-care diagnostics.

AIM: To detect blood withdrawal for patients with arterial blood pressure monitoring to increase patient safety and provide better sample dating. METHODS: Blood pressure information obtained from a patient monitor was fed as a real-time data stream to an experimental medical framework. This framework was connected to an analytical application which observes changes in systolic, diastolic and mean pressure to determine anomalies in the continuous data stream. Detection was based on an increased mean blood pressure caused by the closing of the withdrawal three-way tap and an absence of systolic and diastolic measurements during this manipulation. For evaluation of the proposed algorithm, measured data from animal studies in healthy pigs were used. RESULTS: Using this novel approach for processing real-time measurement data of arterial pressure monitoring, the exact time of blood withdrawal could be successfully detected retrospectively and in real-time. The algorithm was able to detect 422 of 434 (97%) blood withdrawals for blood gas analysis in the retrospective analysis of 7 study trials. Additionally, 64 sampling events for other procedures like laboratory and activated clotting time analyses were detected. The proposed algorithm achieved a sensitivity of 0.97, a precision of 0.96 and an F1 score of 0.97. CONCLUSION: Arterial blood pressure monitoring data can be used to perform an accurate identification of individual blood samplings in order to reduce sample mix-ups and thereby increase patient safety.

Development and investigation of a magnetic resonance imaging-compatible microlens-based optical detector.

A noncontact optical detector for in vivo imaging has been developed that is compatible with magnetic resonance imaging (MRI). The optical detector employs microlens arrays and might be classified as a plenoptic camera. As a resulting of its design, the detector possesses a slim thickness and is self-shielding against radio frequency (RF) pulses. For experimental investigation, a total of six optical detectors were arranged in a cylindrical fashion, with the imaged object positioned in the center of this assembly. A purposely designed RF volume resonator coil has been developed and is incorporated within the optical imaging system. The whole assembly was placed into the bore of a 1.5 T patient-sized MRI scanner. Simple-geometry phantom studies were performed to assess compatibility and performance characteristics regarding both optical and MR imaging systems. A bimodal ex vivo nude mouse measurement was conducted. From the MRI data, the subject surface was extracted. Optical images were projected on this surface by means of an inverse mapping algorithm. Simultaneous measurements did not reveal influences from the magnetic field and RF pulses onto optical detector performance (spatial resolution, sensitivity). No significant influence of the optical imaging system onto MRI performance was detectable.

Investigating line- versus point-laser excitation for three-dimensional fluorescence imaging and tomography employing a trimodal imaging system.

The adoption of axially oriented line illumination patterns for fluorescence excitation in small animals for fluorescence surface imaging (FSI) and fluorescence optical tomography (FOT) is being investigated. A trimodal single-photon-emission-computed-tomography/computed-tomography/optical-tomography (SPECT-CT-OT) small animal imaging system is being modified for employment of point- and line-laser excitation sources. These sources can be arbitrarily positioned around the imaged object. The line source is set to illuminate the object along its entire axial direction. Comparative evaluation of point and line illumination patterns for FSI and FOT is provided involving phantom as well as mouse data. Given the trimodal setup, CT data are used to guide the optical approaches by providing boundary information. Furthermore, FOT results are also being compared to SPECT. Results show that line-laser illumination yields a larger axial field of view (FOV) in FSI mode, hence faster data acquisition, and practically acceptable FOT reconstruction throughout the whole animal. Also, superimposed SPECT and FOT data provide additional information on similarities as well as differences in the distribution and uptake of both probe types. Fused CT data enhance further the anatomical localization of the tracer distribution in vivo. The feasibility of line-laser excitation for three-dimensional fluorescence imaging and tomography is demonstrated for initiating further research, however, not with the intention to replace one by the other.

RANGE: Gene Transfer of Reversibly Controlled Polycistronic Genes.

We developed a single vector recombinant adeno-associated viral (rAAV) expression system for spatial and reversible control of polycistronic gene expression. Our approach (i) integrates the advantages of the tetracycline (Tet)-controlled transcriptional silencer tTS(Kid) and the self-cleaving 2A peptide bridge, (ii) combines essential regulatory components as an autoregulatory loop, (iii) simplifies the gene delivery scheme, and (iv) regulates multiple genes in a synchronized manner. Controlled by an upstream Tet-responsive element (TRE), both the ubiquitous chicken ß-actin promoter (CAG) and the neuron-specific synapsin-1 promoter (Syn) could regulate expression of tTS(Kid) together with two 2A-linked reporter genes. Transduction in vitro exhibited maximally 50-fold regulation by doxycycline (Dox). Determined by gene delivery method as well as promoter, highly specific tissues were transduced in vivo. Bioluminescence imaging (BLI) visualized reversible "ON/OFF" gene switches over repeated "Doxy-Cycling" in living mice. Thus, the reversible rAAV-mediated N-cistronic gene expression system, termed RANGE, may serve as a versatile tool to achieve reversible polycistronic gene regulation for the study of gene function as well as gene therapy.Molecular Therapy - Nucleic Acids (2013) 2, e85; doi:10.1038/mtna.2013.15; published online 9 April 2013.

Iterative reconstruction of projection images from a microlens-based optical detector.

A microlens-based optical detector was developed to perform small animal optical imaging. In this paper we present an iterative reconstruction algorithm yielding improved image quality and spatial resolution as compared to conventional inverse mapping. The reconstruction method utilizes the compressive sensing concept to cope with the undersampling nature of the problem. Each iteration in the algorithm contains two separate steps to ensure both the convergence of the least-square solution and the minimization of the l(1)-norm of the sparsifying transform. The results estimated from measurements, employing a Derenzo-like pattern and a Siemens star phantom, illustrate significant improvements in contrast and spatial resolution in comparison to results calculated by inverse mapping.

Theranostic cRGD-BioShuttle Constructs Containing Temozolomide- and Cy7 For NIR-Imaging and Therapy.

Innovative and personalized therapeutic approaches result from the identification and control of individual aberrantly expressed genes at the transcriptional and post-transcriptional level. Therefore, it is of high interest to establish diagnostic, therapeutic and theranostic strategies at these levels. In the present study, we used the Diels-Alder Reaction with inverse electron demand (DAR(inv)) click chemistry to prepare a series of cyclic RGD-BioShuttle constructs. These constructs carry the near-infrared (NIR) imaging agent Cy7 and the chemotherapeutic agent temozolomide (TMZ). We evaluated their uptake by and their efficacy against integrin α(v)ß(3)-expressing MCF7 human breast carcinoma cells. In addition, using a mouse phantom, we analyzed the suitability of this targeted theranostic agent for NIR optical imaging. We observed that the cyclic RGD-based carriers containing TMZ and/or Cy7 were effectively taken up by α(v)ß(3)-expressing cells, that they were more effective than free TMZ in inducing cell death, and that they could be quantitatively visualized using NIR fluorescence imaging. Therefore, these targeted theranostic agents are considered to be highly suitable systems for improving disease diagnosis and therapy.

Bayesian reconstruction strategy of fluorescence-mediated tomography using an integrated SPECT-CT-OT system.

Following the assembly of a triple-modality SPECT-CT-OT small animal imaging system providing intrinsically co-registered projection data of all three submodalities and under the assumption and investigation of dual-labeled probes consisting of both fluorophores and radionuclides, a novel multi-modal reconstruction strategy is presented in this paper aimed at improving fluorescence-mediated tomography (FMT). The following reconstruction procedure is proposed: firstly, standard x-ray CT image reconstruction is performed employing the FDK algorithm. Secondly, standard SPECT image reconstruction is performed using OSEM. Thirdly, from the reconstructed CT volume data the surface boundary of the imaged object is extracted for finite element definition. Finally, the reconstructed SPECT data are used as a priori information within a Bayesian reconstruction framework for optical (FMT) reconstruction. We provide results of this multi-modal approach using phantom experimental data and illustrate that this strategy does suppress artifacts and facilitates quantitative analysis for optical imaging studies.

Geometrical co-calibration of a tomographic optical system with CT for intrinsically co-registered imaging.

A mathematical approach for geometric co-calibration of a dual-modal small-animal imaging system is presented. The system comprises an optical imaging setup for in vivo bioluminescence and fluorescence detection, as well as an x-ray CT, both mounted on a common rotatable gantry enabling fully simultaneous imaging at axially overlapping fields-of-view. Geometric co-calibration is performed once by imaging a single cylindrical light-emitting source with both modalities over 360 degrees at two axial positions, respectively. Given the three-dimensional coordinates of the source positions in the reconstructed CT volume data along with their two-dimensional locations projected at the optical detector plane, the following intrinsic system parameters are calculated: (i) the intrinsic geometric parameters of the optical detection system-five parameters for each view and (ii) the relative positional relationship between the optical and CT systems-two parameters for each view. After co-calibration is performed, experimental studies using phantoms demonstrate the high degree of intrinsic positional accuracy between the optical and CT measurements. The most important advantage of this approach is that dual-modal data fusion is accomplished without any post-registration strategies.

Image formation with a microlens-based optical detector: a three-dimensional mapping approach.

A ray-based approach that models the geometric mapping properties of a flat optical detector based on a microlens array is presented. The investigated optical detector substitutes a single-aperture lens optic for planar and tomographic data acquisition in space-constrained small-animal imaging applications. The formalism implements forward mapping of a three-dimensional object volume onto a two-dimensional sensor surface as well as the backprojection (inverse mapping) of acquired sensor data sets. The object focus distance is the sole free parameter for the inverse mapping. By variation of the object focus distance, arbitrary object surface areas within the computed object images can be focused. The inverse mapping algorithm was applied to an experimentally acquired sensor data set from a three-dimensional phantom. The results are compared with focal point image formation.

Intensity of androgen and epidermal growth factor receptor immunoreactivity in samples of radical prostatectomy as prognostic indicator: correlation with clinical data of long-term observations.

PURPOSE: We analyzed the potential prognostic significance of the immunohistochemical expression of androgen and growth factor receptors determined in prostatectomy specimens of patients with prostate cancer. MATERIALS AND METHODS: A cohort of 211 patients with locally confined prostate cancer treated with radical prostatectomy with or without antiandrogen pretreatment between January 1, 1990 and August 31, 1996 was observed prospectively. Prostatectomy samples were processed immunohistochemically to visualize androgen and growth factor receptors, of which immunoreaction intensity was scored relative to that of positive control tissue. Clinical postoperative data were processed using the Kaplan-Meier method, log rank test, and univariate and multivariate explorative Cox modeling to evaluate the contribution to overall and relapse-free survival. RESULTS: There were statistical dependencies between the androgen receptor and epidermal growth factor receptor staining indexes. Following data stratification according to the epidermal growth factor receptor staining index the prognosis associated with a low androgen receptor staining index was worse than that with a higher androgen receptor staining index. Cox regression analysis for relapse-free survival confirmed that the risk factors low androgen receptor and increased epidermal growth factor receptor staining were associated with significantly increased relative risk. Univariate Kaplan-Meier analysis showed that patients with grade 3 carcinoma had a worse prognosis than those with better differentiated carcinoma, whereas antiandrogen pretreatment had no influence on overall survival or relapse-free survival. CONCLUSIONS: Using a multivariate proportional hazards regression model for data on a cohort of 211 patients with 68 showing relapse/progress or death from disease a low intensity of androgen receptor staining indicated a poor prognosis.

Angiostatin overexpression in Morris hepatoma results in decreased tumor growth but increased perfusion and vascularization.

UNLABELLED: Growth of malignant tumors is dependent on sufficient blood supply. Thus, inhibition of tumor angiogenesis is emerging as a promising target in the treatment of malignancies. Human angiostatin (hANG) is one of the most potent inhibitors of endothelial cell proliferation, angiogenesis, and tumor growth in vivo. However, its mechanisms operating in vivo are not well understood. METHODS: To obtain more information about functional changes in the angiogenic process, we established Morris hepatoma (MH3924A) cell lines expressing hANG (hANG-MH3924A). The effects of hANG expression on proliferation and apoptosis of human umbilical vein endothelial cells (HUVECs) were measured in coculture experiments in vitro. To evaluate changes in tumor perfusion and blood volume, H2 15O and 68Ga-DOTA-albumin (DOTA is 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid) were used for PET studies in vivo. Additionally, immunohistologic quantification of vascularization, apoptosis, and proliferation as well as gene array analyses were performed. RESULTS: Our in vitro experiments demonstrate reduced proliferation and increased apoptosis in HUVECs when being cocultured with hANG-MH3924A. In support, tumor growth of hANG-MH3924A is diminished by 95% in vivo. However, tumor perfusion and blood volume are increased in hANG-MH3924A corresponding to an increased microvessel density. Furthermore, hANG-transfected tumors show changes in expression of genes related to apoptosis, stress, signal transduction, and metabolism. CONCLUSION: hANG expression leads to inhibition of tumor growth, increased apoptosis, and changes in the expression of multiple genes involved in stress reactions, signal transduction, and apoptosis, which indicates a multifactorial reaction of tumors. An enhanced microvessel density is seen as part of these reactions and is associated with increased perfusion as measured by PET.

Comparison of noncontact and fiber-based fluorescence-mediated tomography.

We present a comparative experimental phantom study of fiber-based and noncontact fluorescence tomography with respect to quantitation and localization of reconstructed fluorescent inclusions in turbid media such as tissue. Noncontact acquisition is usually considered potentially superior to fiber-based techniques because of the availability of a large number of detector readouts through a CCD. Our results indicate, however, that noncontact acquisition itself might improve the quality of reconstructions significantly, even without increasing the number of detectors and thus keeping the inverse problem moderately complex.