On the Effect of DCE MRI Slice Thickness and Noise on Estimated Pharmacokinetic Biomarkers – A Simulation Study

Simulation of a dynamic contrast-enhanced magnetic resonance imaging (DCE MRI) multiple sclerosis brain dataset is described. The simulated images in the implemented version have 1×1×1mm3 voxel resolution and arbitrary temporal resolution. Addition of noise and simulation of thick-slice imaging is also possible. Contrast agent (Gd-DTPA) passage through tissues is modelled using the extended Tofts-Kety model. Image intensities are calculated using signal equations of the spoiled gradient echo sequence that is typically used for DCE imaging. We then use the simulated DCE images to study the impact of slice thickness and noise on the estimation of both semi- and fully-quantitative pharmacokinetic features. We show that high spatial resolution images allow significantly more accurate modelling than interpolated low resolution DCE images.acceptedVersio

Illumination profile characterization of a light applicator

International audienc

On image segmentation methods applied to glioblastoma: state of art and new trends

International audienceBecause of high heterogeneity and invasiveness, treatment of GlioBlastoma Multiform (GBM) still remains a complex challenge. Several recent advanced therapies have improved precision of treatment deliverance. Multimodality imaging plays an increasingly important role in this process and images segmentation has become an essential part of the pipeline of standard treatment planning system. With the sophistication of multimodality information, the development of reliable and robust segmentation algorithms to overcome manual segmentation and optimize targeted treatment is highly expected. In this paper, we first introduce targeted therapies applied in the GBM clinical care, from routine or research. Different segmentation methods from state of the art are highlighted to achieve GBM delineation. New trends in GBM segmentation such as machine learning and multimodal features are discussed. These additional frameworks may achieve segmentation with refining capacities, active tumour probability mapping and, even, tumour relapse prediction capacities

5-ALA Photodynamic Therapy in Neurosurgery, Towards the Design of a Treatment Planning System: A Proof of Concept

International audiencePurpose: Glioblastoma (GBM) treatment still remains a complex challenge. Among alternatives or adjuvant therapies, photodynamic therapy (5-ALA PDT) appears to be a promising approach. 5-ALA PDT can be delivered intraoperatively, early after tumour resection, or interstitially according to brain tumour location. A treatment planning system was designed to manage dosimetry issues before PDT delivery.Methods: The TPS was developed according to a specific workflow from stereotactic image registration to light fluence rate modelling. Here, we describe a proof of concept of a treatment planning system (TPS) dedicated to interstitial 5-ALA PDT. This tool enables the planning of a whole treatment in surgical stereotactic conditions. Stereotactic registration and dosimetry components are detailed and evaluated. The registration process is compared to a commercial solution (Leksell Gamma Plan®, Elekta®, Sweden) defined as the ground truth and dosimetry model implemented in our TPS and is compared to numerical simulations.Results: Registration achieved a sub-millimetric mean relative error that matched the standard MRI resolution. Dosimetry comparison showed a negligible error between analytical and numerical models and enabled a validation of the dosimetry algorithm implemented.Conclusions: A treatment planning system was designed to achieve 5-ALA PDT simulations before the patients underwent surgery. Similarly, for radiation therapy, we proposed a system to plan and evaluate the 5-ALA PDT dosimetry for optimizing treatment delivery. Although this system remains to be perfected, this preliminary work aimed to demonstrate the feasibility of planning 5-ALA PDT treatments in stereotactic conditions. Future improvements will mainly focus on the optimization of the treatment delivery, automatic segmentation and GPU-accelerated Monte-Carlo management to take into account GBM tissue heterogeneity

Latest technologies of homogeneous light distribution for photodynamic therapy of non-planar anatomical surfaces

International audiencePhotodynamic therapy remains a promising treatment of precancerous and cancerous lesions in several medical fields (dermatology , gynaecology, oncology and so on.. .). To deliver an optimized light dose and prevent over – or – under treatment, a controlled, homogeneous and stable light delivery is one of the major concerns. Currently, most of sources used for photodynamic therapy do not fit with the complexity of human anatomy, and cannot ensure the homogeneity of the light delivery [1]. To overcome this issue, the development of flexible light sources could be an interesting solution. In addition to ensure a compliant therapy, the development of these technologies could provide therapeutic solutions for non-planar anatomical surfaces, such as pleural cavity, curved surfaces, and corporal extremities [2]. This communication aims to describe the different methods of optical fibres integration into a flexible structure, in order to improve light illumination during PDT. Initially, optical fibres were developed to transmit the input light energy with minimum losses to their distal end. Usually called Dis-tal End Emitting Optical Fibres (DEEOF), they use, under several conditions, the total reflection of the light property which confines light rays inside the core and propagates them along the fibre [3]. Based on the DEEOF properties, several methods were developed to enable the light emission not only distal, but through the side-surface of optical fibres. The side emission effect is the result of the light leaking from the core to the external surface of the fibre. The integration of these Side Emitting Optical Fibres (SEOF) into a flexible structures seems to be one of the best technical options to overcome the lack of homogeneity of the light distribution in PDT. Several techniques will be presented among the winding of a SEOF around a flexible material, the embroidery within a thin textile substrate, the integration of SEOF within woven and knitted structures [4]

EP-1694: DW-MRI as a predictor of tumor response to hypofractionated stereotactic boost for prostate cancer

International audienc

Real-time light dosimetry for intra-cavity photodynamic therapy

International audiencePhotodynamic therapy (PDT) is an emerging technic in oncology. The success by the achievement of the desired therapeutic effect of a PDT procedure relies on the accurate photosensitizer (PS) concentration distribution in tissues and on the homogeneous light delivery. To resolve the last issue in presence of the variability in target geometries (volume, elastic, solid, hollow organs and cavities), we propose a novel approach based on the light distribution modeling combined with spatial localization of the light applicator and real time display of the applied dose using computed tomogra-phy (CT) images. CT scans of the thorax cavity are acquired before the surgery to construct the thorax cavity. Fiducial markers consisting of 5 mm diameter capsule filled with paraffin oil are attached to the patient around the region to be imaged. A spatial registration is applied to compute a transformation between the patient position in the operating room and the images. The light distribution profile around the diffusing tip of the light applicator was characterized by two complementary methods: direct measurements of the light power using sensors and dose distribution characterization using a light sensitive camera. This model takes into account the absorption and the diffusion around the applicator. For the real time localiza-tion of the light applicator, an electromagnetic 3D tracking device is used to track the applicator movements. This tracking system is composed of a control unit with plugs to connect a transmitter and up to 4 six degrees-of-freedom sensors. By combining the model and the positions, a complete 3D light dose distribution is estimated and displayed on the CT images. The validation of the approach is realized in the conditions of a protocol of malignant pleural mesothelioma treatment. To compare and evaluate our estimated light dose, we operate direct measurements of the light power, as it was done in the work by Zhu et al. [1], using sensors that consist of isotropic probes able of collecting lights from different direction. All them are connected to a dosimetry system composed of an optical multiplexer, an optical power-meter, and a home-made software. Preliminary experiments of the method are conducted on a thorax phantom. The surface of the chest wall of the phantom was 1270 cm 2. With a laser emitting at 3 W, the treatment was performed for 10 nm. As results, differences less than 10% were observed between the measured values and the model based estimations. Reference [1] T

Photodynamic therapy for actinic keratoses: How effective are two white led light doses compared with two standard light doses?

International audienc