Integration of functional imaging and tumor motion in intensity modulated radiation therapy for non-small cell lung cancer

Conventional treatment of locally advanced non-small cell lung cancer patients with concomitant chemo-radiation achieves poor tumor local control rates and strongly affects the patient outcome. Although it appears essential to implement dose intensification strategies, this remains challenging due to the proximity of highly radiosensitive organs, which may result in unacceptable toxicities. A potential solution would be to escalate the dose in restricted areas within the tumor identified as potentially radio-resistant, by functional imaging (FDG-PET), and using high conformal radiation treatment delivery and optimized tumor motion management. This concept mainly requires an accurate definition of the target volumes in order to spare healthy tissues. In this context, we validated a gradient-based segmentation method for primary lung tumor definition on FDG-PET imaging by comparison with surgical specimens. Then, in a clinical trial, we assessed how an individualized and non-uniform escalated dose based on FDG-PET images would affect the tumor local control and the radio-induced toxicities. Finally, we investigated the tumor motion caused by breathing and studied the feasibility of the mid-position strategy in helical radiation treatment for lung tumors.La radio-chimiothérapie concomitante est le traitement de choix pour les patients atteints de cancer bronchique localement avancé non à petites cellules. Cependant, le taux de récidive locale après un tel traitement reste élevé et affecte négativement le pronostic de ces patients. Bien que les stratégies d’intensification de dose paraissent essentielles, celles-ci sont limitées par la proximité des organes sains. Par conséquent, une augmentation de la dose sur une partie restreinte de la tumeur, identifiée par l’imagerie fonctionnelle FDG-PET, associée à une prise en charge optimale du mouvement tumoral, pourrait améliorer le contrôle tumoral local tout en limitant les toxicités. Cette approche nécessite une délimitation rigoureuse des volumes tumoraux afin d’épargner les tissus sains. C’est dans ce contexte que ce travail, scindé en trois phases, s'inscrit. Nous avons d’abord validé une méthode de délimitation automatique des tumeurs pulmonaires basée sur les gradients d’intensité dans les images FDG-PET par comparaison avec les pièces chirurgicales de lobectomie. Ensuite, dans le cadre d'une étude clinique, nous avons évalué l’impact d’une augmentation individualisée de la dose guidée par l’imagerie FDG-PET sur le contrôle tumoral local et sur les toxicités radio-induites. Enfin, nous avons étudié le mouvement tumoral lié à la respiration et intégré une stratégie, nommée mid-position, dans la planification du traitement des tumeurs pulmonaires, délivré de manière hélicoïdale.(MED - Sciences médicales) -- UCL, 201

Influence de la cécité sur la perception de l'espace.

Thèse de doctorat -- Université catholique de Louvain, 198

Abilities and strategies of blind and sighted subjects in visuo-spatial imagery.

An active visuo-spatial memory task was used in order to determine the characteristics of mental imagery in subjects with and without visual experience. Subjects were instructed to generate a mental representation of verbally presented 2D patterns that were placed in a grid and to indicate how many pattern elements were in corresponding positions in the two halves of the grid according to a specific grid axis (vertical or horizontal). Unexpectedly, results showed a similar performance in early blind, late blind and sighted subjects. However, subjects' debriefing showed that the three groups used different strategies. The sighted and the late blind subjects took advantage of a visuo-spatial strategy. They generated a mental image of the matrix and they simplified this image to maintain only the relevant information in memory. In contrast, the early blind subjects encoded each pattern element by its location in a (X,Y) coordinate system without visual representation. This indicates that both early and late blind subjects are able to perform an active visuo-spatial imagery task as well as sighted subjects although they use different strategies

The role of visual experience in mental imagery

The mental imagery of participants who became blind early in life (EB participants), participants who became blind later in life (LB participants), and sighted participants was compared in two experiments. In the first experiment, the participants were asked to image common objects and to estimate how far away these objects appeared in their image. In the second experiment, the participants were asked to point to the left and right sides of three objects, imaged at three increasing distances. The LB participants' performance of the tasks in both experiments was similar to that of the sighted participants, whereas the performance of the EB participants differed. The results reflect the close relationship between the development of visual perception and the properties of images

Imaging after radiation therapy of thoracic tumors.

Radiation-induced lung disease (RILD) is frequent after therapeutic irradiation of thoracic malignancies. Many technique-, treatment-, tumor- and patient-related factors influence the degree of injury sustained by the lung after irradiation. Based on the time interval after the completion of the treatment RILD presents as early and late features characterized by inflammatory and fibrotic changes, respectively. They are usually confined to the radiation port. Though the typical pattern of RILD is easily recognized after conventional two-dimensional radiation therapy (RT), RILD may present with atypical patterns after more recent types of three- or four-dimensional RT treatment. Three atypical patterns are reported: the modified conventional, the mass-like and the scar-like patterns. Knowledge of the various features and patterns of RILD is important for correct diagnosis and appropriate treatment. RILD should be differentiated from recurrent tumoral disease, infection and radiation-induced tumors. Due to RILD, the follow-up after RT may be difficult as response evaluation criteria in solid tumours (RECIST) criteria may be unreliable to assess tumor control particularly after stereotactic ablation RT (SABR). Long-term follow-up should be based on clinical examination and morphological and/or functional investigations including CT, PET-CT, pulmonary functional tests, MRI and PET-MRI

Use of an ultrasonic echolocation prosthesis by early visually deprived cats.

The aim of this study was to design an animal model of sensory substitution in the case of blindness. Six kittens were binocularly enucleated; as adults, they were fitted with an ultrasonic echolocation prosthesis. This device provided the animals with auditory signals that coded distance and direction of obstacles. Animals were trained by operant conditioning to use the prosthesis in various behavioral situation. The results showed that visually deprived animals tried to solve the task using natural information and that they only used artificial information provided by the prosthesis when they were unable to succeed with natural cues. Under these conditions, it was asserted that in a jumping test these animals evaluated depth by means of the prosthesis; in a locomotion task in a maze, it was also demonstrated that they could use the prosthesis for avoiding obstacles

LUPUS ERYTHEMATEUX SYSTEMIQUE ET DEPOTS DERMIQUES ORGANISES

SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe

Occipito-parietal cortex activation during visuo-spatial imagery in early blind humans.

Using positron emission tomography, regional cerebral blood flow was studied in five early blind and five control volunteers during visuo-spatial imagery. Subjects were instructed to generate a mental representation of verbally provided bidimensional patterns that were placed in a grid and to assess pattern symmetry in relation to a grid axis. This condition was contrasted with a verbal memory task. Cerebral activation in both groups was similar during the visuo-spatial imagery task. It involved the precuneus (BA 7), superior parietal lobule (BA 7), and occipital gyrus (BA 19). These results are in accordance with previous studies conducted in sighted subjects that indicated that the same occipito-parietal areas are involved in visual perception as well as in mental imagery dealing with spatial components. The dorsal pathway seems to be involved in visuo-spatial imagery in early blind subjects, indicating that this pathway undergoes development in the absence of vision

Pattern recognition with the optic nerve visual prosthesis.

A volunteer with retinitis pigmentosa and no residual vision was chronically implanted with an optic nerve electrode connected to an implanted neurostimulator and antenna. An external controller with telemetry was used for electrical activation of the nerve which resulted in phosphene perception. Open-loop stimulation allowed the collection of phosphene attributes and the ability to elicit perception of simple geometrical patterns. Low perception thresholds allowed for large current intensity range within safety limits. In a closed-loop paradigm, the volunteer was using a head-worn video camera to explore a projection screen. The volunteer underwent performance evaluation during the course of a training program with 45 simple patterns. After learning, the volunteer reached a recognition score of 63% with a processing time of 60 s. Mean performance in orientation discrimination reached 100% with a processing time of 8 s