This is LIP’s core project in instrumentation for radiation therapy, and is developed in partnership with one Portuguese Oncology Institute, the Hospital of the University of Coimbra, and several medical research centers. The aim is to improve radiotherapy by optimizing the treatment in near real time, so that the irradiation can better accommodate the tumor and spare surrounding healthy tissue. To do this, we use  X- or gamma-rays emitted orthogonally to the treatment beam.

The OR Imaging technique may be divided into two main branches: OrthoCT (orthogonal computer tomography) for monitoring radiotherapy (high-energy x-rays); and O-PGI (orthogonal prompt-gamma imaging) for monitoring proton therapy. The LIP team pursues the two lines of research.

As an example of recent progress, the results of the analysis of a cavity irradiated inside an acrylic, cylindrical phantom using a small-scale OrthoCT system recently proved for the first time that it is possible to obtain images of the interior of an object without rotating the X-ray source. As for O-PGI studies, a multi-leaf collimator has been fully optimized using Geant4 simulation and our own reconstruction routines. The optimization was based on the analysis of images obtained after the irradiation of the NCAT phantom (cardiac-torso anthropomorphic phantom) with realistic, therapeutic proton beams. The most difficult of the three scenarios considered was the irradiation of the pituitary gland. Here, edematous tissue may account for a Bragg peak shift as small as 2 mm, which the O-PGI system was able to discriminate clearly. Work is now ongoing in order to devise an optimum crystal granularity and positioning so that the 2-mm resolving power is maintained with a realistic O-PGI system. Organ motion (e.g. lung) and vertebra motion in pediatric total body irradiation will also be analyzed via Monte Carlo simulations.

Photos

Contacts

Group Leader:  

Paulo Crespo

crespo@lip.pt