David W. Meer

Learn More
Treating moving targets using a scanning gantry for proton therapy is a promising but very challenging, not yet clinically demonstrated treatment modality. The interference of organ motion with the sequence of the beam delivery produces uncontrolled dose inhomogeneities within the target. One promising approach to overcome this difficulty is to increase the(More)
This paper examines the stability of the exible-object impedance c ontroller when coupled to an arbitrary passive environment. A simple representative system is developed to study the problem based on phenomena observed in a more c omplex, experimental system. Analysis of this representative system leads to several conclusions regarding factors that limit(More)
Organ motion is one of the major obstacles in radiotherapy and charged particle therapy. Even more so, the theoretical advantages of dose distributions in scanned ion beam therapy may be lost due to the interplay between organ motion and beam scanning. Several techniques for dealing with this problem have been devised. In re-scanning, the target volume is(More)
In order to be able to treat mobile tumours with active, scanned proton therapy, adequate motion mitigation techniques have to be applied. Re-scanning is such an approach, where the interplay effect between tumour motion and treatment delivery is statistically smeared out. Different re-scanning methods have been used for the irradiation of a spherical(More)
— The electron-proton collider HERA is being upgraded to provide higher luminosity from the end of the year 2001. In order to enhance the selectivity on exclusive processes a Fast Track Trigger (FTT) with high momentum resolution is being built for the H1 Collaboration. The FTT will perform a 3-dimensional reconstruction of curved tracks in a magnetic field(More)
In proton radiation therapy nuclear reactions of high-energy protons hitting beam line components (e.g. colli-mators or other beam shaping devices) lead to the production of secondary neutrons which may result in significant neutron dose equivalent values (typically of the order of mSv per treatment Gy), depending on the treatment techniques [1]. For(More)
Line scanning represents a faster and potentially more flexible form of pencil beam scanning than conventional step-and-shoot irradiations. It seeks to minimize dead times in beam delivery whilst preserving the possibility of modulating the dose at any point in the target volume. Our second generation proton gantry features irradiations in line scanning(More)
A search for squarks in ¡-parity violating supersymmetry is performed in ¢ ¤ £ ¦ ¥ collisions at HERA at a centre of mass energy of § © ¨ ¨ GeV, using H1 data corresponding to an integrated luminosity of § © pb ¦. The direct production of single squarks of any generation in positron-quark fusion via a Yukawa coupling is considered, taking into account(More)
Mitigation of organ motion in active, scanning proton therapy is a challenge. One of the easiest methods to implement is re-scanning, where a treatment plan is applied several times with accordingly smaller weights. As a consequence, motion effects are averaged out. For discrete spot scanning, a major drawback of this method is the treatment time, which(More)