Identification of Stylosanthes guianensis varieties using molecular genetic analysis

Molecular genetic diversity and population structure analysis were used to clarify the controversial botanical classification of Stylosanthes guianensis. The accessions were clustered in nine groups, each of which was mainly composed of only one of the four botanical varieties

Detection of mixed-range proton pencil beams with a prompt gamma slit camera

With increasing availability of proton and particle therapy centers for tumor treatment, the need for in vivo range verification methods comes more into the focus. Imaging of prompt gamma rays emitted during the treatment is one of the possibilities currently under investigation. A knife-edge shaped slit camera was recently proposed for this task and measurements proved the feasibility of range deviation detection in homogeneous and inhomogeneous targets. In the present paper, we concentrate on laterally inhomogeneous materials, which lead to range mixing situations when crossed by one pencil beam: different sections of the beam have different ranges. We chose exemplative cases from clinical irradiation and assembled idealized tissue equivalent targets. One-dimensional emission profiles were obtained by measuring the prompt gamma emission with the slit camera. It could be shown that the resulting range deviations can be detected by evaluation of the measured data with a previously developed range deviation detection algorithm. The retrieved value, however, strongly depends on the target composition, and is not necessarily in direct relation to the ranges of both parts of the beam. By combining the range deviation detection with an analysis of the slope of the distal edge of the measured prompt gamma profile, the origin of the detected range deviation, i.e. the mixed range of the beam, is also identified. It could be demonstrated that range mixed prompt gamma profiles exhibit less steep distal slopes than profiles from beams traversing laterally homogeneous material. For future application of the slit camera to patient irradiation with double scattered proton beams, situations similar to the range mixing cases are present and results could possibly apply

Measurement of prompt gamma profiles in inhomogeneous targets with a knife-edge slit camera during proton irradiation

Proton and ion beam therapies become increasingly relevant in radiation therapy. To fully exploit the potential of this irradiation technique and to achieve maximum target volume conformality, the verification of particle ranges is highly desirable. Many research activities focus on the measurement of the spatial distributions of prompt gamma rays emitted during irradiation. A passively collimating knife-edge slit camera is a promising option to perform such measurements. In former publications, the feasibility of accurate detection of proton range shifts in homogeneous targets could be shown with such a camera. We present slit camera measurements of prompt gamma depth profiles in inhomogeneous targets. From real treatment plans and their underlying CTs, representative beam paths are selected and assembled as one-dimensional inhomogeneous targets built from tissue equivalent materials. These phantoms have been irradiated with monoenergetic proton pencil beams. The accuracy of range deviation estimation as well as the detectability of range shifts is investigated in different scenarios. In most cases, range deviations can be detected within less than 2 mm. In close vicinity to low-density regions, range detection is challenging. In particular, a minimum beam penetration depth of 7 mm beyond a cavity is required for reliable detection of a cavity filling with the present setup. Dedicated data post-processing methods may be capable of overcoming this limitation

Early Detection of Agglomeration in Conical Spouted Beds Using Recurrence Plots

The agglomeration of particles in a conical spouted bed was investigated using a recurrence plot (RP) and recurrence quantification analysis (RQA) of the pressure fluctuations (PFs) and acoustic emission (AE) signals. Experiments were carried out in a 45° conical spouted bed with sugar particles (dp = 720 μm; ?p = 1580 kg/m3). Water was sprayed incrementally into the bed to produce agglomerates during the operation. Several recurrence quantification parameters were calculated during the agglomeration process, and the most suitable ones were chosen for early prediction of the agglomeration in the bed. The results show that recurrence rate, determinism, and laminarity of PFs and AE signals increase during the agglomeration process, which indicate that bed behavior becomes more periodic and deterministic in nature. Additional examination of the RQA parameters show that AE signals are substantially more sensitive to the hydrodynamic changes that occur in the bed, compared to those of PFs, and therefore can detect changes earlier, with more accuracy.</p

Prompt gamma imaging with a slit camera for real-time range control in proton therapy: Experimental validation up to 230 MeV with HICAM and development of a new prototype

Treatments delivered by proton therapy are affected by uncertainties on the range of the beam within the patient. To reduce these margins and deliver safer treatments, different projects are currently investigating real-time range control by imaging prompt gammas emitted along the proton tracks in the patient. This study reports on the development and test of a prompt gamma camera using a slit collimator to obtain a 1-dimensional projection of the beam path on a scintillator detector. A first prototype slit camera using the HICAM gamma detector, originally developed for low-energy gamma-ray imaging in nuclear medicine and modified for this purpose, was tested successfully up to 230 MeV beam energy. Results now confirm the potential of this concept for real-time range monitoring with millimeter accuracy in pencil beam scanning mode for the whole range of clinical energies. With the experience gained, a new prototype is under study for clinical beam currents. In this work, we present both the profiles obtained at 230 MeV using HICAM and the description of the new gamma camera prototype design