Innovative thin silicon detectors for monitoring of therapeutic proton beams: preliminary beam tests

To fully exploit the physics potentials of particle therapy in delivering doses with high accuracy and selectivity, charged particle therapy needs further improvement. To this scope, a multidisciplinary project (MoVeIT) of the Italian National Institute for Nuclear Physics (INFN) aims at translating research in charged particle therapy into clinical outcomes. New models in the treatment planning system are being developed and validated, using dedicated devices for beam characterization and monitoring in radiobiological and clinical irradiations. Innovative silicon detectors with an internal gain layer (LGAD) represent a promising option, overcoming the limits of currently used ionization chambers. Two devices are being developed: one to directly count individual protons at high rates, exploiting the large signal-to-noise ratio and fast collection time in small thicknesses (1ns in 50 μm) of LGADs, the second to measure the beam energy with time-of-flight techniques, using LGADs optimized for excellent time resolutions (Ultra-Fast Silicon Detectors, UFSDs). The preliminary results of the first beam tests with a therapeutic beam will be presented and discussed

Method and system for the automatic recognition of lesions in a set of breast magnetic resonance images

A method of identification of potential lesions of a breast from tomographic image datasets of a chest region of a patient, the- datasets comprising a plurality of voxels (2) each having an intensity value, the images including a region of interest (10) which comprises at least one breast (6). The method comprises the steps of: acquiring a set of images after the administration of a contrast agent to the patient; normalizing (254) the intensity of voxels (2) belonging to the region of interest (10) of the acquired images according to at least one normalization factor; classifying (255) each of the normalized voxels (2) on the basis of a classification criterion, in such a way as to identify regions (40) representing potential lesions. The method is characterized in that the normalization factor is based on normalization voxels (2) corresponding to an anatomical structure (34), the normalization voxels (2) having intensity values enhanced due to the administration of the contrast agent

Temporal Decrease of Trivalent Chromium Concentration in a Standardized Algal Culture Medium: Experimental Results and Implications for Toxicity Evaluation

The fate of two trivalent chromium salts (nitrate and chloride) in ISO algal culture medium was followed over 72h; i.e., the typical duration of algal toxicity tests. Fifty percent of the initial Cr spikes was lost from the solutions by 24h, with losses up to 90% after 72h. Monitoring of the temporal variability of Cr(III) concentrations in algal culture media appears necessary to better characterize the toxicity of trivalent chromium to alga

Performance of a fully automatic lesion detection system for breast DCE-MRI

PURPOSE: To describe and test a new fully automatic lesion detection system for breast DCE-MRI. MATERIALS AND METHODS: Studies were collected from two institutions adopting different DCE-MRI sequences, one with and the other one without fat-saturation. The detection pipeline consists of (i) breast segmentation, to identify breast size and location; (ii) registration, to correct for patient movements; (iii) lesion detection, to extract contrast-enhanced regions using a new normalization technique based on the contrast-uptake of mammary vessels; (iv) false positive (FP) reduction, to exclude contrast-enhanced regions other than lesions. Detection rate (number of system-detected malignant and benign lesions over the total number of lesions) and sensitivity (system-detected malignant lesions over the total number of malignant lesions) were assessed. The number of FPs was also assessed. RESULTS: Forty-eight studies with 12 benign and 53 malignant lesions were evaluated. Median lesion diameter was 6 mm (range, 5-15 mm) for benign and 26 mm (range, 5-75 mm) for malignant lesions. Detection rate was 58/65 (89%; 95% confidence interval [CI] 79%-95%) and sensitivity was 52/53 (98%; 95% CI 90%-99%). Mammary median FPs per breast was 4 (1st-3rd quartiles 3-7.25). CONCLUSION: The system showed promising results on MR datasets obtained from different scanners producing fat-sat or non-fat-sat images with variable temporal and spatial resolution and could potentially be used for early diagnosis and staging of breast cancer to reduce reading time and to improve lesion detection. Further evaluation is needed before it may be used in clinical practice

Fluence Beam Monitor for High-Intensity Particle Beams Based on a Multi-Gap Ionization Chamber and a Method for Ion Recombination Correction

This work presents the tests of a multi-gap detector (MGD), composed of three parallel-plate ionization chambers (ICs) with different gap widths, assembled to prove the capability of correcting for charge volume recombination which is expected to occur when high fluence rates are delivered. Such beam conditions occur with a compact accelerator for charged particle therapy developed to reduce the costs, to accomplish faster treatments and to exploit different beam delivery techniques and dose rates as needed, for example, for range modulation and FLASH irradiations, respectively. The MGD was tested with carbon ions at the Centro Nazionale di Adroterapia Oncologica (CNAO Pavia, Italy), and with protons in two different beam lines: at Bern University Hospital with continuous beams and at the Laboratori Nazionale del Sud (Catania, Italy) of the Italian National Center of Nuclear Physics (INFN) with pulsed beams. For each accelerator, we took measurements with different beam intensities (up to the maximum rate of ionization achievable) and changed the detector bias voltage (V) in order to study the charge collection efficiency. Charge recombination models were used to evaluate the expected collected charge and to measure the linearity of the rate of ionization with the beam fluence rate. A phenomenological approach was used to determine the collection efficiency (f1) of the chamber with thinnest gap from the relative efficiencies, f1/f2 and f1/f3, exploiting the condition that, for each measurement, the three chambers were exposed to the same rate of ionization. Results prove that two calibration curves can be determined and used to correct the online measurements for the charge losses in the ICs for recombination