Ion beam therapy is a rapidly growing technique for tumor radiation therapy. Ions allow for a high dose deposition in the tumor region, while sparing the surrounding healthy tissue. For this reason, the highest possible accuracy in the calculation of dose and its spatial distribution is required in treatment planning. On one hand, commonly used treatment planning software solutions adopt a simplified beam-body interaction model by remapping pre-calculated dose distributions into a 3D water-equivalent representation of the patient morphology. On the other hand, Monte Carlo (MC) simulations, which explicitly take into account all the details in the interaction of particles with human tissues, are considered to be the most reliable tool to address the complexity of mixed field irradiation in a heterogeneous environment. However, full MC calculations are not routinely used in clinical practice because they typically demand substantial computational resources. Therefore MC simulations are usually only used to check treatment plans for a restricted number of difficult cases. The advent of general-purpose programming GPU cards prompted the development of trimmed-down MC-based dose engines which can significantly reduce the time needed to recalculate a treatment plan with respect to standard MC codes in CPU hardware. In this work, we report on the development of fred, a new MC simulation platform for treatment planning in ion beam therapy. The code can transport particles through a 3D voxel grid using a class II MC algorithm. Both primary and secondary particles are tracked and their energy deposition is scored along the trajectory. Effective models for particle-medium interaction have been implemented, balancing accuracy in dose deposition with computational cost. Currently, the most refined module is the transport of proton beams in water: single pencil beam dose-depth distributions obtained with fred agree with those produced by standard MC codes within 1-2% of the Bragg peak in the therapeutic energy range. A comparison with measurements taken at the CNAO treatment center shows that the lateral dose tails are reproduced within 2% in the field size factor test up to 20 cm. The tracing kernel can run on GPU hardware, achieving 10 million primary [Formula: see text] on a single card. This performance allows one to recalculate a proton treatment plan at 1% of the total particles in just a few minutes.

A novel radioguided surgery (RGS) technique for cerebral tumors using β − radiation is being developed. Checking for a radiotracer that can deliver a β − emitter to the tumor is a fundamental step in the deployment of such a technique. This paper reports a study of the uptake of 90 Y-DOTATOC in meningiomas and high-grade gliomas (HGGs) and a feasibility study of the RGS technique in these types of tumor. Estimates were performed assuming the use of a β − probe under development with a sensitive area 2.55 mm in radius to detect 0.1-mL residuals. Methods: Uptake and background from healthy tissues were estimated on 68 Ga-DOTATOC PET scans of 11 meningioma patients and 12 HGG patients. A dedicated statistical analysis of the DICOM images was developed and validated. The feasibility study was performed using full simulation of emission and detection of the radiation, accounting for the measured uptake and background rate. Results: All meningioma patients but one with an atypical extracranial tumor showed high uptake of DOTATOC. In terms of feasibility of the RGS technique, we estimated that by administering a 3 MBq/kg activity of radiotracer, the time needed to detect a 0.1-mL remnant with 5% false-negative and 1% falsepositive rates is less than 1 s. Actually, to achieve a detection time of 1 s the required activities to administer were as low as 0.2-0.5 MBq/kg in many patients. In HGGs, the uptake was lower than in meningiomas, but the tumor-to-nontumor ratio was higher than 4, which implies that the tracer can still be effective for RGS. It was estimated that by administering 3 mBq/kg of radiotracer, the time needed to detect a 0.1-mL remnant is less than 6 s, with the exception of the only oligodendroma in the sample. Conclusion: Uptake of 90 Y-DOTATOC in meningiomas was high in all studied patients. Uptake in HGGs was significantly worse than in meningiomas but was still acceptable for RGS, particularly if further research and development are done to improve the performance of the β − probe. Radi oguided surgery (RGS) helps the surgeon evaluate the completeness of a tumor resection while minimizing the amount of healthy tissue removed (1). The surgeon is provided with vital and real-time information on the location and extent of the lesion and can assess the resection margins. The technique uses a radiolabeled tracer preferentially taken up by the tumor to discriminate cancerous tissue from healthy organs, as well as a probe (2) sensitive to the emission released by the tracer to identify in real time the targeted tumor focus. The radiopharmaceutical is administered to the patient before surgery.Current clinical applications of RGS are radioimmunoguided surgery for colon cancer (3,4), complete sentinel-node mapping for malignant melanoma (5) and breast cancer (6,7), and detection of parathyroid adenoma (8) and bone tumors (such as osteoid osteoma). There are also clinical studies on applications in neuroendocrine tumors (9,10).Established methods use a combination of a g-emitting tracer with a g-radiation-detec...

Laser-driven particle acceleration, obtained by irradiation of a solid target using an ultra-intense (I > 1018 W/cm2) short-pulse (duration <1 ps) laser, is a growing field of interest, in particular for its manifold potential applications in different domains. Here, we provide experimental evidence that laser-generated particles, in particular protons, can be used for stress testing materials and are particularly suited for identifying materials to be used in harsh conditions. We show that these laser-generated protons can produce, in a very short time scale, a strong mechanical and thermal damage, that, given the short irradiation time, does not allow for recovery of the material. We confirm this by analyzing changes in the mechanical, optical, electrical, and morphological properties of five materials of interest to be used in harsh conditions.

A novel radioguided surgery (RGS) technique exploiting β − radiation has been proposed. To develop such a technique, a suitable radiotracer able to deliver a β − emitter to the tumor has to be identified. A first candidate is represented by 90 Y-labeled DOTATOC, a compound commonly used today for peptide radioreceptor therapy. The application of this β − RGS to neuroendocrine tumors (NET) requires study of the uptake of DOTATOC and its time evolution both in tumors and in healthy organs and evaluation of the corresponding performance of the technique. Methods: Uptake by lesions and healthy organs (kidneys, spleen, liver and healthy muscle) was estimated on 177 Lu-DOTATOC SPECT/CT scans of 15 patients affected by NET with different localizations, treated at IRCCS-Arcispedale Santa Maria Nuova, Reggio Emilia, Italy. For each patient, SPECT/CT images, acquired at 0.5, 4, 20, 40, and 70 h after injection, were studied. For each lesion, the tumor-tonontumor ratio (TNR) with respect to all healthy organs and its time evolution were studied. A subset of patients showing hepatic lesions was selected, and the TNR with respect to the nearby healthy tissue was calculated. By means of a Monte Carlo simulation of the probe for β − RGS, the activity that is to be administered for a successful detection was estimated lesion-by-lesion. Results: Uptake of DOTATOC on NETs maximized at about 24 h after injection. The cases of hepatic lesions showed a TNR with respect to the tumor margins compatible with the application of β − RGS. In particular, 0.1-mL residuals are expected to be detectable within 1 s with 5% false-negative and 1% false-positive by administering the patient as little as 1 MBq/kg. Conclusion: The balance between tumor uptake and metabolic washout in healthy tissue causes the TNR to increase with time, reaching its maximum after 24 h, and this characteristic can be exploited when a radiotracer with a long halflife, such as 90 Y, is used. In particular, if 90 Y-DOTATOC is used with liver NET metastases, the proposed RGS technique is believed to be feasible by injecting an activity that is one third of that commonly used for PET imaging.