Comprehensive dosimetric characterization of novel silicon carbide detectors with UHDR electron beams for FLASH radiotherapy

BACKGROUND

The extremely fast delivery of doses with ultra high dose rate (UHDR) beams necessitates the investigation of novel approaches for real-time dosimetry and beam monitoring. This aspect is fundamental in the perspective of the clinical application of FLASH radiotherapy (FLASH-RT), as conventional dosimeters tend to saturate at such extreme dose rates.

PURPOSE

This study aims to experimentally characterize newly developed silicon carbide (SiC) detectors of various active volumes at UHDRs and systematically assesses their response to establish their suitability for dosimetry in FLASH-RT.

METHODS

SiC PiN junction detectors, recently realized and provided by STLab company, with different active areas (ranging from 4.5 to 10 mm2) and thicknesses (10-20 µm), were irradiated using 9 MeV UHDR pulsed electron beams accelerated by the ElectronFLASH linac at the Centro Pisano for FLASH Radiotherapy (CPFR). The linearity of the SiC response as a function of the delivered dose per pulse (DPP), which in turn corresponds to a specific instantaneous dose rate, was studied under various experimental conditions by measuring the produced charge within the SiC active layer with an electrometer. Due to the extremely high peak currents, an external customized electronic RC circuit was built and used in conjunction with the electrometer to avoid saturation.

RESULTS

The study revealed a linear response for the different SiC detectors employed up to 21 Gy/pulse for SiC detectors with 4.5 mm2/10 µm active area and thickness. These values correspond to a maximum instantaneous dose rate of 5.5 MGy/s and are indicative of the maximum achievable monitored DPP and instantaneous dose rate of the linac used during the measurements.

CONCLUSIONS

The results clearly demonstrate that the developed devices exhibit a dose-rate independent response even under extreme instantaneous dose rates and dose per pulse values. A systematic study of the SiC response was also performed as a function of the applied voltage bias, demonstrating the reliability of these dosimeters with UHDR also without any applied voltage. This demonstrates the great potential of SiC detectors for accurate dosimetry in the context of FLASH-RT.

3D Bioprinting and Microfluidic-Based Devices for Cancer Detection and Drug Treatment: Focus on Prostate Cancer

The burden of increasing cancer incidence among the population, and, in particular, of prostate cancer in men living in highly developed countries, brings with it, on one hand, the need for new devices that allow a faster and earlier diagnosis, ideally in a non-invasive way and with low consumption of expensive reagents, and on the other the need for the assessment of new in vitro models that allow a more reliable assessment of cancer features, including its microenvironment and sensibility to different drugs. At the crossroads of these features, microfluidic devices are found. These, taking advantage of the chemical-physical properties of cells and human samples, have demonstrated great sensitivity and sensibility at an on-chip scale. Many fields of biomedical sciences have tried to exploit all their potentialities: from the detection of antigens in the early phases of the disease (when they are very low concentrated, but the treatment is more effective) to isolation and characterization of circulating tumor cells. However, the development of in vitro 3D models to better assess and comprehend the fundamental dynamics of tumor microenvironment and metastasis using 3D bioprinting techniques. The aim of the present review is to describe the potential of these two different cutting-edge technologies for the detection and treatment of prostate cancer, in the perspective of a possible future combination of them that allows scientists to fill the gaps present in the field to improve patient care and treatment.

Single-Ion Counting with an Ultra-Thin-Membrane Silicon Carbide Sensor

In recent times, ion implantation has received increasing interest for novel applications related to deterministic material doping on the nanoscale, primarily for the fabrication of solid-state quantum devices. For such applications, precise information concerning the number of implanted ions and their final position within the implanted sample is crucial. In this work, we present an innovative method for the detection of single ions of MeV energy by using a sub-micrometer ultra-thin silicon carbide sensor operated as an in-beam counter of transmitted ions. The SiC sensor signals, when compared to a Passivated Implanted Planar Silicon detector signal, exhibited a 96.5% ion-detection confidence, demonstrating that the membrane sensors can be utilized for high-fidelity ion counting. Furthermore, we assessed the angular straggling of transmitted ions due to the interaction with the SiC sensor, employing the scanning knife-edge method of a focused ion microbeam. The lateral dimension of the ion beam with and without the membrane sensor was compared to the SRIM calculations. The results were used to discuss the potential of such experimental geometry in deterministic ion-implantation schemes as well as other applications.

Microfluidic/HPLC combination to study carnosine protective activity on challenged human microglia: Focus on oxidative stress and energy metabolism

Carnosine (β-alanyl-L-histidine) is a naturally occurring endogenous peptide widely distributed in excitable tissues such as the brain. This dipeptide possesses well-demonstrated antioxidant, anti-inflammatory, and anti-aggregation properties, and it may be useful for treatment of pathologies characterized by oxidative stress and energy unbalance such as depression and Alzheimer's disease (AD). Microglia, the brain-resident macrophages, are involved in different physiological brain activities such synaptic plasticity and neurogenesis, but their dysregulation has been linked to the pathogenesis of numerous diseases. In AD brain, the activation of microglia towards a pro-oxidant and pro-inflammatory phenotype has found in an early phase of cognitive decline, reason why new pharmacological targets related to microglia activation are of great importance to develop innovative therapeutic strategies. In particular, microglia represent a common model of lipopolysaccharides (LPS)-induced activation to identify novel pharmacological targets for depression and AD and numerous studies have linked the impairment of energy metabolism, including ATP dyshomeostasis, to the onset of depressive episodes. In the present study, we first investigated the toxic potential of LPS + ATP in the absence or presence of carnosine. Our studies were carried out on human microglia (HMC3 cell line) in which LPS + ATP combination has shown the ability to promote cell death, oxidative stress, and inflammation. Additionally, to shed more light on the molecular mechanisms underlying the protective effect of carnosine, its ability to modulate reactive oxygen species production and the variation of parameters representative of cellular energy metabolism was evaluated by microchip electrophoresis coupled to laser-induced fluorescence and high performance liquid chromatography, respectively. In our experimental conditions, carnosine prevented LPS + ATP-induced cell death and oxidative stress, also completely restoring basal energy metabolism in human HMC3 microglia. Our results suggest a therapeutic potential of carnosine as a new pharmacological tool in the context of multifactorial disorders characterize by neuroinflammatory phenomena including depression and AD.

Radiation Hardness Study of Silicon Carbide Sensors under High-Temperature Proton Beam Irradiations

Silicon carbide (SiC), thanks to its material properties similar to diamond and its industrial maturity close to silicon, represents an ideal candidate for several harsh-environment sensing applications, where sensors must withstand high particle irradiation and/or high operational temperatures. In this study, to explore the radiation tolerance of SiC sensors to multiple damaging processes, both at room and high temperature, we used the Ion Microprobe Chamber installed at the Ruđer Bošković Institute (Zagreb, Croatia), which made it possible to expose small areas within the same device to different ion beams, thus evaluating and comparing effects within a single device. The sensors tested, developed jointly by STLab and SenSiC, are PIN diodes with ultrathin free-standing membranes, realized by means of a recently developed doping-selective electrochemical etching. In this work, we report on the changes of the charge transport properties, specifically in terms of the charge collection efficiency (CCE), with respect to multiple localized proton irradiations, performed at both room temperature (RT) and 500 °C.

Label-Free Enrichment of Circulating Tumor Plasma Cells: Future Potential Applications of Dielectrophoresis in Multiple Myeloma

In multiple myeloma (MM), circulating tumor plasma cells (CTPCs) are an emerging prognostic factor, offering a promising and minimally invasive means for longitudinal patient monitoring. Recent advances highlight the complex biology of plasma cell trafficking, highlighting the phenotypic and genetic signatures of intra- and extra-medullary MM onset, making CTPC enumeration and characterization a new frontier of precision medicine for MM patients, requiring novel technological platforms for their standardized and harmonized detection. Dielectrophoresis (DEP) is an emerging label-free cell manipulation technique to separate cancer cells from healthy cells in peripheral blood samples, based on phenotype and membrane capacitance that could be successfully tested to enumerate and isolate CTPCs. Herein, we summarize preclinical data on DEP development for CTPC detection, as well as their clinical and research potential.

PD-1, PD-L1 and cAMP immunohistochemical expressions are associated with worse oncological outcome in patients with bladder cancer

PURPOSE

In this study, we aimed to identify prognostic factors of cancer mortality in patients who received radical cystectomy and to identify genomic alterations in a sub-cohort of patients with locally advanced (pT3-4) and/or positive lymph nodes bladder cancer (BC).

METHODS

We collected 101 BC samples from 2010 to 2018 who previously received radical cystectomy. Immunohistochemical slides were evaluated for PPAR, cAMP, IMP3, Ki67, CDK4, POU5F1, Cyclin E and MDM2, p65, CD3, CD4, CD8, CD20, CD68, CD163, FOXP3, PD-1 and PD-L1 expression. We calculated a prognostic score (PS) based on the positivity to PD-1, PD-L1 and of cAMP (final score ranging from 0 to 3). DNA of each sample have been used for sequencing by NGS in a sub-cohort of 6 patients with locally advanced (pT3-4) and/or positive lymph nodes BC.

RESULTS

PD-1 ⁺ (HR [hazard ratio] 2.59; p = 0.04), PD-L1⁺ (HR = 6.46; p < 0.01) and cAMP⁺ (HR 3.04; p = 0.02) were independent predictors of cancer-specific mortality (CSM). Increase of PS (score = 0 as reference) was associated with CSM, 0.81 (p = 0.80), 4.72 (p = 0.01) and 10.51 (p < 0.0) for PS 1, 2 and 3, respectively. ERBB2 was the gene most frequently mutated.

CONCLUSION

BC exhibited heterogenous protein expression and variable genomic features. Identification of expression of PD-1, PD-L1 and cAMP could help in predicting oncological outcomes.

The Role of Dielectrophoresis for Cancer Diagnosis and Prognosis

Liquid biopsy is emerging as a potential diagnostic tool for prostate cancer (PC) prognosis and diagnosis. Unfortunately, most circulating tumor cells (CTC) technologies, such as AdnaTest or Cellsearch®, critically rely on the epithelial cell adhesion molecule (EpCAM) marker, limiting the possibility of detecting cancer stem-like cells (CSCs) and mesenchymal-like cells (EMT-CTCs) that are present during PC progression. In this context, dielectrophoresis (DEP) is an epCAM independent, label-free enrichment system that separates rare cells simply on the basis of their specific electrical properties. As compared to other technologies, DEP may represent a superior technique in terms of running costs, cell yield and specificity. However, because of its higher complexity, it still requires further technical as well as clinical development. DEP can be improved by the use of microfluid, nanostructured materials and fluoro-imaging to increase its potential applications. In the context of cancer, the usefulness of DEP lies in its capacity to detect CTCs in the bloodstream in their epithelial, mesenchymal, or epithelial-mesenchymal phenotype forms, which should be taken into account when choosing CTC enrichment and analysis methods for PC prognosis and diagnosis.

Silicon carbide X-ray beam position monitors for synchrotron applications

In this work, the performance of thin silicon carbide membranes as material for radiation hard X-ray beam position monitors (XBPMs) is investigated. Thermal and electrical behavior of XBPMs made from thin silicon carbide membranes and single-crystal diamond is compared using finite-element simulations. Fabricated silicon carbide devices are also compared with a 12 µm commercial polycrystalline diamond XBPM at the Swiss Light Source at the Paul Scherrer Institute. Results show that silicon carbide devices can reach equivalent transparencies while showing improved linearity, dynamics and signal-to-noise ratio compared with commercial polycrystalline diamond XBPMs. Given the obtained results and availability of electronic-grade epitaxies on up to 6 inch wafers, it is expected that silicon carbide can substitute for diamond in most beam monitoring applications, whereas diamond, owing to its lower absorption, could remain the material of choice in cases of extreme X-ray power densities, such as pink and white beams.

SiCILIA-Silicon Carbide Detectors for Intense Luminosity Investigations and Applications

Silicon carbide (SiC) is a compound semiconductor, which is considered as a possible alternative to silicon for particles and photons detection. Its characteristics make it very promising for the next generation of nuclear and particle physics experiments at high beam luminosity. Silicon Carbide detectors for Intense Luminosity Investigations and Applications (SiCILIA) is a project starting as a collaboration between the Italian National Institute of Nuclear Physics (INFN) and IMM-CNR, aiming at the realization of innovative detection systems based on SiC. In this paper, we discuss the main features of silicon carbide as a material and its potential application in the field of particles and photons detectors, the project structure and the strategies used for the prototype realization, and the first results concerning prototype production and their performance.

Analysis of the role of the particle-wall interaction on the separation efficiencies of field flow fractionation dielectrophoretic devices

In this paper we have used both analytical models and finite element simulations to analyze the role of the particle-wall dipole interaction in field-flow fractionation dielectrophoretic (FFF-DEP) devices. We identify the existence of "anomalous" regions where the dielectrophoretic response is altered, independently of the complex dielectric permittivity of the particles and suspending medium. In these regions the interaction between the particle and the conductive (isolating) walls induces cohesive (repulsive) forces, independently of the Clausius-Mossotti term. We quantify the impact of such an effect, which can critically decrease the specificity and sensitivity of both continuous- and batch-mode FFF-DEP. We find a scale invariant relation correlating the particles radius (Rp ) and the electrodes width (Wel ), which permits the design of dielectrophoretic schema capable of avoiding the generation of such regions. Specifically, to avoid the generation of the anomalous DEP regions, Wel should be chosen smaller than ∼5.2 Rp . For this reason, interdigitate schema with electrode widths of 14 μm and gaps of 50 μm could improve the separation efficiency of FFF-DEP devices in the case of rare cells separation in blood samples.

Theoretical and experimental study of the role of cell-cell dipole interaction in dielectrophoretic devices: application to polynomial electrodes

Background

We aimed to investigate the effect of cell-cell dipole interactions in the equilibrium distributions in dielectrophoretic devices.

Methods

We used a three dimensional coupled Monte Carlo-Poisson method to theoretically study the final distribution of a system of uncharged polarizable particles suspended in a static liquid medium under the action of an oscillating non-uniform electric field generated by polynomial electrodes. The simulated distributions have been compared with experimental ones observed in the case of MDA-MB-231 cells in the same operating conditions.

Results

The real and simulated distributions are consistent. In both cases the cells distribution near the electrodes is dominated by cell-cell dipole interactions which generate long chains.

Conclusions

The agreement between real and simulated cells’ distributions demonstrate the method’s reliability. The distribution are dominated by cell-cell dipole interactions even at low density regimes (10⁵ cell/ml). An improved estimate for the density threshold governing the interaction free regime is suggested.

High-dose chemotherapy combined with escalating doses of cyclosporin A and an autologous bone marrow transplant for the treatment of drug-resistant solid tumors: a phase I clinical trial

High response rates are seen in patients undergoing dose-intensive chemotherapy and autologous marrow transplantation due to the ability of the therapy to overcome inherent or acquired drug resistance. However, relapse rates are also high because this drug resistance reversal is incomplete. Because both P-glycoprotein- and platinum-induced resistance appear to be clinically important and can be reversed in vitro with a short exposure of cyclosporin A (CSA) at 2000 and 5000 ng/ml, respectively, we undertook a trial of high-dose chemotherapy with carboplatin (1500mg/m2), mitoxantrone (75 mg/m2), and cyclophosphamide (120 mg/kg) over a 5-day period combined with escalating doses of CSA. Thirty-seven patients with primarily breast cancer (61% doxorubicin resistant) and ovarian cancer (85% platinum resistant) were treated with CSA given as a bolus 18 h prior to chemotherapy, followed by a 5-day infusion at doses of 5.0-28.2 mg/kg/day and the chemotherapy. The maximum tolerated dose of CSA was a bolus of 5.5 mg/kg and an infusion of 15. 9 mg/kg/day, which gave a mean serum CSA level of 1544 ng/ml. The dose-limiting toxicity was severe mucositis and enteritis, leading to infectious complications. Nephrotoxicity was seen in 42% and, while usually mild and reversible, was fatal in two patients with pretreatment creatinine clearances h80 ml/min. Grade III-IV isolated hyperbilirubinemia was seen in 39%, but appeared to be of no clinical significance. The overall response rate for the 26 patients with measurable/evaluable disease was 73% and 63% for those with doxorubicin- or platinum-resistant disease. The median overall survival and progression-free survival for the group were 18.1 and 8. 0 months. The overall survival for the nine patients with doxorubicin-resistant breast cancer was 19.3 months. Although we did not achieve CSA levels needed to reverse platinum resistance in vivo, levels approaching those needed to reverse P-glycoprotein resistance were reached at the maximum tolerated dose. The strategy of combining dose intensity with drug resistance reversal deserves further study, especially with the advent of potentially less toxic agents available to reverse P-glycoprotein-mediated resistance.

A phase II trial of high-dose mitoxantrone, carboplatin, and cyclophosphamide with autologous bone marrow rescue for recurrent epithelial ovarian carcinoma: analysis of risk factors for clinical outcome

Despite high initial response rates to platinum-based chemotherapy, most patients with advanced ovarian carcinoma die of drug-resistant disease. Drug resistance can be overcome in the hematologic malignancies and lymphomas with high-dose therapy and bone marrow transplantation (BMT) when used early, suggesting that this therapy may also be of value in ovarian carcinoma. As a prelude to the use of high-dose chemotherapy with BMT early in the management of advanced ovarian carcinoma, we evaluated a new high-dose regimen in patients with relapsed/refractory ovarian carcinoma to define toxicities and responses. Thirty patients were treated, of whom 20 were platinum resistant and 22 had > 1 cm maximum diameter disease. They received mitoxantrone (75 mg/m2), carboplatin (1500 mg/m2), and cyclophosphamide (120 mg/kg), followed by an autologous BMT. Overall, 89% responded, with clinical complete responses seen in 88 vs 47% (P = 0.06) of platinum-sensitive vs -resistant disease. There was only one early death (3.3%) due to Aspergillus pneumonia. Median survival for all 30 patients was 29 months, and at 3 years 23% are alive without disease. There was a 10.1- vs 5.1-month progression-free survival for patients with platinum-sensitive versus -resistant disease, and at a median follow-up of 12 months, 80% of the platinum-sensitive patients are alive. This regimen is safe, and for platinum-sensitive disease appears superior to other salvage therapies. Its use should be explored earlier in the management of advanced ovarian carcinoma.

[The therapy of peripheral obstructive arteriopathies: rational bases]

The authors underline the relations among the anatomical lesion progression, the appearance of the clinical signs (claudicatio) of tissue ischaemia and the thromboembolic event in vascular districts like myocardium and brain, at high morbidity and mortality risk. They widely state the pathogenetic mechanism of the atherosclerotic arterial disease and the compensative mechanisms that may prevent the ischaemic effects of the vascular obstruction. It has been considered the importance of the hemorheologic changes and their influence on the development of the ischaemic syndrome. The therapeutic choice in relation to physiopathologic and hemorheologic events in the peripheral obstructive arterial disease is considered.

Dysontogenetic neoplasms of the thyroid gland in infancy: two case reports

Two rare cases of benign dysontogenetic neoplasms of the thyroid gland in pediatric age are presented, which were observed at the E.N.T. department of the Bambino Gesù Hospital of Rome, and successfully operated. The first case turned out to be a dysembryoma, classified as monodermic because of its origin from derivatives of only one germinal layer, the entoderm. The second case, a teratoma, presented a high seric concentration of AFP as the consequence of the synthetic activity of the share of embryonal epatic tissue present in the neoformation. Criteria to distinguish thyroid from cervical teratomata and to classify the different types of dysontogenetic neoplasms are discussed. The usual clinical and pathological manifestations of teratomas of the neck in infancy are mentioned. The necessity of a prompt surgical removal and of pre- and postoperative thyroid function studies is mentioned.