Unlocking synchrotron sources for THz spectroscopy at sub-MHz resolution.

Synchrotron radiation (SR) has proven to be an invaluable contributor to the field of molecular spectroscopy, particularly in the terahertz region (1-10 THz) where its bright and broadband properties are currently unmatched by laboratory sources. However, measurements using SR are currently limited to a resolution of around 30 MHz, due to the limits of Fourier-transform infrared spectroscopy. To push the resolution limit further, we have developed a spectrometer based on heterodyne mixing of SR with a newly available THz molecular laser, which can operate at frequencies ranging from 1 to 5.5 THz. This spectrometer can record at a resolution of 80 kHz, with 5 GHz of bandwidth around each molecular laser frequency, making it the first SR-based instrument capable of sub-MHz, Doppler-limited spectroscopy across this wide range. This allows closely spaced spectral features, such as the effects of internal dynamics and fine angular momentum couplings, to be observed. Furthermore, mixing of the molecular laser with a THz comb is demonstrated, which will enable extremely precise determinations of molecular transition frequencies.

Peri-lead edema after deep brain stimulation surgery for Parkinson's disease: a prospective magnetic resonance imaging study.

BACKGROUND AND PURPOSE: The aim of this study was to define the prevalence and characteristics of peri-electrode edema in a prospective cohort of patients undergoing deep brain stimulation (DBS) surgery and to correlate it with clinical findings. METHODS: We performed brain magnetic resonance imaging (MRI) between 7 and 20 days after surgery in 19 consecutive patients undergoing DBS surgery for Parkinson's disease. The T2-weighted hyperintensity surrounding DBS leads was characterized and quantified. Any evidence of bleeding around the leads was also evaluated. Clinical and follow-up data were recorded. In a subgroup of patients, a follow-up MRI was performed 3-6 weeks after surgery. We also retrospectively reviewed the post-operative computed tomography scans of patients who underwent DBS at our center since 2013. RESULTS: Magnetic resonance imaging showed a peri-lead edematous reaction in all (100%) patients, which was unilateral in three patients (15.8%). In six patients (31.6%), we detected minor peri-lead hemorrhage. Edema completely resolved in eight out of 11 patients with a follow-up MRI and was markedly reduced in the others. Most patients were asymptomatic but six (31.6%) manifested various degrees of confusional state without motor symptoms. We found no significant correlation between edema volume, distribution and any clinical feature, including new post-operative neurological symptoms. The retrospective computed tomography analysis showed that peri-electrode hypodensity consistent with edema is absent at early post-operative imaging but is common at scans performed >3 days after surgery. CONCLUSIONS: Peri-electrode edema is a common, transient reaction to DBS lead placement and a convincing relation between edema and post-operative clinical status is lacking.

Dynamics of a broad-band quantum cascade laser: from chaos to coherent dynamics and mode-locking.

The dynamics of a multimode quantum cascade laser, are studied in a model based on effective semiconductor Maxwell-Bloch equations, encompassing key features for the radiation-medium interaction such as an asymmetric frequency dependent gain and refractive index as well as the phase-amplitude coupling provided by the linewidth enhancement factor. By considering its role and that of the free spectral range, we find the conditions in which the traveling wave emitted by the laser at the threshold can be destabilized by adjacent modes, thus leading the laser emission towards chaotic or regular multimode dynamics. In the latter case our simulations show that the field oscillations are associated to self-confined structures which travel along the laser cavity, bridging mode-locking and solitary wave propagation. In addition, we show how a RF modulation of the bias current leads to active mode-locking yielding high-contrast, picosecond pulses. Our results compare well with recent experiments on broad-band THz-QCLs and may help in the understanding of the conditions for the generation of ultrashort pulses and comb operation in mid-IR and THz spectral regions.

Perioperative benefit and outcome of thoracic epidural in esophageal surgery: a clinical review.

Surgery for esophageal cancer is a highly stressful and painful procedure, and a significant amount of analgesics may be required to eliminate perioperative pain and blunt the stress response to surgery. Proper management of postoperative pain has invariably been shown to reduce the incidence of postoperative complications and accelerate recovery. Neuraxial analgesic techniques after major thoracic and upper abdominal surgery have long been established to reduce respiratory, cardiovascular, metabolic, inflammatory, and neurohormonal complications.The aim of this review is to evaluate and discuss the relevant clinical benefits and outcome, as well as the possibilities and limits of thoracic epidural anesthesia/analgesia (TEA) in the setting of esophageal resections. A comprehensive search of original articles was conducted investigating relevant literature on MEDLINE, Cochrane reviews, Google Scholar, PubMed, and EMBASE from 1985 to July2017. The relationship between TEA and important endpoints such as the quality of postoperative pain control, postoperative respiratory complications, surgical stress-induced immunosuppression, the overall postoperative morbidity, length of hospital stay, and major outcomes has been explored and reported. TEA has proven to enable patients to mobilize faster, cooperate comfortably with respiratory physiotherapists and achieve satisfactory postoperative lung functions more rapidly. The superior analgesia provided by thoracic epidurals compared to that from parenteral opioids may decrease the incidence of ineffective cough, atelectasis and pulmonary infections, while the associated sympathetic block has been shown to enhance bowel blood flow, prevent reductions in gastric conduit perfusion, and reduce the duration of ileus. Epidural anesthesia/analgesia is still commonly used for major 'open' esophageal surgery, and the recognized advantages in this setting are soundly established, in particular as regards the early recovery from anesthesia, the quality of postoperative pain control, and the significantly shorter duration of postoperative mechanical ventilation. However, this technique requires specific technical skills for an optimal conduction and is not devoid of risks, complications, and failures.

Vascular pentraxin 3 controls arterial thrombosis by targeting collagen and fibrinogen induced platelets aggregation.

AIM: The long pentraxin PTX3 plays a non-redundant role during acute myocardial infarction, atherosclerosis and in the orchestration of tissue repair and remodeling during vascular injury, clotting and fibrin deposition. The aim of this work is to investigate the molecular mechanisms underlying the protective role of PTX3 during arterial thrombosis. METHODS AND RESULTS: PTX3 KO mice transplanted with bone marrow from WT or PTX3 KO mice presented a significant reduction in carotid artery blood flow following FeCl3 induced arterial thrombosis (-80.36±11.5% and -95.53±4.46%), while in WT mice transplanted with bone marrow from either WT or PTX3 KO mice, the reduction was less dramatic (-45.55±1.37% and -53.39±9.8%), thus pointing to a protective effect independent of a hematopoietic cell's derived PTX3. By using P-selectin/PTX3 double KO mice, we further excluded a role for P-selectin, a target of PTX3 released by neutrophils, in vascular protection played by PTX3. In agreement with a minor role for hematopoietic cell-derived PTX3, platelet activation (assessed by flow cytometric expression of markers of platelet activation) was similar in PTX3 KO and WT mice as were haemostatic properties. Histological analysis indicated that PTX3 localizes within the thrombus and the vessel wall, and specific experiments with the N-terminal and the C-terminal PTX3 domain showed the ability of PTX3 to selectively dampen either fibrinogen or collagen induced platelet adhesion and aggregation. CONCLUSION: PTX3 interacts with fibrinogen and collagen and, by dampening their pro-thrombotic effects, plays a protective role during arterial thrombosis.

Electrically pumped photonic-crystal terahertz lasers controlled by boundary conditions.

Semiconductor lasers based on two-dimensional photonic crystals generally rely on an optically pumped central area, surrounded by un-pumped, and therefore absorbing, regions. This ideal configuration is lost when photonic-crystal lasers are electrically pumped, which is practically more attractive as an external laser source is not required. In this case, in order to avoid lateral spreading of the electrical current, the device active area must be physically defined by appropriate semiconductor processing. This creates an abrupt change in the complex dielectric constant at the device boundaries, especially in the case of lasers operating in the far-infrared, where the large emission wavelengths impose device thicknesses of several micrometres. Here we show that such abrupt boundary conditions can dramatically influence the operation of electrically pumped photonic-crystal lasers. By demonstrating a general technique to implement reflecting or absorbing boundaries, we produce evidence that whispering-gallery-like modes or true photonic-crystal states can be alternatively excited. We illustrate the power of this technique by fabricating photonic-crystal terahertz (THz) semiconductor lasers, where the photonic crystal is implemented via the sole patterning of the device top metallization. Single-mode laser action is obtained in the 2.55-2.88 THz range, and the emission far field exhibits a small angular divergence, thus providing a solution for the quasi-total lack of directionality typical of THz semiconductor lasers based on metal-metal waveguides.

Invited review: Animal-based indicators for on-farm welfare assessment for dairy goats.

This paper reviews animal-based welfare indicators to develop a valid, reliable, and feasible on-farm welfare assessment protocol for dairy goats. The indicators were considered in the light of the 4 accepted principles (good feeding, good housing, good health, appropriate behavior) subdivided into 12 criteria developed by the European Welfare Quality program. We will only examine the practical indicators to be used on-farm, excluding those requiring the use of specific instruments or laboratory analysis and those that are recorded at the slaughterhouse. Body condition score, hair coat condition, and queuing at the feed barrier or at the drinker seem the most promising indicators for the assessment of the "good feeding" principle. As to "good housing," some indicators were considered promising for assessing "comfort around resting" (e.g., resting in contact with a wall) or "thermal comfort" (e.g., panting score for the detection of heat stress and shivering score for the detection of cold stress). Several indicators related to "good health," such as lameness, claw overgrowth, presence of external abscesses, and hair coat condition, were identified. As to the "appropriate behavior" principle, different criteria have been identified: agonistic behavior is largely used as the "expression of social behavior" criterion, but it is often not feasible for on-farm assessment. Latency to first contact and the avoidance distance test can be used as criteria for assessing the quality of the human-animal relationship. Qualitative behavior assessment seems to be a promising indicator for addressing the "positive emotional state" criterion. Promising indicators were identified for most of the considered criteria; however, no valid indicator has been identified for "expression of other behaviors." Interobserver reliability has rarely been assessed and warrants further attention; in contrast, short-term intraobserver reliability is frequently assessed and some studies consider mid- and long-term reliability. The feasibility of most of the reviewed indicators in commercial farms still needs to be carefully evaluated, as several studies were performed under experimental conditions. Our review highlights some aspects of goat welfare that have been widely studied, but some indicators need to be investigated further and drafted before being included in a valid, reliable, and feasible welfare assessment protocol. The indicators selected and examined may be an invaluable starting point for the development of an on-farm welfare assessment protocol for dairy goats.

Evaluation of stability of allergen extracts for sublingual immunotherapy during transport under unfavourable temperature conditions with an innovative thermal insulating packaging.

Many pharmaceutical and biotechnological products are temperature-sensitive and should normally be kept at a controlled temperature, particularly during transport, in order to prevent the loss of their stability and activity. Therefore, stability studies should be performed for temperature-sensitive products, considering product characteristics, typical environmental conditions, and anticipating environmental extremes that may occur during product transport in a specific country. Staloral products for sublingual immunotherapy are temperature sensitive and are labelled for maintenance under refrigerated conditions (2-8°C). Given the peculiar climatic context of Italy and the great temperature fluctuations that may occur during transport, this study was aimed at evaluating the impact of a new engineered thermal insulating packaging for Staloral. In particular, the purpose was to assess whether the new packaging could create a container condition able to preserve the stability and immunological activity of the product during the transport phase throughout Italy. The results showed that the range of temperatures that can affect the product, in the area surrounding the product packaging, may reach a peak of 63°C during transport under the most unfavourable climatic conditions, i.e. in a non-refrigerated van during the summer season, from the site of production in France to the patient's house in Catania, the city with the highest temperatures in Italy. However, the highest temperature reached inside the vaccine did not exceed 45°C over a period of about 2 h. The ELISA inhibition test on samples subjected to the extreme temperature conditions previously defined (45°C) showed an immunological activity higher than 75% of that initially measured and was comparable to those obtained with samples stored at controlled temperature (5°C). This means that, even in the worst case scenario, the structure of the allergen extracts is not influenced and the vaccine potency is preserved.

Measurement of the intrinsic linewidth of terahertz quantum cascade lasers using a near-infrared frequency comb.

We report the measurement of the frequency noise power spectral density of a quantum cascade laser emitting at 2.5THz. The technique is based on heterodyning the laser emission frequency with a harmonic of the repetition rate of a near-infrared laser comb. This generates a beatnote in the radio frequency range that is demodulated using a tracking oscillator allowing measurement of the frequency noise. We find that the latter is strongly affected by the level of optical feedback, and obtain an intrinsic linewidth of ~230Hz, for an output power of 2mW.

Phase-locking of a 2.5 THz quantum cascade laser to a frequency comb using a GaAs photomixer.

We report the heterodyne detection and phase locking of a 2.5 THz quantum cascade laser (QCL) using a terahertz frequency comb generated in a GaAs photomixer using a femtosecond fiber laser. With 10 mW emitted by the QCL, the phase-locked signal at the intermediate frequency yields 80 dB of signal-to-noise ratio in a bandwidth of 1 Hz.

Short communication: Breed differences affecting dairy cattle welfare in traditional alpine tie-stall husbandry systems.

The aim of this investigation was to compare the prevalence of indicators of poor welfare among 5 Italian cattle breeds (Italian Holstein-Friesian, Italian Bruna, Pezzata Rossa Italiana, Grigia Alpina, and Pezzata Rossa d'Oropa) kept in tie-stalls in the Italian Alps under similar housing and management conditions. We recorded the presence of integument alterations (hairless patch areas, lesion/swollen areas, or overgrown claws) and lameness in 612 cows. Additionally, we checked 834 cows for the presence of physical malformations ("open" shoulders). In general, the prevalence of welfare problems showed a decreasing trend from the more productive to the less productive breeds. Local breeds (Grigia Alpina and Pezzata Rossa d'Oropa) showed a significantly lower prevalence of welfare problems compared with the other 3 breeds, whereas Italian Holstein-Friesian usually had the highest percentage of individuals with problems. No differences were found between Pezzata Rossa Italiana and Italian Bruna, both of which showed fewer problems than Italian Holstein-Friesian. The effect of the breed significantly affected the welfare of dairy cows in tie-stalls in alpine traditional husbandry systems. The prevalence of the negative welfare indicators studied was lower in local breeds, which are better adapted to local breeding conditions. Our results indicate an urgent need to promote changes in the criteria used for genetic selection in the dairy industry and underline the importance of maintaining the diversity of local breeds, which should be carefully chosen for each specific environmental condition.

Prenylcysteine oxidase 1, an emerging player in atherosclerosis.

The research into the pathophysiology of atherosclerosis has considerably increased our understanding of the disease complexity, but still many questions remain unanswered, both mechanistically and pharmacologically. Here, we provided evidence that the pro-oxidant enzyme Prenylcysteine Oxidase 1 (PCYOX1), in the human atherosclerotic lesions, is both synthesized locally and transported within the subintimal space by proatherogenic lipoproteins accumulating in the arterial wall during atherogenesis. Further, Pcyox1 deficiency in Apoe-/- mice retards atheroprogression, is associated with decreased features of lesion vulnerability and lower levels of lipid peroxidation, reduces plasma lipid levels and inflammation. PCYOX1 silencing in vitro affects the cellular proteome by influencing multiple functions related to inflammation, oxidative stress, and platelet adhesion. Collectively, these findings identify the pro-oxidant enzyme PCYOX1 as an emerging player in atherogenesis and, therefore, understanding the biology and mechanisms of all functions of this unique enzyme is likely to provide additional therapeutic opportunities in addressing atherosclerosis.

A role for CD4+ NK1.1+ T lymphocytes as major histocompatibility complex class II independent helper cells in the generation of CD8+ effector function against intracellular infection.

Major histocompatibility complex (MHC) class II (A beta) knockout mice were vaccinated with ts-4, an attenuated mutant strain of Toxoplasma gondii, which in normal animals induces strong T cell immunity mediated by interferon gamma (IFN-gamma). After challenge with the lethal parasite strain RH, the knockout mice displayed decreased resistance consistent with absence of CD4+ effectors. Nevertheless, these animals generated CD8+ lymphocyte effectors capable of mediating partial protection through IFN-gamma secretion. Moreover, in vivo neutralization experiments indicated that the development of resistance in knockout mice depends on CD4+ cells as well as interleukin 2 (IL-2). The identity of the IL-2-producing protective cell population was further characterized as CD4+, NK1.1+ by in vitro depletion studies and reverse transcriptase-PCR analysis of fluorescence-activated cell sorter (FACS)-purified CD4+ NK1.1+ T lymphocytes. These results demonstrate that in the absence of conventional MHC class II-restricted CD4+ T lymphocytes, CD8 priming persists and mediates partial protective immunity to T. gondii. Moreover, the data argue that CD4+, NK1.1+ cells, previously implicated in the initiation of T helper cell 2 (Th2) responses through their production of IL-4, can also play a role as alternative IL-2-secreting helper cells in Th1-mediated host resistance to infection.

Characterization of mixed allogeneic chimeras. Immunocompetence, in vitro reactivity, and genetic specificity of tolerance.

Mixed allogeneically reconstituted mice (B10 + B10.D2----B10) that specifically accept B10.D2 tail skin allografts were examined for in vivo and in vitro immunocompetence, patterns of hematopoietic repopulation, and in vitro reactivity. In vitro, mixed allogeneic chimeras (B10 + B10.D2----B10) manifested specific tolerance in mixed lymphocyte reactions and cell-mediated lympholysis to B10 and B10.D2 splenocytes, with normal responses to third-party (B10.BR) cells. Such chimeras were immunocompetent in B cell and helper T cell responses, as assessed by their primary plaque forming cell responses to in vivo sheep red blood cell immunization. This is in contrast to fully allogeneic chimeras, which responded less well. In addition, survival of the mixed allogeneic chimeras in a conventional animal facility was superior to that of fully allogeneic chimeras, and similar to syngeneically reconstituted (B10----B10) mice. Specific tolerance to skin grafts, degree of allogeneic engraftment, and persistence of chimerism was also assessed in a noncongenic mixed allogeneic combination (B10 + C3H----B10). Such animals manifested specific hyporeactivity to C3H skin allografts, but eventual chronic rejection of the grafts occurred in spite of stable and persistent mixed chimerism. MHC-congenic (B10.BR) skin grafts were accepted indefinitely in the same animals, suggesting that skin-specific non-major histocompatibility complex antigens were responsible for rejection of the C3H skin allografts.

Impact of alcohol consumption on winter sports-related injuries.

INTRODUCTION: This study was carried out to evaluate data about trauma-related winter sports, including risk factors such as high speed, gender, age, alcohol consumption, details about the accident and snow conditions. METHODS: A retrospective review was conducted to determine the injury patterns and crash circumstances in holiday skiers and snowboarders. The data recorded were obtained from the database of the Pre-Hospital Emergency Registry of six skiing areas in the Dolomite mountains during the winter seasons November 2004-May 2009, injury data for major traumas from Ski Patrol Injury reports (helicopter, ambulance or ski slopes' patrol reports), and intrahospital Emergency Department data. Alcohol concentration in blood was detected in 200 individuals suffering from major trauma. RESULTS: A total of 4550 injured patients, predominantly male (69%), mean age 22 years (range 16-72), were included in the observational analysis. Knee, wrist and shoulder injuries were frequently associated with major thoracic, abdominal or head traumas (64% of cases). Suboptimal technical level, high speed, low concentration, snow or weather conditions, faulty equipment and protective devices were among the various causes of accidents. The analysis revealed that high alcohol blood concentration was present in 43% of 200 patients. CONCLUSIONS: Even though the major causes of accidents were excessive speed, excessive fatigue, technical errors and bad weather conditions, alcohol abuse was often discovered. Random sampling and a non-systematic detection of alcohol blood levels likely led to an underestimation of alcohol consumption-related injuries. It is recommended that investigations into alcoholic intoxication in injured skiers should be carried out on a large scale.

Predictable surface emission patterns in terahertz photonic-crystal quantum cascade lasers.

We demonstrate a framework to understand and predict the far-field emission in terahertz frequency photonic-crystal quantum cascade lasers. The devices, which employ a high-performance three-well active region, are lithographically tunable and emit in the 104-120 microm wavelength range. A peak output power of 7 mW in pulsed mode is obtained at 10 K, and the typical device maximum operating temperature is 136 K. We identify the photonic-crystal band-edge states involved in the lasing process as originating from the hexapole and monopole modes at the G point of the photonic band structure, as designed. The theoretical far-field patterns, obtained via finite-difference time-domain simulations, are in excellent agreement with experiment. Polarization measurements further support the theory, and the role of the bonding wires in the emission process is elucidated.

INNOVATIVE SOLUTIONS FOR PERSONAL RADIATION SHIELDING IN SPACE.

Personal radiation shielding is likely to play an important role in the strategy for radiation protection of future manned interplanetary missions. There is potential for the successful adoption of wearable shielding devices, readily available in case of accidental exposures or used for emergency operations in low-shielded areas of the habitat, particularly in case of solar particle events (SPEs). Based on optimization of available resources, conceptual models for radiation protection spacesuits have been proposed, with elements made of different materials, and the first prototype of a water-fillable garment was designed and manufactured in the framework of the PERSEO project, funded by the Italian Space Agency, leading to the successful test of such prototype for ease of use and wearability on-board the International Space Station. We present results of Monte Carlo calculations offering a proof-of-principle validation of the shielding efficacy of such prototype in different SPE environments and shielding conditions.

Risk Factors for Early Mortality in Liver Transplant Patients.

BACKGROUND: Liver transplantation (LT) is an established treatment for patients with end-stage liver disease. The significant advances in surgical technique, immunosuppression therapy, and anesthesiological management have dramatically improved short- and long-term outcomes. The aim of this study is to correlate specific surgical and anesthesiological variables with causes of early death in LT recipients. METHODS: A retrospective observational analysis of adult patients who underwent LT in the period 2012 to 2016 and died within 90 days following LT was conducted. Exclusion criteria were intraoperative death, split liver, and domino transplant. Death was considered a dependent variable and classified into 3 different groups: death by sepsis, vascular events not related to the graft, and primary non-function. Donor and recipient variables were considered and analyzed using Fisher's exact test. RESULTS: Statistically significative associations (P value < .05) were found between renal function support, retransplantation, and the number of fresh frozen plasma units transfused in one group and early death due to sepsis in the other. CONCLUSIONS: This study identified some risk factors associated with the specific cause of early death in liver transplantation. The clinical implications of these findings are the ability to stratify patients at high risk of early death by planning more intensive and accurate management for them.

WHAT ROLES FOR TRACK-STRUCTURE AND MICRODOSIMETRY IN THE ERA OF -omics AND SYSTEMS BIOLOGY?

Ionizing radiation is a peculiar perturbation when it comes to damage to biological systems: it proceeds through discrete energy depositions, over a short temporal scale and a spatial scale critical for subcellular targets as DNA, whose damage complexity determines the outcome of the exposure. This lies at the basis of the success of track structure (and nanodosimetry) and microdosimetry in radiation biology. However, such reductionist approaches cannot account for the complex network of interactions regulating the overall response of the system to radiation, particularly when effects are manifest at the supracellular level and involve long times. Systems radiation biology is increasingly gaining ground, but the gap between reductionist and holistic approaches is becoming larger. This paper presents considerations on what roles track structure and microdosimetry can have in the attempt to fill this gap, and on how they can be further exploited to interpret radiobiological data and inform systemic approaches.

Dose-averaged LET calculation for proton track segments using microdosimetric Monte Carlo simulations.

PURPOSE: There is an increasing interest in calculating linear energy transfer (LET) distributions for proton therapy treatments in order to assess the influence of this quantity in biological terms. Microdosimetric Monte Carlo (MC) simulations are useful tools to calculate dose-averaged LET, as this has been broadly proposed as the most adequate quantity to characterize these biological effects. However, a straightforward uniform sampling of the scoring site turns out to be computationally unaffordable. In contrast, some issues have been pointed out with the more efficient weighted sampling approach, frequently used in literature. Here, we address the issues associated with the latter method and propose adequate corrections to achieve reliable calculations of dose-averaged LET values from microdosimetry. METHODS AND MATERIALS: Proton track structures have been simulated with Geant4-DNA considering two different approaches. One version employs a uniform sampling for placing the spherical site and is used as the reference. The other one uses a weighted sampling by considering the spatial distribution of transfer points. Some corrections are proposed for calculating a dose-averaged LET comparable to the reference case. An additional MC approach is proposed to obtain the weighted mean of the energy imparted per electronic collision of the proton within the site, the δ 2 function, related to the straggling distribution, as an intermediate step in the LET calculation. RESULTS: Energy imparted per event distributions are different when employing either sampling methods, due to the different geometrical randomness. We have found an agreement below (0.15 ± 0.05) keV/µm in the worst case for uniform and weighted methods in dose-averaged LET values when the weighted sampling results are corrected according to our proposal. Our analysis is restricted to spherical sites of 1 and 10 µm diameter and monoenergetic beams in the range from 2 to 90 MeV. CONCLUSIONS: This work shows a reliable and computational-efficient method to perform calculations of track segment dose-averaged LET using MC simulations for proton therapy beams, including the necessary considerations for obtaining the straggling distribution characteristics. The validity of this approach remains as long as the stopping power of the proton can be considered as constant along its track within the site.