SciFi detector and associated method for real-time determination of profile and output factor for small fields in stereotactic radiotherapy

PURPOSE

For determining small-field profile and output factor during stereotactic radiotherapy quality assurance (QA) procedures, we propose a novel system based on the scintillating fiber (SciFi) detector with output image acquisition and processing to allow real-time monitoring of profile and output factor.

MATERIALS AND METHODS

The employed detector is a SciFi detector made of tissue-equivalent scintillating plastic fibers arranged in 6-layer fiber ribbons with a fiber pitch of 275 μm in each layer. The scintillating signal at the detector output is acquired by a sCMOS (scientific complementary metal-oxide-semiconductor) camera and represents the projected field profile along the fibers axis. An iterative reconstruction method of the field from its projected profile based on a priori knowledge of some features of the radiation field defined by the stereotactic cones is suggested. The detector with implemented data processing has been tested in clinical conditions, for determining beam profiles and output factors, using cone collimators of different sizes from 4 to 15 mm diameter. The detector under test was placed at 1.4 cm depth and 98.6 cm source to surface distance (SSD) in a water-equivalent phantom and irradiated by a 6 MV photon beam.

RESULTS

The reconstructed field profiles obtained from the detector are coherent with data from EBT3 radiochromic films, with differences within ±0.32 mm for both the FWHM and the penumbra region. For real-time determination of the field output factor, the measured data are also in good agreement with data independently determined by the French Institute for Radiological Protection and Nuclear Safety (IRSN) based on radiochromic films and thermoluminescent 1 × 1 mm2 micro-cubes dosimeters (TLD). The differences are within ±1.6% for all the tested cone sizes.

CONCLUSIONS

We propose and have tested a SciFi plastic scintillating detector with an optimized signal processing method to characterize small fields defined by cone collimators. It allows the determination of key field parameters such as full width at half maximum (FWHM) and field output factors. The results are consistent with those independently measured using TLD and radiochromic films. As the SciFi detector does not require a correction factor, it is in line with the International Atomic Energy Agency (IAEA) and the American Association of Physicists in Medicine (AAPM) TRS-483 recommendations, and can be suitable for online QA of small radiation fields used in photon beam radiotherapy, and is compatible with MRI-LINAC.

Dual shape recovery of red blood cells flowing out of a microfluidic constriction

Micropipette aspiration, optical tweezers, rheometry, or ecktacytometry have been used to study the shape recovery of healthy human Red Blood Cells (RBCs) and measure associated relaxation times of the order of 100-300 ms. These measurements are in good agreement with the Kelvin-Voigt model, which describes the cell as a visco-elastic material, predicting that its relaxation time only depends on cell intrinsic properties. However, such mechanical solicitation techniques are far from being relevant regarding RBC solicitation in vivo. In this paper, we report for the first time the existence of two different behaviors of the RBC shape recovery while flowing out of a microfluidic constricted channel. The calculation of the viscous stress corresponding to the frontier between the two recovery modes confirms that the RBC resistance to shear μ is the elastic property dominating the transition between the two recovery behaviors. We also quantified associated recovery times τ r and report values as low as 4 ms-which is almost two decades smaller than the typical RBC relaxation time-at high viscosity and flow velocity of the carrier fluid. Although we cannot talk about relaxation time because the cell is never at rest, we believe that the measured shape recovery time arises from the coupling of the cell intrinsic deformability and the hydrodynamic stress. Depending on the flow conditions, the cell mechanics becomes dominant and drives the shape recovery process, allowing the measurement of recovery times of the same order of magnitude than relaxation times previously published. Finally, we demonstrated that the measurement of the shape recovery time can be used to distinguish Plasmodium falciparum (causing malaria) infected RBCs from healthy RBCs.

Fate of petroleum hydrocarbons in bioturbated pristine sediments from Caleta Valdés (Patagonia Argentina): An ex situ bioassay

Petroleum can pollute pristine shorelines as a consequence of accidental spills or chronic leaks. In this study, the fate of petroleum hydrocarbons in soft pristine sediment of Caleta Valdés (Argentina) subject to ex situ simulated oil pollution was assessed. Sedimentary columns were exposed to medium and high concentrations of Escalante Crude Oil (ECO) and incubated in the laboratory during 30 days. Levels of aliphatic hydrocarbons at different depths of the sedimentary column were determined by gas chromatography. Oil penetration was limited to the first three centimetres in both treatments, and under this depth, hydrocarbons were clearly biogenic (terrestrial plants) as in the whole sedimentary column of the control assay. Bioturbation by macrobenthic infauna was strongly impacted by oil pollution which resulted in reduced sediment oxygenation and low burial of petroleum hydrocarbons. This may partly explain the limited hydrocarbon biodegradation observed, as indicated by the relatively high values of the ratios nC17/pristane, nC18/phytane, and total resolved aliphatic hydrocarbons/unresolved complex mixture. Correspondingly, at the end of the experiment the most probable number of hydrocarbon-degrading bacteria reached ~ 10³ MPN g^-1 dry weight. These values were lower than those found in chronically polluted coastal sediments, reflecting a low activity level of the oil-degrading community. The results highlight the low attenuation capacities of Caleta Valdés pristine sediments to recover its original characteristics in a short time period if an oil spill occurs. In this work, we present a novel and integrative tool to evaluate the fate of petroleum hydrocarbons and their potential damage on pristine sediments.

Effects of doxorubicin administration on bone strength and quality in sedentary and physically active Wistar rats

Doxorubicin (DOX) is used in pediatric cancer treatment. This study assessed the effects of 7 weeks of DOX and 10-week recovery on bone quality and biomechanical properties in sedentary and exercised Wistar rats. DOX decreases femur diaphysis radial growth and biomechanical properties. Some of these DOX effects were aggravated by exercise.

INTRODUCTION

Bone growth in pre-pubertal years critically influences adult fracture risk. DOX is widely used in the treatment of pediatric cancers, but there is limited evidence on its potential negative effects on bone growth. Exercise improves bone growth in children, but there is no evidence if it protects against DOX-induced bone toxicity. This study investigates the early and intermediate effects of a 7-week course of DOX on bone histomorphometry and strength in sedentary and exercised growing animal models.

METHODS

Sixty-eight male Wistar rats (8 weeks) were treated with DOX (2 mg kg^-1) or vehicle for 7 weeks and afterward housed in standard cages or in cages with a running wheel and killed 2 or 10 weeks after last DOX administration. Femurs and blood were collected for assaying geometry, trabecular microarchitecture (histology), biomechanical properties (three-point bending and shearing of the femoral neck), bone calcium content and density (atomic absorption spectroscopy), and bone turnover markers (ELISA).

RESULTS

DOX treatment reduced the femur diaphysis radial growth, with DOX-treated animals having a lower tissue area, cortical area, cortical thickness, and moment of inertia. DOX also decreased distal femur trabecular bone volume and trabecular number and increased trabecular separation. Femur diaphysis stiffness and maximum load were also reduced in past DOX-treated animals. Exercise was shown to worsen the effects of past DOX treatment on the femur diaphysis mechanical properties.

CONCLUSION

DOX negatively affects bone geometry, trabecular microarchitecture, and femur mechanical properties in growing Wistar rats. Exercise further aggravates the detrimental effects of past DOX treatment on bone mechanical properties.

[Cognitive remediation therapy for children and adolescents with anorexia nervosa in France: an exploratory study]

OBJECTIVE

Cognitive remediation therapy (CRT) seems to be increasingly interesting in the treatment of anorexia nervosa for adult patients. We attempted to apply this support to a group of young inpatients, initially to assess its feasibility and acceptability, and then to improve its content for therapeutic application and future research.

METHODS

Ten 12- to 17-year-old inpatients with primary DSM-IV diagnosis of anorexia nervosa participated in a 10-week intervention program with a one-hour group session of CRT per week. All 10 patients were assessed before the intervention and those who completed the 10 sessions were assessed after. Assessment included a clinical examination by a psychiatrist, a battery of clinical inventories, and set-shifting tests. Moreover, each patient wrote a letter providing feedback on the intervention for subsequent analysis.

RESULTS

Only two patients completed all 10 sessions, the other eight who were discharged from the hospital in the meantime could not attend the sessions for practical reasons. After the 10 sessions, an improvement in BMI and in measured levels of some psychopathological symptoms was observed in our two patients. Most neuropsychological task performances were improved after cognitive remediation. Feedback from the 10 patients was generally positive.

CONCLUSION AND IMPLICATIONS FOR PRACTICE

This preliminary investigation suggests that cognitive remediation therapy is acceptable and feasible in this population. Replication of these findings requires a larger sample, improvement of the trial design, more sensitive measures, and another training format to avoid loss of so many participants.

One year of Lamivudine therapy for portuguese patients with chronic hepatitis B

OBJECTIVE

To assess the efficacy of lamivudine treatment on hepatitis B e antigen (HBeAg) and/or hepatitis B surface antigen (HBsAg) seroconversion, on other virological and serological markers of response including hepatitis B virus (HBV) DNA and serum aminotransferases, and the safety of lamivudine treatment in hepatitis B patients.

PATIENTS

This phase III open-label study evaluated the virological and biochemical response to lamivudine in 70 Portuguese patients with HBeAg positive chronic hepatitis B. Patients were treated with lamivudine 100mg once daily for 12 months.

METHODS

Antiviral activity was assessed by measuring alanine aminotransferase (ALT)/aspartate aminotransferase (AST) levels at all protocol visits, and hepatitis B serology and HBV DNA were performed at baseline and at month 12 visits. Evaluation of safety and tolerance was based on clinical adverse events and laboratory analyses.

RESULTS

The primary endpoint was virological response at month 12, defined as loss of detectable HBeAg from serum with a reduction of HBV DNA to undetectable levels, and this was observed in 19/69 (27.5%) of patients. Almost half of the patients were HBV DNA negative by this time. Mean ALT values decreased steadily during treatment and by 12 months 61% of patients had values within the normal range. HBeAg seroconversion (HBeAg negative, HBeAb positive) was achieved in 27.9% of patients by 12 months, although all patients remained HBsAg positive.

CONCLUSION

Lamivudine was well tolerated and the incidence of adverse events was similar to those reported in previous studies. Lamivudine treatment resulted in virological and biochemical improvements in HBeAg positive chronic hepatitis B patients, with HBeAg seroconversion in one-third of patients.

The efficacy of folk medicines in the management of type 2 diabetes mellitus: results of a randomized controlled trial of Syzygium cumini (L.) Skeels

OBJECTIVE

To investigate whether a tea prepared from leaves of jambolan, Syzygium cumini (L.) Skeels, has an antihyperglycaemic effect in patients with type 2 diabetes mellitus.

RESEARCH DESIGN AND METHODS

Patients with type 2 diabetes mellitus were enrolled in a double-blind, double-dummy, randomized clinical trial. The three experimental groups received a tea prepared from leaves of S. cumini plus placebo tablets, placebo tea plus glyburide tablets or placebo tea plus placebo tablets.

RESULTS

In total, 27 patients were allocated to one of the treatment groups and followed for 28 days. Fasting blood glucose levels decreased significantly with glyburide and did not change with S. cumini tea or placebo. Body mass index, creatinine, gamma-glutamyl transferase, alkaline phosphatase, aspartate aminotransferase (SGOT), alanine aminotransferase (SGPT), 24-h glicosuria, 24-h proteinuria, triglycerides, total, low-density lipoprotein and high-density lipoprotein cholesterol did not vary significantly between the different groups.

CONCLUSIONS

Tea prepared from leaves of S. cumini has no hypoglycaemic effect.

[Hypertensive cardiopathy. Functional evaluation during isometric effort after regression of left ventricular hypertrophy]

OBJECTIVE

Echocardiographic evaluation of the response to isometric exercise of hypertensive patients with and without left ventricular hypertrophy.

PARTICIPANTS

28 patients with severe arterial hypertension on long-term follow-up with or without regression of left ventricular hypertrophy on medical therapy; a control group of 10 healthy volunteers.

METHODS

Two groups were considered: Group A persistent left ventricular hypertrophy and group B normalization of the left ventricular wall thickness and mass index. The arterial blood pressure and heart rate were evaluated and an echocardiographic record was obtained both at rest and after isometric exercise (maximal effort for 1 to 1.5 minutes). The following echocardiographic data were obtained: left ventricular diameters and thickness of septum and posterior wall during systole and diastole. Volumes, shortening and ejection fractions, cardiac output and index, mass index, end-systolic stress, contractility index and periferal resistance were calculated as usual.

RESULTS

During isometric exercise there was a rise in systolic, diastolic and mean arterial pressures and heart rate. Systolic function was normal in all groups at rest. The shortening fraction was not altered in normotensive individuals with isometric exercise. Hypertensive patients showed a significant reduction within normal limits, however. End-systolic stress increased significantly in all groups although the rise was greater in hypertensive patients. The cardiac index rose significantly only in normotensives and hypertensive patients without left ventricular hypertrophy (group B). On the contrary the periferal resistance rose significantly only in hypertensive patients with left ventricular hypertrophy (group A). The contractility index (end-systolic stress/end-systolic volume index) increased significantly only in normotensive and hypertensive patients without left ventricular hypertrophy.

CONCLUSIONS

There are functional alterations in hypertensive heart disease which although not evident at rest, can be revealed by isometric exercise. The regression of left ventricular hypertrophy back to normal, sets a trend for normalization of function and cardiac inotropic reserve, suggesting the importance of a complete regression of ventricular hypertrophy.

Dermatophytes in Portugal (1972-1981)

For the years 1972-1981, 7 333 isolates of dermatophytes belonging to 14 species were obtained from glabrous skin (32%), feet (28%), groin (19%), scalp (8%), toenails (7%), fingernails (3%) and beard (1%). T. rubrum represented 50% of all the isolates and was the most frequent species on glabrous skin, groin and nails. T. mentagrophytes (24%) was mainly obtained from the feet, E. floccosum (9%) from the groin and T. megninii (4%) from uncovered areas of the skin, fingernail and beard. These 4 species predominated in men. M. canis was the commonest agent on the scalp and in children up to 11 years. T. violaceum, previously the main cause of tinea capitis, and T. tonsurans have been decreasing for the period of this study, just as T. schoenleinii for the years 1962-71. The rising prevalence of T. rubrum was observed since 1962. In the whole it seems stable after 1969, but the analysis of the main sites involved shows that in the glabrous skin this species increased from 1962 to 1974; in the groin it was gone up from 30% during 1962-1965, to 64% in the years 1969-1971; in the feet the evolution was slower and only in 1980 T. rubrum became more frequent than T. mentagrophytes. The increase in certain species, whereas others become rare, lacks a satisfactory explanation.