18 research outputs found
Dose verification in carcinoma of uterine cervix patients undergoing 3D conformal radiotherapy with Farmer type ion chamber
No full textExternal beam radiotherapy (EBRT) for carcinoma of uterine cervix is a basic line of treatment with three dimensional conformal radiotherapy (3DCRT) in large number of patients. There is need for an established method for verification dosimetry. We tried to document absorbed doses in a group of carcinoma cervix patients by inserting a 0.6 cc Farmer type ion chamber in the vaginal cavity. A special long perspex sleeve cap is designed to cover the chamber for using in the patient′s body. Response of ionization chamber is checked earlier in water phantom with and without cap. Treatment planning was carried out with X-ray computed tomography (CT) scan and with the chamber along with cap in inserted position, and with the images Xio treatment planning system. Three measurements on 3 days at 5-6 fraction intervals were recorded in 12 patients. Electrometer measured charges are converted to absorbed dose at the chamber center, in vivo. Our results show good agreement with planned dose within 3% against prescribed dose. This study, is a refinement over our previous studies with transmission dosimetry and chemicals in ampules. This preliminary work shows promise that this can be followed as a routine dose check with special relevance to new protocols in the treatment of carcinoma cervix with EBRT
Synthesis, optoelectronic properties and applications of halide perovskites
Get PDFHalide perovskites have emerged as a class of most promising and cost-effective semiconductor materials for next generation photoluminescent, electroluminescent and photovoltaic devices. These perovskites have high optical absorption coefficients and exhibit narrow-band bright photoluminescence, in addition to their halide-dependent tuneable bandgaps, low exciton binding energies, and long-range carrier diffusion. These properties make these perovskites superior to classical semiconductors such as silicon. Most importantly, the simple synthesis of perovskites in the form of high quality films, single crystals, nanocrystals and quantum dots has attracted newcomers to develop novel perovskites with unique optoelectronic properties for optical and photovoltaic applications. Here, we comprehensively review recent advances in the synthesis and optoelectronic properties of films, microcrystals, nanocrystals and quantum dots of lead halide and lead-free halide perovskites. Followed by the classification of synthesis, we address the ensemble and single particle properties of perovskites from the viewpoints of the confinement and transport of charge carriers or excitons. Further, we correlate the charge carrier properties of perovskite films, microcrystals, nanocrystals and quantum dots with the crystal structure and size, halide composition, temperature, and pressure. Finally, we illustrate the emerging applications of perovskites to solar cells, LEDs, and lasers, and discuss the ongoing challenges in the field
Clinical implementation of brass mesh bolus for chest wall postmastectomy radiotherapy and film dosimetry for surface dose estimates
No full textComparison of the Dosimetric Benefits of Two Different Three-dimensional Conformal Radiotherapy Treatment Approaches for Postmastectomy Radiotherapy
No full textIntroduction:
Breast cancer is the most common cancer among women in urban areas in India, which is treated with external beam radiotherapy as a part of a multimodality treatment approach. Delivering external beam radiation therapy to the chest wall and nodal basins is challenging because of the anatomical morphology of the chest wall as well as the near proximity of critical structures. In the current study, we aim to compare the dose volumetric histograms of different organs at risk (OAR) and target volume in carcinoma breast patients whose supraclavicular field is included for radiation therapy using two different three-dimensional conformal radiotherapy (3D-CRT) techniques.
Materials and Methods:
All patients received a prescribed dose of 50 Gy to the postmastectomy chest wall and nodal basins in 25 fractions. Patients underwent standard computed tomography simulation at 3.5 mm slice spacing, in the supine position. Then, patient clinical target volume (CTV) was created using GEC-ESTRO guidelines, and planning target volume was created with an institution-specific margin around CTV. OAR parameters assessed using dose-volume histograms obtained using treatment planning techniques are compared in terms of the ipsilateral lung (V 5, V 10, V 20, V 30, and mean dose), contralateral lung (V 5, V 10, V 20, V 30, and mean dose), heart (V 5, V 25, max, mean, and minimum dose), esophagus (V 35, V 50, and mean dose), contralateral breast (V 5, D 5, minimum, maximum, and mean dose), and spinal cord doses (maximum dose).
Results:
Technique 1 and Technique 2 3D-CRT treatment plans were clinically comparable for postmastectomy radiotherapy (PMRT). Technique 1 plans showed significantly better dose coverage and minimum dose to the spinal cord. On the other hand, Technique 2 plans showed significantly better sparing of normal tissues.
Conclusion:
The choice of radiotherapy technique in PMRT is a very important factor in the protection of neighboring normal structures and the identification of associated risks. Technique 1 can provide significantly superior dose coverage and minimum dose to the spinal cord, whereas Technique 2 offers better sparing of normal tissues
Simultaneous measurement of In vivo and transit mid-plane doses with ionization chambers in gynecological malignancy patients undergoing three-dimensional conformal radiotherapy
No full textIn vivo dose estimations through transit signal measured with thimble chamber positioned along the central axis at electronic portal imaging device level in medical linear accelerator in carcinoma of the middle-third esophagus patients undergoing three-dimensional conformal radiotherapy
No full textOn-line estimations of delivered radiation doses in three-dimensional conformal radiotherapy treatments of carcinoma uterine cervix patients in linear accelerator
No full textTransmission of radiation fluence through patient′s body has a correlation to the planned target dose. A method to estimate the delivered dose to target volumes was standardized using a beam level 0.6 cc ionization chamber (IC) positioned at electronic portal imaging device (EPID) plane from the measured transit signal (S t ) in patients with cancer of uterine cervix treated with three-dimensional conformal radiotherapy (3DCRT). The IC with buildup cap was mounted on linear accelerator EPID frame with fixed source to chamber distance of 146.3 cm, using a locally fabricated mount. S t s were obtained for different water phantom thicknesses and radiation field sizes which were then used to generate a calibration table against calculated midplane doses at isocenter (D iso,TPS ), derived from the treatment planning system. A code was developed using MATLAB software which was used to estimate the in vivo dose at isocenter (D iso,Transit ) from the measured S t s. A locally fabricated pelvic phantom validated the estimations of D iso,Transit before implementing this method on actual patients. On-line dose estimations were made (3 times during treatment for each patient) in 24 patients. The D iso,Transit agreement with D iso,TPS in phantom was within 1.7% and the mean percentage deviation with standard deviation is −1.37% ±2.03% (n = 72) observed in patients. Estimated in vivo dose at isocenter with this method provides a good agreement with planned ones which can be implemented as part of quality assurance in pelvic sites treated with simple techniques, for example, 3DCRT where there is a need for documentation of planned dose delivery
Mn-doped ZnO microspheres prepared by solution combustion synthesis for room temperature NH3 sensing
Get PDFDespite being the most favorable ammonia (NH3) gas sensors, metal oxide semiconductors fail to deliver high selectivity and room temperature (RT) sensing. Tuning the metal oxide with doping is an attractive way of overcoming these disadvantages. Herein, we report Mn-doped ZnO microspheres as promising sensors for highly sensitive and selective RT sensing of NH3. ZnO and 2 wt% Mn-doped ZnO microspheres were synthesized by a low-cost and fast solution combustion synthesis, and their structure, morphology, and gas sensing properties were investigated. Mn-doping resulted in a change in the lattice parameters, an increase in the oxygen vacancies, and surface acidity of ZnO as confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Temperature programmed desorption (TPD), respectively. Mn-doped ZnO showed a response (Ra/Rg) of 20.2 in 100 ppm NH3, which is significantly higher than ZnO. The sensor showed high selectivity, three times higher than that of ZnO, and good stability. Improvement in the sensing performance of Mn-doped ZnO is attributed to the increase in the defects and surface acidity with Mn-doping. © 2022 The Author(s
Semen abnormalities, sperm DNA damage and global hypermethylation in health workers occupationally exposed to ionizing radiation.
No full textBACKGROUND: Cytogenetic studies have demonstrated that low levels of chronic radiation exposure can potentially increase the frequency of chromosomal aberrations and aneuploidy in somatic cells. Epidemiological studies have shown that health workers occupationally exposed to ionizing radiation bear an increased risk of hematological malignancies. OBJECTIVES: To find the influence of occupational radiation exposure on semen characteristics, including genetic and epigenetic integrity of spermatozoa in a chronically exposed population. METHODS: This cross sectional study included 134 male volunteers of which 83 were occupationally exposed to ionizing radiation and 51 were non-exposed control subjects. Semen characteristics, sperm DNA fragmentation, aneuploidy and incidence of global hypermethylation in the spermatozoa were determined and compared between the non-exposed and the exposed group. RESULTS: Direct comparison of the semen characteristics between the non-exposed and the exposed population revealed significant differences in motility characteristics, viability, and morphological abnormalities (P<0.05-0.0001). Although, the level of sperm DNA fragmentation was significantly higher in the exposed group as compared to the non-exposed group (P<0.05-0.0001), the incidence of sperm aneuploidy was not statistically different between the two groups. However, a significant number of hypermethylated spermatozoa were observed in the exposed group in comparison to non-exposed group (P<0.05). CONCLUSIONS: We provide the first evidence on the detrimental effects of occupational radiation exposure on functional, genetic and epigenetic integrity of sperm in health workers. However, further studies are required to confirm the potential detrimental effects of ionizing radiation in these subjects
