Comparison of dosimetric parameters between intensity modulated and three-dimensional conformal radiotherapy planning for adjuvant therapy of gastric cancer

Background: Adjuvant chemoradiotherapy is the standard treatment for gastric carcinoma, but the optimal radiation modality remains uncertain. This study aimed to compare intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT) in terms of dosimetry for adjuvant gastric cancer treatment. Methods: 21 patients with stage IIB-IIIC gastric cancer, treated between January and June 2021, underwent surgery followed by adjuvant chemoradiation with both IMRT and 3D-CRT plans. Dosimetric parameters were calculated for the planned target volume (PTV) and organs at risk (OAR). Results: Both IMRT and 3D-CRT provided comparable PTV coverage. However, IMRT significantly improved kidney sparing, reducing the mean V20 value by 23% (p=0.01) for the right kidney and 26% (p=0.02) for the left kidney compared to 3D-CRT. IMRT also decreased the mean irradiated volume for both kidneys and the liver, as well as the V30 value for the liver, although these differences were not statistically significant. The dosimetric parameters for the spinal cord were comparable between IMRT and 3D-CRT plans. Conclusions: IMRT demonstrated better kidney sparing compared to 3D-CRT in adjuvant radiotherapy for gastric cancer, while PTV coverage was similar. Long-term follow-up is necessary to assess clinical outcomes and local recurrence rates for both treatment plans

An Evaluation of ionization chambers for the relative dosimetry of kilovoltage x-ray beams

In this work, the authors have evaluated ten different ionization chambers for the relative dosimetry of kilovoltage x-ray beams in the energy range of 50-280 kVp. Percentage depth doses in water and relative detector response (in Solid Water and in air) were measured for each of the x-ray beams studied using a number of chambers. Measured depth dose data were compared with Monte Carlo calculated depth doses using the EGSnrc Monte Carlo package and the BEAMnrc user code. The accuracy of the phase space files generated by BEAMnrc was verified by calculating the half-value layer and comparing with the measured half-value layer of each x-ray beam. The results indicate that the Advanced Markus, Markus, NACP, and Roos parallel plate ionization chambers were suitable for the measurement of depth dose data in this beam quality range with an uncertainty of less than 3%, including in the regions close to the water surface. While the relative detector response of the Farmer and scanning thimble chambers exhibited a better energy response, they were not suitable for depth dose measurements in the first 5 mm below the water surface with differences of up to 12% in the surface dose measurement for the 50 kVp x-ray beam. These differences were due to dose artifacts generated by the chamber size and the dose gradient. However, at depths greater than 5 mm, the Farmer and thimble scanning chambers gave uncertainties of less than 3% for the depth dose measurements for all beam energies. The PTW PinPoint 31006 chamber was found to give varying dose differences of up to 8% depending on the x-ray beam energy; this was attributed to the steel central electrode. The authors recommend that one of the parallel plate ionization chambers investigated be used to determine depth dose data for kilovoltage x-ray beams in the energy range studied and give correct dose information close to the surface and at depth in the water phantom.11 page(s

Post-displacement status of climate migrants in Rajshahi City, Bangladesh

Some big cities in Bangladesh have been experiencing a massive and rapid influx of rural people due to the impacts of climate change, and therefore the urban administration encounters enormous challenges. This study aims to investigate the drivers of climate-induced migration and the post-displacement status of the migrants living in the urban slum of Rajshahi City. Using a semi-structured questionnaire survey, this study conducted interviews with 50 migrants residing in two slums in Rajshahi City. An interpretive phenomenological analysis (IPA) approach was implemented to evaluate the survey data. This study finds that food insecurity and flood are the two significant climate drivers of migration. Among the non-climate drivers, lack of alternative livelihood is the major reason. It should be noticed that the climate migrants in many cases do not get the opportunity to improve their living standards; they are usually occupied with low-pay professions like maid, van and rickshaw puller, and scrap collector. The study also reveals that migrants, especially females and children, need several basic physiological, economic, social, and health services. Most children have no chance to attend school. Compared to males, females have more opportunities for some support and allowances. Overall, an inadequate level of change has taken place in the lives of migrants, which raises the concern if migration is ever a way to resolve a problem or the beginning of many other problems. Further researches may concentrate on the impact of migration on the dynamics of social capital among slum dwellers

Practical time considerations for optically stimulated luminescent dosimetry (OSLD) in total body irradiation

Total body irradiation (TBI) treatments are used to treat the whole body in preparation for hematopoietic stem cell (or bone marrow) transplantation. Our standard clinical regimen is a 12 Gy in 6 fraction, bi-daily technique using 6 MV X-rays at an extended Source-to-Surface distance (SSD) of 300 cm. Utilizing these characteristics, the beam dose rate is reduced below 7 cGy/min as is standard for TBI treatment. Dose received by the patient is monitored using optically stimulated luminescent dosimetry (OSLD). This work presents some practical calibration corrections based on time-dependant factors for OSLD calibration related to TBI procedure. Results have shown that a negligible difference is seen in OSL sensitivity for 6 MV X-rays irradiated in standard SSD (100 cm) and high dose rate (600 cGy/min) conditions compared to extended SSD (300 cm) and low TBI dose rate (6 cGy/min) conditions. Results have also shown that whilst short term signal fading occurs in the OSL after irradiation at a high dose rate (37% reduction in signal in the first 15 min), thereafter, negligible differences are seen in the OSL signal between 600 and 7 cGy/min irradiations. Thus a direct comparison can be made between calibration OSLs and clinical TBI OSLs between 15 min and 2 h. Finally a table is presented to provide corrections between calibration OSL readout and clinical TBI dose readout for a period up to 7 days. Combining these three results allows users to pre-irradiate their calibration OSLs at standard dose rate and SSD, up to 1 week prior to clinical treatment, and still provide accurate in-vivo dosimetry. This can help with time saving and work efficiency in the clinic

Extrapolated skin dose assessment with optically stimulated luminescent dosimeters

Anovel method is described for the measurement and calculation of surface and skin dose during megavoltage x-ray therapy utilising an extrapolation technique with optically stimulated Dosimeters. The technique utilises three configurations of an Optically Stimulated Luminescence (OSL) detector which provide different effective depth of measurement points. This allows the user to assess percentage build up dose at effective depths of 0.35, 0.55 and 0.85 mm. Performing an extrapolation technique, percentage dose at other effective depths such as the surface (0mm) or the Basal Cell layer (70 μm) depth can be estimated. Results have shown that extrapolated percentage dose of Dmax at a depth of 0.048 mm are 17.3%±2.3%, 28.2%±3.5% and 37.8%±3.8% for field sizes of 10cm × 10cm, 20cm × 20cm and 30cm × 30cm respectively. Comparative results measured with the Attix chamber which has an estimated effective depth of 0.048 mm were 16.5%, 28% and 36.8% respectively, thus showing close agreement (within 1%) with the extrapolation technique. The OSL extrapolation technique will allow users of OSL detectors to accurately assess surface and skin dose using this technique.</p