ARTICLE Download: 4| View: 12| Comments: 0
Subject: Physical Sciences, Radiation & Radiography Keywords: radiation track chemistry; chemical track structure; oxygen effect; oxygen depletion; ion beam therapy; ROS; superoxide anion
Online: 5 December 2019 (03:32:18 CET)
The radiosensitivity of biological systems is strongly affected by the system oxygenation. On the nanoscopic scale and molecular level, this effect is considered to be strongly related to the indirect damage of radiation. Even though particle track radiolysis has been the object of several studies, still little is known about the nanoscopic impact of target oxygenation on the radical yields. We present here an extension of the chemical module of the Monte Carlo particle track structure code TRAX, taking into account the presence of dissolved molecular oxygen in the target material. The impact of the target oxygenation level on the chemical track evolution and the yields of all the relevant chemical species is studied in water under different irradiation conditions: different linear energy transfer (LET) values, different oxygenation levels, and different particle types. Especially for low LET radiation, a large production of two highly toxic species (HO2• and O2•− ), which are not produced in anoxic conditions, is predicted and quantified in oxygenated solutions. The remarkable correlation between the HO2• and O2•− production yield and the oxygen enhancement ratio observed in biological systems suggests a direct or indirect involvement of HO2• and O2•− in the oxygen sensitization effect. The results are in agreement with available experimental data and previous computational approaches. An analysis of the oxygen depletion rate in different radiation conditions is also reported.
Tue, 15 October 2019
ARTICLE Download: 59| View: 119| Comments: 0 | doi:10.20944/preprints201910.0168.v1
Subject: Physical Sciences, Radiation & Radiography Keywords: neutron imaging; neutron detector; X-ray detector; CCD camera; CMOS camera; collimator; X-rays; image processing; computed tomography; CT reconstruction
Online: 15 October 2019 (11:15:26 CEST)
Neutron computed tomography (nCT) has been established at many major neutron sources worldwide, using high-end equipment requiring major investment and development. Many older and smaller reactors would be capable of doing nCT as well, but cannot afford the investment before feasibility is proven. We have developed a compact low-cost but high-quality detection system using a new cooled CMOS camera that can either be fully integrated into a sophisticated setup, or used with a rudimentary CT control and motion system to quickly evaluate feasibility of neutron CT at a given beam line facility. Exchanging the scintillation screen makes it feasible for X-rays as well, even for visible light (and transparent samples) using a matte screen. The control system uses a hack to combine motion control with existing imaging software so it can be used to test several dozen different cameras without writing specific drivers. Freeware software can do reconstruction and 3D imaging.
Fri, 23 August 2019
ARTICLE Download: 42| View: 196| Comments: 1 | doi:10.20944/preprints201907.0269.v2
Subject: Physical Sciences, Radiation & Radiography Keywords: computed tomography; radiation dose; cancer risk; CTPA; lung effective diameter
Online: 23 August 2019 (10:53:52 CEST)
The present study aims to investigate radiation doses from Computed Tomography Pulmonary Angiography (CTPA) examinations based on the patient’s size and to estimate the probability of cancer risk induced from the examination. Data from 100 patients who had undergone CTPA examinations, such as scanning acquisition parameters, patient demography, as well as radiation dose exposure, were collected and analysed. All subjects which aged above 18 y/o were scanned using a Philips Brilliance 128 multi-detector CT (MDCT) scanner. The mean dose value for Volume Computed Tomography Dose Index (CTDIvol), Dose-Length Product (DLP) and effective dose (E) were 11.06 ± 7.17 mGy, 400.38 ± 259.10 mGy.cm and 8.68 ± 5.47 mSv respectively. In addition, with respective of patient’s effective diameter, the mean SSDE value for Group 1, Group 2 and Group 3 were 9.93 ± 3.89, 13.70 ± 9.04 and 22.29 ± 7.35, respectively. Cancer risk per million procedure was calculated based on te recommendation by the International Commission on Radiological Protection Publication 103 report. The organ dose and cancer risk attained for breast, lung and liver were 17.05 ± 10.40 mGy (194 per one million procedure), 17.55 ± 10.86 mGy (192 per one million procedure) and 15.04 ± 9.75 mGy (53 per one million procedure), respectively. In conclusion, CTDIvol underestimated, and SSDE was more accurate in describing the radiation dose. Lung and breast with larger lung effective diameter received the highest dose exposure which increase the probability of the cancer risk. Therefore, it is important to apply optimised protocols in order to reduce patient’s exposure during CTPA examination.
Wed, 24 July 2019
ARTICLE Download: 33| View: 90| Comments: 0 | doi:10.20944/preprints201907.0269.v1
Subject: Physical Sciences, Radiation & Radiography Keywords: Computed Tomography; radiation dose; radiation cancer risk; CT Pulmonary Angiography; effective diameter
Online: 24 July 2019 (10:42:37 CEST)
Computed Tomography (CT) scan examinations has greater demands especially in CT Pulmonary Angiography (CTPA) owing to the public and radiology personnel worries towards CT radiation exposure and risks. The aim of present study is to evaluate the comprehensive radiation exposure in computed tomography pulmonary angiography (CTPA) and its cancer risk. The records of 100 patients who had undergone CTPA were retrieved. The radiation dose exposure, scanning acquisition protocol as well as patient characteristics were noted. Radiation exposure were presented as Volume Computed Tomography Dose Index (CTDIvol), Size-Specific Dose Estimate (SSDE), Dose-Length Product (DLP), and effective dose (E) and organ dose. Effective cancer risk per million procedure was calculated by referring to the International Commission on Radiological Protection Publication 103. The CTDIvol, SSDE, DLP were comparable within different effective diameter groups. The average effective dose received by a patient was 8.68 mSv. The organ dose and effective cancer risk attained for breast, lung and liver were 17.05 ± 10.40 mGy (194 per one million procedure), 17.55 ± 10.86 mGy (192 per one million procedure) and 15.04 ± 9.75 mGy (53 per one million procedure), respectively. In conclusion, CTDIvol was undervalued and SSDE was more accurate in describing radiation dose exposure. The lungs and breast of subjects with large effective diameter were higher risk of developing cancer as they received the highest exposure. Therefore, extra safety measures should be considered for large-sized patients undergoing CTPA.Purpose: This study evaluates the comprehensive radiation exposure in computed tomography pulmonary angiography (CTPA) and its cancer risk.
Mon, 24 June 2019
REVIEW Download: 79| View: 161| Comments: 0 | doi:10.20944/preprints201906.0231.v1
Subject: Physical Sciences, Radiation & Radiography Keywords: bystander effect, genomic instability, lethal mutations,radiotherapy, diagnostic radiology
Online: 24 June 2019 (08:34:26 CEST)
Non-targeted effects (NTE) such as bystander effects or genomic instability have been known for many years but their significance for radiotherapy or medical diagnostic radiology are far from clear. Central to the issue are reported differences in response of normal and tumour tissues to signals from directly irradiated cells. This review will discuss possible mechanisms and implications of these different responses and will then discuss possible new therapeutic avenues suggested by the analysis. Finally, the importance of NTE for diagnostic radiology and nuclear medicine which stems from the dominance of NTE in the low dose region of the dose response curve will be presented. Areas such as second cancer induction and microenvironment plasticity will be discussed.
Mon, 28 May 2018
ARTICLE Download: 190| View: 224| Comments: 0 | doi:10.20944/preprints201805.0386.v1
Subject: Physical Sciences, Radiation & Radiography Keywords: magnetic resonance imaging; arterial spin labelling; renal MRI; perfusion; renal ASL
Online: 28 May 2018 (06:26:31 CEST)
Purpose: A number of imaging readout schemes have been proposed for renal arterial spin labelling (ASL) to quantify kidney cortex perfusion, including gradient echo based methods of balanced fast field echo (bFFE) and gradient-echo echo-planar imaging (GE-EPI), or spin echo based schemes of spin-echo echo planar imaging (SE-EPI) and turbo spin-echo (TSE). Here, we compare these imaging schemes to evaluate the optimal imaging scheme for pulsed ASL (PASL) assessment of human kidney cortex perfusion at 3 T. Methods: Ten healthy volunteers with normal renal function were scanned using each 2D multislice imaging scheme, in combination with a respiratory triggered FAIR (flow-sensitive alternating inversion recovery) ASL scheme on a 3 T Philips Achieva scanner. All volunteers returned for a second identical scan session within two weeks of the first scan session. Comparisons were made between the imaging schemes in terms of perfusion weighted image (PWI) signal-to-noise ratio (SNR) and perfusion quantification, temporal SNR (tSNR), spatial coverage, and repeatability. Results: For each imaging scheme, renal cortex perfusion was calculated (bFFE: 276 ± 29 mL/100 g/min, GE-EPI: 222 ± 18 mL/100 g/min, SE-EPI: 201 ± 36 mL/100 g/min, TSE: 200 ± 20 mL/100 g/min). Perfusion was found to be higher for GE based readouts compared to SE based readouts, with significantly higher measured perfusion for the bFFE readout compared to all other schemes (P < 0.05), attributed to the greater vascular signal present. Despite the PWI-SNR being significantly lower for SE-EPI compared to all other schemes (P < 0.05), the SE-EPI readout gave the highest tSNR and was found to be the most reproducible scheme for the assessment of kidney cortex, with a CoV of 17.2%, whilst minimizing variability of the perfusion weighted signal across slices for whole kidney perfusion assessment. Conclusion: For the assessment of kidney cortex perfusion, SE-EPI provides optimal tSNR, minimal variability across slices and repeatable data acquired in a short scan time with low specific absorption rate.
Fri, 11 May 2018
ARTICLE Download: 251| View: 278| Comments: 0 | doi:10.20944/preprints201805.0176.v1
Subject: Physical Sciences, Radiation & Radiography Keywords: gel dosimetry; radiation dosimetry; radio-fluorogenic gel, luminescent dosimetry
Online: 11 May 2018 (05:29:00 CEST)
In radiotherapy, accurate deposition of energy to the targeted volume is vital to ensure effective treatment. Gel dosimeters are attractive detection systems, as tissue substitutes with potential to yield three-dimensional dose distributions. Radio-fluorogenesis is creation fluorescent chemical products in response to energy deposition from high-energy radiation. This report shares studies of a radio-fluorogenic gel dosimetry system, gelatin with coumarin-3-carboxlyic acid (C3CA), for the quantification of imparted energy. Aqueous solutions exposed to ionizing radiation result in the production of hydroxyl free radicals through water radiolysis. Interactions between hydroxyl free radicals and coumarin-3-carboxylic acid produce a fluorescent product. 7-hydroxy-coumarin-3-carboxylic acid has a blue (445 nm) emission, following UV to near UV (365–405 nm) excitation. Effects of C3CA concentration and pH buffers were investigated for this system. The response of the system was explored with respect to strength, type, and exposure rate of high-energy radiation. Results show a linear dose response relationship with a dose-rate dependency and no energy or type dependencies. This report supports the utility of gelatin-C3CA for phantom studies of radio-fluorogenic processes.
Fri, 8 July 2016
ARTICLE Download: 2754| View: 1345| Comments: 1 | doi:10.20944/preprints201607.0009.v1
Subject: Physical Sciences, Radiation & Radiography Keywords: Antennas; Communication systems; Electromagnetic analysis; Measurements; Radio propagation; Waveguides
Online: 8 July 2016 (03:44:51 CEST)
In this research paper, design and development of pyramidal horn antenna for J-band application is reported. It is particularly designed for 17 dB gain and half beam width about 25 degrees at 6.93 GHz. Horn aperture, horn axial length and distance from the throat of the antenna to aperture are the main design constraints which are calculated and used for the antenna design and simulation. Beam width in E-plane and H-plane horn is calculated and it is 19.18 dB and 22.86 dB respectively. The reported antenna design shows good performance for J-band in radiometry, satellite, and radar applications.