dose measurements
Recently Published Documents


TOTAL DOCUMENTS

823
(FIVE YEARS 103)

H-INDEX

33
(FIVE YEARS 2)

2022 ◽  
Vol 12 (2) ◽  
pp. 600
Author(s):  
Serenella Russo ◽  
Silvia Bettarini ◽  
Barbara Grilli Leonulli ◽  
Marco Esposito ◽  
Paolo Alpi ◽  
...  

High-energy small electron beams, generated by linear accelerators, are used for radiotherapy of localized superficial tumours. The aim of the present study is to assess the dosimetric performance under small radiation therapy electron beams of the novel PTW microSilicon detector compared to other available dosimeters. Relative dose measurements of circular fields with 20, 30, 40, and 50 mm aperture diameters were performed for electron beams generated by an Elekta Synergy linac, with energy between 4 and 12 MeV. Percentage depth dose, transverse profiles, and output factors, normalized to the 10 × 10 cm2 reference field, were measured. All dosimetric data were collected in a PTW MP3 motorized water phantom, at SSD of 100 cm, by using the novel PTW microSilicon detector. The PTW diode E and the PTW microDiamond were also used in all beam apertures for benchmarking. Data for the biggest field size were also measured by the PTW Advanced Markus ionization chamber. Measurements performed by the microSilicon are in good agreement with the reference values for all the tubular applicators and beam energies within the stated uncertainties. This confirms the reliability of the microSilicon detector for relative dosimetry of small radiation therapy electron beams collimated by circular applicators.


Author(s):  
Don Johnson Nocum ◽  
John Robinson ◽  
Mark Halaki ◽  
Magnus Bath ◽  
John D. Thompson ◽  
...  

Abstract This study sought to achieve radiation dose reductions for patients receiving uterine artery embolisation (UAE) by evaluating radiation dose measurements for the preceding generation (Allura) and upgraded (Azurion) angiography system. Previous UAE regression models in the literature could not be applied to this centre’s practice due to being based on different angiography systems and radiation dose predictor variables. The aims of this study were to establish whether radiation dose is reduced with the upgraded angiography system and to develop a regression model to determine predictors of radiation dose specific to the upgraded angiography system. A comparison between Group I (Allura, n = 95) and Group II (Azurion, n = 95) demonstrated a significant reduction in KAP (kerma-area product) and Ka, r (reference air kerma) by 63% (143.2 Gy·cm2 vs 52.9 Gy·cm2; P < 0.001, d = 0.8) and 67% (0.6 Gy vs 0.2 Gy; P < 0.001, d = 0.8), respectively. The multivariable linear regression (MLR) model identified the UAE radiation dose predictors for KAP on the upgraded angiography system as total fluoroscopy dose, Ka, r, and total uterus volume. The predictive accuracy of the MLR model was assessed using a Bland-Altman plot. The mean difference was 0.39 Gy·cm2 and the limits of agreement (LoA) were +28.49 and -27.71 Gy·cm2, and thus illustrated no proportional bias. Our findings validated the upgraded angiography system and its advance capabilities to significantly reduce radiation dose for our patients. Interventional radiologist and interventional radiographer familiarisation of the system’s features and the implementation of the newly established MLR model would further facilitate dose optimisation for all centres performing UAE procedures using the upgraded angiography system.


2022 ◽  
Author(s):  
S.Q. Pelegrineli ◽  
A.X. Silva ◽  
W.S.S. Filho ◽  
L.S.R. Oliveira ◽  
R.M. Stenders ◽  
...  

This study proposes a quick, easy, and low-cost method that can be used to assess the radiological safety of an irradiation line used for cargo and container inspection facilities. The radiation-emitting equipment used was a Smiths Heimam particle accelerator model HCVP4029 operating at 4.5 MeV. The radiation dose measurements were performed using a personal radiation monitor Ultra Radac mod MRAD 111 (Geiger–Muller). The ambient equivalent dose H*(10) was estimated for two facilities: A (real) (1.12E-03 mSv per scan) and B (fictitious) (3.25E-03 mSv per scan). The dimensionless factor R, which represents a ratio between two specific scanning (Ss) quantities regarding the facilities A and B, is introduced as a reference for assessing the level of radiological safety. This study compares facilities A and B by using a simple alternative safety assessment based on the R factor. The dimensionless R-value appears to be able to facilitate both the personnel’s and the general public’s perception of risk levels, even with no fixed scale.


Life ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 31
Author(s):  
Fawzia E. M. Elbashir ◽  
Wassim Ksouri ◽  
Mohamed Hassan Eisa ◽  
Sitah Alanazi ◽  
Farouk Habbani ◽  
...  

This paper presents guidelines for the calibration of radiation beams that were issued by the International Atomic Energy Agency (IAEA TRS 398), the American Association of Physicists in Medicine (AAPM TG 51) and the German task group (DIN 6800-2). These protocols are based on the use of an ionization chamber calibrated in terms of absorbed dose to water in a standard laboratory’s reference quality beam, where the previous protocols were based on air kerma standards. This study aims to determine uncertainties in dosimetry for electron beam radiotherapy using internationally established high-energy radiotherapy beam calibration standards. Methods: Dw was determined in 6-, 12- and 18 MeV electron energies under reference conditions using three cylindrical and two plane-parallel ion chambers in concert with the IAEA TRS 398, AAPM TG 51 and DIN 6800-2 absorbed dose protocols. From mean measured Dw values, the ratio TRS 398/TG 51 was found to vary between 0.988 and 1.004, while for the counterpart TRS 398/DIN 6800-2 and TG 51/DIN 6800-2, the variation ranges were 0.991–1.003 and 0.997–1.005, respectively. For the cylindrical chambers, the relative combined uncertainty (k = 1) in absorbed dose measurements was 1.44%, while for the plane-parallel chambers, it ranged from 1.53 to 1.88%. Conclusions: A high degree of consistency was demonstrated among the three protocols. It is suggested that in the use of the presently determined dose conversion factors across the three protocols, dose intercomparisons can be facilitated between radiotherapy centres.


2021 ◽  
Author(s):  
Katia Manolova Sergieva

The clinical specialty of radiotherapy is an essential part of the multidisciplinary process of treatment of malignant neoplasms. Modern radiotherapy is a very complex process of treatment planning and delivery of radiation dose. Radiotherapy reached a very high degree of complexity and sophistication and expected to represent an added value for the cancer patients in terms of clinical outcomes and improved radiation protection. The concept of verifying the realized dose in the medical applications of ionizing radiation was introduced in the early 20th century shortly after the first application of X-rays for the treatment of cancer. Dosimetry audit identify areas for improvement and provide confidence in safety and efficacy, which are essential to creating a clinical environment of continuous development and improvement. Over the years, the audits have contributed to good dosimetry practice and accuracy of dose measurements in modern radiotherapy. Dosimetry audit ensures, that the correct therapeutic dose is delivered to the patients undergoing radiotherapy and play a key role in activities to create a good radiation protection and safety culture. Patient safety is of paramount importance to medical staff in radiotherapy centers and safety considerations are an element in all aspects of the day-to-day clinical activities.


Author(s):  
Leonie Brodbek ◽  
Jana Kretschmer ◽  
Katrin Büsing ◽  
Hui Khee Looe ◽  
Bjoern Poppe ◽  
...  

Abstract The RUBY head phantom in combination with the System QA insert MultiMet can be used for simultaneous point dose measurements at an isocentric and two off-axis positions. This study investigates the suitability of the system for systematic integral end-to-end testing of single-isocenter multiple target stereotactic treatments. Several volumetric modulated arc therapy plans were optimized on a planning CT of the phantom positioned in a stereotactic mask on the stereotactic treatment board. The plans were created for three artificial spherical target volumes centred around the measurement positions in the MultiMet insert. Target diameters between 5 and 40 mm were investigated. Coplanar and non-coplanar plans were optimized using the collapsed cone algorithm of the Oncentra Masterplan treatment planning system and recalculated with the Monte Carlo algorithm of the Monaco treatment planning system. Measurements were performed at an Elekta Synergy linear accelerator. The head phantom was positioned according to clinical workflow comprising immobilization and CBCT imaging. Simultaneous point dose measurements at all target positions were performed with three PinPoint 3D chambers (type 31022) as well as three microDiamond (type 60019) detectors and compared to the treatment planning system calculations. Furthermore, the angular dependence of the detector response was investigated to estimate the associated impact on the measured point dose values. Considering all investigated plans, PTV diameters and positions, the point doses calculated with the Monaco treatment planning system and the microDiamond measurements differed within 3.5%, whereas the PinPoint 3D showed differences of up to 6.9%. Point dose differences determined in comparison to the Oncentra Masterplan dose calculations were larger. The RUBY system was shown to be suitable for end-to-end testing of complex treatment scenarios such as single-isocenter multiple target plans.


Author(s):  
Alina Elter ◽  
Carolin Rippke ◽  
Wibke Johnen ◽  
Philipp Mann ◽  
Emily Hellwich ◽  
...  

Abstract Objective: In MR-guided radiotherapy (MRgRT) for prostate cancer treatments inter-fractional anatomy changes such as bladder and rectum fillings may be corrected by an online adaption of the treatment plan. To clinically implement such complex treatment procedures, however, specific end-to-end tests are required that are able to validate the overall accuracy of all treatment steps from pre-treatment imaging to dose delivery. Approach: In this study, an end-to-end test of a fractionated and online adapted MRgRT prostate irradiation was performed using the so-called ADAM-PETer phantom. The phantom was adapted to perform 3D polymer gel (PG) dosimetry in the prostate and rectum. Furthermore, thermoluminescence detectors (TLDs) were placed at the center and on the surface of the prostate for additional dose measurements as well as for an external dose renormalization of the PG. For the end-to-end test, a total of five online adapted irradiations were applied in sequence with different bladder and rectum fillings, respectively. Main results: A good agreement of measured and planned dose was found represented by high γ-index passing rates (3 %⁄ 3 mm criterion) of the PG evaluation of 98.9 % in the prostate and 93.7 % in the rectum. TLDs used for PG renormalization at the center of the prostate showed a deviation of -2.3 %. Significance: The presented end-to-end test, which allows for 3D dose verification in the prostate and rectum, demonstrates the feasibility and accuracy of fractionated and online-adapted prostate irradiations in presence of inter-fractional anatomy changes. Such tests are of high clinical importance for the commissioning of new image-guided treatment procedures such as online adaptive MRgRT.


2021 ◽  
Vol 94 (1126) ◽  
pp. 20210436 ◽  
Author(s):  
Beth A. Schueler ◽  
Kenneth A Fetterly

Data suggest that radiation-induced cataracts may form without a threshold and at low-radiation doses. Staff involved in interventional radiology and cardiology fluoroscopy-guided procedures have the potential to be exposed to radiation levels that may lead to eye lens injury and the occurrence of opacifications have been reported. Estimates of lens dose for various fluoroscopy procedures and predicted annual dosages have been provided in numerous publications. Available tools for eye lens radiation protection include accessory shields, drapes and glasses. While some tools are valuable, others provide limited protection to the eye. Reducing patient radiation dose will also reduce occupational exposure. Significant variability in reported dose measurements indicate dose levels are highly dependent on individual actions and exposure reduction is possible. Further follow-up studies of staff lens opacification are recommended along with eye lens dose measurements under current clinical practice conditions.


Author(s):  
Akintayo Daniel Omojola ◽  
Michael Onoriode Akpochafor ◽  
Samuel Olaolu Adeneye ◽  
Isiaka Olusola Akala ◽  
Azuka Anthonio Agboje

Sign in / Sign up

Export Citation Format

Share Document