No abstract available

[en] Area monitoring ensures radiation exposure at an acceptable level, which must be lower than the legal limit. Experimental measurements were taken in an ionizing radiation calibration laboratory. The specified reference radiation to radiation protection N80 was used. Five area monitors were used. The ranges of dose rate inaccuracy measured in rate mode for times ≤ 2 and ≥ 3s were from 10 to 48% and from 1 to 15%, respectively. The inaccuracy ranges measured in integrated mode for times ≤ 2 and ≥ 3s were from 4 to 8% and from 0 to 22%, respectively. (paper)

[en] The setting of two biplane X ray systems were evaluated (image intensifier (II) and flat panel (PP)), through DICOM tags from 32 images created during the characterization of both systems. The technical parameters adjusted for systems were: 63,8 to 80,0 kV and 15,0 to 388,0 mA, for the system with II and 52,0 to 77,0 kV and 25,0 to 476,0 mA, for the system with PP detector. Both equipment presented a different mA adjustment, when moving from fluoroscopy modes low dose (FL), medium dose (FM) and high dose (FH) to cine mode (CI). Two dosimetric quantities were evaluated, the first one was the dose-area product (DAP) which gave as a result for FB mode, between 0,03 to 0,35 uGycm²/image (II) and from 0,05 a 0,69 uGycm²/image (PP), when the polymethyl methacrylate (PMMA) thickness was incremented from 4 to 16 cm. In cine mode the DAP quantity showed, percentage values from 24 to -1 % for the same PMMA increment. Skin cumulative dose was the second quantity evaluated and showed an increment of incident air kerma (KAI)/image in factors from 17 to 35 (II) and 15 to 28 (PP) when used in CI mode instead of FB mode, to the different PMMA thicknesses used. This dose increment for CI mode must be considered by cardiologists, to use the fluoroscopic run as an alternative to document part of the procedures when there is no need to use a high quality image (author)

[en] Recent studies have indicated the increase of the incidence of lens opacities for low radiation doses. Considering epidemiological data, the International Commission on Radiological Protection (ICRP) issued a statement that changed the absorbed dose threshold for the eye lens. The statement also recommends a reduction in the dose limits to the eye lens for occupationally exposed persons; now it is considered to be 20 mSv in a year averaged over five years. For this research two types of thermoluminescent dosimeters TL were used in the construction of the curve tandem. (LiF-100H e LiF-200). For system calibration three monitors were irradiated for each radiation beam. The monitors were irradiated with 4 mGy kerma at 1.5 m from the focal point. The Tandem curve was obtained by the ratio between the values of the energy dependence curves of each dosimeter. Data obtained for the corresponding x-ray beams to radiation reference N60 to N120 are more accurate for determining the energy - steepest part of the curve. The results are shown similar to similar studies and confirm the possibility of using the method for determining the unknown energy radiation fields. (author)

[en] Volpara is a software that performs quantitative and specific breast density calculations through the analysis of mammographic images. Additionally, based on the Dance model, Volpara calculates the AGD. However, instead of using the factor (c), which in the Dance method is the conversion factor for a standard breast with 50% glandularity, the software utilizes information about the specific breast density of each patient. Due to this, the AGD calculated by Volpara tends to be a value closer to reality when compared to the AGD calculated by DICOM Header. The main objective of this study is to compare the AGD calculated by VolparaDensity and DICOM header. (author)

[en] Radiation dose and image quality for paediatric protocols in a biplane x-ray system used for interventional cardiology have been evaluated. Entrance surface air kerma (ESAK) and image quality using a test object and polymethyl methacrylate (PMMA) phantoms have been measured for the typical paediatric patient thicknesses (4-20 cm of PMMA). Images from fluoroscopy (low, medium and high) and cine modes have been archived in digital imaging and communications in medicine (DICOM) format. Signal-to-noise ratio (SNR), figure of merit (FOM), contrast (CO), contrast-to-noise ratio (CNR) and high contrast spatial resolution (HCSR) have been computed from the images. Data on dose transferred to the DICOM header have been used to test the values of the dosimetric display at the interventional reference point. ESAK for fluoroscopy modes ranges from 0.15 to 36.60 μGy/frame when moving from 4 to 20 cm PMMA. For cine, these values range from 2.80 to 161.10 μGy/frame. SNR, FOM, CO, CNR and HCSR are improved for high fluoroscopy and cine modes and maintained roughly constant for the different thicknesses. Cumulative dose at the interventional reference point resulted 25-45% higher than the skin dose for the vertical C-arm (depending of the phantom thickness). ESAK and numerical image quality parameters allow the verification of the proper setting of the x-ray system. Knowing the increases in dose per frame when increasing phantom thicknesses together with the image quality parameters will help cardiologists in the good management of patient dose and allow them to select the best imaging acquisition mode during clinical procedures

[en] The aim of this work was to investigate the differences in dose settings and image quality among 10 X-ray systems used for interventional cardiology in Chile. Entrance surface air kerma (ESAK) was measured on a phantom of 20 cm thickness of polymethyl methacrylate slabs. Image quality was evaluated using DICOM images of a test object Leeds TOR 18-FG for cine mode acquisition, through the numerical parameters signal-to-noise ratio (SNR), high-contrast spatial resolution (HCSR) and figure of merit. ESAK rate values for fluoroscopy modes ranged between 7.1 and 121.7 mGy min^-1. For cine mode, ESAK values per frame ranged from 63 to 400 μGy fr^-1. SNR and HCSR parameters for cine mode varied from 4.8 to 8.6 and 0.4 to 10, respectively. FOM values resulted from 6.9 to 64.5 among the different X-ray systems. Results show important differences between systems and point out the need to launch an optimisation programme. (authors)

[en] Mammography is the main radiographic technique for imaging the breast, being indicated for cancer diagnosis and clinical monitoring. In Brazil, the National Quality Program in Mammography (NQPM) was developed. This program provides radiation exposure reference levels and evaluates the image system quality through a visual inspection of images obtained with the breast phantom. Texture is an important characteristic that can be used to identify or describe an image. It refers to the spatial arrangement of pixel’s gray levels in a given region. Texture analysis technique can be used to obtain spatial resolution results from phantom’s grids present in the images. Therefore, the aim of this work is to develop texture analysis algorithms to perform an automatic quality evaluation of Brazilian College of Radiology (BCR) breast phantom images. For this study, BCR phantom images were collected from different facilities in Belo Horizonte, Brazil. The methodology consists in selecting a region of interest (ROI) and then performing image background subtraction and filtration. Thereafter, statistical values are calculated to quantify the gray level spatial distribution. Statistical parameters were used to quantify the differences between periodic models. These algorithms were developed in MATLAB and the test objects evaluations were made following the NQPM parameters. The visual and computerized evaluations were compared. The results showed that the developed algorithms can differentiate the four different grids of BCR phantom images. The use of these digital image processing techniques in the test object images allows an objective evaluation. Therefore, the developed algorithms help to improve the evaluation performed by quality assurance programme specialists. (authors)

[en] Radiation dose and image quality for paediatric protocols in all five X-ray fluoroscopy systems used for interventional cardiology procedures existing in Chile have been evaluated. Entrance surface air kerma (ESAK) and image quality using a test object (TO) and polymethyl methacrylate (PMMA) phantoms have been measured for the typical paediatric patient thicknesses (4-16 cm of PMMA). Images from fluoroscopy (low (FL), medium and high) and cine (CI) modes have been archived in DICOM format. Signal-to-noise ratio (SNR), figure of merit (FOM) and high-contrast spatial resolution (HCSR) have been computed from the images. The ratio between the maximum and the minimum value of ESAK per frame for a given fluoroscopy mode between the five systems ranges from 2 to 5 and from 14 to 38 for CI mode. SNR, FOM and HCSR showed a great variability for the different acquisition modes (AMs) and PMMA thickness. In the near future, it is urgent to upgrade Chilean legislation on radiation protection to incorporate quality assurance programmes that will allow us to evaluate and optimise the X-ray systems used in medical applications. Increments in doses per frame when increasing phantom thickness and when used CI runs instead of FL runs can be considered by the cardiologist in the good management of patient dose and allow them to select the best imaging AM during clinical procedures. (authors)

[en] Breast cancer is the most common cancer among women, and early detection is critical to its diagnosis and treatment. Mammography is the best method for breast-cancer screening and is capable of reducing mortality rates To date, the most effective method for early detection of breast cancer has been x-ray mammography for which the screen/film (SF) technique has been the gold standard. Digital mammography has been proposed as a substitute for film mammography given the benefits inherent to digital technology. The purpose of our study was to compare the technical performance of digital mammographic and screen-film mammography. A PMMA phantom with objects to simulate breast structures. For the screen/film (SF) technique the results showed that 54% mammography units did not achieve the minimum acceptable performance as far the image quality. Besides, 67% services showed inadequate performance in their processing systems, which had significant influence on the image quality. At the mean glandular dose only 44% of digital systems evaluated were compliant in all thicknesses of PMMA. The average glandular dose AGD was 90 % higher than in screen/film systems. (authors)