Incident Air Kerma Research Articles

RADIATION DOSE ESTIMATION WITH CALDOSE_X VERSION 5.0 IN RADIOLOGICAL LABORATORY DEPARTMENT OF RADIODIAGNOSTIC AND RADIOTHERAPY TECHNIQUE

Background: Media in the educational perspective is a strategic instrument in determining the success of the teaching and learning process. On radiographic examination, each patient is always at risk of exposure to ionizing radiation that is not necessary. Students need to learn whether the exposure factors which they use on patients is still below of the diagnostic reference level. This article purpose to get an overview of the radiation dose estimation using CALDose_X version 5.0 software as a laboratory-learning instrument in Radiological Laboratory Department of Radio diagnostic and Radiotherapy Technique, Poltekkes Kemenkes Semarang. Methods: This article contains a description of using this software. The sample type is purposive sampling, which consist of seven types of radiographic examinations belong to The Head of Bapeten Regulation Number 8 of 2011. Entrance surface air kerma (ESAK) value from each exposure factors compared with Bapeten dose limit. Results: The result showed this software able to calculate the incident air kerma of radiographic examination based on the output parameters of an X-ray tube. All of ESAK values confirm with the Bapeten dose limit. Conclusion: The CALDose_X version 5.0 can be proposed as an instructional media to teach students in estimating absorbed dose to organs and tissues of the human body, the effective dose as well as the patient’s cancer risk for radiographic examinations.

Relationship between body habitus and image quality and radiation dose in chest X-ray examinations: A phantom study

PurposeTo evaluate the influence of being overweight on image quality (IQ), radiation dose and acquisition parameters when undertaking adult chest X-ray (CXR) examinations using routine acquisition protocols. MethodsThe Lungman chest phantom, with and without chest plates, was used to simulate the chest region for larger size and average adult patients, respectively. Radiographic acquisitions were conducted using 17 X-ray machines located in eight hospitals using their routine clinical protocols. IQ was assessed using relative visual grading analysis (VGA) and 2 alternative forced choice (2AFC) by six observers. Incident air kerma (IAK) was measured using a solid-state dosimeter. ResultsIQ mean (range) scores between the hospitals were 16.2 (12.0–21.3) with a 56.0% difference and 20.9 (14.1–23.6) with a 50.2% difference for the standard and larger size phantoms, respectively. IAK mean (range) scores 63 µGy (19–136 µGy) with a 150% difference and 159 µGy (27–384 µGy) with a 173% difference for the standard and larger size phantoms, respectively. The chest plates had a significant negative impact on IQ (P = 0.001) and lead to an increased in IAK by approximately 50%. ConclusionVisual measures of IQ and IAK showed large differences between hospitals for standard and larger phantom sizes; differences within the hospitals was lower. Overall, Lungman with chest plates was found to degrade IQ and increase radiation dose by a factor of two. Further optimisation is required especially for the larger sized patient’s imaging protocols for all eight hospitals.

291. Digital breast tomosynthesis mean glandular dose evaluation

Purpose Digital Breast Tomosynthesis (DBT) is a 3D-imaging technique which allows a high-resolution tissues visualization. During a DBT procedure a series of single projection images is acquired over a limited-angle range. The Mean Glandular Dose (MGD) is the dosimetric index currently employed in mammography and it has been adopted as reference dosimetric index in the European guidelines [1] . Aim of this work was to evaluate the MGD in DBT procedures in order to study the unavoidable cumulative dose (DBT + conventional mammography) increasing of the whole diagnostic exam. Methods 50 2D breast examinations with associate DBT investigations of doubt sign were selected. MGD consolle values and all the exposure information (kV, mAs, HVL, tube/filter combination, breast thickness) were recorded for each 2D view and DBT acquisition. Air Kerma was measured by the use of a Piranha Detector and it was evaluated as a mAs function for fixed KVs and tube/filter combinations. These measurements allowed to calculate the MGD, using tabulated g-, c-, s- and T-Monte Carlo factors obtained by radiation transport calculations, according to European guidelines. g-, c-, s-factors convert incident air kerma to absorbed dose for a specific composition and size breast; T-factor [2] correct the MGD for the angle projection. Results For single breast DBT procedures average MGD value was 1.66 ± 0.51 mGy with 2.90 mGy max value. Average dose for single breast due to all conventional projection was 3.67 ± 1.03 mGy. The average cumulative dose for single breast was 4.77 ± 1.80 mGy. Therefore, an average increase of 34.7% of the cumulative dose was registered when a DBT investigation was performed. Conclusion DBT procedures involve an important benefit for the purpose of a more exhaustive diagnostic information with a limited increasing risks associated with the absorbed dose.

A novel method for comparing radiation dose and image quality, between and within different x-ray units in a series of hospitals

Objectives: To develop a novel method for comparing radiation dose and image quality (IQ) to evaluate adult chest x-ray (CXR) imaging among several hospitals. Methods: CDRAD 2.0 phantom was used to acquire images in eight hospitals (17 digital x-ray units) using local adult CXR protocols. IQ was represented by image quality figure inverse (IQFinv), measured using CDRAD analyser software. Signal to noise ratio, contrast to noise ratio and conspicuity index were calculated as additional measures of IQ. Incident air kerma (IAK) was measured using a solid-state dosimeter for each acquisition. Figure of merit (FOM) was calculated to provide a single estimation of IQ and radiation dose. Results: IQ, radiation dose and FOM varied considerably between hospitals and x-ray units. For IQFinv, the mean (range) between and within the hospitals were 1.42 (0.83–2.18) and 1.87 (1.52–2.18), respectively. For IAK, the mean (range) between and within the hospitals were 93.56 (17.26–239.15) μGy and 180.85 (122.58–239.15) μGy, respectively. For FOM, the mean (range) between and within hospitals were 0.05 (0.01–0.14) and 0.03 (0.02–0.05), respectively. Conclusions: The suggested method for comparing IQ and dose using FOM concept along with the new proposed FOM, is a valid, reliable and effective approach for monitoring and comparing IQ and dose between and within hospitals. It is also can be beneficial for the optimisation of x-ray units in clinical practice. Further optimisation for the hospitals/x-ray units with low FOM are required to minimise radiation dose without degrading IQ.

Dosimetry and optimization in digital radiography based on the contrast-detail resolution

Contrast-detail (C-D) curves are useful in evaluating the radiographic image quality in a global way. The objective of the present study was to obtain the C-D curves and the inverse image quality figure. Both of these parameters were used as an evaluation tool for abdominal and chest imaging protocols. The C-D curves were obtained with the phantom CDRAD 2.0 in computerized radiography and the direct radiography systems (including portable devices). The protocols were 90 and 102 kV in the range of 2 to 20 mAs for the chest and 80 kV in the range of 10 to 80 mAs for the abdomen. The incident air kerma values were evaluated with a solid state sensor. The analysis of these C-D curves help to identify which technique would allow a lower value of the entrance surface air kerma, Ke, while maintaining the image quality from the point of view of C-D detectability. The results showed that the inverse image quality figure, IQFinv, varied little throughout the range of mAs, while the value of Ke varied linearly directly with the mAs values. Also, the complete analysis of the curves indicated that there was an increase in the definition of the details with increasing mAs. It can be concluded that, in the transition phase for the use of the new receptors, it is necessary to evaluate and adjust the practised protocols to ensure, at a minimum, the same levels of the image quality, taking into account the aspects of the radiation protection of the patient.

Reducing the risk of skin injuries in cardiac catheterization procedures: Optimization proposal for obese patients

PurposeDuring interventional cardiology procedures, high doses of X-ray may be delivered to patients. This is especially critical in cases of obese patients and/or high obliquity projections. High dose rates can then be produced in patients’ skin as well as insufficient image quality due to regulatory limitations in the X-ray tube output working in the fluoroscopy mode. In this paper, an optimization action is proposed to reduce patient entrance dose rate and preserve image quality in cases of thick patients. MethodsThe action is based on the evaluation of dose rate to the patient and image quality in a new fluoroscopy protocol with less frame rate (7.5 vs. 15 frames/s) and higher spectral shape filter (0.4 vs. 0.1 mm Cu). The new protocol is tested in an angiography room using a PMMA phantom and a test object. ResultsThe new fluoroscopy protocol (7.5 fr/s and 0.4 mm Cu) reduces entrance surface air kerma in 70%–10% (depending on PMMA thickness), preserving the incident air kerma per frame at the image detector. While at lower PMMA thickness, the MTF measured with bar pattern is better for the default protocol; at PMMA thickness between 32 and 37 cm, the optimized protocol produces better image quality indicators. ConclusionsThis work demonstrates that in the case of high thicknesses of PMMA (32–37 cm), increasing spectral beam filter and reducing frame rate may help improve image quality and maintain entrance surface air kerma so as to fulfil the regulatory requirements.

OA194] Calculation of the patient size for abdominal radiography in terms of water equivalent diameter

Purpose Estimate the patient size, in terms of water equivalent diameter (WED), for conventional abdominal anterior-posterior (AP) radiography by using parameters available in the DICOM-header. Methods The hypothesis of the present project was that the ratio of the incident air-kerma on the patient to the detector air-kerma relates to the patient size in conventional radiography. The incident air-kerma to the patient is provided by the dose area product (DAP) divided by the exposed area ( A exp ) . On the other hand, the standardized exposure index (EI) [1] is related to the detector air-kerma. Thus the ratio of both is expected to be associated to the patient size: EI DAP / A exp ∼ size patient . This hypothesis was tested on 120 adult patients who had an abdominal AP radiography and abdominal computed tomography (CT) scan within 1 year. The DAP, A exp and EI were extracted for every radiography from the dose management platform used in the hospital. The CT images were used to calculate the average WED CT over all axial slices [2] . The WED CT was plotted against the ratio ( EI DAP / A exp ) from the radiography and a curve fit was applied. The methodology was validated on 18 new patients with both an abdominal radiography and CT. The estimated WED ( WED est ) of these patients was found by using their DAP, A exp , EI and the previously fitted curve. The WED est was then compared to the WED as calculated from their CT ( WED CT ) . Results An exponential curve fit was applied to the data with a good correlation of R2 = 0.84 between the WED CT and the ratio EI DAP / A exp . In the validation part, the mean percentage difference between WED est and WED CT of the new patients was −1% and all differences were within ± 10%. Conclusions The proposed and validated methodology allows for the calculation of an attenuation-based patient size metric for conventional radiography using parameters captured by a dose management platform from the DICOM-header.

2018 ACC/HRS/NASCI/SCAI/SCCT Expert Consensus Document on Optimal Use of Ionizing Radiation in Cardiovascular Imaging: Best Practices for Safety and Effectiveness.

2018 ACC/HRS/NASCI/SCAI/SCCT Expert Consensus Document on Optimal Use of Ionizing Radiation in Cardiovascular Imaging: Best Practices for Safety and Effectiveness.

OA246] A virtual study to determine the potential of dual-energy imaging for detectability of microcalcifications in breast screening

Purpose Nowadays, the gold technique for screening and diagnosing the breast for lesions is the two-dimensional mammography. This technique experiences some limitations which appear when screening dense breasts. This calls for demand of new methods to improve the visualization of abnormalities. The aim of this work is to show how dual energy X-ray imaging technique may improve the visualization and detectability of abnormalities in mammographic examinations by removing the background clutter. The focus of this study is on improving the visualization of small calcifications. Methods The main part of the study is carried by use of two software tools. A dedicated LUCMRGen software application is used to design a computational breast phantom, comprised of an acrylic semi-cylinder container of thickness 45 mm and a diameter of 100 mm. The phantom was filled with 4970 acrylic spheres with radii between 1 mm and 8 mm. Simulated microcalcifications were designed as spheres with radiuses ranging from 0.3 to 1 mm, placed at different locations in the phantom. The assigned properties of the calcifications were hydroxy apatite, aluminium oxide, and calcium carbonate. Thereafter, mammographic X-ray images were generated using the XRAYImagingSimulator software tool. X-ray images were simulated with low energies from 18 to 21 keV, while the high energy beams were from 40 to 60 keV. Dual energy (DE) images were calculated by weighted subtraction of pairs of low and high energy images. For all simulations, the total incident air kerma at the surface of the model was set to 4 mGy. Dual-energy images were evaluated quantitatively by means of Contrast to Noise Ratio for each of the 16 DE combinations per calcification. Results Results showed that hydroxy apatite calcifications are best visible at combination of 20–40 keV; CaCO3 are best visible at combination of 21–45 keV, while Al2O3 are best visible at combination of 21–60 keV. A physical phantom, replica of the software one is under construction. Experimental validation is planned and results will be presented at the conference. Conclusions The dual energy imaging method offers the potential of improving the visualization of calcifications in mammography when the small calcifications are obscured by overlapping tissues.

Skin models and their impact on mean glandular dose in mammography

PurposeTo quantify the influence of different skin models on mammographic breast dosimetry, based on dosimetric protocols and recent breast skin thickness findings. MethodsBy using an adapted PENELOPE (v. 2014) + PenEasy (v. 2015) Monte Carlo (MC) code, simulations were performed in order to obtain the mean glandular dose (MGD), the normalized MGD by incident air Kerma (DgN), and the glandular depth dose (GDD(z)). The geometry was based on a cranio-caudal mammographic examination. Monoenergetic and polyenergetic beams were implemented, for a breast thickness from 2 cm to 9 cm, with different compositions. Seven skin models were used: a 5 mm adipose layer; a skin layer ranging from 5 mm to 1.45 mm, a 1.45 mm skin thickness with a subcutaneous adipose layer of 2 mm and 3.55 mm. ResultsThe differences, for monoenergetic beams, are higher (up to 200%) for lower energies (8 keV), thicker and low glandular content breasts, decreasing to less than 5% at 40 keV. Without a skin layer, the differences reach a maximum of 1240%. The relative difference in DgN values for 1.45 mm skin and 5 mm adipose layers and polyenergetic beams varies from −14% to 12%. ConclusionsThe implemented MC code is suitable for mammography dosimetry calculations. The skin models have major impacts on MGD values, and the results complement previous literature findings. The current protocols should be updated to include a more realistic skin model, which provides a reliable breast dose estimation.

Comparison of incident air kerma (ki) of common digital and analog radiology procedures in Kohgiluyeh and Boyer-Ahmad province

Abstract Introduction: Although in many developed countries, Analog radiography (AR) is replaced with digital radiography (DR) but AR is still widely used in many countries included Iran. Therefore, dosimetrically assessment of delivered dose is very important to avoid unnecessary patient dose. Materials and Methods: In this study, all imaging centers in Kohgiluyeh and Boyer-Ahmad were selected. The initial information included the mean kVp and mAs used by the personnel to perform each radiological procedure were gathered through a questionnaire. Barracuda dosimeter was then used to measure Incident air kerma (ki). Data obtained from digital radiography (DR) and analogue radiography (AR) were then analyzed and compared to each other. Results: The mean incident air kerma (ki) for five radiological procedures (chest AP&Lat, Skull AP&Lat, Lumbar spine AP&Lat, Thoracic spine AP&Lat and Pelvis) in digital devices were 0.38&1.34, 2.1&1.94, 4.99&7.83, 4.18& 6.41 and 4.33 mGy and those for analogue devices were 0.7&1.28, 3.05&3.02, 7.25&9.9, 7.125&8.36 and 5.36 mGy, respectively. Discussion and Conclusion: The use of low kVp or high mAs is one of the reasons to increase the incident air kerma (ki) in analogue methods comparing to digital methods in all procedures except the chest (in Lateral view). Also the results, surprisingly, showed that in some of the analogue methods incident air kerma (ki) was less than digital methods which is most probably because of the auto-exposure conditions.

A patient-centric approach to quality control and dosimetry in CT including CBCT

One measurement and an algebraic formula are used to calculate the incident air kerma (Ka,i) at the skin after any CT examination, including cone-beam CT (CBCT) and multi-slice CT (MSCT).Empty scans were performed with X-ray CBCT systems (dental, C-arm and linac guidance scanners) as well as two MSCT scanners. The accumulated Ka,i at the flat panel (in CBCT) or the maximum incident air kerma at the isocentre (in MSCT) were measured using a solid-state probe. The average Ka,i(skin), at the skin of a hypothetical patient, was calculated using the proposed formula. Additional measurements of dose at the isocentre (DFOV) and kerma-area product (KAP), as well as Ka,i(skin) from thermoluminiscence dosimeters (TLDs) and size-specific dose estimates are presented for comparison.The Ka,i(skin) for the standard head size in the dental scanner, the C-arm (high dose head protocol) and the linac (head protocol) were respectively 3.33 ± 0.19 mGy, 15.15 ± 0.76 mGy and 3.23 ± 0.16 mGy. For the first MSCT, the calculated Ka,i(skin) was 13.1 ± 0.7 mGy and the TLDs provided a Ka,i(skin) between 10.3 ± 1.1 mGy and 13.8 ± 1.4 mGy.Estimation of patient air kerma in tomography with an uncertainty below 7% is thus feasible using an empty scan and conventional measurement tools. The provided equations and website can be applied to a standard size for the sake of quality control or to several sizes for the definition of diagnostic reference levels (DRLs). The obtained incident air kerma can be directly compared to the Ka,i from other X-ray modalities as recommended by ICRU and IAEA.

Patient radiation doses in intraoral and panoramic X-ray examinations in Sudan

Radiation doses were measured for the first time in intraoral and panoramic dental radiology at Sudanese hospitals. Doses were determined using various exposure settings for adults and children in 8 intraoral and 6 panoramic X-ray devices. The study sample was equally divided between devices using a digital image receptor (DR) and those using conventional screen film (SF). Radiation doses are reported in terms of incident air kerma (IAK) (intraoral radiology) and kerma area product (PKA) (panoramic radiology). IAK values in intraoral radiology were: 1.45 mGy (DR), 4.45 mGy (SF), and 3.01 mGy (combined). For panoramic radiology, PKA values ranged: from 35.8 to 103.2 mGy cm2 (average: 70.4 mGy cm2) for children and from 65.7 to 151.4 mGy cm2 (average: 103.4 mGy cm2) for adults. The results showed that the downward trend in patient doses can be achieved using digital imaging. The study revealed important concerns surrounding radiation protection, such as the lack of regular quality assurance programs and the use of circular collimators.

Evaluation of Radiation Exposure on Mass Screening Examination for Gastric Cancer Using an Air Kerma-area Product Meter

The present study grasped the radiation exposure per examination by incident air kerma (air kerma-area product; KAP and incident air kerma; Ka, e) using an air kerma-area product meter of our division with mobile population based gastric cancer screening. Initially, we measured the air kerma rate at the patient entrance reference point using an air kerma-area product meter and calibrated dosimeter, for three devices which an air kerma-area product meter was equipped, inspected the indication error of them. The error was 4.3% at the maximum, and accuracy was confirmed. The 816 patients who underwent gastric cancer screening in our division, the median values of KAP and Ka, e of the standard gastrography method 1 were 645.7 mGy·cm2, 37.4 mGy, respectively. The radiation dose of males were significantly higher than females, and the radiation dose increased in proportion to the BMI. The median values of calculated KAP and Ka, e of the standard gastrography method 1 for standard body size were 633.8 mGy·cm2, 37.0 mGy, respectively. We suggest that the patient exposure in gastrography can be optimized using an air kerma-area product meter.

Average absorbed breast dose in mammography: a new possible dose index matching the requirements of the European Directive 2013/59/EURATOM

BackgroundThe new European Directive 2013/59/EURATOM requires that patients are informed about the risk associated with ionising radiation and that detailed information on patient exposure is included in the radiological report. This implies a revision of the routinely used dose indexes to obtain quantities related to individual exposure evaluable from acquisition parameters. Here we propose a new mammography dose index consistent with the average glandular dose (AGD).MethodsAn equation has been developed for calculating the average absorbed breast dose (2ABD). It depends on incident air kerma ka,i and on energy absorption coefficient μen; ka,i can be calculated for each anode-filter combination, based on kVp, mAs, the yield of the tube used Ytb, and the breast thickness d; μen depends on kVp and has been evaluated for each anode-filter combination. 2ABD has been compared to AGD evaluated by Dance or Wu methods, which represent the reference standards, for 20 patients of our university hospital.ResultsThe incident air kerma ka,i, calculated as a function of kVp, mAs, Ytb and d, was in good agreement with the same quantity directly measured: the relative uncertainty is < 0.10. The results of the comparison between 2ABD and AGD evaluated by both Dance and Wu methods appear to be consistent within the uncertainties.Conclusions2ABD is easily evaluable for each mammogram from the acquisition parameters. It can be proposed as a new suitable dose index, consistent with AGD, matching the requirements of the 2013 European Directive.

Abstract ID: 148 Calculation Backscatter factors for pediatric diagnostic radiology using Monte Carlo Methods

Dosimetry in pediatric radiology is essential since children present greater radiosensitivity in relation to adults. The dose is estimated from the entrance skin dose calculated from air kerma and backscatter factor (BSF). However, the backscatter factors presented in guidelines for use in pediatric radiology were calculated for adults [1] . The purpose of this work is to calculate backscatter factors for children and adults, comparing the influence of patient dimensions on dose estimation in pediatric radiology. Monte Carlo simulation was used for calculations, using the PENELOPE 2014 code with the penEasy 2015 extension. The geometric model consists of a box simulating the chest with dimensions 30 × 30 cm2 and 10 cm thick for a newborn child and 15 cm thick for an adult, with homogeneous composition: soft tissue and PMMA. An ionization chamber was modeled as an air volume with dimension 2.5 × 3.8 × 2.5 cm3. Monoenergetic beams with energy between 10 and 100 keV and polyenergetic beams with a tube potential between 50 and 130 kV were simulated. Three field areas were used 10 × 10, 20 × 20 and 25 × 25 cm2. The code was modified to provide the entrance skin dose and incident air kerma. The BSF were determined from the ratio between these quantities. The BSF values obtained in this work were compared with values from the literature, showing differences smaller than 4%. For monoenergetic beam, BSF increases with energy increasing up to approximately 60 keV, where a maximum value is observed. For the polyenergetic beam, BSF increases monotonically with the tube potential. The BSF for acrylic are around 9% higher than for soft tissue, due to its higher density and effective atomic number. BSF increases up to 20% with field size. It is observed that the BSF values calculated for the adult are up to 15% higher than those calculated for children. These results point to the need for using appropriate BSF for children’s dimensions.

Abstract ID: 203 Breast model validation for Monte Carlo evaluation of normalized glandular dose coefficients in mammography

In Monte Carlo simulations for estimation of normalized glandular dose coefficients (i.e. the ratio between the mean glandular dose (MGD) and incident air kerma at the breast upper surface), the radiosensitive breast tissue is modelled as a homogeneous mixture of adipose and glandular tissue. However, such an assumption has been shown to lead to an overestimation in MGD by an average of 30% [1] , [2] . This work aimed at comparing the homogeneous breast models proposed by different authors and in different quality assurance protocols to patient specific breast phantoms. To obtain these phantoms, uncompressed breast images were acquired with a CT scanner dedicated to the breast and segmented to classify each voxel into 4 categories: air, skin tissue, adipose tissue and glandular tissue. Then the compression which breasts undergo during a mammography exams was simulated via software in order to obtain 3D compressed patient specific breast phantoms which present an heterogeneous glandular distribution similar to that of the irradiated breast. The homogeneous breast phantom was simulated either with a 4-mm skin thickness (as adopted in the USA protocol), or with a 5-mm adipose layer simulating the skin and the subcutaneous adipose layer (as adopted in the EU protocol) or with a skin thickness of 1.45 mm (i.e. the skin thickness estimated from 3D breast images). A pre-validated Monte Carlo code based on GEANT4 toolkit ver. 10.00 [3] was employed to calculate the dose differences between the standard models and the patient specific breast phantom. This study provided an insight into possible bias of the standard models for breast dosimetry and an indication of new breast model for future normalized glandular dose calculations.

Air kerma calculation in Monte Carlo simulations for deriving normalized glandular dose coefficients in mammography

The estimation of the mean glandular dose in mammography using Monte Carlo simulations requires the calculation of the incident air kerma evaluated on the breast surface. In such a calculation, caution should be applied in considering explicitly the presence of the top compression paddle, since Compton scattering in this slab may produce a large spread of the incidence angles of x-ray photons on the scoring surface. Then, the calculation of the incident air kerma should contain the ‘effective’ area of the scoring surface, which takes into account the angle of incidence of photons on such a surface. Using Geant4 Monte Carlo simulations with a code previously validated according to the Task Group 195 of the American Association of Physicists in Medicine, we show that for typical x-ray spectra and energy range adopted in mammography, the resulting discrepancy in the calculation of the incident air kerma may lead to an overestimation from a minimum of 10% up to 12% of normalized dose coefficients and, hence, of the corresponding mean glandular dose if this contribution is not considered.

Study on patient dosimetry and image quality in digital mammography

Abstract Introduction Digital mammography present many advantages in comparison to conventional mammography, such as high dynamic range and the post-processing of acquired images. One problem is that protocols may not be optimized, resulting in higher absorbed doses to patients. The objective of this work is to evaluate image quality and to estimate mean glandular doses (MGD) in patients submitted to mammography examinations with three digital systems and one screen-film system in Recife, Brazil. Methods To estimate the MGD, the parameters used to acquire images of 5475 patients, with ages between 40 and 64 years and compressed breasts between 2 and 9 cm, were registered. The MGD was calculated by multiplying the incident air kerma with conversion coefficients depending on the anode/filter, breast glandularity and half-value layer. The image quality evaluation of the digital systems was made using objective and subjective European criteria. Results The results showed MGDs in the range of 0.4-10.3 mGy and the higher values were observed with digital systems. It was also observed that in the digital systems the use of compression force is not adequate and the irradiation parameters are not optimized. The images failed to reproduce the pectoral muscle and the contrast-to-noise ratio was not adequate for one system, indicating the need to improve the patient’s positioning and the exposure parameters. Conclusion It can be concluded that the use of non-optimized irradiation parameters is causing the higher doses with digital systems, highlighting the insufficient compression force.

Evaluation of a breast software model for 2D and 3D X-ray imaging studies of the breast

IntroductionIn X-ray imaging, test objects reproducing breast anatomy characteristics are realized to optimize issues such as image processing or reconstruction, lesion detection performance, image quality and radiation induced detriment. Recently, a physical phantom with a structured background has been introduced for both 2D mammography and breast tomosynthesis. A software version of this phantom and a few related versions are now available and a comparison between these 3D software phantoms and the physical phantom will be presented. MethodsThe software breast phantom simulates a semi-cylindrical container filled with spherical beads of different diameters. Four computational breast phantoms were generated with a dedicated software application and for two of these, physical phantoms are also available and they are used for the side by side comparison. Planar projections in mammography and tomosynthesis were simulated under identical incident air kerma conditions. Tomosynthesis slices were reconstructed with an in-house developed reconstruction software. In addition to a visual comparison, parameters like fractal dimension, power law exponent β and second order statistics (skewness, kurtosis) of planar projections and tomosynthesis reconstructed images were compared. ResultsVisually, an excellent agreement between simulated and real planar and tomosynthesis images is observed. The comparison shows also an overall very good agreement between parameters evaluated from simulated and experimental images. ConclusionThe computational breast phantoms showed a close match with their physical versions. The detailed mathematical analysis of the images confirms the agreement between real and simulated 2D mammography and tomosynthesis images. The software phantom is ready for optimization purpose and extrapolation of the phantom to other breast imaging techniques.