Average Glandular Dose Values Research Articles

Estimation of the absorbed dose in simultaneous digital breast tomosynthesis and mechanical imaging.

Use of mechanical imaging (MI) as complementary to digital mammography (DM), or in simultaneous digital breast tomosynthesis (DBT) and MI - DBTMI, has demonstrated the potential to increase the specificity of breast cancer screening and reduce unnecessary biopsies compared with DM. The aim of this study is to investigate the increase in the radiation dose due to the presence of an MI sensor during simultaneous image acquisition when automatic exposure control is used. A radiation dose study was conducted on clinically available breast imaging systems with and without an MI sensor present. Our estimations were based on three approaches. In the first approach, exposure values were compared in paired clinical DBT and DBTMI acquisitions in 97 women. In the second approach polymethyl methacrylate (PMMA) phantoms of various thicknesses were used, and the average glandular dose (AGD) values were compared. Finally, a rectangular PMMA phantom with a 45mm thickness was used, and the AGD values were estimated based on air kerma measurements with an electronic dosemeter. The relative increase in exposure estimated from digital imaging and communications in medicine headers when using an MI sensor in clinical DBTMI was . For the phantom measurements of various thicknesses of PMMA, the relative increases in the AGD for DM and DBT measurements were, on average, and , respectively. The relative increase in the AGD using the electronic dosemeter was in DM and in DBT. The average difference in dose between the methods was . Our measurements suggest that the use of simultaneous breast radiography and MI increases the AGD by an average of . The increase in dose is within the acceptable values for mammography screening recommended by European guidelines.

Physical and dosimetric characterisation of different Contrast-Enhanced digital mammographic systems: A multicentric study

PurposeContrast-enhanced digital mammography (CEDM) is a relatively new imaging technique recombining low- and high-energy mammograms to emphasise iodine contrast. This work aims to perform a multicentric physical and dosimetric characterisation of four state-of-the-art CEDM systems. MethodsWe evaluated tube output, half-value-layer (HVL) for low- and high-energy and average glandular dose (AGD) in a wide range of equivalent breast thicknesses. CIRS phantom 022 was used to estimate the overall performance of a CEDM examination in the subtracted image in terms of the iodine difference signal (S). To calculate dosimetric impact of CEDM examination, we collected 4542 acquisitions on patients. ResultsEven if CEDM acquisition strategies differ, all the systems presented a linear behaviour between S and iodine concentration. The curve fit slopes expressed in PV/mg/cm2 were in the range [92–97] for Fujifilm, [31–32] for GE Healthcare, [35–36] for Hologic, and [114–130] for IMS. Dosimetric data from patients were matched with AGD values calculated using equivalent PMMA thicknesses. Fujifilm exhibited the lowest values, while GE Healthcare showed the highest. ConclusionThe subtracted image showed the ability of all the systems to give important information about the linearity of the signal with the iodine concentrations. All the patient-collected doses were under the AGD EUREF 2D Acceptable limit, except for patients with thicknesses ≤35 mm belonging to GE Healthcare and Hologic, which were slightly over. This work demonstrates the importance of testing each CEDM system to know how it performs regarding dose and the relationship between PV and iodine concentration.

Average Glandular Dose (AGD) and Radiation Dose Optimization in Screen-Film and Digital X-ray Mammography

We determined the average glandular dose (AGD) from the craniocaudally (CC) and mediolateral oblique (MLO) views of 496 breasts (247 women) at eight clinics in Sudan. The incident air kerma from the X-ray tube output values and the typical patient-specific breast exposure factors were measured. The AGD values were inferred from the measured incident air kerma and breast-specific dose-conversion coefficients. The AGD per CC and MLO projection and per woman ranged from 0.56 to 2.89 mGy (average: 1.36), 0.48 to 2.08 mGy (average: 1.19), and 2.08 to 9.94 mGy (average: 5.10). The proposed national diagnostic reference levels (mGy) for digital mammography are 1.8 and 1.6 mGy for CC and MLO projection, respectively. Establishing the proposed diagnostic reference levels is an essential step in ensuring patient protection from radiation and will help promote dose optimization for X-ray mammography at the national level and beyond. These results provide important baseline data that can be used to formulate national diagnostic reference levels.

Local Diagnostic Reference Levels for Full-Field Digital Mammography and Digital Breast Tomosynthesis in a Tertiary Hospital in Malaysia.

A set of national diagnostic reference levels (DRLs) was established in Malaysia for a range of breast thicknesses in 2013, but no updates for full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT). Due to the increasing number of DBTs used and concern over radiation exposure, this study aimed to explore and establish local diagnostic reference levels for FFDM and DBT in Malaysia health facilities at different compressed breast thickness (CBT) ranges. The CBT, kilovoltage peak (kVp), Entrance surface dose (ESD), and average glandular dose (AGD) were retrospectively extracted from the mammography Digital Imaging and Communications in Medicine (DICOM) header. The 75th and 95th percentile values were obtained for the AGD distribution of each mammography projection for three sets of CBT range. The difference in AGD values between FFDM and DBT at three CBT ranges was determined. The DRLs for FFDM were 1.13 mGy, 1.52 mGy, and 2.87 mGy, while DBT were 1.18 mGy, 1.88 mGy, and 2.78 mGy at CBT ranges of 20–39 mm, 40–59 mm, and 60–99 mm, respectively. The AGD of DBT was significantly higher than FFDM for both mammographic views (p < 0.005). All three CBT groups showed a significant difference in AGD values for FFDM and DBT (p < 0.005). The local DRLs from this study were lower than the national DRLs, with the AGD of FFDM significantly lower than DBT.

DOSIMETRY IN DIGITAL BREAST TOMOSYNTHESIS: COST-EFFICIENT APPROACH FOR THE SOUTH AMERICAN PERSPECTIVES.

The measurement of air kerma in air (Kair) to estimate average glandular dose (AGD) received during digital breast tomosynthesis (DBT) studies is sometimes a difficult task. In this work, a novel methodology was implemented to measure Kair and half-value layer while the X-ray tube is rotating. A low economic cost support (LCS) was built to place aluminium sheets and a calibrated dosemeter. Three Fujifilm Innovality equipment were used and two dosemeters calibrated on W-Al energies. Validation of the new methodology was made against standard scheme and it was applied to estimate AGD for 300 patients and 7 phantoms. Validation analysis was satisfactory. The difference in the AGD calculated with the LCS and DICOM Header was lower than ±10%. AGD values ranged from 0.77 to 2.11mGy and 0.85 to 2.15mGy for phantoms and patients, respectively. The novel methodology has a potential use for DBT equipment without stationary mode.

Average glandular doses reported by mammography units: how reliable are they?

Introduction. Average glandular dose (AGD) values displayed by mammography units are often used to compare doses with diagnostic reference levels, with acceptable and achievable dose levels given with in the European guidelines on breast cancer screening, or between mammography units. The aim of the work was to check the reliability of displayed AGD values by comparing them with independently calculated values. Material and methods. The comparison was performed for five mammography units, for 20 groups of patients (50 patients each), examined in various periods between the years 2015 and 2020. AGD values were calculated independently for the same patients using the results of measurements. Results. Observed differences between displayed and calculated doses affected their comparison with acceptable and achievable dose levels. Conclusions. The displayed AGD values should be used with caution. If reliable information on AGD values is needed, they should be independently calculated using the results of measurements.

Abstract P5-01-02: Glandular dose in contrast-enhanced dual-energy mammography

Abstract INTRODUCTION Estimation of the Average Glandular Dose (AGD) absorbed by the breast during x-ray based examination is an established part of quality control procedures for breast imaging, both for standard mammography and new techniques as digital breast tomosynthesis (DBT) and contrast enhanced digital mammography (CEDM). It is however fundamental that every optimization program obtains an adequate imaging quality. In our study we evaluated the AGD absorbed by the breast, during CEDM examinations, performed with Dual Energy (DE) technique in our Department. MATERIALS AND METHODS We retrospectively evaluated 37 DE mammograms; we reported and analyzed AGD, Entrance Skin Exposure (ESE), anode/filter combinations, breast thickness, kV (kilovolt), mAs (milliAmpere per second), and compression in daN (decaNewton) values, for each mammography view obtained on high and low energy. In 10 Patients, it was possible to compare DE with a recent standard mammography performed on the same mammography unit. RESULTS AGD values for the entire DE study, in craniocaudal and mediolateral oblique views, resulted between 4.23 mGy and 13.44 mGy; based on the breast thickness (27-79 mm) and on the anod/filter combination. We found out a significantly lower AGD for small breast thicknesses and Mo/Rh and Mo/Cu combination compared to Rh/Rh and Rh/Cu. In the whole study evaluation, the AGD percentage report due to low and high energy acquisitions resulted between 76.8% and 81.6%, and between 18.4% and 23.2%, respectively. For the 10 Patients in which was possible a direct comparison with the data obtained with recent standard mammography, resulted a ratio between DE AGD and standard mammography AGD variable from 1.43 to 2.48 (mean value: 2.0), again with lower AGD values obtained with Mo/Rh - Mo/Cu combination and for small breast thicknesses. AGD ratio between low energy and standard mammography acquisition resulted between 1.23 and 3.31. DISCUSSION CEDM is proving to have all the potential to get a definite role in diagnosis and breast tumor staging, providing a direct correlation between morphologic and functional imaging. In our study we assessed the dosimetry to determine if an additional x-ray exposure will be a limit to DE use and, if that is the case, in which measure. Data in the literature on DE dosimetry are still spare and extremely heterogenous. In any case, the increase of delivered dose could be justifiable when compared to the great benefits given by this technique in breast cancer early diagnosis and staging, especially in dense breast tissue, in the follow-up of Patients with breast cancer history and in case of MRI incompatibility. Furthermore, when compared to MRI, CEDM is an easy-access, low-cost, fast and well accepted exam by the patient. CONCLUSIONS Although the risk of induced carcinogenesis associated with x-ray breast modalities is small, dosimetric aspects should be considered both for the risk evaluation and for optimization of acquisition systems; with the advance of the technologies we will be able to have a dose reduction by maintaining high quality standards. Results obtained from this preliminary study needs to be extended by a larger case study to get a complete evaluation and comprehension of the phenomenon. Citation Format: Cossu E, Castellani F, Fiaschetti V, Mariateresa M, Tiziana R, Angelo T. Glandular dose in contrast-enhanced dual-energy mammography [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-01-02.

INSTITUTIONAL BREAST DOSES IN DIGITAL MAMMOGRAPHY.

The objective of this study was to survey breast dose in screening mammography, establish institutional doses and compare them with the corresponding dose values. Three hundred women between the ages of 40 and 80 years old participated in the study. All mammographic examinations were performed with a digital mammography system. The women characteristics (age, weight, height, BMI), technical and exposure parameters (anode/filter material, projection, compressed breast thickness (CBT), compression force, tube voltage, tube load), the entrance surface dose (ESD) and the average glandular dose (AGD) were recorded. The mean, median, 75th and 95th percentiles of the AGD and ESD distributions were estimated for all examinations, for right and left breast, as well as for CBT within 55-65 mm, for Cranio-Caudal (CC) and Medio-Lateral Oblique (MLO) projections. A statistical analysis was also performed, to investigate the impact of the recorded parameters on the ESD and AGD. The mean/median values of the ESD and AGD for all examinations, for CC and MLO projections were 4.60/4.29 and 5.42/5.25 mGy and 1.18/1.13 and 1.32/1.30 mGy, respectively. The mean/median values of the ESD and AGD for CC and MLO projections at CBT range 55-65 mm were 5.29/5.08 and 5.56/5.42 mGy and 1.30/1.24 and 1.36/1.32 mGy, respectively. The 75th percentile for CC and MLO projections were estimated 5.79 and 6.17 mGy, as well as 1.41 and 1.48 mGy in terms of ESD and AGD values, respectively. The 95th percentile of the ESD and AGD for CC and MLO projections were also 7.40 and 7.53 mGy and 1.76 and 1.78 mGy, respectively. The tube voltage, tube load, age and CBT had a significant influence on the dose values. The estimated values were found to be comparable, or in most cases lower, than the corresponding 75th and 95th percentile values from previous studies.

OA247] Calculation of breast dose with the regression model

Purpose To know breast doses for 2D digital mammography and 3D tomosynthesis equipment ensure that determining risks for breast which organ is radiosensitive. In this study, main objective is to construct a mathematical model, using multiple linear regression analysis method, which takes into account the exam specific parameters such as patient age, breast thickness, breast surface area, force, tube voltage and effective tube current and provides an estimation of the actual breast dose during 2D digital mammography and 3D tomosynthesis exams. Methods A dosimetric quality control test has been carried out to determine the reliabilities of Entrance Skin Dose (ESD) and Average Glandular Dose (AGD) values given by the digital mammography device following each exam. Patient data have been derived from the Picture Archiving and Communication System (PACS) for a retrospective evaluation. Radiologists have separated patients into 4 groups represented as A, B, C and D based on the BI-RADS criteria which account for breast composition. Each group included 50 patients to yield statistically meaningful results. A database has been constructed that contains dose information and the exposure parameters specific to mammography exams. Breast surface area determined by manually drawn regions of interest (ROI) has also been included in the database. AGD and ESD values have separately been analyzed with respect to each exposure parameter. It has been investigated whether there were significant differences between the data sets by applying Kruskal–Wallis analysis. Mathematical model has been constructed on the base of multiple regression analysis to determine the effects of independent variables on AGD and ESD. Results The dosimetric quality control of the digital mammography device was performed and it was found that the device was operating under optimum conditions. Kruskal Wallis tests carried out between AGD, ESD and independent variables have resulted in p values lower than 0.05. In the model based on multiple regression, AGD and ESD corresponded to the 95.4% and 93.9% of variance, respectively. Conclusion The constructed model provides a practical method to calculate AGD and ESD by using the exposure parameters without need to any conversion factors.

P048] Comparison of breast radiation dose for digital breast tomosynthesis estimated according compressed breast thickness by using breast phatom

Purpose To compare the surface radiation dose (ESD) and Average Glandular Dose (AGD) of digital breast tomosynthesis (DBT) examination according compressed breast thickness by using breast phantoms. Methods Because of mammary glands have relatively high radiation sensitivity, that breast dose evaluation for mammography was using entrance surface dose (ESD) and average glandular dose (AGD). Many studies were proven that radiation dose from DBT was higher than that of Digital mammography. The DBT system determines target material, filtration and tube voltage by compressed breast thickness and adjusts to exposure output (mAs) using an automatic exposure control (AEC) system to obtain appropriate image density in clinical practice. An automatic exposure control (AEC) is proposed for ESD and AGD measurement s during DBT exposure. AGD and ESD were estimated using breast phantom thickness categories: 22 mm, 32 mm, 45 mm and 55 mm in clinical practice. Results On DBT examination of 55 mm breast phantom, the mean ESD and AGD were 6.37 mGy and 1.95 mGy, respectively. The mean ESD and AGD values for DBT in 45 mm were 4.32 mGy and 1.43 mGy. The mean ESD and AGD values for DBT in 32 mm were 2.72 mGy and 1.08 mGy. The mean ESD and AGD values for DBT in 22 mm were 1.92 mGy and 0.91 mGy. The ESD was 2–3 times higher compared with the AGD. Conclusions In DBT examination, The ESD and AGD were descending as breast phantom thickness decreases. This study suggests that it is useful for the quality control in DBT examination to mention values of ESD for each breast thickness as well as AGD.

Characterization of optically stimulated luminescence for assessment of breast doses in mammography screening

Landauer optically stimulated luminescence (OSL) technology nanoDot dosimeters (OSLDs) are characterized for use in mammography screening at various tube voltages, mAs values and target/filter combinations. The average glandular dose (AGD) for a 50-mm breast, based on the representative compressed breast thickness of a 45-mm polymethyl methacrylate (PMMA) phantom, is assessed using OSLDs with different beam conditions. Further, the linearity of the OSLD response is measured and angular dependence tests are performed for various tube potentials, mAs and target/filter combinations. The breast-absorbed doses are measured at various depths for a 32-kVp X-ray beam at 100 mAs, with a Mo/Rh target/filter combination. The measured incident air kerma values at different lateral positions exhibit a maximum deviation of 6%, and the average relative response of the OSLDs at the reference point (center) with respect to various lateral positions is found to be 1.001 ± 0.09%. The calculated AGD values are in the 1.3 ± 0.1−3.5 ± 0.2 mGy range, depending on the tube potential, tube loading and target/filter combinations. An exposure setup featuring the auto-exposure control (AEC) mode, 28 kVp, 73.8 mAs, and a Mo/Rh target/filter combination may be preferred for mammography screening for a compressed breast thickness of 45 mm.

Radiation exposure of digital breast tomosynthesis using an antiscatter grid compared with full-field digital mammography.

Our study aim was to assess the radiation dose of digital breast tomosynthesis (DBT) in comparison to full-field digital mammography (FFDM) in a clinical setting. Two-hundred four patients were consecutively included, of which 236 complementary DBT and FFDM examinations were available. All acquisitions were performed on a single commercially available mammography system capable of FFDM and DBT acquisitions using an antiscatter grid. The average glandular dose (AGD) was calculated for each examination using the Dance method. For this, tube output and half-value layer were measured, and the required exposure parameters (target/filter material, tube voltage, tube load, compressed breast thickness) were retrieved from the DICOM metadata. The DBT and FFDM AGD values were pairwise tested, and a subanalysis with respect to breast thickness was performed. The mean (SD) AGD values for a single-view DBT and FFDM were 1.49 (0.36) mGy and 1.62 (0.55) mGy, respectively, which are small but statistically significant differences. This difference may be partially attributed to the small difference in the mean breast thickness between FFDM and DBT (3 mm). In this patient population, the AGD was lower for DBT than for FFDM in 61% of the patients. When patients were categorized according to breast thickness, the AGD of DBT was only significantly smaller than the AGD of FFDM for breast thickness categories larger than 50 mm, indicating that the dose reduction for DBT compared with FFDM was more pronounced in thick breasts. The radiation dose of patients undergoing a single-view DBT was comparable to a single-view FFDM. For patients with thicker breasts, the radiation dose of DBT was slightly lower than FFDM.

Towards personalized compression in mammography: A comparison study between pressure- and force-standardization

ObjectiveTo compare a conventional 14 decanewton (daN) force-standardized compression protocol with a personalized 10kilopascal (kPa) pressure-standardized protocol. MethodsA new add-on contact area detector, which enables pressure-standardized compression, is validated in a double-blinded intra-individual comparison study. Breast screening participants (433) received one craniocaudal (CC) and one mediolateral oblique (MLO) compression for both breasts. Three of these compressions were force-standardized, and one, blinded and randomly assigned, was pressure-standardized. Participants scored their pain experience on an 11-point numerical rating scale (NRS). Three experienced breast-screening radiologists, blinded for compression protocol, indicated which images required retakes. ResultsAn unanticipated under-compression issue that occurred at forces below 5daN was effectively solved with minimal extra radiographer training during the study. For pressure-standardized compressions obtained at 5daN or more, the compressed breasts thickness increased on average 4.2% (MLO)—6.3% (CC), average pain scores were reduced by 10% (MLO)—17% (CC) and the proportion of women experiencing severe pain (NRS≥7) was reduced by 27% (MLO)—32% (CC), compared with force-standardized compressions (all p-values <0.05). Average glandular dose (AGD) and proportions of retakes were similar for both protocols. ConclusionPressure-standardized compressions resulted in AGD values and a retake proportion similar to force-standardized compressions, while pain was significantly reduced.

Dose assessment in contrast enhanced digital mammography using simple phantoms simulating standard model breasts

Slabs of polymethyl methacrylate (PMMA) or a combination of PMMA and polyethylene (PE) slabs are used to simulate standard model breasts for the evaluation of the average glandular dose (AGD) in digital mammography (DM) and digital breast tomosynthesis (DBT). These phantoms are optimized for the energy spectra used in DM and DBT, which normally have a lower average energy than used in contrast enhanced digital mammography (CEDM). In this study we have investigated whether these phantoms can be used for the evaluation of AGD with the high energy x-ray spectra used in CEDM. For this purpose the calculated values of the incident air kerma for dosimetry phantoms and standard model breasts were compared in a zero degree projection with the use of an anti scatter grid. It was found that the difference in incident air kerma compared to standard model breasts ranges between −10% to +4% for PMMA slabs and between 6% and 15% for PMMA-PE slabs. The estimated systematic error in the measured AGD for both sets of phantoms were considered to be sufficiently small for the evaluation of AGD in quality control procedures for CEDM. However, the systematic error can be substantial if AGD values from different phantoms are compared.

Patient investigation of average glandular dose and incident air kerma for digital mammography

Our aim in this study was to investigate the incident air kerma (IAK) and average glandular dose (AGD) for polymethylmethacrylate (PMMA) phantoms and patient breasts for each thickness by use of digital mammography units, and to determine the correlation between phantom and patient measurements. An additional aim was to calculate the numerical value of the diagnostic reference level (DRL) for digital mammography in Japan based on the AGD from patient measurements. Patient-based IAK and AGD values were calculated for 300 patients who underwent mammographic examinations at three institutions. On examination of a 40-mm PMMA phantom, the IAK and the AGD were 7.89 and 1.84 mGy, respectively. The mean patient breast thickness was 37.6 mm, and the mean IAK and the AGD calculated from actual patient data for breast thicknesses between 40 mm and 50 mm were 8.91 and 2.08 mGy, respectively. Approximately 20 % of the 300 patients had IAK >10 mGy. The distributions of patient-based IAK and AGD values were higher than the IAK and AGD values for the PMMA phantom. The patient dose with use of the PMMA phantom can be underestimated. The DRL was calculated from patient-based AGDs of the regular breast thickness as 2.0 mGy in Japan.

SU‐E‐I‐59: Patient‐Based Average Glandular Dose Estimations in Taiwan

Purpose: The objective of the study was to investigate the average glandular dose (AGD) distributions based on the patients with average‐sized breasts in Taiwan. Methods: Patient data were collected from 199 mammography units of 167 facilities (76% of the units in Taiwan) during 2012 in Taiwan. For each unit, exposure parameters including target/filter, kVp and tube loadings of 15 patients with average‐compressed breast size of 4.2±0.5 cm in craniocaudal (CC) views were recorded by the technologists. Half value layer (HVL) and radiation exposure per mAs were measured at specific beam quality during the annual on‐site inspection. Entrance skin exposure for each patient was thus estimated based on the radiation output data, patient exposure techniques and compressed breast thickness. Both the conversion factors calculated by Dance and Wu were used for further AGD calculations for comparisons. Average of the AGDs of the 15 patients may served as the represented mean AGD for each mammographic unit, and dose distributions could also be obtained for further evaluations. Results: Based on the conversion factors calculated by Dance, AGDs ranged from 95.8 to 505.7 mrad, and the mean, median and 3rd quartile of the estimated AGD of the 199 mammographic units was 191.9 mrad, 172.2 mrad, and 228.0 mrad, respectively. By calculating AGDs using Wu's conversion factors, AGDs ranged from 73.3 to 390.4 mrad, and the mean, median and 3rd quartile of the estimated AGD of the 199 mammographic units was 156.1 mrad, 143.5 mrad, and 186.2 mrad, respectively. Estimated AGDs using Wu's correction factors got the lower AGD values compared to the AGDs estimated by Dance method. Conclusion: AGD distributions based on nationwide represented patient data may serve as a baseline dose database for future diagnostic reference level (DRL) establishment in mammography in Taiwan. This work was supported by grants from Atomic Energy Council of Taiwan(AEC10101003L).

Average Glandular Dose in Digital Mammography and Breast Tomosynthesis

To determine the average glandular dose (AGD) in digital full-field mammography (2 D imaging mode) and in breast tomosynthesis (3 D imaging mode). Using the method described by Boone, the AGD was calculated from the exposure parameters of 2247 conventional 2 D mammograms and 984 mammograms in 3 D imaging mode of 641 patients examined with the digital mammographic system Hologic Selenia Dimensions. The breast glandular tissue content was estimated by the Hologic R2 Quantra automated volumetric breast density measurement tool for each patient from right craniocaudal (RCC) and left craniocaudal (LCC) images in 2 D imaging mode. The mean compressed breast thickness (CBT) was 52.7 mm for craniocaudal (CC) and 56.0 mm for mediolateral oblique (MLO) views. The mean percentage of breast glandular tissue content was 18.0% and 17.4% for RCC and LCC projections, respectively. The mean AGD values in 2 D imaging mode per exposure for the standard breast were 1.57 mGy and 1.66 mGy, while the mean AGD values after correction for real breast composition were 1.82 mGy and 1.94 mGy for CC and MLO views, respectively. The mean AGD values in 3 D imaging mode per exposure for the standard breast were 2.19 mGy and 2.29 mGy, while the mean AGD values after correction for the real breast composition were 2.53 mGy and 2.63 mGy for CC and MLO views, respectively. No significant relationship was found between the AGD and CBT in 2 D imaging mode and a good correlation coefficient of 0.98 in 3 D imaging mode. In this study the mean calculated AGD per exposure in 3 D imaging mode was on average 34% higher than for 2 D imaging mode for patients examined with the same CBT.

Dose to population as a metric in the design of optimised exposure control in digital mammography

This paper describes a method for automatic optimisation of parameters (AOP) in digital mammography systems. Using a model of the image chain, contrast to noise ratio (CNR) and average glandular dose (AGD) are computed for possible X-ray parameters and breast types. The optimisation process consists of the determination of the operating points providing the lowest possible AGD for each CNR level and breast type. The proposed metric for the dose used in the design of an AOP mode is the resulting dose to the population, computed by averaging the AGD values over the distribution of breast types in the population. This method has been applied to the automatic exposure control of new digital mammography equipment. Breast thickness and composition are estimated from a low dose pre-exposure and used to index tables containing sets of optimised operating points. The resulting average dose to the population ranges from a level comparable to state-of-the-art screen/film mammography to a reduction by a factor of two. Using this method, both CNR and dose are kept under control for all breast types, taking into consideration both individual and collective risk.

Optimisation of X-ray examinations in Lithuania: start of implementation in mammography

Optimisation of medical X-ray examinations is very important for the enhancement of the reliability of the examination and for the reduction of the radiation dose to patients. Results of investigations of doses to patients during mammography using thermoluminescence dosemeters at different hospitals are presented together with a brief overview of the situation for mammography in Lithuania. It is shown that the entrance surface air kerma varies in a broad range and differed from hospital to hospital. Nevertheless the calculated values of average glandular dose (AGD) for a 'standard' breast being relatively high were comparable with those (3.2 mGy per exposure at net optical density 1.4) currently accepted by international authorities. Differences in AGD values evaluated at different hospitals demonstrate the existing potential for optimisation of the mammography screening procedures. The results of this investigation will be included in a database for patient doses in Lithuania and used for establishing a national reference dose level for mammography. Currently, reference levels recommended by international authorities are used in Lithuania.