Diagnostic reference levels for digital mammography in New South Wales

A Survey of Mean Glandular Doses and Suggestions on National Diagnostic Reference Levels for Digital Mammography in China

ABSTRACT

The primary purpose of this study was to report the mean glandular doses and to determine the national diagnostic reference levels for digital mammography based on data between 2016 and 2018 in China. The data from 19,076 mammograms (4,769 examinations) by random sampling from 118 digital mammography systems were compiled. Exposure factors included age, compressed breast thickness, kVp, mAs, target/filter combination, entrance surface air kerma, and mean glandular doses, which were retrospectively surveyed and recorded from the monitor. The national diagnostic reference levels (75th percentiles) in mean glandular dose were calculated across median value obtained for all included data and stratified to specific compressed breast thickness ranges. The patients' ages ranged from 22 to 88 y, with a median age of 45. The applied voltage and output medians were 28 kVp and 75.1 mAs for all exposure, respectively. The median CBTs were 45 mm and 48 mm for craniocaudal views and mediolateral oblique views, and the corresponding median mean glandular doses were 1.32 mGy and 1.40 mGy, respectively. The national diagnostic reference level at compressed breast thickness of 40-50 mm was 1.67 mGy for CC views and 1.71 mGy for MLO views. The median mean glandular doses varied significantly and increased with compressed breast thickness, demonstrating the necessity of establishing DRL according to breast thickness and optimizing the clinic's digital mammography practice in China.

Proposed DRLs for mammography in Switzerland

The aim of this study is to propose diagnostic reference levels (DRLs) values for mammography in Switzerland. For the data collection, a survey was conducted among a sufficient number of centres, including five University hospitals, several cantonal hospitals, and large private clinics, covering all linguistic regions of Switzerland to be representative of the clinical practice. The data gathered contained the mean glandular dose (MGD), the compressed breast thickness (CBT), the mammography model and the examination parameters for each acquisition. The data collected was sorted into the following categories: 2D or digital breast tomosynthesis (DBT) examination, craniocaudal (CC) or mediolateral oblique (MLO) projection, and eight categories of CBT ranging from 20 mm to 100 mm in 10 mm intervals. A total of 24 762 acquisitions were gathered in 31 centres on 36 mammography units from six manufacturers. The analysis showed that the data reflects the practice in Switzerland. The results revealed that the MGD is larger for DBT than for 2D acquisitions for the same CBT. From 20-30 mm to 90-100 mm of CBT, the 75th percentile of the MGD values obtained increased from 0.81 mGy to 2.55 mGy for 2D CC acquisitions, from 0.83 mGy to 2.96 mGy for 2D MLO acquisitions, from 1.22 mGy to 3.66 mGy for DBT CC acquisitions and from 1.33 mGy to 4.04 mGy for DBT MLO acquisitions. The results of the survey allow us to propose Swiss DRLs for mammography according to the examination type (2D/DBT), projection (CC/MLO) and CBT. The proposed values are very satisfactory in comparison with other studies.

Glandular doses and diagnostic reference levels (DRLs) for Saudi breast cancer screening programme (2012-2021)

The aim of this study was to report the diagnostic reference levels (DRLs) corresponding to different compressed breast thickness (CBT) ranges. To achieve this, mammographic examinations with 187,788 exposures were analysed. The mean average glandular (AGD) dose was calculated per view, examination, and center. Moreover, the DRL values corresponding to different CBT ranges were reported. The result of the mean AGD per view was found to be 1.36 mGy for craniocaudal (CC) and 1.54 mGy for Mediolateral oblique (MLO), while the mean AGD per examination for all women was 1.45 mGy. The DRL values corresponding to CBTs between 20 to 79 mm ranges were below 2 mGy. These results were from a population of mean age = 49 ± 8 years and mean CBT = 58 ± 8 mm, and was imaged with mean exposures of 29 ± 1 kVp and 74 ± 31 mAs, and a mean compression force of 135±37 N. In conclusion, good mammography practice has been shown, as DRL values are within the limits suggested by the international organizations.

Radiation dose to breast during digital mammography in Tanzania

The aim of this study was to evaluate the mean glandular dose (MGD), to assess the potential for optimization, and to propose diagnostic reference levels (DRLs). MGD was estimated from air kerma measurements and patient information collected during mammography examinations. The 75th percentile values were determined as the third quartile of the median MGD values for all hospitals, and DRLs set as 75th percentile of MGD values. The estimated median values of MGD ranged from 1.5 to 3.9 mGy for craniocaudal projection for median range of 15-59 mm compressed breast thickness (CBT). For a CBT range of 15-63 mm, the median MGD value was 1.5-5.1 mGy for medio-lateral oblique projection. Comparison with other studies showed that the MGD values obtained in this study were relatively high. The magnitude and wide variation of the exposure parameters suggest existing potential for optimization. The training of radiology staff was identified as a top priority.

Trends in patient dose and compression force for digital (DR) mammography systems over an eleven-year period

This study evaluated trends in patient dose and compression force for screening digital (DR) mammography systems. The results of five audits (carried out in 2011, 2014, 2018, 2020 and 2022) were compared. For every audit, anonymised screening examinations from each system consisting of the standard craniocaudal (CC) and mediolateral oblique (MLO) views of both breasts were analysed. Exposure parameters were extracted from the Digital Imaging and Communications in Medicine (DICOM) header and the mean glandular dose (MGD) for each image was calculated. Trends in the distribution of MGD, compressed breast thickness, compression force and compression force per radiographer were investigated. The mean MGD per image (and mean compressed breast thickness) was 1.20 mGy (58 mm), 1.53 mGy (59 mm), 1.83 mGy (61 mm), 1.94 mGy (60 mm) and 2.11 mGy (61 mm) for 2011, 2014, 2018, 2020 and 2022 respectively. The mean (and standard deviation) compression force was 114 (32) N, 112 (29) N, 108 (27) N, 104 (24) N and 100 (23) N for 2011, 2014, 2018, 2020 and 2022 respectively. The mean MGD per image has increased over time but remains below internationally established Diagnostic Reference Levels (DRLs). This increase is primarily due to a change in the distribution of the different manufacturers and digital detector technologies, rather than an increase in the dose of the individual systems over time. The mean compression force has decreased over time in response to client feedback surveys. The standard deviation has also reduced, indicating more consistent application of force.

Clinical image quality assessment and mean glandular dose for full field digital mammography

This study aims to assess the image quality (IQ) of 12 mammographic units and to identify units with potential optimisation needs. Data for 350 mammography examinations meeting inclusion criteria were collected retrospectively from April 2021 to April 2022. They were categorised based on the medical reports into 10 normal cases, 10 cases displaying calcifications and 10 cases presenting lesions. Two radiologists assessed the IQ of 1400 mammograms, evaluating system performance per Boitaet al's study and positioning performance following European guidelines. To measure agreement between the two radiologists, the Cohen's Kappa coefficient (κ) was computed, quantifying the excess of agreement beyond chance. The visual grading analysis score (VGAS) was computed to compare system and positioning performance assessments across different categories and facilities. Median average glandular dose (AGD) values for cranio caudal and medio lateral oblique views were calculated for each category and facility and compared to the national diagnostic reference levels. The health facilities were categorised by considering both IQ VGAS and AGD levels. Inter-rater agreement between radiologists ranged from poor (κ< 0.20) to moderate (0.41 <κ< 0.60), likely influenced by inherent biases and distinct IQ expectations. 50% of the facilities were classified as needing corrective actions for their system performance as they had IQ or high AGD that could increase recall rate and radiation risk and 50% of the health facilities exhibited insufficient positioning performance that could mask tumour masses and microcalcifications. The study's findings emphasise the importance of implementing quality assurance programs to ensure optimal IQ for accurate diagnoses while adhering to radiation exposure guidelines. Additionally, comprehensive training for technologists is essential to address positioning challenges. These initiatives collectively aim to enhance the overall quality of breast imaging services, contributing to improved patient care.

Estimating Local Diagnostic Reference Levels for Mammography in Dubai

As the total volume of mammograms in Dubai is increasing consistently, it is crucial to focus on the process of dose optimization by determining dose reference levels for such sensitive radiographic examinations as mammography. This work aimed to determine local diagnostic reference levels (DRLs) for mammography procedures in Dubai at different ranges of breast thickness. A total of 2599 anonymized mammograms were randomly retrieved from a central dose survey database. Mammographic cases for screening women aged from 40 to 69 years were included, while cases of breast implants and breast thickness outside the range of 20-100 mm were excluded. Mean, median, and 75 percentiles were obtained for the mean glandular dose (MGD) distribution of each mammography projection for all compressed breast thickness (CBT) ranges. The local DRLs for mammography in Dubai were found to be between 0.80 mGy and 0.82 mGy for the craniocaudal (CC) projection and between 0.89 mGy and 0.971.8 mGy for the mediolateral oblique (MLO) projection. Local DRLs were proposed according to different breast thicknesses, starting from 20 to 100 mm. All groups of CBT showed a slight difference in MGD values, with higher values in MLO views rather than CC views. The local DRLs in this study were lower than some other Middle Eastern countries and lower than the standard reference levels reported by the International Atomic Energy Agency (IAEA) at 3 mGy/view.

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.

National diagnostic reference levels: What they are, why we need them and what's next

Diagnostic reference levels (DRLs) are an optimisation tool for medical imaging procedures using ionising radiation. They give an indication of the expected radiation dose received by an average-sized patient undergoing a given imaging procedure. Comparison of typical (median) exposure levels for common imaging procedures with DRLs helps imaging facilities identify procedures that may be amenable to further optimisation. Undertaking comparisons with published DRLs is a requirement for medical imaging facilities under the Code for Radiation Protection in Medical Exposure and for their access to Medicare rebates under the Diagnostic Imaging Accreditation Scheme (DIAS). The Australian Radiation Protection and Nuclear Safety Agency has created the National Diagnostic Reference Level Service to facilitate the collection of data for the establishment of national DRLs in Australia and to assist imaging facilities in comparing their typical doses with the national DRLs. National DRLs have been established in computed tomography, nuclear medicine, and for image-guided and interventional procedures. DRLs must be subject to ongoing review and revision by the national authority to ensure they reflect current practice. This ongoing cycle of assessment and review helps to ensure that the ratio of benefit to risk for patients is maximised.

SCATTER RADIATION INTENSITIES IN HORIZONTAL AND VERTICAL PLANES ABOUT DIGITAL BREAST TOMOSYNTHESIS SYSTEM

Digital breast tomosynthesis (DBT) is a main imaging modality for breast imaging. However, shielding calculations for DBT are commonly based on previous technology with softer beam spectra. In addition, shielding calculations often assume some patient attenuation is provided in locations to the posterior of the patient but without quantification of this attenuation. In this work, recent research in DBT shielding is validated by measuring scatter radiation in the vertical plane. It is also extended upon by measuring the scatter radiation in the horizontal plane and the effect of patient attenuation. These measurements are weighted by our local patient compressed breast thickness distribution to provide a simple scattering factor. Air kerma distributions are provided demonstrating the distribution of scatter radiation around the DBT system in the presence of patient body attenuation. The highest air kerma measured in any direction from a 4-view per patient screening tomosynthesis exam based on the local patient workload is 55 μGy at 1 m. This value can be used to conservatively treat the scatter radiation as an isotropic distribution for shielding assessments. This work is consistent with many recent publications, with the notable exception of the forward scattered peak which is smaller than previous studies. Under our locally encountered breast thickness distribution, the increased scatter radiation and consequent increased minimum shielding requirements is small in most cases. With 400 patients per week, the air kerma at 1 m is 22 mGy and, for a fully occupied public area 2 m away, this requires a gypsum plasterboard thickness of 18.0 mm which is 3.6 mm more than previous data suggests. Although the increase is minimal, standard manufacturing thicknesses of shielding material may not be automatically assumed to be sufficient and careful consideration of the scatter radiation is warranted.

Diagnostic reference levels in digital mammography: a systematic review

Diagnostic reference levels (DRLs) in digital mammography (DM) serve as a useful benchmark for dose monitoring and optimisation, allowing comparison amongst countries, institutions and mammography units. A systematic review of DRLs in DM, published in 2014, reported a lack of consistent and internationally accepted protocol in DRLs establishment, thereby resulting in wide variations in methodologies which complicates comparability between studies. In 2017, the International Commission of Radiation Protection (ICRP) published additional guidelines and recommendations to provide clarity in the protocol used in DRLs establishment. With the continuing evolvement of technology, optimisation of examinations and updates in guidelines and recommendations, DRLs should be revised at regular intervals. This systematic review aims to provide an update and identify a more consistent protocol in the methodologies used to establish DRLs. Searches were conducted through Web of Science, PubMed-MEDLINE, ScienceDirect, CINAHL and Google Scholar, which resulted in 766 articles, of which 19 articles were included after screening. Relevant data from the included studies were summarised and analysed. While the additional guidelines and recommendations have provided clarifications in the methodologies used in DRLs establishment, such as data source (i.e. the preference to use data derived from patient instead of phantoms to establish DRLs), protocol (i.e. stratification of DRLs by compressed breast thickness and detector technology, and the use of median value for DRLs quantity instead of mean) and percentiles used to establish DRLs (i.e. set at the 75th percentile with a minimum sample size of 50 patients), other differences such as the lack of a standard dose calculation method used to estimate mean glandular dose continues to complicate comparisons between studies and different DM systems. This systematic review update incorporated the updated guidelines and recommendations from ICRP which will serve as a useful resource for future research efforts related to DRLs, dose monitoring and optimisation.

A review of screening mammography: The benefits and radiation risks put into perspective

INTRODUCTION/BACKGROUND

In medical imaging a benefit to risk analysis is required when justifying or implementing diagnostic procedures. Screening mammography is no exception and in particular concerns around the use of radiation to help diagnose cancer must be addressed.

METHODS

The Medline database and various established reports on breast screening and radiological protection were utilised to explore this review.

RESULTS/DISCUSSION

The benefit of screening is well argued; the ability to detect and treat breast cancer has led to a 91% 5-year survival rate and 497 deaths prevented from breast cancer amongst 100,000 screened women. Subsequently, screening guidelines by various countries recommend annual, biennial or triennial screening from ages somewhere between 40-74 years. Whilst the literature presents different perspectives on screening younger and older women, the current evidence of benefit for screening women <40 and ≥75 years is currently not strong. The radiation dose and associated risk delivered to each woman for a single examination is dependent upon age, breast density and breast thickness, however the average mean glandular dose is around 2.5-3 mGy, and this would result in 65 induced cancers and 8 deaths per 100,000 women over a screening lifetime from 40-74 years. This results in a ratio of lives saved to deaths from induced cancer of 62:1.

CONCLUSION

Therefore, compared to the potential mortality reduction achievable with screening mammography, the risk is small.

Local diagnostic reference levels for digital mammography: Two hospitals study in northwest, Nigeria

BACKGROUND

Mammography involves the use of low energy X-rays to image the breast tissue. Although low dose radiation is used, the use of ionising radiation implies the risk of inducing breast cancer. Thus, the study established local DRLs for digital mammography for in-house dose optimisation.

METHODS

This was a retrospective study that had a total of 240 women that presented for mammography at the two tertiary institutions located in the Northwest region of Nigeria. Patient demographic information including compressed breast thickness (CBT), which is the breast tissue thickness across the imaging plate, and mean glandular dose (MGD) were recorded. Data were analysed based on descriptive and inferential statistics using SPSS statistical software. The DRLs based on MGD and CBT were established and compared with the relevant data in the literature.

RESULTS

Local DRLs based on MGD and CBT were established at the 75th percentile (craniocaudal (CC): 1.50 mGy; 57 mm; mediolateral (MLO): 1.60 mGy; 63 mm) and 95th percentile (CC: 3.74 mGy; 69 mm; MLO: 3.61 mGy; 76 mm). The MGD based on manual exposure was significantly (p < 0.005) higher compared to the automatic optimisation parameter (AOP) mode which suggests the need to continuously adhere to the use of AOP mode for in-house dose optimisation.

CONCLUSION

The study established local DRLs for the digital mammography systems at the 75th and 95th percentiles which compared well with the values established in the literature. Manual selection of parameters should only be employed where there are legitimate indications as it is associated with high exposure. Also, manual selection of parameters should be based on preset tables as a function of compressed breast thickness.

Establishment of regional diagnostic reference levels for digital mammography in Western Province of Sri Lanka

The radiation dose to the breasts should be kept to a minimum as breast tissues are highly sensitive to radiation. In mammography, the mean glandular dose (MGD) is used to specify the patient dose. In this study, data on the MGD during diagnostic mammographic examinations was collected using the database from six digital mammography facilities available in the Western Province in Sri Lanka. Examinations involving breast pathology, breast implants, or compressed breast thicknesses (CBT) outside the range of 20-110 mm were excluded in this study. The mean MGD per breast was 3.50 mGy, with a mean CBT of 57 mm. The mean MGD per facility varies from 1.58 to 2.27 mGy, with overall 75th and 95th percentiles of 2.15 and 2.82 mGy, respectively. The 75th and 95th percentile MGD per image, for the average CBT of 57 ± 12 mm, were 2.00 and 2.65 mGy respectively. The 75th percentile value of the MGD is suggested for the Western Province and it depends on the specific CBT.

Breast-iRRISC: a novel model for predicting the individualised lifetime risk of radiation-induced breast cancer from a single screening event

OBJECTIVES

This work establishes the prototype of a new innovative risk model that aims to evaluate the total risk involved with screening mammography for each individual female. This has been specifically designed to accommodate any combination of lifetime screening regimes, using only the information gathered from a single mammographic examination.

METHODS

This model prototype was developed with the aid of a large dataset of images from the Cancer Institute New South Wales (CINSW) with over 30,000 images from over 7000 examinations. Each examination is derived from a separate female.

RESULTS

This prototype which we have called Breast Individualised Risk of Radiation-Induced Screening Cancer (Breast-iRRISC) is a novel tool for the assessment of the lifetime risk involved with screening mammography. The results demonstrate the applicability of this approach to the various screening regimes utilised around the globe, in addition to the personalised screening frequency patterns females have undergone and are likely to receive in the future.

CONCLUSIONS

This unique tailored approach to risk assessment will further empower females and clinicians towards a more informed clinical decision process regarding future imaging pathways. It will also inform health policy decisions regarding alternate screening durations and intervals.

ADVANCES IN KNOWLEDGE

Breast-iRRISC is a novel tool that provides females, clinicians and health policymakers around the globe with the ability to quantify the lifetime risk of radiation-induced breast cancer from screening mammography on an individual level from a single exposure.

Mammography Diagnostic Reference Levels (DRLs) in Ghana

INTRODUCTION

Diagnostic Reference Levels (DRLs) are essential for optimisation in mammography. A local DRL for screen-film mammography has been established in Ghana but none exists for the digital mammography systems. Furthermore, technological advancement is phasing out the use of screen-film mammography and replacing it with digital mammography systems. This study aims to establish the local DRLs used in digital mammography across three institutions in Ghana to guide mammography practice.

METHODS

Average glandular dose (AGD), compressed breast thickness (CBT), age of patients, entrance surface exposure (ESE), kVp, and mAs were retrospectively extracted from three digital mammography systems. The 75th and 95th percentile values were obtained for the AGD of each mammography projection and at CBT of 60 ± 5 mm. The correlation between the AGD and CBT, kVp, mAs, and ESE were investigated.

RESULTS

The 75th percentile for the AGD at CBT of 60 ± 5 mm for Centres 1, 2, 3, and all centres were 2.3, 1.8, 2.1, and 2.0 mGy respectively. The DRLs obtained were comparably higher than international studies except those of the United Kingdom. The AGD showed a strong positive correlation with the CBT, kVp, mAs, and ESE. There was variability in the AGD applied across the three centres for the craniocaudal (CC) and mediolateral oblique (MLO) projections. The mean AGD, mAs, and ESE for all the three centres and per centre recorded were higher than previous studies, but the mean kVp and CBT were lower than previous studies.

CONCLUSION

The higher DRLs estimated in this preliminary study indicates that there is a need for dose optimisation in digital mammography practice in Ghana to improve radiation protection.

IMPLICATIONS FOR PRACTICE

The findings will guide the process of optimisation and limit the variations in the radiation dose during mammography practice.

Mammography diagnostic reference levels in Western Australia

Mammography dose data has been collected from Western Australian units to establish Diagnostic Reference Levels for the state. Reference levels have been determined for a variety of phantom thicknesses for both full field digital mammography units and digital breast tomosynthesis units. Levels for the American College of Radiology (ACR) Phantom have been established as 1.3 mGy and 1.5 mGy mean glandular dose for full field digital mammography and digital breast tomosynthesis respectively. 2 cm PMMA was 0.9 mGy and 1.0 mGy and 6 cm PMMA had values of 2.0 mGy and 2.3 mGy. This data can be utilised to help establish national reference levels in the future.

Three-layer heterogeneous mammographic phantoms for Monte Carlo simulation of normalized glandular dose coefficients in mammography

Normalized glandular dose (DgN) coefficients obtained using homogeneous breast phantoms are commonly used in breast dosimetry for mammography. However, glandular tissue is heterogeneously distributed in the breast. This study aimed to construct three-layer heterogeneous mammographic phantoms (THEPs) to examine the effect of glandular distribution on DgN coefficient. Each layer of THEPs was set to 25%, 50%, or 75% glandular fraction to emulate heterogeneous glandular distribution. Monte Carlo simulation was performed to attain mean glandular dose (MGD) and air kerma at 22-36 kVp and W/Al, W/Rh, and W/Ag target-filter combinations. The heterogeneous DgN coefficient was calculated as functions of the mean glandular fraction (MGF), breast thickness, tube voltage, and half-value layer. At 50% MGF, the heterogeneous DgN coefficients for W/Al, W/Rh, and W/Ag differed by 40.3%, 36.7%, and 31.2%. At 9-cm breast thickness, the DgN values of superior and inferior glandular distributions were 25.4% higher and 29.2% lower than those of uniform distribution. The proposed THEPs can be integrated with conventional breast dosimetry to consider the heterogeneous glandular distribution in clinical practice.

CHALLENGES IN CLINICAL PRACTICE OF CR MAMMOGRAPHY IN TANZANIA

The aim of this study was to evaluate the clinical practice of CR mammography in Tanzania. The equipment performance and operational conditions were studied; and mean glandular dose (DG) estimated to 75 women undergoing diagnosis at three mammography facilities. All mammograms during this study were reported to be useful for the intended diagnosis. The median DG for craniocaudal and mediolateral oblique projections ranged from 1.27 ± 0.18 mGy to 1.9 ± 0.27 mGy and from 1.3 ± 0.18 mGy to 1.9 ± 0.27 mGy, respectively, and were below the national regulatory guidance of 2.5 mGy. Despite this positive result, unavoidable inappropriate use of beam quality and tube loading settings which could have been through appropriate staff training and performing routine quality control were not uncommon. This work provides an insight of current operational conditions of CR in Tanzania and what strategy should be employed to this service to improve patient care in the country.

PORTUGUESE STUDY OF MEAN GLANDULAR DOSE IN MAMMOGRAPHY AND COMPARISON WITH EUROPEAN REFERENCES

To characterise the mean glandular dose (MGD) in a sample of healthcare providers for digital mammography in Portugal. To compare the achieved values with European references. The MGD was measured on a poly-methyl-methacrylate phantom (45 mm) for each system using dosimeters. In addition, MGD was estimated using exposure settings collected from mammography exams in clinical context. Data were collected from 25 computed-radiography systems (CR) and 13 integrated digital (DR). For both measurements (phantom and clinical exposures), the average MGD for CR was higher compared to the DR. For CR the mean MGD was 1.85 mGy (CC projection) and 2.10 mGy (MLO projection). For DR systems the corresponding values were 1.54 mGy (CC) and 1.68 mGy (MLO). The average MGD obtained using both methods and for both technologies is within the acceptable reference range proposed by European guidelines (<2.5 mGy). Dose Reference Levels implementation should be the next step to optimise mammography practice in Portugal.

Integrating mammographic breast density in glandular dose calculation

OBJECTIVE

This work proposes the use of mammographic breast density (MBD) to estimate actual glandular dose (AGD), and assesses how AGD compares to mean glandular dose (MGD) estimated using Dance et al method.

METHODS

A retrospective sample of anonymised mammograms (52,405) was retrieved from a central database. Technical parameters and patient characteristics were exported from the Digital Imaging and Communication in Medicine (DICOM) header using third party software. LIBRA (Laboratory for Individualized Breast Radiodensity Assessment) software package (University of Pennsylvania, Philadelphia, USA) was used to estimate MBDs for each mammogram included in the data set. MGD was estimated using Dance et al method, while AGD was calculated by replacing Dance et al standard glandularities with LIBRA estimated MBDs. A linear regression analysis was used to assess the association between MGD and AGD, and a Bland-Altman analysis was performed to assess their mean difference.

RESULTS

The final data set included 31,097 mammograms from 7728 females. MGD, AGD, and MBD medians were 1.53 , 1.62 mGy and 8% respectively. When stratified per breast thickness ranges, median MBDs were lower than Dance's standard glandularities. There was a strong positive correlation (R2 = 0.987, p < 0.0001) between MGD and AGD although the Bland-Altman analysis revealed a small statistically significant bias of 0.087 mGy between MGD and AGD (p < 0.001).

CONCLUSION

AGD estimated from MBD is highly correlated to MGD from Dance method, albeit the Dance method underestimates dose at smaller CBTs. Advances in knowledge: Our work should provide a stepping-stone towards an individualised dose estimation using automated clinical measures of MBD.