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.

Variations in breast cancer detection rates during mammogram-reading sessions: does experience have an impact?

OBJECTIVES: To examine whether radiologists' performances are consistent throughout a reading session and whether any changes in performance over the reading task differ depending on experience of the reader. METHODS: The performance of ten radiologists reading a test set of 60 mammographic cases without breaks was assessed using an ANOVA, 2 × 3 factorial design. Participants were categorized as more (≥2,000 mammogram readings per year) or less (<2,000 readings per year) experienced. Three series of 20 cases were chosen to ensure comparable difficulty and presented in the same sequence to all readers. It usually takes around 30 min for a radiologist to complete each of the 20-case series, resulting in a total of 90 min for the 60 mammographic cases. The sensitivity, specificity, lesion sensitivity, and area under the ROC curve were calculated for each series. We hypothesized that the order in which a series was read (i.e. fixed-series sequence) would have a significant main effect on the participants' performance. We also determined if significant interactions exist between the fixed-series sequence and radiologist experience. RESULTS: Significant linear interactions were found between experience and the fixed sequence of the series for sensitivity (F[1] =5.762, p = .04, partial η2 = .41) and lesion sensitivity. (F[1] =6.993, p = .03, partial η2 = .46). The two groups' mean scores were similar for the first series but progressively diverged. By the end of the third series, significant differences in sensitivity and lesion sensitivity were evident, with the more experienced individuals demonstrating improving and the less experienced declining performance. Neither experience nor series sequence significantly affected the specificity or the area under the ROC curve. CONCLUSIONS: Radiologists' performance may change considerably during a reading session, apparently as a function of experience, with less experienced radiologists declining in sensitivity and lesion sensitivity while more experienced radiologists actually improve. With the increasing demands on radiologists to undertake high-volume reporting, we suggest that junior radiologists be made aware of possible sensitivity and lesion sensitivity deterioration over time so they can schedule breaks during continuous reading sessions that are appropriate to them, rather than try to emulate their more experienced colleagues. ADVANCES IN KNOWLEDGE: Less-experienced radiologists demonstrated a reduction in mammographic diagnostic accuracy in later stages of the reporting sessions. This may suggest that extending the duration of reporting sessions to compensate for increasing workloads may not represent the optimal solution for less-experienced radiologists.

Reading High Breast Density Mammograms: Differences in Diagnostic Performance between Radiologists from Hong Kong SAR/Guangdong Province in China and Australia.

BACKGROUND: Variations in the performance of radiologists reading mammographic images are well reported, but key parameters explaining such variations in different countries are not fully explored. The main aim of this study is to investigate performances of Chinese (Hong Kong SAR and Guangdong Province) and Australian radiologists in interpreting dense breast mammographic images. METHODS: A test set, contained 60 mammographic examinations with high breast density, was used to assess radiologists' performance. Twelve Chinese and thirteen Australian radiologists read all the cases independently and were asked to identify all lesions and provide a grade from 1 to 5 to each lesion. Case sensitivity, specificity, lesion sensitivity, AUC and JAFROC were used to assess radiologists' performances. Demographic information and reading experience were also collected from the readers. Performance scores were compared between the two populations and the relationships between performance scores and their reading experience were discovered. RESULTS: For radiologists who were less than 40-year-old, lesion sensitivity, AUC and JAFROC were significantly lower in Chinese radiologists than those in Australian (52.10% vs 71.45%, p=0.043; 0.76 vs 0.84, p=0.031; 0.59 vs 0.72, p=0.045; respectively). Australian radiologists with less than 10 years of reading experience had higher AUC and JAFROC scores compared with their Chinese counterparts (0.83 vs 0.76, p=0.039; 0.70 vs 0.56, p=0.020, respectively). CONCLUSIONS: We found that younger Australian radiologists performed better at reading dense breast cases which is likely to be linked to intensive fellowship training, immersion in a screening program and exposure to the benefits of a performance-measuring education tool.

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.

Mean glandular dose in digital mammography: a dose calculation method comparison.

Our objective was to analyze the agreement between organ dose estimated by different digital mammography units and calculated dose for clinical data. Digital Imaging and Communication in Medicine header information was extracted from 52,405 anonymized mammograms. Data were filtered to include images with no breast implants, breast thicknesses 20 to 110 mm, and complete exposure and quality assurance data. Mean glandular dose was calculated using methods by Dance et al., Wu et al., and Boone et al. Bland-Altman analysis and regression were used to study the agreement and correlation between organ and calculated doses. Bland-Altman showed statistically significant bias between organ and calculated doses. The bias differed for different unit makes and models; Philips had the lowest bias, overestimating Dance method by 0.03 mGy, while general electric had the highest bias, overestimating Wu method by 0.20 mGy, the Hologic organ dose underestimated Boone method by 0.07 mGy, and the Fujifilm organ dose underestimated Dance method by 0.09 mGy. Organ dose was found to disagree with our calculated dose, yet organ dose is potentially beneficial for rapid dose audits. Conclusions drawn based on the organ dose alone come with a risk of over or underestimating the calculated dose to the patient and this error should be considered in any reported results.

Diagnostic reference levels for digital mammography in New South Wales.

INTRODUCTION: This work aims to explore radiation doses delivered in screening mammography in Australia, with a focus on whether compressed breast thickness should be used as a guide when determining patient derived diagnostic reference levels (DRLs). METHODS: Anonymized mammograms (52,405) were retrieved from a central database, and DICOM headers were extracted using third party software. Women with breast implants, breast thicknesses outside 20-110 mm and images with incomplete exposure or quality assurance (QA) data were excluded. Exposure and QA information were utilized to calculate the mean glandular dose (MGD) for 45,054 mammograms from 61 units representing four manufacturers using previously well-established methods. The 75th and 95th percentiles were calculated across median image MGDs obtained for all included data and according to specific compressed breast thickness ranges. RESULTS: The overall median image MGD, minimum, maximum were: 1.39, 0.19 and 10.00 mGy, respectively, the 75th and 95th percentiles across all units' median image MGD for 60 ± 5 mm compressed breast thickness were 2.06 and 2.69 mGy respectively. Median MGDs, minimum, maximum, 75th and 95th percentiles were presented for nine compressed breast thickness ranges, DRLs for NSW are suggested for the compressed breast thickness range of 60 ± 5 mm for the whole study and three detector technologies CR, DR, and photon counting to be 2.06, 2.22, 2.04 and 0.79 mGy respectively. CONCLUSION: MGD is dependent upon compressed breast thickness and it is recommended that DRL values should be specific to compressed breast thickness and image detector technology.

Diagnostic reference levels in digital mammography: a systematic review.

This study aims to review the literature on existing diagnostic reference levels (DRLs) in digital mammography and methodologies for establishing them. To this end, a systematic search through Medline, Cinahl, Web of Science, Scopus and Google scholar was conducted using search terms extracted from three terms: DRLs, digital mammography and breast screen. The search resulted in 1539 articles of which 22 were included after a screening process. Relevant data from the included studies were summarised and analysed. Differences were found in the methods utilised to establish DRLs including test subjects types, protocols followed, conversion factors employed, breast compressed thicknesses and percentile values adopted. These differences complicate comparison of DRLs among countries; hence, an internationally accepted protocol would be valuable so that international comparisons can be made.