Gisella Gennaro

Digital breast tomosynthesis versus digital mammography: a clinical performance study

ObjectiveTo compare the clinical performance of digital breast tomosynthesis (DBT) with that of full-field digital mammography (FFDM) in a diagnostic population.MethodsThe study enrolled 200 consenting women who had at least one breast lesion discovered by mammography and/or ultrasound classified as doubtful or suspicious or probably malignant. They underwent tomosynthesis in one view [mediolateral oblique (MLO)] of both breasts at a dose comparable to that of standard screen-film mammography in two views [craniocaudal (CC) and MLO]. Images were rated by six breast radiologists using the BIRADS score. Ratings were compared with the truth established according to the standard of care and a multiple-reader multiple-case (MRMC) receiver-operating characteristic (ROC) analysis was performed. Clinical performance of DBT compared with that of FFDM was evaluated in terms of the difference between areas under ROC curves (AUCs) for BIRADS scores.ResultsOverall clinical performance with DBT and FFDM for malignant versus all other cases was not significantly different (AUCs 0.851 vs 0.836, p = 0.645). The lower limit of the 95% CI or the difference between DBT and FFDM AUCs was −4.9%.ConclusionClinical performance of tomosynthesis in one view at the same total dose as standard screen-film mammography is not inferior to digital mammography in two views.

Dose comparison between screen/film and full-field digital mammography

The study purpose was the comparison between doses delivered by a full-field digital mammography system and a screen/film mammography unit, both using the same type of X-ray tube. Exposure parameters and breast thickness were collected for 300 screen/film (GE Senographe DMR) and 296 digital mammograms (GE Senographe 2000D). The entrance surface air kerma (ESAK) was calculated from anode/filter combination, kVp and mAs values and breast thickness, by simulating spectra through a program based on a catalogue of experimental X-ray spectra. The average glandular dose (AGD) was also computed. Results showed an overall reduction of average glandular dose by 27% of digital over screen/film mammography. The dose saving was about 15% for thin and thick breasts, while it was between 30% and 40% for intermediate thicknesses. Full-field digital mammography dose reduction is allowed by wider dynamic range and higher efficiency of digital detector, which can be exposed at higher energy spectra than screen/film mammography, and by the separation between acquisition and displaying processes.

Evaluation of the minimum iodine concentration for contrast-enhanced subtraction mammography

Early manifestation of breast cancer is often very subtle and is displayed in a complex and variable pattern of normal anatomy that may obscure the disease. The use of dual-energy techniques, that can remove the structural noise, and contrast media, that enhance the region surrounding the tumour, could help us to improve the detectability of the lesions. The aim of this work is to investigate the use of an iodine-based contrast medium in mammography with two different double exposure techniques: K-edge subtraction mammography and temporal subtraction mammography. Both techniques have been investigated by using an ideal source, like monochromatic beams produced at a synchrotron radiation facility and a clinical digital mammography system. A dedicated three-component phantom containing cavities filled with different iodine concentrations has been developed and used for measurements. For each technique, information about the minimum iodine concentration, which provides a significant enhancement of the detectability of the pathology by minimizing the risk due to high dose and high concentration of contrast medium, has been obtained. In particular, for cavities of 5 and 8 mm in diameter filled with iodine solutions, the minimum concentration needed to obtain a contrast-to-noise ratio of 5 with a mean glandular dose of 2 mGy has been calculated. The minimum concentrations estimated with monochromatic beams and K-edge subtraction mammography are 0.9 mg ml(-1) and 1.34 mg ml(-1) for the biggest and smallest details, respectively, while for temporal subtraction mammography they are 0.84 mg ml(-1) and 1.31 mg ml(-1). With the conventional clinical system the minimum concentrations for the K-edge subtraction mammography are 4.13 mg ml(-1) (8 mm diameter) and 5.75 mg ml(-1) (5 mm diameter), while for the temporal subtraction mammography they are 1.01 mg ml(-1) (8 mm diameter) and 1.57 mg ml(-1) (5 mm diameter).

Combination of one-view digital breast tomosynthesis with one-view digital mammography versus standard two-view digital mammography: per lesion analysis

AbstractObjectiveTo evaluate the clinical value of combining one-view mammography (cranio-caudal, CC) with the complementary view tomosynthesis (mediolateral-oblique, MLO) in comparison to standard two-view mammography (MX) in terms of both lesion detection and characterization.MethodsA free-response receiver operating characteristic (FROC) experiment was conducted independently by six breast radiologists, obtaining data from 463 breasts of 250 patients. Differences in mean lesion detection fraction (LDF) and mean lesion characterization fraction (LCF) were analysed by analysis of variance (ANOVA) to compare clinical performance of the combination of techniques to standard two-view digital mammography.ResultsThe 463 cases (breasts) reviewed included 258 with one to three lesions each, and 205 with no lesions. The 258 cases with lesions included 77 cancers in 68 breasts and 271 benign lesions to give a total of 348 proven lesions. The combination, DBT(MLO)+MX(CC), was superior to MX (CC+MLO) in both lesion detection (LDF) and lesion characterization (LCF) overall and for benign lesions. DBT(MLO)+MX(CC) was non-inferior to two-view MX for malignant lesions.ConclusionsThis study shows that readers’ capabilities in detecting and characterizing breast lesions are improved by combining single-view digital breast tomosynthesis and single-view mammography compared to two-view digital mammography.Key Points• Digital breast tomosynthesis is becoming adopted as an adjunct to mammography (MX) • DBT(MLO)+MX(CC)is superior to MX(CC+MLO)in lesion detection (overall and benign lesions) • DBT(MLO)+MX(CC)is non-inferior to MX(CC+MLO)in cancer detection • DBT(MLO)+MX(CC)is superior to MX(CC+MLO)in lesion characterization (overall and benign lesions) • DBT(MLO)+MX(CC)is non-inferior to MX(CC+MLO)in characterization of malignant lesions

Grid removal and impact on population dose in full-field digital mammography

The study purpose was to determine the impact of anti-scatter grid removal on patient dose, in full field digital mammography. Dose saving, phantom based, was evaluated with the constraint that images acquired with and without grid would provide the same contrast-to-noise ratio (CNR). The digital equipment employed a flat panel detector with cesium iodide for x-ray to light conversion, 100 microm pixel size; the x-ray source was a dual-track tube with selectable filtration. Poly(methyl-emathocrylate) (PMMA) layers in the range 20-70 mm were used to simulate the absorption of different breast thickness, while two Al foils, 0.1 and 0.2 mm thick were used to provide a certain CNR. Images with grid were acquired with the same beam quality as selected in full automatic exposure mode and the mAs levels as close as possible, and the CNR measured for each thickness between 20 and 70 mm. Phantom images without grid were acquired in manual exposure mode, by selecting the same anode/filter combination and kVp as the image with grid at the same thickness, but varying mAs from 10 to 200. For each thickness, an image without aluminum was acquired for each mAs value, in order to obtain a flat image to be used to subtract the scatter nonuniformity from the phantom images. After scatter subtraction, the CNR was measured on images without grid. The mAs value that should be set to acquire a phantom image without grid so that it has the same CNR as the corresponding grid image was calculated. Therefore, mAs reduction percentage was determined versus phantom thickness. Results showed that dose saving was lower than 30% for PMMA equivalent breast thinner than 40 mm, decreased below 10% for intermediate thickness (45-50 mm), but there was no dose gain for thickness beyond 60 mm. By applying the mAs reduction factors to a clinical population derived from a data base of 4622 breasts, dose benefit was quantified in terms of population dose. On the average, the overall dose reduction was about 8%. It was considered small, not sufficient to justify a clinical implementation, and the anti-scatter grid was maintained.

Are phantoms useful for predicting the potential of dose reduction in full-field digital mammography?

A phantom study was performed in full-field digital mammography to investigate the opportunity and the magnitude of a possible dose reduction that would leave the image quality above the accepted thresholds associated with some classical phantoms. This preliminary work is intended to lay the groundwork for a future clinical study on the impact of dose reduction on clinical results. Three different mammography phantoms (ACR RMI 156, CIRS 11A and CDMAM 3.4) were imaged by a full-field digital mammography unit (GE Senographe 2000D) at different dose levels. Images were rated by three observers with softcopy reading and scoring methods specific to each phantom. Different types of data analysis were applied to the ACR (American College of Radiology) and the other two phantoms, respectively. With reference to the minimum acceptance score in screen/film accreditation programmes, the ACR phantom showed that about 45% dose reduction could be applied, while keeping the phantom scores above that threshold. A relative comparison was done for CIRS and CDMAM, for which no threshold is defined. CIRS scoring remained close to the reference level down to 40% dose reduction, the inter- and intra-observer variability being the main source of uncertainty. Contrast-detail curves provided by CDMAM overlapped down to 50% dose reduction, at least for object contrast values ranging between 30% and 3%. This multi-phantom study shows the potential of further reducing the dose in full-field digital mammography beyond the current values. A common dose reduction factor around 50% seems acceptable for all phantoms. However, caution is required before extrapolating the results for clinical use, given the limitations of these widely used phantoms, mainly related to their limited dynamic range and uniform background.

Cytological and histological structures identification with the technique IBIL in elemental microanalysis

Abstract Ion beam induced luminescence (IBIL) is applied to the inspection of histological and cytological specimens, dried and placed in vacuum. It is shown to offer a way for a precise aiming of a proton microbeam on the sample for a subsequent traditional microanalysis. We used the nuclear microprobe of the Laboratori Nazionali di Legnaro and its IBIL facility to identify biostructures stained with some usual fluorescent dyes, capable of discriminating tissues and cells of different nature or different parts of a cell. To this purpose we produced low dose IBIL maps of the region of interest, employing a high sensitivity light detector. We describe the experimental set-up, propose a peculiar support for specimens, specify the properties of few widespread used staining procedures and evaluate their IBIL emission.

Clinical Performance of Digital Breast Tomosynthesis Versus Full-Field Digital Mammography: Preliminary Results

Preliminary results of a clinical study designed to compare clinical performance of digital breast tomosynthesis (DBT) versus standard full-field digital mammography (FFDM) in a diagnostic population are presented and discussed. Paired tomosynthesis and mammography examinations were analyzed by three experienced radiologists. One hundred single-breast cases were analyzed. Findings were rated in terms of lesion conspicuity, classified using the ACR BIRADS scale and compared with the truth. Statistically significant differences were found in lesion conspicuity for all radiologists, showing tomosynthesis superior to mammography. Finding classifications (BIRADS) were evaluated by ROC analysis. The results obtained from tomosynthesis images were consistently superior to FFDM for all readers. The difference was statistically significant for one radiologist. The results demonstrated DBT superiority for conspicuity of findings and showed potential for superior clinical performance.

Automated analysis of phantom images for the evaluation of long-term reproducibility in digital mammography

The performance of an automatic software package was evaluated with phantom images acquired by a full-field digital mammography unit. After the validation, the software was used, together with a Leeds TORMAS test object, to model the image acquisition process. Process modelling results were used to evaluate the sensitivity of the method in detecting changes of exposure parameters from routine image quality measurements in digital mammography, which is the ultimate purpose of long-term reproducibility tests. Image quality indices measured by the software included the mean pixel value and standard deviation of circular details and surrounding background, contrast-to-noise ratio and relative contrast; detail counts were also collected. The validation procedure demonstrated that the software localizes the phantom details correctly and the difference between automatic and manual measurements was within few grey levels. Quantitative analysis showed sufficient sensitivity to relate fluctuations in exposure parameters (kV(p) or mAs) to variations in image quality indices. In comparison, detail counts were found less sensitive in detecting image quality changes, even when limitations due to observer subjectivity were overcome by automatic analysis. In conclusion, long-term reproducibility tests provided by the Leeds TORMAS phantom with quantitative analysis of multiple IQ indices have been demonstrated to be effective in predicting causes of deviation from standard operating conditions and can be used to monitor stability in full-field digital mammography.

Radiation dose with digital breast tomosynthesis compared to digital mammography: per-view analysis

AbstractObjectivesTo compare radiation dose delivered by digital mammography (FFDM) and breast tomosynthesis (DBT) for a single view.Methods4,780 FFDM and 4,798 DBT images from 1,208 women enrolled in a screening trial were used to ground dose comparison. Raw images were processed by an automatic software to determine volumetric breast density (VBD) and were used together with exposure data to compute the mean glandular dose (MGD) according to Dance’s model. DBT and FFDM were compared in terms of operation of the automatic exposure control (AEC) and MGD level.ResultsStatistically significant differences were found between FFDM and DBT MGDs for all views (CC: MGDFFDM=1.366 mGy, MGDDBT=1.858 mGy; p<0.0001; MLO: MGDFFDM=1.374 mGy, MGDDBT=1.877 mGy; p<0.0001). Considering the 4,768 paired views, Bland-Altman analysis showed that the average increase of DBT dose compared to FFDM is 38 %, and a range between 0 % and 75 %.ConclusionsOur findings show a modest increase of radiation dose to the breast by tomosynthesis compared to FFDM. Given the emerging role of DBT, its use in conjunction with synthetic 2D images should not be deterred by concerns regarding radiation burden, and should draw on evidence of potential clinical benefit.Key Points• Most studies compared tomosynthesis in combination with mammography vs. mammography alone. • There is some concern about the dose increase with tomosynthesis. • Clinical data show a small increase in radiation dose with tomosynthesis. • Synthetic 2D images from tomosynthesis at zero dose reduce potential harm. • The small dose increase should not be a barrier to use of tomosynthesis.