A review on automatic mammographic density and parenchymal segmentation

Breast cancer is the most frequently diagnosed cancer in women. However, the exact cause(s) of breast cancer still remains unknown. Early detection, precise identification of women at risk, and application of appropriate disease prevention measures are by far the most effective way to tackle breast cancer. There are more than 70 common genetic susceptibility factors included in the current non-image-based risk prediction models (e.g., the Gail and the Tyrer-Cuzick models). Image-based risk factors, such as mammographic densities and parenchymal patterns, have been established as biomarkers but have not been fully incorporated in the risk prediction models used for risk stratification in screening and/or measuring responsiveness to preventive approaches. Within computer aided mammography, automatic mammographic tissue segmentation methods have been developed for estimation of breast tissue composition to facilitate mammographic risk assessment. This paper presents a comprehensive review of automatic mammographic tissue segmentation methodologies developed over the past two decades and the evidence for risk assessment/density classification using segmentation. The aim of this review is to analyse how engineering advances have progressed and the impact automatic mammographic tissue segmentation has in a clinical environment, as well as to understand the current research gaps with respect to the incorporation of image-based risk factors in non-image-based risk prediction models

Imaging of the Breast

Early detection of breast cancer combined with targeted therapy offers the best outcome for breast cancer patients. This volume deal with a wide range of new technical innovations for improving breast cancer detection, diagnosis and therapy. There is a special focus on improvements in mammographic image quality, image analysis, magnetic resonance imaging of the breast and molecular imaging. A chapter on targeted therapy explores the option of less radical postoperative therapy for women with early, screen-detected breast cancers

Experimental evaluation of the z-resolution in different clinical Digital Breast Tomosynthesis systems using commercial phantoms

Digital Breast Tomosynthesis (DBT) is an advanced mammography technique based on the reconstruction of a pseudo-volumetric image. To date, image quality represents the most deficient section of DBT quality control protocols. In fact, related tests are not yet characterized by either action levels or typical values. This thesis work focuses on the evaluation of one aspect of image quality: the z-resolution. The latter is studied in terms of Artifact Spread Function (ASF), a function that describes the signal spread of a detail along the reconstructed focal planes. To quantify the ASF numerically, its Full Width at Half Maximum (FWHM) is calculated and used as a representative index of z-resolution. Experimental measurements were acquired in 24 DBT systems, of 7 different models, currently in use in 20 hospital facilities in Italy. The analysis, performed on the clinical reconstructed images, of 5 different commercial phantoms, lead to the identification of characteristic FWHM values for each type of DBT system. The ASF clearly showed a dependence on the size of the detail, providing higher FWHM values for larger objects. The z-resolution was found to be positively influenced by the acquisition angle: Fujifilm sistematically showed wider ASF profiles in ST mode (15°) than in HR mode (40°). However, no clear relationship was found between angular range and ASF, among different DBT systems, due to the influence of the peculiarities of each reconstruction algorithm. The experimental approach shown in this thesis work can be proposed as a z-resolution quality control test procedure. Contextually, the values found could be used as a starting point for identifying typical values to be included in the test, in a DBT protocol. Clearly, a statistically significant number of images is needed to do this. The equipment involved in this work is located in hospitals and is not available for research purposes, so only a limited amount of data was acquired and processed

Evaluation of image receptor angulation during mediolateral oblique positioning for optimised pressure and area distribution in mammography

BackgroundMammography is the gold standard diagnostic tool for the screening and diagnosis of breast cancer; however, it is associated with pain and discomfort. The pain and discomfort are mostly due to positioning and the compression applied during the procedure. Currently there are variations in the way clients are positioned for mammography and the amount of compression applied during the procedure. In addition, there are sparse guidelines and published literature on mammographic positioning and the application of compression. It is suggested that for the medio lateral oblique (MLO) position, for an effective compression force balance and increased breast footprint, the sternal angle and the image receptor (IR) be parallel to each other. This aim of this research is to evaluate the angle of IR during MLO positioning for optimised pressure and area distribution; this in turn may help reduce pain and discomfort associated with the procedure.MethodThe experimental work described in this report is in two phases. Phase one was an anthropomorphic phantom study to establish a structured and reproducible method of using the angle of the sternum to measure the correct angle of the IR for MLO projection. An inclinometer was used to measure the sternal angle of phantom model used. Six sets of compressions were made on the breast phantom with the IR at different angles ranging from 400 to 700 at 50 angle increments. Contact pressure and contact area footprint readings between breast phantom/paddle interface and breast phantom/IR interface were recorded using Xsensor pressure mapping system. Pressure uniformity (PU) and area uniformity (AU) between phantom breast/paddle interface and phantom breast phantom/IR interface were then calculated.Phase two was a human study with participants to investigate contact pressure and area balance on MLO compressions using two angles. A digital inclinometer was used to measure the angle at which the sternum for each participant. This angle was referred to as the ‘experimental angle’. The other angle was a ‘reference angle’ of 450. Compression at the ‘experimental angle’ may result into a better distribution of pressure through the breast and juxtathoracic structures, this may reduce the pain associated with the procedure. In addition to this, compression at this angle may increase breast surface area. The hypotheses set out to ascertain if there is no significant difference between contact pressure distribution when the IR is positioned parallel to the sternal angle (experimental angle) and it is positioned at a reference angle.An Xsensor pressure mapping system was used to record and analyse pressure distribution and surface area for compressions at the ‘experimental angle’ and the ‘reference angle’ (450). Pressure and area balance between the IR and compression paddle on both of these angles were compared and T-test conducted to accept or reject the hypotheses set out. In addition, participants were asked to score their pain experience after each compression, that is, compression at the ‘reference angle’ and the ‘experimental angle’. ResultsThe results from phase one indicated there was greater balance of pressure between breast/IR interface and breast/paddle interface at IR angle 600 compared the rest of IR angles investigated. PU of zero indicated equal distribution of pressure from the IR and the paddle. IR angled at 600 recorded a PU value of 0.21 which was the closest to zero from the PU recorded for the various angles. AU of zero indicates equal distribution of area footprint from the IR and the paddle. IR at 600 (Sternal angle for phantom model) produced the greatest area footprint balance compared to the other angles with AU of 0.05. An IR angled at 600, being parallel to the sternal angle of the phantom model which was recorded at 600 on the inclinometer, was the angle which produced the greatest balance of pressure and area footprint.The results from human study indicated there was no significant difference between contact pressure and area distribution when the IR is positioned parallel to the experimental angle or positioned at a reference angle.ConclusionFor the phantom study it has been shown that positioning the IR parallel to the angle of the sternum produces a more balanced contact pressure distribution and improved breast surface area footprint. The human study demonstrated no statistically significant difference between pressure and area balance on the reference angle and the experimental angle.For pain experienced score, although there was a 95% chance that the actual pain score for the compression on the reference angle fell within 3.81 and 5.76. and that of the experimental angle fell within 3.02 and 4.79, there was no statistically significant difference between pain experienced from compression on both angles