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Effective radiation attenuation calibration for breast density: compression thickness influences and correction
John J Heine, Ke Cao, Jerry A Thomas
BioMedical Engineering OnLine , 2010, DOI: 10.1186/1475-925x-9-73
Abstract: A thickness correction was developed and evaluated using a fully specified two-component surrogate breast model. A previously developed calibration approach based on effective radiation attenuation coefficient measurements was used in the analysis. Water and oil were used to construct phantoms to replicate the deformable properties of the breast. Phantoms consisting of measured proportions of water and oil were used to estimate calibration errors without correction, evaluate the thickness correction, and investigate the reproducibility of the various calibration representations under compression thickness variations.The average thickness uncertainty due to compression paddle warp was characterized to within 0.5 mm. The relative calibration error was reduced to 7% from 48-68% with the correction. The normalized effective radiation attenuation coefficient (planar) representation was reproducible under intra-sample compression thickness variations compared with calibrated volume measures.Incorporating this thickness correction into the rigid breast tissue equivalent calibration method should improve the calibration accuracy of mammograms for risk assessments using the reproducible planar calibration measure.Breast density is a significant breast cancer risk factor [1-3]. When estimating breast density from mammograms, the breast is considered as a two-component model consisting of adipose and fibroglandular (abbreviated as glandular hereafter) tissue to varying degrees. One method of measuring breast density uses binary labeling resulting in areas of radiographically dense tissue (glandular tissue) or adipose (non-dense) tissue. Breast density is then estimated as the ratio of the radiographically dense area to the total breast area (dense + adipose) [4-6]. Binary labeling techniques have repeatedly produced a measure that correlates well with breast cancer [2] without considering inter-image acquisition technique differences.Recent work has focused on calibration to c
A Simple Method of Determining the Effective Attenuation Coefficient
Grzegorz Domański , Bogumi Konarzewski , Zdzis aw Paw owski , Krzysztof Zaremba , Janusz Marzec , Artur Trybu a , Robert Kurjata
Polish Journal of Medical Physics And Engineering , 2007, DOI: 10.2478/v10013-007-0001-x
Abstract: This paper presents a simple method of determining the effective attenuation coefficient from steady-state diffuse reflectance measurements.
On the attenuation coefficient of monomode periodic waveguides  [PDF]
Alexandre Baron,Simon Mazoyer,Wojciech Smigaj,Philippe Lalanne
Physics , 2011, DOI: 10.1103/PhysRevLett.107.153901
Abstract: It is widely accepted that, on ensemble average, the transmission T of guided modes decays exponentially with the waveguide length L due to small imperfections, leading to the important figure of merit defined as the attenuation-rate coefficient alpha = -/L. In this letter, we evidence that the exponential-damping law is not valid in general for periodic monomode waveguides, especially as the group velocity decreases. This result that contradicts common beliefs and experimental practices aiming at measuring alpha is supported by a theoretical study of light transport in the limit of very small imperfections, and by numerical results obtained for two waveguide geometries that offer contrasted damping behaviours.
Effect of atmospheric environment on the attenuation coefficient of light in water  [PDF]
Juan Liu,Jiulin Shi,Yijun Tang,Kaixing Zhu,Yuan Ge,Xuegang Chen,Xingdao He,Dahe Liu
Physics , 2014,
Abstract: The attenuation coefficient of 532 nm light in water under different atmospheric conditions was investigated. Measurements were made over a two-year period at the same location and show that the attenuation coefficient is significantly influenced by the atmospheric environment. It is lowest when the atmospheric pressure is high and temperature is low, and is highest when the atmospheric pressure is low and temperature is high. The maximum attenuation coefficient of pure water in these studies was about three times the minimum value. The mechanism of the phenomena is discussed. These results are also important in underwater acoustics.
Attenuation correction with Region Growing Method used in the Positron Emission Mammography System  [PDF]
Xiao-Yue Gu,Lin Li,Peng-Fei Yin,Ming-Kai Yun,Chai Pei,Xin Fan,Xian-Chao Huang,Xiao-Li Sun,Long Wei
Physics , 2014, DOI: 10.1088/1674-1137/39/10/108202
Abstract: Positron Emission Mammography imaging system (PEMi) is a nuclear medicine diagnosis method dedicated for breast imaging. It provides a better resolution in detection of millimeter-sized breast tumors than whole-body PET. To address the requirement of semi-quantitative analysis with the radiotracer concentration map of the breast, a new attenuation correction method based on three-dimensional seeded region growing image segmentation (3DSRG-AC) solution was developed. The method gives a 3D connected region as the segmentation result instead of image slices. The continuously segmentation property makes this new method free of activity variation of breast tissues. Threshold value chosen is the key point for the segmentation process. The first valley of the grey level histogram of the reconstruction image is set as the lower threshold, which works fine in clinical application. Results show that attenuation correction for PEMi improves the image quality and the quantitative accuracy of radioactivity distribution determination. Attenuation correction also improves the probabilities to detect small and early breast tumors.
A comparative evaluation of two full-field digital mammography units
D Smith, CP Lawinski, A Mackenzie, DS Evans, NSA Wells, D Emerton, CA Lewis
Breast Cancer Research , 2000, DOI: 10.1186/bcr207
Abstract: The Senographe 2000D uses a caesium iodide/amorphous silicon flat panel detector and provides a field size of 19 × 23 cm. Automatic exposure control is via the detector, and the grid can be removed for magnification techniques. The image is displayed on a high-resolution monitor and can be manipulated using a number of image processing tools.The Trex Digital Mammography System uses an array of 12 charge couple device (CCD) cameras. The data are 'stitched' together by the associated software to provide a single image. This is displayed on a high-resolution monitor, although currently the manufacturer recommends reporting from laser printer hard copy images. KCARE has carried out an evaluation of both of these units in terms of breast dose and image quality using a range of standard test objects. The results of these evaluations will be discussed and where possible compared to film screen systems.
Evaluation of the potential in radiation dose reduction for full-field digital mammography
Kay-Uwe Kasch, Belal A. Moftah
Polish Journal of Medical Physics And Engineering , 2008, DOI: 10.2478/v10013-008-0008-y
Abstract: This study evaluates the image quality for different radiation doses in full-field digital mammography (FFDM). The potential of dose reductions is evaluated for both, the transition from screen-film mammography (SFM) to FFDM as well as within FFDM due to the optimization of exposure parameters. Exposures of a 4.5 cm breast phantom rendering different contrasts as well as bar patterns were made using a FFDM system (GE Senographe 2000D). For different kVp and mAs settings as well as different target/filter combinations chosen for the above exposures, average glandular dose (AGD), signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and modulation transfer function (MTF) were determined. To benchmark the results, relative change of AGD was evaluated against SNR, CNR and MTF. Eventually, the results were normalized to AGD's rendered by settings typically used in today's clinical routine. For standard settings (automatic mode), both FFDM and SFM deliver approximately the same AGD of about 2.2 mGy. From that, AGD reduction can be substantial in FFDM if only SNR and high contrast CNR are considered. In this case, reduction of up to 40% can be achieved in a wide kVp range if switching from the standard target/filter combination Mo/Rh to Rh/Rh. However, if low contrast CNR is to remain unchanged, dose reduction is practically impossible. The change of peak voltage and target/filter material had no influence on MTF. Assuming current CNR requirements as standards, significant dose reduction in FFDM cannot be achieved. Only by compromising low contrast CNR levels AGD of up to 40% can be saved at current standards of SNR and high contrast CNR.
Assessment of full field digital mammography (FFDM) detected microcalcification is not hindered by low spatial resolution
L Bartella, N Perry, KC Young, CP Lawinski, D Evans
Breast Cancer Research , 2002, DOI: 10.1186/bcr477
Abstract: To evaluate replacement of analogue microfocus technique by on-screen digital magnification for microcalcification, and to analyse the relative importance of spatial resolution versus contrast detail test scores.We performed phantom image quality testing on our digital unit (GE 2000D), using the TORMAX and TORMAM phantoms. We subsequently compared these results with average scores for over 90 film-screen mammography systems.Although our digital unit had a lower spatial resolution (6–7 Ip/mm) than the film-screen systems (up to 15 Ip/mm), both TORMAX and TORMAM scores were superior for digital soft-copy reporting compared to hard-copy reporting, film-screen technique and analogue microfocus magnification.Despite lower spatial resolution, the superior contrast and image manipulation abilities of FFDM obviate the need for conventional microfocus magnification in the radiographic work up of microcalcifications. Sufficient information is provided on FFDM upon which to base a decision to proceed to diagnostic interventional procedures such as core biopsy or mammotome excision.
Tissue attenuation coefficient estimation using bubble harmonics with frequency diversity  [PDF]
Sheng-Kai Tsao, Jenho Tsao
Journal of Biomedical Science and Engineering (JBiSE) , 2012, DOI: 10.4236/jbise.2012.55035
Abstract: In a previous work, we developed a consistent TAC (tissue attenuation coefficient) estimator using bubble echoes. Based on temporal averaging, we can improve the estimation precision of TAC for the tissue bounded between two vessels. In this paper, we extend it to use frequency diversity for saving interrogation time by transmit multiple narrowband signals in each pulse. At first, we analyze the deterministic and stochastic properties of the diversity signals. Then a multi-band maximum likelihood diversity combiner is developed. We also provide diversity gains of different diversity estimators for comparing their estimation efficiencies. In the experimental work, we design a simplified phantom for demonstrating the performance of the purposed estimator. It is shown that the TAC estimation rate can be improved by frequency diversity. The convergence rates of single-band and multi-band estimators are compared and it is shown that the multi-band estimator is more consistent than the single-band estimator.
Efficacy of Magnetic Resonance Imaging in BIRADS 3, 4 and 5 Patients Detected on Full Field Digital Mammography: Our Experience  [PDF]
Atul Patil, Samadhan Pawar, Raj Nagarkar, Bhargav Gaikwad
Open Journal of Clinical Diagnostics (OJCD) , 2019, DOI: 10.4236/ojcd.2019.91003
Abstract:

Aim of the study: To perform Dynamic contrast enhanced MRI of breast in patients with positive findings (BIRADS 3, 4 and 5) detected on screening mammography; to correlate the findings of digital mammography and contrast enhanced MRI of breast with histopathological examinations. Settings and Design: A prospective observation study was conducted at a single centre, i.e. HCG Manavata Cancer Centre. Materials and Methods: Screening mammography was performed on patients with age > 40 years and on patients with age 35 - 40 years having positive family history. The positive mammography was reported and the lesions classified according to BIRADS criteria for mammography. Results: Mammographic examination of the breast lesions yielded an overall sensitivity of 97.67% and a specificity of 85.71%. In our study we combined both morphologic and dynamic parameters and its modification into BIRADS category for lesion classification. The sensitivity of MRI examinations was 97.67% while the specificity was 71.43%. Spiculated margins were encountered only in malignant lesions (p = 0.0006). Statistical correlation was obtained between the pathologically proven benign and malignant lesions regarding their enhancement pattern with p value of <0.001. Conclusion: As per the results, dynamic contrast MRI had high sensitivity but limited specificity. We did not find any significant difference between FFDM and MRI in terms of diagnostic accuracy. The use of DWI showed high specificity at cut off point of ADC value0.85 mm2/s. Thus, DWI can

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