Monte Carlo evaluation of glandular dose in cone-beam X-ray computed tomography dedicated to the breast: Homogeneous and heterogeneous breast models

Sarno, Antonio; Mettivier, Giovanni; Tucciariello, Raffaele M.; Bliznakova, Kristina; Boone, John M.; Sechopoulos, Ioannis; Lillo, Francesca Di; Russo, Paolo

doi:10.1016/j.ejmp.2018.05.021

Cited by 24 publications

(63 citation statements)

References 52 publications

(98 reference statements)

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“…A common model for breast dosimetry includes an internal breast volume composed of a homogeneous mixture of glandular and adipose tissue, surrounded by an envelope of skin tissue. New 3D breast imaging techniques (dedicated breast computed tomography, BCT) [3] provided a detailed 3D description of the breast anatomy in patients, so permitting more realistic breast models for dosimetry in 2D and 3D X-ray breast imaging [4][5][6][7][8][9]. In particular, the assumption of a breast skin thickness of 4-5 mm for the breast model -as commonly adopted in quality assurance protocols [10][11][12][13] -was questioned recently, on the basis of measurements obtained by clinical BCT scans [4,14]: they indicated a skin thickness, on average, of 1.45 mm, with no evidence of subcutaneous fat layer [4].…”

Section: Introductionmentioning

confidence: 99%

“…In 2D mammography, the MGD estimate is higher for a thinner skin layer [4,15,16]. Moreover, in BCT -where higher photon energies than in mammography are adopted -the skin model presents some impact on the (photon energy dependent) MGD estimates adopted for clinical scans [9]. The determination of the 3D dose distribution in the breast volume in BCT can be affected by the breast model, as well [17].…”

Section: Introductionmentioning

confidence: 99%

“…As a further investigative aspect, in quality assurance protocols [11][12][13] breast models for MGD estimates do not consider the heterogeneous distribution of the breast glandular tissue within the organ volume: indeed, they assume that the inner portion of the breast is made of a homogeneous mixture of glandular and adipose tissue. This model simplification may produce a bias in MGD estimates, when compared to estimates based on patient specific structured models derived from clinical BCT scans [5,6,8,9]. In particular, this assumption neglects the large variability in the glandular tissue texture and it is representative of a hypothetical "average" breast [1,8,9].…”

Section: Introductionmentioning

confidence: 99%

“…This model simplification may produce a bias in MGD estimates, when compared to estimates based on patient specific structured models derived from clinical BCT scans [5,6,8,9]. In particular, this assumption neglects the large variability in the glandular tissue texture and it is representative of a hypothetical "average" breast [1,8,9].…”

Section: Introductionmentioning

confidence: 99%

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Normalized glandular dose coefficients in mammography, digital breast tomosynthesis and dedicated breast CT

et al. 2018

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To provide mean glandular dose (MGD) estimates via Monte Carlo (MC) simulations as a function of the breast models and scan parameters in mammography, digital breast tomosynthesis (DBT) and dedicated breast CT (BCT). Methods: The MC code was based on GEANT4 toolkit. The simulated compressed breast was either a cylinder with a semi-circular section or ad hoc shaped for oblique view (MLO). In DBT we studied the influence of breast models and exam parameters on the T-factors (i.e. the conversion factor for the calculation of the MGD in DBT from that for a 0-degree projection), and in BCT we investigated the influence on the MGD estimates of the ion chamber volume used for the air kerma measurements. Results: In mammography, a model representative of a breast undergoing an MLO view exam did not produce substantial differences (0.4%) in MGD estimates, when compared to a conventional cranio-caudal (CC) view breast model. The beam half value layer did not present a significant influence on T-factors in DBT (< 0.8%), while the skin model presented significant influence on MGD estimates (up to 3.3% at 30 degrees scan angle), increasing for larger scan angles. We derived a correction factor for taking into account the different ion chamber volume used in MGD estimates in BCT. Conclusions: A series of MC code modules for MGD estimates in 2D and 3D breast imaging have been developed in order to take into account the most recent advances in breast models.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Normalized glandular dose coefficients in mammography, digital breast tomosynthesis and dedicated breast CT

et al. 2018

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“…No irregular lesions have been so far modelled and included in that breast model. Breast cancer computational models are important for the development of new breast imaging techniques, as well as for realistic models for X-ray breast dosimetry [23,24]. As a large number of different breast cancer models would be normally used, there is a strong need to develop a method for generating patterns of irregular formations, typically in the case of malignant tumours.…”

Section: Introductionmentioning

confidence: 99%

Models of breast lesions based on three-dimensional X-ray breast images

et al. 2019

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This paper presents a method for creation of computational models of breast lesions with irregular shapes from patient Digital Breast Tomosynthesis (DBT) images or breast cadavers and whole-body Computed Tomography (CT) images. The approach includes six basic steps: (a) normalization of the intensity of the tomographic images; (b) image noise reduction; (c) binarization of the lesion area, (d) application of morphological operations to further decrease the level of artefacts; (e) application of a region growing technique to segment the lesion; and (f) creation of a final 3D lesion model. The algorithm is semi-automatic as the initial selection of the region of the lesion and the seeds for the region growing are done interactively. A software tool, performing all of the required steps, was developed in MATLAB. The method was tested and evaluated by analysing anonymized sets of DBT patient images diagnosed with lesions. Experienced radiologists evaluated the segmentation of the tumours in the slices and the obtained 3D lesion shapes. They concluded for a quite satisfactory delineation of the lesions. In addition, for three DBT cases, a delineation of the tumours was performed independently by the radiologists. In all cases the abnormality volumes segmented by the proposed algorithm were smaller than those outlined by the experts. The calculated Dice similarity coefficients for algorithm-radiologist and radiologist-radiologist showed similar values. Another selected tumour case was introduced into a computational breast model to recursively assess the algorithm. The relative volume difference between the ground-truth tumour volume and the one obtained by applying the algorithm on the synthetic volume from the virtual DBT study is 5% which demonstrates the satisfactory performance of the proposed segmentation algorithm. The software tool we developed was used to create models of different breast abnormalities, which were then stored in a database for use by researchers working in this field. Anthropomorphic voxel breast phantoms with realistic tissue

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Radiation dosimetry of a clinical prototype dedicated cone‐beam breast CT system with offset detector

2021

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Purpose A clinical‐prototype, dedicated, cone‐beam breast computed tomography (CBBCT) system with offset detector is undergoing clinical evaluation at our institution. This study is to estimate the normalized glandular dose coefficients (DgNCT) that provide air kerma‐to‐mean glandular dose conversion factors using Monte Carlo simulations. Materials and methods The clinical prototype CBBCT system uses 49 kV x‐ray spectrum with 1.39 mm 1st half‐value layer thickness. Monte Carlo simulations (GATE, version 8) were performed with semi‐ellipsoidal, homogeneous breasts of various fibroglandular weight fractions (fg=0.01,0.15,0.5,1false), chest wall diameters (d=8,10,14,18,20 cm), and chest wall to nipple length (l=0.75d), aligned with the axis of rotation (AOR) located at 65 cm from the focal spot to determine the DgNCT. Three geometries were considered – 40×30‐cm detector with no offset that served as reference and corresponds to a clinical CBBCT system, 30×30‐cm detector with 5 cm offset, and a 30×30‐cm detector with 10 cm offset. Results For 5 cm lateral offset, the DgNCT ranged 0.177‐0.574 mGy/mGy and reduction in DgNCT with respect to reference geometry was observed only for 18 cm (6.4%±0.23%) and 20 cm (9.6%±0.22%) diameter breasts. For the 10 cm lateral offset, the DgNCT ranged 0.221‐0.581 mGy/mGy and reduction in DgNCT was observed for all breast diameters. The reduction in DgNCT was 1.4%±0.48%, 7.1%±0.13%, 17.5%±0.19%, 25.1%±0.15%, and 27.7%±0.08% for 8, 10, 14, 18, and 20 cm diameter breasts, respectively. For a given breast diameter, the reduction in DgNCT with offset‐detector geometries was not dependent on fg. Numerical fits of italicDgNitalicCTd,l,fg were generated for each geometry. Conclusion The DgNCT and the numerical fit, DgNitalicCTd,l,fg would be of benefit for current CBBCT systems using the reference geometry and for future generations using offset‐detector geometry. There exists a potential for radiation dose reduction with offset‐detector geometry, provided the same technique factors as the reference geometry are used, and the image quality is clinically acceptable.

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Monte Carlo evaluation of glandular dose in cone-beam X-ray computed tomography dedicated to the breast: Homogeneous and heterogeneous breast models

Abstract: A dataset of monoenergetic and polyenergetic DgN coefficients for BCT was provided. Patient specific breast models showed a different volume distribution of glandular dose and determined a DgN 8% lower, on average, than homogeneous breast model.

Cited by 24 publications

References 52 publications

Normalized glandular dose coefficients in mammography, digital breast tomosynthesis and dedicated breast CT

Normalized glandular dose coefficients in mammography, digital breast tomosynthesis and dedicated breast CT

Models of breast lesions based on three-dimensional X-ray breast images

Radiation dosimetry of a clinical prototype dedicated cone‐beam breast CT system with offset detector

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