Characterization of scatter radiation in cone beam CT mammography

Liu, Bob; Glick, Stephen J.; Groiselle, C.J.

doi:10.1117/12.595396

Cited by 17 publications

(15 citation statements)

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“…Scatter was modeled into the simulations of BT and CTBI using the following procedure. First, Monte Carlo simulations 40,41 were performed using the GEANT software package to track x-ray transport through a uniformly dense breast model ͑with an average composition of 50% adipose and 50% fibroglandular tissue͒ similar in shape to the breast models used for BT and CTBI here. For each breast phantom, a spatially variant scatter-to-primary ͑SPR͒ map ͑over all energies͒ was computed for each projection view.…”

Section: F Scattermentioning

confidence: 99%

A computer simulation study comparing lesion detection accuracy with digital mammography, breast tomosynthesis, and cone‐beam CT breast imaging

et al. 2006

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Although conventional mammography is currently the best modality to detect early breast cancer, it is limited in that the recorded image represents the superposition of a three-dimensional (3D) object onto a 2D plane. Recently, two promising approaches for 3D volumetric breast imaging have been proposed, breast tomosynthesis (BT) and CT breast imaging (CTBI). To investigate possible improvements in lesion detection accuracy with either breast tomosynthesis or CT breast imaging as compared to digital mammography (DM), a computer simulation study was conducted using simulated lesions embedded into a structured 3D breast model. The computer simulation realistically modeled x-ray transport through a breast model, as well as the signal and noise propagation through a CsI based flat-panel imager. Polyenergetic x-ray spectra of Mo/Mo 28 kVp for digital mammography, Mo/Rh 28 kVp for BT, and W/Ce 50 kVp for CTBI were modeled. For the CTBI simulation, the intensity of the x-ray spectra for each projection view was determined so as to provide a total average glandular dose of 4 mGy, which is approximately equivalent to that given in conventional two-view screening mammography. The same total dose was modeled for both the DM and BT simulations. Irregular lesions were simulated by using a stochastic growth algorithm providing lesions with an effective diameter of 5 mm. Breast tissue was simulated by generating an ensemble of backgrounds with a power law spectrum, with the composition of 50% fibroglandular and 50% adipose tissue. To evaluate lesion detection accuracy, a receiver operating characteristic (ROC) study was performed with five observers reading an ensemble of images for each case. The average area under the ROC curves (Az) was 0.76 for DM, 0.93 for BT, and 0.94 for CTBI. Results indicated that for the same dose, a 5 mm lesion embedded in a structured breast phantom was detected by the two volumetric breast imaging systems, BT and CTBI, with statistically significant higher confidence than with planar digital mammography, while the difference in lesion detection between BT and CTBI was not statistically significant.

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Section: F Scattermentioning

confidence: 99%

A computer simulation study comparing lesion detection accuracy with digital mammography, breast tomosynthesis, and cone‐beam CT breast imaging

et al. 2006

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“…Often in the literature, a single regular geometrical object, usually a cylinder, is used to determine 2D SPRs as a measure of the system performance and object scatter characteristics that need correction [1–3, 7]. However, these simple cylindrical geometries do not adequately represent the intersection of the incident 3D cone beam with the spectrum of complex geometrical shapes posed by various pendant breast geometries, nor the subsequent x-ray interactions modulated by these complex shapes.…”

Section: Introductionmentioning

confidence: 99%

Characterization of X-ray scattering for various phantoms and clinical breast geometries using breast CT on a dedicated hybrid system

Shah

Mann

Tornai

2017

XST

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OBJECTIVE The purpose of this study was to utilize a dedicated breast CT system using a 2D beam stop array to physically evaluate the scatter to primary ratios (SPRs) of different geometric phantoms and prospectively acquired clinical patient data. METHODS Including clinically unrealizable compositions of 100% glandular and 100% fat, projection images were acquired using three geometrically different phantoms filled with fluids simulating breast tissue. The beam stop array method was used for measuring scatter in projection space, and creating the scatter corrected primary images. 2D SPRs were calculated. Additionally, a new figure of merit, the 3D normalized scatter contribution (NSC) volumes were calculated. RESULTS The 2D SPR values (0.52–1.10) were primarily dependent on phantom geometry; a secondary dependence was due to their uniform density; 2D SPRs were low frequency and smoothly varying in the uniformly filled phantoms. SPRs of clinical patient data followed similar trends as phantoms, but with noticeable deviations and high frequency components due to the heterogeneous distribution of glandular tissue. The maximum measured patient 2D SPRs were all <0.6, even for the largest diameter breast. These results demonstrate modest scatter components with changing object geometries and densities; the 3D NSC volumes with higher frequency components help visualize scatter distribution throughout the reconstructed image volumes. Furthermore, the SPRs in the heterogeneous clinical breast cases were underestimated by the equivalent density, uniformly filled phantoms. CONCLUSIONS These results provide guidance on the use of uniformly distributed density and differently shaped phantoms when considering simulations. They also clearly demonstrate that results from patients can vary considerably from 2D SPRs of uniformly simulated phantoms.

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“…The accuracy of the results of our study depend on Geant4's predictions on dosimetry, total and individual linear attenuation coefficients in soft tissue, and x-ray scatter, characteristics which have been extensively validated for both DBCT (18,41) and for planar and tomosynthesis imaging of the breast (42)(43)(44)(45).…”

Section: Discussionmentioning

confidence: 99%

Monte Carlo and Phantom Study of the Radiation Dose to the Body from Dedicated CT of the Breast

et al. 2008

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Purpose-To prospectively determine the radiation dose absorbed by the organs and tissues of the body during a dedicated computed tomography of the breast (DBCT) study using Monte Carlo methods and a phantom. Materials and Methods-Using the Geant4Monte Carlo toolkit, the Cristy anthropomorphic phantom and the geometry of a prototype DBCT was simulated. The simulation was used to track x-rays emitted from the source until their complete absorption or exit from the simulation limits. The interactions of the x-rays with the 65 different volumes representing organs, bones and other tissues of the anthropomorphic phantom that resulted in energy deposition were recorded. These data were used to compute the radiation dose to the organs and tissues during a complete DBCT acquisition relative to the average glandular dose to the imaged breast (ROD, relative organ dose), using the xray spectra proposed for DBCT imaging. The effectiveness of a lead shield for reducing the dose to the organs was investigated.Results-The maximum ROD among the organs was for the ipsilateral lung with a maximum of 3.25%, followed by the heart and the thymus. Of the skeletal tissues, the sternum received the highest dose with a maximum ROD to the bone marrow of 2.24%, and to the bone surface of 7.74%. The maximum ROD to the uterus, representative of that of an early-stage fetus, was 0.026%. These maxima occurred for the highest energy x-ray spectrum (80 kVp) analyzed. A lead shield does not protect substantially the organs that receive the highest dose from DBCT.Discussion-Although the dose to the organs from DBCT is substantially higher than that from planar mammography, they are comparable or considerably lower than those reached by other radiographic procedures and much lower than other CT examinations. Advances in Knowledge1. Our study, based on Monte Carlo methods and an anthropomorphic phantom, found that although the radiation dose received by the organs and tissues of the body outside the primary x-ray field from DBCT is considerably higher than that from planar mammography, it is still low (less than 8% of the average glandular dose to the imaged breast), and comparable to other radiographic applications.2. The inclusion of a 1 mm lead sheet inside the table top between the patient and the x-ray source does not substantially lower the dose to the higher-exposed organs, but it does decrease the dose to the uterus (by up to a factor of twenty). 3.The dose deposited in the uterus, representative of that deposited in an early-stage fetus, is low (less than 0.03% of the average glandular dose to the imaged breast). Implications for Patient Care 1.Our study results provide information on the radiation dose to the organs of the body from dedicated breast computed tomography. 2.In regards to using this procedure for women in early stages of pregnancy, we found low dose levels absorbed by the uterus during DBCT imaging.

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Characterization of scatter radiation in cone beam CT mammography

Cited by 17 publications

References 0 publications

A computer simulation study comparing lesion detection accuracy with digital mammography, breast tomosynthesis, and cone‐beam CT breast imaging

A computer simulation study comparing lesion detection accuracy with digital mammography, breast tomosynthesis, and cone‐beam CT breast imaging

Characterization of X-ray scattering for various phantoms and clinical breast geometries using breast CT on a dedicated hybrid system

Monte Carlo and Phantom Study of the Radiation Dose to the Body from Dedicated CT of the Breast

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