The objectives of this study were to develop and evaluate a breast tissue equivalent phantom that can be used for dual purposes, conventional x-ray imaging and ultrasonography. This phantom was designed based on the prototype of an intralipid-gel soft tissue mimicking phantom used for laser photothermal therapy. The glandularities and the densities of the phantom can be adjusted by modifying the ratio of intralipid and other ingredients and adding fiber powders. An adipose tissue phantom and a glandular tissue phantom were firstly developed and phantoms of different glandularities were further developed through mixing different weight proportions of adipose and glandular. To validate the properties of the phantom for the applications of x-ray imaging techniques, three methods were employed: (1) the compositions of the elements contained in the phantoms were estimated through calculations; (2) the x-ray mass attenuation coefficients of the phantom were calculated based on the elemental compositions; (3) the x-ray photon energies deposit in the phantoms with different glandularities were simulated using Geant4 Simulation Tool Kit. The results showed high agreements with the real breast tissues at corresponding breast glandularities. For the application in ultrasonography, the elasticity of the phantom was determined by measuring the value of Young’s modulus and the value of 39 ± 10 kPa indicated the satisfactory of the requirement of being used as phantom for ultrasound imaging. Therefore, the phantoms developed in this study potentially provided a solution of dualpurpose breast tissue mimicking phantom in the needs of different level of glandularity.
The objective of this study was to demonstrate the capability of the high-energy in-line phase contrast imaging in detecting the breast tumors which are undetectable by conventional x-ray imaging but detectable by ultrasound. Experimentally, a CIRS multipurpose breast phantom with heterogeneous 50% glandular and 50% adipose breast tissue was imaged by high-energy in-line phase contrast system, conventional x-ray system and ultrasonography machine. The high-energy in-line phase contrast projection was acquired at 120 kVp, 0.3 mAs with the focal spot size of 18.3 μm. The conventional x-ray projection was acquired at 40 kVp, 3.3 mAs with the focal spot size of 22.26 μm. Both of the x-ray imaging acquisitions were conducted with a unique mean glandular dose of 0.08 mGy. As the result, the high-energy in-line phase contrast system was able to detect one lesion-like object which was also detected by the ultrasonography. This object was spherical shape with the length of about 12.28 mm. Also, the conventional x-ray system was not able to detect any objects. This result indicated the advantages provided by high-energy in-line phase contrast over conventional x-ray system in detecting lesion-like object under the same radiation dose. To meet the needs of current clinical strategies for high-density breasts screening, breast phantoms with higher glandular densities will be employed in future studies.
The objective of this study is to demonstrate the potential of using the High-energy in-line phase contrast x-ray imaging to detect lesions that are indistinguishable by conventional x-ray mammography but are detectable by supplemental ultrasound screening within dense breasts. For this study, a custom-made prototype x-ray/ultrasound dualmodality phantom that mimics dense breast is created to include embedded carbon fiber disks with multiple diameters and thicknesses. The phase contrast image is acquired using a prototype at 120kVp, 67μA, exposure time of 16.7sec and focal spot size of 18.3μm with average glandular dose (AGD) of 0.3mGy under a geometric magnification of 2.48. The conventional x-ray image is acquired with a bench top system operating at 40kVp, 300μA, exposure time of 50sec and same AGD. The results demonstrate that conventional x-ray imaging is unable to detect any of the carbon fiber disks, while phase contrast imaging and ultrasonography are able to detect most or all of the disks under the applied experimental conditions. These results illustrate phase contrast imaging is capable of detecting targets in a dual-modality phantom which simulates lesions in dense breast tissue, when the simulated lesions are not distinguishable by conventional mammography. Therefore mammographic screening with phase contrast technique could eventually replace both x-ray and ultrasonography for screening detection of small lesions with microcalcification in dense breasts where pathologic lesions are masked due to highly glandular tissue. These results encourage further investigation using high glandular density phantoms to further evaluate the effectiveness of phase contrast imaging as a single modality test, which combines the advantages of both x-ray and ultrasound imaging in cancer screening of patients with dense breasts.
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