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Session: Cancer
Session starts: Friday 25 January, 10:30
Presentation starts: 10:45
Room: Lecture room 559

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Gijs Hendriks (Medical UltraSound Imaging Center; Radboudumc Nijmegen)
Chuan Chen (Medical UltraSound Imaging Center; Radboudumc Nijmegen)
Hendrik Hansen (Medical UltraSound Imaging Center; Radboudumc Nijmegen)
Chris de Korte (Medical UltraSound Imaging Center; Radboudumc Nijmegen)

Abstract:
Background: Mammography is the gold standard in breast cancer detection but has reduced sensitivity in women with dense breast (i.e. an increased glandular-to-fat tissue ratio). The automated breast volume scanner (ABVS) was introduced as ultrasound alternative for mammography. In ABVS scanning, a linear ultrasound transducer (153 mm, 14L5BV) translates over the breast while collecting ultrasound data to reconstruct a 3-D volume of the breast. Studies report high sensitivity of ABVS in breast screening, however, the specificity is limited. Quasi-static elastography might be a solution to increase the specificity since malignant lesion are often stiffer compared to benign lesions. Aim: The aim of this study was to implement 3-D quasi-static elastography in ABVS and to verify feasibility in a patient study. Methods: Female patients who were scheduled for a breast exam in our hospital (Radboudumc Nijmegen) were recruited and signed an informed consent. Next to their regular breast exam, two additional breast ultrasound RF-data volumes were acquired using the ABVS with lifting the transducer (1 mm) in between scans. Displacements were calculated using coarse-to-fine cross-correlation of the acquired volumes. The 3-D strain tensor was derived from the displacements using a least-squares strain estimator. The principal strains were calculated by the eigenvalues of the tensor, because breathing was allowed between the two volumetric scans (2x15 seconds) and consequently the main strain component was not necessarily in the axial direction. Next, the principal strain component with largest absolute value (ε(principal1)) was normalized by the median of ε(principal1) in the subcutaneous fat divided by ε(prinicipal1) values. Finally, the median normalized strain (ε(norm)) was calculated in annotated lesions or in random areas if no lesions were detected. Results: 29 patients participated in which 1 invasive ductal carcinoma (IDC), 2 ductal carcinoma in situ (DCIS), 1 other malignant lesion (OM), 3 fibro-adenoma (FA), 7 cysts and 4 other benign lesions (OB) were detected. The ε(norm) values were 3.5 (IDC); 0.9 and 2.1 (DCIS), 1.3 (OM), 0.8±0.5 (FA) and 1.3±0.6 (OB) in median ± iqr. In 11 subjects without lesion, ε(norm) (1.3±0.8) were found close to 1 as expected for healthy tissue. IDC and one DCIS showed increased ε(norm) compared to benign lesions (FA, Cysts, OB). DCIS lesions (especially low-grade) are often considered as pre-cancerous, can be less stiff compared to IDC which may explain the strain ratio within the range for benign tissues and lesions for the other DCIS lesion. Strains in cysts were not calculated given their hypoechoic properties. Conclusion: 3-D quasi-static elastography was successfully developed for ABVS. Initial in-vivo results showed that IDC can be discriminated from benign lesions.