Effects of phase cancellation and receiver aperture size on broadband ultrasonic attenuation for trabecular bone in vitro

Phase cancellation in ultrasound due to large receiver size has been proposed as a contributing factor to the inaccuracy of estimating broadband ultrasound attenuation (BUA), which is used to characterize bone quality. Transducers with aperture size ranging from 2 to 5 mm have been used in previous attempts to study the effect of phase cancellation. However, these receivers themselves are susceptible to phase cancellation because aperture size is close to one center wavelength (about 3 mm at 500 KHz in water). This study uses an ultra small receiver (aperture size: 0.2 mm) in conjunction with a newly developed two-dimensional (2-D) synthetic array system to investigate the effects of phase cancellation and receiver aperture size on BUA estimations of bone tissue. In vitro ultrasound measurements were conducted on 54 trabecular bone samples (harvested from sheep femurs) in a confocal configuration with a focused transmitter and synthesized focused receivers of different aperture sizes. Phase sensitive (PS) and phase insensitive (PI) detections were performed. The results show that phase cancellation does have a significant effect on BUA. The normalized BUA (nBUA) with PS is 8.1% higher than PI nBUA while PI BUA is well correlated with PS BUA. Receiver aperture size also influences the BUA reading for both PI and PS detection and smaller receiver aperture tends to result in higher BUA readings. The results also indicate that the receiver aperture size used in the confocal configuration with PI detection should at least equal the aperture of the transmitter to capture most of the energy redistributed by the interference and diffraction from the trabecular bone.     

Goserelin plus letrozole as first- or second-line hormonal treatment in premenopausal patients with advanced breast cancer

A promising new option as the treatment of choice for premenopausal patients with metastatic breast cancer (MBC) could be the combination of a luteinising hormone-releasing hormone analog and an aromatase inhibitor. Very little data about the use of goserelin with anastrozole in advanced breast cancer are available, and no cohort studies on the efficacy of goserelin with letrozole in advanced premenopausal breast cancer patients have been reported. We present the single-centre, retrospective, experience of goserelin plus letrozole in a total of 52 premenopausal women with MBC. All patients received goserelin 3.6 mg by subcutaneous injection every 4 weeks along with letrozole 2.5 mg daily as first-line (n=36) and second-line (n=16) hormonal treatment. The median duration of goserelin with letrozole treatment was 11 (range, 2-61) months, and the median duration of overall follow-up was 31 (range, 3-66) months. The objective response rate (ORR) was 21.1%, with two complete response (CR) (3.8%) and nine partial response (PR) (17.3%). Stable disease (SD) lasting more than 6 months was achieved by 26 patients (50.0%). Thus, goserelin with letrozole conferred clinical benefit (CB) in 37 women (71.1%). The progression-free survival (PFS) was 10 months. CR was exclusively observed in hormone receptor-double-positive patients. Drug therapy was well tolerated; no grade 3/4 toxicities were reported. Goserelin plus letrozole appears to be an efficacious and well-tolerated regimen in women with advanced breast cancer. Further prospectively randomized studies involving more patients and longer follow-up are indicated.