Fat injection to correct contour deformities of the reconstructed breast:a single surgeon experience

Aim:Autologous fat grafting has gained acceptance as a technique to improve aesthetic outcomes in breast reconstruction.The purpose of this study was to share our clinical experience using autologous fat injection to correct contour deformities during breast reconstruction.Methods:A single surgeon,prospectively maintained database of patients who underwent autologous fat injection during breast reconstruction from January 2008 to November 2013 at McGill University Health Center was reviewed.Patient characteristics,breast history,type of breast reconstruction,volume of fat injected,and complications were analyzed.Results:One hundred and twenty-four patients benefited from autologous fat injection from January 2008 to November 2013,for a total of 187 treated breasts.The patients were on average 49.3 years old(±8.9 years).Fat was harvested from the medial thighs(20.5%),flanks(39.1%),medial thighs and flanks(2.9%),trochanters(13.3%),medial knees(2.7%),and abdomen(21.9%).An average of 49.25 mL of fat was injected into each reconstructed breast.A total of 187 breasts in 124 patients were lipo-infiltrated during the second stage of breast reconstruction.Thirteen breasts(in 12 separate patients)were injected several years after having undergone lumpectomy and radiotherapy.Of the 187 treated breasts,118 were reconstructed with expanders to implants,45 with deep inferior epigastric perforator flaps,9 with latissimus dorsi flaps with implants,4 with transverse rectus abdominis myocutaneous flaps,and 13 had previously undergone lumpectomy and radiotherapy.Six complications were noted in the entire series,for a rate of 3.2%.All were in previously radiated breasts.Average follow-up time was 12 months(range:2-36 months).Conclusion:Fat injection continues to grow in popularity as an adjunct to breast reconstruction.Our experience demonstrates a low complication rate as compared to most surgical interventions of the breast and further supports its safety in breast reconstruction.However,caution should be used when treating previously radiated breasts.

Low rank approximation in G0W0 calculations

The single particle energies obtained in a Kohn-Sham density functional theory(DFT) calculation are generally known to be poor approximations to electron excitation energies that are measured in transport,tunneling and spectroscopic experiments such as photo-emission spectroscopy. The correction to these energies can be obtained from the poles of a single particle Green's function derived from a many-body perturbation theory. From a computational perspective, the accuracy and efficiency of such an approach depends on how a self energy term that properly accounts for dynamic screening of electrons is approximated. The G_0W_0 approximation is a widely used technique in which the self energy is expressed as the convolution of a noninteracting Green's function(G_0) and a screened Coulomb interaction(W_0) in the frequency domain. The computational cost associated with such a convolution is high due to the high complexity of evaluating W_0 at multiple frequencies. In this paper, we discuss how the cost of G_0W_0 calculation can be reduced by constructing a low rank approximation to the frequency dependent part of W_0. In particular, we examine the effect of such a low rank approximation on the accuracy of the G_0W_0 approximation. We also discuss how the numerical convolution of G_0 and W_0 can be evaluated efficiently and accurately by using a contour deformation technique with an appropriate choice of the contour.