RESUMEN
This paper demonstrates that optimization strategies derived from the field of compressed sensing (CS) improve computational performance in inverse treatment planning (ITP) for high-dose-rate (HDR) brachytherapy. Following an approach applied to low-dose-rate brachytherapy, we developed a reformulation of the ITP problem with the same mathematical structure as standard CS problems. Two greedy methods, derived from hard thresholding and subspace pursuit are presented and their performance is compared to state-of-the-art ITP solvers. Applied to clinical prostate brachytherapy plans speed-up by a factor of 56-350 compared to state-of-the-art methods. Based on a Wilcoxon signed rank-test the novel method statistically significantly decreases the final objective function value (p < 0.01). The optimization times were below one second and thus planing can be considered as real-time capable. The novel CS inspired strategy enables real-time ITP for HDR brachytherapy including catheter optimization. The generated plans are either clinically equivalent or show a better performance with respect to dosimetric measures.
Asunto(s)
Braquiterapia/métodos , Catéteres/normas , Neoplasias de la Próstata/radioterapia , Radiometría/métodos , Planificación de la Radioterapia Asistida por Computador/métodos , Humanos , Masculino , Dosificación RadioterapéuticaRESUMEN
This work discusses a novel strategy for inverse planning in low dose rate brachytherapy. It applies the idea of compressed sensing to the problem of inverse treatment planning and a new solver for this formulation is developed. An inverse planning algorithm was developed incorporating brachytherapy dose calculation methods as recommended by AAPM TG-43. For optimization of the functional a new variant of a matching pursuit type solver is presented. The results are compared with current state-of-the-art inverse treatment planning algorithms by means of real prostate cancer patient data. The novel strategy outperforms the best state-of-the-art methods in speed, while achieving comparable quality. It is able to find solutions with comparable values for the objective function and it achieves these results within a few microseconds, being up to 542 times faster than competing state-of-the-art strategies, allowing real-time treatment planning. The sparse solution of inverse brachytherapy planning achieved with methods from compressed sensing is a new paradigm for optimization in medical physics. Through the sparsity of required needles and seeds identified by this method, the cost of intervention may be reduced.
Asunto(s)
Algoritmos , Braquiterapia/métodos , Planificación de la Radioterapia Asistida por Computador/métodos , Humanos , Masculino , Neoplasias de la Próstata/radioterapia , Dosificación RadioterapéuticaRESUMEN
Heparin-associated thrombocytopenia may be a potentially devastating event when linked with thrombosis. Two cases of heparin-associated thrombocytopenia are presented, one with thrombosis that culminated in maternal death. Heparin-associated platelet antibody was seen in both patients. The incidence and management of heparin-associated thrombocytopenia are discussed.
Asunto(s)
Anticuerpos/análisis , Heparina/inmunología , Complicaciones Hematológicas del Embarazo/inmunología , Adolescente , Adulto , Plaquetas/inmunología , Seno Cavernoso , Femenino , Heparina/efectos adversos , Humanos , Inmunoglobulina G/análisis , Embarazo , Complicaciones Hematológicas del Embarazo/etiología , Trombosis de los Senos Intracraneales/etiología , Trombosis de los Senos Intracraneales/inmunología , Trombocitopenia/etiología , Trombocitopenia/inmunologíaRESUMEN
Intrauterine specimens were obtained from 22 patients with endometritis and 24 control patients following cesarean section by using both a new protected swab and a standard anaerobic swab. The protected swab improved the value of the direct smear and Gram stain, resulted in fewer false-positive cultures, better defined endometrial flora in patients with endometritis, and permitted major savings in laboratory personnel time and materials.