Efficacy and feasibility of 3D printed redesigned Venezia™ applicator for treating advanced cervix and recurrent endometrial cancer.

PURPOSE: Venezia™ is an interstitial brachytherapy applicator for treating advanced cervical and vaginal vault recurrent cancer. However, there are limitations that lead to suboptimal target coverage. 3D printing introduction allows the redesign of Venezia™ for bulky and irregular-shaped tumors. METHODS: This study first describes three new designs included: 1) add-on needles template allowed for an extra layer of straight and oblique needles, 2) redesigned vaginal cap so straight and oblique needles can be used together and 3) redesigned central tube allowed vaginal vault interstitial needle insertion. Drawbacks to original Venezia™ and rationale for using these new designs were discussed. Dosimetric analysis by comparing the original Venezia™ with new design for 10 cases in Oncentra treatment planning system v4.5 (Elekta, Stockholm, Sweden) to observe the dose differences in gross tumor volume (GTV), high risk clinical target volume (HRCTV), intermediate clinical target volume (IRCTV) and organs at risk. RESULTS: For the dosimetric comparison, there were statistically significantly increased median minimal dose to 98% (D98%) of GTV, 90% (D90%) of HRCTV, and IRCTV for the new design with p-value of 0.008, 0.005 and 0.0018, respectively. Comparing the physical dose of D98% of GTV, D90% of HRCTV, and IRCTV when using the new design, it averagely increased by 11.7%, 8.0%, 19.4%, respectively per fraction. CONCLUSIONS: Dosimetric comparison revealed the new designs increased the dose to GTV, HRCTV and IRCTV and fulfilled the dose constraints of bladder, rectum and sigmoid. The 3D printed new design is biocompatible, inexpensive and can be patient specific.

A System-Independent Derivation of Preferential Attachment from the Principle of Least Effort.

Preferential attachment (PA) is a widely observed behavior in many living systems and has been used in modeling many networks. The aim of this work is to show that the mechanism of PA is a consequence of the fundamental principle of least effort. We derive PA directly from this principle in maximizing an efficiency function. This approach not only allows a better understanding of the different PA mechanisms already reported but also naturally extends these mechanisms with a non-power law probability of attachment. The possibility of using the efficiency function as a general measure of attachment efficiency is also investigated.

Complications of bezoar in children: what is new?

A bezoar is a mass found trapped in the gastrointestinal system. The condition may be associated with pica, especially in developmentally retarded children. Clinical manifestations are usually nonspecific. Endoscopic diagnosis and removal of the foreign materials is often indicated. Occasionally, severe complications may occur. We report two cases to illustrate the clinical features and complications in these children. In the first case, a reliable history was not obtained in the developmentally delayed girl which precluded prompt diagnosis, but the grossly dilated stomach on plain abdominal radiograph gave clues to an underlying insidious mechanical obstruction of upper gastrointestinal tract. In the second case of a normal child, the unrelenting symptoms and weight loss prompt further investigations which revealed the diagnosis. Literature on pediatric bezoar is reviewed. Oesophagoduodenoscopy is the investigation of choice for diagnostic confirmation, but surgical facilities must be available to deal with acute complications.