Effects of gas-filled temporary breast tissue expanders on radiation dose from modulated rotational photon beams

Air Versus Saline in Tissue Expanders: A Systematic Review of the Literature

BACKGROUND

 There has been a greater focus in recent literature proposing air to be a superior medium to saline in tissue expanders. This study aims to review the literature and assess the quality of data on the efficacy and safety of air as an alternative medium to saline in tissue expanders, in the setting of postmastectomy two-stage reconstruction.

METHODS

 A systematic review regarding air inflation of tissue expanders was conducted using PubMed, Embase, Cochrane Library, and Web of Science. The methods followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Three reviewers separately performed data extraction and comprehensive synthesis.

RESULTS

 A total of 427 articles were identified in our search query, of which 11 met the inclusion criteria. Three pertained to inflation with room air, and eight pertained to inflation with CO2 using the AeroForm device. They were comparable to decreased overall complication rates in the room air/CO2 cohort compared to saline, although statistical significance was only observed in one of five two-arm studies. Investigating specific complications in the five two-arm studies, significantly lower rates of skin flap necrosis were only observed in two CO2-based studies. Studies rarely discussed other safety profile concerns, such as the impacts of air travel, radiation planning, and air extravasation beyond descriptions of select patients within the cohort.

CONCLUSION

 There is insufficient evidence to suggest improved outcomes with room air inflation of tissue expanders. Further work is needed to fully characterize the benefits and safety profiles of air insufflation before being adopted into clinical practice.

Dosimetric evaluation of a patient-specific 3D-printed oral positioning stent for head-and-neck radiotherapy

As head-and-neck radiotherapy treatments become more complex and sophisticated, and the need to control and stabilise the positioning of intra-oral anatomy becomes more important, leading the increasing use of oral positioning stents during head-and-neck radiotherapy simulation and delivery. As an alternative to the established practice of creating oral positioning stents using wax, this study investigated the use of a 3D printing technique. An Ender 5 3D printer (Creality 3D, Shenzhen, China) was used, with PLA+ "food-safe" polylactic acid filament (3D Fillies, Dandenong South, Australia), to produce a low-density 3D printed duplicate of a conventional wax stent. The physical and dosimetric effects of the two stents were evaluated using radiochromic film in a solid head phantom that was modified to include flexible parts. The Varian Eclipse treatment planning system (Varian Medical Systems, Palo Alto, USA) was used to calculate the dose from two different head-and-neck treatment plans for the phantom with each of the two stents. Examination of the resulting four dose distributions showed that both stents effectively pushed sensitive oral tissues away from the treatment targets, even though most of the phantom was solid. Film measurements confirmed the accuracy of the dose calculations from the treatment planning system, despite the steep density gradients in the treated volume, and demonstrated that the 3D print could be a suitable replacement for the wax stent. This study demonstrated a useful method for dosimetrically testing novel oral positioning stents. We recommend the development of flexible phantoms for future studies.