Feasibility of a pregnancy intervention mimicking viral transmission mitigation measures on the incidence of preterm birth in high-risk pregnant women enrolled in antenatal clinics in Melbourne, Australia: protocol for a pilot, randomised trial

INTRODUCTION

Preterm birth is a leading cause of perinatal morbidity and mortality. During the COVID-19 pandemic, reduction in rates of preterm birth in women exposed to viral mitigation measures was reported by multiple studies. In addition, others and we observed a more pronounced reduction of preterm birth in women who had previously experienced a preterm birth. The aim of this pilot study is to establish the feasibility of a lifestyle intervention based on viral mitigation measures in high-risk pregnancies, with the ultimate aim to reduce the incidence of preterm birth.

METHODS AND ANALYSIS

One hundred pregnant women, enrolled in antenatal clinics at two tertiary maternity centres in Melbourne, Australia, who have had a previous preterm birth between 22 and 34 weeks gestation will be recruited. This is a two-arm, parallel group, open-label randomised controlled feasibility trial: 50 women will be randomised to the intervention group, where they will be requested to comply with a set of lifestyle changes (similar to the viral mitigation measures observed during the pandemic). Another 50 women will be randomised to the control group, where they will undergo standard pregnancy care. The primary outcome of this trial is feasibility, which will be assessed by measuring patient eligibility rate, recruitment rate, compliance rate and data completion rate. Secondary outcomes include incidence of preterm birth, maternal satisfaction, maternal quality of life and other pregnancy outcomes. Standard methods in statistical analysis for randomised controlled trials on an intention to treat basis will be followed.

ETHICS AND DISSEMINATION

This trial has been approved by the Monash Human Research Ethics Committee; approval reference number RES-22-0000-122A. Study findings will be reported and submitted to peer-reviewed journals for publication, and presentation at conferences.

TRIAL REGISTRATION NUMBER

ACTRN12622000753752; Pre-results.

3D prompt gamma imaging for proton beam range verification

We tested the ability of a single Compton camera (CC) to produce 3-dimensional (3D) images of prompt gammas (PGs) emitted during the irradiation of a tissue-equivalent plastic phantom with proton pencil beams for clinical doses delivered at clinical dose rates. PG measurements were made with a small prototype CC placed at three different locations along the proton beam path. We evaluated the ability of the CC to produce images at each location for two clinical scenarios: (1) the delivery of a single 2 Gy pencil beam from a hypo-fractionated treatment (~9  ×  10⁸ protons), and (2) a single pencil beam from a standard treatment (~1  ×  10⁸ protons). Additionally, the data measured at each location were combined to simulate measurements with a larger scale, clinical CC and its ability to image shifts in the Bragg peak (BP) range for both clinical scenarios. With our prototype CC, the location of the distal end of the BP could be seen with the CC placed up to 4 cm proximal or distal to the BP distal falloff. Using the data from the simulated full scale clinical CC, 3D images of the PG emission were produced with the delivery of as few as 1  ×  10⁸ protons, and shifts in the proton beam range as small as 2 mm could be detected for delivery of a 2 Gy spot. From these results we conclude that 3D PG imaging for proton range verification under clinical beam delivery conditions is possible with a single CC.

Feasibility Studies of a New Event Selection Method to Improve Spatial Resolution of Compton Imaging for Medical Applications

A Compton imaging method for medical applications that includes new energy determination and data filtering techniques has been tested using several point sources with known emission lines. Using a prototype Compton camera, a distance-of-closest approach technique has been employed to determine the initial energy of the incoming γs and to ensure the reconstructed source position is within an acceptable distance from the known γ source location. Further analysis is done by implementing a Compton line filtering technique, keeping only those interactions whose deposited energy in the first interaction matches the theoretical energy deposition predicted by the Compton equation. Using this new event filtering method, we see improvements in the full width at half maximum in the lateral profiles of γ point sources of up to 70% over standard Compton imaging methods, as well as achievable spatial resolutions in the reconstructed images of better than 2 mm. In addition, this new Compton imaging method was able to reconstruct an extended source of γ rays emitted during irradiation of a water tank with a clinical proton radiotherapy beam.