Upright patient positioning for pelvic radiotherapy treatments.

Radiotherapy is typically delivered in supine position. However, upright positioning may affect organ volume, positioning, and movement, compared to supine/prone positioning which might have beneficial impacts. In this study, we report patient positioning data in an upright positioning system designed by Leo Cancer Care®. Sixteen patients with pelvic tumors were included in this study. They had 3 setups in an upright position: an initial setup with acquisition of reference optical images, and 2 repositioning setups. The intra-fraction motion was assessed during two 20-minute chair rotation sessions. The patient comfort in supine and upright position was assessed with a 5-point Likert scale questionnaire. Eight women and 8 men treated on regular linacs between October 2021 and June 2022 were included. Their median age and weight were 62.5 years (35 to 81 years) and 75.1 kg (41 to 107 kg). The inter-fraction shift means were -0.5 mm (SD = 2.5), -0.4 mm (SD = 1.3) and -0.9 mm (SD = 2.7) in left-right (LR), antero-posterior (AP), and cranio-caudal (CC) directions, respectively. The intrafraction shifts after 20 min were 0.0 mm (SD = 1.5), 0.2 mm (SD = 1.1) and 0.0 mm (SD = 0.3) in LR, CC, and AP directions, respectively. Average global comfort was 4.1 (3 to 5) for the upright position and 3.9 (2 to 5) for the supine position. In conclusion, the first study on pelvic cancer patients positioned in upright position on a chair is promising, and it opens a potential new direction for the treatment of cancer patients. Evaluation of thoracic and head and neck tumors is ongoing, and imaging with vertical CT is expected to start soon.

Phonophoresis: efficiency, mechanisms and skin tolerance.

Phonophoresis or sonophoresis is the use of ultrasound to increase percutaneous absorption of a drug. The technique has been widely used in sports medicine since the sixties. Controlled studies in humans in vivo have demonstrated absence or mild effects of the technique with the parameters currently used (frequency 1-3 MHz, intensity 1-2 W/cm(2), duration 5-10 mins, continuous or pulse mode). However, it was demonstrated in 1995 that administration of macromolecules with conserved biological activity was feasible in animals in vivo using low frequency ultrasound. This led to new research into this method of transdermal administration. The aim of this review is to present the main findings published with low frequency and high frequency ultrasound over the last ten years, and to discuss the respective roles of thermal, cavitational and non-cavitational effects on the reduction of the skin barrier. Particular attention is paid to the biological effects on living skin which might be of importance for tolerance and practical use in humans.

In vitro study of low-frequency ultrasound-enhanced transdermal transport of fentanyl and caffeine across human and hairless rat skin.

The effect of low-frequency sonophoresis on fentanyl and caffeine permeation through human and hairless rat skin was studied in vitro. Experiments were performed using 20 kHz ultrasound applied at either continuous or discontinuous mode and with an average intensity of 2.5 W/cm(2). The results showed that low-frequency ultrasound enhanced the transdermal transport of both fentanyl and caffeine across human and hairless rat skin. This was explained by both increasing flux during sonication and shortening the lag time. Discontinuous mode was found to be more effective in increasing transdermal penetration of fentanyl while transdermal transport of caffeine was enhanced by both continuous and pulsed mode. Histological and electron microscopy studies showed that human and hairless rat skin was unaffected by ultrasound exposure. Further studies will be necessary to determine the relative contribution of ultrasound parameters in low-frequency ultrasound-induced percutaneous enhancement of drug transport.

Clinical, histologic, and electron microscopy study of skin exposed to low-frequency ultrasound.

The use of low-frequency ultrasound has been proposed to enhance the transdermal transport of various drugs, a technique referred to as sonophoresis. The aim of the present study was to determine the safety of low-frequency sonophoresis on human and rat skin by evaluating their structural modifications after ultrasound exposure. Human skin samples and hairless rats were exposed to 20 kHz ultrasound in vitro and in vivo, respectively. Ultrasound was used with average intensities ranging from 0.25 to 7 W/cm(2) in pulsed or continuous mode. Hairless rats were also exposed to a heat source mimicking the temperature versus time profile during sonication. Skin samples were observed under optical and electron microscopy to detect any structural changes. Human skin samples exposed to intensities lower than 2.5 W/cm(2) showed no modification. For hairless rats, slight and transient erythema was observed after 2.5 W/cm(2) exposure, whereas deep lesions (dermal and muscle necrosis) were observed 24 hr later. These lesions were also observed when a plastic film was placed between the coupling medium and the animals' skin during sonication. In contrast, no histologic lesion could be seen when a heat source was applied to animal skin. Low-frequency ultrasound induces delayed and deep lesions in hairless rat skin at 2.5 W/cm(2) which are not only attributable to the increase in temperature at the skin surface during ultrasound exposure. By using the same ultrasound conditions, human skin seems to be less sensitive in vitro.