Cross-imaging system comparison of backscatter coefficient estimates from a tissue-mimicking material

A key step toward implementing quantitative ultrasound techniques in a clinical setting is demonstrating that parameters such as the ultrasonic backscatter coefficient (BSC) can be accurately estimated independent of the clinical imaging system used. In previous studies, agreement in BSC estimates for well characterized phantoms was demonstrated across different laboratory systems. The goal of this study was to compare the BSC estimates of a tissue mimicking sample measured using four clinical scanners, each providing RF echo data in the 1-15 MHz frequency range. The sample was previously described and characterized with single-element transducer systems. Using a reference phantom for analysis, excellent quantitative agreement was observed across the four array-based imaging systems for BSC estimates. Additionally, the estimates from data acquired with the clinical systems agreed with theoretical predictions and with estimates from laboratory measurements using single-element transducers

Photoacoustic signal characterization of cancer treatment response: Correlation with changes in tumor oxygenation

Frequency analysis of the photoacoustic radiofrequency signals and oxygen saturation estimates were used to monitor the in-vivo response of a novel, thermosensitive liposome treatment. The liposome encapsulated doxorubicin (HaT-DOX) releasing it rapidly (<20 s) when the tumor was exposed to mild hyperthermia (43 °C). Photoacoustic imaging (VevoLAZR, 750/850 nm, 40 MHz) of EMT-6 breast cancer tumors was performed 30 min pre- and post-treatment and up to 7 days post-treatment (at 2/5/24 h timepoints). HaT-DOX-treatment responders exhibited on average a 22% drop in oxygen saturation 2 h post-treatment and a decrease (45% at 750 nm and 73% at 850 nm) in the slope of the normalized PA frequency spectra. The spectral slope parameter correlated with treatment-induced hemorrhaging which increased the optical absorber effective size via interstitial red blood cell leakage. Combining frequency analysis and oxygen saturation estimates differentiated treatment responders from non-responders/control animals by probing the treatment-induced structural changes of blood vessel

Correction: Photoacoustic Imaging of Cancer Treatment Response: Early Detection of Therapeutic Effect from Thermosensitive Liposomes.

[This corrects the article DOI: 10.1371/journal.pone.0165345.]

Longitudinal monitoring of oxygen saturation with photoacoustic imaging

Assessing the response of cancer treatments non-invasively on an individual (or patient) basis has the potential to impact cancer treatment. The need for a modality that provides multifaceted information about the structural and metabolic changes that occur within tumors is important, especially because of the vasculature and the role it plays in tumor growth. One such modality capable of imaging the anatomy and functionality of vasculature is photoacoustic (PA) imaging. In this study, in vivo PA imaging and estimation of oxygen saturation (SO2) was performed longitudinally to monitor the efficacy of thermosensitive liposome delivery vehicles. By mapping the distribution of oxygen in 12 animals treated with doxorubicin-loaded thermosensitive liposomes, early SO2 changes (within hours) were predictive of treatment success as assessed by volumetric tumor growth after 2 weeks. Twelve saline-treated animals showed no observable, early changes in SO2 and displayed larger intertumoral variability in oxygen distribution compared to the treated group. The longitudinal variations in estimated tumor oxygenation, particularly in the first 5 hours post treatment, demonstrate the unique sensitivity of PA imaging to monitor these functional changes in tumor vasculature.</p

Photoacoustic radiofrequency spectroscopy for monitoring cancer treatment response

Frequency analysis of the photoacoustic (PA) signals was combined with functional PA estimations of tumor oxygenation to monitor the in-vivo response of a temperature sensitive liposome treatment. Mouse breast cancer tumors were imaged using the Vevo LAZR system (Fujifilm VisualSonics, Toronto, Canada) before treatment and 30 min/2h/5h/24h/7d post-treatment. Treatment consisted of an injection of either the liposome (HaT-DOX) or saline followed by heating of the tumour in a water bath for 1 hour at 43°C. The tumor oxygenation and the slope of the normalise power spectrum decreased by 22% and 45% at 750 nm, respectively as early as 30 minutes post-treatment. The combined analysis was able to differentiate responding mice from their non-responding counterparts and the control group. These results suggest that probing both structural (spectral slope) and functional (oxygen saturation) changes that occur during cancer treatment can aid in identifying treatment response.</p

Cancer treatment response evaluation using photoacoustic signal envelop statistics: A preliminary study

Cancer is a major public health problem all over the world. It is currently the second leading cause of death in the United States, and is expected to surpass heart diseases as the leading cause of death in the next few years. To overcome this problem, researchers are discovering new treatments and developing imaging technologies that can aid in early detection of cancer. In this work, we investigate the use of signal envelope statistics to monitor and quantify structural changes in tissues during cell death. Ultrasound backscatter and photoacoustic data were obtained from three mice treated with, Hat-DOX, DOX and saline. The signal envelope statistics were examined by fitting the Rayleigh and Generalized Gamma distributions. The fit parameters showed sensitivity to structural changes in the cells in photoacoustic and ultrasound images. The results indicate that photoacoustic signal statistics can be potentially used to monitor structural changes within a tumor, raising the possibility of monitoring cancer therapy efficacy.</p

Chingalire Women’s Travelling Theatre: Touring with Trousers

This paper is an initial investigation into the establishment of the Chingalire Women’s Traveling Theatre (CWTT) in Malawi, and its impact on the group and their local community. The paper touches on issues of gender inequality in Malawi by showing how the theatre company challenges the commonly accepted cultural and gender hegemonies through theatre performance. Malawi has an ancient drumming, ritual and dance culture. Since colonial times drama has joined the ranks of performative expression of both the urban and rural populations. Historically the expatriate community or, post-independence, the male population and non-governmental organisations (NGOs) have largely dominated drama. Inspired by hearing the voices of women in drama on the radio, ten mothers formed the Chingalire Women’s Traveling Theatre in July 2016. The purpose of the company is to travel through rural areas of Malawi using theatre to explore issues such as gender-based violence, the environment and the importance of education to the rural community; discussions with those communities form part of the enterprise. The rehearsals and performances give voice to the experiences and opinions of women who might otherwise remain silent. The group decided to play male characters themselves wearing trousers as a signifier. Women were prevented from wearing trousers by law until 1994, and in 2012 there were BBC reports from Blantyre that women were still being beaten for dressing in trousers. There is therefore personal risk inherent in this undertaking. Using interviews with the founding members of the company and with the chief of Chingalire village, Ben Mankhamba, this article seeks to contextualise the achievement of this female-led project, to analyse some of the work they have already undertaken and to offer insights as to what the theatre company might achieve in the future and what impact their work might have

Schematic of the mode of action of a temperature sensitive liposome (TSL) for intravascular release.

<p>The TSL passes through normal unheated vasculature intact (a), but on reaching the heated tumor (b) drug is released in a burst-release fashion, creating a high local drug concentration which permeates into the tumor tissue.</p

Size and oxygenation relationships.

<p>Correlation between the changes in the size of the tumor treated with (a) HT-HaT-DOX and (b) HT-Saline at endpoint (from day 0) and the changes in mean sO₂ between the values observed for 30 min pre-treatment and 2 h post-treatment. Each point is the average of 21 sO₂ histograms at the 2 h timepoint. The major and minor axes of each ellipse represent the standard deviations of the change in sO₂ and change in tumor size, respectively. † identifies a datapoint for a HT-HaT-DOX treatment that did not show regression, nor a characteristic drop in sO₂ at 2 h post-treatment.</p