Quantitative ultrasound imaging of therapy response in bladder cancer in vivo.

Background and aimsQuantitative ultrasound (QUS) was investigated to monitor bladder cancer treatment response in vivo and to evaluate tumor cell death from combined treatments using ultrasound-stimulated microbubbles and radiation therapy.MethodsTumor-bearing mice (n=45), with bladder cancer xenografts (HT- 1376) were exposed to 9 treatment conditions consisting of variable concentrations of ultrasound-stimulated Definity microbubbles [nil, low (1%), high (3%)], combined with single fractionated doses of radiation (0 Gy, 2 Gy, 8 Gy). High frequency (25 MHz) ultrasound was used to collect the raw radiofrequency (RF) data of the backscatter signal from tumors prior to, and 24 hours after treatment in order to obtain QUS parameters. The calculated QUS spectral parameters included the mid-band fit (MBF), and 0-MHz intercept (SI) using a linear regression analysis of the normalized power spectrum.Results and conclusionsThere were maximal increases in QUS parameters following treatments with high concentration microbubbles combined with 8 Gy radiation: (ΔMBF = +6.41 ± 1.40 (±SD) dBr and SI= + 7.01 ± 1.20 (±SD) dBr. Histological data revealed increased cell death, and a reduction in nuclear size with treatments, which was mirrored by changes in quantitative ultrasound parameters. QUS demonstrated markers to detect treatment effects in bladder tumors in vivo

Quantitative ultrasound characterization of tumor cell death: ultrasound-stimulated microbubbles for radiation enhancement.

The aim of this study was to assess the efficacy of quantitative ultrasound imaging in characterizing cancer cell death caused by enhanced radiation treatments. This investigation focused on developing this ultrasound modality as an imaging-based non-invasive method that can be used to monitor therapeutic ultrasound and radiation effects. High-frequency (25 MHz) ultrasound was used to image tumor responses caused by ultrasound-stimulated microbubbles in combination with radiation. Human prostate xenografts grown in severe combined immunodeficiency (SCID) mice were treated using 8, 80, or 1000 µL/kg of microbubbles stimulated with ultrasound at 250, 570, or 750 kPa, and exposed to 0, 2, or 8 Gy of radiation. Tumors were imaged prior to treatment and 24 hours after treatment. Spectral analysis of images acquired from treated tumors revealed overall increases in ultrasound backscatter intensity and the spectral intercept parameter. The increase in backscatter intensity compared to the control ranged from 1.9±1.6 dB for the clinical imaging dose of microbubbles (8 µL/kg, 250 kPa, 2 Gy) to 7.0±4.1 dB for the most extreme treatment condition (1000 µL/kg, 750 kPa, 8 Gy). In parallel, in situ end-labelling (ISEL) staining, ceramide, and cyclophilin A staining demonstrated increases in cell death due to DNA fragmentation, ceramide-mediated apoptosis, and release of cyclophilin A as a result of cell membrane permeabilization, respectively. Quantitative ultrasound results indicated changes that paralleled increases in cell death observed from histology analyses supporting its use for non-invasive monitoring of cancer treatment outcomes

Quantitative ultrasound imaging of therapy response in bladder cancer in vivo

BACKGROUND AND AIMS: Quantitative ultrasound (QUS) was investigated to monitor bladder cancer treatment response in vivo and to evaluate tumor cell death from combined treatments using ultrasound-stimulated microbubbles and radiation therapy. METHODS: Tumor-bearing mice (n=45), with bladder cancer xenografts (HT- 1376) were exposed to 9 treatment conditions consisting of variable concentrations of ultrasound-stimulated Definity microbubbles [nil, low (1%), high (3%)], combined with single fractionated doses of radiation (0 Gy, 2 Gy, 8 Gy). High frequency (25 MHz) ultrasound was used to collect the raw radiofrequency (RF) data of the backscatter signal from tumors prior to, and 24 hours after treatment in order to obtain QUS parameters. The calculated QUS spectral parameters included the mid-band fit (MBF), and 0-MHz intercept (SI) using a linear regression analysis of the normalized power spectrum. RESULTS AND CONCLUSIONS: There were maximal increases in QUS parameters following treatments with high concentration microbubbles combined with 8 Gy radiation: (ΔMBF = +6.41 ± 1.40 (±SD) dBr and SI= + 7.01 ± 1.20 (±SD) dBr. Histological data revealed increased cell death, and a reduction in nuclear size with treatments, which was mirrored by changes in quantitative ultrasound parameters. QUS demonstrated markers to detect treatment effects in bladder tumors in vivo

Results of statistical analysis performed on the “<i>Quantification of normalized fraction of condensed or fragmented nuclei</i>” using one-tailed paired t-test.

<p>Results of statistical analysis performed on the “<i>Quantification of normalized fraction of condensed or fragmented nuclei</i>” using one-tailed paired t-test.</p

Average changes in midband-fit parameter.

<p>Each bar represents the mean of midband-fit values of five mouse-borne tumors (n = 5). The error bar indicates the standard error within the sample size. Statistical testing using 2-way ANOVA indicates the effects caused by the changes in both microbubble concentration and dose of radiation to be very significant for every graph (<i>p</i><0.0001). Each graph shows the average changes in midband-fit for varied microbubble concentration and radiation doses at a fixed ultrasound pressure: 250 kPa, 570 kPa, and 750 kPa.</p

High magnification light microscope images of PC-3 xenografts immuno-stained with cyclophilin A.

<p>Tumors treated with ultrasound pulses at 750-staining. Each panel demonstrates a representative region of cell death occurred in the tumor. Microbubble concentrations are given as 8 µL/kg, 80 µL/kg, and 1000 µL/kg. The scale bar represents 25 µm.</p

Results of statistical analysis performed on the “Quantification of Ceramide” using 2-way ANOVA without replication.

<p>Results of statistical analysis performed on the “Quantification of Ceramide” using 2-way ANOVA without replication.</p

Results of statistical analysis performed on the “<i>Average Changes in Midband-fit, 0-MHz Intercept, and Slope parameter</i>” using 2-way ANOVA without replication.

<p>Results of statistical analysis performed on the “<i>Average Changes in Midband-fit, 0-MHz Intercept, and Slope parameter</i>” using 2-way ANOVA without replication.</p

Results of statistical analysis performed on the “Quantification of normalized fraction of condensed or fragmented nuclei” using 2-way ANOVA without replication.

<p>Results of statistical analysis performed on the “Quantification of normalized fraction of condensed or fragmented nuclei” using 2-way ANOVA without replication.</p

High-frequency ultrasound B-mode images of PC-3 xenografts.

<p>B-Mode (left) and on the right side of each row, respective representative normalized power spectra are shown. (A) Tumors treated with varying radiation doses (0–8 Gy) without ultrasound-microbubble treatment. (B) Tumors treated with varying microbubble concentrations (8–1000 µL/kg) combined with 750 kPa of ultrasound pulse and 8 Gy-radiation. (C) Tumors treated with varying ultrasound pressures (250–750 kPa) combined with 8 µL/kg of microbubbles and 8 Gy-radiation. The scale bar represents 2 mm.</p