Hypocrellin B-mediated sonodynamic action induces apoptosis of hepatocellular carcinoma cells

Objective

The present study aims to investigate apoptosis of hepatocellular carcinoma cells induced by hypocrellin B-mediated sonodynamic action.

Methods

The hypocrellin B concentration was kept constant at 2.5 μM and cells from the hepatocellular carcinoma HepG2 cell line were exposed to ultrasound with an intensity of 0.46 W/cm² for 8 s. Cell cytotoxicity was quantified using an MTT assay 24 h after sonodynamic therapy (SDT) of hypocrellin B. Apoptosis was investigated using a flow cytometry with Annexin V-FITC and propidium iodine staining. Intracellular reactive oxygen species (ROS) levels were detected using a flow cytometry with 2,7-dichlorodihydrofluorecein diacetate (DCFH-DA) staining.

Results

The cytotoxicity of hypocrellin B-mediated sonodynamic action on HepG2 cells was significantly higher than those of other treatments including ultrasound alone, hypocrellin B alone and sham treatment. Flow cytometry showed that hypocrellin B-induced sonodynamic action markedly enhanced the apoptotic rate of HepG2 cells. Increased ROS was observed in HepG2 cells after being treated with hypocrellin B-mediated sonodynamic action.

Conclusions

Our data demonstrated that hypocrellin B-mediated sonodynamic action remarkably induced apoptosis of HepG2 cells, suggesting that apoptosis is an important mechanism of cell death induced by hypocrellin B-mediated SDT.     

Apoptosis of ovarian cancer cells induced by methylene blue-mediated sonodynamic action

Objective

The present study aims to investigate apoptosis of ovarian cancer cells induced by methylene blue (MB)-mediated sonodynamic therapy (SDT).

Methods

The MB concentration was kept constant at 100 μM and ovarian cancer HO-8910 cells were exposed to ultrasound therapy for 5 s with an intensity of 0.46 W/cm². The cytotoxicity was investigated 24 h after MB-mediated sonodynamic action. Apoptosis was analyzed using a flow cytometer with Annexin V-FITC and propidium iodine (PI) staining as well as fluorescence microscopy with Hoechst 33258 staining. Intracellular reactive oxygen species (ROS) level was measured by flow cytometer with 2,7-dichlorodihydrofluorescein diacetate (DCFH-DA) staining.

Results

The cytotoxicity of MB-mediated SDT on HO-8910 cells after MB-mediated SDT was significantly higher than those of other treatments including ultrasound alone, MB alone and sham treatment. Flow cytometric analysis showed a significant increase in the early and late apoptotic cell populations by MB-mediated SDT of HO-8910 cells. Nuclear condensation and increased ROS levels were also found in HO-8910 cells treated by MB-mediated SDT.

Conclusions

Our findings demonstrated that MB-mediated sonodynamic action significantly induced apoptosis of HO-8910 cells and an increase in intracellular ROS level. This indicates that apoptosis is an important mechanism of cell death induced by MB-mediated SDT. Thus, MB-mediated SDT might be a potential therapeutic strategy for combating ovarian cancer.     

Effects of therapeutic pulsed ultrasound and dimethylsulfoxide phonophoresis on oxidative stress parameters after injury induced by eccentric exercise

Introduction

The aim of the study was to evaluate the effects of TPU together with DMSO on oxidative stress parameters after eccentric exercise.

Methods

Thirty and six animals were divided in control; eccentric exercise (EE); EE + saline gel 0.9%; EE + TPU 0.8 W/cm²; EE + DMSO gel; EE + TPU + DMSO gel and submitted to one 90-min downhill run (1.0 km h⁻¹). TPU was used 2, 12, 24, 46 h after exercise session and 48 h after the animals were killed and the gastrocnemius muscles were surgically removed. Production of superoxide anion, creatine kinase (CK) levels, lipoperoxidation, carbonylation, and antioxidants enzymes were analyzed.

Results

Showed that TPU and gel-DMSO improved muscle healing. Moreover, superoxide anion production, TBARS level and protein carbonyls levels, superoxide dismutase and catalase activity were all decreased in the group TPU plus gel-DMSO.

Discussion

Our results show that DMSO is effective in the reduction of the muscular lesion and in the oxidative stress after eccentric exercise only when used with TPU.     

Protoporphyrin IX-mediated sonodynamic action induces apoptosis of K562 cells

Objectives

The present study aims to investigate apoptosis of human leukemia K562 cells induced by protoporphyrin IX (PpIX)-mediated sonodynamic therapy (PpIX-SDT).

Methods

The uptakes of intracellular PpIX in K562 cells were detected by flow cytometry. The sub-cellular localization of PpIX was imaged by confocal microscope. The cytotoxic effect of PpIX-SDT was assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenylter-trazolium bromide tetrazolium) assay. Apoptosis was evaluated by chromatin condensation with DAPI (4′-6-diamidino-2-phenylindole) staining, decrease of mitochondria membrane potential (MMP), re-distribution of Bax, and the expression changes of the key apoptosis-associated protein (Caspase-3 and polypeptide poly (ADP-robose) polymerase). The possible mechanism of SDT-induced apoptosis was investigated by detecting by intracellular ROS (reactive oxygen species) generation and effect of ROS scavenger-NAC (N-acetylcysteine) on SDT induced apoptosis.

Results

The intracellular PpIX increased quickly within 2 h after PpIX administration and PpIX mainly localized in the mitochondria. Compared with PpIX alone and ultrasound alone groups, the synergistic cytotoxicity of PpIX plus ultrasound was significantly boosted. In addition, the ultrasound induced some extent of chromatin condensation and MMP loss was greatly enhanced by the presence of 2 μg/ml PpIX, where PpIX alone treatment showed no or only slight effect. Time-dependent Bax translocation, caspase-3 activation and PARP cleavage were detected in SDT treatment groups. Besides, intracellular ROS production was significantly enhanced after SDT, and the general ROS scavenger NAC could obviously alleviate the SDT-caused cell viability loss, MMP loss, Bax redistribution and nuclear changes.

Conclusions

These results indicated that PpIX-mediated sonodynamic action could induce apoptosis on K562 cells, and the intracellular ROS was involved in the PpIX-SDT induced apoptosis.     

Ultrasound induces cellular destruction of nasopharyngeal carcinoma cells in the presence of curcumin

Objectives

Curcumin, a natural pigment from the traditional Chinese herb, has shown promise as an efficient enhancer of ultrasound. The present study aims to investigate ultrasound-induced cellular destruction of nasopharyngeal carcinoma cells in the presence of curcumin in vitro.

Methods

Nasopharyngeal carcinoma cell line CNE2 cells were incubated by 10 μm curcumin and then were treated by ultrasound for 8 s at the intensity of 0.46 W/cm². Cytotoxicity was evaluated using MTT assay and light microscopy. Mitochondrial damage was analyzed using a confocal laser scanning microcopy with Rhodamine 123 and ultrastructural changes were observed using a transmission electron microscopy (TEM).

Results

MTT assay showed that cytotoxicity induced by ultrasound treatment alone and curcumin treatment alone was 18.16 ± 2.37% and 24.93 ± 8.30%, respectively. The cytotoxicity induced by the combined treatment of ultrasound and curcumin significantly increased up to 86.67 ± 7.78%. TEM showed that microvillin disappearance, membrane blebbing, chromatin condensation, swollen mitochondria, and mitochondrial myelin-like body were observed in the cells treated by ultrasound and curcumin together. The significant collapse of mitochondrial membrane potential (MMP) was markedly observed in the CNE2 cells after the combined treatment of curcumin and ultrasound.

Conclusions

Our findings demonstrated that ultrasound sonication in the presence of curcumin significantly killed the CNE2 cells and induced ultrastructural damage and the dysfunction of mitochondria, suggesting that ultrasound treatment remarkably induced cellular destruction of nasopharyngeal carcinoma cells in the presence of curcumin.     

Noninvasive estimation of the ocular elastic modulus for age-related macular degeneration in the human eye using sequential ultrasound imaging

Introduction

Elastic modulus estimation may be an important clinical criterion, as it seems to affect such eye parameters as intraocular pressure, ocular pulsation, blood flow, effect of topical medications, and post-refractive surgery complications. The purpose of this study was to examine the differences in elasticity in the ocular axial length, posterior wall thickness (posterior pole), and retina-choroid thickness under normal and aged-related macular degeneration (AMD) conditions in the human eye by directly estimating the elastic modulus with sequential and noninvasive ultrasound image processing.

Materials and Methods

In this study, 25 healthy subjects and 20 patients with non-neovascular AMD participated in the experiment. The deformation of the ocular axial length, posterior wall thickness and retina-choroid complex thickness was captured using high-resolution ultrasonography before and after loading. The B-mode (20 MHz) and A-mode (8 MHz) frames were obtained and processed with an echo tracking technique. The elastic modulus was estimated using changes in ocular axial length, posterior wall thickness and retina-choroid complex thickness and with applied stress measurements.

Results

There was a significant difference (p < 0.05) in the ocular axial length elastic modulus between the AMD and healthy subjects (AMD patients: 95.165 ± 26.431 kPa, vs. healthy subjects: 49.539 ± 25.867 kPa). Moreover, there was a statistically significant difference (p < 0.05) in the posterior wall thickness elastic modulus between AMD patients and healthy subjects (AMD patients: 50.519 ± 12.295 kPa, vs. healthy subjects: 20.519 ± 11.827 kPa). However, no statistically significant difference (p-value > 0.05) was found in the retina-choroid complex elastic modulus between the two groups (AMD patients: 20.134 ± 3.898 kPa, vs. healthy subjects: 15.630 ± 4.250 kPa).

Conclusion

Although the results were obtained examining a relatively low number of patients, it would appear that noninvasive ultrasound estimation of the local elastic moduli of ocular axial length and posterior wall thickness is suited to aid in detection of the non-exudative AMD thus manifesting its potential as a screening tool in symptom-free individuals.     

Parametric harmonic-to-fundamental ratio contrast echocardiography: a novel approach to identification and accurate measurement of left ventricular area under variable levels of ultrasound signal attenuation

Objectives

We introduced a harmonic-to-fundamental ratio (HFR) of the radiofrequency (RF) signals that reduces confounding effects of attenuation. We studied whether HFR analysis of RF signals received from contrast microbubbles allows accurate measurement of the left ventricular (LV) cavity area under varying levels of attenuation.

Background

Attenuation is a fundamental problem in ultrasound imaging and limits the use of clinical echocardiography.

Methods

RF data from short axis systolic and diastolic scans were obtained from 14 open-chest dogs following left-atrial bolus of Optison. Attenuation was induced by interposed silicone pads calibrated to induce 7 dB or 14 dB reductions of the backscattered RF signal. RF images were reconstructed from the RF signals, HFR values calculated for each image pixel for 0 dB, 7 dB and 14 dB attenuation conditions, and LV area obtained by summation of “LV cavity pixels”. A reference LV cavity area was obtained from endocardial border tracings in enhanced scans by experts.

Results

Correlation of the HFR-defined and reference areas at systole was R = 0.95, R = 0.94, and R = 0.91 for 0 dB, 7 dB and 14 dB levels of attenuation, respectively, and at diastole was R = 0.95 for 0 dB, 7 dB and 14 dB levels of attenuation. The mean difference from both systolic and diastolic values was <1.45 cm² (i.e. negligible) in all attenuation settings.

Conclusion

Our novel HFR method supports precise measurement of the LV cavity area in contrast images with simulated high attenuation of ultrasound signals.     

Phantom investigation of phase-inversion-based dual-frequency excitation imaging for improved contrast display

Objective

The goal of this work is to examine the effects of pulse-inversion (PI) technique in combination with dual-frequency (DF) excitation method to separate the high-order nonlinear responses from microbubble contrast agents for improvement of image contrast. DF excitation method has been previously developed to induce the low-frequency ultrasound nonlinear responses from bubbles by using the composition of two high-frequency sinusoids (f₁ and f₂).

Motivation

Although the simple filtering was conventionally utilized to provide signal separation, the PI approach is better in the sense that it minimizes the mutual interferences among these high-order nonlinear responses in the presence of spectral overlap. The novelty of the work is that, in addition to the common PI summation, the PI subtraction was also applied in DF excitation method.

Methods

DF excitation pulses having an envelope frequency of 3 MHz (i.e., f₁ = 8.5 MHz and f₂ = 11.5 MHz) with pulse lengths of 3-10 μs and the pressure amplitudes from 0.5 to 1.5 MPa were used to interrogate the nonlinear responses of SonoVue™ microbubbles in the phantom experiments. The high-order nonlinear responses in the DF excitation were extracted for contrast imaging using PI summation for even-order nonlinear components or PI subtraction for odd-order nonlinear ones.

Results

Our results indicated that, as compared to the conventional filtering technique, the PI processing effectively increases the contrast-to-tissue ratio (CTR) of the third-order nonlinear response at 5.5 MHz and the fourth-order nonlinear response at 6 MHz by 2-5 dB. For these high-order nonlinear components, the CTR increase varies with the transmission pressures from 0.5 to 1.5 MPa due to the microbubbles’ displacement induced by the radiation force of DF excitation.

Conclusions

For DF excitation technique, the PI processing can help to extract either the odd-order or the even-order nonlinear components for higher CTR estimates.     

Sonodynamic action of pyropheophorbide-a methyl ester induces mitochondrial damage in liver cancer cells

Sonodynamic therapy with pyropheophorbide-a methyl ester (MPPa) presents a promising aspect in treating liver cancer. The present study aims to investigate the mitochondrial damage of liver cancer cells induced by MPPa-mediated sonodynamic action. Mouse hepatoma cell line H₂₂ cells were incubated with MPPa (2 μM) for 20 h and then exposed to ultrasound with an intensity of 0.97 W/cm² for 8 s. Cytotoxicity was investigated 24 h after sonodynamic action using MTT assay and light microscopy. Mitochondrial membrane potential (ΔΨm) was analyzed using flow cytometry with rhodamine 123 staining and ultrastructural changes were observed using transmission electron microscopy (TEM).The cytotoxicity of MPPa-mediated SDT on H₂₂ cell line was 73.00 ± 3.42%, greater than ultrasound treatment alone (28.12 ± 5.19%) significantly while MPPa treatment alone had no significant effect on H₂₂ cells. Moreover, after MPPa-mediated SDT cancer cells showed swollen mitochondria under TEM and a significant collapse of mitochondrial membrane potential. Our findings demonstrated that MPPa-mediated SDT could remarkably induce cell death of H₂₂ cells, and highlighted that mitochondrial damage might be an important cause of cell death induced by MPPa-mediated SDT.     

Dual-high-frequency ultrasound excitation on microbubble destruction volume

Objective and motivation

The goal of this work was to test experimentally that exposing air bubbles or ultrasound contrast agents in water to amplitude modulated wave allows control of inertial cavitation affected volume and hence could limit the undesirable bioeffects.

Methods

Focused transducer operating at the center frequency of 10 MHz and having about 65% fractional bandwidth was excited by 3 μs 8.5 and 11.5 MHz tone-bursts to produce 3 MHz envelope signal. The 3 MHz frequency was selected because it corresponds to the resonance frequency of the microbubbles used in the experiment. Another 5 MHz transducer was used as a receiver to produce B-mode image. Peak negative acoustic pressure was adjusted in the range from 0.5 to 3.5 MPa. The spectrum amplitudes obtained from the imaging of SonoVue^TM contrast agent when using the envelope and a separate 3 MHz transducer were compared to determine their cross-section at the - 6 dB level.

Results

The conventional 3 MHz tone-burst excitation resulted in the region of interest (ROI) cross-section of 2.47 mm while amplitude modulated, dual-frequency excitation with difference frequency of 3 MHz produced cross-section equal to 1.2 mm.

Conclusion

These results corroborate our hypothesis that, in addition to the considerably higher penetration depth of dual-frequency excitation due to the lower attenuation at 3 MHz than that at 8.5 and 11.5 MHz, the sample volume of dual-frequency excitation is also smaller than that of linear 3-MHz method for more spatially confined destruction of microbubbles.     

Continuous-wave ultrasound reflectometry for surface roughness imaging applications

Background

Measurement of surface roughness irregularities that result from various sources such as manufacturing processes, surface damage, and corrosion, is an important indicator of product quality for many nondestructive testing (NDT) industries. Many techniques exist, however because of their qualitative, time-consuming and direct-contact modes, it is of some importance to work out new experimental methods and efficient tools for quantitative estimation of surface roughness.

Objective and method

Here we present continuous-wave ultrasound reflectometry (CWUR) as a novel nondestructive modality for imaging and measuring surface roughness in a non-contact mode. In CWUR, voltage variations due to phase shifts in the reflected ultrasound waves are recorded and processed to form an image of surface roughness.

Results

An acrylic test block with surface irregularities ranging from 4.22 μm to 19.05 μm as measured by a coordinate measuring machine (CMM), is scanned by an ultrasound transducer having a diameter of 45 mm, a focal distance of 70 mm, and a central frequency of 3 MHz. It is shown that CWUR technique gives very good agreement with the results obtained through CMM inasmuch as the maximum average percent error is around 11.5%.

Conclusion

Images obtained here demonstrate that CWUR may be used as a powerful non-contact and quantitative tool for nondestructive inspection and imaging of surface irregularities at the micron-size level with an average error of less than 11.5%.     

Volume reconstruction of freehand three-dimensional ultrasound using median filters

Objectives

This paper aims to apply median filters for reducing interpolation error and improving the quality of 3D images in a freehand 3D ultrasound (US) system.

Background and motivation

Freehand 3D US imaging has been playing an important role in obtaining the entire 3D impression of tissues and organs. Reconstructing a sequence of irregularly located 2D US images (B-scans) into a 3D data set is one of the key procedures for visualization and data analysis.

Methods

In this study, we investigated the feasibility of using median filters for the reconstruction of 3D images in a freehand 3D US system. The B-scans were collected using a 7.5 MHz ultrasound probe. Four algorithms including the standard median (SM), Gaussian weighted median (GWM) and two types of distance-weighted median (DWM) filters were proposed to filter noises and compute voxel intensities. Qualitative and quantitative comparisons were made among the results of different methods based on the image set captured in freehand from the forearm of a healthy subject. A leave-one-out approach was used to demonstrate the performance of the median filters for predicting the removed B-scan pixels.

Results

Compared with the voxel nearest-neighbourhood (VNN) and distance-weighted (DW) interpolation methods, the four median filters reduced the interpolation error by 8.0-24.0% and 1.2-21.8%, respectively, when 1/4 to 5 B-scans was removed from the raw B-scan sequence.

Conclusions

In summary, the median filters can improve the quality of volume reconstruction by reducing the interpolation errors and facilitate the following image analyses in clinical applications.     

Noninvasive detection of intimal xanthoma using combined ultrasound, strain rate and photoacoustic imaging

Background and motivation

The structure, composition and mechanics of carotid artery are good indicators of early progressive atherosclerotic lesions. The combination of three imaging modalities (ultrasound, strain rate and photoacoustic imaging) which could provide corroborative information about the named arterial properties could enhance the characterization of intimal xanthoma.

Methods

The experiments were performed using a New Zealand white rabbit model of atherosclerosis. The aorta excised from an atherosclerotic rabbit was scanned ex vivo using the three imaging techniques: (1) ultrasound imaging of the longitudinal section: standard ultrasound B-mode (74 Hz frame rate); (2) strain rate imaging: the artery was flushed with blood and a 1.5 Hz physiologic pulsation was induced, while the ultrasound data were recorded at higher frame rate (296 Hz); (3) photoacoustic imaging: the artery was irradiated with nanosecond pulsed laser light of low fluence in the 1210-1230 nm wavelength range and the photoacoustic data was recorded at 10 Hz frame rate. Post processing algorithms based on cross-correlation and optical absorption variation were implemented to derive strain rate and spectroscopic photoacoustic images, respectively.

Results

Based on the spatio-temporal variation in displacement of different regions within the arterial wall, strain rate imaging reveals differences in tissue mechanical properties. Additionally, spectroscopic photoacoustic imaging can spatially resolve the optical absorption properties of arterial tissue and identify the location of lipid pools.

Conclusions

The study demonstrates that ultrasound, strain rate and photoacoustic imaging can be used to simultaneously evaluate the structure, the mechanics and the composition of atherosclerotic lesions to improve the assessment of plaque vulnerability.     

Third harmonic transmit phasing for SNR improvement in tissue harmonic imaging with Golay-encoded excitation

Background

Ultrasound tissue harmonic signal generally provides superior image quality as compared to the linear signal. However, since the generation of the tissue harmonic signal is based on finite amplitude distortion of the propagating waveform, the penetration and the sensitivity in tissue harmonic imaging are markedly limited because of the low signal-to-noise ratio (SNR).

Methods

The method of third harmonic (3f₀) transmit phasing can improve the tissue harmonic SNR by transmitting at both the fundamental (2.25 MHz) and the 3f₀ (6.75 MHz) frequencies to achieve mutual enhancement between the frequency-sum and the frequency-difference components of the second harmonic signal. To further increase the SNR without excessive transmit pressure, coded excitation can be incorporated in 3f₀ transmit phasing to boost the tissue harmonic generation.

Results

Our analyses indicate that the phase-encoded Golay excitation is suitable in 3f₀ transmit phasing due to its superior transmit bandwidth efficiency. The resultant frequency-sum and frequency-difference components of tissue harmonic signal can be simultaneously Golay-encoded for SNR improvement. The increase of the main-lobe signal with the Golay excitation in 3f₀ transmit phasing are consistent between the tissue harmonic measurements and the simulations. B-mode images of the speckle generating phantom also demonstrate the increases of tissue harmonic SNR for about 11 dB without noticeable compression artifacts.

Conclusion

For tissue harmonic imaging in combination with the 3f₀ transmit phasing method, the Golay excitation can provide further SNR improvement. Meanwhile, the axial resolution can be effectively restored by pulse compression while the lateral resolution remains unchanged.     

Development of a 0.014-in., anti-solenoid loop MR imaging guidewire for intravascular 3.0-T MR imaging

Purpose

This study aimed to develop a 0.014-in., anti-solenoid loop (ASL) magnetic resonance imaging guidewire (MRIG) for intravascular 3.0-T MR imaging.

Materials and Methods

We first designed the ASL MRIG, which was made of a coaxial cable with its extended inner conductor and outer conductor connected to two micro-anti-solenoids. We then evaluated in vitro the functionality of the ASL MRIG by imaging a “vessel” in a phantom and achieving signal-to-noise ratio (SNR) and SNR contour map of the new 0.014-in. ASL MRIG. Subsequently, we validated in vivo the feasibility of using the ASL MRIG to generate intravenous 3.0-T MR images of parallel iliofemoral arteries of near-human-sized living pigs.

Results

In vitro evaluation showed that the 0.014-in. ASL MRIG functioned well as a receiver coil with the 3.0-T MR scanner, clearly displaying the vessel wall with even distribution of MR signals and SNR contours from the ASL MRIG. Of the in vivo studies, the new ASL MRIG enabled us to successfully generate intravenous 3.0-T MR imaging of the iliofemoral arteries.

Conclusion

This study confirms that it is possible to build such small-looped MRIG at 0.014 in. for intravascular 3.0-T MR imaging.     

Fractal dimension of 40 MHz intravascular ultrasound radio frequency signals

Objective

Fully automatic tissue characterization in intravascular ultrasound systems is still a challenge for the researchers. The present work aims to evaluate the feasibility of using the Higuchi fractal dimension of intravascular ultrasound radio frequency signals as a feature for tissue characterization.

Methods

Fractal dimension images are generated based on the radio frequency signals obtained using mechanically rotating 40 MHz intravascular ultrasound catheter (Atlantis SR Plus, Boston Scientific, USA) and compared with the corresponding correlation images.

Conclusion

An inverse relation between the fractal dimension images and the correlation images was revealed indicating that the hard or slow moving tissues in the correlation image usually have low fractal dimension and vice-versa. Thus, the present study suggests that fractal dimension images may be used as a feature for intravascular ultrasound tissue characterization and present better resolution then the correlation images.     

Gas challenge-blood oxygen level-dependent (GC-BOLD) MRI in the rat Novikoff hepatoma model

Purpose

The purpose of the study was to investigate the relationship between gas challenge-blood oxygen level-dependent (GC-BOLD) response angiogenesis and tumor size in rat Novikoff hepatoma model.

Materials and Methods

Twenty adult male Sprague-Dawley rats (weighting 301-325 g) were used for our Animal Care and Use Committee-approved experiments. N1-S1 Novikoff hepatomas were grown in 14 rats with sizes ranging from 0.42 to 2.81 cm. All experiments were performed at 3.0 T using a custom-built rodent receiver coil. A multiple gradient-echo sequence was used for R2^? measurements, first during room air (78% N₂/20% O₂) breathing and then after 10 min of carbogen (95% O₂/5% CO₂) breathing. After image acquisition, rats were euthanized, and the tumors were harvested for histological evaluation.

Results

The R2^? change between air and carbogen breathing for small hepatomas was positive; R2^? changes changed to negative values for larger hepatomas. We found a significant positive correlation between tumor R2^? change and tumor microvessel density (MVD) (r=0.798, P=.001) and a significant inverse correlation between tumor R2^? change and tumor size (r=−0.840, P<.0001).

Conclusions

GC-BOLD magnetic resonance imaging measurements are well correlated to MVD levels and tumor size in the N1-S1 Novikoff hepatoma model; GC-BOLD measurements may serve as noninvasive biomarkers for evaluating angiogenesis and disease progression and/or therapy response.     

Surface modification with fibronectin or collagen to improve the cell adhesion

Objective

The surface of biomaterials plays a critical role in determining bioactivity. The aim of this study was to evaluate the cell adhesion and proliferation of ADSCs on the surface of biomaterial which is modified with fibronectin or collagen.

Materials and methods

Adipose-derived stromal cells (ADSCs) were obtained from SD rats, expanded in culture, and seeded onto scaffold surface-modified with fibronectin or collagen. To characterize cellular attachment, cells were incubated on scaffold for 1 and 2 h and then counted the cells attached onto the scaffold. The MTT assay was chosen to evaluate the proliferation at days 1, 4, 7 and 14. After 7 d of culture, scanning electron microscope was chosen to observe cell morphology and attachment of ADSCs on the scaffolds.

Results

Attachment at 1 and 2 h of cells on scaffold modified with fibronectin was significantly greater than in control, but not with collagen. The MTT assay revealed that ADSCs proliferation tendency was nearly parallel to that in control. The scanning electron microscope (SEM) showed that ADSCs in experiment expanded thoroughly and excreted much extracellular materials.

Conclusions

Surface modification with fibronectin or collagen can enhance the attachment of cultured ADSCs on the scaffold, but it had not evident effect to proliferation.     

Blood oxygen level-dependent MRI for the monitoring of neoadjuvant chemotherapy in breast carcinoma: initial experience

Purpose

To determine the feasibility of using R2? map MRI for pretreatment diagnosis and monitoring of tumor response to neoadjuvant chemotherapy (NAC) in patients with breast cancer.

Material and Methods

Twenty-eight women with breast cancer, as evidenced by pathology, underwent MR imaging prior to and after chemotherapy. All patients were examined by conventional MRI and R2? map imaging. Subjects were divided into major histological response (MHR) and non-major histological response (NMHR) groups. Mean R2? values of cancerous and normal glandular tissues were measured before and following NAC. Differences in R2? and ΔR2?% values between these two groups were compared with paired or independent t tests. The relationship between ΔR2?% and histological response was examined using Spearman's correlation test.

Results

Before NAC, the average R2? values in carcinoma were lower than in normal glandular tissue (P<.05). After two to four cycles of NAC, the R2? values in carcinoma were increased (P<.05 ), but this change was not significant in normal glandular tissue. After NAC, ΔR2?% was significantly higher in MHR as compared to NMHR (P<.05). The ΔR2?% correlated with the histological response (r=0.581, P<.01).

Conclusion

In women undergoing NAC for breast cancer treatment, R2? and ΔR2?% appear to provide predictive information of tumor response which is probably associated with changes in tumor angiogenesis and tissue oxygenation. R2? map imaging of breasts may therefore be useful in monitoring tumor response to NAC.     

In vitro comparative study of vibro-acoustography versus pulse-echo ultrasound in imaging permanent prostate brachytherapy seeds

Background

Permanent prostate brachytherapy (PPB) is a common treatment for early stage prostate cancer. While the modern approach using trans-rectal ultrasound guidance has demonstrated excellent outcome, the efficacy of PPB depends on achieving complete radiation dose coverage of the prostate by obtaining a proper radiation source (seed) distribution. Currently, brachytherapy seed placement is guided by trans-rectal ultrasound imaging and fluoroscopy. A significant percentage of seeds are not detected by trans-rectal ultrasound because certain seed orientations are invisible making accurate intra-operative feedback of radiation dosimetry very difficult, if not impossible. Therefore, intra-operative correction of suboptimal seed distributions cannot easily be done with current methods. Vibro-acoustography (VA) is an imaging modality that is capable of imaging solids at any orientation, and the resulting images are speckle free.

Objective and methods

The purpose of this study is to compare the capabilities of VA and pulse-echo ultrasound in imaging PPB seeds at various angles and show the sensitivity of detection to seed orientation. In the VA experiment, two intersecting ultrasound beams driven at f₁ = 3.00 MHz and f₂ = 3.020 MHz respectively were focused on the seeds attached to a latex membrane while the amplitude of the acoustic emission produced at the difference frequency 20 kHz was detected by a low frequency hydrophone.

Results

Finite element simulations and results of experiments conducted under well-controlled conditions in a water tank on a series of seeds indicate that the seeds can be detected at any orientation with VA, whereas pulse-echo ultrasound is very sensitive to the seed orientation.

Conclusion

It is concluded that vibro-acoustography is superior to pulse-echo ultrasound for detection of PPB seeds.