Collagen and Chondrocyte Concentrations Control Ultrasound Scattering in Agarose Scaffolds

Ultrasound imaging has been proposed for diagnostics of osteoarthritis and cartilage injuries in vivo. However, the specific contribution of chondrocytes and collagen to ultrasound scattering in articular cartilage has not been systematically studied. We investigated the role of these tissue structures by measuring ultrasound scattering in agarose scaffolds with varying collagen and chondrocyte concentrations. Ultrasound catheters with center frequencies of 9 MHz (7.1–11.0 MHz, −6 dB) and 40 MHz (30.1–45.3 MHz, −6 dB) were applied using an intravascular ultrasound device. Ultrasound backscattering quantified in a region of interest starting right below sample surface differed significantly (p < 0.05) with the concentrations of collagen and chondrocytes. An ultrasound frequency of 40 MHz, as compared with 9 MHz, was more sensitive to variations in collagen and chondrocyte concentrations. The present findings may improve diagnostic interpretation of arthroscopic ultrasound imaging and provide information necessary for development of models describing ultrasound propagation within cartilage.     

Measurements of Scattering Effects Within Tissue-like Media at Two Wavelengths of 632.8 nm and 680 nm

. Measurements have been performed in order to determine the effective attenuation coefficient μ_eff and the scattering phase function S(θ) for different mixtures of Intralipid-10% and -20% (scattering medium) and ink (absorbing medium) at wavelengths of 632.8 nm and 680 nm. Particle size distributions have been recorded by means of a nanosizer type apparatus for the fat Intralipid emulsions and for the mixtures of Intralipid showing that the Mie theory may be applied in these conditions. The evolution of the effective attenuation coefficient μ_eff has been plotted against the concentration of Intralipid emulsions in distilled water, with or without an added absorber. However, the evolution of the anisotropy coefficient g, deduced from S(θ), was only studied as a function of the concentration of an added absorber. The overall results demonstrate that the relationship between μ_eff and the concentration of the dilution of the Intralipid emulsions is not linear. In contrast, the anisotropy coefficient g remains stable independently of the amount of an added absorber. These findings agree qualitatively with those reported by other authors, the few observed differences can be mainly attributed at least in part to the dispersion in Intralipid-10% composition. Paper received 11 May 1998; accepted after revision 25 June 1999.     

Measurements of argon laser light attenuation in the skin ‘in vivo’ using a unique animal model

A dorsal skin flap chamber model for microcirculation studies permits direct irradiation of subcutaneous arterioles and venules ‘in vivo’ as well as irradiation of the same vessels through the skin of unanaesthetized hamsters. A system has been developed to permit vital and video microscopy while selected vessels of the microvascular system are being irradiated. Information relating to light attenuation in the skin can be obtained by comparing the response curves of irradiation aimed directly to the blood vessels to those of laser light delivered to vessels through the skin. Selected vessels have been irradiated with the argon laser (488 nm and 514.5 nm) adjusting the power to deliver radiant exposures 1 to 55 J cm⁻² on a 250 μm diameter spot during a 20 ms irradiation time and embolized or stationary coaguli are produced in response to the irradiation. The radiant exposure threshold for production of embolized coaguli when irradiation is directed at the surface of the skin is 1.45 times larger than the threshold when the vessel is directly irradiated. The skin to vessel threshold ratio for the production of stationary coaguli is 1.39. Higher doses are required through the skin because of light attenuation due to absorption and scattering. These ratios are compared with the predictions of two light distribution models based on Beer's law and the Monte Carlo solution of the radiative transfer equation.     

非晶态人脑组织康普顿散射的某些特征

本实验主要目的是测量非晶态人脑（ Ｍｅｌａｎｉｎ） 的Ｘ 光散射，以此作为推断人脑组织中Ｍｅｌａｎｉｎ结构的依据。通过实验及计算机数据处理，得出康普顿散射峰的某些特征     

Analysis of Trabecular Bone Structure with Multidetector Spiral Computed Tomography in a Simulated Soft-Tissue Environment

We investigated the influence of soft tissue (ST) on image quality by high-resolution multidetector computed tomography (MDCT) scans and assessed the effect of surrounding ST on the quantification of trabecular bone structure. Eight bone cores obtained from human proximal femoral heads discarded during hip replacement surgery were scanned with micro-computed tomography (μCT) as well as with MDCT both without (w/o) and with (w) simulated surrounding ST, where a phantom imitated a human torso. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured in all scans. Apparent trabecular bone structure parameters were calculated and compared to similar parameters obtained in coregistered sections of the μCT scans. Residual errors were calculated as root-mean-square (RMS) errors relative to the μCT measurements. Compared to μCT results, trabecular structure parameters were overestimated by MDCT both w and w/o ST. SNR and CNR were significantly higher in the scans w/o ST. Significant correlations between μCT and MDCT results were found for bone fraction (r = 0.90 w/o ST, r = 0.84 w ST), trabecular number, and separation. RMS ranged from 10% to 15% for MDCT w/o ST and from 10% to 17% for MDCT w ST. Only bone fraction showed significantly different RMS and correlations for scans w/o vs. w ST (P < 0.05). This study showed that MDCT is able to visualize trabecular bone structure in an in vivo-like setting at skeletal sites within the torso such as the proximal femur. Even though ST scatter compromises image quality substantially, the major characteristics of the trabecular network can still be appreciated and quantified. Funding source Seed grant by the Department of Radiology, University of California, San Francisco, CA, USA     

Gamma-irradiation enhances apoptosis induced by cannabidiol, a non-psychotropic cannabinoid, in cultured HL-60 myeloblastic leukemia cells

Two non-psychotropic cannabinoids, cannabidiol (CBD) and cannabidiol-dimethylheptyl (CBD-DMH), induced apoptosis in a human acute myeloid leukemia (AML) HL-60 cell line. Apoptosis was determined by staining with bisBenzimide and propidium iodide. A dose dependent increase of apoptosis was noted, reaching 61 and 43% with 8 μg/ml CBD and 15 μg/ml CBD-DMH, respectively, after a 24 h treatment. Prior exposure of the cells to γ-irradiation (800 cGy) markedly enhanced apoptosis, reaching values of 93 and 95%, respectively. Human monocytes from normal individuals were resistant to either cannabinoids or γ-irradiation. Caspase-3 activation was observed after the cannabinoid treatment, and may represent a mechanism for the apoptosis. Our data suggest a possible new approach to treatment of AML.     

Tissue parameters determining the visual appearance of normal skin and port-wine stains

Port-wine stain is a congenital birthmark consisting of an abnormal density of blood vessels in the upper dermis. The enlarged blood volume gives the lesion a red to purple colour. The aim of the treatments is to destroy the vessels to the extent necessary for obtaining a normal skin coloration. Thus, in principle, all relevant information about the lesion should be contained in a reflectance spectrum in the visible. However, the relation between the reflectance spectrum and tissue parameters such as scattering, melanin content and blood distribution is somewhat composite. This work tries to enlighten this relation in terms of a very simple analytical mathematical model, and it is demonstrated that such a model at least will contribute to a qualitative understanding of the relevance of the various parameters.     

Artifactual echoes in B-mode images due to multiple scattering

In B-mode images, echoes, which appear to arise from inherently anechoic regions due to scattering from neighbouring echogenic regions, can be considered artifactual. We have observed multiple scatter contributions to such artifactual echoes in images of plane boundaries between random scattering phantoms and anechoic regions. For the strongest scattering phantom studied, multiple scatter echoes were 3-9% of the average phantom signal using two sharply focused transducers, an annular array in pulse echo mode, and an annular array/cone hybrid. Multiple scatter was less than 5% for a conventional transducer. Echo amplitudes were also measured in normal excised human liver and breast tissue. It was estimated that artifactual echoes due to multiple scatter would be negligible in B-mode images of liver. However, for breast imaging, the level of artifactual echoes was estimated to be similar to that found for our strongest scattering phantom.     

Modified Doxorubicin for Improved Encapsulation in PVA Polymeric Micelles

Polyvinylalcohol, partially substituted with lipophilic acyl chains, generates polymeric micelles in aqueous phase, containing a hydrophobic core able to encapsulate lipophilic drugs. Two types of polymers were obtained by conjugation of polyvinylalcohol with oleoyl or linoleoyl chains as pendant groups. The polymers, at a substitution degree of ∼1%, are soluble in water and form polymeric micelles whose size increases with polymer concentration. Doxorubicin was hydrophobized, by linking an oleoyl chain via amide bond, to make the drug more similar to the substituted polymers and promote its encapsulation into the inner core of the micelles. The properties of the drug-polymer systems were evaluated in solution by dynamic light scattering technique and correlated to the physicochemical characteristics of the drug and the substituted polymers. Solubilization tests revealed that the similarity of the chain, in both the polymer and the drug, promotes better drug encapsulation in the oleoyl than linoleoyl derivative. The drug-polymer systems are stable in phosphate buffer saline (pH 7.4) at 37°C, and the release of the drug is activated by the presence of the proteolytic enzyme pronase-E. The enzyme activated drug release and the size of the polymeric micelles, compatible with the pore dimensions of the tumor vessels, make these systems interesting for targeting lipophilic drugs to solid tumors, where the proteolytic enzyme concentration strongly raises with respect to the other body compartments.     

Scatter radiation and the effects of air gaps in cephalometric radiography

Objectives The scatter radiation and scatter rejection effect of air gaps in cephalometric radiography were evaluated using an effective scatter point source (ESPS) model. Methods A 16-cm-thick water-equivalent phantom was used to measure the scatter fraction. The distance from the source to the center of the object (SOD) was 150, 200, or 300 cm. The air gap was varied from 0 to 96 cm for each SOD. A photostimulable phosphor plate was used as the X-ray sensor. The measured scatter fraction ESPS model was used to simulate the scatter rejection by the air gap, and the predictions were compared with the grid. Results There was excellent agreement between the ESPS model and the scatter measurements. The air gap reduced the scatter radiation, especially for an SOD of 200 or 300 cm, while keeping an object magnification of 1.1 in view of the signal-to-noise ratio improvement factor. Conclusions The results suggest that a grid should not be used in cephalometric radiography.