Therapeutic effect of local photothermal heating of gold nanoparticle-coated self-expandable metallic stents for suppressing granulation tissue formation in the mouse colon.

PURPOSE: To investigate the therapeutic effect of local photothermal (PT) heating on suppression of stent-induced granulation tissue formation in mouse colon. MATERIALS AND METHODS: A gold nanoparticle (GNP)-coated self-expandable metallic stent (SEMS) was prepared using a two-step synthesis process for local PT heating under near-infrared laser irradiation. Twenty-four mice were randomly divided into two groups of 12 and subjected to SEMS placement in the colon. Group A received a GNP-coated SEMS without local heating and Group B received a GNP-coated SEMS and underwent local heating at 55°C after SEMS placement. The therapeutic effect of local heating was assessed by comparing the histopathological, immunohistochemical, and endoscopic results. RESULTS: Four mice were excluded because of stent migration (n = 3, group B) or death (n = 1, group A). Stent-induced granulation tissue-related variables were significantly lower in group B than in group A (p < 0.001). In vivo endoscopic images, 4 weeks after stent placement, showed granulation tissue formation over the wire mesh in group A and relatively good patency of the stented colon with no definite irregularities in group B. There was more vascular endothelial growth factor (VEGF) positivity in group A than in group B. CONCLUSION: Local PT heating suppresses granulation tissue formation after stent placement in mouse colon.

Dose-Decreasing Effect of the First Reversed Laser Beam Collimator for C-Arm Type Angiographic Equipment.

This is a study on the dose-decreasing effect of the first reversed laser beam collimator (RLBC) for C-arm type angiographic equipment. A laser beam was located at the center of each plane at an oblique angle to the angiographic equipment detector. A field of view, which could be seen with the naked eye, was made by focusing the laser beam in the direction of the X-ray source. The height of the table was fixed at 75 cm and the iron balls were located within 2 mm of the top, bottom, left, and right edges of the output image. The time needed for location fixing, fluoroscopy, and measurement of dose area product (DAP) were compared by having 30 radiologists perform location fixing by looking at the fluoroscopic image while performing location fixing (no radiation) and while the RLBC was turned on. In the next test, the time needed for location fixing, fluoroscopy, and DAP were compared when varying the location of the iron balls from 2 to 10 mm from the edges of the output image. The results showed that the time needed for location fixing, the time needed for fluoroscopy, and DAP decreased, both in the first test and the second test. This study confirmed that the use of a RLBC for C-arm type angiographic equipment decreases both the time needed to perform the procedure and the radiation dose received. It is expected that continuous advancement of RLBC technology will contribute greatly to decreasing the dose of radiation needed and improving convenience during angiography.

Analysis of enlarged images using time-of-flight magnetic resonance angiography, computed tomography, and conventional angiography.

This study aimed to assess the accuracy of time-of-flight magnetic resonance angiography, computed tomography, and conventional angiography in depicting the actual length of the blood vessels. Three-dimensional time-of-flight magnetic resonance angiography and computed tomography angiography were performed using a flow phantom model that was 2.11 mm in diameter and had a total area of 0.26 cm(2). After this, volume rendering technique and the maximum intensity projection method as well as two-dimensional digital subtraction angiography and three-dimensional rotational angiography based on conventional angiography were conducted. For three-dimensional time-of-flight magnetic resonance angiography, 8 channel sensitivity encoding (SENSE) head coil for the 3.0 Tesla equipment was used. Fluid was added to the normal saline solution at various rates, such as 11.4, 20.0, 31.4, 40.0, 51.5, 60.0, 71.5, 80.1, 91.5, and 100.1 cm/s using an automatic contrast media injector. Each image was thoroughly examined. After reconstructing the image using the maximum intensity projection method, the length of the conduit in the center of the coronal plane was measured 30 times. After performing computed tomography angiography with the 64-channel CT scanner and 16-channel CT scanner, the images were sent to TeraRecon. Then, the length of the conduit in the center of the coronal plane of each image was measured 30 times after reconstructing the images using volume rendering and maximum intensity projection techniques. For conventional angiography, three-dimensional rotational angiography and two-dimensional digital subtraction angiography were used. Images obtained by three-dimensional rotational angiography were reconstructed and enhanced by 33, 50, and 100 % in the 128 Matrix and the 256 Matrix, respectively on the Xtra Vision workstation. The maximum intensity projection was used for the reconstruction, and the length of the conduit was measured 30 times in the center of the coronal plane of each image. Measurements using the two-dimensional digital subtraction angiography were obtained 30 times in the center of the image. As a result, the lumen length measured by three-dimensional enhanced flow MR angiography images was a minimum of 2.51 ± 0.12 mm when the fluid velocity was 40 cm/s. The images obtained by computed tomography angiography were larger than the actual images obtained by using the test equipment and the reconstruction method. Among the reconstruction methods of three-dimensional rotational angiography, the lumen length in the image reconstructed by 100 % in the 256 matrix was the smallest; 2.76 ± 0.009 mm. In the 128 matrix, as the scope of reconstruction was widened, the length of the vessel was increased by 0.710 units. In the 256 matrix, as the scope of reconstruction was widened, the length of the vessel was decreased by 0.972 units. In two-dimensional digital subtraction angiography, the lumen length in the image was 2.22 ± 0.095 mm. Although this image was magnified similar to the image reconstructed by 100 % in the 256 matrix of three-dimensional rotational angiography (P < 0.05), it was closest to the actual image among the images compared in this study. In conclusion, images obtained by two-dimensional digital subtraction angiography were closer to the actual images compared to the images obtained by other procedures. It can be concluded that vascular images obtained by magnetic resonance angiography, CT angiography, and conventional angiography were larger than the actual images.

A study on the usefulness of methylcellulose in rectal CT based on the analysis of the differences in absorption of radiation-permeable and radiation-impermeable materials.

PURPOSE: The purpose of this study was to use various radiation-permeable and radiation-impermeable materials, used to facilitate the observation of a lesion during a rectal computed tomography (CT) scan, in order to determine the best material to use. MATERIALS AND METHODS: In regard to the study method, the radiation-permeable and radiation-impermeable materials of physiological saline, methylcellulose, contrast medium, ultrasound gel, and air were used to perform scanning with scan parameters that were used in general abdominal scanning. The GSI mode was used for material analysis. RESULTS: According to the results of the phantom study, the average CT value was 25.5 ± 5.9 HU for physiological saline, 77.6 ± 7.3 HU for methylcellulose, 3,070 ± 0.1 HU for contrast medium, 74.1 ± 11.9 HU for ultrasound gel, and -954.1 ± 10.3 HU for air. According to the analysis of materials by energy, contrast medium and physiological saline showed a dramatic decrease in the CT value as energy increased. Methylcellulose showed a gradual decrease in CT value, whereas air showed a small change in CT value according to the graph. CONCLUSIONS: Out of these materials, methylcellulose had the advantage of reducing discomfort in patients, and was more convenient for examiners before and after the rectal CT scan.

Study on a method to improve T1 image contrast by the subtraction technique for 3.0 T brain examination.

The purpose of this study is to describe the enhanced gray/white brain matter delineation achieved by a novel subtraction technique. We subtracted T2-weighted from T1-weighted images. The resulting images were analyzed for contrast-to-noise ratio and reader preference. Our results show superior outcomes for the subtracted images. This improvement could be used to better identify tumor enhancement or cortical dysplasia.