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Biomedical subjects

Masahiro Endo

Publications and source records attributed to Masahiro Endo.

At least 19 recordsLinked to original sources
PubMed2007

Cardiac imaging using 256-detector row four-dimensional CT: preliminary clinical report.

PURPOSE: Along with the increase of detector rows on the z-axis and a faster gantry rotation speed, the spatial and temporal resolutions of the multislice computed tomography (CT) have been improved for noninvasive coronary artery imaging. We investigated the feasibility of the second specification prototype 256-detector row four-dimensional CT for assessing coronary artery and cardiac function. MATERIALS AND METHODS: The subjects were five patients with coronary artery disease. Contrast medium (40-60 ml) was intravenously administered at the rate of 3-4 ml/s. The patient's whole heart was scanned for 1.5 s to cover at least one cardiac cycle during breathholding without electrocardiographic gating. Parameters used were 0.5 mm slice thickness, 0.5 s/rotation, 120 Kv, and 350 mA, with a half-scan reconstruction algorithm (temporal resolution 250 ms). Twenty-six transaxial datasets were reconstructed at intervals of 50 ms. RESULTS: The assessability of the coronary arteries in AHA segments 1, 2, 3, 5, 6, 7, 9, and 11 was visually evaluated, resulting in 29 of 32 (90.9%) segments being assessable. Functional assessment was also performed using animated movies without banding artifacts in all cases. CONCLUSIONS: The 256-detector row four-dimensional CT can assess the coronary artery and cardiac function using data during 1.5 s without banding artifacts.

Aged↗
PubMed2007

A novel synthetic tissue-adhesive hydrogel using a crosslinkable polymeric micelle.

We prepared a novel tissue-adhesive hydrogel by using a polymeric micelle consisting of an aldehyde-terminated poly(ethylene glycol)-poly(D,L-lactide) (PEG-PLA) block polymer. A Schiff base is chemically formed between the amino groups in a polyallylamine and the aldehyde groups on the surface of polymeric micelles. The hydrogel was formed in approximately 2 s when the polymeric micelle solution and polyallylamine solution are mixed in vitro. The hydrogel was rapidly formed in vivo, and it adhered to a tissue surface. Our novel tissue-adhesive hydrogel creates no risk of infectious contaminations, because it consists of only synthetic materials. Further, PEG and PLA are known to be biocompatible and noncytotoxic. The results obtained in the present study show that a hydrogel prepared by the formation of a Schiff base between aldehyde and amine groups will potentially address the need for novel tissue-adhesive materials.

Cross-Linking Reagents↗
PubMed2006

Preliminary study: color map of hepatocellular carcinoma using dynamic contrast-enhanced 256-detector row CT.

To distinguish hepatocellular carcinoma (HCC) from normal liver tissue, a color map was made by dynamic contrast-enhanced 256-detector row CT developed at our institute. Dynamic enhanced CT of the liver of three patients with HCC was studied. The CT has 912 (transverse) x 256 (cranio-caudal) elements, each measuring approximately 0.5 mm x 0.5mm at the center of rotation. Scanning for 10 s (1.0 s/rotation) was started 30 s after intravenous injection of contrast medium. The reconstruction increment was 0.62 mm with a time interval of 0.1s and a matrix size of 512 x 512 x 256. Color maps were generated to show the gradient of the regression line of the time-density change. Due to volume acquisition, the 3D color map can be created using continuous 10-s scanning. The densities of the HCC and liver were decreased and increased during scanning, respectively. The HCC was detected clearly in the color map as a downward-sloping region. Dynamic enhanced 256-detector row CT could be useful for detecting malignant tumors in the liver with a short scan time.

Aged↗
PubMed2006

Four-dimensional measurement of lung tumor displacement using 256-multi-slice CT-scanner.

The concept of internal target volume is of marked importance for radiotherapy to lung tumors as respiration-induced motion is important. Individualized assessment of motion is required as tumor site may not predict the extent or pattern of tumor motion. We performed volumetric cine scanning using the 256-multi-slice CT (256MSCT) to study tumor motion during free breathing in 14 inpatients who were treated with carbon-ion radiotherapy. Motion assessment in 16 respiratory phases of the cine CT revealed most tumors to show hysteresis-like behavior. Isocenter displacement between peak exhalation and inhalation for the average of the right and left lungs were 7 mm, 7 mm and 15 mm for the upper, middle and lower lobes, respectively. Cine CT with the 256MSCT improved the evaluation of tumor displacement and overcomes some of the limitations associated with current CT methods. Volumetric cine CT data provides useful data on motion for planning in all radiation approaches for lung tumors.

Aged↗
PubMed2006

Candidate image processing for real-time volumetric CT subtraction angiography.

Since a 256-slice CT can perform real time observation of the volumetric cine images at multiple angles, volumetric CT angiography can provide much useful clinical information. Conventional CT subtraction angiography is generated by subtracting the non-enhanced CT image (mask CT image) from each contrast-enhanced CT image. Since even conventional CT subtraction angiography takes a few minutes to compute the image, volumetric CT subtraction angiography images require computation of an enormous amount of volumetric cine data (image base CT subtraction angiography: ICTSA) which means an excessively long calculating time. To reduce calculating time, we developed the raw data base CT subtraction angiography (RCTSA) that subtracts raw data instead of the reconstructed four-dimensional image sets. Image quality of the two image processing methods was evaluated in phantom and animal studies. Evaluation items were image noise, CT number uniformity, and subtracting RCTSA from ICTSA. ICTSA calculates the number of volume data; however, RCTSA uses the number of CT rotations. Moreover, since RCTSA can also be started subtraction early in the process of data acquisition, it reduced the number of calculations considerably. As there is a longer CT acquisition time, RCTSA shortens the ratio of the calculating time compared to that of ICTSA. RCTSA is useful image processing to reduce CT subtraction angiography examination time instead of ICTSA.

Angiography, Digital Subtraction↗
PubMed2006

Utility of 256-slice cone beam tomography for real four-dimensional volumetric analysis without electrocardiogram gated acquisition.

PURPOSE: Current ECG-gated multislice CT can reveal any cardiac phase data, including four-dimensional (4D) images, but cannot acquire the whole heart in one scanning, and arrhythmias impair the quality of the images. We used a prototype 256-slice cone beam CT (Athena, Sony Toshiba), with which the whole heart can be acquired in one scanning. MATERIALS AND METHODS: A pulsating device with contrast material (300 mgI/dl) diluted 10x with saline was moved at 5, 40, 60, 70, and 90 to-and-fro movements/min. Non-ECG-gated 256-slice cone beam CT with 256 x 0.5 mm slice thickness was performed during one to-and-fro motion at each rate. After acquisition, each to-and-fro motion was divided into 20 frames, and each volume was measured and volumetric curves were constructed. RESULTS: Even without ECG-gated acquisition, the configuration of the pulsating device at any rate continued to the through plane without any gaps, and the 4D movie of the pulsating device could be observed at any rate except 60 movements/min. Volumes of end-diastole (ED) and end-systole (ES), and ejection fraction (EF) at static state were 81.7, 17.5 ml, and 79% respectively. ED volumes were 81.7, 81.7, 70.3, 63.7, 68.3 and 65.9 ml, ES volumes were 17.5, 30.9, 39.8, 62.7, 55.0 and 43.2 ml, and EF was 79, 62, 43, 2, 19 and 34% at 0, 5, 40, 60, 70, and 90 to-and-fro movements/min, respectively. The ratios of ED volume, using the static state as the reference, were 100, 86, 78, 84 and 81%, those of ES volume were 177, 227, 358, 314 and 247%, and those of EF were 78, 54, 3, 24 and 43% at 5, 40, 60, 70, and 90 to-and-fro movements/min, respectively. From the configuration of volumetric curves, only 5/min could be evaluated. At 60 movements/min, the same device images without any motion were observed in 4D images during one to-and-fro motion. This may be because one to-and-fro time and one scanning time were the same (1 s). CONCLUSION: Even without ECG-gated acquisition, this new 256-slice cone beam CT achieved real 4D analysis of the pulsating device. The ED volume and the configuration of volumetric curve could only be evaluated up to 5 movements/min, but because of poor spatial resolution (1 s/rotation), even at 5 movements/min ES volume tended to be overestimated. As a result, EF tended to be underestimated, which may be improved in the next generation (0.5 s/rotation).

Cardiac Volume↗
PubMed2006

Superiority of synchrony of 256-slice cone beam computed tomography for acquiring pulsating objects. Comparison with conventional multislice computed tomography.

PURPOSE: A prototype 256-slice cone beam computed tomography (CT) provides complete volumetric data within a single gantry rotation (1 s/rotation) with 0.5 mm slice-thickness. MATERIALS AND METHODS: Calcified phantoms (200-400 HU) were attached to the balloon of a pulsating phantom and moved at a rate of 5-90/min. Acquisition was performed during one to-and-fro motion at each pulsation rate without electrocardiogram (ECG)-gating. Each period was divided into 10 phases, and compared to conventional multislice CT scanning without ECG-gating. RESULTS: At 5-20/min, the configuration of calcified phantoms continued to the through-plane without gaps. At 60/min, duplicated calcified phantoms at end-systole and end-diastole were observed without motion. At 90/min, motion could be observed without gaps but was more blurred, and total calcified volume, Agatston scores, mean and max CT values of three phantoms were almost equal compared with those at static state. However, at 60/min, total calcified volume, scores, mean and max CT values of three phantoms were decreased to 64%, 37%, 80% and 56%, respectively, compared with those at static state. In multislice CT, even at lower rates, there were gaps in the through-plane. At 60/min, total calcified volume, scores, mean and max CT values of three phantoms were decreased to only 8%, 3%, 79% and 53%, respectively, compared with static state. CONCLUSION: This new prototype's unique character (synchrony) enables the acquisition of pulsating objects. These can be acquired without gaps in the through-plane even in the absence of ECG-gating. However, its present temporal resolution only permits accurate quantitative evaluation of calcium up to 20/min.

Electrocardiography↗
PubMed2006

Improvement in banding artefacts in four-dimensional computed tomography for radiotherapy planning.

Respiratory-gated CT (RGCT) and four-dimensional CT (4DCT) scan techniques cover consecutive segments of the respiratory cycle. However, motion artefacts may occur in fast respiratory phases such as mid-inhalation and -exhalation. CT imaging involves the use of a number of x-ray tube positions for each couch position. We investigated the fundamental nature of motion artefacts using a constant-velocity moving phantom in motion in the CT plane or perpendicular to the CT plane, and in pigs to simulate a human model. Artefacts and movement distance were evaluated in a moving phantom and artificially ventilated pigs with a 256-multi-detector row CT (256MDCT). The phantom moved in the CT plane or perpendicular to the CT plane with a constant velocity. Backprojection used variable initial backprojection angles (IBAs). The phantom length for motion perpendicular to the CT plane was independent of IBA but was represented by phantom diameter plus the distance of movement per gantry rotation. In contrast, that for the motion in the CT plane was dependent on IBA, as represented by phantom diameter plus the distance of movement per rotation for IBA perpendicular to the phantom movement direction, and phantom diameter plus half the distance of movement per gantry rotation for other IBAs. Results for volumetric CT images with different IBAs showed the presence of banding artefacts. Similar findings were seen in artificially ventilated pigs. Motion artefacts are unavoidable in both conventional CT and 256MDCT. Banding artefacts will be improved if the same IBAs at each couch position are accounted for during image reconstruction. This improvement will be beneficial in respiratory gated and 4D radiation therapies.

Algorithms↗
PubMed2006

Respiratory correlated segment reconstruction algorithm towards four-dimensional radiation therapy using carbon ion beams.

PURPOSE: To enhance the precision of treatment planning for tumors which move under respiration, we developed a respiratory-correlated segment reconstruction method (RS) based on the Feldkamp--Davis--Kress algorithm (FDK) which provides high temporal resolution and a high signal-to-noise ratio. We compared full-scan (FS-FDK) and RS-FDK with regard to dose distribution in heavy ion treatment planning. MATERIALS AND METHODS: Data acquisition for RS-FDK is done using a respiratory sensing system in cine scan mode with a 256-multi-detector row CT (256-MDCT). To evaluate the accuracy of irradiation of moving tumors, dose distributions with each algorithm were compared in heavy ion treatment planning using beam parameters obtained with FS-FDK. RESULTS: Images obtained using RS-FDK did not show motion artifacts and visualized the edges of the liver and pulmonary vessels more clearly than those with FS-FDK. The iso-dose distributions for FS-FDK covered the target volume; in contrast, RS-FDK with the beam parameter of FS-FDK image provided an insufficient dose to the target and a considerable dose to normal tissues around it. CONCLUSIONS: The information provided by RS-FDK improves accuracy in the prescription of dose-to-target volume. Further, RS-FDK allows greater precision in the delivery of radiotherapy, including 4D radiation therapy.

Aged↗
PubMed2006

A combination-weighted Feldkamp-based reconstruction algorithm for cone-beam CT.

The combination-weighted Feldkamp algorithm (CW-FDK) was developed and tested in a phantom in order to reduce cone-beam artefacts and enhance cranio-caudal reconstruction coverage in an attempt to improve image quality when utilizing cone-beam computed tomography (CBCT). Using a 256-slice cone-beam CT (256CBCT), image quality (CT-number uniformity and geometrical accuracy) was quantitatively evaluated in phantom and clinical studies, and the results were compared to those obtained with the original Feldkamp algorithm. A clinical study was done in lung cancer patients under breath holding and free breathing. Image quality for the original Feldkamp algorithm is degraded at the edge of the scan region due to the missing volume, commensurate with the cranio-caudal distance between the reconstruction and central planes. The CW-FDK extended the reconstruction coverage to equal the scan coverage and improved reconstruction accuracy, unaffected by the cranio-caudal distance. The extended reconstruction coverage with good image quality provided by the CW-FDK will be clinically investigated for improving diagnostic and radiotherapy applications. In addition, this algorithm can also be adapted for use in relatively wide cone-angle CBCT such as with a flat-panel detector CBCT.

Algorithms↗
PubMed2006

Noise properties for three weighted Feldkamp algorithms using a 256-detecotor row CT-scanner: case study for hepatic volumetric cine imaging.

In cone-beam geometry, image quality may be degraded or artifacts may occur if the cone angle is substantially wide. This is because a cone-beam scan along a circular orbit does not collect the complete set of data required to make an exact reconstruction of all volumetric data. To increase temporal resolution and thus image quality in cone-beam geometry, Silver proposed the new half-scan algorithm (NHS-FDK), which extends Parker's weighting function (HS-FDK) by utilizing a larger range up to 2pi. Here, we evaluated these algorithms for hepatic contrast-enhanced CT in cine scan mode using a 256-detector row CT. The full-scan (FS-FDK) images show uniform distribution of the image noise and CT-number uniformity. Image noise and CT-number uniformity with HS-FDK and NHS-FDK images follow the initial projection angle. HS-FDK images therefore have more changeable higher intensity (brighter) and a lower intensity (darker) areas than respective FS-FDK and NHS-FDK images. We concluded that, considering the trade-off between image quality and temporal resolution, the NHS-FDK algorithm is useful in volumetric cine imaging for the abdomen.

Aged↗
PubMed2006

Imaging of gefitinib-related interstitial lung disease: multi-institutional analysis by the West Japan Thoracic Oncology Group.

Gefitinib (Iressatrade mark) is an epidermal growth factor receptor tyrosine kinase inhibitor that has been approved for the treatment of lung cancer in Japan, however, after marketing several cases of severe pulmonary toxicity were reported. The West Japan Thoracic Oncology Group conducted an independent survey of acute pulmonary toxicity and interstitial lung disease (ILD) caused by gefitinib in its member's institutions. The purpose of this study was to clarify the image characteristics of ILD caused by the molecular-targeting drug gefitinib. A total of 1976 patients had been treated with gefitinib between August and December 2002, and 102 of them were suspected of having acute pulmonary toxicity and ILD. A final definite diagnosis of gefitinib-induced ILD was made by at least three radiologists based on a review and analysis of the chest radiography and CT findings plus the clinical data in the medical records. The imaging findings were classified into four patterns: (A) a nonspecific area with ground-glass attenuation, (B) a multifocal area of airspace consolidations, (C) patchy distribution of ground-glass attenuation accompanied by interlobar septal thickening, and (D) extensive bilateral ground-glass attenuation or airspace consolidations with traction bronchiectasis. CT as well as chest radiography had been performed in 65 of the 102 patients at the onset of ILD, and chest radiography alone had been performed in 26. After excluding 11 cases with insufficient data and 21 cases concluded to be other pulmonary diseases, 70 patients were diagnosed with gefitinib-induced ILD. Finally, the diagnostic image findings were classified as pattern A in 29 cases, pattern B in 7 cases, pattern C in 3 cases, pattern D in 20 cases and others in 11 cases. The CT images were classified as pattern A, B, C, and D in 24, 7, 1, and 12 cases, respectively. The mortality rate was significantly higher in the patients with pattern D than the other patterns. Pattern D were thought to represent the features of diffuse alveolar damage. In conclusion, the molecular-targeting drug gefitinib induces pulmonary toxicity at a certain rate and the imaging findings of ILD induced by gefitinib are similar to those of pulmonary toxicity induced by conventional antineoplastic agents.

Adult↗
PubMed2006

Properties of the prototype 256-row (cone beam) CT scanner.

We evaluated Feldkamp artifacts, which are specific to cone-beam computed tomography (CT), in phantom and clinical studies using the 256-multidetector-row CT (256MDCT), and compared the reconstruction accuracy of axial and helical scans. Image noise, slice sensitivity profile (SSP) and artifacts with the 256MDCT were evaluated using a phantom, and the results were compared to those of a 64MDCT. We also examined chest and abdomen scans produced with the 256MDCT in volunteers. For the axial scan, Feldkamp artifacts were visualized as high-frequency streak-like artifacts that are oriented horizontally at the edge of the scan region in the phantom study. Similar results were obtained with the volunteers in soft-tissue regions near either bony structures or air pockets. Feldkamp artifacts with the 256MDCT can lead to misdiagnosis if not correctly identified and minimized via helical scanning. Image noise was less for axial than helical scans, while SSP was better with helical than axial scans. Feldkamp artifacts observed in the 256MDCT images, however, did not generally affect the interpretation of images. The 256MDCT promises more accurate diagnosis, and will provide volumetric cine images of wider cranio-caudal coverage, enabling new applications of CT.

Adult↗
PubMed2006

Physical evaluation of CT scan methods for radiation therapy planning: comparison of fast, slow and gating scan using the 256-detector row CT scanner.

Although slow-rotation CT scanning (slow-scan CT: SSCT) has been used for radiation therapy planning, based on the rationale that the average duration of the human respiratory cycle is 4 s, a number of physical and quantitative questions require answering before it can be adopted for clinical use. This study was performed to evaluate SSCT physically in comparison with other scan methods, including respiratory-gated CT (RGCT), and to develop procedures to improve treatment accuracy. Evaluation items were geometrical accuracy, volume accuracy, water equivalent length and dose distribution using the 256-detector row CT with three scan methods. Fast-scan CT (FSCT) was defined as obtaining all respiratory phases in cine scan mode at 1.0 s per rotation. FSCT-ave was the averaged FSCT images in all respiratory phases, obtained by reconstructing short time intervals. SSCT has been defined as scanning with slow gantry rotation to capture the whole respiratory cycle in one rotation. RGCT was scanned at the most stable point in the respiratory cycle, which provides the same image as that by FSCT at the most stable point. Results showed that all evaluation items were dependent on motion characteristics. The findings of this study indicate that 3D planning based solely on SSCT under free breathing may result in underdosing of the target volume and increase toxicity to surrounding normal tissues. Of the three methods, RGCT showed the best ability to significantly increase the accuracy of dose distribution, and provided more information to minimize the margins. FSCT-ave is a satisfactory radiotherapy planning alternative if RGCT is not available.

Algorithms↗
PubMed2006

Corrosion of stainless steel sternal wire after long-term implantation.

A variety of metallic components have been used in medical devices where lifelong durability and physical strength are demanded. To investigate the in vivo changes of implanted metallic medical devices in humans, stainless steel sternal wires removed from patients were evaluated. Stainless steel (316L) sternal wires removed from four patients after 10, 13, 22, and 30 years of implantation were evaluated using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Macroscopically, the removed specimens maintained their metallic luster and color. Under SEM, small holes were observed sporadically at 10 years and they tended to connect in the drawing direction. The longer the implanted duration, the more numerous and deeper were the crevices observed. By EDS, sulfur, phosphorus, and calcium were identified in all areas at 10 years, in addition to the component elements of stainless steel, comprising iron, chromium, nickel, and manganese. Corrosion products observed at 30 years were identified as calcium phosphate. In conclusion, stainless steel sternal wires develop corroded pores that grow larger and deeper with time after implantation; however, the pores remain shallow even after decades of implantation and they may not be a cause of mechanical failure. An amount of metal ions equivalent to the corroded volume must have been released into the human body, but the effect of these metal ions on the body is not apparent.

Bone Wires↗
PubMed2006

Physical evaluation of the weighted Feldkamp algorithms applied to the 256-detector row CT scanner for volumetric cine imaging.

RATIONALE AND OBJECTIVES: To improve effective scan time and image quality in cone-beam computed tomography (CT), Parker's weighting function (half scan [HS]-Feldkamp-Davis-Kress [FDK]) extended to a larger range up to 2pi was proposed as new half-scan algorithm (NHS-FDK). We conducted a practical physical evaluation of NHS-FDK and HS-FDK using 256-detector row CT. MATERIALS AND METHODS: Three types of weighting function (full-scan [FS-FDK], HS-FDK, and NHS-FDK) were evaluated by using 256-detector row CT for five variables, ie, point spread function, image noise, CT number uniformity, Feldkamp artifact, temporal resolution, and clinical evaluation. RESULTS: Image noise, Feldkamp artifact, and temporal resolution were dependent on weighting function. Image noise magnitude was independent of projection angle for all regions of interest with FS-FDK, but showed a symmetric pattern with projection angle with HS-FDK and NHS-FDK. With regard to temporal resolution, NHS-FDK did not remove the motion artifact in the heart except in such slower motion organs as the pulmonary vessels, whereas HS-FDK reduced the motion artifact in the heart. HS-FDK had an even more incomplete data region in the Radon space than FS-FDK, suggesting that it would provide poor image quality distant to the midplane in the longitudinal direction. In practical testing in human subjects, HS-FDK showed inferior performance in all variables except temporal resolution. CONCLUSION: Despite its inferiority to FS-FDK for static objects, HS-FDK may be useful in chest imaging. Contrary to previous findings using static images, NHS-FDK failed to show advantages over HS-FDK or FS-FDK in a moving phantom and human subjects.

Adult↗
PubMed2006

Magnitude and effects of x-ray scatter in a 256-slice CT scanner.

We developed a prototype 256-slice CT scanner that employs continuous rotation of a cone-beam with a larger cone angle than conventional multidetector CTs (MDCT) to ensure a wide field of view. However, a larger cone angle may result in image deterioration due to increased x-ray scatter. Scattered radiation causes the detected signals to deviate from the true measurement of primary x-ray intensity and may result in artifacts (e.g., cupping and streak artifacts), quantitative inaccuracy in reconstructed CT number, and degradation of contrast-to-noise ratio (CNR). To reduce the effects of scatter, the 256-slice scanner incorporates an antiscatter collimator. Here, we estimated the magnitude of x-ray scatter in the prototype 256-slice CT scanner under clinical scan conditions and quantified the effects of this scatter on CT number accuracy, image noise, uniformity, and low contrast detectability. Although most experiments were performed with the antiscatter collimator, we also estimated the magnitude of x-ray scatter without the collimator to evaluate the scatter rejection efficiency of the collimator. The scatter-to-primary energy fluence ratio (SPR) without the collimator increased as cone angle increased, with estimated values of 49.7% for a 138 mm beam width with a phantom of 200 mm diameter, and 78.5% for a 320 mm diameter phantom. Estimated SPR was drastically decreased with the collimator, with an SPR reduction rate (ratio of SPR with and without the collimator) of 12.7% and 16.8% for the 200 and 320 mm diameter phantoms, respectively. The reduction in x-ray scatter by the collimator resulted in a considerable reduction in scatter effects. The measured uniformity was good and was independent of scatter amount. Although scatter still affected CT number accuracy, this could be corrected by rescaling. Further, although the CNR was decreased, in theory at least, the change was so subtle that it had no substantial effect on low-contrast detectability.

Algorithms↗