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2005 Volume 61 Issue 12 Pages
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2005 Volume 61 Issue 12 Pages
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2005 Volume 61 Issue 12 Pages
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[in Japanese]
Article type: Article
2005 Volume 61 Issue 12 Pages
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2005 Volume 61 Issue 12 Pages
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YOSHIHARU HIGASHIDA, [in Japanese], [in Japanese], [in Japanese], [in ...
Article type: Article
2005 Volume 61 Issue 12 Pages
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SHINJI TANAKA, [in Japanese], [in Japanese], [in Japanese], [in Japane ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1576-1579
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TATSUO HONMA
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2005 Volume 61 Issue 12 Pages
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KOSUKE MATSUBARA, KICHIRO KOSHIDA, MASAYUKI SUZUKI, MAYUMI HAYAKAWA, H ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1581-1586
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Excessive radiation exposure in pediatric computed tomography(CT)scanning has become a serious problem, and it is difficult to select scan parameters for the scanning of small patients such as children. We investigated differences in absorbed dose and standard deviation(SD)in Hounsfield unit(HU)caused by differences in the form of the subject using a body-type phantom with removable body parts. Using four X-ray CT scanners, measurements were made with values from 50 mAs to 300 mAs, with slices of 50 mAs, using scan protocols that were assumed to perform thorough examinations. The results showed that the mAs values and absorbed doses were almost proportional, and the absorbed doses in the phantom without body parts were about 1.1-2.2-fold higher than those of the phantom with body parts at the same points. The SD values obtained indicated that the absorbed doses in the phantom with body parts were 0.3-0.6 times those of the phantom without body parts when the mAs values used were adjusted so that both SD values were the same. The absorbed doses in various patient forms can be estimated from these results, and they will become critical data for the selection of appropriate scan protocols.
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MASANOBU UEMURA, YOSHIYUKI ASAI, MICHIHIRO YAMAGUCHI, YUKO SHINTANI, S ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1587-1591
Published: December 20, 2005
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Although there are remarkable differences in maximum luminance in cathode ray tube(CRT)and liquid crystal display(LCD)monitors and film/viewer systems, these differences cannot be recognized in our perception of them. To clarify the reason for this conflict, we analyzed the psychophysical gradient(δ), which is based on the minimum perceptible luminance difference(ΔL_<min>)and can express contrast visually recognized by observers. In this study, we first confirmed the compatibility of the psychophysical analysis to the CRT and the LCD monitors by using their threshold contrasts(C_ts). Second, we calculated and compared the δ's of the above output devices. The C_ts values of each device were in good agreement. Moreover, the Moon & Spencer model, which expressed the perceptibility of luminance change, was well suited to the measured C_ts over the whole luminance range. The psychophysical analysis is therefore available not only for the film/viewer system, but also for the CRT and LCD systems. The difference of physical gradient G of the luminance characteristics curve among the output devices was larger than 20 times, whereas that of δ was within 3 times. The display devices listed in the order of decreasing δ were film/viewer>LCD>CRT. These results corresponded to the visual contrast sensation and our clinical experience, which cannot recognize remarkable differences in perception. By using the psychophysical analysis, we clarified the reason for the conflict between the results of physical evaluation and the contrast visually recognized by observers.
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TATSUSHI TOMOMITSU, HIROAKI MIMURA, KENYA MURASE, TERUKI SONE, MASAO F ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1592-1598
Published: December 20, 2005
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Bone strength depends on bone quality(architecture, turnover, damage accumulation, and mineralization)as well as bone mass. In this study, human bone architecture was analyzed using fractal image analysis, and the clinical relevance of this method was evaluated. The subjects were 12 healthy female controls and 16 female patients suspected of having osteoporosis(age range, 22-70 years; mean age, 49.1 years). High-resolution CT images of the distal radius were acquired and analyzed using a peripheral quantitative computed tomography(pQCT)system. On the same day, bone mineral densities of the lumbar spine(L-BMD), proximal femur(F-BMD), and distal radius(R-BMD)were measured by dual-energy X-ray absorptiometry(DXA). We examined the correlation between the fractal dimension and six bone mass indices. Subjects diagnosed with osteopenia or osteoporosis were divided into two groups(with and without vertebral fracture), and we compared measured values between these two groups. The fractal dimension correlated most closely with L-BMD(r=0.744) . The coefficient of correlation between the fractal dimension and L-BMD was very similar to the coefficient of correlation between L-BMD and F-BMD(r=0.783)and the coefficient of correlation between L-BMD and R-BMD(r=0.742). The fractal dimension was the only measured value that differed significantly between both the osteopenic and the osteoporotic subjects with and without vertebral fracture. The present results suggest that the fractal dimension of the distal radius can be reliably used as a bone strength index that reflects bone architecture as well as bone mass.
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NARUOMI YASUDA, YOKO ISHIKAWA, YOSHIE KODERA
Article type: Article
2005 Volume 61 Issue 12 Pages
1599-1608
Published: December 20, 2005
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Multidetector-row computed tomography(MDCT)has dramatically increased the speed of scanning, and allows high-resolution imaging compared with conventional single detector-row CT(SDCT). However, the use MDCT makes use of an increase in volume scanning, and causes a simultaneous increase in radiation dose to the patient. Thus, the radiation dose from the X-ray CT has become a problem in recent years. In this study, nonlinear wavelet-based edge preservation de-noising using trimmed-thresholding was applied to reconstructed low-dose chest MDCT images, and optimal wavelet processing including wavelet functions and thresholding methods was examined. Moreover, the usefulness of the de-noising for reducing radiation dose was examined. As a result of optimized edge preservation de-noising, noise reduction was achieved with little deterioration in image quality, and the wavelet function used at that time was Coiflet's with shorter support. As a result, almost the same quality of reconstructed image of the chest phantom was obtained for conventional scanning and low-dose scanning with the wavelet de-noising method using trimmed-thresholding. That is, the radiation dose from MDCT could be reduced using this wavelet-based de-noising method.
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SHINICHIRO MORI, RYOSUKE KOHNO, TEIJI NISHIO, HIDEYUKI MIZUNO, HIROYO ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1609-1615
Published: December 20, 2005
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To reduce errors in the carbon beam distribution between the treatment planning system and the actual situation, we evaluated the geometrical accuracy, volume accuracy, water-equivalent length(WEL), and treatment planning, and compared the results of evaluation of axial and helical scan methods with various scan parameters. The results indicated that both scan methods showed good geometrical accuracy for thin slice images, but for thick slice images it is easier to understand the phantom as a sphere from the helical as compared with the axial scan. Treatment planning with a thin slice thickness(ST) provided accurate dose distribution for both scan methods, and the dose distribution on the treatment planning system was almost the same as that in the actual situation. Not all institutes, however, can obtain thin slice CT images, and some have used thick slice CT images in planning. For the axial scan, such thick slice images induced differences in dose distribution between treatment planning and the actual situation. Helical scans with a small, reconstructed increment reduced these differences even with relatively thick CT images. To achieve a more accurate dose distribution, radiation therapy planning should be performed using a thin ST for both scan methods or the helical scan with a small, reconstructed increment. Although we reached this conclusion using a carbon beam, it also may be applicable to proton beam therapy.
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EIICHIRO OKUMURA, SHIGERU SANADA, MASAYUKI SUZUKI, YOSHITO TSUSHIMA, O ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1616-1622
Published: December 20, 2005
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When interpreting enhanced computer tomography(CT)images of the upper abdomen, radiologists visually select a set of images of the same anatomical positions from two or more CT image series(i.e., non-enhanced and contrast-enhanced CT images at arterial and delayed phase)to depict and to characterize any abnormalities. The same process is also necessary to create subtraction images by computer. We have developed an automated image selection system using a template-matching technique that allows the recognition of image sets at the same anatomical position from two CT image series. Using the template-matching technique, we compared several anatomical structures in each CT image at the same anatomical position. As the position of the liver may shift according to respiratory movement, not only the shape of the liver but also the gallbladder and other prominent structures included in the CT images were compared to allow appropriate selection of a set of CT images. This novel technique was applied in 11 upper abdominal CT examinations. In CT images with a slice thickness of 7.0 or 7.5 mm, the percentage of image sets selected correctly by the automated procedure was 86.6±15.3% per case. In CT images with a slice thickness of 1.25 mm, the percentages of correct selection of image sets by the automated procedure were 79.4±12.4%(non-enhanced and arterial-phase CT images)and 86.4±10.1%(arterial- and delayed-phase CT images). This automated method is useful for assisting in interpreting CT images and in creating digital subtraction images.
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AKIHIRO TAKEMURA, MASAYUKI SUZUKI, HAJIME HARAUCHI, YUSUKE OKUMURA
Article type: Article
2005 Volume 61 Issue 12 Pages
1623-1631
Published: December 20, 2005
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In this paper, we propose a tracking technique for a micro guide wire in a sequence of fluorograms. A technique in which the region-growing technique was embedded was developed. It gives the center line of a micro guide wire. A sequence of 1, 024×1, 024×16 bit fluorograms(111 frames)with a carotid phantom and head phantom was obtained with a CAS-8000V(Toshiba America Medical Systems, Inc., CA, USA)C-arm angiography system and a Hi-Torque Standard micro guide wire(Advanced Cardiovascular Systems, Inc., CA, USA). To evaluate the technique, we manually traced the guide wire in each sequence frame three times, and a "true" single-width micro guide wire was created from them. The number of pixels on the true guide wire and inside the two-pixel tolerance of the center line was counted in each fluorogram, and the percentage of that count based on the number of all pixels on the true guide wire was calculated as true positive(TP). In addition, the number of pixels on the center line and outside the two-pixel tolerance of the true guide wire was counted in each frame as false positive(FP). The tracking technique has a mean TP of 94.8% and a mean FP of 5.1 pixels/frame. Several frames have low TP and high FP, but the technique could continue to track the micro guide wire until the end of the sequence. We therefore concluded that we had developed an accurate automatic tracking technique for micro guide wires in fluoroscopic sequences.
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KOICHI CHIDA, YOSHIAKI MORISHIMA, YOSHIAKI KATAHIRA, HIROO CHIBA, MASA ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1632-1637
Published: December 20, 2005
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Since cardiac interventional procedures deliver high doses of radiation to the physician, radiation protection for the physician in cardiac catheterization laboratories is very important. One of the most important means of protecting the physician from scatter radiation is to use additional lead shielding devices, such as tableside lead drapes and ceiling-mounted lead acrylic protection. During cardiac interventional procedures(cardiac IVR), however, it is not clear how much lead shielding reduces the physician dose. This study compared the physician dose [effective dose equivalent(EDE)and dose equivalent(DE)]with and without additional shielding during cardiac IVR. Fluoroscopy scatter radiation was measured using a human phantom, with an ionization chamber survey meter, with and without additional shielding. With the additional shielding, fluoroscopy scatter radiation measured with the human phantom was reduced by up to 98%, as compared with that without. The mean EDE(whole body, mean±SD)dose to the operator, determined using a Luxel badge, was 2.55±1.65 and 4.65±1.21 mSv/year with and without the additional shielding, respectively(p=0.086). Similarly, the mean DE(1ens of the eye)to the operator was 15.0±9.3 and 25.73±5.28 mSv/year, respectively(p=0.092). In conclusion, although tableside drapes and lead acrylic shields suspended from the ceiling provided extra protection to the physician during cardiac IVR, the reduction in the estimated physician dose(EDE and DE)during cardiac catheterization with additional shielding was lower than we expected. Therefore, there is a need to develop more ergonomically useful protection devices for cardiac IVR.
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HITOSHI TSUCHIYA, HIROMASA KUROSAKI, SOICHI HIRAMOTO, MISAYO SEKI, KEI ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1638-1644
Published: December 20, 2005
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Techniques such as 4M-4E matrices and the SHEL model have been proposed in recent years as tools for analyzing medical accidents and developing countermeasures. There have been hardly any reports, however, describing their use for the development of risk strategies in the medical setting. After using the SHEL model, Toranomon Hospital is currently using "Why Why Why Analysis" and has had several successes as a result of its use. With this in mind, a comparative study was conducted between "Why Why Why Analysis" and several previously reported accident countermeasure tools, root cause analysis(RCA), used at Veterans Hospitals in the US, and quality control(QC), used in the industrial sector. As a result, "Why Why Why Analysis" as applied in radiology work was determined to be easy to deploy even for beginners as compared with the other tools, able to accommodate complaints as well as accidents, and useful on the basis of having both practical and expandable functions for improving radiology work.
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HIROKI OHTANI
Article type: Article
2005 Volume 61 Issue 12 Pages
1645-1650
Published: December 20, 2005
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It is expected that proton beam radiotherapy will become an effective treatment for tumors. For an organ for which a correct dose prescription is required, a proton beam has the ability to provide the dose most suitable for the specific purpose. We measured the charged particle equilibrium factor of proton beams in water using a plane parallel ionization chamber. The maximum energy of the proton beam used in this study was 70 MeV, produced from an isochronous cyclotron. We assume that the charged particle equilibrium factor can be separated into longitudinal and lateral components, that is, the factor E(Z, R)is dependent on depth, Z, and field radius, R; such that E(Z, R)=E(Z)E(R). The E(Z)-factor of primary protons was considered in order to investigate the influence of secondary charged particles. From the results, the charged particle equilibrium factor for the longitudinal component does not remain sharp with the decrease of water depth, and the lateral component is not maintained with the decrease of field size. However, the longitudinal components of primary protons at shallow depth were in equilibrium.
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AKIKO HORII, AYA CHIHARA, KATSUHIRO ICHIKAWA, YOSHIE KODERA, MITSURU I ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1651-1655
Published: December 20, 2005
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We measured modulation transfer functions(MTFS)of liquid crystal displays(LCDs)by rectangular waveform analysis. This method consists of taking a picture of the bar pattern on the display surface with a digital camera, and analyzing the picture with a personal computer. The displays used are LCDS of 1M(about 1 million pixels), 2M, 3M, and 5M, and a cathode ray tube(CRT)display with a pixel number of 5M. Two kinds of 2M displays were used, an in-plane switching(IPS)system and vertical alignment(VA)system, from which liquid crystal operation mode differs. MTFS increased as pixels increased. For the LCDs, MTFS in the horizontal direction were higher than those in the vertical direction except for the 2M VA system. For the LCD of the 2M VA system, MTF in a horizontal direction was equal to MTF in a vertical direction. For the displays with the same number of pixels(5M), MTF of a LCD was higher than that of a CRT display. MTFS of LCDS are influenced by the pixel form, pixel composition, and the liquid crystal operation mode.
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MASAO MATSUMOTO, TATSUYA YAMAZAKI, MAKOTO NOKITA, SHINSUKE HAYASHIDA, ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1656-1665
Published: December 20, 2005
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We investigated the clinical usefulness of a newly developed flat-panel detector(FPD)system by comparing its physical imaging properties and low-contrast detectability with those of a current FPD system. The newly developed CsI-based indirect FPD(Canon, CXDI-40C)and current Gd_20_2S-based FPD(Canon CXDI-11)systems were used. Characteristic curves, resolution properties, radiographic noise, detective quantum efficiencies(DQES)and low-contrast detectability for both systems were measured. The new FPD system showed considerably lower noise levels than those of the current FPD system. DQE(0)s of the new and current FPD systems were 75% and 35%, respectively. Observer performance tests of the contrast-detail(C-D)phantom indicated that the new FPD system can significantly improve low-contrast performance over that obtainable with the current FPD system under the same conditions of exposure. The new FPD system provided approximately 50% reduction in exposure while providing comparable detectability. The newly developed FPD system provides radiographic images with excellent inherent physical image quality and low-contrast performance.
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YUICHIRO TSUCHIYA, YOSHIE KODERA
Article type: Article
2005 Volume 61 Issue 12 Pages
1666-1674
Published: December 20, 2005
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The purpose of this study was to develop a method of kinetic analysis for picture archiving and communication system(PACS)management and computer-aided diagnostic application in dynamic chest radiography. The main analytical technique used in this study was a new algorithm that converts dynamic radiographs into a color-static image. The algorithm is a visualization technique for kinetic information that uses the intensity-density transformation and the direction classification in optical flow. The image made by the new algorithm was defined as a "kinetic map, " and, by analysis using the kinetic map, a patient collation system and nodule detection system were constructed. By analysis that used an artificial neural network of certain feature vectors as kinetic map similarity, the collation system obtained good identification performance. Temporal subtraction processing between a current-status map with simulated nodule and previous-status map detected the region of abnormality as the simulated nodule. It is expected that our method of analysis will be useful as a screening examination for risk management and computer-aided diagnostic application in dynamic chest radiography.
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TSUTOMU GOMI, JUN MIYAGAWA, HIROSHI HIRANO
Article type: Article
2005 Volume 61 Issue 12 Pages
1675-1680
Published: December 20, 2005
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The purpose of this study was to compare direct and indirect detectors in terms of their presampled modulation transfer function(MTF), Wiener spectrum(WS), and noise-equivalent quanta(NEQ). Measurements were made on two flat-panel detectors, the GE Revolution XR/d(indirect)and Shimadzu Safire(direct)radiographic techniques. The presampled MTFS of the systems were measured using an edge method. The WS calculated the difference in uniform images that changed exposure to radiation using the two-dimensional Fourier method. The NEQ were assessed from the measured MTF, WS, and estimated signal-to-noise ratios(SNR). The system linearity was excellent in the direct Safire system. Presampled MTF was notably higher for the direct Safire system. For the direct Safire system, the WS was relatively uniform across all frequencies. In comparison, the indirect Revolution XR/d system exhibited a drop in the WS at high frequencies. At lower frequencies, the NEQ for the indirect Revolution XR/d system was noticeably higher than the direct Safire system. For the direct Safire system, the NEQ at mid to high spatial frequencies were higher linearity.
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MASANORI MATSUSHIMA, RIE TANAKA, YUZO KIKUCHI, SHIGERU SANADA, TOMOYAS ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1681-1688
Published: December 20, 2005
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To analyze shifts in the isocenter of images, we developed a semi-automated superimposing image-verification system that is capable of automatically quantifying shifts in the isocenter through image analysis with a personal computer(PC). The accuracy and usefulness of this software were examined through a comparison of nine portal images with a simulation image and by comparing nine portal images with a DRR image, using a human pelvic phantom. The difference between the known magnitude of shift and the magnitude of shift detected with this method was analyzed as detection error. When the portal images were compared with the simulation image, the 95% confidence interval(95% CI)of detection errors(mean±SD)was 0.57±0.36 mm(95% CI : 0.49-0.65 mm). When the portal images were compared with the DRR image, the respective figures were 0.68±0.38 mm(95% CI : 0.59-0.77 mm). No significant difference was noted between these two categories of comparison(N.S). The absolute detection error(mean±SD)in all directions was 0.34±0.34 mm for the comparison of portal images with the simulation image and 0.41±0.36 mm for the comparison of portal images with the DRR image. This system seems to be appropriate for verification of the treatment field by improving the accuracy of radiotherapy as a method of computer-assisted landmark recognition during image comparison.
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RIE TANAKA, MASANORI MATSUSHIMA, YUZO KIKUCHI, SHIGERU SANADA
Article type: Article
2005 Volume 61 Issue 12 Pages
1689-1699
Published: December 20, 2005
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Visual comparison of a reference image with a verification image is commonly used for setup verification in external beam radiation therapy. However, it sometimes lacks reproducibility and provides insufficient quantitative evidence. The present study was performed to develop computerized methods for determining landmarks to verify a portal image with digital reconstruction radiograph(DRR), and to investigate the clinical effectiveness of our method. Our computer algorithm consisted of three mam procedures--preprocessing, determination of landmarks, and verification--none of which required manual operation. Finally, our system indicated the distance for setup correction. We evaluated the accuracy of our system using pelvic phantom images, and the maximum magnitude of error was shown to be 1.12(n=9). The results indicated that the error range of our system was sufficiently small to examine patient positioning error, which should be less than 5 mm, as described in AAPM report TG40. Our system will aid operators in positioning patients accurately for external radiation therapy.
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TOSHIZO KATSUDA, MASANORI TAKESHITA, TADAO KUWANO, CHIKAZUMI KURODA, M ...
Article type: Article
2005 Volume 61 Issue 12 Pages
1700-1703
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This study examined the usefulness of a pulse oximeter in hepatic digital subtraction angiography(DSA)with oxygen administration for breath holding. Oxygen saturation and dissociation times were measured using a pulse oximeter. Twenty-eight patients inhaled oxygen at a rate of 3 liters/min through a nasal tube. Saturation times ranged from 0 to 140 seconds to achieve arterial oxygen-hemoglobin saturation of almost 100%. Dissociation times ranged from 0 to 600 seconds after oxygen termination.
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Article type: Appendix
2005 Volume 61 Issue 12 Pages
1704-1705
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2005 Volume 61 Issue 12 Pages
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Article type: Appendix
2005 Volume 61 Issue 12 Pages
1707-1710
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Article type: Appendix
2005 Volume 61 Issue 12 Pages
1711-1712
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Article type: Index
2005 Volume 61 Issue 12 Pages
1713-1719
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Article type: Index
2005 Volume 61 Issue 12 Pages
1720-1727
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2005 Volume 61 Issue 12 Pages
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2005 Volume 61 Issue 12 Pages
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2005 Volume 61 Issue 12 Pages
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2005 Volume 61 Issue 12 Pages
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2005 Volume 61 Issue 12 Pages
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2005 Volume 61 Issue 12 Pages
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2005 Volume 61 Issue 12 Pages
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