Toshizo Katsuda

National Cerebral and Cardiovascular Center, Ōsaka, Ōsaka, Japan

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Publications (55)19.22 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: To improve the safety of the use of a power injector for pediatric contrast CT, we newly developed a saline test injection mode for a power injector and investigated its usefulness. We used an injection route and investigated the relationship of the injection pressure to the injection rate of saline and the contrast medium. From this relationship, we investigated it was possible to estimate the change of pressure injection of contrast medium from the pressure change of saline injection. The correlation between the saline test injection pressure and the contrast medium injection pressure was investigated in 64 clinical cases. The detection rate of side effects from the saline test injection was investigated in 473 patients. Regarding the correlation between the injection rate and pressure for both saline and contrast, the pressure rose as the rate increased. The contrast medium injection pressure could be estimated from the correlation observed with saline. The clinical data were obtained had a relationship similar to that with phantom data. The detection rate of side effects from the saline test injection was 4.4 % in the clinical cases. In these cases, examinations were completed by re-establishing an injection route or administering hypnotics. Our results suggest that contrast medium pressure can be estimated from a saline test injection, thus aiding in prediction of the risk of injection abnormality. Reactions to injections could be observed in the present study, facilitating the prevention of examination failure. Countermeasures can be taken against the cause of the reaction, and the examination can be performed after confirming the absence of a reaction to injection. Therefore, a saline test injection may be useful in pediatric contrast CT.
    Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine. 06/2013;
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    ABSTRACT: Recently developed radiochromic films can easily be used to measure absorbed doses because they do not need development processing and indicate a density change that depends on the absorbed dose. However, in GAFCHROMIC EBT2 dosimetry (GAF-EBT2) as a radiochromic film, the precision of the measurement was compromised, because of non-uniformity problems caused by image acquisition using a flat-bed scanner with a transmission mode. The purpose of this study was to improve the precision of the measurement using a flat-bed scanner with a reflection mode at the low absorbed dose dynamic range of GAF-EBT2. The calibration curves of the absorbed dose versus the film density for GAF-EBT2 were provided. X-rays were exposed in the range between ~0 and 120 mGy in increments of about 12 mGy. The results of the method using a flat-bed scanner with the transmission mode were compared with those of the method using the same scanner with the reflection mode. The results should that the determination coefficients (r 2 ) for the straight-line approximation of the calibration curve using the reflection mode were higher than 0.99, and the gradient using the reflection mode was about twice that of the one using the transmission mode. The non-uniformity error that is produced by a flat-bed scanner with the transmission mode setting could be almost eliminated by converting from the transmission mode to the reflection mode. In light of these findings, the method using a flat-bed scanner with the reflection mode (only using uniform white paper) improved the precision of the measurement for the low absorbed dose range.
    Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine 03/2013; · 0.89 Impact Factor
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    ABSTRACT: Proximal femoral bone mineral density (BMD) can be measured by dual energy X-ray absorptiometry method in the neck, trochanter, intertrochanter, total and Ward's triangle area. Ward's triangle area of the proximal femur is a smaller area to measure than the others, and the position varies, depending on the status of inner rotation of the target leg. In this study, the measurements of the proximal femoral BMD in women were carried out on the neck, trochanter, intertrochanter, total and Ward's triangle area with the, subjects' legs turned 15 degrees toward the inside. The Ward's BMD were measured using Ward's cognitive method, in which the measured BMD were compared among age groups of 50-59, 60-69, 70-79 and 80-89 to determine whether this process could reveal decreased femoral BMD in elderly women. The correlation between BMD and age was tested using the Pearson correlation coefficient. In all measured parts, the BMD of women age 50-59 were significantly higher than those of women age 80-89. The correlations between BMD and age were negative in all measured parts, and the most negative correlation was between age and Ward's BMD. The study using Ward's cognitive method showed an inverse correlation between Ward's BMD and age in women.
    Acta medica Okayama 02/2012; 66(1):17-21. · 0.65 Impact Factor
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    ABSTRACT: High-density barium sulfate (HDB) has been recommended by the Japanese Society of Gastroenterological Cancer Screening (JSGCS) and used in many medical facilities. However, it is not confirmed that the new method using HDB is superior in diagnostic validity compared to the conventional method using moderate-density barium sulfate (MDB). Pre viously, the authors reported that both methods showed simi lar validity in terms of sensitivity and specificity in gastric cancer screening. In this study, sensitivity and specificity were re-examined in more detail by area under receiver-operating characteristic (ROC) curves (AUC) analysis, especially on the sex (male, female) and the ages (>50, <50, >55, <55, >60, <60) of subjects. The results showed that the diagnostic validity of the method using HDB is almost same to that of the conven tional method using MDB. Clinical improvement in gastric cancer screening is in need of further studies on the new me thod using HDB. Keywordsgastric cancer screening–high-density barium sulfate–sensitivity and specificity–AUC analyses–sex and ages of subjects
    12/2011: pages 671-674;
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    ABSTRACT: The aim of this study was to determine whether additional radiographs, as judged necessary by the radiographer, improves cancer detection during gastric cancer screening. We analyzed 144 gastric cancer cases among 137 744 individuals who underwent X-ray screening for gastric cancer. Radiographs were obtained by 17 radiographers at a screening center in Japan from April 2004 to March 2008. Additional radiographs were taken based on the radiographer's judgment in cases of suspected cancer. During double-blind reinterpretation of the cancer case radiographs by two radiologists, we determined the number of cancer cases that were detected by standard radiographs alone. We next determined the number of cancer cases detected using both standard radiographs and additional radiographs. Compared to the number of cancer cases detected with standard radiographs alone (120 cases detected, 24 cases undetected), the number of cancer cases detected with both standard and additional radiographs (137 cases detected, 7 cases undetected) significantly increased (17 cases; P < 0.001, McNemar test). We found that taking additional radiographs, when judged necessary by the radiographer during radiographic gastric cancer screening, improves cancer detection.
    Japanese journal of radiology 04/2011; 29(3):177-86. · 0.73 Impact Factor
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    ABSTRACT: Although the half-value layer (HVL) is one of the important parameters for quality assurance (QA) and quality control (QC), constant monitoring has not been performed because measurements using an ionization chamber (IC) are time-consuming and complicated. To solve these problems, a method using radiochromic film and step-shaped aluminum (Al) filters has been developed. To this end, GAFCHROMIC EBT2 dosimetry film (GAF-EBT2), which shows only slight energy dependency errors in comparison with GAFCHROMIC XR TYPE-R (GAF-R) and other radiochromic films, has been used. The measurement X-ray tube voltages were 120, 100, and 80 kV. GAF-EBT2 was scanned using a flat-bed scanner before and after exposure. To remove the non-uniformity error caused by image acquisition of the flat-bed scanner, the scanning image of the GAF-EBT2 before exposure was subtracted after exposure. HVL was evaluated using the density attenuation ratio. The effective energies obtained using HVLs of GAF-EBT2, GAF-R, and an IC dosimeter were compared. Effective energies with X-ray tube voltages of 120, 100, and 80 kV using GAF-EBT2 were 40.6, 36.0, and 32.9 keV, respectively. The difference ratios of the effective energies using GAF-EBT2 and the IC were 5.0%, 0.9%, and 2.7%, respectively. GAF-EBT2 and GAF-R proved to be capable of measuring effective energy with comparable precision. However, in HVL measurements of devices operating in the high-energy range (X-ray CT, radiotherapy machines, and so on), GAF-EBT2 was found to offer higher measurement precision than GAF-R, because it shows only a slight energy dependency.
    Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine 03/2011; 34(2):213-22. · 0.89 Impact Factor
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    ABSTRACT: Lymphoscintigraphy is an effective method for detecting sentinel lymph nodes (SLNs). However, the rate and degree of SLN detection is not uniform. We quantified SLNs detected with lymphoscintigraphy, and investigated correlations with factors that may influence detection. We then attempted to predict SLN metastasis from lymph node counts, comparing the predictions to subsequent biopsy results. We assessed lymph node counts in 100 breast cancer patients in whom a single SLN was detected with a fixed lymphoscintigraphy procedure. We examined correlations between the counts and factors known to influence lymphoscintigraphic SLN detection (age, body mass index, tumor size, and presence or absence of metastasis), and determined reference values (lymph node counts of 10.0, 19.4 and 53.0) which were used to predict SLN metastasis in 100 subsequent patients. The predictions were then compared with the SLN biopsy findings. SLN counts correlated strongly with the presence or absence of metastasis, with metastasis-positive lymph nodes showing significantly lower counts than negative nodes (p < 0.001). Prediction of SLN metastasis achieved a 100% positive predictive value at a reference value of 10.0, and a 100% negative predictive value at a reference value of 53.0. At a reference value of 19.4, the sensitivity, specificity, and diagnostic accuracy were 77.8, 73.2, and 74.0%, respectively. The SLN counts detected with lymphoscintigraphy were significantly lower in metastasis-positive lymph nodes than in metastasis-negative lymph nodes. This suggests that prediction of SLN metastasis in breast cancer is possible using lymphoscintigraphy.
    Annals of Nuclear Medicine 12/2010; 25(3):221-6. · 1.41 Impact Factor
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    ABSTRACT: Our aim in this study was to evaluate hyoid bone movement trajectories and the age-related changes during swallowing in healthy subjects by ultrasonography. Data were obtained from 30 healthy volunteers (15 men, 15 women) in three age groups (20-39, 40-59, 60-79 years). The subjects were examined while sitting in an upright position, with the back against a wall to control movement. The transducer was placed in a longitudinal scan above the larynx. The subjects were then given 5 mL of mineral water. The water bolus was held in their mouth until they were forced to do a rapid swallow. The imaging was repeated five times for averaging. The movement was divided into 4 phases: slowly ascending phase (A-B, Elevation); rapidly ascending phase (B-C, Anterior); temporary pause phase (position of maximum rise, Remain); and rapidly and slowly descending shifts toward the resting position phase (C-D, Return). We easily visualized the hyoid bone trajectory by using ultrasonography. In all cases, ultrasonographic analysis of the hyoid bone was confirmed to have a similar trajectory, as determined with videofluoroscopy. The average swallowing duration measurements increased with age. The measurement of the maximally elevated point of the hyoid bone decreased with age. The movement of the hyoid bone during swallowing can be visualized by US. The trajectory of the hyoid bone in sagittal section indicated the capability of swallowing, and may detect some anomalies in swallowing.
    Radiological Physics and Technology 10/2010; 4(1):73-7.
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    ABSTRACT: Purpose: In magnetic resonance imaging (MRI), the diffusion-weighted image (DWI) is an important technique for diagnosis of acute infarction; however, in a 1.0 Tesla low-performance MR unit, chronic ischemia is often detected as a high signal and misdiagnosed as acute infarction. Fluid-attenuated inversion recovery (FLAIR)-DWI was used in an attempt to solve this problem, and the availability is discussed. Materials and methods: MR imaging was performed in 35 patients, after acute infarction (n = 19), and with chronic ischemia (n = 16). Conventional-DWI (C-DWI) and FLAIRDWI were used for all patients. The echo time (TE) was 140 ms. The signal-to-noise ratio (SNRs) and apparent diffusion coefficient (ADC) map in the region of acute infarction or chronic ischemia and contralateral normal brain were estimated. Results: In all regions, ADC was not significantly different between C-DWI and FLAIR-DWI (p >0.05). In chronic ischemia and acute infarction, the SNR of ischemic regions using FLAIR-DWI was significantly lower than that of C-DWI (p <0.05). Furthermore, the SNR of acute infarction regions was significantly higher than that in chronic ischemic regions (p <0.05). Conclusion: In a low-performance MR unit, the discrimination between chronic ischemia and acute infarction was improved by using FLAIR-DWI. KeywordsFLAIR-diffusion weighted imaging-chronic ischemic infarction-magnetic resonance image-1.0Tesla
    01/2010: pages 255-258;
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    ABSTRACT: The purpose of this study was to investigate the potential benefits of additional x-rays in detecting gastric cancer during x-ray screening. We analyzed 151 gastric cancer cases among 136,450 individuals who underwent x-ray screening for gastric cancer. X-rays were performed by 10 radiographers at a single screening center in Japan from 2000 to 2002. Additional x-rays were taken based on the radiographer’s judgement in cases of suspected cancer lesions. During reinterpretation of the x-rays of cancer cases by 2 radiologists, we determined the number of cancer cases that were detected by standard x-rays alone. We next determined the number of cancer cases detected using both standard x-rays and additional x-rays. We then investigated whether additional x-rays increased the rate of cancer detection. The number of cancer cases detected by standard x-rays alone was 122 and the number of cancer cases detected by standard x-rays and additional x-rays was 151. We observed a significant increase in cancer detection with the use of additional x-rays when judged necessary by the radiographer (29 cases, P = 0.007, Wilcoxon signed..ranks test). No statistically significant correlation was observed between the number of additional x-rays performed and the increased rate of cancer detection due to additional xrays taken arbitrarily (rs = - 0.38, P = 0.28, Spearman’s rank correlation). We found that additional x-rays, performed when judged to be necessary by the radiographer during screening, can identify cases of cancer which are not detectable with the standard x-rays alone. Keywordsradiographer-additional photography-x-ray examination-gastric cancer screening
    01/2010: pages 185-188;
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    ABSTRACT: The use of high-density barium sulfate was recommended by the Japan Society of Gastroenterological Cancer Screening (JSGCS) in 2004. We evaluated the diagnostic validity of gastric cancer screening that used high-density barium sulfate. The study subjects were 171 833 residents of Osaka, Japan who underwent gastric cancer screening tests at the Osaka Cancer Prevention and Detection Center during the period from 1 January 2000 through 31 December 2001. Screening was conducted using either high-density barium sulfate (n = 48 336) or moderate-density barium sulfate (n = 123 497). The subjects were followed up and their medical records were linked to those of the Osaka Cancer Registry through 31 December 2002. The results of follow-up during 1 year were defined as the gold standard, and test performance values were calculated. The sensitivity and specificity of the screening test using moderate-density barium sulfate were 92.3% and 91.0%, respectively, while the sensitivity and specificity of the high-density barium test were 91.8% and 91.4%, respectively. The results of area under receiver-operating-characteristic (ROC) curve analysis revealed no significant difference between the 2 screening tests. Screening tests using high- and moderate-density barium sulfate had similar validity, as determined by sensitivity, specificity, and ROC curve analysis.
    Journal of Epidemiology 01/2010; 20(4):287-94. · 2.11 Impact Factor
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    ABSTRACT: To keep radiation doses during computed tomography (CT) examinations as low as reasonably achievable, performing a detailed dose measurement is important. A flexible acrylic sheet roll CT dosimetry phantom (SRCT-P) with radiochromic film (RF) was developed to estimate in detail the dose distribution during pediatric CT examination. The SRCT-Ps were elliptically-shaped by rolling up flexible acrylic sheets (1.1 g/cm3). The dose distributions in the SRCT-P (body thickness and width: 6-8 cm [neonates], 10-12 cm [infants], and 14-16 cm [three-year-old children]) were evaluated. RFs were positioned from the center to the surface along the long- and short-axis directions in each SRCT-P. The scanning parameters of the single detector CT were 120 kV, 250 mA, 1.0 sec/rot, a slice thickness of 5 mm, and a 1.0 beam pitch. When the mean center dose at 10-12 cm on the SRCT-P was taken as 100%, the mean center doses at 6-8..or 14-16 cm were 145..or 43%, respectively, and the mean surface doses for 0, 90, and 180 degrees at 6-8, 10-12, and 14-16 cm of the SRCT-P were as follows: 158%, 159%, and 140%; 132%, 125%, and 116%; and 164%, 128%, and 131%, respectively. The center dose was increased with a decrease in the phantom size. The surface doses were decreased with decreasing phantom sizes of 14-16 to 10-12 cm; however, surface doses were increased with decreasing phantom sizes of 10-12 to 6-8 cm. The detail dose distribution of a CT examination can be measured separately by using a SRCT-P with a RF. Keywordsradiochromic film-computed tomography-phantom-radiation dosimetry
    12/2009: pages 45-48;
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    ABSTRACT: The effective energy of diagnostic X-rays is important for quality assurance and quality control purposes. However, the half-value layer (HVL), which is necessary to evaluate the effective energy, has not been ascertained because of the high cost of the ionization chamber (IC) required and because the measurements are time-consuming and complicated. To solve these problems, a method using radiochromic film (RCF) and step-shaped aluminum (SSAl) filters has been developed. Gafchromic EBT (GAF-EBT), which has a weak energy dependence, was used as the RCF. The X-ray tube voltage for HVL was measured as 120 kV. The SSAl filter area, the full exposure area, and the non-exposure area were set on the GAF-EBT so as to obtain correct data. The density ratio of the SSAl filter area was calculated using the densities of the full exposure area and the non-exposure area. The GAF-EBT was scanned using a flat-bed scanner before and after exposure. To remove the image acquisition error of the flat-bed scanner, the scanning image of the GAF-EBT before exposure was subtracted from it after exposure. The HVL was evaluated using the density attenuation ratio of the GAF-EBT. Then, the effective energies obtained using the GAF-EBT and the IC were compared. The HVL and the effective energy with X-ray tube voltage of 120 kV using the GAF-EBT were 4.56 mm and 41.0 keV, respectively. The difference ratio of the effective energy between the GAF-EBT and IC methods was 5.9%. The effective energy can be measured using GAF-EBT easily and with high precision. The measurement time using GAF-EBT is extremely short compared with the IC method. Moreover, the effective energy can be measured inexpensively using the GAFEBT. Keywordshalf-value layer-effective energy-radiochromic film-Gafchromic EBT
    12/2009: pages 58-61;
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    ABSTRACT: Thickness irregularity of active layer is made to express density irregularity. True data by the X-rays are extracted by exposing Ultraviolet (UV) rays that prohibited exposure are exposed for radiochromic film (RF). When UV is exposed, the density irregularity is corrected. In addition, RF is initialized, thereby improving of data acquisition. GAFCHROMIC EBT (GAF-EBT) film was exposed to UV light at 360 nm twice with a 2 hour interval. The distance from the UV tube to the GAF-EBT film was 165 cm. The GAF-EBT films were scanned after the first and second UV exposure, using a flat bed scanner. Analyses were performed by the density profile curve of the short and long axes of the GAFEBT. The density irregularity of the active layer of the film was corrected to 2.19 ± 0.49 (pixel value) by subtracting the density obtained with the first UV exposure from that with the second UV exposure of GAF-EBT on the short axis. On the long axis, the density irregularity of the active layer of GAFEBT was corrected to 2.67 ± 0.65 (pixel value). Uniform UV exposure data was identified. The measurement precision of the GAF-EBT film and its usefulness are improved by this method. KeywordsRadiochromic Film-Active Layer-Irregularity-Ultraviolet Exposure
    12/2009: pages 227-230;
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    ABSTRACT: The aim of this study was to evaluate the film-reading ability of radiographers in detecting gastric cancer during screening X-ray examinations. A test set of 100 patients (50 negative and 50 positive; mean age 62 years, range 33-78 years) given a stomach X-ray examination were selected from those who underwent gastric cancer screening in Osaka, Japan, between 2000 and 2003. Eleven radiographers and four radiologists scored the test set on a five-point scale. A receiver operating characteristic (ROC) analysis was performed, and the area under the ROC curve (AUC) was defined as a measure of film-reading ability to detect cancer. No significant difference (two-tailed P = 0.962, Welch's t-test) was observed between averaged AUC values from radiographers (0.76, range 0.85-0.62) and radiologists (0.75, range 0.86-0.62). Film-reading ability of radiographers in detecting gastric cancer during screening X-ray examinations was not significantly different from that of radiologists. Our results suggest that radiographers can assist radiologists to detect gastric cancer during screening.
    Japanese journal of radiology 10/2009; 27(8):291-6. · 0.73 Impact Factor
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    ABSTRACT: Although the half-value layer (HVL) is one of the important parameters for QA and QC, constant monitoring has not been performed because the measurements using an ionization chamber (IC) are time-consuming and complicated. To solve these problems, the use of radiochromic film (GAFCHROMIC XR TYPE R: GAF-R) with step-shaped aluminum (Al) filters, referred to herein as the simple process method, has been developed. The measurement X-ray tube voltages were 120 kV, 100 kV, and 80 kV. The Al filter area, the full exposure area, and the unexposed area were set on the GAF-R so as to obtain correct data. The HVL was evaluated using the density attenuation ratio. The HVLs obtained using the GAF-R and an 1C dosimeter were compared. HVLs with X-ray tube voltages of 120 kV, 100 kV, and 80 kV using the GAF-R were 4.10 mm, 3.55 mm and 2.97 mm, respectively. The difference ratios of the HVLs using the GAF-R and the IC were 1.2%, 7.6%, and 10.0%, respectively. The HVL at 120 kV can be routinely and quickly measured using the simple process method. Therefore, an IC dosimeter is not needed for HVL measurements for QA and QC. However, the HVL measurements of low energy (100 kV and 80 kV) need attention.
    Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine 09/2009; 32(3):150-8. · 0.89 Impact Factor
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    ABSTRACT: In dynamic liver magnetic resonance imaging (MRI) studies, there are problems with misregistration when subtraction images are processed. For reduction of the misregistration, a functional residual capacity (FRC) phase breath-hold (FRC B-H) method was used. Sixty patients (32 males and 28 females, aged 33-85 years, median age 69 years) were examined. The subjects were chronologically categorized into two groups: a voluntary expiratory (VE) B-H group and a FRC B-H group. The blood-flow phase images were classified as plain, arterial, portal and parenchymal phases. To evaluate the reproducibility of liver positions between VE B-H and FRC B-H in each phase (between Plain and Arterial, Arterial and Portal, Plain and Parenchymal), the misregistration areas were compared on the top of the liver. The misregistration area between Plain-Arterial, Arterial-Portal and Plain-Parenchymal in VE B-H was 731.0+/-1153.6, 1134.9+/-1357.2 and 628.4+/-844.5 (cm(2)), respectively. The misregistration area between each phase in FRC B-H was 386.4+/-874.9, 574.5+/-1086.1 and 279.8+/-551.2 (cm(2)), respectively. Using the Mann-Whitney U-test as quantitative analysis, the difference in misregistration areas between two groups was statistically significant (p<0.05). Differences in the qualitative analysis were also significant according to the chi(2) test (p<0.05). The liver positions with FRC B-H were markedly more reproducible than those with VE B-H. To improve the registration accuracy of subtraction dynamic liver MRI, the FRC B-H should be used.
    European journal of radiology 09/2009; 71(3):506-12. · 2.65 Impact Factor
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    ABSTRACT: Recently, high-concentration barium sulfate has been developed and is used in many medical facilities. This study compared radiation dose using high-concentration and moderate-concentration barium sulfate. The dose was evaluated with an experimental method using a gastric phantom and with a clinical examination. In the former, the dose and X-ray tube load were measured on the phantom with two concentrations of barium sulfate. In the latter, the fluoroscopic dose-area product (DAP), the radiographic DAP and their sum, the total DAP, were investigated in 150 subjects (112 males, 38 females) treated with both concentrations of barium sulfate. The effective dose was calculated by the software of PCXMC in every case. The results of the experimental evaluation indicated that the effective dose and X-ray tube load were greater with high-concentration barium sulfate than with moderate-concentration barium sulfate (p < 0.05). The results of the clinical evaluation indicated that the fluoroscopic DAP was greater with moderate-concentration barium sulfate than with high-concentration barium sulfate (p < 0.05), but the radiographic DAP was quite the reverse, so the total DAP and effective dose were almost same with both concentrations of barium sulfate. We conclude that high-concentration barium sulfate does not increase radiation dose in mass screening for gastric cancer.
    Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine 07/2009; 32(2):88-91. · 0.89 Impact Factor
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    ABSTRACT: The effective energy of diagnostic X-rays is important for quality assurance (QA) and quality control (QC). However, the half-value layer (HVL), which is necessary to evaluate the effective energy, is not ubiquitously monitored because ionization-chamber dosimetry is time-consuming and complicated. To verify the applicability of GAFCHROMIC XR type R (GAF-R) film for HVL measurement as an alternative to monitoring with an ionization chamber, a single-strip method for measuring the HVL has been evaluated. Calibration curves of absorbed dose versus film density were generated using this single-strip method with GAF-R film, and the coefficient of determination (r2) of the straight-line approximation was evaluated. The HVLs (effective energies) estimated using the GAF-R film and an ionization chamber were compared. The coefficient of determination (r2) of the straight-line approximation obtained with the GAF-R film was more than 0.99. The effective energies (HVLs) evaluated using the GAF-R film and the ionization chamber were 43.25 keV (5.10 mm) and 39.86 keV (4.45 mm), respectively. The difference in the effective energies determined by the two methods was thus 8.5%. These results suggest that GAF-R might be used to evaluate the effective energy from the film-density growth without the need for ionization-chamber measurements.
    Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine 04/2009; 32(1):26-9. · 0.89 Impact Factor
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    ABSTRACT: Performing a detailed dose measurement is important to keep radiation doses during computed tomography (CT) examinations as low as reasonably achievable. To estimate in detail the dose distribution during pediatric CT examination of the head, a sheet roll CT dosimetry phantom (SRCT-P) with radiochromic film (RF) was developed. The dose distributions in the SRCT-P (diameters of 6 [premature baby], 10 [neonate], and 14 [infant] cm) were evaluated. The SRCT-Ps were made by rolling up flexible acrylic sheets (1.1 g/cm3). RFs were positioned every 5 mm along the radius at each SRCT-P, starting at 10 mm (center) and ending on the surface. The dose distribution along the z-axis at the center or on the surface showed a flat or wave pattern, respectively. When the mean surface dose at 10 cm diameter was taken as 100%, the mean surface doses at 6 or 14 cm diameters were 105 or 96%, respectively, and the mean center doses at 6, 10, and 14 cm were 109, 99, and 74%, respectively. The maximum-minimum doses and dose distribution of a CT examination can be measured separately by using the SRCT-P with RF.
    Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine 01/2009; 31(4):339-44. · 0.89 Impact Factor

Publication Stats

67 Citations
19.22 Total Impact Points

Institutions

  • 2013
    • National Cerebral and Cardiovascular Center
      Ōsaka, Ōsaka, Japan
  • 2008–2010
    • Okayama University
      • • Department of Radiological Technology
      • • Graduate School of Health Sciences
      Okayama, Okayama, Japan
    • Himeji Dokkyo University
      Himezi, Hyōgo, Japan
  • 2005
    • Osaka Prefectural Medical Center for Respiratory and Allergic Diseases
      Ōsaka, Ōsaka, Japan
  • 1996–1998
    • Osaka Medical Center for Cancer and Cardiovascular Diseases
      Ōsaka, Ōsaka, Japan