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To investigate how changing the injection duration at cardiac computed tomography angiography (CCTA) affects contrast enhancement in newborns and infants.Included were 142 newborns and infants with confirmed congenital heart disease who underwent CCTA between January 2015 and December 2018. In group 1 (n = 71 patients), the injection duration was 8 s; in group 2 (n = 71) it was 16 s. Our findings were assessed by one-to-one matching analysis to estimate the propensity score of each patient. We compare the CT number for the pulmonary artery (PA), ascending aorta (AAO), left superior vena cava (SVC), AAO and PA enhancement ratio, and the scores for visualization between the two groups.In group 1, median CT number and ranges was 345 (211-591) HU in the AAO, 324 (213-567) HU in the PA, and 62 (1-70) HU in the SVC. These values were 465 (308-669) HU, 467 (295-638) HU, and 234 (67-443) HU, respectively, in group 2 (p 0.05). The median score for volume-rendering visualization on 3D images of the CCTA was 2 in group 1 and 3 in group 2; the score for visualization of the left SVC of the maximum intensity projection images was 2 in group 1 and 3 in group 2 (p 0.05). The CT number for the AAO and PA enhancement ratio was 15.2 in group 1 and 9.2 in group 2 (p 0.05).The 16-sec injection protocol yielded significantly higher CT numbers for the AAO, PA, and the SVC than the 8-sec injection protocol; the visualization scores were also significantly higher in group 2.In newborns and infants, the longer injection time for CCTA yields stable and higher contrast enhancement at identical CM concentrations.

To compare the computed tomography (CT) number for paediatric cardiac computed tomography angiography (CCTA) and visualisation score of the three-dimensional (3D) images using the conventional T-shaped extended tube (T-tube) and spiral flow-generating extended tube (spiral-tube) connected between the contrast injector and cannula.In total, 108 patients suspected to have congenital heart disease (CHD) were considered for inclusion. We utilised the T-tube for intravenous contrast and spiral-tube in 54 patients each. Observers individually inspected randomized volume rendering images of the internal thoracic artery, each acquired from the with or without spiral-tube groups, using a four-point scale. We compared the mean CT number of the ascending aorta (AAO) and pulmonary artery (PA), contrast noise ratio (CNR), CT number for the AAO and PA enhancement ratio, and the visualisation scores between the groups.There were no significant differences in patient characteristics between the with or without spiral-tube groups (p 0.05). The mean CT number ±standard deviation for the AAO and PA, and the CNR without or with spiral-tube groups were 441.2 ± 89.2 and 489.8 ± 86.1 HU for the AAO, 436.3 ± 100.6 and 475.3 ± 85.2 HU for the PA, and 9.5 ± 2.2 and 10.8 ± 2.4 for the CNR, respectively (p 0.05). In the spiral-tube group, the CT number, CNR, and visualisations score of the 3D images were significantly higher for the AAO and PA than those in the T-tube group (p 0.05).The spiral-tube proved to be beneficial in improving the CT number for the AAO and PA, CNR, and visualisation score compared with the conventional T-tube during paediatric CCTA.The spiral-tube may allow the visualisation of smaller blood vessels than those visualised by the conventional T-tube for paediatric patients in CCTA.

This study aims to predict endoleak after endovascular aneurysm repair (EVAR) using machine learning (ML) integration of patient characteristics, stent-graft configuration, and a selection of vessel lengths, diameters and angles measured using pre-operative computed tomography angiography (CTA).We evaluated 1-year follow-up CT scans (arterial and delayed phases) in patients who underwent EVAR for the presence or absence of an endoleak. We also obtained data on the patient characteristics, stent-graft selection, and preoperative CT vessel morphology (diameter, length, and angle). The extreme gradient boosting (XGBoost) for the ML system was trained on 30 patients with endoleaks and 81 patients without. We evaluated 5217 items in 111 patients with abdominal aortic aneurysms, including the patient characteristics, stent-graft configuration and vascular morphology acquired using pre-EVAR abdominal CTA. We calculated the area under the curve (AUC) of our receiver operating characteristic analysis using the ML method.The AUC, accuracy, 95% confidence interval (CI), sensitivity, and specificity were 0.88, 0.88, 0.79-0.97, 0.85, and 0.91 for ML applying XGBoost, respectively.The diagnostic performance of the ML method was useful when factors such as the patient characteristics, stent-graft configuration and vessel length, diameter and angle of the vessels were considered from pre-EVAR CTA.Based on our findings, we suggest that this is a potential application of ML for the interpretation of abdominal CTA scans in patients with abdominal aortic aneurysms scheduled for EVAR.

The purpose of this study was to demonstrate that dose reduction does not compromise image quality when combining high helical pitch (HP) and the ECG-Edit function during low HP retrospectively gated computed tomography angiography (CTA).This study made use of a pulsating cardiac phantom (ALPHA 1 VTPC). The heart rate (HR) of the cardiac phantom was changed in five intervals, every 5 beats per minute (bpm), from 40 to 60 bpm. Evaluation of a range of HR was important because data loss might occur when combining a low HR and high HP. We performed retrospectively gated CTA scans five times using a low HP (0.16) and high HP (0.24), for each of the five HR intervals, using a 64-detector row CT scanner. The CT volume dose index (CTDIData loss occurred with a HR of 40 bpm and 45 bpm when using HP 0.24. The CTDIThe ECG-Edit function is potential useful for repairing the lost data in patients with a low HR, and when combined with a high HP, it is possible to reduce the radiation dose by approximately 33%.The ECG-Edit function and high HP may be a viable option in pediatric CTA studies.

This study aimed to compare the correlation between the computed tomography (CT) enhancement rate of the venous to portal venous phase (VP-ER) and the extracellular volume (ECV) fraction with shear-wave ultrasound elastography (USE) findings in patients with liver fibrosis.We included 450 patients with clinically suspected liver cirrhosis who underwent triphasic dynamic CT studies and USE. We compared the USE results with the unenhanced CT phase, with enhancement in the hepatic artery phase (HAP), portal venous phase (PVP), and venous phase (VP), and with the ECV fraction and the VP-ER. We also compared the area under the curve (AUC) of the receiver operating characteristic (ROC) curve of the ECV fraction and VP-ER with that of the values obtained with USE.The VP-ER was the most highly correlated with the liver stiffness value determined with USE (Pearson's correlation coefficient: r = 0.37), followed by enhancement in the PVP (r = -0.25), CT number on unenhanced CT scans (r = -0.22), the ECV fraction (r = 0.19), enhancement in the VP (r = 0.059), and enhancement in the HAP (r = -0.023) (all p 0.01). The VP-ER showed a significantly higher AUC than the ECV fraction (0.75 vs 0.62) when the liver stiffness was15 kPa in USE studies (p = 0.04).Compared to the ECV fraction, the VP-ER is more useful for predicting all degrees of liver fibrosis on routine triphasic dynamic CT images.Although improvement is needed, the VP-ER has a higher diagnostic ability for liver fibrosis than the ECV fraction in clinical practice.

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.

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.

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.

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 (p0.05). Differences in the qualitative analysis were also significant according to the chi(2) test (p0.05).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.

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.

To evaluate in detail the dose distribution during computed tomography (CT), a sheet roll CT dosimetry phantom (SRCT-P) with a radiochromic film (RF) was experimentally developed. The SRCT-P was made by rolling up a vinyl chloride sheet in a cylindrical shape to arbitrarily select the SRCT-P diameter, dose measurement position, and depth. The SRCT-P centre core consisted of a plastic hose in which a 10 mm acrylic bar with a RF was inserted. To determine the availability of the SRCT-P, the surface and centre doses (at a 5 mm radius) at each SRCT-P diameter (6-16 cm; every 2 cm) were measured. The ratios of the centre-to-surface doses (D(centre)/D(surface)) systematically increased, from 80 to 111%, for decreasing SRCT-P diameters, between 16 and 6 cm, respectively. The centre dose approached the surface dose as the SRCT-P diameter decreased. To use a RF for a CT dose measurement, further detailed research and analysis is necessary. However, this study has shown that a SRCT-P is useful and beneficial for the measurement of the dose distribution during a CT examination.

It has been reported that if the physician suspects cancer during standard mammography (craniocaudal and mediolateral oblique views), undertaking additional mammography under the physician’s order improves the diagnostic accuracy of breast cancer. The aim of our study was to determine whether additional mammography, as judged necessary by the radiographer, improves the diagnostic accuracy of breast cancer during mammography. Our Institutional Review Board approved the study. Mammography was performed at a single hospital in Osaka, Japan between June 2009 and March 2010. A total of 2636 individuals underwent mammography as workup. Of the 101 cases of cancer finally diagnosed, we examined a total of 75 cases were additional mammography had been undertaken. Three physicians certified as film readers by the Central Committee on Quality Control of Mammographic Screening in Japan, reinterpreted mammograms. The first reinterpretation involved only standard mammograms and the second included both standard and additional mammograms. Films were categorized by consensus on a five-point scale defining the degree to which cancer was suspected. To determine a category difference between standard mammograms alone, and both standard and additional mammograms, we used the Wilcoxon signed ranks test. A P value of

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. To solve these problems, a method using radiochromic film and step-shaped aluminum (Al) filters has been developed. In this study, GAFCHROMIC EBT2 dosimetry film (GAF-EBT2) and GAFCHROMIC XR TYPE-R dosimetry film (GAF-R) has been used. The measurement X-ray tube voltage was 120 kV. Two radiochromic films were scanned using a flat-bed scanner. To remove the nonuniformity error of scanned images, image J version 1.40g image analysis software has been used. HVL was evaluated using the density attenuation ratio. The HVLs and second HVLs of GAF-EBT2, GAF-R, and an IC dosimeter were compared. The HVLs (second HVLs) at 120 kV using GAF-EBT2, GAF-R, and an IC dosimeter were 4.47 mm (10.97 mm), 4.17 mm (8.61 mm), and 4.03 mm (10.35 mm) respectively, and the effective energies were 40.6 keV, 39.3 keV, and 38.7 keV, respectively. The difference ratios of the second HVLs using GAF-EBT2 (GAF-R) and an IC dosimeter were 6.0% (– 16.8%), –10.6% (–11.6%), and 5.1% (–0.2%), respectively. In addition, the difference ratio of the second HVLs at 120 kV using GAF-EBT2 and GAF-R was 27.4%. GAF-EBT2 and GAF-R proved to be capable of measuring effective energy within an error range of less than 5%. 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.

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; P0.001, McNemar test).We found that taking additional radiographs, when judged necessary by the radiographer during radiographic gastric cancer screening, improves cancer detection.

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.

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.

The efficacy of high-concentration barium sulfate has been reported from several perspectives, but not in terms of radiation exposure. This study compared the exposure doses used with high-concentration and moderate-concentration barium sulfate. The exposure dose was evaluated with an experimental method, using a gastric phantom, and with a clinical examination. In the former, the exposure dose and X-ray tube load were measured on the phantom applied with both concentrations barium sulfate. In the latter, the fluoroscopic exposure dose, the radiographic exposure dose, and their sum, the total exposure dose, were investigated in 150 subjects (112 males, 38 females) treated with both concentration barium sulfate. The results of the experimental evaluations indicated that the exposure 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 evaluations indicated that the fluoroscopic exposure dose was greater with moderate-concentration barium sulfate than with high-concentration barium sulfate (P < 0.05), but the radiographic exposure dose was quite the reverse, so the total exposure dose was the same with both concentrations barium sulfate. We conclude that high-concentration barium sulfate does not increase the radiation exposure in mass screening for gastric cancer.

Although it is considered that the half-value layer (HVL) of diagnostic X-rays is important for quality assurance (QA) and quality control (QC), the HVL is not constantly 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 instead of monitoring the ionization-chamber, a single-strip method for measuring the HVL has been evaluated.

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

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.

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 cylindrically-shaped by rolling up flexible acrylic sheets (1.1 g/cm s ). The dose distributions in the SRCTP (diameters of 6 cm [premature baby], 10 cm [neonates], and 14 cm [infants]) were evaluated. RFs were positioned every 5 mm along the radius at each SRCT-P, starting at center and ending on the surface. In this study, the absorbed dose and the dose distribution in the phantom were measured at 100 or 120 kV of the x-ray tube voltage. The other scanning parameters of the CT were 250 mA, 1.0 sec/rot, 1.25 x 8 mm slice thickness, and a 1.0 beam pitch. The mean center doses at 100 or 120 kV in 6, 10 and 14 cm of the SRCT-P were 37.0 or 64.2 mGy; 36.5 or 52.2 mGy; and 19.5 or 40.2 mGy, respectively. The mean surface doses in 100 or 120 kV at 6, 10 and 14 cm of the SRCTP were 33.9 or 57.9 mGy; 34.0 or 46.8 mGy; and 20.0 or 47.3 mGy, respectively. The absorbed dose was increased with a decrease in the phantom size. However, at 100 kV, the mean depth dose distributions at 6 or 10 cm of the SRCT-P were shown about the same value. The results indicated that the dose distribution in pediatric head CT becomes complex with patient head size and the tube voltage.

Purpose: During acquisition of rapid high resolution (HR) T2 weighted (T2W) liver magnetic resonance (MR) images using a 1.0-Tesla (T) scanner, the liver is segmented into odd and even sections that are acquired at two different times using the multi-breath-hold (MBH) strategy. Misalignment between the two breath-hold (B-H) images may result in the occurrence of a blind area and a decrease in diagnostic accuracy. Here, a functional residual capacity (FRC) B-H method was developed to overcome this problem. Material and methods: Twenty-five volunteers were enrolled. The sagittal images were reconstructed from whole liver transverse images. The misalignments of the abdominal wall were measured in the anterior-posterior (AP) direction and were compared between each two B-H phases, maximum inspiration, maximum expiration, voluntary expiration and FRC using one-way repeated measures ANOVA. Differences between groups were compared using the t-test for multi-group comparisons. In addition, qualitative analysis of misalignment was performed between VE and FRC in 52 clinical patients and the χ 2 test was performed. Results: Misalignment of the liver position using FRC was significantly smaller than the other B-H methods (p < 0.05). Significant differences between the VE B-H and FRC B-H were also observed in the qualitative analysis (p < 0.05).

Until now, the evaluations of the film reading performance of radiographers have been studied to assist diagnosis and to alleviate the shortage of radiologists. However, little has been reported on evaluating the film reading by radiographers in X-ray examination of the stomach. To investigate whether present radiographer can assist diagnosis in X-ray examination of the stomach or not, the film reading performance of untrained radiographer to detect cancer was evaluated. The institutional review board approved this retrospective study and informed consent was not required. A test set films of 100 cases (50 negative and 50 positive; mean age, 55 years; range, 33–78) in X-ray examination of the stomach were selected from 192,404 people in gastric cancer screening that was performed in Osaka, Japan between 2000 and 2002. The positive cases were defined as cancer cases, which were selected by 10 on the grade of five scales for difficulty. The negative cases were selected at random from without cancers that were confirmed by screening result at least two years later. Eleven radiographers and one radiologist scored the test set on a 5-point scale. A receiver operating characteristic (ROC) analysis was performed and area under the ROC curve (AUC) was defined as the film reading performance of radiographer or radiologist to detect cancer. The ROC analysis was performed according to the method of DeLong et al. A p value of less than 0.05 was required for significance. As a result, 5 of the 11 radiographers’ AUC (0.85–0.79) were slightly lower than the radiologist’s AUC (0.86) (p> 0.05). However, the other 6 radiographers’ AUC (0.74–0.62) were lower than the radiologist’s AUC (0.86) (p < 0.05). The highest AUC of radiographer (AUC, 0.85; sensitivity, 78%; specificity, 84%) and the AUC of radiologist (AUC, 0.86; sensitivity, 86%; specificity, 76%) were almost equal (p = 0.673). These results show a possibility that untrained radiographers with higher film reading performance to detect cancer can assist diagnosis in X-ray examination of the stomach, because some higher film reading performance of several untrained radiographers was comparable to that of a radiologist.

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.

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.

Dynamic liver MRI images have been obtained under expiration breath holding (BH). However, problems with obtaining reproducible liver positions often observed. This study investigated ways to improve the reproducibility of liver position on dynamic liver MRI.After giving informed consent, 60 patients (32 males and 28 females, ages 33-85, median age 69) were examined by liver dynamic MRI under two types of BH. The BH phases were voluntary expiration (VE) phase without any explanations and functional residual capacity (FRC) phase after careful explanation was provided. Plain images, arterial phase images, portal phase images and parenchymal phase images were obtained. For statistical evaluation of reproducibility, the area of the 2nd or 3rd images from top of the liver was measured in each phase using a threshold value of half maximum. Misregistration areas were calculated by finding the remainder of the liver area in the plain-arterial (Pl-A) phase, arterial-portal (A-Po) phase, plain-parenchymal (Pl-Pa) phase. Contingency table analysis was done due to the misregistration was occurred or not.Misregistration of liver image on the VE and the FRC of three phase types were statistical significant on the Pl-A (p0.01), on the A-Po (p0.01) and on the Pl-Pa (p0.05), respectively.The FRC phase following careful explanation of the BH provided significantly improved reproducibility of liver position on dynamic liver MRI. Therefore, precise subtraction images could be obtained for routine clinical examinations without slice matching.

During acquisition of rapid high resolution (HR) T2 weighted (T2W) liver magnetic resonance (MR) images using a 1.0-Tesla (T) scanner, the liver is segmented into odd and even sections that are acquired at two different times using the multi-breath-hold (MBH) strategy. Misalignment between the two breath-hold (B-H) images may result in the occurrence of a blind area and a decrease in diagnostic accuracy. Here, a functional residual capacity (FRC) B-H method was developed to overcome this problem.Twenty-five volunteers were enrolled. The sagittal images were reconstructed from whole liver transverse images. When the B-H phases are different, misalignment may occur in the craniocaudal and anterior-posterior (AP) directions. In this study, misalignments of the abdominal wall were measured in the AP direction. The misalignment was compared between four B-H phases, maximum inspiration (MI), maximum expiration (ME), voluntary expiration (VE) and FRC using one-way repeated measures ANOVA. Differences between groups were compared using the t-test for multi-group comparisons. In addition, qualitative analysis of misalignment was performed between VE and FRC in 52 clinical patients and the chi(2) test was performed.The misalignment widths of FRC, ME, MI and VE B-Hs were 2.7+/-3.8, 6.4+/-7.4, 9.1+/-8.4 and 6.0+/-6.7 mm, respectively. Misalignment of the liver position using FRC was significantly smaller than for the other B-H methods (p0.05). Significant differences between the VE B-H and FRC B-H were also observed in the qualitative analysis (p0.05).The liver positions obtained when using FRC B-H were significantly more reproducible than when using the other B-H methods. The FRC B-H method resulted in a reduction in the blind area and an extension of the diagnostic area to the whole liver.

To precisely measurement the high-resolution dose delivered during Computed Tomography (CT) examination, a histogram evaluation technique was performed using GAFCHROMIC-EBT (GAF-EBT). GAF-EBT strips were posted at the 12 o’clock position on a cylindrical phantom measuring 20 cm in diameter. Exposure parameters were 120 kV, 250 mA, 1.0 sec/rot, 320 mm Field of View. Slice Thickness (ST) was set to 5 mm. Helical Pitches (HPs) ranged between 0.6 – 1.4 in increments of 0.2. Calibration curves and dose profiles were generated according to the relationship between Net Pixel Value (NPV) and absorbed dose. Dose histograms were obtained based on each dose profile and analyzed using the dose evaluation methods for Single Detector (SD) CT. The calibration curve corresponded to NPV = 0.6346 x absorbed dose [cGy] and the coefficient of determination = 0.992. Maximal doses on the phantom surface were 4.39 cGy (HP = 0.6), 3.52 cGy (HP = 0.8), 3.11 cGy (HP = 1.0), 2.97 cGy (HP = 1.2), and 2.89 cGy (HP = 1.4). The modes of absorbed dose on the dose histogram were 3.7 cGy (HP = 0.6), 2.8 cGy (HP = 0.8), 2.5 cGy (HP = 1.0), 2.4 cGy (HP = 1.2), and 2.2 cGy (HP = 1.4). When HP was 0.6, 36.6 % of the dose intensity ratios were greater than 4 cGy. At other HPs, 2 – 2.9 cGy areas were frequently observed. Dose profiles using GAF-EBT was able to easily measure the dose distributions and maximal dose. Furthermore, it was able to clarify the characteristic of the dose intensity ratio of SDCT. It was also shown that the dose histogram analysis method is available for measuring the absorbed dose from Multi Detector CT as well as Single Detector CT.

In dynamic liver MRI, reproducibility of the liver position is quite poor when making subtraction images. To improve this, moving directions and positions were analyzed to determine any recognizable pattern of liver motion.

Currently, it is imperative to establishing a useful method of dose measurement for computed tomography (CT) and interventional radiology (IVR). This study investigated the usefulness of high-resolution GAFCHROMIC XR Type R Film (GAF-R film) for measurement of exposure dose for CT and IVR based on directional dependence.

Currently, acquisitions of dynamic liver MR image information have been obtained under voluntary expiration phase (VE) breath holding (BH). However, during subtraction processing of axial images, there is a problem with reproducibility of the liver position. Therefore, it is important for this study to improve the reproducibility of organ position.

PURPOSE: Dynamic liver MRI images have been obtained under expiration breath holding (BH). However, problems with obtaining reproducible liver positions often observed. This study investigated ways to improve the reproducibility of liver position on dynamic liver MRI. MATERIALS AND METHODS: After giving informed consent, 60 patients (32 males and 28 females, ages 33-85, median age 69) were examined by liver dynamic MRI under two types of BH. The BH phases were voluntary expiration (VE) phase without any explanations and functional residual capacity (FRC) phase after careful explanation was provided. Plain images, arterial phase images, portal phase images and parenchymal phase images were obtained. For statistical evaluation of reproducibility, the area of the 2nd or 3rd images from top of the liver was measured in each phase using a threshold value of half maximum. Misregistration areas were calculated by finding the remainder of the liver area in the plain-arterial (Pl-A) phase, arterial-portal (A-Po) phase, plain-parenchymal (Pl-Pa) phase. Contingency table analysis was done due to the misregistration was occurred or not. RESULTS: Misregistration of liver image on the VE and the FRC of three phase types were statistical significant on the Pl-A (p < 0.01), on the A-Po (p < 0.01) and on the Pl-Pa (p < 0.05), respectively. CONCLUSION: The FRC phase following careful explanation of the BH provided significantly improved reproducibility of liver position on dynamic liver MRI. Therefore, precise subtraction images could be obtained for routine clinical examinations without slice matching.