Despite neonatal radiosensitivity, accurate lens dose assessments in computed tomography (CT) are lacking. We assessed the neonatal head CT eye lens dose under various scanning conditions, including vertical table displacement and organ-based exposure modulation (OEM), using the GAFCHROMIC LD-V1 (LD-V1), which can measure two-dimensional dose distributions, and we evaluated the limitations of conventional dose indices. The lens dose decreased with increasing distance from the isocentre for the Canon 320. Whereas, for the Canon 80 and Siemens, the dose peaked at +25 mm and then decreased. For the OEM, the dose reduction effect decreased at 30°. The CT dose index volume remained consistent. Spatially resolved dosimetry using the LD-V1 reveals beam overlap and positioning-related dose anomalies that cannot be captured by point dosimeters or conventional indices. The LD-V1 can effectively evaluate superficial dose distributions and guide dose optimization in neonatal imaging.

This study aimed to evaluate the directional dependence of GAFCHROMIC LD-V1 (LD-V1) and assess its utility in evaluating the performance of radiation-protective eyewear. To evaluate directional dependence, a piece of LD-V1 was placed on the surface of a semicylindrical acrylic phantom and irradiated with X-rays at angles ranging from 0° to 90° with the perpendicular incidence on the orange polyester surface set to 0° and from 180° to 270° with the perpendicular incidence on the white polyester surface set to 180°. For the eyewear evaluation, six pieces of LD-V1 were placed on a head phantom, and the simulated patient phantom was irradiated for 1 h with and without radiation-protective eyewear at head orientations of 0° and 45° relative to the bed. The sensitivity at 0° was considered 100 %, and the relative sensitivity at 90° and 270° was 44.7 %. The radiation protection rates of the eyewear lenses were 58.7 % and 92.4 % for the right and left eyes, respectively, at 0°, and 80.9 % and 82.2 %, respectively, at 45°. The results demonstrate that LD-V1 is an effective method for evaluating radiation-protective eyewear performance, providing a detailed assessment of the lens radiation protection rate and dose distribution on the face. LD-V1 is suitable for dosimetry on curved surfaces, offering sufficiently accurate measurements as long as the X-ray beam is not parallel to the film surface, where sensitivity significantly drops. These findings suggest that LD-V1 is a valuable tool for practical radiation protection evaluation in clinical settings.

The GAFCHROMIC LD‐V1 radiochromic film is widely used in dosimetry because it can provide high‐resolution two‐dimensional dose distributions without processing. This study aimed to evaluate the response characteristics at different effective energies, from the low‐energy range of mammography to the high‐energy range of computed tomography. Net pixel value (NPV)‐absorbed dose calibration curves for the GAFCHROMIC LD‐V1 were generated using x‐rays with effective energies of 18, 30, 50, and 80 keV to reflect those used in different diagnostic radiographic modalities. The film response was analyzed using calibration curves at each energy level. The coefficients of determination for the calibration curves at 18, 30, 50, and 80 keV were 0.9992, 0.9997, 0.9999, and 0.9976, respectively. The pixel value change at 30 keV was the largest and most sensitive, while the smallest change in pixel value and lowest sensitivity were noted at 18 keV. Because the energy dependence of the GAFCHROMIC LD‐V1 is significant below 18 keV and above 80 keV, it is necessary to establish an appropriate NPV‐absorbed dose calibration curve for energies below 18 keV and consider the possibility of underestimating the dose at energies above 80 keV.

Gafchromic LD-V1 (LD-V1) is a highly sensitive radiochromic film used as a radiation measurement technique that can be applied to the surface of an object because of its flexibility. However, if radiation is incident on the film from an angle other than perpendicular, the film’s sensitivity may change depending on the angle of incidence. In this study, we investigated the directional dependence of LD-V1 on the surface of an acrylic phantom. The relative sensitivity at the angle of perpendicular incidence of X-rays on the film was 54.5%, while the relative sensitivity at other angles exceeded 90%. The LD-V1 can perform measurements at angles other than perpendicular X-ray incidence.

Purpose: Radiochromic film is used for quality assurance and quality control of X-ray equipment in the diagnostic radiology. In addition, three-dimensional dose distribution of computed tomography (CT) is measured. To correct the nonuniformity and uncertainty of radiochromic films for dose measurement of CT, the films are preirradiated ultraviolet (UV)-A rays. There is a difference in the UV protection strength of radiochromic films. A concern exists about the effects of the UV-A irradiation intensity. We thus irradiated with UV-A rays from the backsides of the films to assess if backside irradiation was possible. Materials and Methods: Gafchromic XR-QA2 and RTQA2 were used in this study. The UV-A rays were simultaneously irradiated on the front and backsides of each film for 12 h. The yellow layer of each film was scanned and imaged. The average pixel values ± standard deviations (SDs) were compared. In the statistical analysis, a paired t-test was performed. To compare, the active-layer densities engendered by the UV-A rays. Calibration curve was created with 48 h of preirradiation of UV-A. Results: The mean pixel values ± SD for Gafchromic XR-QA2 on the front and backsides were 130.776 ± 0.812 and 81.015 ± 1.128, respectively. On the other hand, the mean pixel values ± SD for Gafchromic RTQA2 on the front and backsides were 62.299 ± 1.077 and 133.761 ± 1.365, respectively. The statistical results of the paired t-test were significantly different (P < 0.01) between both films. Fitting equation of the calibration curve is shown below. y = -390.47 ± 200 + (443.45 ± 10x80).5068 ± 0.0434. Conclusion: Based on the relationship between the sensitivity of the active layer to UV-A rays and the strength of UV protection on the surface, we concluded that backside irradiation is recommended for Gafchromic XR-QA2, and frontside irradiation is recommended for Gafchromic RTQA2.

In recent years, radiochromic films have begun to be used for dosimetry in mammography; however, the most sensitive GAFCHROMIC XR-QA2 (XR-QA2) film is no longer available owing to its discontinuation. In this study, we evaluated the sensitivity characteristics of GAFCHROMIC LD-V1 (LD-V1) as an alternative to XR-QA2 in the field of mammography, at a low dose and low energy. Our results show that the average ratio of the concentration change of LD-V1 divided by the concentration change of XR-QA2 at each absorbed dose was 53.7%, indicating the sensitivity of LD-V1 to be approximately half of XR-QA2. In addition, the linearity of the concentration change is sufficient even within a dose range of 0.59-14.52 mGy, which is lower than the manufacturer's recommended dose range. Therefore, the LD-V1 is capable of accurate dose assessment even with a low dose and the low level of energy used in mammography.

Abstract During a single scan using computed tomography, an X‐ray tube orbits along a 360°‐circular path around the patient. A scan obtained using the half‐cylindrical type phantoms with a radiochromic film sandwiched in between reveals a pixel value map illustrating the two‐dimensional (2D) dose distribution. A three‐dimensional (3D) dose distribution can be obtained with a 360° rotation of the 2D dose map. This study evaluates the concept and methodology of creating a 3D dose map to develop a phantom with a radiochromic film for obtaining the 3D dose distribution. The coronal and axial plane dose distributions were also evaluated. A single scan computed tomography image obtained using a half‐cylindrical type of acrylic phantom with a sandwiched radiochromic film was studied. The diameters of the phantoms were 10 and 16 cm, and their lengths were 30 cm. A 2D image of the XR‐QA2 film was obtained using an image scanner and image processing software. A red channel image was used to obtain the 3D dose distribution using a computing platform. A pseudo color was applied to the red channel image from which cross‐sectional color images were obtained. Half of the cross‐sectional pixel data were rotated by 360° to generate the data for each axial plane. The image created was saved, and a 3D pixel value map was constructed. The dose measurement procedure for the 3D dose distribution was developed using half‐cylindrical acrylic phantoms with a radiochromic film.

Mammography is one of the most effective diagnostic methods for the early detection of breast cancer; however, it poses the risk of radiation exposure. To date, mammography dosimetry has been performed according to the mean glandular dose; however, the actual exposure in the breast has not been assessed. Here, we have measured dose distributions and depth doses using both radiochromic films and mammographic phantoms, and a three-dimensional intra-mammary dose assessment was conducted. The absorbed dose distribution at the surface was markedly higher on the chest wall side but lower on the nipple side. The absorbed doses in the depth direction exponentially decreased. The glandular tissue near the surface may be irradiated with an absorbed dose of 7.0 mGy or higher. Since LD-V1 could be placed inside the phantom, the absorbed dose inside the breast could also be evaluated in three dimensions.

Traditionally, large bowel obstruction (LBO) can be due to a neoplasm, most often colorectal cancer. Also, fecal impaction (FI) is a common disease, which occurs in a variety of ages and is significantly increased in the elderly. This case report is of LBO caused by FI, in which ultrasonography (US) proved to be useful for diagnosis and follow-up. A 60-year-old female had abdominal pain after taking a laxative as part of bowel preparation for colonoscopy. The US diagnostic findings were a marked dilation of the bowel, due to watery stool, in the ascending colon, and a clear FI, in the descending colon. Computed tomography showed similar findings to the US. There was a large amount of defecation after treatment and US demonstrated an improvement in the ileus. Ten days after admission, a colonoscopy revealed no stenosis or tumor, as a cause for the ileus.

X-ray CT dose measurement has mainly been performed using an ionization chamber dosimeter. Therefore, the dose distribution has not been sufficiently studied. We investigated the importance of evaluating the two or three-dimensional dose distributions for X-ray computed tomography (CT). To confirm this purpose, we investigated the effects of phantom size and exposure parameters on the phantom diameter. We performed 12 scans using XR-QA2 film and cylindrical acrylic phantoms of two lengths. The tube current and slice thicknesses were varied as exposure parameters. The dose distribution of the primary and scattered radiation was visu-alised using ImageJ. The results were evaluated using the profile curves, three-dimensional surface plots, and subtrac-tion dose images. We observed changes in the dose distributions for scans with and without phantoms. However, no significant differ-ence in the dose distribution was observed with changes in the lengths of the phantom. To visualise the dose distribution, three-dimensional surface plots and subtraction images were found helpful. We must confirm that the dose distribution does not change for phantoms with multiple diameters in future studies. For using a clinical application, accurate quantitative assessment of dose distribution requires improved accuracy of the calibration curve.

In this paper, we propose a novel radiochromic film (RCF)-based computed tomography (CT) dosimetry method, which is different from the method based on CT dose index. RCF dosimetry using Gafchromic QA2 films was performed using two lengths of film-folding phantoms. The phantom was exposed to X-ray CT through a single scan, while the RCF was sandwiched between the phantoms. We analysed the dose profile curve in two directions to investigate the dose distribution. We observed a difference in the dose distribution as the phantom size changed. Our results contradict with the results of previous studies such as Monte Carlo simulation or direct measurement. The ability to visually evaluate 2D dose distributions is an advantage of RCF dosimetry over other methods. This research investigated the ability of 2D X-ray CT dose evaluation using RCF and film-folding phantom.

This study developed a phantom with a shape similar to that of the breast and use GAFCHROMIC films that can be placed inside the phantom to measure the detailed breast dose distribution in mammography. GAFCHROMIC EBT3 was placed on the block cube breast phantom and irradiated with a mammography device to measure the absorbed dose distribution inside the phantom in the horizontal and depth directions. The dose distribution in the horizontal plane was the highest in the centre on the chest wall side, and it decreased in a fan shape. Along the depth of the phantom, the doses absorbed across the entire cross-section were 16.15 mGy at the surface and 7.51, 3.25 and 1.68 mGy at depths of 10, 20 and 30 mm, respectively. Compared with the mean glandular dose, the proposed method can measure breast dose distributions in greater detail and is applicable to various breast shapes.

The purpose of this study is to develop a method for use at extremely low-dose ranges and to decrease the uncertainty outside the recommended range of Gafchromic RTQA2 (RTQA2). By this method, the CT dose including the scattered radiation region can be grasped. The base density was increased by ultraviolet (UV)-ray preirradiation. RTQA2 was irradiated with UV-A rays for 26 and 40 h. Subsequently, RTQA2 was exposed to 2, 4, 6, 8, 10, 25, 50, 75, 100, 150, 200 and 250 mGy X-rays using a segmentation method. Calibration curves with and without UV-A irradiation were compared. The calibration curve with 40-h UV-A ray irradiation was the most linear, and a steeper slope area was not observed. The uncertainty in the calibration curve was reduced (p < 0.05). UV-A ray irradiation is an effective method for treating RTQA2; the accuracy in the extremely low-dose range of RTQA2 was improved.

Knowledge of the effective energy of 320-multidetector computed tomography (CT) is important for quality assurance and quality control. Evaluation in two dimensions is necessary because the effective energy varies depending on the shape of the wedge filter located in the CT device. The purpose of this study was to measure the two-dimensional effective energy distribution of the CT using GAFCHROMIC EBT3 (EBT3), which has a weak energy dependence. The exposure parameters of the 320-multidetector CT were 120 kV, 500 mA, and 5.0 s, and the X-ray tube was stopped at the 0 o’clock position. To avoid scattered radiation, the distance between the EBT3 and other scatterers was set to 200 mm or more. The Al filter thickness was increased from 2 to 20 mm. The irradiated area was divided into 54 compartments, and the density attenuation ratio was measured. The half-value layers (HVLs) were determined using the density attenuation ratios. The effective energies were obtained from the HVLs, and the two-dimensional effective energy distribution was evaluated. Because the thickness of the wedge filter in the longitudinal direction (parallel to the bed) remained unchanged, the variation in the effective energy was negligible in this direction. On the other hand, in the lateral direction (perpendicular to the bed), because the wedge filter gradually thickened from the center to the side, the effective energy from the center to the side increased. The two-dimensional effective energy distribution of the CT could thus be measured using EBT3.

This study assessed the accuracy of shape and size representation of spherical objects on full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT) images. Six 5-mm-thick polymethylmethacrylate slabs were positioned on the breast support table with 9 aluminum spherical objects of 30 (± 0.1) mm diameters between the first and second slabs. X-ray imaging was performed using FFDM and DBT (angular range 15°–40°, with correction of magnification), and repeated with the objects placed between the third and fourth slabs, and subsequently between the fifth and sixth slabs. The aspect ratio of the spherical objects and longer diameter were measured to evaluate the shape and size, respectively. A Steel-Dwass test was performed for comparative analysis. A P value <0.05 was considered significant. No significant differences in the aspect ratio of the spherical objects imaged using FFDM, DBT15°, or DBT40° images were observed (overall median: 1.02, overall range: 1.00–1.06). The longer diameter on the FFDM was increasingly magnified (median, range) with increasing distances of 20 mm (32.5, 31.8–33.5 mm) and 40 mm (33.6, 32.9–34.7 mm) between the breast support table and object center. However, in the case of DBT, the longer diameter was approximately the same as that of the actual object (overall, 30.4, 30.0–31.7 mm). At each height, the longer diameter was significantly different between the FFDM and DBT15° images and between the FFDM and DBT40° images (all P = 0.001), with no significant difference in that between the DBT15° and DBT40° images. The size on the FFDM images was magnified as compared to the size of the actual objects, and that on the DBT images was approximately the same as that of the actual objects. Thus, preoperative tumor size determination using FFDM images should be avoided.

Radiochromic films (RFs) have been developed for the measurement of the absorbed dose of low-energy photons. RFs are self-developing and radiation sensitive, and the amount of darkening is proportional to the absorbed dose. RFs are easy to handle due to their insensitivity to interior room light. However, the precision of the measurement has been questioned because of the change in density caused by the scan timing of the image acquisition using a flat-bed scanner. In this study, the density change of a flat-bed scanner was investigated using the temporal and the repetition scans. To obtain the image density, Gafchromic XR-QA2 films (XR-QA2s) were irradiated at 0 and 20 mGy (air-kerma) using 75 kVp (30 keV). The XR-QA2s were scanned every hour (0–6 h) from power activation to investigate the temporal light source change of a flat-bed scanner (EPSON ES-10000G). In addition, ten consecutive scans were performed every hour. The scan parameters were RGB (48-bit) mode, 100 dpi, and reflection mode. Image data of the XR-QA2s were divided into R, G, and B modes, and the R (16-bit) mode was used. The temporal light source change after power activation was small. However, in ten consecutive scans, the density of the first scan was the highest. The densities decreased with more scans. This result indicated that the precision of the dose measurement has about a 3% error due to the repeated scans. To obtain an accurate dose measurement, the image data obtained under the same conditions, such as the same time from power activation or same number of consecutive scans, must be used.

The popularization of 3-Tesla magnetic resonance imaging (MRI) has improved the quality of images and shortened typical examination times. However, a side effect of this is increased exposure to radio frequency (RF) radiation. The amount of RF exposure can be controlled using a technique called variable refocus flip angle (vRFA). Controlling vRFA is also an important for improving the signal to noise ratio (SNR) and for reducing blurring on MRI images. In this study, we examined the influence of controlling vRFA and echo train length (ETL) on SNR. To do this, we used a device that can arbitrarily control three angles—the fifth RFA, the RFA centered in k-space, and the final RFA. Using a phantom, T1 and T2 values were made equal to gray- and white-matter, respectively. The repetition time was 5000 ms and echo time 90 ms. By setting the fifth RFA to 40° and using an ETL of 11–15, the signal shifted smoothly to a pseudo steady-state (PSS), and a stable signal was obtained. Further, we were able to suppress blurring by gently changing the k-space-centered RFA. In the final echo, we were able to maintain PSS by increasing the final RFA up to 180°, resulting in a high SNR. Results of this study showed the changes reduced RF exposure. Using an ETL of 30, blurring was reduced, though RFA control was similar to that used with ETLs of 11–15; although slightly higher RF exposure was required to obtain a high SNR, the fifth RFA was required to be 60°–90°.

Purpose: The purpose of this study is to build a system for effective dose display immediately after the gastric cancer X-ray screening. Materials and Methods: The regression equation of effective dose and dose area product (DAP) was introduced from the data of 500 persons including DAP and effective dose calculated using program for X-ray Monte Carlo. Results: The effective dose was 5.39 mSv of median, 1.18 mSv of minimum, and 38.38 mSv of maximum. The regression equation was Y=0.354+0.0003772X (Y: effective dose, mSv, X: DAP, mGy cm2). Using the regression equation, the effective dose can be estimated from DAP and displayed just after the individual screening. Conclusions: "Effective dose display system" was constructed to display effective dose immediately after gastric cancer X-ray screening. This system is on the way to be reformed by improving the regression equation on larger data.