T. Gotanda

Reducing Non-uniformity Error of Radiochromic Film in the Diagnostic Range by Ultraviolet Exposure: Preliminary Study

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.

Measurement of half-value layer for QA and QC: Simple method using radiochromic film density

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.

Dose Distribution in Pediatric CT Abdominal Examination: Phantom Study

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.

High Concentration Barium Sulfate Used in Gastric Cancer Screening ¿ Viscosity Change Dependent on the Volume of Artificial Gastric Juice-

High concentration barium sulfate has been de- veloped and used in mass screening for gastric cancer. Howev- er, high concentration barium sulfate flows out from the sto- mach faster than moderate concentration one, which often interferes with diagnosis. The speed of flow is seemed to de- pend on the viscosity of barium sulfate. Previously, the authors reported viscosity changes of high concentration barium sul- fate with pH and temperature changes. In this study, it is ex- amined that the viscosity of barium sulfate also changes with artificial gastric juice volume. The results indicate that the viscosity of high concentration barium sulfate is more stable than that of moderate concentration one and the image of gastric phantom with high concentration barium sulfate is evaluated to be better than that with moderate concentration one. The study on characteristics of barium sulfate may im- prove radiography technology in mass screening for gastric cancer.

Half-Value Layer Measurement for Effective Energy, Using Radiochromic Film and Step-Shaped Aluminum Filter

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.

Do additional x-rays taken by a radiographer during x-ray screening for gastric cancer improve detection?

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.

The availability of diffusion-weighted imaging with the fluid-attenuated inversion recovery method (FLAIR-DWI) with a low-performance MR unit in chronic ischemia disease

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.

High Concentration Barium Sulfate Used in Gastric Cancer Screening

High concentration barium sulfate has been developed and used in mass screening for gastric cancer. However, high concentration barium sulfate flows out from the stomach faster than moderate concentration one, which often interferes with diagnosis. The speed of flow is seemed to depend on the viscosity of barium sulfate. Previously, the authors reported viscosity changes of high concentration barium sulfate with pH and temperature changes. In this study, it is examined that the viscosity of barium sulfate also changes with artificial gastric juice volume. The results indicate that the viscosity of high concentration barium sulfate is more stable than that of moderate concentration one and the image of gastric phantom with high concentration barium sulfate is evaluated to be better than that with moderate concentration one. The study on characteristics of barium sulfate may improve radiography technology in mass screening for gastric cancer.

Studies on Viscosity, pH and Temperature of High Concentration Barium Sulfate in Mass Screening for Gastric Cancer — Particle size distribution —

Recently, mass screening for gastric cancer has been popularized in Japan. In the screening, gastric radiography is carried out using a contrast medium, usually barium sulfate. Recently, a high concentration barium sulfate has been developed and is currently used in several medical facilities. However, high concentration barium sulfate flows out of the stomach faster than a solution of lower concentration used in the past, which interferes with the diagnosis. The flow rate is dependent on the viscosity of barium sulfate, which changes based on gastric pH and temperature. In this study, the viscosity changes of barium sulfate induced by pH and temperature changes were examined. Two types of high concentration barium sulfate, 185B barium and 200C barium, and one type of moderate concentration barium sulfate, 145A barium, were used in this study. The radiographs of gastric phantoms applied with the three types of barium sulfate were also tested under several different pH and temperature conditions. Furthermore, we analyzed the particle size distribution of the three types of barium sulfate. The results indicated that 185B barium is the best among three types tested for gastric radiography. This study of characteristics of barium sulfate may improve radiography technology in mass screenings for gastric cancer.

Study on the measurement of ejection fraction (EF) using left ventriculogram

A standard to measure ejection fraction (EF) is the method using left ventriculogram. Recently, many radiological technologists (RTs) have opportunities to measure EF. In this study, six RTs engaging in angiocardiography examination, i.e. two experts, two experienced and two inexperienced RTs, measured EF using left ventriculograms of 72 cases (Female. 15, Mail. 57, Ages were varied from 31 to 82.). The measured values were examined on correlation and further approved by repeated measure ANOVA and T-test for multigroup. Correlations between measured values by expert RT and measured values by other RTs were observed, but there were differences among the measured values of experts, experienced and inexperienced RTs. It is considered that these results offer useful guidance for RTs to improve precision.