Hideo Yamazaki

Diagnostic validity of high-density barium sulfate in gastric cancer screening: follow-up of screenees by record linkage with the Osaka Cancer Registry.

Background 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. Methods 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. Results 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. Conclusions Screening tests using high- and moderate-density barium sulfate had similar validity, as determined by sensitivity, specificity, and ROC curve analysis.

Radiation dose in mass screening for gastric cancer with high-concentration barium sulfate compared with moderate-concentration barium sulfate.

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.

Improved detection of gastric cancer during screening by additional radiographs as judged necessary by the radiographer

PurposeThe aim of this study was to determine whether additional radiographs, as judged necessary by the radiographer, improves cancer detection during gastric cancer screening.Materials and methodsWe 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.ResultsCompared 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).ConclusionWe found that taking additional radiographs, when judged necessary by the radiographer during radiographic gastric cancer screening, improves cancer detection.

Film-reading ability of radiographers in detecting gastric cancer during screening using X-ray examination

PurposeThe aim of this study was to evaluate the film-reading ability of radiographers in detecting gastric cancer during screening X-ray examinations.Materials and methodsA 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.ResultsNo 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).ConclusionFilm-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.

Exposure Dose Reduction of Lead Acrylic Filter for Gastric Cancer Mass Screening

It is important to reduce x-ray exposure in subjects who undergo mass screening for gastric cancer. We constructed three types of lead acrylic filters and evaluated their ability to reduce exposure. X-ray tube load increase, dose area reduction, density of gastric phantom images and lead acrylic filter shadows were evaluated. Three different thicknesses of lead acrylic filters were examined, one was a regular thickness, another was half the thickness, and the other was twofold the thickness. Objectivization, reduction rate of exposure, x-ray tube load increase, and the density of each gastric phantom image was taken with or without the three types of lead acrylic filters. The filter shadow in the image of the gastric phantoms using the three types of lead acrylic filters were evaluated with 4 levels. Dose area reductions using the three types of filters were 6.03%, 10.92%, and 13.64%, for the half thickness, regular thickness, and twofold thickness, respectively (p 0.05). There was no significant difference between the density of gastric phantom images with or without the filters (p>0.05). The lead acrylic filter shadows were significantly difference among the three types filters (p<0.05). We conclude that the use of lead acrylic filters is effective for the reduction of exposure in screening for gastric cancer. A lead acrylic filter of twofold thickness is most effective for the reduction of exposure.

The usefulness of film reading to detect cancer by untrained radiographer in X-ray examination of the stomach

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.

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.