Gastrointestinal examinations with digital radiography

[Image quality and detection performance of a direct digital radiography system]

The physical characteristics of a direct amorphous Selenium (a-Se) digital fluoroscopy and radiography system were investigated. Pre-sampled modulation transfer functions (MTF) were measured using a slit method. Noise power spectra were determined for different input exposures by fast Fourier transform of uniformly exposed samples. The MTFs of direct digital radiography systems showed significantly higher values than those of indirect digital radiography and screen-film systems. The direct digital radiography systems showed higher noise levels compared with those of indirect systems under roughly the same exposure conditions. Contrast-detail analysis was performed to compare detection by direct digital radiography systems with that of the screen-film (FUJI HG-M2/UR2) systems. The average contrast-detail curves of digital and film images were obtained from the results of observation. Image quality figures (IQF) were also calculated from the individual observer performance tests. The results indicated that digital contrast-detail curves and IQF are, on average, are equal those of the screen-film system.

Gastric cancer screening of a high-risk population in Japan using serum pepsinogen and barium digital radiography

With the aim of developing more efficient gastric cancer screening programs for use in Japan, we studied a new screening program that combines serum pepsinogen (PG) testing and barium digital radiography (DR). A total of 17 647 middle-aged male subjects underwent workplace screening over a 7-year period using a combination of PG testing and DR. This program's effectiveness, as well as other characteristics of the program, was analyzed. Forty-nine cases of gastric cancer were detected (comprising 88% early cancer cases). The detection rate was 0.28%, and the positive predictive value was 0.85%. The PG test detected 63.3% of cases, DR detected 69.4% of cases, and both tests were positive in 32.7% of cancer cases. The two methods were almost equally effective, and were considerably more effective than conventional screening using photofluorography. Each screening method detected a distinct gastric cancer subgroup; the PG test efficiently detected asymptomatic small early cancer with intestinal type histology, while DR was efficient at detecting cancers with depressed or ulcerated morphology and diffuse type histology. The cost for the detection of a single cancer was much less than that for conventional screening. In fact, it is possible to further reduce the cost of detecting a single cancer to a cost comparable to that of surgically resecting a single gastric cancer. Thus, it is probable that a highly efficient gastric cancer screening system can be implemented by combining the two screening methods. Such a screening program would be beneficial in a population at high risk for gastric cancer.

Diagnosis of gastric cancers: comparison of conventional radiography and digital radiography with a 4 million-pixel charge-coupled device

PURPOSE

To evaluate the differences in accuracy and observer performance at conventional radiography and at digital radiography with a 4 million-pixel charge-coupled device (CCD) for the diagnosis of gastric cancers.

MATERIALS AND METHODS

A prospective study was performed of 225 patients with suspected gastric cancer who were referred to our hospital from January 1997 through February 1997. One hundred twelve patients were examined at conventional radiography and 113 were examined at digital radiography, and 24 and 27 patients had gastric cancer, respectively. Six radiologists interpreted the images, with attention to tumor findings. They were blinded to the clinical details, and their interpretations were rated against those of three other radiologists who examined the patients and who were aware of the clinical information such as endoscopic features and/or histopathologic findings in biopsy specimens. Receiver operating characteristic (ROC) analysis was used to compare the differences in observer performance for the diagnosis of gastric cancers at conventional radiography and at digital radiography.

RESULTS

The overall sensitivity was 64.6% at conventional radiography versus 75.3% at digital radiography (P =. 287); specificities were 84.5% and 90.5%, respectively (P =.011); and the positive predictive values were 53.1% and 71.3%, respectively (P =.036). ROC analysis clearly showed higher diagnostic performance at digital radiography than at conventional radiography.

CONCLUSION

The data demonstrate the high diagnostic value of digital radiography with a 4 million-pixel CCD for gastric cancers. The technique has considerable potential as an alternative to conventional gastrointestinal radiography.

Normal oesophageal transit time on digital radiography

OBJECTIVE

To develop a simple radiological technique for measuring normal oesophageal transit time.

DESIGN

72 patients with no oesophageal or gastrointestinal complaints underwent manometry and radiological oesophageal transit time (ROTT). ROTT was perfomed using 2 ml of fluid barium on a digital X-ray machine. Digital image acquisition started with the beginning of swallowing using 1 frame/s for 15 s. These images were printed on a single film. The effect of ageing on ROTT was also assessed.

RESULTS

ROTT had a mean value of 10.08 s. ROTT was divided into three segments: proximal-to-left-main-bronchus; retrocardiac; and inferior oesophageal sphincter segments. The mean transit time across these segments was 2.84, 3.07, and 4.15 s, respectively. ROTT in patients over 40 years was longer than in patients under 40 years.

CONCLUSION

ROTT is a physiological, rapid, non-invasive, and reproducible technique for measuring the normal oesophageal transsit time, without discomfort to patients.

Value of digital fluoroscopy for the diagnosis of pneumatosis coli

Two cases are presented of benign pneumatosis coli diagnosed on digital fluoroscopic barium enema examinations, in which the gas-filled cysts in the colonic wall were only recognized by postprocessing of the images (i.e. increasing the brightness and contrast settings) at the computer workstation. When digital barium enemas are performed, we therefore recommend image postprocessing to evaluate polypoid lesions in order to differentiate pneumatosis coli from true colonic neoplasms.

Physical and clinical evaluation of a 2,048 x 2,048-matrix image intensifier TV digital imaging system in bone radiography

RATIONALE AND OBJECTIVES

To evaluate the potential utility of a 2,048 x 2,048-matrix image intensifier television digital radiography (DR) system versus a conventional screen-film (S-F) system for bone radiography.

METHODS

Basic imaging properties were evaluated including resolution properties, Wiener spectra, and detectabilities of low-contrast signals. DR images were obtained with the same exposure (iso-dose) or one-third the exposure (low-dose) used with the S-F system. The visibility of pathologic details of metastatic disease on bone radiographs of 27 patients was evaluated subjectively by six radiologists.

RESULTS

Resolution properties of the DR system were slightly superior to those of the S-F system at low-frequency range, but the S-F system showed considerably higher resolution properties at the high-frequency range. The noise levels for iso-dose DR were slightly greater than those for S-F imaging at low spatial frequency; however, low-dose digital radiographs showed higher noise levels. Visibility of details of diagnostic features on bone radiographs was similar with both systems, but the low-dose digital radiographs were slightly inferior.

CONCLUSION

High-resolution image intensifier television DR systems may be clinically useful for bone radiography.

Comparison of film-screen combination and digital fluorography in gastrointestinal barium examinations in a clinical setting

OBJECTIVE

Digital fluoroscopy systems have been developed for gastrointestinal barium studies. We compare the performance of a commercially available digital fluoroscopy system with conventional film-screen combinations in gastrointestinal barium studies.

METHODS

Two consecutive groups of outpatients underwent diagnostic barium examinations of esophagus, stomach, or colon using either a film-screen technique (n = 32) or a digital fluoroscopy system with an 8-bit gray scale (n = 31). A standardized biphasic protocol was employed in all patients by the same set of investigators and scored subjectively for contrast performance in single-contrast and double-contrast mode and for spatial resolution.

RESULTS

For the whole group there were no significant differences between the two techniques. In the subgroup of esophagus studies, digital fluoroscopy performed better during the full-column part of the examination. In the subgroup of colon studies, the film-screen technique performed better during the double-contrast part of the examination. To reach sufficient spatial resolution with the digital system (884(2) matrix), the smallest input screen had to be used (23 cm), resulting in a higher number of exposures than with the film-screen combination (P = 0.006). The average amount of film used was not significantly different.

CONCLUSION

In a clinical setting the contrast performance and spatial resolution of digital fluoroscopy systems can be comparable with conventional film-screen combinations.

Clinical usefulness of digital radiography in the gastrointestinal tract: efficacy of magnification method

We assessed the performance capabilities of image intensifier digital radiography (II DR) in the detection of minute lesions in patients with early stomach cancer. The DR system was a prototype II DR system developed by Toshiba Corp (Tokyo, Japan). This system was able to acquire images with a 1,024- x 1,024-pixel matrix and 12 bits. Radiography was performed using a 0.3-mm tube focus. For the detectability of early stomach cancer, DR was judged to be superior to conventional screen-film system (CFSS) (DR superior, 55.7%; CFSS superior, 22.6%). In depicting the characteristics of the surface of the lesion, DR was also judged to be superior to CFSS (DR superior, 56.6%; CFSS superior, 17.0%). The II DR system used in this study was able to achieve almost the same spatial resolution as conventional radiography using the magnification method. It was also able to visualize subtle findings of early gastric cancer more clearly by the use of postprocessing. In addition, II DR has the advantages of reducing the patient exposure dose and permitting the acquisition of real-time images.

Gastrointestinal examinations with a 2,048- x 2,048-pixel image intensifier television digital radiography system

The clinical usefulness of a 2,048- x 2,048-pixel matrix image intensifier television digital radiography system was evaluated. Screen-film and digital images (with and without postprocessing) of the upper and lower gastrointestinal (GI) tract were used for clinical evaluation. For the upper GI tract, digital images processed with unsharp mask techniques were comparable in quality to screen-film images before and after upgrading the system. For the lower GI tract, screen-film images were better than digital images, except for those processed with a 2,048- x 2,048-line monitor was comparable to a screen-film system.

Double-contrast barium enema study with computed radiography: assessment in detection of colorectal polyps

Feasibility and diagnostic performance of digital radiography in gastrointestinal imaging have not been fully investigated. We performed double-contrast barium enema study with computed radiography (CR-DCBE) on a routine basis, and the efficacy of this system for detection of colorectal polyps was investigated. The files of 76 patients, who had undergone both CR-DCBE and colonoscopy, were reviewed by two observers who were blinded to the colonoscopic findings. The radiation dose of CR-DCBE was reduced to 50% of conventional film-screen system. By using colonoscopic findings as a reference, the sensitivity and positive predictive value for colorectal polyps were 66% to 71% and 32% to 41%, respectively. There was no significant interobserver difference. The use of postprocessing with gray-scale reversal and edge enhancement did not significantly improve the results. The sensitivity for polyps smaller than 1 cm was comparable with published data of conventional film-screen systems. Our preliminary results show that CR-DCBE has an acceptable sensitivity for detection of colorectal polyps. It is suggested that the use of CR is a promising approach to digital gastrointestinal radiography.

Hospital-wide PACS with a digital image intensifier TV system

Tokyo Hitachi Hospital, Hitachi Ltd., has used a hospital-wide PACS for over 1 year. The system runs a 100 Mb/s optical fiber network over the whole hospital including wards and outpatient clinic rooms, with 11 image workstations. The network links digital imaging modalities such as X-CT, MRI, computed radiography (CR) and digital radiography (DR) with a 2048 x 2048 (2k x 2k) matrix image intensifier television (I.I.-TV) system. These modalities generate about 200 images/day. The system has managed over 300,000 images of about 8000 patients so far. Although being still under improvement, the system has really been used for routine work. The hospital-wide PACS of a small hospital has been proved to be very useful for both image diagnosis and image management.