Original Film Images Research Articles

Diagnostic accuracy of chest X-rays acquired using a digital camera for low-cost teleradiology

Store-and-forward telemedicine, using e-mail to send clinical data and digital images, offers a low-cost alternative for physicians in developing countries to obtain second opinions from specialists. To explore the potential usefulness of this technique, 91 chest X-ray images were photographed using a digital camera and a view box. Four independent readers (three radiologists and one pulmonologist) read two types of digital (JPEG and JPEG2000) and original film images and indicated their confidence in the presence of eight features known to be radiological indicators of tuberculosis (TB). The results were compared to a “gold standard” established by two different radiologists, and assessed using receiver operating characteristic (ROC) curve analysis. There was no statistical difference in the overall performance between the readings from the original films and both types of digital images. The size of JPEG2000 images was approximately 120KB, making this technique feasible for slow internet connections. Our preliminary results show the potential usefulness of this technique particularly for tuberculosis and lung disease, but further studies are required to refine its potential.

Computed dental radiography system versus conventional dental X-ray films for detection of simulated proximal caries

The diagnostic accuracy of intraoral images obtained with a first generation Computed Dental Radiography (CDR) digital dental imaging system is compared with the diagnostic accuracy of conventional dental x-ray film images using a receiver operating characteristics (ROC) analysis. Fifteen dentition phantoms were constructed. Each contained 4 teeth, consisting of premolar and molar teeth with 6 proximal surfaces. Mechanical defects were created randomly on the proximal surfaces and plugged with dentine powder to simulate caries. Fifteen images of each modality were rated by nine dentists in separate sessions according to their confidence in their ability to detect the simulated caries. The images examined were as follows: original CDR images, CDR images magnified 2×, CDR images magnified 4 ×, Ektaspeed Plus dental x-ray film images, and Ultraspeed dental x-ray film images, both unmagnified and magnified 2 ×. A series of ROC curves indicated the limited usefulness of magnification for the CDR system, and consistently similar success in detecting simulated proximal caries for original CDR images and original film images. The magnification of original film images did not always promote greater success than that obtained with the original film images.

Automated analysis of the American College of Radiology mammographic accreditation phantom images.

A significant metric in federal mammography quality standards is the phantom image quality assessment. The present work seeks to demonstrate that automated image analyses for American College of Radiology (ACR) mammographic accreditation phantom (MAP) images may be performed by a computer with objectivity, once a human acceptance level has been established. Twelve MAP images were generated with different x-ray techniques and digitized. Nineteen medical physicists in diagnostic roles (five of which were specially trained in mammography) viewed the original film images under similar conditions and provided individual scores for each test object (fibrils, microcalcifications, and nodules). Fourier domain template matching, used for low-level processing, combined with derivative filters, for intermediate-level processing, provided translation and rotation-independent localization of the test objects in the MAP images. The visibility classification decision was modeled by a Bayesian classifer using threshold contrast. The 50% visibility contrast threshold established by the trained observers' responses were: fibrils 1.010, microcalcifications 1.156, and nodules 1.016. Using these values as an estimate of human observer performance and given the automated localization of test objects, six images were graded with the computer algorithm. In all but one instance, the algorithm scored the images the same as the diagnostic physicists. In the case where it did not, the margin of disagreement was 10% due to the fact that the human scoring did not allow for half-visible fibrils (agreement occurred for the other test objects). The implication from this is that an operator-independent, machine-based scoring of MAP images is feasible and could be used as a tool to help eliminate the effect of observer variability within the current system, given proper, consistent digitization is performed.

Mammographic image processing using wavelet processing techniques

Mammograms with masses corresponding to biopsy-proven cancer were processed using algorithms based on the wavelet transform. Five radiologists assessed the visibility of malignant masses in ten processed mammograms as compared with the original film images. Mammograms processed using these algorithms demonstrated some improvement in feature visualization. Wavelet-based methods of image enhancement could prove to be useful in mammography and merit further study.

Digitized radiographs in skeletal trauma: a performance comparison between a digital workstation and the original film images.

To evaluate the diagnostic performance of a teleradiology system in skeletal trauma. Radiographs from 180 skeletal trauma patients were digitized (matrix, 2,000 x 2,500) and transmitted to a remote digital viewing console (1,200-line monitor). Four radiologists interpreted both the original film images and digital images. Each reader was asked to identify, locate, and characterize fractures and dislocations. Receiver operating characteristic curves were generated, and the results of the original and digitized film readings were compared. All readers performed better with the original film when interpreting fractures. Although the patterns varied between readers, all had statistically significant differences (P < .01) for the two image types. There was no statistically significant difference in performance with the two images when dislocations were diagnosed. The system tested is not a satisfactory alternative to the original radiograph for routine reading of fracture films.

35-mm film scanner as an intraoral dental radiograph digitizer: I: A quantitative evaluation

A 35-mm slide scanner digital imaging system was tested for its suitability in digitizing intraoral dental radiographic film for quantitative studies. The system (Nikon model LS-35 10AF Nikon Electronic Imaging, Nikon, Inc., Melville, N.Y.) uses a charge-coupled device linear photodiode array. The data content in the original film images was evaluated, and the system performance assessed objectively with the use of specially designed test films. Radiometric and geometric performances for the digitizing system were extracted from measurements and observations, and these were compared with published data for two other film digitizing systems (video camera DAGE MTI, Michigan City, Ind. and Barneyscan 35-mm film digitizer Barneyscan, Berkeley, Calif.). The techniques used to evaluate this system are easy and suitable for evaluation of any digitizing system. This scanner system (Nikon) was superior to previously evaluated systems in transforming and recording radiographic film densities across the range (0.3 to 2.0 optical density units) of clinically relevant optical densities. The scanner offers substantial advantage over the other digitizing systems for gray scale information from clinically important optical densities.

Evaluation of teleradiology for interpretation of intravenous urograms.

The diagnostic yield of a commercial teleradiology/picture archiving and communication system (ATT-Philips Comm View T/PACS) was evaluated for 100 urograms. A single image from each examination was digitized (2048 x 1684 x 12-bit pixels) and transmitted from a satellite hospital over a T-1 line using the T/PACS system. The video display of each digitized image was reviewed independently by four radiologists. The same four radiologists reviewed the original film images at a different time without knowledge of their T/PACS interpretation. There was no statistically significant difference in the sensitivity for clinical findings between T/PACS (86%) and film (89%). The false positive rate, however, was significantly higher with T/PACS than with film (44 versus 32 false positive findings per 100 films). We conclude that T/PACS of the type studied here demonstrates sufficient sensitivity for the detection of clinically important urographic findings in the emergency setting. A final reading of the original films is still necessary, however, to assure appropriate specificity.

A technique for anatomic feature extraction and tracking on sequential digital X-ray images

The Craniofacial Research Instrumentation Laboratory at the University of California, San Francisco, has been developing systems for the acquisition and display of biostereometric data. Stereo photographs and X-ray images of the head are used to analyze growth and treatment effects during orthodontic treatment and orthognathic surgery. Recent efforts have been directed towards automating anatomic feature location and tracking on series of time-separated cranial X-rays. Two tests were performed to evaluate the potential accuracies that could be achieved in feature tracking. In both tests, a series of cranial X-rays was converted to digital images using an array camera [Charge Injection Device (CID)] connected to a real-time video digitizer module or “frame grabber” installed in a microcomputer. The first test series consisted of a single X-ray image which was translated and rotated three times. The second series of images consisted of three actual cranial X-rays of a single subject, acquired over a period of approximately two years. A number of anatomic features were manually selected on the first image of each series. The features were automatically tracked on subsequent digital images, and their locations compared to those derived from manual digitizing of the original film images.