X-ray imaging using amorphous selenium: feasibility of a flat panel self-scanned detector for digital radiology

We investigate a concept for making a large area, flat-panel detector for digital radiology. It employs an x-ray sensitive photoconductor to convert incident x-radiation to a charge image which is then electronically read out with a large area integrated circuit. The large area integrated circuit, also called an active matrix, consists of a two-dimensional array of thin film transistors (TFTs). The potential advantages of the flat-panel detector for digital radiography include: instantaneous digital radiographs without operator intervention; compact size approaching that of a screen-film cassette and thus compatibility with existing x-ray equipment; high quantum efficiency combined with high resolution. Its potential advantages over the x-ray image intensifier (XRII)/video systems for fluoroscopy include: compactness; geometric accuracy; high resolution, and absence of veiling glare. The feasibility of the detector for digital radiology was investigated using the properties of a particular photoconductor (amorphous selenium) and active matrix array (with cadmium selenide TFTs). The results showed that it can potentially satisfy the detector design requirements for radiography (e.g., chest radiography and mammography). For fluoroscopy, the images can be obtained in real-time but the detector is not quantum noise limited below the mean exposure rate typically used in fluoroscopy. Possible improvements in x-ray sensitivity and noise performance for the application in fluoroscopy are discussed.     

Exposures to patient and personnel in computed axial tomography

Distribution of radiation exposure circumcranially for patients undergoing brain scanning with EMI computed tomographic equipment was measured using thermoluminescent dosimeters. The exposures are found to lie in the range of 1-5 R depending on position relative to tube motion. The maximum exposure of 5 R in CT scanning lies between the estimated exposure of 1.2 R for skull radiography and approximately 10 R for angiographic examination. Measured exposures are reported corresponding to locations of the patients' eyes, thyroid, chest and gonads, and at various locations in the vicinity of the unit.     

Postoperative analgesia. Specificity in the elderly]

PURPOSE: A system for the examination and measurement of the weight-bearing knee was adapted to computed radiography (CR) and to a picture archiving and communication system (PACS). The examination and measurement system was developed on examination equipment used for QUESTOR precision radiography (QPR). For an easier and more standardised localisation of bony landmarks on the screen, 4 measuring assistance tools (MATs) were developed. The aim of this study was to evaluate the usefulness of the tools developed and of image post-processing, specifically as magnification (zoom) and filtering (edge enhancement), by determining intra-observer variation in the measurement of angles and distances. MATERIAL AND METHODS: The original QPR measurement program, generating 19 angles and distances corrected for parallax and magnification, was converted and installed on a multi-modality workstation (Imtec Image 1200). A CR system (Fuji AC-2) was used for the generation of the related images and the measurements were made on the workstation. Four unilateral examinations of weight-bearing knees were undertaken. These examinations were measured twice under 5 different measurement conditions by 4 viewers. RESULTS AND CONCLUSIONS: The most important factor in reducing intra-observer variation was the ability to magnify (zoom) the images. The MATs also reduced variation. Filtering (edge enhancement), however, did not affect precision.     

The radiological investigation of lumbar spondylolysis

Lumbar spondylolysis represents a stress fracture of the pars interarticularis and occurs most commonly at the L5 level. Pars defects can be imaged with plain radiography, bone scintigraphy, computed tomography (CT) and magnetic resonance imaging (MRI). Plain radiographic projections of particular value include the coned lateral view of the lumbosacral junction, which displays the majority of defects, and the anteroposterior view with 30 degrees cranial angulation. The value of oblique radiography is unproven. Planar bone scintigraphy (PBS) is more sensitive than radiography and single photon emission computed tomography (SPECT) more sensitive and specific than PBS. Both these techniques, however, are less specific than radiography and CT. CT, when performed with a reverse gantry angle and thin sections, is the investigation of choice for identifying radiographically occult lyses. Conventional lumbar spine MRI techniques are valuable for demonstrating normality of the pars, but may be associated with a high false positive rate for the diagnosis of pars defects.     

Use of computed radiography in the study of an historic painting

The authors demonstrate the use of radiography in the investigation of an historic painting and describe the potential benefits of computed radiography compared with conventional screen-film radiography. The subject for the comparison was a 16 x 19-foot oil-on-canvas painting, Scipio Africanus Freeing Massiva, by Giovanni Battista Tiepolo. Radiographs of the painting were obtained by using a portable, industrial radiographic unit and both conventional screen-film and photostimulable phosphor plate cassettes. For this investigation, computed radiography had a number of advantages over screen-film radiography, largely due to its wider dynamic range and its capabilities for enhancing the digital images with image processing tools such as magnification, edge enhancement, colorization, and airbrushing. The ability to electronically combine images from the large painting into a single composite image file was extremely valuable, as this technique was much less cumbersome and resulted in much higher quality composite images than could be achieved with conventional radiography. An additional advantage of computed radiography includes the capability to easily archive and transmit these images in a digital format for subsequent review.     

Brain death and organ donation

Large-scale picture archiving and communication systems (PACS) have not been widely implemented in this or other countries. In almost all radiology departments film remains the medium for diagnostic interpretation and image archive. Chest imaging is the dominant screening examination performed within most imaging departments and as such, is an extremely high-volume, low-margin examination. Digital technologies are being applied to chest imaging to overcome limitations of screen-film receptors (limited latitude) and current film management systems (single-image copy). Efficient management of images and information is essential to the success of a chest imaging program. In this article we report on a digital imaging and communications in medicine (DICOM)-based centralized printing network for chest imaging. The system components and their operational characteristics are described. Our experience integrating DICOM-compliant equipment supplied by several vendors is described. We conclude that the print model supported by DICOM is adequate for cross-sectional (eg, computed tomography and magnetic resonance) imaging but is too simplistic to be generally applied to projection radiography.     

Guidelines for the selective ordering of admission chest radiography in adult obstructive airway disease

STUDY OBJECTIVE: To validate previously developed guidelines for the selective use of chest radiography in adults admitted for exacerbation of obstructive airway disease. DESIGN: Prospective, observational cohort study using criteria developed in a previous retrospective study. PARTICIPANTS: Unselected convenience sample of 128 adults with obstructive airway disease who did not respond to standard emergency department treatment and required admission. SETTING: Municipal hospital ED and inpatient medical service. INTERVENTIONS: Patients were categorized as "complicated" or "uncomplicated" according to previously developed criteria. Management was recorded as altered if the patient's physician answered the question, "Did the chest radiography alter your management of this patient?" affirmatively. RESULTS: Of 27 patients whose management was altered by the chest radiography, 26 were classified as complicated, for a sensitivity of 96% (95% confidence interval [CI], 81, 100). One of 44 admissions classified as uncomplicated had management altered by the chest radiography (negative predictive value, 98%, 95% CI, 88, 100). This chest radiography was later reread as normal. Classification as an uncomplicated patient with obstructive airway disease was strongly associated with either a normal chest radiography or a radiographic finding that was clinically unimportant (P = .0002). CONCLUSION: Patients with acute exacerbation of obstructive airway disease who are otherwise uncomplicated do not benefit from routine admission chest radiography. The use of this simple clinical strategy would safely reduce the number of chest radiographs by about one-third in this and similar patient populations, decreasing both health care costs and exposure to ionizing radiation.     

Clinical application of region-of-interest techniques to radiologic imaging

In region-of-interest (ROI) imaging, a filter with a central aperture is used to substantially reduce patient dose outside of an ROI while maintaining or improving image quality within the ROI. The benefits of ROI imaging can be realized by using standard imaging equipment. ROI imaging has been clinically applied to gastrointestinal radiology and interventional procedures. In gastrointestinal procedures, ROI fluoroscopy without image processing can be used without adversely affecting the procedure or interfering with spot radiography. ROI fluoroscopy can reduce the dose-area product by a factor of 1.7 for gastrointestinal procedures. In interventional neuroradiologic procedures, equalized display brightness is achieved with road mapping during fluoroscopy and with standard digital subtraction techniques during angiography. In interventional radiology, ROI filters can generally reduce the patient skin dose to levels below the threshold for skin effects, thus eliminating these effects across more than 85% of the field of view.     

Double contrast technique in the proximal stomach

The double contrast technique is of particular value in the proximal stomach, where one is able to detect ulcers and masses not recognized on a conventional upper gastrointestinal series. Pseudotumors which may occur in the fundus with the conventional barium technique are readily resolved. When a lesion in the proximal stomach is suspected by conventional radiography, immediate use of double contrast radiography may confirm or better delineate the lesion. Double contrast examination of the proximal stomach may thus be used as a primary or immediate secondary procedure to increase radiologic accuracy.     

Electron transfer kinetics at a biotin/avidin patterned glassy carbon electrode

STUDY DESIGN: Comparison of findings in plain radiography and conventional tomography with findings in plain radiography and magnetic resonance imaging of the upper cervical spine in consecutive patients with rheumatoid arthritis and with known or suspected abnormalities of the cervical spine. OBJECTIVES: To determine whether plain radiography and magnetic resonance imaging provide enough information to dispense with tomography in investigations of cervical spine involvement in rheumatoid arthritis. SUMMARY OF BACKGROUND DATA: With the recent advances in magnetic resonance imaging technology and the proliferation of magnetic resonance imaging techniques for specific clinical conditions. METHODS: Twenty-eight patients with rheumatoid arthritis and with known or suspected abnormalities of the cervical spine underwent a clinical neurologic examination; plain radiography, including full flexion lateral radiography; anteroposterior and lateral tomography at C1-C2; and magnetic resonance imaging at the same level in neutral position and in flexion. Two radiologists evaluated one image set consisting of plain radiography and conventional tomographic images and another image set consisting of plain radiography and magnetic resonance images, for each patient. RESULTS: Compared with conventional tomography and plain radiography, magnetic resonance imaging and plain radiography showed cystic lesions and erosions of the odontoid process and vertical atlantoaxial subluxation more often, showed anterior subluxation as often, and showed lateral atlantoaxial subluxation less often. CONCLUSION: Magnetic resonance imaging produces sufficiently distinct images of destruction of the odontoid and subluxations for it to replace conventional tomography in investigations of upper cervical spine involvement in rheumatoid arthritis.     

Must radiation dose for CT of the maxilla and mandible be higher than that for conventional panoramic radiography?

We evaluated the feasibility of performing preoperative spiral CT of the maxilla and mandible with a radiation dose similar to that used for conventional panoramic radiography. The skin entrance doses of radiation used for spiral CT (collimation, 1 mm; pitch, 2; tube voltage, 80 kV; tube current, 40 mA) and for panoramic radiography (75 kV, 8 mA, 15 seconds) were measured in one patient by using thermoluminescent dosimeter chips. Results were 0.56 +/- 0.06 mGy for CT and 0.59 +/- 0.04 mGy for radiography. Image quality was adequate for preoperative implant planning. Spiral CT of the mandible and maxilla may therefore be feasible with a radiation dose of similar magnitude as that used for conventional panoramic radiography.     

Valgus stress radiography in normal ankles

Deltoid ligament injury is thought to be rare. Signs of complete rupture of the deltoid ligament may be subtle or interpreted as another injury condition and thus are often missed acutely. No standardized method has been created to evaluate medial ligament insufficiency in acute or chronic laxity. To establish a diagnostic test for suspected isolated ruptures of the deltoid ligament, 32 subjects with no previous ankle injury underwent valgus stress radiography and nonstressed radiography of both ankles. Stress radiography in this study showed that there is a measurable but minimal range of talar tilt on valgus stress in previously uninjured ankles. This study provides the basis for diagnosis of the rare isolated rupture of the deltoid ligament of the ankle.     

Cartilaginous disorders of the chest

Cartilaginous disorders of the thorax can arise in the parenchyma, airways, chest wall, and axial skeleton. At radiography, pulmonary hamartoma is characterized by "popcorn" calcification or fat density, either of which is diagnostic. Bronchiectasis is best demonstrated at high-resolution computed tomography (CT) and has a "tramline" or "signet ring" appearance. Tracheopathia osteochondroplastica appears at CT as multiple sessile submucosal nodules with or without calcification along the cartilaginous portion of the trachea. In relapsing polychondritis, the trachea and mainstem bronchi have diffuse or focal thickening with luminal narrowing at radiography. Costochondritis of the chest wall has become more prevalent with increased intravenous drug abuse and may be demonstrated at CT as soft-tissue swelling along with underlying cartilaginous fragmentation and bone destruction. Enchondromas are expansile and may display a calcified cartilaginous matrix at radiography. In osteochondroma, the thickness of the cartilaginous cap determines the likelihood of malignant degeneration. At radiography, chondroblastomas have a round contour, sharp margins, and cortical scalloping, whereas chondrosarcomas are large masses with indistinct margins, cortical breakthrough, and soft-tissue extension. By identifying either a process affecting a cartilage-containing structure or a cartilaginous matrix within a lesion, the chest radiologist may be able to narrow the list of differential diagnostic possibilities substantially.     

Common errors in panoramic radiography of edentulous patients

PURPOSE: Instructions for patient positioning during panoramic radiography usually describe positioning dentate patients, and errors in patient positioning are commonly identified by distortion of the dentition. The purposes of this study were to identify common errors in panoramic radiography of edentulous patients, describe the image distortions that can be expected with positioning errors in edentulous patients, and review quality assurance methods that improve the diagnostic value of panoramic films. MATERIALS AND METHODS: Panoramic films were randomly selected from the inactive files of 75 edentulous patients seen at the dental school for complete denture construction. The radiographs were numbered and reviewed by a board-certified oral and maxillofacial radiologist trained to identify errors in panoramic radiography. RESULTS: Of the 75 panoramic radiographs examined, only 6 films (8.0%) were free of errors, and 67 films (89.3%) had one or more errors in patient positioning and 33 films (44.0%) had one or more technical errors. The most common positioning errors were positioning the chin too high (32 films, 41.3%) and positioning the patient too far forward (26 films, 34.7%). CONCLUSIONS: Without modification, manufacturer's instructions for positioning dentate patients during panoramic radiography may result in positioning errors on the panoramic radiographs of edentulous patients. Proper training and appropriate attention to detail while exposing and developing panoramic films are required to ensure maximum diagnostic benefits for edentulous patients.     

Rapid detection of traumatic effusion using surgeon-performed ultrasonography

BACKGROUND: In the injured patient, rapid assessment of the thorax can yield critical information for patient management and triage. OBJECTIVES: The objectives of this prospective study were (1) to determine if experienced surgeon sonographers could successfully use a focused thoracic ultrasonographic examination to detect traumatic effusion, and (2) to compare the accuracy and efficiency of ultrasonography with supine portable chest radiography. METHODS: Surgeon-sonographers performed thoracic ultrasonographic examinations on patients with blunt and penetrating torso injuries during the Advanced Trauma Life Support secondary survey. All patients also underwent portable chest radiography. Performance times for ultrasonography and chest radiography were recorded. Comparisons were made of the performance times and accuracy of both tests in detecting traumatic effusion. RESULTS: In 360 patients, there were 40 effusions, 39 of which were detected by ultrasonography and 37 of which were detected by chest radiography. The 97.5% sensitivity and 99.7% specificity observed for thoracic ultrasonography were similar to the 92.5% sensitivity and 99.7% specificity for portable chest radiography. Performance time for ultrasonography was significantly faster than that for chest radiography (1.30 +/- 0.08 vs. 14.18 +/- 0.91 minutes, p < 0.0001). CONCLUSION: Surgeons can accurately perform and interpret a focused thoracic ultrasonographic examination to detect traumatic effusion. Surgeon-performed thoracic ultrasonography is as accurate but is significantly faster than supine portable chest radiography for the detection of traumatic effusion.     

Incremental cost of department-wide implementation of a picture archiving and communication system and computed radiography

PURPOSE: To determine the incremental cash flows associated with department-wide implementation of a picture archiving and communication system (PACS) and computed radiography (CR) at a large academic medical center. MATERIALS AND METHODS: The authors determined all capital and operational costs associated with PACS implementation during an 8-year time horizon. Economic effects were identified, adjusted for time value, and used to calculate net present values (NPVs) for each section of the department of radiology and for the department as a whole. RESULTS: The chest-bone section used the most resources. Changes in cost assumptions for the chest-bone section had a dominant effect on the department-wide NPV. The base-case NPV (i.e., that determined by using the initial assumptions) was negative, indicating that additional net costs are incurred by the radiology department from PACS implementation. PACS and CR provide cost savings only when a 12-year hardware life span is assumed, when CR equipment is removed from the analysis, or when digitized long-term archives are compressed at a rate of 10:1. CONCLUSION: Full PACS-CR implementation would not provide cost savings for a large, subspecialized department. However, institutions that are committed to CR implementation (for whom CR implementation would represent a sunk cost) or institutions that are able to archive images by using image compression will experience cost savings from PACS.     

Utility of axillary views in postmastectomy patients

This study was performed to determine the utility of routine axillary radiography in postmastectomy patients. The records of 185 postmastectomy patients who had undergone axillary radiography were retrospectively reviewed. Of 499 views obtained, only 10 (2%) were reported as abnormal. Only one of the 10 patients with abnormal studies had a demonstrated recurrence that corresponded to the mammographic finding. This patient also had positive physical examination results at that time. Eight of the 185 patients developed local recurrences, four of which were in the axilla of the affected side. These four cases were all detected at physical examination; two patients underwent relatively concurrent axillary radiography. One of these two patients with abnormal physical examination results had a positive axillary view obtained in the same month. The other of these two patients with abnormal physical examination results had a negative axillary view obtained 3 months earlier. The authors conclude that routine axillary radiography is not useful in postmastectomy patients.     

Digital radiography in paediatrics: radiation dose considerations and magnitude of possible dose reduction

The purpose of this study was to evaluate the radiation doses received by paediatric patients examined using a digital radiography unit, and to compare these doses with those received from conventional screen-film systems. In this way, guidelines could be drawn up concerning the magnitude of possible dose reductions achievable using digital radiography. The study was undertaken on approximately 900 patients undergoing abdomen, chest, pelvis and skull examinations. Patients were categorized into the following age groups: 0-1 month, 1-12 months, 1-5 years, 5-10 years and 10-15 years. Approximately half were X-rayed using a Fuji computed radiography system and half using a conventional screen-film system. Entrance surface dose was calculated from the recorded exposure parameters and measured X-ray tube outputs. Dose-area product was recorded directly. Image quality was assessed clinically using criteria recommended by a working group of the Commission of the European Communities. Apart from chest examinations, it was found possible to reduce doses by about 40% on average, by using a computed radiography system instead of a 600 speed screen-film combination. There was no significant difference in the dose for chest examinations. Satisfactory image quality can therefore be achieved by using computed radiography as a 1000 speed system for abdomen, pelvis and skull examinations, and as a 600 speed system for chests. Since very few departments appear to use screen-film systems of speeds greater than 400, then, for most departments, the use of computed radiography would result in dose reductions of at least 60%, or 33% for chests.     

Panoramic radiography using an intraoral tube. Method, anatomy, radiography and dosimetry

BACKGROUND: There are two techniques giving a panoramic view of the dental arch: orthopantomography and intraoral tube panoramic radiography. The last one is not very well known because images, with a characteristic and variable deformity if compared with orthopantomography are not useful for routinary use in dentistry. The poor radiographic and pathologic anatomy knowledge of intraoral tube panoramic radiography, and the slight improvements brought to the method particularly in order to reduce the dose, partly depend on the scant attention given to the method by investigators, and partly on the dyshomogeneous anatomic sites enlargement and overlapping with consequent deformity of all of them. With intraoral tube panoramic radiography, X-ray exposition is emitted using a miniaturized cylindrical source placed inside the oral cavity and the radiographic film is in contact with the skin of the face. Based on the orientation of the collimator and the inclination of the tube major axis in the oral cavity, a central technique (exposition of either superior or inferior dental arch) and a lateral technique (simultaneous exposition of the two hemiarches of the same side) are recognized. The aim of this study is to give a significative contribution to maxillo-facial characteristic appearance and dosimetry knowledge in intraoral tube panoramic radiography. METHODS: It consists of: a) a "laboratory" part concerning the evaluation of the enlargement, deformation and visibility of different structures, obtained by positioning about fifty different markers in different maxillary and mandibular anatomic sites, and b) an in vivo dosimetry part obtained with intraoral and extraoral termoluminiscent dosimeters. An original dispositive allowed the right positioning of the film and its adherence to the screen. Deformity characteristics are analitically described and discussed in relation with the different sites. RESULTS AND CONCLUSIONS: The use of intensifying screens allowed a good reduction of dose, (mean absorbed doses ranging from 25 microGy in the intraoral sites to 1936 microGy in the extraoral sites) without reducing the image quality thanks to the device performed "ad hoc".     

Hodgkin disease and non-Hodgkin lymphoma: plain chest radiographs and chest computed tomography of thoracic involvement in previously untreated patients

PURPOSE: To provide further information about the presentation of thoracic involvement in Hodgkin disease and non-Hodgkin lymphoma and to compare chest radiography with chest CT findings. MATERIALS AND METHODS: We reviewed the chest radiographs and the CT images of 100 Hodgkin and 100 non-Hodgkin patients, all of them untreated. Our data were compared with those of literature series: the latest study comparing the different patterns of Hodgkin and non-Hodgkin disease appeared in 1976 and it compared chest radiography with conventional tomography, not with CT. RESULTS: Intrathoracic involvement (75% vs 48%) and adenopathy (74% vs 28%) were more frequent in Hodgkin than in non-Hodgkin lymphoma. Ninety-nine per cent of the patients with intrathoracic involvement (74/75) had nodal disease. Paratracheal/prevascular nodes were most frequently involved, namely in 72/74 Hodgkin (97%) and in 27/28 non-Hodgkin patients (96%). The lung parenchyma was more often involved in non-Hodgkin (24%) than in Hodgkin (8%) patients; it was associated with mediastinal/hilar adenopathy in all Hodgkin and in 10/24 (42%) non-Hodgkin cases. Parenchymal involvement was demonstrated with chest radiography in 7/8 Hodgkin (88%) and in 13/24 non-Hodgkin patients (54%). Chest radiography showed paratracheal/prevascular adenopathy more often in Hodgkin (54/72, 75%) than in non-Hodgkin (15/27, 56%) cases. Subcarinal and internal mammary adenopathy was poorly depicted with plain films, while hilar adenopathy was generally identified with both CT and chest radiography. Chest radiography usually missed posterior mediastinal and anterior diaphragmatic adenopathy. CONCLUSIONS: The differences in the presentation of Hodgkin vs non-Hodgkin disease are not sufficiently distinctive to permit radiographic differentiation of the two conditions, but some patterns are helpful. Recognizing the frequency of thoracic involvement and that of the additional CT findings in Hodgkin and non-Hodgkin patients makes a sound basis for lymphoma imaging.