Large Image Intensifier Research Articles

Effect of Introduction of Mini C-arm Image Intensifier in Orthopaedic Theatre

Image intensifier screening is commonly used in orthopaedic theatres. There has been concern regarding the cumulative radiation dose to surgeons and theatre personnel. The mini C-arm intensifier has been reported to scatter less radiation and have a reduced radiation dose to patients and theatre staff. A 2-month prospective survey of usage of radiographer-operated large intensifier and surgeon-operated mini C-arm image intensifier in a district general hospital orthopaedic theatre department. A total of 153 cases required image intensifier screening - 63% used the large intensifier and 37% the mini C-arm intensifier. There were difficulties with equipment with the large intensifier in 16% of cases. There were delays in 11% of cases using the large intensifier. The total radiographer attendance time was 123 h. For the mini C-arm intensifier, there were no equipment difficulties or delays. The minimum radiographer time saved by using this machine was 21.9 hours. The mini C-arm intensifier has saved 15% of the radiographer workload with its current pattern of usage in our department. There have been no problems or delays as a result of its usage in theatre. Usage of the large image intensifier resulted in a 16% problem rate and 11% delay rate. Other departments are encouraged to consider acquisition of a mini C-arm intensifier to facilitate theatre throughput, reduce risk to the patient and theatre personnel, and reduce demands on the radiology department.

大胸筋移行術を行った前鋸筋麻ひ例の肩甲上腕リズムの解析

We experienced a case of serratus anterior paralysis due to long thoracic nerve palsy which was treated by pectoralis major muscle transfer. The aim of this paper is to report the analysis of pre- and post- operative scapulo-humeral rhythm of this case.The patient is an 18-year-old girl. Before surgery she could abduct her arm only 90 degrees with a prominent winged scapula and her scapulo-humeral rhythm was markedly disturbed. We performed pectoralis major muscle transfer. After surgery, abduction improved to 180 degrees and her scapulo-humeral rhythm was improved, however, the winged scapula persisted.The anatomical size of the scapula was determined by taking two anterio-posterior view roentgenograms from a distance of one and two meters respectively. The pre- and post- operative scapulo-humeral rhythm was recorded on a video recorder by use of a large image intensifier and then analyzed.Before surgery, with abduction, the inferior angle scapula moved medially and the vertebral border of the scapula moved upward even with optimum abduction. Moreover, the upward rotation angle was small during this process. After surgery, the abnormal motion of the inferior angle and the vertebral border was minimized and became close to the normal rhythmic pattern with an increase in the upward rotation angle.

Sources of error in quantitative coronary angiography.

Many studies have reported the accuracy of quantitative coronary angiography (QCA) based on experiments using moderated-size phantoms imaged under unrealistic radiographic conditions. However, these observations may not be generalizable to the setting of clinical angiography. To determine QCA accuracy in a realistic radiographic setting and evaluate the impact of the x-ray system line spread function, plexiglass phantoms were imaged inside and out of a human thorax. A realistic radiographic background was associated with a 38% increase in variability of results (p < 0.05). Low concentrations of contrast and large image intensifier input screens were associated with significantly larger errors and variability in results (p < 0.05). There was a systematic overestimation of diameter in the smallest phantom. A mathematical model of the x-ray line spread function was developed that explains the observed overestimation of the smallest phantom and provide a rational approach for correction of the line spread function for QCA. Many factors encountered in clinical coronary angiography such as nonuniform radiographic background, low concentrations of contrast, and small vessel diameters have a significant adverse impact on the accuracy and/or variability of gradient-based edge detection QCA systems.

Digital fluoroscopic radiology: evaluation of the clinical impact

The use of digital image intensifier radiography (DIIR) for examinations in projection radiography is becoming more common. Fluoroscopic controlled contrast studies (barium- or iodine-based), particularly of the gastrointestinal tract, can be performed quickly and easily with a considerable decrease in radiation exposure. A wide dynamic range permits a constant high image quality with fewer incorrect exposure. The limited spatial resolution of large image intensifier input screens is the major drawback of DIIR. Digital image acquisition enables post-processing, digital storage and transfer of images, thus allowing an integration into PACS-systems. Imaging capabilities and clinical applications are described here.

Effects of optimization and image processing in digital chest radiography: An ROC study with an anthropomorphic phantom

A digital system for chest radiography based on a large image intensifier was compared to a conventional film-screen system. The digital system was optimized with regard to spatial and contrast resolution and dose. The images were digitally processed for contrast and edge enhancement. A simulated pneumothorax and two simulated nodules were positioned over the lungs and the mediastinum of an anthropomorphic phantom. Observer performance was evaluated with ROC analysis. Five observers assessed the processed digital images and the conventional full-size radiographs. The time spent viewing the full-size radiographs and the digital images was recorded. For the simulated pneumothorax, the results showed perfect performance for the full-size radiographs and detectability was high also for the processed digital images. No significant difference in the detectability of the simulated nodules was seen between the two imaging systems. The results for the digital images showed a significantly improved detectability for the nodules in the mediastinum as compared to a previous ROC study where no optimization and image processing was available. No significant difference in detectability was seen between the former and the present ROC study for small nodules in the lung. No difference was seen in the time spent assessing the conventional full-size radiographs and the digital images. The study indicates that processed digital images produced by a large image intensifier are equal in image quality to conventional full-size radiographs for low-contrast objects such as nodules.

Digital chest radiography: should images be presented in negative or positive mode?

The observer performance for video monitor images presented in positive mode (‘bones black’) was compared to that of images presented in negative mode (‘bones white’) in a digital system for chest radiography based on a large image intensifier. In the first part of the study (I), the original, non-linear grey-scale reversal performed in the computer of the digital image intensifier system (DS 1000) was studied together with fixed and variable settings of light and contrast. In the second part of the study (II), true grey-scale reversal performed in a minicomputer (Micro VAX II) where the images were also processed with edge and contrast enhancement, was studied. The time spent viewing the images was also recorded. Before the second part of the study, the image intensifier system was optimized with regard to spatial and contrast resolution and dose settings. Simulated pathology was randomly positioned over the lungs and the mediastinum of an anthropomorphic phantom. Observer performance was evaluated with Receiver Operating Characteristic (ROC) analysis on the digital images. In the first part of the study, a significant advantage for the positive images was seen, but no significant difference between fixed and variable settings of light and contrast. In the second part of the study, no significant difference in the detectability of the test structures was seen between positive and negative images. A significant improvement in the detectability was seen between the first and the second part of the study for the nodules over the mediastinum in both negative and positive images. No significant difference in the time spent observing positive and negative images, was seen. If negative mode is chosen for image presentation, true grey-scale reversal is necessary for adequate contrast resolution.

Radiographic reporting directly from the TV monitor of a digital chest radiography system

The practical usefulness of a digital large image intensifier system was tested on 400 consecutive, routine chest examinations. Reading and reporting was carried out directly from the digital images on the TV monitors. For each patient images were also read independently from 100 mm photofluorograms. When the reports for each examination were compared, there was total agreement in reporting in 40% of the cases and clinically insignificant differences in interpretation in 56%. In the remaining 16 patients (4%), the opinion of the observers differed as to whether significant disease was present or not. However, these disagreements could not be related to imaging technique. We believe that a majority of chest examinations can be performed with digital technique and can be read directly from the monitor screen.

Digital Chest Radiography with a Large Image Intensifier

A digital system for chest radiography based on a large image intensifier was compared with a conventional film-screen system. The diagnostic performance was evaluated with special reference to the digital monitor images with a modified version of receiver operating characteristic (ROC) analysis--free response ROC (FROC) analysis--on a chest equivalent phantom. Measurements of spatial resolution and energy imparted were also performed. The detectability of low-contrast objects as well as spatial resolution was better for the full-size film-screen radiographs than for both the digital monitor images and the 100 mm photofluorograms. The image-intensifier system has a potential for considerable dose savings in relation to the conventional technique provided that fluoroscopy is excluded in the positioning of the patients.

Digital Chest Radiography with a Large Image Intensifier

Digital Chest Radiography with a Large Image Intensifier

Large-image intensifier photofluorography and conventional radiography in pulmonary emphysema

Large-image intensifier photofluorography and conventional radiography in pulmonary emphysema

Large-image intensifier photofluorography and conventional radiography in pulmonary emphysema

Large-image intensifier photofluorography and conventional radiography in pulmonary emphysema

Basic imaging properties of a large image intensifier-TV digital chest radiographic system.

The basic imaging properties of a large (57 cm) image intensifier (I.I.)-TV digital imaging system were examined to determine the effects of various physical parameters on the quality of the digital chest images obtained, and also to explore the clinical usefulness of the system. The characteristic curve of the digital system, which relates the output pixel value to the input relative x-ray intensity, was measured with an aluminum stepwedge. MTFs were determined using slit images, and the veiling-glare fraction was measured with a lead-disk technique. Noise Wiener spectra were obtained from uniformly exposed images. The current limitations of the large II-TV digital chest system are its low spatial resolution, and the presence of large amounts of veiling glare and structure mottle. Advantages of this system over other digital chest imaging systems include the high speed of image data acquisition and the capability of "real-time" dynamic imaging of the chest at a radiation dose comparable to that in conventional radiography of the chest.

Development of the EXITE Detector: A New Imaging Detector for 20 - 300 keV Astronomy

We report on the development and testing of a detector to be used in the Energetic X-ray Imaging Telescope Experiment (EXITE). It consists of a 34 cm diameter NaI(Tl) cyrstal coupled directly to a single large image intensifier tube with associated silicon PIN diode readout. The measured spatial and energy resolutions at 122 keV are 6mm (FWHM) and 9% (FWHM), respectively. This energy resolution is ~50% better than that of any previously flown hard x-ray experiment. These resolutions decrease with the square root of the energy of the incident x-ray, indicating that they are determined by the number of photons emitted in the NaI(Tl) scintillator light flash.