Digital Projection Radiography Research Articles

A questionnaire study of radiography educator opinions about patient lead shielding during digital projection radiography

BackgroundIn projection radiography, lead rubber shielding has long been used to protect the gonads both within and outside the collimated field. However, the relative radio-sensitivity of the gonads is considered lower than previously, and doses from digital projection radiography are reported as being lower than in previous eras. These factors, along with technical difficulties encountered in placing lead shielding effectively, lead to varied opinions on the efficacy of such shielding in peer reviewed literature. This current study has investigated what is currently being taught as good practice concerning the use of lead shielding during projection radiography. MethodAn online questionnaire was distributed to a purposive sample of 44 radiography educators across 15 countries, with the aim of establishing radiography educators' opinions about patient lead shielding and its teaching. ResultsFrom the 27 responding educators, 57% (n = 15) teach students to apply gonadal shielding across a range of radiographic examinations; only 22% (n = 6) do the same for the breast, despite respondents being aware that the breast has higher relative radio-sensitivity than the gonads. Radiation protection was the primary reason given for using shielding. Students are generally expected to apply patient lead shielding during assessments, although a small number of respondents report that students must justify whether or not to apply lead shielding. Educators generally held the opinion that no matter what they are taught, students are influenced by what they see radiographers do in clinical practice. ConclusionsThe current study has not found consensus in literature or in radiography educators' opinions concerning the use of patient lead shielding. Findings suggest that a large scale empirical study to establish a specific evidence base for the appropriate use of lead shielding across a range of projection radiography examinations would be useful.

Visualisierung bioresorbierbarer Fadenanker-Implantate mit digitaler Projektionsradiografie und Magnetresonanztomografie

During the last few years bioabsorbable suture anchors have become widely established along side metallic suture anchors in orthopaedic surgery. However, there are still some difficulties in evaluating the postoperative situation after implanting bioabsorbable suture anchors. The aim of this study was to examine the visualisation of bioabsorbable suture anchors with digital projection radiography and magnetic resonance imaging. Ten Mitek-Anchor-Panalok® suture anchors made of polylactic acid were implanted in an ex-vivo animal study design. After implantation the specimens were examined with digital projection radiography and MRI. The analysis was performed with regard to the bony defects and the anchor material itself. With digital projection radiography and MRI, it was possible to detect the bony defects after implantation of the anchors. The anchor material could not be visualised. The results of this study demonstrate that neither digital projection radiography nor MRI is well suited for the detection of the bioabsorbable suture anchors in the postoperative situation. Whereas the bony defects can be well described, the anchors cannot be directly visualised. The visualisation of bioabsorbable anchors remains a clinical problem in orthopaedic surgery.

A dose index as a tool to estimate paediatric patient doses in digital projection radiography

Radiation exposure during childhood is estimated to have a lifetime risk up to seven times greater than exposures at adult age. Therefore, paediatric patient dose monitoring is a major concern in radiology. The aim of this study is to evaluate the validity of a dose index, displayed at the digital imaging and communication in medicine (DICOM) header of the images, as a dosimetric quantity to estimate the entrance surface dose (ESD) for each procedure. It was carried out over a sample of 156 paediatric patients who underwent a chest examination. National Radiation Protection Board Report 318 model was used to categorise patients by age and to estimate their thickness. Corrected dose index values were compared with calculated ESD, estimated from tube output and radiographic technique. The deviation between both values remained within 2% for every age group, except for patients up to 1 y. Therefore, the index could be used to estimate ESD, allowing to manage greater patient dose databases.

Automated detection of changes in patient exposure in digital projection radiography using exposure index from DICOM header metadata

Purpose. Automated collection of image data from DICOM headers enables monitoring of patient dose and image quality parameters. Manual monitoring is time consuming, owing to the large number of exposure scenarios, thus automated methods for monitoring needs to be investigated. The aim of the present work was to develop and optimise such a method. Material and methods. Exposure index values from digital systems in projection radiography were collected over a period of five years, representing data from 1.2 million projection images. The exposure index values were converted to detector dose and an automated method for detection of sustained level shifts in the resulting detector dose time series was applied using the statistical analysis tool R. The method combined handling of outliers, filtering and estimation of variation in combination with two different statistical rank tests for level shift detection. A set of 304 time series representing central body parts was selected and the level shift detection method was optimised using level shifts identified by ocular evaluation as the gold standard. Results. Two hundred and eighty-one level changes were identified that were deemed in need of further investigation. The majority of these changes were abrupt. The sensitivity and specificity of the optimised and automated detection method concerning the ocular evaluation were 0.870 and 0.997, respectively, for detected abrupt changes. Conclusions. An automated analysis of exposure index values, with the purpose of detecting changes in exposure, can be performed using the R software in combination with a DICOM header metadata repository containing the exposure index values from the images. The routine described has good sensitivity and acceptable specificity for a wide range of central body part projections and can be optimised for more specialised purposes.

Workflow Efficiency Comparison of a New CR System with Traditional CR and DR Systems in an Orthopedic Setting

Workflow efficiency is a crucial factor in selecting computed radiography (CR) versus digital radiography (DR) systems for digital projection radiography operations. DR systems can be more efficient, but present higher costs and limitations in performing some radiographic exams. A newly developed CR system presents a good alternative with its faster line-by-line instead of pixel-by-pixel image plate-scanning technology and a more efficient workstation. To evaluate workflow characteristics, a time-motion study was conducted to compare radiographic exam times of the new CR system with traditional CR and DR systems in a high-volume orthopedic operation. Approximately 200 exams for each modality were documented from the moment when a patient entered the X-ray room to the moment when all images were sent to the PACS archive using a timer and speech-recognition software. Applying Welch ANOVA and Tamhane's T2 tests, average exam times for the new CR system were significantly faster (18-42%; P ≤ 0.025) than for the traditional CR system. Average exam times for the DR system were also faster than for the new CR system by 22-36% (P<0.001) with one exception. In the case where the new CR system was located outside the X-ray room, using a one-technologist workflow model, average single-study exam times were not significantly different from those found when using DR. Therefore, the new CR system may be comparable in efficiency with the DR system for this particular setting and operation.

Patient dose in digital projection radiography

In projection radiography, two types of digital imaging systems are currently available, computed radiography (CR) and direct radiography (DR): a difference between them can be stated in terms of dose and image quality. In the Radiology Emergency Department of our hospital, a flat-panel DR equipment (Siemens Axiom Aristos FX) and two CR systems (Kodak CR-850) are employed. In 2006, five standard radiographic examinations (abdomen, chest, lumbar spine, pelvis, skull) were considered: doses delivered to patients in terms of both entrance skin dose (ESD) and effective dose (E) were calculated and compared in order to study the dosimetric discrepancies between CR and DR. Assessment of image quality is undertaken by Consultant Radiologists to ensure that the quality criteria for diagnostic radiographic images of the European guidelines were met. Results showed that both ESD and E in DR are lower than that in CR; all images met the criteria in the European Guidelines for both modalities and were used for reporting by the radiologists. Since the operators are the same and the image quality is comparable in both modalities, this study shows that in the considered examinations, DR can perform better than CR from a dosimetric point of view.

Pulmonary nodule detection with digital projection radiography: an ex-vivo study on increased latitude post-processing

To evaluate increased image latitude post-processing of digital projection radiograms for the detection of pulmonary nodules. 20 porcine lungs were inflated inside a chest phantom, prepared with 280 solid nodules of 4-8 mm in diameter and examined with direct radiography (3.0x2.5 k detector, 125 kVp, 4 mAs). Nodule position and size were documented by CT controls and dissection. Four intact lungs served as negative controls. Image post-processing included standard tone scales and increased latitude with detail contrast enhancement (log-factors 1.0, 1.5 and 2.0). 1280 sub-images (512x512 pixel) were centred on nodules or controls, behind the diaphragm and over free parenchyma, randomized and presented to six readers. Confidence in the decision was recorded with a scale of 0-100%. Sensitivity and specificity for nodules behind the diaphragm were 0.87/0.97 at standard tone scale and 0.92/0.92 with increased latitude (log factor 2.0). The fraction of "not diagnostic" readings was reduced (from 208/1920 to 52/1920). As an indicator of increased detection confidence, the median of the ratings behind the diaphragm approached 100 and 0, respectively, and the inter-quartile width decreased (controls: p<0.001, nodules: p=0.239) at higher image latitude. Above the diaphragm, accuracy and detection confidence remained unchanged. Here, the sensitivity for nodules was 0.94 with a specificity from 0.96 to 0.97 (all p>0.05). Increased latitude post-processing has minimal effects on the overall accuracy, but improves the detection confidence for sub-centimeter nodules in the posterior recesses of the lung.

The digital hospital information technology in radiology

The experiences that were made in the radiology department at the Danubehospital/Vienna concerning the digital archive and digital communication via the LAN showed: - the diagnostic qualities of digital projection radiography regarding spatial resolution are adequate or just about sufficient, the excellent contrast resolution is an advantage of great value; - monitor-reporting is feasible in clinical routine without drawbacks; - the HIS-RIS-PACS integration is not yet sufficient; a consistent user-interface is necessary and the requested automatic and intelligent perfecting-algorithms are needed (both are high priority topics; implementation and clinical evaluation are expected soon). Autorouting of reported examinations to the peripheral wards is an other top priority topic; a feasible technical solution will be beneficial for the radiologists and clinicians; - digital communication can accelerate data-exchange and contribute to the reduction of the length of stay in hospital; - digital archives are highly costeffective; - digital archives shouldn't cause any legal problems as durability, and availability of images and reports is better than in the conventional system; - not yet sufficiently solved are questions concerning archive access and electronic signatures.

A comparison of quantitative dual-energy radiographic absorptiometry and dual photon absorptiometry of the lumbar spine in postmenopausal women

Noninvasive bone densitometry is an important aspect in the detection and management of osteoporosis and other forms of metabolic disease of calcified tissue. A system using quantitative dual-energy digital projection radiography (QDR) of the lumbar spine was systematically tested against dual-photon absorptiometry (DPA) of the lumbar spine in 131 women over 55 years of age and free from major risk factors for osteoporosis. All subjects were scanned by both QDR and DPA under the same conditions. Measurements for a given subject were made within 15 minutes of each other. Bone mineral densities (BMD) were determined for four individual levels in the lumbar spine (L1-L4). Regression equations for BMD vs. age, height, and weight were calculated. The results of this investigation indicate that DPA- and QDR-derived BMD values are comparable. BMD values derived by QDR were consistently lower than those obtained by DPA (DPA=1.115 QDR+0.137, r=0.942). The L2 lumbar region was the most strongly correlated determination.

ROC: Methodik zum Vergleich der diagnostischen Leistung bildgebender Verfahren

ROC analysis permits an evaluation of the diagnostic performance of imaging systems by incorporating the individual decision threshold of the diagnostician that determines the relation between sensitivity and specificity of a tested system. It therefore facilitates the comparison between different imaging systems and observers. A thorough knowledge and sophistication of this methodology is of special importance in the comparison of digital and conventional projection radiography because the images in question may have a very similar character. The method is explained and special points of interest (standard of "truth", size of sample, lesion conspicuity and localisation, viewing time and determination of significance) are emphasised.

Digitale Radiographie in der Thoraxdiagnostik

Technologies and performance of digital projection radiography are reviewed. Storage phosphor imaging plates can be used in existing diagnostic equipment and the resulting digital images permit the recognition of fine interstitial changes, if a high frequency edge enhancement is performed. While a generalized enhancement of low and medium spatial frequencies and a grey scale reversal do not improve the detectability of pulmonary nodules, selective enhancement of low frequencies in the mediastinal and retro-diaphragmatic areas may well improve diagnostic performance. Dose can be reduced if the resulting signal-to-noise ratio is adequate for diagnosis. Further dose savings can be achieved by the reduced number of retakes. Dual energy techniques improve the detectability and differential diagnosis of pulmonary nodules. The further development of picture archiving and communication systems (PACS) will turn the digital projection radiography into the method of choice for the diagnosis of chest disease.

A comparison of quantitative dual-energy radiographic absorptiometry and dual photon absorptiometry of the lumbar spine in postmenopausal women

Noninvasive bone densitometry is an important aspect in the detection and management of osteoporosis and other forms of metabolic disease of calcified tissue. A system using quantitative dual-energy digital projection radiography (QDR) of the lumbar spine was systematically tested against dual-photon absorptiometry (DPA) of the lumbar spine in 131 women over 55 years of age and free from major risk factors for osteoporosis. All subjects were scanned by both QDR and DPA under the same conditions. Measurements for a given subject were made within 15 minutes of each other. Bone mineral densities (BMD) were determined for four individual levels in the lumbar spine (L1-L4). Regression equations for BMD vs. age, height, and weight were calculated. The results of this investigation indicate that DPA- and QDR-derived BMD values are comparable. BMD values derived by QDR were consistently lower than those obtained by DPA (DPA = 1.115 QDR + 0.137, r = 0.942). The L2 lumbar region was the most strongly correlated determination.

Performance characteristics of a dual-energy detector for digital scan projection radiography.

An energy discriminating x-ray detector has been developed for dual-energy, scan projection digital radiography. The detector is comprised of a pair of x-ray intensifying screen/linear photodiode arrays, aligned one behind the other. Energy discrimination is achieved by employing a low atomic number phosphor in the front screen and a high atomic number phosphor in the back screen. The x-ray response, modulation transfer function, and defective quantum efficiency of the detector are reported along with the experimental methodology utilized for the measurements. Also presented is an analysis which indicates that in a typical patient's lung field, the detector can resolve the projected density (g/cm2) of a 3-mm-thick, 1-cm2 area of bone to better than 1.5%.

Imaging performance of a digital storage phosphor system.

The imaging performance of a storage phosphor system (SPS) for digital projection radiography is studied in which the x-ray image is temporarily stored in a light-stimulable phosphor plate which is subsequently read out by a scanning laser beam. The imaging performance of this system has been analyzed for two types of imaging plates. The spatial resolution is described by the modulation transfer function and the signal-to-noise (S/N) ratios of the recorded image data are measured in terms of noise-equivalent quanta and detective quantum efficiency. Their dependence on detector entrance dose and spatial frequency is discussed. A detailed analysis of the different sources of image noise is given to outline the intrinsic features and limits of the system. Finally, the S/N behavior of the SPS is compared with published data of screen-film systems.

Fast computer processing for tissue highlighting in computed tomographic cross-sectional imaging and digital scan projection radiography.

A simple, fast, computer method of simultaneously highlighting edge detail and emphasising soft-tissue contrast is discussed. An objective comparison is made with conventional blurred mask subtraction using the signal-to-noise ratio from phantom scans. The use of the algorithm for inner ear studies and digital scanned projection radiography is presented.

Digital projection radiography of the chest.

Direct and film-based radiographic systems are undergoing evaluation by observer performance studies for use in digital imaging of the chest. Many issues intrinsic to digital imaging are not settled, including the minimal pixel size necessary for images of accurate diagnostic quality, the characteristics of the display console, and the usefulness of digital imaging processing techniques. The chest is a particularly difficult anatomic region for examination by digital radiography because of the broad spectrum of disease findings encountered. These issues are discussed in reference to four reports that use observer performance tests for evaluating various facets of chest diagnosis using digital radiography.

Application of Si-microstrip-detectors in medicine and structural analysis

Current X-ray imaging techniques in medicine (computer tomography, digital projection radiography) use linear arrays of discrete radiation sensors. The detector requirements are specified and a possible application of microstrip detectors in digital projection radiography is described. The potential of microstrip detector arrays in structural analysis is discussed.

Zukunftstendenzen bei bildgebenden Verfahren

Digital Projection Radiography employs the technology of CT and is intended to replace conventional x-ray film in certain fields. Advantages are high density and contrast resolution, a significant reduction of radiation dose and the possibility of manipulating the picture. Disadvantages are low spatial resolution and the impossibility of dynamic studies.