Flat-panel Detector Radiography Research Articles

Dependence of low contrast detail on exposure dose and tube voltage in digital flat-panel detector radiography—a pre-clinical phantom study

Purpose. Pre-clinical determination of reasonable simplified examination protocols before clinical application to assess the performance of a direct digital radiography (DDR) system. Material and methods. The experimental setup consists of a DDR system with fixed flat-panel detector (CsI). A phantom with low-contrast structures (LCS) was examined in two settings in order to simulate standard radiographs: (1) small peripheral joints like the wrist (no patient phantom, no anti-scatter grid) and (2) big proximal joints like the hip (20 cm water tank patient simulation and with an anti-scatter grid). Setup (1) was manually exposed at 55 kV/2 mAs, 60 k V/1.6 mAs and 65 k V/1.25 mAs. Setup (2) was automatically exposed at 1.6, 2.5, 4 and 6 μGy per kV-setting (80 ± 5 kV). Contrast-detail curves (CDC) were generated by analyzer software. Results. Exposures of setup (1) showed similar CDC (p = 0.99) with a decreasing curve with larger diameter of LCS. In all exposures of setup (2) CDC were similar for all kV-settings (p > 0.93) with a decreasing curve with larger LCS diameter. CDC insignificantly decrease with increasing exposure dose (p > 0.38). Conclusion. Low-contrast detectability was independent of kV and marginally dependent on the dose, both within a certain range. This could be used to further reduce radiation dose and simplify examination protocols to be tested in a further clinical study.

Round Window Membrane Insertion With Perimodiolar Cochlear Implant Electrodes

The round window membrane (RWM) approach is designed to provide an atraumatic approach to scala tympani implantation with the goal of enhanced preservation of hearing and vestibular receptor function. Perimodiolar electrode designs offer advantages in electrophysiologic testing. However, perimodiolar arrays have only been investigated in insertion trials using temporal bone material. The aim of the present study was to evaluate perimodiolar electrode placement in a clinical trial. The prospective nonrandomized study included 27 patients (October 2010 to February 2011). Due to the RWM approach, cochlear implantation electrode insertion was performed using a perimodiolar electrode array fitted with a stylet that enables movement through the first cochlear turn by withdrawing the stylet. We judged the feasibility of RWM approaches with perimodiolar electrodes and the electrode placement using flat panel detector radiography. Hearing preservation, vestibular receptor function (vestibular evoked myogenic potentials, subjective haptic vertical, and caloric irrigation), and subjective vertigo were evaluated in all RWM approaches. For anatomic reasons, RWM insertions were possible in 21 cases (78%). The basilar membrane disruption rate was 19% in RWM insertions using perimodiolar electrodes. In those patients with the electrode position within the scala tympani, vestibular receptor functions and subjective vertigo remained unchanged. The residual hearing preservation was unsatisfactory. The mean pure-tone average loss was 21 dB. We believe that if performed regularly, the RWM insertion technique has almost no negative effects on vestibular receptor function and produces no vertigo. However, cochlear hair cells may be more sensitive to electrode insertion traumas than vestibular receptor cells. The use of perimodiolar electrodes may require more atraumatic electrodes to achieve hearing preservation.

Dual-energy subtraction radiography improves laryngeal delineation in patients with moderate to severe cervical spondylosis

To investigate the feasibility of dual-energy subtraction (DES) in patients with moderate-severe cervical spondylosis for improving delineation of the larynx on flat panel detector (FPD) radiography. For 118 patients, we graded conventional/DES anterior-posterior views for delineation of the vocal cords, subglottis, and pyriform sinus using a 5-point scale and lateral views from conventional laryngeal FPD radiography to determine cervical spondylosis severity on a scale from 0 (none) to 3 (severe). We compared the delineation of each anatomical structure in both groups of grades 0-1 and grades 2-3 of spondylosis severity between conventional and DES methods and the improved delineation rate for each anatomical structure by DES compared to the conventional method between both groups. With DES, the delineation of each anatomical structure was significantly better than with conventional radiography for both groups (P<0.0001). The improved delineation rate of the vocal cord and subglottis using DES was significantly higher in grades 2-3 than in grades 0-1 (P<0.05), although there was no significant difference in the delineation rate of the pyriform sinus between the groups (P=0.847). DES provides better delineation of the laryngeal anatomy than conventional FPD radiography predominantly in patients with moderate-severe cervical spondylosis.

Postoperative follow-up of olecranon fracture by digital tomosynthesis radiography

Digital tomosynthesis with flat-panel detector radiography is a novel application that allows easy, swift volume data acquisition of any anatomical site of interest with arbitrary patient posture. A single sweep of the X-ray tube provides multiple tomographic images of high resolution. We present the first patient with olecranon fracture who underwent internal fixation and 1-year postoperative follow-up with tomosynthesis. The minimal metallic artifact by this modality successfully provided detailed information regarding the healing process of the fracture.

Detection of small pulmonary nodules on chest radiographs: efficacy of dual-energy subtraction technique using flat-panel detector chest radiography

To investigate the effect of a double-exposure dual-energy subtraction (DES) technique on the diagnostic performance of radiologists detecting small pulmonary nodules on flat-panel detector (FPD) chest radiographs. Using FPD radiography 41 sets of chest radiographs were obtained from 26 patients with pulmonary nodules measuring <or=20mm and from 15 normal participants. Each dataset included standard and corresponding DES images. There were six non-solid, 10 part-solid, and 10 solid nodules. The mean size of the 26 nodules was 15+/-4.8mm. Receiver operating characteristic (ROC) analysis was performed to compare the performance of the eight board-certified radiologists. For the eight radiologists, the mean value of the area under the ROC curve (AUC) without and with DES images was 0.62+/-0.05 and 0.68+/-0.05, respectively; the difference was statistically significant (p=0.02). For part-solid nodules, the difference of the mean AUC value was statistically significant (AUC=0.61+/-0.07 versus 0.69+/-0.05; p<0.01); for non-solid nodules it was not (AUC=0.62+/-0.1 versus 0.61+/-0.09; p=0.73), and for solid nodules it was not (AUC=0.75+/-0.1 versus 0.78+/-0.08; p=0.23). For nodules with overlapping bone shadows, the difference of the mean AUC value was statistically significant (p=0.03), for nodules without overlapping, it was not (p=0.26). Use of a double-exposure DES technique at FPD chest radiography significantly improved the diagnostic performance of radiologists to detect small pulmonary nodules.

Effects of dual-energy subtraction chest radiography on detection of small pulmonary nodules with varying attenuation: receiver operating characteristic analysis using a phantom study

The aim of this study was to investigate the detectability of simulated pulmonary nodules with different X-ray attenuation by flat-panel detector (FPD) chest radiography using a dual-exposure dual-energy subtraction (DES) technique. Using a FPD radiography system, we obtained 108 sets of chest radiographs of a chest phantom. They consisted of 54 sets each of chest radiographs with and without simulated nodules. Each data set contained a standard and a corresponding dual-energy subtracted chest radiograph (DES image). The diameters of the simulated nodules were 8, 10, and 12 mm, respectively; nodules of each size manifested attenuation of -450, -200, and 30 Hounsfield units (HU). We performed receiver operating characteristic (ROC) analysis to compare the observers' performance in detecting nodules. For the -450 HU nodules the mean areas under the ROC curve (AUC) without and with DES images were 0.66 and 0.77, respectively; the difference was significant (paired t-test, P < 0.01). For nodules with -200 and 30 HU, there was no significant difference in the AUC value (0.79 vs. 0.77, P = 0.13; 0.92 vs. 0.94, P = 0.17, respectively). The addition of DES images to standard chest radiographs improved the performance of radiologists charged with detecting simulated nodules with an attenuation of -450 HU.

Dual-Energy Subtraction Imaging for Diagnosing Vocal Cord Paralysis with Flat Panel Detector Radiography

ObjectiveTo investigate the clinical feasibility of dual energy subtraction (DES) imaging to improve the delineation of the vocal cord and diagnostic accuracy of vocal cord paralysis as compared with the anterior-posterior view of flat panel detector (FPD) neck radiography.Materials and MethodsFor 122 consecutive patients who underwent both a flexible laryngoscopy and conventional/DES FPD radiography, three blinded readers retrospectively graded the radiographs during phonation and inspiration on a scale of 1 (poor) to 5 (excellent) for the delineation of the vocal cord, and in consensus, reviewed the diagnostic accuracy of vocal cord paralysis employing the laryngoscopy as the reference. We compared vocal cord delineation scores and accuracy of vocal cord paralysis diagnosis by both conventional and DES techniques using κ statistics and assessing the area under the receiver operating characteristic curve (AUC).ResultsVocal cord delineation scores by DES (mean, 4.2 ± 0.4) were significantly higher than those by conventional imaging (mean, 3.3 ± 0.5) (p < 0.0001). Sensitivity for diagnosing vocal cord paralysis by the conventional technique was 25%, whereas the specificity was 94%. Sensitivity by DES was 75%, whereas the specificity was 96%. The diagnostic accuracy by DES was significantly superior (κ = 0.60, AUC = 0.909) to that by conventional technique (κ = 0.18, AUC = 0.852) (p = 0.038).ConclusionDual energy subtraction is a superior method compared to the conventional FPD radiography for delineating the vocal cord and accurately diagnosing vocal cord paralysis.

Ability of chest X-ray to detect faint shadows documented as ground-glass attenuation in images of computed tomography: A comparison between flat-panel detector radiography and film-screen radiography

Purpose To compare flat-panel detector (FPD) radiography and film-screen (FS) radiography in detectability of faint shadows documented as ground-glass attenuation (GGA) areas in images of computed tomography (CT). Materials and methods Study population was comprised of 50 patients who underwent FS and another 50 patients who underwent FPD. Standard of reference (SOR) was determined on the basis of area of GGA in all cross-sections of CT, in terms of GGA extent and presence or absence of GGA in each trisected lung fields (GGA distribution). Eight radiologists assessed the GGA extent with the 5-grade scale and the GGA distribution. Inter-observer variances of the GGA extents and distributions, degree of divergences and correspondence in the GGA extent and distributions with SOR, were compared between the FS and FPD by the jackknife method and Fisher's exact test. Results Inter-observer variance in the GGA extent and distribution were slightly larger in the FS than in the FPD. The GGA extent scale corresponded with SOR in the FS statistically significantly better ( p = 0.001), as the correct ratio was 0.428 in the FS and 0.310 in the FPD. Divergence in the GGA extent scale with SOR was smaller in the FS, as average kappa pseudo-value of Kendall's rank correlation coefficient was 0.474 in the FS and 0.433 in the FPD. Conclusion These results indicate that some lesions of GGA documented in CT may not be reflected and are difficult to be detected in chest X-ray radiographs with the FPD.

Digital amorphous silicon flat-panel detector radiography at different exposure doses versus mammography film: possibility of radiation dose reduction in detecting rheumatologic bone defects

Radiographic examinations of the skeleton are the most commonly performed radiologic procedures, even outnumbering examinations of the chest. The imaging systems used in skeletal radiography must meet high standards in terms of contrast and spatial resolution to effectively visualize the high contrast between bone and soft tissue as well as fine bone structures. To determine the performance of amorphous silicon flat-panel detector radiography compared to mammography film in detecting rheumatologic bone defects at different exposure doses. The study enrolled 44 patients with known or presumed skeletal changes of the hand associated with inflammatory rheumatic diseases. Following a clinically indicated radiographic examination of the peripheral extremities using mammography film, a survey radiograph of one hand was taken in the posteroanterior (PA) view by digital radiography, at the same exposure dose and at a dose reduced to one quarter of the mammography film doses. Four independent radiologists scored the resultant images using the Sharp/van der Heijde and Ratingen scoring methods. The study received University of Cologne Ethics Committee and German Federal Radiation Protection Agency approval. Compared to mammography film, digital flat-panel detector radiography produced a significantly better image quality at identical uptake doses. A greater number of erosions were detected with the digital flat-panel detector than with mammography film at the same and at reduced doses. Although the spatial resolution of the digital flat-panel system used in this study was poorer than mammography film, this was compensated for by its wider dynamic range and improved contrast resolution, even at the reduced dose.

Should 3K zoom function be used for detection of pneumothorax in cesium iodide/amorphous silicon flat-panel detector radiographs presented on 1K-matrix soft copies?

The purpose of the study was to evaluate observer performance in the detection of pneumothorax with cesium iodide and amorphous silicon flat-panel detector radiography (CsI/a-Si FDR) presented as 1K and 3K soft-copy images. Forty patients with and 40 patients without pneumothorax diagnosed on previous and subsequent digital storage phosphor radiography (SPR, gold standard) had follow-up chest radiographs with CsI/a-Si FDR. Four observers confirmed or excluded the diagnosis of pneumothorax according to a five-point scale first on the 1K soft-copy image and then with help of 3K zoom function (1K monitor). Receiver operating characteristic (ROC) analysis was performed for each modality (1K and 3K). The area under the curve (AUC) values for each observer were 0.7815, 0.7779, 0.7946 and 0.7066 with 1K-matrix soft copies and 0.8123, 0.7997, 0.8078 and 0.7522 with 3K zoom. Overall detection of pneumothorax was better with 3K zoom. Differences between the two display methods were not statistically significant in 3 of 4 observers (p-values between 0.13 and 0.44; observer 4: p = 0.02). The detection of pneumothorax with 3K zoom is better than with 1K soft copy but not at a statistically significant level. Differences between both display methods may be subtle. Still, our results indicate that 3K zoom should be employed in clinical practice.

Dose Reduction in Patients Undergoing Chest Imaging: Digital Amorphous Silicon Flat-Panel Detector Radiography Versus Conventional Film-Screen Radiography and Phosphor-Based Computed Radiography

We sought to compare the radiation dose delivered to patients undergoing clinical chest imaging on a full-field digital amorphous silicon flat-panel detector radiography system with the doses delivered by a state-of-the-art conventional film-screen radiography system and a storage phosphor-based computed radiography system. Image quality was evaluated to ensure that the potential reduction in radiation dose did not result in decreased image acuity. SUBJECTS AND METHODS. Three groups of 100 patients each were examined using the amorphous silicon flat-panel detector, film-screen, or computed radiography systems. All patient groups were matched for body mass index, sex, and age. To measure the entrance skin dose, we attached 24 calibrated thermoluminescent dosimeters to every patient. The calculation of the effective dose, which represents the risk of late radiation-induced effects, was based on measurements on an anthropomorphic phantom. Image quality of all three systems was evaluated by five experienced radiologists, using the European Quality Criteria for Chest Radiology. In addition, a contrast-detail phantom study was set up to assess the low-contrast detection of all three systems. The amorphous silicon flat-panel detector radiography system allowed an important and significant reduction in both entrance skin dose and effective dose compared with the film-screen radiography (x 2.7 decrease) or computed radiography (x 1.7 decrease) system. In addition, image quality produced by the amorphous silicon flat-panel detector radiography system was significantly better than the image quality produced by the film-screen or computed radiography systems, confirming that the dose reduction was not detrimental to image quality. The introduction of digital flat-panel radiography systems based on amorphous silicon and cesium iodide is an important step forward in chest imaging that offers improved image quality combined with a significant reduction in the patient radiation dose.