Thomas M. Bernhardt

Diagnostic potential of virtual bronchoscopy: advantages in comparison with axial CT slices, MPR and mIP?

The aim of this study was to evaluate the diagnostic potential of virtual endoscopy (VE) and to compare it with axial CT slices, multiplanar reconstructions (MPR), minimal intensity projections (mIP), and bronchoscopy in patients diagnosed with bronchogenic carcinoma. Thirty patients underwent a spiral CT. Axial CT images were transferred to an Onyx workstation (Silicon Graphics, Sun Microsystems, Mountain View, Calif.) for performing virtual endoscopy. Accuracy for this procedure was tested by three radiologists on a monitor in comparison with axial CT slices, MPR, mIP, and bronchoscopy concerning the localization and degree of stenoses. Endoluminal tumors were identified by virtual bronchoscopy with no statistically significant difference of localization or grading of stenosis in comparison with bronchoscopy, axial CT slices, MPR and mlP. Axial CT slices, MPR, and mlP showed poorer results with over- or underestimation of stenoses compared with VE and bronchoscopy. Passing of stenoses was only possible with VE in 5 patients. Virtual endoscopy is a non-invasive method for identification of endoluminal tumors and is comparable to real bronchoscopy.

Diagnostic performance of a flat-panel detector at low tube voltage in chest radiography: a phantom study.

Rationale and Objectives:To evaluate a large area, cesium iodide amorphous silicon flat-panel detector (CsI/a-Si) at 3 tube voltages to detect simulated interstitial lung disease, nodules, and catheters. Methods:Simulated interstitial lung disease, nodules, and catheters were superimposed over a chest phantom. Images were generated at 125 kVp, 90 kVp, and 70 kVp at the same surface dose and reduced effective dose equivalent for 90 kVp and 70 kVp and printed on hard copies. Fifty-four thousand observations were analyzed by receiver operating characteristic (ROC). Results:Detectability of linear, miliary, reticular pattern, and nodules over lucent lung as well as of catheters and nodules over obscured chest areas increased at 90 and/or 70 kVp with higher Az values; however, only it was statistically significant for reticular pattern at 70 kVp and nodules at 90 kVp compared with 125 kVp (P <0.05). The detection of ground-glass pattern was worse at lower kVp (P >0.05). Conclusion:For most simulated patterns, differences in diagnostic performance at 70 kVp/90 kVp and 125 kVp were not significant, except for reticular pattern and nodules over lucent lung.

Portable flat-panel detector for low-dose imaging in a pediatric intensive care unit: comparison with an asymmetric film-screen system.

Objective:We sought to evaluate the diagnostic performance of a portable indirect flat-panel detector for low-dose imaging as compared with an asymmetric film-screen system in a pediatric intensive care unit. Materials and Methods:A total of 120 neonates underwent chest radiographs using a portable flat-panel detector (digital speed 800) and an asymmetric film-screen system (400 speed). Four readers evaluated the detection of 11 anatomic and 5 pathologic landmarks and 4 support devices. Statistical analysis was performed using repeated analysis of variance. The level of statistical significance was P = 0.05. Results:The detection of 4 anatomic/4 pathologic landmarks and 2 support devices was significantly better using the flat-panel detector as compared with the asymmetric film-screen system (P < 0.05). Another 8 anatomic and one pathologic landmarks were detected equally well or slightly better with the flat-panel detector (P > 0.05). Conclusions:The portable flat-panel detector offers the potential of a 50% dose reduction with equal or significantly better detection of clinically important structures.

Digital selenium radiography: detection of subtle pulmonary lesions on images acquired with and without an additional antiscatter grid

OBJECTIVE the objective of this ROC-study was to evaluate the diagnostic efficacy of images acquired with a grid in digital selenium radiography compared to that on images obtained with the integrated air gap only. MATERIALS AND METHODS seven types of simulated lesions were superimposed onto an anthropomorphic chest phantom. Selenium radiography images were obtained either with or without an additional antiscatter grid. For images acquired with a grid either a similar or increased exposure level was used. Both normal and obese patients were simulated. RESULTS When a grid was used with an equivalent detector dose and a higher exposure, diagnostic performance was significantly improved as compared to images obtained with only the air gap. ROC curve areas for mediastinal nodules and catheters were substantially higher for images acquired with a grid and the same exposure level compared to images obtained without a grid. However, detection of linear, net-shaped and reticulonodular structures in peripheral lung regions was significantly worse when a grid was used with an equivalent exposure level. Concerning the interpretation of images obtained from the normal and obese phantom models, no substantial differences were observed. CONCLUSION a marked improvement in diagnostic performance could be achieved by means of the use of an additional antiscatter grid and an equivalent detector dose. However, when the same exposure was used, images acquired with the grid allowed a better detection of mediastinal structures although a worse performance was evident in radiolucent lung regions. Therefore, the routine use of a grid without increased exposure is not recommended.

Ergebnisse einer Langzeituntersuchung zum Fatigue-Effekt in der digitalen Selenradiographie (THORAVISION)

Zusammenfassung In der digitalen Selenradiographie (DSR) ubernimmt amorphes Selen die Funktion des Strahlendetektors fur die Rontgenstrahlung. Das auf der Selenoberflache nach Wechselwirkung mit der Selenschicht entstandene elektrische Ladungsmuster wird mit speziellen Sensoren beruhrungsfrei abgetastet und in einem System schneller Bildgebung weiterbearbeitet. Je nach Beschaffenheit der Selenschicht und in Abhangigkeit von der Energiedosis konnen Veranderungen der Strahlenempfindlichkeit der Selenschicht auftreten, die als Ermudungs- bzw. Fatigue-Effekt bezeichnet werden. Dadurch kann die praktische Bildauswertung beeintrachtigt werden. Zwei konstruktiv gleiche Selentrommeln, deren Nutzungszeiten ca. I Jahr auseinander lagen, zeigten bei gleichen Testbedingungen (150 kV, 31,2mAs) unterschiedliche Fatigue-Zeiten von 50 Sekunden bis maximal 3 Minuten. Die in den Selenschichten ablaufenden Erholungsprozesse konnen durch Exponentialfunktionen erster Ordnung angenahert werden. Die charakteristischen Parameter dieser Funktionen variieren zwischen den Selenschichten beider Trommeln, so das die Fatigue-Reaktion von der Art bzw. Zusammensetzung der Schicht mitbestimmt wird, In der Arbeit werden Schlusfolgerungen fur den Praxiseinsatz der DSR am THORA VISION mitgeteilt.