EVALUATION OF TWO CHEST TOMOSYNTHESIS CYSTIC FIBROSIS SCORING SYSTEMS USING HIGH-RESOLUTION COMPUTED TOMOGRAPHY BRODY SCORING AS REFERENCE.

PURPOSE: To evaluate two chest tomosynthesis (CTS) scoring systems for cystic fibrosis (CF), one system developed by Vult von Steyern et al. (VvS) and one system based on the Brody scoring system for high-resolution computed tomography (HRCT) (modified Brody (mB)). Brody scoring of HRCT was used as reference. METHODS: In conjunction with routine control HRCT at clinical follow-up, 10 consecutive adult CF patients underwent CTS for research purposes. Four radiologists scored the CTS examinations using the mB and VvS scoring systems. All scores were compared to the Brody HRCT scores. The agreement between the evaluated CTS scoring systems and the reference HRCT scoring system was determined using Spearman's rank correlation coefficient and the intraclass correlation coefficient (ICC). MAJOR FINDINGS: Spearman's rank correlation coefficient showed strong correlations between HRCT score and both the mB and the VvS CTS total scores (median rs = 0.81 and 0.85, respectively). The ICC showed strong correlation between the CTS scoring systems and the reference: 0.88 for mB and 0.85 for VvS scoring. The median time for scoring was 20 and 10 minutes for the mB and VvS scoring systems, respectively. CONCLUSIONS: Both evaluated CTS scoring systems correlate well with the reference standard Brody HRCT scoring. The VvS CTS scoring system has a shorter reading time, suggesting its advantage in clinical practice.

Detection of Pulmonary Nodule Growth with Chest Tomosynthesis: A Human Observer Study Using Simulated Nodules.

RATIONALE AND OBJECTIVES: Chest tomosynthesis has been suggested as a suitable alternative to CT for follow-up of pulmonary nodules. The aim of the present study was to investigate the possibility of detecting pulmonary nodule growth using chest tomosynthesis. MATERIALS AND METHODS: Simulated nodules with volumes of approximately 100 mm3 and 300 mm3 as well as additional versions with increasing volumes were created. The nodules were inserted into images from pairs of chest tomosynthesis examinations, simulating cases where the nodule had either remained stable in size or increased in size between the two imaging occasions. Nodule volume growths ranging from 11% to 252% were included. A simulated dose reduction was applied to a subset of the cases. Cases differing in terms of nodule size, dose level, and nodule position relative to the plane of image reconstruction were included. Observers rated their confidence that the nodules were stable in size or not. The rating data for the nodules that were stable in size was compared to the rating data for the nodules simulated to have increased in size using ROC analysis. RESULTS: Area under the curve values ranging from 0.65 to 1 were found. The lowest area under the curve values were found when there was a mismatch in nodule position relative to the reconstructed image plane between the two examinations. Nodule size and dose level affected the results. CONCLUSION: The study indicates that chest tomosynthesis can be used to detect pulmonary nodule growth. Nodule size, dose level, and mismatch in position relative to the image reconstruction plane in the baseline and follow-up examination may affect the precision.

Evaluation of a corrected implementation of a method of simulating pulmonary nodules in chest tomosynthesis.

Background A method of simulating pulmonary nodules in tomosynthesis images has previously been developed and evaluated. An unknown feature of a rounding function included in the computer code was later found to introduce an artifact, affecting simulated nodules in low-signal regions of the images. The computer code has now been corrected. Purpose To perform a thorough evaluation of the corrected nodule-simulation method, comparing the detection rate and visual appearance of artificial nodules with those of real nodules in an observer performance experiment. Material and Methods A cohort of 64 patients with a total of 129 pulmonary nodules was used in the study. Artificial nodules, each matching a corresponding real nodule by size, attenuation, and anatomical location, were generated and simulated into the tomosynthesis images of the different patients. The detection rate and visual appearance of artificial nodules generated using both the corrected and uncorrected computer code were compared to those of real nodules. The results were evaluated using modified receiver operating characteristic (ROC) analyses. Results The difference in detection rate between artificial and real nodules slightly increased using the corrected computer code (uncorrected code: area under the curve [AUC], 0.47; 95% CI, 0.43-0.51; corrected code: AUC, 0.42; 95% CI, 0.38-0.46). The visual appearance was however substantially improved using the corrected computer code (uncorrected code: AUC, 0.70; 95% CI, 0.63-0.76; corrected code: AUC, 0.49; 95% CI, 0.29-0.65). Conclusion The computer code including a correct rounding function generates simulated nodules that are more visually realistic than simulated nodules generated using the uncorrected computer code, but have a slightly different detection rate compared to real nodules.

EFFECT OF RADIATION DOSE LEVEL ON ACCURACY AND PRECISION OF MANUAL SIZE MEASUREMENTS IN CHEST TOMOSYNTHESIS EVALUATED USING SIMULATED PULMONARY NODULES.

The aim of the present study was to investigate the dependency of the accuracy and precision of nodule diameter measurements on the radiation dose level in chest tomosynthesis. Artificial ellipsoid-shaped nodules with known dimensions were inserted in clinical chest tomosynthesis images. Noise was added to the images in order to simulate radiation dose levels corresponding to effective doses for a standard-sized patient of 0.06 and 0.04 mSv. These levels were compared with the original dose level, corresponding to an effective dose of 0.12 mSv for a standard-sized patient. Four thoracic radiologists measured the longest diameter of the nodules. The study was restricted to nodules located in high-dose areas of the tomosynthesis projection radiographs. A significant decrease of the measurement accuracy and intraobserver variability was seen for the lowest dose level for a subset of the observers. No significant effect of dose level on the interobserver variability was found. The number of non-measurable small nodules (≤5 mm) was higher for the two lowest dose levels compared with the original dose level. In conclusion, for pulmonary nodules at positions in the lung corresponding to locations in high-dose areas of the projection radiographs, using a radiation dose level resulting in an effective dose of 0.06 mSv to a standard-sized patient may be possible in chest tomosynthesis without affecting the accuracy and precision of nodule diameter measurements to any large extent. However, an increasing number of non-measurable small nodules (≤5 mm) with decreasing radiation dose may raise some concerns regarding an applied general dose reduction for chest tomosynthesis examinations in the clinical praxis.

AN ANALYSIS OF THE POTENTIAL ROLE OF CHEST TOMOSYNTHESIS IN OPTIMISING IMAGING RESOURCES IN THORACIC RADIOLOGY.

The aim of the study was to investigate the potential role of chest tomosynthesis (CTS) at a tertiary referral centre by exploring to what extent CTS could substitute chest radiography (CXR) and computed tomography (CT). The study comprised 1433 CXR, 523 CT and 216 CTS examinations performed 5 years after the introduction of CTS. For each examination, it was decided if CTS would have been appropriate instead of CXR (CXR cases), if CTS could have replaced the performed CT (CT cases) or if CT would have been performed had CTS not been available (CTS cases). It was judged that (a) CTS had been appropriate in 15 % of the CXR examinations, (b) CTS could have replaced additionally 7 % of the CT examinations and (c) CT would have been carried out in 63 % of the performed CTS examinations, had CTS not been available. In conclusion, the potential role for CTS to substitute other modalities during office hours at a tertiary referral centre may be in the order of 20 and 25 % of performed CXR and chest CT, respectively.

VISIBILITY OF STRUCTURES OF RELEVANCE FOR PATIENTS WITH CYSTIC FIBROSIS IN CHEST TOMOSYNTHESIS: INFLUENCE OF ANATOMICAL LOCATION AND OBSERVER EXPERIENCE.

The aims of this study were to assess the visibility of pulmonary structures in patients with cystic fibrosis (CF) in digital tomosynthesis (DTS) using computed tomography (CT) as reference and to investigate the dependency on anatomical location and observer experience. Anatomical structures in predefined regions of CT images from 21 patients were identified. Three observers with different levels of experience rated the visibility of the structures in DTS by performing a head-to-head comparison with visibility in CT. Visibility of the structures in DTS was reported as equal to CT in 34 %, inferior in 52 % and superior in 14 % of the ratings. Central and peripheral lateral structures received higher visibility ratings compared with peripheral structures anteriorly, posteriorly and surrounding the diaphragm (p ≤ 0.001). Reported visibility was significantly higher for the most experienced observer (p ≤ 0.01). The results indicate that minor pathology can be difficult to visualise with DTS depending on location and observer experience. Central and peripheral lateral structures are generally well depicted.

INFLUENCE OF THE IN-PLANE ARTEFACT IN CHEST TOMOSYNTHESIS ON PULMONARY NODULE SIZE MEASUREMENTS.

The aim of the present study was to investigate how the in-plane artefact present in the scan direction around structures in tomosynthesis images should be managed when measuring the size of nodules in chest tomosynthesis images in order to achieve acceptable measurement accuracy. Data from measurements, performed by radiologists, of the longest diameter of artificial nodules inserted in chest tomosynthesis images were used. The association between the measurement error and the direction of the longest nodule diameter, relative to the scan direction, was evaluated using the Kendall rank correlation coefficient. All of the radiologists had chosen to not include the artefact in the measurements. Significant association between measurement error and the direction of the longest diameter was found for nodules larger than 12 mm, which indicates that, for these nodules, there is a risk of underestimating the nodule size if the in-plane artefact is omitted from manual diameter measurements.

THE APPLICATION OF IMPROVED, STRUCTURED AND INTERACTIVE GROUP LEARNING METHODS IN DIAGNOSTIC RADIOLOGY.

This study provides an example on how it is possible to design environments in a diagnostic radiology department that could meet learning demands implied by the introduction of new imaging technologies. The innovative aspect of the design does not result from the implementation of any specific tool for learning. Instead, advancement is achieved by a novel set-up of existing technologies and an interactive format that allows for focussed discussions between learners with different levels of expertise. Consequently, the study points to what is seen as the underexplored possibilities of tailoring basic and specialist training that meet the new demands given by leading-edge technologies.

Chest tomosynthesis: technical and clinical perspectives.

The recent implementation of chest tomosynthesis is built on the availability of large, dose-efficient, high-resolution flat panel detectors, which enable the acquisition of the necessary number of projection radiographs to allow reconstruction of section images of the chest within one breath hold. A chest tomosynthesis examination obtains the increased diagnostic information provided by volumetric imaging at a radiation dose comparable to that of conventional chest radiography. There is evidence that the sensitivity of chest tomosynthesis may be at least three times higher than for conventional chest radiography for detection of pulmonary nodules. The sensitivity increases with increasing nodule size and attenuation and decreases for nodules with subpleural location. Differentiation between pleural and subpleural lesions is a known pitfall due to the limited depth resolution in chest tomosynthesis. Studies on different types of pathology report increased detectability in favor of chest tomosynthesis in comparison to chest radiography. The technique provides improved diagnostic accuracy and confidence in the diagnosis of suspected pulmonary lesions on chest radiography and facilitates the exclusion of pulmonary lesions in a majority of patients, avoiding the need for computed tomography (CT). However, motion artifacts can be a cumbersome limitation and breathing during the tomosynthesis image acquisition may result in severe artifacts significantly affecting the detectability of pathology. In summary, chest tomosynthesis has been shown to be superior to chest conventional radiography for many tasks and to be able to replace CT in selected cases. In our experience chest tomosynthesis is an efficient problem solver in daily clinical work.

Evaluation of an improved method of simulating lung nodules in chest tomosynthesis.

BACKGROUND: Simulated pathology is a valuable complement to clinical images in studies aiming at evaluating an imaging technique. In order for a study using simulated pathology to be valid, it is important that the simulated pathology in a realistic way reflect the characteristics of real pathology. PURPOSE: To perform a thorough evaluation of a nodule simulation method for chest tomosynthesis, comparing the detection rate and appearance of the artificial nodules with those of real nodules in an observer performance experiment. MATERIAL AND METHODS: A cohort consisting of 64 patients, 38 patients with a total of 129 identified pulmonary nodules and 26 patients without identified pulmonary nodules, was used in the study. Simulated nodules, matching the real clinically found pulmonary nodules by size, attenuation, and location, were created and randomly inserted into the tomosynthesis section images of the patients. Three thoracic radiologists and one radiology resident reviewed the images in an observer performance study divided into two parts. The first part included nodule detection and the second part included rating of the visual appearance of the nodules. The results were evaluated using a modified receiver-operating characteristic (ROC) analysis. RESULTS: The sensitivities for real and simulated nodules were comparable, as the area under the modified ROC curve (AUC) was close to 0.5 for all observers (range, 0.43-0.55). Even though the ratings of visual appearance for real and simulated nodules overlapped considerably, the statistical analysis revealed that the observers to were able to separate simulated nodules from real nodules (AUC values range 0.70-0.74). CONCLUSION: The simulation method can be used to create artificial lung nodules that have similar detectability as real nodules in chest tomosynthesis, although experienced thoracic radiologists may be able to distinguish them from real nodules.

Rediscovering radiology: new technologies and remedial action at the worksite.

This study contributes to social studies of imaging and visualization practices within scientific and medical settings. The focus is on practices in radiology, which are bound up with visual records known as radiographs. The study addresses work following the introduction of a new imaging technology, tomosynthesis. Since it was a novel technology, there was limited knowledge of how to correctly analyse tomosynthesis images. To address this problem, a collective review session was arranged. The purpose of the present study was to uncover the practical work that took place during that session and to show how, and on what basis, new methods, interpretations and understandings were being generated. The analysis displays how the diagnostic work on patients' bodies was grounded in two sets of technologically produced renderings. This shows how expertise is not simply a matter of providing correct explanations, but also involves discovery work in which visual renderings are made transparent. Furthermore, the results point to how the disciplinary knowledge is intertwined with timely actions, which in turn, partly rely on established practices of manipulating and comparing images. The embodied and situated reasoning that enabled radiologists to discern objects in the images thus display expertise as inherently practical and domain-specific.

Nodule detection in digital chest radiography: effect of system noise.

Apart from the image content that is the reproduction of anatomy and possible lesions, an X-ray image also contains system noise due to the limited number of photons and other internal noise sources in the system (image plate artefacts, electronic noise, etc.). The aim of this study was to determine the extent to which the system noise influences the detection of subtle lung nodules in five different regions of the chest. This was done by conducting a receiver operating characteristic (ROC) study with five observers on two different sets of images; clinical chest X-ray images and images of a LucAl phantom at similar dose levels found in the different regions of the chest. In both image types, mathematically simulated nodules (with a full-width-at-fifth-maximum of 10 mm) were added to the images at varying contrast levels. As a measure of the influence of system noise on the detection of subtle lung nodules, the ratio between the contrast needed to obtain an area under the ROC curve of 0.80 in the system noise images to that needed in the clinical images was used. The contrast ratio between system noise images and clinical images ranged from approximately 0.02 (in the hilar region) to 0.18 (in the lower mediastinal region). The maximum difference in contrast needed for the corresponding system noise images, collected at the lowest and the highest dose represented in the anatomical image, was a factor of 2. These results indicate that probably no region in a chest X-ray image is limited by the number of quanta to the detector for the detection of 10 mm lung nodules when a radiation dose corresponding to a system with speed class 200 (leading to a detector dose of approximately 9 muGy behind the parenchyma) is used.