Valeria Fisichella

Learning aspects and potential pitfalls regarding detection of pulmonary nodules in chest tomosynthesis and proposed related quality criteria.

Background In chest tomosynthesis, low-dose projections collected over a limited angular range are used for reconstruction of an arbitrary number of section images of the chest, resulting in a moderately increased radiation dose compared to chest radiography. Purpose To investigate the effects of learning with feedback on the detection of pulmonary nodules for observers with varying experience of chest tomosynthesis, to identify pitfalls regarding detection of pulmonary nodules, and present suggestions for how to avoid them, and to adapt the European quality criteria for chest radiography and computed tomography (CT) to chest tomosynthesis. Material and Methods Six observers analyzed tomosynthesis cases for presence of nodules in a jackknife alternative free-response receiver-operating characteristics (JAFROC) study. CT was used as reference. The same tomosynthesis cases were analyzed before and after learning with feedback, which included a collective learning session. The difference in performance between the two readings was calculated using the JAFROC figure of merit as principal measure of detectability. Results Significant improvement in performance after learning with feedback was found only for observers inexperienced in tomosynthesis. At the collective learning session, localization of pleural and subpleural nodules or structures was identified as the main difficulty in analyzing tomosynthesis images. Conclusion The results indicate that inexperienced observers can reach a high level of performance regarding nodule detection in tomosynthesis after learning with feedback and that the main problem with chest tomosynthesis is related to the limited depth resolution.

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.

Primary Three-Dimensional Analysis with Perspective-Filet View Versus Primary Two-Dimensional Analysis: Evaluation of Lesion Detection by Inexperienced Readers at Computed Tomographic Colonography in Symptomatic Patients

Background: “Perspective-filet view” is a novel three-dimensional (3D) viewing technique for computed tomography colonography (CTC). Studies with experienced readers have shown a sensitivity for perspective-filet view similar to that of 2D or 3D endoluminal fly-through in detection of colorectal lesions. It is not known whether perspective-filet view, compared to axial images, improves lesion detection by inexperienced readers. Purpose: To compare primary 3D analysis using perspective-filet view (3D Filet) with primary 2D analysis, as used by inexperienced CTC readers. Secondary aims were to compare lesion detection by 3D Filet when used by experienced and inexperienced readers, and to evaluate the effect of combined 3D Filet + 2D analysis. Material and Methods: Fifty symptomatic patients were prospectively enrolled. An experienced reader performed 3D Filet analysis followed by complete 2D analysis (3D Filet + 2D), before colonoscopy with segmental unblinding. Two inexperienced readers (readers 2 and 3), blinded to CTC and colonoscopy findings, retrospectively performed 3D Filet analysis and, after 5 weeks, 2D analysis. True positives ≥6 mm detected by the inexperienced readers with 3D Filet and/or 2D were combined to obtain 3D Filet + 2D. Results: Colonoscopy revealed 116 lesions: 16 lesions ≥10 mm, 19 lesions 6–9 mm, and 81 lesions ≤5 mm. For the experienced reader, sensitivities for lesions ≥6 mm with 3D Filet and 3D Filet + 2D were 77% and 83%, respectively. For the inexperienced readers, sensitivities for lesions ≥6 mm with 3D Filet and 2D were 51% and 57% (reader 2) and 40% and 43% (reader 3), respectively. There was no significant difference between 3D Filet and 2D regarding sensitivity and reading time. For lesions ≥6 mm, 3D Filet + 2D improved the sensitivity of reader 2 to 63% and of reader 3 to 51%. Conclusion: Lesion detection by inexperienced readers using perspective-filet view is comparable to that obtained by 2D. Lesion detection improves by combining 3D Filet + 2D, but not to the level of an experienced reader.

Survey update on implementation, indications, and technical performance of computed tomography colonography in sweden:

Background: Computed tomographic colonography (CTC) has gained increased acceptance in the last few years as a valid substitute for double-contrast barium enema (DCBE). However, implementation of new technologies is complex, since several factors may influence the process. Purpose: To evaluate the current situation in Sweden concerning implementation of CTC, as compared to a previous national survey in 2005. Material and Methods: In December 2008, a structured, self-assessed questionnaire regarding implementation and technical performance of CTC was mailed to all radiology departments in Sweden. In March 2009, departments who had not replied were contacted by e-mail or by telephone. All (100%, 119/119) departments answered the questionnaire. Results: CTC is currently performed in 50/119 (42%) departments, i.e., 18 additional departments compared to 2005. Twenty-three out of 60 (38%) responding departments stated that they intend to start to perform CTC in the near future. DCBE is currently performed in 77/119 (65%) departments, 12 departments less compared to 2005. The most common reasons for non-implementation of CTC are non-availability of spiral CT scanner (41%, 26/64) and/or multidetector-row CT scanner (39%, 25/64), and lack of doctors’ time (34%, 22/64). Only 3% (2/64) of departments are “awaiting further scientific documentation” on CTC, a significant reduction compared to 2005 (P=0.002). Until 2009, 59% (29/49) of CTC centers had performed more than 200 CTCs compared to 13% (4/32) of CTC centers in 2005. Intravenous contrast material is routinely administered in 86% (42/49), and carbon dioxide is used to distend the colon in 90% (44/49). Almost all radiology departments (93%, 93/100) currently believe that CTC will “absolutely” or “probably” replace barium enema in the future, while in 2005 only 56% (55/99) gave similar answers. Conclusion: The survey reflects a further transition process from DCBE to CTC, with attitudes of radiologists increasingly in favor of CTC, although DCBE is still performed by the majority of radiology departments. DCBE should be replaced by colonoscopy and CTC, but the transition requires both human and economic resources.

Availability, Indications, and Technical Performance of Computed Tomographic Colonography: A National Survey

Purpose: To determine the availability, indications, and technique of computed tomographic colonography (CTC) in Sweden and to investigate opinions on its future role in colon imaging. Material and Methods: In May 2004, a questionnaire on CTC was mailed to all Departments of Radiology in Sweden, and one year later a telephone interview was conducted with the departments that intended to start a CTC service. Results: Ninety-nine departments (83%) answered the questionnaire, indicating that 23/99 (23.2%) offered a CTC service. Reasons for non-implementation of CTC were lack of CTC training in 34/73 (46.6%) and non-availability of multi-detector row CT scanners in 33/73 (45.2%), while 26% were awaiting further scientific documentation on CTC. Incomplete colonoscopy was the main indication for CTC in 21/23 (91.3%) departments performing CTC. Dual positioning, room air insufflation, and thin-slice collimation were used in all the responding departments. The number of CTC studies performed varied from 1–5 (26.1%) to more than 200 (17.4%). Intravenous contrast material was routinely administered by 9/23 (39.1%) departments. Out of 30 (39.5%) departments that in 2004 intended to start CTC, 9 (30%) had done so by June 2005. A total of 32/99 (32.3%) departments had therefore started CTC by June 2005. Half of the departments that replied believed that CTC would absolutely or probably replace barium enema in the future. Conclusion: The survey shows relatively limited diffusion of CTC practice in Sweden, with approximately one-third of radiology departments offering a CTC service, mostly on a small scale. A wider dissemination of CTC requires further scientific documentation of its capability, intensified educational efforts, and additional funding.

Extended analysis of the effect of learning with feedback on the detectability of pulmonary nodules in chest tomosynthesis

In chest tomosynthesis, low-dose projections collected over a limited angular range are used for reconstruction of section images of the chest, resulting in a reduction of disturbing anatomy at a moderate increase in radiation dose compared to chest radiography. In a previous study, we investigated the effects of learning with feedback on the detection of pulmonary nodules in chest tomosynthesis. Six observers with varying degrees of experience of chest tomosynthesis analyzed tomosynthesis cases for presence of pulmonary nodules. The cases were analyzed before and after learning with feedback. Multidetector computed tomography (MDCT) was used as reference. The differences in performance between the two readings were calculated using the jackknife alternative free-response receiver operating characteristics (JAFROC-2) as primary measure of detectability. Significant differences between the readings were found only for observers inexperienced in chest tomosynthesis. The purpose of the present study was to extend the statistical analysis of the results of the previous study, including JAFROC-1 analysis and FROC curves in the analysis. The results are consistent with the results of the previous study and, furthermore, JAFROC-1 gave lower p-values than JAFROC-2 for the observers who improved their performance after learning with feedback.

Global Implementation of Computed Tomography Colonography

This chapter is a series of short essays composed by key researchers and advocates of computed tomography colonography from several different countries. I hope this will help document some important historical information regarding the development of computed tomography colonography on a global scale. This information is not available in print in any single source and often incorporates a historical perspective never before appearing in print. Each section has its own style, content, and references. The essays are listed in alphabetical order of the country discussed: Argentina, Austria, Belgium, Canada, France, Germany, Ireland, Israel, Italy, Japan, Korea, Sweden, and the United Kingdom. Authors provided photographs of themselves and/or their research team, which are provided in an appendix at the back of the book.