Stefan Diederich

Spiral CT of pulmonary nodules: interobserver variation in assessment of lesion size.

Abstract. The aim of this study was to assess interobserver variability in size determination of pulmonary nodules at spiral CT. Twenty-three patients with known pulmonary nodules (diameter 2–40 mm, mean diameter 7 mm) underwent spiral chest CT (collimation 5 mm, pitch 1). Images were reconstructed at 3- and 5-mm intervals (RI). Hard copies were analyzed by two radiologists who recorded every nodule with regard to location, diagnostic confidence (“definite,”“probable”) and nodule size in increments of 1 mm with specific attention to correct classification into one of three size classes (≤ 5 mm, 6–10 mm, > 10 mm). Interobserver variability was determined with Pearsons correlation coefficient and k measure. Of a total of 286 nodules, 103 nodules were found accordingly by both readers at 3 mm RI, and 96 at 5 mm RI. There was a good correlation of measurements (in millimeters) between both readers (Pearsons correlation coefficient: 0.89–0.95). Interobserver variability in categories was good at both reconstruction intervals (k: 0.61 at 3 mm, 0.74 at 5 mm RI) and very good (0.81) at 5 mm RI when uncertain nodules were excluded. Spiral CT allows reproducible size determination of pulmonary nodules as shown by good interobserver agreement in exact size measurement and categorization into three size classes.

Automatic detection of pulmonary nodules in low-dose screening thoracic CT examinations

Computed tomography of the chest can be used as a screening method for lung cancer in a high-risk population. However, the detection of lung nodules is a difficult and time-consuming task for radiologists. The developed technique should improve the sensitivity of the detection of lung nodules without showing too many false positive nodules. In a study, which should evaluate the feasibility of screening lung cancer, about 1400 thoracic studies were acquired. Scanning parameters were 120 kVp, 5 mm collimation pitch of 2, and a reconstruction index of 5 mm. This results in a data set of about 60 to 70 images per exam. In the images the detection technique first eliminates all air outside the patient, then soft tissue and bony structures are removed. In the remaining lung fields a three-dimensional region detection is performed and rule-based analysis is used to detect possible lung nodules. This technique was applied to a small subset (n equals 17) of above studies. Computation time is about 5 min on an O2 workstation. The use of low-dose exams proved not be a hindrance in the detection of lung nodules. All of the nodules (n equals 23), except one with a size of 3 mm, were detected. The false positive rate was less than 0.3 per image. We have developed a technique, which might help the radiologist in the detection of pulmonary nodules in CT exams of the chest.

Detection of pulmonary nodules with overlapping vs non-overlapping image reconstruction at spiral CT.

Abstract. The aim of this study was to analyze whether overlapping image reconstruction increases numbers of pulmonary nodules detected at helical CT. Forty-eight helical CT scans (21with a slice thickness of 10 mm; 27 with a slice thickness of 5 mm) of patients with known pulmonary nodules were reconstructed both with overlapping and non-overlapping image reconstruction. Two readers recorded number and size of pulmonary nodules as well as diagnostic confidence. With overlapping image reconstruction each reader diagnosed more pulmonary nodules (slice thickness 10 mm: +24.0 and +26.7 %, both p < 0.01; slice thickness 5 mm: +9.5 and +11.9 %, both not significant) and more “definite” nodules (slice thickness 10 mm: +20.3 %, p < 0.05, and +30.8 %, p < 0.005; slice thickness 5 mm: +18.0 and +17.0 %, both p < 0.05). Nodules diagnosed with overlapping image reconstruction only were almost exclusively smaller than the slice thickness. The increase in number of nodules detected was not associated with a decrease in diagnostic confidence. Overlapping image reconstruction improves detection of pulmonary nodules smaller than the slice thickness at spiral CT.

Consensus report on the radiological management of patients with gastrointestinal stromal tumours (GIST): recommendations of the German GIST Imaging Working Group

Abstract The aim was to reach consensus in imaging for staging and follow-up as well as for therapy response assessment in patients with gastrointestinal stromal tumours (GIST). The German GIST Imaging Working Group was formed by 9 radiologists engaged in assessing patients with GIST treated with targeted therapy. The following topics were discussed: indication and optimal acquisition techniques of computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET)/CT; tumour response assessment considering response criteria and measurement techniques on CT, MRI and PET/CT; result interpretation; staging interval and pitfalls. Contrast-enhanced CT is the standard method for GIST imaging. MRI is the method of choice in case of liver-specific questions or contraindications to CT. PET/CT should be used for early response assessment or inconclusive results on morphologic imaging. All imaging techniques should be standardized allowing a reliable response assessment. Response has to be assessed with respect to lesion size, lesion density and appearance of new lesions. A critical issue is pseudoprogression due to myxoid degeneration or intratumoural haemorrhage. The management of patients with GIST receiving a targeted therapy requires a standardized algorithm for imaging and an appropriate response assessment with respect to changes in lesion size and density.

Low-dose CT: new tool for screening lung cancer?

Abstract. Lung cancer is the leading cause of death from malignant tumours as it is very common and has a poor prognosis at advanced tumour stages. Prognosis could be improved by treatment at early stages. As these stages are usually asymptomatic, a diagnostic test that would allow detection of early tumour stages in a population at risk could potentially reduce mortality from lung cancer. Previous approaches using chest radiography and sputum cytology in smokers have been disappointing. Fluorescent bronchoscopy and molecular markers are not yet applicable in clinical routine. Because of its high sensitivity for small pulmonary nodules, which are the most common manifestation of early lung cancer, CT appears suitable as a screening test. Low-dose examination parameters can and should be used for this purpose. From clinical practice it is well known that chest CT often demonstrates small pulmonary nodules, which do not represent lung cancer. Therefore, non-invasive diagnostic algorithms are required to avoid unnecessary biopsies in benign lesions. In preliminary studies of low-dose CT using algorithms based on size and density of detected nodules a large proportion of asymptomatic lung cancers and a large proportion of early, resectable tumour stages were found with a small proportion of invasive procedures for benign nodules. Before this technology can be recommended for broad application, however, further information is required regarding appropriate inclusion criteria (smoking habits, age groups) and screening intervals. Most importantly, further data are required to clarify whether lung cancer screening using low-dose CT can actually reduce mortality from lung cancer.

Performance of a flat-panel detector in the detection of artificial erosive changes: comparison with conventional screen-film and storage-phosphor radiography.

Abstract.The purpose of this study was to compare a large-area, direct-readout, flat-panel detector system with a conventional screen-film system, a storage-phosphor system, and a mammography screen-film system with regard to the detection of artificial bone erosions simulating rheumatoid disease, and to assess its diagnostic performance with decreasing exposure dose. Six hundred forty regions were defined in 160 metacarpophalangeal and proximal interphalangeal joint specimens from 20 monkey paws (4 regions per joint). Artificial bone erosions were created in 320 of these 640 regions. Specimens were enclosed in containers filled with water to obtain absorption and scatter radiation conditions similar to those of a human hand. Imaging was performed using a flat-panel system, a speed class 200 screen-film system, a mammography screen-film system, and a storage-phosphor system under exactly matched conditions. Different exposure doses equivalent to speed classes of S=100, 200, 400, 800, 1600, and 3200 were used. In all images the presence or absence of a lesion was assessed by three radiologists using a five-level confidence scale. Receiver operating characteristic (ROC) analysis was performed for a total of 21,120 observations (1920 for each imaging modality and exposure level) and diagnostic performance estimated by the area under the ROC curve (Az). The significance of differences in diagnostic performance was tested with analysis of variance. The ROC analysis showed Az values of 0.809 (S=200), 0.768 (S=400), 0.737 (S=800), 0.710 (S=1600), and 0.685 (S=3200) for the flat-panel system, 0.770 for the speed class 200 screen-film system, 0.781 (S=200), 0.739 (S=400), 0.724 (S=800), 0.680 (S=1600) for the storage-phosphor system, and 0.798 for the mammography screen-film system. Analysis of variance showed significant differences between different combinations of imaging modalities and exposure doses ( p <0.05). The diagnostic performance of the flat-panel detector system is superior to that of a screen-film system and a storage-phosphor system for the detection of erosive lesions at clinical exposure settings (S=200). Using the flat-panel system the exposure dose can be reduced by 50% to obtain a diagnostic performance comparable to a speed class 200 screen-film system.

Chest CT for suspected pulmonary complications of oncologic therapies: how I review and report

In cancer patient during or following oncologic therapies with respiratory symptoms and pulmonary pathology at chest CT the differential diagnosis includes infection, therapy-induced disease and tumour progression.Although CT morphology may be typical or even pathognomonic in some conditions the diagnosis is usually made by a synopsis of imaging, clinical and laboratory features.Close communication with referring colleagues and a good knowledge of potential side effects of therapeutic concepts, their time course and CT morphology is crucial in the differential diagnosis.This review describes a personal approach to the radiological diagnosis of therapy-induced pulmonary abnormalities in cancer patients.

Automatic detection of pulmonary nodules at spiral CT: first clinical experience with a computer-aided diagnosis system

We evaluated the practical application of a Computer-Aided Diagnosis (CAD) system for viewing spiral computed tomography (CT) of the chest low-dose screening examinations which includes an automatic detection of pulmonary nodules. A UNIX- based CAD system was developed including a detection algorithm for pulmonary nodules and a user interface providing an original axial image, the same image with nodules highlighted, a thin-slab MIP, and a cine mode. As yet, 26 CT examinations with 1625 images were reviewed in a clinical setting and reported by an experienced radiologist using both the CAD system and hardcopies. The CT studies exhibited 19 nodules found on the hardcopies in consensus reporting of 2 experienced radiologists. Viewing with the CAD system was more time consuming than using hardcopies (4.16 vs. 2.92 min) due to analyzing MIP and cine mode. The algorithm detected 49% (18/37) pulmonary nodules larger than 5 mm and 30% (21/70) of all nodules. It produced an average of 6.3 false positive findings per CT study. Most of the missed nodules were adjacent to the pleura. However, the program detected 6 nodules missed by the radiologists. Automatic nodule detection increases the radiologistss awareness of pulmonary lesions. Simultaneous display of axial image and thin-slab MIP makes the radiologist more confident in diagnosis of smaller pulmonary nodules. The CAD system improves the detection of pulmonary nodules at spiral CT. Lack of sensitivity and specificity is still an issue to be addressed but does not prevent practical use.

Beurteilung des Therapieerfolgs - konventionelle versus neue Methoden*

Zur Beurteilung des Therapieerfolgs bei Patienten mit thorakalen Tumoren werden neben konventionellen Verfahrenzunehmend neue Methoden, wie Regressionsgrading, CAD-Volumetrie (computerassistierte Volumetrie), Bestimmung der Tumordichte und Tumorperfusion sowie Positronen-Emissions-Tomographie (PET) mit18F-Fluordesoxyglucose (FDG) und alternativen Tracern, untersucht. Ergänzend zu den objektiv messbaren Parametern sind für den Therapieerfolg auch die den Patienten unmittelbar betreffenden Endpunkte Lebensqualität und tumorassoziierte Symptomatik relevant. Der Beitrag beschreibt den potenziellen Stellenwert neuer Verfahren und Endpunkte aus Sicht eines Pathologen, Radiologen, Nuklearmediziners, Strahlentherapeuten, Thoraxchirurgen, Onkologen und Hausarztes.

Comparison of the diagnostic performance of a CAD system for automatic detection of pulmonary nodules with single and double reading and its dependency on nodule size

Objective: Assess the performance of a computer aided diagnosis (CAD) system for automatic detection of pulmonary nodules at CT scans compared to single and double reading by radiologists. Material and methods: A nodule detection CAD system (Siemens LungCare NEV VB10) was applied to low-dose-CT (LDCT) scans of nine patients with pulmonary metastases and compared to findings of three radiologists; standard-dose-CT (SDCT) was acquired simultaneously to establish ground truth. Study design was approved by the Institutional Review Board and the appropriate German authorities. Ground truth was established by fusion of sets of detected nodules from independent reading by three radiologists at LDCT and SDCT scans and CAD results. Special focus was taken on the size of nodules detected only by CAD compared to the size of all detected nodules. Results: Average sensitivity of 54% (range 51-55%) was observed for single reading by one radiologist. Application of the CAD system demonstrated a similar sensitivity of 55%. Double reading by two radiologists increased sensitivity to an average of 67% (range 67-68%). The difference to single reading was significant (p<0.001). Use of CAD as second opinion after single reading increased the sensitivity to 79% (range 77-81%) which proved to be significantly better than double reading (p<0.001). 11% of nodules with a size of more than 4 mm were detected only by CAD. Conclusion: CAD as second reader offered a significant increase in sensitivity compared to conventional double reading. Therefore, CAD is a valuable second opinion for the detection of pulmonary nodules.