Cornelia Schaefer-Prokop

FDG PET and PET/CT: EANM procedure guidelines for tumour PET imaging: version 1.0

The aim of this guideline is to provide a minimum standard for the acquisition and interpretation of PET and PET/CT scans with [18F]-fluorodeoxyglucose (FDG). This guideline will therefore address general information about [18F]-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) and is provided to help the physician and physicist to assist to carrying out, interpret, and document quantitative FDG PET/CT examinations, but will concentrate on the optimisation of diagnostic quality and quantitative information.

Computer-aided detection of interstitial abnormalities in chest radiographs using a reference standard based on computed tomography

A computer-aided detection (CAD) system is presented for the localization of interstitial lesions in chest radiographs. The system analyzes the complete lung fields using a two-class supervised pattern classification approach to distinguish between normal texture and texture affected by interstitial lung disease. Analysis is done pixel-wise and produces a probability map for an image where each pixel in the lung fields is assigned a probability of being abnormal. Interstitial lesions are often subtle and ill defined on x-rays and hence difficult to detect, even for expert radiologists. Therefore a new, semiautomatic method is proposed for setting a reference standard for training and evaluating the CAD system. The proposed method employs the fact that interstitial lesions are more distinct on a computed tomography (CT) scan than on a radiograph. Lesion outlines, manually drawn on coronal slices of a CT scan of the same patient, are automatically transformed to corresponding outlines on the chest x-ray, using manually indicated correspondences for a small set of anatomical landmarks. For the texture analysis, local structures are described by means of the multiscale Gaussian filter bank. The system performance is evaluated with ROC analysis on a database of digital chest radiographs containing 44 abnormal and 8 normal cases. The best performance is achieved for the linear discriminant and support vector machine classifiers, with an area under the ROC curve (Az) of 0.78. Separate ROC curves are built for classification of abnormalities of different degrees of subtlety versus normal class. Here the best performance in terms of Az is 0.90 for differentiation between obviously abnormal and normal pixels. The system is compared with two human observers, an expert chest radiologist and a chest radiologist in training, on evaluation of regions. Each lung field is divided in four regions, and the reference standard and the probability maps are converted into region scores. The system performance does not significantly differ from that of the observers, when the perihilar regions are excluded from evaluation, and reaches Az=0.85 for the system, with Az=0.88 for both observers.

MDCT angiography for detection of pulmonary emboli: Comparison between equi-iodine doses of iomeprol 400 mgI/mL and iodixanol 320 mgI/mL

OBJECTIVESnTo compare iomeprol 400 and iodixanol 320 in pulmonary artery MDCTA in subjects with suspected pulmonary embolism.nnnMETHODSnEighty randomized subjects received equi-iodine intravenous doses (48 g) of iomeprol 400 (n=40) or iodixanol 320 (n=40), via power injector at 4 mL/s. Four-row (35 subjects) and 64-row (45 subjects) scanners were used. Lumen attenuation was determined on-site and by two off-site blinded readers in the main, lobar, segmental and subsegmental pulmonary arteries. Statistical comparison between groups was performed for demographics and lumen attenuation.nnnRESULTSnThere were no between-group differences (p>0.05) in demographics. Pulmonary artery attenuation was significantly (p<or=0.03) higher with iomeprol 400 for all readers. Attenuation quality was excellent in more patients after iomeprol 400 than after iodixanol-320 (80% vs. 62.5%; 82.5% vs. 77.5%; off-site readers 1 and 2, respectively). No safety concerns were noted.nnnCONCLUSIONnThe greater iodine delivery rate achievable with iomeprol 400 compared to iodixanol-320 at equi-iodine dose and injection rate permits consistently greater attenuation at all levels of the pulmonary arterial tree.

Comparison of automated 4-chamber cardiac views versus axial views for measuring right ventricular enlargement in patients with suspected pulmonary embolism

PURPOSEnCompare the right ventricle to left ventricle (RV/LV) diameter ratio obtained from axial pulmonary CT angiograms (CTPA) with those derived from automatically generated 4-chamber (4-CH) reformats in patients with suspected pulmonary embolism (PE).nnnMETHODSnIn this institutional review board-approved study we included 120 consecutive non ECG-gated CTPA from 3 institutions (mean age 60 ± 16 years; 71 women). Twenty 64-slice CTPA with PE and 20 without PE were selected per institution. For each patient the RV/LV diameter ratio was obtained from both axial CTPA images and automatically generated 4-CH reformats. Measurements were performed twice in two separated sessions by 2 experienced radiologists and 2 residents. The differences between the measurements on both views were evaluated.nnnRESULTSnThe 4-CH view was successfully obtained in 113 patients. The mean axial and 4-CH diameter ratios were comparable for three of the four readers (p = 0.56, p = 0.13, p = 0.08). Although the mean diameters (1.0 and 1.03 respectively) for one resident were significantly different (p = 0.013), the difference of 0.03 seems negligible in clinical routine. Three readers achieved equally high intra-reader agreements with both measurements (ICCs of 0.94, 0.95 and 0.96), while one reader showed a different variability with ICCs of 0.96 for the axial view and 0.91 for the 4-CH view. The inter-reader agreement was equally high for both measurement types with ICCs of 0.95 and 0.94, respectively.nnnCONCLUSIONnIn patients with suspected PE, RV/LV diameters ratio can be measured with the same reproducibility and accuracy using an automatically generated 4-CH view compared to the axial view.

Abwägen von Dosisbedarf und Bildqualität in der digitalen Radiographie

Projection radiography is in an advanced stage of progressive transition from conventional screen-film imaging to digital image acquisition modalities. The radiographic technique, including examination parameters such as tube voltage, tube current and filtration has frequently been adopted from screen-film technology. Digital systems, however, are characterized by their flexibility as the dose can be reduced at the expense of image quality and vice versa. The imaging parameters need to be individually optimized according to the best performance of a system. The traditional means of dose adjustment, such as positioning and collimation, are as valid for digital techniques as they were for conventional techniques. Digital techniques increasingly offer options for dose reduction. At the same time there is a risk to accidentally substantially increase patient dose due to the lack of visual control. Therefore, the implementation of dose indicators and dose monitoring is mandatory for digital radiography. The use of image quality classes according to the dose requirements of given clinical indications are a further step towards modern radiation protection.ZusammenfassungDie Projektionsradiographie befindet sich in einer bereits weit fortgeschrittenen Umbruchphase zwischen konventionellen Film-Folien-Systemen und digitalen Verfahren. Die radiographische Technik einschließlich der Expositionsparameter wurde vielerorts einfach von Film-Folien-Systemen übernommen. Digitale Systeme sind sehr flexibel, die Dosis kann auf Kosten der Bildqualität gesenkt werden. Die Aufnahmetechnik muss für jedes System optimiert werden. Die Strahlenschutzgrundsätze der Einstelltechnik wie Kollimation und Positionierung sind für konventionelle und digitale Verfahren in gleicher Weise gültig. Die digitale Technik bietet viele Möglichkeiten zur Dosisreduktion, gleichzeitig besteht die Gefahr eines unbemerkten Dosisanstiegs wegen der fehlenden optischen Kontrolle. Daher sind die Anwendung von Dosisindikatoren und eine longitudinale Dosisüberwachung unerlässlich. Die Einführung von Bildqualitätsklassen zur indikationsabhängigen Dosisgestaltung von Untersuchungen ist ein weiterer Fortschritt für den Strahlenschutz.AbstractProjection radiography is in an advanced stage of progressive transition from conventional screen-film imaging to digital image acquisition modalities. The radiographic technique, including examination parameters such as tube voltage, tube current and filtration has frequently been adopted from screen-film technology. Digital systems, however, are characterized by their flexibility as the dose can be reduced at the expense of image quality and vice versa. The imaging parameters need to be individually optimized according to the best performance of a system. The traditional means of dose adjustment, such as positioning and collimation, are as valid for digital techniques as they were for conventional techniques. Digital techniques increasingly offer options for dose reduction. At the same time there is a risk to accidentally substantially increase patient dose due to the lack of visual control. Therefore, the implementation of dose indicators and dose monitoring is mandatory for digital radiography. The use of image quality classes according to the dose requirements of given clinical indications are a further step towards modern radiation protection.

Balance of required dose and image quality in digital radiography

Projection radiography is in an advanced stage of progressive transition from conventional screen-film imaging to digital image acquisition modalities. The radiographic technique, including examination parameters such as tube voltage, tube current and filtration has frequently been adopted from screen-film technology. Digital systems, however, are characterized by their flexibility as the dose can be reduced at the expense of image quality and vice versa. The imaging parameters need to be individually optimized according to the best performance of a system. The traditional means of dose adjustment, such as positioning and collimation, are as valid for digital techniques as they were for conventional techniques. Digital techniques increasingly offer options for dose reduction. At the same time there is a risk to accidentally substantially increase patient dose due to the lack of visual control. Therefore, the implementation of dose indicators and dose monitoring is mandatory for digital radiography. The use of image quality classes according to the dose requirements of given clinical indications are a further step towards modern radiation protection.ZusammenfassungDie Projektionsradiographie befindet sich in einer bereits weit fortgeschrittenen Umbruchphase zwischen konventionellen Film-Folien-Systemen und digitalen Verfahren. Die radiographische Technik einschließlich der Expositionsparameter wurde vielerorts einfach von Film-Folien-Systemen übernommen. Digitale Systeme sind sehr flexibel, die Dosis kann auf Kosten der Bildqualität gesenkt werden. Die Aufnahmetechnik muss für jedes System optimiert werden. Die Strahlenschutzgrundsätze der Einstelltechnik wie Kollimation und Positionierung sind für konventionelle und digitale Verfahren in gleicher Weise gültig. Die digitale Technik bietet viele Möglichkeiten zur Dosisreduktion, gleichzeitig besteht die Gefahr eines unbemerkten Dosisanstiegs wegen der fehlenden optischen Kontrolle. Daher sind die Anwendung von Dosisindikatoren und eine longitudinale Dosisüberwachung unerlässlich. Die Einführung von Bildqualitätsklassen zur indikationsabhängigen Dosisgestaltung von Untersuchungen ist ein weiterer Fortschritt für den Strahlenschutz.AbstractProjection radiography is in an advanced stage of progressive transition from conventional screen-film imaging to digital image acquisition modalities. The radiographic technique, including examination parameters such as tube voltage, tube current and filtration has frequently been adopted from screen-film technology. Digital systems, however, are characterized by their flexibility as the dose can be reduced at the expense of image quality and vice versa. The imaging parameters need to be individually optimized according to the best performance of a system. The traditional means of dose adjustment, such as positioning and collimation, are as valid for digital techniques as they were for conventional techniques. Digital techniques increasingly offer options for dose reduction. At the same time there is a risk to accidentally substantially increase patient dose due to the lack of visual control. Therefore, the implementation of dose indicators and dose monitoring is mandatory for digital radiography. The use of image quality classes according to the dose requirements of given clinical indications are a further step towards modern radiation protection.

Digitale Thoraxradiographie: Flat-panel-Detektor oder Speicherfolie?

ZusammenfassungFlat-Panel-Detektoren zeichnen sich durch ein verbessertes Handling und eine höhere Dosiseffizienz aus.Sie erlauben eine Effizienzsteigerung des Workflows sowie eine Dosisreduktion um bis zu 50% gegenüber bisher üblichen Systemen der Empfindlichkeit 400. Ob die verbesserte Dosisausbeute jedoch zur Dosisreduktion oder sinnvoller zur Verbesserung der Bildqualität im Thorax einzusetzen ist, ist noch nicht klar und obliegt derzeit der subjektiven Präferenz des Radiologen.Wird die Dosis nicht verringert, eröffnet das niedrigere Bildrauschen die Möglichkeit, durch geeignete Bildverarbeitung im Mediastinum die Kontraste zu verstärken und in der Lunge die Darstellung kleiner oder kontrastarmer Strukturen weiter zu verbessern. Hierfür sind neuartige Multifrequenzfilterungen besonderes geeignet. Spezielle Anwendungen der Zweispektrenradiographie und temporalen Subtraktion profitieren von der neuen Detektortechnologie und werden auch im Zusammenhang mit der automatischen Detektion pulmonaler Läsionen weiter vorangetrieben werden, auch wenn sie derzeit noch keine breite praktische Anwendung finden. Die Speicherfolienradiographie stellt aufgrund ihrer größeren Flexibilität bzgl. der Gerätekonfiguration, ihrer Einsatzmöglichkeiten in der Intensiv- und Notfallradiographie sowie aus ökonomischen Gründen ein nach wie vor ernstzunehmendes Alternativverfahren dar.Dies wird dadurch unterstützt, dass auch die Bildqualität der Speicherfolienradiographie einen hohen Standard hat und aufgrund neuer Entwicklungen in Detektortechnologie und Bildverarbeitung kontinuierlich verbessert werden konnte.AbstractFlat panel detectors are characterized by improved handling and increased dose efficiency. This allows for increasing of work flow efficiency and for reducing the exposure dose by about 50% compared to current systems with a sensitivity of 400.Whether the increased dose efficiency should be used to reduce acquisition dose or to increase image quality in the chest, will be shown by further clinical experience and will be also determined by the subjective preference of the radiologists.The decreased level of image noise opens new perspectives for image processing that way that elaborated multifrequency processing allows for optimizing the display of very small and low contrast structures that was so far limited by overlying image noise.Specialized applications of dual energy subtraction and temporal subtraction will also profit by the new detector technology and will be further driven forward in context with applications such as computed assisted diagnosis even though this is currently not yet broadly applied.Storage phosphor radiography still represents an important alternative technique based on its larger flexibility with respect to equipment configuration, its broader application options in intensive care and emergency radiology and due to economic reasons.These facts are further underlined by the fact that image quality also in storage phosphor radiography could be constantly increased by improving detector technology and image processing and consequently has a high standard.

EORTC Imaging Group

Imaging data have the potential to provide information on disease profiling pertaining to diagnosis, prognosis, selection of therapy, monitoring of response to therapy and pharmacokinetic information of drugs. Selection of the most appropriate imaging modality for a specific task will be vital for diagnosis, stratification, treatment response or treatment efficacy, toxicity assessment, and treatment outcome measures (progression-free survival). The EORTC Imaging Group was formed to establish and maintain the scientific and clinical value of advanced imaging in EORTC clinical trials. The group focuses on the development of specific analytical and review procedures as well as quality control procedures, in the context of clinical trials conducted by the EORTC groups.

Two K versus 4 K storage phosphor chest radiography: detection performance and image quality

The purpose of this study was to evaluate the effect of matrix size (4-K versus 2-K) in digital storage phosphor chest radiographs on image quality and on the detection of CT-proven thoracic abnormalities. In 85 patients who underwent a CT of the thorax, we obtained two additional posteroanterior storage phosphor chest radiographs, one with a matrix size of 3,520×4,280 (=4-K) and the other with a matrix size of 1,760×2,140 (=2-K). Acquisition, processing and presentation parameters were identical for all radiographs. Two radiologists evaluated the presence of mediastinal, pleural, and pulmonary abnormalities on hard copies of the radiographs, applying ROC analysis. In addition, four radiologists were asked to subjectively rank differences in image quality and to assess the demarcation of anatomic landmarks comparing the images in a blinded side-by-side manner. These data were analyzed using a two-sided binomial test with a significance level of P<0.05. Both tests, the ROC analysis of the detection performance and the binomial test of the subjective quality ratings, did not reveal significant differences between the two matrix sizes. Compared to 2-K radiographs, 4-K storage phosphor chest radiographs do not provide superior detection performance or image quality when evaluated in identical hard copy formats.

Radiation Risk Associated with Lung Cancer Screening

Computed tomographic (CT) cancer screening has seen a steady increase in interest with the introduction of multislice CT scanners. The recent publication of the US National lung screening trial has proven a statistically significant reduction of cancer-related mortality and has boosted the discussion about the usefulness of introducing population-wide screening for lung cancer. While the potential benefits of screening are obvious, radiation dose may pose a long-term risk for the screened individual. This article describes the basis for radiation risk estimation and discusses the current dose controversy with special emphasis on CT screening for lung cancer. While there is no and probably never will be epidemiologic evidence for cancer induction in the dose range used for a single lung cancer screening examination, a non-negligible population risk cannot be ruled out considering the current evidence. Precise predictions of cancer risks are difficult because they depend heavily on the underlying statistical or radiobiologic model. While the risk of most radiation-induced cancers decreases with age, the relative risk of radiation-induced lung cancer peaks in the time interval between 40 and 70 years of age. However, if performed in a dose-conscious fashion, individual risks of lung cancer screening are very small and far outweighed by the published benefits of screening.