Peter Herzog

High-resolution MR-imaging of the liver with T2-weighted sequences using integrated parallel imaging: comparison of prospective motion correction and respiratory triggering.

To compare high‐resolution T2‐weigthed images of the liver with and without integrated parallel acquisition techniques (iPAT) using either breath‐hold sequences in combination with prospective acquisition motion correction (PACE) or respiratory triggering.

Multislice CT Imaging of Pulmonary Embolism

Abstract. In recent years CT has been established as the method of choice for the diagnosis of central pulmonary embolism (PE) to the level of the segmental arteries. The key advantage of CT over competing modalities is the reliable detection of relevant alternative or additional disease causing the patients symptoms. Although the clinical relevance of isolated peripheral emboli remains unclear, the alleged poor sensitivity of CT for the detection of such small clots has to date prevented the acceptance of CT as the gold standard for diagnosing PE. With the advent of multislice CT we can now cover the entire chest of a patient with 1-mm slices within one breath-hold. In comparison with thicker sections, the detection rate of subsegmental emboli can be significantly increased with 1-mm slices. In addition, the interobserver correlation which can be achieved with 1-mm sections by far exceeds the reproducibility of competing modalities. Meanwhile use of multislice CT for a combined diagnosis of PE and deep venous thrombosis with the same modality appears to be clinically accepted. In the vast majority of patients who receive a combined thoracic and venous multislice CT examination the scan either confirms the suspected diagnosis or reveals relevant alternative or additional disease. The therapeutic regimen is usually chosen based on the functional effect of embolic vascular occlusion. With the advent of fast CT scanning techniques, also functional parameters of lung perfusion can be non-invasively assessed by CT imaging. These advantages let multislice CT appear as an attractive modality for a non-invasive, fast, accurate, and comprehensive diagnosis of PE, its causes, effects, and differential diagnoses.

Magnetic resonance imaging-guided focused ultrasound treatment of symptomatic uterine fibroids: impact of technology advancement on ablation volumes in 115 patients.

ObjectivesThe aim of this study was to assess the impact of the advanced technology of the new ExAblate 2100 system (Insightec Ltd, Haifa, Israel) for magnetic resonance imaging (MRI)–guided focused ultrasound surgery on treatment outcomes in patients with symptomatic uterine fibroids, as measured by the nonperfused volume ratio. Materials and MethodsThis is a retrospective analysis of 115 women (mean age, 42 years; range, 27–54 years) with symptomatic fibroids who consecutively underwent MRI-guided focused ultrasound treatment in a single center with the new generation ExAblate 2100 system from November 2010 to June 2011. Mean ± SD total volume and number of treated fibroids (per patient) were 89 ± 94 cm3 and 2.2 ± 1.7, respectively. Patient baseline characteristics were analyzed regarding their impact on the resulting nonperfused volume ratio. ResultsMagnetic resonance imaging–guided focused ultrasound treatment was technically successful in 115 of 123 patients (93.5%). In 8 patients, treatment was not possible because of bowel loops in the beam pathway that could not be mitigated (n = 6), patient movement (n = 1), and system malfunction (n = 1). Mean nonperfused volume ratio was 88% ± 15% (range, 38%-100%). Mean applied energy level was 5400 ± 1200 J, and mean number of sonications was 74 ± 27. No major complications occurred. Two cases of first-degree skin burn resolved within 1 week after the intervention. Of the baseline characteristics analyzed, only the planned treatment volume had a statistically significant impact on nonperfused volume ratio. ConclusionsWith technological advancement, the outcome of MRI-guided focused ultrasound treatment in terms of the nonperfused volume ratio can be enhanced with a high safety profile, markedly exceeding results reported in previous clinical trials.

Is post-mortem CT of the dentition adequate for correct forensic identification?: comparison of dental computed tomograpy and visual dental record

The gold standard for identification of the dead is the visual dental record. In this context, several authors emphasize computed tomography (CT) as valuable supportive tool for forensic medicine. However, studies focusing on diagnostic accuracy of post-mortem computed tomography (PMCT) are still missing. Therefore, the aim of this study was to compare diagnostic accuracy of the visual dental record and post-mortem computed tomography (PMCT) of the dentition for identification of the dead. Ten whole skulls were included into the study. The entire dentition of each skull was first examined with the visual dental record as a gold standard and second using dental PMCT scans, performed on a 64-multi-detector CT (MDCT). 3D reformations, multi-planar reformations (MPR), and CT–orthopantomography (OPG) were performed in the post-processing. All examinations were analyzed by three independent investigators regarding the criteria for identification of the dead, e.g., in case of disaster. PMCT for the dental identification of the dead was difficult to perform and time consuming. Due to dental overlays and corresponding artifacts, the definite periphery of the dental fillings/inlays was not accurately defined resulting in 2.9% incorrect and 64.1% false negative findings, especially synthetic inlays were hardly or not recognizable at all. For the identification of the dead especially in case of disasters with large numbers of victims, the visual dental record is still to be considered the gold standard. In the identification process itself, there is no room for error at all, although some non-concordant information may occur. Thus, PMCT should only be performed for identification in individual cases due to the relatively high error rate.

CT Perfusion Imaging of the Lung in Pulmonary Embolism

Recent years have seen an increasing importance of computed tomography (CT) in the diagnosis of pulmonary embolism (PE), mainly brought about by the advent of fast CT image acquisition techniques (Kauczor et al. 1999; Remy-Jardin and Remy 1999; Schoepf et al. 2000a, b). Competing imaging modalities are in decline: nuclear scanning allows functional assessment of lung ventilation and perfusion but lacks spatial resolution (PIOPED-Investigators 1990). Once the first line of defense in the diagnostic algorithm of PE, this modality is currently withdrawing to diagnostic niches due to limited availability, poor inter-observer correlation (Blachere et al. 2000), and notorious lack of specificity (PIOPED-Investigators 1990). Pulmonary angiography, the one-time gold standard for the diagnosis of PE, is becoming increasingly tarnished (Diffin et al. 1998; Stein et al. 1999). Its ability to detect isolated peripheral emboli does not seem to exceed the accuracy of computed tomography (Diffin et al. 1998; Stein et al. 1999).

Detection of Cardiac Metastasis by Positron-Emission Tomography–Computed Tomography

A 59-year-old woman was referred for staging of breast cancer with known hepatic metastases before inclusion in a chemotherapy trial. She had undergone breast-conserving surgery and adjuvant radiotherapy 8 years earlier at primary diagnosis. On a routine CT scan, a right atrial mass measuring 25×22 mm was detected (see Figure 2). The polyp-like pedunculated appearance and the location at the crista terminalis were suggestive of a myxoma. At the time of diagnosis, the ECG was unremarkable and …

[CT angiography of the coronary arteries with a 16-row spiral tomograph. Effect of spatial resolution on image quality].

ZusammenfassungFragestellung. Evaluation der Bildqualität der koronaren CT-Angiographie (CTA) mit einem 16-Mehrzeilen-Spiral-CT (MSCT), bei einer Rekonstruktion von 0,75-mm-Schichten für optimale räumliche Auflösung und Vergleich mit 1,3-mm-Schichten, die die räumliche Auflösung eines 4-MSCT simulieren. Methodik. Bei 10 Patienten wurde die CTA der Herzkranzgefäße mit einem 16-MSCT und 0,75 mm Kollimation durchgeführt. Die Rohdaten wurden retrospektiv unter Verwendung zweier unterschiedlicher Einstellungen rekonstruiert. A: B20f smooth Kernel, 1,3 mm Schichtdicke axialer MPR mit 0,7 mm Inkrement. B: B35f “HeartView”-medium-smooth Kernel, 0,75 mm Schichtdicke, 0,5 mm Inkrement. Zwei Regions of interest (ROI) wurden in den akquirierten axialen Schichten im Bereich der Aortenwurzel (AR) und im Bereich des linken Ventrikels (LV) platziert. Das Bildpunktrauschen wurde über die Standardabweichung der CT-Dichtewerte ermittelt.Zwei Untersucher evaluierten die Darstellung der Koronararterien in standardisierten MIP-Projektionen in Left-anterior-, right-anterior- und left-anterior-cranial-Ansicht von Einstellung A und B. Jede MIP-Projektion wurde anhand einer Fünfpunkteskala bzgl. der Gefäß- und Plaqueabgrenzung bewertet. Die ermittelten Punkte jedes Datensatzes wurden addiert und verglichen. Ergebnisse. Es wurde kein signifikanter Unterschied zwischen den gemessenen CT-Dichtewerte für die Einstellungen A und B ermittelt (A: 283,0 in AR/295,9 im LV und B: 282,9 in AR/297,2 im LV; p >0,2). Zwischen A und B wurde aber ein signifikanter Unterschied bzgl. des Bildpunktrauschens deutlich (A: 4,46 in AR/1,67 im LV und B: 8,16 in AR/7,38 im LV; p <0,01). Die aus den Daten von B berechneten Maximum-Intensitäts-Projektionen (MIP) erlaubten eine deutlich bessere Abgrenzung der Herzkranzgefäße und evtl. vorhandener atherosklerotischer Läsionen. Schlussfolgerung. Aus dünnschichtiger Rekonstruktion resultiert ein höheres Bildpunktrauschen im Vergleich zu simulierten Bilddaten einer 4-MSCT-Angiographie der Koronargefäße. Die MIP-Rekonstruktionen profitieren jedoch von der verbesserten räumlichen Auflösung.AbstractPurpose. To evaluate image quality of coronary CT angiography with retrospectively ECG-gated 16 multi-slice spiral CT (MSCT), reconstructed with 0.75 mm slice thickness for optimal spatial resolution and with 1.3 mm slice thickness, to produce spatial resolution comparable to a 4-MSCT. Materials and methods. Ten patients underwent coronary CT angiography with a 16-MSCT (Siemens Sensation 16, Forchheim, Germany) with 0.75 mm detector collimation. Raw helical CT data were retrospectively reconstructed using two different settings. Setting A: B20f smooth kernel, axial MPR with 1.3 mm slice thickness and 0.7 mm increment. Setting B: B35f “HeartView” medium-smooth kernel, 0.75 mm slice thickness, 0.5 mm increment. In the axial slices two regions of interest (ROIs) were placed in the area of the aortic root (AR) and more caudal in the area of the left ventricle (LV). Image noise was determined by the standard deviation of the CT numbers.Two readers determined visibility of coronary arteries by standardized maximum intensity projections (MIP) post-processing in left, right anterior and left anterior oblique projection plane from setting A and B. Each projection was rated on a five point rating scale concerning plaque delineation. Points determined for each data set were summed up and used for comparison. Results. No significant difference between the CT-numbers was found for setting A and B (A: 283.0 in AR/295.9 in LV and B: 282,9 in AR/297.2 in LV; p >0.2). However, the image noise was significantly different for setting A and B (A: 4.46 in AR/1.67 in LV and B: 8.16 in AR/7.38 in LV; p <0.01). Better delineation of the coronary arteries and atherosclerotic lesions could be achieved from MIP projections in setting B compared to setting A. Conclusion. Higher image noise is present in coronary 16-MSCT with thin-slice reconstruction compared to simulated 4-MSCT. However the MIP-reconstructions benefit most from the higher spatial resolution.

CT-Angiographie der Koronararterien mit einem 16-Mehrzeilen-Spiral-CT Einfluss der räumlichen Auflösung auf die Bildqualität

ZusammenfassungFragestellung. Evaluation der Bildqualität der koronaren CT-Angiographie (CTA) mit einem 16-Mehrzeilen-Spiral-CT (MSCT), bei einer Rekonstruktion von 0,75-mm-Schichten für optimale räumliche Auflösung und Vergleich mit 1,3-mm-Schichten, die die räumliche Auflösung eines 4-MSCT simulieren. Methodik. Bei 10 Patienten wurde die CTA der Herzkranzgefäße mit einem 16-MSCT und 0,75 mm Kollimation durchgeführt. Die Rohdaten wurden retrospektiv unter Verwendung zweier unterschiedlicher Einstellungen rekonstruiert. A: B20f smooth Kernel, 1,3 mm Schichtdicke axialer MPR mit 0,7 mm Inkrement. B: B35f “HeartView”-medium-smooth Kernel, 0,75 mm Schichtdicke, 0,5 mm Inkrement. Zwei Regions of interest (ROI) wurden in den akquirierten axialen Schichten im Bereich der Aortenwurzel (AR) und im Bereich des linken Ventrikels (LV) platziert. Das Bildpunktrauschen wurde über die Standardabweichung der CT-Dichtewerte ermittelt.Zwei Untersucher evaluierten die Darstellung der Koronararterien in standardisierten MIP-Projektionen in Left-anterior-, right-anterior- und left-anterior-cranial-Ansicht von Einstellung A und B. Jede MIP-Projektion wurde anhand einer Fünfpunkteskala bzgl. der Gefäß- und Plaqueabgrenzung bewertet. Die ermittelten Punkte jedes Datensatzes wurden addiert und verglichen. Ergebnisse. Es wurde kein signifikanter Unterschied zwischen den gemessenen CT-Dichtewerte für die Einstellungen A und B ermittelt (A: 283,0 in AR/295,9 im LV und B: 282,9 in AR/297,2 im LV; p >0,2). Zwischen A und B wurde aber ein signifikanter Unterschied bzgl. des Bildpunktrauschens deutlich (A: 4,46 in AR/1,67 im LV und B: 8,16 in AR/7,38 im LV; p <0,01). Die aus den Daten von B berechneten Maximum-Intensitäts-Projektionen (MIP) erlaubten eine deutlich bessere Abgrenzung der Herzkranzgefäße und evtl. vorhandener atherosklerotischer Läsionen. Schlussfolgerung. Aus dünnschichtiger Rekonstruktion resultiert ein höheres Bildpunktrauschen im Vergleich zu simulierten Bilddaten einer 4-MSCT-Angiographie der Koronargefäße. Die MIP-Rekonstruktionen profitieren jedoch von der verbesserten räumlichen Auflösung.AbstractPurpose. To evaluate image quality of coronary CT angiography with retrospectively ECG-gated 16 multi-slice spiral CT (MSCT), reconstructed with 0.75 mm slice thickness for optimal spatial resolution and with 1.3 mm slice thickness, to produce spatial resolution comparable to a 4-MSCT. Materials and methods. Ten patients underwent coronary CT angiography with a 16-MSCT (Siemens Sensation 16, Forchheim, Germany) with 0.75 mm detector collimation. Raw helical CT data were retrospectively reconstructed using two different settings. Setting A: B20f smooth kernel, axial MPR with 1.3 mm slice thickness and 0.7 mm increment. Setting B: B35f “HeartView” medium-smooth kernel, 0.75 mm slice thickness, 0.5 mm increment. In the axial slices two regions of interest (ROIs) were placed in the area of the aortic root (AR) and more caudal in the area of the left ventricle (LV). Image noise was determined by the standard deviation of the CT numbers.Two readers determined visibility of coronary arteries by standardized maximum intensity projections (MIP) post-processing in left, right anterior and left anterior oblique projection plane from setting A and B. Each projection was rated on a five point rating scale concerning plaque delineation. Points determined for each data set were summed up and used for comparison. Results. No significant difference between the CT-numbers was found for setting A and B (A: 283.0 in AR/295.9 in LV and B: 282,9 in AR/297.2 in LV; p >0.2). However, the image noise was significantly different for setting A and B (A: 4.46 in AR/1.67 in LV and B: 8.16 in AR/7.38 in LV; p <0.01). Better delineation of the coronary arteries and atherosclerotic lesions could be achieved from MIP projections in setting B compared to setting A. Conclusion. Higher image noise is present in coronary 16-MSCT with thin-slice reconstruction compared to simulated 4-MSCT. However the MIP-reconstructions benefit most from the higher spatial resolution.

Strahlendosis und Möglichkeiten zur Dosisreduktion in der Mehrschicht-CT

ZusammenfassungDie Mehrschichtcomputertomographie (MSCT) hat seit ihrer Einführung vor wenigen Jahren eine weite Verbreitung erfahren und sich bei zahlreichen Indikationen als leistungsfähiges Verfahren etabliert. Problematisch ist die z. T. deutlich höhere Strahlenexposition der Patienten, sowohl im Vergleich zur Einzelschicht-CT wie auch im Vergleich zu anderen diagnostischen Verfahren.Die MSCT bietet jedoch zahlreiche Möglichkeiten zur Dosiseinsparung. Durch Wahl adäquater Aufnahmeparameter, die bessere Dosiseffektivität im Vergleich zur Einzelschicht-CT sowie durch die Einschränkung von Mehrphasenuntersuchungen kann die Dosis deutlich reduziert werden. Moderne Untersuchungsgeräte bieten darüber hinaus intelligente technische Lösungen und Verbesserungen zur Dosiseinsparung wie die EKG-gestützte oder die körperquerschnittsabhängige Röhrenstrommodulation.Als neues Anwendungsfeld ist die Niedrigdosis-CT in der Krankheitsfrüherkennung hinzugekommen. Hierbei werden mit extrem reduzierter Dosis dünnschichtige Datensätze von Hochkontrastobjekten aufgenommen, wobei die Strahlenexposition in der selben Größenordnung liegt wie vergleichbare konventionelle Röntgenübersichtsaufnahmen.Bei Beachtung der genannten Möglichkeiten kann die Strahlenexposition bei der MSCT gegenüber der Einzelschicht-CT insgesamt reduziert werden.AbstractSince its introduction a few years ago, multidetector row CT (MDCT) has become a widely used diagnostic procedure and has been proven to be a valuable tool for various indications. A major issue using this new modality is the inherent risk of applying increased radiation exposure, when compared to single-slice CT or other imaging modalities.However, MDCT offers some valuable options to save radiation exposure, such as choosing optimized exposure parameters or its superior dose efficiency in comparison to single-slice CT. Multi-phasic examinations should be restricted to indications where definitely necessary. Modern scanners offer intelligent tools for further reduction of radiation dose, such as ECG- or bodyshape-based realtime dose modulation. A new field of applications is the low-dose CT for early detection of diseases. While acquiring thin slices with high spatial resolution, the dose can be reduced to similar values as in conventional radiography, especially when examining under high-contrast conditions.Using all these various options available, radiation exposure can sometimes even be lower than using a conventional single-slice helical CT.

[Interventional MRI of the breast. Indications, technique, results and perspectives].

ZusammenfassungDer zunehmende Einsatz der MRT in der Mammadiagnostik erhöht den Stellenwert geeigneter Biopsieverfahren für abklärungsbedürftige Befunde, die ausschließlich im MRT sichtbar werden. MR-gestützte Biopsieverfahren sind kostenaufwändig und zeitintensiv. Die standardisierte Qualität der indikationsstellenden MRT-Untersuchung ist deshalb von entscheidender Bedeutung für den sinnvollen Einsatz MR-gestützter Biopsieverfahren.Bei geeigneter Indikationsstellung ist die MR-geführte Vakuumbiopsie eine sehr sichere Abklärungsmethode, die auch bei kleinen Herdbefunden eine zuverlässige histopathologische Diagnose erlaubt. Bislang war der Biopsievorgang bei einer MR-geführten Vakuumbiopsie aufgrund der fehlenden Kompatibilität der Nadeln nicht der Bildgebung zugänglich. Besondere Sorgfalt gilt daher der Überprüfung der Repräsentativität der Probengewinnung durch postinterventionelle Aufnahmen und die histopathologische Korrelation der bildgebenden Befunde. Künftige Entwicklungen werden MR-kompatible Biopsienadeln in Herdlokalisation abbilden können und damit Lokalisationsunsicherheiten und Zeitaufwand der Methode weiter minimieren. Für die Abklärung von Zweitherden bei bereits bestehender Operationsindikation bleibt die MR-gestützte Nadelmarkierung ipsi- und kontralateraler Zweitherde eine technisch einfache und schnell durchführbare Methode.AbstractWith the use of diagnostic MR imaging of the breast MR guided minimal invasive interventions are increasingly needed to obtain histologic proof of lesions, that are occult at mammography and ultrasound. MR guided interventions are time consuming and expensive. Therefore it is necessary to insure, that the diagnostic MR examination of the referring institution establishing the indication for biopsy is of high quality.Assuming accurate patient selection percutaneous MR vacuum-assisted biopsy is a safe and accurate method for the evaluation of even small enhancing breast lesions. Up to now the imaging of the biopsy procedure itself is not possible due to a lack of compatibility of the biopsy needle. Careful reviewing of imaging and pathologic findings is therefore recommended. Several newly developed MR compatible devices will allow more precise placement and imaging of the biopsy needle. Procedure times will be reduced. For the evaluation of additional enhancing lesions in patients with breast carcinoma referred for operation the preoperative wire localization is remaining a wide-spread safe and simple method.With the use of diagnostic MR imaging of the breast MR guided minimal invasive interventions are increasingly needed to obtain histologic proof of lesions, that are occult at mammography and ultrasound. MR guided interventions are time consuming and expensive. Therefore it is necessary to insure, that the diagnostic MR examination of the referring institution establishing the indication for biopsy is of high quality.Assuming accurate patient selection percutaneous MR vacuum-assisted biopsy is a safe and accurate method for the evaluation of even small enhancing breast lesions. Up to now the imaging of the biopsy procedure itself is not possible due to a lack of compatibility of the biopsy needle. Careful reviewing of imaging and pathologic findings is therefore recommended. Several newly developed MR compatible devices will allow more precise placement and imaging of the biopsy needle. Procedure times will be reduced. For the evaluation of additional enhancing lesions in patients with breast carcinoma referred for operation the preoperative wire localization is remaining a wide-spread safe and simple method.