M. Thelen

Focal airtrapping at expiratory high-resolution CT: comparison with pulmonary function tests

Abstract. This study was undertaken to determine prevalence, extent, and severity of focal airtrapping at expiratory high-resolution CT, and to compare focal airtrapping with age, gender, pulmonary function tests, and blood gas analysis. Two-hundred seventeen patients with and without pulmonary disease underwent paired inspiratory/expiratory high-resolution CT. Six scan pairs with corresponding scan levels were visually assessed for focal – not diffuse – airtrapping using a four-point scale. Pulmonary function tests and blood gas analysis were available for correlation in all patients (mean interval 5 days). Focal airtrapping with lower lung predominance was observed in 80 % of patients. Twenty-six of 26 patients with restrictive lung function impairment exhibited focal airtrapping (mean score 2.4), whereas only 72 of 98 (74 %) patients with obstruction did (mean score 1.5; p < 0.05). Fifty-eight of 70 (83 %) patients with normal lung function (mean score 1.8) and 19 of 23 (83 %) patients with mixed impairment (mean score 1.8) had focal airtrapping. Focal airtrapping showed negative correlations with static lung volumes (–0.27 to –0.37; p < 0.001) in all patients and moderate positive correlations with dynamic parameters (0.3–0.4; p < 0.001) in patients with obstruction. No significant correlations were found with age, gender, and blood gas analysis. Visual assessment of focal – not diffuse – airtrapping at expiratory high-resolution CT does not correlate with physiological evidence of obstruction as derived from pulmonary function tests since the perception of focal airtrapping requires an adequate expiratory increase in lung density.

MR arthrography of the shoulder: comparison of low-field (0.2 T) vs high-field (1.5 T) imaging.

The objective of this study was to compare the image quality, sensitivity, specificity, and diagnostic accuracy of an open low-field MR system (0.2 T) with a standard high-field MR system (1.5 T) after arthrography of the shoulder. Thirty-eight patients either with suspected chronic instability (n=12) or rotator cuff abnormalities (n=26) were examined. In-tra-articular injection of diluted Gd-DTPA was followed in randomized order either first by imaging on an open 0.2-T system or on a 1.5-T system. The image material was evaluated independently by two radiologists in a blinded fashion with respect to overall image quality and the detection of rotator cuff as well as capsular and labral abnormalities. Surgical correlation was available in 27 (71%) of 38 patients. For both systems, sensitivity and specificity for rotator cuff tears were 100% each, and for labrum pathologies, these values were 100 and 93%, respectively. The agreement for detection of labral pathologies between low-field and high-field examinations was good (ϰ=0.69, ϰ=0.61). For the detection of full-thickness tears of the rotator cuff, the agreement between the low-field and high-field MR examinations was very good and significant (ϰ=0.94, ϰ=1, p<0.001). Overall image quality was rated good in 17 (45 %) and fair in 21 (55 %) of 38 cases on the 0.2-T MR system, and good in 32 (84%) and fair in 6 (16%) of 38 cases on the 1.5-T system. Motion artifacts were considered low in 24 (63 %) and moderate in 14 (37 %) of 38 cases for the 0.2-T system and low in 34 (89%) and moderate in 4 (11 %) for 1.5-T system. Based on our results, low-field MR compares favorably to high-field MR in the detection of major abnormalities of the glenohumeral joint, at least when MR arthrography is used. Disadvantages are the duration of the examination and thus the risk of reduced image quality caused by motion artifacts.

Low-field MR arthrography of the shoulder joint: technique, indications, and clinical results.

Abstract. In the age of cost containment and urgent reductions in health care expenditures, new options have to be explored to satisfy both diagnostic requirements and economic limitations. The introduction of low-field MR systems for assessment of joint disorders seemed to be an option for lower costs. The purpose of this article is to summarize available experiences with low-field MR arthrography of the glenohumeral joint with respect to image quality and diagnostic accuracy in detecting labral and rotator cuff lesions. Up to now, there has been only a limited number of studies available dealing with low-field MR arthrography of the glenohumeral joint. They reveal that, despite a minor image quality in comparison with high-field imaging, low-field MR arthrography of the shoulder allows for sufficient evaluation of intra- and extra-articular structures in the detection of major abnormalities such as glenohumeral instability or rotator cuff disease. Furthermore, open-configured MR scanners enable kinematic studies: Besides the analysis of normal motion, pathological findings in patients with instabilities and impingement syndrome can be delineated. They further offer the possibility for performing MR imaging-guided arthrography of the shoulder. This was first described using an open C-arm scanner with a vertically oriented magnetic field so that MR arthrography may be performed in one setting.

Evaluation of changes in central airway dimensions, lung area and mean lung density at paired inspiratory/expiratory high-resolution computed tomography

Abstract.The aim of this study was to improve the understanding of interdependencies of dynamic changes in central airway dimensions, lung area and lung density on HRCT. The HRCT scans of 156 patients obtained at full inspiratory and expiratory position were evaluated retrospectively. Patients were divided into four groups according to lung function tests: normal subjects (n=47); obstructive (n=74); restrictive (n=19); or mixed ventilatory impairment (n=16). Mean lung density (MLD) was correlated with cross-sectional area of the lung (CSAL), cross-sectional area of the trachea (CSAT) and diameter of main-stem bronchi (DB). The CSAL was correlated with CSAT and DB. MLD correlated with CSAL in normal subjects (r=−0.66, p<0.0001) and patients with obstructive (r=−0.62, p<0.0001), restrictive (r=−0.83, p<0.0001) and mixed ventilatory impairment (r=−0.86, p<0.0001). The MLD correlated with CSAT in the control group (r=−0.50, p<0.0001) and in patients with obstructive lung impairment (r−0.27, p<0.05). In patients with normal lung function a correlation between MLD and DB was found (r=−0.52, p<0.0001). CSAL and CSAT correlated in the control group (r=0.67, p<0.0001) and in patients with obstructive lung disease (r=0.51, p<0.0001). The CSAL and DB correlated in the control group (r=0.42, p<0.0001) and in patients with obstructive lung disease (r=0.24, p<0.05). Correlations for patients with restrictive and mixed lung disease were constantly lower. Dependencies between central and peripheral airway dimensions and lung parenchyma are demonstrated by HRCT. Best correlations are observed in normal subjects and patients with obstructive lung disease. Based on these findings we postulate that the dependencies are the result of air-flow and pressure patterns.

Magnetic resonance imaging of coronary artery occlusions in the navigator technique

Non-invasive assessment of coronary arteries is possible with magnetic resonance imaging (MRI). Respiratory gated MR coronary angiography is a new imaging technique that permits reconstruction of the coronary arteries based on a three-dimensional (3D) data set obtained from the free-breathing patient. In this study, respiratory gated MR angiography (MRA) was performed to assess coronary artery occlusions. MRI was performed in 25 patients who had been referred for conventional coronary angiography because of suspected coronary artery disease. Coronary artery occlusion was evaluated in the proximal and middle vessel segments after multiplanar coronary reconstruction of the MR images. Five patients were excluded from the study; in the remaining 20 patients 120 coronary artery segments were analyzed. Good image quality could be obtained for 85% of the segments. Eighteen of the 24 occlusions were confirmed by MRI, the overall sensitivity was 75% and the specificity was 100%. The best results were found in the proximal left anterior descending (LAD) and descending parts of the right coronary artery (RCA), where all occlusions were confirmed. These results showed that coronary artery occlusions can be detected in the proximal and middle LAD and RCA using 3D respiratory gated MRA. Further technical improvements, especially in spatial resolution, are necessary before MRA can become a reliable diagnostic tool in the non-invasive evaluation of coronary arteries.

Kernspintomographische Darstellung koronarer Bypassgefäße – Vergleich der Haste- und Fisp-3-D-Angiographiesequenz mit der konventionellen Koronarangiographie

The aim of the study was to evaluate the patency of coronary artery bypass grafts (CABG) with the 2D and 3D magnetic resonance (MR) imaging techniques. 29 patients with 74 bypass grafts and a total of 91 distal anastomoses were studied on a 1.5 Tesla scanner using a phased array body coil. A 2D T-2 weighted breathhold turbo spin echo sequence (Haste) and a 3D breath hold contrast enhanced MR angiography sequence (Fisp-3-D) were performed. With the Haste and Fisp-3-D sequences 55 of the 58 patent and 15 of the 16 occluded grafts were recognized; the sensitivity and specifity were 95% and 94%, respectively. With the Haste sequence 74% (47/63) and with the Fisp-3-D sequence 64% (40/63) of the distal anastomoses were seen in good image quality. Only 3 of 8 significant grafts stenoses were detected. The patency of CABGs can be evaluated non-invasively with the Haste and the Fisp-3-D angiography sequences. Better results can be expected with the development of a blood-pool contrast medium and the combination of MR flow measurements with imaging techniques. Das Ziel der Studie war die kernspintomographische Evaluierung koronarer Bypassgefäße mit der Haste- und Fisp-3-D-Angiographiesequenz unter besonderer Berücksichtigung der distalen Bypassanastomose. Eingeschlossen wurden 29 Patienten mit 74 Bypassgefäßen und insgesamt 91 distalen Anastomosen. Eingesetzt wurden eine 2dimensionale, T-2-gewichtete Turbo-Spin-Echo-Sequenz (Haste) sowie eine 3dimensionale, kontrastmittelunterstützte Angiographiesequenz (Fisp-3-D) in Atemanhaltetechnik. Sowohl mit der Haste- als auch der Fisp-3-D-Sequenz konnten 55 der 58 offenen und 15 der 16 verschlossenen Bypässe korrekt beurteilt werden, die Sensitivität und Spezifität betrug 95% und 94%. Überlegen war die Haste-Sequenz (47/63) der Fisp-3-D-Sequenz (40/63) in der Beurteilung der distalen Anastomosen. Bypasstenosen konnten lediglich in 3 von 8 Fälen diagnostiziert werden. Mit der Kernspintomographie ist mit beiden genannten Sequenzen eine nichtinvasive Evaluierung koronarer Bypassgefäße möglich, wobei die Haste-Sequenz in der Beurteilung distaler Bypassanteile überlegen ist. Eine Verbesserung der Aussagekraft der Methode ist durch den Einsatz von gefäßständigen Kontrastmitteln sowie durch die Kombination mit funktionellen Parametern wie der MR-Flußmessung zu erwarten.

Radiodiagnostik der Lunge

ZusammenfassungDie radiologischen Schnittbildverfahren, insbesondere die CT, haben sich innerhalb kurzer Zeit einen herausragenden Stellenwert in der Diagnostik von Lungenerkrankungen erworben. Dies umfasst in erster Linie die morphologische Darstellung pathologischer Prozesse mit hoher räumlicher Auflösung. Moderne technische Entwicklungen und kombinierte Untersuchungsstrategien eröffnen neue Einsatzgebiete und auch funktionelle Aussagen, die nach einer aktuellen Standortbestimmung gemeinsam mit den nuklearmedizinischen Verfahren verlangen. Dazu gehört die Diagnostik der Lungenembolie mittels Spiral-CT-Angiographie und MR-Angiographie der Pulmonalarterien. Hier hat sich mittlerweile die CT als alternatives Verfahren der Wahl etabliert und die Rolle der Pulmonalisangiographie als Goldstandard infrage gestellt. Die reine direkte Darstellung der durchströmten Pulmonalarterien und des thromboembolischen Materials wird durch Diagnostik intrapulmonaler und kardialer Veränderungen, Perfusionsuntersuchungen sowie MR-basierte Flussmessungen zur hämodynamischen Beurteilung erweitert. Nachdem Untersuchungen der Ventilation lange Zeit eine Domäne der Nuklearmedizin waren, eröffnen aktuelle Entwicklungen in der MRT neue Verfahren zur direkten Visualisierung der Lungenbelüftung, z. B. mittels polarisierter Edelgase. Aus diesen Verfahren lassen sich auch neue funktionelle Parameter der Ventilation ableiten. In der Diagnostik von Tumoren und Entzündungen überzeugt die CT insbesondere durch ihre hohe Sensitivität, z. B. beim Screening auf intrapulmonale Rundherde mittels Niedrigdosis-CT oder bei der Früherkennung pneumonischer Infiltrate bei Risikopatienten. Insbesondere bei der Charakterisierung intrapulmonaler Rundherde ist eine Kombination mit nuklearmedizinischen Verfahren (PET) grundsätzlich anzustreben.AbstractRadiological cross-sectional imaging modalities, particularly computed tomography (CT) have become the mainstays for diagnosing lung disease in recent years. These enable morphological visualization of pathological processes with the greatest possible spatial resolution. Modern technical developments and complementary strategies have led to new applications and new functional assessments which need to be reviewed together with state-of-the-art techniques in nuclear imaging. The diagnosis of pulmonary embolism using spiral CT angiography and magnetic resonance (MR) angiography certainly belongs in this category. CT has become the an alternative modality of first choice, and it is also challenging pulmonary angiography as the gold standard. Direct visualization of patent pulmonary arteries and thromboembolic material is complemented by that of effects on the pulmonary parenchyma and right heart function; it also provides perfusion studies and MR-based flow measurement to assess hemodynamic compromise. Ventilation studies have long been a domain of nuclear imaging, and new techniques for the direct visualization of ventilation are emerging from recent developments in the field of MR imaging, for example, using hyperpolarized inert gases. New functional parameters of ventilation can be derived from these studies. For the diagnosis of metabolically active disease, such as tumor and pneumonia, CT offers very high sensitivity, for example, in screening for intrapulmonary nodules using low-dose CT and in the early detection of pulmonary infiltrates in high-risk patients. Especially for characterizing pulmonary nodules there is a need to combine nuclear medicine techniques, such as in positron-emission tomography.

Die Lungentuberkulose – aktuelle radiologische Diagnostik einer alten Krankheit

ZusammenfassungInzidenz. Abnehmende Inzidenzen aktiver Tuberkulose in den Industrieländern haben diese Erkrankung aus dem Bewusstsein vieler verdrängt. Dennoch stellt die Tuberkulose weiterhin weltweit die am häufigsten zum Tode führende Infektionskrankheit dar. In den Industrieländern tragen Faktoren wie Einwanderungsbewegungen, zunehmende Verarmung und die Zunahme immunsupprimierter Patienten, insbesondere durch die HIV-Epidemie, dazu bei, dass ein Reservoir für die Tuberkulose aufrecht erhalten wird. Diagnose. Eine frühzeitige Diagnose ist wegen der spezifischen Therapiemöglichkeiten entscheidend für den Krankheitsverlauf; im Falle von multiresistenten Stämmen ist sie wichtig zur Verhinderung einer weiteren Ausbreitung. Bei der Diagnosefindung kommt der Thoraxübersichtsaufnahme und Computertomographie als radiologischen Verfahren eine zentrale Rolle zu. Befunde. Da die Tuberkulose ein breitgefächertes Spektrum von Befunden aufweist, herrscht oft Unklarheit über die zugrunde liegende Diagnose. Bei immunsupprimierten Patienten, aber auch immunkompetenten Patienten wird von atypischen Präsentationen berichtet. Der vorliegende Übersichtsbeitrag beschäftigt sich mit dem aktuellen Stand der Diagnostik bei der Lungentuberkulose.AbstractIncidence. Decreasing numbers of tuberculosis cases in the western countries have led to diminished attention towards this disease. But worldwide, tuberculosis still is the leading cause of mortality due to any one single infectious agent. In the industrialized countries, immigration, growth of low-income groups and increasing numbers of immunocompromised patients, mainly due to the HIV epidemic, supply a reservoir for tuberculosis. Diagnosis. Because of the option of a specific therapy, early diagnosis of tuberculosis is crucial for the course of the disease. In cases of multidrug resistant strains, further spread has to be prevented. Radiology with chest films and computed tomography has a central role in diagnosing tuberculosis. Findings. However, as the disease produces a broad spectrum of radiographic findings, there are often difficulties in determining the underlying diagnosis. Additionally, there have been reports of atypical presentations of tuberculosis in immunocompromised as well as immunocompetent patients. This article reviews the current state of radiological diagnosis of pulmonary tuberculosis.

Depiction of anomalous coronary vessels and their relation to the great arteries by magnetic resonance angiography

Abstract. Three-dimensional respiratory-gated coronary MR angiography (MRA) allowed accurate analysis of the anatomy of the coronary arteries and their relation to the adjacent anatomic structures in two patients with anomalous origin and proximal course of the coronary vessels. Together with functional tests, it decisively influenced further therapy.

Non-invasive magnetic resonance imaging of coronary bypass grafts. Comparison of the haste- and navigator techniques with conventional coronary angiography

Objective: The aim was the study was to evaluate the patency of coronary artery bypass grafts with the 3D Navigator and the Haste magnetic resonance imaging techniques. Material and methods: Thirty-four patients with 82 grafts (18 internal mammarian artery and 64 saphenous venous grafts) were examined at 1.5 T using a phased arrray body coil. A 2D T-2 weighted turbo spin echo sequence (Haste) and a 3D-angiography sequence in navigator technique were used. Reference method was the conventional coronary angiography that was performed within 7 days. Results: With the HASTE sequence 54 of 56 patent and 12 of the 16 occluded grafts were recognized, the sensitivity and specificity was 96 and 75%. The distal anastomosis could be assessed in 28 of 76 cases. With the Haste sequence 54 of the 56 patent and 12 of the 14 occluded grafts were detected correctly. Eight patent and two occluded grafts were judged as not assessable. The sensitivity and specificity was 96 and 85%. Sixty-six percent (50/76) of the distal anastomosis were identified correctly. With both sequences none of the bypass stenosis could be detected. Conclusions: The patency of coronary bypass grafts can be evaluated noninvasively with a sensitivity of 96% and a specificity of 76%. No inference can be made with respect to the nature of bypass graft stenosis. Better results can be expected with the development of a blood pool contrast medium, an improvement of the spatial resolution and in the combination of flow measurements.