[Acute aortic diseases. Diagnostic imaging and therapy]. / Akute Aortenerkrankungen. Aktuelle Diagnostik und Therapie.

Diagnostic imaging is crucial in the work-up of acute aortic diseases. Current imaging algorithms enable radiologists differentiating the various entities with subsequent clinically relevant treatment options. Within this educational overview we focus on non-traumatic acute aortic disease. Recent developments of cross sectional imaging are summarized. As for acute aortic disease, we discuss dissections, intramural hematoma, penetrating aortic ulcer, and aortitis. Current treatment options are presented.

[Contrast agents in radiology: current agents approved, recommendations, and safety aspects]. / Kontrastmittel in der Radiologie: Aktuelle Zulassungen, Empfehlungen und Sicherheitshinweise.

The manuscript summarizes current approved contrast media and their indications. Contrast agents that are discussed include iodinated contrast agents, magnetic resonance (MR) contrast agents, and ultrasound contrast agents. Allergic and non-allergic renal adverse events are described. The clinical issue of metformin and the administration of contrast agents are updated. Nephrogenic systemic fibrosis (NSF) is discussed and safety issues of available MR contrast agents are analyzed. The most recent changes in European Society of Urogenital Radiology (ESUR) guidelines are also presented.

[Value of MRI in preoperative diagnostics of proximal humeral fractures compared to CT and conventional radiography]. / Wertigkeit der MRT in der präoperativen Diagnostik proximaler Humerusfrakturen vs. CT und konventionelles Röntgen.

PURPOSE: The diagnostic value of X-rays, computed tomography (CT) and magnetic resonance imaging (MRI) for proximal humeral fractures (PHF) was compared in order to test the hypothesis that MRI gives relevant additional information. MATERIALS AND METHODS: In this study 30 displaced PHFs were investigated with X-ray, CT and MRI procedures. Fracture analysis was performed and the diagnostic values of the three methods were compared to each other. In the MRI relevant musculotendinous concomitant injuries and prognostic factors of the head perfusion were also evaluated. RESULTS: In 7 out of 30 PHFs the X-rays did not show the correct number of fragments. The posteromedial metaphyseal extension and the caput-diaphysis angle were measured to be significantly greater in the X-rays than in CT and MRI. Relevant additional information obtained by MRI were 7 out of 30 rotator cuff tears and 11 out of 30 differentiated medial periostal hinges. CONCLUSIONS: X-ray imaging is the basis method for the diagnosis of PHF but needs further multiplanar imaging to demonstrate complete fracture patterns. Imaging of fractures is equally good for MRI and CT and MRI also provides additional therapy-relevant information about the rotator cuff and head perfusion.

Nephrogenic systemic fibrosis.

Nephrogenic systemic fibrosis (NSF) is a relative new disease affecting predominantly patients with severely impaired kidney function. Strict adherence to a concordant clinical and pathological definition has allowed for careful separation of this entity from other fibrosing disorders, leading eventually to the realization that gadolinium based contrast agents were closely associated with its onset. Gadodiamide and similarly unstable Gd-CA should therefore not be used in patients with renal insufficiency. The clinical symptoms of NSF vary considerably from patient to patient. NSF should be suspected in renal failure patients presenting any possible NSF symptom appearing in the weeks after Gd-enhanced MRI. Suspected cases should have a skin biopsy taken from an affected region for the histological confirmation or rejection of the diagnosis. There are no established curative treatments to NSF patients. Prevention is the only alternative. Guidelines for the daily routine seem to be the right way. When NSF is identified the primary goal is reversal of underlying renal failure or renal transplantation. In addition, use of physical therapy and pain control is mandatory. One of the best news in late 2007 is the decreasing rate of newly detected NSF cases. In the case this development continues, NSF may become an historical disease in the near future.

Measurements of magnetism-related forces and torque moments affecting medical instruments, implants, and foreign objects during magnetic resonance imaging at all degrees of freedom.

We designed a novel force/torque moment transducer with six degrees of freedom. This new sensor is used for measuring the forces and torque moments exerted by static magnetic resonance imaging (MRI) fields on various medical implants, instruments, and ballistic shell fragments. To determine the location of strongest effect the inhomogeneity of the magnetic field between the entrance of the MRI-tube (portal), and the imaging section was measured. Force and torque moments of a sample of 45 objects were measured at two positions, at the portal, and in the center of the imaging section. We classified the objects regarding to the magnetism-related forces measured in the homogeneous part of the MRI tube. About one-third of the objects was non- or weakly magnetic, one-third moderately, and the last third was strongly magnetic. Forces within the inhomogeneous area of the magnetic field at the entrance part of the tube were up to half a magnitude larger than forces inside the homogeneous imaging section. Here the greatest potential risks to patients might occur.

Investigation of the imaging properties of an x-ray film scanner.

In this note, the imaging properties of a CCD x-ray film scanner were investigated. The relationship between optical density and the logarithm of output pixel value provides information on the linearity of the system. The resolution properties of the scanner can be characterized by the presampling modulation transfer function which was calculated from a set of line spread functions with various alignments relative to the sampling grid. Our results show that the scanner is linear up to 2.0 optical density units, which leads to restrictions in digitizing x-ray films with higher optical density. The measured MTF shows the good spatial resolution of the CCD scanner which is demonstrated on an example.

Electrocardiograph-triggered two-dimensional time-of-flight versus optimized contrast-enhanced three-dimensional MR angiography of the peripheral arteries.

We determined whether the accuracy of magnetic resonance angiography (MRA) in the peripheral run-off vessels can be improved by using contrast-enhanced (CE) three-dimensional (3D) technique in comparison to electrocardiograph (ECG)-triggered two-dimensional (2D) time-of-flight (TOF) technique. In a prospective study 20 patients with occlusions of the pelvic and/or femoral arteries underwent a CE 3D MRA (repetition time (TR): 5 ms, (TE) echo time: 2 ms, flip angle (FA): 30 degrees ) and an ECG-triggered 2D time-of-flight (TOF) technique (TR: 408 resp. 608 ms, TE: 7 ms, FA: 70 degrees) of the run-off vessels on a 1.5 T MR system. Each patient received a contrast material volume of 0.15 mmol/kg of body weight of gadolinium (Gd)/DTPA using an automatic injector. The tube system to the patient was flushed by 50 mL of a saline solution applied with the same injection rate as the contrast material administration. The start of the 3D MR sequence was tailored individually to the applied contrast material after determination of circulation times by a prior bolus. All patients underwent each conventional or digital arteriography for comparison, as well. The visualization of the run-off vessels was ranked on a scale of 0-3 (0 = poor, 1 = fair, 2 = good, 3 = excellent) by three blinded reviewers. They also graded the vascular segments as either occluded or significantly altered (>50% reduction in diameter) or free of significant stenosis. CE 3D MRA was significantly faster in imaging the run-off vessels in comparison to the ECG-triggered 2D TOF technique. All 160 vascular segments were visualized with the 3D method, whereas only 142/160 segments were seen with 2D technique. The resulting image quality ranking of all vascular segments was significantly higher (p < 0.05) using CE 3D MRA (2.8) than with the 2D TOF technique (2.4). The detection of the stenoses was possible with both techniques. The grading of seven of seven stenoses was correct with 3D method and in five of seven cases with the 2D TOF technique. All vessel occlusions were detected by using both techniques. Small collaterals were visualized in more detail with the CE 3D MR angiography. These data demonstrate an improvement in image quality and accuracy of MRA of the peripheral arteries using a CE 3D technique in comparison to an ECG-triggered 2D TOF sequence.

3D MR angiography of the entire aorta: modified application of the body-phased array coil for a single-shot technique.

OBJECTIVE: Evaluation of different contrast-enhanced MR angiography imaging protocols for visualization of the entire aorta in breath-hold technique. METHODS AND PATIENTS: Three different CE (0.15 mmol/kg) MRA protocols were evaluated by phantom and patient studies: (1) two separate MRA with conventional application of the body-phased array coil; (2) a single-shot MRA with modified application of the body-phased array coil; (3) a single-shot MRA with the body coil. Duplex sonography, CTA and DSA were used as standard of reference. RESULTS: In all examinations the entire aorta could be visualized. The best SNR was acquired with protocol (1). The SNR of protocol (2) was reduced if the sagittal body diameter of the patient was greater than 20 cm and decreased significantly with diameters over 30 cm. By the use of protocol (3) the SNR was notably poor. The quality scored for the visualization of the entire aorta was 97.5% (protocol 1); 92.5% (protocol 2); and 80.0% (protocol 3). CONCLUSION: In most cases the modified application of the body-phased array coil allows the imaging of the entire aorta as a single-shot 3D CE MRA in diagnostic quality.

[The tilted screen-cassette ("grid cut-off" effect). A problem of bedside thoracic diagnosis]. / Die verkippte Rasterkassette ("grid cut-off"-Effekt). Ein Problem der bettseitigen Thoraxdiagnostik.

Tilting of a grid during portable radiography leads to uneven exposures, and errors greater than 3 degrees can lead to errors in interpretation. Differentiation from abnormal findings can be made by recognising exposure difference of extrathoracic comparable areas. The difficulties caused by tilting of the grid can be reduced by increasing the film focus distance and by using suitable grids. A new cassette holder with an integrated balance makes it possible to correct tilting of the grid rapidly and effectively. This results in improved image quality which can be applied not only to conventional exposure systems but is also of advantage when using digital methods.

[Initial experiences with the MR "magnitude contrast angiography of the lower extremities]. / Erste Erfahrungen mit der MR-"Magnitude Contrast Angiography" an den unteren Extremitäten.

45 patients with occlusive peripheral vascular disease were examined by MR angiography in a retrospective study. A FISP 3D sequence was used by acquiring a rephased and a dephased data set. The individual slices were post-processed by using a maximum-intensity-projection algorithm. The MRA results of the popliteal and tibioperoneal arteries were compared to conventional or digital angiography. In comparing these techniques MR angiography cannot be accepted for pre- and postoperative staging of patients with occlusive peripheral vascular disease. In future new MRA techniques may be useful in postoperative staging of patients with peripheral vascular stenosis.

[The acetabular prosthesis: detection of a migration using ruler and pencil? Measurements on a pelvic phantom in comparison with a 3D computer simulation]. / Hüftpfannenprothese: Nachweis einer Migration mit Lineal und Bleistift? Messungen am Beckenphantom im Vergleich mit einer 3D-Computersimulation.

Conventional X-ray films were made with varying degrees of tilt of a pelvic phantom containing an acetabular prosthesis. The position of the prosthesis was then reconstructed graphically. The measurement errors were calculated and an estimate was made for the tilt. There is a linear correlation between the measurement error and the tilt of the prosthesis. Therefore a tilt dependent maximum error can be calculated. This error is very small for small degrees of tilt, so that acetabular migration can in this instance be evaluated with greater confidence than with other graphical methods. The error also correlates with the determination of the selected region of the acetabulum, but not with the position of the central focus spot or image magnification.

[2-D-time-of-flight MR angiography of the peripheral blood vessels. Experimental and clinical studies on value of this method in arterial occlusive diseases]. / 2-D-Time-of-Flight-MR-Angiographie der peripheren Gefässe. Experimentelle und klinische Studien zur Wertigkeit der Methode bei AVK.

PURPOSE: A retrospective study was performed in 70 patients with peripheral vascular disease who underwent MR angiography of the lower extremity. MATERIAL AND METHODS: MR angiography was performed with a 2-D-TOF sequence including a travelling presaturation to suppress the venous signal. Postprocessing images were obtained with the MIP algorithm. The MRA results were compared with conventional or digital angiography in all patients. RESULTS: Only 19 stenoses out of 31 which showed a degree of stenosis between 30 and 99% could be visualised by MR angiography. 9 stenoses were correctly classified by MRA. In 9 cases the degree of stenosis was overestimated, in one case it was underestimated. All 56 occlusions were correctly detected. 12 severe stenoses diagnosed with conventional angiography were graded as occlusions with MR angiography. CONCLUSIONS: MR angiography cannot be accepted in preoperative staging of patients with peripheral vascular disease. The postoperative examination seems to be a practical noninvasive alternative.

[Contrast-enhanced MR angiography of the arterial and portovenous system of the liver with varying concentrations of contrast medium]. / Kontrastmittel-gestützte 3D-MR-Angiographie des arteriellen und portalvenösen Gefässsystems der Leber mit unterschiedlicher KM-Konzentration.

PURPOSE: To evaluate the diagnostic value of a higher concentrated contrast medium (gadobutrol) for contrast-enhanced MRA of the hepatic arteries and portovenous system. MATERIALS AND METHODS: The examinations were performed on a 1.5-Tesla whole body imaging system (Magnetom Symphony Quantum, Siemens) with a 30-mTesla/m gradient field strength using a phased-array body coil. A 3D FLASH sequence (TR/TE/FA 3.88 ms/1.44 ms/25(3)) was used imaging the hepatic arteries and portovenous system after determination of the circulation time. The study included 50 patients, with 25 patients (group 1) injected with 0.2 mmol Gd-GTPA/kg body weight and 25 patients (group 2) injected with 0.1 mmol gadobutrol/kg body weight. The signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR) were calculated for both groups. The image quality was graded by three radiologists on a 5-point scale. RESULTS: The highest SNR was measured in group 1, with no statistically significant differences of the SNR in the abdominal aortal, coeliac trunk and common hepatic artery. CNR was also similar in both groups. Likewise, portal, superior mesenteric and splenic veins showed no statistically significant differences. All cases were found to have a good image quality. CONCLUSION: For MRA of the hepatic arteries and the portal veins, the higher concentrated Gd-DTPA contrast medium gadobutrol can be used at half the dosage recommended for the standard Gd-DTPA contrast medium.

[The determination of the T2* relaxation time for characterizing trabecular bone]. / Bestimmung der T2*-Relaxationszeit zur Charakterisierung des trabekulären Knochens.

Spongy bone produces local magnetic field inhomogeneities and leads to shortening of the transverse relaxation time from bone marrow. This increased signal decay affects the T2 relaxation time. Measurements of the T2* time from the 4th lumbar vertebra were carried out in 48 normals and 20 patients with osteoporosis. A special multigradient echo technique was used, the echo times selected in relation to phase coherence of the water and fat signals. T2* times showed slight increase in relation to age. Patients with osteoporosis showed significantly increased T2* times (19.9 +/- 3.8 ms) compared to the normal control group (13.4 +/- 1.9 ms). From these findings it is possible to judge the quality of the trabecular structure.

[Contrast media-enhanced 3D MR angiography of the peripheral vessels using a "tracking technique": preliminary results]. / Kontrastmittelgestützte 3D-MR-Angiographie der peripheren Gefässe in "Schrittverschiebe-Technik": Erste Ergebnisse.

PURPOSE: A single bolus contrast-enhanced (CE) 3D MR angiography (MRA) of the peripheral vessels was evaluated using a combination of two surface coils with manual incrementation of the patient table. METHODS: Fifteen patients with peripheral arterial occlusive disease were examined using an ultrafast CE 3D MRA (TR/ TE/FA 5 ms/2 ms/30 degrees). For imaging of the vessels from the distal aorta to the arteries of the lower limbs a combination of a body-array coil and a flexible extremity coil was applied. A coil-interface was designed for a connection of the two coils. The examinations were performed after a single bolus of 0.15 mmol Gd-DTPA/kg. The tracking technique included a manual incrementation of the patient table and the coil-interface had to be switched from the body-array coil to the flexible extremity coil. For acquisition delay measurement of the MR sequence the individual transit times of the contrast material were detected by using a test bolus. RESULTS: CE 3D MRA was technically successful in 14/15 cases. In one case two vascular segments were not imaged. The qualitative evaluation of all vascular segments documented a high quality without any significant differences between the proximal and the distal arteries (p < 0.05). All hemodynamically significant stenoses (n = 15) and all vessel occlusions (n = 36) were detected. CONCLUSION: The single bolus CE 3D MRA using a tracking technique is a favourable method in the evaluation of patients with peripheral arterial occlusive disease.

[Stent artifacts in 3D MR angiography: experimental studies]. / Stent-Artefakte in der 3D MR Angiographie: Experimentelle Studien.

PURPOSE: The purpose of this phantom study was to evaluate the visualization of vascular stents by using contrast-enhanced (CE) 3D MR angiography (MRA). METHODS: The measurements were performed on a Magnetom Vision operating at 1.5 T with 25 mT/m gradients by using a head coil; a 3D FISP sequence (TR/TE/FA 4.6 ms/1.8 ms/30 degrees) was used. A phantom was designed with a length of 20 cm and consisted of a plastic cylinder filled with hydrogel. Tubes were used to install 7 different stents (Strecker, Boston Scientific; Cragg, Mintec; Wall, Schneider; Memotherm, Angiomed; St-Come, Trigon-MTS; Sinus, Optimed; Palmaz, Johnson & Johnson) with different metal components. The tubes were perfused with a solution of water and Gd-DTPA. Four radiologists evaluated the image quality. The measurements of the endoluminal stent diameters were compared with the findings obtained by digital subtraction angiography. The signal intensities were measured before (inflow), within (stent) and after (outflow) the different stent types. RESULTS: The endoluminal diameter of the Cragg stent and the strecker graft were easily detectable. The signal loss within the lumen of the Wall stent was approx. 10% in relation to the inflow and outflow measurements. The result was an only slightly reduced image quality. The other grafts (St-Come, Sinus, Palmaz, Memotherm) showed significant signal losses ranging from 65% to 96%. A correct diagnosis was not possible within these graft lumina. CONCLUSION: Contrast-enhanced MR angiography can be used to evaluate vascular stents. A prerequisite is the application of particular commercially available grafts.

[Preoperative MR-mammography in diagnosed breast carcinoma. Useful information or useless extravagance?]. / Präoperative MR-Mammographie bei bekanntem Mammakarzinom. Sinnvolle Mehrinformation oder sinnloser Mehraufwand?

In a retrospective study the value of MR mammography in cases of radiological well-known carcinoma of the breast was evaluated preoperatively in 76 cases of histopathologically verified carcinoma one lesion was missed by MR imaging. Compared to the results of conventional X-ray mammography additional malignant lesions were detected in 5 patients ipsilaterally and in another 8 patients contralaterally by MR mammography only. In additional 4 cases MR mammography demonstrated suspicious lesions contralaterally, but histopathology revealed benign lesions. The therapeutic procedure was changed in 15 cases (18.5%) due to the findings of MR imaging: Ipsilateral mastectomy instead of tumorectomy (n = 5) or primary chemotherapy instead of operation (n = 1); contralateral additional tumorectomy (n = 3) or mastectomy (n = 2) by carcinoma and open biopsy (n = 4) by benign finding.

[Experimental evaluation of vessel diameter from 0.3 to 8 mm in CE MR angiography]. / Experimentelle Validierung der Kontrastmittel-verstärkten MR-Angiographie an Gefässdurchmessern von 0,3 - 8 mm.

PURPOSE: To evaluate the detection rate of vascular stenosis in contrast-enhanced 3D MR angiography using a flow phantom. MATERIAL AND METHODS: The examinations were performed on a 1.5 T whole body imaging system (Magnetom Symphony/Quantum) with 30 mT/m gradient field strength using a body-phased-array coil. Different 3D sequences (TR/TE/FA < 5 ms/< 2 ms/25 degrees ) with slice thicknesses ranging from 0.67 to 1.25 mm were applied. A gelantine-filled plastic cylinder with PVC tubes of 8 mm diameter was used as a vascular phantom. The tubes had concentric and excentric stenoses (50 - 90 %) of different lengths. For the detection of different vessel diameters another phantom with 0.3 - 8 mm silicon tubes was used. Both systems were flushed with a solution of Gd-DTPA (0.15 mmol/l) and saline at flow rates from 50 to 200 cm/s. The phantoms were positioned 0 degrees, 45 degrees, and 90 degrees towards the z-axis. RESULTS: The degree of stenosis was under- and overestimated in less than 10 %. The sequence with the highest spatial resolution provided the best results. Detection and evaluation of tubes >/= 2 mm proved to be reliable. CONCLUSION: Contrast-enhanced 3D MR angiography provides an almost exact evaluation of the degree of stenosis in the phantom study. Evaluation of vessel diameters < 2 mm is not possible.

[Signal characteristics of malignant and benign lesions in dynamic 2D-MRT of the breast]. / Signalverhalten maligner und benigner Läsionen in der dynamischen 2D-MRT der Mamma.

In a retrospective study of 400 dynamic MR examinations of the breast the signal/time ratio of 62 histopathologically correlated lesions (19 benign, 42 malignant) was evaluated. Points of evaluation were initial signal enhancement (1st and 2nd minute), post-initial signal appearance (2nd to 5th minute) and signal distribution (homogeneous, marginal). Based on these criteria, a point system was defined to help in the assessment of lesions in dynamic breast-MR imaging. The overall sensitivity of this method was 95.3%, the specificity to 89.5% and the accuracy to 93.5%. Pitfalls resulted in two cases of non-invasive carcinoma and in two patients with fibroadenoma.

[Experiences with digital luminescence radiography (DLR) in pediatric radiology]. / Erfahrungen mit der digitalen Lumineszenz-radiographie (DLR) in der pädiatrischen Radiologie.

X-ray examinations represent a variety of indications with different demands on exposure latitude, spatial and contrast resolution of screen-film-system combinations in paediatric radiography. The value of digital luminescent radiography (DLR) was compared to conventional x-ray examinations carried out with screen-film-systems, speed class 200, by analysing matched digital and conventional exposures in 200 abdominal, 600 skeletal and 300 chest examinations. The exposure of DLR was reduced to 50% of conventional exposure. Analysing the results in abdominal and skeletal radiography, DLR proved to be diagnostically equivalent to conventional radiography despite the reduction in exposure dose. DLR of the newborn chest compared to conventional x-ray studies was not always sufficient due to lower digital spatial resolution.