Combined PET/MRI: Global Warming-Summary Report of the 6th International Workshop on PET/MRI, March 27-29, 2017, Tübingen, Germany.

The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants critically assessed the current state of PET/MRI, both clinically and as a research tool, and attempted to chart future directions. The meeting addressed the use of PET/MRI and workflows in oncology, neurosciences, infection, inflammation and chronic pain syndromes, as well as deeper discussions about how best to characterise the tumour microenvironment, optimise the complementary information available from PET and MRI, and how advanced data mining and bioinformatics, as well as information from liquid biomarkers (circulating tumour cells and nucleic acids) and pathology, can be integrated to give a more complete characterisation of disease phenotype. Some issues that have dominated previous meetings, such as the accuracy of MR-based attenuation correction (AC) of the PET scan, were finally put to rest as having been adequately addressed for the majority of clinical situations. Likewise, the ability to standardise PET systems for use in multicentre trials was confirmed, thus removing a perceived barrier to larger clinical imaging trials. The meeting openly questioned whether PET/MRI should, in all cases, be used as a whole-body imaging modality or whether in many circumstances it would best be employed to give an in-depth study of previously identified disease in a single organ or region. The meeting concluded that there is still much work to be done in the integration of data from different fields and in developing a common language for all stakeholders involved. In addition, the participants advocated joint training and education for individuals who engage in routine PET/MRI. It was agreed that PET/MRI can enhance our understanding of normal and disrupted biology, and we are in a position to describe the in vivo nature of disease processes, metabolism, evolution of cancer and the monitoring of response to pharmacological interventions and therapies. As such, PET/MRI is a key to advancing medicine and patient care.

[Diagnostic performance of contrast-enhanced MR angiography of the aortoiliac arteries with the blood pool agent Vasovist: initial results in comparison to intra-arterial DSA]. / Diagnostische Wertigkeit der kontrastverstärkten Magnetresonanzangiografie der Beckenstrombahn mit dem intravaskulären Kontrastmittel Vasovist: Erste klinische Erfahrungen im Vergleich zur i. a. DSA.

PURPOSE: To prospectively assess the accuracy of contrast-enhanced MR angiography of the aortoiliac arteries using the blood pool agent Vasovist compared to unenhanced time-of-flight MRA. Conventional digital subtraction angiography served as the standard of reference. MATERIALS AND METHODS: Twenty-nine patients with suspected or known peripheral arterial occlusive disease (PAOD) were examined by means of contrast-enhanced aortoiliac MR angiography using a dosage of 0.03 mmol/kg bodyweight Vasovist. Unenhanced two-dimensional time-of-flight (TOF) MRA of the same anatomic region was performed immediately prior to injection of the contrast agent. This study was approved by the local Institutional Review Board and informed consent was obtained from all subjects. Both contrast-enhanced and unenhanced MRA images were compared to conventional angiography with respect to the presence of vascular stenosis. Three independent, blinded readers evaluated vessel stenosis and occlusion on the basis of DSA and MR angiographic image readings. Sensitivity, specificity, accuracy, and the area under the receiver operating characteristic curve were analyzed. Correlations between readers of conventional angiograms were calculated and compared to the MR results. RESULTS: In the case of pooled readings, unenhanced TOF MR angiography had a sensitivity of 42.6 %, a specificity of 78.4 % and an accuracy of 74.9 % for detection of clinically significant (>50 %) stenosis. Vasovist-enhanced MRA showed significant improvement in sensitivity (83.3 %), specificity (88.8 %) and accuracy (88.3 %) compared to TOF MRA (p<0.01). The areas under the receiver operating characteristic curve for quantitative measurements increased significantly (p<0.01) in the case of Vasovist-enhanced MRA compared to TOF MRA. All readers found fewer images uninterpretable with Vasovist enhancement and the agreement regarding stenosis location and degree of stenosis between MR angiography and DSA improved substantially after Vasovist administration compared to the noncontrast examination. CONCLUSION: MR angiography using the blood pool agent Vasovist is a feasible and minimally invasive alternative to DSA and provides angiograms of the aortoiliac region with high sensitivity, specificity, and diagnostic accuracy.

Synthetic MRI for Clinical Neuroimaging: Results of the Magnetic Resonance Image Compilation (MAGiC) Prospective, Multicenter, Multireader Trial.

BACKGROUND AND PURPOSE: Synthetic MR imaging enables reconstruction of various image contrasts from 1 scan, reducing scan times and potentially providing novel information. This study is the first large, prospective comparison of synthetic-versus-conventional MR imaging for routine neuroimaging. MATERIALS AND METHODS: A prospective multireader, multicase noninferiority trial of 1526 images read by 7 blinded neuroradiologists was performed with prospectively acquired synthetic and conventional brain MR imaging case-control pairs from 109 subjects (mean, 53.0 ± 18.5 years of age; range, 19-89 years of age) with neuroimaging indications. Each case included conventional T1- and T2-weighted, T1 and T2 FLAIR, and STIR and/or proton density and synthetic reconstructions from multiple-dynamic multiple-echo imaging. Images were randomized and independently assessed for diagnostic quality, morphologic legibility, radiologic findings indicative of diagnosis, and artifacts. RESULTS: Clinical MR imaging studies revealed 46 healthy and 63 pathologic cases. Overall diagnostic quality of synthetic MR images was noninferior to conventional imaging on a 5-level Likert scale (P < .001; mean synthetic-conventional, -0.335 ± 0.352; Δ = 0.5; lower limit of the 95% CI, -0.402). Legibility of synthetic and conventional morphology agreed in >95%, except in the posterior limb of the internal capsule for T1, T1 FLAIR, and proton-density views (all, >80%). Synthetic T2 FLAIR had more pronounced artifacts, including +24.1% of cases with flow artifacts and +17.6% cases with white noise artifacts. CONCLUSIONS: Overall synthetic MR imaging quality was similar to that of conventional proton-density, STIR, and T1- and T2-weighted contrast views across neurologic conditions. While artifacts were more common in synthetic T2 FLAIR, these were readily recognizable and did not mimic pathology but could necessitate additional conventional T2 FLAIR to confirm the diagnosis.

Dark lumen MR colonography: can high spatial resolution VIBE imaging improve the detection of colorectal masses?

PURPOSE: To assess whether the detection of colorectal lesions can be improved using high spatial resolution VIBE imaging. MATERIALS AND METHODS: 48 patients underwent same-day dark lumen MR colonography (MRC) and conventional colonoscopy (CC) as the standard for the detection of colorectal masses. MRC was performed using contrast-enhanced standard and high spatial resolution T1-weighted 3D VIBE sequences. The findings and the image quality of the standard and high spatial resolution VIBE sequences were compared qualitatively and quantitatively. The findings of both sequences regarding colorectal lesions were compared to those of a subsequently performed colonoscopy. RESULTS: The high spatial resolution VIBE sequence significantly improved the quantitative image quality (CNR 54.0 vs. 36.8). However, high spatial resolution VIBE imaging did not detect more colorectal lesions than the standard VIBE sequence. In addition, none of the sequences employed was able to detect lesions with a diameter of less than 5 mm (CC 40 lesions). However, 13 colorectal lesions with a diameter of greater than 5 mm were detected by both sequences (CC 15). CONCLUSION: High spatial resolution VIBE imaging did not improve the detection of colorectal masses and MRC fails to detect colorectal lesions with a diameter of less than 5 mm.

Peripheral magnetic resonance angiography.

Peripheral vascular disease (PVD) is a common disorder in western society. Reflecting on the risks and costs of contrast arteriography, magnetic resonance angiography is a powerful noninvasive imaging modality for the diagnostic workup of patients with peripheral vascular disease. This article reviews the current state of the art of magnetic resonance angiography of the peripheral vasculature.

MR-angiography: the role of contrast agents.

Contrast-enhanced 3D MR angiography (MRA) permits comprehensive assessment of the supraaortic arteries as well as the arterial system in the chest, abdomen and lower extremities. 3D MRA combines intravenous injection of a non-nephrotoxic, paramagnetic, extracellular contrast agent that increases the signal intensity of blood by shortening its T1 value with the acquisition of a fast 3D data set. High contrast between the vascular lumen and surrounding tissues, inherent three-dimensionality and the ability to collect image data in the chest and abdomen under apnea conditions all contribute to excellent image quality. This review provides clinical applications of 3D MRA in the chest, abdomen and lower extremities based upon the available literature and several clinical examples.

[MR Angiography: First choice for diagnosis of the arterial vascular system]. / MR-Angiographie: Erste Wahl bei der Abklärung des arteriellen Gefässsystems.

Contrast medium-enhanced, 3D MR angiography enables an extensive and diagnostically accurate evaluation of arterial vessels in the neck, thorax, abdomen, and limbs. Advances in the field of MR apparatus technology and the introduction of contrast-medium enhanced MR angiographic techniques have made this development possible. Contrast medium-enhanced MR angiography combines the intravenous bolus administration of a paramagnetic contrast medium with the rapid acquisition of 3D datasets. The possibilities for obtaining data in the thorax and abdomen within one breath-hold, the resulting high contrast between vessel lumen and surrounding soft tissue as well as the inherent 3D nature of the images allow for diagnostically relevant image quality. In many centers contrast-enhanced 3D MR angiography has widely replaced the conventional digital subtraction roentgenography for the clarification of pathologies in arterial vessels. This review presents a survey of the technical background of contrast medium eýnhanced 3D MRA. In addition, the spectrum of indications is given and discussed on the basis of clinical examples.

[Hypothenar hammer syndrome: causes, sequelae and diagnostic aspects]. / Das Hypothenar-Hammer-Syndrom--Ursachen, Folgen und diagnostische Aspekte.

PURPOSE: To investigate the reasons and disease course of Hypothenar Hammer Syndrome. INTRODUCTION: Occlusion of the ulnar artery at the level of the hamate bone due to repetitive trauma to the hypothenar eminence is implicated as the cause of the rarely diagnosed hypothenar hammer syndrome (HHS). The thrombotic occlusion and the formation of an aneurysm of the ulnar artery and the superficial palmar arch with possible peripheral embolism of the digital arteries are a direct cause of the chronic damage to the vessel wall. Generally, HHS is diagnosed too late for recanalization to be a viable therapeutic option. METHODS: From 1996 to 1998 the diagnosis of an HHS was made in 8 patients at our hospital. Etiology, clinical settings and disease course were assessed. RESULTS: Our analysis suggests that HHS may be caused by a single severe trauma in addition to repetitive injuries. The pathogenesis of the syndrome is dependent on the vascular anatomy of the individual hand. Interindividual variations in the arterial supply of the affected hand influences the clinical symptomatology with possible masking of arterial occlusions. CONCLUSION: An exact investigation concerning the pathogenesis of HHS is a precondition for treating the disease and may help to establish HHS as an occupational disease. MR-angiography may be a new approach for assessing HHS.

[Whole-body MRA on a rolling table platform (AngioSURF)]. / Ganzkörper-MRA auf einer rollenden Tischplattform (AngioSURF).

PURPOSE: Development of a technique for whole-body MR angiography based on a rolling table platform and integration of a surface coil. MATERIAL AND METHODS: The developed rolling table platform AngioSURF (System for Unlimited Rolling Field-of-view) with integrated surface coil can be mounted on top of the original patient table of a Siemens Symphony System. Data acquisition was performed with a standard body array surface coil. The system was tested on three volunteers and one patient with angiographically documented vascular pathology. Data acquisition was performed with a 3D-FLASH-sequence (TR/TE 2.1/0.7 ms, flip angle: 20 degrees, FOV 40 x 40 cm, 80 partitions, matrix 512 x 420 with zero interpolation). Five data sets were collected in immediate succession during continuous injection of a paramagnetic contrast agent. Time of acquisition per data set was 10 seconds. Table repositioning was performed manually within 3 seconds. Thus the total acquisition time amounted to 72 seconds. RESULTS: No problems with handling occurred in any of the four cases. The excellent image quality enables detailed assessment of the displayed vascular territories. CONCLUSIONS: The rolling table platform with integrated surface coil (AngioSURF) allows diagnostic display of the arterial vascular system from supraaortic vessels to the distal trifurcation arteries in only 72 seconds.

[Contrast-enhanced 3D MR venography of central thoracic veins: preliminary experience]. / Kontrastmittelverstärkte 3D-MR-Venographie der oberen Thoraxapertur: Erste Erfahrungen.

PURPOSE: To evaluate the usefulness of three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) venography for evaluation of thoracic central veins. MATERIALS AND METHODS: Over a 4-month period, 14 patients with suspected central venous abnormalities were examined on a 1.5 T scanner (Magnetom Sonata, SIEMENS, Germany) by means of MR venography. A FLASH-3D sequence using the following parameters was employed: TR 1.6 ms, TE 0.6 ms, TA 3.74 s, flip: 15 degrees, slab thickness 110 mm, effective slice thickness: 2.75 mm, 40 partitions, FOV 360 mm, matrix 140 x 256. 10 s prior to imaging 20 ml of Gd-DOPTA (Multihance, BRACCO, Italy) were automatically injected (MEDRAD, Pittsburgh, USA) flushed by 20 ml of normal saline (flow 4 ml/s). Six 3D data sets were acquired in immediate succession in under 24 s. Results were corroborated with findings from duplex sonography. RESULTS: MR venograms were of diagnostic quality for all 14 patients. Compared to duplex sonography thromboses, post-thrombotic changes as well as functional compressions were reliably detected. Unsuspected findings were found in two patients. CONCLUSION: The outlined strategy allows for dynamic diagnostic imaging of central thoracic veins. Gadolinium-enhanced breath-hold 3D MR venography is easy to perform, well tolerated and highly accurate in assessing central venous pathology.

Risk factors in young patients with peripheral atherosclerosis.

BACKGROUND: Risk factors and especially the combination of multiple risk factors are associated with the development of atherosclerosis. Therefore, patients with an early manifestation of atherosclerotic disease are likely to show an extraordinary risk profile. We analysed the frequencies and severity of risk factors in young patients with manifest peripheral arterial occlusive disease as compared to old patients. METHODS: We analysed the risk profiles in 303 patients who were sent for interventional treatment of a symptomatic peripheral arterial occlusive disease. The risk profiles were described for different age groups (54 patients under 50 years of age, 194 patients from 51 to 74 years, 55 patients over 75 years). Multiple linear regression analysis and analysis of variance were performed to look for age-dependent effects. RESULTS: Elevated total cholesterol, and triglyceride levels and nicotine abuse were more frequent in patients younger than 50 years. Diabetes mellitus and hypertension were more frequent in patients older than 75 years. The different frequencies for smoking, diabetes mellitus and hypertension were age-related (p<0.05). Concerning laboratory parameters such as HDL- and LDL-cholesterol, fibrinogen, lipoprotein(a) and homocysteine there were no relevant age-related differences in frequency nor in absolute values with the exception of the hematocrit and uric acid. The coincidence with clinically manifest myocardial infarction was 11.15% in the patients under 50 years compared to 20.6% in those aged 51-74 years and 16.4% in those over 75 years, for cerebral stroke it was 5.6%, 17.5% and 14.5%, respectively. Patients under 50 years with peripheral arterial occlusive disease and a history of myocardial infarction were characterised by high levels of total cholesterol, triglyceride and lipoprotein(a). Excluding patients with prior myocardial infarction patients did not show any difference in risk profile between the three age groups. CONCLUSIONS: In a population suffering from manifest peripheral arterial occlusive disease the risk profile in patients under 50 years is not different from that in older patients. In contrast an additional myocardial infarction in such a population is associated with pathological lipid profiles.

Stenosis-jet can cause a dissection of the superficial femoral artery.

A dissection of the superficial femoral artery mainly occurs due to trauma or manipulation of the artery by means of interventional procedures. In contrast to dissections of the carotid arteries which are known to occur spontaneously we present the case of a stenosis of the superficial femoral artery that led to a dissection caused by the stenosis-jet. The dissection on the other hand caused an appositional thrombus which led to the embolic occlusion of the pedal-arteries. In case of peripheral embolisms in patients with or without history of peripheral arterial occlusion disease it is important to look for a causing arterial pathology preferably by duplex sonography.

Recurrent exercise induced subclavian vein thrombosis in a conductor.

We present a case of a young male patient with recurrent subclavian vein thrombosis due to conducting after prior successful thrombolytic therapy. Musculoskeletal problems are common among musicians. A thoracic outlet syndrome associated to a profession induced thrombosis in a musician has not been described before. Surgical removal of the first rip can prevent recurrent thrombotic occlusion of the subclavian vein, but was not performed in this patient. Considering the specific situation of a young musician there is no information whether surgical or conservative treatment is suitable to allow a successful career as an active musician.

Value of transesophageal echocardiography, esophago-gastroduodenoscopy and retinoscopy prior to intra-arterial fibrinolytic therapy in patients with peripheral arterial disease.

BACKGROUND: We prospectively investigated the need for esophagogastroduodenoscopy (EGD), transesophageal echocardiography (TEE) and retinoscopy for pre-interventional screening in patients with peripheral arterial occlusive disease (PAD) prior to intraarterial fibrinolytic therapy. PATIENTS AND METHODS: 212 consecutive patients suffering from PAD (164 male and 48 female, mean age: 64 +/- 11 years, 161 patients stage II of Fontaine's classification, 10 patients at stage III and 41 patients at stage IV) referred for interventional treatment were included. 173 EGDs, 169 TEEs and 188 retinoscopies were performed within one week prior to fibrinolysis. 114 patients had all three examinations. RESULTS: Pathologic findings were detected in 56 (49%) of the 114 patients: 23 erosions, 12 ulcers, 2 esophagites, 1 gastric carcinomata, 3 intracardiac thrombi, 5 aortic thrombi, 11 diabetic and 5 hypertensive retinopathies and 1 with retinal aneurysms. 30 patients (25%) received fibrinolytic therapy, despite a contraindication: The one patient with ventricular thrombus was treated as an ultimate therapy, and amputation was prevented. Two patients showing plaques covered by large thrombi in the descending thoracic aorta were treated because cranial embolism should not occur. Four diabetic patients with multilevel disease, severe claudication and prior retinal bleeding were treated. Fibrinolytic therapy was started on 23 patients after complete healing of the mucosal lesions. CONCLUSION: TEE revealed potential sources of embolization in 4% of the patients and is justified to reduce the individual risk. Retinoscopy should be done in patients with diabetes mellitus and hypertension, and if prior bleeding is present fibrinolysis should be done only if other treatment-regimes are not available.

[New techniques in computed tomography. Significance for urology]. / Neue Techniken in der Computertomographie. Bedeutung für die Urologie.

Computed tomographic (CT) imaging has become the modality of choice for the assessment of patients with urological malignancies. Recently, multi-slice CT imaging was introduced, providing faster acquisition times and higher resolution leading to improved image quality. Several studies show that thin-slice, high-resolution acquisition strategies lead to an improved accuracy for T-staging, especially of renal cell carcinomas. Three-dimensional post-processing techniques for the visualization of the vascular supply as well as the ureter (CT-angiography and CT-urography) are helpful for surgical planning. Compared to conventional imaging strategies unenhanced CT images render higher sensitivities and specificities for detecting stone disease in patients with acute flank pain. In the USA unenhanced CT imaging has almost replaced conventional urography, as no contrast agent is administered and the examination time is shorter. PET/CT examinations provide information on the morphology and function of tumors in one examination. However, there are only few data available for the assessment of urologic tumors.

[Vascular imaging with magnetic resonance angiography (MRA)]. / Gefässdarstellung mittels Magnetresonanzangiographie (MRA).

Magnetic resonance angiography (MRA) has become firmly established within the scope of diagnostic imaging procedures for assessing many pathological conditions and, depending on the questions posed, is often used on its own or as a supplementary method. MRA allows the (non)-invasive visualization of the vasculature by using the effects of moving spins on the magnetic resonance signal. MRA techniques can be classified into two different techniques depending on how the contrast is achieved: Time-of-flight (TOF) and phase contrast (PC) methods. Both methods have advantages and limitations as an imaging technique. This article outlines the basic understanding of MRA as well as the recent rapid expansion in MRA acquisition and processing techniques.

[The anxious patient during magnetic resonance tomography (MRI) examination. Health care economic aspects of patient education]. / Der ängstliche Patient während der Magnetresonanztomographie (MRT)-Untersuchung. Gesundheitsökonomische Aspekte der Patientenaufklärung.

Due to the increasing debate of limiting costs in the public health system, the use of magnetic resonance imaging (MRI) has been under discussion for several times. Diagnostic imaging by means of MRI is an expensive but informative and safe method. Instead of looking on cost-benefit analysis, it is shown how the efficiency of MRI can be increased by improving patient information about this imaging method. Because of the technical conditions, up to 40% of the patients show anxiety-related-reactions. These reactions include slight discomfort up to claustrophobic reactions and panic attacks. Therefore, correct and complete informing of patients prior to MRI examinations by the physicians is very important. The given information should include technical aspects about MRI and in addition, the physician has a chance to evaluate the patients' disposition to anxiety-related-reactions. To prepare risk patients for successful MRI technics like music, prone positioning, sedatives and relaxation exercises are available. By taking patients' anxiety into consideration and using the techniques mentioned above, unnecessary costs for unsuccessful or repeated MRI examinations can be avoided and the overall costs for clinical diagnostics will be reduced.

[Therapeutic ultrasound for the recanalization of peripheral vascular occlusions]. / Einsatz des therapeutischen Ultraschalls zur Rekanalisation peripherer Gefässverschlüsse.

Since the development of percutaneous transluminal angioplasty several techniques such as laser or atherectomy devices have been developed for recanalization of peripheral arterial occlusions. In a first clinical study we investigated if also the application of intravascular ultrasound can be useful for recanalization of occluded peripheral arteries. We applied an ultrasound angioplasty device (ACOLYSIS, ANGIOSONICS, USA) in a percutaneous approach in 8 patients with peripheral arterial occlusions (7 femoro-popliteal segments, 1 external iliac artery-occlusion). All patients suffered from severe leg ischemia due to subacute thrombotic occlusions. The ultrasound transmitter was introduced and advanced under fluoroscopic guidance to the site of the lesion. After activation the ultrasound transmitter was slowly advanced into the occlusion easily creating a channel within the occlusive material. Depending on the length of the occlusion (5-16 cm) treatment times ranged from 120-480 s. To further reduce the mass of the occlusive material an aspiration thrombectomy was performed in all cases leading to a complete recanalization in 6 cases. In 2 cases a remaining stenosis was successfully dilated. Intra-vascular ultrasonic devices can be useful for recanalization of occluded peripheral arteries. With the use of high-energy ultrasound a selective injury of the occlusive material can be induced without damaging the surrounding arterial wall. This selectivity is based on the differences in elasticity between the atherosclerotic plaque and the media layers. Especially if thrombolytic therapy of longer peripheral arterial occlusions fails or is contraindicated ultrasound angioplasty may be a new approach for recanalization.