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.

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.

[Multicenter analysis of tolerance and clinical safety of the extracellular MR contrast agent gadobenate dimeglumine (MultiHance)]. / Multizentrische Analyse der Verträglichkeit und klinischen Sicherheit des extrazellulären MR-Kontrastmittels Gadobenat-Dimeglumin (MultiHance).

PURPOSE: Retrospective analysis of the occurrence of adverse events and the diagnostic efficacy of a paramagnetic contrast agent with weak intermittent protein binding and high relaxivity. MATERIALS AND METHODS: Postmarketing surveillance studies for gadobenate dimeglumine (MultiHance, BRACCO Altana Pharma, Constance) were conducted in Germany between 1998 and 2006 and then retrospectively analyzed. Demographic data, relevant comorbidities, and allergies were recorded. The safety and tolerability of MultiHance were logged on a standardized data sheet. RESULTS: A total of 38,568 patients were included in the study. 829 patients (2.1%) had a known intolerance against contrast media. The examined regions included the central nervous system, the liver, and the vascular bed. The injection rate with automated injectors (n = 10456) varied between 1.0 und 3.0 ml/sec in 86.5% of patients. Adverse events totaled 1.2%. 11 patients (0.03%) experienced serious adverse events. The most frequent findings were nausea, vomiting and a feeling of warmth. CONCLUSION: MultiHance is a safe and very well tolerated contrast agent for magnetic resonance imaging (MRI) with a profile and frequency of adverse events similar to other extracellular MR contrast materials.

Cancer patients and characteristics of pulmonary embolism.

OBJECTIVE: To check the hypothesis that cancer patients suffer from extended pulmonary embolism (PE) more frequently than patients without cancer we analysed PEs proved by computed tomography (CT)-imaging. PATIENTS AND METHODS: One hundred and fifty consecutive CT scans at the University Hospital of Essen from March 2002 until December 2004 which proved a definite case of pulmonary embolism were retrospectively reviewed (79 men, 71 women; mean age 57+/-15 years). Underlying disease and blood parameters were included (haemoglobin, haematocrit, fibrinogen and total protein, if determined within 48 h before the CT scans). RESULTS: Patients with malignant disease were older (59+/-12 years vs. 54+/-19 years, p=0.05) and tend to have a higher rate of central PEs (52% vs. 34%, p=0.08) than patients without malignancies. The odds of a central PE in cancer patients was about twice as high as in patients without a malignant disease (Odds ratio: 2.08, 95%-confidence interval: 1.06-4.10; age-adjusted Odds ratio 1.88, 95%-confidence interval: 0.92-3.84). Additional adjustment for the clinical information dyspnoea, inhospital patient and clinically expected PE did not deteriorate the odds. Thrombus density determined in patients with central PE only shows a trend towards a lower density in patients with malignant disease (52+/-13 HE vs. 45+/-15 HE, p=0.13). There is no statistical evidence that thrombus density is related to one of the blood parameters or even blood density measured in the pulmonary artery. CONCLUSION: Although this is a retrospective study including a small number of patients it shows that cancer patients are at a higher risk for central PE than patients without cancer. Characteristics of the intrapulmonal thrombus in cancer and non-cancer patients seem to be different.

[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.

[Whole body MRI--diagnostic strategy of the future?]. / Ganzkörper-MRT--Diagnostische Strategie der Zukunft?

Whole body magnetic resonance imaging (MRI) opens new opportunities in diagnostic radiology as systemic disease entities can be examined with high sensitivity. This can lead to a change of paradigm, so that not only organ-related but rather disease-specific MRI examination protocols can be applied which focus on the underlying pathophysiology of the disease. Whole body MRI has already been successfully used for several oncological and non-oncological indications. In addition, whole body MRI has broadened the discussion regarding its use for secondary prevention. Compared to computed tomography, MRI does not use radiation. Although whole body MRI is still in an early stage, the enormous medical and economical potential can be envisioned.

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.

Measuring tongue volumes and visualizing the chewing and swallowing process using real-time TrueFISP imaging--initial clinical experience in healthy volunteers and patients with acromegaly.

This study assessed both two-dimensional (2D) TrueFISP imaging for quantifying tongue volume and real-time TrueFISP imaging for evaluating chewing and swallowing in healthy volunteers and patients with acromegaly. In 50 healthy volunteers, tongue volumes were measured using a 2D TrueFISP sequence. Chewing and swallowing were visualized using a real-time TrueFISP sequence. Ten patients with acromegaly were examined twice with the same magnetic resonance imaging protocol: once prior to therapy and a second time 6 months after therapy. Prior to therapy, healthy volunteers had an average tongue volume of 140 ml for men and 90 ml for women, and patients with acromegaly had an average tongue volume of 180 ml for men and 145 ml for women. However, 6 months after therapy the mean tongue volumes in patients with acromegaly had decreased to 154 ml in the men and to 125 ml in the women. The chewing and swallowing process was normal in all volunteers. Prior to therapy, just two patients showed a chewing and swallowing pathology, which disappeared after therapy. Patients with acromegaly had larger tongue volumes than healthy volunteers, and TrueFISP imaging proved feasible for visualizing chewing and swallowing in real time and is capable of detecting possible pathologies. Furthermore, TrueFISP imaging can be used to monitor therapeutic approaches in patients with acromegaly.

[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.

[Cardiovascular whole-body MRI: possibilities and limitations in prevention]. / Kardiovaskuläre Ganzkörper-MRT: Möglichkeiten und Grenzen in der Früherkennung.

Cardiovascular disease is a major challenge to the healthcare with increasing prevalence in western societies. Hence, early detection of cardiovascular pathologies and preventative strategies will experience growing relevance in the future. Magnetic resonance imaging (MRI) nowadays allows a comprehensive analysis of the cardiovascular system. By combining separate examinations of brain, arterial vasculature, and heart the technique permits early detection of pathological changes with high diagnostic accuracy void of adverse events. Such a protocol has been proven feasible and technically robust and can be performed within 45 min. Inherent limitations are low spatial resolution of whole-body MR angiography and lack of functional stress testing of the heart. However, while being suitable as a fast and comprehensive imaging technique for cardiovascular screening purposes, medical consequences and socioeconomic relevance must further be elucidated.

Gadobenate dimeglumine (MultiHance) for magnetic resonance angiography: review of the literature.

Although limited in number, reports describing the use of Gd-BOPTA for 3D CE-MRA reveal that this agent is safe, well tolerated and effective for CE-MRA at doses up to 0.3 mmol/kg bodyweight. The use of Gd-BOPTA leads to additional diagnostically relevant information comparable to that attainable with conventional DSA and superior to that on non-enhanced MRA in most arterial territories. In studies in which Gd-BOPTA is compared at equal dose with other gadolinium-based MR contrast agents, Gd-BOPTA has consistently shown significantly better quantitative and qualitative performance. Thus, Gd-BOPTA can be considered to have a very favorable risk/benefit ratio for MRA. In summary, it is likely the documented superiority of Gd-BOPTA for MR angiography will lead to its broad usage for this indication wherever the agent becomes available.

[Prevention without radiation--a strategy for comprehensive early detection using magnetic resonance tomography]. / Prävention ohne Strahlen--eine Strategie zur umfassenden Früherkennung mittels Magnetresonanztomographie (MRT).

Recent advances in hardware technology, noninvasiveness, lack of radiation and high diagnostic accuracy combine to allow the usage of magnetic resonance imaging (MRI) for disease screening in asymptomatic people. 175 volunteers were examined by means of a comprehensive 60-minute MR-screening-protocol covering four organ systems: the brain, the arterial vasculature, the heart and the colon. In 28% of the cases vascular pathology (cerebral, peripheral or cardiovascular) was detected. In up to 17% of the single examination parts relevant incidental findings were seen. The outlined comprehensive MR-protocol is an accurate and patient-friendly imaging tool for the detection of vascular pathology as well as colonic polyps. The socio-economic relevance of this screening exam has to be further investigated in larger patient cohorts.

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.

[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.

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.

0.5 M Gd chelate (Magnevist) versus 1.0 M Gd chelate (Gadovist): dose-independent effect on image quality of pelvic three-dimensional MR-angiography.

To compare the effect on image quality of a 1.0 M gadolinium (Gd) chelate to that of a conventional 0.5 M Gd chelate, five healthy volunteers and seven patients with angiographically documented aorto-iliac disease underwent a mono-station three-dimensional magnetic resonance angiography (MRA) exam (Siemens SONATA, Erlangen, Germany) twice, once using Gadovist 1.0 and the other time using Magnevist as the contrast agent. All subjects received a fixed volume of Gadovist 1.0, corresponding to a dose between 0.1 and 0.15 mmol/kg body weight followed by a saline flush. For the Magnevist exam, the contrast agent volumes and flow rates were doubled. For both quantitative and qualitative analysis of the angiographic data sets, the arterial tree was divided into nine segments. 1 M Gadovist 1.0-enhanced three-dimensional MRA data sets were characterized by significantly higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values compared to 0.5 M Magnevist-enhanced images. The data revealed mean SNR/CNR increases exceeding 70% (P < 0.01). Although there was no statistically significant difference in the rating of image quality (P > 0.05), the Gadovist 1.0 exam led to better delineation of the arterial morphology, especially of small vessels.

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.

[Modern diagnostic concepts in dissection and aortic occlusion]. / Moderne Diagnostikkonzepte bei Dissektion und Aortenverschluss.

For the diagnostic work-up of the aorta, non-invasive cross-sectional imaging techniques have almost replaced invasive catheter angiography. CT- and MR-angiography are supplemented by sonography which is used predominantly for the assessment of abdominal aortic aneurysm and dissections of the thoracic aorta. This review deals with the diagnostic approach to two disease entities involving the aorta: aortic dissection and aortic occlusion. Transoesophageal echocardiography (TEE), CT- and MR-angiography (MRA) are used in the assessment of aortic dissection. Published sensitivity and specificity values regarding the detection and classification of dissections into Stanford A and Stanford B range between 96-100% for all three modalities. Results for multislice CTA have not yet been reported, but can be expected to be at least as good. The ability to delineate additional information regarding the precise morphology of true and false lumen, entry and reentry-sites, the development of thrombus or paraaortic hematomas, as well as the assessment of aortic regurgitation or involvement of coronary arteries depend on the chosen technique. Reflecting the ability to collect functional imaging data, both TEE and MRA are superior to CTA in the assessment of aortic valve involvement, while TEE is the modality of choice for evaluation of coronary arteries. Sonography is of limited use in the assessment of abdominal dissections. For the evaluation of patients with suspected aortic occlusion both CTA and MRA represent the imaging modalities of choice. Both provide for a comprehensive and precise depiction of the underlying aortic morphology, the extent of collateral flow as well as delineation of distal run-off vessels. MRA should be employed in patients with impaired renal function as paramagnetic contrast agents are not nephrotoxic.

Whole-body MR imaging in 30 seconds with real-time true FISP and a continuously rolling table platform: feasibility study.

A technique for whole-body magnetic resonance (MR) imaging in only 30 seconds was developed on the basis of a rolling table platform with integrated surface coils and real-time true fast imaging with steady-state precession. In five patients, all hepatic and pulmonary lesions with a diameter exceeding 8 mm were detected by using thoracic and abdominal helical computed tomography as the reference method. Whole-body MR imaging with real-time true fast imaging with steady-state precession is feasible and may be suitable for tumor screening and staging.