Stefan O. Schönberg

MR-IMPACT II: Magnetic Resonance Imaging for Myocardial Perfusion Assessment in Coronary artery disease Trial: perfusion-cardiac magnetic resonance vs. single-photon emission computed tomography for the detection of coronary artery disease: a comparative multicentre, multivendor trial

AIMS Perfusion-cardiac magnetic resonance (CMR) has emerged as a potential alternative to single-photon emission computed tomography (SPECT) to assess myocardial ischaemia non-invasively. The goal was to compare the diagnostic performance of perfusion-CMR and SPECT for the detection of coronary artery disease (CAD) using conventional X-ray coronary angiography (CXA) as the reference standard. METHODS AND RESULTS In this multivendor trial, 533 patients, eligible for CXA or SPECT, were enrolled in 33 centres (USA and Europe) with 515 patients receiving MR contrast medium. Single-photon emission computed tomography and CXA were performed within 4 weeks before or after CMR in all patients. The prevalence of CAD in the sample was 49%. Drop-out rates for CMR and SPECT were 5.6 and 3.7%, respectively (P = 0.21). The primary endpoint was non-inferiority of CMR vs. SPECT for both sensitivity and specificity for the detection of CAD. Readers were blinded vs. clinical data, CXA, and imaging results. As a secondary endpoint, the safety profile of the CMR examination was evaluated. For CMR and SPECT, the sensitivity scores were 0.67 and 0.59, respectively, with the lower confidence level for the difference of +0.02, indicating superiority of CMR over SPECT. The specificity scores for CMR and SPECT were 0.61 and 0.72, respectively (lower confidence level for the difference: -0.17), indicating inferiority of CMR vs. SPECT. No severe adverse events occurred in the 515 patients. CONCLUSION In this large multicentre, multivendor study, the sensitivity of perfusion-CMR to detect CAD was superior to SPECT, while its specificity was inferior to SPECT. Cardiac magnetic resonance is a safe alternative to SPECT to detect perfusion deficits in CAD.

Multicenter assessment of reliability of cranial MRI

Clinical utility of magnetic resonance imaging (MRI) for the diagnosis and assessment of neurodegenerative diseases may depend upon the reliability of MRI measurements, especially when applied within a multicenter context. In the present study, we assessed the reliability of MRI through a phantom test at a total of eleven clinics. Performance and entry criteria were defined liberally in order to support generalizability of the results. For manual hippocampal volumetry, automatic segmentation of brain compartments and voxel-based morphometry, multicenter variability was assessed on the basis of MRIs of a single subject scanned at ten of the eleven sites. In addition, cranial MRI scans obtained from 73 patients with Alzheimers disease (AD) and 76 patients with mild cognitive impairment were collected at subset of six centers to assess differences in grey matter volume. Results show that nine out of eleven centers tested met the reliability criteria of the phantom test, where two centers showed aberrations in spatial resolution, slice thickness and slice position. The coefficient of variation was 3.55% for hippocampus volumetry, 5.02% for grey matter, 4.87% for white matter and 4.66% for cerebrospinal fluid (CSF). The coefficient of variation was 12.81% (S.D.=9.06) for the voxel intensities within grey matter and 8.19% (S.D.=6.9) within white matter. Power analysis for the detection of a difference in the volumes of grey matter between AD and MCI patients across centers (d=0.42) showed that the total sample size needed is N=180. In conclusion, despite minimal inclusion criteria, the reliability of MRI across centers was relatively good.

Dual energy CT in clinical practice

Physical Implementation: Physical Background .- Dual Source CT.- Layer Detector.- Gemstone Detector.- Postprocessing and Visualization.- Vascular System: Head and Neck.- Aorta.- Peripheral Arteries.- Plaque Imaging.- Thoracic Imaging: Lung Perfusion.- Lung Ventilation.- Pulmonary Nodules and Lung Cancer.- Myocardial Perfusion.- Coronary Imaging.- Abdominal Imaging: Liver Imaging.- Kidney Imaging.- Pancreas.- Kidney Stone Differentiation.- Extremities: Tendons and Ligaments.- Gout.

Superior diagnostic performance of perfusion-cardiovascular magnetic resonance versus SPECT to detect coronary artery disease: The secondary endpoints of the multicenter multivendor MR-IMPACT II (Magnetic Resonance Imaging for Myocardial Perfusion Assessment in Coronary Artery Disease Trial)

BackgroundPerfusion-cardiovascular magnetic resonance (CMR) is generally accepted as an alternative to SPECT to assess myocardial ischemia non-invasively. However its performance vs gated-SPECT and in sub-populations is not fully established. The goal was to compare in a multicenter setting the diagnostic performance of perfusion-CMR and gated-SPECT for the detection of CAD in various populations using conventional x-ray coronary angiography (CXA) as the standard of reference.MethodsIn 33 centers (in US and Europe) 533 patients, eligible for CXA or SPECT, were enrolled in this multivendor trial. SPECT and CXA were performed within 4 weeks before or after CMR in all patients. Prevalence of CAD in the sample was 49% and 515 patients received MR contrast medium. Drop-out rates for CMR and SPECT were 5.6% and 3.7%, respectively (ns). The study was powered for the primary endpoint of non-inferiority of CMR vs SPECT for both, sensitivity and specificity for the detection of CAD (using a single-threshold reading), the results for the primary endpoint were reported elsewhere. In this article secondary endpoints are presented, i.e. the diagnostic performance of CMR versus SPECT in subpopulations such as multi-vessel disease (MVD), in men, in women, and in patients without prior myocardial infarction (MI). For diagnostic performance assessment the area under the receiver-operator-characteristics-curve (AUC) was calculated. Readers were blinded versus clinical data, CXA, and imaging results.ResultsThe diagnostic performance (= area under ROC = AUC) of CMR was superior to SPECT (p = 0.0004, n = 425) and to gated-SPECT (p = 0.018, n = 253). CMR performed better than SPECT in MVD (p = 0.003 vs all SPECT, p = 0.04 vs gated-SPECT), in men (p = 0.004, n = 313) and in women (p = 0.03, n = 112) as well as in the non-infarct patients (p = 0.005, n = 186 in 1–3 vessel disease and p = 0.015, n = 140 in MVD).ConclusionIn this large multicenter, multivendor study the diagnostic performance of perfusion-CMR to detect CAD was superior to perfusion SPECT in the entire population and in sub-groups. Perfusion-CMR can be recommended as an alternative for SPECT imaging.Trial registrationClinicalTrials.gov, Identifier: NCT00977093

Lung Mri at 1.5 and 3 Tesla: Observer Preference Study and Lesion Contrast Using Five Different Pulse Sequences

Objectives:To compare the image quality and lesion contrast of lung MRI using 5 different pulse sequences at 1.5 T and 3 T. Materials and Methods:Lung MRI was performed at 1.5 T and 3 T using 5 pulse sequences which have been previously proposed for lung MRI: 3D volumetric interpolated breath-hold examination (VIBE), true fast imaging with steady-state precession (TrueFISP), half-Fourier single-shot turbo spin-echo (HASTE), short tau inversion recovery (STIR), T2-weighted turbo spin-echo (TSE). In addition to 4 healthy volunteers, 5 porcine lungs were examined in a dedicated chest phantom. Lung pathology (nodules and infiltrates) was simulated in the phantom by intrapulmonary and intrabronchial injections of agarose. CT was performed in the phantom for correlation. Image quality of the sequences was ranked in a side-by-side comparison by 3 blinded radiologists regarding the delineation of pulmonary and mediastinal anatomy, conspicuity of pulmonary nodules and infiltrates, and presence of artifacts. The contrast of nodules and infiltrates (CNODULES and CINFILTRATES) defined by the ratio of the signal intensities of the lesion and adjacent normal lung parenchyma was determined. Results:There were no relevant differences regarding the preference for the individual sequences between both field strengths. TSE was the preferred sequence for the visualization of the mediastinum at both field strengths. For the visualization of lung parenchyma the observers preferred TrueFISP in volunteers and TSE in the phantom studies. At both field strengths VIBE achieved the best rating for the depiction of nodules, whereas HASTE was rated best for the delineation of infiltrates. TrueFISP had the fewest artifacts in volunteers, whereas STIR showed the fewest artifacts in the phantom. For all but the TrueFISP sequence the lesion contrast increased from 1.5 T to 3 T. At both field strengths VIBE showed the highest CNODULES (6.6 and 7.1) and HASTE the highest CINFILTRATES (6.1 and 6.3). Conclusion:The imaging characteristics of different pulse sequences used for lung MRI do not substantially differ between 1.5 T and 3 T. A higher lesion contrast can be expected at 3 T.

Peripheral magnetic resonance angiography with continuous table movement in combination with high spatial and temporal resolution time-resolved MRA With a total single dose (0.1 mmol/kg) of gadobutrol at 3.0 T.

Purpose:To prove the concept of peripheral continuous table movement (CTM) MR-angiography (MRA) in combination with high spatial and temporal resolution time-resolved TWIST-MRA in a single MR-examination at 3.0 T with a single dose (0.1 mmol/kg) of gadobutrol in total. Materials and Methods:We included 22 consecutive patients (15 m/7 f, mean age: 64 years) referred for peripheral MRA with clinical symptoms of peripheral arterial occlusive disease Fontaine stages II–IV. All of them underwent both CTM-MRA (TR: 2.4 ms/TE: 1.0 ms/flip angle: 21 degree) of the entire run-off vessels and TWIST-MRA (TR: 2.8 ms/TE: 1.1 ms/flip angle: 20 degree) of the calf station during a single MR-examination. All examinations were performed on a 3.0 T MR system (Tim Trio). Spatial resolution of the CTM-MRA datasets was technically limited to an acquired resolution of 1.2 × 1.2 × 1.96 mm3 reconstructed to 1.2 mm isotropic. The TWIST-MRA was acquired with 1.1 × 1.1 × 1.35 mm3 and reconstructed to 1.1 mm isotropic with a temporal resolution of 5.5 seconds in the calf station. A total of 0.1 mmol/kg BW gadobutrol diluted 1:1 with saline was injected at a flow rate of 1.5 mL/s of which 0.07 mmol/kg was administered for the CTM-MRA and 0.03 mmol/kg for the TWIST-MRA.CTM-MRA run off datasets were qualitatively assessed using a 4 point scale (4 = excellent, 1 = nondiagnostic) followed by TWIST-MRA datasets for the calf using the same scale. Additional relevant findings only visible in the TWIST-MRA were documented. Results:All datasets could be evaluated with a total of 397 assessable segments. CTM-MRA was diagnostic in 99% (393/397 segments) with image quality judged as excellent in 54% (213/397 segments), good in 42% (14/397), and moderate in 4% (14/397) of analyzed segments respectively. Nondiagnostic image quality was seen in 1% (4/397 segments). Venous overlay in the calf station was found in 27% (6/22 patients). TWIST-MRA was diagnostic in 100% (115/115 segments), throughout with good or excellent image quality. In 14 of 22 patients additional relevant findings were detected by TWIST-MRA. Conclusion:Single-dose gadobutrol CTM-MRA in combination with a high spatial and temporal resolution TWIST-MRA at 3.0 T is a reliable technique with good image quality. Despite the use of single dose contrast agent large field of view coverage and dynamic images can be acquired. Because of its robustness, this imaging approach of the vasculature has great potential for a broad clinical use.

Diabetes Mellitus: Long-term Prognostic Value of Whole-Body MR Imaging for the Occurrence of Cardiac and Cerebrovascular Events

PURPOSE To study the predictive value of whole-body magnetic resonance (MR) imaging for the occurrence of cardiac and cerebrovascular events in a cohort of patients with diabetes mellitus (DM). MATERIALS AND METHODS This HIPAA-compliant study was approved by the institutional review board. Informed consent was obtained from all patients before enrollment into the study. The authors followed up 65 patients with DM (types 1 and 2) who underwent a comprehensive, contrast material-enhanced whole-body MR imaging protocol, including brain, cardiac, and vascular sequences at baseline. Follow-up was performed by phone interview. The primary endpoint was a major adverse cardiac and cerebrovascular event (MACCE), which was defined as composite cardiac-cerebrovascular death, myocardial infarction, cerebrovascular event, or revascularization. MR images were assessed for the presence of systemic atherosclerotic vessel changes, white matter lesions, and myocardial changes. Kaplan-Meier survival and Cox regression analyses were performed to determine associations. RESULTS Follow-up was completed in 61 patients (94%; median age, 67.5 years; 30 women [49%]; median follow-up, 70 months); 14 of the 61 patients (23%) experienced MACCE. Although normal whole-body MR imaging excluded MACCE during the follow-up period (0%; 95% confidence interval [CI]: 0%, 17%), any detectable ischemic and/or atherosclerotic changes at whole-body MR imaging (prevalence, 66%) conferred a cumulative event rate of 20% at 3 years and 35% at 6 years. Whole-body MR imaging summary estimate of disease was strongly predictive for MACCE (one increment of vessel score and each territory with atherosclerotic changes: hazard ratio, 13.2 [95% CI: 4.5, 40.1] and 3.9 [95% CI: 2.2, 7.5], respectively), also beyond clinical characteristics as well as individual cardiac or cerebrovascular MR findings. CONCLUSION These initial data indicate that disease burden as assessed with whole-body MR imaging confers strong prognostic information in patients with DM. Online supplemental material is available for this article.

First multimodal embolization particles visible on x-ray/computed tomography and magnetic resonance imaging.

Objectives:Embolization therapy is gaining importance in the treatment of malignant lesions, and even more in benign lesions. Current embolization materials are not visible in imaging modalities. However, it is assumed that directly visible embolization material may provide several advantages over current embolization agents, ranging from particle shunt and reflux prevention to improved therapy control and follow-up assessment. X-ray- as well as magnetic resonance imaging (MRI)-visible embolization materials have been demonstrated in experiments. In this study, we present an embolization material with the property of being visible in more than one imaging modality, namely MRI and x-ray/computed tomography (CT). Characterization and testing of the substance in animal models was performed. Materials and Methods:To reduce the chance of adverse reactions and to facilitate clinical approval, materials have been applied that are similar to those that are approved and being used on a routine basis in diagnostic imaging. Therefore, x-ray-visible Iodine was combined with MRI-visible Iron (Fe3O4) in a macroparticle (diameter, 40–200 μm). Its core, consisting of a copolymerized monomer MAOETIB (2-methacryloyloxyethyl [2,3,5-triiodobenzoate]), was coated with ultra-small paramagnetic iron oxide nanoparticles (150 nm). After in vitro testing, including signal to noise measurements in CT and MRI (n = 5), its ability to embolize tissue was tested in an established tumor embolization model in rabbits (n = 6). Digital subtraction angiography (DSA) (Integris, Philips), CT (Definition, Siemens Healthcare Section, Forchheim, Germany), and MRI (3 Tesla Magnetom Tim Trio MRI, Siemens Healthcare Section, Forchheim, Germany) were performed before, during, and after embolization. Imaging signal changes that could be attributed to embolization particles were assessed by visual inspection and rated on an ordinal scale by 3 radiologists, from 1 to 3. Histologic analysis of organs was performed. Results:Particles provided a sufficient image contrast on DSA, CT (signal to noise [SNR], 13 ± 2.5), and MRI (SNR, 35 ± 1) in in vitro scans. Successful embolization of renal tissue was confirmed by catheter angiography, revealing at least partial perfusion stop in all kidneys. Signal changes that were attributed to particles residing within the kidney were found in all cases in all the 3 imaging modalities. Localization distribution of particles corresponded well in all imaging modalities. Dynamic imaging during embolization provided real-time monitoring of the inflow of embolization particles within DSA, CT, and MRI. Histologic visualization of the residing particles as well as associated thrombosis in renal arteries could be performed. Visual assessment of the likelihood of embolization particle presence received full rating scores (153/153) after embolization. Conclusions:Multimodal-visible embolization particles have been developed, characterized, and tested in vivo in an animal model. Their implementation in clinical radiology may provide optimization of embolization procedures with regard to prevention of particle misplacement and direct intraprocedural visualization, at the same time improving follow-up examinations by utilizing the complementary characteristics of CT and MRI. Radiation dose savings can also be considered. All these advantages could contribute to future refinements and improvements in embolization therapy. Additionally, new approaches in embolization research may open up.

Impact of blood glucose, diabetes, insulin, and obesity on standardized uptake values in tumors and healthy organs on 18F-FDG PET/CT

INTRODUCTION Chronically altered glucose metabolism interferes with (18)F-FDG uptake in malignant tissue and healthy organs and may therefore lower tumor detection in (18)F-FDG PET/CT. The present study assesses the impact of elevated blood glucose levels (BGL), diabetes, insulin treatment, and obesity on (18)F-FDG uptake in tumors and biodistribution in normal organ tissues. METHODS (18)F-FDG PET/CT was analyzed in 90 patients with BGL ranging from 50 to 372 mg/dl. Of those, 29 patients were diabetic and 21 patients had received insulin prior to PET/CT; 28 patients were obese with a body mass index >25. The maximum standardized uptake value (SUV(max)) of normal organs and the main tumor site was measured. Differences in SUV(max) in patients with and without elevated BGLs, diabetes, insulin treatment, and obesity were compared and analyzed for statistical significance. RESULTS Increased BGLs were associated with decreased cerebral FDG uptake and increased uptake in skeletal muscle. Diabetes and insulin diminished this effect, whereas obesity slightly enhanced the outcome. Diabetes and insulin also increased the average SUV(max) in muscle cells and fat, whereas the mean cerebral SUV(max) was reduced. Obesity decreased tracer uptake in several healthy organs by up to 30%. Tumoral uptake was not significantly influenced by BGL, diabetes, insulin, or obesity. CONCLUSIONS Changes in BGLs, diabetes, insulin, and obesity affect the FDG biodistribution in muscular tissue and the brain. Although tumoral uptake is not significantly impaired, these findings may influence the tumor detection rate and are therefore essential for diagnosis and follow-up of malignant diseases.

Myocardial perfusion imaging with gadobutrol : A comparison between 3 and 1.5 tesla with an identical sequence design

Objectives:To implement myocardial first-pass perfusion imaging at 3 Tesla and to evaluate the potential benefit with regard to signal parameters in comparison to 1.5 Tesla using identical sequence settings and an intraindividual comparison. Materials and Methods:In 16 volunteers, myocardial first-pass perfusion imaging was performed at 1.5 Tesla (Magnetom Avanto) and 3 Tesla (Magnetom TIM Trio) after injection of 0.05 mmol/kg body weight Gadobutrol using an accelerated saturation recovery TurboFLASH technique (GRAPPA; R = 2) at 1.5 and 3 Tesla. Detailed sequence parameters (TR 2.3 milliseconds, TE 0.93 milliseconds, flip angle 15°, bandwidth 780 Hz/px) as well as spatial resolution were kept identical for both field strengths. Artifacts were assessed quantitatively and qualitatively, signal-to-noise ratio (SNR) and contrast enhancement ratio (CER) were calculated from raw data signal intensity–time curves. A linear fit on the upslope was performed for semiquantitative perfusion analysis. Results:SNR was significantly higher at 3 Tesla than at 1.5 Tesla (35.7 ± 11.9 vs. 18.0 ± 5.5, P < 0.001). CER was significantly greater at 3 Tesla than at 1.5 Tesla (2.2 ± 0.9 vs. 1.4 ± 0.5, P < 0.001). Maximum upslope was significantly higher at 3 Tesla than at 1.5 Tesla (3.3 ± 2.4 vs. 2.0 ± 1.0, P < 0.001). A qualitative examination of all images for artifacts by 2 board-certified radiologists yielded no significant differences between the field strengths. Conclusions:Three Tesla significantly improves CER and SNR compared with 1.5 Tesla with identical sequence parameters. In addition, the most important semiquantitative perfusion parameter maximum upslope is significantly increased. This may allow for an improvement of spatial resolution and potentially for a better delineation of perfusion defects. However, further studies are necessary to potentially demonstrate a benefit of 3 Tesla perfusion imaging in a clinical setting.