Diverse findings in cranial CT and scintigraphy in space occupying lesions (author's transl)

Incongruent statements in CT and scintigraphy may disturb therapy planning. Many years of scintigraphy have presented here an established method. Cranial CT was performed here with 2000 persons in one year. Parallel CT and scintigraphy was performed in about 350 cases. There were some cases with positive findings in CT and negative in scintigraphy and vice versa. These cases will be compared with the definite diagnosis, we will discuss the different findings and the relevance of both methods as a diagnostic aid for the neurosurgeon and therapeutic radiologist.     

Detection of mechanical ventricular asynchrony by high temporal resolution cine MRI

The purpose was to assess the feasibility of high temporal resolution cine MRI (HTRC-MRI) to detect and to quantify mechanical ventricular asynchrony in patients with left bundle branch block (LBBB). Inter- and intraventricular delays were quantified by HTRC-MRI in 32 patients with (n=17) and without (n=15) LBBB. In patients with LBBB, delays by HTRC-MRI were correlated with echocardiographic parameters using pulsed wave Doppler echocardiography (PW-Echo) and tissue Doppler imaging (TDI-Echo). The interventricular delay by HTRC-MRI was 110+/-50 ms in patients with and -1+/-18 ms in patients without LBBB (P<0.0001). The intraventricular delay was 336+/-86 ms in patients with compared to 40+/-49 ms in patients without LBBB (P<0.0001). A strong correlation (r=0.78, P=0.0002) and good agreement (mean difference: 39+/-36 ms) was found for the interventricular delay between HTRC-MRI and PW-Echo. A good correlation (r=0.66, P=0.0042), but a large discrepancy (mean difference: 257+/-64 ms) was found for the intraventricular delay between HTRC-MRI and TDI-Echo. Detection and quantification of mechanical ventricular asynchrony using HTRC-MRI is feasible. However, further comparison with other imaging modalities is required.     

Assessment of functional anatomy of the mitral valve in patients with mitral regurgitation with cine magnetic resonance imaging: comparison with transesophageal echocardiography and surgical results

The ability of magnetic resonance imaging (MRI) to accurately define the functional anatomy of mitral regurgitation was assessed. Transesophageal echocardiography (TEE) and cine MRI were performed on 43 patients with mitral regurgitation and were compared for the jet number, location, direction and presence of a prolapse (atrial displacement, malapposition or a flail). In 36 patients, diagnostic accuracy in reference to surgery was assessed. Comparing TEE and MRI the jet number and location were judged in concordance in 86% of patients. Jet location did not show a significant difference (Wilcoxon: P = 0.66) and both modalities correlated strongly (Spearman: r = 0.68, P<0.0001). Jet direction was judged with high concordance (kappa=0.63). Additionally, prolapse evaluation showed high concordance (kappa: valve, 0.63; anterior mitral leaflet, 0.70; posterior mitral leaflet, 0.73). Compared with surgery, the sensitivity for the detection of malapposition of any leaflet or one of both leaflets ranged between 75% and 93% for TEE and 71% and 89% for MRI. Specificities ranged between 88 and 96% for TEE and 88 and 100% for MRI. TEE detected torn chordae in all ten patients, six of which were missed by MRI. MRI is comparable with TEE in prolapse and jet evaluation. MRI is inferior to TEE in depicting anatomical details such as torn chordae.     

Coronary vessel-wall and lumen imaging using radial k-space acquisition with MRI at 3 Tesla

This study investigates the feasibility of imaging the coronary lumen and vessel-wall, using MRI with a radial k-space trajectory at 3 T. Such radial trajectories offer the advantage of greater vessel sharpness than traditional Cartesian trajectories. This field strength offers an increased signal-to-noise ratio (SNR) compared with 1.5 T, which compensates for the slight SNR reduction due to the radial sequence. Images of the coronary lumen were acquired for seven healthy volunteers. In ten volunteers the vessel wall was scanned, with blood suppression using oblique-slab adiabatic re-inversion. Scans were performed during free breathing, using prospective respiratory navigator-gating. Coronary lumen scans had SNR of 16.0±1.9 and contrast-to-noise ratio (CNR) of 10.3±2.1, showing acceptable image quality. Vessel wall images showed good image quality, with mean SNR of 16.6±2.0/5.8±2.8/10.1±2.2 for vessel wall/lumen/epicardial fat. The wall-blood CNR was 10.7±2.7, and wall-fat CNR was 6.5±2.5. It is concluded that radial gradient-echo imaging at 3 T is a promising method for coronary vessel-wall imaging, and is also feasible for imaging the coronary lumen.     

Prediction of myocardial recovery by dobutamine magnetic resonance imaging and delayed enhancement early after reperfused acute myocardial infarction

The purpose was to study dobutamine magnetic resonance cine imaging (DOB-MRI) and delayed myocardial contrast enhancement (DE) early after reperfused acute myocardial infarction (AMI) for the predicion of segmental myocardial recovery and to find the optimal dose of dobutamine. Fifty patients (56±12 years, 42 males) with reperfused AMI underwent DOB-MRI and DE studies 3.5 (1–19) days after reperfusion. In DOB-MRI systolic wall thickening (SWT) was measured in 18 segments at rest and during dobutamine at 5, 10 and 20 μg*kg⁻¹*min⁻¹. Dysfunctional segments were identified and the extent of DE was measured for each segment. Segmental recovery was examined after 8 (5–15) months. Two hundred-forty-eight segments were dysfunctional with presence of DE in 193. DOB-MRI showed the best prediction of recovery at 10 μg*kg⁻¹*min⁻¹ of dobutamine with sensitivity of 67%, specificity of 63% and accuracy of 66% using a cut-off value for SWT of 2.0 mm. DE revealed a sensitivity of 68%, specificity of 65% and accuracy of 67% using a cut-off value of 46%. Combined analysis of DOB-MRI and DE did not improve diagnostic performance. Early prediction of segmental myocardial recovery after AMI is possible with DOB-MRI and DE. No improvement is achieved by dobutamine >10 μg*kg⁻¹*min⁻¹ or a combination of DOB-MRI and DE.     

Value of T2-weighted, first-pass and delayed enhancement, and cine CMR to differentiate between acute and chronic myocardial infarction

The aim of this study was to analyze the diagnostic accuracy of edema on T2-weighted (T2w) cardiac magnetic resonance imaging (CMR), presence of microvascular obstruction (MO) on first-pass enhancement (FPE) or on delayed enhancement (DE) CMR, and wall thinning on cine CMR to differentiate between acute (AMI) and chronic myocardial infarction (CMI) in patients with infarction on DE-CMR. Fifty patients were imaged 5 ± 3 days (baseline) and 8 ± 3 months (follow-up) after AMI at 1.5 T. Imaging findings were graded as present or absent in a blinded consensus reading. Edema was present at baseline in 48 (96%) patients and absent at follow-up in 49 (98%) patients. At baseline, MO was present in 29 (58%) patients on FPE-CMR and in 24 (48%) patients on DE-CMR (P  = ns). At follow-up, persisting hypoenhancement was observed in ten (20%) patients on FPE-CMR, whereas two (4%) patients showed persisting hypoenhancement on DE-CMR (P<0.05). Wall thinning was present in 4 (8%) patients at baseline and in 20 (40%) patients at follow-up. Edema had high sensitivity (96%), specificity (98%), and accuracy (97%) to differentiate between AMI and CMI. Accuracy of all other imaging findings was lower compared to that of edema (P<0.001). In the presence of infarction on DE-CMR, T2w-CMR reliably differentiates between AMI and CMI. This study was funded in part by the Pinguin-Stiftung, Düsseldorf, Germany and by the Schering Company, Berlin, Germany.     

Detection of small pulmonary nodules in high-field MR at 3 T: evaluation of different pulse sequences using porcine lung explants

To evaluate two MR imaging sequences for the detection of artificial pulmonary nodules inside porcine lung explants. 67 agarose nodules ranging 3–20 mm were injected into ten porcine lungs within a dedicated chest phantom. The signal on T1-weighted images and radiopacity were adjusted by adding 0.125 mmol/l Gd-DTPA and 1.5 g/l of iodine. A T1-weighted three-dimensional gradient-echo (T1-3D-GRE; TR/TE:3.3/1.1 ms, slice:8 mm, flip-angle:10°) and a T2-weighted half-Fourier fast-spin echo sequence (T2-HF-FSE; TR/TE:2000/66 ms, slice:7 mm, flip-angle:90°) were applied in axial orientation using a 3-T system (Intera, Philips Medical Systems, Best, The Netherlands), followed by CT (16×0.5 mm) as reference. Nodule sizes and locations were assessed by three blinded observers. In nodules of >10 mm, sensitivity was 100% using 3D-GRE-MRI and 94% using the HF-FSE sequence. For nodules 6–10 mm, the sensitivity of MRI was lower than with CT (3D-GRE:92%; T2-HF-FSE:83%). In lesions smaller than 5 mm, the sensitivity declined to 80% (3D-GRE) and 53% (HF-FSE). Small lesion diameters were overestimated with both sequences, particularly with HF-FSE. This study confirms the feasibility of 3 T-MRI for lung nodule detection. In lesions greater than 5 mm, the sensitivity of the 3D-GRE sequence approximated CT (>90%), while sensitivity and PPV with the HF-FSE sequence were slightly inferior.     

Magnetic resonance imaging of the coronary vessel wall at 3 T using an obliquely oriented reinversion slab with adiabatic pulses.

Three-dimensional methods offer volumetric coverage in coronary vessel wall imaging, in addition to high signal-to-noise ratios (SNR). To increase SNR further, it is desirable to implement such 3D methods at 3 T. At this field strength, the pulse sequence must be robust to main field and RF inhomogeneities. To achieve this, the double inversion-recovery (DIR) preparation was adapted to use adiabatic pulses, with a slab-selective reinversion replacing the previously used 2D pencil-beam. The slab was oriented obliquely, in order to avoid upstream blood (e.g., left ventricle) or the navigator beam. Phantom experiments suggest that at 3 T, this approach improves both the net profile of the DIR pulse pair and the restoration of magnetization in the navigator region. Using this method, the feasibility of 3D coronary vessel wall imaging was demonstrated at 3 T. Fourteen healthy subjects were scanned using a segmented gradient-echo sequence with prospective navigator gating. Good-quality images of left and right coronary arteries were obtained, with SNR values of 29.7 +/- 7.5 (vessel wall); 10.5 +/- 4.4 (blood); 14.3 +/- 5.2 (fat); and 45.6 +/- 18.0 (myocardium). No problems occurred with ECG-gating or power deposition (SAR) limits.