Rene Schilling

Osteochondral Lesions of the Talus: Retrograde Drilling with High-Field-Strength MR Guidance

The institutional review board approved the use of cadaveric specimens, and informed consent was obtained from all volunteers. The authors performed and assessed a magnetic resonance (MR)-assisted navigation method for minimally invasive retrograde drilling of talar osteochondral lesions. For this method, a single imaging plane is sufficient for navigation during intervention. To accomplish this objective, a passive MR navigation device was used to evaluate 16 cadaveric ankle joints. Use of this interactive MR-assisted navigation method in combination with a passive aiming device allowed precise and rapid retrograde drilling of talar osteochondral lesions.

Gadobutrol for magnetic resonance imaging of chronic myocardial infarction: intraindividual comparison with gadopentetate dimeglumine.

Objectives:To compare 0.15 mmol/kg gadobutrol with 0.20 mmol/kg gadopentetate dimeglumine with regard to late gadolinium enhancement (LGE) of infarcted myocardium at magnetic resonance (MR) imaging. Materials and Methods:Twenty patients with history of chronic myocardial infarction underwent 2 cardiac MR examinations at 1.5 Tesla. For the evaluation of myocardial infarction, late gadolinium enhancement (LGE) imaging was performed with an inversion recovery-prepared gradient-echo sequence 15 minutes after administration of either gadobutrol (r1 = 5.2 mmol−1s−1) or gadopentetate dimeglumine (r1 = 4.1 mmol−1s−1). The dose of the contrast agents was adjusted based on the relaxivity of both contrast agents. Hence, gadobutrol and gadopentetate dimeglumine were administered at 0.15 mmol/kg and 0.20 mmol/kg, respectively. Contrast-to-noise ratios (CNR) between infarcted myocardium and remote myocardium (CNRremote) and between infarcted myocardium and left ventricular lumen (CNRlumen) were assessed by 2 independent readers. Additionally, infarct size was assessed semiautomatically by using a threshold of 5 standard deviations above the mean signal intensity of remote myocardium. Results:Subendocardial or transmural LGE was present in 16 of 20 (80%) patients. The optimal inversion time for LGE imaging did not differ significantly between gadobutrol and gadopentetate dimeglumine (275 ± 21 milliseconds [range, 240–320 milliseconds] and 282 ± 23 milliseconds [range, 240–330 milliseconds], respectively; P = 0.32). The CNRremote after administration of gadobutrol (40.0 ± 4.6; 95% confidence interval [CI]: 30.3; 49.7) and gadopentetate dimeglumine (40.6 ± 4.6; 95% CI: 30.9; 50.3) did not show significant differences (P = 0.90), whereas gadobutrol yielded a significantly higher CNRlumen (6.2 ± 3.6; 95% CI: −1.5; 13.9) compared with gadopentetate dimeglumine (0.8 ± 3.6; 95% CI: −6.9; 8.5). Infarct size after administration of gadobutrol (23.7 ± 4.7 mL; 95% CI: 13.6; 33.7) and gadopentetate dimeglumine (23.7 ± 4.7 mL;95% CI: 13.7; 33.8) was not statistically different (P = 0.94). There was an excellent correlation between gadobutrol- and gadopentetate dimeglumine-enhanced assessment of infarct size (Spearman r = 0.99 and r = 0.97 for reader 1 and 2, respectively). Conclusion:This pilot study shows that 0.15 mmol/kg gadobutrol is an effective contrast agent for LGE imaging with better delineation of infarcted myocardium from left ventricular lumen than 0.20 mmol/kg gadopentetate dimeglumine.

Reviving the Dinosaur: Virtual Reconstruction and Three-dimensional Printing of a Dinosaur Vertebra

PURPOSE To demonstrate the feasibility of using computed tomography (CT) to confirm the identity of an unprepared fossil and to use the CT dataset to separate the fossilized bone from its surrounding sediment matrix and produce a three-dimensional (3D) print. MATERIALS AND METHODS The examined object was a plaster jacket containing an unprepared fossil. CT was performed with a 320-section multidetector unit. A marching cube-based method was used to transform the voxel CT dataset into triangle-based, editable geometry. Then, a comprehensive postprocessing step was performed to isolate the geometry of the vertebra from its surrounding fossilized matrix. Finally, the resulting polygon mesh describing only the vertebra was used for a physical 3D reconstruction by using a selective laser sintering machine. RESULTS The CT examination provided enough data to assign the fossil to the genus Plateosaurus. In addition, much valuable information about the fossil has been gained-in particular the visualization of multiple fractures and the destruction of the anterior rim of the vertebral body. Finally, the results show that the 3D print generated, including the fractures and the anterior destruction, may be considered an accurate copy of the bone with the unprepared fossil. CONCLUSION The authors demonstrated the feasibility and potential utility of combining CT with 3D printing, providing a nondestructive method to future paleontologists.

Development of a signal-inducing bone cement for magnetic resonance imaging

To develop a signal‐inducing bone cement for musculoskeletal procedures in magnetic resonance imaging (MRI).

Intraindividual comparison of T1 relaxation times after gadobutrol and Gd-DTPA administration for cardiac late enhancement imaging

PURPOSE To evaluate T1-relaxation times of chronic myocardial infarction (CMI) using gadobutrol and gadopentetate dimeglumine (Gd-DTPA) over time and to determine the optimal imaging window for late enhancement imaging with both contrast agents. MATERIAL AND METHODS Twelve patients with CMI were prospectively included and examined on a 1.5 T magnetic resonance (MR) system using relaxivity-adjusted doses of gadobutrol (0.15 mmol/kg) and Gd-DTPA (0.2 mmol/kg) in random order. T1-relaxation times of remote myocardium (RM), infarcted myocardium (IM), and left ventricular cavity (LVC) were assessed from short-axis TI scout imaging using the Look-Locker approach and compared intraindividually using a Wilcoxon paired signed-rank test (α<0.05). RESULTS Within 3 min of contrast agent administration (CA), IM showed significantly lower T1-relaxation times than RM with both contrast agents, indicating beginning cardiac late enhancement. Differences between gadobutrol and Gd-DTPA in T1-relaxation times of IM and RM were statistically not significant through all time points. However, gadobutrol led to significantly higher T1-relaxation times of LVC than Gd-DTPA from 6 to 9 min (220 ± 15 ms vs. 195 ± 30 ms p<0.01) onwards, resulting in a significantly greater ΔT1 of IM to LVC at 9-12 min (-20 ± 35 ms vs. 0 ± 35 ms, p<0.05) and 12-15 min (-25 ± 45 ms vs. -10 ± 60 ms, p<0.05). Using Gd-DTPA, comparable ΔT1 values were reached only after 25-35 min. CONCLUSION This study indicates good delineation of IM to RM with both contrast agents as early as 3 min after administration. However, we found significant differences in T1 relaxation times with greater ΔT1 IM-LVC using 0.15 mmol/kg gadobutrol compared to 0.20 mmol/kg Gd-DTPA after 9-15 min post-CA suggesting earlier differentiability of IM and LVC using gadobutrol.

Percutaneous transhepatic cholangiodrainage under real-time MRI guidance: Initial experience in an animal model

AIMS To assess percutaneous transhepatic cholangiodrainage (PTCD) under real-time MRI-guidance and compare it to procedures performed under fluoroscopy. METHODS We developed an in vitro model for MRI-guided and conventional PTCD, using an animal organ set including liver and bile ducts placed in an MRI-compatible box and tested it in a 1.0-Tesla open MRI-scanner. Prototype 18G needles and guide wires, standard guide wires, dilatation bougies, and drainages were used (MRI-compatible). MRI-visualization was by means of a bFFE real-time sequence using a surface coil (Flex-L). Outcome measurements were success rates and time needed for bile duct puncture using real-time MRI-guidance versus conventional radiologic methods in the model. Cannulation and drainage placement were also analysed. RESULTS Fifty MRI-guided experiments were performed, leading to rapid (mean: 43s, range: 15-72s) and successful puncture and cannulation in 96% of procedures. Median drainage placement time was 321.5s (range: 241-411s). In 35 control experiments under fluoroscopy, puncture success was 69%, whereas times were significantly longer (mean 273s, range 45-631s). CONCLUSIONS Initial in vitro experience shows that PTCD can be successfully and rapidly performed under real-time MRI-guidance and demonstrates improved performance compared to the conventional radiologic approach.