Purpose To develop R2* mapping techniques corrected for confounding factors and optimized for noise performance. Theory and Methods Conventional R2* mapping is affected by two key confounding factors: noise-related bias and the presence of fat in tissue. Noise floor effects introduce bias in magnitude-based reconstructions, particularly at high R2* values. The presence of fat, if uncorrected, introduces severe protocol-dependent bias. In this work, the bias/noise properties of different R2* mapping reconstructions (magnitude-and complex-fitting, fat-uncorrected, and fat-corrected) are characterized using Cramer-Rao Bound analysis, simulations, and in vivo data. A framework for optimizing the choice of echo times is provided. Finally, the robustness of liver R2* mapping in the presence of fat is evaluated in 28 subjects. Results Fat-corrected R2* mapping removes fat-related bias without noise penalty over a wide range of R2* values. Complex nonlinear least-squares fitted and fat-corrected R2* reconstructions that account for the spectral complexity of fat provide robust R2* estimates with low bias and optimized noise performance over a wide range of echo times combinations and R2* values. Conclusion The use of complex fitting and fat-correction improves the robustness, noise performance, and accuracy of R2* measurements, and are necessary to establish R2* as quantitative imaging biomarker in the liver.

The authors hypothesized that magnetization transfer contrast (MTC) could be used to improve flow contrast in time-of-flight (TOF) magnetic resonance (MR) angiography. Two- and three-dimensional flow-compensated gradient-echo images were obtained with and without MTC. MTC images were obtained by applying low-power radio-frequency (RF) radiation with a frequency offset from the bulk "free" water resonance frequency before the excitation RF pulse. The signal intensity of stationary tissue decreased as the power applied for the MTC pulse was increased. A smaller decrease occurred in venous signal intensity as measured in the superior sagittal sinus, and less change was seen in the arterial signal intensity as measured in the middle cerebral artery. Cerebrospinal fluid showed no MTC effect. The use of MTC improved small-vessel depiction on maximum-intensity projection images. The authors conclude that use of MTC can substantially enhance the quality of TOF MR angiography of the brain.

Background Long segment laryngotracheoesophageal clefts (LTECs) are very rare large‐airway malformations. Over the last 40 years mortality rates declined substantially due to improved intensive care and surgical procedures. Nevertheless, long‐term morbidity, comorbidity, and clinical outcomes have rarely been assessed systematically. Methods In this retrospective case series, the clinical presentation, comorbidities, treatment, and clinical outcomes of all children with long‐segment LTEC that were seen at our department in the last 15 years were collected and analyzed systematically. Results Nine children were diagnosed with long segment LTEC (four children with LTEC type III and five patients with LTEC type IV). All children had additional tracheobronchial, gastrointestinal, or cardiac malformations. Tracheostomy for long‐time ventilation and jejunostomy for adequate nutrition was necessary in all cases. During follow‐up one child died from multiorgan failure due to sepsis at the age of 43 days. The clinical course of the other eight children (median follow‐up time 5.2 years) was stable. Relapses of the cleft, recurrent aspirations, and respiratory tract infections led to repeated hospital admissions. Conclusions Long‐segment LTECs are consistently associated with additional malformations, which substantially influence long‐term morbidity. For optimal management, a multidisciplinary approach is essential.

Purpose Intraindividual comparison of a 1.0 molar and two 0.5 molar Gadolinium (Gd) based contrast agents (GBCA) with weak/no protein binding using equimolar dosing in dynamic and static Magnetic Resonance Angiography (MRA) of the supraaortic vessels. Material & Methods In this IRB approved study a total of 20 healthy volunteers (29±6y) underwent three consecutive supraaortic MRA exams on a 3T MR system. Order of GBCA (Gadobutrol, Gadobenate dimeglumine, Gadoterate meglumine) was randomized with a minimum interval of 48h between exams. Prior to and 45 minutes after each exam circulatory parameters were recorded. Total GBCA dose per MRA exam was 0.1mmol/kg with a 0.03/0.07 mmol/kg split for dynamic and static MRA respectively, injected at a rate of 2ml/s. Two blinded readers qualitatively assessed static MRA data sets independently using pairwise rankings (superior, inferior, equal). In addition quantitative analysis was performed with SNR and CNR evaluation as well as vessel sharpness analysis of static MRA employing an in house developed semi-automated tool. Dynamic MRA was evaluated in terms of maximal SNR. Statistical analysis was performed using Cohen’s kappa, Wilcoxon rank tests as well as mixed effects models. Results No significant differences of hemodynamic parameters were observed. In static MRA Gadobutrol was rated superior to Gadoterate meglumine(p0.0002) and equal to Gadobenate dimeglumine(p0.057) with good to excellent reader agreement (kappa 0.663 – 0.83). In static MRA SNR was significantly higher using1M Gadobutrol as compared to either 0.5M agent (p0.0458/0.0325) and CNR significantly higher as compared to Gadoterate meglumine (p 0.033) while CNR values of Gadobutrol datasets were not significantly different as compared to Gadobenate dimeglumine(p 0.134). Differences in CNR between Gadobenate dimeglumine and Gadoterate meglumine were not significant (p 0.779). Differences in vessel sharpness between the different GBCAs were also not significant (p > 0.05). Maximal SNR in dynamic MRA using Gadobutrol was significantly higher to both comparators at the level of the proximal and distal ICA (p 0.022, 0.002/p 0.04, 0.012). Conclusion At equimolar doses 1MGadobutrol demonstrates higher SNR/CNR to Gadobenate dimeglumine and Gadoterate meglumine with superior image quality as compared to Gadoterate meglumine for dynamic and static carotid MRA. Despite the shortened bolus with Gadobutrol no blurring of vessel edges is observed.

Since the introduction of contrast-enhanced MR angiography (MRA), several different techniques for imaging the peripheral arteries have evolved. All of them provide good diagnostic image quality, whereas some older techniques suffer from drawbacks, such as long acquisition time, impaired image quality from venous enhancement, and limited spatial resolution. MRA provides the most comprehensive modality offering the ability to tailor the examination to the patient and the specific question to be answered. The drawbacks experienced at the introduction of MRA to clinical routine have largely been overcome or at least diminished, so that the benefits of MRA outbalance the limitations.