Reproducibility of non-contrast enhanced multi breath-hold ultrashort echo time functional lung MRI.

PURPOSE: To evaluate the intraindividual reproducibility of functional lung imaging using non-contrast enhanced multi breath-hold 3D-UTE MRI. METHODS: Ten healthy volunteers underwent non-contrast enhanced 3D-UTE MRI at three time points for same-day and different-day measurements employing a stack-of-spirals trajectory at 3 T. At each time point, inspiratory and expiratory breathing states were acquired for tidal and deep breathing, each within a single breath-hold. For functional image analysis, fractional ventilation (FV) was calculated pixelwise after image registration from the MR signal change. To decouple FV from breathing depth, the individual lung volume was used for volume adjustment (rFV). Reproducibility evaluation was performed in eight lung segments. Statistical analyses included two way mixed intraclass correlation (ICC), sign-test, Friedman-test and modified Bland-Altman analyses. RESULTS: FV from tidal breathing showed an ICC of 0.81, a bias of 1.3% and an interval of confidence (CI) ranging from -67.1 to 69.6%. FV from deep breathing was higher reproducible with an ICC of 0.92 (bias, -0.2%; CI, -34.2 to 33.7%). Following volume adjustment, reproducibility of rFV for tidal breathing improved (ICC, 0,86; bias, 2.0%; CI, -34.3 to 38.3%), whereas it did not bear significant benefits for deep breathing (ICC, 0.89; bias, 2.8%; CI, -24.9 to 30.5%). Reproducibility was independent from the examination day. CONCLUSION: Non-contrast-enhanced multi breath-hold 3D-UTE MRI allows for highly reproducible ventilation imaging.

Non-contrast pulmonary perfusion MRI in patients with cystic fibrosis.

PURPOSE: This study aimed to assess the feasibility of Self-gated Non-Contrast-Enhanced Functional Lung (SENCEFUL) MRI for detection of pulmonary perfusion deficits in patients with cystic fibrosis. METHODS: Twenty patients with cystic fibrosis and 20 matched healthy controls underwent SENCEFUL-MRI at 1.5 T with reconstruction of perfusion and perfusion phase maps (i.e. comparable to pulse wave delays). Four blinded readers rated both types of maps separately followed by simultaneous assessment thereof. Perfusion phase data was plotted in histograms and a Peak-to-Offset ratio was calculated for comparison to subjective scoring and correlation (Spearman) to lung function parameters. Sensitivity, specificity and positive and negative predictive values were calculated for subjective scoring and Peak-to-Offset ratios. Intraclass correlation (ICC) was used to assess the interrater agreement. RESULTS: Readers attributed pathological ratings 2.2-3.5 times more frequently to the CF-group. The sensitivity with regard to a correct assignment to CF was similar between ratings (perfusion only vs. perfusions phase only vs. simultaneous assessment: 0.54-0.56), while specificity increased from 0.75 to 0.85 for simultaneous assessment. ICC was 0.77-0.84 for subjective scoring. ROC-analysis of Peak-to-Offset ratios on a mean per-subject basis revealed a sensitivity of 0.75 and specificity of 0.85 (PPV 0.83, NPV 0.77). Functional pulmonary parameters indicative of bronchial obstruction and Peak-to-Offset ratios showed positive correlation (FEV1: 0.77; FEF75: 0.76). CONCLUSIONS: SENCEFUL-MRI bears the potential for monitoring CF including disease-associated patterns of altered pulmonary perfusion. The proposed Peak-to-Offset ratio derived from pulmonary perfusion phase measurements could represent an objective future marker for perfusion impairment.

UTE-SENCEFUL: first results for 3D high-resolution lung ventilation imaging.

PURPOSE: This study aimed to develop a 3D MRI technique to assess lung ventilation in free-breathing and without the administration of contrast agent. METHODS: A 3D-UTE sequence with a koosh ball trajectory was developed for a 3 Tesla scanner. An oversampled k-space was acquired, and the direct current signal from the k-space center was used as a navigator to sort the acquired data into 8 individual breathing phases. Gradient delays were corrected, and iterative SENSE was used to reconstruct the individual timeframes. Subsequently, the signal changes caused by motion were eliminated using a 3D image registration technique, and ventilation-weighted maps were created by analyzing the signal changes in the lung tissue. Six healthy volunteers and 1 patient with lung cancer were scanned with the new 3D-UTE and the standard 2D technique. Image quality and quantitative ventilation values were compared between both methods. RESULTS: UTE-based self-gated noncontrast-enhanced functional lung (SENCEFUL) MRI provided a time-resolved reconstruction of the breathing motion, with a 49% increase of the SNR. Ventilation quantification for healthy subjects was in statistical agreement with 2D-SENCEFUL and the literature, with a mean value of 0.11 ± 0.08 mL/mL for the whole lung. UTE-SENCEFUL was able to visualize and quantify ventilation deficits in a patient with lung tumor that were not properly depicted by 2D-SENCEFUL. CONCLUSION: UTE-SENCEFUL represents a robust MRI method to assess both morphological and functional information of the lungs in 3D. When compared to the 2D approach, 3D-UTE offered ventilation maps with higher resolution, improved SNR, and reduced ventilation artifacts.

Grade of retraction and tendon thickness correlates with MR-spectroscopically measured amount of fatty degeneration in full thickness supraspinatus tears.

BACKGROUND: The amount of fatty degeneration (FD) has major impact on the clinical result and cuff integrity after rotator cuff repair. A quantitative analysis with magnet resonance imaging (MRI) spectroscopy was employed to analyze possible correlation of FD with tendon retraction, tendon thickness and patients' characteristics in full thickness supraspinatus tears. METHODS: Forty-two patients with full-thickness supraspinatus tears underwent shoulder MRI including an experimental spectroscopic sequence allowing quantification of the fat fraction in the supraspinatus muscle belly. The amount of fatty degeneration was correlated with tendon retraction, tendon thickness, patients' age, gender, smoker status, symptom duration and body mass index (BMI). Patients were divided in to three groups of retraction (A) 0-10 mm (n=), (B) 11-20 mm (n=) and (C) < 21 mm (n=) and the means of FD for each group were calculated. RESULTS: Tendon retraction (R = 0.6) and symptom duration (R = 0.6) correlated positively, whereas tendon thickness correlated negatively (R = - 0.6) with the amount of FD. The fat fraction increased significantly with tendon retraction: Group (A) showed a mean fat mount of 3.7% (±4%), group (B) of 16.7% (±8.2%) and group (C) of 37.5% (±19%). BMI, age and smoker-status only showed weak to moderate correlation with the amount of FD in this cohort. CONCLUSION: MRI spectroscopy revealed significantly higher amount of fat with increasing grade of retraction, symptom duration and decreased tendon thickness. Thus, these parameters may indirectly be associated with the severity of tendon disease.

Quantitative MRI comparison of multifidus muscle degeneration in thoracolumbar fractures treated with open and minimally invasive approach.

BACKGROUND: Minimally invasive pedicle screw fixation has less approach-related morbidity than open screw placement and is allegedly less traumatizing on paravertebral muscles, as there is no requirement to mobilize and retract the adjacent muscle portion. The approach-related long-term effects to the morphology of the paravertebral muscles are unknown. The purpose of this study was to compare the long-term amount of fatty degeneration of the multifidus muscle in patients treated with a classical open or a minimally invasive approach. METHODS: Fourteen Patients meeting inclusion criteria were selected. In all patients a singular fracture of the thoracolumbar spine with a two-level posterior instrumentation was treated, either using an open approach or a minimally invasive approach. All patients underwent quantitative MRI spectroscopy for quantification of the fatty degeneration in the multifidus muscle as a long-term proof for muscle loss after minimum 4-year follow-up. Clinical outcome was assessed using Oswestry Low Back Pain Disability Questionnaire, SF-36 and VA-scale for pain. RESULTS: The minimally invasive approach group failed to show less muscle degeneration in comparison to the open group. Total amount of fatty degeneration was 14.22% in the MIS group and 12.60% in the open group (p = 0.64). In accordance to MRI quantitative results there was no difference in the clinical outcome after a mean follow up of 5.9 years (±1.8). CONCLUSION: As short-term advantages of minimal invasive screw placement have been widely demonstrated, no advantage of the MIS, displaying a significant difference in the amount of fatty degeneration and resulting in a better clinical outcome could be found. Besides the well-known short-term advantage of minimally invasive pedicle screw placement, a long-term advantage, such as less muscle degeneration and thus superior clinical results, compared to the open approach could not be shown.

Myocardial lipid content in Fabry disease: a combined 1H-MR spectroscopy and MR imaging study at 3 Tesla.

BACKGROUND: Fabry disease is characterized by a progressive deposition of sphingolipids in different organ systems, whereby cardiac involvement leads to death. We hypothesize that lysosomal storage of sphingolipids in the heart as occurring in Fabry disease does not reflect in higher cardiac lipid concentrations detectable by 1H magnetic resonance spectroscopy (MRS) at 3 Tesla. METHODS: Myocardial lipid content was quantified in vivo by 1H-MRS in 30 patients (12 male, 18 female; 18 patients treated with enzyme replacement therapy) with genetically proven Fabry disease and in 30 healthy controls. The study protocol combined 1H-MRS with cardiac cine imaging and LGE MRI in a single examination. RESULTS: Myocardial lipid content was not significantly elevated in Fabry disease (p = 0.225). Left ventricular (LV) mass was significantly higher in patients suffering from Fabry disease compared to controls (p = 0.019). Comparison of patients without signs of myocardial fibrosis in MRI (LGE negative; n = 12) to patients with signs of fibrosis (LGE positive; n = 18) revealed similar myocardial lipid content in both groups (p > 0.05), while the latter showed a trend towards elevated LV mass (p = 0.076). CONCLUSIONS: This study demonstrates the potential of lipid metabolic investigation embedded in a comprehensive examination of cardiac morphology and function in Fabry disease. There was no evidence that lysosomal storage of sphingolipids influences cardiac lipid content as measured by 1H-MRS. Finally, the authors share the opinion that a comprehensive cardiac examination including three subsections (LGE; 1H-MRS; T1 mapping), could hold the highest potential for the final assessment of early and late myocardial changes in Fabry disease.

Quantitative pixelwise myocardial perfusion maps from first-pass perfusion MRI.

OBJECTIVE: To calculate and evaluate absolute quantitative myocardial perfusion maps from rest first-pass perfusion MRI. METHODS: 10 patients after revascularization of myocardial infarction underwent cardiac rest first-pass perfusion MRI. Additionally, perfusion examinations were performed in 12 healthy volunteers. Quantitative myocardial perfusion maps were calculated by using a deconvolution technique, and results were compared were the findings of a sector-based quantification. RESULTS: Maps were typically calculated within 3 min per slice. For the volunteers, myocardial blood flow values of the maps were 0.51 ± 0.16 ml g(-1) per minute, whereas sector-based evaluation delivered 0.52 ± 0.15 ml g(-1) per minute. A t-test revealed no statistical difference between the two sets of values. For the patients, all perfusion defects visually detected in the dynamic perfusion series could be correctly reproduced in the maps. CONCLUSION: Calculation of quantitative perfusion maps from myocardial perfusion MRI examinations is feasible. The absolute quantitative maps provide additional information on the transmurality of perfusion defects compared with the visual evaluation of the perfusion series and offer a convenient way to present perfusion MRI findings. ADVANCES IN KNOWLEDGE: Voxelwise analysis of myocardial perfusion helps clinicians to assess the degree of tissue damage, and the resulting maps are a good tool to present findings to patients.

Non-invasive determination of myocardial lipid content in Fabry disease by 1H-MR spectroscopy.

PURPOSE: In Fabry disease (FD), a progressive deposition of sphingolipids is reported in different organs. The present study applied 1H magnetic resonance spectroscopy (MRS) to investigate the myocardial lipid content in FD. MATERIALS AND METHODS: In patients (PTS, n = 15) with genetically proven FD, 1H MRS of the heart was acquired in the same examination as routine cardiac cine and late enhancement MR imaging. Healthy volunteers (n = 11) without history of cardiac disease served as control (CTL). Myocardial triglycerides in vivo were quantified in 1H MRS. Left ventricular (LV) ejection fraction (EF) and late enhancement were assessed for the determination of LV systolic function, and onset or absence of myocardial fibrosis. RESULTS: All 1H MRS revealed resonances for intramyocardial triglycerides. Clinical parameters, e.g. EF (PTS 64 ± 2 % vs. CTL 61 ± 1 %) were similar in PTS and CTL or showed a non-significant trend (LV mass). Apart from a single patient with elevated myocardial triglycerides, no significant impact of Fabry disease on the triglyceride/water resonance ratio (PTS 0.47 ± 0.11 vs. CTL 0.52 ± 0.11 %) was observed in our patient cohort. CONCLUSION: A comprehensive cardiac evaluation of morphology, function as well as metabolism in Fabry PTS with suspected cardiac involvement is feasible in a single examination. No significant effect of myocardial triglyceride deposition could be observed in patients. The remarkably high myocardial triglyceride content in one patient with advanced FD warrants further studies in PTS with an extended history of the disease.

Quantitative myocardial perfusion imaging with a MR cold pressor test.

The response of myocardial blood flow to sympathetic stimulation with cold is modulated by endothelium-related factors. As endothelial dysfunction is an early step in patients with coronary artery disease, the aim of this study was to establish a cold pressor test (CPT) setting for quantitative analysis of myocardial perfusion in a MR scanner. First pass perfusion studies were performed in 10 healthy volunteers using a 1.5 T MR scanner with a multislice steady state free precession perfusion trueFISP sequence in prebolus technique (1 cc/4 cc gadobenate dimeglumine). MR-CPT was established using an over head ice-water bath of the left hand. First pass perfusion imaging was started after 1 min to assure an adequate stimulus followed by a second series after 15 min to evaluate the rest perfusion. After motion correction images were segmented with an adapted, automated tool, myocardial contours were determined. Perfusion was quantitatively evaluated after contamination and baseline correction by deconvolution with the arterial input function using an exponential function model as residuum. All data could be evaluated. Mean myocardial perfusion rose from 0.61 ± 0.22 cc/g/min at rest to 1.15 ± 0.34 cc/g/min under CPT. MR myocardial perfusion values show a comparable increase under CPT as published positron emission tomography data. Consequently, CPT for the presence of endothelial dysfunction is feasible in the MR environment.