Synthetic Inversion Image Generation using MP2RAGE T1 Mapping for Surgical Targeting in Deep Brain Stimulation and Lesioning.

BACKGROUND: Advances in MRI technology have increased interest in direct targeting for deep brain stimulation (DBS). Various imaging sequences have been shown to provide increased contrast of numerous common DBS targets, such as T1-weighted, Fast Gray Matter Acquisition T1 Inversion Recovery (FGATIR), gray matter nulled, and Edge-Enhancing Gradient Echo (EDGE); however, the continual increase in the number of necessary sequences has led to an increase in imaging time, which is undesirable. Additionally, carefully timed inversion pulses can often lead to less-than-ideal contrast in some subjects, particularly in ultra-high field MRI, where B1+ field inhomogeneity can lead to substantial contrast variation. OBJECTIVES: This study proposes using 3D MP2RAGE-based T1 maps to retrospectively synthesize images of any desired inversion time, including T1-weighted, FGATIR, and EDGE contrasts, to visualize specific DBS targets at both 3T and 7T. METHOD: First, a systematic sequence optimization framework was applied to optimize MP2RAGE T1 mapping sequence parameters for the purpose of DBS planning. Next, we show that synthetic inversion-time images can be generated through a mathematical transformation of the T1 maps. The sequence was then applied to patients undergoing preoperative planning for DBS at 3T and 7T to generate synthetic contrasts used in surgical planning. RESULTS: We show that synthetic image contrasts can be generated across a full range of inversion times at 3T and 7T, including commonly used sequences for DBS targeting, such as T1-weighted, FGATIR, and EDGE. Acquisition through a single sequence shortens scan time compared to acquiring the sequences independently without affecting image quality or contrast. CONCLUSIONS: The generation of synthetic images for DBS targeting allows faster acquisition of many key sequences, as well as the ability to optimize contrast properties post-acquisition to account for the variable B1+ effects present in ultra-high field MRI. The proposed approach has the potential to reduce imaging time and improve the accuracy of DBS targeting at 1.5T, 3T, and 7T.

Optimization of fast gray matter acquisition T1 inversion recovery (FGATIR) on 7T MRI for deep brain stimulation targeting.

Deep brain stimulation (DBS) is an increasingly utilized treatment for multiple neurological disorders. Continued improvements in DBS outcome are, in part, related to increasing ability to directly visualize stimulation targets by MRI. However, it is challenging to image DBS targets with conventional MRI techniques due to limited contrast. Fast Gray Matter Acquisition T1 Inversion Recovery (FGATIR) is a commonly used MRI sequence that improves visualization of several key DBS targets by suppressing white matter (WM) signal to better reveal deep-brain gray matter (GM) structures. Due to increased signal level at high field strength, application of FGATIR on 7T MRI may allow higher spatial resolution and better DBS targeting accuracy. However, successful utilization of FGATIR requires meticulous sequence optimization involving multiple parameters to maximize GM signal while suppressing WM. This is further complicated by the transmit RF field (B1+) inhomogeneity on 7T, which can cause severe contrast degradation. In this work, we introduce a systematic approach to optimize FGATIR and to improve visualization of thalamic DBS targets on 7T. FGATIR optimization is cast into a constrained optimization problem whose objective function and constraints are designed to maximize the GM-WM contrast-to-noise ratio (CNR) while accounting for B1+ inhomogeneity. This approach allows a systematic search for optimal parameters across the multi-dimensional parametric space while limiting the negative effect of B1+ variation. Bloch equation simulations were performed to solve the proposed optimization problem and to compare the sequence derived from this method against the sequence optimized without considering B1+ inhomogeneity. The results showed that this approach can improve GM-WM CNR in the presence of B1+ inhomogeneity, especially in some high relative B1+ areas where several key thalamic DBS targets are located. Additionally, in vivo images were acquired on a clinical 7T MRI to further validate this approach. Severe contrast degradation in the thalamus was observed when B1+ effect was not considered in sequence optimization, while the proposed approach yielded improved image contrast in the thalamus with key DBS targets well-defined. These results demonstrated that the proposed method allowed optimization of FGATIR on 7T to better visualize thalamic DBS targets, which may lead to improved DBS targeting accuracy as well as treatment outcome.

Non-contrast myocardial perfusion using a novel 4D magnetic resonance arterial spin labeling technique: initial experience.

The aim of this study is to develop a novel non-contrast 4-dimensional MR arterial spin labeling (4D-ASL) technique (3D acquisition and time) and to investigate myocardial perfusion on healthy volunteers without administration of contrast materials. A non-contrast 4D-ASL technique was developed using the time-spatial labeling inversion pulse (Time-SLIP) to obtain myocardium perfusion of eight volunteers at 1.5 T. The tagging slab was placed on the proximal ascending aorta to invert the blood magnetization and mid-ventricle 3D images at diastolic phase were acquired with multiple tagging delays. The time resolved 3D images with various inversion times (TI) were registered and segmented for the visualization of myocardial signal changes along the TI, and perfusion curves were generated to identify the perfusion peaks. Blood flow from basal to apical slices was observed in all volunteers. Peak flow at the mid-ventricle was observed 200-400 ms after the blood was tagged at the aortic root blood. After the perfusion peak, all signals returned to the base line. The 4D Time-SLIP technique permits non-contrast perfusion images with high temporal resolution, which may potentially differentiate normal from diseased myocardium.

Real-Time Optimal Synthetic Inversion Recovery Image Selection (RT-OSIRIS) for Deep Brain Stimulation Targeting.

Deep brain stimulation (DBS) is a method of electrical neuromodulation used to treat a variety of neuropsychiatric conditions including essential tremor, Parkinson's disease, epilepsy, and obsessive-compulsive disorder. The procedure requires precise placement of electrodes such that the electrical contacts lie within or in close proximity to specific target nuclei and tracts located deep within the brain. DBS electrode trajectory planning has become increasingly dependent on direct targeting with the need for precise visualization of targets. MRI is the primary tool for direct visualization, and this has led to the development of numerous sequences to aid in visualization of different targets. Synthetic inversion recovery images, specified by an inversion time parameter, can be generated from T1 relaxation maps, and this represents a promising method for modifying the contrast of deep brain structures to accentuate target areas using a single acquisition. However, there is currently no accessible method for dynamically adjusting the inversion time parameter and observing the effects in real-time in order to choose the optimal value. In this work, we examine three different approaches to implementing an application for real-time optimal synthetic inversion recovery image selection and evaluate them based on their ability to display continually-updated synthetic inversion recovery images as the user modifies the inversion time parameter. These methods include continuously computing the inversion recovery equation at each voxel in the image volume, limiting the computation only to the voxels of the orthogonal slices currently displayed on screen, or using a series of lookup tables with precomputed solutions to the inversion recovery equation. We find the latter implementation provides for the quickest display updates both when modifying the inversion time and when scrolling through the image. We introduce a publicly available cross-platform application built around this conclusion. We also briefly discuss other details of the implementations and considerations for extensions to other use cases.

Diagnostic utility of 7T neuromelanin imaging of the substantia nigra in Parkinson's disease.

Parkinson's disease (PD) is a prevalent neurodegenerative disorder that presents a diagnostic challenge due to symptom overlap with other disorders. Neuromelanin (NM) imaging is a promising biomarker for PD, but adoption has been limited, in part due to subpar performance at standard MRI field strengths. We aimed to evaluate the diagnostic utility of ultra-high field 7T NM-sensitive imaging in the diagnosis of PD versus controls and essential tremor (ET), as well as NM differences among PD subtypes. A retrospective case-control study was conducted including PD patients, ET patients, and controls. 7T NM-sensitive 3D-GRE was acquired, and substantia nigra pars compacta (SNpc) volumes, contrast ratios, and asymmetry indices were calculated. Statistical analyses, including general linear models and ROC curves, were employed. Twenty-one PD patients, 13 ET patients, and 18 controls were assessed. PD patients exhibited significantly lower SNpc volumes compared to non-PD subjects. SNpc total volume showed 100% sensitivity and 96.8% specificity (AUC = 0.998) for differentiating PD from non-PD and 100% sensitivity and 95.2% specificity (AUC = 0.996) in differentiating PD from ET. Contrast ratio was not significantly different between PD and non-PD groups (p = 0.07). There was also significantly higher asymmetry index in SNpc volume in PD compared to non-PD cohorts (p < 0.001). NM signal loss in PD predominantly involved the inferior, posterior, and lateral aspects of SNpc. Akinetic-rigid subtype showed more significant NM signal loss compared to tremor dominant subtype (p < 0.001). 7T NM imaging demonstrates potential as a diagnostic tool for PD, including potential distinction between subtypes, allowing improved understanding of disease progression and subtype-related characteristics.

7 T Lesion-Attenuated Magnetization-Prepared Gradient Echo Acquisition for Detection of Posterior Fossa Demyelinating Lesions in Multiple Sclerosis.

OBJECTIVES: Detection of infratentorial demyelinating lesions in multiple sclerosis (MS) presents a challenge in magnetic resonance imaging (MRI), a difficulty that is further heightened in 7 T MRI. This study aimed to assess the efficacy of a novel MRI approach, lesion-attenuated magnetization-prepared gradient echo acquisition (LAMA), for detecting demyelinating lesions within the posterior fossa and upper cervical spine on 7 T MRI and contrast its performance with conventional double-inversion recovery (DIR) and T2-weighted turbo spin echo sequences. MATERIALS AND METHODS: We conducted a retrospective cross-sectional study in 42 patients with a confirmed diagnosis of MS. All patients had 7 T MRI that incorporated LAMA, 3D DIR, and 2D T2-weighted turbo spin echo sequences. Three readers assessed lesion count in the brainstem, cerebellum, and upper cervical spinal cord using both DIR and T2-weighted images in one session. In a separate session, LAMA was analyzed alone. Contrast-to-noise ratio was also compared between LAMA and the conventional sequences. Lesion counts between methods were assessed using nonparametric Wilcoxon signed rank test. Interrater agreement in lesion detection was estimated by intraclass correlation coefficients. RESULTS: LAMA identified a significantly greater number of lesions than DIR + T2 (mean 6.4 vs 3.0; P < 0.001). LAMA also exhibited better interrater agreement (intraclass correlation coefficient [95% confidence interval], 0.75 [0.41-0.88] vs 0.61 [0.35-0.78]). The contrast-to-noise ratio for LAMA (3.7 ± 0.9) significantly exceeded that of DIR (1.94 ± 0.7) and T2 (1.2 ± 0.7) (all P 's < 0.001). In cases with no lesions detected using DIR + T2, at least 1 lesion was identified in 83.3% with LAMA. Across all analyzed brain regions, LAMA consistently detected more lesions than DIR + T2. CONCLUSIONS: LAMA significantly improves the detection of infratentorial demyelinating lesions in MS patients compared with traditional methods. Integrating LAMA with standard magnetization-prepared 2 rapid acquisition gradient echo acquisition provides a valuable tool for accurately characterizing the extent of MS disease.

Enhancing outcomes in deep brain stimulation: a comparative study of direct targeting using 7T versus 3T MRI.

OBJECTIVE: The aim of this study was to compare outcomes of direct targeting in deep brain stimulation (DBS) for essential tremor using 7T MRI versus 3T MRI. The authors hypothesized that 7T MRI direct targeting would be noninferior to 3T MRI in early tremor outcomes. METHODS: A retrospective study was conducted on patients undergoing unilateral thalamic DBS for essential tremor between 2021 and 2023. Two matched cohorts were assessed, one using 7T MRI and the other using 3T MRI for surgical planning. The primary endpoint was the percentage improvement in the Fahn-Tolosa-Marin Tremor Rating Scale (TRS) scores. Additionally, the authors assessed optimized programming settings and variance in electrode position on postoperative imaging. Demographic and clinical data were compared using the nonparametric Mann-Whitney U-test. The squared Euclidean distance of each contact from the group mean centroid was calculated and averaged across the entire cohort to provide the variance (i.e., the mean squared distance) of electrode contact position. RESULTS: A total of 34 patients were analyzed, with 17 in each cohort. There were no significant differences in demographic information or mean surgical dates between the groups. There were no differences in intraoperative target repositioning or adverse events. The 7T group had a significantly greater TRS improvement than the 3T group (64.9% ± 11.4% vs 50.9% ± 16.4%, p = 0.004). Patients in the 7T cohort also had a lower mean stimulation current compared with those in the 3T cohort (2.0 ± 0.8 mA vs 2.7 ± 0.9 mA, p = 0.01). Image evaluation revealed that although the mean electrode position was comparable between 7T and 3T, the 7T electrode positioning was more clustered, indicating a lower variance in the final electrode location. The mean Euclidean distance between the individual electrode tips and the group centroid was significantly less at 7T than at 3T (1.82 ± 0.68 mm vs 2.75 ± 0.81 mm, p = 0.001). CONCLUSIONS: Despite concerns for increased artifacts and distortions at 7T, the authors show that these effects can be mitigated with an appropriate workflow, leading to improved surgical outcomes with direct targeting using 7T MRI. Their results suggest similar accuracy but greater precision in targeting with 7T MRI compared with 3T MRI, resulting in lower stimulation currents and improved tremor reduction. Future studies are needed to assess outcomes related to 7T MRI in targeting other subcortical structures.

Optimization of MP2RAGE T1 mapping with radial view-ordering for deep brain stimulation targeting at 7 T MRI.

PURPOSE: Deep brain stimulation (DBS) is an effective treatment of various neurological disorders. Due to higher intrinsic signal, 7 T MRI can potentially improve delineation of DBS targets. However, the severe RF transmit field (B1+) inhomogeneity at 7 T can compromise the image contrast of traditional single-contrast sequences for DBS targeting, leading to sub-optimal target visualization. The Magnetization Prepared 2 Rapid Acquisition Gradient Echo (MP2RAGE)-based T1 mapping provides an alternative to the traditional single-contrast techniques by allowing retrospective synthesis of images at arbitrary inversion times to aid in visualization of various DBS targets. With this approach, optimization of sequence parameters to create T1 maps with low noise and low quantification bias is critical, as these characteristics directly affect the noise and uniformity of the synthetic images. In this work, we perform sequence optimization for MP2RAGE-based T1 mapping using a radial view-ordering technique to improve image quality, and demonstrate the clinical utility of T1 mapping approach for DBS targeting. METHODS: We first introduce a systematic sequence optimization framework for 7 T MP2RAGE T1 mapping by formulating it into a constrained, multi-dimensional optimization process considering the effect of B1+ inhomogeneity on image noise, T1 quantification bias, and image blurring. With this framework, we investigate the use of radial view-order approach for T1 mapping, in lieu of the conventional linear view-ordering. Bloch's equation-based simulations were performed to compare the T1 maps generated using different approaches. Images of healthy volunteer and patients were acquired on a clinical 7 T MRI scanner for validation and to demonstrate the utility of T1 mapping for DBS targeting. RESULTS: Numerical experiments demonstrated that the proposed framework allowed optimization of image SNR in T1 maps while controlling the quantification bias and image blurring, therefore facilitating the selection of optimal sequence parameters for visualizing DBS targets. The optimized sequence using radial view-ordering offered 40-60% noise reduction compared to the linear view-ordering. The improvement of SNR was confirmed in the in vivo examples. Clinical images showed that the synthetic images generated from the optimized T1 maps allowed clear visualization of DBS targets. CONCLUSION: We demonstrated the optimization of MP2RAGE T1 mapping with radial view-ordering technique for DBS targeting at 7 T and showed that the optimized sequence allows retrospective generation of synthetic inversion time images commonly utilized in DBS targeting, such as fast gray matter acquisition T1 inversion recovery (FGATIR) and edge-enhancing gradient echo (EDGE) sequences.

Clinical application of ultra-high resolution compressed sensing time-of-flight MR angiography at 7T to detect small vessel pathology.

3D time-of-flight (TOF) MR angiography (MRA) benefits from ultra-high-field MRI (≥7 T) due to improved contrast and increased signal-to-noise ratio. However, high-resolution TOF MRA at 7T usually requires longer acquisition times. In addition, relatively higher specific absorption rate (SAR) at 7T limits the choice of optimal pulse sequence parameters, especially if venous saturation is employed. Here, we illustrate the clinical application of ultra-high resolution cerebral 7T TOF MRA using compressed sensing in cases of artery of Percheron and lacunar infarcts, which showed superior resolution and exquisite details pertinent to the clinical diagnosis. The technical challenges associated with high-resolution 7T imaging were alleviated by optimization of sequence parameters and utilization of compressed sensing acceleration.

7T MRI in transient ischemic attacks: Have we only seen the tip of the iceberg?

Transient ischemic attack (TIA) has gained significant attention recently due to the increased incidence of subsequent stroke. However, there are many nonvascular clinical mimics of TIA, creating a need for improved biomarkers to identify a vascular origin. Following the recent approval of ultra-high field (UHF) 7T MRI in clinical practice, several clinical studies have highlighted its added utility in neuroimaging compared to lower-field 1.5T and 3T MRI, particularly in epilepsy and multiple sclerosis. Our case series of three patients with TIA illustrates that 7T MRI can depict small areas of intracortical microhemorrhages and microinfarctions, which could not be resolved with 3T or 1.5T MRI. There are currently no reports of intracortical localization of microhemorrhages in patients with TIA. This discovery may enhance our understanding and characterization of cerebrovascular abnormalities in TIAs. In addition, UHF imaging could potentially be utilized to distinguish transient neurological episodes secondary to cerebrovascular events from other differential considerations. Our cases highlight the underestimation of imaging abnormalities in cases of TIA and support the potential expanded application of clinical 7T to assess patients with TIA. Future studies are necessary at 7T redundant to determine the true incidence of such lesions in TIA and to examine the correlation between cortical microhemorrhages and subsequent ischemic stroke, hemorrhagic events, and neurocognitive impairment.

Central Vein Sign in Multiple Sclerosis: A Comparison Study of the Diagnostic Performance of 3T versus 7T MRI.

BACKGROUND AND PURPOSE: An early and accurate diagnosis of multiple sclerosis remains challenging in clinical neurology. Established diagnostic methods have less than desirable sensitivity and specificity. An accurate, noninvasive diagnostic test for MS could have a major impact on diagnostic criteria. We compared the frequency of detection of the central vein sign (CVS) in white matter lesions of MS and controls on 7T T2*-weighted and SWI to 3T SWI. Additionally, we assessed the diagnostic performance of 7T T2*, 7T SWI, and 3T SWI for MS. MATERIALS AND METHODS: A retrospective case-control study was performed of patients with MS having both 7T MRI and 3T MRI. A control group of patients without MS was selected. Diagnosis of MS was established by board-certified neurologists with fellowship training in autoimmune neurology in line with the 2017 McDonald criteria. Percentage of lesions with a CVS was blindly measured for each technique. Diagnostic performance was computed by sensitivity, specificity, and positive and negative likelihood ratios (LRs). RESULTS: Sixty-one patients with MS (903 lesions) and 39 controls (1088 lesions) were included. 7T T2* showed significantly more CVS (87%) than both 7T SWI (73%) and 3T SWI (31%) (all P < .001). CVS was identified in the control group in ≤6% of lesions on all sequences. Using a threshold of >40% of lesions with CVS on 7T T2* and >15% on 7T SWI, both sequences had an accuracy = 100%, sensitivity = 100%, specificity = 100%, infinite positive LR, and zero negative LR. Using an optimal threshold of >12%, 3T SWI had an accuracy = 96.0%, sensitivity = 93.4%, specificity = 100%, infinite positive LR, and negative LR = 0.066. CONCLUSIONS: 7T MRI had 100% sensitivity and specificity for the diagnosis of MS and is superior to 3T. Future revisions to MS diagnostic criteria may consider recommendations for 7T MRI and inclusion of CVS as a biomarker.

Ischemic extent as a biomarker for characterizing severity of coronary artery stenosis with blood oxygen-sensitive MRI.

PURPOSE: To investigate whether a statistical analysis of myocardial blood-oxygen-level-dependent (mBOLD) signal intensities can lead to the identification and quantification of the ischemic area supplied by the culprit artery. MATERIALS AND METHODS: Cardiac BOLD images were acquired in a canine model (n = 9) with controllable LCX stenosis at rest and during adenosine infusion on a 1.5T clinical scanner. Statistical distributions of myocardial pixel-intensities derived from BOLD images were used to compute an area metric (ischemic extent, IE). True myocardial perfusion was estimated from microsphere analysis. IE was compared against a standard metric (segment-intensity-response, SIR). Additional animals (n = 3) were used to investigate the feasibility of the approach for identifying ischemic territories due to LAD stenosis from mBOLD images. RESULTS: Regression analyses showed that IE and myocardial flow ratio between rest and adenosine infusion (MFR) were exponentially related (R(2) > 0.70, P < 0.001, for end-systole and end-diastole), while SIR and MFR were linearly related to end-systole (R(2) = 0.51, P < 0.04) and unrelated to end-diastole (R(2) ≈ 0, P = 0.91). Receiver-operating-characteristic analysis that IE was superior to SIR for detecting critical stenosis (MFR ≤ 2) in end-systole and end-diastole. Feasibility studies on LAD narrowing demonstrated that the proposed approach could also identify oxygenation changes in the LAD territories. CONCLUSION: The proposed evaluation of cardiac BOLD magnetic resonance imaging (MRI) offers marked improvement in sensitivity and specificity for detecting critical coronary stenosis at 1.5T compared to the mean segmental intensity approach. Patient studies are now warranted to determine its clinical utility.

Renal injury is a third hit promoting rapid development of adult polycystic kidney disease.

The 'two-hit' model is a widely accepted genetic mechanism for progressive cyst formation in autosomal dominant polycystic kidney disease. We have previously shown that adult inactivation of Pkd1 using the Mx1Cre(+) allele causes a late onset of focal cystic disease. An explanation for the delayed appearance of cysts is the requirement for an additional independent factor, or 'third hit'. Here we show that renal injury leads to massive cystic disease in the same mouse line. Cysts are labeled with a collecting duct/tubule marker, Lectin Dolichos biflorus Agglutinin, which correlates with the site of Cre-mediated recombination in the collecting system. 5-Bromo-2'-deoxyuridine labeling reveals that cyst-lining epithelial cells are comprised of regenerated cells in response to renal injury. These data demonstrate, for the first time, a role for polycystin-1 in kidney injury and repair and indicate that renal injury constitutes a 'third hit' resulting in rapid cyst formation in adulthood.

Determination of the optimal first-order gradient moment for flow-sensitive dephasing magnetization-prepared 3D noncontrast MR angiography.

Flow-sensitive dephasing (FSD) magnetization preparation has been developed for black-blood vessel wall MRI and noncontrast MR angiography. The first-order gradient moment, m(1) , is a measure of the flow-sensitization imparted by an FSD preparative module. Determination of the optimal m(1) for each individual is highly desirable for FSD-prepared MR angiography. This work developed a 2D m(1)-scouting method that evaluates a range of m(1) values for their effectiveness in blood signal suppression in a single scan. The feasibility of using the 2D method to predict blood signal suppression in 3D FSD-prepared imaging was validated on a flow phantom and the popliteal arteries of 5 healthy volunteers. Excellent correlation of the blood signal measurements between the 2D scouting and 3D FSD imaging was obtained. Therefore, the optimal m(1) determined from the 2D m(1)-scouting scan may be directly translated to 3D FSD-prepared imaging. In vivo studies of additional 10 healthy volunteers and 2 patients have demonstrated the proposed method can help significantly improve the signal performance of FSD MR angiography, indicating its potential to enhance diagnostic confidence. Further systematic studies in patients are warranted to evaluate its clinical value.

On the mechanisms enabling myocardial edema contrast in bSSFP-based imaging approaches.

The biophysical mechanisms influencing balanced steady-state free precession (bSSFP) based edema imaging in the setting of acute myocardial infarction are not well understood. To assess the various mechanisms that enable the detection of myocardial edema on bSSFP-based imaging approaches (cine bSSFP and T(2)-prepared bSSFP), experiments were conducted in canine models subjected to ischemia-reperfusion injury. Results showed that in addition to relaxation effects, the alteration in thermal equilibrium (M(0)) (including magnetization transfer) has a significant contribution to the image contrast between edematous and healthy myocardium. The relative signal-intensity ratios between edematous and healthy myocardium were: 1.51 ± 0.18 (cine bSSFP) and 1.58 ± 0.20 (T(2)-prepared bSSFP); the theoretically estimated relative relaxation and M(0) effects were: 1.17 ± 0.09 and 1.30 ± 0.19, respectively (cine bSSFP), and 1.49 ± 0.23 and 1.06 ± 0.07, respectively (T(2)-prepared bSSFP). There were no significant difference between cine bSSFP and T(2)-prep bSSFP relative signal-intensity ratios. However, the relative relaxation effect in cine bSSFP was significantly lower than in T(2)-prep bSSFP (P < 0.05), and the M(0) effect in cine bSSFP was significantly higher than in T(2)-prep bSSFP (P < 0.05). Hence the acquisition strategies that wish to maximize myocardial edema contrast in cine bSSFP imaging should take both relaxation and M(0) effects into account.

T(2) -weighted STIR imaging of myocardial edema associated with ischemia-reperfusion injury: the influence of proton density effect on image contrast.

PURPOSE: To investigate the contribution of proton density (PD) in T(2) -STIR based edema imaging in the setting of acute myocardial infarction (AMI). MATERIALS AND METHODS: Canines (n = 5), subjected to full occlusion of the left anterior descending artery for 3 hours, underwent serial magnetic resonance imaging (MRI) studies 2 hours postreperfusion (day 0) and on day 2. During each study, T(1) and T(2) maps, STIR (TE = 7.1 msec and 64 msec) and late gadolinium enhancement (LGE) images were acquired. Using T(1) and T(2) maps, relaxation and PD contributions to myocardial edema contrast (EC) in STIR images at both TEs were calculated. RESULTS: Edematous territories showed significant increase in PD (20.3 ± 14.3%, P < 0.05) relative to healthy territories. The contributions of T(1) changes and T(2) or PD changes toward EC were in opposite directions. One-tailed t-test confirmed that the mean T(2) and PD-based EC at both TEs were greater than zero. EC from STIR images at TE = 7.1 msec was dominated by PD than T(2) effects (94.3 ± 11.3% vs. 17.6 ± 2.5%, P < 0.05), while at TE = 64 msec, T(2) effects were significantly greater than PD effects (90.8 ± 20.3% vs. 12.5 ± 11.9%, P < 0.05). The contribution from PD in standard STIR acquisitions (TE = 64 msec) was significantly higher than 0 (P < 0.05). CONCLUSION: In addition to T(2) -weighting, edema detection in the setting of AMI with T(2) -weighted STIR imaging has a substantial contribution from PD changes, likely stemming from increased free-water content within the affected tissue. This suggests that imaging approaches that take advantage of both PD as well as T(2) effects may provide the optimal sensitivity for detecting myocardial edema.

Sirolimus combined with oseltamivir and corticosteroid treatment for a puerpera with severe pneumonia caused by 2009 pandemic H1N1: A case report.

Severe pneumonia in patients infected with the 2009 pandemic H1N1 (pH1N1) virus was partially attributed to excessive immune response. Anti-virus treatment for these patients was insufficient. Here we reported the therapy effect of sirolimus, an immunosuppressor, combined with oseltamivir and corticosteroid for a puerpera with severe pneumonia caused by pH1N1 virus. This patient has infected with the pH1N1 virus in late pregnancy, and antiviral therapy was not implemented timely. She developed severe pneumonia and ARDS rapidly and need receive a cesarean section on the 39th week after pregnancy. After giving birth to a healthy baby, she received a combination of oseltamivir, sirolimus and corticosteroid, and improved in the following days. Moreover, the cytokines in serum and viral loads in BALF decreased significantly. She recovered without infectious symptoms and was discharged. Sirolimus combined with oseltamivir and corticosteroid is likely responsible for lowering the viral loads, reducing the patient's cytokine level, and further improving her clinical outcomes. It provides evidence that adjuvant treatment was beneficial to patients with severe pneumonia induced by the pH1N1 virus.

Parametric dependence of myocardial blood oxygen level dependent, balanced steady-state free-precession imaging at 1.5 T: theory and experiments.

Myocardial blood oxygen level dependent, balanced steady-state free precession (bSSFP) imaging is a relatively new technique for evaluating myocardial oxygenation changes in the presence of coronary artery stenosis. However, the dependence of myocardial bSSFP blood oxygen level dependent signal on imaging parameters has not been well studied. In this work, modeling capillaries as cylinders that act as magnetic perturbers, the Monte Carlo method was used to simulate spin relaxation via diffusion in a field variation inside and outside blood vessels. bSSFP signal changes at various levels of capillary blood oxygen saturation, for a range of pulse repetition times, flip angle, capillary blood volume fraction, vessel wall permeability, water diffusion coefficient, vessel angle to static magnetic field, and the impact of bulk frequency shifts were studied. The theoretical dependence of bSSFP blood oxygen level dependent contrast on pulse repetition times and flip angle was confirmed by experiments in an animal model with controllable coronary stenosis. Results showed that, with the standard bSSFP acquisition, optimum bSSFP blood oxygen level dependent contrast could be obtained at pulse repetition times = 6.0 ms and flip angle = 70 degrees . Additional technical improvements that preserve the image quality may be necessary to further increase the myocardial bSSFP blood oxygen level dependent sensitivity at 1.5 T through even longer pulse repetition times.

Artifact-reduced two-dimensional cine steady state free precession for myocardial blood- oxygen-level-dependent imaging.

PURPOSE: To minimize image artifacts in long TR cardiac phase-resolved steady state free precession (SSFP) based blood-oxygen-level-dependent (BOLD) imaging. MATERIALS AND METHODS: Nine healthy dogs (four male, five female, 20-25 kg) were studied in a clinical 1.5 Tesla MRI scanner to investigate the effect of temporal resolution, readout bandwidth, and motion compensation on long repetition time (TR) SSFP images. Breath-held 2D SSFP cine sequences with various temporal resolutions (10-204 ms), bandwidths (239-930 Hz/pixel), with and without first-order motion compensation were prescribed in the basal, mid-ventricular, and apical along the short axis. Preliminary myocardial BOLD studies in dogs with controllable coronary stenosis were performed to assess the benefits of artifact-reduction strategies. RESULTS: Shortening the readout time by means of increasing readout bandwidth had no observable reduction in image artifacts. However, increasing the temporal resolution in the presence of first-order motion compensation led to significant reduction in image artifacts. Preliminary studies demonstrated that BOLD signal changes can be reliably detected throughout the cardiac cycle. CONCLUSION: Artifact-reduction methods used in this study provide significant improvement in image quality compared with conventional long TR SSFP BOLD MRI. It is envisioned that the methods proposed here may enable reliable detection of myocardial oxygenation changes throughout the cardiac cycle with long TR SSFP-based myocardial BOLD MRI.