Search

Background A previous study demonstrated the feasibility of using 3D radial ultrashort echo time (UTE) oxygen-enhanced MRI (UTE OE-MRI) for functional imaging of healthy human lungs. The repeatability of quantitative measures from UTE OE-MRI needs to be established prior to its application in clinical research. Purpose To evaluate repeatability of obstructive patterns in asthma and cystic fibrosis (CF) with UTE OE-MRI with isotropic spatial resolution and full chest coverage. Study Type Volunteer and patient repeatability. Population Eighteen human subjects (five asthma, six CF, and seven normal subjects). Field Strength/Sequence Respiratory-gated free-breathing 3D radial UTE (80 μs) sequence at 1.5T. Assessment Two 3D radial UTE volumes were acquired sequentially under normoxic and hyperoxic conditions. A subset of subjects underwent repeat acquisitions on either the same day or ≤15 days apart. Asthma and CF subjects also underwent spirometry. A workflow including deformable registration and retrospective lung density correction was used to compute 3D isotropic percent signal enhancement (PSE) maps. Median PSE (MPSE) and ventilation defect percent (VDP) of the lung were measured from the PSE map. Statistical Tests The relations between MPSE, VDP, and spirometric measures were assessed using Spearman correlations. The test–retest repeatability was evaluated using Bland–Altman analysis and intraclass correlation coefficients (ICC). Results Ventilation measures in normal subjects (MPSE = 8.0%, VDP = 3.3%) were significantly different from those in asthma (MPSE = 6.0%, P = 0.042; VDP = 21.7%, P = 0.018) and CF group (MPSE = 4.5%, P = 0.0006; VDP = 27.2%, P = 0.002). MPSE correlated significantly with forced expiratory lung volume in 1 second percent predicted (ρ = 0.72, P = 0.017). The ICC of the test–retest VDP and MPSE were both ≥0.90. In all subject groups, an anterior/posterior gradient was observed with higher MPSE and lower VDP in the posterior compared to anterior regions (P ≤ 0.0021 for all comparisons). Data Conclusion 3D radial UTE OE-MRI supports quantitative differentiation of diseased vs. healthy lungs using either whole lung VDP or MPSE with excellent test–retest repeatability. Level of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2017.

Purpose To achieve motion robust high resolution 3D free-breathing pulmonary MRI utilizing a novel dynamic 3D image navigator derived directly from imaging data. Methods Five-minute free-breathing scans were acquired with a 3D ultrashort echo time (UTE) sequence with 1.25 mm isotropic resolution. From this data, dynamic 3D self-navigating images were reconstructed under locally low rank (LLR) constraints and used for motion compensation with one of two methods: a soft-gating technique to penalize the respiratory motion induced data inconsistency, and a respiratory motion-resolved technique to provide images of all respiratory motion states. Results Respiratory motion estimation derived from the proposed dynamic 3D self-navigator of 7.5 mm isotropic reconstruction resolution and a temporal resolution of 300 ms was successful for estimating complex respiratory motion patterns. This estimation improved image quality compared to respiratory belt and DC-based navigators. Respiratory motion compensation with soft-gating and respiratory motion-resolved techniques provided good image quality from highly undersampled data in volunteers and clinical patients. Conclusion An optimized 3D UTE sequence combined with the proposed reconstruction methods can provide high-resolution motion robust pulmonary MRI. Feasibility was shown in patients who had irregular breathing patterns in which our approach could depict clinically relevant pulmonary pathologies. Magn Reson Med 79:2954-2967, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

This review focuses on the state-of-the-art of the three major classes of gas contrast agents used in magnetic resonance imaging (MRI)—hyperpolarized (HP) gas, molecular oxygen, and fluorinated gas—and their application to clinical pulmonary research. During the past several years there has been accelerated development of pulmonary MRI. This has been driven in part by concerns regarding ionizing radiation using multidetector computed tomography (CT). However, MRI also offers capabilities for fast multispectral and functional imaging using gas agents that are not technically feasible with CT. Recent improvements in gradient performance and radial acquisition methods using ultrashort echo time (UTE) have contributed to advances in these functional pulmonary MRI techniques. The relative strengths and weaknesses of the main functional imaging methods and gas agents are compared and applications to measures of ventilation, diffusion, and gas exchange are presented. Functional lung MRI methods using these gas agents are improving our understanding of a wide range of chronic lung diseases, including chronic obstructive pulmonary disease, asthma, and cystic fibrosis in both adults and children. J. Magn. Reson. Imaging 2015.

Purpose To assess the feasibility of spatial–temporal constrained reconstruction for accelerated regional lung perfusion using highly undersampled dynamic contrast-enhanced (DCE) three-dimensional (3D) radial MRI with ultrashort echo time (UTE). Methods A combined strategy was used to accelerate DCE MRI for 3D pulmonary perfusion with whole lung coverage. A highly undersampled 3D radial UTE MRI acquisition was combined with an iterative constrained reconstruction exploiting principal component analysis and wavelet soft-thresholding for dimensionality reduction in space and time. The performance of the method was evaluated using a 3D fractal-based DCE digital lung phantom. Simulated perfusion maps and contrast enhancement curves were compared with ground truth using the structural similarity index (SSIM) to determine robust threshold and regularization levels. Feasibility studies were then performed in a canine and a human subject with 3D radial UTE (TE = 0.08 ms) acquisition to assess feasibility of mapping regional 3D perfusion. Results The method was able to accurately recover perfusion maps in the phantom with a nominal isotropic spatial resolution of 1.5 mm (SSIM of 0.949). The canine and human subject studies demonstrated feasibility for providing artifact-free perfusion maps in a simple 3D breath-held acquisition. Conclusion The proposed method is promising for fast and flexible 3D pulmonary perfusion imaging. Magn Reson Med 73:555–564, 2015. © 2014 Wiley Periodicals, Inc.

Purpose To develop and demonstrate a breathheld 3D radial ultrashort echo time (UTE) acquisition to visualize co-registered lung perfusion and vascular structure. Materials and Methods Nine healthy dogs were scanned twice at 3 Tesla (T). Contrast-enhanced pulmonary perfusion scans were acquired with a temporally interleaved three-dimensional (3D) radial UTE (TE = 0.08 ms) sequence in a breathhold (1 s time frames over a 33 s breathhold). The 3D breathheld volume was reconstructed into time-resolved perfusion datasets, and a composite vascular structure dataset. For structural comparison, a 5 min respiratory-gated 3D radial UTE scan was acquired. Data were analyzed by quantitative metrics and radiologist scoring. Results Appropriate time-course of contrast was seen in all subjects. Right ventricle to aorta transit times were 7.4 ± 2.0 s. Relative lung enhancement was a factor of 8.4 ± 1.5. Radiologist scoring showed similarly excellent visualization of the pulmonary arteries to the subsegmental level in breathheld (94% of cases) and respiratory-gated (100% of cases) acquisitions (P = 0.33) despite the aggressive under sampling in the breathheld scan. Similarly, differentiation of lung tissue and airways was achieved by both acquisition methods. Conclusion A time-resolved 3D radial UTE sequence for simultaneous imaging of pulmonary perfusion and co-registered vascular structure is feasible. J. Magn. Reson. Imaging 2015;41:52–59. © 2013 Wiley Periodicals, Inc.

Purpose To develop and evaluate a free-breathing chemical-shift-encoded (CSE) spoiled gradient-recalled echo (SPGR) technique for whole-heart water–fat imaging at 3 Tesla (T). Methods We developed a three-dimensional (3D) multi-echo SPGR pulse sequence with electrocardiographic gating and navigator echoes and evaluated its performance at 3T in healthy volunteers (N = 6) and patients (N = 20). CSE-SPGR, 3D SPGR, and 3D balanced-SSFP with chemical fat saturation were compared in six healthy subjects with images evaluated for overall image quality, level of residual artifacts, and quality of fat suppression. A similar scoring system was used for the patient datasets. Results Images of diagnostic quality were acquired in all but one subject. CSE-SPGR performed similarly to SPGR with fat saturation, although it provided a more uniform fat suppression over the whole field of view. Balanced-SSFP performed worse than SPGR-based methods. In patients, CSE-SPGR produced excellent fat suppression near metal. Overall image quality was either good (7/20) or excellent (12/20) in all but one patient. There were significant artifacts in 5/20 clinical cases. Conclusion CSE-SPGR is a promising technique for whole-heart water–fat imaging during free-breathing. The robust fat suppression in the water-only image could improve assessment of complex morphology at 3T and in the presence of off-resonance, with additional information contained in the fat-only image. Magn Reson Med 72:718–725, 2014. © 2013 Wiley Periodicals, Inc.

Purpose To investigate the utility of hyperpolarized He-3 MRI for detecting regional lung ventilated volume (VV) changes in response to exercise challenge and leukotriene inhibitor montelukast, human subjects were recruited with Exercise Induced Bronchoconstriction (EIB), a condition described by airway constriction following exercise leading to reduced Forced Expiratory Volume in 1 second (FEV1) coinciding with ventilation defects on hyperpolarized He-3 MRI.

Pulmonary Embolism (PE) is an important cause of death in the industrialized world (1,2). Ionizing radiation administered for medical imaging is of increasing clinical concern, particularly for younger patients and female patients (3,4). In a recent epidemiological study, medical radiation at the 50 mSv level was shown to have increased incidence of brain malignancy and leukemia above what could be expected in an unexposed population (5). Chest radiation for younger women is potentially problematic due to its cumulative effects and the radiation sensitivity of breast tissue (3,6). In symptomatic patients with a clinical suspicion for pulmonary embolus, the currently accepted reference standard is computed tomographic angiography (CTA-PE) (7–12). An alternative test that requires no ionizing radiation for the detection of pulmonary embolism would be highly beneficial, so long as it has sufficient effectiveness (4–12). There is recent evidence showing that the number of pulmonary embolism (PE) diagnoses has significantly increased in the United States without a corresponding significant drop in death rate (13–15). CTA-PE is a frequently ordered test that maybe over-used (16). This high degree of usage by clinicians likely reflects the excellent performance (efficacy) of CTA-PE and its ability to diagnose even tiny, subsegmental pulmonary emboli. Recently, some authors have challenged the necessity to treat all sub-segmental PE with anti-coagulation (13,14,17), noting the 4–8% incidence of serious bleeding complications from treatment of PE (1,14,18,19). For this reason, alternative exams such as pulmonary MR angiography (MRA-PE), which have a lower accuracy (efficacy) than CTA-PE for diagnosis of subsegmental PE, may be more than adequate for detection of clinically significant emboli that require anticoagulation. (17,20–24). Use of patient outcomes for the determination of test effectiveness is often employed when there is no available reference standard to determine the efficacy of a test. Recently, Douglas and colleagues have suggested that the determination of test effectiveness, as established by patient outcomes, is actually much more important for the evaluation of clinical utility than test efficacy (29). Lack of a measurable adverse clinical event over the follow-up period is a useful surrogate for utility of a test in this situation. In the clinical evaluation of heart disease, the patient outcome surrogate is a Major Adverse Cardiac Event (MACE) during the chosen follow-up interval (29). In the nuclear medicine literature, outcomes analysis have be used for many years in the determination of test negativity in the workup of suspected PE (30). Use of 1-year outcomes for the determination of CTA-PE effectiveness has been reported by the highly respected cardio-pulmonary radiology group in Lille, France (31). They studied 185 patients and found that CTA-PE had a negative predictive value of 98%, with three episodes of fatal PE (31). Early work on the efficacy of MRA-PE was published in 1999 by Gupta and colleagues has now been shown to be on target with current results (25). They found that larger PEs (lobar and segmental) are well seen with contrast enhanced MRA-PE, but that the sub-segmental PEs were frequently missed (25). There are many studies showing that MRA-PE is a test of lower efficacy than CTA-PE for the diagnosis of subsegmental pulmonary embolism (20,21,28,32–34). However, a conclusion from the PIOPED III study was that if the MRA-PE could be performed in a technically adequate manner, that MRA-PE is highly diagnostic for this condition (20). The purpose of our retrospective study was to determine the effectiveness of MRA-PE in symptomatic patients, using the clinical outcome measure of Venous ThromboEmbolism (VTE, deep venous thrombosis and/or PE) or death from PE as determined by review of the electronic medical record (EMR) for 3 months following the MRA-PE and a second review at 1 year.

Purpose To demonstrate the feasibility of direct virtual coil (DVC) in the setting of 4D dynamic imaging used in multiple clinical applications. Theory and Methods Three dynamic imaging applications were chosen: pulmonary perfusion, liver perfusion, and peripheral MR angiography (MRA), with 18, 11, and 10 subjects, respectively. After view-sharing, the k-space data were reconstructed twice: once with channel-by-channel (CBC) followed by sum-of-squares coil combination and once with DVC. Images reconstructed using CBC and DVC were compared and scored based on overall image quality by two experienced radiologists using a five-point scale. Results The CBC and DVC showed similar image quality in image domain. Time course measurements also showed good agreement in the temporal domain. CBC and DVC images were scored as equivalent for all pulmonary perfusion cases, all liver perfusion cases, and four of the 10 peripheral MRA cases. For the remaining six peripheral MRA cases, DVC were scored as slightly better (not clinically significant) than the CBC images by Radiologist A and as equivalent by Radiologist B. Conclusion For dynamic contrast-enhanced MR applications, it is clinically feasible to reduce image reconstruction time while maintaining image quality and time course measurement using the DVC technique. Magn Reson Med 71:783–789, 2014. © 2013 Wiley Periodicals, Inc.

Purpose: To demonstrate the feasibility of performing single breathhold, noncardiac gated, ultrafast, high spatial-temporal resolution whole chest MR pulmonary perfusion imaging in humans. Materials and Methods: Eight subjects (five male, three female) were scanned with the proposed method on a 3 Tesla clinical scanner using a 32-channel phased-array coil. Seven (88%) were healthy volunteers, and one was a patient volunteer with sarcoidosis. The peak lung enhancement phase for each subject was scored for gravitational effect, peak parenchymal enhancement and severity of artifacts by three cardiothoracic radiologists independently. Results: All studies were successfully performed by MR technologists without any additional training. Mean parenchymal signal was very good, measuring 0.78 ± 0.13 (continuous scale, 0 = “none” 1 = “excellent”). Mean level of motion artifacts was low, measuring 0.13 ± 0.08 (continuous scale, 0 = “none” 1 = “severe”). Conclusion: It is feasible to perform single breathhold, noncardiac gated, ultrafast, high spatial-temporal resolution whole chest MR pulmonary perfusion imaging in humans. J. Magn. Reson. Imaging 2013;38:751–756. © 2013 Wiley Periodicals, Inc.

Purpose To optimize 3D radial ultrashort echo time MRI for high resolution whole-lung imaging. Methods 3D radial ultrashort echo time was implemented on a 3T scanner to investigate the effects of: (1) limited field-of-view excitation, (2) variable density readouts, and (3) radial oversampling. Improvements in noise performance and spatial resolution were assessed through simulation and phantom studies. Their effects on lung and airway visualization in five healthy male human subjects (mean age 32 years) were compared qualitatively through blinded ordinal scoring by two cardiothoracic radiologists using a nonparametric Friedman test (P < 0.05). Relative signal difference between endobronchial air and adjacent lung tissue, normalized to nearby vessel, was used as a surrogate for lung tissue signal. Quantitative measures were compared using the paired Student's t-test (P < 0.05). Finally, clinical feasibility was investigated in a patient with interstitial fibrosis. Results Simulation and phantom studies showed up to 67% improvement in SNR and reduced blurring for short T2* species using all three optimizations. In vivo images showed decreased artifacts and improved lung tissue and airway visualization both qualitatively and quantitatively. Conclusion The use of limited field-of-view excitation, variable readout gradients, and radial oversampling significantly improve the technical quality of 3D radial ultrashort echo time lung images. Magn Reson Med 70:1241–1250, 2013. © 2012 Wiley Periodicals, Inc.

Purpose: To determine optimal delay times and flip angles for T1-weighted hepatobiliary imaging at 1.5 Tesla (T) with gadoxetic acid and to demonstrate the feasibility of using a high-resolution navigated optimized T1-weighted pulse sequence to evaluate biliary disease. Materials and Methods: Eight healthy volunteers were scanned at 1.5T using a T1-weighted three-dimensional (3D)-SPGR pulse sequence following the administration of 0.05 mmol/kg of gadoxetic acid. Navigator-gating enabled acquisition of high spatial resolution (1.2 × 1.4 × 1.8 mm3, interpolated to 0.7 × 0.7 × 0.9 mm3) images in approximately 5 min of free-breathing. Multiple breath-held acquisitions were performed at flip angles between 15° and 45° to optimize T1 weighting. To evaluate the performance of this optimized sequence in the setting of biliary disease, the image quality and biliary excretion of 51 consecutive clinical scans performed to assess primary sclerosing cholangitis (PSC) were evaluated. Results: Optimal hepatobiliary imaging occurs at 15–25 min, using a 40° flip angle. The image quality and visualization of biliary excretion in the PSC scans were excellent, despite the decreased liver function in some patients. Visualization of reduced excretion often provided diagnostic information that was unavailable by conventional magnetic resonance cholangiopancreatography (MRCP). Conclusion: High-resolution navigated 3D-SPGR hepatobiliary imaging using gadoxetic acid and optimized scan parameters is technically feasible and can be clinically useful, even in patients with decreased hepatobiliary function. J. Magn. Reson. Imaging 2012;36:890–899. © 2012 Wiley Periodicals, Inc.

Purpose: To investigate the value of gadoxetic acid-enhanced three-dimensional T1-weighted MR cholangiography (T1w-MRC) in comparison to three-dimensional T2-weighted MR cholangiopancreaticography (T2w-MRCP) in patients with primary sclerosing cholangitis (PSC). Materials and Methods: Thirty-four MR exams in 29 patients (46.0 ± 16.1 years; 19 men, 10 women) scanned within a 14-month period were retrospectively included. Two abdominal radiologists independently evaluated image quality regarding image contrast, image quality degradation due to artifacts, and visualization quality of ducts. The order of biliary tree branches that were visualized and reader preference toward each method were recorded. Helpfulness of T1w-MRC was scored in consensus. Confirmatory endoscopic retrograde cholangiopancreaticography (ERCP) performed within 3 months of the MR examination was available in 8 patients. Results: Image quality of T1w-MRC and T2w-MRCP was graded good to excellent in all cases. There were advantages for both T1w-MRC (functional information, less degradation due to artifacts) and T2w-MRCP (higher order of visualized branches, better branch depiction). Both readers showed preference for T2w-MRCP; however, both readers found gadoxetic acid–enhanced T1w-MRC helpful in the majority of cases. Conclusion: Gadoxetic acid-enhanced T1w-MRC is complementary to, but should not replace, T2w-MRCP. T1w-MRC is a useful adjunct to T2w-MRCP for morphologic evaluation and provides additional diagnostic information. J. Magn. Reson. Imaging 2012;36:632–640. © 2012 Wiley Periodicals, Inc.

Purpose: To evaluate the signal to noise ratio (SNR) and contrast to noise ratio (CNR) performance of 0.05 mmol/kg gadoxetic acid and 0.1 mmol/kg gadobenate dimeglumine for dynamic and hepatobiliary phase imaging. In addition, flip angles (FA) that maximize relative contrast-to-noise performance for hepatobiliary phase imaging were determined. Materials and Methods: A cross-over study in 10 volunteers was performed using each agent. Imaging was performed at 3 Tesla (T) with a 32-channel phased-array coil using breathheld 3D spoiled gradient echo sequences for SNR and CNR analysis, and for FA optimization of hepatobiliary phase imaging. Results: Gadobenate dimeglumine (0.1 mmol/kg) had superior SNR performance during the dynamic phase, statistically significant for portal vein and hepatic vein in the portal venous and venous phase (for all, P < 0.05) despite twice the approved dose of gadoxetic acid (0.05 mmol/kg), while gadoxetic acid had superior SNR performance during the hepatobiliary phase. Optimal FAs for hepatobiliary phase imaging using gadoxetic acid and gadobenate dimeglumine were 25–30° and 20–30° for relative contrast liver versus muscle (surrogate for nonhepatocellular tissues), and 45° and 20° (relative contrast liver versus biliary structures), respectively. Conclusion: Gadobenate dimeglumine may be preferable for applications that require dynamic phase imaging only, while gadoxetic acid may be preferable when the hepatobiliary phase is clinically important. Hepatobiliary phase imaging with both agents benefits from flip angle optimization. J. Magn. Reson. Imaging 2011;. © 2011 Wiley-Liss, Inc.

Geometric distortions and poor image resolution are well known shortcomings of single-shot echo-planar imaging (ss-EPI). Yet, due to the motion immunity of ss-EPI, it remains the most common sequence for diffusion-weighted imaging (DWI). Moreover, both navigated DW interleaved EPI (iEPI) and parallel imaging (PI) methods, such as sensitivity encoding (SENSE) and generalized autocalibrating parallel acquisitions (GRAPPA), can improve the image quality in EPI. In this work, DW-EPI accelerated by PI is proposed as a self-calibrated and unnavigated form of interleaved acquisition. The PI calibration is performed on the b = 0 s/mm2 data and applied to each shot in the rest of the DW data set, followed by magnitude averaging. Central in this study is the comparison of GRAPPA and SENSE in the presence of off-resonances and motion. The results show that GRAPPA is more robust than SENSE against both off-resonance and motion-related artifacts. The SNR efficiency was also investigated, and it is shown that the SNR/scan time ratio is equally high for one- to three-shot high-resolution diffusion scans due to the shortened EPI readout train length. The image quality improvements without SNR efficiency loss, together with motion tolerance, make the GRAPPA-driven DW-EPI sequence clinically attractive.

Multiple-region MRI (mrMRI) represents a generalization of the Shannon sampling theorem to permit sparse k-space sampling whenever the scanned object or its high-contrast edges are confined to multiple known regions. Use of an optimal mrMRI sampling pattern produces an image with root-mean-squared (RMS) noise over the supporting regions equal to the RMS noise in a conventional Fourier image with the same total area of support. Analytical solutions for such sampling patterns have been described previously for all arrangements of two or three (noncollinear) supporting regions. This work describes a robust numerical method for creating a library of optimal and near-optimal mrMRI sampling patterns for more complicated geometries. The average noise amplification over all sampling patterns in the demonstration library was only 4%, with 30% of the sampling patterns resulting in no noise amplification whatsoever.

With conventional Fourier transform (FT) magnetic resonance imaging (MRI), it is difficult to perform contrast-enhanced three-dimensional (3D) MR angiography (MRA) with the temporal and spatial resolution necessary to depict the carotid arteries. However, locally focused (LF) MRI is a more efficient method that utilizes prior knowledge of the image content to reconstruct images from sparse k-space samples. In this paper, we show how LF MRI can be used to perform high-resolution gadolinium (Gd)-enhanced 3D carotid MRA in less than 10 seconds. First, the accuracy of the technique was demonstrated by comparing LF and conventional (FT) images of a vascular phantom. Then the method was used to perform Gd-enhanced 3D MRA of a patient's carotid arteries. Instead of using bolus timing, the arterial phase was retrospectively identified in a consecutive series of images, just as in X-ray angiography. J. Magn. Reson. Imaging 1999;9:663–669. © 1999 Wiley-Liss, Inc.

Traditional Fourier MR imaging (FT MRI) utilizes the Whittaker-Kotel'nikov-Shannon (WKS) sampling theorem. This theorem specifies the spatial frequency components which need to be measured to reconstruct an image with a known field of view (FOV). In this paper, we generalize this result in order to find the optimal k-space sampling for images that vanish except in multiple, possibly non-adjacent regions within the FOV. This provides the basis for "multiple region MRI" (mrMRI), a method of producing such images from a traction of the k-space samples required by the WKS theorem. Image reconstruction does not suffer from noise amplification and can be performed rapidly with fast Fourier transforms, just as in conventional FT MRI. The mrMRI method can also be used to reconstruct images that have low spatial-frequency components throughout the entire FOV and high spatial frequencies (i.e. edges) confined to multiple small regions. The greater efficiency of mrMRI sampling can be parlayed into increased temporal or spatial resolution whenever the imaged objects have signal or "edge" intensity confined to multiple small portions of the FOV. Possible areas of application include MR angiography (MRA), interventional MRI, functional MRI, and spectroscopic MRI. The technique is demonstrated by using it to acquire Gd-enhanced first-pass 3D MRA images of the carotid arteries without the use of bolus-timing techniques.

Certain interventional MR procedures would benefit from T2-weighted imaging because of the sensitivity of T2-weighted images to tissue damage and target lesion contrast. To acquire such images with reasonable temporal resolution, a single-shot acquisition should be used because of the inherently long TR needed for T2 weighting. Unfortunately, most scanners require long readout times (eg, greater than 150 msec) and high bandwidths (eg, greater than 120 kHz) to perform conventional single-shot imaging with high spatial resolution. The resulting images are thus degraded by unacceptable artifacts and noise levels. This study illustrates how to create locally focused MR images that have high spatial resolution in a region of interest and lower spatial resolution elsewhere in the image. Because these images can be created from sparse k-space data, a scanner with modest gradients (eg, 10 mT/m maximal amplitude, 500 microsec minimal rise time) can acquire them after a single excitation with relatively short readout time and low bandwidth. This technique may make it practical to monitor interventions with T2-weighted imaging. The method was illustrated by reconstructing dynamic changes, which were simulated experimentally by moving objects in the vicinity of a normal human head.