3D Fast Low-angle Shot Sequence Research Articles

Voxel-Based Morphometry of Progressive Supranuclear Palsy Using a 3D Fast Low-angle Shot Localizer Image: A Comparison with Magnetization-Prepared Rapid Gradient Echo.

Voxel-based morphometry (VBM) is widely used to investigate white matter (WM) atrophy in patients with progressive supranuclear palsy (PSP). In contrast to high-resolution 3D T1-weighted imaging such as magnetization-prepared rapid acquisition with gradient echo (MPRAGE) sequences, the utility of other 3D sequences has not been sufficiently evaluated. This study aimed to assess the feasibility of using a 3D fast low-angle shot sequence captured as a localizer image (L3DFLASH) for VBM analysis of WM atrophy patterns in patients with PSP. This retrospective study included 12 patients with pathologically or clinically confirmed PSP, and 18 age- and sex-matched healthy controls scanned with both L3DFLASH and MPRAGE sequences. Image processing was conducted with the Computational Anatomy Toolbox 12 in statistical parametric mapping 12. In addition to the atrophic WM pattern of PSP on VBM, we assessed the WM volume agreement between the two sequences using simple linear regression and Bland-Altman plots. Despite the slightly larger clusters on MPRAGE, VBM using both sequences showed similar characteristics of PSP-related WM atrophy, including in the midbrain, pons, thalamus, and precentral gyrus. In contrast, VBM showed gray matter (GM) atrophy of the precuneus and right superior parietal lobule exclusively on L3DFLASH. Unlike the measured values of total intracranial volume, GM, and cerebrospinal fluid on MPRAGE, the value of WM was larger on L3DFLASH. In contrast to the total intracranial volume, brainstem, and frontal and occipital lobes, the correlation with WM volume in other regions was relatively low. However, the Bland-Altman plots demonstrated strong agreement, with over 90% of the values falling within the agreement limits. Both MPRAGE and L3DFLASH are useful for detecting PSP-related WM atrophy using VBM.

Diagnostic Performance and Safety of a Novel Ferumoxytol-Enhanced Coronary Magnetic Resonance Angiography.

Currently, noninvasive arteriography for the diagnosis of coronary artery disease is clinically limited to the computed tomography scanning, where patients have to be exposed to the radiation and risks associated with iodinated contrast. We aimed to investigate the diagnostic performance and safety of a novel ferumoxytol-enhanced coronary magnetic resonance angiography (CMRA) in patients with suspected coronary artery disease. Thirty patients, 19 males, with a median age of 63 years old, and 17 with renal insufficiency, who were scheduled for invasive coronary angiography, were enrolled. Ferumoxytol was administered intravenously with a dose of 3 mg/kg during CMRA. Images were acquired with an ECG-triggered, navigator-gated, inversion recovery-prepared 3D fast low-angle shot sequence, and the image quality was assessed by a 4-point scale. Eighteen-segment coronary artery model was adopted to evaluate the visibility of the coronary arteries, and the image quality and stenosis were evaluated in nine segments. The diagnostic performance of CMRA is described as sensitivity, specificity, positive and negative predictive values, and accuracy with the invasive coronary angiography results as reference. The patients' vital signs were monitored during CMRA, and their hepatic and renal functions were followed up for 3 months to evaluate the safety of ferumoxytol. Two hundred fifty-two of the 270 study segments were identified by CMRA, and their quality score reached 3.6±0.7. Referring to the invasive coronary angiography results, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of ferumoxytol-enhanced CMRA reached 100.0%, 66.7%, 92.3%, 100.0%, and 93.3% respectively in patient-based analysis; 91.4%, 90.9%, 86.5%, 94.3%, and 91.1%, respectively in vessel-based analysis; and 92.3%, 96.7%, 83.7%, 98.6%, and 96.0%, respectively in segment-based analysis. No ferumoxytol-related adverse event was observed during the 3-month follow-up. Ferumoxytol-enhanced CMRA demonstrated good diagnostic performance and excellent safety in the diagnosis of significant coronary stenosis, providing an alternative to coronary computed tomography angiography for the diagnosis of coronary artery disease. URL: https://www. gov; Unique identifier: NCT05032937.

7T MRI of distal radius trabecular bone microarchitecture: How trabecular bone quality varies depending on distance from end-of-bone.

To use 7T magnetic resonance imaging (MRI) to determine how trabecular bone microarchitecture varies at the epiphysis, metaphysis, and diaphysis of the distal radius. The distal radius of 24 females (mean age = 56 years, range = 24-78 years) was scanned on a 7T MRI using a 3D fast low-angle shot sequence (0.169 × 0.169 × 1 mm). Digital topological analysis was applied at the epiphysis, metaphysis, and diaphysis to compute: total trabecular bone volume; trabecular thickness, number, connectivity, and erosion index (a measure of network resorption). Differences and correlations were assessed using standard statistical methods. The metaphysis and epiphysis had 83-123% greater total bone volume and 14-16% greater trabecular number than the diaphysis (both P < 0.0001). The erosion index was significantly higher at the diaphysis than the metaphysis and epiphysis (both P < 0.01). The most elderly volunteers had lower trabecular number (<66 years mean 0.29 ± 0.01; ≥66 years, 0.27 ± 0.02, P < 0.05) and higher erosion index (<66 years mean 1.18 ± 0.17; age ≥66 years, mean 1.42 ± 0.46, P < 0.05) at the epiphysis; differences not detected by total trabecular bone volume. 7T MRI reveals trabecular bone microarchitecture varies depending on scan location at the end-of-bone, being of overall higher quality distally (epiphysis) than proximally (diaphysis). Age-related differences in trabecular microarchitecture can be detected by 7T MRI. The results highlight the potential sensitivity of 7T MRI to microarchitectural differences and the potential importance of standardizing scan location for future clinical studies of fracture risk or treatment response. 3 J. Magn. Reson. Imaging 2017;45:872-878.

Three-dimensional contrast-enhanced magnetic resonance angiography for anterolateral thigh flap outlining: A retrospective case series of 68 patients.

Flap transfer is increasingly used for repairing limb defects secondary to trauma or tumor, and appropriate preoperative planning plays a critical role. The present study aimed to examine the use of three-dimensional (3D) contrast-enhanced magnetic resonance angiography (CE-MRA) in evaluating the blood supply distribution and perforating branch pattern of anterolateral thigh (ALT) flaps. Bilateral donor lower limbs were scanned in 68 patients (136 limbs) using a Siemens Avanto 1.5 T magnetic resonance imaging scanner with a 3D fast low-angle shot sequence, following the thin-slab maximum intensity projection (TS-MIP) technique. The lateral femoral circumflex artery (LFCA) was visualized in all patients: 101 limbs (101/136, 74.3%) were type I; 20 limbs (20/136, 14.7%) were type II; 3 limbs (3/136, 2.2%) were type III; and 12 limbs (12/136, 8.8%) were type IV. Tertiary branches were identified in 94 limbs (94/136, 69.1%). Donor flaps were outlined according to MRA TS-MIP findings in 4 patients. All flaps survived uneventfully following the transfer. In donor flap outlining, 3D CE-MRA with the TS-MIP technique allowed an accurate, direct visualization of the branching pattern and distribution profile of the LFCA supplying the ALT flap.

The Role of Dynamic Magnetic Resonance Imaging in the Evaluation of Pulmonary Nodules and Masses

Objective: The aim of our study was to determine whether or not dynamic magnetic resonance imaging (MRI) with kinetic and morphological parameters can reveal significant differences between malignant and benign pulmonary lesions, and thus to evaluate the use of dynamic MRI in the management of pulmonary nodules. Patients and Methods: Thirty-one patients (4 women and 27 men) underwent 1.5 T MRI, where 10 consecutive dynamic series were performed every 30 s by using 3D fast low-angle shot sequences. The percentage increase in the signal intensity of the lesions was determined for each time point. Time-enhancement curves of the lesions were drawn and classified into four types: A, B, C and D. Early peak (EP) and maximum peak (MP) values of the curves were calculated and compared with the diagnoses of the patients. The usefulness of these parameters was tested statistically. In addition to the comparison of the parameters between the groups, receiver-operating characteristic analysis was used to assess sensitivity, specificity, and both positive and negative predictive values of EP and MP parameters. Results: Of the 31 pulmonary lesions, 16 (52%) were malignant. These showed a stronger enhancement with higher median values of EP and MP (77.08 and 123.15, respectively) than those corresponding to the benign lesions (14.45 and 32.53, respectively). There were significant differences between the benign and malignant lesions (p < 0.001). Sensitivity, specificity, positive predictive value and negative predictive value were 75, 93, 92 and 78% for EP and 93, 86, 88 and 93% for MP, respectively. Conclusion: A combination of kinetic and morphological evaluation in dynamic MRI provided accurate differentiation between benign and malignant pulmonary lesions. It was a useful and noninvasive method of evaluating pulmonary nodules.

Paramagnetic perfluorocarbon-filled albumin-(Gd-DTPA) microbubbles for the induction of focused-ultrasound-induced blood–brain barrier opening and concurrent MR and ultrasound imaging

This paper presents new albumin-shelled Gd-DTPA microbubbles (MBs) that can concurrently serve as a dual-modality contrast agent for ultrasound (US) imaging and magnetic resonance (MR) imaging to assist blood–brain barrier (BBB) opening and detect intracerebral hemorrhage (ICH) during focused ultrasound brain drug delivery. Perfluorocarbon-filled albumin-(Gd-DTPA) MBs were prepared with a mean diameter of 2320 nm and concentration of 2.903×109 MBs ml–1 using albumin-(Gd-DTPA) and by sonication with perfluorocarbon (C3F8) gas. The albumin-(Gd-DTPA) MBs were then centrifuged and the procedure was repeated until the free Gd3+ ions were eliminated (which were detected by the xylenol orange sodium salt solution). The albumin-(Gd-DTPA) MBs were also characterized and evaluated both in vitro and in vivo by US and MR imaging. Focused US was used with the albumin-(Gd-DTPA) MBs to induce disruption of the BBB in 18 rats. BBB disruption was confirmed with contrast-enhanced T1-weighted turbo-spin-echo sequence MR imaging. Heavy T2*-weighted 3D fast low-angle shot sequence MR imaging was used to detect ICH. In vitro US imaging experiments showed that albumin-(Gd-DTPA) MBs can significantly enhance the US contrast in T1-, T2- and T2*-weighted MR images. The r1 and r2 relaxivities for Gd-DTPA were 7.69 and 21.35 s−1mM−1, respectively, indicating that the MBs represent a positive contrast agent in T1-weighted images. In vivo MR imaging experiments on 18 rats showed that focused US combined with albumin-(Gd-DTPA) MBs can be used to both induce disruption of the BBB and detect ICH. To compare the signal intensity change between pure BBB opening and BBB opening accompanying ICH, albumin-(Gd-DTPA) MB imaging can provide a ratio of 5.14 with significant difference (p = 0.026), whereas Gd-DTPA imaging only provides a ratio of 2.13 and without significant difference (p = 0.108). The results indicate that albumin-(Gd-DTPA) MBs have potential as a US/MR dual-modality contrast agent for BBB opening and differentiating focused-US-induced BBB opening from ICH, and can monitor the focused ultrasound brain drug delivery process.

“One-stop-shop” cardiac MRI at 3.0T for the detection of coronary artery disease

We present one-stop-shop cardiac MRI findings in a 58-year-old male patient with suspected coronary artery disease (CAD) who was scheduled for a primary diagnostic invasive coronary angiography. The patient was instructed to refrain from any beverage or foods containing caffeine, and antianginal medication within 24 hours before the MRI study. The study was performed on a 3.0T whole-body clinical scanner (MAGNETOM Tim Trio, Siemens Healthcare, Erlangen, Germany) equipped with a 12-element cardiac coil. The one-stop-shop cardiac MRI procedure consisted of four major protocols performed in the following order: 1) cine imaging for assessment of left ventricular function; 2) adenosine gadolinium first-pass imaging for assessment of stress perfusion; 3) coronary MRA for assessment of coronary artery anatomy; and 4) delayed enhancement MRI for assessment of myocardial infarction. After localizer sequences, a FLASH sequence was used for cine imaging. The following sequence parameters were used: TR/TE/flip-angle = 5.00 ms/2.44 ms/13°. The short-axis views were distributed to cover the entire left ventricle and two long-axis views (four- and two-chamber views) were also acquired. Adenosine was then administered intravenously at 140 µg/kg/min with the heart rate and blood pressure monitored. After 3 min of the adenosine infusion, an intravenous bolus injection of 0.05 mmol/kg gadolinium contrast material (Magnevist, Schering, Berlin, Germany) was administered into an antecubital vein on the opposing arm with the use of a power injector (Spectris, Medrad, Indianola, Pennsylvania) at a rate of 4 ml/s, followed by a 20 ml saline flush at 4 ml/s. A SR-Turbo-FLASH sequence was used for perfusion imaging with the following parameters: TR/TE/flip-angle = 2.38/1.14/12°, FOV = 270×360 mm2, matrix = 94×192, spatial resolution = 2.9×1.9×10 mm3, GRAPPA factor = 2, TI = 100 ms, and the number of slices = 3. Whole-heart coronary MRA with additional slow infusion of contrast material (0.15 mmol/kg at 0.3 ml/sec) was acquired after perfusion imaging. A navigator-gated, electrocardiography-triggered, fat saturated, segmented 3D fast low-angle shot sequence [1,2], with the following image parameters was used: TR/TE/flip-angle = 3.0/1.4/20°, readout bandwidth = 610 Hz/pixel, voxel size = 1.3 × 1.3 × 1.3 mm3 interpolated to 0.65 × 0.65 × 0.65 mm3, GRAPPA factor = 2, inversion prepulse delay = 200 ms. Delayed enhancement images were acquired by phase sensitive inversion recovery sequences after coronary MRA for viability study. The total examination time was 33 min. Acquisition time of whole-heart coronary MRA procedure was 9.1 min with a navigator acceptance rate of 34%. Data reformation and analysis were performed on a commercially available workstation (Leonardo, Siemens Healthcare, Erlangen, Germany). Figure 1 shows “one-stop-shop” cardiac MRI images at 3.0T from the 58-year-old male patient with suspected CAD. Figure 1 “One-stop-shop” cardiac MRI images at 3.0T from a 58-year-old male patient with suspected CAD. Perfusion image (A) demonstrates perfusion defects in the mid anteroseptal and inferoseptal segments. Coronary MRA images (B and C) show significant ... This work shows the feasibility of a comprehensive protocol one-stop-shop for cardiac MRI at 3.0T. It is possible to complete the cine imaging, perfusion imaging, coronary MRA, and delayed enhancement imaging in a single study within 35 minutes. The major advantage of this approach is that it offers functional studies for the detection of ischemia, tissue characterization for the detection and quantification of myocardial infarction as well as luminal assessment of the coronary arteries in a single noninvasive and radiation free test. This may be extremely useful for better selecting patients to undergo an invasive procedure. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology [3].

Comparison between different implementations of the 3D FLASH sequence for knee cartilage quantification

To compare several sequence implementations of the 3D FLASH sequence in the context of quantitative cartilage imaging. Test-retest coronal fast low angle shot (FLASH) sequences with water excitation were acquired in knees of 12 healthy participants, using two 1.5 T scanners from the same manufacturer. On one of the scanners, the FLASH was additionally compared with a FLASH VIBE, 75% with 100% slice resolution, a non-selective with a conventional spatial pulse, and "asymmetric echo allowed" with "not allowed". Implementations of the FLASH showed systematic differences of up to 3.3%, but these were not statistically significant. Precision errors were similar between protocols, but tended to be smallest for the FLASH VIBE with 100% slice resolution (0.6-6.7%). In the medial tibia cartilage volume and thickness differed significantly (P < 0.01; 6.2 and 5.9%) between the two scanners. Using a validated FLASH sequence, one can reduce slice resolution to 75% and allow asymmetric echo without sacrificing precision, in order to reduce the total acquisition time. However, in longitudinal studies, the scanner and the specific sequence implementation should be kept constant between baseline and follow-up, in order to avoid systematic off-sets in the measurements.

Investigation of motion artifacts associated with fat saturation technique in 3D flash imaging

Fast low-angle shot (FLASH) imaging is widely used in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) because it permits fast and accurate T1 measurement in vivo. Suppression of the fat signal is necessary for most FLASH applications; otherwise, fat will appear hyperintense. The fat saturation technique is one popular method to reduce fat images on clinical scanners. However, fat saturation combined with the 3D FLASH sequence in breast DCE-MRI scans results in heavy ghosting artifacts caused by heartbeat. We used simulation and experimental scans to determine the cause of these artifact-enhancement phenomena. We simulated imaging of motion in the x, y, and z directions, with and without fat saturation, to investigate the origin of artifacts. Fourier transform (FT) of the whole field of view was used in the simulation, and we assumed that the uniform phantom was static during one TR. The amplitude of each echo was considered a factor in the FT data. Images were reconstructed using FT data from different phantom positions multiplied by the amplitude factor. Phantom experiments and volunteer studies were implemented to verify the conclusion. Both phantom and volunteer results showed artifacts similar to those in simulation images. We found that FLASH sequence without fat saturation is insensitive to motion. Fat saturation radiofrequency pulses placed before each group of echoes disrupted the steady state of the signal amplitude and produced a low-pass filter effect that enhanced the motion artifacts. We conclude that the low-pass filter effect associated with the fat saturation technique is responsible for dramatically increased motion artifacts.

Three-dimensional Reconstructed Contrast–enhanced MR Angiography for Internal Iliac Artery Branch Visualization before Uterine Artery Embolization

To evaluate the feasibility of three-dimensional (3D) reconstructed contrast-enhanced (CE) magnetic resonance (MR) angiography in mapping the pelvic arteries in women before uterine artery embolization (UAE). CE MR angiography studies before UAE in 49 women (age range, 38-57 years; mean, 47.04 y +/- 4.7 [SD]) who underwent UAE for uterine leiomyomas between February 2005 and February 2007 were retrospectively evaluated by two radiologists in consensus. Studies were performed on a 1.5-T MR unit with a 3D fast low-angle shot sequence in the coronal direction. Reconstruction was performed with 3D computed tomographic angiography reconstruction software. In the current study, 98 internal iliac arteries (IIAs) from 49 women were studied. The superior and inferior gluteal arteries were visualized in all cases (N = 98; 100%), the lateral sacral artery in 86 cases (88%), the iliolumbar artery in 84 (86%), the obturator artery in 81 (83%), the internal pudendal artery in 96 (98%), and the uterine artery in 95 (97%). The superior vesical and middle rectal arteries were seen in 21 (21%) and 11 (11%) cases, respectively. The mean length of the uterine artery was 12.56 cm (range, 4.6-22.2 cm), and it showed the longest traceable length among all branches. The uterine artery showed five patterns of origin. The superior gluteal artery showed constant origin from the posterior division of the IIA, whereas the iliolumbar and obturator arteries showed the most variations in origin. Three-dimensional reconstructed CE MR angiography can detect most branches of the IIA in addition to their point of origin. Therefore, it can be used as a mapping tool of the pelvic arterial tree before UAE.

Three‐dimensional gradient‐echo imaging for percutaneous MR‐guided laser therapy of liver metastasis

To evaluate the use of three-dimensional (3D) gradient-echo (GRE) magnetic resonance imaging (MRI) for percutaneous MR-guided catheter placement for laser therapy of liver metastases. Thirty-four patients were included. A total of 122 MR-guided percutaneous punctures of 67 liver metastases were performed on a 1.5T scanner (Symphony and Sonata; Siemens, Erlangen, Germany) using a 5.5F microcatheter system and titanium needle (Monocath; MeoMedical, Augsburg, Germany). In 88 of 122 procedures, a 2D fast low-angle shot (FLASH) T1-weighted GRE breath-hold sequence was acquired in the axial plane and if necessary in a second plane. Sequences were acquired and reviewed using the panel in the control room. In 34 of 122 procedures a 3D FLASH T1-weighted fat-saturated GRE (volume-interpolated breath-hold examination (VIBE)) sequence was acquired in the axial plane only. Acquisition and 3D review were controlled under sterile conditions with a panel inside the examination room (Syngo; Siemens). The 3D FLASH sequence significantly decreased the mean number of acquisitions needed to place the microcatheter with the titanium needle in the metastasis compared to interventions with the 2D FLASH sequence (2.9 +/- 0.83 vs. 4.4 +/- 1.63). With 2D FLASH imaging, acquisition in a second plane was necessary in 78 instances (20% of acquired 2D sequences) to ensure adequate positioning of the device during the procedure. The artifact caused by the titanium needle was smaller with the 3D FLASH sequence. The conspicuity of liver metastases and morphology (liver edge and vessels) was acceptable with both sequences. The 3D FLASH sequence improved differentiation when two to four titanium needles were inserted, due to smaller susceptibility artifacts caused by the needles. 3D GRE imaging with the capability to perform multiplanar reconstruction (MPR) shortens the procedure by reducing the number of sequences needed. Improved visibility of the titanium needles allows more precise insertion of multiple needles into the metastasis.

Three-dimensional magnetic resonance imaging after ultrasonography for assessment of fetal gastroschisis

A 24-year-old woman (Gravida I, Para I) at estimated 32 weeks of pregnancy was referred to our department for evaluation of a suspected fetal gastroschisis. Ultrasound scan revealed multiple loops of dilated bowel outside the fetal abdomen and absence of membrane surrounding the herniated loops of the intestines. Three-dimensional (3D) magnetic resonance imaging was performed to obtain more information on the bowel both outside and inside the abdomen. Images were constructed with T1-weighted fat-suppressed 3D fast low-angle shot sequences using a maximum intensity projection algorithm. The 3D images made possible the realization of fetal bowel conditions with greater definition and accuracy.

Accuracy of fat-suppressed three-dimensional spoiled gradient-echo FLASH MR imaging in the detection of patellofemoral articular cartilage abnormalities.

To determine the accuracy of T1-weighted fat-suppressed (FS) three-dimensional (3D) fast low-angle shot (FLASH) magnetic resonance (MR) imaging for the detection of articular cartilage abnormalities of the patellofemoral joint. Forty-one patients with suspected internal derangement of the knee were examined with a T1-weighted FS 3D FLASH sequence and subsequently underwent arthroscopy. The patellofemoral articular cartilage was graded blindly on both the MR and arthroscopic images with a modification of the Noyes classification scheme. For the detection of abnormal articular cartilage of the patellofemoral joint with the FS 3D FLASH sequence, sensitivity was 81%, specificity was 97%, and accuracy was 97%. Of the lesions detected on MR images, 77% were graded identically on MR and arthroscopic images. For the remaining 23%, MR imaging and arthroscopic ratings were within one grade of each other. T1-weighted FS 3D FLASH imaging is accurate for the detection and grading of articular cartilage abnormalities of the patellofemoral joint.