Fast Spin-echo Technique Research Articles

Denoising of three-dimensional fast spin echo magnetic resonance images of knee joints using spatial-variant noise-relevant residual learning of convolution neural network

PurposeTwo-dimensional (2D) fast spin echo (FSE) techniques play a central role in the clinical magnetic resonance imaging (MRI) of knee joints. Moreover, three-dimensional (3D) FSE provides high-isotropic-resolution magnetic resonance (MR) images of knee joints, but it has a reduced signal-to-noise ratio compared to 2D FSE. Deep-learning denoising methods are a promising approach for denoising MR images, but they are often trained using synthetic noise due to challenges in obtaining true noise distributions for MR images. In this study, inherent true noise information from two number of excitations (2-NEX) acquisition was used to develop a deep-learning model based on residual learning of convolutional neural network (CNN), and this model was used to suppress the noise in 3D FSE MR images of knee joints. MethodsA deep learning-based denoising method was developed. The proposed CNN used two-step residual learning over parallel transporting and residual blocks and was designed to comprehensively learn real noise features from 2-NEX training data. ResultsThe results of an ablation study validated the network design. The new method achieved improved denoising performance of 3D FSE knee MR images compared with current state-of-the-art methods, based on the peak signal-to-noise ratio and structural similarity index measure. The improved image quality after denoising using the new method was verified by radiological evaluation. ConclusionA deep CNN using the inherent spatial-varying noise information in 2-NEX acquisitions was developed. This method showed promise for clinical MRI assessments of the knee, and has potential applications for the assessment of other anatomical structures.

The Effect of Imaging Parameters on SAR and Temperature Rise during MRI Examinations Using the Fast Spin Echo Technique: The Effects of Increasing the FA of the Refocusing RF and ETL

The Effect of Imaging Parameters on SAR and Temperature Rise during MRI Examinations Using the Fast Spin Echo Technique: The Effects of Increasing the FA of the Refocusing RF and ETL

A robust 3D fast spin-echo technique for fast examination of the brachial plexus.

To introduce a 3D fast spin-echo (FSE) sequence technique that may replace conventional clinical 2D FSE sequences for examining the brachial plexus. A 3D FSE sequence with motion-sensitized driven equilibrium magnitude preparation, triple-echo Dixon, and outer-volume suppression techniques, dubbed as MSDE-CUBE-fTED, was compared with clinical 2D T2-weighted and T1-weighted FSE sequences on the conventional brachial plexus exam of 14 volunteers. The resulting images were evaluated by two radiologists for fat suppression, blood flow suppression, nerve visualization, scalene muscle shape, surrounding fat planes, and diagnostic confidence. The inter-rater agreement of the reviewers was also measured. In addition, the signal magnitude ratios and contrast-to-noise ratios between nerve-to-vessel, nerve-to-muscle, and fat-to-muscle were compared. The MSDE-CUBE-fTED sequence scored significantly higher than the T2-weighed FSE sequence in all visualization categories (P < 0.05). Its score was not significantly different from that of the T1-weighted FSE in muscle and fat visualization (P ≥ 0.5). The inter-rater agreements were substantial (Gwet's agreement coefficient ≥ 0.7). The signal magnitude and contrast ratios were significantly higher in the MSDE-CUBE-fTED sequence (P < 0.05). Our results suggest that the MSDE-CUBE-fTED sequence can make a potential alternative to standard T2- and T1-weighted FSE sequences for examining the brachial plexus.

High-resolution Compressed-sensing T1 Black-blood MRI : ANew Multipurpose Sequence in Vascular Neuroimaging?

In vasculopathies of the central nervous system, reliable and timely diagnosis is important against the background of significant morbidity and sequelae in cases of incorrect diagnosis or delayed treatment. Magnetic resonance imaging (MRI) plays amajor role in the detection and monitoring of intracranial and extracranial vascular pathologies of different etiologies, in particular for evaluation of the vessel wall in addition to luminal information, thus allowing differentiation between various vasculopathies. Compressed-sensing black-blood MRI combines high image quality with relatively short acquisition time and offers promising potential in the context of neurovascular vessel wall imaging in clinical routine. This case review gives an overview of its application in the diagnosis of various intracranial and extracranial entities. An optimized high-resolution compressed-sensing black-blood 3D T1-weighted fast (turbo) spin echo technique (T1 CS-SPACE prototype) precontrast and postcontrast application at 3T was used for the evaluation of various vascular conditions in neuroradiology. In this article seven cases of intracranial and extracranial arterial and venous vasculopathies with representative imaging findings in high-resolution compressed-sensing black-blood MRI are presented. High-resolution 3D T1 CS-SPACE black-blood MRI is capable of imaging various vascular entities in high detail with whole head coverage and low susceptibility for motion artifacts and within acceptable scan times. It represents ahighly versatile, non-invasive technique for the visualization and differentiation of awide variety of neurovascular arterial and venous disorders.

Diffusion-weighted Renal MRI at 9.4\u2009Tesla Using RARE to Improve Anatomical Integrity

Diffusion-weighted magnetic resonance imaging (DWI) is a non-invasive imaging technique sensitive to tissue water movement. By enabling a discrimination between tissue properties without the need of contrast agent administration, DWI is invaluable for probing tissue microstructure in kidney diseases. DWI studies commonly make use of single-shot Echo-Planar Imaging (ss-EPI) techniques that are prone to suffering from geometric distortion. The goal of the present study was to develop a robust DWI technique tailored for preclinical magnetic resonance imaging (MRI) studies that is free of distortion and sensitive to detect microstructural changes. Since fast spin-echo imaging techniques are less susceptible to B0 inhomogeneity related image distortions, we introduced a diffusion sensitization to a split-echo Rapid Acquisition with Relaxation Enhancement (RARE) technique for high field preclinical DWI at 9.4 T. Validation studies in standard liquids provided diffusion coefficients consistent with reported values from the literature. Split-echo RARE outperformed conventional ss-EPI, with ss-EPI showing a 3.5-times larger border displacement (2.60 vs. 0.75) and a 60% higher intra-subject variability (cortex = 74%, outer medulla = 62% and inner medulla = 44%). The anatomical integrity provided by the split-echo RARE DWI technique is an essential component of parametric imaging on the way towards robust renal tissue characterization, especially during kidney disease.

A multi-band double-inversion radial fast spin-echo technique for T2 cardiovascular magnetic resonance mapping of the heart

BackgroundDouble inversion recovery (DIR) fast spin-echo (FSE) cardiovascular magnetic resonance (CMR) sequences are used clinically for black-blood T2-weighted imaging. However, these sequences suffer from slice inefficiency due to the non-selective inversion pulses. We propose a multi-band (MB) encoded DIR radial FSE (MB-DIR-RADFSE) technique to simultaneously excite two slices. This sequence has improved signal-to-noise ratio per unit time compared to a single slice excitation. It is also motion robust and enables the reconstruction of high-resolution black-blood T2-weighted images and T2 maps for the excited slices.MethodsHadamard encoded MB pulses were used in MB-DIR-RADFSE to simultaneously excite two slices. A principal component based iterative reconstruction was used to jointly reconstruct black-blood T2-weighted images and T2 maps. Phantom and in vivo experiments were performed to evaluate T2 mapping performance and results were compared to a T2-prepared balanced steady state free precession (bSSFP) method. The inter-segment variability of the T2 maps were assessed using data acquired on healthy subjects. A reproducibility study was performed to evaluate reproducibility of the proposed technique.ResultsPhantom experiments show that the T2 values estimated from MB-DIR-RADFSE are comparable to the spin-echo based reference, while T2-prepared bSSFP over-estimated T2 values. The relative contrast of the black-blood images from the multi-band scheme was comparable to those from a single slice acquisition. The myocardial segment analysis on 8 healthy subjects indicated a significant difference (p-value < 0.01) in the T2 estimates from the apical slice when compared to the mid-ventricular slice. The mean T2 estimate from 12 subjects obtained using T2-prepared bSSFP was significantly higher (p-value = 0.012) compared to MB-DIR-RADFSE, consistent with the phantom results. The Bland-Altman analysis showed excellent reproducibility between the MB-DIR-RADFSE measurements, with a mean T2 difference of 0.12 ms and coefficient of reproducibility of 2.07 in 15 clinical subjects. The utility of this technique is demonstrated in two subjects where the T2 maps show elevated values in regions of pathology.ConclusionsThe use of multi-band pulses for excitation improves the slice efficiency of the double inversion fast spin-echo pulse sequence. The use of a radial trajectory and a joint reconstruction framework allows reconstruction of TE images and T2 maps for the excited slices.

Breath-hold black-blood T1rho mapping improves liver T1rho quantification in healthy volunteers.

Background Recent researches suggest that T1rho may be a non-invasive and quantitative technique for detecting and grading liver fibrosis. Purpose To compare a multi-breath-hold bright-blood fast gradient echo (GRE) imaging and a single breath-hold single-shot fast spin echo (FSE) imaging with black-blood effect for liver parenchyma T1rho measurement and to study liver physiological T1rho value in healthy volunteers. Material and Methods The institutional Ethics Committee approved this study. 28 healthy participants (18 men, 10 women; age = 29.6 ± 5.1 years) underwent GRE liver T1rho imaging, and 20 healthy participants (10 men, 10 women; age = 36.9 ± 10.3 years) underwent novel black-blood FSE liver T1rho imaging, both at 3T with spin-lock frequency of 500 Hz. The FSE technique allows simultaneous acquisition of four spin lock times (TSLs; 1 ms, 10 ms, 30 ms, 50msec) in 10 s. Results For FSE technique the intra-scan repeatability intraclass correlation coefficient (ICC) was 0.98; while the inter-scan reproducibility ICC was 0.82 which is better than GRE technique's 0.76. Liver T1rho value in women tended to have a higher value than T1rho values in men (FSE: 42.28 ± 4.06 ms for women and 39.13 ± 2.12 ms for men; GRE: 44.44 ± 1.62 ms for women and 42.36 ± 2.00 ms for men) and FSE technique showed liver T1rho value decreased slightly as age increased. Conclusion Single breath-hold black-blood FSE sequence has better scan-rescan reproducibility than multi-breath-hold bright-blood GRE sequence. Gender and age dependence of liver T1rho in healthy participants is observed, with young women tending to have a higher T1rho measurement.

Free-breathing black-blood CINE fast-spin echo imaging for measuring abdominal aortic wall distensibility: a feasibility study

The paper reports a free-breathing black-blood CINE fast-spin echo (FSE) technique for measuring abdominal aortic wall motion. The free-breathing CINE FSE includes the following MR techniques: (1) variable-density sampling with fast iterative reconstruction; (2) inner-volume imaging; and (3) a blood-suppression preparation pulse. The proposed technique was evaluated in eight healthy subjects. The inner-volume imaging significantly reduced the intraluminal artifacts of respiratory motion (p = 0.015). The quantitative measurements were a diameter of 16.3 ± 2.8 mm and wall distensibility of 2.0 ± 0.4 mm (12.5 ± 3.4%) and 0.7 ± 0.3 mm (4.1 ± 1.0%) for the anterior and posterior walls, respectively. The cyclic cross-sectional distensibility was 35 ± 15% greater in the systolic phase than in the diastolic phase. In conclusion, we developed a feasible CINE FSE method to measure the motion of the abdominal aortic wall, which will enable clinical scientists to study the elasticity of the abdominal aorta.

Abstract WP135: Is Hyperintense Carotid Plaque on T1-weighted Images an Independent Risk Factor for Symptomatic Carotid Stenosis?

Introduction: Carotid plaque showing hyperintensity on T1-weighted magnetic resonance imaging reflects unstable plaque consisting of lipid/necrosis and/or hemorrhage and has been reported as a risk factor for embolic complications during carotid endarterectomy (CEA) or stenting. However, it remains unclear whether hyperintense plaque is related to stroke events. Thus, we evaluated the difference in the intraplaque signal between asymptomatic and symptomatic patients with carotid stenosis. Methods: We prospectively collected and retrospectively analyzed 68 patients who underwent CEA (age, 53-79 years; 61 men and 7 women; 52 symptomatic and 16 asymptomatic). Using a fast spin-echo technique at 1.5 T, the contrast ratio (CR) of carotid plaque to adjacent muscle was calculated on axial images based on maximum plaque size. Differences in patient characteristics (age, sex, hypertension, dyslipidemia, diabetic mellitus, and degree of stenosis) as well as CRs between symptomatic and asymptomatic patients were examined using Fisher’s exact test, the Mann-Whitney test, and multivariable logistic regression analysis. Results: The CRs of the carotid plaque were significantly higher in the symptomatic group than in the asymptomatic group (0.97-2.32 [median, 1.55] and 0.95-2.01 [1.32], respectively; p = 0.026). In addition, age, hypertension, and stenosis degree were significantly higher in the former than in the latter (p = 0.013- 0.003). Multivariate logistic regression analysis revealed that only hypertension and CRs of the plaque were independent risks of symptomatic stenosis (odds ratio, 11.0 and 2.7; 95% confidence interval, 2.0-62.0 and 1.1-6.6; p = 0.007 and 0.025; respectively). Conclusion: CRs of the carotid plaque as well as hypertension were significantly and independently related with symptomatic patients, suggesting that hyperintense plaque can be a risk factor of stroke events in patients with carotid stenosis.

Speed in Clinical Magnetic Resonance.

The relevant clinical accelerated magnetic resonance techniques that are available currently for routine patient examinations are reviewed, presenting and discussing the benefits therein when compared with more conventional scans. The focus is on clinical use and practicality, with the review divided into 3 sections. Improvements in 3-dimensional acquisition are first discussed, specifically controlled aliasing in parallel imaging results in higher acceleration, related radial techniques, and CAIPI-Dixon-TWIST-VIBE. Simultaneous multislice imaging is then reviewed, focusing on current implementation for 2-dimensional imaging, including both echo-planar and fast spin echo techniques. The final topic is that of sparse reconstruction (data sparsity), discussing the principles therein, challenges, and current applications. Guidance in terms of clinical use for accelerated techniques is provided, focusing on enabling faster and improved clinical scan results.

T1-Weighted Magnetic Resonance Carotid Plaque Imaging: a Comparison between Conventional and Fast Spin-Echo Techniques

Magnetic resonance imaging is widely used to evaluate the intraplaque components of the cervical carotid artery. The non-gated T1-weighted spin-echo (SE) technique has been reported to have an excellent ability for discriminating stable and unstable plaques. However, the diagnostic performance of various SE-based techniques remains unclear. Hence, we compared plaque signals obtained by 3 kinds of SE-based methods with histological findings. We prospectively examined 40 patients who underwent carotid endarterectomy by using 1.5-T scanners and obtained 2-dimensional (2D) conventional spin-echo (CSE), 2D fast spin-echo (FSE), and 3-dimensional (3D)-FSE images with identical repetition times. We calculated contrast ratios (CRs) of the plaques against adjacent muscles and compared these values with the pathological classification of the specimens. The CRs of type VII-VIII (calcific/fibrous), IV-V (lipid-rich/necrotic), and VI (complex/hemorrhagic) plaques were significantly different between all the methods (P <.001) and were discriminated from each other at sensitivities of 83%-100% and specificities of 94%-100%. The CRs of type IV-V plaques significantly differed between the methods (low to high, 2D-FSE, 2D-CSE, and 3D-FSE; P <.05); those of the type VI plaques were significantly lower with the 2D-FSE method than with the other methods (P <.01). The SE-based T1-weighted images can readily discriminate plaque characteristics with high sensitivities and specificities, although the signal intensity of unstable plaques was significantly high on the 3D-FSE images and significantly low on the 2D-FSE images.

Feasibility of fat fraction quantification by measuring J-coupling related signal modulation in multi echo fast spin echo sequences

Introduction Echo spacing in Fast Spin Echo techniques can affect signal intensity mainly of fatty tissue and is presented as effectively prolonged T2 relaxation time (magnetic fat liquefaction). Purpose The aim of this study is to measure signal intensity in multi echo Fast Spin Echo techniques with variable echo spacing in order to examine the feasibility of fat quantification from J-coupling related signal modulation. T2 maps were calculated from all different acquisition schemes. Materials and methods A phantom containing porcine fat, vegetable oils, gadolinium doped agarose gels that mimic fat magnetic relaxation properties, double distilled water at controlled temperature of 36–38 °C was scanned at 1.5 T utilizing a single slice multi echo SE technique with equidistant echoes of variable TE intervals (6.7–40 ms). Results Fat signal modulation as a function of echo spacing varied significantly between short and long echo spacing acquisitions (28.97–56.26%) and this dependence could be approximated by a linear sequence ( Δ S fat = S short ESP - S long ESP = 3.38*n*TE + 27.18, residual 7,88 for n ranging from 1 to 12) for a wide range of routinely used TEs in clinical practice (13.4–160.8 ms) while effect on water was minimal ( Δ S water = 22.11%, SD for same TE range: 0.53). Difference of calculated T2 relaxation times between sequences with different echo spacing ranged from 9.5 to 35%. Conclusion Echo spacing in MESE sequences may serve as a metric of signal manipulation and fat quantification. Bright fat sequences should be avoided for T2 relaxation parametric maps.

Fast all-optical nuclear spin echo technique based on EIT

We demonstrate an all-optical Raman spin echo technique, using Electromagnetically Induced Transparency (EIT) to create the different pulses of the spin echo sequence: initialization, pi-rotation, and readout. The first pulse of the sequence induces coherence directly from a mixed state, and the technique is used to measure the nuclear spin coherence of an inhomogeneously broadened ensemble of rare-earth ions (Pr$^{3+}$). In contrast to previous experiments it does not require any preparatory hole burning pulse sequences, which greatly shortens the total duration of the sequence. The effect of the different pulses is characterized by quantum state tomography and is compared with simulations. We demonstrate two applications of the technique by using the spin echo sequence to accurately compensate a magnetic field across our sample, and to measure the coherence time at high temperatures up to 11 K, where standard preparation techniques are difficult to implement. We explore the potential of the technique and possible applications.

MRI sequences for the detection of individual lymph nodes in regional breast radiotherapy planning.

In regional radiotherapy (RT) for patients with breast cancer, lymph node (LN) targets are delineated on CT, defined by anatomical boundaries. By identifying individual LNs, MRI-based delineations may reduce target volumes and thereby toxicity. We optimized MRI sequences for this purpose. Our aim was to evaluate the techniques for LN delineation in RT planning. Supine MRI was explored at 1.5 T in RT position (arms in abduction). 5 MRI techniques were optimized in 10 and evaluated in 12 healthy female volunteers. The scans included one T1 weighted (T1w), three T2 weighted (T2w) and a diffusion-weighted imaging (DWI) technique. Quantitative evaluation was performed by scoring LN numbers per volunteer and per scan. Qualitatively, scans were assessed on seven aspects, including LN contrast, anatomical information and insensitivity to motion during acquisition. Two T2w fast spin-echo (FSE) methods showed the highest LN numbers (median 24 axillary), high contrast, excellent fat suppression and relative insensitivity to motion during acquisition. A third T2w sequence and DWI showed significantly fewer LNs (14 and 10) and proved unsuitable due to motion sensitivity and geometrical uncertainties. T1w MRI showed an intermediate number of LNs (17), provided valuable anatomical information, but lacked LN contrast. Explicit LN imaging was achieved, in supine RT position, using MRI. Two T2w FSE techniques had the highest detection rates and were motion insensitive. T1w MRI showed anatomical information. MRI enables direct delineation of individual LNs. Our optimized MRI scans enable accurate target definition in MRI-guided regional breast RT and development of personalized treatments.

Comparison of Magnetic Resonance Urography (MRU) with Intravenous Pyelography (IVP) in Evaluation of Patients with Hydronephrosis on Ultrasonography Due to Pelvi-Ureteric Junction Obstruction

The objective of this study was to compare Magnetic Resonance Urography (MRU) with Intravenous Pyelography (IVP) in evaluation of patients with hydronephrosis on ultrasonography. 49 patients of hydronephrosis on USG were enrolled for the study from Jan. 2011 to Dec. 2012. All patients under went Intravenous Urography (IVU). MRU was done to determine the anatomical details and function of each renal unit. MRU was performed on a 1.5 tesla unit (Magneton Avento; Siemens, Erlangen, Germany). Static T2-weighted Magnetic Resonance Urography (MRU) was performed by using a standard fast spin echo technique. Dynamic study was performed after injecting intravenous diuretic followed by Gadolinium contrast media. Morphological results of MRU were compared with IVU. The anatomical findings were compared with operative findings. Stastical analysis was performed and data expressed as mean ± SD. MRU showed PUJ obstruction in 41 out of 45 patients (91.1%). We concluded that MRU can provide complete diagnostic evaluation of entire urinary tract in a single session and has potential to replace IVP.

Forensic age estimation via 3-T magnetic resonance imaging of ossification of the proximal tibial and distal femoral epiphyses: Use of a T2-weighted fast spin-echo technique

Radiation exposure during forensic age estimation is associated with ethical implications. It is important to prevent repetitive radiation exposure when conducting advanced ultrasonography (USG) and magnetic resonance imaging (MRI). The purpose of this study was to investigate the utility of 3.0-T MRI in determining the degree of ossification of the distal femoral and proximal tibial epiphyses in a group of Turkish population. We retrospectively evaluated coronal T2-weighted and turbo spin-echo sequences taken upon MRI of 503 patients (305 males, 198 females; age 10–30 years) using a five-stage method. Intra- and interobserver variations were very low. (Intraobserver reliability was κ=0.919 for the distal femoral epiphysis and κ=0.961 for the proximal tibial epiphysis, and interobserver reliability was κ=0.836 for the distal femoral epiphysis and κ=0.885 for the proximal tibial epiphysis.)Spearman's rank correlation analysis indicated a significant positive relationship between age and the extent of ossification of the distal femoral and proximal tibial epiphyses (p<0.001). Comparison of male and female data revealed significant between-gender differences in the ages at first attainment of stages 2, 3, and 4 ossifications of the distal femoral epiphysis and stage 1 and 4 ossifications of the proximal tibial epiphysis (p<0.05). The earliest ages at which ossification of stages 3, 4, and 5 was evident in the distal femoral epiphysis were 14, 17, and 22 years in males and 13, 16, and 21 years in females, respectively. Proximal tibial epiphysis of stages 3, 4, and 5 ossification was first noted at ages 14, 17, and 18 years in males and 13, 15, and 16 years in females, respectively.MRI of the distal femoral and proximal tibial epiphyses is an alternative, noninvasive, and reliable technique to estimate age.

Assessment of neonatal BPBP

The incidence of neonatal brachial plexus palsy is about 1 in 1000 live births with up to 20% having some sequelae but only 8% requiring surgery. Surgical complications can occur and therefore the indications for and the timing of surgery is of paramount importance. The indications are determined by clinical examinations and investigations. It is necessary to rule out differential diagnoses but we do need to consider whether investigations that we perform accurately reveal the extent and severity of the neurological lesion. These investigations are x-rays, CT myelography, MRI and electromyography and nerve conduction studies. None of these investigations would appear to be as reliable as they are when they are applied to adults. CT myelography and an MRI require general anaesthetic . There is a low sensitivity but a high specificity of root avulsion in the presence of a pseudomeningocele and absence of rootlets. Improving fast spin-echo MRI techniques may be of greater benefit in the future. The reliability of electromyography and nerve conduction studies differs from that in adult lesions which may be due to a number of different factors. They are accurate for neuropraxia and avulsion but less satisfactory for a neuroma in continuity, in determining recovery of function and indeed in their performance. The results of EMG and NCS may be unduly optimistic. Therefore, clinical examination remains the main basis upon which surgery is indicated. The thesis of Tassin and the work of Gilbert have suggested that the presence or absence of elbow flexion is a good indicator of the return of shoulder function. The indications for surgery in C5-6 and C5-6-7 lesions are based upon this clinical finding. Others have questioned as to whether this is an accurate method of determination of surgical necessity. Clarke claims improvement of the predictability of recovery by including the return of other muscle functions and combining these into a test score, but it is uncertain whether this score improves the accuracy of assessment of C5-6 lesions. Most would agree that surgery by 3 months in pan-plexus lesions is appropriate. I perform routine clinical examinations, preferably on a 2 week basis from the time of the first presentation. Close documentation from as early an age as possible is vital to determining the presence or absence of specific muscle function and the rate of any recovery. I operate for failure of biceps recovery at 4 months in C5,6+/-7 lesions and by 3 months in pan-plexus lesions. Beyond this time, neurosurgical exploration may be indicated for failure to improve. Nerve transfers, for instance accessory to suprascapular nerve, have been effective up to 15 months of age. X-rays of the chest, cervical spine and shoulder are routine and, although the reliability of EMG and NCS is less than satisfactory, these are performed at 3 months. MRI examination will become a routine investigation but at the moment it is not my practice to routinely order these on all children.

Detection of Vessel Wall Lesions in Spontaneous Symptomatic Vertebrobasilar Artery Dissection Using T1-weighted 3-dimensional Imaging

Spontaneous intracranial vertebrobasilar artery dissection (iVBD) is a cause of ischemic stroke and subarachnoid hemorrhage in young adults that can be detected noninvasively by using multisequence magnetic resonance imaging (MRI). However, MRI findings are sometimes difficult to interpret, and its accuracy tends to be suboptimal, especially during the acute period. Therefore, we investigated whether 3-dimensional (3D) vessel wall imaging (VWI) technique could readily detect iVBD lesions in acute phase patients. Sixteen consecutive patients with acute ischemic stroke caused by iVBD were prospectively examined with a 1.5-T magnetic resonance scanner. T1-weighted (T1W) 3D-VWI was obtained using a flow-sensitized 3D fast spin-echo technique. In addition, multisequence MRI comprising magnetic resonance angiography (MRA), basiparallel anatomical scanning (BPAS), and axial T1W imaging (T1WI) were also examined. Presence of luminal stenosis, aneurysmal dilatation, intramural high signal, and intimal flap/double lumen of the vertebral and basilar arteries were visually assessed using each technique. On 3D-VWI, luminal stenosis, aneurysmal dilatation, intramural high signal, and intimal flap were observed in 16 (100%), 11 (68.8%), 16 (100%), and 1 (6.3%) patients, respectively. In contrast, on conventional techniques, these findings were observed in 15 (93.8%, MRA with BPAS), 12 (75.0%, MRA with BPAS), 12 (75.0%, T1WI), and 12 (75.0%, MRA) patients, respectively. The T1W 3D-VWI can directly visualize vessel wall iVBD lesions during the acute period of stroke compared with multisequence MRI.

TH‐A‐BRF‐05: MRI of Individual Lymph Nodes to Guide Regional Breast Radiotherapy

Purpose:In regional radiotherapy (RT) for breast‐cancer patients, direct visualization of individual lymph nodes (LNs) may reduce target volumes and Result in lower toxicity (i.e. reduced radiation pneumonitis, arm edema, arm morbidity), relative to standard CT‐based delineations. To this end, newly designed magnetic resonance imaging (MRI) sequences were optimized and assessed qualitatively and quantitatively.Methods:In ten healthy female volunteers, a scanning protocol was developed and optimized. Coronal images were acquired in supine RT position positioned on a wedge board on a 1.5 T Ingenia (Philips) wide‐bore MRI. In four volunteers the optimized MRI protocol was applied, including a 3‐dimensional (3D) T1‐weighted (T1w) fast‐field‐echo (FFE). T2w sequences, including 3D FFE, 3D and 2D fast spin echo (FSE), and diffusion‐weighted single‐shot echo‐planar imaging (DWI) were also performed. Several fatsuppression techniques were used. Qualitative evaluation parameters included LN contrast, motion susceptibility, visibility of anatomical structures, and fat suppression. The number of visible axillary and supraclavicular LNs was also determined.Results:T1 FFE, insensitive to motion, lacked contrast of LNs, which often blended in with soft tissue and blood. T2 FFE showed high contrast, but some LNs were obscured due to motion. Both 2D and 3D FSE were motion‐insensitive having high contrast, although some blood remained visible. 2D FSE showed more anatomical details, while in 3D FSE, some blurring occurred. DWI showed high LN contrast, but suffered from geometric distortions and low resolution. Fat suppression by mDixon was the most reliable in regions with magnetic‐field inhomogeneities. The FSE sequences showed the highest sensitivity for LN detection.Conclusion:MRI of regional LNs was achieved in volunteers. The FSE techniques were robust and the most sensitive. Our optimized MRI sequences can facilitate direct delineation of individual LNs. This can Result in smaller target volumes and reduced toxicity in regional RT compared to standard CT planning.

Meniscal tears: comparison of the conventional spin-echo and fast spin-echo techniques through image processing

BackgroundConventional spin-echo (PD-CSE) and fast spin-echo (PD-FSE) techniques are frequently used to detect meniscal tears. However, the time delay for imaging with PD-CSE has resulted in its replacement with faster techniques, such as proton density fast spin-echo (PD-FSE), which has become a frequent tool at most diagnostic centres.Qualitative analysis shows that the PD-CSE technique is more sensitive, but other authors have not found significant differences between the aforementioned techniques. Therefore, we performed a quantitative analysis in this study that aims to measure differences in the quality of the images obtained with both techniques.MethodsWe compared the PD-CSE and PD-FSE techniques by quantitatively analysing the obtained proton density images: the area shown, as well as the brightness and lesion contrast of the obtained image.A set of 100 images from 50 patients thought to contain meniscal tears of the knee were selected. These 100 images were obtained from all individuals using both the PD-CSE and PD-FSE techniques. The images were processed using software developed in Delphi. In addition to these quantifications, three physicians, who are specialists in radiology and capable of analysing magnetic resonance (MR) images of the musculoskeletal system, qualitatively analysed the diagnostic sensitivity of both techniques.ResultsOn average, samples obtained via the PD-CSE technique contained 22% more pixels in the lesion area. The contrast differed by 28%, and the brightness differed by 31%. The two techniques were correlated using Student’s t-test, which showed a statistically significant difference. The specialists detected meniscal tears in 30 of the images obtained via the PD-CSE technique, while only 72% of these cases were detected via the PD-FSE technique.ConclusionsThe PD-CSE technique was shown to be superior to PD-FSE for all of the evaluated properties, making its selection preferable.