Two-dimensional Echo Research Articles

Evaluation of optimised 3D turbo spin echo and gradient echo MR pulse sequences of the knee at 3T and 1.5T

IntroductionTo investigate the impact of parameter optimisation for novel three-dimensional 3D sequences at 1.5T and 3T on resultant image quality. MethodsFollowing institutional review board approval and acquisition of informed consent, MR phantom and knee joint imaging on healthy volunteers (n = 16) was performed with 1.5 and 3T MRI scanners, respectively incorporating 8- and 15-channel phased array knee radiofrequency coils. The MR phantom and healthy volunteers were prospectively scanned over a six-week period. Acquired sequences included standard two-dimensional (2D) turbo spin echo (TSE) and novel three-dimensional (3D) TSE PDW (SPACE) both with and without fat-suppression, and T2∗W gradient echo (TrueFISP) sequences. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured for knee anatomical structures. Two musculoskeletal radiologists evaluated anatomical structure visualisation and image quality. Quantitative and qualitative findings were investigated for differences using Friedman tests. Inter- and intra-observer agreements were determined with κ statistics. ResultsPhantom and healthy volunteer images revealed higher SNR for sequences acquired at 3T (p-value <0.05). Generally, the qualitative findings ranked images acquired at 3T higher than corresponding images acquired at 1.5T (p < 0.05). 3D image data sets demonstrated less sensitivity to partial volume averaging artefact (PVA) compared to 2D sequences. Inter- and intra-observer agreements for evaluation across all sequences ranged from 0.61 to 0.79 and 0.71 to 0.92, respectively. ConclusionBoth 2D and 3D images demonstrated higher image quality at 3T than at 1.5T. Optimised 3D sequences performed better than the standard 2D PDW TSE sequence for contrast resolution between cartilage and joint fluid, with reduced PVA artefact. Implications for practiceWith rapid advances in MRI scanner technology, including hardware and software, the optimisation of 3D MR pulse sequences to reduce scan time while maintaining image quality, will improve diagnostic accuracy and patient management in musculoskeletal MRI.

Magnetic resonance diffusion tensor imaging of cervical microstructure in normal early and late pregnancy in vivo

Cervical remodeling is an important aspect of birth timing. Before cervical ripening, the collagen fibers are arranged in a closely interweaved network, but during ripening, the fibers become disorganized and the cervix becomes more hydrated. To quantitatively measure cervical remodeling, we need a noninvasive method to monitor changes in cervical collagen fiber organization and hydration invivo. To use diffusion tensor imaging to image and quantify the spatial and temporal differences in cervical microstructure between normal early and late pregnancies. After institutional review board approval and consent, a group of healthy women in early pregnancy (22 patients at 12-14 weeks' gestation) and a group in late pregnancy (27 patients at 36-38 weeks' gestation) underwent magnetic resonance imaging on a Siemens MAGNETOM Vida 3 Tesla unit. Diffusion tensor imaging of the cervix in the axial plane was performed with a two-dimensional single-shot echo planar imaging diffusion-weighted sequence. In early and late pregnancy groups, the differences of the diffusion tensor imaging measures were compared between the subglandular zone and the outer stroma regions of the cervix. In addition, the diffusion tensor imaging measures were compared between the early and late pregnancy groups. Finally, for the late pregnancy group, the diffusion tensor imaging measures were compared between the primipara and multipara groups. Diffusion tensor imaging measures of microstructure significantly differed between the subglandular zone and outer stroma regions of the cervix in both early and late pregnancies. In the subglandular zone, fractional anisotropy was lower in the late pregnancy group than in the early pregnancy group (0.37 [0.34-0.42] vs 0.50 [0.43-0.58]; P<.0005), suggesting increased collagen fiber disorganization in this zone. In addition, mean diffusivity was higher in the late pregnancy group than in the early pregnancy group (1.84 [1.73-2.02] mm2/sec×10-3 vs 1.56 [1.42-1.69] mm2/sec×10-3; P=.001), suggesting increased hydration in the subglandular zone. In the outer stroma, neither fractional anisotropy (0.44 [0.40-0.50] vs 0.41 [0.37-0.43]; P=.095) nor mean diffusivity (2.09 [1.92-2.25] mm2/sec×10-3 vs 2.12 [2.04-2.24] mm2/sec×10-3; P=.269) significantly differed between early pregnancy and late pregnancy, suggesting insignificant temporal microstructural changes in this cervical zone. Diffusion tensor imaging measures did not significantly differ between cervixes from primiparous and multiparous women in late pregnancy. This invivo study demonstrates that diffusion tensor imaging can noninvasively quantify the microstructural differences in collagen fiber organization and hydration in cervical subregions between early pregnancy and late pregnancy.

Clinical utility of fat-suppressed 3-dimensional controlled aliasing in parallel imaging results in higher acceleration sampling perfection with application optimized contrast using different flip angle evolutions MRI of the knee in adults.

To compare htree-dimensional CAIPIRINHA SPACE and two-dimensional turbo spin echo (2D TSE) MRI in the diagnosis of knee pathology in symptomatic adult patients. From February to September in 2018, 120 patients who underwent a knee MRI using both 3D CAIPIRINHA SPACE and 2D TSE MRI were enrolled. The signal-to-noise ratios (SNRs) and contrast-to-noise ratio (CNR) of the 2D and 3D MRI were compared using a paired t-test. Two radiologists independently evaluated both 2D and 3D MRI images using scoring systems for the menisci, ligaments, and cartilage. Intermethod, inter- and intrareader agreements were determined using an intraclass correlation coefficient (ICC). The diagnostic performance of both methods was measured in 44 patients with arthroscopy. The mean scan time of 3D CAIPIRINHA SPACE MRI (4' 43") was shorter than that of 2D TSE MRI (17' 27"). The mean SNR and CNR of 3D CAIPIRINHA SPACE was higher than those of 2D TSE MRI (mean difference, 3.97 of SNR and 1.58 of CNR; p < 0.001 and p = .038, respectively). Intermethod (ICC, 0.84-1.0) and inter-reader (ICC, 0.75-0.97), and intra-reader agreements (ICC, 0.87-1.0) were good or excellent. The diagnostic accuracy of 3D CAIPIRINHA SPACE sequence was equal for ligament (95.5%) and better for meniscal and cartilage evaluation (84.1% each), compared to 2D TSE MRI (79.5% each). The fat-suppressed 3D CAIPIRINHA SPACE MRI maybe useful in clinical practice for the evaluation of the knee in place of the 2D conventional MRI protocol. 1. The 3D CAIPIRINHA SPACE MRI of the knee joint may be acceptable to be used in clinical practice showing comparable imaging quality compared to conventional 2D TSE MRI.2. Compared with arthroscopic findings as the gold-standard, the diagnostic performance of 3D CAIPIRINHA SPACE MRI was equal or better for knee joint evaluation than that of 2D TSE MRI, as well as with shorter scan time.

Evaluation of feasibility and image quality of a new radial quantitative T2 weighted imaging sequence for liver MRI

ObjectivesTo evaluate the clinical feasibility of a new T2 weighted sequence to calculate T2 relaxation times (T2RT) of liver lesions using two-dimensional radial turbo spin echo (2DRTSE) and to evaluate this sequence by performing image quality and relaxation time comparison of multiple liver lesions. Materials and methodsThis prospective analysis of 2DRTSE sequences (using 22 echoes) was performed in 19 patients with 36 liver lesions. Two radiologists independently obtained T2RTs for liver lesions and scored image quality and image artifacts. Lesions were classified as cyst, hemangioma, solid, or necrotic. T2RT values were compared. Inter-reader agreement was evaluated. ResultsThe 2DRTSE images were considered good quality with few artifacts by both radiologists. Nineteen patients were included in the study, with a total of 36 liver lesions. Two of the liver lesions were classified as cysts, 7 as hemangiomas, 4 as necrotic lesions, and 23 as solid lesions. The concordance correlation coefficient was 0.996 for the calculated T2RT of each liver lesion between the two readers, indicating good agreement. There was statically significant difference of the calculated T2RT for each lesion type. ConclusionThe 2DRTSE sequence can be performed and provides good T2W image quality and a quantitative T2RT map of the entire abdomen. The liver lesions can be distinguished based on the calculated T2RT using this technique. 2DRTSE could potentially supplant the current T2-weighted imaging sequence with the benefit of quantitative T2RTs.

Quality comparison between three-dimensional T2-weighted SPACE and two-dimensional T2-weighted turbo spin echo magnetic resonance images for the brachytherapy planning evaluation of prostate and periprostatic anatomy

PurposeThe purpose of this study was to compare an isotropic three-dimensional (3D) T2-weighted sequence sampling perfection with application-optimized contrasts by using flip angle evolution (SPACE) with an axial two-dimensional T2-weighted turbo spin echo (TSE) sequence with regard to overall image quality and the delineation of normal prostate and periprostatic anatomy for low-dose-rate prostate cancer brachytherapy planning evaluation. Methods and MaterialsPatients (n = 69) with prostate cancer who had pelvic magnetic resonance imaging (MRI) for low-dose-rate brachytherapy treatment planning were included. Three radiologists independently assessed the visibility of nine anatomic structures on each sequence by using a 5-point scale and overall image quality by using a 4-point scale. The significance of the differences in diagnostic performance was tested with a Wilcoxon signed rank test. ResultsNo significant intersequence differences were found for most (7/9) anatomical structures and overall image quality. The mean scores for visibility of anatomical structures on the 3D SPACE and 2D TSE sequences, respectively, were as follows: the zonal anatomy (3.7; 3.9, p = 0.05), prostate capsule (3.9; 4.0, p = 0.08), neurovascular bundle (2.9; 2.9, p = 0.9), rectoprostatic angle (3.8; 3.8, p = 0.35), rectum (4.2; 4.3, p = 0.26), urethra (3.8; 3.9, p = 0.12), urinary bladder (4.6; 4.6, p = 0.61), and overall image quality (2.9; 2.9, p = 0.33). 3D SPACE was superior for delineation of the genitourinary diaphragm (3.8; 3.6, p = 0.003), whereas 2D TSE was superior for delineation of the seminal vesicles (3.5; 4.0, p < 0.0001). ConclusionsAnatomic delineation of the prostatic and periprostatic anatomy provided by the 3D SPACE sequence is as robust in quality as that provided by a conventional 2D TSE sequence with superior delineation of the genitourinary diaphragm. For MRI-based brachytherapy treatment planning, the 3D SPACE sequence with subcentimeter isotropic resolution can replace the 2D TSE sequence and be incorporated into standard MRI protocols.

SUN-914 Peptide Receptor Radionuclide Therapy for an Inoperable Small Cell Neuroendocrine Tumor in the Philippines

Background: Peptide Receptor Radionuclide Therapy treatment for neuroendocrine tumors is a well-tolerated treatment option for patients not amenable to receiving chemotherapy and radiotherapy. Clinical Case: A 42-year-old female was evaluated by a cardiologist for complaints of new onset recurrent throat discomfort, chest pain and palpitations. Two-Dimensional echo showed a large extra-cardiac mass compressing the main pulmonary artery. Chest CT with contrast reveal a 5.8 x 6.0 x 7.2 cm enhancing lobulated anterior mediastinal mass. Attempts to excise the mass failed due to the proximity to major blood vessels. Biopsy revealed a Carcinoid Tumor that was Chromogranin A positive but was asymptomatic for carcinoid syndrome. Everolimus treatment was given but was halted due to stomatitis. The patient remained fully functional. Re-evaluation of the mass with FDG PET show an increase in tumor size. Biopsy tissue re-testing showed small cell neuroendocrine carcinoma. Urine 5-hydroxyindoleacetic acid, plasma 5-hydroxyindoleacetic acid, and serum Chromogranin A were normal. A 68Ga-DOTATATE PET/CT scan reveal a slight increase in the mass that was intensely DOTATATE-avid. Two sessions of Peptide Receptor Radionuclide Therapy (PRRT) Lutetium-177 DOTATATE given at an 8-month interval were given. SPECT/CT re-evaluation showed good response and no evidence of metastases. A 68Ga-DOTA-octreotate PET-CT scan was done and showed good response to treatment. According to treatment guidelines, small cell neuroendocrine carcinoma that are non-resectable are treated with radiotherapy plus chemotherapy. But since the patient is fully functional and has minimal symptoms, other means of treatment such as PRRT may be well suited due to good tolerability and good treatment outcomes. Conclusion: PRRT is a promising treatment for NETs that is well tolerated giving better functionality and quality of life for patients opting not to undergo chemotherapy and radiotherapy. Reference: Cadiot, G. (2019). French and European Neuroendocrine Tumor Society consensus guidelines. Annales d’Endocrinologie, 80(3), p.174.

Excited-State Vibronic Dynamics of Bacteriorhodopsin from Two-Dimensional Electronic Photon Echo Spectroscopy and Multiconfigurational Quantum Chemistry.

Owing to the ultrafast time scale of the photoinduced reaction and high degree of spectral overlap among the reactant, product, and excited electronic states in bacteriorhodopsin (bR), it has been a challenge for traditional spectroscopies to resolve the interplay between vibrational dynamics and electronic processes occurring in the retinal chromophore of bR. Here, we employ ultrafast two-dimensional electronic photon echo spectroscopy to follow the early excited-state dynamics of bR preceding the isomerization. We detect an early periodic photoinduced absorptive signal that, employing a hybrid multiconfigurational quantum/molecular mechanical model of bR, we attribute to periodic mixing of the first and second electronic excited states (S1 and S2, respectively). This recurrent interaction between S1 and S2, induced by a bond length alternation of the retinal chromohore, supports the hypothesis that the ultrafast photoisomerization in bR is initiated by a process involving coupled nuclear and electronic motion on three different electronic states.

Echo rozwiązuje kliniczną zagadkę — opis przypadku amyloidozy serca

We present the case of a 53-year-old woman with New York Heart Association (NYHA) class III heart failure, despite optimal pharmacological therapy. Her medical history included: myocardial infarction with nonobstructive coronary arteries (MINOCA), heart failure with reduced ejection fraction and quadrantanopia with sensory neuropathy diagnosed as ischaemic stroke. Transthoracic echocardiography showed significant left ventricular hypertrophy with a ‘granular’ myocardial texture, global systolic dysfunction and restrictive mitral filling pattern. Two-dimensional (2D) transthoracic echo strain analysis demonstrated decreased global longitudinal strain with apical sparing, and helped to fit all the pieces of the jigsaw together to reach a consistent clinical diagnosis of cardiac amyloidosis.

Determination of sulfur-33 electric-field-gradient tensors in elemental sulfur by 2D nutation echo NQR

Four 33S quadrupolar frequencies of 33S-enriched elemental sulfur, α-S8, were observed in the range of 23.122–23.280 MHz at the temperature of 140 K. Two-dimensional nutation echo 33S NQR techniques were carried out for each quadrupolar frequency, providing the 33S EFG tensor information; the quadrupolar coupling constant, CQ, of 44.6(5) - 45.7(4) MHz and the asymmetry parameter, ηQ, of 0.30(10) – 0.49(7). Quantum chemical calculations were performed to complete the spectral assignment, and to obtain the 33S EFG tensor orientations with respect to the molecular frame.

Assessment of knee pain from MR imaging using a convolutional Siamese network.

It remains difficult to characterize the source of pain in knee joints either using radiographs or magnetic resonance imaging (MRI). We sought to determine if advanced machine learning methods such as deep neural networks could distinguish knees with pain from those without it and identify the structural features that are associated with knee pain. We constructed a convolutional Siamese network to associate MRI scans obtained on subjects from the Osteoarthritis Initiative (OAI) with frequent unilateral knee pain comparing the knee with frequent pain to the contralateral knee without pain. The Siamese network architecture enabled pairwise learning of information from two-dimensional (2D) sagittal intermediate-weighted turbo spin echo slices obtained from similar locations on both knees. Class activation mapping (CAM) was utilized to create saliency maps, which highlighted the regions most associated with knee pain. The MRI scans and the CAMs of each subject were reviewed by an expert radiologist to identify the presence of abnormalities within the model-predicted regions of high association. Using 10-fold cross-validation, our model achieved an area under curve (AUC) value of 0.808. When individuals whose knee WOMAC pain scores were not discordant were excluded, model performance increased to 0.853. The radiologist review revealed that about 86% of the cases that were predicted correctly had effusion-synovitis within the regions that were most associated with pain. This study demonstrates a proof of principle that deep learning can be applied to assess knee pain from MRI scans. • Our article is the first to leverage a deep learning framework to associate MR images of the knee with knee pain. • We developed a convolutional Siamese network that had the ability to fuse information from multiple two-dimensional (2D) MRI slices from the knee with pain and the contralateral knee of the same individual without pain to predict unilateral knee pain. • Our model achieved an area under curve (AUC) value of 0.808. When individuals who had WOMAC pain scores that were not discordant for knees (pain discordance < 3) were excluded, model performance increased to 0.853.

Comparative quantification of primary mitral regurgitation by computer modeling and simulated echocardiography.

Clinical investigations have demonstrated that mitral regurgitation (MR) quantification using echocardiography (echo) may significantly underestimate or overestimate the regurgitant volume, especially for two-dimensional (2D) echo. Computer modeling and simulated echo were conducted to evaluate the fundamental assumptions in the echo quantification of primary MR that is due to posterior mitral leaflet prolapse. The theoretical flaw of the proximal isovelocity surface area (PISA) method originates from the assumption that the MR flow rate is the product of the isovelocity surface area and aliasing velocity, which is only valid when the velocity vectors are perpendicular to the isovelocity surface. Other factors such as the Doppler angle effect, the view planes of 2D echo, and the single time instant of PISA were also analyzed. We find that the hemielliptic PISA method gives the smallest error for moderate and severe MR cases compared with other PISA methods. Compared with the PISA method, the volumetric technique (VT) is theoretically more robust. By considering correction factors that are caused by nonflat velocity profiles and the closing volume of the aortic valve, the accuracy of the VT method can be significantly improved. The corrected volumetric technique provides more accurate results compared with the PISA methods, especially for mild MR.NEW & NOTEWORTHY We evaluate the accuracy of common echocardiography techniques for the quantification of primary mitral regurgitations using computer modeling. The hemielliptic proximal isovelocity surface area (PISA) method gives the smallest error (within 15%) for moderate and severe mitral regurgitation cases compared with other PISA methods. The volumetric method is theoretically more robust than the PISA method. The accuracy of the volumetric method can be improved by a correction factor around 0.7 because of the nonflat velocity profiles and the closing volume of the aortic valve.

Serum visfatin level in prediabetics and its relation to left ventricular function

IntroductionVisfatin is a molecule of clinical relevance, released mainly from visceral fat (hence it named as such) and could be a promising biomarker with diagnostic and prognostic significance in metabolic syndrome. Very little is known about visfatin and its relation with prediabetes.ObjectiveThe present study was conducted to demonstrate the relationship between serum visfatin level and prediabetes and its relation to left ventricular function.Patients and methodsWe studied 60 prediabetic patients recently diagnosed according to ADA criteria 2014 and classified into two groups according to the BMI. They were compared with 30 healthy matched controls. All groups underwent complete history taking, general examination, laboratory investigations (including homeostasis model assessment-insulin resistance and serum visfatin level), and two-dimensional transthoracic echo Doppler study at baseline and 8 months thereafter only for the patient groups.ResultsThis study showed that there is a positive correlation between serum visfatin level and prediabetes and left ventricular function.ConclusionSerum visfatin is an early and strong predictor of prediabetes and left ventricular dysfunction.

P5974Prognostic value of global tangential strain by three-dimensional echocardiography heart failure patients with intermediate ECG criteria for cardiac resynchronization therapy

Abstract Background In the current clinical guidelines, cardiac resynchronization therapy (CRT) is recommended in heart failure (HF) patients with left bundle branch block (LBBB) with QRS width ≥150ms as Class I indication. In terms of HF patients with intermediate ECG criteria, prediction for benefit of CRT is still controversial in routine echocardiography. Purpose The aim was to assess whether three-dimensional (3D) echocardiographic indexes of global LV function at baseline has a prognostic value following CRT implantation in patients who fulfilled with intermediate ECG criteria. Methods We studied 62 HF patients who fulfilled with the indication criteria of CRT implantation according to current the clinical guidelines. In addition to routine two-dimensional echo, 3D echo dataset was acquired for determination of 3D global tangential strain (GTS) and 3D global longitudinal strain (GLS). We tracked predefined unfavorable outcomes for 3 years after CRT implantation: death, hospitalization due to worsening HF. Results LBBB with QRS width ≥150ms was evident in 26 of 62 patients (aged 68±11 years with 160±26 ms of QRS duration and 29±7% of LV ejection fraction), and the other 36 patients only fulfilled intermediate ECG criteria (QRS width 120–149ms or non-LBBB). Unfavorable events occurred in 21 patients (34%). The median GTS was −15.4%. Although GLS was not predictive, GTS greater than −15.4% had high probability of unfavorable outcomes over 3 years (Log-rank, p&lt;0.05). There is no difference in the probability of unfavorable outcomes between LBBB and intermediate ECG criteria. Baseline GTS in patients with intermediate ECG criteria was associated with unfavorable outcomes: −12.6±2.6% vs. −17.3±3.8% (p&lt;0.05). Outcome was better in the intermediate ECG criteria patients with GTS ≤−15.4% than in those with LBBB and in those with intermediate ECG criteria patients with GTS &gt;−15.4% (Log-rank: p&lt;0.05, p&lt;0.0001, respectively). Conclusions Baseline GTS by 3D echocardiography is useful for predicting outcome over 3 years after CRT implantation regardless of the ECG criteria for CRT indication.

Two-Dimensional Spatial Coherence for Ultrasonic DMAS Beamforming in Multi-Angle Plane-Wave Imaging

Ultrasonic multi-angle plane-wave (PW) coherent compounding relies on delay-and-sum (DAS) beamforming of two-dimensional (2D) echo matrix in both the dimensions PW transmit angle and receiving channel to construct each image pixel. Due to the characteristics of DAS beamforming, PW coherent compounding may suffer from high image clutter when the number of transmit angles is kept low for ultrafast image acquisition. Delay-multiply-and-sum (DMAS) beamforming exploits the spatial coherence of the receiving aperture to suppress clutter interference. Previous attempts to introduce DMAS beamforming into multi-angle PW imaging has been reported but only in either dimension of the 2D echo matrix. In this study, a novel DMAS operation is proposed to extract the 2D spatial coherence of echo matrix for further improvement of image quality. The proposed 2D-DMAS method relies on a flexibly tunable p value to manipulate the signal coherence in the beamforming output. For p = 2.0 as an example, simulation results indicate that 2D-DMAS outperforms other one-dimensional DMAS methods by at least 9.3 dB in terms of ghost-artifact suppression. Experimental results also show that 2D-DMAS provides the highest improvement in lateral resolution by 32% and in image contrast by 15.6 dB relative to conventional 2D-DAS beamforming. Nonetheless, since 2D-DMAS emphasizes signal coherence more than its one-dimensional DMAS counterparts, it suffers from the most elevated speckle variation and the granular pattern in the tissue background.

Evaluation of cortical bone perfusion using dynamic contrast enhanced ultrashort echo time imaging: a feasibility study.

Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) has been used to study perfusion in a wide variety of soft tissues including the bone marrow. Study of perfusion in hard tissues such as cortical bone has been much more limited because of the lack of detectable MR signal from them using conventional pulse sequences. However, two-dimensional (2D) ultrashort echo time (UTE) sequences detect signal from cortical bone and allow fast imaging of this tissue. In addition, adiabatic 2D inversion recovery UTE (IR-UTE) sequences can provide excellent signal suppression of soft tissues, such as muscle and marrow, and allow cortical bone to be seen with high contrast and reduced artefacts. We aimed to assess the feasibility of using 2D UTE and 2D IR-UTE sequences to perform DCE-MRI in the cortical bone of rabbits and human volunteers. Cortical bone perfusion was studied in rabbits (n=12) and human volunteers (n=3) using 2D UTE and 2D IR-UTE sequences on a clinical 3T scanner. Dynamic data with an in-plane resolution of ~0.5×0.5 mm2, single slice thickness of 3 mm for rabbits and 10 mm for human volunteers, and temporal resolution of 23 s for 2D UTE imaging of rabbits, 28 s for 2D UTE imaging of human volunteers, and 60 s for 2D IR-UTE imaging of both the rabbits and human volunteers were acquired before and after the injection of a Gd contrast agent (Gd-BOPTA: Multihance; Bracco Imaging SpA, Milan, Italy). The dose was 0.06 mmol/kg for rabbits and 0.2 mmol/kg for human subjects. Kinetic analyses based on the Brix model, as well as simple calculations of maximum enhancement (ME) and enhancement slope (ES), were performed. The 12 rabbits showed a mean Ktrans of 0.36±0.07 min-1, Kep of 8.42±3.17 min-1, ME of 28.30±6.83, ES of 0.35±0.18 for the femur with the 2D UTE sequence, and a mean Ktrans of 0.45±0.10 min-1, Kep of 9.80±0.50 min-1, ME of 48.84±12.12, and ES of 0.69±0.27 for the femur with the 2D IR-UTE sequence. Lower ME and ES values were observed in the tibial midshaft of healthy human volunteers compared to rabbits. These results show that 2D UTE and 2D IR-UTE sequences are capable of detecting dynamic contrast enhancement in cortical bone in both rabbits and healthy human volunteers. Clinical studies with these techniques are likely to be feasible.

Accelerating anatomical 2D turbo spin echo imaging of the ankle using compressed sensing

IntroductionTo assess the feasibility and diagnostic value of compressed sensing for accelerating two-dimensional turbo spin echo imaging of the ankle. Materials and methodsAnkles of 20 volunteers were scanned (mean age 30.2 ± 7.3 years, 13 men) at 3 T MRI. Coronal and sagittal intermediate-weighted (IM) sequences with fat saturation as well as axial T2- and coronal T1-weighted sequences were acquired using parallel imaging based on sensitivity encoding (SENSE) only as well as with a combination of compressed sensing (CS) and SENSE. Compressed sensing is a technique that acquires less data through k-space random undersampling and enables a reduction in total acquisition time by 20%. All images were reviewed by two radiologists, image quality was graded using a 5-point Likert scale and signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of different anatomical structures of the ankle were assessed and compared between sequences with SENSE only and with the combination of CS and SENSE using Wilcoxon signed-rank tests and Cohen’s kappa. ResultsThere was a substantial to perfect agreement for the rating between the images acquired with SENSE only and with the combination of CS and SENSE when assessing cartilage, subchondral bone and ligaments (κ = 0.75 - 0.89). SNR was slightly higher for the combination of CS and SENSE sequences compared to the sequences acquired with SENSE only, yet this finding was not significant (P = 0.18-0.62). Moreover, CNR of cartilage/fluid, subchondral bone/cartilage, ligaments/fluid and ligaments/fat did not show significant differences between the sequences acquired with SENSE only and the combination of CS and SENSE (P > 0.05). The interreader agreement was substantial to excellent for both techniques (κ=0.75 - 0.89). ConclusionsCompressed sensing reduced the acquisition time of conventional MR imaging of the ankle by 20% without decreasing diagnostic image quality, SNR and CNR.

Three-dimensional T1-weighted gradient echo is a suitable alternative to two-dimensional T1-weighted spin echo for imaging the canine brain.

Volumetric imaging (VOL), a three‐dimensional magnetic resonance imaging (MRI) technique, has been described in the literature for evaluation of the human brain. It offers several advantages over conventional two‐dimensional (2D) spin echo (SE), allowing rapid, whole‐brain, isotropic imaging with submillimeter voxels. This retrospective, observational study compares the use of 2D T1‐weighted SE (T1W SE), with T1W VOL, for the evaluation of dogs with clinical signs of intracranial disease. Brain MRI images from 160 dogs who had T1W SE and T1W VOL sequences acquired pre‐ and postcontrast, were reviewed for presence and characteristics of intracranial lesions. Twenty‐nine of 160 patients were found to have intracranial lesions, all visible on both sequences. Significantly better grey‐white matter (GWM) differentiation was identified with T1W VOL (P < .001), with fair agreement between the two sequences (weighted κ = 0.35). Excluding a mild reduction in lesion intensity in three dogs precontrast on the T1W VOL images compared to T1W SE, and meningeal enhancement noted on the T1W VOL images in one dog, not identified on T1W SE, there was otherwise complete agreement between the two sequences. The T1W VOL sequence provided equivalent lesion evaluation and significantly improved GWM differentiation. Images acquired were of comparable diagnostic quality to those produced using a conventional T1W SE technique, for assessment of lesion appearance, number, location, mass effect, and postcontrast enhancement. T1W VOL, therefore, provides a suitable alternative T1W sequence for canine brain evaluation and can facilitate a reduction in total image acquisition time.

Pyrene, a Test Case for Deep-Ultraviolet Molecular Photophysics.

We determined the complete relaxation dynamics of pyrene in ethanol from the second bright state, employing experimental and theoretical broadband heterodyne detected transient grating and two-dimensional photon echo (2DPE) spectroscopy, using pulses with duration of 6 fs and covering a spectral range spanning from 250 to 300 nm. Multiple lifetimes are assigned to conical intersections through a cascade of electronic states, eventually leading to a rapid population of the lowest long-living excited state and subsequent slow vibrational cooling. The lineshapes in the 2DPE spectra indicate that the efficiency of the population transfer depends on the kinetic energy deposited into modes required to reach a sloped conical intersection, which mediates the decay to the lowest electronic state. The presented experimental–theoretical protocol paves the way for studies on deep-ultraviolet-absorbing biochromophores ubiquitous in genomic and proteic systems.

Short-lag spatial coherence imaging using minimum variance beamforming on dual apertures

BackgroundShort-lag spatial coherence (SLSC) imaging, a newly proposed ultrasound imaging scheme, can offer a higher lesion detectability than conventional B-mode imaging. It requires a high focusing quality which can be satisfied by the synthetic aperture imaging mode. However, traditional nonadaptive synthesis for the SLSC still offers an unsatisfactory resolution. The spatial coherence estimation on the receive aperture cannot fully utilize the coherence information in two-dimensional (2D) echo data.MethodsTo overcome these drawbacks, an improved SLSC scheme with adaptive synthesis on dual apertures is proposed in this paper. The minimum variance (MV) beamformer is applied in synthesizing both the receiving and transmitting apertures, while the SLSC function is estimated on both apertures as well. In this way, the resolution is enhanced by the MV implementation, while the coherence in dual apertures is fully utilized.ResultsSimulations, phantom experiments, and in vivo studies are conducted to evaluate the performance of the proposed method. Results demonstrate that the proposed method achieves the best performance in terms of the contrast ratio (CR), contrast-to-noise ratio (CNR), and the speckle signal-to-noise ratio (SNR). Specifically, compared with the delay-and-sum (DAS) method, the proposed method achieves 42.5% higher CR, 412.7% higher CNR, and 402.9% higher speckle SNR in simulations. The resolution is also better than the DAS and conventional SLSC beamformers.ConclusionsThe proposed method is a promising technique for improving the SLSC imaging quality and can provide better visualization for medical diagnosis.

Sulfur-33 NQR investigation of the electric-field-gradient tensor in an organosulfur compound

Abstract 33S nuclear quadrupole resonance (NQR) frequencies of 33S-enriched S-4-phenyl 4-toluenethiosulfonate were observed in the range of 22.96–23.31 MHz at temperatures between 110 and 300 K. A single sharp signal was observed at all the temperatures. The two-dimensional (2D) nutation echo method was applied at 150 K, providing the 33S electric field gradient (EFG) tensor information, the quadrupolar coupling constant, C Q, of 42.3 MHz and the asymmetry parameter, ηQ, of 0.80(9). Quantum chemical calculations were performed to obtain the 33S EFG tensor orientations with respect to the molecular frame.