Contrast Image Sequences Research Articles

Approach to imaging modalities in the setting of suspected infection.

Imaging plays an important role in the workup of musculoskeletal infection, in conjunction with clinical history and physical exam. There are multiple imaging modalities that can be of clinical utility in the setting of suspected infection, each with their own benefits and limitations. Radiography is a low-cost, accessible modality providing a broad osseous overview, but can be insensitive for early osteomyelitis. Ultrasound plays a more limited role in the workup of musculoskeletal infection, but can be useful in the pediatric population or for real-time guidance for joint and soft tissue aspirations. Computed tomography (CT) plays an important role in the timely and accurate diagnosis of critically ill patients in the emergency setting. Its superior soft tissue characterization allows for diagnosis of abscesses, and it can help confirm the clinical diagnosis of necrotizing fasciitis when soft tissue gas is present. Magnetic resonance imaging (MRI) is often the modality of choice in the diagnosis of infection, as its superior contrast resolution allows for clear delineation of the presence and extent of both soft tissue infection and osteomyelitis. Additionally, the use of intravenous contrast and advanced imaging sequences such as diffusion weighted imaging (DWI) further increases the diagnostic utility of MRI in the assessment for infection. Familiarity with the diagnostic utility of each imaging modality will allow the radiologist to appropriately guide imaging workup in the setting of clinically suspected infection.

P34 TAKOTSUBO SYNDROME OR UNKNOWN MYOCARDIAL ISCHEMIA? THE ROLE OF CARDIAC MAGNETIC RESONANCE IN DIFFERENTIAL DIAGNOSIS

Abstract There are numerous clinical conditions in which symptoms and signs may overlap, among these myocardial Ischemia in the absence of obstructive coronaropathy (INOCA/MINOCA), gets into differential diagnosis with a plethora of clinical pictures such as Takotsubo syndrome, myocarditis and cardiomyopathies. In this setting, cardiac magnetic resonance has a critical discriminating role. Herein we report the clinical case of a 52–year old patient suffering from hypertension and dyslipidaemia, with a history of chest pain episodes and recent intense psychophysical stress. After symptoms exacerbation, ambulance was called, loss of conscience was witnessed, observing ventricular fibrillation, subjected to prompt DC shock. Once in Emergency room, ECG showed ST–elevation in V1, V2 and AVR for which urgent coronary angiography was performed. It surprisingly resulted negative for epicardial coronary artery disease. Moderate left ventricular dysfunction (LVEF 45%) was found on 2D ultrasound along with apex akinesia, while mild elevation myocardial necrosis enzymes was seen at blood tests. The clinical picture characterized by female sex, history of psychophysical stress, by association of chest pain, ischemic type alterations of repolarization at ECG, akinesia of the apex and the concomitant slight elevation of myocardial necrosis enzymes in the absence of epicardial coronary lesions, highly suggested Tako–Tsubo Syndrome. In order to confirm the diagnosis, cardiac MRI was performed which, unexpectedly, showed the presence of oedema on T2–weighted STIR sequences at the level of the left ventricular apex, associated to same site transmural fibrosis at post–contrast imaging sequences, thus eliciting the hypothesis of a MINOCA. After a new retrosternal pain with transient ST–elevation in V1, a IVUS – guided new coronary angiography examination was performed, resulting intoIVA diffuse coronary spasm, reduced after intravenous nitrate administration. Final diagnosis was “MINOCA complicated by primary VF‘‘ and a subcutaneous AICD implant CMR imaging by virtue of its ability to provide information about cardiac structure and function and simultaneously, to define the characterization of tissues, together with the data of dynamic coronary spasm, proved to be essential in this case to establish the diagnosis, often misunderstood, of MINOCA, hence allowing to define the best therapeutic strategy. ​

Imaging in Gastric Cancer: Current Practice and Future Perspectives

Gastric cancer represents one of the most common oncological causes of death worldwide. In order to treat patients in the best possible way, the staging of gastric cancer should be accurate. In this regard, endoscopy ultrasound (EUS) has been considered the reference standard for tumor (T) and nodal (N) statuses in recent decades. However, thanks to technological improvements, computed tomography (CT) has gained an important role, not only in the assessment of distant metastases (M status) but also in T and N staging. In addition, magnetic resonance imaging (MRI) can contribute to the detection and staging of primary gastric tumors thanks to its excellent soft tissue contrast and multiple imaging sequences without radiation-related risks. In addition, MRI can help with the detection of liver metastases, especially small lesions. Finally, positron emission tomography (PET) is still considered a useful diagnostic tool for the staging of gastric cancer patients, with a focus on nodal metastases and peritoneal carcinomatosis. In addition, it may play a role in the treatment of gastric cancer in the coming years thanks to the introduction of new labeling peptides. This review aims to summarize the most common advantages and pitfalls of EUS, CT, MRI and PET in the TNM staging of gastric cancer patients.

Synchronized strobed phase contrast and fluorescence microscopy: the interlaced standard reimagined.

We propose a simple, cost-effective method for synchronized phase contrast and fluorescence video acquisition in live samples. Counter-phased pulses of phase contrast illumination and fluorescence excitation light are synchronized with the exposure of the two fields of an interlaced camera sensor. This results in a video sequence in which each frame contains both exposure modes, each in half of its pixels. The method allows real-time acquisition and display of synchronized and spatially aligned phase contrast and fluorescence image sequences that can be separated by de-interlacing in two independent videos. The method can be implemented on any fluorescence microscope with a camera port without needing to modify the optical path.

Evaluation of Takayasu's arteritis activity by ultrasound localization microscopy

Abstract Objectives Use of sulphur hexafluoride microbubbles (MB) with ultrasound can provide arterial wall enhancement. The use of ultrafast imaging with MB super-localization offers the possibility of ultrasound localization microscopy (ULM) and thus a visualization of in vivo carotid vasa vasorum. We aim to perform in vivo Vasa vasorum imaging in the carotid wall in Takayasu's arteritis and to provide a correlation with the disease's activity. Methods Patients with Takayasu arteritis were consecutively included in the national referral centre. Assessment of activity was performed by NIH activity index, with measurement of biological inflammation, morphological evaluation by computed tomography (CT) angiography, and 18-fluorodeoxyglucose CT scan. Ultrafast ultrasound imaging was performed with a 7 MHz central frequency linear probe. A dedicated contrast imaging sequence (plane waves with 8 angles, frame rate 500 Hz, voltage 8 V, duration of 8 s), coupled with the intravenous injection of sulphur hexafluoride MB allow us to store the raw radio frequency data of the MB passage. After a pre-processing step to accumulate frames properly including a frames selection and a movement correction, the MB were localized then tracked, allowing reconstruction of the vasa vasorum. The inflammation was quantified through MB tracked and normalized for inter acquisition comparison. Results 16 patients were included. 5 patients (median age 35.8 [24.5–46.0] years, 3 women) had active disease and 11 patients (37.2 [31.7–47.3] years, 9 women) had quiescent disease. The passage of MB allowed the visualisation of microvessels within the arterial wall for active cases. The number of MB detected per second in the wall was 118 [80–169] for active cases vs. 13 [10–15] for quiescent cases (p=0.0005). Conclusion ULM allows visualization of microvessels within the carotid wall, with significantly greater MB passage in active Takayasu arteritis. ULM provides for the first time a precise visualization in vivo of the vasa vasorum and gives access to quantification of the vascularity of the arterial wall. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Société française de cardiologie

The SHARDDS survey: limits on planet occurrence rates based on point sources analysis via the Auto-RSM framework

Context. In the past decade, high contrast imaging allowed the detection and characterisation of exoplanets, brown dwarfs, and circumstellar disks. Large surveys provided new insights about the frequency and properties of massive sub-stellar companions with separations from 5 to 300 au. Aims. In this context, our study aims to detect and characterise potential exoplanets and brown dwarfs within debris disks, considering a diverse population of stars with respect to stellar age and spectral type. We present in this paper the analysis of a set of H-band images taken by the VLT/SPHERE instrument in the context of the SHARDDS survey. This survey gathers 55 main-sequence stars within 100 pc, known to host a high-infrared-excess debris disk, allowing us to potentially better understand the complex interactions between substellar companions and disks. Methods. We rely on the Auto-RSM framework to perform an in-depth analysis of the considered targets, via the computation of detection maps and contrast curves. A clustering approach is used to divide the set of targets into multiple subsets, in order to reduce the computation time by estimating a single optimal parametrisation for each considered subset. Detection maps generated with different approaches are used along with contrast curves to identify potential planetary companions. Planet detection and planet occurrence frequencies are derived from the generated contrast curves, relying on two well-known evolutionary models, namely AMES-DUSTY and AMES-COND. Finally, we study the influence of the observing conditions and observing sequence characteristics on the performance measured in terms of contrast. Results. The use of Auto-RSM allows us to reach high contrast at short separations, with a median contrast of 105 at 300 mas, for a completeness level of 95%. A new planetary characterisation algorithm, based on the RSM framework, is developed and tested successfully, showing a higher astrometric and photometric precision for faint sources compared to standard approaches. Apart from the already known companion of HD 206893 and two point-like sources around HD 114082 which are most likely background stars, we did not detect any new companion around other stars. A correlation study between achievable contrasts and parameters characterising high contrast imaging sequences highlights the importance of the Strehl ratio, wind speed at a height of 30 meters, and presence of wind-driven halo to define the quality of high contrast images. Finally, planet detection and occurrence rate maps are generated and show, for the SHARDDS survey, a high sensitivity between 10 and 100 au for substellar companions with masses >10 MJ.

Importance of Multiparametric Magnetic Resonance Imaging in Prostate Cancer Diagnosis and Local Invasion Assessment

Amaç: Prostat kanseri (PCa) tanısı ve kanser dışı prostat hastalıklarından (KDPH) ayırımında multiparametrik manyetik rezonans görüntülemenin (mpMRG) önemi değerlendirilmiştir. 
 Materyal Metod: Aralık 2017 ile Ocak 2020 tarihleri arasında, prostat kanseri (PCa) ön tanısı ile mpMRG yapılan 99 hastanın görüntüleri retrospektif olarak değerlendirildi. Standart MpMRG çekim protokolü T2A TSE (aksiyel-koronal-sagital), T1A TSE (axial-koronal-sagital), difüzyon ağırlıklı görüntüleme (DAG) ve T1A dinamik kontrastlı inceleme (DKİ) sekanslarından oluştu. Lezyonların lokasyonu, morfolojisi, ekstraprostatik yayılımı (EPY), T2A sinyal intensite (T2SI) değerleri, difüzyon kısıtlılığı, kontrastlanma eğri paternleri, maksimum kontrastlanma değeri (Cmax), maksimum kontrastlanmaya ulaşması için geçen süre (akselerasyon zaman: AZ) değerlendirildi. Bulgular arasındaki ilişki SPSS 20.0 programı ile değerlendirildi.
 Bulgular: Değerlendirilen 99 olgunun 75’inin Prostat Ca (PCa), 24’ünün KDPH histopatolojik tanısı vardı. Tüm hastaların yaş ortalaması 66.5±7.4 idi. Periferal zon yerleşimli lezyonlarda “apparent diffusion coefficient” (ADC) (p

The muscle twitch profile assessed with motor unit magnetic resonance imaging

Localised signal voids in diffusion‐weighted (DW) images of skeletal muscle have been postulated to occur as a result of muscle fibre contraction and relaxation. We investigated the contrast mechanism of these signal voids using a combination of modelling and experimental measurements by employing DW and phase contrast (PC) imaging sequences. The DW signal and PC signal were simulated for each time point of a theoretical muscle twitch. The model incorporated compaction (simulating actively contracting muscle fibres) and translation (simulating passively moving surrounding fibres). The model suggested that the DW signal depended on contraction time and compaction whereas the PC signal depended on contraction time, compaction and translation. In a retrospective study, we tested this model with subgroup analyses on 10 healthy participants. Electrical nerve stimulation was used to generate muscle twitches in lower leg muscles; the resulting force was measured using an MR‐compatible force transducer. At current levels causing a visible muscle twitch (~13 mA), the width of the first signal drop in the DW signal (mean ± SD: 103 ± 20 ms) was comparable with the force contraction time (93 ± 34 ms; intraclass correlation coefficient [ICC] = 0.717, P = .010). At current levels activating single motor units (~9 mA), the contraction time determined from the DW signal was 75 ± 13 ms and comparable with the PC contraction time (81 ± 15 ms; ICC = 0.925, P = .001). The maximum positive velocity was 0.55 ± 0.26 cm/s and the displacement was 0.20 ± 0.10 mm. Voxel‐wise analysis revealed localised DW changes occurring together with more widespread phase changes. In conclusion, local signal attenuations in DW images following muscle fibre activation are primarily caused by compaction. The PC sequence also detects translating muscle tissue being passively pulled. The magnitude of the changes in DW and PC images depends on the twitch's contractile properties and percentage contraction. DW imaging and PC imaging can therefore measure twitch profiles of skeletal muscle fibres.

Superharmonic Ultrasound for Motion-Independent Localization Microscopy: Applications to Microvascular Imaging From Low to High Flow Rates.

Recent advances in high frame rate biomedical ultrasound have led to the development of ultrasound localization microscopy (ULM), a method of imaging microbubble (MB) contrast agents beyond the diffraction limit of conventional coherent imaging techniques. By localizing and tracking the positions of thousands of individual MBs, ultrahigh resolution vascular maps are generated which can be further analyzed to study disease. Isolating bubble echoes from tissue signal is a key requirement for super-resolution imaging which relies on the spatiotemporal separability and localization of the bubble signals. To date, this has been accomplished either during acquisition using contrast imaging sequences or post-beamforming by applying a spatiotemporal filter to the B-mode images. Superharmonic imaging (SHI) is another contrast imaging method that separates bubbles from tissue based on their strongly nonlinear acoustic properties. This approach is highly sensitive, and, unlike spatiotemporal filters, it does not require decorrelation of contrast agent signals. Since this superharmonic method does not rely on bubble velocity, it can detect completely stationary and moving bubbles alike. In this work, we apply SHI to ULM and demonstrate an average improvement in SNR of 10.3-dB in vitro when compared with the standard singular value decomposition filter approach and an increase in SNR at low flow ( [Formula: see text]/frame) from 5 to 16.5 dB. Additionally, we apply this method to imaging a rodent kidney in vivo and measure vessels as small as [Formula: see text] in diameter after motion correction.

Respiratory motion correction for liver contrast-enhanced ultrasound by automatic selection of a reference image.

Respiratory motion correction is necessary for the quantitative analysis of liver contrast-enhanced ultrasound (CEUS) image sequences. Most respiratory motion correction methods are based on the dual mode of CEUS image sequences, including contrast and grayscale image sequences. Due to free-breathing motion, the acquired two-dimensional (2D) ultrasound cine might show the in-plane and out-of-plane motion of tumors. The registration of an entire 2D ultrasound contrast image sequence based on out-of-plane images is ineffective. For the respiratory motion correction of CEUS sequences, the reference image is usually considered the standard for the deletion of any out-of-plane images. Most methods used for the selection of the reference image are subjective in nature. Here, a quantitative selection method for an optimal reference image from CEUS image sequences in the B mode and contrast mode was explored. The original high-dimensional ultrasound grayscale image data were mapped into a two-dimensional space using Laplacian Eigenmaps (LE), and K-means clustering was adopted. The center image of the larger cluster with a near-peak contrast intensity was considered the optimal ultrasound reference image. In the ultrasound grayscale image sequence, the images with the maximum correlations to the reference image in the same time interval were selected as the corrected image sequence. The effectiveness of this proposed method was then validated on 18 CEUS cases of VX2 tumors in rabbit livers. Correction smoothed the time-intensity curves (TICs) extracted from the region of interest of the CEUS image sequences. Before correction, the average of the total mean structural similarity (TMSSIM) and the average of the mean correlation coefficient (MCC) from the image sequences were 0.45±0.11 and 0.67±0.16, respectively, and after correction, the average TMSSIM and MCC increased (P<0.001) by 31% to 0.59±0.11 and by 21% to 0.81±0.11, respectively. The average deviation value (DV) index of the TICs from the image sequences prior to correction was 92.16±18.12, and correction reduced the average to 31.71±7.31. The average TMSSIM and MCC values after correction using the mean frame of the reference image (MBMFRI) were clearly lower than those after correction using the proposed method (P<0.001). Moreover, the average DV after correction using the MBMFRI was obviously higher than that after correction using the proposed method (P<0.001). The breathing frequency of rabbits is notably faster than that of human beings, but the proposed correction method could reduce the effect of the respiratory motion in the CEUS image sequences. The reference image was selected quantitatively, which could improve the accuracy of the quantitative analysis of rabbit liver CEUS sequences using the reference image method based on the current standard of manual selection and the MBMFRI. Thiseasy-to-operatemethod can potentially be used in both animal studies and clinical applications.

An Initiative to Reduce Unnecessary Gadolinium-Based Contrast in Multiple Sclerosis Patients

ObjectivePatients with multiple sclerosis (MS) routinely undergo serial contrast-enhanced MRIs. Given concerns regarding tissue deposition of gadolinium-based contrast agents (GBCAs) and evidence that enhancement of lesions is only seen in patients with new disease activity on noncontrast imaging, we set out to implement a prospective quality improvement project whereby intravenous contrast would be reserved only for patients with evidence of new disease activity on noncontrast images. MethodsTo prospectively implement such a protocol, we leveraged our in-house computer-assisted detection (CAD) software and 3-D laboratory radiology technologists to perform real-time preliminary assessments of the CAD-processed T2 fluid attenuated inversion recovery (FLAIR) noncontrast images as a basis for deciding whether to inject contrast. Before implementation, we held multidisciplinary meetings with neurology, neuroradiology, and MR technologists and distributed surveys to objectively assess opinions and obstacles to clinical implementation. We evaluated reduction in GBCA utilization and technologist performance relative to final neuroradiologist interpretations. ResultsDuring a 2-month trial period, 153 patients were imaged under the new protocol. Technologists using the CAD software were able to identify patients with new or enlarging lesions on FLAIR images with 95% accuracy and 97% negative predictive value relative to final neuroradiologist interpretations, which allowed us to avoid the use of contrast and additional imaging sequences in 87% of patients. DiscussionA multidisciplinary effort to implement a quality improvement project to limit contrast in MS patients receiving follow-up MRIs allowed for improved safety and cost by targeting patients that would benefit from the use of intravenous contrast in real-time.

Multiple cell tracking by generalised labelled multi-Bernoulli filter

Cell detection and tracking in microscopy images are of great importance to medical research and related fields. In this paper, a generalised labelled multi-Bernoulli (GLMB) track-before-detect (TBD) filter is proposed for the tracking of multiple cells. In this filter, GLMB based on random finite set (RFS) theory is used to jointly estimate the positions and the numbers of cells in images, and TBD is adopted to track cells without explicit detection step. The experimental results indicate that the proposed method can accurately discover cells and maintain their tracks in low contrast image sequences.

Multiple cell tracking by generalised labelled multi-Bernoulli filter

Cell detection and tracking in microscopy images are of great importance to medical research and related fields. In this paper, a generalised labelled multi-Bernoulli (GLMB) track-before-detect (TBD) filter is proposed for the tracking of multiple cells. In this filter, GLMB based on random finite set (RFS) theory is used to jointly estimate the positions and the numbers of cells in images, and TBD is adopted to track cells without explicit detection step. The experimental results indicate that the proposed method can accurately discover cells and maintain their tracks in low contrast image sequences.

SU‐E‐J‐223: A BOLD Contrast Imaging Sequence to Evaluate Oxygenation Changes Due to Breath Holding for Breast Radiotherapy: A Pilot Study

Purpose:To develop a robust MRI sequence to measure BOLD breath hold induced contrast in context of breast radiotherapy.Methods:Two sequences were selected from prior studies as candidates to measure BOLD contrast attributable to breath holding within the breast: (1) T2* based Gradient Echo EPI (TR/TE = 500/41ms, flip angle = 60°), and (2) T2 based Single Shot Fast Spin Echo (SSFSE) (TR/TE = 3000/60ms). We enrolled ten women post‐lumpectomy for breast cancer who were undergoing treatment planning for whole breast radiotherapy. Each session utilized a 1.5T GE MRI and 4 channel breast coil with the subject immobilized prone on a custom board. For each sequence, 1–3 planes of the lumpectomy breast were imaged continuously during a background measurement (1min) and intermittent breath holds (20–40s per breath hold, 3–5 holds per sequence). BOLD contrast was quantified as correlation of changes in per‐pixel intensity with the breath hold schedule convolved with a hemodynamic response function. Subtle motion was corrected using a deformable registration algorithm. Correlation with breath‐holding was considered significant if p&lt;0.001.Results:The percentage of the breast ROI with positive BOLD contrast measured by the two sequences were in agreement with a correlation coefficient of R=0.72 (p=0.02). While both sequences demonstrated areas with strong BOLD response, the response was more systematic throughout the breast for the SSFSE (T2) sequence (% breast with response in the same direction: 51.2%±0.7% for T2* vs. 68.1%±16% for T2). In addition, the T2 sequence was less prone to magnetic susceptibility artifacts, especially in presence of seroma, and provided a more robust image with little distortion or artifacts.Conclusion:A T2 SSFSE sequence shows promise for measuring BOLD contrast in the context of breast radiotherapy utilizing a breath hold technique. Further study in a larger patient cohort is warranted to better refine this novel technique.

Optimization of multi-pulse sequences for nonlinear contrast agent imaging using a cMUT array

Capacitive micromachined ultrasonic transducer (cMUT) technology provides advantages such as wide frequency bandwidth, which can be exploited for contrast agent imaging. Nevertheless, the efficiency of traditional multi-pulse imaging schemes, such as pulse inversion (PI), remains limited because of the intrinsic nonlinear character of cMUTs. Recently, a new contrast imaging sequence, called bias voltage modulation sequence (BVM), has been specifically developed for cMUTs to suppress their unwanted nonlinear behavior. In this study, we propose to optimize contrast agent detection by combining the BVM sequence with PI and/or chirp reversal (CR). An aqueous dispersion of lipid encapsulated microbubbles was exposed to several combinations of multi-pulse imaging sequences. Approaches were evaluated in vitro using 9 inter-connected elements of a cMUT linear array (excitation frequency of 4 MHz; peak negative pressure of 100 kPa). For sequences using chirp excitations, a specific compression filter was designed to compress and extract several nonlinear components from the received microbubble responses. A satisfactory cancellation of the nonlinear signal from the source is achieved when BVM is combined with PI and CR. In comparison with PI and CR imaging modes alone, using sequences incorporating BVM increases the contrast-to-tissue ratio by 10.0 dB and 4.6 dB, respectively. Furthermore, the combination of BVM with CR and PI results in a significant increase of the contrast-to-noise ratio (+29 dB). This enhancement is attributed to the use of chirps as excitation signals and the improved preservation of several nonlinear components contained within the contrast agent response.

Evaluation of bias voltage modulation sequence for nonlinear contrast agent imaging using a capacitive micromachined ultrasonic transducer array

Many clinical diagnoses have now been improved thanks to the development of new techniques dedicated to contrast agent nonlinear imaging. Over the past few years, Capacitive Micromachined Ultrasonic Transducers (cMUTs) have emerged as a promising alternative to traditional piezoelectric transducers. One notable advantage of cMUTs is their wide frequency bandwidth. However, their use in nonlinear imaging approaches such as those used to detect contrast agents have been challenging due their intrinsic nonlinear character. We propose a new contrast imaging sequence, called bias voltage modulation (BVM), specifically developed for cMUTs to suppress their inherent nonlinear behavior. Theoretical and experimental results show that a complete cancellation of the nonlinear signal from the source can be reached when the BVM sequence is implemented. In-vitro validation of the sequence is performed using a cMUT probe connected to an open scanner and a flow phantom setup containing SonoVue microbubbles. Compared to the standard amplitude modulation imaging mode, a 6 dB increase of contrast-to-tissue ratio was achieved when the BVM sequence is applied. These results reveal that the problem of cMUT nonlinearity can be addressed, thus expanding the potential of this new transducer technology for nonlinear contrast agent detection and imaging.

MRI of trabecular bone using a decay due to diffusion in the internal field contrast imaging sequence

To characterize the DDIF (Decay due to Diffusion in the Internal Field) method using intact animal trabecular bone specimens of varying trabecular structure and porosity, under ex vivo conditions closely resembling in vivo physiological conditions. The DDIF method provides a diffusion contrast which is related to the surface-to-volume ratio of the porous structure of bones. DDIF has previously been used successfully to study marrow-free trabecular bone, but the DDIF contrast hitherto had not been tested in intact specimens containing marrow and surrounded by soft tissue. DDIF imaging was implemented on a 4.7 Tesla (T) small-bore, horizontal, animal scanner. Ex vivo results on fresh bone specimens containing marrow were obtained at body temperature. Control measurements were carried out in surrounding tissue and saline. Significant DDIF effect was observed for trabecular bone samples, while it was considerably smaller for soft tissue outside the bone and for lipids. Additionally, significant differences were observed between specimens of different trabecular structure. The DDIF contrast is feasible despite the reduction of the diffusion constant and of T(1) in such conditions, increasing our confidence that DDIF imaging in vivo may be clinically viable for bone characterization.

Integrative Bildgebung zur Therapieplanung bei Shuntvitien im Erwachsenenalter

Shunts between the pulmonary and systemic circulation may occur at atrial, ventricular or arterial level. Non-invasive imaging has substantially improved morbidity and mortality in these patients. Method of choice to visualize shunts is echocardiography. Especially the 3D transesophageal approach is a powerful tool to characterize atrial septal defects and to guide interventional closure. In addition, magnetic resonance imaging has proven a valuable tool to quantify shunt volumes using pulse sequences for phase contrast imaging sequences, to visualize shunts or conduits with 4D angiography sequences and to characterize further congenital cardiovascular defects.

Pediatric Positron Emission Tomography–Computed Tomography Protocol Considerations

Pediatric body oncology positron emission tomography-computed tomography studies require special considerations for optimal diagnostic performance while limiting radiation exposure to young patients. Differences from routine adult procedures include the patient preparation phase, radiopharmaceutical dose, computed tomography acquisition parameters, and approach to computed tomography contrast materials and imaging sequence. Attention to these differences define the best practice for positron emission tomography-computed tomography examinations of children with cancer contributing to optimal care of these patients.

Golay Pulse Encoding for Microbubble Contrast Imaging in Ultrasound

We present a technique that uses Golay phase encoding, pulse inversion, and amplitude modulation (GPIAM) for microbubble contrast agent imaging with ultrasound. This technique improves the contrast-to-tissue ratio (CTR) by increasing the time-bandwidth product of the insonating waveforms. A nonlinear pulse compression algorithm is used to compress the signal energy upon receive. A 6.5-dB improvement in CTR was observed using an 8-chip GPIAM sequence compared to a conventional pulse-inversion amplitude-modulation sequence. The CTR improvement comes at the cost of a reduction in frame rate: GPIAM coding uses four input pulses whereas most contrast imaging sequences require two or three pulses. Our results showed that the microbubble response can be phase encoded and subsequently compressed using a nonlinear matched-filtering algorithm, in order to enhance the signal from the contrast agent, while maintaining resolution and suppressing the tissue signal.