Traditional poster

When - after neoadjuvant chemoradiation for rectal cancer - imaging could accurately select the complete responders, surgery might safely be omitted and patients can undergo a wait-and-see policy. This study aims to evaluate whether MRI at 1.5T is accurate enough to select patients for wait-and-see and can safely be used as a follow-up tool.

FDG-PET/CT can assess morphological and metabolic information at same time, and widely utilized for N-stage assessment in non-small cell lung cancer (NSCLC) patients. In the last decade, short inversion time inversion recovery (STIR) turbo spin-echo (SE) imaging has been determined at least as valuable as PET/CT in this setting. Recently, diffusion-weighted image (DWI) is suggested as new technique for differentiation of metastatic lymph nodes from non-metastatic lymph nodes. The purpose of this study was to prospectively and directly compare capability of N-stage assessment among integrated FDG-PET/CT, STIR turbo SE imaging and DWI in NSCLC patients.

The purpose of this study was to examine the utility of DWI-MRI for the assessment of early response to chemotherapy in patients with advanced lung cancer by comparing FDG-PET. Twenty-two lung cancer patients received MRI, FDG-PET, and CT examination before and after 1 cycle of chemotherapy. Progression-free survival (PSF) between responder and non-responder against chemotherapy was compared by means of % change of ADC and SUV. Both index indicated that responder demonstrated significant longer PSF and DWI-MRI will be a promising tool for the assessment of the early response to chemotherapy.

Solitary pulmonary nodule (SPN) is one of the most common findings in chest imaging. It is important to avoid unnecessary intervention for benign lesions, thereby lowering the associated mortality / morbidity. In this study, we applied perfusion MRI to evaluate perfusion characteristics of SPN and feasibility of perfusion MRI as a diagnostic tool to differentiate malignant from benign SPN. Perfusion MRI parameters and TI curve has great potential to differentiate malignant vs. benign SPN, thus to avoid unnecessary surgical interventions.

This preliminary work demonstrates the feasibility of pre-treatment assessment of lung ventilation and post-treatment detection of radiation-induced lung damage using 3He-MRI for NSCLC patients.

In vivo 31P magnetic resonance spectroscopy illustrates that human melanoma xenografts can be acidified by induction of hyperglycemia combined with administration of lonidamine, an inhibitor of mitochondrial respiration. In melanoma xenograft (10-13 mm diameter), intracellular pH (pHi, measured by chemical shift of the Pi resonance) was reduced by ~0.7 unit during i.v. infusion of glucose (0.6 M) for 120 min along with administration of lonidamine (50 mg/kg). Preliminary result of this study shows that lonidamine combined with hyperglycemia acidified human melanoma xenografts by reducing pHi, a more critical parameter for thermosensitization to improve tumor response to alkylating agents.

The goal of this study was to evaluate a non-invasive magnetic resonance imaging method of fat quantification as a measure of yellow bone marrow in the pelvis and spine. This is a new technology that will enable monitoring of response to therapy and assessment of the effectiveness of strategies to reduce hematology toxicity.

Motion-sensitized driven-equilibrium (MSDE) sequence has been reported to effectively suppress signals from flowing blood in vessels that can mimic the brain metastases on post-contrast T1-weighted images. We performed an observer test to determine whether use of a 3D turbo spin-echo (TSE) sequence with MSDE increases radiologistsf diagnostic performances in detecting brain metastases comparing to a conventional 3D gradient-echo sequence (MPRAGE). A jackknife free-response receiver operating characteristic (JAFROC) analysis showed that TSE with MSDE increases radiologistsf diagnostic performances compared to MPRAGE. The reading time was also significantly shortened by use of MSDE.

Pretreatment DCE-MRI was performed on neck nodal metastases of 12 patients who underwent surgery. Surgical specimens were analyzed with immunohistochemistry (IHC) assays for Ki-67 (reflecting cellular proliferation) and HIF-1α (hypoxia inducible transcription factor). Spearman correlation was used to correlate DCE-MRI and molecular marker data. Significant correlation results were observed between DCE-MRI data (Ktrans and ve) and tumor hypoxia, and proliferation as measured by Ki67 and HIF-1á expression levels, respectively. Future studies with larger patient populations need to be carried out to confirm pretreatment DCE-MRI findings and molecular marker results in biopsy samples for better patient management.

Oncology patients undergo multiple imaging investigations to stage their disease. The aim of this study was to investigate the feasibility of a focused primary tumour (breast or prostate) examination in combination with a WB-MRI for staging of distant disease. If successful we propose the addition of this technique could allow the omission of other examinations, such as radionuclide imaging, thereby streamlining the current imaging pathway. We conclude that focused primary tumour examinations in combination with a WB-MRI for staging of distant disease is feasible. However, the technique needs to validated in a much larger cohort than the one studied.

The study aimed to explore the role of Whole-body DWI in clear cell renal cell carcinoma (RCC) and obtain the imaging characteristics of metastases. Ten patients with histologically confimed clear cell RCC and possible metastatic lesions were underwent standard Whole-body DWI, chest CT and routine MR examinations before chemotherapy. The results showed that the whole body DWI was very sensitive to the metastatic lesions in clear cell RCC and DWI showed its high rate of detection in pulmonary metastases. Whole body DWI had revealed great potential in metastatic screening of clear cell RCC.

By using Whole Body MR and PET/CT approach to investigate metastatic disease can lead a better understanding of cancer aggressiveness. Functional imaging such as DWI/ADC, DCE-MR and 11C Choline PET is feasible and thus, combined DWI/ADC mapping, and PET/CT provides radiological biomarkers of molecular environment and could provide targets imaging treatment response.

Efficient mitigation of the RF inhomogeneity using transmit coil arrays relies on the knowledge of the individual B1-maps. As the number of transmit channels increases, so does the acquisition time of all maps. Here we focus on a fast 2D sequence proposed by Fautz et al. which we adapt for multi-slice B1-mapping. We compare its results with that of the 3D AFI sequence on a spherical phantom surrounded by 8 transmit elements at 7T. We show comparable performance with a 12-fold increase in speed, making accurate B1-mapping of the human head feasible in 1.5 minutes for 8 transmit channels.

There is great demand for fast B1 mapping techniques, e.g. for correction of quantitative T1 maps. However, most methods suffer from long experiment durations. The technique presented here is based on magnetization prepared FLASH imaging with specially designed preparation and excitation pulses to allow for multislice imaging, speeding up the acquisition. Systematic errors due to relaxation effects are avoided by intensity correction of individual k-space lines. The method allows for fast B1 mapping with whole brain coverage, an in-plane resolution of 4 mm, a slice thickness of 3 mm, and an accuracy of 2% within 46 s.

Here we present a novel method for automated RF flip angle calibration based on the Bloch-Siegert shift. The Bloch-Siegert shift is an effect where spin resonance frequency shifts when an off-resonance RF field is applied. Two off-resonance RF pulses were added to a slice-selective spin echo sequence. The off-resonance pulses induce a phase shift in the acquired signal that is proportional to B12. The signal is spatially localized in two dimensions- by slice selection and readout filter, and the signal weighted average B1 over the slice is calculated. This calibration from a starting system transmit gain to measured average flip angle is used to calculate the transmit gain setting needed to produce the desired flip angle. This is shown here at 3 Tesla in the brain, shoulder, abdomen, breast, and wrist with a total scan time for a robust implementation of 1.6 seconds.

B₁⁺ mapping is a critical step in the design of RF pulses for parallel transmit systems. We used the Bloch-Siegert (BS) B₁⁺ mapping method and a 2-channel parallel transmit enabled 7T scanner to produce fast, robust and accurate B₁⁺ maps through the human brain. Both B₁⁺ magnitude and phase are obtained from a single sequence, employing +/-4kHz off-resonance BS pulses. B₁⁺ magnitude and phase maps acquired with a 26s BS scan are compared with those acquired with a 640s classical double angle scan, showing that the BS method is a very good candidate for efficient B₁⁺ mapping at 7T.

Compensation of B1 variations in vivo requires mapping both the magnitude and the phase of each channel's RF magnetic field. Since the field distribution is strongly dependent on the specific size, shape, and positioning of the tissue, such mapping must be made for each subject. We present a practical method for acquiring these maps within 10 minutes in phantoms and human subjects at 7T.

The potential to accelerate the B1⁺ mapping measurement by means of compressed sensing (CS) was investigated. Joint sparsity constraint accounting for the common sparsity support in different TX channels, and higher dimensional undersampling space, also including the coil dimension, allow for considerable acceleration even for the low resolution data acquired in B1⁺ mapping. The basic feasibility of the proposed method is evaluated on simulations and in vivo data from a 3T 8-channel parallel transmit system.

We present a simultaneous δ B₀ and high-dynamic range B₁ mapping technique using an adiabatic partial passage pulse. The double angle method, the gold standard for B₁ mapping, requires 66% longer to acquire the same B₁ range. The high dynamic range is useful for mapping the fields from ablation wires or surface coils, where significant B₀ variation will also be present.

We present a fast B1+ mapping method for parallel transmit system and validate the performance on water phantom in 7T. The measured flip angle matches with the flip angle simulated by the Bloch equation.

The purpose of this study was to develop a rapid, image-guided RF transmitter gain calibration procedure for high-field MRI and evaluate its performance through phantom and in vivo experiments at 3T and 7T. Using a single-shot TurboFLASH pulse sequence, a series of “saturation-no-recovery” images was acquired by varying the flip angle of the preconditioning pulse. In the resulting images, the signal null occurs in regions where the flip angle of the preconditioning pulse is 90°, and the mean signal within a region-of-interest can be plotted as a function of the nominal flip angle to quantitatively calibrate the RF transmitter gain.

The double angle Look-Locker method is an efficient 3D method of mapping transmit B1 inhomogeneity. It makes uses inversion pulses and samples the recovering magnetization using SPGR trains at two different angles. This leads to two time constants that can be combined to find the achieved flip angle. If the SPGR trains at the two angles are interleaved the inversion pulses can be omitted entirely, and the same information can still be extracted. This reduces SAR, simplifies data analysis and still yields nearly the same performance in terms of measuring the flip angle.

In this work, using 3D numerical simulations and verifications with a 7T scanner equipped with a transmit array system we conduct a comprehensive study using B1 shimming for potential 7T whole-body applications. Different from previous works [2], this study includes the optimizations of the B1+ field, local/average SAR and the resulting temperature elevation in the tissue.

RF inhomogeneity greatly affects the quality of MR imaging at high field strength, and compensation methods typically require accurate B1+ maps for optimum performance. Comparison of B1+ mapping methods based on experimental results alone is limited by lack of knowledge of the true B1+ field distribution. MRI simulation allows for comparison of the true, input B1+ field distribution with a simulated map. This study simulates AFI and a flip angle series method at 3T, utilizing MRI and electromagnetic field simulations. The simulation maps correspond closely to the input B1+ and one another. Experimental maps deviate significantly from one another.