Physically plausible K-space trajectories for Compressed Sensing in MRI: From simulations to real acquisitions

International audienceMagnetic resonance imaging (MRI) is a medical imaging technique used in radiology to image the anatomy and function of the body in both health and disease. MRI is probably one of the most successful application fields of compressed sensing (CS). Despite recent advances, there is still a large discrepancy between theories and actual applications. Overall, many important questions related to sampling theory remain open. In this work, we address one of them: given a set of hardware constraints (e.g. sampling Fourier coefficients along smooth curves), how to optimally design a sampling pattern? We first derive three key aspects that should be carefully designed by inspecting the literature, namely admissibility, limit of the empirical measure and coverage speed. To fulfill them jointly, we then propose an original approach which consists of projecting a probability distribution onto a set of admissible measures. The proposed algorithm allows to handle arbitrary hardware constraints (gradient magnitude, slew rate) and then automatically generates efficient sampling patterns. The MR images reconstructed using the proposed approach have a significantly higher SNR (2-3 dB) than those reconstructed using more standard sampling patterns (e.g. radial, spiral), both for medium and very high resolution imaging. Likewise, reconstructions from highly undersampled data acquired in experiments performed on a 7T SIEMENS MR scanner show the superiority of our sampling schemes over traditional MR samplings and proved that very large acceleration factor (up to 40-fold) are practically achievable with CS-MRI

Summary of the Standards, Options and Recommendations for the use of positron emission tomography with 2-[18F]fluoro-2-deoxy-D-glucose (FDP-PET scanning) in oncology (2002)

GuidelinePractice GuidelineResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

Gemcitabine with a specific conformal 3D 5FU radiochemotherapy technique is safe and effective in the definitive management of locally advanced pancreatic cancer

The aim of this phase II study was to assess the feasibility and efficacy of a specific three-dimensional conformal radiotherapy technique with concurrent continuous infusion of 5-fluorouracil (CI 5FU) sandwiched between gemcitabine chemotherapy in patients with locally advanced pancreatic cancer. Patients with inoperable cancer in the pancreatic head or body without metastases were given gemcitabine at 1000 mg m−2 weekly for 3 weeks followed by a 1-week rest and a 6-week period of radiotherapy and concurrent CI 5FU (200 mg m−2 day−1). The defined target volume was treated to 54 Gy in 30 daily fractions of 1.8 Gy. After 4 weeks' rest, gemcitabine treatment was re-initiated for three cycles (days 1, 8, 15, q28). Forty-one patients were enrolled. At the end of radiotherapy, one patient (2.4%) had a complete response and four patients (9.6%) had a partial response; at the end of treatment, three patients (7.3%) had a complete response and two patients (4.9%) had a partial response. Median survival time was 11.7 months, median time to progression was 7.1 months, and median time to failure of local control was 11.9 months. The 1- and 2-year survival rates were 46.3 and 9.8%, respectively. Treatment-related grade 3 and 4 toxicities were reported by 16 (39.0%) and four (9.8%) patients, respectively. Sixteen out of 41 patients did not complete the planned treatment and nine due to disease progression. This approach to treatment of locally advanced pancreatic cancer is safe and promising, with good local control for a substantial proportion of patients, and merits testing in a randomised trial

Systematic review, including meta-analyses, on the management of locally advanced pancreatic cancer using radiation/combined modality therapy

There is no consensus on the management of locally advanced pancreatic cancer, with either chemotherapy or combined modality approaches being employed (Maheshwari and Moser, 2005). No published meta-analysis (Fung et al, 2003; Banu et al, 2005; Liang, 2005; Bria et al, 2006; Milella et al, 2006) has included randomised controlled trials employing radiation therapy. The aim of this systematic review was to compare the following: (i) chemoradiation followed by chemotherapy (combined modality therapy) vs best supportive care (ii) radiotherapy vs chemoradiation (iii) radiotherapy vs combined modality therapy (iv) chemotherapy vs combined modality therapy (v) 5FU-based combined modality treatment vs another-agent-based combined modality therapy. Relevant randomised controlled trials were identified by searching databases, trial registers and conference proceedings. The primary end point was overall survival and secondary end points were progression-free survival/time-to-progression, response rate and adverse events. Survival data were summarised using hazard ratio (HR) and response-rate/adverse-event data with relative risk. Eleven trials involving 794 patients met the inclusion criteria. Length of survival with chemoradiation was increased compared with radiotherapy alone (two trials, 168 patients, HR 0.69; 95% confidence interval (CI) 0.51–0.94), but chemoradiation followed by chemotherapy did not lead to a survival advantage over chemotherapy alone (two trials, 134 patients, HR 0.79; CI 0.32–1.95). Meta-analyses could not be performed for the other comparisons. A survival benefit was demonstrated for chemoradiation over radiotherapy alone. Chemoradiation followed by chemotherapy did not demonstrate any survival advantage over chemotherapy alone, but important clinical differences cannot be ruled out due to the wide CI

Study protocol: a multi-centre randomised study of induction chemotherapy followed by capecitabine +/- nelfinavir with high- or standard-dose radiotherapy for locally advanced pancreatic cancer (SCALOP-2)

Background Induction chemotherapy followed by chemoradiation is a treatment option for patients with locally advanced pancreatic cancer (LAPC). However, overall survival is comparable to chemotherapy alone and local progression occurs in nearly half of all patients, suggesting chemoradiation strategies should be optimised. SCALOP-2 is a randomised phase II trial testing the role of radiotherapy dose escalation and/or the addition of the radiosensitiser nelfinavir, following induction chemotherapy of gemcitabine and nab-paclitaxel (GEMABX). A safety run-in phase (stage 1) established the nelfinavir dose to administer with chemoradiation in the randomised phase (stage 2). Methods Patients with locally advanced, inoperable, non-metastatic pancreatic adenocarcinoma receive three cycles of induction GEMABX chemotherapy prior to radiological assessment. Those with stable/responding disease are eligible for further trial treatment. In Stage 1, participants received one further cycle of GEMABX followed by capecitabine-chemoradiation with escalating doses of nelfinavir in a rolling-six design. Stage 2 aims to register 262 and randomise 170 patients with responding/stable disease to one of five arms: capecitabine with high- (arms C + D) or standard-dose (arms A + B) radiotherapy with (arms A + C) or without (arms B + D) nelfinavir, or three more cycles of GEMABX (arm E). Participants allocated to the chemoradiation arms receive another cycle of GEMABX before chemoradiation begins. Co-primary outcomes are 12-month overall survival (radiotherapy dose-escalation question) and progression-free survival (nelfinavir question). Secondary outcomes include toxicity, quality of life, disease response rate, resection rate, treatment compliance, and CA19–9 response. SCALOP-2 incorporates a detailed radiotherapy quality assurance programme. Discussion SCALOP-2 aims to optimise chemoradiation in LAPC and incorporates a modern induction regimen