We aimed to evaluate the diagnostic agreement between radiofrequency (RF) intravascular ultrasound (IVUS) and optical coherence tomography (OCT) for thin-cap fibroatheroma (TCFA) in non-infarct... Show moreWe aimed to evaluate the diagnostic agreement between radiofrequency (RF) intravascular ultrasound (IVUS) and optical coherence tomography (OCT) for thin-cap fibroatheroma (TCFA) in non-infarct-related coronary arteries (non-IRA) in patients with ST-segment elevation myocardial infarction (STEMI). In the Integrated Biomarker Imaging Study (IBIS-4), 103 STEMI patients underwent OCT and RF-IVUS imaging of non-IRA after successful primary percutaneous coronary intervention and at 13-month follow-up. A coronary lesion was defined as a segment with >= 3 consecutive frames (approximate to 1.2 mm) with plaque burden >= 40% as assessed by grayscale IVUS. RF-IVUS-derived TCFA was defined as a lesion with > 10% confluent necrotic core abutting to the lumen in > 10% of the circumference. OCT-TCFA was defined by a minimum cap thickness < 65 mu m. The two modalities were matched based on anatomical landmarks using a dedicated matching software. Using grayscale IVUS, we identified 276 lesions at baseline (N = 146) and follow-up (N = 130). Using RF-IVUS, 208 lesions (75.4%) were classified as TCFA. Among them, OCT identified 14 (6.7%) TCFA, 60 (28.8%) thick-cap fibroatheroma (ThCFA), and 134 (64.4%) non-fibroatheroma. All OCT-TCFA (n = 14) were confirmed as RF-TCFA. The concordance rate between RF-IVUS and OCT for TCFA diagnosis was 29.7%. The reasons for discordance were: OCT-ThCFA (25.8%); OCT-fibrous plaque (34.0%); attenuation due to calcium (23.2%); attenuation due to macrophage (10.3%); no significant attenuation (6.7%). There was a notable discordance in the diagnostic assessment of TCFA between RF-IVUS and OCT. The majority of RF-derived TCFA were not categorized as fibroatheroma using OCT, while all OCT-TCFA were classified as TCFA by RF-IVUS. ClinicalTrials.gov Identifier NCT00962416. Show less
Aims Pulmonary vein isolation (PVI), the standard for atrial fibrillation (AF) ablation, is most commonly applied with radiofrequency (RF) energy, although cryoballoon technology (CRYO) has gained... Show moreAims Pulmonary vein isolation (PVI), the standard for atrial fibrillation (AF) ablation, is most commonly applied with radiofrequency (RF) energy, although cryoballoon technology (CRYO) has gained widespread use. The aim was to compare the second-generation cryoballoon and the irrigated RF energy regarding outcomes and safety.Methods and results Of 4657 patients undergoing their first AF ablation, 982 with CRYO and 3675 with RF energy were included from the Swedish catheter ablation registry and the Atrial Fibrillation Ablation Long-Term registry of the European Heart Rhythm Association of the European Society of Cardiology. The primary endpoint was repeat AF ablation. The major secondary endpoints included procedural duration, tachyarrhythmia recurrence, and complication rate. The re-ablation rate after 12 months was significantly lower in the CRYO vs. the RF group, 7.8% vs. 11%, P=0.005, while freedom from arrhythmia recurrence (30 s duration) did not differ between the groups, 70.2 % vs. 68.2%, P=0.44. The result was not influenced by AF type and lesion sets applied. In the Cox regression analysis, paroxysmal AF had significantly lower risk for re-ablation with CRYO, hazard ratio 0.56 (P=0.041). Procedural duration was significantly shorter with CRYO than RF, (meanSD) 133.6 +/- 45.2 min vs. 174.6 +/- 58.2 min, P<0.001. Complication rates were similar; 53/982 (5.4%) vs. 191/3675 (5.2%), CRYO vs. RF, P=0.806.Conclusion The lower re-ablation rates and shorter procedure times observed with the cryoballoon as compared to RF ablation may have important clinical implications when choosing AF ablation technique despite recognized limitations with registries. Show less
This thesis reports on the utility of high permittivity dielectric materials for adjusting the radiofrequency (RF) field in high field MR. The performance-driven trend towards higher static... Show moreThis thesis reports on the utility of high permittivity dielectric materials for adjusting the radiofrequency (RF) field in high field MR. The performance-driven trend towards higher static magnetic field strengths drives MR operation into the regime where the dimensions of the body section being imaged are comparable to the RF wavelength. This results in areas of RF interference within the body, and associated variations in signal intensity and tissue contrast, which can severely reduce the diagnostic image quality. However, the underlying electromagnetic interactions raise the question of whether these mechanisms may also be exploited to establish a remediation. This approach is termed "dielectric shimming," and is the subject of this thesis. The main conclusions from this thesis are that dielectric shimming presents a very simple and effective method for improving MR operation at high field strength. The high permittivity materials allow for tailoring the B1 field without increasing SAR. The technique improves body applications at 3T as well as neuro applications at 7T, and theoretical foundations are presented to harness and exploit this approach. The obtained solutions are low-cost, vendor-independent, do not require any major hardware or software modifications and can therefore be very easily implemented in clinical protocols. Show less
The main purpose of this thesis was to evaluate the effectiveness and safety of CT-guided radiofrequency ablation for the treatment of spinal and non-spinal osteoid osteomas. Furthermore, the... Show moreThe main purpose of this thesis was to evaluate the effectiveness and safety of CT-guided radiofrequency ablation for the treatment of spinal and non-spinal osteoid osteomas. Furthermore, the technical requirements needed for safe radiofrequency ablation and the clinical outcome after radiofrequency ablation of spinal and non-spinal osteoid osteomas are discussed. The possible causes of treatment failure and methods for the detection of treatment failure were also analysed with the purpose of optimizing patient selection and the radiofrequency procedures, and solving high risk parameters for failure of treatment. Chapter two discusses the clinical outcome of a large series of 97 patients with spinal and non-spinal osteoid osteomas treated by radiofrequency ablation. Chapter three describes the theoretical and technical background of radiofrequency ablation. The concept of the treatment zone as well as related safety issues are also discussed. In Chapter four the possible mechanisms causing treatment failure are discussed. The potential role of CT and MRI imaging in the detection of recurrent or residual osteoid osteoma is addressed in Chapter five. Finally the treatment outcome of a group of 25 patients with spinal osteoid osteoma treated by radiofrequency ablation is presented in Chapter 6. A general discussion is provided in Chapter 7. Show less
