Progress and promises of human cardiac magnetic resonance at ultrahigh fields: a physics perspective.

A growing number of reports eloquently speak about explorations into cardiac magnetic resonance (CMR) at ultrahigh magnetic fields (B0≥7.0 T). Realizing the progress, promises and challenges of ultrahigh field (UHF) CMR this perspective outlines current trends in enabling MR technology tailored for cardiac MR in the short wavelength regime. For this purpose many channel radiofrequency (RF) technology concepts are outlined. Basic principles of mapping and shimming of transmission fields including RF power deposition considerations are presented. Explorations motivated by the safe operation of UHF-CMR even in the presence of conductive implants are described together with the physics, numerical simulations and experiments, all of which detailing antenna effects and RF heating induced by intracoronary stents at 7.0 T. Early applications of CMR at 7.0 T and their clinical implications for explorations into cardiovascular diseases are explored including assessment of cardiac function, myocardial tissue characterization, MR angiography of large and small vessels as well as heteronuclear MR of the heart and the skin. A concluding section ventures a glance beyond the horizon and explores future directions. The goal here is not to be comprehensive but to inspire the biomedical and diagnostic imaging communities to throw further weight behind the solution of the many remaining unsolved problems and technical obstacles of UHF-CMR with the goal to transfer MR physics driven methodological advancements into extra clinical value.

Biocompatibility of alginates for grafting: impact of alginate molecular weight.

Optimising microencapsulation technology towards the effective clinical transplantation has created the need for highly biocompatible alginates. Therefore, in this study the biocompatibility of different beads prepared from alginates with varying average molecular weight was examined. In some experiments the beads were covered with a multilayer membrane surrounded by an alginate layer. First of all, we found that beads made of a lower weight average alginate elicted a much stronger fibrotic response compared to beads made of a higher weight average alginate (LV-alginate > MV-alginate). The results were confirmed by the observation that the extent of tissue fibrosis was significantly increased in multilayer capsules made of an alginate with a lower weight average (core and surface LV-alginate, Mw 0.7-1 * 10(6) g/mol, viscosity of a 0.1% solution 1-2.5 mPa s(-1)) compared to multilayer capsules made of an alginate with a higher weight average (core and surface MV-alginate; Mw 1.2-1.3 * 10(6) g/mol, viscosity of a 0.1% solution 5-7 mPa s(-1)). It should be stressed, that the pro-fibrotic effect of the LV-alginate alginate in the core was only partially reversed by a MV-alginate on the surface of the multilayer capsules. On the basis of the raised data, it can be assumed that the molecular weight average of the alginates have an decisive effect on the biocompatibility. Therefore, it seems to be recommendable to reduce the low molecular weight fractions of the alginate during the purification process to improve the biocompatibility.

Intraportal transplantation of allogenic pancreatic islets encapsulated in barium alginate beads in diabetic rats.

The survival of microencapsulated islets transplanted into the unmodified peritoneal cavity is limited, even if capsular overgrowth is restricted to a minimum, due to an insufficient oxygen supply to the islets. Therefore, research efforts should focus on finding or creating a transplantation site, which permits a closer contact between the encapsulated islets and the blood. For this reason, the liver could be an interesting candidate. The aim of the present study was to test the hypothesis that the intraportal transplantation of allogenic islets encapsulated in small-sized barium alginate beads is safe and succeeds to induce normoglycemia in diabetic rats. The intraportal transplantation of 1,500 islets encapsulated in barium alginate beads leads within 10 h and up to 24 h to blood sugar concentrations below 40 mg/dL, most likely due to an acute cell lysis of the graft. Afterwards, the reappearance of the diabetic state could be detected in these animals. Most likely these findings are induced by a sudden hypoxia to the islets. We believe that the occlusion of small- and medium-sized portal venules by the alginate beads is responsible for this effect. Therefore, in forthcoming studies, barium alginate beads, with a diameter below 350 micro m, stabilized with medical approved additives should be used.

[Interdisciplinary diagnosis and therapy of ischemic-osteomyelitic diabetic foot syndrome]. / Interdisziplinäre Diagnostik und Therapie des ischämisch-osteomyelitischen diabetischen Fusssyndroms.

Advanced stages of the diabetic foot syndrome complicated by ischemia and osteomyelitis frequently result in minor amputation, followed by impaired wound healing and higher-level amputation in the context of regular health structures. Even in specialized foot care centers, peripheral arterial occlusive disease and osteomyelitis still represent the greatest challenge in the strife for limb salvage. Whereas the treatment of nonischemic foot lesions has increasingly become a matter of conservative medicine within recent years, for advanced diabetic foot wounds a multidisciplinary treatment policy is essential. A well-coordinated treatment concept aiming at the elimination of the most relevant prognostic factors ischemia and osteomyelitis is required to achieve high limb salvage rates. Surgical revascularization by distal bypass is a crucially important element of this approach. Percutaneous transluminal angioplasty represents a complementary option for short-segment arterial occlusive disease. Foot-sparing minor surgery improves healing time and rates. A specialized diabetologic foot care clinic provides preclinical diagnosis, planning of inpatient procedures, and selection of patients requiring hospitalization for surgical intervention. In addition, it safeguards postinterventional care for wounds with secondary healing and measures of secondary prevention.

[Pedal bypass surgery in diabetic foot syndrome: indications, technique and outcome]. / Pedale Bypasschirurgie beim diabetischen Fusssyndrom: Indikation, Technik und Ergebnisse.

Peripheral arterial occlusive disease in the diabetic patients is characterized predominantly by long segmental occlusion of the tibial arteries with patent segments of pedal arteries. Neuropathy and high susceptibility for foot infection explain the dramatically increased risk of major amputation. The pattern of arteriosclerotic disease allows construction of pedal bypasses especially by the use of short autologous vein grafts employing distal origin of the bypass. Indication and performance of the bypass procedure rely on a complete angiographic evaluation of the arterial system of the diseased limb. Besides the dorsalis pedis artery with its major branches as preferentially used recipient vessel, the posterior tibial artery and its plantar branches may be anastomosed. Thus, improved foot perfusion will allow necessary minor amputations with safe wound healing. The use of autologous vein grafts is associated with a high late patency rate of more than 70% and a late limb salvage rate of more than 80%. Pedal artery bypass grafting should routinely be part of the therapeutic strategies in advanced diabetic foot syndrome with critical limb ischemia and impending limb loss.