Optimal field splitting for large intensity-modulated fields

The multileaf travel range limitations on some linear accelerators require the splitting of a large intensity-modulated field into two or more adjacent abutting intensity-modulated subfields. The abutting subfields are then delivered as separate treatment fields. This workaround not only increases the treatment delivery time but it also increases the total monitor units (MU) delivered to the patient for a given prescribed dose. It is imperative that the cumulative intensity map of the subfields is exactly the same as the intensity map of the large field generated by the dose optimization algorithm, while satisfying hardware constraints of the delivery system. In this work, we describe field splitting algorithms that split a large intensity-modulated field into two or more intensity-modulated subfields with and without feathering, with optimal MU efficiency while satisfying the hardware constraints. Compared to a field splitting technique (without feathering) used in a commercial planning system, our field splitting algorithm (without feathering) shows a decrease in total MU of up to 26% on clinical cases and up to 63% on synthetic cases.     

Optimal leaf sequencing with elimination of tongue-and-groove underdosage

The individual leaves of a multileaf collimator (MLC) have a tongue-and-groove or stepped-edge design to minimize leakage radiation between adjacent leaves. This design element has a drawback in that it creates areas of underdosages in intensity-modulated photon beams unless a leaf trajectory is specifically designed such that for any two adjacent leaf pairs, the direct exposure under the tongue-and-groove is equal to the lower of the direct exposures of the leaf pairs. In this work, we present a systematic study of the optimization of a leaf sequencing algorithm for segmental multileaf collimator beam delivery that completely eliminates areas of underdosages due to tongue-and-groove or stepped-edge design of the MLC. Simultaneous elimination of tongue-and-groove effect and leaf interdigitation is also studied. This is an extension of our previous work (Kamath et al 2003a Phys. Med. Biol. 48 307) in which we described a leaf sequencing algorithm that is optimal for monitor unit (MU) efficiency under most common leaf movement constraints that include minimum leaf separation. Compared to our previously published algorithm (without constraints), the new algorithms increase the number of sub-fields by approximately 21% and 25%, respectively, but are optimal in MU efficiency for unidirectional schedules.     

The pharmacology of aggressive behavioural phenomena elicited by muscarine injected into the cerebral ventricles of conscious cats

Atropine and scopolamine, injected intraventricularly, abolished typical emotional behaviour with aggression and autonomic and motor phenomena, as well as with clonic-tonic convulsions of intraventricularly injected muscarine. On the other hand, adrenergic and dopaminergic blocking agents, antihistamines, 5-hydroxytryptamine antagonists, antiepileptic drugs, and 5-hydroxytryptamine, administered intraventricularly, failed to antagonize the gross behavioural effects of intraventricular muscarine. However, ganglionic and sometimes neuromuscular blocking agents, as well as catecholamines and histamine injected intraventricularly, antagonized the emotional behaviour with aggression and depressed the autonomic and motor phenomena of small doses of intraventricular muscarine. In addition, emotional behaviour with aggression and autonomic and motor phenomena evoked by high doses of intraventricular muscarine were resistant to these antagonists administered intraventricularly. From these experiments it is concluded that the sites activated by muscarine in the CNS producing aggressive behaviour have the following characteristics: in high doses muscarine acted on muscarinic cholinoceptive sites, while in small doses it activated the cholinoceptive sites having muscarinic and nicotinic characteristics. Finally, the ability of single intraventricular injections of muscarine to trigger and to maintain the long-lasting gross behavioural effects cannot be ascribed to a rapid detonator transmission, but rather to an action that differs from a conventional transmitter function.     

25 Jahre Notfall+Rettungsmedizin – reine Männersache?

Notfall + Rettungsmedizin -     

Locally delivered antimicrobials in the management of periodontitis: a critical review of the evidence for their use in practice

Plaque bacteria are the primary initiators of periodontal disease in susceptible persons and therapy is largely based on mechanical bacterial biofilm disruption. Patients' response to periodontal treatment is unpredictable and periodontal stability is not always achieved. Locally delivered antimicrobials (LDAs) may be used as adjuncts to mechanical therapy in treatment of recalcitrant deep (> or = 5mm), active, non-responding sites, providing the patient's oral hygiene is adequate. Their use as a monotherapy cannot be justified. The literature reveals that LDAs are safe and that they achieve statistically significant, yet clinically modest, gains in clinical attachment and reductions in pocket depths. Clinical Relevance: It has been suggested that LDAs may improve the clinical outcome in the treatment of recurrent and refractory cases of periodontitis when used as an adjunct to scaling and root surface instrumentation. This paper examines and discusses the evidence.     

Multiple biomarker use for detection of adverse events in patients presenting with symptoms suggestive of acute coronary syndrome

BACKGROUND: We investigated multiple biomarkers of various pathophysiologic pathways to determine their relationships with adverse outcomes in patients presenting with symptoms of acute coronary syndrome. METHODS: We obtained plasma specimens from 457 patients on admission and measured 7 biomarkers: myeloperoxidase (MPO), soluble CD40 ligand (CD40L), placental growth factor (PlGF), metalloproteinase-9 (MMP-9), high-sensitivity C-reactive protein (hsCRP), cardiac troponin I (cTnI), and N-terminal pro-B-type natriuretic peptide (NT-proBNP). We used the Modification of Diet in Renal Disease formula to calculate the estimated glomerular filtration rate (eGFR). Endpoints were cardiac events (myocardial infarction, percutaneous coronary intervention, coronary artery bypass graft, cardiac death) and all-cause mortality. We estimated cumulative event rates over a 4-month period with the Kaplan-Meier method and relative risk (RR) with the Cox proportional hazards model. RESULTS: Patients with increased PlGF, NT-proBNP, hsCRP, or cTnI or decreased eGFR had 11% to 20% higher all-cause mortality rates than patients with concentrations within reference intervals: 20.4% (eGFR), 16.0% (PlGF), 15.8% (hsCRP), 12.7% (NT-proBNP), and 11.3% (cTnI; all P < or = 0.03). No differences in mortality rates were observed between those with increased vs normal concentrations of MPO, CD40L, or MMP-9. Decreased eGFR (RR 3.4, P = 0.004) and increased NT-proBNP (RR 7.9, P = 0.04) were independently predictive of mortality, and PlGF (RR 2.0, P = 0.08) approached significance. Patients with increased NT-proBNP (12.3%) or cTnI (33.8%) had higher cardiac event rates (each P <0.02), with increased MPO (11.1%) showing a trend (P = 0.09). Patients in whom both cTnI and MPO were increased had a cardiac event rate of 43%. CONCLUSION: Multiple biomarkers that are likely indicative of different underlying pathophysiologic mechanisms are independently predictive of increased risk for adverse events in patients with acute coronary syndrome.     

Effects of Dietary Exposure to Zearalenone (ZEN) on Carp (Cyprinus carpio L.)

The mycotoxin zearalenone (ZEN) is frequently contaminating animal feeds including feed used in aquaculture. In the present study, the effects of dietary exposure to ZEN on carp (Cyprinus carpio L.) were investigated. ZEN at three different concentrations (low dose: 332 µg kg⁻¹, medium dose: 621 µg kg⁻¹ and high dose: 797 µg kg⁻¹ final feed, respectively) was administered to juvenile carp for four weeks. Additional groups received the mycotoxin for the same time period but were fed with the uncontaminated diet for two more weeks to examine the reversibility of the ZEN effects. No effects on growth were observed during the feeding trial, but effects on haematological parameters occurred. In addition, an influence on white blood cell counts was noted whereby granulocytes and monocytes were affected in fish treated with the medium and high dose ZEN diet. In muscle samples, marginal ZEN and α-zearalenol (α-ZEL) concentrations were detected. Furthermore, the genotoxic potential of ZEN was confirmed by analysing formation of micronuclei in erythrocytes. In contrast to previous reports on other fish species, estrogenic effects measured as vitellogenin concentrations in serum samples were not increased by dietary exposure to ZEN. This is probably due to the fact that ZEN is rapidly metabolized in carp.     

The effect of nifedipine and verapamil on the pendular movements of the rabbit isolated ileum

The inhibitory effect of calcium antagonists such as nifedipine and verapamil on the pendular movements of the rabbit isolated ileum was investigated. Nifedipine and verapamil depressed or abolished the pendular movements. The inhibitory effects of nifedipine and verapamil were concentration-dependent. Nifedipine is about 1000 times more potent than verapamil. Calcium ions failed to reverse the inhibitory effects of nifedipine and verapamil. Calcium antagonists which influence the motor activity of the digestive tract, therefore, could have therapeutic use independent of their action on the cardiovascular system.