4D particle therapy PET simulation for moving targets irradiated with scanned ion beams.

Particle therapy positron emission tomography (PT-PET) allows for an in vivo and in situ verification of applied dose distributions in ion beam therapy. Since the dose distribution cannot be extracted directly from the ß(+)-activity distribution gained from the PET scan the validation is done by means of a comparison between the reconstructed ß(+)-activity distributions from a PT-PET measurement and from a PT-PET simulation. Thus, the simulation software for generating PET data predicted from the treatment planning is an essential part of the dose verification routine. For the dose monitoring of intra-fractionally moving target volumes the PET data simulation needs to be upgraded by using time resolved (4D) algorithms to account correctly for the motion dependent displacement of the positron emitters. Moreover, it has to consider the time dependent relative movement between target volume and scanned beam to simulate the accurate positron emitter distribution generated during irradiation. Such a simulation program is presented which properly proceeds with motion compensated dose delivery by scanned ion beams to intra-fractionally moving targets. By means of a preclinical phantom study it is demonstrated that even the sophisticated motion-mitigated beam delivery technique of range compensated target tracking can be handled correctly by this simulation code. The new program is widely based on the 3D PT-PET simulation program which had been developed at the Helmholtz-Zentrum Dresden-Rossendorf, Germany (HZDR) for application within a pilot project to simulate in-beam PET data for about 440 patients with static tumor entities irradiated at the former treatment facility of the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany (GSI). A simulation example for a phantom geometry irradiated with a tracked (12)C-ion beam is presented for demonstrating the proper functionality of the program.

Analysis of the fluctuations of a single-tethered, quantum-dot labeled DNA molecule in shear flow.

A novel technique for analyzing the conformational fluctuations of a single, surface-tethered DNA molecule by fluorescence microscopy is reported. Attaching a nanometer-sized fluorescent quantum dot to the free end of a λ-phage DNA molecule allows us to study the fluctuations of a native DNA molecule without the mechanical properties being altered by fluorescent dye staining. We report on the investigation of single-tethered DNA in both the unperturbed and the shear flow induced stretched state. The dependence of the observed fractional extension and the magnitude of fluctuations on the shear rate can be qualitatively interpreted by Brochard's stem-and-flower model. The cyclic dynamics of a DNA molecule is directly observed in the shear flow experiment.

Fetal microscopic lesions in porcine reproductive and respiratory syndrome virus-induced abortion.

Microscopic lesions in four cases of abortion caused by porcine reproductive and respiratory syndrome virus (PRRSV) were characterized by arteritis, myocarditis, and encephalitis. Fetal PRRSV infection was confirmed by virus isolation or immunohistochemistry and serology. Although fetal microscopic lesions in PRRSV abortions are rarely reported, diagnosticians should consider PRRSV when these lesions occur.

[Mobility of patients with coxarthrosis]. / Uber die Gehfähigkeit von Patienten mit Coxarthrose.

The common methods of evaluating walking capacity of patients with osteoarthritis of the hip reported in literature are all inaccurate and are based on symptoms. It has been proved, that these informations are to uncertain and therefore have to be replaced by objective criterias. A method of assessment was developed which can easily be applied in clinical routine without great apparative means. With a pedometer and a stopwatch the time can be measured which the patient needs to pass a distance of 30 meters as quick as possible (MAX 30). Similarly the maximal walking distance (MAX DIST) is evaluated as well as the average walking distance (MEDIAN). It could be shown, that walking capacity is not dependent on the amount of degenerative changes, duration of hip disease and hip motion. Walking capacity is negatively influenced by pain, muscle atrophy and lack of training. Patients with osteoarthritis of the hip are able to walk on average 3 km without interruption, thereby they develop a speed of 4 km/h on average. So they are not much slower than healthy subjects. The two must important aims of conservative treatment of hip disease must be alleviation of pain and improvement of muscular strength. Main indication criterium for hip replacement is walking capacity, not the radiological assessed amount of degenerative changes.

[Sialic acid--an acute phase reactant and a concomitant of tumors]. / Sialinsäure--ein Akut-Phasen-Reaktant und Tumorbegleitparameter.

Sialic acid is an acute phase reagent with tumour burden reflecting fluctuations of serum level. The parameter is unsuitable for an early recognition of cancer. Sialic acid could be used as a parameter in questions concerning tumour burden: the diagnosis of tumour stage, the control of growth after therapy, the prediction of recidivation. The small specificity of an increased serum level of sialic acid will presumably be only of little use in tumour diagnostics.