The photoionisation threshold region of homogeneous Argon and Krypton clusters Ar, and Kr, for n up to 24 formed in a free jet expansion has been studied in detail, using the threshold photoelectron photoion coincidence (TPEPICO) time of flight technique. Measurements performed at a variety of different expansion conditions (nozzle temperature and stagnation pressure) demonstrate that fragmentation of larger clusters contributes substantially to the shape of the TPEPICO spectra even for the smallest clusters and at all photon energies higher than about 200 meV to 400 meV above the ionisation threshold. The determination of ionisation potentials for these cluster ions is discussed and careful estimates are given and compared with recent theoretical values.

Exact preoperative localization of the dural defect is an essential requirement for successful surgery of CSF fistula. Eighteen digital subtraction cisternography (DSC) results reported here were performed upon 16 patients with CSF rhinorrhea and 1 patient with CSF otorrhea. The exact site of the dural lesion could be proved in 9 out of 11 cases with active CSF leakage. In 4 cases the fistula was located in the cribriform plate, whereas it was found in the planum sphenoidale and the middle cranial fossa in 2 and 3 cases respectively. The frontal basal cisterns could not be filled sufficiently with the contrast agent due to haematoma and a prefixed chiasm accompanied by arachnoid adhesions in two cases. DSC performed during the non-drip period (3 cases) and in patients suspected to have a CSF rhinorrhea (3 cases) did not reveal the site of leakage. The investigation was followed by CT cisternography which allowed delineation of the lesion in the coronal view. In addition, MR with heavily T2-weighted images (modification of the rapid acquisition with relaxation enhancement imaging) was performed upon 6 cases out of which the CSF fistula could be demarcated clearly in 4 patients, three with a traumatic CSF leakage and the other with an encephalomeningocele. Surgery performed successfully in 9 cases confirmed the predicted site of dural dehiscence. Being a dynamic investigation making the actual site of the CSF fistula visible, DSC is recommended in addition to CT cisternography which continues to be the most sensitive method for diagnosing dural and bony defects. It is suggested that heavily T2-weighted MR images are useful in detecting the fistula in severe CSF rhinorrhea.

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