Dose-rate scaling factor estimation of THOR BNCT test beam.

In 1998, an epithermal neutron test beam was designed and constructed at the Tsing Hua Open-Pool Reactor (THOR) for the purpose of preliminary dosimetric experiments in boron neutron capture therapy (BNCT). A new epithermal neutron beam was designed at this facility, and is currently under construction, with clinical trials targeted in late 2004. Depth dose-rate distributions for the THOR BNCT test beam have been measured by means of activation foil and dual ion chamber techniques. Neutron and structure-induced gamma spectra measured at the test beam exit were configured into a source function for the Monte Carlo-based treatment planning code NCTPlan. Dose-rate scaling factors (DRSFs) were determined to normalize computationally derived dose-rate distributions with experimental measurements in corresponding mathematical and physical phantoms, and to thus enable accurate treatment planning using the NCTPlan code. A similar approach will be implemented in characterizing the new THOR epithermal beam in preparation for clinical studies. This paper reports the in-phantom calculated and experimental dosimetry comparisons and derived DRSFs obtained with the THOR test beam.     

Prevalence,Distribution and Factors Associated with the Presence and the Potential for Malignancy of Cutaneous Neoplasms in 174 Dogs Admitted to a Clinic in Northern Greece

One hundred and seventy-four dogs diagnosed with cutaneous neoplasms in the Animal Medical and Surgical Clinic, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki, were studied. Thirty-one types of neoplasm were diagnosed, among which mast cell tumours (13.8%), hepatoid gland adenomas (9.8%), lipomas (5.7%) and histiocytomas (5.7%) were the most common. The prevalence of epithelial, mesenchymal, lymphohistiocytic and melanocytic tumours was 47.7, 40.8, 8.6 and 2.9%, respectively. Potentially malignant neoplasms were less frequently recorded than benign neoplasms. The tumours were single (80.5%) or multiple (19.5%) and located on the head and neck (18.4%), the body trunk (49.4%), the limbs (25.9%) or at multiple sites (6.3%). The factors evaluated in multivariable logistic regression models for possible association with the odds of a tumour's potential for malignancy included the age, the sex and the breed of the dog, as well as the histological type of the neoplasm. Dogs with mesenchymal tumours had two times higher odds of potential for malignancy than those with epithelial tumours. In contrast, dogs with either lymphohistiocytic or melanocytic tumours did not have increased risk of malignancy compared with dogs with epithelial tumours. The odds of tumour malignancy linearly increased with increasing age of the dog by a factor of 1.1 per year. Finally, the effect of the sex and the breed of the dog on the risk of developing cutaneous neoplasms was investigated in an age-matched case–control sample of 348 dogs by conditional logistic regression analysis. The odds of neoplasm presence were two times higher in pure bred dogs than in mongrels but did not differ between cross-breeds and mongrels.     

The Rigiflex TTS: A New Method to Dilate Benign Esophageal Stenosis

Abstract: This paper dicusses the use of esophageal dilatation with a Rigiflex TTS balloon. This method was used 45 times on 11 patients affected by anastomotic or a severe grade peptic esophageal stenosis. Fluoroscopic guidance was used in 36 procedures (80%) without effecting the mean duration of the treatment (12 minutes). The results were considered satisfactory when these goals had been achieved: a) dilatation of the stenosis over 15 mm; b) a dysphagia free-time of more than 6 months. A satisfactory result was achieved in 10 patients (90.9%), without deaths and major complications. 5 patients received 1 dilatation and the other 5 needed, 3-3-4-7–11 procedures respectively to obtain a satisfactory result. On these basis we consider that its great efficacy, security and tolerability depend on the following characteristics of the Rigiflex TTS balloon: 1) “radial” dilatation; 2) the possibility of introducing the balloon through the operative channel of the fiberscope; 3) direct visualization of the stenosis during dilatation. The following disadvantages with this method are: the absence of a tactile sensation of dilatation and the elevated cost of the instrument. We conclude that the Rigiflex TTS balloon is an important alternative to guide-wire techniques, especially for the treatment of severe esophageal strictures.