Delivering RapidArc®: A comprehensive study on accuracy and long term stability.

PURPOSE: To establish the reliability and accuracy of a UNIQUE Linac in delivering RapidArc treatments and assess its long term stability. MATERIALS AND METHODS: UNIQUE performance was monitored and analyzed for a period of nearly two years. 2280 Dynalog files, related to 179 clinical RapidArc treatments were collected. Different tumor sites and dose scheduling were included, covering the full range of our treatment plans. Statistical distributions of MLC motion error, gantry rotation error and MU delivery error were evaluated. The stochastic and systematic nature of each error was investigated together with their variation in time. RESULTS: All the delivery errors are found to be small and more stringent tolerances than those proposed by TG142 are suggested. Unlike MLC positional errors, where a linear relationship with leaf speed holds, other Volumetric Modulated Arc Therapy (VMAT) parameters reveal a random nature and, consequently, a reduced clinical relevance. MLC errors are linearly related only to leaf speed no matter the shape of the MLC apertures. Gantry rotation and MU delivery are as accurate as major competing Linacs. UNIQUE was found to be reliable and accurate throughout the investigation period, regardless of the specific tumor sites and fractionation schemes. CONCLUSIONS: The accuracy of RapidArc treatments delivered with UNIQUE has been established. The stochastic nature of delivery errors is proven. Long term statistics of the delivery parameter errors do not show significant variations, confirming the reliability of the VMAT delivery system.

A comparison of the sedative and analgesic properties of pethidine (meperidine) and butorphanol in dogs.

OBJECTIVES: To compare the analgesic and sedative effects of butorphanol and pethidine (meperidine) in dogs. METHODS: Twenty-eight female dogs undergoing ovariectomy (20) or ovariohysterectomy (8) were randomly divided into two groups. Pre-anaesthetic medication in group B consisted of 20 µg/kg intramuscular (im) acepromazine and 0·4 mg/kg butorphanol, while group P received 20 µg/kg acepromazine with 5 mg/kg pethidine. The resulting sedation (simple descriptive scale), propofol dose required to induce anaesthesia, several intraoperative cardiorespiratory variables and postoperative pain (Colorado Pain Scoring System) were compared between the two groups. A 0·2 mg/kg meloxicam dose was administered intravenously to all animals at the end of the 4 hours observation period, or earlier if the pain score was more than 13. RESULTS: Sedation scores, propofol induction doses and intraoperative cardiorespiratory variables were not different between groups. Postoperative pain scores were also similar although one dog in group B required rescue analgesia. Five dogs in group P vomited postoperatively. CLINICAL SIGNIFICANCE: Either butorphanol and pethidine, combined with acepromazine, produced reliable sedation and analgesia up to 4 hours after intramuscular injection in dogs.