Frameless Hypofractionated Gamma Knife Radiosurgery for Residual or Recurrent Craniopharyngioma.

BACKGROUND: The management of craniopharyngiomas is challenging, usually requiring multidisciplinary care. Gamma Knife radiosurgery (GKRS) is an essential technique for residual/recurrent craniopharyngiomas. OBJECTIVE: To evaluate the efficacy of frameless hypofractionated GKRS (hfGKRS) for craniopharyngioma and factors which affect tumor control and complications. METHODS: This retrospective study involved 24 patients managed with hfGKRS. Clinical and radiological data, tumor characteristics, and procedural details were analyzed. RESULTS: There were 15 (62.5%) female patients. The median age was 38.5 years (range, 3-66 years). The mean tumor volume was 2.4 (1.93) cm 3 , with a mean solid volume of 1.6 (1.75) cm 3 . The median marginal dose was 20 Gy (range, 18-25 Gy) delivered in a median of 5 fractions (range, 3-5). During a median radiological follow-up of 23.5 months (range, 12-50 months), tumor progression was noted in 5 (20.8%) patients. The 2-year and 4-year progression-free survival were 81.8% and 61.4%, respectively. No deaths were identified at a median clinical follow-up of 31.3 months (range, 12-54 months). Visual deficits attributable to progression were noted in 3 (12.5%) patients with pre-GKRS visual field defects. An additional 4 (16.7%) patients with pre-GKRS visual deficit developed new minor visual field defects. Four (16.7%) patients showed improvement of vision after GKRS. There were no new-onset post-GKRS hormonal deficits. CONCLUSION: The management of craniopharyngioma requires a multidisciplinary approach, and irradiation represents effective treatment option for residual/recurrent tumors after surgery. To the best of our knowledge, this is the first study that addresses the efficacy of frameless hfGKRS in managing craniopharyngiomas over sufficient follow-up.

Novel Clinically Weight-Optimized Dynamic Conformal Arcs (WO-DCA) for Liver SBRT: A Comparison with Volumetric Modulated Arc Therapy (VMAT).

PURPOSE: To evaluate the feasibility of shortening the duration of liver stereotactic radiotherapy (SBRT) without jeopardizing dosimetry or conformity by utilizing weight-optimized dynamic conformal arcs (WO-DCA) as opposed to volumetric modulated arc therapy (VMAT) for tumors away from critical structures. METHODS: Nineteen patients with liver metastasis were included, previously treated with 50 Gy in 4 fractions with VMAT technique using two partial coplanar arcs of 6 MV beams delivered in high-definition multi-leaf collimator (HD-MLC). Two coplanar partial WO-DCA were generated on Pinnacle treatment planning system (TPS) for each patient; and MLC aperture around the planning target volume (PTV) was automatically generated at different margins for both arcs and maintained dynamically around the target during arc rotation. Weight of the two arcs using optimization method was adjusted between the arcs to maximize tumor coverage and protect organs at risk (OAR) based on the RTOG-0438 protocol. RESULTS: The WO-DCA plans successfully "agreed" with the standard VMAT for OAR (liver, spinal cord, stomach, duodenum, small bowel, and heart) and PTV (Dmean, D98%, D2%, CI, and GI), with superior mean quality assurance (QA) pass rate (97.06 vs 93.00 for VMAT; P < 0.001 and t = 8.87). Similarly, the WO-DCA technique additionally reduced the beam-on time (3.26 vs 4.43; P < 0.001) and monitor unit (1860 vs 2705 for VMAT; P < 0.001) values significantly. CONCLUSION: The WO-DCA plans might minimize small-field dosimetry errors and defeat patient-specific VMAT QA requirements due to the omission of MLC beam modulation through the target volume. The WO-DCA plans may additionally enable faster treatment delivery times and lower OAR without sacrificing target doses in SBRT of liver tumors away from critical structures.

Optimisation of biomass catalytic depolymerisation conditions by using response surface methodology.

The aim of this study is to present the optimum operating conditions for reducing energy consumption in the process of obtaining bio-oil from the mixture of sawdust, waste lubricating oil, lime, and commercial catalyst. In the study where the catalytic pressureless depolymerisation (also called Katalytische Drucklose Verölung - KDV) was applied, the operating conditions were analysed with response surface methodology. According to the analysis of variance results, a mathematical model was obtained for specific product yield (bio-oil amount/energy consumption g kWe-1). Effects of temperature (260°C-290°C), catalyst rate (1-2 wt.%) and reaction time (0.5-1 h) were investigated. The optimum conditions for the three independent variables (temperature, catalyst rate, reaction time) were 279 ± 2°C, 2 wt.% and 0.5 h, respectively. Maximum specific product yield was obtained as 970.17 g kWe-1. While the reaction time was the most effective regarding the amount of bio-oil obtained at 1 kWe energy consumption, the temperature was found to be the least effective. In addition to these, bio-oil obtained under optimum conditions were characterised and compared with standard diesel specifications.

Effects of operational parameters on bio-oil production from biomass.

In this study, the production of bio-oil from the pyrolysis of furniture sawdust, waste lubricating oil and their mixtures were investigated under certain operating conditions in the presence of lime and zeolites, by using a laboratory scale horizontal tubular reactor placed in a furnace. The main focus was to investigate the mutual effect of lime and commercial zeolite on the amount of the bio-oil production from furniture sawdust and waste lubricating oil. The selected operating parameters were pyrolysis temperatures and heating rate of 300°C and 650°C and flash heating or gradual heating rate (30°C/min). Additionally, three different additives were tested as catalysts; namely, lime (CaO), commercial zeolite (4A) and a natural zeolite (klinoptilolite). The amount of the produced bio-oil was analyzed by gas chromatography-flame ionization detector. The distribution of solid, liquid and gaseous products was determined for each operational condition. It was seen that the amount of the bio-oil was influenced by the amounts of sawdust and zeolite in the mixture. Experimental results showed that higher temperatures were more effective for the higher bio-oil amount. Additionally, heating rate was quite significant at 300°C whereas it has a minor effect on the bio-oil amount at 650°C. The highest bio-oil yield was obtained for the mixture of sawdust and waste lubricating oil in the presence of both lime and commercial zeolite with flash heating rate at 650°C.