This paper presents a layout optimization method of the spot locations of pencil beam scanning for particle beam cancer therapy. With the pencil beam scanning technique, the particle beam is scanned from spot to spot in the tumor by using scanning magnets. To provide clinically ideal dose distributions and less-invasive treatment to the patients, both the spot locations and the number of particles given to each spot should be optimized. However, the spot layout is fixed with a lattice pattern in many prior studies. We propose the optimization method to derive the non-lattice spot layout to realize an acceptable dose distribution with a reduced number of spots. With the proposed method, a large enough number of spots were located densely at the initial state, and then the spots with the smallest contribution were removed one by one through iterations. The number of particles given to each spot was determined by solving a quadratic problem. Furthermore, we also propose the idea to accelerate the optimization process by simultaneously removing multiple spots. The algorithm was confirmed by numerical examples of both two-dimensional and three-dimensional cases. The dose quality with the optimized spot layout was better than that with the conventional lattice spot patterns, with all tested cases. In the optimized spot layout, the spots were located on the closed lines which were concentric to the target contour. We also confirmed the proposed method of multiple-remotion can accelerate the optimization process without violating the dose quality.
In order to reproduce the real driving condition of an automobile in the laboratory, the door mirror noise of the automobile was estimated by the wind tunnel test giving the uniform flow. Moreover, the scale model of the door mirror was analyzed by the wind tunnel for clarifying the relationship between the flow field around the door mirror and the aerodynamic noise. In particular, we discussed the low frequency narrow band noise and the flow field around the door mirror because the noise was 10dB larger than the background noise in the real automobile wind tunnel test. The experimental results indicated that when the clearance between the base and the visor of the door mirror is changed it influenced to the noise level in the low frequency domain. The noise level was increased due to the width of the wake when the clearance between the base and the visor was increased. From above results, we could grasp the phenomena about the narrow band noise in the vicinity of the 300 Hz generated from the actual automobile door mirror as it caused by the vortex shedding from the base.
Anatomical variations of hepatic arteries may be problematic in pancreaticoduodenectomy (PD). We experienced pancreatic head cancer in a patient with rare variation of hepatic artery and performed PD successfully with the resection of this artery. A 75-year-old woman showed pancreatic head tumor on CT. Preoperative CT detected rare variation of hepatic artery; posterior segmental branch of right hepatic artery (RHA-PB) originating from posterior inferior pancreaticoduodenal artery. The image also demonstrated that there was a junction between RHA-PB and anterior branch of right hepatic artery (RHA-AB). We performed PD for suspected pancreatic head cancer. We divided RHA-PB for complete resection of cancer because we preoperatively knew that there was the junction between RHA-PB and RHA-AB. She was discharged uneventfully, and there was no evidence of local recurrence throughout the whole course. Careful preoperative assessment of hepatic blood supply is the key to perform successful PD even in this troublesome situation.
For the purpose of combating desertification, it is important to understand mechanisms of the wind-blown sand movement, which is essentially a complicated two-phase flow phenomenon of sand particles and air. Therefore, we investigated the flow field around a model dune and the erosion process of the dune. In this study, we employed a porous fence, which was installed on the model dune, and examined its effect on the sand movement. The erosion process and its relationship with the turbulent intensity and the flow around the dune were discussed focusing on dependence of the flow field on the fence porosity. We tested four types of porous fences, which had different porosities: 0% (no permeability), 10%, 30%, and 50%. How a position of the fence affects suppression of the dune erosion was also examined. In the present experimental range, it can be concluded that the most effective fence position to suppress the sand movement should depend on porosity of the fence.
Introduction: The possibility of converting to an extended operation and the incidence of complications are said to be high in emergent surgery for acute appendicitis with an appendiceal abscess or mass. Recently clinical reports on ‘ Interval Appendectomy' (IA) for appendiceal abscess or mass are encountered, which comprises conservative therapy followed by elective appendectomy. Our hospital has employed IA since April, 2014. Here we make a presentation of our clinical outcomes for IA and discuss the efficacy of it. Methods: The indications for IA in our hospital are follows: 1) Abdominal CT shows an appendiceal mass or abscess (>1cm): 2) Abdominal examination does not reveal panperitonitis. In cases which satisfy our criteria, we plan to perform appendectomy 2-3 months after nonoperative treatment with antibiotics or percutaneous drainage. We employed this protocol, 14 cases, since April 2014 until March 2015. Also before designing this protocol, we performed emergent appendectomy (EA) for similar cases. Since January 2010 until April 2014, we experienced EA 11cases. We compared these two groups(IA 14 cases and EA 11 cases). Results: Conservative treatment was successful in 12 of the IA 14 patients (85.7%) with an average of 11 days of hospital stays. And in 2 patients, shifts to the emergent surgery were required because of uncontrolled infection. Between this IA 12 cases and EA 11 cases, we compared operation time, volume of bleeding, operative method, complications, total hospital stays and total hospital costs. In operation time (78.2minutes vs 149.5minutes; p=0.0019), volume of bleeding (4.92g vs 302.5g; p=0.0005), operative method (laparoscope=12 vs laparoscope/conversion to laparotomy/laparotomy=2/3/6; p < 0.0001, appendectomy=12 vs appendectomy/cecum partial resection/ileocecal resection=3/2/6; p=0.0002) and complications (SSI=1 vs SSI/ abscess formation/ileus=3/1/1; p=0.0368), IA were significantly superior. And also in total hospital stays (14.0days vs 12.7days; p=0.5712) and total hospital cost (9655.5dollars vs 11538.8dollars; p=0.1244), there were no statistic differences between IA and EA. Conclusion: 1)In IA cases, conversion to an extended operation was not seen and there were few complications. 2) We don't have longer hospital stays or higher total hospital cost in performing IA. For these reasons, we conclude that interval appendectomy is effective for acute appendicitis with an appendiceal abscess or mass.
