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Magnetic Resonance Imaging (MRI) is increasingly being used for improving tumor delineation and tumor tracking in the presence of respiratory motion. The purpose of this work is to design and build an MR compatible motion platform and to use it for evaluating the geometric accuracy of MR imaging techniques during respiratory motion. The motion platform presented in this work is composed of a mobile base made up of a flat plate and four wheels. The mobile base is attached from one end and through a rigid rod to a synchrony motion table by Accuray® placed at the end of the MRI table and from the other end to an elastic rod. The geometric accuracy was measured by placing a control point‐based phantom on top of the mobile base.In‐house software module was used to automatically assess the geometric distortion. The blurring artifact was also assessed by measuring the Full Width Half Maximum (FWHM) of each control point. Our results were assessed for 50, 100, and 150 mm radial distances, with a mean geometric distortion during the superior–inferior motion of 0.27, 0.41, and 0.55 mm, respectively. Adding the anterior–posterior motion, the mean geometric distortions increased to 0.4, 0.6, and 0.8 mm. Blurring was observed during motion causing an increase in the FWHM of ≈30%. The platform presented in this work provides a valuable tool for the assessment of the geometric accuracy and blurring artifact for MR during motion. Although the main objective was to test the spatial accuracy of an MR system during motion, the modular aspect of the presented platform enables the use of any commercially available phantom for a full quality control of the MR system during motion.

To rank a variety of ventures in the order of their profitability, a yardstick is needed in which both the profit and the time at which this profit is realized are included. This paper describes methods for evaluating two of the more common yardsticks, i.e., the present day value or the total profit for a fixed interest rate and the internal rate of return. No attempt is made to present arguments in favor of either of these criteria. Based on a number of simplifying assumption, tables and graphs have been prepared with the aid of which the profitability of single incomes, constant incomes, and three types of declining incomes can be calculated for a wide range or interest rates. Two examples are given to explain the use of the graphs and tables. Introduction The total profit of a venture is by definition the difference between the total net income and the capital investment. Where, as is usually the case, the investor has a choice of ventures in which he can invest his money, he will need a single yardstick to rank these ventures according to their profitability. It is at once obvious that the total profit cannot always be a sufficient criterion: a smaller profit returned to its investor after a short time may be more desirable than a larger one, for which the investor has to wait a long time. A yardstick by which ventures can be ranked uniquely according to their degree or profitability must therefore incorporate the monetary value of the profits and the time at which they are returned to the investor. Several yardsticks are being used in the oil industry which more or less approach this criterion. In the present paper only two will be considered: the present day value (or deferred value) or the total profit, and the internal rate of return ["yield", "earning power", "rate of return," etc.]

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