ABSTRACT
We report on the design, fabrication, and first tests of a tomographic scanner developed for proton computed tomography (pCT) of head-sized objects. After extensive preclinical testing, pCT is intended to be employed in support of proton therapy treatment planning and pre-treatment verification in patients undergoing particle-beam therapy. The scanner consists of two silicon-strip telescopes that track individual protons before and after the phantom, and a novel multistage scintillation detector that measures a combination of the residual energy and range of the proton, from which we derive the water equivalent path length (WEPL) of the protons in the scanned object. The set of WEPL values and the associated paths of protons passing through the object over a 360° angular scan are processed by an iterative, parallelizable reconstruction algorithm that runs on modern GP-GPU hardware. In order to assess the performance of the scanner, we have performed tests with 200 MeV protons from the synchrotron of the Loma Linda University Medical Center and the IBA cyclotron of the Northwestern Medicine Chicago Proton Center. Our first objective was calibration of the instrument, including tracker channel maps and alignment as well as the WEPL calibration. Then we performed the first CT scans on a series of phantoms. The very high sustained rate of data acquisition, exceeding one million protons per second, allowed a full 360° scan to be completed in less than 10 minutes, and reconstruction of a CATPHAN 404 phantom verified accurate reconstruction of the proton relative stopping power in a variety of materials.
ABSTRACT
Surveys have shown that 80% of Americans don't trust corporate executives and--worse--that roughly half of all managers don't trust their own leaders. Mergers, downsizing, and globalization have accelerated the pace of change in organizations, creating a crisis of trust that didn't exist a generation ago. Leaders who understand how trust is built can actively influence its development, resulting in a more supportive and productive work environment and, not incidentally, a competitive advantage in the war for talent. Building on research in social psychology, and on his 15 years of experience consulting on trust, the author has developed a model for predicting whether trust or distrust will be chosen in a given situation. It helps managers analyze ten factors at play in the decision-making process. Hundreds of top executives have used it to diagnose and address the root causes of distrust in their work relationships. Some of the factors in the model relate to the decision maker: How tolerant of risk, how well-adjusted, and how relatively powerful is he or she? Others relate to the specific situation: How closely aligned are the interests of the parties concerned? Does the person who is asking to be trusted demonstrate competence? Predictability and integrity? Frequent and honest communication? Sue, a relatively new VP of sales, used the trust model to manage her relationship with Joe, an employee nearing retirement who was not performing well in a new sales role. Fearing for his job, Joe wasn't initially inclined to trust her. Sue took concrete steps to communicate openly with Joe, explore other options for him, and show concern for his well-being. When joe was transferred, he let his former colleagues know how pleased he was with Sue's handling of the situation. As a result, the level of trust increased in Sue's department, even though it was experiencing major change.