An MPC‐based position controller for a tilt‐rotor tricopter VTOL UAV

This study presents a novel framework, namely, the fusion of a conventional controller and a linear model predictive controller, for the position control of a tilt‐rotor tricopter. While the conventional controller in the outer loop is responsible for the position control, the inner‐loop model predictive control–based controller handles the angular dynamics and vertical body velocity. Furthermore, a novel control allocation algorithm for the proposed controller is introduced. In addition, this study also covers mathematical modeling and trim analysis of the tilt‐rotor tricopter dynamics. An evaluation of the designed control system is accomplished with a nonlinear 6‐degree‐of‐freedom simulation model of the tilt‐rotor tricopter in which realistic actuator limitations are considered. The efficiency of the proposed control algorithm is elaborated for a trajectory tracking problem where basic surveillance operation is considered. The simulation results show that the proposed model predictive controller is able to provide a satisfactory trajectory tracking performance under the realistic actuator limits.     

Indium-111 octreotide scintigraphy in patients with bone tumours of the extremities

Radiolabelled somatostatin analogues are of potential value in the imaging of somatostatin receptor-positive tumours. Recently, somatostatin receptors have been demonstrated in the osteoblast precursor cells. In this preliminary study, we evaluated the uptake characteristics of indium-111 octreotide in two benign and two malignant bone tumours. Tracer accumulation was observed in all four cases, and overall lesion to background ratio (mean±SD) was 2.74±0.84 and 2.98±1.49 at 4 h and 24 h, respectively. There was no clear relationship between I¹¹¹In-octreotide accumulation and the benign or malignant nature of the tumour. In one patient, tracer uptake was inhibited by unlabelled octreotide administration. These results suggest that¹¹¹In-octreotide can be taken up by benign and malignant bone tumours. The inhibition of tumour uptake by treatment with cold octreotide supports the concept that specific uptake mechanisms are responsible for¹¹¹In-octreotide deposition by bone tumours.     

Influence of tumor volume on survival in patients irradiated for non-small-cell lung cancer

PURPOSE: To investigate the importance of CT-defined total tumor volume (TTV) on overall survival (OS) in patients with unresectable or medically inoperable non-small-cell lung carcinoma (NSCLC). METHODS AND MATERIALS: Between 1991 and 1998, 150 evaluable patients with Stage I-IIIB NSCLC were treated with three-dimensionally planned conformal radiotherapy and curative intent at Duke University Medical Center. On the treatment-planning CT, the primary tumor and nodal volumes were identified and subsequently combined to form the TTV. The TTV was compared with the stage and outcome with respect to OS, local progression-free survival, and distant failure-free survival using the Kruskall-Wallis analysis of variance and Kaplan-Meier actuarial method. To account for the potentially confounding effects of therapeutic and patient-specific covariates on survival, the Cox proportional hazard regression model was used. RESULTS: The TTVs in patients with Stage I disease (median 19 cm3) were smaller than in patients with Stage II (median 80 cm3) or Stage III (median 97 cm3; p <0.001) disease. The Stage II TTVs were not significantly different from those of Stage III (post-hoc test according to Bonferroni). Prolonged OS was independently associated with a small TTV (<80 vs. >80 cm3 [median]; p = 0.01), young age (<60 vs. > or =60 years; p = 0.03), high Karnofsky performance status (< o r =70 vs. >70; p = 0.04), and female gender (p = 0.04). Both stage (p = 0.7) and T stage (p = 0.06) were of less importance for OS than was the TTV, according to multivariate modeling. Increased local progression-free survival (p = 0.001) and distant failure-free survival (p = 0.03) were independently associated with a small TTV (i.e., <80 cm3). The results were unchanged if the TTV was analyzed as a continuous variable. CONCLUSION: A strong independent association between a small CT-defined TTV and prolonged survival in patients with NSCLC selected for curative/definitive RT was found. Future therapeutic studies in NSCLC should consider stratifying/adjusting for differences in TTV to avoid confounding effects on survival from variations in the TTV at baseline.