A comprehensive set of transition probabilities and radiative lifetimes of Rydberg states of alkali atoms (for Na, K, Cs, n 30; and for Rb, n 6 50) is obtained by using a simple, exactly solvable potential model for atoms. The results agree well with the available experimental values and other theoretical ones. Scaling relations for evaluating transition probabilities and lifetimes of high Rydberg states are also discussed. The well known (n*)-' scaling law of the transition probabilities A,,,,. with n'= n >> 1 is generally valid; however, we also find deviations from this law for some d-, p and f-* d transitions for Rb. A third-power polynomial is found to be better than the currently used exponential scaling law in predicting the lifetimes of even higher excited states.

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Objectives. To introduce a new implementation of radiomics analysis for cartilage and subchondral bone of the knee and to compare the performance of the proposed models to classic T2 relaxation time in distinguishing knees predisposed to posttraumatic osteoarthritis (PTOA) after anterior cruciate ligament reconstruction (ACLR) and healthy controls. Methods. 114 patients following ACLR after at least 2 years and 43 healthy controls were reviewed and allocated to training ( n = 110 ) and testing ( n = 47 ) cohorts. Radiomics models are built for cartilage and subchondral bone regions of different compartments: lateral femur (LF), lateral tibia (LT), medial femur (MF), and medial tibia (MT) and combined models of four compartments on T2 mapping images. The model performance of discrimination between patients and controls was illustrated with the receiver operating characteristic curve and compared with a classic T2 value-based model. Results. The T2 value model of cartilage yielded moderate predictive performance in discerning patients and controls, with an AUC of 0.731 (95% confidence interval, 0.556–0.875) in the testing cohort, while the radiomics signature of cartilage and subchondral bone of different compartments demonstrated excellent performance, with AUCs of 0.864–0.979. Furthermore, the combined model reported an even better performance, with AUCs of 0.977 (95% confidence interval, 0.919–1.000) for the cartilage and 0.934 (95% confidence interval, 0.865–0.994) for the subchondral bone in the testing cohort. Conclusion. The radiomics features of the cartilage and subchondral bone may be able to provide powerful tools with more sensitive detection than T2 values in differentiating knees at risk for PTOA after ACLR from healthy knees.

Objective. This study was designed to validate the feasibility of wideband high-frequency ultrasound imaging to resolve in vivo the degree, location, and morphologic changes of myocardial infarction (MI) in a rat model. Methods. The left anterior descending coronary artery was ligated in the test group (n = 41), and the sham control group did not have ligation (n = 7). The rats were examined with 10-to 22-MHz echocardiography to evaluate the MI size, location, and geometric formation. Results. The endocardial chamber shape was deformed, with enlargement of the anteroposterior dimension and fractional shortening, and was comparable with the degree of MI both in short-and long-axis sections of the left ventricle. Histologic analysis showed remodeling to different extents corresponding to different MI sizes (small, medium, and large). Conclusions. The results suggest that this technique can be used in vivo to evaluate the MI location, size, and morphologic changes corresponding to the extent of the injury. Key words: high-frequency ultrasound imaging; histologic analysis; left anterior descending coronary artery; myocardial infarction. he rat is a preferred species for studying the pathophysiologic mechanisms of myocardial infarction (MI), cardiomyopathy, and other cardiovascular diseases. 1,2 Noninvasive in vivo study of rat cardiac structure and function has attracted interest in cardiovascular research, especially those involving the left ventricle (LV). The rat infarct model has been used extensively to study LV dysfunction after MI and in the evaluation of experimental therapies for heart failure. 3,4 Two-dimensional (2D) B-mode, M-mode, and Doppler ultrasound have been used to evaluate LV structural and functional remodeling in humans for decades, particularly in patients with MI during the acute phase and for later follow-up. However, the small size and rapid heart rate (300-500 beats per minute) of the rat heart demand an imaging modality with both high temporal resolution and high spatial resolution. 5,6 Recently developed high-resolution echocardiographic systems with high frequencies (>20 MHz) are particularly well suited for the study of the heart in rodent models of MI. These systems can be used for evaluating the heart contractility, mainly LV systolic and diastolic function.