MR-based cardiac and respiratory motion correction of PET: application to static and dynamic cardiac 18F-FDG imaging

Motion of the myocardium deteriorates the quality and quantitative accuracy of cardiac PET images. We present a method for MR-based cardiac and respiratory motion correction of cardiac PET data and evaluate its impact on estimation of activity and kinetic parameters in human subjects. Three healthy subjects underwent simultaneous dynamic ¹⁸F-FDG PET and MRI on a hybrid PET/MR scanner. A cardiorespiratory motion field was determined for each subject using navigator, tagging and golden-angle radial MR acquisitions. Acquired coincidence events were binned into cardiac and respiratory phases using electrocardiogram and list mode-driven signals, respectively. Dynamic PET images were reconstructed with MR-based motion correction (MC) and without motion correction (NMC). Parametric images of ¹⁸F-FDG consumption rates (K_i) were estimated using Patlak's method for both MC and NMC images. MC alleviated motion artifacts in PET images, resulting in improved spatial resolution, improved recovery of activity in the myocardium wall and reduced spillover from the myocardium to the left ventricle cavity. Significantly higher myocardium contrast-to-noise ratio and lower apparent wall thickness were obtained in MC versus NMC images. Likewise, parametric images of K_i calculated with MC data had improved spatial resolution as compared to those obtained with NMC. Consistent with an increase in reconstructed activity concentration in the frames used during kinetic analyses, MC led to the estimation of higher K_i values almost everywhere in the myocardium, with up to 18% increase (mean across subjects) in the septum as compared to NMC. This study shows that MR-based motion correction of cardiac PET results in improved image quality that can benefit both static and dynamic studies.

The short-term outcome of laser endoureterotomy for ureteric stricture

With the advent of new technology, the treatment for ureteric stricture has moved from open surgery to endoscopic procedures. Our goals were to review and determine the prognostic factors for success of laser endoureterotomy for ureteric stricture. This is a cross sectional study for all cases that underwent laser endoureterotomy in a single centre from 2002 to 2009. Standard treatment in this centre utilizes holmium laser. The fiber used was 365nm, setting as 1J and frequency 8 Hz; power output 8 W. Confirmation of adequacy of incision wss by either visualization of extra-ureteric fat or extravasations of contrast on fluoroscopic imaging. Success or recurrence of the endoureterotomy was confirmed objectively with evidence of improvement from imaging. Of these 77 patients, 42 cases (61.8%) of the strictures were from upper ureter. Eight cases (11.7%) of mid-ureteric while lower ureter had 18 cases (26.5%). Length of stricture has been grouped into two groups; Short (<1cm) and long (≥1cm) and their distributions were 47.1% and 26.5% respectively. Follow-up duration ranged from six months to 88 months with an average of 19.6 months. Success rate was 76.5% (52 patients) while 16 patients (23.5%) developed recurrence. Stone disease, positive presenting symptoms and short length of the stricture were identified as variables with good predictor. This study achieved a 76.5% of success rate for this treatment modality for benign ureteric stricture in wellselected patients. Success is more likely if patient is symptomatic (earlier treatment) and previous stone disease present as a risk factor.

Historical changes in the objectives of the periodic health examination

Important historical changes have occurred both in the content of the periodic health examination and in the legitimacy with which this examination has been viewed. These changes reflect fundamental shifts in the objectives of the examination and in the concerns of its advocates, the most prominent of whom have been physicians; leaders in the life insurance, private corporate, and prepaid health care industries; and medical expert panels. The shifting dominance of concerns has driven the development of the periodic health examination, and continual reassessment of the value and limitations of the examination is warranted.

Cultural factors associated with health-risk behavior among the Cheyenne River Sioux

A field study was conducted to identify cultural factors--values, beliefs, and related characteristics--associated with health-risk behavior among adult members of the Cheyenne River Sioux Tribe. The Cultural Values Survey (CVS), an instrument for measuring cultural values and related characteristics, was developed and pilot tested in the study population. This instrument, along with the Health Risk Appraisal (HRA) (an instrument developed by the Centers for Disease Control to quantify major health-related behaviors), was administered to a random sample of 429 adults in the study community. Significant differences between females and males for both cultural characteristics and health-risk behaviors were found. Females had significantly higher HRA-calculated Health Index values than males, reflecting overall healthier behaviors. Females who scored higher on cultural factors consistent with more traditional Lakota Indian lifestyles (e.g., degree of Indian blood, Lakota language spoken in the home, traditional Lakota beliefs) had higher HRA Health Index values than females scoring lower in these characteristics. Males who scored higher in factors related to self-determination (e.g., hard work, personal control, industriousness, individual action) had higher Health Index values than those who scored lower in these areas. Further testing of the CVS instrument, as well as further research from both epidemiologic and social science perspectives is essential to elucidate the nature of the relationship between cultural factors and health-related behavior.