Calculation of the confidence intervals for transformation parameters in the registration of medical images

Images from different individuals typically cannot be registered precisely because anatomical features within the images differ across the people imaged and because the current methods for image registration have inherent technological limitations that interfere with perfect registration. Quantifying the inevitable error in image registration is therefore of crucial importance in assessing the effects that image misregistration may have on subsequent analyses in an imaging study. We have developed a mathematical framework for quantifying errors in registration by computing the confidence intervals of the estimated parameters (3 translations, 3 rotations, and 1 global scale) for the similarity transformation.The presence of noise in images and the variability in anatomy across individuals ensures that estimated registration parameters are always random variables. We assume a functional relation among intensities across voxels in the images, and we use the theory of nonlinear, least-squares estimation to show that the parameters are multivariate Gaussian distributed. We then use the covariance matrix of this distribution to compute the confidence intervals of the transformation parameters. These confidence intervals provide a quantitative assessment of the registration error across the images. Because transformation parameters are nonlinearly related to the coordinates of landmark points in the brain, we subsequently show that the coordinates of those landmark points are also multivariate Gaussian distributed. Using these distributions, we then compute the confidence intervals of the coordinates for landmark points in the image. Each of these confidence intervals in turn provides a quantitative assessment of the registration error at a particular landmark point. Because our method is computationally intensive, however, its current implementation is limited to assessing the error of the parameters in the similarity transformation across images.We assessed the performance of our method in computing the error in estimated similarity parameters by applying that method to real world dataset. Our results showed that the size of the confidence intervals computed using our method decreased – i.e. our confidence in the registration of images from different individuals increased – for increasing amounts of blur in the images. Moreover, the size of the confidence intervals increased for increasing amounts of noise, misregistration, and differing anatomy. Thus, our method precisely quantified confidence in the registration of images that contain varying amounts of misregistration and varying anatomy across individuals.     

An empirical investigation of physicians' attitudes toward intrasibling kidney donation by minor twins

BACKGROUND: A United States consensus group on the live donor concluded that minors (<18 years) can ethically serve as live solid organ donors in exceptional circumstances. More recent international guidelines reject this position. Recent United Network of Organ Sharing data show that minors serve as living donors, albeit infrequently. We examined the attitudes of US physicians toward minors as living donors. METHODS: Four hundred members of the American Society of Transplantation and 160 physicians from the American Academy of Pediatrics Section of Nephrology or Bioethics were surveyed. The physicians were asked whether minors should be permitted to serve as living donors and how their opinion would change depending on the twins' zygosity, age, and increased waitlist time. RESULTS: One hundred seventy of 436 eligible participants (39%) returned surveys. Thirty-two and 39% of respondents would permit a kidney donation between 15-year-old fraternal and identical twins, respectively (P=NS). If the wait time increased from 1 to 6 years, willingness increased to 39% and 45%, respectively (P=NS). Pediatric bioethicists were the most reluctant to prohibit minors as living donors. CONCLUSION: Approximately one-third of US physicians would permit children to serve as donors. Lengthening the wait time is associated with a trend toward greater willingness to permit minor donations. Current policies that give preferential status for a deceased donor organ to minors may help minimize donations by their minor siblings. Nontransplant physicians need education about donor risks to ensure that donations are in the best interest of pediatric donors and recipients.     

Biobank participation and returning research results: perspectives from a deliberative engagement in South Side Chicago

To be respectful of the public, biobank guiding principles and operations should be responsive to and inclusive of the values and beliefs of their participants. In an effort to increase knowledge and inform institutional policies, we conducted a deliberative engagement of individuals from two healthcare facilities in South Side Chicago that serve different socioeconomic communities to consider biobank policies regarding return of research results. We recruited primary caregivers of children receiving care at either a Federally Qualified Health Center or a university-based practice to attend two full-day deliberative engagement sessions, which included four educational presentations followed by focus group discussions. Surveys were administered to assess attitudes before and after the engagement, and an evaluation was conducted to assess the deliberative engagement process. All 45 participants self-identified as African-American. Focus group themes included: (1) overall interest in biobank participation, broad consent, and recontact; (2) root causes of distrust and potential biobank strategies to facilitate trust; (3) perceived positive and negative aspects of receiving research results; and (4) strong interest in receiving and managing their children's research results. Survey data indicated the same degree of interest in receiving results about themselves as about their children. Pre- and post-session findings showed mainly non-significant attitudinal changes in level of interest in biobank participation and return of research results, although there was a decrease in level of concern regarding identification from research data. Our findings reveal shared community insights important in facilitating relationships and policy discussions between biobank researchers and research participants.     

Legal challenges for substance abuse treatment during disasters

Certain groups with preexisting mental and behavioral health conditions, such as substance use disorders, may be especially vulnerable during and shortly after disasters. Researchers have found that substance abuse treatment programs and the individuals they serve experienced major disruptions after the September 11, 2001, attacks on the World Trade Center and the Pentagon and after Hurricane Katrina. This column considers legal challenges that may arise when a rapid influx of licensed providers is needed for substance abuse treatment during disasters and reviews specific legal issues that disasters may raise for opioid treatment programs. Opportunities to mitigate legal challenges and facilitate substance abuse treatment during disasters are discussed.