NEMA NU 4-2008 Comparison of preclinical PET imaging systems

The National Electrical Manufacturers Association (NEMA) standard NU 4-2008 for performance measurements of smallanimal tomographs was recently published. Before this standard, there were no standard testing procedures for preclinical PET systems, and manufacturers could not provide clear specifications similar to those available for clinical systems under NEMA NU 2-1994 and 2-2001. Consequently, performance evaluation papers used methods that were modified ad hoc from the clinical PET NEMA standard, thus making comparisons between systems difficult. Methods: We acquired NEMA NU 4-2008 performance data for a collection of commercial animal PET systems manufactured since 2000: micro- PET P4, microPET R4, microPET Focus 120, microPET Focus 220, Inveon, ClearPET, Mosaic HP, Argus (formerly eXplore Vista), VrPET, LabPET 8, and LabPET 12. The data included spatial resolution, counting-rate performance, scatter fraction, sensitivity, and image quality and were acquired using settings for routine PET. Results: The data showed a steady improvement in system performance for newer systems as compared with first-generation systems, with notable improvements in spatial resolution and sensitivity. Conclusion: Variation in system design makes direct comparisons between systems from different vendors difficult. When considering the results from NEMA testing, one must also consider the suitability of the PET system for the specific imaging task at hand.This work was funded by the Natural Sciences and Engineering Research Council of Canada under Discovery Grant 341628-2007. No other potential conflict of interest relevant to this article was reported.En prens

Supervising the Supervisors—Procedural Training and Supervision in Internal Medicine Residency

At teaching hospitals, bedside procedures (paracentesis, thoracentesis, lumbar puncture, arthrocentesis and central venous catheter insertion) are performed by junior residents and supervised by senior peers. Residents’ perceptions about supervision or how often peer supervision produces unsafe clinical situations are unknown. To examine the experience and practice patterns of residents performing bedside procedures. Cross-sectional e-mail survey of 653 internal medicine (IM) residents at seven California teaching hospitals. Surveys asked questions in three areas: (1) resident experience performing procedures: numbers of procedures performed and whether they received other (e.g., simulator) training; (2) resident comfort performing and supervising procedures; (3) resident reports of their current level of supervision doing procedures, experience with complications as well as perceptions of factors that may have contributed to complications. Three hundred sixty-seven (56%) of the residents responded. Most PGY1 residents had performed fewer than five of any of the procedures, but most PGY-3 residents had performed at least ten by the end of their training. Resident comfort for each procedure increased with the number of procedures performed (p < 0.001). Although residents reported that peer supervision happened often, they also reported high rates of supervising a procedure before feeling comfortable with proper technique. The majority of residents (64%) reported at least one complication and did not feel supervision would have prevented complications, even though many reported complications represented technique- or preparation-related problems. Residents report low levels of comfort and experience with procedures, and frequently report supervising prior to feeling comfortable. Our findings suggest a need to examine best practices for procedural supervision of trainees

A Method for Determination of the Timing Stability of PET Scanners

Abstract—We report on the timing resolution and stability of the MicroPET R4 PET scanner. Its detectors have energy resolutions in the range of 25 % and previously reported timing resolutions 3.2 ns. Our preliminary evaluation of this instrument showed that artefact-free normalization sinograms could only be obtained with a timing window of 10 ns or more in spite of a timing resolution of 3.2 ns. This instrument uses high-speed electronics albeit with 2-ns timing clock. We performed sham transmission scans with nothing in the field of view, and a range of timing windows from 2 to 14 ns and used a 14-ns timing blank scan to generate effective attenuation sinograms as a function of timing window. These showed trues count-rates which fit well to a ERF @ A function. However, the effective attenuation value, which should be 1.0, changes from block to block and becomes very high in some blocks ( 3.5 at 6 ns) suggesting the need for timing alignment. A method was devised to measure the timing stability to a precision better than the timing bin width of 2 ns. Index Terms—Positron emission tomography, timing alignment, timing stability, time-of-flight. I

Respecting tutorial instructors' beliefs and experiences: A case study of a physics teaching assistant

Effective physics instruction benefits from respecting the physics ideas that introductory students bring into the classroom. We argue that it is similarly beneficial to respect the teaching ideas that novice physics instructors bring to their classrooms. We present a case study of a tutorial teaching assistant (TA), Alan. When we first examined Alan’s teaching, we focused our attention on the mismatch between his actions and those advocated by the TA instructors. Further study showed us that Alan cared about helping his students and that his teaching was well integrated with his beliefs about how students learn physics and how teachers can best assist students. Learning about Alan’s beliefs and motivations changed our thinking about what might constitute effective professional development for Alan and other TAs. We advocate a new perspective on TA professional development: one in which TAs are seen as partners in the endeavor of educating students and one that seeks to find and build upon productive elements in their beliefs

Tutorial teaching assistants in the classroom: Similar teaching behaviors are supported by varied beliefs about teaching and learning

As part of a long-term program to develop effective, research-based professional development programs for physics graduate student teaching assistants (TAs), we first identify their current classroom practices and why they engage in these practices. In this paper, we identify a set of teaching practices we call “focusing on indicators,” which occurs when TAs use signs such as key words or diagrams as evidence that students understand the target idea; these indicators are more superficial than a detailed explanation. Our primary finding is that although the three TAs discussed here share a common behavior, the beliefs and motivations that underlie this behavior vary. We argue that TA professional development focused on changing these TAs’ focus-on-indicator behavior is unlikely to be effective. Instead, responsive TA professional development will need to address the TAs’ beliefs that guide the observed classroom behavior

Accounting for tutorial teaching assistants’ buy-in to reform instruction

Successful implementation of tutorials includes establishing norms for learning in the tutorial classroom. The teaching assistants (TAs) who lead each tutorial section are important arbiters of these norms. TAs who value (buy into) tutorials are more likely to convey their respect for the material and the tutorial process to the students, as well as learning more themselves. We present a case study of a TA who does not buy into certain aspects of the tutorials he teaches and demonstrate how his lack of buy-in affects specific classroom interactions. We would hope to design professional development programs to help TAs appreciate the power of tutorial instruction. However, our research suggests that the typical professional development activities offered to tutorial TAs are not likely to be effective. Instead, it appears that what we call the “social and environmental context” of the tutorials—including classroom, departmental, and institutional levels of implementation—has the potential to strongly affect TA buy-in to tutorials and probably outweighs the influence of any particular activity that we might prepare for them