Roadmap toward the 10 ps time-of-flight PET challenge.

Since the seventies, positron emission tomography (PET) has become an invaluable medical molecular imaging modality with an unprecedented sensitivity at the picomolar level, especially for cancer diagnosis and the monitoring of its response to therapy. More recently, its combination with x-ray computed tomography (CT) or magnetic resonance (MR) has added high precision anatomic information in fused PET/CT and PET/MR images, thus compensating for the modest intrinsic spatial resolution of PET. Nevertheless, a number of medical challenges call for further improvements in PET sensitivity. These concern in particular new treatment opportunities in the context personalized (also called precision) medicine, such as the need to dynamically track a small number of cells in cancer immunotherapy or stem cells for tissue repair procedures. A better signal-to-noise ratio (SNR) in the image would allow detecting smaller size tumours together with a better staging of the patients, thus increasing the chances of putting cancer in complete remission. Moreover, there is an increasing demand for reducing the radioactive doses injected to the patients without impairing image quality. There are three ways to improve PET scanner sensitivity: improving detector efficiency, increasing geometrical acceptance of the imaging device and pushing the timing performance of the detectors. Currently, some pre-localization of the electron-positron annihilation along a line-of-response (LOR) given by the detection of a pair of annihilation photons is provided by the detection of the time difference between the two photons, also known as the time-of-flight (TOF) difference of the photons, whose accuracy is given by the coincidence time resolution (CTR). A CTR of about 10 picoseconds FWHM will ultimately allow to obtain a direct 3D volume representation of the activity distribution of a positron emitting radiopharmaceutical, at the millimetre level, thus introducing a quantum leap in PET imaging and quantification and fostering more frequent use of 11C radiopharmaceuticals. The present roadmap article toward the advent of 10 ps TOF-PET addresses the status and current/future challenges along the development of TOF-PET with the objective to reach this mythic 10 ps frontier that will open the door to real-time volume imaging virtually without tomographic inversion. The medical impact and prospects to achieve this technological revolution from the detection and image reconstruction point-of-views, together with a few perspectives beyond the TOF-PET application are discussed.

The effectiveness of the SpineCor brace for the conservative treatment of adolescent idiopathic scoliosis. Comparison with the Boston brace.

BACKGROUND CONTEXT: The Boston brace (Bb) is the most widely used brace design to treat adolescent idiopathic scoliosis (AIS). The dynamic SpineCor (SC) brace is prescribed in several scoliosis clinics worldwide, but its effectiveness remains controversial. PURPOSE: The study aimed to compare the treatment effectiveness of SC in patients with AIS treated by the developers of the brace with that of the Bb at a single institution. STUDY DESIGN/SETTING: This is a retrospective comparison between a cohort of AIS patients treated using the SC brace and a cohort treated using the Bb. PATIENT SAMPLE: We assessed 243 patients treated with either Bb or SC brace to prevent the progression of AIS. OUTCOME MEASURES: The primary outcome was the progression in main Cobb angle when reaching one of the following end point criteria: (1) progression in Cobb angle of ≥6°, (2) main Cobb angle of ≥45°, (3) surgery undertaken, or (4) reaching skeletal maturity (Risser sign of 5 or growth of <1 cm in the previous 6 months). METHODS: Patients were identified at a single institution between 2000 and 2012 following the Scoliosis Research Society criteria for brace treatment: (1) diagnosis of AIS, (2) Risser sign of ≤2, (3) curve magnitude between 25° and 40°, and (4) age ≥10 years. A total of 97 patients treated with SC by the developers of the brace and 146 patients treated with Bb were identified. Data collection and radiograph measurements were performed by a single experienced nurse not involved in the decision-making for brace treatment or in the data analysis. Age and Risser sign at onset of treatment, initialmain Cobb angle, curve type, and duration of follow-up were similar in both cohorts. Statistical analysis was done using chi-square and logistic regression models, with a level of significance of .05. RESULTS: The average progression was 14.7°±11.9° in the SC cohort compared with 9.6°±13.7° in the Bb cohort (p=.003). The average Cobb angle at the end point of the study reached 47°±13° in the SC cohort and 41.7°±14.2° in the Bb cohort (p=.005), whereas at the onset of bracing it was 32.2°±4.9° and 32.2°±4.4°, respectively, for the SC and Bb cohorts. The percentage of patients with a progression of ≥6° was 76% in the SC cohort and 55% in the Bb cohort (p=.001). The proportion of patients reaching 45° in the SC and Bb cohorts was, respectively, 51% and 37% (p=.03), whereas the proportion of patients referred to surgery was 39% and 30%, respectively, for the SC and Bb cohorts (p=.2). The odds of progressing ≥6° and of reaching ≥45° were 2.67 and 2.07 times greater, respectively, when using the SC brace. CONCLUSIONS: The SC brace did not prevent curve progression as effectively as the Bb. Although it has the potential benefit of increasing mobility during brace wear, the SC brace was associated with increased curve progression in comparison with the Bb. There is also a trend for increased risk of requiring surgery when the SC brace is worn.