Repeatability of parametric methods for [18F]florbetapir imaging in Alzheimer’s disease and healthy controls: A test–retest study

Accumulation of amyloid beta (Aβ) is one of the pathological hallmarks of Alzheimer’s disease (AD), which can be visualized using [¹⁸F]florbetapir positron emission tomography (PET). The aim of this study was to evaluate various parametric methods and to assess their test-retest (TRT) reliability. Two 90 min dynamic [¹⁸F]florbetapir PET scans, including arterial sampling, were acquired (n = 8 AD patient, n = 8 controls). The following parametric methods were used; (reference:cerebellum); Logan and spectral analysis (SA), receptor parametric mapping (RPM), simplified reference tissue model2 (SRTM2), reference Logan (rLogan) and standardized uptake value ratios (SUV_r(50–70)). BP_ND+1, DVR, V_T and SUVr were compared with corresponding estimates (V_T or DVR) from the plasma input reversible two tissue compartmental (2T4k_V_B) model with corresponding TRT values for 90-scan duration. RPM (r² = 0.92; slope = 0.91), Logan (r² = 0.95; slope = 0.84) and rLogan (r² = 0.94; slope = 0.88), and SRTM2 (r² = 0.91; slope = 0.83), SA (r² = 0.91; slope = 0.88), SUVr (r² = 0.84; slope = 1.16) correlated well with their 2T4k_V_B counterparts. RPM (controls: 1%, AD: 3%), rLogan (controls: 1%, AD: 3%) and SUV_r(50–70) (controls: 3%, AD: 8%) showed an excellent TRT reliability. In conclusion, most parametric methods showed excellent performance for [¹⁸F]florbetapir, but RPM and rLogan seem the methods of choice, combining the highest accuracy and best TRT reliability.     

Transfer of pediatric trauma patients to a tertiary pediatric trauma centre: appropriateness and timeliness

OBJECTIVE: To study the appropriateness of, and time taken, to transfer pediatric trauma patients in New South Wales to The Children's Hospital at Westmead (CHW), a pediatric trauma center. METHODS: All trauma patients transferred to CHW from June 2003 to July 2004 were included in the study. Indications and time periods relevant to the transfer of the patient from the referring institute were retrieved and analyzed. Pediatric and adult retrieval services were compared. RESULTS: Three hundred ninety-eight patients were transferred to CHW, of whom 332 were from the metropolitan region. Falls and burns were the commonest mechanism of injury. Burn was the commonest indication for transfer (107 of 398). Mean Injury Severity Score was eight. Nearly half the patients had minor injuries (Injury Severity Score<9). Patients spent an average of 5 hours at the referring hospital. Pediatric retrieval ambulances had significantly longer mean transfer times than did nonpediatric ambulance services with a total time spent of about 2.64 hours versus 1.30 hours, respectively. For aeromedical transfers, on the other hand, the difference between pediatric retrieval services and nonpediatric air ambulances was not significant. CONCLUSIONS: The majority of the patients transferred had minor injuries. Pediatric trauma patients spend considerable time in their referring hospitals. Pediatric retrieval services appear to take significantly longer to transfer patients than nonpediatric ambulance transfers even after allowing for patient age and injury severity. Although this did not result in mortality or morbidity, there appears to be considerable scope for a reduction in transfer times through better coordination of these services.