Activity regimes for 82Rb cardiac PET: Effects on absolute MBF and MPI.

BACKGROUND: Selection of optimal tracer activity for 82Rb PET is based on a trade-off between necessary count-statistics in the late static phase and detector saturation in the early blood-pool phase. Administered tracer activity recommended in prescribing information differs substantially from recommendations in current literature. The present study examines the effect on both absolute myocardial blood flow (MBF), myocardial flow reserve (MFR) and relative myocardial perfusion imaging (MPI) of reducing dose. METHODS: Forty patients were scanned twice on a PMT-based PET/CT (GE D690): At recommended activity (1110 MBq) and at either 740 or 370 MBq. MBF, MFR, total perfusion deficit (TPD) and ejection fractions (EF) were quantified. Results were compared using linear regression and Bland-Altman plots. RESULTS: Linear correlation between MBF at 1110 MBq at either reduced activity had an R2 > 0.98. A small bias (± 5%-9%) was observed with opposite signs for 1110/740 and 1110/370. Limits of agreement for MBF were larger for 1110/370. MFR had a lower linear correlation (R2 = 0.96), but wide limits of agreement especially for 1110/370. TPD and EF correlated well at 1110/740 (R2 = 0.96 and 0.99, respectively), but large scatter was observed for 1110/370. CONCLUSION: Reduction of the tracer activity to 740 MBq, significantly reduced dead-time correction factors, while still producing reliable static and gated images. However, despite large dead-time at 1110 MBq, no systematic bias on absolute MBF was observed compared to reduced activities.

Cancer of the external auditory canal and middle ear in Denmark from 1992 to 2001.

BACKGROUND: In the context of the Danish Head and Neck Cancer Group, nationwide material from 1992-2001 was analyzed to study the extent and nature of the disease, evaluate treatment, compare staging systems, and examine prognosis and survival. METHODS: Review of 68 consecutive cases: 47 squamous cell carcinoma, 10 basal cell carcinoma, and 11 other histologies. Moody (modified Pittsburgh) stages were T1 (26), T2 (9), T3 (8), T4 (23), Tx (2). Sixty-four patients were treated with curative intent: 24 primary radiotherapy, 18 primary surgery, and 22 combined. Surgery was limited to tumor excision and mastoidectomy and in 1 case temporal bone excision. RESULTS: Twenty-seven of 28 recurrences involved primary site. Kaplan-Meier analysis showed 5-year locoregional control of 48%, disease-specific survival 57%, and overall survival 44%. CONCLUSION: This nationwide study confirmed that local failure is the main problem, and future improvements should focus on more aggressive local treatment.