Brachytherapy

The NEMA NU 2-2007 standard for whole-body PET scanners (National Electrical Manufacturers Association 2007 ) with appropriately scaled phantoms was utilized to test the Inveon^™ PET system. NEMA NU 2-2007 was developed to address the testing of scanners with intrinsic radiation in the crystals (Watson et al 2004 (link)). LSO contains 2.6% ¹⁷⁶Lu which decays by β-emission and a subsequent cascade of gamma and x-rays. The detection of a β- in one crystal and a single ¹⁷⁶Lu gamma ray (78% at 202 keV and 94% at 307 keV) in a second crystal results in an intrinsic true coincidence event. In addition, random coincidences occur when the annihilation photon from a true decay is detected in coincidence with either the β- or ¹⁷⁶Lu gamma ray. Consequently, the true and randoms intrinsic coincidences are indistinguishable from the true and random coincidences from the extrinsic radiation. This gives rise to the concept of a characteristic extrinsic activity threshold, a_ref, above which the singles rate from extrinsic radiation is greater than that from the intrinsic radiation (Watson et al 2004 (link)). Knowledge of the intrinsic coincidence event rate is important for accurate measurement of the scanner performance and it is also important for the selection of the energy window in imaging small animals at low activity levels (Goertzen et al 2007 (link)).
During the final preparation of this paper NEMA NU 4-2008, Performance Measurements of Small Animal Positron Emission Tomographs was released (National Electrical Manufacturers Association 2008 ).

Analyses have been performed every third year according to the protocol. The primary end points were death from any cause, death from prostate cancer (with death from other causes treated as a competing risk), and risk of metastases in bone, outside the pelvic area, or both. Secondary end points included initiation of androgen-deprivation therapy (with death from any cause treated as a competing risk).
We used Gray’s test to assess treatment effects.⁹ Effect sizes were quantified both by analyzing relative risks with 95% confidence intervals and by determining differences in cumulative incidence (with 95% confidence intervals). Relative risks were estimated with the use of Cox proportional-hazards models in cases in which proportionality was verified by means of visual inspection of the parallelisms of the logarithms of the estimated cumulative incidence. A cumulative incidence approach was used to account for competing risks among various causes of death.¹⁰ To assess the possible modification of the treatment effect, analyses were stratified according to the patient’s age at diagnosis (<65 years vs. ≥65 years) and tumor risk. The subgroup analyses were not included in the main protocol but were specified before the data were reviewed. Risk groups were defined with the use of Gleason scores from the pathological review as follows: low risk, PSA level less than 10 and either a Gleason score of less than 7 or WHO grade 1 (on a scale of 1 to 3, with higher grades indicating more aggressive disease) in tumors that were diagnosed only by means of cytologic assessment; high risk, PSA level of 20 or higher or a Gleason score greater than 7; and intermediate risk, all patients who did not fulfill the criteria for low or high risk. The modification of the effect of radical prostatectomy was tested in the Cox proportional-hazards model by including an interaction term between the subgroup category and randomization group.
The prevalence of the use of palliative treatment was calculated at every other year of follow-up, ending at 18 years after randomization. Palliative treatment was androgen-deprivation treatment (antiandrogen therapy or gonadotropin-releasing hormone analogues or orchiectomy) in patients with or without verified metastases and in patients with metastases who had received other palliative treatment (external or internal palliative radiation therapy, laminectomy, or chemotherapy drugs).