Results are consistent with previous reports that asphalt or coal-tar exposure can cause DNA damage. Urinary 8-epi-PGF remained relatively constant during the week for virtually all subjects, regardless of exposure indicating that neither asphalt nor coal-tar exposure induces an overt oxidative stress. A small, but statistically significant increase in 8OHdG was evident in end-of-week urine samples compared with start-of-week urine samples in roofers exposed to coal-tar. The increase in urinary 8OHdG coupled with the decrease in leukocyte 8-OHdG/dG, suggests that coal-tar exposure induces protective or repair mechanisms that result in reduced levels of steady-state oxidative-DNA damage.

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The physical PET performance of the first prototype of the recently introduced Biograph mCT TOF PET/CT scanner (Siemens Molecular Imaging) has been evaluated. The PET component incorporates 192 detector blocks, 5.4 cm x 5.4 cm in cross-section; each block comprises a 13 x 13 matrix of 4 x 4 x 20 mm 3 crystal elements. The four detector block rings cover a 21.8 cm axial field-of-view with a 78 cm diameter patient port. Data are acquired within a 4.1 ns coincidence time window and with an energy threshold of 435-650 keY. The recent NEMA NU 2-2007 standard [1] was utilized to evaluate the preliminary physical performance of the scanner with additional measurements that specifically addressed the TOF capability.An average spatial resolution of 4.4 mm (FWHM) and 5.2 mm (FWHM) were measured at 1 cm and 10 cm from the center of the transverse field-of-view. The system sensitivity for a line source was 0.96°/0 and 0.94°/0 respectively at 0 cm and 10 cm from the center of the transverse FOV. We report a scatter fraction of 32°/0 and a noise equivalent count (NEC) rate peaking at more than 180 kcps. The energy and timing resolution were measured with a 18F line source resulting in 11.7°/0 (FWHM) and less than 550 ps (FWHM) respectively. We observed no significant variation in time, energy and spatial resolution for a singles count rate of more than 45 Mcps.