No abstract

No abstract

No abstract

No abstract

The design, calibration and evaluation of a facility for in uivo prompt gamma neutron capture analysis of total body nitrogen in children is described. The patient is scanned, in both supine and prone positions, across a vertically collimated beam from a 1 GBq 'S'Cffission source. Two Nal(TI) detectors are placed on either side ofthe patient, perpendicular to both the neutron beam and the scanning direction. The effective dose equivalent delivered to a child during a n 840s scan is approximately 0.14mSv ( O F = IO).Correction factors for nitrogen background (width-dependent), hydrogen background (1.4% of hydrogen gamma ray peak) and the differential attenuation of nitrogen and hydrogen gamma rays (width-dependent) can be applied to the measured nitrogen-tohydrogen gamma ray counts ratio. By using the mass of hydrogen (bared on body mass and fat mass) as an internal standard, the nitrogen mass can then be determined. Mearurements with a urea-containing box phantom show that the current precision (cv) ofthe net nitrogen counts and of the nitrogen-to-hydrogen counts iatio is ~2 . 0 % and +l.5%, respectively. Usingsmall anthropomorphicand other phantoms, estimation ofthe mars ofnitrogen has a precision of +1.4 to 5.4% and a n accuracy of97.1 to 101.5%.