A COMPARISON OF TECHNIQUES IN THE ASSESSMENT OF CHEST-WALL THICKNESS AND COMPOSITION

The thickness and composition of defined regions of the anterior chest wall are important factors in the assessment of pulmonary plutonium b y low-energy x ray counting. Estimates of these quantities are reporte d for seven male subjects investigated by three laboratories using ult rasonic methods and by a fourth laboratory using magnetic resonance im aging. No important bias was found in any one laboratory's estimates o f chest wall thickness relative to those of the others, but difference s of up to 6 mm were noted for individual subjects. The discrepancies are believed principally to reflect the different sampling regimes ado pted to reach a representative mean chest wall thickness over the regi on of interest from measurements at selected points. The adipose-tissu e component was consistently found to be lower when assessed by magnet ic resonance imaging compared with estimates by ultrasound, but the di fferences were unimportant in the context of plutonium assessment.