RT Journal Article SR Electronic T1 A New Method for Determination of Left-to-Right Cardiac Shunts JF Journal of Nuclear Medicine Technology JO J. Nucl. Med. Technol. FD Society of Nuclear Medicine SP 216 OP 219 VO 19 IS 4 A1 Preslar, J. S. A1 Madsen, M. T. A1 Argenyi, E. E. YR 1991 UL http://tech.snmjournals.org/content/19/4/216.abstract AB Left-to-right cardiac shunt quantitation can be determined from first pass radionuclide angiography. The traditional technique fits a gamma variate to the lung time-activity curve (TAC) and a second gamma variate to the recirculation portion of the curve. Problems may arise, however, with the fitting of the gamma variate to the subtracted recirculation curve. We have investigated a new technique in which the recirculation fitting is no longer required. The new method fits a gamma variate to the first-pass portion of the lung TAC. This gamma variate is used to generate a curve which simulates the expected shape of a normal lung TAC in response to systemic recirculation. The simulated data is then subtracted from the observed lung TAC. A correlation coefficient of r = 0.87 was obtained when these two methods were compared. We now prefer the new method since it overcomes the problem of fitting the subtracted recirculation position of the curve.