A SCINTIGRAPHIC SIGN FOR DETECTION OF RIGHT-TO-LEFT SHUNTS

We evaluated the usefulness of a new scintigraphic sign, a quantum mot tling pattern, in diagnosing right-to-left shunt using Tc-99m-MAA part icles. The quantum mottling pattern is characterized by random distrib ution of discrete clumps of radioactivity that are more intense than t he general body background. Forty-nine Tc-99m-MAA scintigrams were ana lyzed retrospectively for presence of a quantum mottling pattern in ex trapulmonary soft tissues and brain. This distinctive pattern was obse rved in every patient (18/18) in whom a right-to-left shunt was confir med by nonscintigraphic means and was noted only in one patient in who m independent proof of a right-to-left shunt was not available. In con trast, application of conventional criteria yielded a true-positive in terpretation for 15/18 patients with right-to-left shunts and a false- positive interpretation for another four patients. Presence of a quant um mottling pattern on Tc-99m-MAA images appears to be a reliable aid for detecting a right-to-left shunt. Use of this sign is likely to imp rove accuracy of the scintigraphic test in patients with small shunts.