Scintigraphic evaluation of small pulmonary right-to-left shunt and therapeutic effect in pulmonary arteriovenous malformation.
OBJECTIVE
Right-to-left shunts of pulmonary arteriovenous malformation (PAVM) can be detected and measured by pulmonary perfusion scans using Tc-99m MAA. In PAVM with a relatively small right-to-left shunt, however, measurement of the shunt ratio may not be reliable. This study re-evaluated pulmonary perfusion scans for a small right-to-left shunt of PAVM.


METHODS
Tc-99m MAA lung scans were performed in five patients with proved PAVM before and after percutaneous transcatheter embolization. The right-to-left shunt ratio was calculated and extrapulmonary uptake was assessed on total-body images.


RESULTS
Lung perfusion scans obtained before embolization revealed brain uptake in four patients, and the shunt ratio ranged from 4.4% to 22.9%. In two patients with a small single PAVM, the shunt ratio was less than 15% before treatment and did not change significantly after successful embolotherapy. The brain uptake, which had been clearly visible before therapy, disappeared after embolization. Renal uptake was seen on pre- and post-therapy scans.


CONCLUSIONS
Changes in brain activity visible on Tc-99m MAA scans might be a more reliable sign than a decreased shunt ratio or a change in renal uptake when evaluating embolization therapy in patients with PAVM who have a small right-to-left shunt.
Sugiyama
M
M
Department of Radiology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Hamamatsu 431-3192, Japan. masahiro@akiha.hama-med.ac.jp
Sakahara
H
H
Igarashi
T
T
Takahashi
M
M
D000328:Adult; D001165:Arteriovenous Malformations / Q000000981:diagnostic imaging* / Q000628:therapy; D001921:Brain / Q000000981:diagnostic imaging; D004621:Embolization, Therapeutic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011651:Pulmonary Artery / Q000000981:diagnostic imaging; D011652:Pulmonary Circulation; D011667:Pulmonary Veins / Q000000981:diagnostic imaging; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D013668:Technetium Tc 99m Aggregated Albumin
D019275:Radiopharmaceuticals; D013668:Technetium Tc 99m Aggregated Albumin