Arteriovenous shunt measurement during endovascular therapy for cerebrospinal lesions.

PURPOSE To determine (a) whether superselective angioscintigraphy with technetium-99m macroaggregated albumin (99mTc-MAA) can be used for the evaluation of arteriovenous shunting in tumors and vascular malformations of the head and spine and (b) whether the amount of microparticles shunted is related to diagnosis, lesion size, or angiographic pattern. METHODS Particles of 99mTc-MAA with a calibrated diameter of 25 to 50 microm were delivered intraarterially in feeders of head and spine tumors and vascular malformations in 38 patients. The first estimation of the proportion of particles reaching the lungs was made on-line in the angiography suite using a hand-held lead-shielded detector. Evaluation of the intralesional shunt (pulmonary shunt index, or PSI) was derived from quantitative gamma camera recordings of tumoral and pulmonary activity after the embolization procedure was complete. RESULTS The PSI value ranged from 48% to 100% for vascular malformations and vascular tumors (n = 11), 82% to 95% for juvenile angiofibromas (n = 4), 63% to 70% for high-grade gliomas (n = 2), 0% to 50% for renal cell carcinoma metastases (n = 4), 0% to 86% for meningiomas (n = 11), and 0% to 36% for paragangliomas (n = 6). Angiographically, the presence of visible arteriovenous channels was predictive of a high PSI. In contrast, the presence of early venous drainage was associated with a wide PSI range. CONCLUSION Superselective 99mTc-MAA angioscintigraphy of tumors and vascular malformations of the head and spine is a valuable method for quantifying an intralesional arteriovenous shunt before embolization.