tokens: To assess whether thallium - 201 thallous chloride ( Tl ) can detect childhood tumors and whether diagnostic effectiveness improves with combined blood flow imaging , 28 children ( 1 . 0 - 18 . 6 years ) were studied using single photon emission computed tomography ( SPECT ) : Tl ( 1 . 3 - 1 . 8 mCi intravenously ) , followed in 13 of the patients by technetium - 99m - hexamethylpropyleneamine oxime ( 99mTc - HMPAO ; 8 - 18 mCi intravenously ) .