Technetium-99m hexakis 2-methoxyisobutyl isonitrile: Human biodistribution, dosimetry, safety, and preliminary comparison to thallium-201 for myocardial perfusion imaging

The biodistribution, dosimetry, and safety of a new myocardial imaging agent, ^99m-Tc-hexakis-2-methoxyisobutyl isonitrile (HEXAMIBI), was evaluated in 17 normal volunteers at rest and exercise (Phase I studies). Technetium-99m HEXAMIBI clears rapidly from the blood with good myocardial uptake and favorable myocardial-to-background ratios for myocardial imaging. Dosimetry allows for administration of up to 30 mCi (1,110 Bq) of [^99mTc]HEXAMIBI. The myocardial images were of good quality and appeared less granular with sharper myocardial walls compared to ²⁰¹T1 images. The clinical efficacy of [^99mTc]HEXAMIBI planar stress and rest imaging was evaluated in a multicenter Phase II clinical trial involving 38 patients. Of 36 patients with significant coronary artery disease, 35 patients (97%) had abnormal ²⁰¹T1 stress images, and 32 (89%) had abnormal [^99mTc]HEXAMIBI stress images (P = N.S.). Technetium-99m HEXAMIBI images correlated in 31/35 patients (86%) who had either scar or ischemia on ²⁰¹T1 images. By segmental myocardial analysis, exact concordance was obtained in 463/570 myocardial segments (81%). This multicenter Phase I and II study indicates that planar [^99mTc]HEXAMIBI stress imaging is safe and compares well with ²⁰¹T1 stress imaging for detection of coronary artery disease.