MIBI

Fig. 3. Structures of myocardial perfusion agents (a) Tc(I)(MIBI)g -sestamibi), where MIBI = 2-methoxyisobutylisonitrile (b)...

The mechanism of uptake and retention of the mono-cationic 99mTc complexes in the myocardium - or other tissues - has not been fully resolved. Most of the mechanistic studies have been conducted with 99mTc (MIBI)6f and "mTc-diphosphine complexes. It has been shown that these mono-cationic complexes are not taken up in myocytes via the Na+/K+-ATPase pump as is 201T1+ [41]. Instead, these cationic tracers are localized and retained in cellular membranes, including mitochondrial membranes [41]. 

Dual isotope SPECT protocols obtain resting images with t1 and stress images with MIBI followed by 24 h xi late redistribution imaging [39, 40]. These protocols have demonstrated good prediction of contractile function recovery after revascularization comparable to simpler single tracer protocols [41]. 

The value of SPECT viability imaging with is well established clinically with overall 70-75% accuracy for predicting recovery of LV function compared to PET [28, 29, 61, 89]. For MIBI, predictive accuracy decreases to 64% compared to PET [106, 107]. Some of these discrepancies are explained by frequent inferior wall attenuation artifacts encountered with SPECT [4, 108]. The randomized trial CHRISTMAS (Carvedilol Hibernating Reversible Ischemia) demonstrated that SPECT MIBI predicted LV functional recovery in patients receiving carvedilol [109] with LVEF improving by 3.8%, more in those patients with... 

K. Yutani, E. Shiba, H. Kusuoka, M. Tatsumi, T. Uehara, T. Taguchi, S.l. Takai, T. Nishimura, Comparison of FDG-PET with MIBI-SPECT in the detection of breast cancer and axillary lymph node metastasis, J. Comput. Assist. Tomogr. 24(2) (2000) 274-280. 

Zafrir B, Zafrir N, Gal T et al. Correlations between ST elevation and Q waves on the predischarge electrocardiogram and the extent location of MIBI perfusion defects in anterior myocardial infarction. Ann Noninvasive Electrocar-diol 2004 9 101. 

DMSA dimercaptosuccinic acid, EDTA ethylenediaminetetraacetic acid, HMPAO hexamethyl propyl-eneamine oxime, DADS J yM-bis(mercaptoacetyl)ethylenediamine, DADT diaminodithiol, ECD ethylcysteinate dimer, MAG3 mercaptoacetyltriglycine, NOEt Et(OEt)NCS2, DTPA diethylene triamine pentaacetate, MDP methylenediphosphonate, HIDA N-(2,6-dimethylphenylcarbamoylmethyl) iminodiacetic acid, DMPE l,2-bis(dimethylphosphino) ethane, BATO boronic acid technetium oxime, MIBI methoxyisobutyl isocyanide... 

Structural characterization of Tc(I) complexes was performed identifying Tc sesta-mibi as a complex with six monodentate methoxyisobutyl isocyanide (MIBI) ligands attached symmetrically to a central Tc(I) atom (Abrams et al. 1983 Jones et al. 1985 Fig. 2.1.20). 

Surfactants might be required to solubilize lipophilic Tc complexes (MIBI) (Berg-stein and Subramanyam 1986) and particulate preparations (macroaggregated albumin, microspheres). 

MDP methylenediphosphonate, HSA human serum albumin, DMSA dimercaptosuccinic acid, DTPA diethylene triamine pentaacetate, HIDA hepatoiminodiacetic acid, EC ethylene dicysteine, HSA human serum albumin, MIBI monodentate methoxyisobutyl isocyanide, MAG3 mercaptoacetyltrigly-cine, ECO ethylene dicysteine dimer, HMPAO hexamethylpropylene amine oxime a eluate (370 MBq), Tc is not considered... 

More recently, developed Tc complexes (e.g. mercaptoacetyltriglycine [MAG3], monodentate methoxyisobutyl isocyanide [MIBI], hexamethylpropylene amine oxime [HMPAO], etc.) require more sophisticated analytical methods to detect additional impurities in the injection solution. This is inherent in the chemical properties of certain Tc pharmaceuticals that need more complex kit formulations and contain several labeled impurities. In addition, special composed solvent systems have to be used. 

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