T/B ratio

The situation is entirely different in the gas phase, especially at low pressures, where coUisional deactivation cannot prevent extensive fragmentation and isomerization of the primary, excited intermediates. This is clearly demonstrated by an apparent t/ b ratio below imity, by the predominant meta orientation, attributable to isomerization of the primary arenium ions into (V) and by the large yields of tritiated products (such as CeHsT from benzene and CeHsCTa from toluene) whose formation requires extensive isotopic scrambling, group migration, and fragmentation. 

The expression levels of Pgp, determined by immunohistochemistry in tumor specimens prior to treatment, was significantly higher in lesions with low T/B(d) ratios when compared with those with high values, indicating that [ Tc]MIBI extrusion is accelerated in Pgp-expressing tumors. Moreover, the higher expression of Pgp was found in non-responders (Fig. 6). The results from this study suggest that the T/B ratio of [ Tc]MIBI at delayed times is useful to predict response to chemotherapy and for in vivo evaluation of Pgp expression status in patients with locally advanced or recurrent breast carcinoma. 

Ak et al. analyzed the relationship between the [ Tc]MIBI uptake and the expression levels of Pgp in 26 patients with newly diagnosed leukemia [104]. The patients underwent a [ Tc]MIBI whole-body planar imaging prior to chemotherapy. Planar images of pelvis and thorax were acquired 20 min postinjection of [ Tc]MIBI. The T/B ratio in bone marrow was compared with the Pgp expression in blast cells from bone marrow aspiration samples determined by flow cytometry. The results of [ TcjMIBI imaging were concordant with the Pgp expression levels found in blast cells. The bone marrow uptake of [ Tc]MIBI was significantly (p<0.001) higher in Pgp-negative patients than in those with Pgp-positive blast cells. Such observations indicate that in vivo... 

After Inj. (min) Case (Initials) Tumor ppm Gd Blood ppm Gd T/B Ratio... 

The T/B ratios varied according to type of tumor and specimen. Despite careful surgical excision to harvest the samples, the pieces of removed tumor tend to be slightly coagulated. Generally, except in recurrent malignant meningioma, T/B ratios were less than 0.3-0.5. 

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