RESUMO
UNLABELLED: The aim of our study was to compare the role of lung perfusion scintigraphy with 1mTc MIBI and 99mTc Tetrofosmin (Mw) for the initial diagnostic evaluation of pulmonary tuberculosis-PTB). MATERIAL AND METHOD: Two groups of new PTB diagnosed patients, without treatment, were studied: group I--41 patients were imaged with 99mTc MIBI (sex ratio men:women = 17:24, mean age 25 years, 26 positive Mycobacterium Tuberculosis (MT) smears, 15 negative MT smears), group II--40 patients were imaged with 99mTc Mw (sex ratio men:women = 21:19; mean age: 32.5 years; 31 positive MT smears, 9 negative MT smears. Both groups received a 7.4 MBq (0.2 mCi)/kg radiotracer i.v. dose. Two anterior planar 3000000 counts/image on the thorax, one at 15 minutes and the other at 60 minutes after radiotracer administration and a SPECT acquisition were performed. For 99mTc Mw, three extra images were, in addition, performed, at 5, 90 and 120 minutes, in order to compare its kinetic with the known 99mTc MIBI kinetic. Clinical, radiological (Rx) and bacteriologic assessments of the patients were also done. RESULTS: Qualitatively, radiotracer uptake classification was coded: without uptake (-); low uptake (+); moderate uptake (++); high uptake (+++). Three identical interest regions were drawn: on the pathologic site, on a homolateral normal pulmonary field and on a myocardial field. The quantification has been assessed using three indexes (counts/pixel): I1= lesion/ normal; I2 = lesion/heart; I3 = normal/heart. We have found a significant difference between the mean value of I1:1.484, in the case of 99mTc MIBI versus 1.95 in the case of 99mTc Mw. The sensibility of the method was 96% for 99mTc MIBI versus 94% for 99mTc Mw, the specificity being 86 % for 99mTc MIBI versus 88% for 99mTc Mw. CONCLUSION: Both radiotracers are useful for the imaging evaluation of PTB, and can give evidence of new sites, related to radiology. The contrast between pathologic and normal uptake is more evident in 99rTc Mw images than in 99mTc MIBI images, how it was demonstrated by the index quantification. The in vivo uptake kinetic for 99mTc Mw seems to be similar with that of 99mTc MIBI for the first 60 minutes but, at 120 minutes showed delayed washout. This can be useful in the differential diagnosis from other lung disease where the radiotracer kinetic is different.
