Application of analytic methodologies for image quantification in neuroendocrine tumor therapy with 177Lu- DOTA

Abstract

Neuroendocrine tumors have annual incidence of 1 to 2 cases per one hundred thousand inhabitants. The177Lu-DOTA-octreotate treatments in 3 or 4 cycles has been effective in controlling disease progressionand, in some cases, promote tumor remission. To estimate radiation side effects in healthy organs, imagequantification techniques have been broadcast for individualized patient dosimetry. In this paper, imagedata processing methods are presented to allowing comparisons between different image conjugate views,combined with attenuation correction and system sensitivity. Images were acquired 24, 72 and 192 h afteradministration of 74GBq of 177Lu-DOTA using a dual-head gamma camera detection system and theywere evaluated with ImageJ software. 4 female patients underwent to two cycles of treatment. Thekidneys, liver and whole-body regions of interest were separately assessed by 4 techniques for countsmethod and 12 techniques for pixel intensity method, considering the main photopeak separately andaided by the attenuation correction map and adjacent windows to photopeak energy. The pixel intensitymethod was combined with mathematical correction for pixels with null value. The results obtained bythe two methods were strongly correlated (r>0.9) (p<0.001). The paired t-test accepted the null hypothesisof compatibility between the two methods (with and without attenuation correction map) (p<0.05), butrejected it when the adjacent windows were combined. No significant tumor reduction (p>0.05) wasfound between the treatment cycles. In conclusion, the pixel intensity method is faster and allows macros,minimizing operator error, and may optimize dosimetry in tumor therapies with 177Lu-DOTA-octreotate.