DNA double-strand breaks in blood lymphocytes induced by two-day ^99mTc-MIBI myocardial perfusion scintigraphy

Objectives: To investigate DNA double-strand breaks (DSBs) in blood lymphocytes induced by two-day ^99mTc-MIBI myocardial perfusion scintigraphy (MPS) using y-H2AX immunofluorescence microscopy and to correlate the results with ^99mTc activity in blood samples. Methods: Eleven patients who underwent two-day MPS were included. DSB blood sampling was performed before and 5min, 1h and 24h after the first and second radiotracer injections. ^99mTc activity was measured in each blood sample. For immunofluorescence microscopy, distinct foci representing DSBs were quantified in lymphocytes after staining for the phosphorylated histone variant y-H2AX. Results: The ^99mTc-MIBI activity measured on days one and two was similar (254±25 and 258±27 MBq; p=0.594). Compared with baseline DSB foci (0.09±0.05/cell), a significant increase was found at 5min (0.19±0.04/cell) and 1h (0.18±0.04/cell) after the first injection and at 5min and 1h after the second injection (0.21±0.03 and 0.19±0.04/cell, respectively; p=0.003 for both). At 24h after the first and second injections, the number of DSB foci had returned to baseline (0.06±0.02 and 0.12±0.05/cell, respectively). ^99mTc activity levels in peripheral blood samples correlated well with DSB counts (r=0.451). Conclusions: DSB counts reflect ^99mTc-MIBI activity after injection for two-day MPS, and might allow individual monitoring of biological effects of cardiac nuclear imaging. Key Points: • Myocardial perfusion scintigraphy using^99mTc induces time-dependent double-strand breaks (DSBs) • γ-H2AX immunofluorescence microscopy shows DSB as an early response to radiotracer injection • Activity measurements of^99mTc correlate well with detected DSB • DSB foci induced by^99mTc return to baseline 24h after radiotracer injection.