RT Journal Article SR Electronic T1 Imaging Cyclophosphamide-Induced Intramedullary Apoptosis in Rats Using 99mTc-Radiolabeled Annexin V JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 309 OP 316 VO 42 IS 2 A1 Francis G. Blankenberg A1 Louie Naumovski A1 Johnathan F. Tait A1 Anneke M. Post A1 H. William Strauss YR 2001 UL http://jnm.snmjournals.org/content/42/2/309.abstract AB Intramedullary apoptosis of hematopoietic tissue is believed to play a major role in the pathophysiology of myelodysplastic syndrome. Annexin V, a specific marker of the early to intermediate phases of apoptosis, has been applied to the in vitro study of bone marrow aspirates. A noninvasive measure of intramedullary apoptosis in vivo that could serially monitor the clinical progression of myelodysplastic syndrome may be helpful. Methods: We used 99mTc-radiolabeled annexin V and radionuclide gamma camera imaging to serially study the sites, extent, and severity of intramedullary apoptosis induced by cyclophosphamide treatment. Results: Intravenously administered radiolabeled annexin V localized preferentially in the femur, pelvis, vertebrae, and spleen; increased uptake in these organs was easily visualized as early as 8 h after injection of 100 mg/kg cyclophosphamide in 8- to 10-wk-old animals. Higher doses of cyclophosphamide (150 mg/kg) in animals of the same age increased annexin V uptake in the bone marrow and splenic tissue and delayed recovery of these organs as seen histologically compared with lower doses. Older animals, 5–6 mo old, showed a slower response to cyclophosphamide treatment and delayed recovery of bone marrow and splenic tissues. Conclusion: Radiolabeled annexin V can be used to detect and directly quantify the degree of intramedullary and splenic apoptosis in a noninvasive fashion using current clinical radionuclide imaging equipment. Annexin V imaging may be useful clinically in the diagnosis and management of myelodysplastic syndrome.