[Radiopharmacokinetic and gammagraphic studies for calculating personalized dosimetry]. / Estudios radiofarmacocinéticos y gammagráficos para cálculos de dosimetría personalizada.

In nuclear medicine radiation absorbed doses are important in the patient's risk/benefit evaluation and are estimated by means of biological and complex mathematical models. The biological model includes radiopharmacokinetic data obtained through blood and urine samples taken at given intervals. A useful mathematical model is the MIRD model and with the value for the time of residence tau the MIRDOSE3 computer program uses several anatomic models and calculates radiation absorbed dose for 25 organs. At the Radiopharmacy Unit of the Nuclear Medicine Department at INCMNSZ two new bone seeking radiopharmaceuticals, 99mTc-ABP and 188Re-ABP, have been designed, characterized and animal-tested. Radiopharmaceutical parameters and sequential scanning were obtained for diagnostic 99mTc-ABP in 10 normal subjects and the aim was to use % 24 hour urine elimination and % bone uptake to calculate radiation absorbed dose and extrapolate the values to 188Re-ABP as the basis for a therapeutic treatment. 99mTc-ABP was eliminated in women's urine 63.2 +/- 7.3%/activity and 70 +/- 11%/activity in men. In women 36.8 +/- 7.3% of the radiopharmaceutical remains on the bone surface and in men 30 +/- 11%. ROIs were drawn on the images and the time-integrated renal cpm/pixel/ROI gave a residence time tau = 0.52 h. Cumulative bone activity A calculated with A = 1.443 (T1/2) A0 was 2358 +/- 469 MBq h for women and 1923 +/- 707 MBq h for men. Residence time tau was 3.19 +/- 0.63 h in women and 2.6 +/- 0.95 h in men. Radiation absorbed dose for the whole body was 0.0020 +/- 0.0004 mGy/MBq for women and 0.0013 +/- 0.0005 mGy/MBq for men. For women's bone marrow it was 0.0063 +/- 0.0013 mGy/MBq and for men 0.0041 +/- 0.0015 mGy/MBq. 188Re-ABP behaves as 99mTc-ABP therefore, the effective dose given by 188Re, a beta emitter, would be for women 0.0936 mSv/MBq and for men 0.0608 mSv/MBq. These characteristics and the radionuclidic characteristics of 188Re indicate that 188Re-ABP might be a good bone metastases pain palliation radiopharmaceutical.

Radiopharmacokinetic data for 99mTc-ABP--a new radiopharmaceutical for bone scanning: comparison with 99mTc-MDP.

Technetium-99m-labeled alendronate is a new radiopharmaceutical for bone scanning developed under strict quality control at the INNSZ. The purpose of this work was to compare the radiopharmacokinetic data and the dosimetry of 99mTc-ABP and 99mTc-MDP in 10 volunteers, after it was tested in laboratory animals. 99mTc-ABP has shorter mean residence time (MRT) and t 1/2 beta; is less protein bound; has a higher renal clearance; smaller Vdss, and similar bone uptake at 1 and 2 h. 99mTc-ABP gives less radiation exposure to the patient with a 740 MBq dose, and the quality of the bone scan is excellent. 99mTc-ABP is a better radiopharmaceutical than 99mTc-MDP for bone scanning.

[99m-Tc alendronate as a new option in bone gammagraphy]. / El 99mTc-alendronato como nueva opción en la gammagrafía ósea.

OBJECTIVE: To compare the quality of bone scans obtained with 99mTc-ABP, a new radiopharmaceutical, and 99mTc-MDP. MATERIAL AND METHODS: A comparative study within subjects was done in nine healthy volunteers, 5 female and 4 male, aged 23 to 39 years. The dose for both radiopharmaceuticals was 740 MBq; radiopharmacokinetic parameters were determined and a whole body bone scan was taken with a MultiSpect 2 gamma camera two hours post administration with a wash-out period of 72 hours between preparations. The images were independently evaluated by three nuclear medicine physicians by drawing of regions of interest (ROIs) on vertebrae, ribs, femur, sternum, joints and skull. Ratios bone/soft tissue were obtained drawing ROIs on several bones. The kappa test and the Wilcoxon rank test were used for statistical comparisons. RESULTS: The agreement on the quality of the images with Tc-ABP and Tc-MDP was fair (kappa 0.4). The femur/soft tissue ratio had a normal distribution and the Wilcoxon test showed no statistical difference between preparations. CONCLUSIONS: Even though bone uptake was higher and faster with Tc-ABP, the quality of the scans obtained with either radiopharmaceutical was similar. We recommend the use of Tc-ABP as a routine bone scan agent because of its less radiation exposure to the patient.