ABSTRACT
BACKGROUND: The rubidium 81/krypton 81m method was suggested for assessment of myocardial blood flow (MBF) three decades ago. This study investigates the novel concept of using 81Rb-/81mKr-labeled coronary guide wires with wire-attached 81Rb activity and diffusable 81mKr gas for assessment of lesion-specific impairment of MBF by evaluation of the 81Rb/81mKr activity ratio. The feasibility of wire production is tested, and application of the method is investigated in the canine model. METHODS AND RESULTS: Conventional coronary guide wires for angioplasty (0.014 in) were labeled with radioactive 81Rb/81mKr by ion bombardment of the wire tip. A total of 16 of the 18 wires labeled in series showed successful 81Rb fixation in combination with free 81mKr gas diffusability during quality control measurements. The suitability of the wires to assess MBF in combination with an external gamma ray detector was investigated in open-chested dogs. Electromagnetic measurement of coronary blood flow (CBF) was used as reference, providing a signal that is directly linked to volumetric MBF. The 81Rb/81mKr ratio tracked changes in CBF reliably in all 6 dogs. The found linear dependence of measured 81Rb/81mKr count rates on measured CBF supports the modeling assumptions made to apply the theoretic basis of the 81Rb/81mKr technique to 81Rb-labeled coronary guide wires. CONCLUSION: 81Rb-/81mKr-labeled coronary guide wires provide a signal that indicates volumetric MBF directly. This unique capability may qualify the technique as a valuable tool for research purposes and as an attractive method for invasive cardiology at centers where the logistic arrangements for short-lived isotope supply are provided.
Subject(s)
Coronary Circulation , Krypton Radioisotopes , Rubidium Radioisotopes , Animals , Dogs , Female , MaleABSTRACT
This study describes methods of measuring simultaneously the renal excretion of two radiopharmaceuticals and of evaluating their different kinetics. For quantification of the dynamic contributions of scattered radiation in a double-radionuclide study a high-resolution pure germanium detector was used. The geometry of the arrangement was a semi-shielded whole-body counter according to E. Oberhausen. An intra-individual comparison of the renal elimination of 99mTc-MAG3 and 131I-Hippuran shows a systemic difference between both tracers depending on the time after injection, its average being around 11% between the 10th and 20th min. The inter-individual comparison shows deviations from the mean between -29 and +20%.
Subject(s)
Iodine Radioisotopes/pharmacokinetics , Iodohippuric Acid/pharmacokinetics , Kidney/diagnostic imaging , Kidney/physiology , Radionuclide Imaging/instrumentation , Technetium Tc 99m Mertiatide/pharmacokinetics , Adult , Female , Humans , Male , Middle Aged , Radionuclide Imaging/methodsABSTRACT
A method is being developed which not only measures cerebral blood flow as a static quantity but also its changes with time. For that purpose a semiconductor device ascertains the proportion of intracerebral 81 Rb and 81mKr activities. By opening the hemato-encephalic barrier in animal experiments a sufficient concentration of intracerebral 81 Rb could be attained and the modified blood circulation after step-wise ligature of all brain arteries brought into relation to the corresponding Rb/Kr quotient. Over the range from undisturbed to completely interrupted cerebral blood flow this quotient varied up to 25% of its initial value.
