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- Author or Editor: Yvonne W. Pollak x
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Objective—To quantitatively assess distractioninduced bone formation in a crural lengthening model in dogs by use of delayed-image bone scintigraphy.
Animals—12 mature Labrador Retrievers.
Procedure—Dogs were randomly allocated to 1 of 3 groups. A circular external skeletal fixation system was mounted on the right crus of each dog. Osteotomy of the distal portion of the tibia and fibula was performed in groups 1 and 2 and was followed by a lengthening procedure of 10 mm in the first group only. The third group served as sham-operated controls. Delayed-image bone scintigraphy with technetium-99m hydroxy methylene diphosphonate was performed 2, 4, and 6 weeks after surgery. Delayedimage–to–region-of-interest, delayed-image–to–crural, and delayed-image–to–femoral scintigraphic activity ratios were calculated. New bone formation was quantified by use of densitometric image analysis, and values for the scintigraphic ratios were compared.
Results—In the distraction and osteotomy groups, delayed-image–to–region-of-interest and delayedimage-to-crural ratios increased significantly. Although densitometric image analysis revealed increased bone formation after distraction, the region-of-interest ratios and crural ratios were similar in both groups. All dogs had increased delayedimage–to–femoral ratios.
Conclusions and Clinical Relevance—Delayed-image bone scintigraphy ratios were not effective at differentiating between the amounts of distraction-induced bone and osteotomy-induced bone. Metabolic bone activity in the adjacent femur was increased as a consequence of circular external skeletal fixator placement. Delayed-image bone scintigraphy was not adequately sensitive to quantitatively monitor bone formation but may be useful as an early predictor of bone healing.
Objectives—To determine the effect of sedation and anesthesia on thyroid and salivary gland uptake of technetium Tc 99m pertechnetate (99mTcO4) in euthyroid cats.
Animals—6 euthyroid cats.
Procedures—Thyroid scintigraphy was performed by use of a high-resolution low-energy parallel-hole collimator after IV injection of 117 to 133 MBq (3.16 to 3.59 mCi) of 99mTcO4 −. The procedure was performed 4 times on each cat during different sedative and anesthetic protocols in a rotating schedule as follows: propofol, ketamine-midazolam-atropine, ketaminemidazolam, and medetomidine. Regions of interest were drawn around thyroid and salivary glands and counts corrected for background and decay. Percentage of 99mTcO4 − uptake in salivary and thyroid glands and thyroid-to-salivary gland 99mTcO4 − uptake ratio were calculated at 20 and 40 minutes. Relative effects of anesthesia and sedation on salivary and thyroid gland 99mTcO4 − uptake were compared.
Results—Significant differences among sedativeanesthetic protocols were found for thyroid gland 99mTcO4 − uptake, salivary gland 99mTcO4 − uptake, and thyroid-to-salivary gland 99mTcO4 − uptake ratio. Thyroid gland 99mTcO4 − uptake for the ketamine-midazolam protocol at 20 and 40 minutes after 99mTcO4 − administration was significantly higher than for the propofol protocol. A significant difference in salivary gland99m TcO4 − uptake was found between ketamine-midazolam and ketamine-midazolam-atropine protocols at 40 minutes. The thyroid-to-salivary gland 99mTcO4 −uptake ratio for the ketamine-midazolam protocol was significantly higher at 40 minutes than for propofol or ketamine-midazolam-atropine protocols.
Conclusions and Clinical Relevance—Sedation and anesthesia have a significant effect on thyroid and salivary gland 99mTcO4 uptake in euthyroid cats that may interfere with thyroid scintigraphic image interpretation.