Noninvasive methods of measuring bone blood perfusion

Abstract

Measurement of bone blood flow and perfusion characteristics in a noninvasive and serial manner would be advantageous in assessing revascularization after trauma and the possible risk of avascular necrosis. Many disease states, including osteoporosis, osteoarthritis, and bone neoplasms, result in disturbed bone perfusion. A causal link between bone perfusion and remodeling has shown its importance in sustained healing and regrowth following injury. Measurement of perfusion and permeability within the bone was performed with small and macromolecular contrast media, using dynamic contrast-enhanced magnetic resonance imaging in models of osteoarthritis and the femoral head. Bone blood flow and remodeling was estimated using (18)F-Fluoride positron emission tomography in fracture healing and osteoarthritis. Multimodality assessment of bone blood flow, permeability, and remodeling by using noninvasive imaging techniques may provide information essential in monitoring subsequent rates of healing and response to treatment as well as identifying candidates for additional therapeutic or surgical interventions.

Figure 1

(A) A coronal T₂-weighted MRI image of the tibial plateau acquired at 3.0 Tesla in a Dunkin-Hartley guinea pig model of osteoarthritis (OA). (B) Dynamic contrast-enhanced (DCE-MRI) time-intensity curves (TIC) taken in the medial tibial plateau are shown following administration of Gd-DTPA. Curves are averaged for animals (n = 6) of 6 months of age before morphologic changes of OA are apparent and for animals of 15 months of age with established changes of OA revealing diminished perfusion.

Figure 2

(A) A time-averaged T₁-weighted image of the tibial plateau acquired at 3.0 Tesla in a Dunkin-Hartley guinea pig following injection of albumin-(Gd-DTPA)³⁰. (B) Time intensity curves show constant uptake throughout the scan in the popliteal artery as well as various regions of bone.

Figure 3

(A) CT and ¹⁸F-Fluoride PET images are shown of an 18-month-old Dunkin-Hartley guinea pig model of OA display differential PET uptake in the medial and lateral tibial plateaus. (B) The TAC is shown for regions of the tibial plateau as well as for the arterial input function that was used in pharmacokinetic and Patlak analysis.

Figure 4

(A) A static transaxial ¹⁸F-Fluoride dynamic PET image in a fracture of the distal radius is shown. Increased uptake can be seen in the cortical region of the distal radius at 2 weeks following insult. Minimal uptake can also be seen in the adjacent ulna, although styloid fractures of the ulna require that the contralateral side also be imaged. Images were coregistered between serial time points and normalized to the standard uptake value. (B) An intensity contour map was used to focus on a region of interest on the cortical uptake at baseline that was then copied to the 1-month and 2-month time points. The subsequent time activity curves for this subject show a gradual decrease in ¹⁸F-Fluoride uptake over the course of normal healing (courtesy of J.P. Dyke, M. Synan, S. Vallabhajosula, S. Goldsmith, O. Paul, J. Lane, and D. Lorich)