[Comparative investigations concerning osteotropic radiopharmaceuticals. III. Scanning with 18F and 99mTc-malignant diseases (author's transl)]

Using PET/CT Bone Scan Dynamic Data to Evaluate Tibia Remodeling When a Taylor Spatial Frame Is Used: Short and Longer Term Differences

Eighteen consecutive patients, treated with a Taylor Spatial Frame for complex tibia conditions, gave their informed consent to undergo Na¹⁸F⁻ PET/CT bone scans. We present a Patlak-like analysis utilizing an approximated blood time-activity curve eliminating the need for blood aliquots. Additionally, standardized uptake values (SUV) derived from dynamic acquisitions were compared to this Patlak-like approach. Spherical volumes of interest (VOIs) were drawn to include broken bone, other (normal) bone, and muscle. The SUV_m(t) (m = max, mean) and a series of slopes were computed as (SUV_m(t_i) − SUV_m(t_j))/(t_i − t_j), for pairs of time values t_i and t_j. A Patlak-like analysis was performed for the same time values by computing ((VOI_p(t_i)/VOI_e(t_i))−(VOI_p(t_j)/VOI_e(t_j)))/(t_i − t_j), where p = broken bone, other bone, and muscle and e = expected activity in a VOI. Paired comparisons between Patlak-like and SUV_m slopes showed good agreement by both linear regression and correlation coefficient analysis (r = 84%, r_s = 78%-SUV_max, r = 92%, and r_s = 91%-SUV_mean), suggesting static scans could substitute for dynamic studies. Patlak-like slope differences of 0.1 min⁻¹ or greater between examinations and SUV_max differences of ~5 usually indicated good remodeling progress, while negative Patlak-like slope differences of −0.06 min⁻¹ usually indicated poor remodeling progress in this cohort.

Evaluation of the incorporation of bone grafts used in maxillofacial surgery with [18F]fluoride ion and dynamic positron emission tomography

This study investigates the incorporation of bone grafts used in maxillofacial surgery by means of [18F]fluoride ion and positron emission tomography (PET). It considers patients who received pedicle grafts for mandibular reconstruction or onlay grafts for alveolar ridge augmentation. Dynamic PET images and arterialized venous blood samples were obtained within a 1-h period after i.v. injection of [18F]fluoride. Assuming a three-compartment model and applying multilinear least squares fitting, bone blood flow (K1) and fluoride influx (Kmlf) were determined. Additionally Patlak plot analysis was used to calculate fluoride influx (Kpat). In cervical vertebral bodies as the reference region, mean values for flow of K1 = 0.1162 +/- 0.0396 ml/min/ml and influx of Kmlf = 0.0508 +/- 0.0193 and Kpat = 0.0385 +/- 0.0102 ml/min/ml were found. Essentially these figures are comparable with physiological values in animal and man reported in the literature. Early after surgery a significant increase in flow and influx compared to vertebral bodies was observed in the regions of osteosyntheses between grafts used for reconstruction and recipient bone (K1 = 0.2181, Kmlf = 0.1000 and Kpat = 0.0666 ml/min/ml) and in onlay grafts (K1 = 0.2842, Kmlf = 0.1637 and Kpat = 0.0827 ml/min/ml). At the same time pedicle grafts showed a significant increase in flow but not in influx (K1 = 0.2042, Kmlf = 0.0774 and Kpat = 0.0529 ml/min/ml). Furthermore Kpat was significantly lower in pedicle grafts than in onlay grafts. In follow-up studies a significant decrease in flow occurred in pedicle grafts and the regions of osteosyntheses. Moreover the latter showed a significant decrease in Kmlf as well. It is concluded that [18F(-)] PET depicted increased blood flow and osteoblastic activity in onlay grafts and regions of osteosyntheses, indicating bone repair in the graft and adjacent host bone early after surgery. For the regions of osteosyntheses the decrease in both parameters corresponded to uncomplicated healing. The lack of increased influx, although flow was increased in pedicle grafts, most likely indicates that some necrosis occurred in these grafts despite patency of anastomoses. It may be concluded that [18F(-)] PET provides further insight into the biology of graft incorporation.