Soft Tissue Background Research Articles

In vivo assessment of trabecular bone structure at the distal radius from high-resolution magnetic resonance images.

In this study a method of assessing trabecular bone structure at the distal end of the radius from high-resolution magnetic resonance images is described. Trabecular bone is segmented from the marrow and soft tissue background using an adaptive threshold, a region growth, and a skeletonization step. From the processed image we measured the connectivity and orientation of the trabecular bone network. Connectivity was assessed by a proposed connectivity index (CI) and marrow space was quantitated by a mean hole area (HA). Significant age-related changes in CI and HA were observed in a mixed group of normal volunteers. CI decreased at a rate of 0.18 yr-1 (r = 0.72, n = 14, p < 0.05) and HA increased at a rate of 0.018 mm2 yr-1 (r = 0.69, n = 14, p < 0.05). Gradient analysis was used to examine trabecular orientation, and revealed that the individual trabeculae at the distal end of the radius are organized anisotropically along the bone. These findings suggest that clinical magnetic resonance scanners can be used to assess trabecular bone structure in vivo.

In vivo assessment of trabecular bone structure at the distal radius from high-resolution computed tomography images

A dedicated computed tomography system was used to acquire transaxial images of the distal radius to assess trabecular bone structure in vivo. We segmented trabecular bone from the marrow and soft tissue background by postprocessing the image with a region grow and skeletonization step. From the processed image we assessed the integrity of the bone by examining the continuity of its trabecular network and by determining the area of the holes comprising its marrow space. The continuity of the bone imaged was assessed by a proposed connectivity index (CI) and the size of the marrow spaces was assessed by calculating a mean hole area () in the bone cross-section. Repeat measurements revealed that the intra-subject variability in CI and was small (). Both CI and were sensitive enough to reflect differences in structure at the head of the radius and at several sites along its shaft. We tested the diagnostic value of assessing bone structure at the distal end of the radius by measuring trabecular bone density, CI and in a mixed group of 26 subjects, nine of whom had suffered a wrist fracture. We found that a trabecular bone density threshold of , corresponding to two standard deviations below the mean density in the 17 non-fractured subjects, separated fractured from non-fractured subjects with a sensitivity of 22% and a specificity of 100%. A CI threshold of -4.7 doubled the sensitivity (44%) and maintained the 100% specificity. An threshold of achieved a sensitivity of 89% and a specificity of 94%. This increased sensitivity achieved by our indices suggests that an in vivo assessment of trabecular bone structure can contribute significantly to the identification of persons at risk of fracture.

Contrast bone cement.

The effects of adding 1.0 cc of aqueous methylene blue dye as a visual contrast agent to a standard 40 g pack of acrylic bone cement are determined. These cements are evaluated: Simplex P (Radiopaque), Zimmer Bone Cement, and Zimmer LVC Bone Cement. Seven tests were performed. Leach out is less than 2.0% and was undetectable after day 8. Biocompatibility using a rabbit model shows contrast and white cement to be equivalent. Tension, compression, and 3- and 4-point bending strengths are not significantly altered except for a slight increase in 4-point bending strength for contrast Zimmer (regular) bone cement. Dough, set, and working times are decreased by 30-150 s. The ASTM F451 intrusion standards are met for all three contrast cements. Viscosity increases more rapidly for contrast cement, but remains sufficiently low (less than 100 N-s/m2) early after mixing to allow good penetration into bone. Ease of removal and visualization of contrast cement are shown by revision of cemented femoral total hip components in synthetic and cadaver femurs and by debriding cement particles from a soft tissue background coated with blood. The use of contrast bone cement appears to be both safe and efficacious for use in initial and revision total joint replacements. Because of the decreased working times, its use is recommended only by experienced surgeons.

Modification of gallium-67 citrate distribution in man following the administration of iron.

Current imaging techniques with 67Ga citrate for the localization of malignant or inflammatory lesions have a number of major limitations. In an effort to improve the lesion-to-background ratio and to reduce the time between 67Ga citrate injection and performing the scan, the 67Ga citrate injection is now routinely preceded by injection of iron-sorbitol citric acid (Jectofer). A series of 147 patients has been studied and shows that (a) the diagnosis can be made at 24 h in 80% of the cases, and (b) when 24 h and 48 h images are read together, diagnosis is at least as accurate as by the standard method, which requires a 72 h interval between injection and scanning. The major differences in appearance are lower activity in the soft-tissue background, relative absence of colonic activity at 24 h and visualization of the bladder in about 40% of cases. We believe that by saturating the free transferrin with iron, uptake into soft tissues and bone is sufficiently modified to enhance the lesion-to-background ratio, thereby making earlier imaging and diagnosis possible.

A Longitudinal Comparison of the Kinetics of 99mTc-MDP and 99mTc-EHDP in Humans

99mTc-MDP and 99mTc-EHDP were compared in 11 volunteers and 20 patients for blood retention, urinary excretion, bone to soft tissue background and overall quality of the radionuclide images. 99mTc-MDP showed significant superiority in most of the parameters tested making it the preferred radiopharmaceutical. However, in those patients exhibiting skeletal disease both 99mTc-MDP and 99mTc-EHDP disclosed the same lesions with approximately equal relief.

Clinical evaluation of tumor scanning with 169-Yb-citrate.

169-Yb-citrate was used as the tumor-scanning agent in 360 patients with malignant tumors and in 55 others with benign lesions and the results compared with 67-Ga-citrate studies in other series. In malignant tumors, the overall positive detection rate for ytterbium was 65.3%; in benign lesions, the false-positive rate was 29.1%. Good results were obtained in the extremities, head and neck, and pelvic area. Of all tumors visualized, squamous cell carcinoma was detected most effectively (77.5%). 169-Yb-citrate has a long shelf life, photon peaks of 178 and 198 kev, clears from the blood more rapidly than 67-Ga-citrate and has an extremely low soft-tissue background uptake. Its main disadvantage is its high radiation dose: 1.74 R/500 muCi whole-body and 5.77 R to the bone.

18F-fluoride for bone imaging

This report summarizes 10 yr of experience with 18F for bone scanning. The fluoride ion is rapidly taken up by an exchange process with bone which is a function of blood flow and exposure of bone crystal surface. 18F results in a lower radiation dose to bone than 85Sr under similar circumstances. The photon energy is not as desirable as that of 87mSr. The radionuclide, which may be given orally, is rapidly cleared from the blood, providing the advantage of an optimal scanning time at 2–4 hr after administration, at which time little soft-tissue background is seen. Among 239 patients followed. 80% of the cases were diagnosed correctly both by roentgenography and scanning. Where these two procedures disagreed, the scan was correct three times as often as the X ray.