Deconvolution analysis of 99mTc-methylene diphosphonate kinetics in metabolic bone disease

The value of local 99mTc(Sn)-MDP bone to soft tissue uptake ratio in osteoporosis, before and during fluoride therapy

The reproducibility and diagnostic value of local bone to soft tissue uptake ratio of 99mTc(Sn)-MDP as a bone tracer was examined in a prospective study in 35 patients who were under investigation and/or treatment for postmenopausal osteoporosis. The ratio of tracer uptake in the second lumbar vertebra (L2) and both femoral shafts was calculated from the number of counts in suitable regions of interest. Results obtained with settings and calculations in the routine practice were compared to the results obtained by revision of all raw data in one run by one person. The results were compared to the serum alkaline phosphatase activity (AP) and to local bone mineral mass as determined by dual photon absorptiometry (DPA). In 15 patients serial measurements during fluoride therapy were also compared to serum osteocalcin values and to bone histomorphometric data. The precision error of the calculation of uptake ratios from raw counts (including selection of region of interest) was 13.9% for the femoral shaft and 14.7% for L2. The mean difference between left and right femoral shaft in individuals was not significant and its variance was small P greater than 0.1). There was a weak but significant linear correlation between local uptake ratio in the spine and AP in the total material (r = 0.328 P less than 0.01). However, changes in local uptake ratio during therapy with fluoride in 15 patients were too small to be of any value and did not correlate with changes in alkaline phosphatase or osteocalcin or trabecular surface covered with osteoblasts.(ABSTRACT TRUNCATED AT 250 WORDS)

Deconvolution using orthogonal polynomials in nuclear medicine: a method for forming quantitative functional images from kinetic studies

A deconvolution technique is described which utilizes orthogonal polynomials (DOP) and handles inevitable noise in such a way that pixel time activity curves can be deconvolved. This solves the issue of quantitative analysis of serial scintigraphic data in a manner that preserves the high spatial resolution inherent in raw data. In the current work a complete mathematical description of the new deconvolution technique is presented. The DOP method is designed for use with an array processor and results in a set of linear response function (LRF) images. Techniques to calibrate the measuring devices and correct for distorted input functions in order to obtain the LRF images in absolute units are described. A simulation study compares the DOP method with the Fourier transform and the discrete deconvolution algorithm both with and without various noise levels. The impact on the convergence of the DOP algorithm of undesired blood activity simultaneously measured with the organ-target activity was simulated.

Radionuclide imaging in metabolic and systemic skeletal diseases

Radionuclide imaging with Tc-99m diphosphonates is not an effective method for detecting or ruling out most osteoporotic diseases including senile osteoporosis or accelerated postmenopausal osteoporosis, and the slow loss of bone tissue generally remains undetected by this modality. Nonetheless, it frequently surpasses or supplements radiographic findings in evaluating the focal complications of metabolic bone disease, including fractures, microfractures, stress fractures, vertebral compressions, Milkman-Looser zones, aseptic necrosis, and acute infarction. In contrast to its secondary role in osteoporosis, bone imaging is of prime importance in investigating hypercalcemia, because the major cause of this abnormality is skeletal metastatic malignancy. In defective bone mineralization due to hyperparathyroidism or osteomalacia, a general increase in diphosphonate skeletal uptake is detected more frequently than radiographic abnormalities. However, normal skeletal images do not rule out metabolic bone disease. Biochemical testing is more reliable in detecting primary hyperparathyroidism. On the other hand, in renal osteodystrophy, biochemical abnormalities are variable and bone imaging is helpful in assessing the severity of skeletal involvement, but not its etiology. Many methods of quantitating the kinetics of Tc-99m diphosphonates have been explored, such as plasma clearance, bone-to-soft-tissue ratios, 24-hour total body retention and 24-hour urinary excretion. None of these have been widely accepted. The value of bone imaging is established in other systemic diseases, most notably in Paget's disease, hypertrophic pulmonary osteoarthropathy, sickle cell disease, fibrous dysplasia, and sympathetic dystrophy.

Evaluation of diffusely high uptake by the calvaria in bone scintigraphy

The present study was undertaken to evaluate the finding of diffusely high uptake by the calvaria in a series of 994 consecutive whole body scans in regard to the incidence and degree, and to discuss the mechanism. A total of 86 patients had positive scans (73 women and 13 men) and there were 71 malignant (27 breast, 16 lung, and 28 other malignancies), and 15 benign disease cases (5 degenerative bone, 3 blood, and 7 miscellaneous diseases). Positive rate of the finding was 8.7% in total, 14.9% in women, and 2.6% in men. The difference between women and men was significant (P less than 0.001). The finding was significantly correlative with the ages of patients. Also the finding is shown to be predominant in women ranging 50-59 years of age. On the other hand, the same finding as was made by Creutzig and his coworker was confirmed in malignant cases under high-dose anticancer drug therapy. On the basis of these results, the finding may be not only a side effect of intensive cytotoxic medication on the skeleton, but also a physiological event relative to bone change with age and postmenopausal osteoporosis.

Studies on diphosphonate kinetics. Part I: Evaluation of plasma elimination curves during 24 h

To improve the understanding of diphosphonate affinity to metabolically active bone, the underlying diphosphonate kinetics have been evaluated and compared to Cr-EDTA kinetics. MDP binds to plasma proteins, varying from 25% initially to approximately 70% after 24 h. The renal clearance of diphosphonate is found to be equal to Cr-EDTA clearance. Using simultaneous bolus injection of 99Tc-MDP and 51Cr-EDTA, it has been possible to obtain a coarse estimate of bone uptake of MDP. This uptake is found to correlate well with s-alkaline phosphatase, but since MDP binding to bone is reversible, the plasma elimination curve is not monoexponential. Therefore it has not been possible to describe the uptake of MDP in bone mathematically.

Model identification and estimation of organ-function parameters using radioactive tracers and the impulse-response function

Examination of the input-output events in functioning organs by the use of the impulse-response function (IRF) for a radioactive tracer is gaining more and more ground in nuclear medicine. This study summarizes the development of deconvolution analysis, laying special stress on the 'model-free' approach. System linearity and time invariance are discussed, and means of eliminating noise in IRFs originating from the input and organ-time-activity curves are outlined. Typical IRFs are illustrated by flow diagrams, time-domain curves, and their representation by Laplace transforms. The cases of nondiffusible and diffusible tracers as well as parenchymally extracted and transported substances are discussed. Methods for the derivation of models and for the calculation of physiologically important parameters from the IRFs are suggested.