Frequent, quantitative bone planar scintigraphy for determination of bone anabolism in growing mice

Background To provide insight into bone turnover, quantitative measurements of bone remodeling are required. Radionuclide studies are widely used in clinical care, but have been rarely used in the exploration of the bone in preclinical studies. We describe a bone planar scintigraphy method for frequent assessment of bone activity in mice across the growing period. Since repeated venous radiotracer injections are hardly feasible in mice, we investigated the subcutaneous route. Methods Repeated 99mTc-hydroxymethylene diphosphonate (HMDP) tracer bone planar scintigraphy studies of the knee region and µCT to measure femur growth rate were performed in eight mice between week 6 and week 27 of life, i.e., during their growth period. Three independent investigators assessed the regions of interest (ROI). An index was calculated based on the counts in knees ROI (normalized by pixels and seconds), corrected for the activity administered, the decay between administration and imaging, and individual weights. Results A total of 93 scintigraphy studies and 85 µCT were performed. Repeated subcutaneous tracer injections were well tolerated and allowed for adequate radionuclide studies. Mean scintigraphic indexes in the knees ROI decreased from 87.4 ± 2.6 × 10−6 counts s−1 pixel−1 MBq−1 g−1 at week 6 to 15.0 ± 3.3 × 10−6 counts s−1 pixel−1 MBq−1 g−1 at week 27. The time constant of the fitted exponential decay was equal to 23.5 days. As control mean femur length assessed by µCT increased from 12.2 ± 0.8 mm at week 6 to 15.8 ± 0.2 mm at week 22. The time constant of the fitted Gompertz law was equal to 26.7 days. A correlation index of −0.97 was found between femur growth and decrease of bone tracer activity count between week 6 and 24. Conclusion This methodological study demonstrates the potential of repeated bone planar scintigraphy in growing mice, with subcutaneous route for tracer administration, for quantitative assessment of bone remodeling.

Characterization of Atypical Pheochromocytomas with Correlative MRI and Planar/Hybrid Radionuclide Imaging: A Preliminary Study

Pheochromocytomas may show atypical imaging findings leading to diagnostic pitfalls. We correlated the results of magnetic resonance imaging (MRI) with those of radionuclide studies in patients with pheochromocytomas. T2-weighted (-w), T1-w chemical-shift and T1-w dynamic contrast enhanced (DCE) MRI sequences were evaluated to assess tumor structure. 131Iodine metaiodobenzylguanidine (MIBG) scintigraphy, 18fluoro (F) deoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) or FDG PET/MRI were evaluated for direct comparison. Of a total of 80 adrenal lesions in 73 patients, 20 in 18 patients were pheochromocytomas. More than half (55%) of the pheochromocytomas (n = 11) had the typical increased signal intensity on T2-w and T1-w DCE, while the remaining (n = 9) lesions showed atypical findings; of these nine latter atypical lesions, seven (35%) were cystic (two totally, three predominantly and two partially) and two (10%) were hemorrhagic on MRI. In these atypical lesions, MIBG scintigraphy (n = 5), FDG PET/CT (n = 6) or FDG PET/MRI (n = 2) showed inhomogeneous tracer uptake in the residual viable tissue providing tumor characterization; however, one predominantly cystic pheochromocytoma showed false negative MIBG scan. Our preliminary results show that cystic degeneration may be frequent in pheochromocytoma being so marked that only a thin rim of viable cells may residue to disclose the true nature of the tumor. MRI findings together with those of correlative planar/hybrid radionuclide images are helpful to characterize these atypical pheochromocytomas. In particular, tumor accumulation of MIBG and/or FDG is able to classify these lesions as not simple cysts; in detail, the presence of partial MIBG uptake allows the diagnosis of pheochromocytomas, while the presence of partial FDG uptake generically reflects the presence of viable solid tissue of such cystic tumors.

Radiation Patterns of Modern Sarcoidosis (Alphabet)

Radiation diagnostics of sarcoidosis in modern conditions is CT, supplemented by radionuclide studies (SPECT, PET), ultrasound, MRI. The paper describes the classic signs of pulmonary sarcoidosis (according to the Statement on Sarcoidosis, 1999), which have changed their characteristics due to the widespread use of CT: variants of lymphadenopathy, dissemination, interstitial involvement. New unfavorable forms of thoracic sarcoidosis are discussed: fibrous sarcoidosis (with a description of the variants of sarcoid fibrosis and their differences from other progressive pulmonary fibrosis) and progressive sarcoidosis (possible causes and patterns). Radiation semiotics of extrapulmonary and comorbid manifestations is touched upon.

SPECT with 67Ga Citrate in the Diagnosis of Systemic Sarcoidosis

Purpose: To study the possibilities of using 67Ga-citrate in patients with systemic manifestations of sarcoidosis to identify foci of pathological accumulation of the drug and assess the degree of process activity. Material and methods: Radionulide study with 67Ga-citrate was performed in 140 patients with respiratory sarcoidosis and suspected extrapulmonary localization. In addition, all patients underwent X-ray examination of the lungs, MSCT of the organs of the chest and abdominal cavity, SPECT of the lungs with radiopharmaceutical macroaggregates of albumin, ultrasound of the abdomen, pelvis, MRI of the head was performed in 16 patients with suspected neurosarcoidosis. Results: Most patients (n = 125) showed changes in the lungs, manifested by a bright glow (yellow or purple) on the computer screen, which indicated a pronounced impaired function of lymphoid tissue. In 22 patients, the changes were recurrent. The results correlated with published data on damage to the nervous system (r = 0.96), musculoskeletal system (r = 0.97), parotid glands (r = 0.91), liver, spleen (r = 0.83) . At the same time, the results for eye damage (r = 0.23), ENT organs (r = 0.15), intestines (r = 0.48) were significantly different. In our study, no heart lesions were detected in any case. Conclusions: The use of positive scintigraphy with Ga-67 citrate, taking into account the whole body scan and SPECT of areas of interest of interest (chest cavity, abdominal cavity, head, pelvis) is effective for the diagnosis of systemic sarcoidosis and in determining the activity of the process. The study is recommended to be performed 72 hours after intravenous administration of the drug. The combination of CT, MRI and radionuclide studies allows you to obtain reliable information about the activity of the process, to identify the localization of increased metabolic activity, that is, the topography of active sarcoidosis.

Optimization of planning radionuclide diagnostic tests in osteoscintigraphy

Purpose of the study. Determining maximum possible number of high-quality radionuclide studies by days of the generator operation.Materials and methods. We studied the factors influencing the capacity of radionuclide diagnostic tests in osteoscintigraphy (OSG) by days of service life of a 99mTc generator GT-4K. The OSG capacity, the required resource of 99mTc and its efficiency in OSG were calculated. The optimal days for the generator delivery were determined.The Pirfotech 99mTc radiopharmaceutical (RFP) prepared with the generator was used for OSG.Scanning, data collection and processing of results were carried out on gamma-cameras of the systems Signature Series, Symbia T16 Siemens, and syngo M1 Applications VB10 Siemens.Parameters of the radioactivity of 99mTc were processed by mathematical methods using the Excel program.Results. We revealed specific factors influencing the OSG capacity: 1) three-hour accumulation of RFP after its administration to the patient; 2) generator activity by days of its operation; 3) the day of the week of the generator delivery. We calculated quantitative indicators of the maximum possible OSG capacity during the generator operation (maximum number of OSG procedures by days of operation, total capacity, preferred day of the week for the generator delivery).Conclusion. The most significant factors in optimal OSG planning by days of the generator operation are the generator specifications, quantity and frequency of generator supply, provision of gamma-cameras.The described technique for scheduling diagnostic procedures can be useful for the efficient use of the generator system which ensures the maximum amount of high-quality RFP from the generator eluate and contributes to the objectification of the cancer process in order to choose the treatment tactics.

Frequent, Quantitative Bone Planar Scintigraphy for Determination of Bone Anabolism in Growing Mice

BackgroundTo provide insight into bone turnover, quantitative measurements of bone remodeling are required. Radionuclide studies are widely used in clinical care, but have been rarely used in the exploration of the bone in preclinical studies. We describe a bone planar scintigraphy method for frequent assessment of bone activity in mice across the growing period. Since repeated venous radiotracer injections are hardly feasible in mice, we investigated the subcutaneous route.MethodsRepeated phosphonate tracer bone planar scintigraphy studies of the knee region and μCT to measure femur growth rate were performed in eight mice between week 6 and week 27 of life, i.e. during their growth period. Three independent investigators assessed the regions of interest (ROI). An index was calculated based on the counts in knees ROI (normalized by pixels and seconds), corrected for the activity administered, the decay between administration and imaging, and individual weights.ResultsA total of 97 scintigraphy studies and 90 μCT were performed. Repeated subcutaneous tracer injections were well tolerated and allowed for adequate radionuclide studies. Mean scintigraphic indexes in the knees ROI decreased from 87.4 ± 13.0x10-6 counts.s-1.pixel-1.MBq-1.g-1 at week 6 to 13.1 ± 3.9x10-6 counts.s-1.pixel-1.MBq-1.g-1 at week 27. The time constant of the fitted exponential decay was equal to 23.6 days. Mean femur length assessed by μCT increased from 12.2 ± 0.8 mm at week 6 to 15.8 ± 0.2 mm at week 24. The time constant of the fitted Gompertz law was equal to 26.7 days.ConclusionThis study demonstrates the potential of repeated bone planar scintigraphy in growing mice, with subcutaneous route for tracer administration, for quantitative assessment of bone remodeling.

Actual problems of nuclear medicine in pediatrics (review)

On the basis of literature data and personal experience, the current state and prospects for the development of nuclear medicine in pediatrics are analyzed. The main directions of radionuclide diagnostics and radionuclide therapy in children are briefly considered. The importance of accu-rate determination of the optimal value of the activity of a specific radiopharmaceutical adminis-tered to a child, taking into account his body weight and the study protocol, was noted. A tendency for an increase in the radiation load on patients is shown due to the widespread introduction into clinical practice of hybrid installations for radionuclide studies, when using which the dose of in-ternal radiation from radiopharmaceuticals is supplemented by the dose of external radiation from X-ray CT. The need to take into account the risk of radiation-induced carcinogenesis in nu-clear medical procedures, the probability of which in children is significantly higher than in adults, is emphasized. The technological and psychological features of these procedures in children are discussed. The necessity of substantial revision of domestic normative documents regulating the use of means and methods of nuclear medicine in pediatrics has been substantiated.

Ventilation and perfusion scintigraphy after lung transplantation

Study objective. Evaluation of the possibilities of ventilation and perfusion scintigraphy in detecting functional disorders and determining the severity of lung damage that may occur after organ transplantation. Material and methods. The study included 27 patients after bilateral lung transplantation; mucoviscidosis was the main cause of terminal respiratory failure in most cases (19 patients; 77.8%). The ventilation scintigraphy was performed with 99mTc-pentatech using a nebulizer, and the perfusion scintigraphy was performed with 99mТс-albumin macroaggregate. The investigations were performed on Infinia II and Discovery 670 NM/CT single-photon emission tomographs (GE, USA). Results. Changes in the quantitative parameters of ventilation and perfusion scintigraphy in patients after lung transplantation were studied. When analyzing the results of radionuclide studies, we identified a restoration of function after lung transplantation, and the appearance of disorders with the development of complications in the early (up to 4 months) and later (more than one year) periods after bilateral lung transplantation. Conclusion. The study has shown that the radionuclide method has wide possibilities for assessing the ventilation and perfusion functions in patients after lung transplantation, helping in the differential diagnosis of obliterating bronchiolitis and graft vascular sclerosis, in assessing the nature of alveolar-capillary diffusion disorders, and determining the extent of functional abnormalities in every individual patient. Monitoring the function of transplanted lungs using scintigraphy allows separate monitoring of ventilation and perfusion changes, which is important for the choice of treatment tactics.

Methods for modeling the kinetics of radiopharmaceuticals with iodine isotopes in nuclear medicine problems

The paper considers modeling methods and develops a unified approach to the construction of mathematical models of the kinetics of radiopharmaceuticals with iodine isotopes in the human body during diagnostic and therapeutic procedures of nuclear medicine. Based on this approach, three- and four-compartment pharmacokinetic models were developed and corresponding calculation programs were created in the C++ programming language for processing and evaluating the results of radionuclide diagnostics and therapy. Various methods for identifying model parameters based on quantitative data from radionuclide studies of the functional state of vital organs are proposed. The results of pharmacokinetic modeling for radionuclide diagnostics of the liver, kidney, and thyroid using iodine-containing radiopharmaceuticals are presented and analyzed. Using clinical and diagnostic data, individual pharmacokinetic parameters of transport of different radiopharmaceuticals in the body (transport constants, half-life periods, maximum activity in the organ and the time of its achievement) were determined. It is shown that the pharmacokinetic characteristics for each patient are strictly individual and cannot be described by averaged kinetic parameters. Within the framework of three pharmacokinetic models, “Activity-time” relationships were obtained and analyzed for different organs and tissues, including for tissues in which the activity of a radiopharmaceutical is impossible or difficult to measure by clinical methods. Also discussed are the features and the results of simulation and dosimetric planning of radioiodine therapy of the thyroid gland. It is shown that the values of absorbed radiation doses are very sensitive to the kinetic parameters of the compartment model. Therefore, special attention should be paid to obtaining accurate quantitative data from ultrasound and thyroid radiometry and identifying simulation parameters based on them. The work is based on the principles and methods of pharmacokinetics. For the numerical solution of systems of differential equations of the pharmacokinetic models we used Runge-Kutta methods and Rosenbrock method. The Hooke-Jeeves method was used to find the minimum of a function of several variables when identifying modeling parameters.