Measurement of gastric emptying time of solids in healthy subjects using scintigraphic method: a revised technique

Biokinetic model of radioiodine I-131 in nine thyroid cancer patients subjected to in-vivo gamma camera scanning: A simplified five-compartmental model

A five-compartmental biokinetic model of I-131 radioiodine based on in-vivo gamma camera scanning results was developed and successfully applied to nine thyroid cancer patients who were administered 1,110 MBq I-131 in capsules for the residual thyroid gland ablation. The I-131 solution activity among internal organs was analyzed via the revised biokinetic model of iodine recommended by the ICRP-30 and -56 reports. Accordingly, a five-compartmental (stomach, body fluid, thyroid, whole body, and excretion) model was established to simulate the metabolic mechanism of I-131 in thyroid cancer patients, whereas the respective four simultaneous differential equations were solved via a self-developed program run in MATLAB. This made it possible to provide a close correlation between MATLAB simulation results and empirical data. The latter data were collected through in-vivo gamma camera scans of nine patients obtained after 1, 4, 24, 48, 72, and 168 hours after radioactive I-131 administration. The average biological half-life values for the stomach, body fluid, thyroid, and whole body of thyroid cancer patients under study were 0.54±0.32, 12.6±1.8, 42.8±5.1, and 12.6±1.8 h, respectively. The corresponding branching ratios I12, I23, I25, I34, I42, and I45 as denoted in the biokinetic model of iodine were 1.0, 0.21±0.14, 0.79±0.14, 1.0, 0.1, and 0.9, respectively. The average values of the AT dimensionless index used to verify the agreement between empirical and numerical simulation results were 0.056±0.017, 0.017±0.014, 0.044±0.023, and 0.045±0.009 for the stomach, thyroid, body fluid + whole body, and total, respectively. The results obtained were considered quite instrumental in the elucidation of metabolic mechanisms in the human body, particularly in thyroid cancer patients.

BIOKINETIC MODEL OF Tc-99m MIBI FOR EIGHT PATIENTS UNDERGONE MYOCARDIAL PERFUSION EXAMINATION via GAMMA CAMERA AND MATLAB PROGRAM: AN IN-VIVO STUDY

Biokinetic model of Tc-99m MIBI for eight patients undergone myocardial perfusion examination was studied using gamma camera and MATLAB program. A six-compartment model was adopted to interpret the metabolic mechanism of each patient. Within the model framework, the respective set of simultaneous differential equations was solved by a self-developed program run in MATLAB. The experimental results exhibited a good fit with the theoretical predictions via the model. The average biological half-lives of body fluid, heart, thyroid, liver, GI Tract and remainder were assessed as [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text][Formula: see text]h, respectively. A dimensionless AT index of disagreement between the experimental data and MATLAB optimal solution was proposed of validating the applied acquisition system and analytical method feasibility. An AT of zero implies a perfect agreement between the theoretical and empirical results, while averages of the derived AT were fluctuated from 3 [Formula: see text] 2 to [Formula: see text] for five compartments. The proposed refined equation estimated the internal dose from gamma-ray as [Formula: see text][Formula: see text]mSv for eight patients according to a fast screening method, which defined human body as a spherical ball to simplify the calculation in reality. The proposed MATLAB-based fitting of in-vivo data with the theoretical results was instrumental for assessing the radiation dose received by the Tc-99m MIBI scan participants.

BIOKINETIC MODEL DEVELOPMENT OF RADIOIODINE-131 VIA IN VIVO GAMMA CAMERA/8-SLICE CT TECHNIQUE: CASE-CONTROL STUDY OF FELINE HYPERTHYROIDISM

Objectives: A biokinetic model of iodine in the thyroid was developed and applied to a case-control study of hyperthyroid cat undertaken the NaI-131 dose administration using a gamma camera/8-slice CT with the in vivo study. Methods: The case-control hyperthyroid cats were administered 55.5 or 3.7[Formula: see text]MBq of I-131 radioactive solution and continuously surveyed by a gamma camera. The scan schedule was preset as 5- or 10-min counting per each hour from the initial time to the sixth hour, then on the 24th, 48th and 72nd hours, respectively. An in-house developed program run in the MATLAB was applied to evaluate the biokinetic model of iodine in the thyroid, in compliance with the ICRP-30 report regulations. The model was defined by five compartments (namely: stomach, body fluid, thyroid, whole body, and excretion) and allowed one to simulate the variations of time-dependent I-131 radioactive concentration among various compartments of each study subject. The numerical simulation via MATLAB was compiled with the empirical evaluation to optimize the time-dependent concentration of I-131 within the above compartments. Results: The derived biological half-life values for stomach, body fluid, thyroid, whole body, and excretion, respectively, were as follows: 17, 3, 10, 5 and 140[Formula: see text]h for hyperthyroid cat, 18, 1, 8, 2, and 40[Formula: see text]h for control #1 cat, and 22, 2, 12, 4, and 20[Formula: see text]h for control #2 cat. The cumulative radioactive doses from both gamma-ray and beta particles were assessed via a simplified algorithm as 0.135, 0.0082, and 0.005 Gy, for hyperthyroid cat, control #1, and control #2 ones, respectively. Conclusion: The derived biokinetic model was found to be helpful in the evaluation of the metabolic mechanism in case of feline hyperthyroidism. The revealed deviations from available human biomodels can be used for refining the radioiodine treatment of pets with hyperthyroidism.

BIOKINETIC AND DOSIMETRIC ASSESSMENT OF FLUORINE 18 IN HEALTHY VOLUNTEERS SUBJECTED TO 18F–NaF PET/CT BONE SCANS VIA COMPARTMENTAL/MATLAB MODELS AND IN-VIVO STUDY

Objective: This study quantified the time-dependent concentration of [Formula: see text]F–NaF in critical organs according to a simplified compartmental biokinetic model with clinical verification. Methods: The eleven volunteers were given [Formula: see text][Formula: see text]MBq [Formula: see text]F–NaF administration, then scanned (with 15[Formula: see text]min-collection, every 20[Formula: see text]min, for 200 consecutive min) with a Philips Gemini GXL PET/CT. The empirical data were collected and normalized as the input dataset for MATLAB program. A six-compartmental model was created as a set of time-dependent differential equations and analyzed by the MATLAB to optimize the correlation between the in vivo data and calculated results. The six compartments were: body fluid, bone, kidney, liver, remainder and excretion, while kidney and liver compartments were conventionally split into two subunits with different half-lives to fit properly the empirical data. Results: The average biological half-lives of body fluid, bone, kidney-1, kidney-2, liver-1, liver-2 and the remainder (rest of body) were assessed as [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text][Formula: see text]min, respectively. A dimensionless AT index of disagreement between the empirical data and MATLAB optimal solutions was proposed of validating the applied acquisition system and analytical method feasibility. The body fluid and bone AT values did not exceed 20%. The proposed refined equation yielded the internal dose from both gamma- and beta-rays ([Formula: see text] cSv as [Formula: see text] cSv/MBq), which exhibited good correlation with literature (0.00168–0.00270 cSv/MBq). Conclusion: The proposed MATLAB-based fitting of in-vivo data with the theoretical results was instrumental for assessing the radiation dose received by the PET/CT bone scan participants.

THE FIRST ATTEMPT OF THE BIOKINETIC GA-67 MODEL APPLICATION TO CANINE LIVER CARCINOMA: CASE-CONTROL STUDY VIAIN-VIVOGAMMA CAMERA/8-SLICE CT TECHNIQUE

The biokinetic model of Ga-67 evolution was elaborated in this study for the case-control group of canine liver carcinoma via in-vivo gamma camera/8-slice CT technique. One liver carcinoma dog and two normal dogs were anesthetized with the further whole body scanning by a gamma camera to acquire the time-dependent Ga-67 concentration variations among eight compartments, namely: 1. body fluid, 2. liver, 3. GI Tract, 4. kidney, 5. heart, 6. remainder, 7. bladder, and 8. excretion. Each compartment was assumed to have a unique biological half-life and to be connected to other ones. The initial simplification of assigned compartments was performed based on the general-purpose biokinetic model recommended by the ICRP-30 report. Each object/dog underwent eight scans within 72[Formula: see text]h. The time-dependent empirical data were normalized to the maximal counts/pixel/sec and then integrated with the theoretical estimates, in order to optimize the correlations among compartments. A self-developed program run in MATLAB was used to reflect the actual performance acquired from the gamma camera scanning, while the dimensionless agreement (AT) was applied to assess the discrepancies between empirical and theoretical results. An AT of zero implies a perfect agreement between the theoretical and empirical results, while AT under 20 indicates an excellent consistency between the optimal computational and empirical data, whereas a wide fluctuation of the obtained ATs in the range of 7%–60% corresponded to a medium range of data disagreement in this study. The liver carcinoma dog has revealed a longer biological half-life than normal dogs in the limited range (40 versus 35 or 15[Formula: see text]h). However, the quantified data for other compartments and branching ratios among compartments provided a quite robust substantiation for constructing the biokinetic model of Ga-67 being administrated in the canine hepatic survey.

A quantitative evaluation of multiple biokinetic models using an assembled water phantom: A feasibility study

This study examined the feasibility of quantitatively evaluating multiple biokinetic models and established the validity of the different compartment models using an assembled water phantom. Most commercialized phantoms are made to survey the imaging system since this is essential to increase the diagnostic accuracy for quality assurance. In contrast, few customized phantoms are specifically made to represent multi-compartment biokinetic models. This is because the complicated calculations as defined to solve the biokinetic models and the time-consuming verifications of the obtained solutions are impeded greatly the progress over the past decade. Nevertheless, in this work, five biokinetic models were separately defined by five groups of simultaneous differential equations to obtain the time-dependent radioactive concentration changes inside the water phantom. The water phantom was assembled by seven acrylic boxes in four different sizes, and the boxes were linked to varying combinations of hoses to signify the multiple biokinetic models from the biomedical perspective. The boxes that were connected by hoses were then regarded as a closed water loop with only one infusion and drain. 129.1±24.2 MBq of Tc-99m labeled methylene diphosphonate (MDP) solution was thoroughly infused into the water boxes before gamma scanning; then the water was replaced with de-ionized water to simulate the biological removal rate among the boxes. The water was driven by an automatic infusion pump at 6.7 c.c./min, while the biological half-life of the four different-sized boxes (64, 144, 252, and 612 c.c.) was 4.8, 10.7, 18.8, and 45.5 min, respectively. The five models of derived time-dependent concentrations for the boxes were estimated either by a self-developed program run in MATLAB or by scanning via a gamma camera facility. Either agreement or disagreement between the practical scanning and the theoretical prediction in five models was thoroughly discussed. The derived biokinetic model represented the metabolic mechanism in the human body and helped to solidify the internal circulatory system into concert with numerical verification.

Quantitative analysis of multiple biokinetic models using a dynamic water phantom: A feasibility study

This study analyzed multiple biokinetic models using a dynamic water phantom. The phantom was custom-made with acrylic materials to model metabolic mechanisms in the human body. It had 4 spherical chambers of different sizes, connected by 8 ditches to form a complex and adjustable water loop. One infusion and drain pole connected the chambers to an auxiliary silicon-based hose, respectively. The radio-active compound solution (TC-99m-MDP labeled) formed a sealed and static water loop inside the phantom. As clean feed water was infused to replace the original solution, the system mimicked metabolic mechanisms for data acquisition. Five cases with different water loop settings were tested and analyzed, with case settings changed by controlling valve poles located in the ditches. The phantom could also be changed from model A to model B by transferring its vertical configuration. The phantom was surveyed with a clinical gamma camera to determine the time-dependent intensity of every chamber. The recorded counts per pixel in each chamber were analyzed and normalized to compare with theoretical estimations from the MATLAB program. Every preset case was represented by uniquely defined, time-dependent, simultaneous differential equations, and a corresponding MATLAB program optimized the solutions by comparing theoretical calculations and practical measurements. A dimensionless agreement (AT) index was recommended to evaluate the comparison in each case. ATs varied from 5.6 to 48.7 over the 5 cases, indicating that this work presented an acceptable feasibility study.