TECNETIUM-99m AS ALTERNATIVE TO PRODUCE SOMATOSTATIN-LABELED DERIVATIVES: COMPARATIVE BIODISTRIBUTION EVALUATION WITH (111)In-DTPA-OCTREOTIDE

Synthetic somatostatin (SST) analogues have been used in the preparation of receptor-specific radiopharmaceuticals for diagnostic and therapy of neuroendocrine tumors. This work studied the labeling conditions with (99m)Tc and biological distribution in Swiss mice of two SST analogs (HYNIC-Tyr(3)-Octreotide and HYNIC-Tyr(3)-Octreotate) and compared the biodistribution pattern with (111)In-DTPA-Octreotide. Biological distribution studies were performed after injection of radiopharmaceuticals on Swiss mice. Labeling procedures resulted on high radiochemical yield for all three preparations and the labeled products presented high in vitro stability. Biological distribution studies evidenced similar general biodistribution of (99m)Tc-labeled peptides when compared with indium-labeled peptide with fast blood clearance and elimination by urinary tract. Kidneys uptake of (99m)Tc-HYNIC-TATE are similar to (111)In-DTPA-Octreotide, and both are significantly higher than (99m)Tc-HYNIC-OCT. All labeled peptides presented similar uptake on liver, but the retention in time at intestines, particularly at large intestine, was more expressive for (111)In-labeled peptide. The %ID of (99m)Tc-HYNIC-OCT and (99m)Tc-HYNIC-TATE in organs with high density of SST receptors like pancreas and adrenals were significant and similar to obtained for (111)In-DTPA-Octreotide, confirming the affinity of these radiopharmaceuticals for the receptors.

The neurobiological substrates of behavioral manifestations during temporal lobe seizures: A neuroethological and ictal SPECT correlation study

Ictal behavior coupled with SPECT findings during 28 seizures in patients with temporal lobe epilepsy (TLE) with unilateral hippocampal sclerosis (13 left; 15 right) was displayed as flowcharts from right-sided (RTLE) plus left-sided (LTLE) seizures. Ictal SPECT was classified blind to neuroethology. Behaviors were categorized as ipsilateral to the epileptogenic zone (IL), contralateral to the epileptogenic zone (CL), or bilateral. SPECT intensity and region were categorized as IL or CL to the epileptogenic zone. All patients developed automatisms and had hyperperfusion in their temporal lobes. Patients` verbal responses to questions had statistical interactions in RTLE but not in LTLE sum. Most CL dystonic posturing was correlated to IL basal ganglia hyperperfusion. Basal ganglia activation occurred in seizures without dystonic posturing and CL manual automatisms, and lack of IL dystonic posturing and the presence of CL cerebellar hemispheric hyperperfusion were also observed. Coupling of neuroethology and SPECT findings reliably evaluates ictal behavior and functionality of associated brain areas. (C) 2010 Elsevier Inc. All rights reserved.

Impact of the background region of interest in the relative renal function

Renal scintigraphy with 99mTc-dimercaptosuccinic acid (99mTc-DMSA) is performed with the aim of detect cortical abnormalities related to urinary tract infection and accurately quantify relative renal function (RRF). For this quantitative assessment Nuclear Medicine Technologist should draw regions of interest (ROI) around each kidney (KROI) and peri-renal background (BKG) ROI, although, controversy still exists about BKG-ROI. The aim of this work was to evaluate the effect of the normalization procedure, number and location of BKG-ROI on the RRF in 99mTc-DMSA scintigraphy.

Estudo da resposta de um dos��metro eletr��nico individual

Introdu����o ��� A monitoriza����o da exposi����o ocupacional a doses de radia����o ionizante pode ser complementada por dos��metros eletr��nicos individuais que permitem uma leitura direta da dose de radia����o recebida. Dada a depend��ncia energ��tica e de d��bito de dose j�� reportada para estes dos��metros, este trabalho pretende determinar a linearidade da resposta de um dos��metro eletr��nico individual e estudar o comportamento da sua resposta em fun����o da energia de radia����o e do d��bito de dose. Metodologia ��� Para estudar a depend��ncia da energia da radia����o do dos��metro eletr��nico pessoal Vertec Bleeper Sv procedeu���se �� sua irradia����o com um equivalente de dose individual, Hp(10), de 500 ��Sv de radia����o gama do Cobalto ��� 60 (60C) e C��sio ��� 137 (137Cs) e das qualidades de radia����o X da s��rie Narrow (N): N���30, N���40, N���60, N���80, N���100 e N���120. Para investigar a depend��ncia da resposta em fun����o do d��bito de dose aplicaram���se �� ampola de raios X as intensidades de corrente el��trica de 1 mA, 5 mA, 10 mA, 15 mA e 20 mA. Resultados ��� N��o existe uma rela����o entre a resposta do detetor e a energia de radia����o a que este �� exposto. Ocorre uma subestima����o superior a 50% na grandeza medida para energias inferiores a 33 keV, mas ostenta uma medida relativamente linear da grandeza Hp(10) para doses inferiores a 100 ��Sv. Tamb��m se constata que, �� medida que o d��bito de dose aumenta, existe uma diminui����o na resposta do dos��metro. O menor decr��scimo na resposta deste dos��metro eletr��nico individual d�����se para as qualidades de radia����o N���30 (1,1%), N���40 (4,1%) e N���120 (20,0%). Conclus��o ��� Verifica���se que a resposta do dos��metro individual Vertec Bleeper Sv depende fortemente da energia da radia����o e do d��bito de dose. ABSTRACT: Introduction ��� The measurement of occupational exposure to radiation doses can be completed with an electronic personal dosemeter that allows a direct reading and alarm function of the received radiation dose. Due to the energy and dose rate dependence already reported for this type of dosemeter, it is intended, with this work, to determine the response linearity of an Electronic Personal Dosemeter and to study its response behavior to the dose rate and radiation energy. Methodology ��� The electronic personal dosemeter Vertec Bleeper Sv energy dependency was evaluated by its irradiation with 500 ��Sv from the radionuclides Cobalt ��� 60 (60C) and Cesium ��� 137 (137Cs) as well as by the radiation qualities of the Narrow (N) series: N���30, N���40, N���60, N���80, N���100 e N���120. To investigate the dose rate dependency, the intensities of electric current of 1 mA, 5 mA, 10 mA, 15 mA and 20 mA were applied to the X���ray tube. Results ��� There is no relationship between the response of the detector and the radiation energy. For energies below 33 keV there is an underestimation over 50% of the radiation dose measured but the detector presents a linear response for energies under 100 ��Sv. A dependency on the dose rate is perceived since as the dose rate increases, the response of the individual monitor decreases. There is a smaller decrease for the radiation qualities of N���30 (1.1%), N���40 (4.1%) and N���120 (20.0%). Conclusion ��� It is concluded that there is a strong dependence of radiation energy and dose rate on the response of an electronic personal dosemeter.

Evaluation of the respiratory motion effect in small animal PET images with GATE Monte Carlo simulations

The rapid growth in genetics and molecular biology combined with the development of techniques for genetically engineering small animals has led to increased interest in in vivo small animal imaging. Small animal imaging has been applied frequently to the imaging of small animals (mice and rats), which are ubiquitous in modeling human diseases and testing treatments. The use of PET in small animals allows the use of subjects as their own control, reducing the interanimal variability. This allows performing longitudinal studies on the same animal and improves the accuracy of biological models. However, small animal PET still suffers from several limitations. The amounts of radiotracers needed, limited scanner sensitivity, image resolution and image quantification issues, all could clearly benefit from additional research. Because nuclear medicine imaging deals with radioactive decay, the emission of radiation energy through photons and particles alongside with the detection of these quanta and particles in different materials make Monte Carlo method an important simulation tool in both nuclear medicine research and clinical practice. In order to optimize the quantitative use of PET in clinical practice, data- and image-processing methods are also a field of intense interest and development. The evaluation of such methods often relies on the use of simulated data and images since these offer control of the ground truth. Monte Carlo simulations are widely used for PET simulation since they take into account all the random processes involved in PET imaging, from the emission of the positron to the detection of the photons by the detectors. Simulation techniques have become an importance and indispensable complement to a wide range of problems that could not be addressed by experimental or analytical approaches.

Avalia����o da dose absorvida na tir��ide, em cintigrafias com 123I e Na99mTcO4 utilizando modelos biocin��ticos e m��todos de Monte Carlo

Mestrado em Radia����es Aplicadas ��s Tecnologias da Sa��de. ��rea de especializa����o: Protec����o contra Radia����es

Estudo da efici��ncia de dete����o de um monitor port��til de contamina����o de superf��cies em fun����o da dist��ncia e do d��bito de emiss��o da fonte

Introdu����o ��� No caso de uma eventual contamina����o radioativa esta deve ser quantificada, pelo que �� necess��rio garantir que as condi����es de funcionamento de um monitor de contamina����o de superf��cies se encontrem adequadamente caracterizadas, atrav��s da determina����o da sua efici��ncia de dete����o. Este estudo tem como objetivo determinar a efici��ncia de dete����o de um monitor de contamina����o e analisar a influ��ncia da dist��ncia e da atividade. Metodologia ��� O monitor de contamina����o Thermo Mini 900E e as fontes radioativas planas de refer��ncia de Carbono ��� 14 (C-14), C��sio ��� 137 (Cs-137), Estr��ncio ��� 90 (Sr-90), Cloro ��� 36 (Cl-36) e Amer��cio ��� 241 (Am-241) com d��bito de emiss��o superficial rastre��vel ao Physikalish Technischen Bundesanstalt (PTB) foram utilizadas. Fontes de Sr-90 e C-14 com dois d��bitos de emiss��o distintos para cada e dist��ncias de 1 a 20mm foram usados para estudar a sua influ��ncia na efici��ncia de dete����o. Resultados ��� Verificou-se que as fontes radioativas emissoras de part��culas de maior energia apresentam uma maior efici��ncia de dete����o e que esta diminui com o aumento da dist��ncia do detetor �� fonte, sendo que os radiois��topos de maior energia apresentam um decr��scimo na efici��ncia de 15% ao longo de 20mm, enquanto os radiois��topos de menor energia apresentam um decr��scimo de 10%. N��o se verificou uma influ��ncia expressiva do d��bito de emiss��o na efici��ncia de dete����o deste monitor de contamina����o. Conclus��o ��� A efici��ncia de dete����o de um monitor de contamina����o port��til �� dependente da dist��ncia deste �� contamina����o bem como do tipo de radia����o emitida e energia dos radiois��topos presentes na contamina����o. - ABSTRACT - Introduction ��� A radioactive contamination needs to be quantified in case it eventually occurs. Therefore it is necessary to ensure that the operating conditions of a surface contamination monitor are characterized by determining its detection efficiency. This experimental study aims to determine the detection efficiency of a contamination monitor and evaluate the distance and surface emission rate influence on the detection efficiency. Methodology ��� A contamination monitor Thermo Mini 900E was tested with reference radiation sources of Carbon ��� 14 (C-14), Cesium ��� 137 (Cs-137), Strontium ��� 90 (Sr-90), Chlorine ��� 36 (Cl-36) and Americium ��� 241 (Am-241) with its emission rate traced to the Physikalish Technischen Bundesanstalt (PTB). Sources of Sr-90 and C-14 with two different emission rates for each one and distances of 1 to 20mm were used to study its influence in the detection efficiency. Results ��� With the increasing of distance, the detection efficiency decreases. The most energetic radiation sources have higher detection efficiency, boasting a 15% decrease over 20mm whereas the sources bearing a smaller efficiency decrease 10%. No influence of the surface emission rate in the detection efficiency was verified. Conclusion ��� Thus, it is concluded that the detection efficiency of a contamination monitor is dependent of the distance between it and the contamination as well as the type and energy of the radioisotopes present in the contamination.

An��logos do neurop��ptido Y marcados com 99mTc para detec����o de receptores Y1 expressos no cancro da mama

Mestrado em Medicina Nuclear. ��rea de especializa����o: Radiofarm��cia.

Synthesis of optimization of [11C] Pittsburgh compound B by the captive solvent method

Mestrado em Medicina Nuclear.

Influence of reconstruction parameters during filtered backprojection and ordered-subset expectation maximization in the measurement of the left-ventricular volumes and function during gated SPECT

A crucial method for investigating patients with coronary artery disease (CAD) is the calculation of the left ventricular ejection fraction (LVEF). It is, consequently, imperative to precisely estimate the value of LVEF--a process that can be done with myocardial perfusion scintigraphy. Therefore, the present study aimed to establish and compare the estimation performance of the quantitative parameters of the reconstruction methods filtered backprojection (FBP) and ordered-subset expectation maximization (OSEM). Methods: A beating-heart phantom with known values of end-diastolic volume, end-systolic volume, and LVEF was used. Quantitative gated SPECT/quantitative perfusion SPECT software was used to obtain these quantitative parameters in a semiautomatic mode. The Butterworth filter was used in FBP, with the cutoff frequencies between 0.2 and 0.8 cycles per pixel combined with the orders of 5, 10, 15, and 20. Sixty-three reconstructions were performed using 2, 4, 6, 8, 10, 12, and 16 OSEM subsets, combined with several iterations: 2, 4, 6, 8, 10, 12, 16, 32, and 64. Results: With FBP, the values of end-diastolic, end-systolic, and the stroke volumes rise as the cutoff frequency increases, whereas the value of LVEF diminishes. This same pattern is verified with the OSEM reconstruction. However, with OSEM there is a more precise estimation of the quantitative parameters, especially with the combinations 2 iterations �� 10 subsets and 2 iterations �� 12 subsets. Conclusion: The OSEM reconstruction presents better estimations of the quantitative parameters than does FBP. This study recommends the use of 2 iterations with 10 or 12 subsets for OSEM and a cutoff frequency of 0.5 cycles per pixel with the orders 5, 10, or 15 for FBP as the best estimations for the left ventricular volumes and ejection fraction quantification in myocardial perfusion scintigraphy.

Image quality of myocardial perfusion-gated studies: effect of ingestion of different fat content in the reduction of extra-myocardial abdominal signal

Myocardial perfusion-gated-SPECT (MP-gated-SPECT) imaging often shows radiotracer uptake in abdominal organs. This accumulation interferes frequently with qualitative and quantitative assessment of the infero-septal region of myocardium. The objective of this study is to evaluate the effect of ingestion of different fat content on the reduction of extra-myocardial uptake and to improve MP-gated-SPECT image quality. In this study, 150 patients (65 ^ 18 years) who were referred for MP-gated-SPECT underwent a 1-day-protocol including imaging after stress (physical or pharmacological) and resting conditions. All patients gave written informed consent. Patients were subdivided into five groups: GI, GII, GIII, GIV and GV. In the first four groups, patients ate two chocolate bars with different fat content. Patients in GV ��� control group (CG) ��� had just water. Uptake indices (UI) of myocardium (M)/liver(L) and M/stomach���proximal bowel(S) revealed lower UI of M/S at rest in all groups. Both stress and rest studies using different food intake indicate that patients who ate chocolate with different fat content showed better UI of M/L than the CG. The UI of M/L and M/S of groups obtained under physical stress are clearly superior to that of groups obtained under pharmacological stress. These differences are only significant in patients who ate high-fat chocolate or drank water. The analysis of all stress studies together (GI, GII, GIII and GIV) in comparison with CG shows higher mean ranks of UI of M/L for those who ate high-fat chocolate. After pharmacological stress, the mean ranks of UI of M/L were higher for patients who ate high- and low-fat chocolate. In conclusion, eating food with fat content after radiotracer injection increases, respectively, the UI of M/L after stress and rest in MP-gated-SPECT studies. It is, therefore, recommended that patients eat a chocolate bar after radiotracer injection and before image acquisition.

Study of the influence of count���s number in myocardium in the determination of reproducible functional parameters in Gated-SPECT studies simulated with GATE

Myocardial Perfusion Gated Single Photon Emission Tomography (Gated-SPET) imaging is used for the combined evaluation of myocardial perfusion and left ventricular (LV) function. But standard protocols of the Gated-SPECT studies require long acquisition times for each study. It is therefore important to reduce as much as possible the total duration of image acquisition. However, it is known that this reduction leads to decrease on counts statistics per projection and raises doubts about the validity of the functional parameters determined by Gated-SPECT. Considering that, it���s difficult to carry out this analysis in real patients. For ethical, logistical and economical matters, simulated studies could be required for this analysis. Objective: Evaluate the influence of the total number of counts acquired from myocardium, in the calculation of myocardial functional parameters (LVEF ��� left ventricular ejection fraction, EDV ��� end-diastolic volume, ESV ��� end-sistolic volume) using routine software procedures.

Impact of the background Region of Interest in the relative renal function

Renal scintigraphy with 99mTc-dimercaptosuccinic acid (99mTc-DMSA) is performed with the aim of detect cortical abnormalities related to urinary tract infection and accurately quantify relative renal function (RRF). For this quantitative assessment Nuclear Medicine Technologist should draw regions of interest (ROI) around each kidney (KROI) and peri-renal background (BKG) ROI although controversy still exists about BKG-ROI. The aim of this work was to evaluate the effect of the normalization procedure, number and location of BKG-ROI on the RRF in 99mTc-DMSA scintigraphy.

Analysis of the interference of endogenous circadian rhythms on 3'- deoxy- 3'- [18F]Fluorothymidine physiological uptake at the human bone marrow

The main purpose of the present study is to determine if the circadian rhythms present in the human bone marrow are likely to influence 3���- deoxy- 3���-[18F] Fluorothymidine (18F-FLT) uptake in the same organ. The 18F-FLT is a Thymidine analogous proliferation agent. The relatively high physiological uptake of this tracer in the bone marrow diminishes the Tumor/Background (T/B) ratio, decreasing the detection accuracy of PET/CT and possibly affecting SUV quantifications.