Design of a preamplifier card for the photomultiplier tubes of a gamma camera / Diseño de una tarjeta preamplificadora para los tubos fotomultiplicadores de una cámara gamma

Abstract The service provided by Gamma Cameras (GC) in Nuclear Medicine departments fails because of their breakdown, generally due to the associated electronics and not to the physical detection components. Therefore, it was decided to develop an electronic system that allows the recovery and optimization of disused GC, starting with the design of the preamplifier for each photomultiplier tube (PMT). The circuit was designed and simulated and the list of components necessary for the construction of the preamplifier was generated, as well as the printed circuit board was designed for its assembly. By simulating the preamplifier, this worked in linear mode. This determines that the amplitude of the output signal is proportional to the amount of charge delivered by the detector. This card allows an automatic adjustment of the signals of the PMTs as modern GC do. Besides, the circuit was designed and simulated for 37 and 75 PMTs, and the printed circuit board was designed for both cases.

Resumen El servicio que prestan las Cámaras Gamma (CG) en los departamentos de Medicina Nuclear falla por roturas de las mismas, generalmente debido a la electrónica asociada y no a los componentes físicos de detección. Por tal razón, se decidió desarrollar un sistema electrónico que permita la recuperación y optimización de las CG en desuso, comenzando con el diseño del preamplificador para cada tubo fotomultiplicador (TFM). Se diseñó y simuló el circuito y se generó la lista de componentes necesarios para la construcción del preamplificador, así como se diseñó la placa de circuitos impresos para su montaje. Al simular el preamplificador este trabajó en modo lineal. Esto determina que la amplitud de la señal de salida sea proporcional a la cantidad de carga entregada por el detector. Esta tarjeta permite un ajuste automático de las señales de los TFMs como lo hacen las CG modernas. Además, se diseñó y simuló el circuito para 37 y 75 TFMs, así como se diseñó la placa de circuitos impreso para ambos casos.

Computed tomography-guided preoperative localization of musculoskeletal lesions using the ROLL technique / Localização pré-operatória guiada por tomografia computadorizada de lesões musculoesqueléticas utilizando a técnica ROLL

Abstract Objective: To describe the preoperative localization of musculoskeletal lesions with the radioguided occult lesion localization (ROLL) technique. Materials and Methods: In all cases, computed tomography-guided injection of technetium-99m sulfur colloid was performed, directly into or near the suspicious lesion, up to 36 hours before the surgical procedure. Lesions were detected intraoperatively with a gamma probe. Results: We report the cases of six patients submitted to radioguided surgery, including three patients with bone lesions suspicious for metastasis, two patients suspected of recurrent sarcoma, and one patient with no previous diagnosis who had a nodular lesion on the left leg. Patients tolerated the procedure well, and no complications were associated with the puncture. All marked lesions were easily identified intraoperatively and were excised with clear margins. Conclusion: The ROLL technique was effective in the intraoperative localization of occult musculoskeletal lesions, demonstrating that it is a feasible and promising technique for the surgical exploration of selected cases.

Resumo Objetivo: Descrever a localização pré-operatória de lesões musculoesqueléticas utilizando a técnica radioguided occult lesion localization (ROLL). Materiais e Métodos: Em todos os casos foi realizada administração guiada por tomografia computadorizada de enxofre coloidal marcado com tecnécio-99m, diretamente no interior ou adjacente à lesão suspeita, até 36 horas antes do procedimento cirúrgico. As lesões foram localizadas no intraoperatório utilizando um gama-probe. Resultados: São descritos seis casos de pacientes submetidos a cirurgia radioguiada, sendo três pacientes com lesões ósseas suspeitas para metástase, dois pacientes com sarcoma recidivado e um paciente com lesão nodular na perna esquerda sem diagnóstico prévio. Os pacientes toleraram bem o procedimento e não ocorreram complicações. Todas as lesões foram identificadas adequadamente no intraoperatório e ressecadas com margens livres. Conclusão: A técnica ROLL foi efetiva na localização intraoperatória de lesões musculoesqueléticas ocultas, demonstrando que este procedimento é factível e promissor para facilitar a exploração cirúrgica em casos selecionados.

Fatores intervenientes na proteção radiológica ocupacional no controle de qualidade em câmaras gama / Intervening Factors in Occupational Radiological Protection in Quality Control in the Gamma Cameras

Introdução: a proteção radiológica é campo do conhecimento que permeia os ambientes radiológicos. Sua aplicação envolve benefícios aos serviços, profissionais e usuários. Objetivo: identificar fatores intervenientes, bem como, dispositivos de proteção radiológica disponíveis em um serviço de medicina nuclear (MN), envolvidos nos testes de Controle de Qualidade em Câmaras Gama (CQCG). Metodologia: realizou-se um estudo observacional, do tipo exploratório e descritivo, em um serviço de MN conveniado com o Instituto Federal da Bahia (IFBA), com ênfase na proteção radiológica em testes de CQCG. A coleta de dados foi realizada em janeiro de 2016. Foram acompanhados testes diários de inspeção visual da integridade física, radiação de fundo da sala de exames, uniformidade intrínseca e centralização da largura da janela energética para cada radionuclídeo. Para os testes semanais, acompanharam-se os de resolução espacial e linearidade. Os dados foram analisados à luz da legislação/normativas vigentes para serviços de MN no Brasil. Resultados: referente à proteção radiológica em testes de CQCG, o serviço dispunha de três aventais plumbíferos e três protetores de tireóide com equivalência de 0,5mm de chumbo, além de pinças utilizadas para manipulação de fontes radioativas. Foi observada a presença de óculos de proteção, entretanto, os mesmos não eram plumbíferos. Os profissionais eram monitorados por dosímetros termoluminescentes de uso individual. Conclusão: de maneira geral, eram observados os fatores de proteção radiológica: tempo, distância e blindagem. O CQCG requer planejamento prévio com protocolo devidamente seguido que poderá minimizar a exposição ocupacional.

Introduction: radiation protection is a field of knowledge that permeates radiological environments. Its application involves benefits to services, professionals and patients. Objective: To identify intervening factors, as well as the radiological protection devices available in a nuclear medicine service (MN) involved in the Quality Control tests in Gamma Camera (CQCG). Methodology: an observational, exploratory and descriptive study was carried out at the MN service in partnership with Instituto Federal da Bahia (IFBA), with emphasis on radiological protection in CQCG tests. Data collection was performed in January 2016. Daily tests were conducted to visually inspect the physical integrity of the system, to test the background radiation of the examination room, and intrinsic uniformity and centralization of the energetic window width for each radionuclide were monitored. For the weekly tests, those of spatial resolution and linearity were monitored. The data was analyzed in accordance with the legislation/regulations for MN services in Brazil. Results: with regard to the radiological protection during CQCG tests, the service had three lead aprons and three thyroid protectors with a 0.5mm equivalence of lead, in addition, tweezers used to manipulate radioactive sources. The presence of protective goggles was observed, however, they did not contain lead. The professionals were monitored by thermoluminescent dosimeters for individual use. Conclusion: in general, the principles of radiation protection of time, distance and shielding were adopted. CQCG requires prior planning with a properly followed protocol that can minimize occupational exposure.

Submandibular sialolithiasis with CT and scintigraphy: CT values and salivary gland excretion in the submandibular glands

PURPOSE: Sialolithiasis is one of the most prevalent large obstructive disorders of the submandibular glands. The aim of this study was to investigate submandibular sialolithiasis with computed tomography (CT) and scintigraphy, with a particular focus on the relationship between CT values of the submandibular glands and their excretion rate. MATERIALS AND METHODS: Fifteen patients with submandibular sialolithiasis who underwent CT and salivary gland scintigraphy were included in this study. The relationship between the CT values of submandibular glands with and without sialoliths and salivary gland excretion measured using salivary gland scintigraphy was statistically analyzed. Dynamic images were recorded on the computer at 1 frame per 20 seconds. The salivary gland excretion fraction was defined as A (before stimulation test [counts/frame]) / B(after stimulation test [counts/frame]) using time-activity curves. RESULTS: The CT values in the submandibular glands with and without sialoliths was 9.9±44.9 Hounsfield units (HU) and 34.2±21.8 HU, respectively (P=.233). Regarding the salivary gland excretion fraction using scintigraphy, the A/B value in the submandibular glands with sialoliths (1.09±0.23) was significantly lower than in the submandibular glands without sialoliths (1.99±0.57, P=.000). CONCLUSION: Assessments of the CT values and the salivary gland excretion fraction using scintigraphy in the submandibular glands seem to be useful tools evaluating submandibular sialolithiasis.

Construcción de un dispositivo para el posicionamiento óptimo del paciente en estudios de gammagrafía mamaria / Construction of a device for optimal positioning of the patient in studies of breast gammagraphy

Los tumores de mama son la causa más común de cáncer en la mujer. El examen ideal para detectar el cáncer de mama es la mamografía. Pero, la misma puede ser dudosa o sus datos no concluyentes, en un importante número de casos, por lo que lleva a procedimientos biópsicos invasivos. El objetivo de este trabajo es optimizar la detección del cáncer de mama por gammagrafía para mejorar el diagnóstico complementario a la mamografía. Para ello, fue diseñado y construido un dispositivo que permite el posicionamiento óptimo del paciente. Los materiales utilizados para su construcción fueron de propiedades poco absorbentes a la radiación gamma. Se evaluó la efectividad de la gammagrafía de mama, utilizando el dispositivo diseñado en dos casos clínicos. En ambos, se confirmó, fehacientemente, el diagnóstico concluyente obtenido por mamografía de casos no dudosos. Se recomendó un protocolo diagnóstico mamografía/gammagrafía que optimizará la selección de pacientes que requieren biopsia.

Breast tumors are the most common cause of cancer in women. The ideal way to detect breast cancer is by a mammography examination. But this test may either be questionable or provide inconclusive data on a significant number of cases, leading to invasive biopsy procedures. The aim of this study is to optimize the detection of breast cancer by gammagraphy to improve the complementary diagnosis provided by a mammography. Consequently and for that reason, a device allowing an optimal patient positioning was designed and built. The materials used for its construction had few gamma radiation absorption properties. The effectiveness of breast gammagraphy was evaluated using by the designed device in two study cases. In both, the definite diagnosis obtained through mammography from doubtful cases was conclusively confirmed. A diagnostic protocol mammogram/gammagraphy was recommended to optimize the selection of patients requiring biopsy.

Dados Preliminares do Valor Prognóstico de um Novo Protocolo deCintilografia Miocárdica Ultrarrápido e com Menos Radiação emGamacâmara CZT / Preliminary Data on the Prognostic Value of a New Protocol of Ultra-fast Myocardial Scintigraphy with Less Radiation in CZT Gamma Camera

A cintilografia miocárdica de perfusão (CMP) é um dos métodos mais utilizados na avaliação de pacientes com suspeita de coronariopatia por seu valor diagnóstico e prognóstico. Duas de suas maiores limitações são o uso de radiação e a duração prolongada dosexames. Entretanto, novas Gamacâmaras de CZT (GC-CZT) têm permitido reduzir as doses dos radiotraçadores empregadas e o tempo de aquisição. O valor prognóstico desses novos protocolos não é conhecido.Objetivo: Determinar o valor prognóstico de um novo protocolo de CMP ultrarrápido e de baixa radiação numa GC-CZT. População: Pacientes com suspeita de coronariopatia consecutivamente submetidos a CMP numa GC-CZT no período de novembro de 2011 a junho de 2012.Metodologia: Foi utilizado protocolo de mesmo dia, iniciado pela fase de repouso com dose de 5 mCi e posterior estresse com dose de 15 mCi de Tc-99m sestamibi. Os tempos de aquisição foram de 6 e 3 minutos, respectivamente. Os exames foram classificados como normais ou anormais e escores de perfusão (SSS, SRS e SDS) foram calculados. Pacientes foram acompanhados mediante contato telefônico semestral. Os eventos avaliados foram morte, infarto não fatal e revascularização tardia (> 60 dias após CMP). Foi utilizado método de Coxpara identificar os preditores.Resultados: Setecentos e noventa e dois pacientes foram acompanhados por 21,3 ± 3,7 meses. A idade média foi de 65,2 ± 12,7 anos, sendo 50,3% do sexo masculino e o IMC médio de 26,9 ± 4,7. Hipertensão arterial foi o fator de risco mais frequente (59,5%), seguidode dislipidemia (51,9%) e diabetes (23,3%). Estresse físico foi empregado em 438 (55,3%) pacientes; 618 (78%) CMP foram normais. A dosimetria média dos exames foi 6 mSv e a duração média, de 48 ± 11 minutos. Durante o seguimentos ocorreram 12 óbitos, 4 infartos não fatais...

Myocardial perfusion scintigraphy (MPS) is one of the most used imaging methods for the evaluation of patients for coronary artery disease (CAD) due to its diagnostic and prognostic value. Two of its main limitations are radiation use and scan duration. However, CZT cameras (CZT-C) have allowed tracer dose and scan time reductions. However, the prognostic value of these new protocols is not known. Objective: To determine the prognostic value of a new, ultrafast, low dose protocol in a CZT-C. Population: Patients with suspect CAD undergoing MPS from 11/2011 to 6/2012 were studied. Methods: They had a 1-day Tc-99m sestamibi protocol starting with rest study (5 mCi dose) followed by stress (15 mCi). Acquisition times were 6 and 3 minutes respectively. MPS studied were classified as normal or abnormal and perfusion scores (SSS, SRS and SDS) were calculated. Patients were accompanied by 6-month phone calls. Events were defined as death, nonfatal myocardial infarction and late revascularization (> 60 days after MPS) and analyzed with the Cox method.Results: 792 patients were followed for 21.3 ± 3.7 months. Age was 65.2 ± 12.7 years, 50.3% were male and body mass index was 26.9 ± 4.7. Hypertension was the most frequent risk factor (59.5%), followed by hypercholesterolemia (51.9%) and diabetes (23.3%). Exercise was used in 438 (55.3%); 618 (78%) MPS studies were normal. Mean dosimetry was 6 mSv and mean scan time, 48 ± 11 minutes. During follow-up, there were 12 deaths...

Evaluación de parámetros tomográficos de una cámara gamma utilizando método Monte Carlo / Evaluation of tomographic ISOCAM Park II gamma camera parameters using Monte Carlo method

En este trabajo se realizó la evaluación de parámetros tomográficos de la cámara gamma Park Isocam II mediante el código Monte Carlo SIMIND. Los parámetros uniformidad, resolución y contraste se evaluaron a través de la simulación del maniquí de Jaszczak. Además, se realizó la evaluación cualitativa del centro de rotación. Los resultados obtenidos en la simulación se evaluaron tomando como referencia las especificaciones del fabricante de la cámara gamma y teniendo en cuenta el Protocolo Nacional de Control de Calidad de Instrumentos de Medicina Nuclear del Centro de Control de Equipos Médicos en Cuba. Se obtuvo un modelo computacional del maniquí de Jaszczak con tres distribuciones diferentes de actividad que se puede usar para realizar estudios con cámaras gamma.

In this paper the evaluation of tomographic ISOCAM Park II gamma camera parameters was performed using the Monte Carlo code SIMIND. The parameters uniformity, resolution and contrast were evaluated by Jaszczak phantom simulation. In addition the qualitative assessment of the center of rotation was performed. The results of the simulation are compared and evaluated against the specifications of the manufacturer of the gamma camera and taking into account the National Protocol for Quality Control of Nuclear Medicine Instruments of the Cuban Medical Equipment Control Center. A computational Jaszczak phantom model with three different distributions of activity was obtained. They can be used to perform studies with gamma cameras.

Análisis de riesgos para el trabajo con un analizador de diagnóstico de cámaras gamma / Risk analysis for working with an analyzer for gamma cameras diagnostic

Se realizó un estudio de los riesgos asociados al trabajo con un analizador para el diagnóstico de cámaras gamma. Para ello se utilizó el método Hazard Rating Number, el cual se basa en la determinación del número de riesgo. Los resultados mostraron que los riesgos con mayor HRN son por electrocución con un valor de 100 y por tocar el contenedor de la fuente con las manos, con 75. Estos riesgos se clasificaron como “Muy Alto” y “Alto” respectivamente. Como “Importante” se clasificaron los siguientes riesgos: caída del contenedor de la fuente (HRN = 25), dosis elevada de la muestra en el contenedor (HRN = 20) y fractura del cristal del detector (HRN = 30). El mal blindaje del contenedor de la fuente (HRN = 10) es un riesgo que se clasificó como “Bajo”. Se indican reglas de seguridad para uso del sistema. También se presenta un plan de acción para la gestión de los riesgos.

In this work, a risk analysis for working with an analyzer for gamma cameras diagnostic was made. The method employed is based on determining the Hazard Rating Number (HRN). The results showed that the risks with higher value of HRN are electrocution with 100 and touch source container with hands with 75. These risks were classified as "Very High" and "High" respectively. The following risks were classified as "Important": Fall of the source container (HRN = 25), high dose of the sample in the container (HRN = 20) and fracture of glass detector (HRN = 30). The wrong shielding of the source container (HRN= 10) is a risk that was classified as "Low". Safety rules for use of the system are indicated. An action plan for risk management is also presented.

The Preoperative Role of Breast-specific Gamma Imaging for the Breast Cancer Patients: In Comparison with Conventional Imaging Modality / 한국유방암학회지

PURPOSE: We wanted to assess the clinical efficacy of breast-specific gamma imaging (BSGI) as compared with that of conventional imaging modalities (mammography, ultrasonography and magnetic resonance imaging) as a preoperative examination for patients with breast cancer. METHODS: From April to May 2009, a retrospective review was performed for the prospectively collected 143 patients who were diagnosed with breast cancer. All the patients received a conventional imaging examination and BSGI before definitive surgery. The patients underwent BSGI with intravenous injection of 30 mCi of (99m)Tc-sestamibi through the contralateral antecubital vein. After 10 minutes, the craniocaudal and mediolateral oblique images were obtained. All the imaging findings were correlated with the final pathologic examination. RESULTS: The mean age of the patients was 49.7+/-9.4 years (range, 27-77). In 143 patients, 166 malignant lesions were identified by pathologic examination (invasive cancer: 96 (67.1%), ductal carcinoma in situ 14 (9.8%) and invasive cancer with carcinoma in situ 33 (23.1%). The conventional imaging modalities found 166 malignant lesions and BSGI found 156 malignant lesions. The rate of correspondence was 94.0% between the conventional imaging modalities and BSGI for malignant lesions. For BSGI, there were 4 false positive findings and 10 false negative findings. BSGI found no occult cancers that were missed by conventional imaging modality. For making the diagnosis of axillary lymph node metastasis, the sensitivity, specificity and accuracy were 33.3%, 92.1%, and 69.9% for BSGI, and 55.6%, 77.5%, and 69.2%, for ultrasonography, respectively. CONCLUSION: BSGI may have the potentiality to make a correct diagnosis in breast cancer patients. However, in this study, it seems that BSGI is not superior to conventional imaging modalities. BSGI is not a standard method to evaluate breast cancer lesions before surgery.

Techniques for computerized quantitation of spatial resolution ,linearity and contrast of a scintillation camera from bar pattern images

A computer based quantitative method was formulated (in FORTRAN 77) for the purpose of monitoring intrinsic spatial resolution, linearity and contrast of a gamma camera. Digital images of ordinary bar pattern phantoms were used for the analysis. Square shaped ROIs of 3x3 ern dimensions in' real space were placed on the digital images of each quadrant with one dimension parallel to the' bars. One dimensional Fourier analysis was performed on profiles derived from each of these using an algorithm formulated specifically for this purpose. After carefully analysing the amplitudes of the first 20 frequencies of images acquired On a 512 matrix size, it was found that only the dominant amplitude was associated with a sUfficiently low ICV which could be used as a useful index to monitor the performance of the camera. This was tested for its integrity and specificity as an index to monitor the spatial resolution and was termed the Fourier Index of Spatial, Resolution (FISR). For the assessment of non-linearity, the bar size [BS (FT)] Has estimated from the frequency of the dominant amplitude. A Contrast index was estimated in count density space using the data in the count profile of each ROI. By estimating the distance betHeen the peaks of this count profile average bar Slze [BS(Cl] was calculated which was used as an alternative method of assessing non-linearity. There was extremely good correlation between the FISR, value and the FWHM and between the FISR and the FWTM values (correlation coefficient \>0.96). There was also very good correlation between the FISR and the contrast index values (correlation coefficient \>0.96). The FISR increased in value with increasing matrix size up to 512 fora Siemens Gammasonics Digitrac 75 camera which had a effective field of view diameter of 38 cm. However, for a 1024 matrix size it did not show any further increase. The percent CV values associated with it were in the range of 0.74 to 2.86, for count densities corresponding to 4 minutes of data acquisition. On the other hand the contrast index value continued to increase with increasing in matrix Slze. The sensitivities associated with the FISR values obtained with 4, 3.5, 3 and 2.5 mm bar sizes were higher than those of the FWHM or FWTM values in showing variations of spatial resolution. The bar size that yielded the maximum sensitivity for a comparatively low percent CV was found to be 3.5 mm. The best bar size to use for the estimation of contrast index values was found to be either 4 or 3.5 mm. The FISR values and -contrast index values, both differentiated extremely well the qualities of images obtained wi th a new Siemens Gammasonics Digi trac 75 camera and a "11 year old mobile Technicare S420 camera. The percentage nonlinearity computed from both BS(FT) and BS(C) values showed the non-linearity that existed in the images of the mobile camera. These were not shown in images from the Siemens camera because it was equipped with linearity correction circuits. The computer quantitation method of estimating the spatial resolution, the linearity and the contrast index studied can be successfully implemented to monitor these qualities of a gamma camera and possess the following advantages: 1. As the value FISR measures more than the spatial resolution, it is a more powerful index than FWHM which can be used to monitor the performance of a gamma camera, 2. Incorporating the software for the above technique would be trivial, as present day computer systems use Fourier techniques for reconstruction, smoothing, etc., 3. Although according to the optimum conditions, the 512 matrix size yielded the maximum value of FISR for the Siemens camera, a 256 matrix could be used successfully, 4. Implementation of this method could well be carried out by having only one PLES phantom of bar spacing 3.5 for all cameras within a department, 5. The measurements can cover the entire field of the detecting system in both directions, 6. The estimations of spatial resolution, linearity and contrast can be completed in about 15 minutes, 7. The measurements involve both the camera and the computer and hence it is a method of monitoring both systems, 8. The FISR values obtained with the 3.5 mm bar size 50 percent more sensitive than the FWHM value in analysing variations of spatial resolution, 9. Action levels could be set at meaningful values so that cameral computer performance could be monitored by inexperienced personnel using a simple graphic display.