Effect of ME Collimator Characteristic, Energy Window Width, and Reconstruction Algorithm Selection on Imaging Performance of Yttrium-90: Simulation Study / 대한핵의학회잡지

PURPOSE: The treatment efficiency of ⁹⁰Y and providing reliable estimates of activity are evaluated by SPECT imaging of bremsstrahlung radiation released during beta therapy. In this technique, the resulting spectrum from ⁹⁰Y is very complex and continuous, which creates difficulties on the imaging protocol. Moreover, collimator geometry has an impressive effect on the spatial resolution, system sensitivity, image contrast, and the signal-to-noise ratio (SNR), which should be optimized.METHODS: We evaluated the effect of energy window width, reconstruction algorithms, and different geometries of a medium-energy (ME) parallel-hole collimator on the image contrast and SNR of ⁹⁰Y SPECT images. The Siemens E.Cam gamma camera equipped with a ME collimator and a digital Jaszczak phantom were simulated by SIMIND Monte Carlo program to generate the ⁹⁰Y bremsstrahlung SPECT images.RESULTS: Our results showed that optimal image quality can be acquired by the reconstruction algorithm of OS-EM in the energy window width of 60 to 400 keV for ⁹⁰Y bremsstrahlung SPECT imaging. Furthermore, the optimal values of the hole diameter and hole length of a ME collimator were obtained 0.235 and 4.4 cm, respectively.CONCLUSIONS: The acquired optimal ME collimator and energy window along with using a suitable reconstruction algorithm lead to improved contrast and SNR of ⁹⁰Y bremsstrahlung images of hot spheres of the digital Jaszczak phantom. This can improve the accuracy and precision of the ⁹⁰Y activity distribution estimation after radioembolization in targeted radionuclide therapy.

Clinical Applications of Technetium-99m Quantitative Single-Photon Emission Computed Tomography/Computed Tomography / 대한핵의학회잡지

Single-photon emission computed tomography/computed tomography (SPECT/CT) is an already established nuclear imaging modality. Co-registration of functional information (SPECT) with anatomical images (CT) paved the way to the wider application of SPECT. Recent advancements in quantitative SPECT/CT have made it possible to incorporate quantitative parameters, such as standardized uptake value (SUV) or %injected dose (%ID), in gamma camera imaging. This is indeed a paradigm shift in gamma camera imaging from qualitative to quantitative evaluation. In fact, such quantitative approaches of nuclear imaging have only been accomplished for positron emission tomography (PET) technology. Attenuation correction, scatter correction, and resolution recovery are the three main features that enabled quantitative SPECT/CT. Further technical improvements are being achieved for partial-volume correction, motion correction, and dead-time correction. The reported clinical applications for quantitative SPECT/CT are mainly related to Tc-99m-labeled radiopharmaceuticals: Tc-99m diphosphonate for bone/joint diseases, Tc-99m pertechnetate for thyroid function, and Tc-99m diethylenetriaminepentaacetic acid for measurement of glomerular filtration rate. Dosimetry before trans-arterial radio-embolization is also a promising application for Tc-99m macro-aggregated albumin. In this review, clinical applications of Tc-99m quantitative SPECT/CT will be discussed.

Capabilities of theMonte Carlo Simulation Codes forModeling of a Small Animal SPECT Camera / 대한핵의학회잡지

PURPOSE: This study aims to compare Monte Carlo-based codes' characteristics in the determination of the basic parameters of a high-resolution single photon emission computed tomography (HiReSPECT) scanner.METHODS: The geometry of this dual-head gamma camera equipped with a pixelated CsI(Na) scintillator and lead hexagonal hole collimator were accurately described in the GEANT4 Application for the Tomographic Emission (GATE), Monte Carlo N-particle extended (MCNP-X), and simulation of imaging nuclear detectors (SIMIND) codes.We implemented simulation procedures similar to the experimental test for calculation of the energy spectra, spatial resolution, and sensitivity of HiReSPECT by using 99mTc sources.RESULTS: The energy resolutions simulated by SIMIND, MCNP-X, and GATE were 17.53, 19.24, and 18.26%, respectively, while it was calculated at 19.15% in experimental test. The average spatial resolutions of the HiReSPECT camera at 2.5 cm from the collimator surface simulated by SIMIND, MCNP-X, and GATE were 3.18, 2.9, and 2.62 mm, respectively, while this parameter was reported at 2.82 mm in the experiment test. The sensitivities simulated by SIMIND, MCNP-X, and GATE were 1.44, 1.27, and 1.38 cps/µCi, respectively, on the collimator surface.CONCLUSIONS: Comparison between simulation and experimental results showed that among these MC codes, GATE enabled to accurately model realistic SPECT system and electromagnetic physical processes, but it required more time and hardware facilities to run simulations. SIMIND was the most flexible and user-friendly code to simulate a SPECT camera, but it had limitations in defining the non-conventional imaging device. The most important characteristics like time and speed of simulation, preciseness of results, and user-friendliness should be considered during simulations.

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.

The Current Status of SPECT or SPECT/CT in South Korea / 대한핵의학회잡지

The first step to nuclear medicine in Korea started with introduction of the gamma camera in 1969. Although planar images with the gamma camera give important functional information, they have the limitations that result from 2-dimensional images. Single-photon emission computed tomography (SPECT) due to its 3-dimensional image acquisition is superior to earlier planar gamma imaging in image resolution and diagnostic accuracy. As demand for a hybrid functional and anatomical imaging device has increased, integrated SPECT/CT systems have been used. In Korea, SPECT/CT was for the first time installed in 2003. SPECT/CT can eliminate many possible pitfalls on SPECT-alone images, making better attenuation correction and thereby improving image quality. Therefore, SPECT/CT is clinically preferred in many hospitals in various aspects.More recently, additional SPECT/CT images taken from the region with equivocal uptake on planar images have been helpful in making precise interpretation as part of their clinical workup in postoperative thyroid cancer patients. SPECT and SPECT/CT have various advantages, but its clinical application has gradually decreased in recent few years. While some researchers investigated the myocardial blood flow with cardiac PET using F-18 FDG or N-13 ammonia, myocardial perfusion SPECT is, at present, the radionuclide imaging study of choice for the risk stratification and guiding therapy in the coronary artery disease patients in Korea. New diagnostic radiopharmaceuticals for AD have received increasing attention; nevertheless, brain SPECT will remain the most reliable modality evaluating cerebral perfusion.

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.

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...

History and perspectives of nuclear medicine in Bangladesh

Bangladesh is one of the smaller states in Asia. But it has a long and rich history of nuclear medicine for over sixty years. The progress in science and technology is always challenging in a developing country. In 1958, work for the first Nuclear Medicine facility was commenced in Dhaka in a tin-shed known as 'Radioisotope Centre' and was officially inaugurated in 1962. Since the late 50s of the last century nuclear medicine in Bangladesh has significantly progressed through the years in its course of development, but still the facilities are inadequate. At present there are 20 nuclear medicine establishments with 3 PET-CTs, 42 gamma camera/SPECTs with 95 physicians, 20 physicists, 10 radiochemists and 150 technologists. The Society of Nuclear Medicine, Bangladesh [SNMB] was formed in 1993 and publishing its official journal since 1997. Bangladesh also has close relationships with many international organizations like IAEA, ARCCNM, AOFNMB, ASNM, WFNMB and WARMTH. The history and the present scenario of the status of nuclear medicine in Bangladesh are being described here

Current Development of Breast-Specific Gamma Imaging (BSGI) Technique / 中国医疗器械杂志

Breast-Specific Gamma Imaging (BSGI) is an improved and optimizing nuclear medicine breast imaging technique on the basis of traditional gamma camera. It uses a high resolution, small field-of-view scintilla detector. The detector is designed with 3 073 individual detector crystals and 48 position-sensitive photomultiplier tubes. The FOV of detector is 15 cm x 20 cm, and optimal system resolution for breast imaging is 3 mm, can detect the diameter of only 2-3 mm small lesions. BSGI has better sensitivity in detecting subcentimetre or nonpalpable breast cancer. The sensitivity for the diagnosis of breast cancer is high, not influenced by the density of the breast tissue, implants, architectural distortion-or scars from prior surgery or radiation. So it is called a high resolution, small field-of-view breast-specific gamma camera.

Validation of Octanoate Breath Test for Measuring Gastric Emptying in Rats

BACKGROUND/AIMS: Lack of simple and repeatable tests hampers gastric emptying studies in rats. The aim of this study was to adapt the 14C-octanoate solid gastric emptying breath test for application in rats, and to validate it against radioscintigraphic method. METHODS: After ingestion of a meal containing 3 mCi 99mTc and 2 microCi 14C-octanoate, 23 male Wistar rats were placed on a gamma camera in a airflow container. Scintigraphic images were taken at regular intervals. The amount of 14CO2 in a regularly replaced hyamine hydroxide solution, capturing CO2 in the outflow air, was counted using liquid scintillation spectrometry. 99mTc gastric retention curves and 14CO2-excretion curves were fitted to their respective data. Three rats underwent the same procedures after administration of atropine. RESULTS: Overall Tr10% (time at which 10% of the original amount of 99mTc remained in the stomach) was 355 +/- 64 minutes; Te90% (time at which 90% of total amount of 14CO2 was excreted) was 325 +/- 106 minutes. Their correlation coefficient was 0.71, R-square 0.50 and P < 0.005. Tr1/2 (50% of original amount of 99mTc remained) was 124 +/- 28 minutes; Te1/2 (50% of total amount of 14CO2 excreted) 114 +/- 32 minutes. Their correlation coefficient was 0.83 with R-square of 0.69 and P < 0.00005. In 12 immobilized animals correlation was even better: correlation coefficient 0.84; R-square 0.71 and P < 0.001 (Tr10% was 388 +/- 117 minutes; Te90% 532 +/- 219 minutes; Tr1/2 of 165 +/- 54 minutes; Te1/2 of 175 +/- 67 minutes). Atropine significantly lengthened all emptying times: 904 +/- 307 and 1461 +/- 684 minutes for Tr10% and Te90%, respectively; and 432 +/- 117 minutes for Tr1/2 and 473 +/- 190 minutes for Te1/2. CONCLUSIONS: We adapted and validated the 14C-octanoate gastric emptying breath test for application in rats.

Gammacamara portátil en la localización intraoperatoria del ganglio centinela en cáncer de mama: experiencia en el Hospital Nacional Guillermo Almenara-EsSalud / Portable gamma camera in intraoperative localization of sentinel node in breast cancer: experience at the Hospital Nacional Guillermo Almenara-EsSalud

Objetivo: Mostrar la experiencia del uso de la gammacamara portátil en la localización intraoperatoria del ganglio centinela en cáncer de mama. Material y Métodos: Fueron incluidas en el estudio 103 pacientes mujeres con diagnostico de cáncer de mama con axila clínica y radiologicamente negativa. Se realizo inyección periareolar de un radiotrazador y de la sustancia colorante azul patente. Se adquirieron imágenes planares de la axila antes y durante la extracción del ganglio centinela. Se utilizo en el intraoperatorio una gammacámara portátil para la visualización del o los ganglios centinelas. Se comprobó ôcampo libreõ en todos los pacientes con la gammacámara portátil. Resultados: El promedio de la edad de los pacientes fue 52.5 años. La media de tamaño tumoral fue de 2.5 cm. La media de ganglios encontrados fue de 1.9 ganglios centinelas por paciente. Se localizaron los ganglios centinelas en el 91.2% de los pacientes, de los cuales 24 pacientes presentaron metástasis. El uso de la gamma cámara intraoperatoria mostro una sensibilidad de 97.8% y especificidad de 88.9% para la visualización de ganglios centinelas. Conclusiones: El empleo de la gammacamara portátil intraoperatoria en la localización del ganglio centinela en cáncer de mama es un método de alta sensibilidad y especificidad, útil para determinar, que todos los ganglios centinelas han sido extirpados, es decir ôcampo libreõ.

Objective: To show the experience of the use of portable gamma camera intraoperative node localization in breast cancer sentinel. Material and Methods: The study included 103 female patients diagnosed with breast cancer with clinical axillary and radiologically negative. Periareolar injection was performed a radiotracer and blue dye substance patent. It planar images acquired before and during axillary sentinel lymph node removal. Was used in the intraoperative a portable gamma camera for viewing or sentinel node was found "free field" for all patients the portable gamma camera. Results: The mean age of patients was 52.5 years. The mean tumor size was 2.5 cm. The average nodes found was 1.9 sentinel nodes per patient. Sentinel nodes were found in 91.2% of patients, of whom 24 patients had metastases. The use of intraoperative gamma camera showed a sensitivity 97.8% and specificity of 88.9% for the visualization of sentinel nodes. Conclusions: The use of intraoperative portable gamma camera in the location of the sentinel node in cancer breast is a method of high sensitivity and specificity, useful to determine that all sentinel nodes have been removed and free field.

A clinical gamma camera-based pinhole collimated system for high resolution small animal SPECT imaging

The main objective of the present study was to upgrade a clinical gamma camera to obtain high resolution tomographic images of small animal organs. The system is based on a clinical gamma camera to which we have adapted a special-purpose pinhole collimator and a device for positioning and rotating the target based on a computer-controlled step motor. We developed a software tool to reconstruct the target’s three-dimensional distribution of emission from a set of planar projections, based on the maximum likelihood algorithm. We present details on the hardware and software implementation. We imaged phantoms and heart and kidneys of rats. When using pinhole collimators, the spatial resolution and sensitivity of the imaging system depend on parameters such as the detector-to-collimator and detector-to-target distances and pinhole diameter. In this study, we reached an object voxel size of 0.6 mm and spatial resolution better than 2.4 and 1.7 mm full width at half maximum when 1.5- and 1.0-mm diameter pinholes were used, respectively. Appropriate sensitivity to study the target of interest was attained in both cases. Additionally, we show that as few as 12 projections are sufficient to attain good quality reconstructions, a result that implies a significant reduction of acquisition time and opens the possibility for radiotracer dynamic studies. In conclusion, a high resolution single photon emission computed tomography (SPECT) system was developed using a commercial clinical gamma camera, allowing the acquisition of detailed volumetric images of small animal organs. This type of system has important implications for research areas such as Cardiology, Neurology or Oncology.

Limitations of 99mTc-DMSA scan in diagnosing acute pyelonephritis in children / 소아과

PURPOSE: We aimed to prove the relative limitation of 99mTc-DMSA scintigraphy (DMSA) compared to computed tomography (CT) in diagnosing acute pyelonephritis (APN) in children. METHODS: Since September 2006, after a 64-channel CT was imported, 10 DMSA false-negative patients have been identified: these patients underwent a CT scan for acute abdomen or acute febrile symptoms and were diagnosed as having APN; however, their DMSA scans were clear. We focused on these 10 DMSA false-negative patients and analyzed their clinical findings and CT results. We used Philips Brilliance Power 64-channel CT scanner for the CT scan and Siemens Orbitor Nuclear Camera 60 Hz for the DMSA scan. RESULTS: The 10 DMSA false-negative patients were mostly males (80%) and infants (80%). They had fever for a mean of 1.1-day duration before admission and showed increase in acute reactants: leukocyte, erythrocyte sedimentation rate, and C-reactive protein. The CT findings of renal lesions were focal in 6 (60%) cases and diffuse in 4 (40%) cases, and most of the lesions were unilateral in 80% of patients. CT proved that 22 renal lesions were neglected by DMSA. Differential renal function test by DMSA was also of no use in the evaluation of renal lesions. CONCLUSION: In this study, DMSA scan showed limitation in finding renal cortical lesions of CT-proven APN patients. DMSA false-negative results seem to occur at early-phase disease of infantile age, but more prospective studies are needed to determine the reasons and their prevalence.

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.

National equipment of intraoperatory gamma detection in the identification of sentinel lymph node in animal model / Equipamento nacional de detecção gama intra-operatória na identificação de linfonodo sentinela

PURPOSE: To investigate a national equipment of intraoperatory gamma detection in the identification of sentinel lymph node. METHODS: Thirty young adult male rats were used. After anesthetized, animals were divided into two groups of 15 animals each. Animals from group A received dextram 500 - Tc99 radiopharmaceutical and patent blue V and those from group B received only patent blue V to map the lymphatic drainage. The presence of radiation in the background area, in the area of injection and of the ex vivo sentinel lymph node of group A were measured. After the exeresis, each lymph node in group A and in group B was mixed forming a new random sequence and the radioactive reading of each lymph node was carried out, using both pieces of equipment. RESULTS: The hottest sentinel lymph node was identified by the national equipment when radiation was measured in the area of limphatic drainage after the Dextran 500 was injected. Also, the ex vivo sentinel lymph node. The national equipment has also detected radiation in the lymph nodes that had not received radiopharmaceutical, leading to false positive, checked by the application of Mann-Whitney tests and Student's paired t-tests. The Cronbach alpha has shown high internal consistency of data 0,9416. CONCLUSIONS: The national equipment of intraoperatory gamma detection identifies the LS and showed false positives LS and needs improvement.

OBJETIVO: Investigar o equipamento nacional de detecção gama intra-operatória na identificação de linfonodo sentinela. MÉTODOS: Foram utilizados 30 ratos machos, adultos jovens. Depois de anestesiados, os animais foram distribuidos em dois grupos de 15 animais cada. O grupo A recebeu radiofármaco dextran 500 - Tc99 e azul patente V e o grupo B, somente azul patente V para realização do mapeamento linfático. Foi realizada a medição da captação radioativa da região de fundo, do sítio de injeção e do linfonodo sentinela ex vivo do grupo A. Após a exérese, cada linfonodo do grupo A e do grupo B foram misturados formando uma nova seqüência aleatória e procedeu a leitura da radioatividade de cada linfonodo com os dois equipamentos. RESULTADOS: O linfonodo sentinela hipercaptante foi identificado pelo equipamento nacional durante as medições da captação radioativa na região do sítio de injeção e linfonodo sentinela ex vivo. O equipamento nacional detectou radiação mesmo nos linfonodos que não receberam o radiofármaco, causando falso positivo, verificado na aplicação dos testes de Mann-Whitney e t pareado de Student. O alfa de Cronbach mostrou alta consistência interna dos dados (0,9416). CONCLUSÕES: O equipamento nacional de detecção gama intra-operatória identifica o linfonodo sentinela e mostra falsos positivos e necessita de aprimoramento.

The Evaluation of Scattering Effects for Various Source Locations within a Phantom in Gamma Camera / 의학물리

(131)I is a radiological isotope being used widely for treatment of cancer as emitting gamma-ray and it is also applied to estimate the function of thyroid for its accumulation in thyroid. However, (131)I is more difficult to quantitate comapred to (99m)Tc, because (131)I has multiple energy gamma-ray emissions compared to (99m)Tc which is a mono energetic gamma-ray source. Especially, scattered ray and septal penetration resulted by high energy gamma ray have a bad influence upon nuclear medicine image. The purpose of this study was to estimate scatter components depending on the different source locations within a phantom using Monte Carlo simulation (GATE). The simulation results were validated by comparing with the results of real experiments. Dual-head gamma camera (ECAM, Chicago, Illinois Siemens) with high energy, general-purpose, and parallel hole collimators (hole radius: 0.17 cm, septal thickness: 0.2 cm, length: 5.08 cm) was used in this experiment. The NaI crystal is 44.5x59.1 cm in height and width and 0.95 cm in thickness. The diameter and height of PMMA phantom were 16 cm and 15 cm, respectively. The images were acquired at 5 different locations of (131)I point source within the phantom and the images of (99m)Tc were also acquired for comparison purpose with low energy source. The simulation results indicated that the scattering was influenced by the location of source within a phantom. The scattering effects showed the same tendency in both simulation and actual experiment, and the results showed that the simulation was very adequate for further studies. The results supported that the simulation techniques may be used to generalize the scattering effects as a function of a point source location within a phantom.

Investigation of Scatter and Septal Penetration in I-131 Imaging Using GATE Simulation / 의학물리

Scatter correction for I-131 plays a very important role to improve image quality and quantitation. I-131 has multiple and higher energy gamma-ray emissions. Image quality and quantitative accuracy in I-131 imaging are degraded by object scatter as well as scatter and septal penetration in the collimator. The purpose of this study was to estimate scatter and septal penetration and investigate two scatter correction methods using Monte Carlo simulation. The gamma camera system simulated in this study was a FORTE system (Phillips, Nederland) with high energy, general-purpose, parallel hole collimator. We simulated for two types of high energy collimators. One is composed of lead, and the other is composed of artificially high Z number and high density. We simulated energy spectrum using a point source in air. We estimated both full width at half maximum (FWHM) and full width at tenth maximum (FWTM) using line spread function (LSF) in cylindrical water phantom. We applied two scatter correction methods, triple energy window scatter correction (TEW) and extended triple energy window scatter correction (ETEW). The TEW method is a pixel-by pixel based correction which is easy to implement clinically. The ETEW is a modification of the TEW which corrects for scatter by using abutted scatter rejection window, which can overestimate or the underestimate scatter. The both FWHM and FWTM were estimated as 41.2 mm and 206.5 mm for lead collimator, respectively. The FWHM and FWTM were estimated as 27.3 mm and 45.6 mm for artificially high Z and high density collimator, respectively. ETEW showed that the estimation of scatter components was close to the true scatter components. In conclusion, correction for septal penetration and scatter is important to improve image quality and quantitative accuracy in I-131 imaging. The ETEW method in scatter correction appeared to be useful in I-131 imaging.

18F-Fluoride-PET in Skeletal Imaging / 핵의학분자영상

Bone scintigraphy using 99mTc-labeled phosphate agents has long been the standard evaluation method for whole skeletal system. However, recent shortage of 99mTc supply and advanced positron emission tomography (PET) technology evoked the attention to surrogate radiopharmaceuticals and imaging modalities for bone. Actually, fluorine-18 (18F) was the first bone seeking radiotracer before the introduction of 99mTc-labeled agents even though its clinical application failed to become pervasive anymore after the rapid spread of Anger type gamma camera systems in early 1970s. However, rapidly developed PET technology made us refocus on the usefulness of 18F as a PET tracer. Early study comparing 18F-Na PET scan and planar bone scintigraphy reported that PET has higher sensitivity and specificity in the diagnosis of metastatic bone lesions than planar bone scan. Subsequent reports comparing between PET and both planar and SPECT bone image also revealed better results of PET scan in similar study groups. Rapid clinical application of PET/CT also accumulated considerable amount of experiences in skeletal evaluation and this modality is known to have better diagnostic power than stand alone PET system as well as bone scan. Furthermore 18F-Na PET/CT revealed better or at least equal results in detection of primary and metastatic bone lesions compared with CT and MRI. Therefore, it is obvious that 18F-Na PET/CT has potential to become new imaging modality for practical skeletal evaluation so continuous and careful evaluation of this modality and radiopharmaceutical must be required.