Characterization of a multi-pinhole molecular breast tomosynthesis scanner.

In recent years, breast imaging using radiolabelled molecules has attracted significant interest. Our group has proposed a multi-pinhole molecular breast tomosynthesis (MP-MBT) scanner to obtain 3D functional molecular breast images at high resolutions. After conducting extensive optimisation studies using simulations, we here present a first prototype of MP-MBT and evaluate its performance using physical phantoms. The MP-MBT design is based on two opposing gamma cameras that can image a lightly compressed pendant breast. Each gamma camera consists of a 250 × 150 mm2 detector equipped with a collimator with multiple pinholes focusing on a line. The NaI(Tl) gamma detector is a customised design with 3.5 mm intrinsic spatial resolution and high spatial linearity near the edges due to a novel light-guide geometry and the use of square PMTs. A volume-of-interest is scanned by translating the collimator and gamma detector together in a sequence that optimises count yield from the scan region. Derenzo phantom images showed that the system can reach 3.5 mm resolution for a clinically realistic 99mTc activity concentration in an 11-minute scan, while in breast phantoms the smallest spheres visible were 6 mm in diameter for the same scan time. To conclude, the experimental results of the novel MP-MBT scanner showed that the setup had sub-centimetre breast tumour detection capability which might facilitate 3D molecular breast cancer imaging in the future.

Ultrafast bone scintigraphy scan for detecting bone metastasis using a CZT whole-body gamma camera.

PURPOSE: To evaluate the feasibility of short whole-body bone scan acquisition times using a novel gamma camera with cadmium-zinc-telluride (CZT) semiconductor detectors. METHODS: We retrospectively enrolled 78 consecutive patients with prostate cancer who underwent bone scintigraphy using a whole-body gamma camera with CZT detectors. After acquisition of list-mode data with 180 s per bed position, anterior and posterior whole-body images were reconstructed using the first 5%, 10%, 25%, 50%, 75% and 100% of the list-mode data. Two experienced nuclear medicine physicians interpreted the images, and interrater agreement and the diagnostic value of the images were determined. Quantitative artificial neural network (ANN) values, bone scan indexes (BSI) and hotspot numbers (HsN) were also calculated by automated diagnostic software. RESULTS: Excellent interrater reliabilities of the visual assessments were obtained for the 100%, 75%, 50%, and 25% images (κ = 0.88, 0.88, 0.88 and 0.88, respectively). The 5% images also showed high diagnostic value (sensitivity 0.94, specificity 0.84 and accuracy 0.86). Intraclass correlation coefficients (ICC) between the 100% images and the reduced acquisition time images were evaluated in quantitative analyses, and excellent correlations were observed for ANN value in the 75% images (ICC 0.77), for BSI in all the reduced acquisition time images (75%, 50%, 25%, 10% and 5%; ICC 0.99, 0.99, 0.99, 0.96 and 0.75, respectively), and for HsN in the 75%, 50%, 25% and 10% images (ICC 0.99, 0.99, 0.98 and 0.90, respectively). CONCLUSION: Whole-body gamma cameras with CZT detectors have the potential to reduce image acquisition times and the dose of radioisotope injected for bone scans.

Gated Tomographic Radionuclide Angiography Using CZT Gamma Camera in Patients Receiving Cardiotoxic Chemotherapy: Going Faster and Less Irradiating.

Tomographic radionuclide angiography (TRNA) can monitor cardiac function in patients receiving cardiotoxic chemotherapy. Gamma cameras using CZT detectors enable dose reduction and quicker acquisitions. We report 80 patients who underwent a 7-minute TRNA acquisition after injection of 550-MBq Tc-labeled human serum albumin. Data were analyzed full and half. Image quality was not visually decreased. There was no significant difference in left ventricular systolic and diastolic volumes and in left and right ventricular ejection fractions between full and half data acquisitions (P < 0.0001). When injecting half activity, effective dose could be reduced to 1.92 mSv.

Assessing a small field of view hybrid gamma camera for perioperative iodine-125 seed localisation.

OBJECTIVE: To examine the imaging capability of a novel small field of view hybrid gamma camera (HGC) using 125I seeds prior to surgical use. METHODS: The imaging performance of the camera system was assessed quantitatively and qualitatively at different source depths, source to collimator distances (SCD), activity levels, acquisition times and source separations, utilising bespoke phantoms. RESULTS: The system sensitivity and spatial resolution of the HGC for 125I were 0.41 cps/MBq (at SCD 48 mm) and 1.53 ± 0.23 mm (at SCD 10 mm) respectively. The camera was able to detect the 125I seed at a SCD of 63 mm (with no scattering material in place) in images recorded within a 1-min acquisition time. The detection of the seeds beneath scattering material (simulating deep-seated tumours) was limited to depths of less than 20 mm beneath the skin surface with a SCD of 63 mm and seed activity of 2.43 MBq. Subjective assessments of the hybrid images acquired showed the capability of the HGC for localising the 125I seeds. CONCLUSION: This preliminary ex vivo study demonstrates that the HGC is capable of detecting 125I seeds and could be a useful tool in radioactive seed localisation with the added benefit of providing hybrid optical γ images for guiding breast conserving surgery. ADVANCES IN KNOWLEDGE: The SFOV HGC could provide high resolution fused optical-gamma images of 125I radioactive seeds indicating the potential use in intraoperative surgical procedure such as RSL.

Four-Minute Bone SPECT Using Large-Field Cadmium-Zinc-Telluride Camera.

PURPOSE: The aim of this study was to determine the minimum acquisition time without decreasing lesion detectability of bone SPECT using a whole-body cadmium-zinc-telluride camera. METHODS: Patients referred for bone SPECT were retrospectively included. SPECT of 30 patients were reframed from native data (16 s/projection) to produce 10-, 5-, and 3-s/projection data sets. A "critical" acquisition time/projection was defined as that below which the SPECT quality becomes insufficient for interpretation, as determined by 3 reviewers using a 4-point scale (0 = quality insufficient for interpretation, 1 = average, 2 = good, 3 = excellent). Three reviewers (blinded to the acquisition time) evaluated SPECT data sets (n = 79), native and reframed with "critical" acquisition times, in a randomized order. A lesion was defined as any uptake considered pathological by a reviewer. Lesion detectability equivalence between native SPECT and reframed SPECT was assessed by calculating a coefficient (κ) for each reviewer. RESULTS: Image quality of the first sample (n = 30) was significantly and progressively less well graded for the reframed data sets by all reviewers. Only 1 patient was graded 0 by each reviewer for the 5-s/projection data set. For the 3-s/projection data set, 3 patients were graded 0. No patients were graded 0 for 10-s/projection data set. The minimal acquisition time, for each projection, was defined as 5 s/projection. The coefficient κ, between native and reframed, with critical acquisition time/projection SPECT was greater than 0.9 for each reviewer. CONCLUSIONS: The more contrasted images of the cadmium-zinc-telluride camera allow performance of 5-s/projection SPECT without loss of lesion detectability. This suggests the possibility of performing whole-body SPECT in a reasonable time or reducing injected doses, especially in pediatric patients.

[Breast-specific gamma imaging in breast cancer]. / 'Breast-specific gamma imaging' bij borstkanker.

Breast-specific gamma imaging (BSGI) is a new technique in nuclear medicine for the diagnosis of breast cancer. After intravenous injection of the radioactive substance 99mTc-sestamibi the breasts are imaged with a gamma camera. The radionuclide assimilates into intracellular mitochondria, which are present in greater numbers in breast cancer cells than in normal cells. This causes a relatively high uptake of the radionuclide in tumours. Along with mammography and ultrasound, MRI is the current gold standard in breast imaging diagnostics. However, MRI is a complex and expensive procedure and has low specificity leading to high false-positive rates. BSGI has equally high sensitivity but is more specific, cheaper and much simpler to interpret. BSGI could replace MRI as a complementary technique to show, exclude or indicate the extent of breast cancer.

A PHANTOM FOR DETERMINATION OF CALIBRATION COEFFICIENTS AND MINIMUM DETECTABLE ACTIVITIES USING A DUAL-HEAD GAMMA CAMERA FOR INTERNAL CONTAMINATION MONITORING FOLLOWING RADIATION EMERGENCY SITUATIONS.

The purpose of this study was to derive calibration coefficients (in terms of cps kBq(-1)) and minimum detectable activities, MDA, (in terms of kBq and corresponding dose rate) for the dual head gamma camera part of an SPECT/CT-instrument when used for in vivo internal contamination measurements in radiation emergency situations. A cylindrical-conical PMMA phantom with diameters in the range of 7-30 cm was developed in order to simulate different body parts and individuals of different sizes. A series of planar gamma camera investigations were conducted using an SPECT/CT modality with the collimators removed for (131)I and (137)Cs, radionuclides potentially associated with radiation emergencies. Energy windows of 337-391 and 490-690 keV were selected for (131)I and (137)Cs, respectively. The measurements show that the calibration coefficients for (137)Cs range from 10 to 19 cps kBq(-1) with MDA values in the range of 0.29-0.55 kBq for phantom diameters of 10-30 cm. The corresponding values for (131)I are 12-37 cps kBq(-1) with MDA values of 0.08-0.26 kBq. An internal dosimetry computer program was used for the estimation of minimum detectable dose rates. A thyroid uptake of 0.1 kBq (131)I (representing MDA) corresponds to an effective dose rate of 0.6 µSv d(-1) A (137)Cs source position representing the colon with an MDA of 0.55 kBq corresponds to an effective dose rate was 1 µSv y(-1) This method using a simple phantom for the determination of calibration coefficients, and MDA levels can be implemented within the emergency preparedness plans in hospitals with nuclear medicine departments. The derived data will help to quickly estimate the internal contamination of humans following radiation emergencies.

Comparison of myocardial perfusion imaging using thallium-201 between a new cadmium-zinc-telluride cardiac camera and a conventional SPECT camera.

PURPOSE OF THE REPORT: Cadmium zinc telluride (CZT) solid-state detectors have been recently introduced in myocardial perfusion imaging. However, they had not been yet validated with thallium-201. This study compares the clinical performances of the CZT ultrafast camera GE DNM 530c with a conventional SPECT camera (CC) using thallium-201. MATERIALS AND METHODS: We prospectively studied with thallium-201 a total of 153 consecutive patients referred for myocardial perfusion imaging at exercise (3-4 mCi) then redistribution (with 1 mCi reinjection). Sequential acquisitions were performed first with a conventional dual-head tomographic Anger camera (CC) in 10 to 15 minutes and then with a CZT camera (CZT) in 5 minutes, in prone position. RESULTS: In all, 9 patients were excluded: 1 for mispositioning, 3 for camera failure, 3 for delayed acquisition after exercise, 1 for nonacceptance of redistribution, 1 for motion. Acquisition was more comfortable with CZT for all patients. Global counts rate was higher with CZT than with CC (3.6±0.57 KCts/s vs. 1.14±0.16). CZT has a 5-fold increased myocardial counts rate compared with CC (448±69 Kcts in 5 minutes vs. 209±40 Kcts in 12.5±1.8 minutes). Quality of CZT images was considered as better in 40%, equal in 56%, and worse in 4% of cases; we found less artifacts with CZT; diagnostic conclusions were the same in 140 of 144 cases (97%); discordances were 2 artifacts with CC and 2 small ischemia (less than 2 segments) missed by CZT. CONCLUSIONS: This new dedicated cardiac CZT camera allows with thallium-201 five minutes acquisitions with an increased image quality and a reliable diagnosis quality.

Video monitoring of neovessel occlusion induced by photodynamic therapy with verteporfin (Visudyne), in the CAM model.

The aim of the present study was to monitor photodynamic angioocclusion with verteporfin in capillaries. Details of this process were recorded under a microscope in real-time using a high-sensitivity video camera. A procedure was developed based on intravenous (i.v.) injection of a light-activated drug, Visudyne, into the chorioallantoic membrane (CAM) of a 12-day-old chicken embryo. The effect of light activation was probed after 24 h by i.v. injection of a fluorescent dye (FITC dextran), and analysis of its fluorescence distribution. The angioocclusive effect was graded based on the size of the occluded vessels, and these results were compared with clinical observations. The time-resolved thrombus formation taking place in a fraction of the field of view was video recorded using a Peltier-cooled CCD camera. This vessel occlusion in the CAM model was reproducible and, in many ways, similar to that observed in the clinical use of verteporfin. The real-time video recording permitted the monitoring of platelet aggregation and revealed size-selective vascular closure as well as some degree of vasoconstriction. Platelets accumulated at intravascular junctions within seconds after verteporfin light activation, and capillaries were found to be closed 15 min later at the applied conditions. Larger-diameter vessels remained patent. Repetition of these data with a much more sensitive camera revealed occlusion of the treated area after 5 min with doses of verteporfin and light similar to those used clinically. Consequently, newly developed light-activated drugs can now be studied under clinically relevant conditions.

Sensitivity and daily quality control of a mobile PET/CT scanner operating in 3-dimensional mode.

UNLABELLED: This study investigated the stability of the sensitivity of a mobile PET/CT scanner and tested a phantom experiment to improve on the daily quality control recommendations of the manufacturer. Unlike in-house scanners, mobile PET/CT devices are subjected to a harsher, continuously changing environment that can alter their performance. The parameter of sensitivity was investigated because it reflects directly on standardized uptake value, a key factor in cancer evaluation. METHODS: A (68)Ge phantom of known activity concentration was scanned 6 times a month for 11 consecutive months using a mobile PET/CT scanner that operates in 3-dimensional mode only. The scans were acquired as 2 contiguous bed positions, with raw data obtained and reconstructed using parameters identical to those used for oncology patients, including CT-extracted attenuation coefficients and decay, scatter, geometry, and randoms corrections. After visual inspection of all reconstructed images, identical regions of interest were drawn on each image to obtain the activity concentration of individual slices. The original activity concentration was then decay-corrected to the scanning day, and the percentage sensitivity of the slice was calculated and graphed. The daily average sensitivity of the scanner, over 11 consecutive months, was also obtained and used to evaluate the stability of sensitivity. RESULTS: Our particular scanner showed a daily average sensitivity ranging from -8.6% to 6.5% except for one instance, when the sensitivity dropped by an unacceptable degree, 34.8%. CONCLUSION: Our 11-mo follow-up of a mobile PET/CT scanner demonstrated that its sensitivity remained within acceptable clinical limits except for one instance, when the scanner had to be serviced before patients could be imaged. To enhance our confidence in the uniformity of sensitivity across slices, we added a phantom scan to the daily quality control recommendations of the manufacturer.

Fundamentos físicos de calidad de imagen en medicina nuclear: métodos para su valoración / Physical factors which characterize image quality in Nuclear Medicine

El presente artículo realiza una descripción físico-matemática de los principales factores físicos que caracterizan la calidad de la imagen en Medicina Nuclear, así como una descripción conceptual de la degradación que sufre la información proveniente del objeto debido al sistema de imagen (cámara gamma). Seguidamente se realiza una presentación crítica de algunos métodos cualitativos y cuantitativos de valoración de la calidad de la imagen, colaterales al tradicional control de calidad del equipamiento, como son el análisis ROC, las Técnicas de Clustering y el Análisis Discriminante. Dentro de estas dos últimas, se analizan los principales factores que determinan la calidad de la imagen y cómo los mismos se traducen en cambios en los valores cuantitativos de las principales variables físicas que la caracterizan. Se realiza además una comparación entre los métodos, resaltando su utilidad para monitorear calidad de imagen, así como sus principales ventajas y desventajas.

Vital dye is enough for inguinal sentinel lymph node biopsy in melanoma patients

OBJETIVO: a importância da detecção gama intra-operatória combinada com corante vital para biópsia de linfonodo sentinela é bem aceita. Nós avaliamos a eficácia do azul patente V na identificação do linfonodo sentinela inguinal. MÉTODOS: Noventa e quatro pacientes portadores de melanoma cutâneo de membro inferior foram submetidos a biópsia de linfonodo sentinela de acordo com protocolo estabelecido. Foram randomizados em dois grupos: Grupo Azul, onde o linfonodo sentinela foi identificado primariamente com o corante vital azul patente V (Guerbet) e o Grupo Sonda, onde o linfonodo sentinela foi identificado primariamente pela sonda de detecção gama (Neoprobe). A idade mediana foi de 44,2 anos e a espessura mediana de Breslow foi 2,1 mm. Linfocintilografia pré-operatória, mapeamento linfático com azul patente V e detecção gama intra-opertaória foram realizados em todos os pacientes. O exame histopatológico do linfonodo sentinela consistiu de hematoxilina-eosina e imunohistoquímica. Se micrometástase estivesse presente, linfadenectomia completa era realizada. O linfonodo sentinela era considerado como identificado pelo corante vital se estivesse azul e identificado pela sonda de detecção gama se demonstrasse pelo menos 10 vezes ou mais radioatividade do que o fundo. RESULTADOS: Foram exploradas 94 regiões inguinais, 145 linfonodos sentinelas foram excisados (70 dirigidos primariamente pelo corante vital e 75 dirigidos pela sonda de detecção gama). Todos os linfonodos sentinelas identificados pela linfocintilografia foram excisados. No grupo azul, todos os linfonodos sentinela foram primariamente idenficados pelo corante vital e todos se apresentavam quentes na leitura pela sonda. No grupo sonda, todos os linfonodos sentinelas foram primariamente identificados pela sonda e estavam corados pelo azul. A coincidência da sonda com o corante vital foi de 100%. CONCLUSAO: Azul patente V foi suficiente para identificar linfonodo sentinela inguinal em pacientes com melanoma cutâneo.

Assessment of 18F-fluorodeoxyglucose dual-head gamma camera in asbestos lung diseases.

The purpose of this study was to evaluate the performance of 18F-fluorodeoxyglucose (18FDG) imaging via coincidence detection emission tomography (CDET) in identifying malignant lesions in subjects exposed to asbestos. A total of 30 patients exposed to asbestos underwent 18FDG-CDET between January 2000 and June 2003. A CDET scan of the thorax and abdomen was performed 60 min after injection of 18FDG in fasting patients, and results were obtained in slices in three axes. The CDET results were compared to those from computed tomography (CT), and pleural or surgical biopsy in patients with positive 18FDG-CDET results. All primary malignant mesotheliomas accumulated 18FDG (n=6), and, in two patients, CDET findings were superior to those of CT, allowing early detection. In two cases, lung carcinomas with malignant pleural effusion were also detected. There were five false positive CDET results: three unilateral pleural thickening, one rounded atelectasis, and one benign lung nodule. All patients with pleural plaques showed no significant 18FDG uptake. Malignant diseases were detected by 18FDG-CDET imaging with a sensitivity of 89% and specificity of 71%. Coincidence detection emission tomography can identify malignant mesothelioma in selected subjects exposed to asbestos. Coincidence detection emission tomography appears to be a useful noninvasive method for the follow-up of subjects with exposure risk of asbestosis.

Performance evaluation of a hand-held, semiconductor (CdZnTe)-based gamma camera.

We have designed and developed a small field of view gamma camera, the eZ SCOPE, based on use of a CdZnTe semiconductor. This device utilises proprietary signal processing technology and an interface to a computer-based imaging system. The purpose of this study was to evaluate the performance of the eZ scope in comparison with currently employed gamma camera technology. The detector is a single wafer of 5-mm-thick CdZnTe that is divided into a 16x16 array (256 pixels). The sensitive area of the detector is a square of dimension 3.2 cm. Two parallel-hole collimators are provided with the system and have a matching (256 hole) pattern to the CdZnTe detector array: a low-energy, high-resolution parallel-hole (LEHR) collimator fabricated of lead and a low-energy, high-sensitivity parallel-hole (LEHS) collimator fabricated of tungsten. Performance measurements and the data analysis were done according to the procedures of the NEMA standard. We also studied the long-term stability of the system with continuous use and variations in ambient temperature. Results were as follows. INTRINSIC ENERGY RESOLUTION: 8.6% FWHM at 141 keV.LINEARITY: There was excellent linearity between the observed photopeaks and the known gamma ray energies for the given isotopes. INTRINSIC SYSTEM UNIFORMITY: For the central field of view, the integral uniformity and the differential uniformity were, respectively, 1.6% and 1.3% with the LEHR collimator and 1.9% and 1.2% with the LEHS collimator. SYSTEM SPATIAL RESOLUTION: The FWHM measurements made at the surface of the collimator were 2.2 mm (LEHR) and 2.9 mm (LEHS).CONTRAST TEST: The average S/N ratios (i.e. counts in the irradiated pixel divided by counts in the surrounding pixels) for the inner ring pixels (8)/outer ring pixels (16) using the LEHS collimator and LEHR collimator were 3.2%/0.2% and 3.7%/0.3%, respectively. COUNT RATE CHARACTERISTICS: We could not determine the maximum count rate and the 20% loss count rate from these data because the plateau was not reached while using the solutions measured. SYSTEM SENSITIVITY: The average acquisitions were 11,052 cpm/MBq (LEHR) and 28,590 cpm/MBq (LEHS). TEMPERATURE DEPENDENCE: The system displayed minimum corresponding shift in cps with temperature changes in the measured temperature range. We designed and developed a semiconductor-based gamma camera using CdZnTe. The basic performance of this camera compares favourably with the existing gamma camera technology that is deployed in the medical field today. The most significant differences include the spatial resolution, sensitivity, high count rate characteristics and energy resolution. We believe that this device will be of value for a number of clinical applications including sentinel node detection and radiopharmaceutical-guided surgery.

Propuesta de estandarización del control de uniformidad intrínseca de las gammacámaras / Standarization of the intrinsic uniformity control of the gammacameras

OBJETIVO: Determinar el resultado de la uniformidad intrínseca (UI) de las gammacámaras usando distintos parámetros de adquisición en el control de calidad semanal (QC). MATERIAL Y MÉTODOS: Cuatro experimentos de UI, empleando fuentes de Tc99m . Modificando los parámetros orientación, distancia, actividad y volumen de la fuente en 10 detectores con fotomultiplicadores de cristal de INa, con siguientes condiciones de adquisición: 4000 kctas, fuente centrada coincidiendo con el centro geométrico del detector, 2 metros de distancia detector/fuente, 0.1 ml de volumen en una jeringuilla de 1 ml y 150 microCi de Tc99m. RESULTADOS: Los resultados respecto a la distancia fuente / detector nos han mostrado que, a mayor separación entre ambas, mejor resultado. El punto de inflexión en general lo encontramos entre 1,5 y 2 m para que el resultado sea correcto. En cuanto a la rotación / fuente los resultados nos demuestran que el detector debe de estar paralelo en su centro geométrico respecto a la dosis, ya que una desviación de tan solo dos grados provocaría un empeoramiento de +0.5 por ciento de promedio. Respecto a qué dosis usar, los resultados muestran que los mejores valores de la UI no se encuentran usando dosis excesivamente bajas ni extremadamente altas (dentro de los límites establecidos por la normativa NEMA). En cuanto al volumen, hemos observado que usando jeringas mayores de 1 ml , mejorábamos sustancialmente el resultado final de la UI en todos los detectores. CONCLUSIONES: Teniendo en cuenta las variaciones que presentan los valores de la UI en función de la distancia y orientación fuente/detector y dosis-volumen de la fuente, recomendamos realizar dichos controles en idénticas condiciones semanalmente, siguiendo la reglamentación NEMA y atendiendo a la evidente mejora de rendimiento demostrada en nuestros experimentos

Transfer of normal 99mTc-ECD brain SPET databases between different gamma cameras.

A stereotactic, normal perfusion database is imperative for optimal clinical brain single-photon emission tomography (SPET). However, interdepartmental use of normal data necessitates accurate transferability of these data sets. The aim of this study was to investigate transfer of three normal perfusion databases obtained in the same large population of healthy volunteers who underwent sequential scanning using multihead gamma cameras with different resolution. Eighty-nine healthy adults (46 females, 43 males; aged 20-81 years) were thoroughly screened by history, biochemistry, physical and full neurological examination, neuropsychological testing and magnetic resonance imaging. After injection of 925 MBq technetium-99m labelled ethyl cysteinate dimer (ECD) under standard conditions, 101 scans were acquired from all subjects (12 repeat studies) on a triple-head Toshiba GCA-9300A (measured average FWHM 8.1 mm). Ninety-one sequential scans were performed on a dual-head Elscint Helix camera (FWHM 9.6 mm) and 22 subjects also underwent imaging on a triple-head Prism 3000 (FWHM 9.6 mm). Images were transferred to the same processing platform and reconstructed by filtered back-projection with the same Butterworth filter (order 8, cut-off 0.9 cycles/cm) and uniform Sorensen attenuation correction (mu = 0.09). After automated rigid intrasubject registration, all subjects were automatically reoriented to a stereotactic template by a nine-parameter affine transformation. The databases were analysed using 35 predefined volumes of interest (VOIs) with normalisation on total VOI counts. For comparison, the high-resolution data were smoothed with a 3D Gaussian kernel to achieve more similar spatial resolution. Hoffman phantom measurements were conducted on all cameras. Partial volume effects after smoothing varied between -6.5% and 10%, depending on VOI size. Between-camera reproducibility was 2.5% and 2.7% for the Toshiba camera versus the Helix and the Prism database, respectively. The highest reduction in between-camera variability was achieved by resolution adjustment in combination with linear washout correction and a Hoffman phantom-based correction. In conclusion, transfer of normal perfusion data between multihead gamma cameras can be accurately achieved, thereby enabling widespread interdepartmental use, which is likely to have a positive impact on the diagnostic capabilities of clinical brain perfusion SPET.

PET imaging using gamma cameras.

This paper will review the recent advances and future developments in the field of coincidence imaging of positron emitters with a conventional Anger-type gamma camera. FDG imaging has shown high clinical importance in cardiology, neurology and especially oncology. Since access to full ring PET is mainly limited to university hospitals, there have been new developments allowing PET imaging on the standard Anger gamma camera. First the principles of coincidence imaging on a gamma camera will be reviewed. We will discuss the limitations of this technique, and the techniques used to partly overcome these limitations. The different configurations of the gamma camera operating in coincidence mode are pointed out. Different corrections for image degrading effects and reconstruction methods are evaluated in the final part.

The clinical application of a dual head gamma camera with coincidence detection in 20 women with suspected ovarian cancer.

OBJECTIVE: To assess the effectiveness of a dual head coincidence gamma camera in identifying ovarian cancer as a less expensive alternative to the traditional 2-[18F] fluoro-2-deoxy-D-glucose (18FDG) system using positron emission tomography. DESIGN: Prospective study. POPULATION: Twenty consecutive women suspected of having ovarian carcinoma. Inclusion was based on abnormal serum CA125 (reference range is 0-35 units/L), ultrasound, computerised tomography or clinical findings. METHODS: Women underwent assessment before staging laparotomy. Two nuclear medicine physicians, who were blinded to the pre-operative assessment, reported on 18FDG- dual head coincidence gamma camera imaging. MAIN OUTCOME MEASURES: The histology and operative staging were compared with the 18FDG- dual head coincidence gamma camera findings. RESULTS: Twelve women had pelvic malignancies (nine primary and three recurrences), seven women had benign pathology and one patient had a borderline malignancy. We were able to image accurately all malignant pelvic masses with dual head coincidence gamma camera, as well as accurately demonstrate disease spread. Two of the benign pelvic masses localised 18FDG. The positive predictive value for detecting malignancy was 86%. CONCLUSIONS: Dual head coincidence gamma camera offers accurate and affordable imaging in suspected ovarian masses, with improved specificity over CA125, ultrasound and computerised tomography. These results are similar to those obtained on more expensive dedicated PET systems. We report on a series of patients believed to have primary or recurrent carcinoma and recognise the need to include patients more likely to have benign lesions to assess false positive results. However, we believe that dual head coincidence gamma camera is useful in the pre-operative assessment of women with suspected ovarian cancer.

Comparaçäo de captaçäo tireoidiana nos equipamentos Captus 600© e Thyrus© / Comparison between thyroid uptake values measured on Captus 600© and Thyrus© equipments

O objetivo deste estudo foi comparar valores de captaçäo tireoidiana medidos em dois equipamentos diferentes: uma sonda própria para as medidas de captaçäo (Captus 600© - Capintec, USA) e uma mini gama-câmera (Thyrus© - Adac Laboratories). Foram estudados 122 pacientes, sendo 110 do sexo feminino e 12 do sexo masculino, com idades variando de 4 a 81 anos (média de 42,2 anos). Administraram-se, por via oral, doses de 0,74 MBq a 3,7 MBq de NaûüûI e as medidas de captaçäo tireoidiana foram realizadas cerca de 24 horas após, em ambos os equipamentos. Para o cálculo da captaçäo utilizou-se, nos dois casos, a medida de um tubo contendo soluçäo padräo devidamente colocado em um "phantom" de pescoço. Aplicou-se o teste de Wilcoxon aos valores obtidos, resultando em z calculado de -4,35, com nível de significância p < 0,001, levando-nos à conclusäo de que há significativa diferença nas medidas de captaçäo nos dois equipamentos

Evaluation of a surgical gamma probe for detection of 18F-FDG.

Because fluorine-18 fluorodeoxyglucose (18F-FDG) is an excellent tumor-localizing radio-pharmaceutical, a hand-held radiation detection probe capable of localizing an area with high 18F-FDG uptake would make radioguided surgery possible. In this laboratory study, we investigated the capability of a widely used intraoperative gamma probe with a cadmium zinc telluride (CdZnTe) detector for detection of 18F-FDG. For sensitivity tests, an 0.1- ml 18F-FDG preparation was made to act as a point source with radioactivities of 1.0, 2.0, and 3.0micro Ci (37 kBq, 74 kBq, 111 kBq). Relative transmission across the side wall of the probe and sensitivity at each source-to-probe distance were measured. For simulation studies, 2 l of 18F-FDG solution (0.02micro Ci, 0.74 kBq/ml) served as normal background. One ml of 18F-FDG was prepared to simulate tumors with radioactivities of 0.05, 0.1, 0.2, and 0.4micro Ci (1.85 kBq, 3.7 kBq, 17.4 kBq, and 14.8 kBq). The ratios of the radioactive concentration of tumor to that of the background were 2.5, 5, 10, and 20:1, respectively. The tested gamma probe was shown to be sensitive to 18F. The high-energy annihilation radiation was detected from the side wall of the probe despite application of a supplementary collimator. The count rate decreased markedly as the source-to-probe distance increased, owing to the effects of the inverse-square law. In the simulation studies, the probe detected a considerable amount of background activity. However, the measured count rate increased with the increasing source-to-background ratio. In our setting, the probe was capable of distinguishing the 18F-FDG source from the background when the source-to-background ratio was no less than 5:1. To make a surgical application feasible, however, collimation or shielding against high background radiation is necessary.