Diagnostic value of quantitative SPECT/CT in assessing active sacroiliitis in patients with axial spondylarthritis and/or inflammatory low back pain

Fundamento. La precisión diagnóstica de la gammagrafía ósea (GO) aumenta con las imágenes SPECT/TAC haciendo conveniente reevaluar su utilidad diagnóstica en la sacroilitis de la espondiloartritis axial (EA). El objetivo fue comparar el rendimiento diagnóstico de la resonancia magnética (RM), la SPECT/TC y ambas pruebas combinadas, y evaluar la correlación entre los índices cuantitativos de ambas técnicas. Métodos. A 31 pacientes con EA activa y 22 con lumbalgia inflamatoria se les realizó una RM y una SPECT/TC de las articulaciones sacroilíacas y se calculó la precisión diagnóstica de ambas técnicas respecto al diagnóstico clínico. La correlación entre ambas pruebas se calculó comparando los índices de actividad del SPECT/TC con los sistemas de puntuación Berlín y SPARCC de RM. Resultados. Los valores de sensibilidad y especificidad de la SPECT/TC cuantitativa, tomando como punto de corte el cociente sacroilíaca/promontorio >1,36, fueron similares a los publicados para la RM. La combinación de ambas técnicas aumentó la sensibilidad manteniendo una alta especificidad. La correlación entre las escalas totales de RM y SPECT/TC fue moderada y mejoraba al utilizar únicamente las escalas de inflamación. Conclusiones. La SPECT/TC cuantitativa muestra una mejor precisión diagnóstica que la GO planar en la sacroilitis activa y una correlación moderada con las puntuaciones de RM. La combinación de ambas técnicas aumenta la precisión diagnóstica. Por tanto, la SPECT/TAC cuantitativa podría tener un papel relevante en el diagnóstico de sacroilitis en pacientes con alta sospecha de EA y RM negativa/no concluyente o en aquellos pacientes en los que no se pueda realizar una RM.(AU)

Background. The diagnostic accuracy of bone scintigraphy (BS) increases with SPECT/CT imaging. It would therefore be appropriate to reassess the diagnostic utility of scintigraphy in sacroiliitis with axial spondyloarthritis (SpA). The aim of this study was to compare the diagnostic performance of MRI, SPECT/CT and a combination of both techniques in sacroiliitis, and to evaluate the correlation between quantitative SPECT/CT indices and quantitative MRI inflammatory lesion scores. Methods. Thirty-one patients with active SpA and 22 patients with inflammatory low back pain underwent MRI and SPECT/CT of the sacroiliac joints. The diagnostic accuracy of both techniques was calculated using clinical diagnosis as the gold standard. The correlation between MRI and SPECT/CT was calculated by comparing the SPECT/CT activity indices and the Berlin/SPARCC scoring systems for MRI. Results. The sensitivity and specificity values in quantitative SPECT/CT, taking the sacroiliac/promontory ratio of >1.36 as the cut-off value, were close to those from MRI published in the literature. The combination of both techniques increased sensitivity while maintaining high specificity. There was a moderate correlation between SPECT/CT and MRI total scores. This correlation was improved by using solely the MRI inflammation scores. Conclusion. Quantitative SPECT/CT showed better diagnostic accuracy than planar scintigraphy and showed a moderate correlation with MRI scores in active sacroiliitis. The combination of both tests increased the diagnostic accuracy. Quantitative SPECT/CT could play a relevant role in the diagnosis of active sacroiliitis in patients with high a suspicion of SpA and a negative/inconclusive MRI test or in patients with whom MRI studies cannot be carried out.(AU)

Diagnostic value of quantitative SPECT/CT in assessing active sacroiliitis in patients with axial spondylarthritis and/or inflammatory low back pain.

BACKGROUND: The diagnostic accuracy of bone scintigraphy (BS) increases with SPECT/CT imaging. It would therefore be appropriate to reassess the diagnostic utility of scintigraphy in sacroiliitis with axial spondyloarthritis (SpA). The aim of this study was to compare the diagnostic performance of MRI, SPECT/CT and a combination of both techniques in sacro-iliitis, and to evaluate the correlation between quantitative SPECT/CT indices and quantitative MRI inflammatory lesion scores. METHODS: Thirty-one patients with active SpA and 22 patients with inflammatory low back pain underwent MRI and SPECT/CT of the sacroiliac joints. The diagnostic accuracy of both techniques was calculated using clinical diagnosis as the gold standard. The correlation between MRI and SPECT/CT was calculated by comparing the SPECT/CT activity indices and the Berlin/SPARCC scoring systems for MRI. RESULTS: The sensitivity and specificity values in quantitative SPECT/CT, taking the sacroiliac/promontory ratio of >1.36 as the cut-off value, were close to those from MRI published in the literature. The combination of both techniques increased sensitivity while maintaining high specificity. There was a moderate correlation between SPECT/CT and MRI total scores. This correlation was improved by using solely the MRI inflammation scores. CONCLUSION: Quantitative SPECT/CT showed better diagnostic accuracy than planar scintigraphy and showed a moderate correlation with MRI scores in active sacroiliitis. The combination of both tests increased the diagnostic accuracy. Quanti-tative SPECT/CT could play a relevant role in the diagnosis of active sacroiliitis in patients with high a suspicion of SpA and a negative/inconclusive MRI test or in patients with whom MRI studies cannot be carried out.

Variation of enterohepatic circulation observed with 75SeHCAT images in the first three hours. Scintigraphic patterns and analysis of their association with the diagnosis of bile acid malabsorption.

OBJETIVE: To evaluate the enterohepatic circulation of 75-Selenium turoselecolic acid (75Se-SeHCAT) during the first 3 h and its correlation with the abdominal retention at the 7th day (AR7), as contribution to the clinical study of biliar acid malabsorption (BAM). MATERIALS AND METHODS: 38 patients with chronic diarrhea were retrospectively studied. Acquisition protocol included static abdominal images at 1st, 2nd and 3rd hour and the 7th day after oral administration of the radiopharmaceutical. Images of 1-3 h determined 5 patterns of enterohepatic circulation that, due to their location, were characterized as: 1) gallbladder 2-3 h, 2) gallbladder 3 h, 3) gallbladder-abdomen 2-3 h, 4) abdomen, 5) upper left abdomen. The association of these patterns with the AR7 (Fisher, STATA) were investigated. Patients were classified as Non BAM (AR7 > 15%), mild-BAM (AR7 15-10%), moderate-BAM (AR7 10-5%) or severe-BAM (AR7 < 5%). RESULTS: 19 patients had an AR7 diagnostic of BAM (7 mild-BAM, 5 moderate-BAM, 7 severe-BAM). The pattern "gallbladder at 2-3 h" was statistically associated with Non BAM (p 0,008), while "gallbladder-abdomen at 2-3 h" was correlated with having BAM (p 0,029). CONCLUSION: Variations detected at the abdominal level in images during the first 3 h were associated with changes in intestinal absorption and the incorporation of the radiopharmaceutical into the pool of bile acids, so visual interpretation of the images at 2nd and 3rd hour could be useful in the final assessment of the study.

Variation of enterohepatic circulation through the image with 75SeHCAT in the first 3 hours. Scintigraphic patterns and análisis of its association with the diagnosis of bile acid malabsorption. / Variación de la circulación enterohepática a través de la imagen con 75SeHCAT en las 3 primeras horas. Patrones gammagráficos y análisis de su asociación con el diagnóstico de malabsorción de ácidos biliares.

OBJETIVE: To evaluate the enterohepatic circulation of 75-Selenium turoselecolic acid (75Se-SeHCAT) during the first 3 hours and its correlation with the abdominal retention at the 7th day (AR7), as contribution to the clinical study of biliar acid malabsorption (BAM). MATERIALS AND METHODS: 38 patients with chronic diarrhea were retrospectively studied. Acquisition protocol included static abdominal images at 1st, 2nd and 3rd hour and the 7th day after oral administration of the radiopharmaceutical. Images of 1 to 3 hours determined 5 patterns of enterohepatic circulation that, due to their location, were characterized as: 1) gallbladder 2-3 hours, 2) gallbladder 3 hours, 3) gallbladder-abdomen 2-3 hours, 4) abdomen, 5) upper left abdomen. The association of these patterns with the AR7 (Fisher, STATA) were investigated. Patients were classified as Non BAM (AR7>15%), mild-BAM (AR7: 15-10%), moderate-BAM (AR7: 10-5%) or severe-BAM (AR7<5%). RESULTS: 19 patients had an AR7 diagnostic of BAM (7 mild-BAM, 5 moderate-BAM, 7 severe-BAM). The pattern "gallbladder at 2-3 hours" was statistically associated with Non BAM (p 0,008), while "gallbladder-abdomen at 2-3 hours" was correlated with having BAM (p 0,029). CONCLUSION: Variations detected at the abdominal level in images during the first 3 hours were associated with changes in intestinal absorption and the incorporation of the radiopharmaceutical into the pool of bile acids, so visual interpretation of the images at 2nd and 3rd hour could be useful in the final assessment of the study.

Field camera versus phantom-based measurement of the gradient system transfer function (GSTF) with dwell time compensation.

PURPOSE: The gradient system transfer function (GSTF) can be used to describe the dynamic gradient system and applied for trajectory correction in non-Cartesian MRI. This study compares the field camera and the phantom-based methods to measure the GSTF and implements a compensation for the difference in measurement dwell time. METHODS: The self-term GSTFs of a MR system were determined with two approaches: 1) using a dynamic field camera and 2) using a spherical phantom-based measurement with standard MR hardware. The phantom-based GSTF was convolved with a box function to compensate for the dwell time dependence of the measurement. The field camera and phantom-based GSTFs were used for trajectory prediction during retrospective image reconstruction of 3D wave-CAIPI phantom images. RESULTS: Differences in the GSTF magnitude response were observed between the two measurement methods. For the wave-CAIPI sequence, this led to deviations in the GSTF predicted trajectories of 4% compared to measured trajectories, and residual distortions in the reconstructed phantom images generated with the phantom-based GSTF. Following dwell-time compensation, deviations in the GSTF magnitudes, GSTF-predicted trajectories, and resulting image artifacts were eliminated (< 0.5% deviation in trajectories). CONCLUSION: With dwell time compensation, both the field camera and the phantom-based GSTF self-terms show negligible deviations and lead to strong artifact reduction when they are used for trajectory correction in image reconstruction.

Radiation dose produced by patients during radiopharmaceutical incorporation in nuclear medicine diagnostic procedures.

OBJECTIVES: The aim of this study was to assess the dose received by members of the public due to close contact with patients undergoing nuclear medicine procedures during radiopharmaceutical incorporation, and comparing it with the emitted radiation dose when the test was complete, in order to establish recommendations. MATERIAL AND METHODS: A prospective study was conducted on 194 patients. H*(10) dose rates were measured at 0.1, 0.5, and 1.0m after the radiopharmaceutical administration, before the image acquisition, and at the end of the nuclear medicine procedure. Effective dose for different close contact scenarios were calculated, according to 95th percentile value (bone scans) and the maximum value (remaining tests). RESULTS: During the radiopharmaceutical incorporation, a person who stays with another injected patient in the same waiting room may receive up to 0.59 mSv. If the patient had a medical appointment, or went to a restaurant or a coffee shop, members of the public could receive 23, 43, and 22 µSv, respectively. After finishing the procedure, these doses are reduced by a factor 3. In most of the studies, the use of private instead of public transport may reduce the dose by more than a factor 6. CONCLUSION: It is recommended to increase the distance between the patients during the radiopharmaceutical incorporation and to distribute them according to the diagnostic procedure. Patients should be encouraged to use private instead of public transport. Depending on the number of nuclear medicine outpatients per year attended by a physician, it could be necessary to apply restrictions.

Radiation dosimetry and biodistribution in non-human primates of the sodium/iodide PET ligand [(18)F]-tetrafluoroborate.

BACKGROUND: [(18)F]-tetrafluoroborate is a PET radiotracer taken up by the sodium/iodide symporter (NIS). Albeit the in vivo behavior in rodents is similar to the (99m)Tc-pertechnetate, no studies exist in primates or in humans. The aims of this study were to evaluate the biodistribution of [(18)F]-tetrafluoroborate in non-human primates with PET and to estimate the absorbed dose in organs. METHODS: Whole-body PET imaging was done in a Siemens ECAT HR+ scanner in two male Macaca fascicularis monkeys. After an i.v. injection of 24.93 ± 0.05 MBq/kg of [(18)F]-tetrafluoroborate, prepared by isotopic exchange of sodium tetrafluoroborate with [(18)F]-fluoride under acidic conditions, eight sequential images from the head to the thigh (five beds) were collected for a total duration of 132 min. The whole-body emission scan was reconstructed applying attenuation and scatter corrections. After image reconstruction, three-dimensional volumes of interest (VOIs) were hand-drawn on the PET transaxial or coronal slices of the frame where the organ was most conspicuous. Time-activity curves for each VOI were obtained, and the organ residence times were calculated by integration of the time-activity curves. Human absorbed doses were estimated using the OLINDA/EXM software and the standard human model. RESULTS: [(18)F]-tetrafluoroborate was able to discriminate clearly the thyroid gland with an excellent signal-to-noise ratio. Most of the radiotracers (residence time) are localised in the organs that express NIS (stomach wall, salivary glands, thyroid, olfactory mucosa), are involved in excretion (kidneys and bladder), or reflect the vascular phase (heart and lungs). Considering the OLINDA source organs, the critical organs were the stomach wall, thyroid and bladder wall, with absorbed doses lower than 0.078 mGy/MBq. The effective dose was 0.025 mSv/MBq. CONCLUSIONS: [(18)F]-tetrafluoroborate is a very useful radiotracer for PET thyroid imaging in primates, with a characteristic biodistribution in organs expressing NIS. It delivers an effective dose slightly higher than the dose produced by (99m)Tc-pertechnetate but much lower than that produced by radioiodine in the form of (131)INa, (123)INa, or (124)INa.

[¹8F]fluorothymidine-positron emission tomography in patients with locally advanced breast cancer under bevacizumab treatment: usefulness of different quantitative methods of tumor proliferation.

OBJECTIVES: To investigate quantitative methods of tumor proliferation using 3'-[(18)F]fluoro-3'-deoxythymidine ([(18)F]FLT) PET in patients with breast cancer (BC), studied before and after one bevacizumab administration, and to correlate the [(18)F]FLT-PET uptake with the Ki67 index. MATERIAL AND METHODS: Thirty patients with newly diagnosed, untreated BC underwent a [(18)F]FLT-PET before and 14 days after bevacizumab treatment. A dynamic scan centered over the tumor began simultaneously with the injection of [(18)F]FLT (385 ± 56 MBq). Image derived input functions were obtained using regions of interest drawn on the left ventricle (LV) and descending aorta (DA). Metabolite corrected blood curves were used as input functions to obtain the kinetic Ki constant using the Patlak graphical analysis (time interval 10-60 min after injection). Maximum SUV values were derived for the intervals 40-60 min (SUV40) and 50-60 min (SUV50). PET parameters were correlated with the Ki67 index obtained staining tumor biopsies. RESULTS: [(18)F]FLT uptake parameters decreased significantly (p<0.001) after treatment: SUV50=3.09 ± 1.21 vs 2.22 ± 0.96; SUV40=3.00 ± 1.18 vs 2.14 ± 0.95, Ki_LV(10-3)=52[22-116] vs 38[13-80] and Ki_DA(10-3)=49[15-129] vs 33[11-98]. Consistency interclass correlation coefficients within SUV and within Ki were high. Changes of SUV50 and Ki_DA between baseline PET and after one bevacizumab dose PET correlated with changes in Ki67 index (r-Pearson=0.35 and 0.26, p=0.06 and 0.16, respectively). CONCLUSIONS: [(18)F]FLT-PET is useful to demonstrate proliferative changes after a dose of bevacizumab in patients with BC. Quantification of tumor proliferation by means of SUV and Ki has shown similar results, but SUV50 obtained better results. A correlation between [(18)F]FLT changes and Ki67 index was observed.

[Validation of segmentation techniques for positron emission tomography using ex-vivo images of oncological surgical specimens]. / Validación de técnicas de segmentación para la tomografía por emisión de positrones mediante imágenes ex-vivo de piezas quirúrgicas oncológicas.

OBJECTIVE: To design a novel ex-vivo acquisition technique to establish a common framework to validate different segmentation techniques for oncological PET images. To evaluate several automatic segmentation algorithms on this set of images. MATERIAL AND METHODS: In 15 patients with cancer, ex-vivo PET studies of surgical specimens removed during surgery were performed after injection of (18)F-FDG. Images were acquired in two scanners: a clinical PET/CT and a high-resolution PET scanner. Real tumor volume was determined in each patient, and a reference image was generated for segmentation of each tumor. Images were segmented with 12 automatic algorithms and with a standard method for PET (relative threshold at 42%) and results were evaluated by quantitative parameters. RESULTS: It has been possible to demonstrate by segmentation of PET images of surgical specimens that on high resolution PET images, 8 out of 12 evaluated segmentation techniques outperformed the standard method, whose value is 42%. However, none of the algorithms outperformed the standard method when applied on images from the clinical PET/CT. Due to the great interest of this set of PET images, all studies have been published on the Internet in order to provide a common framework for validation and comparison of different segmentation techniques. CONCLUSIONS: We have proposed a novel technique to validate segmentation techniques for oncological PET images, acquiring ex-vivo PET studies of surgical specimens. We have demonstrated the usefulness of this set of PET images by evaluating several automatic segmentation algorithms.

Automated analysis of FDG PET as a tool for single-subject probabilistic prediction and detection of Alzheimer's disease dementia.

PURPOSE: To introduce, evaluate and validate a voxel-based analysis method of ¹8F-FDG PET imaging for determining the probability of Alzheimer's disease (AD) in a particular individual. METHODS: The subject groups for model derivation comprised 80 healthy subjects (HS), 36 patients with mild cognitive impairment (MCI) who converted to AD dementia within 18 months, 85 non-converter MCI patients who did not convert within 24 months, and 67 AD dementia patients with baseline FDG PET scan were recruited from the AD Neuroimaging Initiative (ADNI) database. Additionally, baseline FDG PET scans from 20 HS, 27 MCI and 21 AD dementia patients from our institutional cohort were included for model validation. The analysis technique was designed on the basis of the AD-related hypometabolic convergence index adapted for our laboratory-specific context (AD-PET index), and combined in a multivariable model with age and gender for AD dementia detection (AD score). A logistic regression analysis of different cortical PET indexes and clinical variables was applied to search for relevant predictive factors to include in the multivariable model for the prediction of MCI conversion to AD dementia (AD-Conv score). The resultant scores were stratified into sixtiles for probabilistic diagnosis. RESULTS: The area under the receiver operating characteristic curve (AUC) for the AD score detecting AD dementia in the ADNI database was 0.879, and the observed probability of AD dementia in the six defined groups ranged from 8% to 100% in a monotonic trend. For predicting MCI conversion to AD dementia, only the posterior cingulate index, Mini-Mental State Examination (MMSE) score and apolipoprotein E4 genotype (ApoE4) exhibited significant independent effects in the univariable and multivariable models. When only the latter two clinical variables were included in the model, the AUC was 0.742 (95% CI 0.646 - 0.838), but this increased to 0.804 (95% CI 0.714 - 0.894, bootstrap p=0.027) with the addition of the posterior cingulate index (AD-Conv score). Baseline clinical diagnosis of MCI showed 29.7% of converters after 18 months. The observed probability of conversion in relation to baseline AD-Conv score was 75% in the high probability group (sixtile 6), 34% in the medium probability group (merged sixtiles 4 and 5), 20% in the low probability group (sixtile 3) and 7.5% in the very low probability group (merged sixtiles 1 and 2). In the validation population, the AD score reached an AUC of 0.948 (95% CI 0.625 - 0.969) and the AD-Conv score reached 0.968 (95% CI 0.908 - 1.000), with AD patients and MCI converters included in the highest probability categories. CONCLUSION: Posterior cingulate hypometabolism, when combined in a multivariable model with age and gender as well as MMSE score and ApoE4 data, improved the determination of the likelihood of patients with MCI converting to AD dementia compared with clinical variables alone. The probabilistic model described here provides a new tool that may aid in the clinical diagnosis of AD and MCI conversion.

[Contribution of time of flight and point spread function modeling to the performance characteristics of the PET/CT Biograph mCT scanner]. / Aportación del tiempo de vuelo y de la modelización de la respuesta a una fuente puntual a las características de funcionamiento del tomógrafo PET/TAC Biograph mCT.

OBJECTIVE: To characterize the performance of the Biograph mCT PET/CT TrueV scanner with time of flight (TOF) and point spread function (PSF) modeling. MATERIAL AND METHODS: The PET/CT scanner combines a 64-slice CT and PET scanner that incorporates in the reconstruction the TOF and PSF information. PET operating characteristics were evaluated according to the standard NEMA NU 2-2007, expanding some tests. In addition, different reconstruction algorithms were included, and the intrinsic radiation and tomographic uniformity were also evaluated. RESULTS: The spatial resolution (FWHM) at 1 and 10cm was 4.4 and 5.3mm, improving to 2.6 and 2.5mm when PSF is introduced. Sensitivity was 10.9 and 10.2 Kcps/MBq at 0 and 10cm from the axis. Scatter fraction was less than 34% at low concentrations and the noise equivalent count rate (NECR) was maximal at 27.8 kBq/mL with 182 Kcps, the intrinsic radiation produced a rate of 4.42 true coincidences per second. Coefficient of variation of the volume and system uniformity were 4.7 and 0.8% respectively. The image quality test showed better results when PSF and TOF were included together. PSF improved the hot spheres contrast and background variability, while TOF improved the cold spheres contrast. CONCLUSIONS: The Biograph mCT TrueV scanner has good performance characteristics. The image quality improves when the information from the PSF and the TOF is incorporated in the reconstruction.

Quantitative volumetric analysis of gliomas with sequential MRI and ¹¹C-methionine PET assessment: patterns of integration in therapy planning.

PURPOSE: The aim of the study was to evaluate the volumetric integration patterns of standard MRI and (11)C-methionine positron emission tomography (PET) images in the surgery planning of gliomas and their relationship to the histological grade. METHODS: We studied 23 patients with suspected or previously treated glioma who underwent preoperative (11)C-methionine PET because MRI was imprecise in defining the surgical target contour. Images were transferred to the treatment planning system, coregistered and fused (BrainLAB). Tumour delineation was performed by (11)C-methionine PET thresholding (vPET) and manual segmentation over MRI (vMRI). A 3-D volumetric study was conducted to evaluate the contribution of each modality to tumour target volume. All cases were surgically treated and histological classification was performed according to WHO grades. Additionally, several biopsy samples were taken according to the results derived either from PET or from MRI and analysed separately. RESULTS: Fifteen patients had high-grade tumours [ten glioblastoma multiforme (GBM) and five anaplastic), whereas eight patients had low-grade tumours. Biopsies from areas with high (11)C-methionine uptake without correspondence in MRI showed tumour proliferation, including infiltrative zones, distinguishing them from dysplasia and radionecrosis. Two main PET/MRI integration patterns emerged after analysis of volumetric data: pattern vMRI-in-vPET (11/23) and pattern vPET-in-vMRI (9/23). Besides, a possible third pattern with differences in both directions (vMRI-diff-vPET) could also be observed (3/23). There was a statistically significant association between the tumour classification and integration patterns described above (p < 0.001, κ = 0.72). GBM was associated with pattern vMRI-in-vPET (9/10), low-grade with pattern vPET-in-vMRI (7/8) and anaplastic with pattern vMRI-diff-vPET (3/5). CONCLUSION: The metabolically active tumour volume observed in (11)C-methionine PET differs from the volume of MRI by showing areas of infiltrative tumour and distinguishing from non-tumour lesions. Differences in (11)C-methionine PET/MRI integration patterns can be assigned to tumour grades according to the WHO classification. This finding may improve tumour delineation and therapy planning for gliomas.

[Study on the findings of an immediate renal gammagraphy and its effect on the survival of a kidney graft]. / Estudio de los hallazgos de la gammagrafía renal inmediata y su influencia en la supervivencia del injerto renal.

INTRODUCTION: We assessed the effect of the findings of the renal gammagraphy (99mTc-DTPA) taken in the first 24 hours after the transplant in the survival of the kidney transplant. MATERIALS AND METHOD: We retrospectively studied 413 kidney transplants carried out between January 1994 and December 2008, with emphasis on normal gammagraphic findings or alterations in the vascular, parenchymal and excretory stages, as well as their effect on the survival of the graft. RESULTS: Of the 413 transplants, 44 (10.7%) presented alterations in the vascular stage, 256 (62%) in the parenchymal stage and 269 (65.1%) in the excretory stage. The mean follow-up of the entire group was 72.5 months (± 54.1 DE). The univariate analysis shows that the survival of the graft is significantly less in patients with alterations in the vascular stage (OR: 3; IC 95% 1.9 - 4.9 p<0.001), in the excretory stage (OR: 2.5; IC 95% 1.5 - 4; p=<0.001) in the parenchymal stage (OR: 2.21; IC 95% 1.3-3.36; p=0.001). The multivariate studies of the gammagraphic variables that affect the survival of the graft show that the presence of alterations in the vascular stage (OR: 3; IC 95% 1.9-4.9; p<0.001) in the parenchymal stage (OR: 2; IC 95% 1.2-3.3; p=0.005) are directly related to survival. This data is also confirmed by means of the actuarial survival analysis of the graft at 3 and 5 years. CONCLUSIONS: The presence of alterations in the vascular stage and in the parenchymal stage of the renal gammagraphy immediately after the transplant are variables that affect the survival of the graft.

[Neuroimaging in brain tumors]. / Neuroimagen de los tumores cerebrales.

Advances in neuroimaging have modified diagnosis, treatment and clinical management of brain tumors. However, neuropathological study remains necessary in order to get the best clinical management. Surgery and radiotherapy planning are imaging-dependent procedures, and MRI is the standard imaging modality for determining precisely tumor location and its anatomical relationship with surrounding brain structures. In high-grade tumors it has been accepted that tumoral areas with contrast uptake in CT, or T1-weighted MRI contrast enhancement corresponds to solid tumor. However, relationship between MRI and invasive tumor areas remains less defined. Therefore, it is generally accepted that conventional MRI is not sufficient to delineate the real extension of brain tumors. In recent years, PET using 18FDG and amino acid radiotracers ((11)C-Methionine, (18)FDOPA, (18)FET) and SPECT with (201-)Thallium, as well as advanced MRI sequences (Perfusion, Diffusion-weighted, Diffusion tensor imaging and tractography), and functional MRI, have added important complementary information in the characterization, therapy planning and recurrence differential diagnosis of brain tumors. In this continuing education review of neuroimaging in brain tumors, technical aspects and clinical applications of different imaging modalities are approached in a multidisciplinary way.

Evaluation of spatial resolution of a PET scanner through the simulation and experimental measurement of the recovery coefficient.

PURPOSE: In order to measure spatial resolution of a PET tomograph in clinical conditions, this study describes and validates a method based on the recovery coefficient, a factor required to compensate underestimation in measured radioactivity concentration for small structures. METHODS: In a PET image, the recovery factors of radioactive spheres were measured and their comparison with simulated recovery coefficients yielded the tomographic spatial resolution. Following this methodology, resolution was determined in different surrounding media and several conditions for reconstruction, including clinical conditions for brain PET studies. All spatial resolution values were compared with those obtained using classical methods with point and line sources. RESULTS: In each considered condition, spatial resolution of the PET image estimated using the recovery coefficient showed good agreement with classical methods measurements, validating the procedure. CONCLUSION: Measurement of the recovery coefficient provides an assessment of tomographic spatial resolution, particularly in clinical studies conditions.

New MRI, 18F-DOPA and 11C-(+)-alpha-dihydrotetrabenazine templates for Macaca fascicularis neuroimaging: advantages to improve PET quantification.

Normalization of neuroimaging studies to a stereotaxic space allows the utilization of standard volumes of interest (VOIs) and voxel-based analysis (SPM). Such spatial normalization of PET and MRI studies requires a high quality template image. The aim of this study was to create new MRI and PET templates of (18)F-DOPA and (11)C-(+)-alpha-dihydrotetrabenazine ((11)C-DTBZ) of the Macaca fascicularis brain, an important animal model of Parkinson's disease. MRI template was constructed as a smoothed average of the scans of 15 healthy animals, previously transformed into the space of one representative MRI. In order to create the PET templates, (18)F-DOPA and (11)C-DTBZ PET of the same subjects were acquired in a dedicated small animal PET scanner and transformed to the created MRI template space. To validate these templates for PET quantification, parametric values obtained with a standard VOI-map applied after spatial normalization to each template were statistically compared to results computed using individual VOIs drawn for each animal. The high correlation between both procedures validated the utilization of all the templates, improving the reproducibility of PET analysis. To prove the utility of the templates for voxel-based quantification, dopamine striatal depletion in a representative monkey treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was assessed by SPM analysis of (11)C-DTBZ PET. A symmetric reduction in striatal (11)C-DTBZ uptake was detected in accordance with the induced lesion. In conclusion, templates of M. fascicularis brain have been constructed and validated for reproducible and automated PET quantification. All templates are electronically available via the internet.

[Positron emission tomography in breast cancer]. / Tomografía por emisión de positrones en el cáncer de mama.

PET18FDG is an imaging diagnostic technique that shows changes in glycolitic metabolism that appear at a very early phases in the tumoral process. The main limitation of PET in breast cancer is the detection of small tumor lesions and axillary micrometastases. However it offers important information in the staging of high risk patients, in clinical relapse or in therapeutic evaluation. The new PET-CT devices offer advantages over conventional techniques. It provides a greater precision in the localization of tumoral foci. In spite of current difficulties for clinical applications, fluoro-estradiol (18F-ES) offers the possibilty of studying the presence of estrogenic receptors both in the primary and in the metastases. It may prove to be a useful tool to obtain information about therapeutic management and prognosis of breast cancer.