Amyloid brain-dedicated PET images can diagnose Alzheimer's pathology with Centiloid Scale.

PURPOSE: To evaluate whether the Centiloid Scale may be used to diagnose Alzheimer's Disease (AD) pathology effectively with the only use of amyloid PET imaging modality from a brain-dedicated PET scanner. METHODS: This study included 26 patients with amyloid PET images with 3 different radiotracers. All patients were acquired both on a PET/CT and a brain-dedicated PET scanner (CareMiBrain, CMB), from which 4 different reconstructions were implemented. A new pipeline was proposed and used for the PET image analysis based on the original Centiloid Scale processing pipeline, but with only PET images. The Youden's Index was employed to calculate the optimal cutoffs for diagnosis and evaluated by the AUC, accuracy, precision, and recall metrics. RESULTS: The Centiloid Scale (CL) processing pipeline was validated with and without the use of MR images. The CL cutoffs for AD pathology diagnosis on the PET/CT and the 4 CMB reconstructions were 34.4 ±â€¯2.2, 43.5 ±â€¯3.5, 51.9 ±â€¯12.5, 57.5 ±â€¯6.8 and 41.8 ±â€¯1.2 respectively. Overall, for these cutoffs all metrics obtained the maximum score. CONCLUSION: The Centiloid scale applied to PET images allows for AD pathology diagnosis. The CMB scanner can be used with the Centiloid scale to automatically assist in the diagnosis of AD pathology, relieving the large burden of neurodegenerative diseases on a traditional PET/CT.

Objective Image Quality Comparison Between Brain-Dedicated PET and PET/CT Scanners.

As part of a clinical validation of a new brain-dedicated PET system (CMB), image quality of this scanner has been compared to that of a whole-body PET/CT scanner. To that goal, Hoffman phantom and patient data were obtined with both devices. Since CMB does not use a CT for attenuation correction (AC) which is crucial for PET images quality, this study includes the evaluation of CMB PET images using emission-based or CT-based attenuation maps. PET images were compared using 34 image quality metrics. Moreover, a neural network was used to evaluate the degree of agreement between both devices on the patients diagnosis prediction. Overall, results showed that CMB images have higher contrast and recovery coefficient but higher noise than PET/CT images. Although SUVr values presented statistically significant differences in many brain regions, relative differences were low. An asymmetry between left and right hemispheres, however, was identified. Even so, the variations between the two devices were minor. Finally, there is a greater similarity between PET/CT and CMB CT-based AC PET images than between PET/CT and the CMB emission-based AC PET images.

Spinocerebellar Ataxia 36 is a Frequent Cause of Hereditary Ataxia in Eastern Spain.

Background: Autosomal dominant spinocerebellar ataxia 36 (SCA36) is caused by hexanucleotide repeat expansion in the NOP56 gene. Objectives: To assess frequency, clinical and genetic features of SCA36 in Eastern Spain. Methods: NOP56 expansion was tested in a cohort of undiagnosed cerebellar ataxia families (n = 84). Clinical characterization and haplotype studies were performed. Results: SCA36 was identified in 37 individuals from 16 unrelated families. It represented 5.4% of hereditary ataxia patients. The majority were originally from the same region and displayed a shared haplotype. Mean age at onset was 52.5 years. Non-ataxic features included: hypoacusis (67.9%), pyramidal signs (46.4%), lingual fasciculations/atrophy (25%), dystonia (17.8%), and parkinsonism with evidence of dopaminergic denervation (10.7%). Conclusions: SCA36 is a frequent cause of hereditary ataxia in Eastern Spain, and is associated with a strong founder effect. SCA36 analysis should be considered prior to other studies, especially in AD presentations. Parkinsonism reported here broadens SCA36 clinical spectrum.

The sentinel node with technetium-99m for prostate cancer. A safe and mature new gold standard?

BACKGROUND: The objective was to carry out a prospective study to compare the current extended pelvic lymph node dissection (ePLND) to the sentinel node (SN) technique with 99mTcnanocolloid. METHODS: We conducted a prospective study between January 2013 and May 2020. In the first 74 patients, 99mTc-nanocolloid was used. Then from June 2017 onwards, in 38 patients we used a combined radiotracer prepared by adding indocyanine green (ICG). A preoperative SPECT/CT was also performed to check on the SNs. We extracted the SNs guided by a laparoscopic gamma-ray detection probe and/or a fluorescence camera. RESULTS: We included 112 patients with a Briganti nomogram-assessed risk of 5% or more. In 4 out of the total, the radiotracer did not migrate. The mean number of extracted nodes was 21.56 (13.46-29.71) and the mean of extracted SNs was 5.17 (1.83-8.51) (P<0.001). The technique that registered the most nodes with high activity was SPECT/CT, with an average of 4.33 nodes (2.42-6.23) (P<0.001). We found SNs outside the template in 78% of the patients. A total of 46% of the complications were related to ePLND. The SN biopsy showed a sensitivity of 100%, specificity of 97.5%, PVV of 92.86%, and NPV of 100%. CONCLUSIONS: Our results prove that ePLND is a technique with significant morbidity; up to 46% of the complications were related to the ePLND. The SN surgery showed great accuracy in detecting metastases due to the SPECT/CT and a lower rate of complications than ePLND.

Accuracy and prognostic impact of FDG PET/CT and biopsy in bone marrow assessment of follicular lymphoma at diagnosis: A Nation-Wide cohort study.

BACKGOUND: In the workup of follicular lymphoma (FL), bone marrow biopsy (BMB) assessment is a key component of FLIPI and FLIPI2, the most widely used outcome scores. During the previous decade, several studies explored the role of FDG-PET/CT for detecting nodal and extranodal disease, with only one large study comparing both techniques. METHODS: The aim of our study was to evaluate the diagnostic accuracy and the prognostic impact of both procedures in a retrospective cohort of 299 FL patients with both tests performed at diagnosis. In order to avoid a collinearity bias, FLIPI2 was deconstructed in its founding parameters, and the bone marrow involvement (BMI) parameter separately included as: a positive BMB, a positive PET/CT, the combined "PET/CT and BMB positive" or "PET/CT or BMB positive". These variables were also confronted independently with the POD24 in 233 patients treated with intensive regimens. RESULTS: In the total cohort, bone marrow was involved in 124 and 60 patients by BMB and PET/CT, respectively. In terms of overall survival, age > 60 y.o. and the combined "PET/CT or BMB positive" achieved statistical independence as a prognostic factor. In patients treated with an intensive regimen, only the combined "PET/CT or BMB positive" added prognostic value for a shorter overall survival, when confronted with the POD24. CONCLUSION: Our results show that in FL both BMB and PET/CT should be considered at diagnosis, as their combined assessment provides independent prognostic value in the context of the most widely use clinical scores.

Presenilin-1 Mutations Are a Cause of Primary Lateral Sclerosis-Like Syndrome.

BACKGROUND AND PURPOSE: Primary lateral sclerosis (PLS) is a progressive upper motor neuron (UMN) disorder. It is debated whether PLS is part of the amyotrophic lateral sclerosis (ALS) spectrum, or a syndrome encompassing different neurodegenerative diseases. Recently, new diagnostic criteria for PLS have been proposed. We describe four patients of two pedigrees, meeting definite PLS criteria and harboring two different mutations in presenilin 1 (PSEN1). METHODS: Patients underwent neurological and neuropsychological examination, MRI, 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), amyloid-related biomarkers, and next-generation sequencing (NGS) testing. RESULTS: Four patients, aged 25-45 years old, presented with a progressive UMN syndrome meeting clinical criteria of definite PLS. Cognitive symptoms and signs were mild or absent during the first year of the disease but appeared or progressed later in the disease course. Brain MRI showed microbleeds in two siblings, but iron-related hypointensities in the motor cortex were absent. Brain FDG-PET showed variable areas of hypometabolism, including the motor cortex and frontotemporal lobes. Amyloid deposition was confirmed with either cerebrospinal fluid (CSF) or imaging biomarkers. Two heterozygous likely pathogenic mutations in PSEN1 (p.Pro88Leu and p.Leu166Pro) were found in the NGS testing. CONCLUSION: Clinically defined PLS is a syndrome encompassing different neurodegenerative diseases. The NGS testing should be part of the diagnostic workup in patients with PLS, at least in those with red flags, such as early-onset, cognitive impairment, and/or family history of neurodegenerative diseases.

The Role of Imaging Studies in Favor of Possible Cerebellar Multiple System Atrophy: A Case Study.

ABSTRACT: We report a 64-year-old woman whose history started with urinary incontinence and neurological symptoms (cognitive impairment, dysarthria, and gait difficulties). The 18F-FDG PET/CT showed hypometabolism of the whole cerebellum. Then 6 months later, she developed tremor, postural instability, and ataxia, so she was hospitalized to complete study. Blood tests (antibodies, vitamin B12, copper, genetic test of spinocerebellar ataxia) did not have alterations, but imaging studies, along with clinical symptoms, provide the diagnosis of possible multiple system atrophy.

[Sentinel lymph node selective biopsy in prostate cancer.] / Ganglio centinela en cáncer de próstata.

OBJECTIVE: To validate the sentinel lymph node selective biopsy (SLNSB) in the staging of Prostate Cancer with Briganti Index > 5 by comparison with extended lymphadenectomy (ePLND) in a prospective longitudinal study. METHODS: SLNSB has been performed in 84 patients, the first 70 by injection of nanocoloids marked with Tc99m and preoperative SPECT-CT, and in the last 14 with mixed radiotracer (99mTc + ICG). After laparoscop ic removal of sentinel nodes all patients underwent an ePLND. RESULTS: SPECT-CT showed radiotracer deposits outside the territory of the ePLND in 76% of patients and laparoscopic gamma probe in 57%. The median number of sentinel nodes removed was 5.2 with a total average number of lymph nodes removed of 22. In all cases with metastatic nodes (28% in the series) there was at least one positive sentinel node but metastatic sentinel nodes outside of the territory of the ePLND were found in 6/24 patients (25%). The sensitivity, specificity, PPV and NPV of 99mTc were 100%, 96.07%, 90.47% and 100%, respectively. In 5 out of 14 patients with mixed radiotracer, lymph node involvement was detected. In all of them there was at least one sentinel node affected with 99mTc, and only 3 showed fluorescence with 100% sensitivity and 100% NPV for 99mTc and 60% sensitivity and 77.77% NPV for ICG. CONCLUSION: The SLNSB with 99mTc has a high sensitivity and a VPN of 100%, increasing the identification of lymphatic metastases outside the territory of the ePLND. Fluorescence can facilitate the visualization of the sentinel nodes when they have been previously located by the SPECT-CT, although the sensitivity and the NPV of the ICG are lower than that of the 99mTc.

OBJETIVO: Validar la biopsia selectiva de ganglio centinela (BSGC) en la estadificación del Cáncer de Próstata con Indice de Briganti > 5 mediante comparación con la linfadenectomía extendida (LFDe) en un estudio prospectivo longitudinal.MÉTODOS: Se ha realizado BSGC a 84 pacientes, los 70 primeros mediante inyección de nanocoloides marcados con Tc99m y SPECT-TC preoperatoria, y en los 14 últimos con radiotrazador mixto (Tc99m + ICG). A todos los pacientes tras la extracción laparoscópica de los ganglios centinelas se les realizó una LFDe. RESULTADOS: La SPECT-TC mostró depósitos del radiotrazador fuera del territorio de la LFDe en el 76% de los pacientes y la gammasonda laparoscópica en el 57%.La media de ganglios centinelas extraídos fue 5,2 con una media total de ganglios linfáticos extraídos de 22. En todos los casos con ganglios metastáticos (28% de la serie) hubo, al menos, un ganglio centinela positivo, encontrando ganglios centinela metastásicos fuera del territorio de la LFDe en 6/24 pacientes (25%). La sensibilidad, especificidad, VPP y VPN del Tc99m fue del 100%, 96,07%, 90,47% y 100%, respectivamente. En 5 de los 14 pacientes con radiotrazador mixto se detectó afectación ganglionar. En todos ellos hubo como mínimo un ganglio centinela afecto con Tc99m y sólo 3 mostraron fluorescencia, con sensibilidad del 100% y VPN del 100% para el Tc99m y sensibilidad del 60% y VPN del 77,77% para el ICG.CONCLUSIÓN: La BSGC con Tc99m tiene una alta sensibilidad y un VPN del 100%, aumentando la identificación de metástasis linfáticas fuera del territorio de la LFDe. La fluorescencia puede facilitar la visualización de los centinelas cuando se tiene una localización previa de los mismos con el SPECT-TAC, aunque la sensibilidad y el VPN del ICG es inferior al del Tc99m.

Ganglio centinela en cáncer de próstata / Sentinel lymph node selective biopsy in prostate cancer

Objetivo: Validar la biopsia selectiva de ganglio centinela (BSGC) en la estadificación del Cáncer de Próstata con Indice de Briganti > 5 mediante comparación con la linfadenectomía extendida (LFDe) en un estudio prospectivo longitudinal. Métodos: Se ha realizado BSGC a 84 pacientes, los 70 primeros mediante inyección de nanocoloides marcados con Tc99m y SPECT-TC preoperatoria, y en los 14 últimos con radiotrazador mixto (Tc99m + ICG). A todos los pacientes tras la extracción laparoscópica de los ganglios centinelas se les realizó una LFDe. Resultados: La SPECT-TC mostró depósitos del radiotrazador fuera del territorio de la LFDe en el 76% de los pacientes y la gammasonda laparoscópica en el 57%.La media de ganglios centinelas extraídos fue 5,2 con una media total de ganglios linfáticos extraídos de 22. En todos los casos con ganglios metastáticos (28% de la serie) hubo, al menos, un ganglio centinela positivo, encontrando ganglios centinela metastásicos fuera del territorio de la LFDe en 6/24 pacientes (25%). La sensibilidad, especificidad, VPP y VPN del Tc99m fue del 100%, 96,07%, 90,47% y 100%, respectivamente. En 5 de los 14 pacientes con radiotrazador mixto se detectó afectación ganglionar. En todos ellos hubo como mínimo un ganglio centinela afecto con Tc99m y sólo 3 mostraron fluorescencia, con sensibilidad del 100% y VPN del 100% para el Tc99m y sensibilidad del 60% y VPN del 77,77% para el ICG. Conclusión: La BSGC con Tc99m tiene una alta sensibilidad y un VPN del 100%, aumentando la identificación de metástasis linfáticas fuera del territorio de la LFDe. La fluorescencia puede facilitar la visualización de los centinelas cuando se tiene una localización previa de los mismos con el SPECT-TAC, aunque la sensibilidad y el VPN del ICG es inferior al del Tc99m

Objective: To validate the sentinel lymph node selective biopsy (SLNSB) in the staging of Prostate Cancer with Briganti Index > 5 by comparison with extended lymphadenectomy (ePLND) in a prospective longitudinal study. Methods: SLNSB has been performed in 84 patients, the first 70 by injection of nanocoloids marked with Tc99m and preoperative SPECT-CT, and in the last 14 with mixed radiotracer (99mTc + ICG). After laparoscop ic removal of sentinel nodes all patients underwent an ePLND. Results: SPECT-CT showed radiotracer deposits outside the territory of the ePLND in 76% of patients and laparoscopic gamma probe in 57%. The median number of sentinel nodes removed was 5.2 with a total average number of lymph nodes removed of 22. In all cases with metastatic nodes (28% in the series) there was at least one positive sentinel node but metastatic sentinel nodes outside of the territory of the ePLND were found in 6/24 patients (25%). The sensitivity, specificity, PPV and NPV of 99mTc were 100%, 96.07%, 90.47% and 100%, respectively. In 5 out of 14 patients with mixed radiotracer, lymph node involvement was detected. In all of them there was at least one sentinel node affected with 99mTc, and only 3 showed fluorescence with 100% sensitivity and 100% NPV for 99mTc and 60% sensitivity and 77.77% NPV for ICG. Conclusion: The SLNSB with 99mTc has a high sensitivity and a VPN of 100%, increasing the identification of lymphatic metastases outside the territory of the ePLND. Fluorescence can facilitate the visualization of the sentinel nodes when they have been previously located by the SPECT-CT, although the sensitivity and the NPV of the ICG are lower than that of the 99mTc

Impact of amyloid-PET in daily clinical management of patients with cognitive impairment fulfilling appropriate use criteria.

To evaluate the use of amyloid-positron emission tomography (PET) in routine clinical practice, in a selected population with cognitive impairment that meets appropriate use criteria (AUC).A multicenter, observational, prospective case-series study of 211patients from 2 level-3 hospitals who fulfilled clinical AUC for amyloid-PET scan in a naturalistic setting. Certainty degree was evaluated using a 5-point Likert scale: 0 (very low probability); 1 (low probability); 2 (intermediate probability); 3 (high probability); and 4 (practically sure), before and after amyloid PET. The treatment plan was considered as cognition-specific or noncognition-specific.Amyloid-PET was positive in 118 patients (55.9%) and negative in 93 patients (44.1%). Diagnostic prescan confidence according amyloid-PET results showed that in both, negative and positive-PET subgroup, the most frequent category was intermediate probability (45.7% and 55.1%, respectively). After the amyloid-PET, the diagnostic confidence showed a very different distribution, that was, in the negative-PET group the most frequent categories are very unlikely (70.7%) and unlikely (29.3%), while in the positive-PET group were very probable (57.6%) and practically sure (39%). Only in 14/211 patients (6.6%) the result of the amyloid-PET did not influence the diagnostic confidence, while in 194 patients (93.4%), the diagnostic confidence improved significantly after amyloid-PET results. The therapeutic intention was modified in 93 patients (44.1%). Specific treatment for Alzheimer disease was started, before amyloid-PET, in 80 patients (37.9%).This naturalistic study provides evidence that the implementation of amyloid-PET is associated with a significant improvement in diagnostic confidence and has a high impact on the therapeutic management of patients with mild cognitive impairment fulfilled clinical AUC.

Usefulness of Dual-Point Amyloid PET Scans in Appropriate Use Criteria: A Multicenter Study.

BACKGROUND: Biomarkers of neurodegeneration play a major role in the diagnosis of Alzheimer's disease (AD). Information on both amyloid-ß accumulation, e.g., from amyloid positron emission tomography (PET), and downstream neuronal injury, e.g., from 18F-fluorodeoxyglucose (FDG) PET, would ideally be obtained in a single procedure. OBJECTIVE: On the basis that the parallelism between brain perfusion and glucose metabolism is well documented, the objective of this work is to evaluate whether brain perfusion estimated in a dual-point protocol of 18F-florbetaben (FBB) PET can be a surrogate of FDG PET in appropriate use criteria (AUC) for amyloid PET. METHODS: This study included 47 patients fulfilling international AUC for amyloid PET. FDG PET, early FBB (pFBB) PET (0-10 min post injection), and standard FBB (sFBB) PET (90-110 min post injection) scans were acquired. Results of clinical subjective reports and of quantitative region of interest (ROI)-based analyses were compared between procedures using statistical techniques such as Pearson's correlation coefficients and t-tests. RESULTS: pFBB and FDG visual reports on the 47 patients showed good agreement (k  >  0.74); ROI quantitative analysis indicated that both data modalities are highly correlated; and the t-test analysis does not reject the null hypothesis that data from pFBB and FDG examinations comes from independent random samples from normal distributions with equal means and variances. CONCLUSIONS: A good agreement was found between pFBB and FDG data as obtained by subjective visual and quantitative analyses. Dual-point FBB PET scans could offer complementary information (similar to that from FDG PET and FBB PET) in a single procedure, considering pFBB as a surrogate of FDG.

Using CT Data to Improve the Quantitative Analysis of 18F-FBB PET Neuroimages.

18F-FBB PET is a neuroimaging modality that is been increasingly used to assess brain amyloid deposits in potential patients with Alzheimer's disease (AD). In this work, we analyze the usefulness of these data to distinguish between AD and non-AD patients. A dataset with 18F-FBB PET brain images from 94 subjects diagnosed with AD and other disorders was evaluated by means of multiple analyses based on t-test, ANOVA, Fisher Discriminant Analysis and Support Vector Machine (SVM) classification. In addition, we propose to calculate amyloid standardized uptake values (SUVs) using only gray-matter voxels, which can be estimated using Computed Tomography (CT) images. This approach allows assessing potential brain amyloid deposits along with the gray matter loss and takes advantage of the structural information provided by most of the scanners used for PET examination, which allow simultaneous PET and CT data acquisition. The results obtained in this work suggest that SUVs calculated according to the proposed method allow AD and non-AD subjects to be more accurately differentiated than using SUVs calculated with standard approaches.

Intestinal uptake of (99m)Tc-MDP: a case report of protein-losing enteropathy correlated with pathology findings from autopsy.

We present a case of a 60-year-old man with a history of severe hypoproteinemia and constitutional syndrome, suspected to have protein-losing enteropathy (PLE). Bone scintigraphy ((99m)Tc-MDP) performed to rule out the presence of bone metastases incidentally showed abnormal uptake in abdominal soft tissue. The patient unexpectedly died of heart failure, and autopsy revealed microscopic alterations consistent with PLE exclusively in the right colon, corresponding to the area of abnormal uptake. Few similar cases have been published, but none of them reported correlative pathological findings affecting the area of abnormal tracer uptake. In this case of PLE, (99m)Tc-MDP scintigraphy was a useful imaging method for localizing the site of protein loss, showing a focal area of alteration in the right colon. This finding could also have been of great help in case that surgery had been finally performed to control the protein loss.

Effect of transport temperature on the Scantibodies total intact parathyroid hormone immunoradiometric assay using the RIAMAT-280.

BACKGROUND: Inadequate temperature affects the stability of intact parathyroid hormone (i-PTH) kits. Room temperature during transport modifies i-PTH results. METHOD: Percent bound (%B/Bmax) and concentrations (pmol/L) of standards, controls (C1, C2) and pool from eight standard curves were divided into: group I (three curves from kits kept at room temperature for more than 48 h) and group II (five curves from kits kept at 2-8 degrees C) during transport. i-PTH was measured using Scantibodies total i-PTH assay with RIAMAT-280. RESULTS: %B/Bmax for standards, C1 and C2 were significantly higher in group I versus II (P = 0.04). %B/Bmax for the pool were significantly lower in group I (P = 0.001). i-PTH pool concentration in group I was 51% lower (95% confidence interval, 47-53%, P = 0.001); differences were not significant for C1 (P = 0.25) and C2 (P = 0.57) in both groups. CONCLUSION: Room temperature on i-PTH kit during transport alters the standard curve, resulting in a decrease in i-PTH. Using a pool as internal quality control allows the detection of these changes not detected by kit controls.

Stability of stabilized 99mTc-D,L-HMPAO stored in vials and syringes.

UNLABELLED: Our objective was to determine the stability of stabilized (99m)Tc-hexamethylpropylene amine oxime ((99m)Tc-d,l-HMPAO) dispensed by vial and syringe, with the storage time and labeling activity varied. METHODS: (99m)Tc-d,l-HMPAO was labeled according to the manufacturer's instructions, but with modification of the (99m)TcO(4)Na activity. Two groups were prepared: 1,110 MBq (30 mCi) and 2,600-3,700 MBq (70.3-100 mCi). Five minutes after labeling, the radiochemical purity (RCP) of the vial content was determined. Afterward, the same activity was distributed into two 2-mL syringes and into the manufacturer's vial. In one of the syringes, the radiopharmaceutical stayed in contact with the needle for 4 h. At 2 and 4 h after labeling, the RCP of the vial and syringe content was checked and compared. RESULTS: The mean RCP of stabilized (99m)Tc-d,l-HMPAO labeled with 1,110 MBq (30 mCi) and stored in a vial decreased from 93.1% at 5 min to 92.1% at 2 h and to 91.1% at 4 h. With storage in a syringe, the RCP decreased from 89.8% at 2 h to 88.7% at 4 h. This diminution increased for labeling with higher activities (2,600-3,700 MBq [70.3-100 mCi]), ranging from 91.4% at 5 min, 89.0% at 2 h, and 85.3% at 4 h in a vial and from 85.9% at 2 h to 80.2% in a syringe. (99m)TcO(2) and secondary (99m)Tc-HMPAO were the main impurities at t = 0. (99m)TcO(4)(-) was an impurity that increased with time in both vials and syringes but significantly so in syringes. All these impurities were higher with labeling activities in the range of 2,600-3,700 MBq (70.3-100 mCi). Contact of the needle with (99m)Tc-d,l-HMPAO sharply decreased the RCP to 57.1% at 4 h. CONCLUSION: The RCP of stabilized (99m)Tc-d,l-HMPAO decreases significantly in both vials and syringes with high labeling activities. The product is less stable when stored in a syringe than in a vial. The fraction of dose in contact with the needle affects the RCP results.

Influence of the thyroid remnant in the elevation of the serum thyroglobulin after thyroidectomy in differentiated thyroid carcinoma. Importance of the diagnostic iodine total-body scanning.

PURPOSE: Stimulated thyroglobulin (Tg) and (131)I total-body scan (TBS) have been the mainstays of differentiated thyroid carcinoma (DTC), but now diagnostic TBS has been eliminated from some follow-up protocols. Nevertheless, Tg can be negative in the presence of thyroid tissue, and moderately elevated Tg poses management problems. The purpose of this study was to check how many patients have Tg negative but visible thyroid tissue and if diagnostic TBS could be clinically useful. MATERIAL AND METHODS: Retrospective review of 317 exams (stimulated Tg and TBS) of 128 patients with DTC. Patients with high-grade criteria and/or positive autoantibodies are excluded. Tg is considered positive if higher than the sensitivity level of the technique. TBS is positive if thyroid remnant, lymphatic node or metastases are detected. Results are classified in Tg and TBS concordant or discordant. RESULTS: Discordant (131)I TBS and Tg were found in 74/317 studies (23.3%), 48 (65%) being TBS positive and Tg negative. None of 128 patients had a first post-surgery negative scan, but 13 (10%) were Tg negative, even two patients with lymph node uptake. One year after radioiodine treatment, 26 out of 115 patients (initially Tg and TBS concordant positive) showed Tg negative and TBS still positive due to cervical remnants (20 patients), lymph node uptake (one) and metastasis (five); 20 patients remained Tg and TBS positive, but 14 of them only showed thyroid remnants. CONCLUSIONS: We propose to perform periodic diagnostic TBS to improve Tg specificity, at least while neck thyroid activity is detected, even if Tg is negative.