Initial experience of 3 tesla apparent diffusion coefficient values in differentiating benign and malignant thyroid nodules.

PURPOSE: To evaluate the role of diffusion-weighted magnetic resonance imaging (DWMRI) in differentiating benign and malignant thyroid nodules using a 3 Tesla (T) MRI scanner. MATERIALS AND METHODS: Twenty-eight nodules in 25 patients and 14 healthy control cases were included in the study. DWMRI was acquired with 6 b values with a 3T MRI scanner. The apparent diffusion coefficient (ADC) values of the nodules were calculated from reconstructed ADC map images and were compared with the final histopathological diagnoses. RESULTS: The mean ADC value of the benign nodules was 1548 ± 353.4 (×10(-6) mm(2) /s), and the mean ADC of the malignant nodules was 814 ± 177.12 (×10(-6) mm(2) /s). The normal thyroid tissue had a mean ADC value of 1323.43 ± 210.35 × 10(-6) mm(2) /s (958-1689 × 10(-6) mm(2) /s) in the healthy control group. The ADC values were significantly different among the three groups (P = 0.001). An ADC value of 905 × 10(-6) mm(2) /s was determined to be the cutoff value for differentiating benign and malignant nodules, with 90% (55.5-98.3) sensitivity and 100% (81.3-100.0) specificity. CONCLUSION: This study suggests that the ADC values of nodules measured with a 3T MRI scanner could help in differentiating benign thyroid nodules from malignant nodules.

Imaging serotonergic transmission with [11C]DASB-PET in depressed and non-depressed patients infected with HIV.

INTRODUCTION: Site-selective imaging can provide significant insight into the mechanism of HIV-associated neurological disease. The goal of this study was to evaluate the involvement of serotonergic transmission in HIV-associated depression using [(11)C]DASB, a serotonin transporter (5-HTT)-specific radiopharmaceutical for positron emission tomography (PET). METHODS: Nine depressed HIV+ subjects (HIV-D), 9 non-depressed HIV+ subjects (HIV-ND) and 7 healthy controls (HC) underwent an MRI scan and a [(11)C]DASB-PET scan. The outcome measure was 5-HTT binding potential normalized to non-displaceable tissue radioligand (BP(ND)). RESULTS: HIV-ND subjects had lower mean regional 5-HTT BP(ND) estimates across regions compared to HC, while HIV-D subjects demonstrated higher mean regional binding values than HIV-ND subjects in most regions. Prior to correction for the false discovery rate, HIV-ND had significantly lower BP(ND) values compared to HC subjects in two regions (insula and anterior cingulate) and all HIV+ patients had significantly lower binding than HC in all regions except for the midbrain, thalamus and pons. After correction for the false discovery rate, only the insula showed significantly lower binding in HIV+ subjects compared to HC (P<0.0045). Despite a significant difference in the duration of illness between the HIV-D and HIV-ND groups, there was no definite correlation between the duration of illness and BP(ND). CONCLUSION: Lower [(11)C]DASB binding in HIV+ patients compared to HC may reflect serotonergic neuronal loss as a component of generalized HIV-associated neurodegeneration. Higher mean regional BP(ND) values in HIV-D compared to HIV-ND subjects could reflect increased density of 5-HTT, leading to increased clearance of serotonin from the synapse, which could account, in part, for symptoms of depression. The lack of correlation between duration of illness and binding argues against these findings being the result of differential neurodegeneration only. Our findings suggest a possible role for dysregulated serotonergic transmission in HIV-associated depression.

Initial evaluation of 11C-DPA-713, a novel TSPO PET ligand, in humans.

UNLABELLED: Translocator protein (TSPO) is upregulated in activated microglia and thus can serve as a marker of neuroinflammation. Recently, a novel radioligand, (11)C-N,N-diethyl-2-[2-(4-methoxyphenyl)-5,7-dimethyl-pyrazolo[1,5-a]pyrimidin-3-yl]-acetamide ((11)C-DPA-713), has been described that binds to TSPO with high affinity. Here, we report the first examination of (11)C-DPA-713 in human subjects using PET. METHODS: Five healthy controls were studied with PET for 90 min after a bolus injection of high-specific-activity (11)C-DPA-713. For comparison, 2 additional healthy controls were studied with (11)C-R-PK11195. Arterial blood sampling and metabolite analysis were performed to allow the accurate quantification of tracer kinetics. Tracer uptake was evaluated for several brain regions. Tissue time-activity curves were fitted using 1- and 2-tissue-compartment models, with goodness-of-fit tests showing a preference for the 2-tissue model. RESULTS: In the healthy brain, the average plasma-to-tissue clearance and the total volume of distribution were an order of magnitude larger than measured for (11)C-R-PK11195. Accordingly, dose-normalized time-activity curves showed that (11)C-DPA-713 gives a larger brain signal. CONCLUSION: Studies in patient populations will help determine whether (11)C-DPA-713 provides better sensitivity for evaluating increased TSPO expression. This initial study in humans shows that (11)C-DPA-713 is a promising ligand for evaluating TSPO binding with PET.

Protein-losing enteropathy detected by Tc-99m-MDP abdominal scintigraphy.

This case report describes the incidental finding of intestinal leakage during bone scan imaging with Tc-99m methylene diphosphonate (MDP) in a patient with previously diagnosed protein-losing enteropathy (PLE). Most radiopharmaceuticals reported in the literature that are useful for making this diagnosis are not generally available for clinical use in the United States. This report suggests that Tc-99m-MDP is useful for confirming the diagnosis of PLE although further investigations are indicated to determine the accuracy of this method.

Imaging of musculoskeletal bacterial infections by [124I]FIAU-PET/CT.

BACKGROUND: Traditional imaging techniques for the localization and monitoring of bacterial infections, although reasonably sensitive, suffer from a lack of specificity. This is particularly true for musculoskeletal infections. Bacteria possess a thymidine kinase (TK) whose substrate specificity is distinct from that of the major human TK. The substrate specificity difference has been exploited to develop a new imaging technique that can detect the presence of viable bacteria. METHODOLOGY/PRINCIPAL FINDINGS: Eight subjects with suspected musculoskeletal infections and one healthy control were studied by a combination of [(124)I]FIAU-positron emission tomography and CT ([(124)I]FIAU-PET/CT). All patients with proven musculoskeletal infections demonstrated positive [(124)I]FIAU-PET/CT signals in the sites of concern at two hours after radiopharmaceutical administration. No adverse reactions with FIAU were observed. CONCLUSIONS/SIGNIFICANCE: [(124)I]FIAU-PET/CT is a promising new method for imaging bacterial infections.

Advances in imaging of the paranasal sinuses.

Significant changes in surgical technique, surgical instrumentation, and imaging technology have occurred during the past 20 years. These changes have largely resulted from a better understanding of the pathophysiology ofa specific pathologic process, the inflammation of paranasal sinus mucosa. As surgical techniques were adapted to address clinical issues, new instrumentation was developed. Changes in imaging technology were also a result of these and similar issues pressing from other similar medical/surgical fields. The obsolescence of plain-film imaging is being addressed by miniaturization of large and bulky cross-sectional imaging equipment that will gradually become available and embraced by the clinical practice. These changes will bring about greater responsibilities, the foremost of which is vigilance in reducing radiation dose to the patient.