Respiratory-gated imaging in metabolic evaluation of small solitary pulmonary nodules: 18F-FDG PET/CT and correlation with histology.

OBJECTIVE: The aim of the study was to evaluate the effect of 2-((18)F)-fluoro-2-deoxy-D-glucose ((18)F-FDG)-PET/computed tomography (CT) respiratory-gated imaging [four-dimensional (4D)] in the metabolic evaluation of small solitary pulmonary nodules and analyze the cutoff maximum standardized uptake value (SUV(max)) of 2.5 in classifying and distinguishing benign/malignant pulmonary pathologies in 4D studies. MATERIALS AND METHODS: Thirty-two patients with pulmonary lesions measuring 2 cm or less were included during their scheduled (18)F-FDG PET/CT examinations. The whole-body PET/CT acquisition (3D) was followed by a chest-centered PET/CT (4D) study synchronized with the respiratory cycle. The SUV(max) percentage difference (%Diff SUV(max)) was calculated. The nodule size, localization, and relationships with histological/cytological findings were studied. RESULTS: Fifteen nodules were 10 mm or smaller and 17 were larger than 10 mm [mean size = 12 mm (7-20)]. The mean 3D-SUV(max) was 2.5 (0.7-6.1) and the mean 4D-SUV(max) 3.2 (0.9-7.2) (P < 0.001). The mean %Diff SUV(max) was 38% for all patients (7-90), 45% in subcentimetric (7-90%) and 31% (7-75%) in supracentimetric lesions (P = NS). Histology was obtained in 23/32 (72%) cases and the pathologic benign/malignant ratio was 4/19. Malignancies were diagnosed as lung adenocarcinoma, solitary metastases, large cell lung carcinoma, and sarcoma in 13 (41%), 3 (9%), 2 (6%), and 1 (3%) case, respectively. Malignant lesions showed mean 4D-SUV(max) of 3.8 (1.2-7.2). The cutoff SUV(max) of 2.5 did not classify and distinguish between benign/malignant pulmonary pathologies, neither in 3D nor in 4D studies. CONCLUSION: Respiratory gating improves the detectability and metabolic evaluation of solitary pulmonary nodules, mostly those that are subcentimetric. However, as expected, the cutoff SUV(max) of 2.5 does not distinguish between benign/malignant lesions in either 4D or 3D studies.

Diffusion-weighted MRI for uveal melanoma liver metastasis detection.

OBJECTIVES: We aimed to assess the sensitivity of diffusion-weighted (DW) magnetic resonance (MR) imaging for the detection of pathologically confirmed uveal melanoma liver metastases (UMLM). METHODS: Twenty patients who underwent complete surgical resection of their UMLM (N = 83) were included. Pre-surgery liver MR imaging included T2-weighted, T1-weighted, DW and dynamic-gadolinium-enhanced MR sequences. Two radiologists independently reviewed three sets of images (DW / morphologic-dynamic / combined) for each patient using intraoperative and pathological findings as a standard of reference. RESULTS: The sensitivities of the morphologic-dynamic and DW images for UMLM detection were 63 % and 59 %, respectively, for reader #1 (R1) and 64 % and 53 %, for reader #2 (R2). Sensitivity of the combined set was higher than sensitivity in the two other sets (R1:69 %, R2:67 %), but was only significantly different than the sensitivity of the DW images (McNemar test). For the three sets and the two readers, the sensitivity for UMLM smaller than 5 mm (37-46 %) was significantly lower than that for UMLM larger than 5 mm (67-90 %). The sensitivity for UMLM located in the subcapsular area (41-54 %) was significantly lower than that for intraparenchymal UMLM (68-86 %) (Chi-square test). CONCLUSION: Our study shows that the addition of DW imaging to morphologic-dynamic images does not significantly increase MR sensitivities for UMLM detection. KEY POINTS: • The MR imaging sensitivity for uveal melanoma liver metastases (UMLM) was 69 %. • Addition of DW imaging to morphologic-dynamic images does not increase sensitivity significantly. • Sensitivity for subcapsular UMLM was significantly lower than sensitivity for intraparenchymal UMLM. • The T2 shortening effect does not appear to influence lesion detection in DWI.

Clinical impact of nonuniform CT-based attenuation correction in brain perfusion SPECT/CT using (99m)Tc-ECD.

INTRODUCTION: Brain perfusion SPECT is commonly used to evaluate patients with cognitive impairments. Physical limits such as attenuation compromise image quality do not allow the most accurate depiction of radionuclide distribution, and thus, application of attenuation correction (AC) has been recommended. Some reports have demonstrated discordances between the uniform (UAC) and nonuniform CT-based correction (NUAC) procedures. The aim was to study the impact of these discordances on visual interpretation and their concordance with clinical symptoms. METHODS: Twelve patients presenting cognitive impairments were included. Brain perfusion SPECT images were reconstructed using 2 AC methods. Qualitative image assessment was performed as uptake analysis in 21 predefined cortical ROIs for each patient. Interpretation of perfusion patterns was based on a 2-score uptake scale (normal and reduced/pathologic). Variation of uptake scores in UAC- versus NUAC-processed images and their concordance with clinical symptoms were studied. RESULTS: Normal image patterns generated by UAC and NUAC methods were found in 226 (90%) of 252 and in 201 (80%) of 252 ROIs, respectively. No difference between UAC and NUAC methods was found in posterior brain areas. However, differences were recorded in 51 (20%) of 252 ROIs, and this discordance was located in the anterior areas (frontal and temporal lobes), and evaluation changed from normal to pathological patterns using NUAC method. Two years later, patients showing frontal hypoperfusion on NUAC brain SPECT images expressed clinical frontal lobe dysfunctions. CONCLUSIONS: Discordances between UAC- and NUAC-processed images impact visual analysis of brain perfusion SPECT images. The NUAC-processed images show a good concordance with clinical symptoms, suggesting that it is an accurate method to correct attenuation.

Correlation between serum 25-hydroxyvitamin D concentrations and regional cerebral blood flow in degenerative dementia.

BACKGROUND: Chronic low serum vitamin D concentrations are common among the elderly. Recent studies have suggested that its metabolite, 25-hydroxyvitamin D (25-OHD), might be important for preserving cognitive functions through specific brain protective effects. However, this hypothesis is still under discussion. The aim of this study was to assess the correlation between serum 25-OHD concentrations and regional cerebral blood flow in neurodegenerative diseases such as Alzheimer's disease (AD) and dementia of Lewy bodies (DLB). PATIENTS AND METHODS: Radionuclide brain single-photon emission computed tomography/computed tomography (SPECT/CT) images and 25-OHD dosage in noninstitutionalized patients were obtained within 14 days. SPECT/CT examination was carried out using technetium-99m-ethyl cysteinate dimer in 20 consecutive patients (12 AD and eight DLB). Reconstructed images were spatially normalized using Statistical Parametric Mapping version 5 software to a default SPECT template. Voxel-based multiple regression correlation analyses, with age and mini mental state examination scores as confounding factors, were carried out. Findings were considered significant for a threshold P-value less than 0.01 (corrected at cluster level). RESULTS: A positive correlation was found between 25-OHD concentrations and regional cerebral blood flow in the left precuneus cortex (Talairach coordinates: -14, -42, 63) in AD patients. No correlation was detected in DLB patients. CONCLUSION: The results of this study confirm the relationship between 25-OHD concentrations and AD and therefore underline the hypothesis of a potential neuroprotective effect against brain degeneration. These encouraging findings need to be confirmed by larger prospective correlation series.

First experience DaTSCAN imaging using cadmium-zinc-telluride gamma camera SPECT.

We report our first experience of brain DaTSCAN SPECT imaging using cadmium-zinc-telluride gamma camera (CZT-GC) in 2 cases: a 64-year-old patient suffering from essential tremor and a 73-year-old patient presenting with atypical bilateral extrapyramidal syndrome. In both cases, 2 different acquisitions were performed and compared, using a double-head Anger-GC, followed immediately by a second acquisition on CZT-GC. There were no significant visual differences between images generated by different GC. Our first result suggests that DaTSCAN SPECT is feasible on CZT-GC, allowing both injected dose and acquisition time reductions without compromising image quality. This experience needs to be evaluated in larger series.

Brain perfusion SPECT imaging and acetazolamide challenge in vascular cognitive impairment.

Cerebrovascular disease is recognized as a common cause of cognitive impairment and dementia, alone or coexisting with other neurodegenerative diseases, mostly Alzheimer's disease. Vascular cognitive impairment (VCI) is a part of the heterogenous disorders group related to cerebral vessel disease. Although age is one of the most important risk factors for VCI, other common cardiovascular risk factors are also involved. By investigating these risk factors, a high proportion of these cognitive disorders can be prevented and/or delayed. Until now, only treatment of midlife arterial hypertension has been recognized as a preventing factor of vascular dementia. Brain MRI is becoming the method of choice to investigate cerebral vascular pathologies. However, this form of morphological imaging remains inadequate and does not provide useful functional information during VCI exploration, despite which functional imaging such as brain perfusion single-photon computed tomography, performed in baseline conditions and/or after an acetazolamide challenge, is underutilized in VCI exploration. The common strategies for VCI screening have not been standardized until now, and therefore further long-term imaging studies are needed to establish early diagnostic protocols. The present review summarizes the potential benefits of brain perfusion single-photon computed tomography imaging and possible scintigraphic quantification of cerebral hemodynamic reserves in investigation of VCI.

Brain SPECT thallium using cadmium zinc telluride: a first experience.

A 70-year-old man underwent a thallium-201 brain SPECT in the work-up and characterization of a frontotemporal mass. SPECT images were performed on cadmium zinc telluride system during only 5 minutes and after the injection of only 2 mCi. Images demonstrated high thallium uptake in frontotemporal areas considered as a potential malignant tumor. Surgical removal confirmed the diagnosis of malignant glioblastoma. The thallium SPECT fast acquisition imaging on cadmium zinc telluride systems is feasible with reduced injected dose. This method allows a significantly decrease of patient radiation exposure without compromising the image quality. This initial experience needs to be confirmed and optimized in larger clinical studies.